The role of CD73 in esophageal epithelial homeostasis - PROJECT SUMMARY Eosinophilic esophagitis (EoE) is a chronic, debilitating allergic disorder that is increasing in incidence worldwide, resulting significant health care and financial burdens. Current therapeutic approaches in EoE include dietary elimination and limiting inflammatory signaling using corticosteroids or biologics; however, there is increasing recognition of an EoE patient population failing to exhibit clinical and histological remission in response to these interventions. Disruption of esophageal epithelial tissue architecture and barrier function are hallmarks of EoE and achieving healing of the esophageal epithelial barrier represents a significant clinical challenge. Our own published work demonstrates that maintained epithelial remodeling is associated with symptoms in patients with histologically inactive EoE. Moreover, a recent study demonstrated that epithelium of inactive EoE patients fails to normalize at the cellular and molecular level. Despite the importance of esophageal epithelium in EoE pathobiology, we lack the comprehensive understanding of the mechanisms regulating esophageal epithelial homeostasis that is necessary to shape approaches for promoting epithelial healing in EoE. In a recent publication, we identified a CD73+ progenitor population within the basal zone of esophageal epithelium that is critical for tissue renewal. We further found that CD73+ basal cells are depleted in human subjects and mice with EoE inflammation, with the EoE-associated cytokines IL-4 and IL-13 causing a shift from CD73+ to CD73- basal cells in human 3D organoids. CD73 is a membrane-bound ectoenzyme that catalyzes conversion of extracellular adenosine monophosphate into the purine nucleoside adenosine. In the current proposal, we provide robust preliminary data adenosine (1) restores organoid formation, differentiation, and barrier integrity in esophageal keratinocytes with genetic depletion of CD73; and (2) improves epithelial differentiation in IL-13- treated organoids and a mouse model of EoE. Based upon our published and preliminary data, we hypothesize that esophageal homeostasis is mediated by CD73+ epithelial cells and dysregulated purinergic signaling contributes to EoE pathobiology, including epithelial remodeling. We will test this hypothesis by: defining the direct requirement of squamous epithelial CD73 in esophageal homeostasis and response to EoE (Aim 1); identifying the molecular mechanisms through which adenosine signaling supports esophageal epithelial homeostasis (Aim 2); and delineating how levels of CD73 and CD73-associated purines relate to clinical features of EoE patients (Aim 3). This proposal will illuminate the functional and mechanistic roles of CD73 and purinergic signaling in esophageal homeostasis. The proposed studies will also assess the therapeutic utility of restoring purinergic signaling in EoE models and the clinical significance of alterations in CD73 and purines in EoE patients, which may have implications for EoE therapy and clinical management.
