[Function of cytokines in cartilage degradation]

Growth-hormones like Insulin-Like-Growth-Hormone-1 (IGF-1) and Tissue-Growth-Factor-beta (TGF-beta) and Cytokines IL-1, IL-6 and TGF-alpha play an important part in the homeostasis and also degradation of the articular cartilage. IL-1 stimulates the production of proteolytic enzymes and inhibits the synthesis of aggrecan and leads therefore to a degradation of the cartilage. TNF-alpha acts in a similar way, whereas the significance of IL-6 for chondrocytes is not yet fully understood. TGF-beta and IGF-1 in contrast have a positive influence on cartilage metabolism, f. ex. TGF-beta stimulates the synthesis of the natural occurring metalloproteinase-inhibitor (TIMP).