EXPRESSION OF BETA-1 INTEGRINS BY CULTURED ARTICULAR CHONDROCYTES ANDIN OSTEOARTHRITIC CARTILAGE

Expression of beta 1 integrins was studied in vitro as articular chond rocytes reestablished a matrix in culture and in situ in a nonhuman pr imate model of osteoarthritis in order to investigate a potential role for integrins in mediating cell-extracellular matrix interactions in cartilage. Chondrocytes were found to express alpha 1 beta 1, alpha 3 beta 1, and alpha 5 beta 1 integrins both in vitro and in situ. Cell s urface expression of beta 1 integrins increased as chondrocytes were m aintained in culture from 3 to 7 days. Increased beta 1 integrin expre ssion was also observed in osteoarthritic cartilage compared with norm al cartilage. The greatest relative increase in both systems was noted for the alpha 1 beta 1 integrin. The increase in chondrocyte beta 1 i ntegrin expression in vitro was noted in both monolayer and alginate c ultures and occurred prior to detectable changes in the differentiated phenotype of the chondrocyte. Disruption of the cytoskeleton with the drug dihydrocytochalasin B inhibited the cell culture induced increas e in integrin expression, while treatment of cultured cells with TGF-b eta resulted in increased expression of the alpha 5 beta 1 integrin. T he modulation of beta 1 integrin expression noted in vitro and in situ indicates that chondrocytes are capable of regulated expression of be ta 1 integrins and suggests that beta 1 integrins may play an importan t role in mediating chondrocyte-extracellular matrix interactions in c artilage. (C) 1996 Academic Press, Inc.