Clinical validation of a spectroscopic liquid biopsy for early detection of brain cancer
J Cameron1, P Brennan2, G Antoniou1, H Butler1, L Christie1, J Conn1, T Curran3, E Gray4, M Hegarty1, M Jenkinson5, D Orringer6, D Palmer1,7, A Sala1,7, B Smith1 and M Baker1
1Dxcover Ltd
2Translational Neurosurgery, Centre for Clinical Brain Sciences
3Children’s Mercy Research Institute
4Independent Health Economics Consultant
5Institute of Translational Medicine, University of Liverpool & The Walton Centre NHS Foundation Trust
6Department of Neurosurgery, New York University Grossman School of Medicine
7Department of Pure and Applied Chemistry, University of Strathclyde
Abstract
Background: Diagnostic delays impact the quality of life and survival of patients with brain tumors. Earlier and expeditious diagnoses in these patients are crucial to reducing the morbidities and mortalities associated with brain tumors.
Aim: A simple, rapid blood test that can be administered easily in a primary care setting to efficiently identify symptomatic patients who are most likely to have a brain tumor would enable quicker referral to brain imaging for those who need it most
Methods: Blood serum samples from 603 patients were prospectively collected and analyzed. Patients either had non-specific symptoms that could be indicative of a brain tumor on presentation to the Emergency Department, or a new brain tumor diagnosis and referral to the neurosurgical unit, NHS Lothian, Scotland. Patient blood serum samples were analyzed using the Dxcover® Brain Cancer liquid biopsy. This technology utilizes infrared spectroscopy combined with a diagnostic algorithm to predict the presence of intracranial disease.
Results/Conclusions: Our liquid biopsy approach reported an area under the receiver operating characteristic curve of 0.8. The sensitivity-tuned model achieves a 96% sensitivity with 45% specificity (NPV 99.3%) and identified 100% of glioblastoma multiforme patients. When tuned for a higher specificity, the model yields sensitivity of 47% with 90% specificity (PPV 28.4%). This simple, non-invasive blood test facilitates the triage and radiographic diagnosis of brain tumor patients, while providing reassurance to healthy patients. Minimizing time to diagnosis would facilitate identification of brain tumor patients at an earlier stage, enabling more effective, less morbid surgical and adjuvant care.
83
Astrocyte-secreted chordin-like 1 regulates spine density after ischemic injury
E Blanco-Suarez1,2 and N Allen1
1Salk Institute for Biological Studies
2Thomas Jefferson University
Abstract
Background: Astrocyte-secreted Chordin-like 1 (Chrdl1) is a protein highly expressed in the mouse cortex that promotes synaptic maturation and limits plasticity. In absence of Chrdl1, adult mice display juvenile-like plasticity.
Aim: To determine plasticity facilitation in Chrdl1 KO adult mice at different stages after ischemic injury.
Method: We used photothrombotic injury to cause ischemic lesions in the visual cortex of WT and Chrdl1 KO mice. We studied the post-injury expression of Chrdl1 in the peri-infarct area during the acute, the sub-acute and the chronic phases after ischemic injury. We analysed the contribution of astrocytic Chrdl1 to post-injury structural plasticity by analysing dendritic spine density and morphology in YFP-expressing WT and Chrdl1 KO mice at different stages after injury. We also assessed cell death, and reactive astrogliosis, hallmarks of ischemic injury, in absence of astrocytic Chrdl1.
Results/Conclusions: We found that Chrdl1 mRNA is upregulated in astrocytes in the peri-infarct area in both the acute and sub-acute phases (1 and 7 days after injury, respectively). Absence of Chrdl1 prevents ischemia-induced dendritic spine loss in the peri-infarct area and reduces cell death in the core, without impacting reactive astrogliosis. These findings highlight the important role of astrocyte-secreted proteins in regulating structural plasticity in response to ischemic injuries of the central nervous system.
103
Fragmentation of functional resting state networks in a transgenic mouse model of tau pathology
H Endepols1,2, M Anglada-Huguet3, E Mandelkow3,4, E Mandelkow3,4, B Neumaier1,2 and A Drzezga1,2
1University Hospital of Cologne
2Forschungszentrum Jülich GmbH
3Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE)
4Center of Advanced European Studies and Research (Caesar)
Abstract
Background: Transgenic animal models have contributed immensely to the discovery of the pathological mechanisms of human neurodegenerative diseases. However, it is challenging to investigate brain functional connectivity in awake animals using the classical method of fMRI, because this requires head fixation and therefore sedation of the animal. Metabolic connectivity analysis with [18F]FDG-PET offers a way to separate the activity-dependent [18F]FDG accumulation from subsequent scanning under anesthesia, allowing to visualize neuronal networks of the awake brain.
Aim: In the tauopathy mouse model rTg4510, we studied the fronto-thalamo-hippocampal network which is impaired in Alzheimer’s disease (AD) patients.
Method: Eight rTg4510 mice at ages 7–9 months and 8 non-transgenic littermates were injected intraperitoneally with 11.1 ± 0.8 MBq [18F]FDG. The mice spent the 40-min uptake period in single cages. Subsequently, they were anesthetized and measured in a small animal PET scanner (Focus 220, Siemens) for 30min. Images were intensity-normalized to whole brain activity, and three seed-based connectivity analyses were performed per group. A seed was placed either in the frontal cortex, dorsal hippocampus or dorsal thalamus, and correlated with all other voxels of the brain across animals.
Results/Conclusions: In the control group, the emerging correlative pattern was the same for all three seed locations, indicating a uniform fronto-thalamo-hippocampal network. In contrast, rTg4510 mice showed a fragmentation into three distinct networks with minimal overlap.
We conclude that metabolic connectivity is strongly reduced in the brain of rTg4510 mice, indicating that rTg4510 mice reproduce the symptom of functional network impairment found in AD patients.
140
Brain serotonin transporter availability encodes treatment success in patients with obesity
S Hesse1, N Griebsch1, J Kern1, J Kirchmann1, M Rullmann1, J Luthardt1, G Becker1, M Patt1, P Meyer1, A Dietrich2, M Blüher3, A Hilbert4 and O Sabri1
1Department of Nuclear Medicine, University of Leipzig
2Department of Abdominal, Transplant, Thoracic and Vascular Surgery, University of Leipzig
3Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig
4Department of Psychosomatic Medicine and Psychotherapy, Integrated Research and Treatment Center Adiposity Diseases, Behavioral Medicine Research Unit, University of Leipzig
Abstract
Background: To combat global obesity epidemic, the biological mechanism underlying sustainable weight loss needs to be explored in order to identify key molecules as potential biomarkers.
Aim: We investigated whether central serotonin transporters (5-HTT) are involved in mediating substantial weight reduction.
Method: Forty patients with obesity undergoing Roux-en-Y gastric bypass (RYGB) surgery (n = 13; 5 f; BMI 43 ± 4 kg/m2; age 52 ± 8 years) or diet program (n = 27, 21 f; 42 ± 4 kg/m2; 36 ± 10 years), as well as normal-weight (NW) controls (n = 13; 9 f; 24 ± 2 kg/m2; 38 ± 7 years) underwent dynamic PET after bolus injection of 484 ± 10 MBq and 485 ± 7 MBq [11C]DASB at baseline and at 6 months follow-up, respectively. Kinetic modeling (MRTM2) was applied to calculate 5-HTT binding potential (BPND) after co-registration of PET data with individual MRI. Thorough neuropsychological assessment includes Three-Factor Eating Questionnaire (TFEQ) to assess eating behaviour.
Results/Conclusions: BPND was not significantly different between the groups (NW 3.10 ± 0.7; diet 3.47 ± 0.9; RYGB 3.29 ± 1.22; p = 0.51; Figure 1(a)) at baseline. During follow-up, BMI was stable in NW (p = 0.97) while there was modest loss of BMI in the diet group (−1.2 ± 2.4 kg/m2; −3%; p = 0.01) and highly significant BMI reduction in RYGB patients (−10.4 ± 2.5 kg/m2; −24%; p < 0.001; Figure 1(b)). In RYGB, BPND at baseline and BMI reduction showed a significant positive correlation (p = 0.03; Figure 1(c)) while in the diet group a negative correlation between BPND and changes in BMI was observed (r = −0.38, p = 0.04). This was paralleled by a trend towards an association between BPND at baseline and changes in TFEQ (p = 0.08; Figure 1(d)) in RYGB but not in the diet group. These data suggest that 5-HTT was associated with substantial weight loss and changes in eating behaviour after RYGB. More data are needed to assess whether 5-HTT in the dorsal raphe nucleus is a good predictor of treatment success, supportive for treatment decision at an individual level, and on the modulatory function of 5-HTT in other areas of the brain associated with changes of body weight.
143
Numerical simulation study of nanoparticle delivery in cerebral microvessels before and after ischemia
P Chen1, B Dong2 and W Yao1
1Tongren Hospital, Shanghai Jiao Tong University School of Medicine
2School of Nuclear Science and Engineering, Shanghai JiaoTong University
Abstract
Background: At present, there is no effective drug for the treatment of tissue no-reflow phenomenon after stroke recanalization. Rapid advances in nanotechnology hold promise to provide new directions for treating no-reflow phenomenon after stroke. Hemodynamic changes of cerebral microvessels after reperfusion as well as different types of nanoparticles can affect particle flow and adhesion. Finding out the factors and laws that affect nanoparticle adhesion can help researchers design more rational nanoparticles for therapy or imaging.
Aim: To explore the more suitable design schema of nanoparticles for the diagnosis and treatment of no-reflow phenomenon through simulate the flow and adhesion of different nanoparticles in cerebral microvessels by computer.
Method: We first established normal and ischemia-reperfusion cerebral microvascular models. Then, flow and adhesion of different nanoparticles in two microvascular models were simulated by computational fluid particle dynamics. Nanoparticles of 5 different materials with 6 sizes are modified with ligands of different binding strengths to bind to receptors on the microvessel wall.
Results/Conclusions: The results showed that small-sized nanoparticles were more likely to adhere than large-sized nanoparticles in both normal and ischemia-reperfusion models (p < 0.0001). Lesion segment in the ischemia-reperfusion model were more likely to be adhered by large-diameter nanoparticles (p < 0.001). PLGA nanoparticles adhere the most in the normal model, while Fe3O4 nanoparticles adhere the most in the reperfusion model (p < 0.001). The molecular binding strength of the ligands modified on the nanoparticles and the receptors on the blood vessel wall can significantly affect the adhesion of nanoparticles.
156
Spectroscopy based liquid biopsies for traumatic brain injury triage
A Theakstone1, P Brennan2, M Jenkinson3 and M Baker4
1University of Strathclyde
2University of Edinburgh
3University of Liverpool
4Dxcover Limited
Abstract
Background: Computed Tomogram (CT) brain imaging is routinely used to support clinical decision-making in patients with traumatic brain injury (TBI). However, only 7% of scans demonstrate evidence of TBI. The other 93% of scans contribute a significant cost to the healthcare system and a radiation risk to patients.
Aim: There may be better strategies to identify which patients, particularly those with mild TBI, are at risk of deterioration and require hospital admission. This study introduces a blood serum liquid biopsy that utilises ATR-FTIR with machine learning algorithms as a decision-making tool to identify which mild TBI patients will most likely present with a positive CT scan.
Method: Serum samples were obtained from (n = 298) patients who had acquired a TBI and were enrolled in CENTER-TBI, and from asymptomatic control patients (n = 87). Injury patients (all severities) were stratified against non-injury controls. The mild TBI cohort was further examined by stratifying those who had at least one CT abnormality against those who had no CT abnormalities.
Results/Conclusions: The test performed exceptionally well in classifications of mild injury patients vs. non-injury controls (sensitivity = 96.4% and specificity = 98.0%) and also provided a sensitivity of 80.2% when stratifying mild patients with at least one CT abnormality against those without. The results provided illustrate the test ability to identify 4 out of every 5 CT abnormalities and shows great promise to be introduced as a triage tool for CT priority in mild TBI patients.
158
Longitudinal simultaneous cortex-wide Ca2+ imaging and whole-brain functional magnetic resonance imaging in awake mice
F Mandino1, X Shen1, D O’Connor2, B Mukherjee3, K DeLuca3, A Owens3, A Qu1, J Onofrey1,2,4, X Papademetris1,2, S Strittmatter3 and E Lake1
1Department of Radiology and Biomedical Imaging, Yale University School of Medicine
2Department of Biomedical Engineering, Yale University School of Medicine
3Cellular Neuroscience, Neurodegeneration and Repair Program, Departments of Neurology and Neuroscience, Yale School of Medicine
4Department of Urology, Yale School of Medicine
Abstract
Background: Anaesthetics alter brain activity, reduce the richness of functional data, and preclude the implementation of behavioural tasks, encouraging efforts to conduct experiments in awake animals. For these reasons, the last decade has seen a shift towards experiments in awake animals by the majority of optical imagers. However, awake murine fMRI acquisitions are still in their infancy – performed only by a relatively small number of ambitious labs.
Aim: We introduce the first longitudinal simultaneous fMRI and wide-field Ca2+ imaging protocol in awake mice.
Method: Animals are imaged 4 times (at 4–12 months of age) – twice under isoflurane, and twice while awake. Mice undergo two acclimation protocols, one before each awake session. In the first training (10-days), stressors (restraint, illumination, and MRI noise) are introduced gradually and incrementally. In the second ‘refresher’ training (4-days), all stressors are reintroduced at full intensity and duration.
Results/Conclusions: Following acclimation, we observe typical levels of motion in the first awake session. This is encouraging given the added stress of flashing light required for Ca2+ imaging. Following a 3-month break, and the ‘refresher’, we find a marked reduction in motion – comparable to anesthetized levels. This encourages at least two awake imaging sessions in future studies.
Ca2+ data show low motion in the X-Y plane during all sessions indicating that motion in fMRI data is likely restricted to Z or caused by B0 inhomogeneities (body movement). This finding will guide improvements to body restraint and B0 correction. However, we also find body suspension helps preserve head-plate integrity.
171
Microstrokes and capillary dilations – Investigating the effect of capillary alterations
F Schmid1,2, P Jenny1 and B Weber2
1Institute of Fluid Dynamics, ETH Zurich
2Institute of Pharmacology and Toxicology, University of Zurich
Abstract
Background: Capillaries are the most frequent microvascular vessel type and crucial for nutrient exchange. Moreover, there is an increasing body of evidence that capillaries play an important role for blood flow regulation and in pathologies. Nonetheless, our understanding of capillary perfusion characteristics remains limited.
Aim: To characterize the role of capillaries in health and disease, we quantify the relevance of capillary dilation for flow regulation and analyze the impact of microstrokes, i.e. capillary occlusions, on the flow field.
Method: We employ a bi-phasic blood flow model1 to simulate blood flow in realistic microvascular networks (MVNs). To study capillary dilation we compute the flow field in six MVNs for 64 dilation scenarios each. The impact of microstrokes is quantified on the basis of 167 microstroke simulations.2
Results/Conclusions: Microstrokes reduce perfusion in the proximity of the occluded capillary. The level of flow reduction depends on the local vascular topology. Therewith, the occlusion of one capillary bears potential to locally alter and impair blood supply. Dilating ∼18% of capillaries causes a flow increase comparable to dilating all descending arterioles. Thus, from a fluid-dynamical perspective descending arteriole and capillary vasodilations are able to up-regulate blood supply; if the number of responding vessels is sufficiently large.
