Epithelial Mesenchymal Transition in Eosinophilic Esophagitis: Identification and Contributions to Esophageal Remodeling and Fibrosis

RATIONALE: Esophageal remodeling in Eosinophilic Esophagitis (EoE), a food-allergic disease, includes epithelial hyperplasia and subepithelial fibrosis. Epithelial Mesenchymal Transition (EMT) is a process whereby non-motile epithelial cells de-differentiate into motile mesenchymal-like cells during chronic inflammation, and can further differentiate into myofibroblasts. Since the mechanism of esophageal fibrosis in EoE is poorly understood, our objective was to determine whether EMT occurs in EoE and contributes to its pathogenesis. METHODS: Sections from 60 formalin-fixed, paraffin-embedded biopsies from patients with EoE (17), GERD (7), indeterminate esophagitis (15), and normal esophagus (21) were evaluated for EMT by two-color immunofluorescence staining for cells expressing cytokeratin (epithelial) and vimentin (mesenchymal) markers. Sections were analyzed in a blinded fashion by confocal microscopy and graded for the presence/degree of EMT using a 6-point scale. Mean EMT indices/hpf were analyzed for relationships to diagnosis, eosinophils/hpf, and indices for eosinophil peroxidase (EPX) and TGF-beta immunostaining, and esophageal fibrosis. RESULTS: The highest EMT index was associated with a patient diagnosis of EoE (3.25±0.28), followed by indeterminate esophagitis(2.69±0.29)>GERD(1.62±0.39)>normal(1.06±0.15). EMT was positively correlated (all p<0.01) with eosinophils/hpf (r=0.691), EPX (r=0.738) and TGF-beta (r=0.520) staining indices, and esophageal fibrosis scores (r=0.644). CONCLUSIONS: This is the first identification of EMT in EoE. EMT was observed principally in EoE, to a lesser degree in indeterminate esophagitis with fibrosis, whereas it was observed only once in GERD, and not in normal esophagus. The significant correlations of EMT to esophageal eosinophils and their activation, and measures of fibrosis, suggest that EMT may contribute to the subepithelial fibrosis characteristic of EoE pathogenesis.