Mast cell-pain connection in eosinophilic esophagitis

Distinct roles for thymic stromal lymphopoietin (TSLP) and IL-33 in experimental eosinophilic esophagitis

Rationale

Thymic stromal lymphopoietin (TSLP) and IL-33 are alarmins implicated in EoE pathogenesis by activating multiple cells including mast cells (MCs). Whether TSLP or IL-33 have a role in EoE and whether their activities are distinct requires further investigation.

Methods

Experimental EoE was induced in wild type (WT) Il33 -/- and Crlf2 -/- mice. TSLP or IL-5 were neutralized using antibodies. Esophageal histopathology was determined by H&E, anti-Ki67, anti-CD31 and anti-MBP staining. Esophageal RNA was subjected to RNA sequencing. Bone marrow-derived MCs were activated with TSLP and IL-13 was determined (ELISA).

Results

TSLP and IL-33 were overexpressed in human and experimental EoE. Human and mouse esophageal MCs displayed the highest level of Crlf2 (TSLPR) compared to other immune cells. Crlf2 -/- mice were nearly-completely protected from EoE, and TSLP neutralization resulted in decreased basal cell proliferation, eosinophilia, lamina propria thickening and vascularization. Induction of experimental EoE in Il33 -/- mice resulted in reduced eosinophilia but no alterations in tissue remodeling were observed compared to WT mice. RNA sequencing revealed that TSLP regulates the expression of key genes associated with human EoE (e.g. eotaxins, Il19, Klk5, Flg, Il36rn, Il1r2) and suggest a role for TSLP in regulating IL-1 signaling, barrier integrity and epithelial cell differentiation. Experimental EoE was characterized by a MC-associated gene signature and elevated MCs. Activation of MCs with TSLP resulted in secretion of IL-13.

Conclusion

TSLP and IL-33 have non-redundant functions in experimental EoE. This study highlights TSLP as an upstream regulator of IL-13 and a potential therapeutic target for EoE.

One-food versus 4-food elimination diet for pediatric eosinophilic esophagitis: A multisite randomized trial

BACKGROUND

A 6-food elimination diet in pediatric eosinophilic esophagitis (EoE) is difficult to implement and may negatively affect quality of life (QoL). Less restrictive elimination diets may balance QoL and efficacy.

OBJECTIVE

We performed a multisite, randomized comparative efficacy trial of a 1-food (milk) elimination diet (1FED) versus 4-food (milk, egg, wheat, soy) elimination diet (4FED) in pediatric EoE.

METHODS

Patients aged 6 to 17 years with histologically active and symptomatic EoE were randomized 1:1 to 1FED or 4FED for 12 weeks. Primary end point was symptom improvement by Pediatric Eosinophilic Esophagitis Symptom Score (PEESS). Secondary end points were proportion experiencing histologic remission (<15 eosinophils per high-power field); change in histologic features (histology scoring system), endoscopic severity (endoscopic reference score), transcriptome (EoE diagnostic panel), and QoL scores; and predictors of remission.

RESULTS

Sixty-three patients were randomly assigned to 1FED (n = 38) and 4FED (n = 25). In 4FED versus 1FED, mean PEESS improved -25.0 versus -14.5 (P = .04), but remission rates (41% vs 44%; P = 1.00), histology scoring system (-0.25 vs -0.29; P = .77), endoscopic reference score (-1.10 vs -0.58; P = .47), and QoL scores were similar between groups. The EoE transcriptome normalized in those with histologic response to both diets. Baseline peak eosinophil count predicted remission (odds ratio, 0.975 [95% confidence interval, 0.953-0.999], P = .04; cutoff ≤42 eosinophils per high-power field). The 4FED withdrawal rate (32%) exceeded that of 1FED (11%) (P = .0496).

CONCLUSIONS

Although 4FED moderately improved symptoms compared with 1FED, the histologic, endoscopic, QoL, and transcriptomic outcomes were similar in both groups. 1FED is a reasonable first-choice therapy for pediatric EoE, given its effects, tolerability, and relative simplicity.

