The role of secondary growth factor production in thrombin-induced proliferation of vascular smooth muscle cells

alpha-Thrombin is a multifunctional serine proteinase that is concentrated at sites of vascular injury and has been implicated in vascular healing res ponses following balloon injury. In addition to its well-known hemostatic e ffects, thrombin stimulates smooth muscle cell (SMC) proliferation via bind ing of protease activated receptor-1 (PAR-1), a seven transmembrane, G-prot ein-coupled cell surface receptor, Following activation of this receptor, S MC produce and secrete various autocrine growth factors, including platelet -derived growth factor-AA (PDGF-AA), basic fibroblast growth factor (bFGF), heparin binding epidermal growth factor (HBEGF), and transforming growth f actor-beta (TGF beta), The role that autocrine growth factors play in alpha -thrombin-induced proliferation will be discussed in this review.