Positive and Negative Regulation of Th17 Cell Differentiation: Evaluating The Impact of RORC2

Objective: Th17 cells are known to be involved in some types of inflammations and autoimmune disorders. RORC2 is the key transcription factor coordinating Th17 cell differentiation. Thus, blocking RORC2 may be useful in suppressing Th17-dependent inflammatory processes. The aim was to silence RORC2 by specific siRNAs in naïve T cells differentiating to Th17. Time-dependent expression of RORC2 as well as IL-17 and IL-23R were considered before and after RORC2 silencing. Materials and Methods: In this experimental study, naïve CD4+ T cells were isolated from human cord blood samples. Cytokines TGFB plus IL-6 and IL-23 were used to polarize the naïve T cells to Th17 cells in X-VIVO 15 serum free medium. A mixture of three siRNAs specific for RORC2 was applied for blocking its expression. RORC2, IL-17 and IL-23R mRNA and protein levels were measured using qRT-PCR, ELISA and flow cytometry techniques. Pearson correlation and one-way ANOVA were used for statistical analyses. Results: Significant correlations were obtained in time-dependent analysis of IL-17 and IL-23R expression in relation with RORC2 (R=0.87 and 0.89 respectively, p < 0.05). Silencing of RORC2 was accompanied with almost complete suppression of IL-17 (99.3%; p < 0.05) and significant decrease in IL-23R gene expression (77.2%, p < 0.05). Conclusion: Our results showed that RORC2 is the main and the primary trigger for upregulation of IL-17 and IL-23R genes in human Th17 cell differentiation. Moreover, we show that day 3 could be considered as the key day in the Th17 differentiation process.