Altered vitronectin receptor (alpha(v) integrin) function in fibroblasts adhering on hydrophobic glass

Function of integrins is crucial for adhesion, movement, proliferation, and survival of cells. In a recent study we found impaired fibronectin recepto r function on hydrophobic substrata (G. Altankov et al. J Biomater Sci Poly m Edn 1997;8:712-740). Here, we have studied the distribution and function of the vitronectin receptor (alpha(v) integrin) in fibroblasts adhering on hydrophilic glass and hydrophobic octadecyl glass (ODS). The morphology of fibroblasts and the organization of actin cytoskeleton were studied and fou nd to be altered on ODS, where the cells did not spread and possessed conde nsed actin. Pretreatment of the surfaces with serum or pure vitronectin imp roved cell morphology on both substrata, resulting in the development of lo ngitudinal actin stress fibers. It was found with biotinylated vitronectin that comparable quantities of vitronectin were adsorbed from single vitrone ctin solutions or serum on glass and on hydrophobic ODS. The organization o f the vitronectin receptors on the ventral cell surface was investigated in permeabilized cells showing normal focal adhesions in fibroblasts plated o n glass but none of these structures on ODS. The distribution of alpha(v) i ntegrin on the dorsal cell surface was studied on nonpermeabilized living c ells after antibody tagging. While fibroblasts adhering on plain or serum-t reated glass developed a Linear organization of alpha(v) integrin, cells on plain and serum-treated ODS were not able to reorganize the vitronectin re ceptor. Studies on signal transduction with antiphosphotyrosine antibodies revealed co-localization of alpha(v) integrin and phosphotyrosine in focal adhesions on glass and serum-treated glass. However, signaling was almost a bsent on plain ODS and weak on serum-treated ODS. It was concluded that alt erations in vitronectin receptor function on the ventral cell surface cause d by the hydrophobic material surface inhibit signal transfer and subsequen t intracellular events that are important for the organization and function of integrins. (C) 1999 John Wiley & Sons, Inc.