Targeted Demethylation of FOXP3-TSDR Enhances the Suppressive Capacity of STAT6-deficient Inducible T Regulatory Cells.

In vitro induced T regulatory cells (iTregs) are promising for addressing inflammation-driven diseases. However, current protocols for the generation and expansion of iTregs fail to induce extensive demethylation of the Treg-specific demethylated region (TSDR) within the FOXP3 gene, recognized as the master regulator for regulatory T cells (Tregs). This deficiency results in the rapid loss of Foxp3 expression and an unstable regulatory phenotype. Nevertheless, inhibition of STAT6 signaling effectively stabilizes Foxp3 expression in iTregs. Thus, this study aimed to develop a protocol combining epigenetic editing with STAT6 deficiency to improve iTregs' ability to maintain stable suppressive function and a functional phenotype. Our findings demonstrate that the combination of STAT6 deficiency (STAT6-/-) with targeted demethylation of the TSDR using a CRISPR-TET1 tool leads to extensive demethylation of FOXP3-TSDR. Demethylation in STAT6-/- iTregs was associated with enhanced expression of Foxp3 and suppressive markers such as CTLA-4, PD-1, IL-10, and TGF-β. Furthermore, the edited STAT6-/- iTregs exhibited an increased capacity to suppress CD8+ and CD4+ lymphocytes and could more efficiently impair Th1-signature gene expression compared to conventional iTregs. In conclusion, the deactivation of STAT6 and TSDR-targeted demethylation via CRISPR-TET1 is sufficient to induce iTregs with heightened stability and increased suppressive capacity, offering potential applications against inflammatory and autoimmune diseases.