Sage Journals: Discover world-class research

Abstract

Despite the high prevalence, stroke remains incurable due to the limited regeneration capacity in the central nervous system. Neuronal replacement strategies are highly diverse biomedical fields that attempt to replace lost neurons by utilizing exogenous stem cell transplants, biomaterials, and direct neuronal reprogramming. Although these approaches have achieved encouraging outcomes mostly in the rodent stroke model, further preclinical validation in non-human primates (NHP) is still needed prior to clinical trials. In this paper, we briefly review the recent progress of promising neuronal replacement therapy in NHP stroke studies. Moreover, we summarize the key characteristics of the NHP as highly valuable translational tools and discuss (1) NHP species and their advantages in terms of genetics, physiology, neuroanatomy, immunology, and behavior; (2) various methods for establishing NHP focal ischemic models to study the regenerative and plastic changes associated with motor functional recovery; and (3) a comprehensive analysis of experimentally and clinically accessible outcomes and a potential adaptive mechanism. Our review specifically aims to facilitate the selection of the appropriate NHP cortical ischemic models and efficient prognostic evaluation methods in preclinical stroke research design of neuronal replacement strategies.

Keywords

Non-human primate stroke focal cortical ischemic models neuronal replacement neural regeneration endogenous neurogenesis

Introduction

Ischemic stroke (IS) is a leading cause of disability with high socioeconomic cost worldwide.¹ The standard acute-phase interventions such as tissue plasminogen activator (tPA) and mechanical thrombectomy dramatically improved the outcomes of IS patients.² However, once survivors miss the opportunity of revascularization within 24 hours after the initial stroke, they must rely on spontaneous or rehabilitation-supported functional recovery.^3,4 It is reported that almost half of IS patients have lifelong disabilities,⁵ and survivors with motor cortex involvement and descending motor fiber damage had shown motor deficits, especially the impairment of hand dexterity, severely affecting their quality of life.⁶ To date, neurological deficits in IS patients remain incurable due to the limited regeneration capacity in the central nervous system (CNS). Therefore, new effective treatment strategies with a wider therapeutic window and limited side effects are needed for subacute and chronic IS patients to restore tissue repair and functional recovery.

Neuronal replacement strategies are highly diverse and relatively new biomedical fields that utilize newborn neurons to replace damaged or dying ones.⁷ Although this sounds like a daunting challenge, the landmark discovery of lifelong neurogenesis in adult NHP and humans demonstrated that neural stem cells (NSCs) continuously generate newborn neurons and integrate into host neuronal circuitries.^8–10 Currently, there are three main neuronal replacement strategies: exogenous stem cell transplants, biomaterials, and direct neuronal reprogramming.¹¹ These approaches are at different stages of development. The first approach utilizing exogenous cells has proven to achieve encouraging outcomes in rodents, demonstrating that translated cells can survive, differentiate into functional neurons, integrate into host neural circuitry and improve neurological outcomes.^12–14 The latter two approaches utilizing endogenous cells also proved that neuronal replacement is feasible and achieves behavioral recovery in rodent models of stroke.^15,16 Thus, these neuronal replacement strategies offer promising future treatment options for stroke.

From bench to bedside, most initial stroke studies were conducted in rodents in consideration of their abundant source, low cost, and easy operation. Although impressive results were occasionally obtained in rodent models, these clinical trials ultimately failed when translating directly from rodents to humans without an intermediate step.^17,18 Several arguments tried to explain the reason why bench results get “lost in clinical translation.” Specifically, the huge interspecies differences between rodents and humans were considered an important issue.¹⁹ Correspondingly, the Stroke Therapy Academic Industry Roundtable (STAIR) proposed the use of large animals, especially non-human primates (NHP), following lower-order species because of their phylogenetic proximity to humans.^20,21 Thus, NHP stroke models are crucial for the safe and effective clinical translation of cell replacement strategies.

Here, we review (1) the recent progress of promising neuronal replacement therapy in NHP stroke studies; (2) NHP species used in IS study and their advantages in terms of genetics, physiology, neuroanatomy, immunology, and behavior; (3) various methods for establishing NHP focal ischemic models targeting the motor cortex; and (4) a long-term motor functional outcome assessment and a potential adaptive mechanism of neural regeneration via a comprehensive analysis of infarction volume, cerebral blood flow (CBF), neurobehavioral assessment, and neural replacement. Taking this approach, we aim to provide useful information for investigators to select the most appropriate NHP models and efficient prognosis evaluation methods for their neural replacement preclinical research.

Neuronal replacement strategies in NHP stroke studies

Ischemia damage several cell elements of the neurovascular unit (NVU) including neurons, astrocytes, endothelial cells, pericytes, oligodendroglia, and microglia.^22–24 Neurons were found to be most vulnerable and cause widespread damage in infarction and penumbra.^25–28 Neuronal replacement strategies initially aimed to replace the dead neurons with young neurons through tissue engineering or cellular approaches in subacute or chronic stroke.^7,11,29 Subsequently, more researchers proposed its bystander effects, including immunomodulation, angiogenesis, glia replacement, and neuroprotection.^30–32 On one hand, the transplant substrates or biomaterials efficiently reproduce the physical environment of the brain tissue to provide a scaffold for replacement cells (neurons, astrocytes and oligodendrocytes).^33–35 On the other hand, the transplant NSCs or biomaterials release different bioactive molecules and factors to inhibit microglia activation,^36,37 promote neurogenesis^38,39 and improve angiogenesis.^16,40 Thus, neuronal replacement strategies seem a multimechanistic approach through multimodal therapeutic action on multiple cell elements of NVU.⁴¹ Compared to bystander effects, neuronal replacement is more likely to meaningfully restore lost function through the expansion of the available neural substrate.^30,32 For this reason, we will next shift our focus back to neuronal replacement and discuss the recent progress of neuronal replacement therapy in NHP stroke studies.

Exogenous stem cell transplants

Exogenous stem cell transplants have been successful at unprecedented levels, and some have reached the stage of clinical trials.⁴² The transplanted cell lines used for stroke include embryonic stem cells, mesenchymal stem cells, olfactory ensheathing cells, bone marrow mononuclear cells, multipotent adult progenitor cells and induced pluripotent stem cells (iPSCs).^38,43 In analyzing clinical trials, most phase Ι studies have demonstrated safety and functional improvement over baseline.^44–50 Despite the positive progress, limited neuronal replacement is still a common challenge.⁵¹ Further preclinical NHP stroke study is required to better understand important factors determining cell transplantation success, such as transplanted cell type, route of administration, treatment time window, and dosing number. Lee et al.⁵² transplanted human neural stem cells (hNSCs) into the intact brain of NHP without immunosuppression. They revealed that hNSCs could survive and differentiate into neurons without evidence of tumor formation two years after transplantation. Roitberg et al.⁵³ further transplanted hNSCs into the NHP brain after one week of ischemic injury. They found that hNSCs can survive up to 105 days and partly undergo neuronal differentiation. While most hNSCs were mainly situated around the injection tracks and did not repopulate the ischemic lesion. Thus, further efforts will still need to improve graft survival and achieve electrophysiological integration into the damaged brain for functional outcomes in NHP preclinical study before the large-scale application of cell transplantation in clinical.

Biomaterials

Biomaterial strategy is transplanting acellular biomaterials into the injury area with the goal of augmenting endogenous neurogenesis.⁵⁴ In addition to their function as structure support, biomaterials constantly deliver neurotrophic factors or signaling cues to improve the local microenvironment in favor of regeneration.^31,55,56 Biomaterial approaches are demonstrated to enhance and redirect endogenous neuroblast migration from neurogenic niches to specified damaged brain regions and induce the neuroblasts to be differentiated into mature neurons in rodents.^{34,37,57–60} Presently, there are some initial applications to target the NHP stroke brain with biomaterials. Bjugstad et al.⁶¹ explored the tolerability of polyethylene glycol (PEG)-based hydrogel in the striatum and cerebral cortex of healthy NHP. These biomaterials induced mild inflammation and gliosis, which indicate their potential use for neural tissue regeneration. In a chronic NHP stroke study, Cook et al.⁶² injected hyaluronic acid (HA) hydrogel slowly releasing brain-derived neurotrophic factor (BDNF) into the stroke cavity of a macaque monkey. At two weeks after delivery, hydrogel-released BDNF can be detected up to 2 cm from the infarct, a distance relevant to neural repair and recovery in humans. In an acute NHP stroke study, Kawaguchi et al.^63,64 demonstrated that intravenous injection of liposome-encapsulated hemoglobin (LEH) could significantly reduce the volume of infarct area and improve behavioral outcomes at 8 days after middle cerebral artery occlusion (MCAO). However, all the above NHP studies did not provide any data related to endogenous neurogenesis due to short-term observation after stroke. Further investigation of survival, maturity, and synaptic integration of redirected neuroblasts is needed in stable stroke models of NHP with long-term survival time after ischemic injury.

Direct neuronal reprogramming

Direct neuronal reprogramming is the forced conversion of local glia into neurons by transduction with various neurogenic fate determinants.^65,66 This is an attractive approach to simultaneously replace the lost neuronal population and reduce the astroglial scar following brain injury.⁶⁷ NeuroD1-induced neuronal reprogramming has been explored in the focal ischemic injury model in mice. It demonstrated that NeuroD1-mediated reprogramming could regenerate a large number of functional new neurons to restore lost neuronal functions after stroke.^68,69 Based on these successful investigations in rodents, Ge et al.⁷⁰ further tested adeno-associated virus (AAV) NeuroD1-based neuronal reprogramming in an NHP stroke study. They found that NeuroD1 efficiently converts 90% of the infected astrocytes into neurons in the ischemic cortex of the monkey, and those newly regenerated neurons could survive over 1 year. Moreover, this approach not only significantly increased the neuronal density and synaptic formation, but also reduced the number of reactive microglia and macrophages.⁷¹ Although these results suggest direct neuronal reprogramming in vivo seems an effective therapy to regenerate new neurons in NHP following stroke, further studies are still needed to repeatedly verify the safety and stability of in vivo gene operation.

