Site specific inhibition of cartilage proteoglycan synthesis in the murine knee joint. Differences between 3 metabolic stimuli.

Abstract We studied whether inhibition of proteoglycan synthesis on different locations occurs according to a regular stimulus unrelated pattern or whether the response of cartilage is stimulus dependent. Proteoglycan synthesis in murine knee joint cartilage was measured after in vitro and in vivo exposure to 3 metabolic stimuli, iodoacetate, papain and interleukin 1 alpha (IL-1 alpha). Knee joint cartilage was divided in 4 specific areas: the central and peripheral patella and medial and lateral tibial plateau. The effect on proteoglycan synthesis in cartilage from these locations was similar in the in vitro and the in vivo experiments. Papain evoked more inhibition of the proteoglycan synthesis in tibial cartilage than in patellar cartilage. In contrast, iodoacetate caused more inhibition in patellar than in tibial cartilage. The central part of the patella was more vulnerable than the peripheral part of IL-1 alpha and iodoacetate, and both parts were equally sensitive to papain. Differences in sensitivity between central medial and central lateral tibial plateau were found only with iodoacetate, which inhibited proteoglycan synthesis medially more than laterally. Our results indicate that inhibition of proteoglycan synthesis in specific areas of the knee joint is stimulus dependent.