In vivo studies on the effects of human recombinant interleukin-1 beta on articular cartilage.

Interleukin-1 (IL-1) is a cytokine produced by a number of connective-tissue and inflammatory cells which has been shown in organ culture to stimulate the breakdown of cartilage proteoglycans and inhibit their synthesis. Intraarticular injection of human recombinant IL-1 beta into the knee joints of rabbits induced a dose-related decrease in cartilage proteoglycan content and increased infiltration of cells into the synovial fluid. Following a single intraarticular injection, the loss of proteoglycan was maximal at 3 days. By 7 days, proteoglycan content began to return toward control levels. IL-1 also resulted in a dose-related decrease in the ability of cartilage to synthesize new proteoglycan as measured by 35S incorporation. These in vivo effects of IL-1 on articular cartilage closely reflect those effects observed in vitro in organ culture and are consistent with the hypothesis that IL-1 may play a role as a mediator of the loss of cartilage in some arthritic diseases.