Presently, clinical implementation of neuronal replacement therapy for tissue repair and functional restoration is distant. However, these strategies offer expanded therapeutic time window expansions from hours to months and provided treatment options for subacute and chronic stroke patients, so neuronal replacement therapy should be actively pursued in the preclinical and translational space.⁷² Currently, although the safety of these approaches has been initially demonstrated in NHP, further attention should be given to improving neural survival rate, identifying lesion-specific neuronal phenotypes, monitoring neural activity and testing neuroplasticity functional integration in NHP stroke models. Thus, the establishment of chronic models of NHP allowing long-term imaging and neurological readouts are important to accelerate and improve clinical translation of neuronal replacement strategies for stroke.

NHP species used in stroke study

NHP is classified as a gyrencephalic primate whose brains have a highly folded cortex and a lissencephalic primate whose brains have a smaller number of cortical sulci.⁷³ They could also be divided into New World monkeys and Old World monkeys in accordance with different habitats.⁷⁴ Of them, most Old World monkeys belong to gyrencephalic species. Table 1 summarizes the species, common name, gyrification,⁷⁵ habitat, body weight,^76,77 and precision grip of the NHP that are commonly used in stroke studies.

Table 1.

NHP species used in ischemic stroke research.

Species	Common name	Brain structure^a	Habitat origin	Body weight^b	Precision grip
Macaca mulatta	Rhesus macaque	Gyrencephalic	Old World monkey	3900 g	Capable
Macaca fascicularis	Cynomolgus macaque	Gyrencephalic	Old World monkey	5700 g	Capable
Macaca fuscata	Japanese monkey	Gyrencephalic	Old World monkey	8012 g	Capable
Papio anubis	Baboon	Gyrencephalic	Old World monkey	8000 g	Capable
Cercopithecus pygerithus	African green monkey	Gyrencephalic	Old World monkey	4000 g	Capable
Cebus apella	Vervet monkey	Gyrencephalic	New World monkey	3340 g	Incapable
Callithrix jacchus	Common marmoset	Lissencephalic	New World monkey	361 g	Incapable
Saimiri sciureus	Squirrel monkey	Lissencephalic	New World monkey	860 g	Incapable
Aotus lemurinus	Owl monkey	Lissencephalic	New World monkey	925 g	Incapable
Galago senegalensis	Senegal bush baby	Lissencephalic	New World monkey	946 g	Incapable

Images of cerebral cortex of the non-human primates can be viewed in the article.⁷⁵

The information of the average body weight is referred from the articles.^76,77

The most used lissencephalic NHP species to conduct stroke experiments are the common marmoset and squirrel monkeys. Their small body size and brain volume make them easy to operate. Their relatively flat cortex allows cortical surface imaging. In addition, their sensorimotor and visual representation is on the cortical surface, which provides advantages in precise functional mapping by electrophysiological recording.⁷⁸ In addition, they are incapable of precision grip, as characterized by the absence of the ability to hold small objects between the tips of the index finger and the thumb. This disadvantage affects the behavioral assessments after stroke. Moreover, the lissencephalic brain structure is thought to be more rat-like than human-like, which adds an uncertain layer to clinical translation.⁷⁹

The most adopted gyrencephalic species are rhesus macaque and cynomolgus macaque. Such NHPs require high costs for purchasing and feeding, high standard surgical and imaging facilities, high ethical considerations, a professional veterinarian for animal anesthesia and post-operative care, and specific staff for the development and maintenance of the stroke model.⁸⁰ The COVID-19 pandemic worldwide has further aggravated the quantity shortage and substantial appreciation of the prices of macaques. Despite the above limits in economic and ethical factors, gyrencephalic NHP is the best choice for preclinical stroke study because it can better mimic the physiological symptoms after ischemic stroke.

The gyrencephalic NHP has inherent advantages, and next, we take macaques for example. Genetically, a macaque shares more than 92% of the human genomic sequence.⁸¹ Physiologically, macaques have similar long gestations, postnatal development, and lifespan.⁸² Immunologically, macaques share great similarities in leukocyte composition, fibrinolytic protein inflammatory molecules, and hemostatic components to humans.⁸³ They mimic the cerebrovascular reactions and inflammatory response to stroke in humans comprehensively. Behaviorally, macaques are capable of precision grip and bipedal walking, making them suitable for assessing sensory and motor impairment. Neuroanatomically, macaque brains closely resemble human brains on various criteria (Table 2): (1) In terms of mass, the human brain is ∼3,800 times larger than the mouse brain and ∼17 times larger than the macaque brain.⁸⁴ The encephalization quotient is a measure of brain size relative to a taxonomic standard. The encephalization quotient for humans is 7.8, that for macaques is 2.1, and that for rodents is in the 0.4–0.5 range.^84,85 The similar brain mass and size of macaques enable the evaluation of relevant clinical neuroimaging. (2) The circle of Willis in macaques is almost the same as that in humans^86–89 In addition, the distribution, branch, and diameter of the middle cerebral artery (MCA) of macaques closely resemble those of humans.^80,90,91 The similar cerebral vasculature makes it achievable to enter the circle of Willis and reach the MCA endovascularly, which allows for the establishment of an endovascular stroke model of MCAO and the production of the reproducible infraction. (3) Macaques have folded cortex,⁹² numerous cortical neurons,^93–95 a high percentage of white matter,^96–98 and greater myelination⁹⁹ compared to rodents. Thus, macaque stroke models can mimic white matter susceptibility to ischemia and the disconnection of brain connectivity in stroke patients most closely to the pathology seen in humans. (4) The similar location and termination patterns of the corticospinal tract (CST) would be beneficial for evaluating the restoration of fine motor skills and voluntary movements after stroke.^100,101

Table 2.

The neuroanatomical difference between rodents, macaques, and humans.

	Mouse	Rat	Macaque	Human	References
Brain mass	0.3 g	2.0 g	88 g	1508 g	⁸⁴
Encephalization quotient	0.5	0.4	2.1	7.8	^84,85
Circle of Willis	missing ACOA	missing ACOA	missing ACOA and single median ACA	complete circle of Willis	^86–89 ⁸⁰ ^, ^90,91
MCA diameter	–	0.35–0.58 mm	1.2 mm	2.7–3.5 mm	⁹²
Cortex	flat	flat	folded	folded	^93–95
Whole brain neurons	71 M	200 M	6376 M	86060 M	^93–95
Cerebral cortex neurons	4 M	15 M	480 M	16340 M	^96–98
GM/WM	90%/10%	88%/12%	68%/32%	55%/45%	⁹⁹
Myelination	less	less	higher	higher	^100,101
CST	Crossed CST terminations are mainly located in the dorsal and intermediate horns		Crossed CST terminations are mostly found in the contralateral intermediate and ventral horns

ACOA: anterior communicating artery; ACA: single median anterior cerebral artery; MCA: middle cerebral artery; GM: grey matter; WM: white matter; CST: corticospinal tract; -: lack data.

Although NHP is emerging as a unique stroke model with the above advantages, other animal species are encouraged to study the regeneration and pathophysiology of stroke. Recent studies suggested that a zebrafish is a powerful tool in stroke research because of live imaging in vivo, easy genetic manipulation, and rapid reproduction.¹⁰² In addition, other larger animals such as canines, swine, sheep, and cats have also been reported in stroke studies.¹⁰³ These large animals are also attractive models because of similar anatomical and physiological advantages to the human brain, easy access, low cost and accessible ethical acceptance.¹⁰⁴ Indeed, the ethical problem is particularly important because neuronal replacement would require long-term observation in disabled animals. Given the “human-like” deficits and semi-sapience of NHP, other large species may be better alternatives to test many key aspects related to neuronal replacement approaches. NHP primate experimentation, as all in vivo experimental research, should include attendance of professional veterinarians to support and implement proper intra- and postoperative care for experimental subjects. In summary, the use of NHP models should carefully balance their usefulness against logistical, financial and ethical aspects.

Focal cortical ischemia models in NHP

Currently, MCAO models of NHP are primarily used in preclinical thrombolytic therapy and neuroprotectant test.¹⁰⁵ In such models, MCAO extensively injures the cortex and subcortical basal ganglion and is associated with high mortality.¹⁰⁶ Even if NHPs survive, they generally have severe behavioral function deficits and limited functional recovery because of the large-scale brain injury.¹⁰⁷ Thus, the MCAO models of NHP are not ideal for examining the neuronal regeneration and synaptic plasticity that may underlie the recovery following stroke. A relatively smaller focal injury induced in the motor cortex causing a long-term contralateral limb movement disorder is needed to explore adaptive mechanisms that regulate motor recovery in neural regeneration strategies. Ideally, a focal cortical stroke model in NHPs needs to meet three basic criteria: 1) formation of a relatively smaller infarct size in a well-defined motor cortex; 2) persistent notable motor deficits in the contralateral limb, especially dexterous hand function impairments; and 3) a long-term survival period that enables the NHP to enter the chronic phase in which neural repair occurs. Such models are useful to study neural repair and cortical plasticity, thus providing a unique opportunity for developing neural regeneration treatments. Next, we introduce various NHP models of focal ischemic lesions targeting the primary motor cortex (M1) in detail.

