TH17 CELLS PROMOTE INTESTINAL FIBROSIS THROUGH THE PRODUCTION OF AMPHIREGULIN

BACKGROUND & AIMS Intestinal fibrosis is a major serious complication of Crohn’s disease (CD). Gut microbiota-reactive Th17 cells have been established as crucial in the pathogenesis of CD, however, how Th17 cells induce fibrosis is still not completely understood. METHODS Wild-type Th1 cells and Th17 cells, or amphiregulin (Areg)-/- Th17 cells, were transferred into Tcrbxd-/- mice to induce colitis and intestinal fibrosis. CD4+ T cell expression of Areg was determined by qRT-PCR and ELISA. Intestinal fibroblasts were isolated from normal and CD patients and used to determine the effects of Areg on cell proliferation and migration in vitro. Video microscopy and single-cell tracking were used to assess cell migration kinetically. Areg expression was compared in peripheral blood CD4+ T cells, intestinal biopsy tissues, and lamina propria lymphocyte (LPL) from healthy controls and CD patients with or without intestinal fibrosis. RESULTS When transferred into TCRβ/δ-/- mice, although Th1 and Th17 cells induced intestinal inflammation at similar levels, Th17 cells induced more severe intestinal fibrosis than Th1 cells. RNA-seq analysis showed higher levels of AREG expression in Th17 cells compared to Th1 cells, which was further confirmed by qRT-PCR. Transfer of Areg-/- Th17 cells induced less severe fibrosis in TCRβ/δ-/- mice compared with WT Th17 cells. IL-6 but not IL-23 promoted Areg expression in Th17 cells in a time and dose-dependent manner. Treatment with Th17 signature cytokine IL-21, but not IL-17, upregulated T cell expression of Areg. Consistently, IL-21R-/- T cells produced lower levels of Areg. Mechanically, STAT3 mediates Areg expression in Th17 cells, in that IL-6 promoted STAT3 activation, and IL-6 did not induce AREG expression in STAT3-/- T cells. Areg expression was lower in STAT3-/- T cells compared with WT T cells under Th17 conditions. Treatment with RORgt inhibitor, which inhibits Th17 differentiation, suppressed Th17 cell Areg expression, indicating that higher Areg expression requires fully Th17 differentiation. Areg promoted human intestinal fibroblast proliferation and motility, which was mediated by activation of mTOR, and mTOR inhibitors inhibited Areg-induced human intestinal fibroblast proliferation and motility. Finally, Areg expression is increased in peripheral blood CD4+ T cells, intestinal biopsy tissues, and lamina propria lymphocytes of CD patients with fibrosis. CONCLUSION Collectively, these findings reveal that Th17-derived Areg promotes fibrotic responses in both experimental colitis and human CD patients. Thereby, Areg could serve as a potential therapeutic target for fibrosis in CD.