Interleukin-34 Aggravates the Severity of Arthritis in Collagen-Induced Arthritis Mice by Inducing Interleukin-17 Production

To explore the immunological mechanisms underlying the effect of exogenous interleukin-34 (IL-34) on collagen-induced arthritis (CIA) in mouse. We established a CIA mouse model and injected exogenous recombination mouse IL-34 (rmIL-34) intraperitoneally. The articular index (AI) was measured according to the amount of erythema, swelling, or joint rigidity. The concentrations of TNF-, IL-17, and IL-6 in CIA mice sera were measured by enzyme-linked immunosorbent assay (ELISA). The mRNA expression levels of TNF-, IL-17, and IL-6 in CIA synovial tissue were detected by reverse transcription PCR. The CIA mice dosed with rmIL-34 exhibited increased AI. Neutralization of endogenous IL-17 with anti-IL-17 antibody reduced the effect of IL-34. TNF-, IL-17, and IL-6 levels in serum in IL-34-treated CIA mice were increased compared to those in CIA mice. IL-34 increased the expression of TNF- and IL-17 mRNA in synovial tissues of CIA mice, but the gene expression of IL-6 was not affected. The effects of IL-34 on TNF-, IL-17, and IL-6 expression were abolished by anti-IL-17 antibody. In conclusion, IL-34 acts as a proinflammatory factor, aggravating the severity of arthritis in CIA mice by inducing the production of IL-17.