Nonvascular stroke model

In nonvascular models, chemicals are injected into the cortex of the M1 area of NHP to selectively destroy neuron cell bodies to mimic ischemic injury in stroke. For gyrencephalic macaque, ibotenic acid as a neurotoxin that works through activation of N-methyl-D-aspartic acid (NMDA) receptors has been applied to establish IS model. Briefly, ibotenic acid (10 µg/µl) was injected into the hand representation of macaque using a Hamilton microsyringe. 1.0 µl of ibotenic acid was injected at 3 mm depth at each injection site, and penetration sites on the cortical surface were separated by 2 mm.¹⁰⁸ The motor cortical lesion induced by this method severely damage reach and grasp ability and cause long-lasting hand dexterity deficits in monkey.^109,110 For the lissencephalic marmoset monkey, malonate as a mitochondrial toxin causing neural energy failure and subsequent excitotoxicity is typically utilized to induce focal cortical damage. In Le Friec’s study, stereotaxic injection of 3 M malonate into the primary motor cortex causes long-lasting motor deficits of force and dexterity.¹¹¹ In summary, the above nonvascular models successfully induced a focal cortical lesion with anatomical and functional consequences comparable with ischemic stroke, while the pathophysiology obviously differs from that of stroke patients.

Electrocoagulation model

Electrocoagulation of the entire vascular bed of the target cortical tissue via microforceps has been employed to establish stroke models in lissencephalic primates with a flat cortex. The method is simple, that is, the surface vasculature over the target representation area in M1 is permanently occluded using the microforceps connected to bipolar electrocoagulation.¹¹² The border of the infarct could be visually defined because the ischemic tissue turns blanched, and no reperfusion is detected. This model produces an ischemic injury involving all cortical layers but spares the subcortical white matter. In 2003, Nudo et al.⁷⁷ found that the M1 lesions in such a model resulted in paralysis in the contralateral musculature of the distal forelimb and the disruption of the skilled hand use of squirrel monkey.¹¹³ Currently, the electrocoagulation model is widely applied to study cortical plasticity and motor functional recovery post-infraction after stroke in lissencephalic monkeys.^114,115 Taken together, surface electrocoagulation is easy operation, and induced reliable infarcts within a restricted functionally defined cortex. However, this method may affect the electrophysiological test and it is not suitable for macaques because their primary motor cortex with monosynaptic projections to motoneurons partly lies deep in the central sulcus.¹¹⁶

Endothelin-1 (ET-1) injection model

ET-1 is a 21-amino acid peptide with potent vasoconstriction properties.¹¹⁷ ET-1 injection can constrict strongly segmental vessels and reduce regional CBF within a certain period of time. Then, CBF is gradually restored as the effect fades, resulting in ischemia-reperfusion injury.¹¹⁸ The indicator of a successful ET-1-induced occlusion modeling is the vasoconstriction and blanching cortex. Compared with the direct intravascular injection of ET-1 to the MCA segment, intracortical microinjection is considered more suitable for neural regenerative study because it offers the ability to specifically target a representation of the primary motor cortex.

Cortical microinjection of ET-1 has been used to induce focal infarction in NHP. Generally, the monkey was mounted on a stereotaxic apparatus. Following exposure to the motor cortex, micro-injection of ET-1 was made according to a combined MRI and histology atlas of the monkey brain in stereotaxic coordinates.^119–121 Ge et al.⁷⁰ injected ET-1 (2 µg/µl) into the M1 area at six sites based on the stereotaxic atlas of the rhesus monkey brain. 10-µL Hamilton syringe needle was inserted 2–4 mm under the dura and injected five boluses of 500 nl with a distance of 500 µm in each site. They successfully established focal ischemic injury target monkey motor cortex. In Dai et al.’s study, ET-1 was intracortically injected into five sites (5 µg/10 µl/site) of a digit representation with an injection depth of 2.5–3.5 mm under the cortex surface.¹²² They found that ET-1-induced ischemic injury impaired the manual dexterity of the monkey within 28 days after injury.¹²² Herbert et al.¹²³ injected ET-1 (400 pmol/µl) into the shoulder/elbow representation in the M1 cortex. For the subjects with 10 injection sites and a 2.5–4.0 mm depth range, the infarcted tissue involved the precentral gyrus and caused mildly impaired skilled reach performance. Thus, these above studies confirmed that ET-1 microinjection allowed the creation of controlled ischemic lesions based on different doses and depths with low mortality and high repeatability. However, ET-1 may interfere with recovery mechanisms because ET-1 has been shown to induce astrocytosis and facilitates axonal sprouting.^124,125

Photothrombosis model

Photothrombotic stroke is a model of superficial blood vessel occlusion by using light exposure to illuminate the photosensitizer to form a microvascular thrombus.¹²⁶ Rose bengal is the most used photosensitive dye. Following intravenous infusion and circulation in the body, it could initiate chemical reactions when irradiated by a cold light source, further causing endothelial damage, platelet activation, and thrombosis.¹²⁷ Ikeda et al.¹²⁸ applied a photothrombotic method on the lissencephalic marmoset. Specifically, following an intravenous injection of rose bengal (20 mg/kg), green light (533 nm, with 8 mm diameter) was irradiated on the intact skull-covered sensorimotor cortex for 5 min. They successfully created a cortical infraction causing obvious motor functional impairment. Zhu et al.¹²⁹ established a photothrombotic stroke model on gyrencephalic cynomolgus macaques. In surgery, the skull and cerebral dura mater were removed to expose the cortex followed by an intravenous injection of rose bengal (35 mg/kg), then cold light (SCHOTT KL 1500 LCD) was irradiated on the target cortex for 10 min. Later, Yang et al.¹³⁰ applied a green light source on both the M3 segment of the MCA and the adjacent gyrus of macaques for 20 min. Both experimental procedures cause stable focal cortical ischemic injury and contralateral forelimb paralysis in macaques. The local blood flow interruption by this method leads to cerebral edema and neural necrosis in the irradiated area, which are similar to the pathological changes in clinical stroke. The most attractive advantage of this method is the simple process and low cost, making it widely used in a primate model. Meanwhile, its disadvantage is the lack of an ischemic penumbra and the absence of collateral circulation.

Clamp model

In addition to damaging the sensorimotor cortex directly in the above methods, occlusion of the cortical branches of MCA also produces a consistent cortical infraction. The key to this method is to block the M3 or distal M2 branches of the MCA supplying cerebral blood to the M1 area exclusively and accurately. In brief, craniotomy is performed on the lateral temporal bone of the skull, and the dura mater is separated from the tissue. Subsequently, M3 in the Sylvian insular cistern is exposed via the standard microsurgical technique. Two aneurysm clips are placed about 3 mm between them, occluding the M3 segment. Finally, the clips are removed after 90 min of occlusion, and reperfusion is achieved. McEntire et al.¹³¹ utilized this method and successfully produced a necrotic infarct localized in the sensorimotor cortex, which resulted in a significant loss of fine motor function characterized by impaired dexterity. The main advantage of this model is precise infarction with a high success rate and visual confirmation of MCAO. Additionally, this method allows subsequent reperfusion of ischemic tissue when the clip is withdrawn. The main disadvantage is the relatively large traumatic craniotomy, which brings pains to affect monkeys psychologically and physiologically. In addition, the mechanical external obstruction of MCA differs from the clinical pathophysiological processes of natural stroke.

Endovascular stroke model

To mimic the thrombotic cerebrovascular occlusion, endovascular models using interventional methods have been established.¹³² Common emboli for inducing an endovascular MCAO model in NHPs include glue,¹³³ microbeads,^134,135 microcatheters,¹³⁶ balloons,^137,138 autologous blood clot,¹³⁹ microcoils,¹⁴⁰ and silks.¹⁴¹ Notably, only thinner intraluminal devices such as microcoils and silks with sufficiently small diameters are able to block the upper trunk of the M2 even M3 segment specifically causing cortical damage. Zhao et al.¹⁴² introduced a microcoil (1 mm × 10 cm) into the distal M2 segment to occlude the artery for 2 hours in rhesus monkeys, and produced the ischemic infarct area around the Sylvian fissure, including the upper part of Brodmann 4 and 6 areas, which correspond to the distal forelimb in the cortex of primates. In addition, delivery of multiple 5 mm segments of 4–0 silk sutures to the M3 branches of MCA also purely caused cortical strokes without deep nuclei involvement.^143,144 These endovascular models are reproducible, minimally invasive, minimize pain and distress, spare the deep nuclei, and allow serial behavioral assessments in monkeys. However, this method needs high technological requirements and professional operation neurosurgeons.

In summary, the above different methods can produce cortical ischemic injury in NHPs. These methods can be divided into transcranial and endovascular approaches in accordance with the different paths into the brain. In addition, these methods establish a permanent ischemic stroke model or an ischemia-reperfusion model on the basis of whether CBF is restored. Notably, the electrocoagulation method is only suitable for lissencephalic NHP, while the endovascular method only applies to large gyrencephalic NHP. We draw a brief schematic of all the mentioned methods (Figure 1) and describe the advantages and disadvantages of each method (Table 3). Researchers should choose the most appropriate model on the basis of the NHP species, experimental condition, and research purpose comprehensively.

Figure 1.

Schematic diagram of the method for establishing an ischemic stroke model targeting the primary motor cortex in NHP. (a) Nonvascular ischemic stroke model and ET-1 injection model. Chemicals (ibotenic acid or malonate) or vasoconstrictor substance (ET-1) are injected into the target cortex by using a microinjection. (b) Electrocoagulation model. Electrocoagulation of the entire vascular bed of the target cortical tissue is conducted using microforceps. (c) Photothrombosis model. After intravenous injection of rose bengal, photoirradiation is performed on the target cortex or the M3 segment of the MCA. (d) Clamp model. Clips are used to clamp the M3 segment of the MCA. (e) Endovascular stroke model. MicroCoils are placed after entering the upper trunk of the M2 segment through the microcatheter and (f) Endovascular stroke model. Silk sutures are placed after entering the M3 segment through a catheter.

Table 3.

Different methods for establishing ischemic models in NHP.

