Expression and regulation of connective tissue growth factor by transforming growth factor β and tumour necrosis factor α in fibroblasts isolated from strictures in patients with Crohn's disease

Abstract

Abstract Background Connective tissue growth factor (CTGF) stimulates fibroblast proliferation and extracellular matrix production. Fibroblasts may initiate stricture formation in Crohn's disease through overexpression of CTGF. Stricturing that occurs in patients with Crohn's disease after treatment with anti-tumour necrosis factor (TNF) α may be due to dysregulation of CTGF homeostasis. The aim of this study was to examine CTGF expression and regulation in fibroblasts isolated from patients with Crohn's disease. Methods Fibroblasts were isolated by a primary explant technique from serosal biopsies of strictured segments of bowel in eight patients undergoing resection for Crohn's disease and from normal colon in seven patients having resection for benign or malignant colorectal disease. Cells were stimulated with transforming growth factor (TGF) β and TNF-α. CTGF protein and mRNA expression were measured by western blotting and real-time polymerase chain reaction respectively. Results Mean(s.d.) CTGF protein expression in strictured Crohn's fibroblasts was higher than that in normal fibroblasts (56·5(9·7) versus 17·0(10·0) respectively; P = 0·011). In normal and strictured Crohn's fibroblasts, culture with TGF-β increased CTGF protein and mRNA expression. Co-culture of normal fibroblasts with TNF-α suppressed TGF-β-stimulated CTGF expression. Conclusion Increased expression of CTGF in strictured Crohn's fibroblasts underlies its role in fibrosis. TNF-α suppresses fibrosis by downregulating fibroblast CTGF expression, an effect that may be lost following anti-TNF-α treatment, thereby promoting stricture formation.