Inflammation location, but not type, determines the increase in TGF-β1 and IGF-1 expression and collagen deposition in IBD intestine

Background and Aims: Inflammatory bowel disease (IBD) is frequently complicated by extracellular matrix (ECM) changes that may result in fibrosis. Transforming growth factor (TGF)-β1 and insulin-like growth factor (IGF)-1 mediate numerous ECM changes. Our aim was to determine whether TGF-β1 and IGF-1 are involved in intestinal ECM collagen regulation and what impact the inflammatory infiltrate has on their expression. Methods: TGF-β1 and IGF-1 mRNA and protein were assessed in fibrosed Crohn's disease (CD), inflamed CD, inflamed ulcerative colitis (UC), and control intestine using in situ hybridization and immunohistochemistry. Collagen types I and III were quantified by electron immunohistochemistry. Results: In CD, increased TGF-β1 and IGF-1 mRNA expression was transmural. In UC, the increase was confined to the lamina propria and submucosa. In both, distribution of TGF-β1 and IGF-1 protein matched mRNA expression and coincided with the distribution of the inflammatory infiltrate. An increase in the collagen type III:I ratio in both CD and UC also coincided with the inflammatory infiltrate. Conclusions: These findings suggest that TGF-β1 and IGF-1 are involved in intestinal ECM remodeling in IBD, and their enhanced expression depends on the presence and location of inflammatory infiltrates rather than the type of IBD.