Integrin expression on epiphyseal mouse chondrocytes in monolayer culture

The expression of alpha 1-, alpha 3-, alpha v- and alpha 5 beta 1-integrins and their specific ligand binding were investigated in monolayer cultures of chondrocytes from 17-day-old mouse embryos using morphological and immunomorphological methods. After a 1-day culture period alpha v-, alpha 3- and alpha 5 beta 1-integrins were observed on these cells. Immunoelectronmicroscopic investigation revealed localization predominantly in the contact areas with extracellular structures on the cell surface. alpha 1-integrin could not be demonstrated on chondrocytes. After a 5-day culture period the number of fibroblast-like cells with alpha 1-, alpha v- and alpha 5 beta 1-integrins had increased. alpha 3-integrin was hardly recognizable on these cells. Collagen type I and fibronectin could be shown as ligands on the cell surface. The number of chondrocytes with collagen type II on their surface continuously decreased. alpha 3-integrin is obviously responsible for the binding of collagen type II, and alpha 1-integrin for the binding of collagen type I. Therefore, it can be concluded that the changes of chondrocytes to fibroblast-like cells in monolayer culture are accompanied by changes of integrin genes.