OBJECTIVETo observe the effect of intra-articular injection of SB203580, a selective p38 mitogen-activated protein kinase inhibitor, on the expression of matrix metalloproteinase (MMP)-3, MMP-13 in a rat model of osteoarthritis (OA) and to explore the relationship between the MMP-3/MMP-13 expressions and the severity of OA.

METHODSFourty SD rats underwent unilateral anterior cruciate ligament transection (ACLT) and then randomly divided into four groups, with 10 rats in each group. Group A received 0.1 ml intra-articular injection of SB203580 at a high concentration of 100 micromol/L (once a week) immediately after surgery, and group B were treated under the same condition using SB203580 with a low concentration of 10 micromol/ L Group C received 0.1 ml intra-articular normal saline, and group D were not injected as controls after ACLT. All rats were sacrificed seven weeks after the surgery. Macroscopic and immunohistochemical studies were performed on the cartilage. Protein expressions of MMP-3 and MMP-13 were determined by Western blot. RESULTS Cartilage degradation was significantly milder in group A and group B than in the control groups, as shown by morphological studies (P < 0. 05) and immunohistochemical studies (P < 0. 05). The protein expressions of MMP-3 and MMP-13 in cartilage were significantly lower in groups A and B than in groups C and D (P < 0.01).

CONCLUSIONSB203580 can inhibit the expressions of MMP-3 and MMP-13 and thus protect the cartilage.