Anti-apoptotic role of sonic hedgehog on blood platelets

Sonic hedgehog (Shh) is an essential morphogen involved in vertebrate organogenesis. Perturbation of Hh signaling is associated with pathological consequences like tumor formation and chronic lung fibrosis. Platelets are highly sensitive circulating blood cells responsible for hemostasis, while hyperactivity of these cells lead to morbidities like ischemic heart diseases and stroke. Despite being terminally differentiated cells with life span of 10-12 days, platelets have recently been shown to respond to Wnt ligand, another developmental signal similar to Shh. In this study, we demonstrate that components of Shh signaling, Patched and Gli3, are expressed in human platelets consistent with existence of functional Hedgehog signaling in these cells. Shh had potent inhibitory effect on platelet apoptosis induced by ABT-737 or thrombin through attenuation of caspase-3 activity. The Shh-mediated pathway may thus represent a novel endogenous mechanism for regulating platelet activity and life span.