Differential responses of human and rat cartilage to degrading stimuli in-vitro.

Human cartilage biopsies incubated for 2 days in-vitro with 15% synovial fluid from rheumatoid arthritis patients contained less glycosaminoglycans (GAG) than control biopsies. Recombinant human (rHu)-interleukin-1 alpha (IL-1 alpha) and IL-1 beta at 10 or 100 ng mL-1 had no effect on human cartilage GAG levels. Similarly, GAG loss from human cartilage biopsies into medium over 5 days was significantly increased by synovial fluid but unaffected by 100 ng mL-1 IL-1 alpha or IL-1 beta compared with controls. However, when rat femoral head cartilage samples were incubated with 100 ng mL-1 rHu-IL-1 alpha or IL-1 beta for 5 days there was a significant increase in GAG loss from the cartilage into medium, whilst human synovial fluid significantly decreased the loss of GAG from rat cartilage into medium, compared with controls. The results demonstrate that human and rat cartilage differ from each other in their responses to degrading stimuli and suggest that animal cartilage may have limited application for the screening of drugs intended for the treatment of human arthritides.