Increased expression of proton pump and allergic inflammation genes predicts PPI failure in pediatric eosinophilic esophagitis

Proton pump inhibitors (PPIs) are one of the standards of care of eosinophilic esophagitis (EoE) treatment, though PPI response rates are variable ranging from 23 to 63% in pediatric studies. We sought to determine if expression of select genes in esophageal mucosa can predict PPI responsiveness in EoE. Children with a new diagnosis of EoE (15 or more eosinophils/hpf on esophageal biopsy) were prospectively treated with 8 weeks of PPI therapy before follow-up esophagogastroduodenoscopy (EGD). Children with <15 eosinophils/hpf on follow-up were classified as having PPI-Responsive EoE (PPI-R) and ≥ 15 eosinophils/hpf as PPI-Nonresponsive EoE (PPI-NR). Using the Nanostring nCounter Analysis System, mRNA expression of a custom panel of genes was measured in esophageal biopsies. Immunohistochemical staining of biopsies was performed. Among children with EoE, 32% (8/25) had PPI-R EoE. ATP12A, ATP4A, tryptase-beta 2 (TPSB2), CLC and IL13 had higher expression in PPI-NR EoE compared to PPI-R EoE or controls. Immunohistochemical staining of ATP12A was higher among PPI-R EoE and PPI-NR EoE, compared to non-EoE controls. In this study, PPI-NR EoE had significantly higher baseline gene expression of mast cell, cytokine, proton pump, and eosinophil genes compared to PPI-R EoE. PPIs may be involved in an inflammatory cascade of mast cell activation that stimulates IL-13 release, which upregulates ATP12A and ATP4A that leads to eosinophil recruitment. Histologic PPI failure may occur when increased gene expression of these components is high and cannot be overcome pharmacologically, especially in the case of proton pump genes.

Understanding tissue injury and remodelling in eosinophilic oesophagitis: development towards personalised medicine

Eosinophilic oesophagitis (EoE) is a chronic, immune-mediated condition characterised by eosinophilic infiltration of the oesophagus, leading to significant morbidity due to oesophageal dysfunction. The pathogenic course of EoE begins with tissue injury, marked by the intricate interplay of oesophageal barrier dysfunction and T helper 2-mediated inflammation. In response to tissue damage, a subsequent phase of tissue remodelling features a complex interaction between epithelial cells and stromal cells, aimed at tissue repair. The persistence of inflammation drives these mechanisms towards oesophageal fibrostenosis, mainly through the transforming growth factor-dependent, myofibroblast-driven accumulation of the extracellular matrix. Currently, treatment options for EoE are limited, with dietary intervention, proton pump inhibitors and oral steroids serving as first-line therapies. Dupilumab, an antiinterleukin (IL) 4/IL-13 agent, is the only biologic that has been approved by European and American regulatory authorities. However, emerging OMIC technologies significantly advance our understanding of EoE pathogenesis, revealing novel cellular and molecular mechanisms driving the disease. This progress has accelerated the identification of new therapeutic targets and agents, some already under clinical investigation, potentially expanding our therapeutic arsenal and paving the way for more personalised approaches. In this evolving landscape, artificial intelligence (AI) has shown great potential to further elaborate on the complexities of EoE heterogeneity, offering standardised tools for diagnosis, disease phenotyping, and prediction of treatment response. Though still in their early stages, integrating OMICs and AI marks a pivotal step towards precision medicine in EoE.

Nonepithelial Gene Expression Correlates With Symptom Severity in Adults With Eosinophilic Esophagitis

BACKGROUND

The mechanistic basis of the variable symptomatology seen in eosinophilic esophagitis (EoE) remains poorly understood.

OBJECTIVE

We examined the correlation of a validated, patient-reported outcome metric with a broad spectrum of esophageal transcripts to uncover potential symptom pathogenesis.

METHODS

We extracted data from 146 adults with EoE through the Consortium of Eosinophilic Gastrointestinal Disease Researchers. Patients were subgrouped by esophageal dilation history. We compared a validated patient-reported outcome metric, the EoE Activity Index (EEsAI), with a set of transcripts expressed in the esophagus of patients with EoE, the EoE Diagnostic Panel (EDP). We used single-cell RNA sequencing data to identify the cellular source of EEsAI-related EDP genes and further analyzed patients with mild and severe symptoms.

