Microcirculation Dysfunction in Subacute Stroke: The Role of Delayed Capillary Pericyte Loss

Post-recanalization microcirculation dysfunction is common and significantly contributes to poor outcomes in ischemic stroke. Pericytes have been shown to mediate the "no-reflow" phenomenon by constricting capillaries in experimental stroke models, implicating their critical role in early microcirculation dysfunction. However, little is known about the long-term fate of pericytes and their contribution to sustained microcirculation dysfunction in prolonged period of time. We conducted repeated longitudinal observations of pericyte fate and function, as well as blood flow dynamics across multiple vascular segments, using two-photon imaging in PDGFRβ-tdTomato mice subjected to transient middle cerebral artery occlusion (tMCAO) over a 14-day period. Multivariate analysis was performed to identify imaging features independently associated with capillary perfusion on day 14. Types of pericyte death were assessed using immunohistochemistry and Western blot analysis. Fasudil and the RIPK1 inhibitor necrostatin-1 were administered to modulate pericyte dysfunction and survival during the acute and subacute phases of stroke. Outcomes were evaluated by total capillary perfusion, infarct volume, blood brain barrier (BBB) integrity, and neurological function over 14 days. Pericyte loss observed on day 7 post-stroke was independently associated with impaired microcirculation perfusion, as indicated by a reduction in total capillary volume. While fasudil treatment alone improved microcirculation perfusion on day 3, it did not alter pericyte fate or improve outcomes by day 14. Necroptosis was found to contribute to delayed pericyte loss in the ischemic penumbra. Combined therapy with fasudil and necrostatin-1 effectively prevented delayed pericytes loss and improved both microcirculation perfusion and neurological outcomes on day 14. Delayed pericyte loss contributes to irreversible microcirculation dysfunction in the subacute phase of stroke. Targeting pericyte dysfunction and necroptosis following recanalization represents a promising therapeutic strategy for enhance stroke recovery.