The synovial production of collagenase and chondrocyte activating factors in response to cobalt

Addition of CoCl2 solutions to the culture media of confluent monolayers of lapine or human synoviocytes stimulated their production of the neutral proteinases collagenase, gelatinase, and caseinase. With lapine cells, maximum stimulation occurred at 10(-7) M CoCl2, while human cells required 10(-4)-10(-5) M CoCl2 to achieve a maximum stimulation. Production of prostaglandin E2 by lapine cells was enhanced some 30-40% by concentrations of CoCl2 that maximally stimulated synthesis of the neutral proteinases, whereas all concentrations of CoCl2 slightly depressed the production of prostaglandin E2 by human cells. Lapine synovial cells that had been stimulated by CoCl2 also produced a substance, or substances, that provoked the synthesis of collagenase, gelatinase, caseinase, and prostaglandin E2 by monolayers of articular chondrocytes. Chondrocytes themselves, however, resisted activation by CoCl2. These findings may be relevant to the aseptic loosening of joint prostheses.