Matrix metalloproteinases and inhibitor in knee synovial fluid as cartilage biomarkers in rabbits: The effect of high-intensity jumping exercise

Objective. To study the cartilage injury of knee joint in a rabbit model under high-intensity jumping training and to investigate if levels of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-3 (MMP-3), and tisssue inhibitor of matrix metalloproteinase-1 (TIMP-1) in synovial fluid (SF) can be used to predict early sports injury of articular cartilage effectively. Materials and methods. Forty New Zealand white rab bits were divided into two groups randomly: untreated control group (CTRL, n = 8) and jumping training group (TG, n = 32). Concentrations of MMP-1, NBIP-3, and TIMP-1 in SF were measured by ELISA assays at 4 and 13 weeks, respectively. Rabbits were euthanized at 4 and 13 weeks, and knee joints were taken out to be examined histologically. Sulfated glycosaminoglycan (GAG) content, thickness of cartilage and subchondral bone, dead cell ratio, and Mankin grades were measured. Results. At 4 weeks, sulfated GAG content, thickness of subchondral bone, and Mankin grades in TG were significantly higher than control. After 8 weeks, the TG cohort had a further increase in the articular cartilage injury. SF levels of MMP-3, TIMP-1, and MMP-3/TIMP. in TG were significantly higher than control, and the level of these biomarkers was significantly associated with the severity of the articular cartilage pathology. Conclusions. Repetitive and high-intensity jumping movement may induce sports injury in the knee joint cartilage. MMP-1, NMP-3, TIMP-1, and MMP-3/TIMP-1 in the SF may accurately predict the severity and pathological characteristic of the joint cartilage injury. (C) 2007 Elsevier Inc. All rights reserved.