Adhesion of a chondrocytic cell line (USAC) to fibronectin and its regulation by proteoglycan

Background:  Chondrocytes produce various extracellular matrices during chondrogenesis. Fibronectin and proteoglycan are major extracellular matrix proteins in cartilage tissue, but the interactions between them are not clear. Methods:  Recently, we succeeded in establishing a cell line (USAC) with phenotypes of chondrocytes from a human osteogenic sarcoma of the mandible. Using this cell line, cell adhesion to fibronectin, the effect of proteoglycan on the cell adhesion and expression of integrin α5β1 were investigated. Results:  Cells immediately adhered to fibronectin and then spread. Proteoglycan inhibited cell adhesion to fibronectin dose-dependently, whereas collagen did not. The expression of both mRNAs of α5 and β1 subunits was detected 12 h after treatment with proteoglycan, but the expression of β1 subunit mRNA had diminished by 24 h after treatment. Conclusions:  These findings suggest that proteoglycan might modulate signal transduction from fibronectin by decreasing the expression of α5β1 integrin.