Plasticity of perisynaptic astroglia during stroke-induced spreading depolarization revealed by quantitative serial section electron microscopy
S Kirov, J Sword and I Fomitcheva
Medical College of Georgia
Abstract
Background: High astrocytes capacity for glutamate and potassium clearance aids in recovering spreading depolarization (SD)-evoked disturbance of ion homeostasis during stroke. Astrocytes are tightly coupled with neurons, combining with axons and dendrites to form the tripartite synapse.
Aim: To investigate the impact of SD on the ultrastructure of a tripartite synapse.
Methods: SD was evoked by a transient bilateral common carotid artery occlusion in urethane-anesthetized mice. The DC potential and in vivo 2-photon, laser speckle, and intrinsic optical signal imaging were used to monitor onset and recovery from SD. Quantitative serial section electron microscopy was used to study astroglial processes at the axon-spine interface (ASI) during a single SD and recovery. Overall, 480 synapses were randomly selected and analyzed in 3D blind to the conditions (Sham, during SD and Recovery groups).
Results/Conclusions: Astroglial mitochondria were remarkably resilient to SD. Perisynaptic astroglial processes were present at the ASI during SD and after recovery. The percentage of large mushroom dendritic spines with perisynaptic astroglia has increased during recovery from SD. There was a greater decline in the docked vesicles number at bigger synapses corresponding with their larger capacity for neurotransmitter release. The length of the astroglial surround has significantly increased at mushroom spines during recovery. An increase in perisynaptic astroglial ensheathment at larger synapses suggests that as these synapses release more neurotransmitter during SD, they attract astroglial processes to a discrete portion of their perimeters, further enhancing astrocytic ability to protect fine synaptic circuitry in stroke.
Acknowledgments: Supported by NIH RO1NS083858 (SAK)
187
Non-invasive imaging of collateral blood supply characteristics by MR-based arterial spin labeling in cerebrovascular diseases
S Kaczmarz1,2,3, M Reichert1, M Hernandez Petzsche1, G Hoffmann1, J Göttler1,2, K Weiss3, C Preibisch1, J Kirschke1, C Zimmer1, K van de Ven4, M Obara5, H Liebl1, F Hyder2, N Sollmann1,6 and M Helle7
1School of Medicine, Department of Neuroradiology, Technical University of Munich (TUM)
2MRRC, Yale University
3Philips GmbH Market DACH
4Philips Healthcare
5Philips Japan
6Department of Radiology, University Ulm Medical Center
7Philips Research
Abstract
Background: Cerebrovascular diseases (CVD) are a main cause of death in developed countries.1 To improve diagnostics and support delicate treatment decisions, detection of collateral blood supply as an important protective vascular pathway showed great potential.2,3 However, the only clinically available method today is invasive x-ray- and catheter-based digital subtraction angiography (DSA).
Aim: To enable widespread imaging of blood supply patterns in CVD-patients, we propose two non-invasive MR-based arterial spin labeling (ASL) methods. First, super-selective ASL (ss-ASL)4 for individual perfusion territory mapping, second, 4D-sPack5 for time-resolved angiography, combined with an automated planning tool,6 each.
Method: 24 participants (10 young healthy participants and 14 CVD-patients) underwent MRI on a 3T Philips Achieva dStream or Ingenia Elition X. Selective labelling of both internal carotid arteries (ICA) took ∼5 minutes, each. In selected patients, conventional intracranial DSA and dynamic susceptibility contrast (DSC)-based time-to-peak (TTP) were also obtained.
Results/Conclusions: The automated planning tool was confirmed in the healthy cohort. In all CVD-patients, selective ASL depicted detailed collateralization status information. In a patient with moyamoya disease, ss-ASL showed collateral contralateral takeover (Figure 1(a)).7 Furthermore, time-resolved 4D-sPack depicted retrograde filling of the left media territory (Figure 1(b), circle), which explains regionally delayed perfusion in conventional TTP (Figure 4(c), circle). Comparisons of intracranial angiograms by 4D-sPack showed excellent spatial correspondence with DSA,8 capturing even small distal collateral vessels in the contralateral hemisphere (Figure 4(d), arrows). In conclusion, non-invasive selective ASL provides detailed collateralization status information and valuable additional diagnostic information by localized temporal blood supply characteristics.
Novel recovery mechanism of synaptic dysfunction following juvenile global cerebral ischemia via AMPAkine-induced BDNF expression
N Chalmers1, E Teimeier1, J Orfila2, P Herson2 and R Dietz1
1University of Colorado School of Medicine
2Wexner Medical Center The Ohio State University
Abstract
Background: Global cerebral ischemia (GCI) in the developing brain often leads to learning and memory deficits through school age. We recently demonstrated that ischemia-induced reduction in BDNF-TrkB signaling contributes to hippocampal dysfunction after juvenile GCI. AMPAkines are allosteric modulators of AMPA-receptors and some have been shown to augment BDNF expression.
Aim: We hypothesize AMPAkines which augment BDNF will reverse synaptic dysfunction following GCI.
Method: Juvenile mice (PND 20–25) were subjected to 8-minute cardiac arrest and resuscitated. Long-term potentiation (LTP), a cellular model for learning and memory, was measured in acute hippocampal CA1 slices following theta-burst stimulation (TBS: 40 pulses 100Hz). Increase in field excitatory post-synaptic potential slope 60 minutes after TBS was analyzed as a measurement of LTP (baseline 100%). BDNF expression was measured using ELISA from hippocampal tissue. Results reported as mean ± SD.
Results/Conclusion: BDNF expression is decreased at 14d after GCI compared to sham (n = 4, p < 0.05). Injection of AMPAkine LY404187 (1mg/kg) 14d after GCI reversed GCI-induced reduction of BDNF (n = 4, p < 0.05), whereas injection of another AMPAkine, IDRA-21 (1–5mg/kg) had no effect on post-GCI decreased BDNF expression (n = 4). Vehicle-treated slices revealed impaired LTP 14d after GCI. Ex vivo exposure to LY404187 (25 µM) results in recovery of LTP in paired experiments (sham:155 ± 13%; GCI/vehicle:112 ± 12%; GCI/LY404187:156 ± 13%, n = 4, p = 0.01). Similar paired experimental design found no recovery with exposure to IDRA-21 (vehicle:101 ± 13% vs IDRA-21:101 ± 13%, n = 3). The recovery of LY404187 was blocked by the TrkB antagonist ANA-12 (118 ± 19%, n = 3, p = 0.02) indicating that recovery is through BDNF-TrkB signaling. These data indicate that AMPAkine-induced BDNF increase rescues synaptic dysfunction of juvenile GCI.
206
Quantification of collateral blood crossflow by MRI-based vessel-selective imaging in asymptomatic carotid artery stenosis
G Hoffmann1,2, M Reichert1, J Göttler1, M Helle3, K van de Ven4, C Zimmer1,2, M Hernandez Petzsche1, H Liebl1,5, N Sollmann1,6, C Preibisch1,2 and S Kaczmarz1,2,7
1Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich
2TUM-Neuroimaging Center, Klinikum rechts der Isar, Technical University of Munich
3Philips Research
4Philips Healthcare
5Department of Radiology, Neuroradiology and Minimal-Invasive Therapy, Klinikum Bogenhausen
6Department of Diagnostic and Interventional Radiology, University Hospital Ulm
7Philips Healthcare
Abstract
Background: Internal-carotid-artery-stenosis (ICAS) is a frequent health issue and a major risk-factor for ischemic stroke.1 Evaluation of protective collateral blood-crossflow towards hypo-perfused regions has shown great potential to support treatment decisions.2 Compared to established catheter-based modalities for vessel-selective imaging, MRI-based super-selective arterial-spin-labelling (ssASL)3 is a promising non-invasive alternative.
Aim: We aimed to establish a quantitative, ssASL-based assessment of stenotic mal-perfusion and compensatory collateral blood supply in asymptomatic ICAS.
Method: Seven asymptomatic, unilateral ICAS patients (72.7 ± 6.3y, NASCET>70%) and four healthy controls (HC,70.0 ± 6.2y) underwent MRI on a 3T Philips Ingenia. Based on ssASL,3 individual perfusion territories were segmented and MNI-normalized. Cerebral blood flow (CBF) was measured using non-selective pseudo-continuous ASL. Alterations in the blood supply of the frontal circulation were evaluated by three parameters: overlap of individual territories with an atlas,4 grey-matter-CBF lateralization and shifts of territories into opposite hemispheres.
Results/Conclusions: Group-average territories show notable shifts of the contralateral anterior territory towards the ipsilateral hemisphere (Figure 1(a) and (b)) in contrast to HCs (Figure 1(c) and (d)). Statistical analysis of ICAS (Figure 1(e) to (g)) yielded both, a significantly larger overlap with the atlas and higher CBF for hemispheres contralateral to the stenosis (Figure 1(a) and (b)). A clear (non-significant) trend for shifts towards ipsilateral hemispheres was found (Figure 1(c)). For HCs, all parameters were symmetrical.
As hypothesized, our analyses indicate that asymptomatic ICAS induces collateral crossflow towards hypo-perfused territories of ipsilateral hemispheres, similar to symptomatic ICAS.5 This agrees with previously reported vulnerability of vascular borderzones.6 Based on the easily-applicable ssASL-Method, we introduced quantitative measures, which could improve diagnosis and understanding of collateral crossflow.
Changes in blood-cerebrospinal fluid barrier function in a chronic hypertension rat model measured with MRI
C Perera1, D Tolomeo1, Y Ohene2,3, M Lythgoe1, D Thomas4,5,6 and J Wells1
1UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London
2Division of Neuroscience and Experimental Psychology, University of Manchester
3Geoffrey Jefferson Brain Research Centre, University of Manchester
4Neuroradiological Academic Unit, Department of Brain Repair and Rehabilitation, UCL Queen Square Institute of Neurology
5Dementia Research Centre, UCL Queen Square Institute of Neurology
6Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London
Abstract
Background: Chronic hypertension is a risk factor for neurodegenerative diseases. Recent evidence reveals hypertension-induced alterations in brain fluid management in a spontaneous hypertensive rat (SHR) model, alongside neurodegenerative changes.1
Aim: We applied a novel, non-invasive Blood-Cerebrospinal Fluid Barrier Arterial Spin Labelling (BCSFB-ASL) MRI approach to investigate possible derangement of BCSFB function in the SHR model.
Method: BCSFB-ASL non-invasively measures rates of BCSFB-mediated arterial water delivery into ventricular CSF, as a surrogate marker of BCSFB function.2 Multi-TI standard-ASL, BCSFB-ASL data and anatomical images, were obtained in anaesthetized SHRs and Wistar Kyoto (WKY) normotensive controls (male, n = 6 in each group, age: 10 weeks) to extract BCSFB function, CBF, T1CSF, and ventricular volume.2–4
Results/Conclusions: Cortical CBF was significantly reduced in SHRs compared to WKY controls (145 vs 120ml/100g/min, p = 0.018, 2-tailed t-test) (Figure 1(a)). BCSFB-ASL measurements suggested a trend towards elevated BCSFB-mediated water delivery in SHRs, though non-significant (18.7 vs 10.6ml/min/100g (p = 0.16. Figure 1(b)).
Significant decreases in the T1CSF (SHR 3.5, WKY 4.2s, p = 0.002, Figure 1(c)) and ventricular volumes relative to WKYs (SHR 13, WKY 21ml, p = 0.008, Figure 1(d)) were consistent with changes in brain fluid management previously described in older SHR models displaying more profound pathophysiology.1
Here, we provide the first demonstration of BCSFB-ASL in the rat brain, enabling non-invasive assessment of BCSFB function in healthy and hypertensive rats. At this early stage, SHRs displayed decreases in CBF, T1CSF, and ventricular volume. Further work is underway to characterise changes in older subjects where more severe pathology may reveal changes in BCSFB function.
References
NaessensDMP, et al.
Altered brain fluid management in a rat model of arterial hypertension.Fluids Barriers CNS2020;
17: 1–13.a-15a-19EvansPG, et al.
Non-Invasive MRI of blood–cerebrospinal fluid barrier function.Nat Commun2020;
11: 1–11.a-16a-17BuxtonRB, et al.
A general kinetic model for quantitative perfusion imaging with arterial spin labeling.Magn Reson Med1998;
40: 383–396.PereraCHarrisonIFLythgoeMF, et al.
Pharmacological MRI with simultaneous measurement of cerebral perfusion and blood-cerebrospinal fluid barrier function using interleaved echo-time arterial spin labelling.Neuroimage2021;
238: 118270.a-18
219
Characterization of glial-restricted progenitors transduced with lentiviral vectors overexpressing neuregulin-1
P Rogujski1, A Graczyk-Jarzynka2, B Lukomska1 and L Stanaszek1
1NeuroRepair Department, Mossakowski Medical Research Institute, Polish Academy of Sciences
2Laboratory of Immunology, Mossakowski Medical Research Institute, Polish Academy of Sciences
Abstract
Background: Axonal demyelination due to dysfunction of glia is a pathological characteristic of different neurological diseases, thus the replacement of damaged glia is a compelling therapeutic approach. Glial restricted progenitors (GRPs) are promising candidates for transplantation therapy to treat or revert deficits in myelin sheaths. Previous studies revealed that mice GRPs (mGRPs) transplanted into shiverer mice (a mouse model of demyelination) have restricted migratory potential and limited myelinating capacity. Neuregulin-1 (Nrg-1) has been shown to play an essential role in the proliferation, migration and differentiation of GRPs. Therefore, overexpression of Nrg-1 in mGRPs may enhance their regenerative potential and thus comprise a potential treatment for demyelination disorders.
Aim: In this study, mGRPs transduced with lentiviral vectors overexpressing Nrg-1 (mGRPs-Nrg-1) were used to evaluate the effect of this genetic modification on GRP function in vitro.
Method: mGRPs were transduced with lentiviral vector encoding neuregulin-1, mCherry, and puromycin-resistance gene. Overexpression of Nrg-1 in transduced mGRPs was verified by qRT-PCR and Western-blotting techniques. The phenotypes of mGRPs-Nrg-1 were assessed using immunofluorescence staining and flow cytometry. The migratory potential of mGRPs-Nrg-1 was analysed using scratch assay, and their myelinating ability was studied in a co-culture of mGRPs-Nrg-1 with mice dorsal root ganglion neurons.
Results/Conclusions: The results of our studies showed that mGRPs-Nrg-1 retain native glial progenitors’ characteristic (Olig1+, Olig2+, O4+, GFAP+). We noticed that mGRPs-Nrg-1 displayed an enhanced proliferative potential in comparison to unmodified mGRPs. The analyses of migratory and myelinating potentials of mGRPs-Nrg-1 are in progress.
