Regulatory Networks That Govern the Esophageal Epithelial Proliferative Response in Eosinophilic Esophagitis Endotypes
Creators: name: Marella, Sahiti
Publisher: name: My University
Year: 2023
Subjects: subject: Eosinophilic Esophagitis
subject: proliferation
subject: epithelial cell
subject: STAT3
subject: IL-13
subject: proton pump inhibitor
subject: Pathology
subject: Health Sciences

description: Eosinophilic esophagitis (EoE) is a food allergen-driven disease of the esophagus clinically characterized by upper gastrointestinal (GI) symptoms including, dysphagia, vomiting, and food impaction. Histopathological features of EoE include intraepithelial infiltration of eosinophils (≥ 15 Eos/HPF) and esophageal epithelial remodeling (basal zone hyperplasia [BZH] and dilated intercellular spaces [DIS]), which can lead to fibrostenotic sequelae of strictures and narrow-caliber esophagus. There is corroborative clinical and experimental evidence to suggest that EoE is driven by an underlying Interleukin-5 and Interleukin-13 (IL-5 and IL-13) producing CD4+ T helper type 2 (Th2) allergic inflammatory response to dietary food allergens in the esophageal mucosa. Currently, the standard of care treatment for EoE is 8 – 12-week high dose proton pump inhibitor (PPI), however only ~ 50% individuals achieve disease remission. The current gaps in knowledge are 1) the IL-13-induced signaling networks which regulate esophageal epithelial remodeling and 2) the transcriptional programs which distinguish the two distinct EoE endotypes, PPI-responsive EoE (PPI-R EoE) and PPI-unresponsive EoE (PPI-UR EoE). In this dissertation, we identified 82 common differentially expressed genes (DEGs) that were enriched for putative STAT3 target genes (32 DEGs) from RNAseq analyses of esophageal biopsies and IL-13-stimulated esophageal epithelial cells (EPC2-ALI). We show that IL-13 stimulation of EPC2-ALI and primary esophageal cells induced STAT3 and STAT6 phosphorylation and that STAT3 was required for esophageal epithelial proliferation. In vitro studies revealed that IL-13 induced the putative STAT3 target secreted frizzled-related protein 1 (SFRP1) in esophageal cell and that IL-13-induced esophageal cell proliferation was regulated by SFRP1. Employing a validation dataset, we determined that SFRP1 mRNA is increased in esophageal biopsies from patients with active EoE compared to healthy controls or patients in remission and identified an SFRP1+ esophageal suprabasal epithelial cell subpopulation that uniquely expressed the core EoE pro-inflammatory transcriptome genes (CCL26, ALOX15, CAPN14, ANO1, TNFAIP6). Further, we performed comprehensive clinical, histologic and transcriptomics analyses of PPI-R and PPI-UR treatment-naïve EoE individuals at diagnosis and following PPI therapy. We demonstrated PPI-R and PPI-UR EoE esophageal biopsies are clinically and histologically indistinguishable at diagnosis. RNAseq analyses revealed DEGs that were commonly enriched in PPI-R and PPI-UR EoE at diagnosis included the prototypic EoE transcriptomic immune genes (CCL26, TNAIP6, ALOX15, IL-13). The unique genes in PPI-R EoE were enriched for biological processes involved in hydrogen peroxide catabolic process and neuropeptide signaling pathways. The unique genes in PPI-UR EoE were enriched for biological processes associated with DNA replication, cell cycle and cell division. PPI monotherapy induced disease remission in PPI-R EoE individuals, which was associated with loss of Th2 inflammatory and dedifferentiated esophageal epithelial transcriptomic signature. In PPI-UR individuals, PPI monotherapy failed to reduce histologic or endoscopic disease involvement, and persistent disease was associated with presence of Th2 inflammatory and dedifferentiated esophageal epithelial transcriptomic signature, and genes enriched in cellular response to LPS, defense response to virus, and type-I interferon pathway and cell proliferation. Our studies suggest that 1) SFRP1 is a key regulator of IL-13-induced and STAT3-dependent esophageal proliferation and BZH in EoE, 2) there is a critical link between SFRP1+ esophageal suprabasal epithelial cells and the proinflammatory and epithelial remodeling in EoE and 3). SFRP1+ pro-inflammatory esophageal suprabasal (ESB) cells contribute to PPI-unresponsiveness.