RESULTS

The EEsAI correlated with the EDP total score, especially in patients without recent esophageal dilation (r = -0.31; P = .003). We identified 14 EDP genes that correlated with EEsAI scores (r ≥ 0.3; P < .05). Of these, 11 were expressed in nonepithelial cells and three in epithelial cells. During histologic remission, only four of 11 nonepithelial genes (36%) versus all three epithelial genes (100%) had decreased expression to less than 50% of that in active EoE. Fibroblasts expressed five of 11 nonepithelial EEsAI-associated EDP genes (45%). A subset of nonepithelial genes (eight of 11; 73%), but not EoE-representative genes (none of four; 0%; CCL26, CAPN14, DSG1, and SPINK7), was upregulated in patients with EoE with the highest versus lowest symptom burden.

CONCLUSION

The correlation of symptoms and nonepithelial esophageal gene expression substantiates that nonepithelial cells (eg, fibroblasts) likely contribute to symptom severity.

Differential changes in mast cells with food reintroduction in children with eosinophilic esophagitis

Intraepithelial mast cells (MCs) are increased in eosinophilic esophagitis (EoE) and reduced with elimination of dietary antigens. Single food reintroduction can identify triggers of eosinophilia; however, the extent to which specific foods trigger intraepithelial mastocytosis remains unknown. We hypothesized that specific foods drive different degrees of MC inflammation. We previously reported a prospective pediatric EoE cohort treated with a 4-food elimination diet (4FED) with removal of soy, egg, wheat, and milk. We retrieved unstained slides in which baseline, 4FED, and post-4FED diet reintroduction time points were available. Slides were stained with tryptase, and intraepithelial MCs were counted. Comparisons were made by stratifying patients by eosinophilia, basal cell hyperplasia (BCH), endoscopic abnormalities, and symptoms. Pearson correlation was assessed for MCs with eosinophilic, endoscopic, and BCH severity; symptoms; and a novel mucosal activity score combining endoscopic and histologic structural severity. Slides were available from 37 patients with at least 1 food reintroduced. MCs were significantly reduced with 4FED. Wheat led to increased intraepithelial MCs in the upper esophagus and with food-induced eosinophilia, while milk led to significantly increased MCs in the upper and lower esophagus and was significantly associated with patients with food-triggered eosinophilia, endoscopic abnormalities, BCH, and symptoms. MCs best correlated with the mucosal activity score during milk reintroduction. In children with EoE, MCs are reduced with 4FED. During milk reintroduction, significant increases in MCs were observed with all metrics of inflammation along with moderate correlation with structural mucosal activity that was not seen with other foods. This suggests that milk exerts unique effects either directly or indirectly on MCs in the esophagus in EoE patients.

Advances in omics data for eosinophilic esophagitis: moving towards multi-omics analyses

Eosinophilic esophagitis (EoE) is a chronic, allergic inflammatory disease of the esophagus characterized by eosinophil accumulation and has a growing global prevalence. EoE significantly impairs quality of life and poses a substantial burden on healthcare resources. Currently, only two FDA-approved medications exist for EoE, highlighting the need for broader research into its management and prevention. Recent advancements in omics technologies, such as genomics, epigenetics, transcriptomics, proteomics, and others, offer new insights into the genetic and immunologic mechanisms underlying EoE. Genomic studies have identified genetic loci and mutations associated with EoE, revealing predispositions that vary by ancestry and indicating EoE's complex genetic basis. Epigenetic studies have uncovered changes in DNA methylation and chromatin structure that affect gene expression, influencing EoE pathology. Transcriptomic analyses have revealed a distinct gene expression profile in EoE, dominated by genes involved in activated type 2 immunity and epithelial barrier function. Proteomic approaches have furthered the understanding of EoE mechanisms, identifying potential new biomarkers and therapeutic targets. However, challenges in integrating diverse omics data persist, largely due to their complexity and the need for advanced computational methods. Machine learning is emerging as a valuable tool for analyzing extensive and intricate datasets, potentially revealing new aspects of EoE pathogenesis. The integration of multi-omics data through sophisticated computational approaches promises significant advancements in our understanding of EoE, improving diagnostics, and enhancing treatment effectiveness. This review synthesizes current omics research and explores future directions for comprehensively understanding the disease mechanisms in EoE.

