Susceptibility of normal and arthritic human articular cartilage to degradative stimuli

Recombinant interleukin-1 (IL-1) alpha and beta stimulated significant loss of glycosaminoglcan (GAG) content from normal (non-arthritic) articular cartilage explants but only after incubation for 14 days and only in specimens from 8/21 (38%) individuals. By contrast, all cartilage specimens but one from patients with osteoarthritis (OA) and rheumatoid arthritis (RA) were degraded (as judged by their reduced GAG content) by the recombinant cytokines but again only after 14 days' incubation. The reduction in GAG induced by IL-1 was also greater for both OA and RA cartilage than normal cartilage. Synovial fluids (SFs) from RA patients stimulated greater loss of GAG content from OA cartilage explants than normal explants although in both cases the loss was evident within 2 days. It is concluded that cartilage explants from some individuals are susceptible to the degradative effects of IL-1 whereas others are refractory and that arthritic cartilage is more susceptible to degradation by both IL-1 and RA SFs than non-arthritic cartilage.