Expression of interleukin 8 in synovial tissues in patients with internal derangement of the temporomandibular joint and its relationship with clinical variables

Objectives. The objectives of this study were to assay interleukin 8 (IL-8) in synovial tissues of the temporomandibular joint (TMJ) with symptomatic internal derangement, and to assess its relationship with clinical variables. Study design. Forty-six joints in 44 patients were examined using an immunohistochemical technique. As controls, 8 joints in 7 subjects with habitual dislocation without pain were also examined. Results. IL-8 was expressed mainly in the blood vessels beneath the lining cells in 37 of the 46 joints (80%) with internal derangement and in 2 of the 8 control joints. The percentage of IL-8-positive cells was significantly higher in the internal derangement group than in the control group (P =.004). The percentage of IL-8-positive cells showed no correlation with joint pain or number of infiltrating cells. Conclusions. IL-8 was up-regulated in inflamed synovial tissues in patients with internal derangement. Because IL-8 has no significant correlation with clinical variables, IL-8 may play a secondary role in the pathogenesis of the internal derangement of the TMJ.