WNT2b activates epithelial-mesenchymal transition through FZD4: relevance in penetrating Crohn´s disease

BACKGROUND AND AIMS Epithelial-mesenchymal transition (EMT) has been related to fibrosis and fistula formation, common complications associated to Crohn´s disease (CD). The WNT signaling pathway mediates EMT and specific WNT/FZD interactions have been related with the activation of this process in several diseases. We aim to analyze the relevance of EMT and Wnt ligands and receptors in the penetrating behavior of CD. METHODS Intestinal surgical resections were obtained from control and CD patients with a stenotic or penetrating behavior. Fibrosis was determined by the histological analysis of collagen deposition and EMT by confocal microscopy. The expression of WNT ligands, inhibitors and FZD receptors was analyzed by RT-PCR, WB, IH and IF studies. The effects of WNT2b and the role of FZD4 in EMT were analyzed in HT29 epithelial cells. RESULTS Fibrosis and expression of EMT markers were detected in samples from CD patients irrespective of the clinical behavior. However, an increased co-localization of E-CADHERIN and VIMENTIN, an increased number of cells expressing WNT2b and a higher expression of FZD4 and WNT2b/FZD4 interaction were detected in intestinal tissue from the penetrating compared with the stenotic CD behavior. WNT2b induced EMT in HT29 cells through FZD4 activation. CONCLUSION An increased EMT, associated with increased WNT2b/FZD4 interaction is detected in intestinal tissue from CD patients with a penetrating behavior. WNT2b, through FZD4 activation induces EMT in vitro which points to a novel pharmacological target to prevent intestinal penetrating complications of CD.