Enhanced breakdown of bovine articular cartilage proteoglycans by conditioned synovial medium in vitro. The effect of glucocorticoids and protein synthesis inhibitors

Abstract

Addition of conditioned synovial medium (SM) from cultured calf knee-joint synovium to cultures of articular cartilage from the same animal resulted in a significant increase in breakdown of cartilage proteoglycans. Culturing the synovium in the presence of glucocorticoids (hydrocortisone, dexamethasone, prednisolone) or protein synthesis inhibitors (cycloheximide or actinomycin D) reduced the breakdown effect. In contrast, enhancement of proteoglycan breakdown was observed when the cartilage was exposed to glucocorticoids in the presence of SM from synovium cultured without these drugs (control SM). The stimulatory effect on cartilage breakdown of control SM or control SM + glucocorticoids was markedly reduced in the presence of actinomycin D or cycloheximide. The authors conclude that glucocorticoids under certain conditions enhance cartilage degradation and therefore, although they exert the temporary anti-inflammatory effects, treatment of joint diseases with glucocorticoids may not be beneficial in the long-term.