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BACKGROUND AND AIMS: Colonic eosinophilia, an enigmatic finding often referred to as eosinophilic colitis (EoC), is a poorly understood condition. Whether EoC is a distinct disease or a colonic manifestation of eosinophilic gastrointestinal diseases (EGIDs) or inflammatory bowel disease (IBD) is undetermined. METHODS: Subjects with EoC (n=27) and controls (normal [NL, n=20], Crohn disease [CD, n=14]) were enrolled across sites associated with the Consortium of Eosinophilic Gastrointestinal Disease Researchers (CEGIR). EoC was diagnosed as colonic eosinophilia (ascending ≥100, descending ≥85, sigmoid ≥65 eosinophils/high-power field) with related symptoms. Colon biopsies were subjected to RNA sequencing. Associations between gene expression and histologic features were analyzed with Spearman correlation; operational pathways and cellular constituents were computationally derived. RESULTS: We identified 987 differentially expressed genes (EoC transcriptome) between EoC and NL (>1.5-fold change, P < .05). Colonic eosinophil count correlated with 31% of EoC transcriptome, most notably with CCL11 and CLC (r=0.78 and 0.77, P < .001). Among EoC and other EGIDs, there was minimal transcriptomic overlap; and minimal evidence of a strong allergic type 2 immune response compared with other EGIDs. Decreased cell-cycle and increased apoptosis in EoC compared with NL were identified by functional enrichment analysis and immunostaining using Ki-67 and cleaved caspase-3. Pericryptal circumferential eosinophil collars were associated with the EoC transcriptome (P < .001). EoC transcriptome-based scores were reversible with disease remission and differentiated EoC from IBD, even after controlling for colonic eosinophil levels (P < .0001). CONCLUSION: We established EoC transcriptomic profiles, identified mechanistic pathways, and integrated findings with parallel IBD and EGID data. These findings establish EoC as a distinct disease compared with other EGIDs and IBD, thereby providing a basis for improving diagnosis and treatment.

Eosinophilic esophagitis (EoE) can progress to fibrostenosis by unclear mechanisms. Herein, we investigated gene dysregulation in fibrostenotic EoE, its association with clinical parameters and specific pathways, and the functional consequences.Esophageal biopsies from subjects with EoE were collected across 11 Consortium of Eosinophilic Gastrointestinal Disease Researchers sites (n = 311) and 2 independent replication cohorts (n = 83). Inclusion criteria for fibrostenotic EoE were endoscopic rings, stricture, and/or a history of dilation. Endoscopic, histologic, and molecular features were assessed by the EoE Endoscopic Reference Score, EoE Histology Scoring System, EoE Diagnostic Panel, and RNA sequencing. Esophageal endothelial TSPAN12 expression and functional effects on barrier integrity and gene expression were analyzed in vitro.TSPAN12 was the gene most correlated with fibrostenosis (r = -0.40, P.001). TSPAN12 was lower in fibrostenotic EoE and correlated with EoE Endoscopic Reference Score, EoE Diagnostic Panel, and EoE Histology Scoring System (r = 0.34-0.47, P.001). Lower TSPAN12 associated with smaller esophageal diameter (r = 0.44, P = .03), increased lamina propria fibrosis (r = -0.41, P.001), and genes enriched in cell cycle-related pathways. Interleukin (IL)-13 reduced TSPAN12 expression in endothelial cells. Conversely, anti-IL-13 therapy increased TSPAN12 expression. TSPAN12 gene silencing increased endothelial cell permeability and dysregulated genes associated with extracellular matrix pathways. Endothelial cell-fibroblast crosstalk induced extracellular matrix changes relevant to esophageal remodeling.Patients with fibrostenotic EoE express decreased levels of endothelial TSPAN12. We propose that IL-13 decreases TSPAN12, likely contributing to the chronicity of EoE by promoting tissue remodeling through fibroblast-endothelial cell crosstalk.

The Histologic Scoring System (HSS) assesses severity/extent of histologic features (eosinophil density [ED]/basal zone hyperplasia [BZH]/eosinophil abscesses [EA]/eosinophil surface layering [SL]/surface epithelial alteration [SEA]/dyskeratotic epithelial cells [DEC]/dilated intercellular spaces [DIS]/lamina propria fibrosis [LPF]) in eosinophilic esophagitis (EoE). The Endoscopic Reference Score (EREFS) assesses endoscopic feature severity (edema/exudates/furrows/rings/strictures). We correlated HSS components with inflammatory/remodeling EREFS components in placebo-treated EoE patients from 2 trials—phase 2 proof-of-concept (POC; NCT02379052), phase 3 TREET part A (Phase3-PartA; NCT03633617). POC was a 12-week trial in adults, and Phase3-PartA was a 24-week trial in adults and adolescents. Proximal/mid/distal esophagus biopsies were collected at baseline/end of treatment (EOT) and scored by HSS for grade (severity)/stage (extent)/components (higher scores = greater severity). Endoscopies were scored by EREFS (higher scores = greater severity) and inflammatory (edema+exudates+furrows) and remodeling (rings+stricture) subscores calculated. Pearson correlation and single co-variate regression model analyses were performed between baseline HSS grade/stage, total/individual components scores and EREFS total/components scores and subscores, and for the change in scores from baseline at EOT (ΔEOT). Moderate-to-strong correlations (r > 0.3) were observed between total EREFS and HSS grade/stage for baseline/ΔEOT in POC and baseline in Phase3-PartA (Table). Moderate correlations were observed between BZH and EREFS remodeling subscore and rings for ΔEOT in Phase3-PartA; DIS grade and EREFS remodeling subscore and strictures for baseline and ΔEOT in POC but not Phase3-PartA; and EREFS inflammation and remodeling subscores and components for SEA and SL at baseline and ΔEOT in POC. Moderate-to-strong correlations were observed between EREFS inflammation subscore and DIS stage and between edema and DIS grade/stage at baseline in both studies. Similar results were observed using regression analyses. Specific components of HSS and EREFS, reflecting inflammatory and remodeling processes, are closely correlated, when examined by Pearson correlations or regression analyses, and can aid identification of fibrostenotic or inflammatory phenotypes in EoE. Correlations of DIS with endoscopic inflammatory and remodeling features reflect the role of barrier dysfunction in maintaining chronic inflammation that ultimately leads to remodeling.

