Research Article: Role of glycogen synthase kinase-3β and PPAR-γ on epithelial-to-mesenchymal transition in DSS-induced colorectal fibrosis

Date Published: February 16, 2017

Publisher: Public Library of Science

Author(s): Jacopo Di Gregorio, Roberta Sferra, Silvia Speca, Antonella Vetuschi, Caroline Dubuquoy, Pierre Desreumaux, Simona Pompili, Loredana Cristiano, Eugenio Gaudio, Vincenzo Flati, Giovanni Latella, Masaru Katoh.


Intestinal fibrosis is characterized by abnormal production and deposition of extracellular matrix (ECM) proteins by activated myofibroblasts. The main progenitor cells of activated myofibroblasts are the fibroblasts and the epithelial cells, the latter through the epithelial-mesenchymal transition (EMT).

To evaluate the action of the new PPAR-γ modulator, GED-0507-34 Levo (GED) on the expression of EMT associated and regulatory proteins such as TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, and GSK-3β, in a mouse model of DSS-induced intestinal fibrosis.

Chronic colitis and fibrosis were induced by oral administration of 2.5% DSS (w/v) for 6 weeks. GW9662 (GW), a selective PPAR-γ inhibitor, was also administered by intraperitoneal injection at the dose of 1 mg/kg/day combined with GED treatment. All drugs were administered at the beginning of the second cycle of DSS (day 12). 65 mice were randomly divided into five groups (H2O as controls n = 10, H2O+GED n = 10, DSS n = 15, DSS+GED n = 15, DSS+GED+GW n = 15). The colon was excised for macroscopic examination and histological and morphometric analyses. The level of expression of molecules involved in EMT and fibrosis, like TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, GSK-3β and PPAR-γ, was assessed by immunohistochemistry, immunofluorescence, western blot and Real Time PCR.

GED improved the DSS-induced chronic colitis and fibrosis. GED was able to reduce the expression of the main fibrosis markers (α-SMA, collagen I-III and fibronectin) as well as the pivotal pro-fibrotic molecules IL-13, TGF-β and Smad3, while it increased the anti-fibrotic PPAR-γ. All these GED effects were nullified by co-administration of GW with GED. Furthermore, GED was able to normalize the expression levels of E-cadherin and β-catenin and upregulated GSK-3β, that are all known to be involved both in EMT and fibrosis.

The DSS-induced intestinal fibrosis was improved by the new PPAR-γ modulator GED-0507-34 Levo through the modulation of EMT mediators and pro-fibrotic molecules and through GSK-3β induction.

Partial Text

Intestinal fibrosis is one of the main complications of the Inflammatory Bowel Disease (IBD), affecting more than 30% of Crohn’s disease (CD) patients and almost 5% of Ulcerative Colitis (UC) patients [1–3]. Characterized by an uncontrolled production and deposition of extracellular matrix components (ECM), intestinal fibrosis is the main cause of lumen stricture and obstruction that can lead to loss of function of the affected digestive tracts.

The study has been performed at the Institution of Pasteur Animal care facility (Institut Pasteur de Lille, France) according to governmental guidelines and approved by the “Comité d’Ethique en Expérimentation Animale Nord-Pas de Calais” (CEEA n°75; ethic committee for animal experimentation of the region Nord-Pas de Calais–France).

In contrast to the intensive investigations focusing on the immunological mechanisms related to the early phases of intestinal inflammation and repair, the pathophysiology of chronic mucosal wound healing and the late events of repair leading to intestinal fibrosis remain largely unexplored [8, 28, 29]. Consequently, this lack of knowledge has contributed to the lack of development of effective anti-fibrotic drugs and the fact that the intestinal fibrosis still is a frequent indication for surgery in several enteropathies, especially in Crohn’s disease.