Smad3‐Deficient Mice Have Reduced Esophageal Fibrosis and Angiogenesis in a Model of Egg‐Induced Eosinophilic Esophagitis

Abstract

Eosinophilic esophagitis (EoE) is a food-triggered disease associated with esophageal fibrosis and stricture formation in a subset of patients. In the present study we used a murine model of egg (ovalbumin [OVA])-induced EoE to determine whether inhibiting transforming growth factor-β1 (TGF-β1) signaling through the Smad3 pathway would inhibit features of esophageal remodeling including fibrosis, angiogenesis, and basal zone hyperplasia. Wild-type (WT) and Smad3-deficient (KO [knockout]) mice were sensitized intraperitoneally and then challenged chronically with intraesophageal OVA for 1 month. Levels of esophageal eosinophils, esophageal TGF-β1+ and vascular endothelial growth factor (VEGF)+ cells, and features of esophageal remodeling (fibrosis, angiogenesis, basal zone hyperplasia) were quantitated by immunohistochemistry and image analysis. OVA challenge induced a similar increase in the levels of esophageal major basic protein (MBP)+ eosinophils and esophageal TGF-β1+ cells in WT and Smad3 KO mice. Smad3 KO mice challenged with OVA had significantly less esophageal fibrosis and esophageal angiogenesis compared with OVA-challenged WT mice. The reduced esophageal angiogenesis in Smad3 KO mice was associated with reduced numbers of VEGF+ cells in the esophagus. There was a trend toward OVA-challenged Smad3 KO to have reduced basal zone hyperplasia, but this was not statistically significant. In a mouse model of egg-induced EoE, Smad3-deficient mice have significantly less esophageal remodeling, especially fibrosis and angiogenesis that is associated with reduced expression of VEGF. Targeting the TGF-β1/Smad3 pathway may be a novel strategy to reduce esophageal fibrosis and its associated complications such as esophageal strictures in EoE.