Cytokines and inflammation in cartilage degradation.

Since the discovery of humoral factors such as cytokines, which could modulate connective tissue metabolism, questions have arisen concerning their involvement in the pathophysiology of osteoarthritis. At least three cytokines, interleukin (IL-1), tumor necrosis factor, and interleukin-6, were identified in articular tissue and suggested to play a role during inflammation. Osteoarthritic chondrocytes have a higher sensitivity to stimulation by IL-1 with respect to metalloprotease production than normal chondrocytes that seem to be related to an increase in the level of IL-1 receptors. Natural antagonists capable of directly counteracting cytokine action on joint cells have been identified; however, their role in osteoarthritis remains to be determined, particularly in the context of their use for therapeutic intervention.