Abstract Background Intestinal fibrosis is a major complication without preventive or curative treatment, occurring in 20–30% of patients with Crohn’s disease (CD). It can lead to obstructive episodes and the need for intestinal resection (1). Enhancer of Zeste Homolog 2 (EZH2) is an epigenetic regulatory enzyme responsible for histone H3K27 trimethylation and has been shown to play a pro-fibrotic role in the liver, kidney, myocardium, skin, and lung. The aim of this study was to investigate the role of EZH2 in the development of intestinal fibrosis. Methods Two public gene expression datasets (qPCR-based) from colonic and ileal mucosal samples of patients with CD and ulcerative colitis (UC) were analysed. A histological study was performed on a monocentric cohort of 29 patients who underwent surgery for stricturing ileal CD. In vivo, a murine model of chronic dextran sodium sulfate (DSS)-induced colitis was used. In vitro, four cell types involved in intestinal fibrosis—colonic fibroblasts (CCD-18Co), endothelial cells (HIMEC), and epithelial cells (Caco-2 and HT-29)—were exposed to pro-fibrotic conditions (TGF-β, 10–20 ng/mL) with or without an EZH2 inhibitor (GSK126, 0.5–1 µM). Results In patients with CD and UC, EZH2 was significantly overexpressed during the inflammatory phase in the ileocolonic mucosa (p 0.001) and colonic mucosa (p 0.0001), respectively. Histological analysis revealed a gradient of EZH2 expression within epithelial cells, showing a trend toward overexpression distant from the crypts in fibrotic areas. In vivo, male mice with chronic DSS-induced colitis exhibited a significantly higher colon EZH2 expression within intestinal muscular layers (p 0.0001). In vitro, under pro-fibrotic conditions, fibroblasts showed EZH2 overexpression at both the mRNA (p 0.001) and protein levels (p 0.05). A similar trend was observed in both epithelial cells lines (p = 0.06 for Caco-2 and p = 0.42 for HT-29) but not in endothelial cells. Pharmacological inhibition of EZH2 (GSK126, 1µM) under pro-fibrotic conditions prevented ACTA2 upregulation at the mRNA level (p 0.05) and αSMA overexpression in Western blot (p 0.05), but had no effect on collagen or fibronectin expression. Pharmacological inhibition of EZH2 (GSK126, 0.5µM) tended to reduce ACTA2, CTGF and VIM upregulation during TGF-B-induced epithelial–mesenchymal transition in HT-29 cells (p = 0.19; 0.45 and 0.14 respectively). Conclusion These findings support a potential role for EZH2 in the development of intestinal fibrosis. Further studies evaluating the impact of pharmacological EZH2 inhibition in mice with chronic colitis and fibrosis are warranted to confirm its therapeutic relevance in stricturing Crohn’s disease. Reference: (1)Rieder F, Fiocchi C, Rogler G. Mechanisms, Management, and Treatment of Fibrosis in Patients With Inflammatory Bowel Diseases. Gastroenterology. févr 2017;152(2):340-350.e6. Conflict of interest: Dr. Richard, Nicolas: Lecture/consultant fees from AbbVie, Amgen, Celltrion, Ferring, Janssen, Lilly, Sandoz and Takeda. Savoye, Guillaume: No conflict of interest Thiebault, Pierre-Alain: No conflict of interest Rebollo, Elise: No conflict of interest Ratel, Lise: No conflict of interest Aublé, Kanhia: No conflict of interest Bôle-Feysot, Christine: No conflict of interest Guerin, Charlène: No conflict of interest Leboutte, Mathilde: No conflict of interest Marion-Letellier, Rachel: No conflict of interest
Richard et al. (Thu,) studied this question.