Induction of articular cartilage degradation by recombinant interleukin 1 alpha and 1 beta

The purpose of this study was to compare the effects of human recombinant interleukin 1, alpha and beta, on articular cartilage. The effects of rIL-1 alpha and rIL-1 beta on proteoglycan degradation and synthesis following treatment of bovine articular cartilage in serum-free organ culture were quantified. Purified human IL-1 and both rIL-1 alpha and rIL-1 beta induced a two-fold or greater increase in glycosaminoglycan (GAG) release from cultured articular cartilage. Levels or rIL-1 alpha as low as 15 pM induced increased proteoglycan degradation whereas identical levels of rIL-1 beta did not. Killing of the cartilage cells abolished induced GAG release by all forms of IL-1. Analysis of proteoglycan size following IL-1 treatment showed limited degradation of material released into the culture medium or remaining within cartilage. Both forms of recombinant IL-1 inhibited GAG synthesis when continually present in the culture medium. Actinomycin D and cycloheximide inhibited IL-1 dependent cartilage destruction whereas indomethacin did not.