Loss of Vascular TMEM16A Impairs Cerebral Autoregulation and Exacerbates Ischemia-reperfusion Injury.

TMEM16A forms a Ca²⁺-activated Cl⁻ channel in vascular mural cells (smooth muscle cells and pericytes) that generates depolarizing Cl⁻ efflux upon intracellular Ca²⁺ elevation, thereby amplifying agonist-induced vasoconstriction. TMEM16A has been implicated in excessive capillary pericyte constriction following cerebral ischemia, suggesting that its inhibition may improve post-stroke recovery. However, the impact of systemic vascular TMEM16A inhibition on focal reperfusion efficiency and cerebrovascular autoregulation remains unknown. To address this question, mice with inducible mural cell-specific (Myosin Heavy Chain 11 promoter controlled) deletion of TMEM16A were subjected to transient middle cerebral artery occlusion. Reperfusion dynamics and stroke-reperfusion outcome were assessed using laser speckle contrast imaging, cylinder test for motor function, and infarct quantification by 2,3,5-triphenyltetrazolium chloride staining. Systemic cardiovascular parameters were monitored with radiotelemetry. Middle cerebral artery myogenic tone was assessed with pressure myography. Mice lacking TMEM16A in mural cells exhibited impaired reperfusion and worsened stroke outcome compared with wild-type controls, despite unchanged systemic cardiovascular parameters. In wild-type mice, capillary pericytes maintained basal contractile tone in both hemispheres, and this was further enhanced in peri-infarct cortex. In contrast, TMEM16A-deficient capillary pericytes lacked basal tone in both the ipsilateral and contralateral hemispheres. TMEM16A-deficient middle cerebral arteries failed to develop pressure-induced myogenic tone. These findings demonstrate that TMEM16A is required for effective cerebral autoregulation and that its deficiency significantly impairs post-ischemic reperfusion. The results caution against systemic TMEM16A inhibition as a therapeutic strategy for stroke and highlight the need for spatially restricted approaches to modulate cerebral perfusion via the Ca²⁺-activated Cl⁻ channels.