PROJECT SUMMARY A common element mediating the morbidity of esophageal disorders is altered distensibility of the esophageal wall, potentially resulting in impaired food transit, episodic choking, esophageal retention, and aspiration. In this proposal we will develop novel methodologies to quantify esophageal wall distensibility in disease states characterized by either increased or decreased distensibility, phenotype patients accordingly, obtain mucosal biopsies, and investigate the corresponding molecular mechanisms. Patients with eosinophilic esophagitis (EoE), scleroderma (SSc), and achalasia will be studied using functional luminal imaging probe (FLIP) topography and 4D impedance manometry (4D-IM) before and after standard of care (SOC) treatment (or in conjunction with SOC care and Bravo pH-metry in the case of SSc). Our overarching goal is to understand the molecular mechanisms leading to altered esophageal luminal distensibility through mechanistic studies of key mediators of inflammation: inhibitor of nuclear factor kappa-B kinase subunit beta (IKK?) and signal transducer and activator of transcription 3 (STAT3). The significance of this proposal lies in: 1) expanding our understanding of esophageal disease pathogenesis from a one-dimensional focus on neuromuscular function to a comprehensive study of esophageal wall mechanics as the determinant of function and dysfunction; and 2) the central roles of epithelial IKK? and epithelial STAT3 signaling in the regulation of diverse biological processes, such as inflammation, immunity, cell survival, and cell growth. The projects leaders have expertise in esophageal pathophysiology, translational research, animal models of esophageal disease, cell signaling, and epithelial cell biology. Here, we will test the hypothesis that altered esophageal distensibility is mediated through differential IKK? activation in the esophageal mucosa triggered by either eosinophilic inflammation in EoE or abnormal luminal pressurization in achalasia and that STAT3 signaling promotes esophageal smooth muscle atrophy in SSc. To explore these processes, we will undertake three interrelated Specific Aims. In Aim 1, we will investigate epithelial IKK?/NF?B and STAT3 signaling as modulators of altered esophageal luminal distensibility in EoE, SSc, and achalasia using mucosal biopsies in patients phenotyped using FLIP topography and 4D-IM as well as Bravo pH-metry in the case of SSc. In Aim 2, we will determine the role of epithelial IKK? signaling in promoting fibrosis in EoE. Here, we will utilize a novel transgenic mouse model with esophageal epithelial IKK? deletion treated with egg ovalbumin, and 3D organotypic culture. In Aim 3, we will determine the requirement for epithelial STAT3 signaling in promoting esophageal smooth muscle cell loss in SSc esophageal disease. This will be undertaken with a new transgenic mouse model of SSc (esophageal epithelial STAT3 deletion treated with bleomycin). We anticipate that these studies will identify factors leading to abnormal esophageal luminal distensibility in these disease states that may serve as future therapeutic targets.