220
Evaluation of the α-synuclein PET radiotracer (d3)-[11C]MODAG-001 in pigs
N Raval1,2, C Madsen1,2, V Shalgunov3,4, A Nasser1, U Battisti3, E Beaman1, M Juhl5, L Jørgensen1,2,6, M Herth3,4, H Hansen1, P Plavén-Sigray1 and G Knudsen1,2
1Neurobiology Research Unit, Copenhagen University Hospital (Rigshospitalet)
2Faculty of Health and Medical Sciences, University of Copenhagen
3Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen
4Department of Clinical Physiology, Nuclear Medicine & PET, Copenhagen University Hospital (Rigshospitalet)
5Cardiology Stem Cell Centre, Copenhagen University Hospital (Rigshospitalet)
6Copenhagen Spine Research Unit, Copenhagen University Hospital (Rigshospitalet)
Abstract
Background: A PET radiotracer to neuroimage α-synuclein aggregates would be a crucial addition for early diagnosis and treatment development in disorders like Parkinson’s disease. (d3)-[11C]MODAG-001 has recently shown promise for visualization of α-synuclein pre-formed fibrils (α-PFF) in rodents.1
Aim: We aim to evaluate (d3)-[11C]MODAG-001 in pigs, where α-synuclein and control proteins are intracerebrally injected in the prefrontal cortex immediately before scanning.
Method: Four pigs were injected in one hemisphere with 150 µg α-PFF. In the other hemisphere, either 75 µg α-PFF or human brain homogenate from either dementia with Lewy bodies (DLB) or Alzheimer’s disease (AD) was injected. All pigs underwent one or two (d3)-[11C]MODAG-001 PET scans (injected dose: 322 ± 83MBq [6.1 ± 2 µg]) in an HRRT PET scanner. Quantification was performed with the non-invasive Logan graphical analysis using the occipital cortex as a reference region.
Results/Conclusions: The α-PFF and AD homogenate injected regions had high uptake of (d3)-[11C]MODAG-001 compared to the occipital cortex or cerebellum. BPND values in 150 µg α-PFF regions was 0.78, 75 µg α-PFF regions was 0.29, and in AD homogenate region was 0.73. By contrast, DLB homogenate injected region did not differ in uptake and clearance compared to the reference regions. The time-activity curves and BPND values in the 150 µg and 75 µg injected region of α-PFFs show a dose-dependent effect, blockable PET signal by pretreatment with unlabeled MODAG-001, and good test-retest variability.
Despite its limited specificity for cerebral α-synuclein pathology, (d3)-[11C]MODAG-001 shows promise as a lead molecule for future radiotracer development.
Reference
Kuebleret al. EJNMMI 2020.
229
Lateralized supraspinal reorganization during pain and motor dysfunction after rat hemicontusion cervical spinal cord injury
B Sanganahalli1, S Pavuluri2, J Chitturi2, P Herman1, S Elkabes3, R Heary4, F Hyder1 and S Kannurpatti2
1Department of Radiology and Biomedical Imaging, Yale University School of Medicine
2Department of Radiology, Rutgers Biomedical and Health Sciences-New Jersey Medical School
3Department of Neurosurgery, Rutgers Biomedical and Health Sciences-New Jersey Medical School
4Hackensack Meridian School of Medicine, Mountainside Medical Center
Abstract
Background: Afferent nociceptive activation after spinal cord injury (SCI) influences the function of supraspinal regions to establish pain. Clinical evidence indicates poor motor functional recovery in pain positive SCI patients, leading to the hypothesis that sensory-motor integration transforms into sensory-motor interference during pain. Hence, understanding sensorimotor reorganization in animal models of SCI, and cervical spine injury, is crucial for clinical translation to most SCI patients.
Aim: Here we investigate supraspinal sensorimotor changes after a left lateralized moderate hemicontusion cervical SCI in female rats (C4-C5 level, using a 150 kDyne force and a 2.5 mm impactor). To decipher the brain wide (SCI-induced) supraspinal pain modulatory effects, the sensory and motor network overlap was investigated across sham and injured groups.
Method: Functional Magnetic Resonance Imaging (fMRI) was performed at 8 weeks after SCI to determine brain resting state functional connectivity (RSFC).
Results: Animals displayed unilateral level pain and ipsilesional forelimb motor dysfunction which persisted at 6 weeks after SCI. Brain wide analysis using region-based RSFC across 14 regions of interest involved in pain-related activity in the current model, indicated lateral differences after SCI with a relatively weaker right-right connectivity compared to left-left. Enhanced RSFC after SCI was observed across the primary sensory (S1) and motor (M1/M2) networks with a larger enhancement observed from the right hemisphere ROI seed when compared to the left.
Conclusions: SCI significantly expanded the sensory and motor network overlap when compared to sham, supporting the hypothesis that “sensory and motor interference occurs during pain”.
239
Mesenchymal stromal cells attenuate post-stroke pneumonia by upregulation of macrophage LC3-associated phagocytosis
T Li and Z Lu
Department of Neurology, The Third Affiliated Hospital of Sun Yat-sen University
Abstract
Background: Post-stroke pneumonia, has a negative impact on the prognosis of stroke. However, strategies to prevent infection with antibiotics have not shown to improve outcomes in stroke patients. The potential mechanism of antibiotic adverse reactions is related to its effect on macrophages. Immunological fine-tuning of mesenchymal stem cells (MSCs) has been shown to improve clinical outcomes in infectious diseases. We thus hypothesized that MSCs transfer could improve the prognosis of patients with post-stroke pneumonia by modulating macrophage function.
Aim: We aimed to explore the therapeutic value of MSCs transplantation in the prevention and treatment of post-stroke pneumonia, and to clarify the specific mechanism of its immune regulation.
Method: C57/BL6 mice were treated with transient (1 hour) middle cerebral artery occlusion (tMCAO). MSCs were intravenously injected 1 hour after reperfusion, and the model animals were sacrificed 3 days later. The following indicators were assessed, including the ischemic stroke outcomes, pulmonary bacterial load, and inflammation levels. In addition, western blot, QRT-PCR, immunofluorescence and flow cytometry were performed on primary macrophages in vitro to investigate the specific effects and potential mechanisms of MSCs on their phagocytosis.
Results/Conclusions: We report that MSCs transfer protects against post-stroke pneumonia with beneficial stroke outcomes. Mechanically, MSCs release migrasomes that containing dermcidin (DCD) when encountering bacteria responsible for post-stroke pneumonia. DCD subsequently restricts bacteria growth and enhances LC3 associated phagocytosis (LAP) of macrophages, which facilitates bacteria clearance and digestion of the immunol scavengers. MSCs transfer may represent a potential strategy for post-stroke pneumonia.
242
Towards a normative model of dopamine neuroreceptor system using [11C]-(+)-PHNO PET imaging
A Giacomel1, R McCutcheon2, T Dahoun2, P Selvaggi1, D Martins1, O Howes2, F Turkheimer1, S Williams1, M De Groot3, O Dipasquale1 and M Veronese1,4
1Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King’s College London
2Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London
3Clinical Imaging, GlaxoSmithKline (GSK) R&D
4Department of Information Engineering, University of Padova
Abstract
Background: PET imaging provides a unique view on the neurobiological functioning of both healthy and diseased brains, but its use is mainly limited to group level applications. The standardization of PET data structure and archiving offers the possibility of pooling multi-centre multi-study data to build normative models of molecular imaging data for personalised applications.
Aim: To test the feasibility of normative models for PET neuroimaging of the dopamine receptor system.
Method: Binding potential (BPND) estimates obtained from 70 [11C]-(+)-PHNO PET healthy control scans (age = 25.65 ± 6.44 years, M/F = 40/30, BMI = 22.93 ± 2.69 kg/m2) from previous studies, acquired from two scanners, were used to estimate voxel-wise normative models.
Three competitive models (linear, quadratic and logarithmic), widely used in neuroimaging modelling, were estimated using age, sex, BMI and scanner type as covariates. In-sample coefficient of determination (R2), AIC and BIC scores were used as goodness-of-fit indexes.
Results/Conclusions: All models were able to explain a significant amount of BPND variance (R2>0.74) . Both linear and quadratic model performances (R2, AIC, BIC) follow the dopamine signal spatial distribution (the higher the signal the better the fit, Figure 1). The logarithmic model, instead, overfits the data considerably (R2≈0.99, Figure 1) leading to poor discrimination between signal and noise.
In conclusion, we showcase the feasibility of the creation of normative templates for [11C]-(+)-PHNO PET imaging using an approach that can be readily extrapolated to other tracers and could inform future precision medicine applications.
Figure 1. Spatial distribution of Radj2 scores of the estimated models. Last row indexes indicate slice coordinates in the y, x and z plane respectively.
243
CB2-receptor agonist LE-102 restricts lesion progression after transient MCAO – A randomized controlled preclinical trial
E Van Leeuwen1, A Meerwaldt1, C Van Heijningen1, L de Paus2, A van der Toorn1, W Mulder3, M van der Stelt2 and R Dijkhuizen1
1Umc Utrecht
2Leiden University
3Eindhoven University of Technology
Abstract
Background: The immune response after stroke is a major factor in stroke pathobiology and outcome,1 involving a bidirectional interaction between the brain and the immune system.2 A current challenge is to find therapies that support protective effects or alleviate detrimental consequences of the immune response. Activation of the cannabinoid receptor type 2 (CB2) is believed to trigger anti-inflammatory immune processes,3 which may limit progression of ischemic injury.
Aim: To determine if a new CB2 agonist LEI-102 improves ischemic tissue outcome after recanalization, through mitigation of the systemic and cerebral immunological response.
Method: C57BL/6 mice underwent 60-min MCAO and were randomly allocated to subsequent treatment with LEI-102 (10 mg/kg), vehicle (1mmol β-cyclodextrine) or saline (n = 3 × 14). Lesion progression was measured from MRI before and after treatment (blinded analysis). Blood, bone-marrow, spleen and brain tissue were analysed using flow cytometry.
Results/Conclusions: Pre-treatment diffusion MRI data showed no difference in lesion size between groups (p = 0.56). At day 3 post-treatment, mean lesion size on T2 maps was significantly smaller in the LEI-102-treated group as compared to vehicle or saline treatment (p < 0.05). A significant reduction in lesion size between pre- and post-treatment was also measured in LEI-102 treated animals (p < 0.05). Thus, CB2 targeting with LEI-102 offers as a potential strategy to reduce ischemia-reperfusion injury after stroke.
References
AnratherJ, et al. Neurotherapeutics2016; 13: 661–670.a-20IadecolaC, et al. Nat Med2011; 17: 796–808.a-21RomS, et al. Neuroimmune Pharmacol2013; 8: 608–620.a-22
264
Using PET/MRI to measure cerebrovascular reactivity in Moyamoya disease
M Zhao1, A Fan2, G Steinberg3 and G Zaharchuk1
1Department of Radiology, Stanford University
2Department of Biomedical Engineering
3Department of Neurosurgery, Stanford University
Abstract
Background: Cerebrovascular reactivity (CVR) reflects the change in CBF in response to vasodilation. Studies have demonstrated that impaired CVR was associated with a higher risk of stroke. 15O-water PET has been the gold standard for CBF and CVR measurements. But it is impractical in most hospitals due to the requirement of an on-site cyclotron. ASL is a quantitative MRI technique that enables non-invasive CBF and CVR mapping.
Aim: Compare CVR measured by single- and multi-delay ASL using PET as the reference.
Methods: Data were collected from 26 Moyamoya patients (18–64 years, 16 females) using a simultaneous 3T PET/MRI system. Imaging data were acquired using single- and multi-delay ASL and 15O-water PET simultaneously at baseline and 15 minutes after the injection of acetazolamide. Gd-based PWI was acquired at the end of each imaging session. CBF of PET was computed using the single-compartment pharmacokinetic model; CBF of ASL was computed using the general kinetic model. CVR was computed as the percentage of CBF change compared with baseline CBF. Paired t-tests were performed to compare the mean CVR between the affected and unaffected territories.
Results/Conclusions: The figure shows the hemodynamic maps of an example patient. Our quantitative analysis showed that the CVR of the affected regions was significantly lower than the normal regions (by 68%, 52%, and 56% for PET, single-PLD PCASL, and multi-PLD PCASL respectively). Both single and multi-delay ASL were effective in detecting impaired CVR in Moyamoya patients. Multi-delay can potentially replace Gd-based PWI in stroke imaging.
267
IL-17A contributes to the angiotensin II-induced neurovascular coupling impairment through oxidative stress
J Youwakim, D Vallerand and H Girouard
Université De Montréal
Abstract
Background: Hypertension, a multifactorial chronic inflammatory condition, is known as a risk factor for neurodegenerative diseases including stroke and Alzheimer’s disease. These neurodegenerative diseases have been associated with higher concentration of blood interleukin (IL)-17A. However, the role that IL-17A plays in the relationship between hypertension and neurodegenerative diseases remains misunderstood. Since cerebral vasculature is at the crossroads of the effects of hypertension on the brain, we hypothetized that hypertension alters cerebral blood flow regulation including neurovascular coupling (NVC) through IL-17A.
Aim: The objective of the present study is to examine the effects of IL-17A on NVC in the context of hypertension induced by angiotensin (Ang) II.
Method: Ang-II induced hypertensive mice were injected with a neutralizing anti-IL-17A antibody, an IL-17RA receptor antagonist or with an IgG isotype control. NVC was assessed by monitoring cerebral blood flow responses to whiskers stimulation by laser-Doppler flowmetry in anesthetized mice.
Results/Conclusions: Our results show that the neutralization of IL-17A or the specific inhibition of its receptor IL-17RA prevent the Ang II-induced NVC impairment. These treatments also reduce the Ang II-induced cerebral oxidative stress. Moreover, Tempol, a superoxide dismutase mimetic agent, and NADPH oxidase 2 depletion prevent NVC impairment and the increased superoxide anion production induced by chronic IL-17A recombinant administration. These findings suggest that IL-17A, through superoxide anion production, is an important mediator of cerebrovascular dysregulation induced by Ang II. Therefore, targeting this cytokine in hypertension is a promising approach to prevent cerebrovascular dysfunctions and neurodegenerative diseases.
280
First images from the next-generation UHR human brain PET scanner
R Lecomte1, L Arpin2, P Lauzier-Trépanier3, C Thibaudeau2, J Bouchard3, R Espagnet3, A Samson3, J Leroux4, R Fontaine3 and LabPET, GRAMS & IR&T Teams1,2,3
1Sherbrooke Molecular Imaging Center of CRCHUS and Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke
2IR&T Inc
3Interdisciplinary Institute for Technological Innovation – 3IT and Department of Electrical and Computer Engineering, Université de Sherbrooke
4Novalgo Inc
Abstract
Background: Little progress was made during the last decades to improve the spatial resolution of brain PET scanners, even though the achieved state-of-the-art is far worse than the theoretical limit.
Aim: Develop an ultra-high-resolution (UHR) PET imager based on the field-proven LabPET-II technology platform for human brain imaging at the physical resolution limit.
Method: The UHR scanner relies on truly pixelated detectors featuring 1:1:1 coupling of scintillator, photodetector, and electronic readout to reach ∼1.2 mm resolution when imaging the human brain. The basic detector elements consist of 4 × 8 LYSO arrays of 1.12 × 1.12 × 12 mm3 read out by monolithic 4 × 8 APD arrays, assembled into 128-channel modules with a 2.5D architecture for thermal management and parallel signal processing by custom integrated circuits. The UHR scanner consists of 144 rings of 896 pixels (129,024 detectors) forming a 40-cm diameter by 23.5-cm long cylinder. The useful FOV is up to 30-cm diameter. Single events, along with physiological and motion data, are transferred via Ethernet links to the acquisition computer where a software coincidence engine merges and sorts out list-mode events in real-time for quantitative image reconstruction implementing motion correction.
