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

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.

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.

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.

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.