Expression of proinflammatory cytokines in osteoarthritis of the temporomandibular joint
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Objective: This study reports the expression of proinflammatory cytokines in temporomandibular joint (TMJ) of patients affected with temporomandibular osteoarthritis (OA). Design: In twelve OA of the TMJ (OA–TMJ) affected patients and in six healthy volunteer subjects studied as control, the expression of IL1b (interleukin-1b), IL2, IL4, IL5, IL6, IL10, IL12p35, IL12p40, IL17, IFNg (interferon-gamma), TNFa (tumor necrosis factor-alpha), and TNFb mRNAs was evaluated. Using quantitative real-time RT-PCR technique, the cytokine levels, reported as Ct (cycle threshold), DCt (Ct cytokine Ct 18S rRNA) and RQ (relative quantification), in patient and control groups were compared. Results: Expression of IL1b, IL2, IL12p35, IL12p40, IL17, TNFa, TNFb, and IFNg mRNAs was significantly higher in patients as compared with controls. In particular, IL12 was the predominant cytokine expressed in patients (IL12p35 RQ = 30.2 and IL12p40 RQ = 29.0). Conversely, IL10 mRNA levels were higher in controls (RQ = 1.8). Conclusions: These data suggest that not only IL1b, IFNg, and TNFa but also IL10, IL12, and IL17 are involved in the OA–TMJ pathogenesis. Furthermore, an inflammatory response characterised by the predominant expression of IL12 mRNA and down-regulated expression of IL10 mRNA is associated with the degenerative changes observed in OA–TMJ.