Elevated levels of synovial fluid PLA2, stromelysin (MMP-3) and TIMP in early osteoarthrosis after tibial valgus osteotomy in young beagle dogs

• We determined the concentration of markers in cartilage and synovium metabolism in the synovial fluid (SF) of the knee of young beagle dogs with slowly progressive osteoarthrosis. Osteoarthrosis (OA) was induced by a tibial 30°valgus osteotomy to the right hindlimb of 16 dogs. The contralateral knee served as control. The animals were killed 7 (group I) and 18 months (group II) after operation. The levels in SF of chondroitin sulfate (CS), tissue inhibitor of metalloproteinases (TIMP-1), stromelysin (MMP-3), hyaluronan (HA), and the activity of phospholipase A2 enzyme (PLA2) were assayed. The first microscopic signs of cartilage degeneration were observed 7 months postoperatively and the lesions became more severe, including osteophyte formation during the following 11 months. The synovial fluid level of MMP-3 was higher (p = 0.04) at both time-points in the knee joint of the operated hindlimb than in the contralateral joint. On the operated side, 7 months postoperatively, synovial fluid PLA2 activity was higher (p = 0.02) than in the contralateral knee joint, but not 18 months postoperatively. The SF level of TIMP-1 was higher (p = 0.04) in the operated joint than in the contralateral joint 18 months after operation. The molar ratio of MMP-3 to TIMP-1 was higher (p = 0.001) in group II than in group I. The changes observed in the concentration of synovial fluid markers in this slowly progressive canine OA model suggest that activation of an inflammation-related process occurs at an early stage of the OA disease induced by unilateral tibial valgus osteotomy.

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