Gamma delta T cells promote intestinal fibrosis via an interleukin-17A-induced transforming growth factor-beta signaling pathway in fibroblasts.

BACKGROUND

Gamma delta T (γδ T) cells are a subpopulation of T cells enriched in the mucosa and epithelium. Intestinal fibrosis is a common complication of Crohn's disease (CD). This study investigates the role of γδ T cells and their mechanistic involvement in driving fibrotic progression in CD.

METHODS

A mouse model of Crohn's disease-associated intestinal fibrosis was established by intrarectal administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in 50% ethanol. Two separate intervention groups were treated with either an anti-interleukin-17A (anti-IL-17A) antibody or an anti-γδ T cell receptor (anti-γδ TCR) monoclonal antibody (clone GL3). Fibrosis was assessed via histology, enzyme-linked immunosorbent assay (ELISA), and Western blot. Additionally, γδ T cells and fibroblasts were isolated and subjected to Transwell co-culture. Their proliferation, apoptosis, and fibrosis markers were subsequently analyzed using the Cell Counting Kit-8 (CCK-8) assay, flow cytometry, ELISA, and Western blot, respectively.

RESULTS

Compared to the control group, the model group mice showed weight loss, colon shortening, fibrosis, collagen deposition, and elevated IL-17, γδ T cells, and fibroblasts. Anti-IL-17A or GL3 antibody intervention attenuated fibrosis and reduced these factors. In vitro, model cells exhibited increased IL-17, alpha-smooth muscle actin (α-SMA), and collagen expression, which was further upregulated by Transwell co-culture. In vivo, the transforming growth factor-beta (TGF-β)/Smad pathway was activated with upregulated connective tissue growth factor (CTGF) in the model group, while antibody intervention inhibited this pathway. These findings are consistent with the in vitro results.

CONCLUSION

γδ T cells play a significant role in promoting CD intestinal fibrosis, potentially through the secretion of IL-17, which activates fibroblasts and enhances the TGF-β/Smad signaling pathway. Consequently, targeting or depleting these cells represents a promising therapeutic strategy for CD-related intestinal fibrosis.