Perivascular macrophage depletion impairs glymphatic clearance and amplifies cortical hyperexcitability: Preclinical insights with clinical validation

Abstract

Perivascular macrophages (PVMs) are increasingly recognized as key players in maintaining brain homeostasis, yet their role in maintaining neurovascular–metabolic homeostasis has not been fully explored. We hypothesized that PVM depletion compromises cerebrospinal fluid-interstitial fluid exchange through glymphatic system (GS) dysfunction, thereby exacerbating cortical hyperexcitability manifested as increased epilepsy susceptibility and seizure intensity. Using clodronate liposomes (CLOs), we achieved >85% PVM depletion in mice. Following pentylenetetrazole (PTZ) challenge, PVM-depleted mice exhibited anxiety-like behaviors (reduced center time, p < 0.05), impaired working memory (decreased spontaneous alternation, p < 0.05), and increased cortical hyperexcitability, including shorter seizure latency and elevated EEG total power (p < 0.05). Mechanistically, PVM loss led to dysregulation of extracellular matrix components (increased laminin and collagen IV), impairing perivascular space integrity and GS function (reduced CSF tracer clearance, p < 0.05). AQP4 inhibition with TGN-020 further exacerbated PTZ-induced EEG abnormalities (increased total power, p < 0.05). Analysis of human epileptic tissue confirmed elevated collagen IV deposition in the seizure focus (p < 0.05) and a trend toward increased PVM density (p = 0.0638). These results highlight PVMs as essential modulators of the glymphatic–metabolic axis, linking vascular health to brain excitability. Targeting the PVM–GS interface offers therapeutic potential for disorders involving vascular dysfunction and neuronal hyperexcitability.