Methods	Operation	Applicable species	Ischemia	Advantages	Disadvantages	References
Nonvascular models	Transcranial	Both	Non-ischemia	Accurate positioning	Unsimilar pathophysiology	^108–111
Electrocoagulation	Transcranial	Lissencephalic	Permanent	Easy operation	May affect electrophysiological test	^77,112–115
ET-1 injection	Transcranial	Both	Transient	Good repeatability	May interfere with recovery mechanisms	^70,122,123
Photothrombosis	Transcranial	Both	Permanent	Similar to cerebral embolism	lack of a penumbra and collateral blood flow	^128–130
Clamp model	Transcranial	Gyrencephalic	Transient	Precise infarction with high rate	Relatively large wound influences NHP	¹³¹
Endovascular model	Intervention	Gyrencephalic	Transient	Minimally invasive	High technological requirements	^142–144

Outcome measures

In the preclinical stroke study of regenerative therapy in NHP, objective measurement of infraction volume, CBF, and neurobehavioral outcomes is an initial step to judge the validity of interventions. In addition, further evidence of the long-term survival of newborn neurons, synaptic integration in host networks, and functional circuitry repair is essential for mechanistic investigation. Through the tests of neuroimaging, histology, electrophysiology, optogenetics, chemical genetics, single-cell sequencing, virus tracing, and behavior examination, we obtain a clinically and experimentally accessible neurological evaluation to improve the clinical translation of neuronal replacement therapy.

Infarction volume

Stroke patients with larger infarcts generally have worse neurological deficits,¹⁴⁵ so infarction volume measurement is essential to predict functional outcomes. At 24 h after ischemic injury in NHP, infarction volume could be detected by pathological and neuroimaging examination. Nissl's staining solution reacts with the Nissl body in neurons, then clearly discerns the necrotic neurons in the infraction of NHP.^146,147 Hematoxylin–eosin (H&E) staining could reflect not only neural death but also inflammatory infiltration and glial proliferation after stroke.¹⁴⁸ 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining is the most common pathological method for evaluating infarction volume. Nevertheless, TTC staining is generally not applicable to the assessment of infarctions in the chronic stage of stroke.^149,150

Imaging evaluation is also important for assessing infarction volume in NNP stroke. Structural magnetic resonance imaging (MRI) visually shows the size of the ischemic infarction and the volume involved. Ramirez-Garcia et al.¹⁵¹ used MRI to dynamically monitor the infarction size after occlusion of MCA and found that the infarction size correlated with the behavioral sore after stroke in cynomolgus macaques. However, MRI sometimes fails to show the infarct areas in the acute stage (within 4.5 h). By contrast, diffusion weighted imaging (DWI) can reflect the ischemic size and location within minutes after stroke by a quick examination of rapid changes in intracellular and extracellular water contents. Cooke et al.¹³⁴ demonstrated that DWI hyperintensities correspond to histological infarctions stained with H&E in cynomolgus macaques. In addition, diffusion tensor imaging (DTI) is used to visualize the conductive fibers in the neurofunctional region. Chin et al.¹⁵² used DTI and found a significant decrease in fractional anisotropy in the internal capsule of a monkey after 7 days of stroke. Collectively, neuroimaging evaluation is an important non-invasive tool to dynamically monitor the infarction volume of NHPs in vivo.

Regional CBF

Imaging evaluation methods are required to examine changes in vascular occlusion and to confirm the success of cerebral ischemia models during surgery. Transcranial Doppler ultrasound (TCD),¹⁵³ computed tomography angiography (CTA),¹³⁵ digital subtraction angiography (DSA),¹⁵⁴ and magnetic resonance angiography (MRA)¹⁵⁵ arterial spin labeling (ASL)¹⁵⁶ are commonly used to clearly show the interruption or refusion in blood flow during operation in NHP stroke study. To further reflect ischemic changes in brain tissue after the operation, positron emission tomography (PET) is commonly used to monitor CBF, the cerebral metabolic rate of oxygen (CMRO₂), oxygen extraction fraction, and local cerebral blood volume. Takamatsu et al.¹⁵⁷ conducted PET studies and detected the neuroprotective effects of FK-506 only in areas with >40% CMRO₂ reduction at 3 h after reperfusion in cynomolgus monkeys. Perfusion weighted imaging (PWI) also reliably reflects cerebral perfusion through the measurement of relative CBF, relative cerebral blood volume (CBV), and mean transit time. Yi et al.¹⁵⁸ analyzed CBV/CBF maps, which demonstrated a diffusion–perfusion match after the stroke of rhesus macaques. Taken together, there are various available imaging methods for evaluating vascular occlusion and cerebral infarction in NHP. Although high spatial and temporal resolution, expensive testing costs limit its applications to some degree in NHP studies.

Neurobehavioral assessment

Outcome measurements in NHP stroke studies generally focus on neurological functions, including motor, sensory, and cognitive performance. Correspondingly, a series of NHP stroke scales are used to evaluate neurobehavioral outcomes.¹⁰⁶ However, these neurological scales lack a unified standard and rely on the expertise of the examiner. To quantify reparative functional outcomes and improve clinical translation, these scales need to be supplemented by behavioral assessments. Thus, hill and valley, two-tube, and six-well tasks are required to test the limb mobility and space exploration ability of NHP.¹⁵⁹ Additionally, the food reward retrieval tests, such as Klüver board, Brinkman board, and vertical slot tasks are used to evaluate the digit grasping ability.^122,140

The dexterous hand functional test is especially important in cortical ischemic injury targeting M1. In the acute stage of stroke, NHP animals spent a longer time retrieving food and showed decreased successful retrievals. However, spontaneous recovery of manual dexterity improved the scores in the behavioral tasks and even recovered to preoperative levels in the chronic stage.¹⁶⁰ In this regard, researchers generally recorded behavioral tasks using a digital video camera for kinematic analyses by calculating detailed indexes, such as the flexion of the index finger, coordinates of the tip of the thumb, joint angle, operation time, and grasping forms.¹⁶¹ Murata et al.¹⁰⁸ analyzed digit movements frame by frame and found that the behavioral indexes of manual dexterity remained lower until months after M1 lesions. The damaged monkeys frequently used alternate grip strategies to grasp a small object with the affected hand. Thus, comprehensive analysis of stroke scales and behavioral test especially fine manual performance is helpful for researchers to track the functional recovery after stroke after NHP receive neural replacement therapy.

Neural regeneration and repair

Indeed, any neural replacement strategies need to demonstrate that the behavioral recovery is due to the substitution of dying ischemic neurons by newborn neurons, that is providing a causative link between neuronal replacement and behavior improvement. Thus, the newborn neural long-survival, subtype, activity, synaptic formation and functional connectivity with the host are needed to study. First, stroke-induced activation of NSCs and proliferation of neural progenitor cells (IPC) should be detected using mitotic indicators such as 5-bromodeoxyuridine (BrdU) by immunochemistry.^9,162 Second, newborn neurons should survive and fully mature into the neuronal subtype lost with the pathology and restructure the site-specific phenotypes and tissue architecture. Single-cell transcriptomics is an advanced technique for identifying neurogenic-related cell types and differentiation trajectories.^8,10 Third, electrophysiological recording,^163–165 calcium imaging,^166,167 and functional magnetic resonance imaging (fMRI)¹⁶⁸ allow monitoring of adult-born neuronal activity. Fourth, electron microscopy¹⁶⁹ and quantitative analysis of synaptophysin¹⁷⁰ are needed to identify synaptogenesis. Monosynaptic virus tracing and MED64 system are necessary to confirm synaptic contacts between host cells and newborn neurons.^171,172 Fifth, newborn neurons should functionally integrate into the host brain circuitry. Transcranial magnetic stimulation could noninvasively test the cortical motor function by recording the motor evoked potential (MEP) following the magnetic stimulus delivered over the primary motor cortex.¹⁷³ Finally, optogenetic and chemogenetic technology that selectively silences or activates newborn neurons allows for assessing the contribution of regenerative neurons to functional recovery.^174–176 We draw a brief schematic of all the mentioned methods applied in the neural replacement study (Figure 2) and summarize the advantages and disadvantages of each technological approach (Table 4).

Figure 2.

Schematic summary of the technological approaches used to study neural regeneration in neuronal replacement strategies. Combination of “traditional” techniques, such as immunochemistry, electron microscopy, clinical imaging, and electrophysiological recording, and new technological tools, such as single-cell transcriptomics, virus tracing, calcium imaging, photogenetics, and chemical genetics, are needed to study neural subtype, activity, and functional connectivity with the host. (Element 5 reprinted from figure 5 in “NT3-chitosan enables de novo regeneration and functional recovery in monkeys after spinal cord injury” by Jiasheng Rao et al.).

Table 4.

The methods, applications, advantages and disadvantages of the technological approaches used to study neural replacement.

