IL-17A in combination with TNF-α and OSM synergistically shifts the MMP-1: TIMP-1 and MMP-13: TIMP-1 ratios and drives cartilage destruction. Human cartilage explants were cultured in the presence of IL-17A (50 ng/ml) alone and in combination with TNF-α (10 ng/ml) or oncostatin M (OSM; 10 ng/ml). (a to d) Culture supernatants were analysed for the expression of matrix metalloproteinase (MMP)-1, MMP-13, and tissue inhibitor of metalloproteinase (TIMP)-1 by ELISA. Values are the mean and standard error results from nine experiments. * P < 0.05 versus baseline. Cartilage was formalin-fixed and embedded. (e) Proteoglycan staining was demonstrated by safranin O-fast green immunostaining.