Odynophagia and Retrosternal Pain Are Common in Eosinophilic Esophagitis and Associated with an Increased Overall Symptom Severity

BACKGROUND AND AIMS

Dysphagia is the hallmark symptom in eosinophilic esophagitis (EoE). However, data are limited regarding the overall prevalence and potential implications of atypical symptoms like odynophagia and retrosternal pain.

METHODS

Patients enrolled into the Swiss EoE cohort study (SEECS) were analyzed regarding the presence of odynophagia and retrosternal pain. Demographics, other EoE-related symptoms, histologic and endoscopic activity were compared between EoE-patients with vs. without odynophagia and/or retrosternal pain.

RESULTS

474 patients (75.2% male) were analyzed. In their individual course of disease 110 (23.2%) patients stated to have ever experienced odynophagia and 64 (13.5%) retrosternal pain independent of food intake, 24 (5%) patients complained about both symptoms. Patients with odynophagia consistently scored higher in symptom severity (p < 0.001), EREFS score (median 3.0 vs. 2.0, p = 0.006), histologic activity and a lower quality of life (p = 0.001) compared to patients without odynophagia. Sex, age at diagnosis, EoE-specific treatment, complications such as candida or viral esophagitis and disease duration were similar in patients with vs. without odynophagia. Also patients with retrosternal pain scored higher in symptom severity (2.0 vs. 1.0, p = 0.001 and 2.0 vs. 1.0, p < 0.001 in physician and patient questionnaire assessment, respectively). However, there was neither a difference in endoscopic/histologic disease activity nor in quality of life according to presence or absence of retrosternal pain. Due to logistic reasons, a stratification regarding the presence of concomitant dysphagia was not possible.

CONCLUSION

Odynophagia and swallowing-independent retrosternal pain are common symptoms in patients with EoE, associate with an overall higher EoE-related symptom severity and for the case of odynophagia lower quality of life. However, the influence of concomitant dysphagia and its severity remains unclear and needs to be included in future analyses.

Sialylated keratan sulfates on MUC5B are Siglec-8 ligands in the human esophagus

Human sialic acid-binding immunoglobulin-like lectins (Siglecs) are expressed on subsets of immune cells. Siglec-8 is an immune inhibitory Siglec on eosinophils and mast cells, which are effectors in allergic disorders including eosinophilic esophagitis. Inhibition occurs when Siglec-8 is crosslinked by multivalent Siglec ligands in target tissues. Previously we discovered a high-affinity Siglec-8 sialoglycan ligand on human airways composed of terminally sialylated keratan sulfate chains carried on a single protein, DMBT1. Here we extend that approach to another allergic inflammatory target tissue, human esophagus. Lectin overlay histochemistry revealed that Siglec-8 ligands are expressed predominantly by esophageal submucosal glands, and are densely packed in submucosal ducts leading to the lumen. Expression is tissue-specific; esophageal glands express Siglec-8 ligand whereas nearby gastric glands do not. Extraction and resolution by gel electrophoresis revealed a single predominant human esophageal Siglec-8 ligand migrating at >2 MDa. Purification by size exclusion and affinity chromatography, followed by proteomic mass spectrometry, revealed the protein carrier to be MUC5B. Whereas all human esophageal submucosal cells express MUC5B, only a portion convert it to Siglec-8 ligand by adding terminally sialylated keratan sulfate chains. We refer to this as MUC5B S8L. Material from the esophageal lumen of live subjects revealed MUC5B S8L species ranging from ~1-4 MDa. We conclude that MUC5B in the human esophagus is a protein canvas on which Siglec-8 binding sialylated keratan sulfate chains are post-translationally added. These data expand understanding of Siglec-8 ligands and may help us understand their roles in allergic immune regulation.