Results/Conclusions: GATE simulations of the histology based BigBrain atlas demonstrate the ability to resolve FDG radiotracer distribution in cortical or basal brain structures, enabling potential differentiation of details in the entorhinal cortex and locus coeruleus, suspected to be involved in the onset of Alzheimer’s disease. Initial images were obtained using a partial prototype, demonstrating promising results towards microliter volumetric resolution for imaging the human brain.
304
Ketogenic interventions for the aging brain
B Eap, M Nomura, T Garcia and J Newman
Buck Institute for Research on Aging
Abstract
Background: A decline in energy metabolism is central to many age-related diseases. Ketogenic interventions including ketogenic diet, ketone esters, and other exogenous ketones are increasingly being tested in clinical trials for aging-related conditions such as heart failure and dementia. Aging is associated with glucose intolerance and insulin insensitivity, yet what role ketone body metabolism might play in compensating for impaired glucose utilization, especially in the brain of age-related diseases is understudied. In particular, little is known about how the endogenous ketogenic system or its response to interventions is affected by age, or between sexes.
Aim: We aim to understand the age-related changes in the body’s endogenous ketone body production and utilization to help explain the compensatory mechanisms that BHB might play in brain aging.
Method: Aging female and male mice (3 mo., 12 mo., 22 mo.) were fed control, ketogenic diet or a novel ketone ester, bis hexanoyl (R)-1,3-butanediol (BH-BD) to assess age-related changes in ketone body metabolism. Using liquid chromatography-mass spectrometry, we quantified brain BHB levels and looked at brain energetic gene expressions.
Results/Conclusions: We found that brain BHB levels were diet-dependent and observed age and sex-related changes across diets. Lower amounts in control-fed mice were augmented with either ketogenic diet or ketone ester diet, more robustly in male and aged mice. Raising plasma BHB levels and consequently brain BHB levels could help compensate the age-related declines in aerobic glycolysis observed in Alzheimer’s disease and traumatic brain injury.
313
Working memory task performance and synaptic density in aged nonhuman primates
X Fang, G Williams, S Castner, T Toyonaga, Z Felchner, S Najafzadeh, J Ropchan, Y Huang, A Arnsten, T Horvath and R Carson
Yale University
Abstract
Background: Nonhuman primates (NHP) exhibit age-related cognitive impairments associated with progressive loss of function in critical neural circuitry. The dorsolateral prefrontal cortex (dlPFC) plays an important role in integrating sensory information and performing goal-oriented behaviour, evidenced by lesion studies causing worsened working memory (WM) performance and executive function. Post-mortem studies indicate synapse loss in hippocampus and dlPFC.
Aim: To investigate synaptic density in vivo with [11C]UCB-J PET in brain regions related to WM performance in aged NHPs.
Method: NHPs (20.6 ± 2.5y.o., n = 15) were scanned with the SV2A PET tracer [11C]UCB-J. The outcome measure was distribution volume ratio (DVR; cerebellum reference). NHPs were tested with the spatial-delayed response task to assess WM performance, with outcome measures of time delay and number of wells.
Results/Conclusions: A significant positive correlation between DVR and time delay in dlPFC (r = 0.74, p = 0.004) and parietal association cortex (r = 0.66, p = 0.010) were observed, surviving FDR multiple comparison correction. In an exploratory manner, we found a significant relationship between DVR and time delay in hippocampus, caudate, putamen, thalamus, cingulate, insular, and temporal cortices. The relationship between DVR and number of wells was significant in dlPFC, parietal association cortex, putamen, thalamus, and insular cortex.
This is the first in vivo study assessing synaptic density and its relationship to WM performance. There is a relationship between regional synaptic density and WM performance in dlPFC and parietal association cortex, with other brain regions possibly involved. These PET findings are in line with post-mortem studies showing synapse loss in dlPFC but no neuron loss.
322
BOLD-based hemodynamic features inferred from dynamic causal modeling relate to subject’s age range
G Baron1, D Benozzo1, E Gindullina1, E Silvestri1, A Chiuso1 and A Bertoldo1,2
1Department of Information Engineering, University of Padova
2Padova Neuroscience Center
Abstract
Background: Age-related changes in the BOLD response could reflect alterations at the neuro-vascular coupling level rather than simply changes in neural functioning. In this view, a full understanding of the Hemodynamic Response Function (HRF) differences in healthy aging and their implications in the study of brain function is still lacking.
Aim: The aim of this work was to investigate significant age-related changes in HRF between 78 younger (20–30 years) and 31 older (60–80 years) healthy subjects by assessing if age-dependent categories could be predicted through the combination of HRF-derived parameters.
Method: For each subject and each region of interest (ROI) the HRF was robustly extracted from rs-fMRI by means of a novel method for estimating whole-brain effective connectivity (sparse DCM1). Relevant parameters were then computed on each curve, as depicted in the figure.2 Then, a logistic regression model was fitted including the predictors that were retained both by a first-stage univariable selection (two-sample t-test with Holm-Bonferroni correction) and a second-stage cross-validated stepwise selection.
Results/Conclusions: The final model suited both training (R2Cox&Snell = 0.81) and test (AUC = 0.81) data. The most significant predictors were located in visual and somatomotor areas (as observed in2), as in some dorsal attention/control network ROIs that have been associated with worse cognitive performances in elders.3
These Results suggest that the impact of age on the vascular component should be regarded as a possible bias when conducting studies on the aging brain function.
Tacr1 neurons mediate slow vascular oscillations that may underlie glymphatic function
F Juarez Anaya, C Ruff, A Rakymzhan, S Ross and A Vazquez
University of Pittsburgh
Abstract
Background: The glymphatic system is thought to be mediated by slow vascular oscillations that drive the metabolic waste clearance in the brain, which is particularly prominent during slow wave sleep (SWS). Slow rhythms of neural activity have been linked to these slow vascular oscillations, but which neurons are involved remains unknown.
Aim: Here, we tested the involvement of Tacr1 neurons in producing local slow vascular oscillations that are observed during SWS.
Method: We used a combination of approaches including FISH, CUBIC-based whole tissue clearing, neuronal tracing, optogenetic manipulation of Tacr1 neurons expressing Channelrhodopsin2 (ChR2) and in vivo two-photon (2P) calcium imaging of Tacr1 neurons expressing GCaMP6f to investigate the function of Tacr1CreER neurons.
Results/Conclusions: We show that Tacr1 neurons are a unique population of GABAergic neurons that co-express, somatostatin, nitric oxide synthase 1, and chondrolectin. Tacr1 neurons have distinct morphology with extensive local dendrites and long-range axons. Through in vivo 2P calcium imaging, we provide evidence that the correlation between Tacr1 neuronal activity and local vasculature is stronger during SWS. Finally, prolonged activation of Tacr1 neurons produces local vascular oscillations that are similar to those observed during SWS (Figure 1). Together, these findings raise the possibility that Tacr1 neurons regulate slow vascular oscillations that underlie the metabolic waste clearance through the glymphatic system. This vascular regulation could be through the release of nitric oxide, a potent vasodilator.
341
Development of a multiscale model of molecular transport in the brain microcirculation
D Pastor Alonso1, Y Davit1, F Boyer2, M Quintard1 and S Lorthois1
1Institut de Mécanique des Fluides de Toulouse (IMFT), UMR 5502, CNRS, University of Toulouse
2Institute de Mathématiques de Toulouse (IMT), CNRS and Université de Toulouse
Abstract
Background: Modelling molecular transport in the brain is a great challenge due to the complex microvascular architecture and the disparity between the volume occupied by the microcirculation and that of the brain parenchyma [PMID:26443811, 18958033].
Aim: Our goal lies in the development of an accurate description of molecular transport and blood/tissue exchange in large volumes of brain tissue. We focus on the accurate modelling of the concentration gradients in the brain parenchyma, as they drive molecular diffusion from vasculature to the parenchyma and vice versa.
Method: A coupling model is designed where the vascular system is simplified and represented as sources (or sinks) of mass in the parenchyma (Figure 1(a) and (b)). In order to make the coupled system approachable for large volumes, we focus on the influence of each source/sink on its vicinity. This influence is modelled through known analytical functions which strongly simplify the numerical resolution and allow for a coarse cartesian mesh of the volume (Figure 1(c)).
Results/Conclusions: The application of this coupling model in a 2D test case shows that the proposed numerical resolution enables a large reduction in the quantity of unknowns without a large loss in accuracy (Figure 1(d) to (f)), when compared to standard numerical Methods. When extended to 3D, this approach may allow the modelling of transport in large volumes of tissue through the coupling to a 1D effective equation for intravascular transport [M. Berg et al., JFM, 2019].
359
Smooth muscle cells play a role in cerebrovascular pathologies and gait defects in IGF-1 deficiency
S Conley1, L Miller1, M Bickel1, Z Matacchiera1, T Martin1, S Tarantini2, A Yabluchanskiy2, A Csiszar2,3 and Z Ungvari2,3
1University of Oklahoma Health Sciences Center, Department of Cell Biology
2Vascular Cognitive Impairment and Neurodegeneration Program, Oklahoma Center for Geroscience and Healthy Brain Aging, Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center
3International Training Program in Geroscience, Doctoral School of Basic and Translational Medicine/Department of Public Health, Semmelweis University
Abstract
Background: Vascular pathologies are a key contributor to cognitive decline and gait defects in the elderly. Hypertension and age are two main risk factors for vascular defects such as cerebral microhaemorrhages (CMH) and impaired myogenic autoregulation. Levels of circulating insulin-like growth factor 1 (IGF-1) decrease with age in humans and animal models, contributing to vascular pathologies. However, the cellular mechanisms that lead to IGF-1-associated cerebrovascular fragility are not well understood.
Aim: Vascular smooth muscle cells (VSMCs) are critical for maintaining vascular integrity regulating blood flow and vascular tone. We hypothesize that reduced IGF-1 signalling on VSMCs will promote vascular instability and impair protective vascular responses to hypertension, contributing to cognitive decline and gait defects.
Method: We induced hypertension in mice with adult-onset VSMC-specific IGF-1 receptor deficiency (Myh11-CreERT2-Igf1rf/f ROSA26 tdTomatof/f). Subsequently we evaluated the occurrence of CMH, measured cerebral blood flow in response to increasing systemic blood pressure using laser speckle imaging and assessed behaviour and motor coordination using radial arm water maze and rotarod tests.
Results/Conclusions: We have found that VSMC-specific Igf1r deficiency exacerbates the development of hypertension-induced CMH and results in reduced autoregulatory capacity of the cerebral vasculature. Additionally, we observed that VSMC-specific Igf1r deficient mice have impaired spatial learning and motor coordination. These studies suggest that VSMCs play a critical role in the vasoprotective effects of IGF-1 in the cerebral vasculature and that alterations in VSMC function may contribute to age-related cognitive decline in the context of Vascular Cognitive Impairment and Dementia.
362
First in vivo brain kinetic modelling study with a selective radiotracer targeting sphingosine-1-phosphate-5 (S1P5) receptors
R Shaw1,2, T Morgan1,2, C Alcaide-Corral1,2, S Pimlott3, C Lucatelli2, A Sutherland4 and A Tavares1,2
1The University of Edinburgh
2Edinburgh Imaging
3NHS Greater Glasgow and Clyde
4School of Chemistry
Abstract
Background: Multiple sclerosis (MS) leads to a breakdown of the myelin sheath, produced by oligodendrocytes. Currently, there is no way to directly image oligodendrocytes’ activity in vivo. Positron Emission Tomography (PET) imaging with a radiotracer specific to oligodendrocytes could address this research gap.
Aim: Develop, image and model PET scans with a brain penetrant, selective PET radiotracer for the sphingosine-1-phosphate-5 (S1P5) receptor on oligodendrocytes; as a biomarker of oligodendrocyte activity in vivo.
Method: Adult male rats underwent PET imaging over 2 hours post-administration of [18F]TEFM78, a novel and selective radiotracer targeting S1P5 receptors in the brain. Invasive arterial input functions were obtained, radiometabolite and plasma free fraction analyses were conducted. PET images were normalised to the Schiffer-T2 rat brain template.(1) Kinetic modelling analysis of different brain regions was conducted, 1-Tissue, 2-Tissue and Logan models were tested to determine which would be the most appropriate for quantification of [18F]TEFM78 distribution kinetics in the rat brain.
Results/Conclusions: [18F]TEFM78 rapidly clears from the blood (Figure 1(a)) and enters the rat brain (Figure 1(b)). There was moderate metabolism of [18F]TEFM78 in blood (Figure 1(c) and no radiometabolites were observed in the brain tissue. The 1-Tissue model was the best Method for analysing [18F]TEFM78 kinetics in the rat brain (Figure 1(d)). Data supports the use of [18F]TEFM78 as a promising selective S1P5 radiotracer with reversible binding to the target and appropriate metabolic profile.
Reference
SchifferWKMirrioneMMBiegonA, et al.
Serial microPET measures of the metabolic reaction to a microdialysis probe implant. J Neurosci Methods2006;
155: 272–284.a-23
363
The addition of drag reducing polymers to resuscitation fluids provide neuroprotective properties in brain injury
D Bragin1,2, O Bragina2, M Kameneva3, E Nemoto1 and A Divani1
1University of New Mexico
2Lovelace Biomedical Research Institute
3University of Pittsburgh
Abstract
Background: Hemorrhagic shock (HS) during traumatic brain injury (TBI) reduces microvascular cerebral blood flow (mvCBF), leading to microthrombosis and hypoxia. Resuscitation fluids (RF) do not alleviate impaired mvCBF. We hypothesized that drag-reducing polymers (DRPs) would improve mvCBF. We evaluated the efficacy of DRP additive to Ringers, Hetastarch, or Hypertonic Saline (RF+DRP) in improving mvCBF, tissue oxygenation, and outcomes after TBI+HS.
Methods: Fluid-percussion TBI was induced in rats, followed by HS to obtain a mean arterial pressure (MAP) of 40 mmHg. RF or RF+DRP was infused to MAP = 60 mmHg, followed by blood reinfusion to MAP = 70 mmHg. mvCFB, NADH (hypoxia), and oxidative stress were monitored by 2-photon microscopy 4 hours after TB+HS, followed by MRI and Dil-vascular painting. Neurologic outcomes were evaluated. Differences between six treated TBI+HS groups (three RF-only vs. three RF+DRP) were determined using two-way ANOVA for multiple comparisons and post hoc testing using the Mann-Whitney U-test.
Results: RF+DRP reduced microthrombosis and improved mvCBF (82 ± 9.7% vs. 62 ± 9.7%, RF+DRP vs. RF, p < 0.05). RF+DRP decreased tissue hypoxia (77 ± 8.2% vs. 60 ± 10.5%, RF+DRP vs. RF, respectively, p < 0.05), and neuronal necrosis (21 ± 7.2% vs. 36 ± 7.3%, respectively, p < 0.05). Reperfusion-induced oxidative stress (HEt fluorescence) was lower in RF+DRP vs. RF groups (32 ± 6% vs. 28 ± 5%, respectively, p < 0.05). MRI revealed CBF improvement and reduced lesion volumes in the RF+DRP group. Whole-brain visualization revealed multiple microthrombosis, which was ∼30% less in RF+DRP than RF groups (p < 0.05). Neurological outcomes were significantly improved in RF+DRP vs. RF groups (P < 0.05).
