Increased Endoplasmic Reticulum stress specific chaperones characterise CD fibrosis epithelium tissues and participates to in vitro induction of intestinal fibroblasts differentiation

Background: Intestinal fibrosis is a complication of Crohn’s disease (CD) characterized by myofibroblasts and extracellular matrix accumulation within the submucosa and smooth muscles, leading to bowel strictures. No medical treatment exists to treat or reverse intestinal fibrosis leading often to surgical resection. The potential role of intestinal epithelium in the fibrotic process remains poorly defined.
Methods: We performed a pilot study on ileal fibrostricturing CD surgical samples (n=5), comparing the proteome of surface epithelium isolated by laser capture microdissection in normal and fibrotic zones. Confirmation of the specific protein increases was obtained by immunohistochemistry in colonic and ileal samples of CD (n=44) compared to healthy subjects (n=40), as well as in intestinal epithelial cell line under induced Endoplasmic Reticulum (ER) stress. A model of fibroblast to myofibroblast differentiation induction was also challenged using preconditioned media of intestinal epithelial cells after a pulsed ER stress.
Results: Label free proteomics revealed high ER stress in the epithelium surrounding fibrotic bowel wall, involving Anterior gradient protein 2 homolog (AGR2) and 78kDA glucose regulated protein (BiP). Confirmation of both proteins increase was obtained by immunohistochemistry. ER stress induction in intestinal epithelial cells was associated with an intracellular increase of AGR2, BiP and ER stress markers as sXPB1 and CHOP. AGR2 was also detected in the culture medium of these epithelial cells and myofibroblast differentiation was obtained using this culture medium.
Conclusions: The increase of ER stress proteins observed in fibrostenosing tissues together with These preliminary evidences of fibroblast to myofibrobast differentiation obtained by paracrine action of intestinal epithelial cell preconditioned to ER stress induction, suggest a role of epithelial ER stress in Crohn’s disease intestinal fibrosis.