IL-17 Level In Serum And Its Expression In The Synovium Of The Collagen Induced Arthritis Rat

Objective This study was performed to explore the interleukin( IL )-17 level in serum and expression in synovium, and to analyze the relationship with tumor necrosis factor-α(TNF-α) , joint destruction in the collagen induced arthritis (CIA) rat in different periods, so that we realize the effect of IL-17 on CIA and provide a new method of diagnosis and therapy for rheumatoid arthritis (RA).Method Fifty male Wistar rats were randomly divided into 2 groups including the normal control group (being 20 rats) and the model control group (being 30 rats). Collagen II (CII ) and complete Freund's adjuvand were used to induce experimental arthritis (CIA). The normal control group was injected with glacial acetic acid. The severity of arthritis was evaluated by Arthritis Index; IL-17, TNF-αserum level were tested by ELISA in different periods in CIA group and normal groups; Histology of synovial tissue was observed by the microscope. The histology changes included the proliferation of the synovial cells, effusion and infiltration of inflammatory cells, destruction of cartilage and bone; the expression and distribution of IL-17 on synovial membranes in both groups were examined by immunohistochemical methods. The changes of IL-17, TNF-αserum level and arthritis index (AI) in different periods were studied by student's T test. The correlations of between IL-17, TNF-αand pathologic score were studied with linear correlation analysisResults The IL-17 were expressed in both normal and CIA group, the serum level of IL-17 in CIA group in different period was significantly higher than those of the normal group and experiment failed group(p<0.01). The serum level of IL-17 in CIA group start to increase at the early period (two weeks) and reach a high level in the middle (four weeks)and late period (six weeks), which was higher being compared to the early period(p<0.01). The same change was also observed in TNF-αlevel in serum. It was higher in the middle and late period than that in the early period. IL-17 expression in synovium of CIA group was higher than those in the normal group and experiment failed group(p<0.01).The serum level of IL-17 at different period in CIA group was positively correlated with severity of joint destruction and the serum TNF-αlevel in the same period.Conclusion The serum IL-17 , TNF-αlevel in different period and its expression in the synovium of collagen induced arthritis rat are significantly higher in CIA group than those in the control group. It showed that IL-17 has intimate correlation with TNF-αand other cytokines. Those cytokines are mutual influence and promoting, which result to positive feedback and amplify synovial inflammation .It was concluded that IL-17 played an important role in the progress in CIA and the key role in pathogenesis, development and joint destruction in RA; and it correlate with joint destruction and being an important index to judge rheumatoid arthritis'prognosis. The above results provide an experimental basis for diagnosing and treating rheumatoid arthritis (RA).