Aims: Imbalance between matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) may be involved in the breakdown of articular cartilage matrix of the temporomandibular joint (TMJ). Aims: In this study, MMPs, TIMPs, and MMP-1/TIMP-1 complex levels were examined in TMJ synovial fluid samples aspirated from TMJ osteoarthritis (OA) patients (2 males, 8 females
mean age, 29.7 years) and asymptomatic control subjects (2 males, 8 females
mean age, 23.6 years) to determine the likelihood of increased proteolytic activity in the OA joints. Methods: The various types of MMPs and TIMPs were detected by Western blotting with monoclonal antibodies and gelatin zymography. The MMP-1/ TIMP-1 complex level was measured by an enzyme-linked immunosorbent assay kit. All aspirates were first analyzed for total protein content and then individually diluted to make the total protein levels equivalent. Results: The mean MMP-1/TIMP-1 complex concentration in the synovial fluids of the OA patients was 3.92 ± 1.39 ng/mL
this value was significantly lower (P &lt
0.05) than the value from control subjects (5.46 ± 1.32 ng/mL). Matrix metalloproteinase-1 (52 kDa), MMP-3 (57 kDa), TIMP-1 (28 kDa), and TIMP-2 (26 kDa) were detected in all of the normal and the OA samples. However, MMP-1 (28 kDa), MMP-2 (72 kDa), MMP-3 (45 kDa), and MMP-9 (83 kDa) were detected in higher concentration in the OA samples. Conclusion: These findings suggest a strong association between the OA-active joints and the presence of biologically active forms of known tissue degradation enzymes (MMP-1, MMP-3, and MMP-9).