Methods	Applications	Advantages	Disadvantages
Immunofluorescence staining	To label activation of NSCs (Nestin; Vimentin, Sox2; Ascl1) To label proliferation of IPCs (DCX; PSA-NCAM); To label late differentiated neurons (Tuj1, NeuN, MAP2); To label cell proliferation (BrdU, IdU, EdU, Ki67, PHH3); To label synaptogenesis (PSD95, Synapsin1, vGltu1, Homer1); To label cortical layer cytoarchitecture (Tbr1, Satb2, Ctip2, foxp2)	Easy operation; Stable and reliable markers in NHP; Widely used in morphology study and cell count in neural regeneration.	Only applied in postmortem study; Need strict fixation conditions and procedures.
Single-cell transcriptomics	To Identify neurogenic-related cell types, specification trajectories, species differences, and biological function.	High-throughput; Single cell resolution; Providing more molecular details.	High cost; Limited capture rate.
Patch clamp	To record membrane passive properties (RMP, R_input, C_m), intrinsic excitability (AP, Rheobase and Gain) and synaptic excitability (sEPSC, mEPSC, LPP) of new-born neurons in vitro.	Providing more details of eletrophysilogical properties of new-born neurons.	Time and labor consuming; The new-born neuros in biomaterials are easily lost during preparation of acute slices.
Calcium imaging	To quantitatively motor activity of new-born neurons and dendritic spines in alive animals in vivo.	Single cell resolution; High temporal resolution; Visualizing intracellular calcium levels in hundreds of neurons simultaneously.	Limited to monitoring superficial cortical layers; Need imaging system such as two-photon microscopy.
fMRI	Resting-state fMRI to analyze functional connectivity changes; Functional fMRI to detect BOLD signals in corresponding primary somatosensory cortex following a thermal stimuli of the contralateral limbs.	Non-invasive; High spatial and temporal resolution; Dynamically observe neural activity in vivo.	High cost; High technological requirements.
Electron microscopy	To detect synaptic ultrastructure between regenerated neurons.	Providing details of subcellular structure.	Unable to observe live samples; Complicated and difficult sample preparation process.
MED64 system	To record fEPSPs to reflect the electrophysiological connectivity of new neural networks in vitro.	High-throughput; Sensitive to provide high-quality data; Acquire signal from 64 electrodes simultaneously.	Need high tissue viability; The new-born neuros in biomaterials are easily lost during preparation of acute slices.
Tracer method	To tracke synaptic connectivity between host neurons and new-born neuros by BDA or tracing virus with neuronal promoters.	Tracer carrying fluorescent dye visualize synaptic projections and input maps; Combined with tissue clearing, it enable fluorescence imaging in 3D stained tissue, preserving anatomical structures.	The resolution does not allow visualization at the level of individual cell. NHP- specific virus tracer is limited.
Transcranial magnetic stimulation	To record MEP from contralateral muscles following delivery of brief magnetic stimulus over the primary motor cortex.	Easy operation; Non-invasively tests cortical motor function in alive animals.	The reported negative predictive values for MEP status range between 72% and 95%.
Optogenetics	To confirm functional synaptic connectivity between host neurons with new-born neuros by modify electrophysiological properties of specific set of neurons that express opsin proteins sensitive to light of particular wavelength.	Millisecond temporal precision; Single cell spatial resolution; Precise optical controls of specific set of neurons.	Requires advanced surgical skill; Potential heat damage to tissue; Unsuited for long-scale or high-quantity silencing.
Chemical genetics	To assess the contribution of new-born neuronal activity to functional recovery by silencing or activing new-born neuros using DREADDs.	Non-invasive; Nontoxic DREADDs and its ligands; Precise manipulate the signaling pathway of specific GPCR.	Less temporally precise; Systemic administration of CNO agonist depends on metabolism for “off” switch.

NSCs: neural stem cells; IPCs: neural progenitor cells; NHP: non-human primate; RMP: resting membrane potential; R_input: membrane input resistance; Cm: membrane capacitance; AP: action potential; sEPSC: spontaneous excitatory postsynaptic currents; mEPSCs: miniature excitatory postsynaptic currents; LPP: lateral perforant path; fMRI: functional magnetic resonance imaging; BOLD: blood oxygenation level-dependent; fEPSPs: field excitatory post-synaptic potential; BDA: biotinylated dextran amine; MEP: motorevoked potential; DREADDs: designer receptors exclusively activated by designer drugs; GPCRs: G-protein-coupled receptors; CNO: clozapine-N-oxid.

Conclusions

For designing NHP preclinical stroke studies of neuronal replacement strategies, we draw a program flowchart to address three major questions: What NHP species should be selected? Which focal ischemic model should be established? How to measure functional recovery and the underlying mechanism (Figure 3)? NHP is a link between basic research and clinical application because NHP closely resembles humans. The NHP stroke models that damage the cortex targeting M1 are more suitable for the study of neurological deficits caused by long-term cerebral infarction. The researchers should choose the most appropriate NHP stroke models by analyzing the advantages and disadvantages of each model.

Figure 3.

Flowchart describing the most relevant aspects to consider when designing an NHP stroke model in the preclinical study of neuronal replacement strategies. NHP species, stroke model, and outcome measurements are the three major aspects needed to address.

Stroke study in NHP pose significant challenges, including specialized infrastructure, strict ethical considerations, high imaging cost, strict tissue fixation procedures, complex neurobehavioral assessment, and limited application of NHP specific tracer and antibodies. In our view, NHP stroke studies of neuronal replacement should only be undertaken for promising therapies that have been fully tested in rodent species and other lower species. To better enhance the predictive power of NHP in preclinical stroke study, the multi-center preclinical trials by collaborative groups, and more funding from industry support or publicly programs will likely be required. Work of the past decade fueled by technical advances, such as single-cell sequencing, electrophysiology, virus tracing, and photogenetics, would further amplify our knowledge of neuronal circuitry and diversity. In addition, behavioral evaluation and chemical genetic analysis are essential to better quantify a high level of specificity when newborn neurons participate in behavioral recovery following stroke.

Footnotes

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by National Natural Science Foundation of China (Grants 31730030, 31971279, 82272171, 82271403, 82201542, 81941011, 31771053 and 31900749), Beijing Natural Science Foundation (Grant 7222004), and The Key Research and Development Program of Guangzhou (Grant 202206060003).

Acknowledgements

We would like to thank Jiasheng Rao (School of Engineering Medicine, Beihang University, China), and the anonymous reviewers for providing useful comments on the manuscript.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

ORCID iD

Xiaoguang Li

References

Campbell

BCV

De Silva

Macleod

, et al. Ischaemic stroke. Nat Rev Dis Primers 2019; 5: 70.

Mendelson

Prabhakaran

Diagnosis and management of transient ischemic attack and acute ischemic stroke: a review. JAMA 2021; 325: 1088–1098.

Hara

Brain plasticity and rehabilitation in stroke patients. J Nippon Med Sch 2015; 82: 4–13.

Przysada

Leszczak

Baran

, et al. Impact of a rehabilitation program on the change in components of body mass of the upper and lower limbs in people after ischemic stroke. Med Sci Monit 2022; 28: e936397.

Avan

Hachinski

Stroke and dementia, leading causes of neurological disability and death, potential for prevention. Alzheimers Dement 2021; 17: 1072–1076.

Ilves

Lõo

Ilves

, et al. Ipsilesional volume loss of basal ganglia and thalamus is associated with poor hand function after ischemic perinatal stroke. BMC Neurol 2022; 22: 23.

Götz

Bocchi

Neuronal replacement: concepts, achievements, and call for caution. Curr Opin Neurobiol 2021; 69: 185–192.

Hao

Wei

Xiao

, et al. Single-cell transcriptomics of adult macaque hippocampus reveals neural precursor cell populations. Nat Neurosci 2022; 25: 805–817.

Terreros-Roncal

Moreno-Jiménez

Flor-García

, et al. Impact of neurodegenerative diseases on human adult hippocampal neurogenesis. Science 2021; 374: 1106–1113.

10.

Zhou

, et al. Molecular landscapes of human hippocampal immature neurons across lifespan. Nature 2022; 607: 527–533.

11.

Grade

Götz

Neuronal replacement therapy: previous achievements and challenges ahead. NPJ Regen Med 2017; 2: 29.

12.

Grønning Hansen

Laterza

Palma-Tortosa

, et al. Grafted human pluripotent stem cell-derived cortical neurons integrate into adult human cortical neural circuitry. Stem Cells Transl Med 2020; 9: 1365–1377.

13.

Tornero

Tsupykov

Granmo

, et al. Synaptic inputs from stroke-injured brain to grafted human stem cell-derived neurons activated by sensory stimuli. Brain 2017; 140: 692–706.

14.

Tornero

Wattananit

Grønning Madsen

, et al. Human induced pluripotent stem cell-derived cortical neurons integrate in stroke-injured cortex and improve functional recovery. Brain 2013; 136: 3561–3577.

15.

Jiang

Wei

, et al. Conversion of reactive astrocytes to induced neurons enhances neuronal repair and functional recovery after ischemic stroke. Front Aging Neurosci 2021; 13: 612856.

16.

Nih

Gojgini

Carmichael

, et al. Dual-function injectable angiogenic biomaterial for the repair of brain tissue following stroke. Nat Mater 2018; 17: 642–651.

17.

Chamorro

Renú

, et al. The future of neuroprotection in stroke. J Neurol Neurosurg Psychiatry 2021; 92: 129–135.

18.

Kaur

Prakash

Medhi

Drug therapy in stroke: from preclinical to clinical studies. Pharmacology 2013; 92: 324–334.

19.

Dirnagl

Bench to bedside: the quest for quality in experimental stroke research. J Cereb Blood Flow Metab 2006; 26: 1465–1478.

20.

Recommendations for standards regarding preclinical neuroprotective and restorative drug development. Stroke 1999; 30: 2752–2758.

21.

Fisher

Feuerstein

Howells

, et al. Update of the stroke therapy academic industry roundtable preclinical recommendations. Stroke 2009; 40: 2244–2250.

22.

del Zoppo

GJ.

The neurovascular unit in the setting of stroke. J Intern Med 2010; 267: 156–171.

23.

Hawkins

Davis

TP.

The blood-brain barrier/neurovascular unit in health and disease. Pharmacol Rev 2005; 57: 173–185.

24.

Savitz

Baron

J-C

Fisher

, et al. Stroke treatment academic industry roundtable X: brain cytoprotection therapies in the reperfusion era. Stroke 2019; 50: 1026–1031.

25.

Lyden

Buchan

Boltze

, et al. Top priorities for cerebroprotective studies – a paradigm shift: report from STAIR XI. Stroke 2021; 52: 3063–3071.

26.

Lyden

PD.

Cerebroprotection for acute ischemic stroke: looking ahead. Stroke 2021; 52: 3033–3044.

27.

Lyden

Lamb

Kothari

, et al. Differential effects of hypothermia on neurovascular unit determine protective or toxic results: toward optimized therapeutic hypothermia. J Cereb Blood Flow Metab 2019; 39: 1693–1709.

28.

Saver

Chaisinanunkul

Campbell

BCV

, et al. Standardized nomenclature for modified Rankin scale global disability outcomes: consensus recommendations from stroke therapy academic industry roundtable XI. Stroke 2021; 52: 3054–3062.