Conclusions: Resuscitation fluids with added DRP provide neuroprotective in TBI+HS.
Supported by: DOD DM160142, W81XWH-17-2-0053.
373
Perfusion imaging: A biomarker for treatment response in Alzheimer’s disease?
P Moyaert1,2, U Anazodo2,3, E Achten1, S Beun1 and P Clement1
1Department of Medical Imaging, Ghent University Hospital
2Lawson Health Research Institute
3Research Centre for Studies in Aging, McGill University
Abstract
Background: Alzheimer’s disease patients spend on average 4.1 years of their time in nursing homes, putting an enormous economic burden on a healthcare system. This can be reduced by 3–8 months, using acetylcholinesterase inhibitors (AchE-Is). However, only 40% of patients are responsive, highlighting the importance of treatment evaluation1. Currently, treatment responsiveness is often evaluated using cognitive tests, which lack sufficient sensitivity to detect the subtle effects of dementia therapy.
Aim: To support the evidence for the role of perfusion imaging in treatment evaluation
Method: This systematic review was registered on PROSPERO (CRD42020158625) and completed following the PRISMA guidelines. Based on predefined inclusion criteria, all relevant literature was selected. The risk of bias was assessed using the Cochrane risk-of-bias tool.
Results/Conclusions: A total of 40 studies were included. 67.6% of all included studies reported a significant perfusion increase in the frontal, 41.2% in the temporal, 23.5% in the parietal and 30% in the occipital lobe after long-term AchE-I use. Additionally, 20% reported an increase in the cingulate gyrus. In comparison, in non-treated patients, a widespread pathology-related perfusion decrease was observed. For clinical responders (MMSE increase of ≥1) a significantly higher global perfusion was found compared to non-responders (Table 1). Also, perfusion changes appear to be related to AchE-I dosage, but not to the type of AchE-I.
This review demonstrates that an increase in perfusion after AchE-I intake correlates with improved cognition as shown by MMSE. Early assessment of responsiveness may allow treatment optimization, thus delaying institutionalization and associated costs.
A. Summary of significant (p < 0.05) regional cerebral perfusion changes after long-term acetylcholinesterase-inhibitor treatment in patients with dementia. B. Summary of significant (p < 0.05) regional cerebral perfusion changes in cognitive (non-)responders after acetylcholinesterase-inhibitor treatment in patients with Alzheimer’s disease.
A
Treatment response
Author
D
Drug
Disease
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
ACC
PCC
Chaudhary (2012)
6
G
AD
↑
↑
Cho (2009)
4
G
AD
↑
↑
↑
Shimizu (2015)
12
G
AD
↑
↓
↑
↓
↓
Shirayama (2019)
18
G
AD
↑
↓
↑
↑
Litvinenko (2007)
6
G
AD
↑
↑
↑
Chaudhary (2012)
6
R
AD
↑
↑
Shimizu (2015)
12
R
AD
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↓
↑
↑
↑
Compagnone (2018)
6
R
LBD
↓**
Ettorre (2015)
12
R
AD
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↑
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Lojkowska (2003)
12
R
AD
↑
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Lojkowska (2003)
8
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VAD
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↑
Cerci (2007)
15
R
AD
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Ceravolo (2004)
24
R
AD
↑**
↑**
↑**
↑**
Antuono (2009)
14
D
AD
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Ceravolo (2006)
8
D
PDD
↑***
↑***
↑***
Ceravolo (2004)
24
D
AD
↑**
↑**
↑**
↑**
Chaudhary (2013)
25
D
AD
↑
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Cho (2010)
7
D
AD
↑
↑
↑
Fong (2011)
4
D
DLB
↑
↑
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↑
Fong (2011)
16
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Kanaya (2012)
24
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Li (2012)
14
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Mori (2006)
12
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Nakano (2011)
12
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Niwa (2006)
12
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13
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12
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14
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18
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Tateno (2008)
13
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AD
↑*
Ushijima (2006)
3
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Ushijima (2006)
12
D
AD
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Warren (1998)
4
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↓
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Yener (2005)
-
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Yoshida (2010)
6
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B
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6
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Iizuka (2007)
6
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12
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12
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14
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6
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6
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6
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Arrow up: significant perfusion increase compared to baseline; Arrow down: significant perfusion decrease compared to baseline (p<0.05); no arrow: no significant change compared to baseline. * p < 0.01 ** p < 0.001
WattmoCLondosEMinthonL.
Short-term response to cholinesterase inhibitors in Alzheimer’s disease delays time to nursing home placement.Curr Alzheimer Res2018;
15: 905–916.
375
Progressive endothelial S1PR1 disruption and BBB dysfunction in cerebral microvasculature induced by chronic hypoxic hypoperfusion
Y Yang, J Thompson, K Duval, S Hobson, K SantaCruz and M Griego
University of New Mexico
Abstract
Background: Clinical and neuroimaging studies suggested a fundamental role of BBB leakage in the progressive development of cerebral small vessel disease (SVD) pathology. The capillary barrier and survival are regulated by sphingosine-1-phoshate (S1P) and its receptor isoforms (S1PRs). Disruption of endothelial S1P signalling leads to capillary dysfunction, BBB breakdown, and perivascular inflammation.
Aim: To test the hypothesis that chronic hypoxic hypoperfusion down-regulates capillary endothelial S1P receptor 1 (S1PR1), compromising BBB integrity and leading to neuroinflammation, using a rat model of SVD.
Method: Spontaneously hypertensive stroke-prone rats underwent unilateral carotid artery occlusion (UCAO) followed by a Japanese permissive diet (JPD) for up to 9 weeks. Selective S1PR1 agonist SEW2871 was used to activate S1PR1. MRI, Western blot, and histology were used for measurements.
Results/Conclusions: Significant reduction of endothelial S1PR1 was detected at 4 and 9 weeks following UCAO/JPD onset. The endothelial S1PR1 reduction was also seen in human SVD brains. We also found that significant accumulation of pTau in cortex neurons at 9 weeks, when the rats developed extensive inflammation. The timeline of the accumulation of pTau is consistent with significant reduction of S1PR1 seen at 9 weeks. S1PR1 activation by SEW2781 treatment reduced white matter lesions, preserved cerebral blood flow, and significantly reversed the loss of endothelial tight junction proteins induced by the UCAO/JPD. This protective role of the SEW2871 are associated with changes in PI3K/Akt/Rac signalling pathway. Our data suggest that hypoxic hypoperfusion triggers disruption of S1P-S1PR1 signalling, leading to endothelial injury and BBB dysfunction in SVD.
384
Can resveratrol supplementation increase neurovascular coupling capacity in menstrual migraineurs? A pilot study
M Litman1, P Howe1,2,3, R Wong3 and K Coupland1,4
1School of Biomedical Sciences and Pharmacy, University of Newcastle
2Adelaide Medical School, University of Adelaide
3Centre for Health Research, University of Southern Queensland
4Hunter Medical Research Institute
Abstract
Background: Our previous research has shown that menstrual migraineurs have lower neurovascular coupling capacity (NCC) during cognitive tasks than women without migraine. Resveratrol, a vasoactive phytoestrogen, has been shown to improve NCC in various populations including postmenopausal women but has never been tested in menstrual migraineurs.
Aim: To investigate whether resveratrol supplementation can increase NCC in menstrual migraineurs.
Method: A double-blind, placebo-controlled, crossover trial was conducted in 62 menstrual migraineurs who were randomised to resveratrol (150mg/d) or placebo for 3 months then took the alternate treatment for a further 3 months. Ten participants who were able to visit our research centre for testing completed the following cognitive tasks (n-back task, Stroop task and a 7-minute multitasking cognitive test battery) at months 0, 3 and 6 whilst blood flow velocity (BFV) was recorded in their left and right middle cerebral arteries (MCA) using transcranial Doppler ultrasound. The NCC for each cognitive task was calculated as (peak BFV during the cognitive task – resting BFV)/resting BFV and then averaged to form a composite NCC value.
Results/Conclusions: Compared to placebo, resveratrol supplementation did not alter the composite NCC. However, it tended to enhance NCC measured in the left MCA during the multitasking cognitive test battery (P = 0.060). Due to the small sample size, further studies are needed to confirm any effect of resveratrol on NCC in menstrual migraineurs.
391
Involvement of endothelial nitric oxide synthase in cerebral microcirculation and oxygenation in traumatic brain injury
D Atochin1, P Huang1, O Bragina2 and D Bragin2,3,4
1Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, USA
2Lovelace Biomedical Research Institute
3Department of Neurology, University of New Mexico School of Medicine
4National Research Saratov State University
Abstract
Background: We assessed the involvement of endothelial nitric oxide synthase (eNOS) in cerebral microvascular changes after traumatic brain injury (TBI) in eNOS-knockout (eNOS-KO) and wild-type (WT) mice (8/group).
Methods: Cerebral microvascular tone, blood flow (CBF) and tissue oxygenation (NADH) were measured by two-photon microscopy (2PLSM) before, 1 hour, 1 and 3 days after TBI. Cerebrovascular reactivity (CVR) was evaluated by the hypercapnia test (60sec/10%). Laser Doppler cortical flux (cLDF) was measured in the peri-contusion area.
Results: One hour after TBI, cLDF decreased ∼60% from the baseline in both groups (p < 0.05). In the peri-lesion cortex, 2PLSM showed decreased arteriolar diameter, the number of functioning capillaries, wherein CBF and tissue oxygenation were similar in both groups (p < 0.05 from baseline). One day after TBI, cLDF increased to 65.2 ± 6.4% in the WT while decreasing to 56.1 ± 7.2% in the eNOS-KO. 2PLSM revealed a further decrease in all monitored variables, which was milder in WT (p < 0.05 from the baseline). Three days after TBI, cLDF increased to 72 ± 5.2% in the WT but not in the eNOS-KO (55.9 ± 6.4%, p < 0.05 from WT). 2PLSM showed a reduction in arterioles with vasospasm, increase in the number of functioning capillaries, improvement in CBF, and tissue oxygenation in WT while no changes in eNOS-KO (p < 0.05 from WT). Hypercapnia test demonstrated that CVR was impaired in both groups one hour after TBI and improved by the third day in the WT while remaining impaired in eNOS-KO. Conclusion: We demonstrated that the significance of eNOS in maintaining cerebral microcirculation increases with time after TBI.
392
Circadian rhythm-induced changes in the cerebral microvascular blood flow in awake mice
B Li
Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences
Abstract
Previously, we have shown that the efficacy of neuroprotective treatment in ischemic stroke is circadian rhythm-dependent. However, the influence of circadian rhythms on the cortical microcirculation is still not well-understood. In this work, we applied 2-photon microscopy to investigate the circadian-rhythm-associated changes in the microvascular blood flow and oxygenation in the cerebral cortex, focusing on the middle-cerebral-artery (MCA) and the adjacent watershed territories in the awake, head-restrained C57BL/6 mice, through a sealed chronic cranial window. Our Results indicate that the resting-state capillary red-blood-cell (RBC) flux and blood flow in the surfacing venules are significantly higher during the active phase (e.g., during the day) than during the inactive phase (e.g., during the night). Interestingly, the amplitudes of the circadian rhythm-related changes in the capillary RBC flux and the venular blood flow are significantly larger in the watershed region than in the adjacent MCA territory. Our results suggest that the circadian rhythm has an effects on the resting-state cerebral blood flow and oxygenation, and that this effect is greater in the more vulnerable watershed region. These results may help us better understand the cerebral blood flow regulation at different times of the day and improve planning of neuroprotective treatment for ischemic stroke.
398
Gut microbes associated with decreased cerebral blood flow in adult brains with cardiovascular risk factors
T Hammond1, L Sawaki1 and A Lin2
1University of Kentucky
2University of Missouri
Abstract
Background: A primary mechanism by which the gut microbiome interfaces with the brain is through the production of metabolites that enter the brain via the bloodstream. These gut-derived brain metabolites can impact cerebral blood flow (CBF) through short chain fatty acid production and blood brain barrier permeability
Aim: To measure the association of gut microbes and CBF in community dwelling adults.
Method: We recruited 30 participants age 55–85 with cardiovascular risk factors. We measured the gut microbiome using stool samples and CBF using MRI Arterial Spin Labeling and used linear regression methods to identify gut microbial levels associations with cerebral blood flow. We corrected for multiple comparisons using a false discovery rate q < 0.25.
Results/Conclusions: Table 1 shows associations of gut microbiota and CBF in various brain regions. Increased levels of Alistipes, were associated with lower CBF in the insula and subcortical structures involved in sensorimotor integration, motivation, addiction, and emotion. Increased levels of Asaccharobacter celatus were associated with lower CBF in regions of the unimodal and multimodal association cortex involved in language processing. Increased levels of Gordonibacter pamelaeae were associated with lower CBF in regions involved with the dorsal attention network (a top-down control of visual attention and eye movement). Increased levels of Proteobacteria were associated with lower CBF in frontal cortex regions involved in executive function and emotional regulation. Future studies should be conducted to further explore the relationship of these microbes with CBF to see whether their manipulation can optimize brain health.
Associations of gut microbiota and CBF in various brain regions.
Bacteria name
Function of bacteria in the gut
Correlated CBF region
β- coefficient
FDR
Alistipes
Present in chronic Inflammation
Putamen
−0.556
0.0005
Insula
−0.418
0.0169
Accumbens
−0.484
0.0221
Asaccharobacter celatus
Produces equol, a nonsteroidal estrogen
Banks of the superior temporal sulcus
−0.538
0.0238
Middle temporal gyrus
−0.583
0.0621
Pars triangularis
−0.509
0.1251
Pars opercularis
−0.626
0.0367
Gordonibacter pamelaeae
Produces urolithin, an anti-inflammatory metabolite
Pars triangularis
−0.517
0.1247
Posterior cingulate gyrus
−0.615
0.1089
Proteobacteria
Marker of imbalance in gut microbes
Medial orbitofrontal cortex
−0.291
0.1951
Rostral Middle Frontal Cortex
−0.302
0.0329
403
Biomarkers of cerebral microcirculation in posttraumatic cerebral ischemia
A Trofimov1,2, D Agarkova2, A Dubrovin2, K Trofimova1, O Novosadova1, D Martynov3, K Kyrill Lidji-Goryaev1, E Nemoto4, D Bragin4,5,6 and D Atochin7
1Department of Neurological Diseases, Privolzhsky Research Medical University
2Department of Polytrauma, Regional Hospital named after Semashko
3State Technical University named after R.E. Alekseev
4Department of Neurology, University of New Mexico School of Medicine
5Lovelace Biomedical Research Institute
6National Research Saratov State University
7Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School
Abstract
Objectives: Posttraumatic cerebral ischemia (PTCI) is still one of the leading causes of mortality and disability after moderate and severe traumatic brain injury (MSTBI), however, changes in microcirculation parameters at PTCI remain underinvestigated. Microcirculatory parameters were studied for their ability to predict the PTCI development at MSTBI.
