Regulation of fibroblast attachment by interleukin (IL)-1-mediated loss of cartilage damage. Healthy articular cartilage (right) provides no substrate for healthy wt fibroblasts and also hTNFtg synovial fibroblasts (SFs) show only limited attachment to intact cartilage. The loss of proteoglycans as induced by IL-1 (left) greatly facilitates the attachment of SFs, particularly of hTNFtg fibroblasts. This attachment to as yet undefined proteoglycans or proteoglycan fragments is mediated also by syndecan-4 because the loss of syndecan-4 decreases the attachment of SFs to IL-1-treated cartilage. p 1010.