29.

Nottebohm

Neuronal replacement in adult brain. Brain Res Bull 2002; 57: 737–749.

30.

Baker

Kinder

West

FD.

Neural stem cell therapy for stroke: a multimechanistic approach to restoring neurological function. Brain Behav 2019; 9: e01214.

31.

González-Nieto

Fernández-Serra

Pérez-Rigueiro

, et al. Biomaterials to neuroprotect the stroke brain: a large opportunity for narrow time windows. Cells 2020; 9: 1074.

32.

Kung

Chen

HI.

Cell therapy for stroke: a mechanistic analysis. Neurosurgery 2021; 88: 733–745.

33.

Dihné

Hartung

Seitz

RJ.

Restoring neuronal function after stroke by cell replacement: anatomic and functional considerations. Stroke 2011; 42: 2342–2350.

34.

Nih

Sideris

Carmichael

, et al. Injection of microporous annealing particle (MAP) hydrogels in the stroke cavity reduces gliosis and inflammation and promotes NPC migration to the lesion. Adv Mater 2017; 29: 1606471.1-1606471.8.

35.

Samal

Segura

Injectable biomaterial shuttles for cell therapy in stroke. Brain Res Bull 2021; 176: 25–42.

36.

Dabrowska

Andrzejewska

Lukomska

, et al. Neuroinflammation as a target for treatment of stroke using mesenchymal stem cells and extracellular vesicles. J Neuroinflammation 2019; 16: 178.

37.

Ghuman

Mauney

Donnelly

, et al. Biodegradation of ECM hydrogel promotes endogenous brain tissue restoration in a rat model of stroke. Acta Biomater 2018; 80: 66–84.

38.

Palma-Tortosa

Coll-San Martin

Kokaia

, et al. Neuronal replacement in stem cell therapy for stroke: filling the gap. Front Cell Dev Biol 2021; 9: 662636.

39.

Sanchez-Rojas

Gómez-Pinedo

Benito-Martin

, et al. Biohybrids of scaffolding hyaluronic acid biomaterials plus adipose stem cells home local neural stem and endothelial cells: implications for reconstruction of brain lesions after stroke. J Biomed Mater Res B Appl Biomater 2019; 107: 1598–1606.

40.

Bible

Qutachi

Chau

, et al. Neo-vascularization of the stroke cavity by implantation of human neural stem cells on VEGF-releasing PLGA microparticles. Biomaterials 2012; 33: 7435–7446.

41.

Jendelová

Kubinová

Sandvig

, et al. Current developments in cell- and biomaterial-based approaches for stroke repair. Expert Opin Biol Ther 2016; 16: 43–56.

42.

Chrostek

Fellows

Crane

, et al. Efficacy of stem cell-based therapies for stroke. Brain Res 2019; 1722: 146362.

43.

Rodriguez-Polo

Behr

Non-human primate pluripotent stem cells for the preclinical testing of regenerative therapies. Neural Regen Res 2022; 17: 1867–1874.

44.

Banerjee

Bentley

Hamady

, et al. Intra-arterial immunoselected CD34+ stem cells for acute ischemic stroke. Stem Cells Transl Med 2014; 3: 1322–1330.

45.

Friedrich

Martins

Araújo

, et al. Intra-arterial infusion of autologous bone marrow mononuclear cells in patients with moderate to severe Middle cerebral artery acute ischemic stroke. Cell Transplant 2012; 21 Suppl 1: S13–21.

46.

Honmou

Houkin

Matsunaga

, et al. Intravenous administration of auto serum-expanded autologous mesenchymal stem cells in stroke. Brain 2011; 134: 1790–1807.

47.

Kalladka

Sinden

Pollock

, et al. Human neural stem cells in patients with chronic ischaemic stroke (PISCES): a phase 1, first-in-man study. Lancet 2016; 388: 787–796.

48.

Muir

Bulters

Willmot

, et al. Intracerebral implantation of human neural stem cells and motor recovery after stroke: multicentre prospective single-arm study (PISCES-2). J Neurol Neurosurg Psychiatry 2020; 91: 396–401.

49.

Savitz

Misra

Kasam

, et al. Intravenous autologous bone marrow mononuclear cells for ischemic stroke. Ann Neurol 2011; 70: 59–69.

50.

Steinberg

Kondziolka

Wechsler

, et al. Two-year safety and clinical outcomes in chronic ischemic stroke patients after implantation of modified bone marrow-derived mesenchymal stem cells (SB623): a phase 1/2a study. J Neurosurg 2019; 131: 1462–1472.

51.

Boese

Pham

, et al. Neural stem cell therapy for subacute and chronic ischemic stroke. Stem Cell Res Ther 2018; 9: 154.

52.

Lee

Cha

, et al. Long-term survival and differentiation of human neural stem cells in nonhuman primate brain with no immunosuppression. Cell Transplant 2015; 24: 191–201.

53.

Roitberg

Mangubat

Chen

, et al. Survival and early differentiation of human neural stem cells transplanted in a nonhuman primate model of stroke. J Neurosurg 2006; 105: 96–102.

54.

Purvis

O'Donnell

Chen

, et al. Tissue engineering and biomaterial strategies to elicit endogenous neuronal replacement in the brain. Front Neurol 2020; 11: 344.

55.

Cui

Liu

Jin

, et al. The protective effect of polyethylene glycol-conjugated urokinase nanogels in rat models of ischemic stroke when administrated outside the usual time window. Biochem Biophys Res Commun 2020; 523: 887–893.

56.

Esteban-Garcia

Nombela

Garrosa

, et al. Neurorestoration approach by biomaterials in ischemic stroke. Front Neurosci 2020; 14: 431.

57.

Cooke

Wang

Morshead

, et al. Controlled epi-cortical delivery of epidermal growth factor for the stimulation of endogenous neural stem cell proliferation in stroke-injured brain. Biomaterials 2011; 32: 5688–5697.

58.

Fujioka

Kaneko

Ajioka

, et al. β1 integrin signaling promotes neuronal migration along vascular scaffolds in the post-stroke brain. EBioMedicine 2017; 16: 195–203.

59.

Nakaguchi

Jinnou

Kaneko

, et al. Growth factors released from gelatin hydrogel microspheres increase new neurons in the adult mouse brain. Stem Cells Int 2012; 2012: 915160.

60.

Wang

Cooke

Morshead

, et al. Hydrogel delivery of erythropoietin to the brain for endogenous stem cell stimulation after stroke injury. Biomaterials 2012; 33: 2681–2692.

61.

Bjugstad

Redmond

Jr Lampe

, et al. Biocompatibility of PEG-based hydrogels in primate brain. Cell Transplant 2008; 17: 409–415.

62.

Cook

Nguyen

Chun

, et al. Hydrogel-delivered brain-derived neurotrophic factor promotes tissue repair and recovery after stroke. J Cereb Blood Flow Metab 2017; 37: 1030–1045.

63.

Kawaguchi

Haida

Ohba

, et al. Liposome-encapsulated hemoglobin ameliorates ischemic stroke in nonhuman primates: longitudinal observation. Artif Organs 2013; 37: 904–912.

64.

Kawaguchi

Haida

Yamano

, et al. Liposome-encapsulated hemoglobin ameliorates ischemic stroke in nonhuman primates: an acute study. J Pharmacol Exp Ther 2010; 332: 429–436.

65.

Liou

Edwards

Martin

, et al. Neuronal reprogramming for tissue repair and neuroregeneration. Ijms 2020; 21

66.

Vasan

Park

David

, et al. Direct neuronal reprogramming: bridging the gap between basic science and clinical application. Front Cell Dev Biol 2021; 9: 681087.

67.

Zhang

Lei

Guo

, et al. Development of neuroregenerative gene therapy to reverse glial scar tissue back to neuron-enriched tissue. Front Cell Neurosci 2020; 14: 594170.

68.

Chen

Pei

, et al. A NeuroD1 AAV-based gene therapy for functional brain repair after ischemic injury through in vivo astrocyte-to-neuron conversion. Mol Ther 2020; 28: 217–234.

69.

Livingston

Lee

Daniele

, et al. Direct reprogramming of astrocytes to neurons leads to functional recovery after stroke. bioRxiv 2020; 2020: 929091.

70.

Yang

, et al. In vivo neuroregeneration to treat ischemic stroke through neuroD1 AAV-based gene therapy in adult non-human primates. Front Cell Dev Biol 2020; 8: 590008.

71.

Zhang

Chen

Wang

Commentary: in vivo neuroregeneration to treat ischemic stroke through neurod1 AAV-based gene therapy in adult non-human primates. Front Cell Dev Biol 2021; 9: 648020.

72.

Boltze

Modo

Mays

, et al. Stem cells as an emerging paradigm in stroke 4: advancing and accelerating preclinical research. Stroke 2019; 50: 3299–3306.

73.

Higo

Non-human primate models to explore the adaptive mechanisms after stroke. Front Syst Neurosci 2021; 15: 760311.

74.

Gabi

Collins

Wong

, et al. Cellular scaling rules for the brains of an extended number of primate species. Brain Behav Evol 2010; 76: 32–44.

75.

Gonzales

Benefit

McCrossin

, et al. Cerebral complexity preceded enlarged brain size and reduced olfactory bulbs in old world monkeys. Nat Commun 2015; 6: 7580.

76.

Herculano-Houzel

Collins

Wong

, et al. Cellular scaling rules for primate brains. Proc Natl Acad Sci U S A 2007; 104: 3562–3567.

77.

Nudo

Larson

Plautz

, et al. A squirrel monkey model of poststroke motor recovery. ILAR J 2003; 44: 161–174.

78.

Shuaib

Lees

Lyden

, et al. NXY-059 for the treatment of acute ischemic stroke. N Engl J Med 2007; 357: 562–571.

79.

Fukuda

del Zoppo

GJ.