Clinical and molecular correlates of the Index of Severity for Eosinophilic Esophagitis

BACKGROUND

The Index of Severity for Eosinophilic Esophagitis (I-SEE) is a new expert-defined clinical tool that classifies disease severity of eosinophilic esophagitis (EoE).

OBJECTIVE

We aimed to determine whether I-SEE is associated with patient characteristics, molecular features of EoE, or both.

METHODS

We analyzed a prospective cohort of patients with EoE from the Consortium of Eosinophilic Gastrointestinal Disease Researchers (CEGIR). Associations between I-SEE and clinical and molecular features (assessed by an EoE diagnostic panel [EDP]) were assessed.

RESULTS

In 318 patients with chronic EoE (209 adults, 109 children), median total I-SEE score was 7.0, with a higher symptoms and complications score in children than adults (4.0 vs 1.0; P < .001) and higher inflammatory and fibrostenotic features scores in adults than children (3.0 vs 1.0 and 3.0 vs 0, respectively; both P < .001). Total I-SEE score had a bimodal distribution with the inactive to moderate categories and severe category. EDP score correlated with total I-SEE score (r = -0.352, P < .001) and both inflammatory and fibrostenotic features scores (r = -0.665, P < .001; r = -0.446, P < .001, respectively), but not with symptoms and complications scores (r = 0.047, P = .408). Molecular severity increased from inactive to mild and moderate, but not severe, categories. Longitudinal changes of modified I-SEE scores and inflammatory and fibrostenotic features scores reflected histologic and molecular activity.

CONCLUSIONS

I-SEE score is associated with select clinical features across severity categories and with EoE molecular features for nonsevere categories, warranting further validation.

Development and dysfunction of structural cells in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a disorder characterized by dysfunction and chronic local inflammation of the esophagus. The incidence and prevalence of EoE are increasing worldwide. The mechanisms responsible are poorly understood, and effective treatment options are limited. From the lumen outward, the esophagus comprises stratified squamous epithelium, lamina propria, and muscle. The tissue-specific nature of EoE strongly suggests that structural cells in the esophagus are involved in the EoE diathesis. Epithelial basal cell hyperplasia and dilated intercellular spaces are cardinal features of EoE. Some patients with EoE develop lamina propria fibrosis, strictures, or esophageal muscle dysmotility. Clinical symptoms of EoE are only weakly correlated with peak eosinophil count, implying that other cell types contribute to EoE pathogenesis. Epithelial, endothelial, muscle, and fibroblast cells can each initiate inflammation and repair, regulate tissue resident immune cells, recruit peripheral leukocytes, and tailor adaptive immune cell responses. A better understanding of how structural cells maintain tissue homeostasis, respond to cell-intrinsic and cell-extrinsic stressors, and exacerbate and/or resolve inflammatory responses in the esophagus is needed. This knowledge will facilitate the development of more efficacious treatment strategies for EoE that can restore homeostasis of both hematopoietic and structural elements in the esophagus.

Mast Cell Esophagitis: A Novel Entity in Patients with Unexplained Esophageal Symptoms

It is not known whether esophageal mast cells may be a cause of unexplained esophageal symptoms. We aimed to determine the prevalence of esophageal mastocytosis in patients without other underlying causes of symptoms and assess the relationship between symptoms and mast cells. In this retrospective study, we identified adults with esophageal symptoms, a normal endoscopy, normal esophageal biopsies, and no definitive diagnosis during clinical evaluation. We quantified mast cell density (mast cells/mm2) in archived esophageal biopsies using tryptase immunohistochemistry, and compared mast cell levels by clinical features and physiologic testing. In the 87 patients identified (mean age 37, 72% female, 63% white, 92% non-Hispanic), common symptoms were dysphagia (76%), heartburn (71%), and chest pain (25%). Overall, the mean esophageal epithelial mast cell count was 83.0 ± 51.8 mast cells/mm2; 60% of patients had ≥ 60 mast/mm2, and 17% had ≥ 120 masts/mm2. There were no differences in mast cell counts by type of esophageal testing. Mast cell levels did not differ significantly by type of symptoms, atopic status, medications, smoking status, or alcohol use. There were also no major differences in clinical characteristics by mast cell quartiles or thresholds. In conclusion, esophageal mast cell infiltration was common in patients with symptoms unexplained by prior testing, and levels were higher than previously published values for patients with no underlying esophageal condition. Mast cell esophagitis could be a novel cause of unexplained esophageal symptoms in a subset of patients, though it reamins to be determined if such patients benefit from mast cell-targeted treatment.