Aim: The assessment of microcirculatory parameters dynamics after MSTBI.
Methods: 220 moderate and severe (MS) TBI patients were recruited from Trauma Center Level 1. All patients were subjected to perfusion computed tomography (PCT). PCT was performed 2–17 days after TBI. The levels of cerebrovascular resistance (CVR), cerebral arterial compliance (CAC), cerebrovascular time constant (CTC) and critical closing pressure (CCP) were measured using a neuromonitoring complex. The patients were dichotomized into PTCI-positive (n = 207) and PTCI-negative (n = 13) groups for statistical analyses using Student’s t-criterion and multiple regression. P-values were significant at < 0.05.
Results/Conclusions: The levels of CVR and CCP were significantly increased, while CAC and CTC were significantly decreased in PTCI -positive patients (p < 0.05). Multiple regression analyses showed that CCP levels were not significantly associated with PTCI development (p >0.05). The regression analyses also revealed that CVR, CAC and CTC were significantly associated with the development of PTCI (p < 0.05). MSTBI is associated with accelerated changes in microcirculation parameters over time, which may indicate remodeling of cerebral blood flow. CVR, CAC and CTC may be potential biomarkers that reflect the PTCI development in MSTBI patients. A further prospective study is warranted.
409
Hyperventilation therapy often induces misery perfusion in traumatic brain injury
S Tagliabue1, M Kacprzak1,2, I Serra Mochales3, A Re-Perez4, J Baena4, J Fischer1, F Maruccia1,5, M Poca5,6, J Sahuquillo5,6 and T Durduran1,7
1Institut de Ciències Fotòniques
2IBIB
3Centre de Recerca Matemàtica (CRM)
4Neurotrauma Intensive Care Unit, Vall d’Hebron University Hospital
5Neurotraumatology and Neurosurgery Research Unit, Vall d’Hebron University Research Institute, Universidad Autonoma de Barcelona
6Department of Neurosurgery, Vall d’Hebron University Hospital, Universidad Autonoma de Barcelona
7ICREA
Abstract
Background: Misery perfusion (MP) can lead to stroke and can arise during hyperventilation therapy (HVT) administered to reduce elevated intracranial pressure (ICP) after traumatic brain injury (TBI). The risk of MP is high when a decrease in the cerebral blood flow (CBF) is concurrent with an increase in the oxygen extraction fraction (OEF). Unfortunately, bed-side, real-time quantification of MP is not readily available. In this study, we demonstrate that near-infrared and diffuse correlation spectroscopies could detect MP during HVT and quantify its occurrence.
Aim: We sought to detect periods of MP risk and characterize them in duration and magnitude.
Method: Invasive ICP recordings were synchronized with optical signals, that were acquired bilaterally over the frontal lobes of TBI patients during a brief protocol of hyperventilation (goal 30 minutes) mimicking HVT. Statistical analyses were carried out at group and individual level and over the time to define an index of MP risk.
Results/Conclusions: Twenty-seven measurement sessions were performed on eighteen subjects. HVT did not cause MP at the group level and through the whole period. At an individual level and over time twenty-two measurements had at least one MP event with a total of 89 events detected with a minimum duration of 30 seconds (examples in Figure 1). Higher MP risk was associated with presence of craniectomy (p = 0.005) on the measurement hemisphere and worse outcome (p = 0.01).
Hyperventilation has a high risk of causing MP and bed-side optical monitoring should be investigated for personalized management.
Funding: Marato/TV3, RIS3CAT/CECH, AES.
418
Differential role of glutamatergic and GABAergic neurons, and astrocyte in hemodynamics during cortical spreading depolarization
K Han1, H Lim1, S Kim2,3,4 and M Suh1,2,3
1Biomedical Institute for Convergence at SKKU (BICS), Sungkyunkwan University
2Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS)
3Department of Biomedical Engineering, Sungkyunkwan University
4Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University
Abstract
Background: Cortical spreading depolarization (CSD) is referred as a propagating massive depolarization of neurons and glia in the cortex, involving abnormal vascular responses and impaired regulation of cerebral blood flow. NMDA receptor, along with potassium channel, is involved in the generation and propagation of CSD, but the selective contribution of NMDA to CSD and to its associated neurovascular mechanisms is still unclear.
Aim: In this study, we aim to investigate how glutamatergic and GABAergic neurons, and astrocyte differentially contribute to vascular responses during and following NMDA-induced CSD activity.
Method: For in vivo two-photon calcium imaging, GCaMP6f was expressed in glutamatergic neurons, GABAergic neurons, or astrocytes by using transgenic mice or viral delivery. Calcium and vascular imaging were performed with recording of local field potentials (LFPs) to verify a CSD-induced negative direct current (DC) potential. NMDA was focally delivered into layer2/3 of mouse somatosensory cortex via a glass pipette filled with 1mM NMDA.
Results/Conclusions: The NMDA infusion generally induced a local activation of neurons and astrocytes. In occasional cases, it induced CSD events that involved propagating calcium response both in neurons and astrocytes and a huge negative DC potential. At that time, a faster decay of glutamatergic calcium responses was followed by a sustained arteriole vasodilation. On the other hand, GABAergic neurons showed sustained calcium responses during CSD. To sum up, each cellular component of the neurovascular unit may differently contribute to vascular responses by time and a specific type of inhibitory neurons might play a key role in modulating abnormal vascular responses during CSD.
422
Development and characterization of a novel thermoresponsive hydrogel for brain tissue regeneration after stroke
M Bhuiyan1,2, A Ali1 and A Clarkson2
1Center for Bioengineering and Nanomedicine, Faculty of Dentistry, University of Otago
2Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago
Abstract
Background: Stroke is the leading cause of adult disability worldwide. The primary reason for the lasting functional impairment following stroke is the brain’s limited ability to regenerate after an injury. Treatment measures such as systemic delivery of drugs and growth factors are limited by blood brain barrier and off-target effects. Significant work demonstrated that biopolymer hydrogels can assist the localized delivery of therapeutic molecules into the infarct cavity via their ability of controlled release of drugs and growth factors.
Aim: In the present study, silk fibroin was combined with chitosan to prepare a novel injectable thermoresponsive hydrogel (NTH).
Method: The NTH was physically, mechanically, and chemically characterised to evaluate the suitability for injection into the brain. MTT assay and live-dead assay were performed to assess in vitro cytocompatibility using PC12 cells. Finally, NTH was injected into the infarct cavity of an ischemic stroke model to investigate in vivo biocompatibility and effects on reactive astrogliosis.
Results/Conclusions: Rheological analysis demonstrated that NTH retains a similar mechanics to that of brain tissue (∼300 Pa) with an osmolality equivalent to that of cerebrospinal fluid (∼290 mmol/kg). The in vitro cytocompatibility testing showed that NTH is nontoxic to PC12 cells with ∼99% cell viability. The in vivo assessment revealed a smaller infarct cavity and decreased reactive astrogliosis as shown by the expression of glial fibrillary acidic protein (GFAP) and Iba1 in the peri-infarct region. These results suggest that NTH can be combined with drugs or growth factors as a potential therapeutic approach for stroke recovery.
429
Mesenchymal stem cells require interleukin-1 alpha preconditioning to confer neuroprotection after ischaemic stroke in mice
R Wong1, C Smith2,3, S Allan1 and E Pinteaux1
1Division of Neuroscience and Experimental Psychology, The University of Manchester
2Division of Cardiovascular Sciences, The University of Manchester
3Greater Manchester Comprehensive Stroke Centre, Manchester Centre for Clinical Neurosciences, Salford Royal NHS Foundation Trust
Abstract
Background: Mesenchymal stem cells (MSCs) have been proposed as a new potential therapy in stroke. We have recently demonstrated that pre-conditioning with interleukin-1 alpha (IL-1ɑ) drives MSCs toward a potent anti-inflammatory and neurotrophic phenotype.
Aim: The aim of this work was to assess the therapeutic potential of IL-1α preconditioning of MSCs, administered intra-arterially (a clinically relevant approach suggested following efficacy of thrombectomy) after experimental cerebral ischaemia in mice.
Method: Focal ischaemic stroke was induced by filament occlusion of the middle cerebral artery in mice. After 3 h from start of occlusion, animals were treated with vehicle, 9.1x104 non-conditioned or IL-1ɑ preconditioned MSCs by intra-arterial administration. Animals were allowed to recover for 3 or 14 days post-stroke and lesion volume (Cresyl violet/MRI) and functional outcomes were evaluated. In another experiment, cerebral blood flow was measured at 1.5 h after MSC administration using laser speckle imaging.
Results/Conclusions: Preconditioned MSCs reduced lesion volume and neurological deficits compared to vehicle at 3 days post-stroke. A separate cohort of animals recovered to 14 days post-stroke also showed reduced infarct volume at 48h (assessed by MRI) when treated with preconditioned MSCs, along with lower neurological deficits and better weight recovery compared to vehicle. Cerebral blood flow was increased by preconditioned MSC treatment compared to vehicle. Preconditioning MSCs with IL-1α increases their neuroprotective capability and improves functional recovery after delayed intra-arterial administration post-occlusion. With increasing use of thrombectomy the adjunctive use of preconditioned MSCs therefore represents a highly relevant therapy to improve outcomes in ischaemic stroke patients.
433
Insulin-treated diabetic rats demonstrate increased stroke risk when exposed to recurrent hypoglycemia
A Rehni1,2, A Liu1,2, S Cho1,2 and K Dave1,2,3
1Peritz Scheinberg Cerebral Vascular Disease Research Laboratories, University of Miami Miller School of Medicine
2Department of Neurology, University of Miami Miller School of Medicine
3Neuroscience Program, University of Miami Miller School of Medicine
Abstract
Background: Diabetes is a chronic disease, and antidiabetic therapy increases the risk of recurrent hypoglycemia (RH). Hypoglycemia produces a prothrombotic effect in human subjects1 and may increase stroke risk2.
Aim: The goal of the study was to evaluate the minimum duration of RH that increases the thrombosis, a surrogate for stroke, in insulin-treated diabetic (ITD) rats.
Method: ITD rats were randomly assigned to either ITD+RH+Glucose (hyperinsulinemic euglycemia: control) or ITD+RH groups (hyperinsulinemic RH) for 1, 2 or 3h/day exposure for 5 consecutive days. Overnight after the last episode, carotid artery and jugular vein of the rats were linked via a shunt containing a pre-weighted suture, and the shunt was opened for 15 minutes. The suture was then weighed to quantify thrombosis.
Results/Conclusions: The clot weight in 2h and 3h RH-exposed ITD rats were significantly higher by 30% (20 ± 1 mg, n = 5, p < 0.05) and 47% (23 ± 3 mg, n = 7, p < 0.05), respectively, when compared to the 2h (16 ± 1 mg, n = 5) and 3h (16 ± 1 mg, n = 6) control groups (Figure 1). However, the clot weights in the 1h RH-exposed ITD rats (23 ± 2 mg, n = 6, p = 0.08) were not significantly different from the control group (17 ± 1 mg, n = 5). Our results show that RH exposure increases stroke risk in ITD rats, although it is unclear if thrombosis increases with increase in hypoglycemia duration. We are currently working on identifying the mechanisms of RH-induced stroke risk.
Acknowledgement
NIH (NS122808).
References
Diabetes Care2018; 41: 2625–2633.a-24Ann NY Acad Sci2018; 1431: 25–34.
441
Central hormone-sensitive lipase is located at synapses and necessary for normal memory performance in mice
C Skoug1,2, C Holm1 and J Duarte1,2
1Department of Experimental Medical Science, Faculty of Medicine, Lund University
2Wallenberg Centre for Molecular Medicine, Faculty of Medicine, Lund University
Abstract
Background: Hormone-sensitive lipase (HSL) is mainly present in the adipose tissue where it hydrolyses diacylglycerol. Although brain expression of HSL has been reported, its presence in different cellular compartments is uncertain, and its role in regulating brain lipid metabolism remains hitherto unexplored.
Aim: In this study we aimed at mapping the relative distribution of HSL in the rodent brain, and investigating the impact of HSL deletion on brain function and exploring underlying mechanisms.
Method: HSL distribution was evaluated by immunoblotting, immunofluorescence microscopy and activity measurements. HSL-/- mice were screened by behaviour tests, and their brain tissue was analysed by transcriptomics and lipidomics.
Results/Conclusions: HSL occurs throughout the brain, and is especially enriched in synapses. Relative to wild-type littermates, HSL null mice showed impaired short- and long-term memory, but preserved exploratory behaviours. Molecular analysis of the cortex and hippocampus showed increased expression of genes involved in glucose utilization in the hippocampus but not cortex of HSL null mice compared to controls. Lipidomics analyses indicated an impact of HSL deletion on the profile of bioactive lipids, including endocannabinoids and eicosanoids that are known to modulate neuronal activity, cerebral blood blow and inflammation processes. Accordingly, mild increases in expression of pro-inflammatory cytokines suggest low grade inflammation in HSL null mice compared to littermates. We propose that HSL has a homeostatic role in regulating lipids that modulate neuronal activity, metabolism, cerebral blood flow and neuroinflammation. It remains to be tested whether HSL is directly activated during increased neuronal activity or upon neuroinflammatory stimuli.
463
Does exercise modify neurovascular coupling in APOE4 mice?
S Anderle1, K Shaw1, O Bonnar2, A Chagas1, J Henderson1, H Trewhitt1, L Bell1, D Grijseels3 and C Hall1
1University of Sussex
2Massachusetts General Hospital
3University of California San Diego
Abstract
Background: When neurons are active and demand more energy, cerebral vessels respond by increasing the delivery of nutrient-rich blood, a phenomenon called neurovascular coupling (NVC). If NVC is impaired, there is a mismatch between energy demand and supply, which may lead to neuronal damage. We have found that, in active mice carrying the APOE4 gene, a risk factor for Alzheimer’s disease (AD), pial arteries are dysfunctional, with reduced NVC and vasomotion, suggesting that vascular changes could increase the risk of AD.
Aim: Because physical exercise is known to be beneficial in maintaining vascular health, we wondered if exercise may modulate the neurovascular impairment in APOE4 mice.
Method: A cranial window was implanted into the primary visual cortex (V1) of APOE3-TR and APOE4-TR mice. One group of each genotype was given an exercise wheel in their cage. Mouse activity was recorded from the home cage and analysed using DeepLabCut. In vivo haemodynamic measures in V1 are obtained using Laser Doppler flowmetry, and neuronal activity, individual vessel dilations and red blood cell velocity (RBCV) were visualised using two-photon microscopy.
Results/Conclusions: In line with our previous observations, we found that fewer vessels respond to neuronal activation in APOE4 mice compared to APOE3 mice. Furthermore, APOE4 mice that exercise showed significantly more frequent vascular responses to neuronal activation, comparable to that seen in APOE3 mice. Therefore, exercise may be beneficial in reducing neurovascular dysfunction in APOE4 carriers, suggesting that further research on its molecular mechanisms of action could provide new therapeutic targets to combat the onset of AD.
