Tartrate-resistant acid phosphatase, matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 in early stages of canine osteoarthritis

The aim of this study was to determine if the activity of tartrate-resistant acid phosphatase (TRAP) in the synovial fluid (SF) and serum can be used as a marker for diagnosing the early stages of osteoarthritis (OA). We also wished to determine if identifiable differences in the concentrations of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) could be detected in SF between normal joints and OA joints for the diagnosis of early OA. Ten skeletally mature beagle dogs underwent a unilateral surgical transection of the cranial cruciate ligament and medial meniscectomy. Five sham-operated beagle dogs were used as controls. The synovial fluid was collected in 1, 2 and 3 months and examined by western blotting for MMP-2 and ELISA for TIMP-2. The activity of TRAP in the SF and serum was measured using a spectrophotometer. In addition, the presence of TRAP positive cells in the synovium was identified by enzyme histochemistry. The level of the activity of TRAP and MMP-2 in the SF from the induced OA dogs was significantly higher than that of the control over a three-month period (P < 0.05). The TIMP-2 level in the SF was significantly lower in the induced OA dogs than in the control. However, there was no difference in TRAP activity in the serum. Histochemistry revealed a higher number of TRAP positive cells in the synovium from the induced OA dogs. Based on these data, we conclude that the activity of TRAP, MMP-2 and TIMP-2 in SF can be used as a biomarker to diagnose and monitor the early stages of OA.