CHONDROCYTE AND CHONDROSARCOMA CELL INTEGRINS WITH AFFINITY FOR COLLAGEN TYPE-II AND THEIR RESPONSE TO MECHANICAL-STRESS

Mechanical stress is an important regulator of chondrocyte functions b ut the mechanisms by which chondrocytes sense mechanical signals are u nknown. Receptors for matrix molecules are likely involved in the mech anical signaling. In the first part of this study we identified integr ins with affinity for the cartilage-specific collagen type II. We repo rt that the collagen-binding integrins alpha 1 beta 1 and alpha 2 beta 1 isolated from bovine chondrocytes or human chondrosarcoma cells bou nd collagen type II as judged from affinity chromatography. The integr ins alpha 3 beta 1 or alpha 9 beta 1 did not bind collagen type II-Sep harose. In the second part of the study we investigated the effect of mechanical stress on expression of matrix molecules and integrin subun its. Chondrocytes and chondrosarcoma cells, cultured on uncoated flexi ble silicone membranes in the presence of serum, were exposed to mecha nical stress by the Flexercell system. Dynamic stimulation of chondroc ytes for 3 h increased the mRNA expression of collagen type II and agg recan as judged by Northern blotting, while the beta 1-integrin subuni t was not changed. When chondrosarcoma cells were exposed to mechanica l stimulation under the same conditions, mRNA expression of alpha 5 wa s found to increase while beta 1, alpha 2, and alpha v did not increas e to significant levels. In another study the effect of mechanical str ess on integrins was investigated when the cells were cultured on coll agen type II-coated flex-dishes. Three hours of dynamic stress increas ed the mRNA expression of alpha 2-integrin subunit while the level of mRNA for integrin subunits beta 1, alpha 1, alpha 5, and alpha v showe d no or small changes, indicating that matrix components may modulate the expression of integrins during mechanical stress. (C) 1995 Academi c Press, Inc.