Machine learning-based identification and characterization of mast cells in eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is diagnosed and monitored using esophageal eosinophil levels; however, EoE also exhibits a marked, understudied esophageal mastocytosis.

OBJECTIVES

Using machine learning, we localized and characterized esophageal mast cells (MCs) to decipher their potential role in disease pathology.

METHODS

Esophageal biopsy samples (EoE, control) were stained for MCs by anti-tryptase and imaged using immunofluorescence; high-resolution whole tissue images were digitally assembled. Machine learning software was trained to identify, enumerate, and characterize MCs, designated Mast Cell-Artificial Intelligence (MC-AI).

RESULTS

MC-AI enumerated cell counts with high accuracy. During active EoE, epithelial MCs increased and lamina propria (LP) MCs decreased. In controls and EoE remission patients, papillae had the highest MC density and negatively correlated with epithelial MC density. MC density in the epithelium and papillae correlated with the degree of epithelial eosinophilic inflammation, basal zone hyperplasia, and LP fibrosis. MC-AI detected greater MC degranulation in the epithelium, papillae, and LP in patients with EoE compared with control individuals. MCs were localized further from the basement membrane in active EoE than EoE remission and control individuals but were closer than eosinophils to the basement membrane in active EoE.

CONCLUSIONS

Using MC-AI, we identified a distinct population of homeostatic esophageal papillae MCs; during active EoE, this population decreases, undergoes degranulation, negatively correlates with epithelial MC levels, and significantly correlates with distinct histologic features. Overall, MC-AI provides a means to understand the potential involvement of MCs in EoE and other disorders.

Role of Mast Cells in Eosinophilic Gastrointestinal Diseases

Mast cells play a central role in the pathogenesis of eosinophilic gastrointestinal disorders (EGIDs), including eosinophilic esophagitis. Their interactions with immune and structural cells, involvement in tissue remodeling, and contribution to symptoms make them attractive targets for therapeutic intervention. More is being discovered regarding the intricate interplay of mast cells and eosinophils. Recent studies demonstrating that depletion of eosinophils is insufficient to improve symptoms of EGIDs have raised the question of whether other cells may play a role in symptomatology and pathogenesis of EGIDs.

Neuroimmune interplay during type 2 inflammation: Symptoms, mechanisms, and therapeutic targets in atopic diseases

Type 2 inflammation is characterized by overexpression and heightened activity of type 2 cytokines, mediators, and cells that drive neuroimmune activation and sensitization to previously subthreshold stimuli. The consequences of altered neuroimmune activity differ by tissue type and disease; they include skin inflammation, sensitization to pruritogens, and itch amplification in atopic dermatitis and prurigo nodularis; airway inflammation and/or hyperresponsiveness, loss of expiratory volume, airflow obstruction and increased mucus production in asthma; loss of sense of smell in chronic rhinosinusitis with nasal polyps; and dysphagia in eosinophilic esophagitis. We describe the neuroimmune interactions that underlie the various sensory and autonomic pathologies in type 2 inflammatory diseases and present recent advances in targeted treatment approaches to reduce type 2 inflammation and its associated symptoms in these diseases. Further research is needed to better understand the neuroimmune mechanisms that underlie chronic, sustained inflammation and its related sensory pathologies in diseases associated with type 2 inflammation.

