Protection from interleukin 1 induced destruction of articular cartilage by transforming growth factor β: Studies in anatomically intact cartilage in vitro and in vivo

Abstract

The modulation of interleukin 1 (IL-1) effects on proteoglycan metabolism in intact murine patellar cartilage by transforming growth factor β (TGF-β) was investigated in vitro and in vivo. In vitro TGF-β (400 pmol/l) had no effect on basal proteoglycan degradation. Proteoglycan degradation induced by IL-1, however, was suppressed by TGF-β in serum free medium alone and in medium supplemented with 0.5 μg/ml insulin-like growth factor 1. This suggests a specific regulatory role for TGF-β under pathological conditions. In contrast with the suppression of breakdown, synthesis of proteoglycans was stimulated by TGF-β for both basal and IL-1 suppressed proteoglycan synthesis in cultures without insulin-like growth factor. In the presence of insulin-like growth factor no extra effect of TGF-β on proteoglycan synthesis was observed. With insulin-like growth factor, however, TGF-β potentiated the ex vivo recovery of IL-1 induced suppression of proteoglycan synthesis. Analogous to the in vitro effects, TGF-β injected intraarticularly suppressed IL-1 induced proteoglycan degradation. Furthermore, TGF-β injected into the joint counteracted IL-1 induced suppression of proteoglycan synthesis. This indicates that in vivo also TGF-β can ameliorate the deleterious effects of IL-1 on the cartilage matrix.