β1 And β3 integrins have different roles in the adhesion and migration of vascular smooth muscle cells on extracellular matrix

Abstract

Extracellular matrix receptors on ductus arteriosus smooth muscle cells (SMC) must enable the cells to migrate through both interstitial and basement membrane matrices to form intimal mounds during postnatal ductus closure. We examined the role of β 1 and β 3 integrin receptors on SMC adhesion and migration. Using a new assay to measure cell migration, we found that lamb ductus arteriosus SMC attach to and migrate over surfaces coated with fibronectin (FN), laminin (LN), vitronectin (VN), and collagens I (I) and IV (IV). Blocking antibodies, specific to different integrin complexes, showed that SMC adhesion to FN, LN, I, and IV depended exclusively on functioning β 1 integrins with little, if any, contribution by the α v β 3 integrin; on the other hand, cell migration over these substrates depended to a large extent on the α v β 3 receptor. Immunofluorescent staining demonstrated that during the early phase of SMC migration, the β 1 integrins organized rapidly into focal plaques that, with time, gradually covered the cell's basal surface; on the other hand, the β 3 receptor remained concentrated at all times at the cell's margins. Ligand affinity chromatography and immunoprecipitation techniques identified a unique series of β 1 integrins binding to each matrix component: FN ( α 5 β 1, α 3 β 1, α v β 1), LN ( α 1 β 1, α 7 β 1), VN ( α v β 1), I ( α 1 β 1, α 2 β 1), and IV ( α 1 β 1). In contrast, the β 3 integrin, α v β 3, bound to all the substrates tested: FN, LN, VN, I, and IV. The results indicate that β 1 and β 3 integrins may play different roles in attachment and migration as SMC move through the vascular extracellular matrix to produce obliteration of the ductus arteriosus lumen.