1. ¹Department of Surgery, John D Dingell VA Medical Center, Wayne State University, Detroit, MI, USA
2. ²Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI 48201, USA

Correspondence: Dr MD Basson, MD, PhD, Surgical Service (11S), John D Dingell VAMC, 4646 John R Street, Detroit, MI 48201, USA. E-mail: Marc.basson@va.gov

Received 30 May 2008; Revised 9 July 2008; Accepted 9 July 2008; Published online 18 August 2008.

Abstract

Altered transforming growth factor- (TGF) expression may contribute to inflammatory bowel disease and modulate epithelial cell restitution. Interference with TGF-mediated signaling inhibits excisional skin wound healing, but accelerates healing of incisional cutaneous wounds and wounds in some other tissues. Therefore, we sought to clarify the potential role of Smad3-dependent TGF signaling in intestinal mucosal healing in Smad3 null mice. Jejunal serosal application of filter disks saturated with 75% acetic acid yielded a circumscribed reproducible ischemic mucosal ulcer 1 day later. We compared ulcer area at 3 and 5 days to day 1 in Smad3 knockout mice and syngeneic wild-type mice, and evaluated mucosal immunoreactivity at the ulcer edge for TGF, phosphorylated (activated) focal adhesion kinase (pFAK), phosphorylated extracellular signal-related kinase (pERK), proliferating cell nuclear antigen and apoptosis by TUNEL. Ulcer healing in Smad3 null mice was 17% less at day 3 (n=14, P=0.022) and 15% less at day 5 (n=14, P=0.004) than in wild-type littermates. In wild-type mice, pFAK, pERK and TGF immunoreactivity were elevated in epithelium immediately adjacent to the ulcer compared with more distant mucosa. However, this pattern of immunoreactivity for pFAK, pERK and TGF was not observed in Smad3 null mice. Smad3 null mice exhibited increased epithelial proliferation and no differences in apoptotic cell death compared with wild types, suggesting that ulcer healing may reflect differences in restitutive cell migration. Thus, Smad3-dependent disruption of the TGF signaling pathway impairs the healing of murine intestinal mucosal ulcers and alters patterns of activated FAK and ERK immunoreactivity important for cell migration at the ulcer edge. These studies suggest a significant role for Smad3-dependent TGF signaling in intestinal mucosal healing.