Cytokine profile in the synovial fluid of patients with temporomandibular joint disorders: A systematic review

The aim of this study was to review the cytokine profiles in the synovial fluid (SF) of patients with temporomandibular joint disorders (TMJD). Databases were searched from 1965 till September 2015 using different combinations of the following key words: “Temporomandibular joint”; “Cytokine”; “disorder”; and “synovial fluid” and “inflammation”. Titles and abstracts of studies identified using the above-described protocol were screened and checked for agreement. Full-texts of articles judged by title and abstract to be relevant were read and independently evaluated. Hand-searching of the reference lists of potentially relevant original and review articles was also performed. The pattern of the present systematic review was customized to mainly summarize the relevant data. Fifteen studies were included. In 12 studies, cytokine profile of patients with TMJD was assessed using enzyme linked immunosorbent assay; and in 2 studies, histological analysis was performed to assess the cytokine profile of patients with TMJD. Patients with TMJD presented raised levels of interleukin (IL)-6 in 8 studies, IL-1beta (1β) in 5 studies and tumor necrosis factor-alpha (TNF-α) in 5 studies. Two studies showed no significant difference in TNF-α levels in patients with and without TMJD; and IL-1β levels were comparable in patients with and without TMJD in 2 studies. Raised levels of IL-6, TNF-α, IL-1β, IL-8, and IFN-γ in the SF have been associated with inflammation in patients with TMJD. Cytokines IL-10, osteoclastogenesis inhibitory factor/osteoprotegerin (OCIF/OPG), and VEGF found in the SF of TMJs could have an anti-inflammatory effect.