Mucosal neuroimmune mechanisms in gastro-oesophageal reflux disease (GORD) pathogenesis

Gastro-oesophageal reflux disease (GORD) is a chronic condition characterised by visceral pain in the distal oesophagus. The current first-line treatment for GORD is proton pump inhibitors (PPIs), however, PPIs are ineffective in a large cohort of patients and long-term use may have adverse effects. Emerging evidence suggests that nerve fibre number and location are likely to play interrelated roles in nociception in the oesophagus of GORD patients. Simultaneously, alterations in cells of the oesophageal mucosa, namely epithelial cells, mast cells, dendritic cells, and T lymphocytes, have been a focus of GORD research for several years. The oesophagus of GORD patients exhibits both macro- and micro-inflammation as a response to chronic acidic reflux at the epithelium. In other conditions of the GI tract, such as IBS and IBD, well-characterised bidirectional processes between immune cells and mucosal nerve fibres contribute to pathogenesis and symptom generation. Sensory alterations in these conditions such as nerve fibre outgrowth and hypersensitivity can be driven by inflammatory processes, which promote visceral pain signalling. This review will examine what is currently known of the molecular pathways linking inflammation and sensory perception leading to the development of GORD symptoms and explore potentially relevant mechanisms in other GI regions which may indicate new areas in GORD research.

Machine Learning Based Identification and Characterization of Mast cells in Eosinophilic Esophagitis

Background

Eosinophilic esophagitis (EoE) is diagnosed and monitored using esophageal eosinophil levels; however, EoE also exhibits a marked, understudied esophageal mastocytosis.

Objective

Using machine learning, we localized and characterized esophageal mast cells to decipher their potential role in disease pathology.

Methods

Esophageal biopsy samples (EoE, control) were stained for mast cells by anti-tryptase and imaged using immunofluorescence; high-resolution whole tissue images were digitally assembled. Machine learning software was trained to identify, enumerate, and characterize mast cells, designated Mast Cell-Artificial Intelligence (MC-AI).

Results

MC-AI enumerated cell counts with high accuracy. During active EoE, epithelial mast cells increased and lamina propria (LP) mast cells decreased. In controls and EoE remission patients, papillae had the highest mast cell density and negatively correlated with epithelial mast cell density. Mast cell density in the epithelium and papillae correlated with the degree of epithelial eosinophilic inflammation, basal zone hyperplasia, and LP fibrosis. MC-AI detected greater mast cell degranulation in the epithelium, papillae, and LP in EoE patients compared with control individuals. Mast cells were localized further from the basement membrane in active EoE than EoE remission and controls individuals but were closer than eosinophils to the basement membrane in active EoE.

Conclusion

Using MC-AI, we identified a distinct population of homeostatic esophageal papillae mast cells; during active EoE, this population decreases, undergoes degranulation, negatively correlates with epithelial mast cell levels, and significantly correlates with distinct histologic features. Overall, MC-AI provides a means to understand the potential involvement of mast cells in EoE and other disorders.

Clinical Implication

We have developed a methodology for identifying, enumerating, and characterizing mast cells using artificial intelligence; this has been applied to decipher eosinophilic esophagitis and provides a platform approach for other diseases.

Capsule Summary

A machine learning protocol for identifying mast cells, designated Mast Cell-Artificial Intelligence, readily identified spatially distinct and dynamic populations of mast cells in EoE, providing a platform to better understand this cell type in EoE and other diseases.

Mast cells disrupt the function of the esophageal epithelial barrier

Mast cells (MCs) accumulate in the epithelium of patients with eosinophilic esophagitis (EoE), an inflammatory disorder characterized by extensive esophageal eosinophilic infiltration. Esophageal barrier dysfunction plays an important role in the pathophysiology of EoE. We hypothesized that MCs contribute to the observed impaired esophageal epithelial barrier. Herein, we demonstrate that coculture of differentiated esophageal epithelial cells with immunoglobulin E-activated MCs significanly decreased epithelial resistance by 30% and increased permeability by 22% compared with non-activated MCs. These changes were associated with decreased messenger RNA expression of barrier proteins filaggrin, desmoglein-1 and involucrin, and antiprotease serine peptidase inhibitor kazal type 7. Using targeted proteomics, we detected various cytokines in coculture supernatants, most notably granulocyte-macrophage colony-stimulating factor and oncostatin M (OSM). OSM expression was increased by 12-fold in active EoE and associated with MC marker genes. Furthermore, OSM receptor-expressing esophageal epithelial cells were found in the esophageal tissue of patients with EoE, suggesting that the epithelial cells may respond to OSM. Stimulation of esophageal epithelial cells with OSM resulted in a dose-dependent decrease in barrier function and expression of filaggrin and desmoglein-1 and an increase in protease calpain-14. Taken together, these data suggest a role for MCs in decreasing esophageal epithelial barrier function in EoE, which may in part be mediated by OSM.

