Stimulation of migration of human aortic smooth muscle cells by vitronectin: implications for atherosclerosis.

OBJECTIVE: Migration of smooth muscle cells into the neointima has been implicated in atherogenesis. Vitronectin, a serum factor that promotes cell spreading and attachment, accumulates in atherosclerotic human tissues. The aim of this study was to determine the role of vitronectin and its receptor (integrin alpha V beta 3) in migration of smooth muscle cells. METHODS: Human aortic smooth muscle cell migration was studied in modified Boyden chambers. Expression of vitronectin receptor was determined by northern blotting of receptor mRNA and immunoprecipitation of receptor protein. RESULTS: Vitronectin dose dependently increased smooth muscle cell migration by an amount comparable to that induced by platelet derived growth factor, (PDGF)-BB. Antiserum to alpha V beta 3 diminished vitronectin driven migration. Northern blot analysis showed low constitutive expression of alpha V and beta 3 mRNA by smooth muscle cell and rapid induction with transforming growth factor beta (TGF-beta) and thrombin. Immunoprecipitation confirmed increased synthesis of the alpha V beta 3 vitronectin receptor complex by TGF-beta or thrombin. Smooth muscle cells pretreated with TGF-beta or thrombin showed increased vitronectin driven migration. cAMP suppressed induction of migration, but inhibition of protein kinase C increased it. CONCLUSIONS: These results show that vitronectin-induced human aortic smooth muscle cell migration is mediated by alpha V beta 3 vitronectin receptor and expression of the receptor is induced by TGF-beta and thrombin, which in turn induce vitronectin driven, vitronectin receptor modulated smooth muscle cell migration.