468
Glycemic variability disrupts sleep through KATP channel activity
C Carroll1, M Stanley2, R Irmen1, A Mitra3, J Snipes1, M Raichle3,4, D Holtzman4, R Gould1, K Kishida1 and S Macauley1
1Physiology and Pharmacology, Wake Forest School of Medicine
2Zoology, University of British Columbia
3Radiology, Washington University
4Neurology, Washington University
Abstract
Background: Sleep wake cycles are tightly coupled to neuronal activity patterns where disrupted sleep is associated with periods of heightened neuronal activity. Previous work from our lab demonstrated peripheral hyperglycemia is sufficient to increase neuronal activity through inward rectifying, ATP-sensitive potassium (KATP) channels. Therefore, we hypothesized neuronal Kir6.2-KATP channels play a role in maintaining the relationship between metabolism and sleep, and knocking these channels out will uncouple this relationship.
Aim: This study seeks to identify a mechanism linking peripheral metabolism, cerebral metabolism, and sleep using a novel in vivo method.
Method: We implanted biosensors detecting interstitial fluid (ISF) glucose and lactate bilaterally into the hippocampi of wildtype and Kir6.2-/- mice. ISF glucose represents a measure of cerebral metabolism, while ISF lactate is a biomarker of neuronal activity. Biosensors were paired with cortical EEG/EMG recordings to simultaneously stage sleep. We administered injections of saline (2g/kg), glucose (2g/kg), and either insulin (.5U/kg) or glibenclamide (1g/kg), an insulin secretagogue, to evaluate the impact of acute glycemic variability on brain metabolism and sleep.
Results/Conclusions: We found glycemic variability was sufficient to disrupt sleep and this relationship is mediated through Kir6.2-KATP channel activity. In wildtype mice, hyper- and hypo-glycemia increased ISF lactate, indicating increased neuronal activity and wakefulness, and altered metabolic signatures of sleep/wake. However, Kir6.2 −/- mice had a dampened metabolic response and no change in ISF lactate or sleep characteristics following acute glycemic challenges. We therefore concluded Kir6.2-KATP channel activity facilitates the relationship between peripheral and cerebral metabolism, neuronal activity, and sleep.
481
Reversible astrocyte-selective uptake of sodium fluorescein during spreading depolarization
K Schoknecht and J Eilers
Carl-ludwig Institute For Physiology, Medical Faculty, University Leipzig
Abstract
Background: Elevated extracellular potassium ([K+]o) is a known feature of spreading depolarization (SD) and stimulus of astrocytic swelling. We saw astrocytic uptake of sodium fluorescein (NaFlu) – a low molecular weight anionic dye – in the wake of elevated [K+]o.
Aim: We aimed to explore astrocytic swelling and kinetics of NaFlu during SD, [K+]o and glutamate elevation and elucidate underlying mechanisms.
Method: All experiments were performed in acute neocortical slices from adult male C57Bl6 mice. We labeled astrocytes with sulforhodamine-101, measured NaFlu kinetics using 2-photon laser scanning microscopy and recorded local field potentials. Three experimental conditions were investigated: 1) elevated [K+]o (10mM) by isoosmolar exchange of KCl with NaCl, 2) elevated extracellular glutamate (200 µM), 3) focal puff application of KCl (3M) to induce SDs. Putative prevention of astrocytic NaFlu uptake and swelling was tested with pharmacological inhibitors of inward-rectifier potassium channels, excitatory amino acid transporters, sodium-bicarbonate exchanger-1, monocarboxylate transporters and sodium-potassium ATPase.
Results/Conclusions: Elevations of [K+]o lead to a parallel increase of the astrocytic NaFlu intensity and the astrocyte-covered area (in z-projection) by 56% [IQR:43,70] and 25% [IQR:21,34]. NaFlu uptake and swelling were prevented by inhibition of the sodium-potassium ATPase (ouabain 10 µM), while other drugs had no significant effect. Glutamate increased area but not NaFlu intensity. During SDs, astrocytic NaFlu fluorescence and area increased by 17% [IQR:9,27] and 7% [IQR:5,10] and, in contrast to mere [K+]o elevation, swelling preceded NaFlu uptake. Thus, NaFlu may serve as a marker for potassium- but not glutamate-induced astrocytic swelling and suggests [K+]o-independent early swelling during SD.
482
Altered regional cerebral blood flow response to methylene blue in bipolar disorder
A Colasanti1,2, A Russo1, B Örzsik1, P Nwaubani1, R De Marco1, A Pinna1, N Yalin2, N Singh2, F Turkheimer2, F Zelaya2, M Cercignani1,3 and I Asllani1
1Brighton And Sussex Medical School, University of Sussex
2Institute of Psychiatry, Psychology and Neuroscience, King’s College London
3Cardiff University Brain Research Imaging Centre
Abstract
Background: Alterations in frontal lobe mitochondrial electron transport chain (ETC) have been reported in bipolar disorder (BPD).1 Methylene blue (MB) acts as an alternate electron donor at mitochondrial ETC level and supposedly enhances brain oxygen metabolism.
Aim: We hypothesize the effects of acute administration of MB on brain perfusion would be altered in BPD patients relative to controls, reflecting mitochondrial ETC abnormalities and an impaired “oxygen metabolic reserve” in BPD.
Method: Cerebral Blood Flow (CBF) was measured using pseudo-continuous Arterial Spin Labelling in 14 BPD patients and 10 healthy controls after intra-venous administration of MB (0.5 mg/kg) and placebo in a randomized cross-over design.
Results/Conclusions: MB resulted in a widespread CBF reduction, confirming previous observations in a separate non-clinical sample. Focusing on pathologically relevant regions of interest, we observed an interaction between groups and effect of MB in the subgenual cingulate (p = 0.01) where CBF was reduced in BPD patients but not healthy controls, whilst in the frontal lobe this effect was not evident. A post-hoc exploratory voxel-wise analysis also revealed a cluster of MB-induced CBF reductions in the precuneus, with patients and controls equally affected.
Our findings provide confirmatory evidence that an acute administration of MB reduces CBF. However, we hereby observed a differential effect of MB on CBF between BPD patients and healthy controls, specifically in regions relevant to BPD pathophysiology such as the subgenual cingulate. This observation might be of pathophysiological significance and reflect region-specific mitochondrial ETC alterations in BPD.
Reference
Andreazzaet al. Arch Gen Psychiatr2010; 67: 360–368.a-25
489
A deep-learning approach to quantifying structural changes to cerebrovascular networks in moderate traumatic brain injury
M Rozak1,2, J Mester2, A Attarpour1,2, A Dorr2, M Goubran1,2 and B Stefanovic1,2
1University of Toronto
2Sunnybrook Research Institute
Abstract
Background: Traumatic brain injury (TBI) often elicits sustained injury to cerebrovascular networks. While cerebrovascular damage is thought to limit long-term recovery, little is known about the cellular level changes in the brain microvasculature following TBI. Two-photon fluorescence microscopy (2PFM) allows for observation and quantification of microvascular state.
Aim: We developed a segmentation-focused deep learning platform for high-throughput analysis of cerebrovascular networks based on in vivo 2PFM imaging in murine primary somatosensory cortex. We applied this novel pipeline in a model of repeated moderate traumatic brain injury (mTBI).
Method: We employed an mTBI model involving three impacts with a three-day inter-impact interval in nine Thy1-ChR2-YFP mice and seven sham mice. Closed cortical impacts were delivered to the intact skull overlying the forepaw and whisker-barrel cortices. Two weeks following the final impact, mice were implanted with cranial windows centred over the impact coordinates and the underlying cortex imaged on 2PFM during baseline alternated with blue light photostimulation. We developed a deep learning segmentation model with a 3D U-Net-based architecture. The model was trained with data from fifteen mice, validated with data from four mice, and tested with data from six mice. The segmented cerebrovascular networks were rendered as graphs to enable detailed morphological analysis.
Results/Conclusions: Our analysis pipeline produced a wealth of morphological information on cerebrovasculature and neurovascular coupling, including morphological changes following neuronal activation for individual vessels. Its application in the subacute phase of mTBI revealed spatial gradients of sustained cerebrovascular compromise in the concussed cortex.
493
Extracortical modulation of cerebral blood flow and vasomotion via the rostral venterolateral medulla
K Chhabria1, L McElvain1, T Broggini2, P Yao1, B Holloway1 and D Kleinfeld1
1University of California-San Diego
2Universitätsklinikum Frankfurt am Main
Abstract
Background: The regulation of cerebral blood flow (CBF) is achieved by a multiplicity of pathways. These include intrinsic arteriole vasomotion, local neuronal activity, global control related to midbrain modulatory structures, and extracortical regulation via a sympathetic regulator in the rostral venterolateral medulla (RVLM). Early studies (Golanov and Reis, J Physiol, 1996) reported CBF regulation via neurons in RVLM. However, the mechanism(s) and anatomical pathway(s) for this action are yet to be established.
Aims: Firstly, to establish if the C1 neurons in RVLM drive CBF regulation. Secondly, to determine the mechanism of regulation. Thirdly, to establish the neuroanatomy from C1 to cortex.
Methods: We targeted the C1 region of RVLM in dopamine-B-hydroxylase Cre-expressing animals. We injected AAV.DIO.hSyn.mcherry for anterograde tracing experiments. We injected AAV.DIO.hSyn. ChR-EYFP for optogenetic experiments in awake animals. In response to optical activation, CBF was measured over primary vibrissa somatosensory cortex through a thinned skull cranial window via laser-doppler-flowmetry and arteriole diameter was measured via 2P-microscopy. As a control, the electrocardiogram was acquired.
Results: We confirmed the centroid of RVLM activation of cortex through microstimulation mapping experiments. Our neuroanatomical observations show labeling of locus coerulus, zona incerta, lateral hypothalamus, paraventricular nucleus, and paraventricular thalamus. The contribution of each pathway represents ongoing work. Our functional studies show that optogenetic stimulation of C1 neurons led to a 20% increase in CBF and a similar increase in vessel diameter. Trains of stimulation at near the vasomotor frequency of 0.1 Hz could entrain vasomotion, suggesting a specific role for RVLM in brain homeostasis.
503
Zero-echo-time functional magnetic resonance imaging
M MacKinnon1,2,3,4, S Song1,2,4, Y Ma1,2,4, T Chao1,2,4, T Wang1,2,4, L Hsu1,2,4, S Lee1,2,4, W Chang2,5 and Y Shih1,2,4
1Center for Animal MRI, University of North Carolina at Chapel Hill
2Biomedical Research Imaging Center, University of North Carolina at Chapel Hill
3The Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill
4Department of Neurology, University of North Carolina at Chapel Hill
5Department of Radiology, University of North Carolina at Chapel Hill
Abstract
Background: Despite its utility for neuroimaging research, the gold-standard gradient-recalled-echo (GRE) echo planar imaging (EPI) sequence suffers from four major drawbacks: (1) high acoustic noise; (2) sensitivity to magnetic field-inhomogeneity and motion; (3) poor spatial specificity; and (4) low sensitivity.
Aim: To demonstrate a zero-echo-time (ZTE)-fMRI technique that overcomes the four major drawbacks of GRE-EPI.
Method: Experiments were carried out on a Bruker 9.4 T MRI system using head-only excitation (24 rats and 76 mice).
Results/Conclusions: A custom-designed ZTE pulse-sequence (a), has numerous paradigm-shifting benefits for the functional neuroimaging community compared to GRE-EPI. The ZTE technique allows fMRI of animals to be conducted without the stress or anaesthesia confounds and enables imaging of normally invisible areas in GRE-EPI, evidenced by: (b) the negligible acoustic noise of ZTE; (c) reduced stress in mice undergoing ZTE; (d) the insensitivity of ZTE to motion and (e) the preservation of signal in brain areas suffering from field susceptibility. High spatial specificity remains the holy-grail for new fMRI developments. Through modeling of rodent brain biophysical parameters, we have shown that the ZTE-fMRI signal Results from changes in (f-g) CBV and tissue-oxygenation. As changes in tissue oxygenation ( < 30 M from capillaries) and CBV are highly localized, ZTE provides a more spatially localized technique than BOLD-fMRI which has signal changes weighted towards venous vasculature. ZTE is unique in addressing all major drawbacks of GRE-EPI. We validated in vivo that ZTE contrast: (h) is well-predicted by biophysical modeling, (i-k) outperforms GRE-EPI sensitivity in anesthetized rats in a within subject setting, and (l) shows tight coupling to simultaneously recorded CBV using fiber-photometry. We have also established an awake mouse functional connectivity database using ZTE (m).
ZTE provides an ideal fMRI technique to the neuroimaging field.
504
Amplitude of metabolic fluctuations is inversely related to magnitude of basal metabolism in human brain
P Herman1, Y Koush1, G Thompson2, H Blumenfeld1, S Kaczmarz3,4, C Preibisch3, D Sivakolundu1, D Rothman1 and F Hyder1
1Yale University
2iHuman Institute, ShanghaiTech University
3Technical University of Munich
4Philips GmbH Market DACH
Abstract
Background: Gas-free calibrated fMRI extracts ΔCMRO2 (oxidative metabolism) from combined BOLD (i.e., R2’ = R2*-R2) and CBF (ASL, arterial spin labeling) scans. Previous PET/fMRI studies have reported brain-wide activity changes upon eye opening. Here we explore spontaneous metabolic fluctuations in relation to the metabolic state with eyes closed (EC) vs. eyes open (EO).
Aim: We investigated spatial localization of metabolic fluctuations in human brain with EC and EO.
Method: In 20 healthy volunteers we conducted calibrated fMRI (ASL, R2* and R2) on a 3T scanner to define dynamic/steady-state changes in R2’, CBF, and CMRO2 in EC and EO conditions. We removed non-physiological values to exclude extremely large CBF fluctuations. Dynamic fluctuations were calculated in frequency regime with ALFF (amplitude of low frequency fluctuation), similar to fluctuations defined in amplitude regime. Analysis included nodes within and beyond the default mode network (DMN).
Results/Conclusions: We calculated EO vs. EC changes in R2’, CBF, and CMRO2 for steady-state conditions (ΔI/I) and fluctuations (ΔALFF/ALFF), and examined correlations (ρ) between them and their significance (p) (Figure 1). Correlations between ΔI/I and ΔALFF/ALFF were weakly positive for R2’ and CBF, but for CMRO2 the correlation became significantly negative such that regions with larger ΔI/I had smaller ΔALFF/ALFF (e.g., V1 outside DMN) and vice versa (e.g., precuneus inside DMN). This indicates that cortical areas within and beyond DMN have opposite relation between metabolic activity state and metabolic fluctuations. Overall, these results imply that functional connectivity derived from hemodynamic and metabolic fluctuations could provide unique information which has previously been overlooked.
