ROLE OF TNFα, IN RELATION TO IL-1 AND IL-6 IN THE PROTEOGLYCAN TURNOVER OF HUMAN ARTICULAR CARTILAGE

In both young and old human articular cartilage explants, TNFα induced a concentration-dependent, reversible suppression of the proteoglycan (PG) synthesis. Young cartilage was more sensitive to TNFα than old cartilage: 50% suppression of PG synthesis was reached at a TNFα concentration of 5 U/ml for young and 30 U/ml for old cartilage, whereas at 103 U/ml the PG synthesis of young cartilage was blocked and that of old cartilage suppressed by 80%. These inhibition levels of PG synthesis resulted in 25% PG depletion of the explants after 8 days of culture. The release of cartilage PG not enhanced. TNFα induced no detectable amounts of IL-1 (