Synovial apoptosis in temporomandibular joint disc displacement without reduction

Objective. Our hypothesis is that increased apoptosis in synovium might contribute to temporomandibular joint (TMJ) degeneration. To investigate this, we measured soluble Fas (sFas) and nuclear matrix protein (NMP) levels in TMJ synovial fluid from patients with disc displacement without reduction as indicators of apoptosis in the synovium. Patients and methods. Synovial fluid was obtained from 17 joints in 17 patients (11 female, 6 male; mean age, 31.5 +/- 11.9 years; range, 19 to 55). Patients were referred to our clinic because of limited mouth opening, joint sounds, or TMJ pain. Synovial fluid obtained by arthrocentesis for therapeutic reasons was analyzed by enzyme-linked immunosorbent assays for APO-1/Fas and cell death detection (NMP). Results. We studied 12 left (71%) and 5 right (29%) joints with disc displacement without reduction. The chief complaint was pain on the affected side and limited mouth opening. Only 2 patients had a click in the affected joint, whereas 14 reported pain and 17 had the limited mouth opening. All patients experienced a significant (P<.01) increase in maximal mouth opening immediately after arthrocentesis. Mean sFas and NMP levels were 484.9 +/- 466.7 pg/mL (range, 17 to 1501) and 29.2 +/- 13.7 U/mL (range, 8 to 52.8) respectively. Conclusion. Considering reports that increased sFas blocks apoptosis by inhibiting binding of FasL to Fas on the cell membrane, low level of sFas in our patients' synovial fluid (compared with amounts reported in joint inflammation or degeneration) suggests vulnerability to apoptosis in patients with internal derangement. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:693-698)