SHORT SUMMARY Group 2 innate lymphoid cells (ILC2s) produce high levels of IL-5 and IL-13, both of which are important pathogenic mediators in eosinophilic esophagitis (EoE). ILC2s have not been previously described in EoE. Our study demonstrates the novel finding that ILC2s are increased in esophageal biopsies from EoE patients with active disease compared with inactive EoE and non-diseased controls, implicating these cells in EoE pathogenesis.

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Background Eosinophilic esophagitis is an allergic disease of increasing worldwide incidence. Complications are due to tissue remodeling and involve transforming growth factor-β1 (TGFβ1) mediated fibrosis. Plasminogen Activator Inhibitor-1 (PAI-1/serpinE1) can be induced by TGFβ1 but its role in EoE is not known. Objective To understand the expression and role of PAI-1 in EoE. Methods We used esophageal biopsy specimens and plasma samples from control and EoE subjects, primary human esophageal epithelial cells, and EoE fibroblasts in immunohistochemistry, quantitative PCR, and immunoassay experiments to understand the induction of PAI-1 by TGFβ1, the relationship between PAI-1 and esophageal fibrosis, and the role of PAI-1 in fibrotic gene expression. Results PAI-1 expression was significantly elevated in epithelial cells of active EoE biopsies as compared with inactive EoE or control biopsies (p<0.001). Treatment of primary esophageal epithelial cells with recombinant TGFβ1 increased PAI-1 transcription, intracellular protein expression, and secretion. Esophageal PAI-1 expression correlated with basal zone hyperplasia, a fibrosis, and markers of esophageal remodeling including vimentin, TGFβ1, collagen I, fibronectin, and matrix metalloproteases and plasma PAI-1 levels correlated with plasma TGFβ1. PAI-1 inhibition significantly decreased baseline and TGFβ1-induced fibrotic gene expression. Conclusions PAI-1 is significantly elevated in the EoE epithelium, reflects fibrosis, and its inhibition decreases TGFβ1-induced gene expression. Epithelial PAI-1 may serve as a marker of EoE severity and form part of a TGFβ1-induced pro-fibrotic network.

A r t i c l e A m e n d m e n t s2 5The label for Figure 1E misidentified the prion inoculum administered to the mice depicted. The correct label is below. CJD-inoculatedThe JCI regrets the error.