Identification of Integrins Involved in Cell Adhesion to Native and Denatured Type I Collagens and the Phenotypic Transition of Rabbit Arterial Smooth Muscle Cells

Abstract

Rabbit smooth muscle cells (SMC) in primary culture attached to and started proliferating on native and heat-denatured type I collagens, although the amount of cell attachment to denatured collagen was significantly lower. The cells adhered poorly and were unable to grow on commercial gelatin. In contrast, synthetic SMC in secondary culture could adhere to gelatin and grew as well on gelatin as on native type I collagen. The SMC in the contractile state adhered to native type I collagen through the α1β1 and α3β1 integrins. The cells in the intermediate phenotype also adhered to the substrate through the α1β1 and α3β1 integrins, but the relative amount of α3 integrin decreased. The initial adhesion of cells in secondary culture to native type I collagen was mediated only by the α1β1 integrin. The cell-binding sequences did not contain DGEA (Asp-Gly-Glu-Ala) or RGD (Arg-Gly-Asp). In contrast, cell adhesion to heat-denatured type I collagen was mediated only by the α1β1 integrin in the contractile state and by the α1β1, α2β1, and α3β1 integrins in the synthetic state. In heat-denatured type I collagen, the sequences DGEA and RGD served as a recognition site for the α2β1 and α3β1 integrins. Our results suggest that rabbit SMC can recognize the native and denatured type I collagens through interactions with the triple helix-binding receptors and α chain-binding receptors and that the expression pattern of integrins changes in conjunction with the phenotypic properties of vascular SMC.