Models of focal cerebral ischemia in the nonhuman primate. ILAR J 2003; 44: 96–104.

80.

Grow

McCarrey

Navara

CS.

Advantages of nonhuman primates as preclinical models for evaluating stem cell-based therapies for Parkinson's disease. Stem Cell Res 2016; 17: 352–366.

81.

Phillips

Bales

Capitanio

, et al. Why primate models matter. Am J Primatol 2014; 76: 801–827.

82.

Sharp

Jickling

GC.

Modeling immunity and inflammation in stroke: differences between rodents and humans?

Stroke 2014; 45: e179–180.

83.

Tsintou

Dalamagkas

Makris

Taking central nervous system regenerative therapies to the clinic: curing rodents versus nonhuman primates versus humans. Neural Regen Res 2020; 15: 425–437.

84.

Roth

Dicke

Evolution of the brain and intelligence. Trends Cogn Sci 2005; 9: 250–257.

85.

Roth

Dicke

Evolution of the brain and intelligence in primates. Prog Brain Res 2012; 195: 413–430.

86.

Dorr

Sled

Kabani

Three-dimensional cerebral vasculature of the CBA mouse brain: a magnetic resonance imaging and micro computed tomography study. Neuroimage 2007; 35: 1409–1423.

87.

Kapoor

Kak

Singh

Morphology and comparative anatomy of circulus arteriosus cerebri in mammals. Anat Histol Embryol 2003; 32: 347–355.

88.

Lee

RM.

Morphology of cerebral arteries. Pharmacol Ther 1995; 66: 149–173.

89.

Zaninovich

Ramey

Walter

, et al. Completion of the circle of Willis varies by gender, age, and indication for computed tomography angiography. World Neurosurg 2017; 106: 953–963.

90.

Fukuyama

Tsukamoto

Takizawa

, et al. Altered blood flow in cerebral perforating arteries of rat models of diabetes: a synchrotron radiation microangiographic study toward clinical evaluation of white matter hyperintensities. Geriatr Gerontol Int 2015; 15 Suppl 1: 74–80.

91.

Rai

Hogg

Cline

, et al. Cerebrovascular geometry in the anterior circulation: an analysis of diameter, length and the vessel taper. J Neurointerv Surg 2013; 5: 371–375.

92.

Mehra

Henninger

Hirsch

, et al. Preclinical acute ischemic stroke modeling. J Neurointerv Surg 2012; 4: 307–313.

93.

Azevedo

Carvalho

Grinberg

, et al. Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. J Comp Neurol 2009; 513: 532–541.

94.

Herculano-Houzel

The human brain in numbers: a linearly scaled-up primate brain. Front Hum Neurosci 2009; 3: 31.

95.

Herculano-Houzel

Kaas

JH.

Gorilla and orangutan brains conform to the primate cellular scaling rules: implications for human evolution. Brain Behav Evol 2011; 77: 33–44.

96.

Boltze

Nitzsche

Jolkkonen

, et al. Concise review: increasing the validity of cerebrovascular disease models and experimental methods for translational stem cell research. Stem Cells 2017; 35: 1141–1153.

97.

Nitzsche

Boltze

Ludewig

, et al. A stereotaxic breed-averaged, symmetric T2w canine brain atlas including detailed morphological and volumetrical data sets. Neuroimage 2019; 187: 93–103.

98.

Zhang

Sejnowski

TJ.

A universal scaling law between gray matter and white matter of cerebral cortex. Proc Natl Acad Sci U S A 2000; 97: 5621–5626.

99.

Van Essen

Donahue

Coalson

, et al. Cerebral cortical folding, parcellation, and connectivity in humans, nonhuman primates, and mice. Proc Natl Acad Sci U S A 2019; 116: 26173–26180.

100.

Lacroix

Havton

McKay

, et al. Bilateral corticospinal projections arise from each motor cortex in the macaque monkey: a quantitative study. J Comp Neurol 2004; 473: 147–161.

101.

Welniarz

Dusart

Roze

The corticospinal tract: evolution, development, and human disorders. Dev Neurobiol 2017; 77: 810–829.

102.

Chen

Xie

, et al. Zebrafish as a model for in-depth mechanistic study for stroke. Transl Stroke Res 2021; 12: 695–710.

103.

Taha

Bobi

Dammers

, et al. Comparison of large animal models for acute ischemic stroke: which model to use? Stroke 2022; 53: 1411–1422.

104.

Herrmann

Meckel

Gounis

, et al. Large animals in neurointerventional research: a systematic review on models, techniques and their application in endovascular procedures for stroke, aneurysms and vascular malformations. J Cereb Blood Flow Metab 2019; 39: 375–394.

105.

Hirouchi

Suzuki

Mitsuoka

, et al. Neuroimaging and histopathological evaluation of delayed neurological damage produced by artificial occlusion of the Middle cerebral artery in cynomolgus monkeys: establishment of a monkey model for delayed cerebral ischemia. Exp Toxicol Pathol 2007; 59: 9–16.

106.

Lin

Wang

Chen

, et al. Nonhuman primate models of ischemic stroke and neurological evaluation after stroke. J Neurosci Methods 2022; 376: 109611.

107.

Cook

Tymianski

Nonhuman primate models of stroke for translational neuroprotection research. Neurotherapeutics 2012; 9: 371–379.

108.

Kaeser

Wyss

Bashir

, et al. Effects of unilateral motor cortex lesion on ipsilesional hand's reach and grasp performance in monkeys: relationship with recovery in the contralesional hand. J Neurophysiol 2010; 103: 1630–1645.

109.

Murata

Higo

Hayashi

, et al. Temporal plasticity involved in recovery from manual dexterity deficit after motor cortex lesion in macaque monkeys. J Neurosci 2015; 35: 84–95.

110.

Yamamoto

Hayashi

Murata

, et al. Premotor cortical-cerebellar reorganization in a macaque model of primary motor cortical lesion and recovery. J Neurosci 2019; 39: 8484–8496.

111.

Le Friec

Desmoulin

Demain

, et al. A reproducible new model of focal ischemic injury in the marmoset monkey: MRI and behavioural follow-up. Transl Stroke Res 2021; 12: 98–111.

112.

Frost

Barbay

Friel

, et al. Reorganization of remote cortical regions after ischemic brain injury: a potential substrate for stroke recovery. J Neurophysiol 2003; 89: 3205–3214.

113.

Eisner-Janowicz

Barbay

Hoover

, et al. Early and late changes in the distal forelimb representation of the supplementary motor area after injury to frontal motor areas in the squirrel monkey. J Neurophysiol 2008; 100: 1498–1512.

114.

Plautz

Barbay

Frost

, et al. Post-infarct cortical plasticity and behavioral recovery using concurrent cortical stimulation and rehabilitative training: a feasibility study in primates. Neurol Res 2003; 25: 801–810.

115.

Plautz

Barbay

Frost

, et al. Effects of subdural monopolar cortical stimulation paired with rehabilitative training on behavioral and neurophysiological recovery after cortical ischemic stroke in adult squirrel monkeys. Neurorehabil Neural Repair 2016; 30: 159–172.

116.

Rathelot

Strick

PL.

Subdivisions of primary motor cortex based on cortico-motoneuronal cells. Proc Natl Acad Sci U S A 2009; 106: 918–923.

117.

Yanagisawa

Kurihara

Kimura

, et al. A novel potent vasoconstrictor peptide produced by vascular endothelial cells. Nature 1988; 332: 411–415.

118.

Virley

Hadingham

Roberts

, et al. A new primate model of focal stroke: endothelin-1-induced middle cerebral artery occlusion and reperfusion in the common marmoset. J Cereb Blood Flow Metab 2004; 24: 24–41.

119.

Frey

Pandya

Chakravarty

, et al. An MRI based average macaque monkey stereotaxic atlas and space (MNI monkey space). Neuroimage 2011; 55: 1435–1442.

120.

Huang

Heil

Brosch

Associations between sounds and actions in early auditory cortex of nonhuman primates. eLife 2019; 8: e43281.

121.

Martin

Bowden

DM.

A stereotaxic template atlas of the macaque brain for digital imaging and quantitative neuroanatomy. Neuroimage 1996; 4: 119–150.

122.

Dai

Huang

Zhang

, et al. A pilot study on transient ischemic stroke induced with endothelin-1 in the rhesus monkeys. Sci Rep 2017; 7: 45097.

123.

Herbert

Powell

Buford

JA.

Evidence for a role of the reticulospinal system in recovery of skilled reaching after cortical stroke: initial results from a model of ischemic cortical injury. Exp Brain Res 2015; 233: 3231–3251.

124.

Gadea

Schinelli

Gallo

Endothelin-1 regulates astrocyte proliferation and reactive gliosis via a JNK/c-Jun signaling pathway. J Neurosci 2008; 28: 2394–2408.

125.

Uesugi

Kasuya

Hayashi

, et al. SB209670, a potent endothelin receptor antagonist, prevents or delays axonal degeneration after spinal cord injury. Brain Res 1998; 786: 235–239.

126.

Labat-Gest

Tomasi

Photothrombotic ischemia: a minimally invasive and reproducible photochemical cortical lesion model for mouse stroke studies. JoVE 2013; 76: 50370.

127.

Llovera

Pinkham

Liesz

Modeling stroke in mice: Focal cortical lesions by photothrombosis. JoVE 2021; 6: 171.

128.

Ikeda

Harada

Ohwatashi

, et al. A new non-human primate model of photochemically induced cerebral infarction. PLoS One 2013; 8: e60037.

129.

朱华李秦, 徐艳峰et al. 光化学法制作食蟹猴局部脑缺血模型 %J 中国比较医学杂志. 2008; : 32–34 + 91.

130.

Yang

Han

Zhang

, et al. Extracellular vesicle-mediated delivery of circular RNA SCMH1 promotes functional recovery in rodent and nonhuman primate ischemic stroke models. Circulation 2020; 142: 556–574.