Eosinophilic esophagitis (EoE) is a chronic allergic inflammatory disease. Multiple genetic risk factors linked to EoE have been identified; however, these studies have been primarily focused on populations of European ancestry. There is a lack of studies leveraging the genetic architecture of Black or African American (AA) populations for the identification of loci involved in EoE susceptibility. Herein, we present admixture mapping (AM) and genome-wide association analysis (GWAS) of EoE using the participants of AA populations.We conducted AM and GWAS of EoE using 137 EoE cases and 1465 healthy controls from AA population. Samples were genotyped using the Multi-Ethnic Genotyping Array (MEGA). Genotype imputation was carried out with the CAAPA reference panel using the Michigan Imputation Server. Global and local ancestry inference was carried out using RFMix v2, followed by fine-mapping analysis based on imputed genotypes, and RNAseq analysis. After standard quality control filtering, over 6,000,000 variants were tested by logistic regression adjusted for sex, age, and global ancestry.Global African ancestry proportion was found to be significantly lower among cases than controls (0.751 vs. 0.786, p-value = 0.012). Case-only AM identified four significant loci (9p13.3, 12q24.22-23, and 15q11.2) associated with EoE, two of which (12q24.22-23 and 9p13.3) were further replicated in the case-control analysis. At the two loci (12q24.23 and 9p13.3), the associations were observed for excess African ancestry. Fine mapping and multi-omic functional annotations prioritized the variants rs11068264 (FBXW8) and rs7307331 (VSIG10) at 12q24.23 and rs2297879 (ARHGEF39) at 9p13.3. GWAS identified one genome-wide significant locus at chromosome 1p22.3 (rs17131726, p-value = 2.39e-27, DDAH1) and 10 other suggestive loci including FAM179A (rs145050353), SCAND3 (rs56100858), TBC1D13 (rs114834583), MT2 (rs34800257) and PCSK2 (rs75293413) associated with EoE at p-value1×10We have identified an African ancestry specific genetic susceptibility locus DDAH1 at 1p22.3, 1p22.3, 9p13.3, and 12q24.23, through GWAS and admixture mapping for EoE in AA, providing evidence of ancestral specific inheritance of EoE. These findings highlight the need of independent genetic studies of different ancestries for EoE.

Recent advances in rare disease research are accelerated by the work of consortia that have been supported by the National Institutes of Health. Development of such consortia rely on multidisciplinary relationships and engagement with patient advocacy groups, as well as the National Institutes of Health and industry and academic partners. In this rostrum we present the development of such a process that focuses on eosinophilic gastrointestinal diseases. Principal investigators, patient advocacy groups, research assistants, and trainees work together to perform natural history studies that promote clinical trial readiness tools, conduct clinical trials, train a new generation of investigators, and perform innovative pilot studies.

Mast cells and basophils are granulocytes critical in the pathogenesis of allergic disease due to the release of preformed and newly synthesized mediators. Tetraspanins are emerging as novel modulators of signals for cellular activation, however, mechanistic understanding of their function is currently lacking. We found tetraspanin CD151 to be specifically induced in human and mouse mast cells upon IgE stimulation, suggesting a functional role in activation of these cells. Here, we show that CD151 modulates IgE-induced mast cell activation by exerting selective control over downstream pathways regulating de novo synthesis of cytokines IL-4, IL-13 and TNF-α. Mechanistically, CD151 selectively targets IgE-induced activation of ERK1/2, associated with cytokine production, but has no regulatory effect on PLCγ1 or calcium release necessary for degranulation. Inhibition of ERK1/2 blocks the exaggerated induction of cytokines by CD151 deficient mast cells. In vivo, CD151 deficiency significantly exacerbates IgE-mediated late phase response in a murine model of passive cutaneous anaphylaxis. Collectively, our data indicate that CD151 functions in the late phase of IgE-induced mast cell activation by limiting cytokine synthesis.

Mast cells play a critical role in atopic dermatitis through the release of preformed and de novo synthesized pro-inflammatory mediators. In 1878, HR Crocker described the use of topical thymol in the treatment of advanced eczema. We hypothesized that the efficacy of thymol in eczema is due to a direct effect on mast cells. The effect of topical thymol was assessed on allergic murine ear swelling in the mast cell-dependent passive cutaneous anaphylaxis (PCA) model as well as on ear swelling directly and mast cells in vitro. Thymol dose-dependently inhibited PCA when administered topically prior to antigen challenge. Thymol induced a dose-dependent immediate ear swelling in mice, however lacked late phase swelling seen in PCA. This effect was associated with increased mast cell degranulation histologically and was inhibited in histamine deficient mice. Thymol induced mast cell degranulation and mRNA transcription in vitro, but prevented protein secretion. This was due to decreased mast cell viability from apoptosis. Mast cell activation from thymol occurred via sustained calcium flux. Thymol-induced calcium flux was not inhibited in TRPV3 KO mast cells, but was inhibited by HC-030031, a selective TRPA1 antagonist, and 2-APB, an IP3 receptor antagonist. However, HC-030031 and 2-APB were unable to prevent thymol-induced cell death. We are currently investigating the mechanism by which thymol leads to activation-induced cell death in mast cells.