FOXP3-engineered regulatory T cells restore intestinal barrier integrity in Crohn's disease enteroids via PDGF-AA

Epithelial regeneration and barrier integrity are impaired in inflammatory bowel diseases, including Crohns disease (CD), yet current therapies largely target immune inflammation without directly promoting mucosal repair. While regulatory T cells are classically immunomodulatory, their capacity to directly support human intestinal stem cells (ISCs) and barrier function remains unclear. In this study, we tested the hypothesis that FOXP3-expressing regulatory T cells--engineered CD4LVFOXP3 and thymic-derived Treg (tTreg)--directly support human ISC maintenance and restore epithelial barrier function independent of their immunomodulatory function. Using CD patient ISCs-derived enteroids that display disease-associated damage, we established co-culture with FOXP3-engineered Treg cell-CD4LVFOXP3 or thymic-derived Treg (tTreg). The presence of either CD4LVFOXP3 or tTreg cells enhanced enteroid growth, improved epithelial barrier function, and restored apical-basal polarity of ISCs, indicating reparative capacity. Conversely, activated conventional CD4+ T cells reduced barrier function and abrogated apical-basal polarity. Integrating secretome profiling with ligand add-back and receptor or ligand blockade, we identify the PDGF-AA-PDGFR axis as a key regulator of Treg-mediated intestinal epithelial barrier integrity, but dispensable for Treg suppressive capacity. Collectively, our data delineate a direct, human tissue-intrinsic role of FOXP3-driven Treg in the interaction with ISCs via PDGF-AA-PDGFR, enhancing epithelial barrier function and positioning CD4LVFOXP3 as a treatment approach coupling immunoregulation with epithelial repair. One Sentence SummaryRegulatory T cells improve the intestinal epithelial barrier function, primarily, through the PDGF-AA-PDGFR axis