Hyaluronan Inhibits Matrix Metalloproteinase-13 in Human Arthritic Chondrocytes via CD44 and P38

We investigated the effects of hyaluronan (HA) on interleukin-1 beta (IL-1 beta)-stimulated matrix metalloproteinase (MMP)-13 production in human chondrocytes from patients with osteoarthritis (OA) or rheumatoid arthritis (RA). Secreted levels of MMP-13 in conditioned media were detected by immunoblotting, while intracellular MMP-13 synthesis in articular cartilage was evaluated by immunofluorescence microscopic analysis. Mitogen-activated protein kinases (MAPKs), p38, extracellular signal-regulated kinases (ERK), and c-jun NH2-terminal kinase (JNK) were assessed by Western blotting. IL-1 beta (2 ng/ml) stimulates the secretion of MMP-13 in both OA and RA chondrocytes. Inhibition studies using specific MAPK inhibitors revealed that IL-1 beta induced MMP-13 via p38 in both OA and RA chondrocytes. HA down-regulates IL-1 beta-stimulated MMP-13 and phosphorylated p38 (p-p38) in a dose-dependent manner (0.1, 1, 2, and 4 mg/ml). When used at 4 mg/ml, HA inhibits p-p38 phosphorylation by more than 60%. In response to IL-1 beta, RA chondrocytes express a higher level of p-p38 than that of OA chondrocytes. Inhibition of CD44, using a blocking antibody, significantly reversed the inhibitory effect of HA on both MMP-13 and p-p38. Our study clearly shows that HA inhibits IL-1 beta-induced MMP-13 via its principal receptor, CD44, and subsequent intracellular p38 MAPK signaling in OA and RA chondrocytes. (C) 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J. Orthop. Res. 29: 258-264, 2011