Histamine and substance P in synovial fluid of patients with temporomandibular disorders.

Although psychosocial factors and malocclusion are regarded as potential causes of temporomandibular disorders (TMD), the underlying pathogenesis is poorly understood. Recent studies suggest that substance P (SP), which has been associated with both psychosocial factors and malocclusion, and histamine, whose release can be induced by SP, may be implicated in the pathogenetic process. This study was designed to measure the concentration of histamine and SP in synovial fluid (SF) of both 38 patients with TMD and 11 healthy controls, and analyse the correlation between histamine and SP. Patients with TMD were divided into three subgroups: displaced disc with reduction (DDR), displaced disc without reduction (DDNR) and osteoarthritis (OA), with 10, 13, 15 subjects in every subgroup, respectively. After collecting SF samples, histamine and SP levels were measured by enzyme-linked immunosorbent assay analysis (ELISA) and calibrated by bicinchoninic acid (BCA)-quantified protein level in the samples. The results suggest that OA group presented a significantly higher level of both histamine and SP than DDNR, DDR and healthy control groups. Histamine or SP in DDR and DDNR groups tend to be higher than control group, but no significance was found. Painful TMJs show higher histamine and SP than painless TMJs. Correlation analysis reveals a significant correlation between histamine and SP concentrations. Collectively, this study showed the changes of histamine and SP in the SF from different stages of TMD and found a significant correlation between the two substances, suggesting their potential implication in the pathogenesis of TMD.