Objective To investigate the roles of histone H3K27me3 methylation and its regulatory enzymes JMJD3 and EZH2 in the differentiation of Th17 cells in ankylosing spondylitis (AS), to unveil their potential involvement in the pathogenesis of AS, and to provide new strategies and targets for the clinical treatment of AS by analyzing the methylation state of H3K27me3 and its interactions with Th17-related factors.

Methods A total of 84 AS patients (42 active AS patiens and 42 patients in the stable phase of AS) were enrolled for the study, while 84 healthy volunteers were enrolled as the controls. Blood samples were collected. Peripheral blood mononuclear cells were isolated. ELISA assay was performed to examine Th17 cells and the relevant cytokines IL-21, IL-22, and IL-17. The mRNA expressions of RORc, JAK2, and STAT3 were analyzed by RT-PCR, the protein expressions of RORc, JAK2/STAT3 pathway protein, H3K27me3 and the relevant protease (EZH2 and JMJD3) were determined by Western blot. Correlation between H3K27me3, EZH2 and JMJD3 and the key signaling pathway molecules of Th cell differentiation was analyzed by Pearson correlation analysis.

Results The mRNA expressions of RORc, JAK2, and STAT3 were significantly higher in the active phase group than those in the stable phase group (P<0.05). The relative grayscale values of H3K27me3 and EZH2 in the active phase group were lower than those of the stable phase group, which were lower than those of the control group, with the differences being statistically significant (P<0.05). The relative grayscale values of JMJD3, RORc, JAK2, pJAK2, STAT3, and pSTAT3 proteins were significantly higher in the active phase group than those in the stable phase group, which were higher than those in the control group (all P<0.05). The proportion of Th17 and the expression level of inflammatory factors in the active period group were higher than those in the other two groups (P<0.05). H3K27me3 was negatively correlated with RORc, JAK2, STAT3, and IL-17, JMJD3 was positvely correlated with JAK2, STAT3, and IL-17, and EZH2 was negatively correlated with JAK2, STAT3, and IL-17 (all P<0.05).

Conclusion The low expression of H3K27me3 in AS is influenced by the gene loci JMJD3 and EZH2, which can regulate the differentiation of Th17 cells and thus play a role in the pathogenesis and progression of AS.