Impaired Calcium Signaling in Precapillary Sphincters and Pericytes Perturbs Neurovascular Regulation after an Ischemic Stroke

Abstract Ischemic stroke disrupts neurovascular uncoupling, in which neuronal activity fails to evoke appropriate microvascular blood flow responses, despite successful recanalization of upstream arteries. The cellular mechanisms underlying this dysfunction remain poorly defined. We examined Ca²⁺ signaling and contractile dynamics of vascular smooth muscle cells, precapillary sphincters and contractile pericytes, using two-photon microscopy and laser speckle imaging in awake mice subjected to transient middle cerebral artery occlusion. During occlusion, precapillary sphincters exhibited pronounced Ca²⁺ elevations and constriction, amplifying downstream capillary resistance. Following reperfusion, elevated Ca²⁺ signals persisted without proportional diameter changes, indicating early uncoupling between Ca²⁺ dynamics and vascular responses. In the chronic phase, loss of precapillary sphincters-associated contractile pericytes was associated with capillary dilation and persistent neurovascular uncoupling. Although partial recovery of pericyte coverage and Ca²⁺ activity occurred, stimulus-evoked vascular responses remained blunted. These findings highlight precapillary sphincters as a key contributor to ischemia-induced microvascular dysfunction.