Enhanced breakdown in vitro of bovine articular cartilage proteoglycans by conditional synovial medium. The effect of superoxide dismutase and catalase.

We have previously reported that addition of conditioned medium derived from fragment cultures of synovial tissue dissected from bovine knee-joints (SM) to cultures of articular cartilage derived from the same knee-joint resulted in enhanced breakdown of cartilage proteoglycans, measured as the release of [35S]sulphate from pieces of prelabelled cartilage. It has also been reported that oxygen-centered free radicals can degrade cartilage proteoglycans and that superoxide dismutase and catalase can reduce such degradation. Here we report that superoxide dismutase and catalase do not significantly affect the degradation of articular cartilage proteoglycans enhanced by conditioned synovial medium. It therefore appears that oxygen-centered free radicals are of at most minor importance for the degradation of cartilage enhanced by conditioned synovial medium.