Transforming Growth Factor-α and Epidermal Growth Factor Receptor in Colonic Mucosa in Active and Inactive Inflammatory Bowel Disease

Abstract

Transforming growth factor-α (TGF-α) is overexpressed in colonic carcinomas and promotes mucosal wound healing. It may be implicated in chronic inflammatory bowel disease (IBD). We analyzed the expression of TGF-α and its receptor, epidermal growth factor receptor (EGF-r), in the colonic mucosa of patients with Crohn's disease (CD) or ulcerative colitis (UC), in active or inactive stages, as compared with controls. Proteins and mRNA were detected in biopsies from the right and left colon and in surgical colonic specimens. Immunoblot analysis revealed TGF-α protein as a 29 k Da band. This band was normally expressed in uninvolved colonic mucosa of patients with CD or UC whether in active or inactive stages, but decreased or absent in involved mucosa of active IBD, even when TGF-α mRNA and EGF-r protein were detected. In the unaffected mucosa of CD, the intensity of TGF-α immunoreactivity was similar to that of controls in the right colon but stronger (P 0.05) in the left colon. There was no TGF-α overexpression in dysplastic regions. In conclusion, in active IBD disease, the decreased TGF-α protein amount seems not only related to epithelial cell loss but reflects a down-regulation at least at the protein level. We speculate that TGF-α does not play a role within the active stage but may be implicated later in the repair process.