506
Demonstration of age-related increases in blood-brain barrier permeability and microvascular rarefaction in mouse cerebral cortex
A Nyul Toth1,2,3, S Tarantini1,3,4, J DelFavero1, F Yan5, P Balasubramanian1, A Yabluchanskiy1, C Ahire1, T Kiss1,6,7, T Csipo1,3, A Lipecz1,3, A Farkas2,8, I Wilhelm2,9, I Krizbai2,9, Q Tang5, A Csiszar1,3,6, Z Ungvari1,3,4,6
1Vascular Cognitive Impairment and Neurodegeneration Program, Reynolds Oklahoma Center on Aging/Oklahoma Center for Geroscience, Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center
2International Training Program in Geroscience, Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network (ELKH)
3International Training Program in Geroscience, Doctoral School of Basic and Translational Medicine/Department of Public Health, Semmelweis University
4Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center
5Stephenson School of Biomedical Engineering, Gallogly College of Engineering, The University of Oklahoma
6International Training Program in Geroscience, Theoretical Medicine Doctoral School/Departments of Medical Physics and Informatics and Cell Biology and Molecular Medicine
7International Training Program in Geroscience, First Department of Pediatrics, Semmelweis University
8Department of Physiology, Anatomy and Neuroscience, University of Szeged
9Institute of Life Sciences, Vasile Goldis Western University of Arad
Abstract
Background: Age-related blood-brain barrier disruption and cerebromicrovascular rarefaction contribute importantly to the pathogenesis of both vascular cognitive impairment and dementia (VCID) and Alzheimer’s disease (AD). Recent advances in geroscience research enable development of novel interventions to reverse age-related alterations of the cerebral microcirculation for prevention of VCID and AD.
Aim: To facilitate this research there is an urgent need for sensitive and easy-to-adapt imaging methods, which enable longitudinal assessment of changes in BBB permeability and brain capillarization in aged mice, that could be used in vivo to evaluate treatment efficiency.
Method: To enable longitudinal assessment of changes in BBB permeability and capillary density in mice equipped with a chronic cranial window, we adapted and optimized intravital two-photon imaging and optical coherence tomography (OCT) approaches.
Results/Conclusions: Our Methods have been optimized for longitudinal (over the period of 36 weeks) in vivo assessment of cerebromicrovascular health in preclinical geroscience research. By assessing relative fluorescence changes over the baseline within a volume of brain tissue, after qualitative image subtraction of the brain microvasculature, we confirmed that old 24 month old C57BL/6J mice cumulative permeability of the microvessels to fluorescent tracers of different molecular weights (0.3 kDa to 40 kDa) is significantly increased as compared to that of 5 month old mice. Real-time recording of vessel cross-sections showed that apparent solute permeability of single microvessels is significantly increased in aged mice vs. young mice. Cortical capillary density, assessed both by intravital two-photon microscopy and OCT was also decreased in aged mice vs. young mice.
507
Differences in excitatory and inhibitory neuron oxygen metabolism elucidated by optical imaging in awake mice
A Toader1 and A Vazquez2
1Department of Electrical and Computer Engineering, University of Pittsburgh
2Department of Radiology, University of Pittsburgh
Abstract
Background: Two major types of neurons exist in the mammalian brain: excitatory neurons and inhibitory neurons. Many studies show that metabolic consumption is proportional to overall brain activity, but it is not known whether oxygen metabolism is different between different types of neurons.
Aim: The majority of studies assessing the cerebral metabolic rate of oxygen consumption (CMRO2) have been conducted in anesthetized animals. By design, anesthetics act to suppress neuronal activity, potentially confounding results. We sought to examine CMRO2 in awake mice and compare our results with those from anesthetized subjects.
Method: Transgenic mice expressing the optogenetic protein Channelrhodopsin (ChR2) in targeted neurons were used for awake experimentation. In Thy1-ChR2 mice, excitatory neurons were targeted (n = 4), and in VGAT-ChR2 mice, inhibitory neurons were targeted (n = 2). We also examined inhibitory sub-type mice targeting somatostatin (SST-cre, n = 3) and neuropeptide-Y (NPY-cre, n = 4). Neurons were optogenetically stimulated using a 473nm laser. The neuronal response was recorded using a laser doppler flow (LDF) probe and wide-field optical mapping (WFOM) at 2 wavelengths (572 and 620nm). The CMRO2 response was calculated as a percent change relative to pre-stimulation baseline.
Results/Conclusions: Optogenetic stimulation of Thy1 mice increased CMRO2 by 25.0%, VGAT by 24.8%, SST by 9.2% and NPY by 8.7% (see Figure 1). We used the YFP emission as a rough measure of the number of targeted neurons for normalization. Normalized CRMO2 responses suggest inhibitory neurons consume more oxygen than excitatory neurons by a factor of 1.39, while CMRO2 from inhibitory sub-types were similar to CMRO2 of VGAT.
516
Reduced Folate Carrier-1 is expressed in cerebral pericytes and might have a role in ischemia
G Gurler1, N Belder1, M Sever1, G Uruk1, H Karatas1,2 and M Yemisci1,2,3
1Institute of Neurological Sciences and Psychiatry, Hacettepe University
2Neuroscience and Neurotechnology Center of Excellence (NÖROM)
3Faculty of Medicine, Department of Neurology, Hacettepe University
Abstract
Background: Reduced Folate Carrier-1(RFC1) is expressed in cerebral endothelial cells. Transcriptomic studies showed it was enriched in cerebral pericytes. RFC1 protein was not demonstrated in the pericytes. Furthermore, its role in the pathophysiology of neurological diseases overlooked despite its potential role in silent brain infarction.
Aim: 1)To determine RFC1 immunohistochemically in cerebral pericytes; 2) silence RFC1 gene in the brain in vivo by a custom designed RFC1-targeted Accell siRNA or modify RFC1 levels by its competitive inhibitor Methotrexate(MTX); 3) investigate its role in cerebral ischemia.
Method: We used male and female adult Swiss albino mice brain sections and microvessels isolated from the brain to immunohistochemically characterize RFC1 protein in pericytes. We administered RFC1-targeted siRNA(50uM) intracortically (n = 4) or MTX (400 mg/kg) intraperitoneally (n = 6). Middle cerebral artery occlusion(MCAo) was induced by intraluminal monofilament technique for 90 minutes and recanalization for 1-hour, 24-hours, and 48-hours. We harvested brains for Western blotting (n = 3/time-point), immunohistochemistry (n = 3/time-point), microvessel isolation (n = 3/time-point), RT-qPCR (n = 2). We colocalized RFC1 using confocal microscopy with pericyte markers platelet-derived growth factor receptor beta (PDGRFR-beta), Aminopeptidase N(CD13), Neural/glial antigen 2(NG2). Vessels are marked with Lectin.
Results/Conclusions: We showed that RFC1 protein is found in cerebral pericytes. MTX upregulated RFC1 protein after 1-hour but not permanently(p = 0.034, n = 4). RFC1-targeted-siRNA knocked-down RFC1 mRNA levels to 30.4% in cortex after 48-hours(p = 0.021). RFC1 is decreased by ischemia at all time points immunohistochemically(p < 0.05), and in Western blotting (n = 3/time-point, p < 0.05). Microvessels isolated from ischemic hemisphere showed punctate and disturbed RFC1 immunolabeling compared to microvessels from contralateral region. Our study demonstrated that RFC1 protein is expressed in cerebral pericytes, may be modified, and might have a role in cerebral ischemia/recanalization.
This study is supported by Hacettepe University No:TDK-2020-18590 and TÜBİTAK No:120N690
523
Diffusion MRI highlights accelerated aging after a single juvenile concussion
A Obenaus1,2, J Lee2, B Rodriguez Grande3, M Fournier3, T Clément3, A Trotier4, S Miraux4, N Marchi5 and J Badaut2,3,4
1University of California, Irvine
2Loma Linda University
3CNRS UMR5287, University of Bordeaux
4Centre de Résonance Magnétique des Systèmes Biologiques, UMR 5536
5Cerebrovascular and Glia Research Laboratory, University of Montpellier
Abstract
Background: Juvenile concussions have the potential to elicit cognitive, adaptive, and socio-behavioral decrements. Unknown is how early life concussions can lead to enduring effects into late adulthood. Studying how an early concussive event progresses to long term deficits in adulthood is critical for outcome prediction and the development of appropriate treatments. We hypothesized that a single concussion leads to an altered brain maturation, producing temporally evolving microstructural deficits that lead to late-in-life cognitive and behavioral deficits.
Methods: We investigated the long-term effects of concussion in C57Bl6 mice at postnatal day 17 and mapped the temporal evolution of alteration in long-term behavior and cognitive outcomes. Diffusion-tensor MRI (DTI) and structural MRI were examined at 7 temporal epochs from 1–18mo post-concussion with regional MRI tissue metrics with confirmatory immunohistochemistry.
Results/Conclusions: Concussions led to increased glial fibrillary acidic protein and neurofilament-light in blood samples and impaired spatial learning and memory was evident at 18mo. DTI longitudinal analysis from 1–18mo post-concussion revealed that jmTBI produced temporally dependent deficits that were concurrent with behavioral impairments. DTI alterations were concentrated at earlier timepoints (1–3 m) and were correlated to behavioral deficits at 18m. We demonstrate that a single juvenile concussion early in life leads to lasting behavioral impairments later in life and which are linked to early regional tissue deficits. Our work not only establishes that juvenile concussions are chronic in nature with the potential to produce long-lasting effects but provides an unprecedented insight into how an early concussion may produce adverse effects later in life.
538
Molecular connectivity: A systematic review of studies
A Sala1,2,3, A Lizarraga1,4, S Caminiti5,6,7, C Habeck8, S Jamadar9, D Perani5,6,7, J Pereira10,11, M Veronese12,13 and I Yakushev1,4
1Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, School of Medicine
2GIGA-Consciousness, Coma Science Group, University of Liege
3Centre du Cerveau2, University Hospital of Liege
4Neuroimaging Center (TUM-NIC), Klinikum rechts der Isar, Technical University of Munich, School of Medicine
5Vita-Salute San Raffaele University
6In vivo human molecular and structural neuroimaging Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute
7Nuclear Medicine Unit, San Raffaele Hospital
8Cognitive Neuroscience Division, Department of Neurology, Columbia University
9Turner Institute for Brain and Mental Health, Monash Biomedical Imaging, Monash University
10Department of Neurobiology, Care Sciences and Society, Karolinska Institutet
11Memory Research Unit, Department of Clinical Sciences, Malmö Lund University
12Department of Neuroimaging, King’s College London
13Department of Information Engineering, University of Padua
Abstract
Background: In the past two decades, brain connectomics has become a leading topic of neuroscience. Whereas the majority of brain connectivity studies have utilized functional MRI, molecular imaging is increasingly accepted in the field.
Aim: To review PET studies that analyzed imaging data in the context of brain connectivity or networks.
Method: We performed a systematic review of studies published before November 2021. PubMed and Scopus were searched for original articles in any language, using keywords brain, PET, connectivity, networks, connectomics. Abstracts were screened by two independent reviewers, full-texts by one reviewer. Out of 5448 initially identified records 398 full-texts were assessed for eligibility. Finally, 343 articles verified as molecular connectivity studies were selected.
Results/Conclusion: These studies utilized 27 radiotracers, targeting 18 processes across the categories glucose metabolism (65.6%), cerebral blood flow (24.5%), proteinopathies (8.2%), and neurotransmission (5.2%). Healthy individuals were the target population in 26% of studies. Patients with 51 clinical conditions were studied, with Alzheimer’ (20.7%) and Parkinson’s disease (20.4%) being most common. Brain connectivity/networks were estimated based on subject-series (85%), time-series (9.6%), a hybrid approach (3.5%), or topographical similarity (1.8%). Utilized statistical approaches could be categorized into interregional correlations (32.4%), principal component analyses (31.8%), seed-based interregional correlation (29.4%), graph theory analyses (17%), independent component analysis (7%), structural equation modelling (6.7%), and graphical lasso (4%).
A database with these studies including their major characteristics will soon be made available at molecularconnectivity.com. As the number of molecular connectivity studies is increasing exponentially, we encourage researches to update the database.
543
Potential sources of variability for neuro-vascular responses in awake mice
Y Kim1, M Fukada2 and A Vazquez3
1Department of Bioengineering, University of Pittsburgh
2Department of Radiology, University of Pittsburgh
3Department of Radiology, University of Pittsburgh
Abstract
Background: Repeated sensory stimulation produces variable hemodynamic responses. Previous work has shown that neuronal responses can be variable and vascular responses convey some of this variability. Neuronal response variability can be due to differences in neuromodulatory input and/or brain-state. Some neuromodulators also work to directly modulate vessel tone.
Aim: The goal of this work is to determine the relationship between evoked neuronal and vascular response variability, whisker movement, and pupil diameter as an indirect measure of alertness and neuromodulation input.
Method: We conducted repeated whisker stimulation and rest experiments in transgenic mice expressing the calcium sensor RGECO1a (Thy1-RGECO1a, n = 2). We imaged cortical neuronal activity (excitatory neurons) and hemodynamic responses (intrinsic optical imaging at 580nm and 620nm), while also imaging whisker movement and pupil diameter. Pupil diameter can also be used as an indicator of sympathetic tone which is known to influence cerebro-vascular tone.
Results/Conclusions: We observe variability in neuronal and vascular responses evoked by repeated whisker stimulation as well as variability in pupil diameter (expected). Some of the hemodynamic response variability to whisker stimulation is neuronal in origin (r = 0.423, p < 0.005). Comparisons between fluctuations in pupil diameter and neuronal baseline (RGECO1a) or hemodynamic baseline (IOS-580) exhibited peak correlation of −0.41 (+6.5-sec) and −0.49 (+9.8-sec), respectively. Pupil diameter improved the explained variance of whisker responses by 19.8% for neuronal responses and by 33.2% for hemodynamic responses, indicating a stronger vascular effect than neuronal effect. Data from resting-state experiments show similar results, suggesting that alertness has a stronger modulatory influence on vessel tone than neuronal activity.
574
Single-nucleus RNA sequencing suggests altered immune response pathways in microglia and astrocytes in bipolar disorder
Q Amosse1,2, S Tsartsalis1,2, K Ceyzériat2, B Tournier1,2 and P Millet1,2
1University of Geneva
2University Hospital of Geneva
Abstract
Background: Bipolar disorder (BD) is a chronic mental disorder causing considerable disabilities. The mechanisms underlying BD are poorly understood. Studies suggest that BD patients present a chronic inflammation. Nevertheless, whether this chronic inflammation is associated to pathophysiological mechanisms in the central nervous system (CNS) is less studied.
Aim: This work, supported by the Swiss National Science Foundation (No.184713) hypothesizes alterations in immune response pathways in glial cells in the CNS of BD patients. Plus, we hypothesized that genetic risk associated genes through genome-wide association studies (GWAS) are modulated in those cells. We used single-nucleus RNA sequencing (snRNAseq) to investigate transcriptomic alterations of glial cells in BD.
Methods: We isolated nuclei from BD and control cingulate cortex post-mortem human tissue samples. Using fluorescence-activated cell sorting, we enriched our samples in microglia and astrocytes that were then processed with the 10X Genomics Chromium Controller and sequenced. Bioinformatic quality controls and treatment allowed to identify and isolate microglia and astrocytes in which Differential gene expression (DGE), functional enrichment analysis (FEA) was performed separately in each cell type.
Results/Conclusion: The DGE analysis then FEA highlighted the alteration of type-I and type-II Interferon (IFN) pathways in both microglia and astrocytes. Interestingly, almost all the 30 genes associated to GWAS loci were expressed in those cells, notably ADCY2, that was significantly upregulated in astrocytes of BD subjects. Our results suggest that GWAS genes map onto glial cells which play a role in the pathophysiology of BD and may represent targets for inflammation-related therapeutic approaches.