131.

McEntire

Choudhury

Torres

, et al. Impaired arm function and finger dexterity in a nonhuman primate model of stroke: motor and cognitive assessments. Stroke 2016; 47: 1109–1116.

132.

Chandra

Chen

, et al. Endovascular ischemic stroke models in nonhuman primates. Neurotherapeutics 2018; 15: 146–155.

133.

D'Arceuil

Duggan

, et al. Middle cerebral artery occlusion in Macaca fascicularis: acute and chronic stroke evolution. J Med Primatol 2006; 35: 78–86.

134.

Cook

Teves

Tymianski

A translational paradigm for the preclinical evaluation of the stroke neuroprotectant Tat-NR2B9c in gyrencephalic nonhuman primates. Sci Transl Med 2012; 4: 154ra133.

135.

Sato

Chin

Kato

, et al. White matter activated glial cells produce BDNF in a stroke model of monkeys. Neurosci Res 2009; 65: 71–78.

136.

Sun

Zhang

Chen

, et al. Differential temporal evolution patterns in brain temperature in different ischemic tissues in a monkey model of middle cerebral artery occlusion. J Biomed Biotechnol 2012; 2012: 980961.

137.

Gao

Liu

, et al. A reversible middle cerebral artery occlusion model using intraluminal balloon technique in monkeys. J Stroke Cerebrovasc Dis 2006; 15: 202–208.

138.

Kharlamov

LaVerde

Nemoto

, et al. MAP2 immunostaining in thick sections for early ischemic stroke infarct volume in non-human primate brain. J Neurosci Methods 2009; 182: 205–210.

139.

Chen

, et al. Intranasal salvinorin a improves neurological outcome in rhesus monkey ischemic stroke model using autologous blood clot. J Cereb Blood Flow Metab 2021; 41: 723–730.

140.

Debatisse

Wateau

Cho

, et al. A non-human primate model of stroke reproducing endovascular thrombectomy and allowing long-term imaging and neurological read-outs. J Cereb Blood Flow Metab 2021; 41: 745–760.

141.

Fan

, et al. Nonhuman primate models of focal cerebral ischemia. Neural Regen Res 2017; 12: 321–328.

142.

Zhao

Shang

Chen

, et al. A more consistent intraluminal rhesus monkey model of ischemic stroke. Neural Regen Res 2014; 9: 2087–2094.

143.

Diaz

Merino

McCann

, et al. Urokinase-type plasminogen activator promotes N-cadherin-mediated synaptic recovery in the ischemic brain. J Cereb Blood Flow Metab 2021; 41: 2381–2394.

144.

Tong

Zhang

Kempf

, et al. An enhanced model of middle cerebral artery occlusion in nonhuman primates using an endovascular trapping technique. AJNR Am J Neuroradiol 2015; 36: 2354–2359.

145.

Strand

Sagberg

Gulati

, et al. Brain infarction following meningioma surgery-incidence, risk factors, and impact on function, seizure risk, and patient-reported quality of life. Neurosurg Rev 2022; 45: 3237–3244.

146.

Marshall

Cross

Jackson

, et al. Clomethiazole protects against hemineglect in a primate model of stroke. Brain Res Bull 2000; 52: 21–29.

147.

Sasaki

Honmou

Radtke

, et al. Development of a middle cerebral artery occlusion model in the nonhuman primate and a safety study of i.v. infusion of human mesenchymal stem cells. PLoS One 2011; 6: e26577.

148.

Komotar

Mocco

Mack

, et al. Co-registration of radiographic and pathologic infarct territory in a non-human primate model of stroke. Neurol Res 2005; 27: 634–637.

149.

Kito

Nishimura

Susumu

, et al. Experimental thromboembolic stroke in cynomolgus monkey. J Neurosci Methods 2001; 105: 45–53.

150.

Susumu

Yoshikawa

Akiyoshi

, et al. Effects of intra-arterial urokinase on a non-human primate thromboembolic stroke model. J Pharmacol Sci 2006; 100: 278–284.

151.

Ramirez-Garcia

Harrison

Fernandez-Ruiz

, et al. Stroke longitudinal volumetric measures correlate with the behavioral score in non-human primates. Neuroscience 2019; 397: 41–55.

152.

Chin

Sato

Mase

, et al. Transient decrease in cerebral motor pathway fractional anisotropy after focal ischemic stroke in monkey. Neurosci Res 2010; 66: 406–411.

153.

Sawada

Nishimura

Suzuki

, et al. SMTP-7, a novel small-molecule thrombolytic for ischemic stroke: a study in rodents and primates. J Cereb Blood Flow Metab 2014; 34: 235–241.

154.

Chen

Hussain

, et al. Selective intra-arterial brain cooling improves long-term outcomes in a non-human primate model of embolic stroke: Efficacy depending on reperfusion status. J Cereb Blood Flow Metab 2020; 40: 1415–1426.

155.

LaVerde

Jungreis

Nemoto

, et al. Sodium time course using 23Na MRI in reversible focal brain ischemia in the monkey. J Magn Reson Imaging 2009; 30: 219–223.

156.

Sander

Mandeville

Wey

, et al. Effects of flow changes on radiotracer binding: simultaneous measurement of neuroreceptor binding and cerebral blood flow modulation. J Cereb Blood Flow Metab 2019; 39: 131–146.

157.

Takamatsu

Tsukada

Noda

, et al. FK506 attenuates early ischemic neuronal death in a monkey model of stroke. J Nucl Med 2001; 42: 1833–1840.

158.

Choi

Lee

, et al. Sustained diffusion reversal with in-bore reperfusion in monkey stroke models: confirmed by prospective magnetic resonance imaging. J Cereb Blood Flow Metab 2017; 37: 2002–2012.

159.

Le Gal

Bernaudin

Toutain

, et al. Assessment of behavioural deficits following ischaemic stroke in the marmoset. Behav Brain Res 2018; 352: 151–160.

160.

Sasaki

Isa

Pettersson

, et al. Dexterous finger movements in primate without monosynaptic corticomotoneuronal excitation. J Neurophysiol 2004; 92: 3142–3147.

161.

Darian-Smith

Monkey models of recovery of voluntary hand movement after spinal cord and dorsal root injury. ILAR J 2007; 48: 396–410.

162.

Hao

Duan

Hao

, et al. Neural repair by NT3-chitosan via enhancement of endogenous neurogenesis after adult focal aspiration brain injury. Biomaterials 2017; 140: 88–102.

163.

Amatrudo

Weaver

Crimins

, et al. Influence of highly distinctive structural properties on the excitability of pyramidal neurons in monkey visual and prefrontal cortices. J Neurosci 2012; 32: 13644–13660.

164.

Medalla

Chang

Calderazzo

, et al. Treatment with mesenchymal-derived extracellular vesicles reduces injury-related pathology in pyramidal neurons of monkey perilesional ventral premotor cortex. J Neurosci 2020; 40: 3385–3407.

165.

Zhu

Eom

Hunt

RF.

Transplanted interneurons improve memory precision after traumatic brain injury. Nat Commun 2019; 10: 5156.

166.

Falkner

Grade

Dimou

, et al. Transplanted embryonic neurons integrate into adult neocortical circuits. Nature 2016; 539: 248–253.

167.

Linaro

Vermaercke

Iwata

, et al. Xenotransplanted human cortical neurons reveal species-specific development and functional integration into mouse visual circuits. Neuron 2019; 104: 972–986.e976.

168.

Hernandez-Castillo

Nashed

Fernandez-Ruiz

, et al. Increased functional connectivity after stroke correlates with behavioral scores in non-human primate model. Sci Rep 2017; 7: 6701.

169.

Rao

Zhao

Zhang

, et al. NT3-chitosan enables de novo regeneration and functional recovery in monkeys after spinal cord injury. Proc Natl Acad Sci U S A 2018; 115: E5595–e5604.

170.

Latchoumane

Betancur

Simchick

, et al. Engineered glycomaterial implants orchestrate large-scale functional repair of brain tissue chronically after severe traumatic brain injury. Sci Adv 2021; 7: eabe0207.

171.

Palma-Tortosa

Tornero

Grønning Hansen

, et al. Activity in grafted human iPS cell-derived cortical neurons integrated in stroke-injured rat brain regulates motor behavior. Proc Natl Acad Sci U S A 2020; 117: 9094–9100.

172.

Rosenzweig

Salegio

Liang

, et al. Chondroitinase improves anatomical and functional outcomes after primate spinal cord injury. Nat Neurosci 2019; 22: 1269–1275.

173.

Stinear

CM.

Prediction of motor recovery after stroke: advances in biomarkers. Lancet Neurol 2017; 16: 826–836.

174.

Galvan

Caiola

Albaugh

DL.

Advances in optogenetic and chemogenetic methods to study brain circuits in non-human primates. J Neural Transm (Vienna) 2018; 125: 547–563.

175.

Galvan

Stauffer

Acker

, et al. Nonhuman primate optogenetics: recent advances and future directions. J Neurosci 2017; 37: 10894–10903.

176.

Kojima

Ting

Soetedjo

, et al. Injections of AAV vectors for optogenetics in anesthetized and awake behaving non-human primate brain. JoVE 2021; 4: 174.

Non-human primate models of focal cortical ischemia for neuronal replacement therapy

Abstract

Keywords

Introduction

Neuronal replacement strategies in NHP stroke studies

Exogenous stem cell transplants

Biomaterials

Direct neuronal reprogramming

NHP species used in stroke study

Focal cortical ischemia models in NHP

Nonvascular stroke model

Electrocoagulation model

Endothelin-1 (ET-1) injection model

Photothrombosis model

Clamp model

Endovascular stroke model

Outcome measures

Infarction volume

Regional CBF

Neurobehavioral assessment

Neural regeneration and repair

Conclusions

Footnotes

Funding

Acknowledgements

Declaration of conflicting interests

ORCID iD

References