Pericytes in the brain and heart: functional roles and response to ischemia and reperfusion.

In the last 20 years there has been a revolution in our understanding of how blood flow is regulated in many tissues. Whereas it used to be thought that essentially all blood flow control occurred at the arteriole level, it is now recognised that control of capillary blood flow by contractile pericytes plays a key role both in regulating blood flow physiologically and in reducing it in clinically-relevant pathological conditions. In this article we compare and contrast how brain and cardiac pericytes regulate cerebral and coronary blood flow, focusing mainly on the pathological events of cerebral and cardiac ischemia. The cerebral and coronary capillary beds differ dramatically in morphology, yet in both cases pericyte-mediated capillary constriction plays a key role in restricting blood flow after ischemia and possibly in other pathological conditions. We conclude with suggestions for therapeutic approaches to relaxing pericytes, which may prove useful in the long term for reducing pericyte-induced ischemia.