Genetic and Molecular Contributors in Eosinophilic Esophagitis

PURPOSE OF REVIEW

Eosinophilic esophagitis (EoE) is an allergic inflammatory esophageal disorder with a complex underlying genetic and molecular etiology. The interest of the scientific community in EoE has grown considerably over the past three decades, and the understanding of the genetic and molecular mechanisms involved in this disease has greatly increased.

RECENT FINDINGS

In this article, we aim to provide both historic aspects and updates on the recent genetic and molecular advances in the understanding of EoE. Although EoE is a relatively newly described disorder, much progress has been made toward identifying the genetic and molecular factors contributing to the disease pathogenesis by a variety of approaches with next-generation sequencing technologies, including genome-wide association study, whole exome sequencing, and bulk and single-cell RNA sequencing. This review highlights the multifaceted impacts of various findings that have shaped the current molecular and genetic landscape of EoE, providing insights that facilitate further understanding of the disease process.

Molecular analysis of duodenal eosinophilia

BACKGROUND

Eosinophilic duodenitis (EoD), characterized by nonspecific gastrointestinal symptoms and increased numbers of duodenal eosinophils, may be in the eosinophilic gastrointestinal disease spectrum. However, diagnostic thresholds and pathogenic processes of duodenal tissue eosinophilia are inadequately characterized.

OBJECTIVE

We aimed to define an EoD transcriptome and pathologic pathways.

METHODS

RNA sequencing and histologic features of human duodenal biopsy samples were analyzed as a function of duodenal eosinophils levels. For analyses, we defined EoD as more than 52 peak eosinophils/hpf (n = 8), duodenal eosinophilia as 30 to 52 eosinophils/hpf (n = 11), and normal controls as fewer than 30 eosinophils/hpf (n = 8). Associations between gene expression and histologic features were analyzed with Spearman correlation.

RESULTS

We identified 382 differentially expressed genes (EoD transcriptome) between EoD and normal controls (>2-fold change [adjusted P < .05]). The EoD transcriptome distinguished EoD from controls (duodenal eosinophilia and normal controls). The duodenal eosinophil count was correlated with a distinct EoD transcriptome when 50 to 60 peak eosinophils/hpf were present. The EoD transcriptome was enriched in genes involved in IL-4/IL-13 signaling, mast cells, and myeloid progenitor cells. Among duodenal histologic features, lamina propria eosinophil sheets was the most associated with transcriptomic changes (r = 0.66; P < .01). EoD gene signatures were shared with eosinophilic esophagitis and eosinophilic gastritis but not with eosinophilic colitis or celiac disease.

CONCLUSION

We have identified an EoD transcriptomic signature that emerges at 50 to 60 peak eosinophils/hpf and established EoD as part of a spectrum of upper eosinophilic gastrointestinal disorder associated with type 2 immunity and distinct from eosinophilic colitis and celiac disease. These findings provide a basis for improving diagnosis and treatment.

Esophageal mast cells may be associated with the perception of symptoms in patients with eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is a type 2 helper T-cell (Th2)-mediated allergic disease that involves mast cells. This study aimed to clarify the relationship between perception of symptoms and mast cell levels in patients with EoE.

METHODS

We enrolled patients with asymptomatic esophageal eosinophilia (aEE) and those with symptomatic EoE. Immunofluorescence staining was performed on esophageal biopsy specimens to quantify mast cell-related molecules, such as tryptase, proteinase-activated receptor (PAR)-2, and vasoactive intestinal peptide receptor (VPAC)-1.

RESULTS

We evaluated 28 and 58 patients with aEE and EoE, respectively. There were no significant differences in clinical and endoscopic features and peak eosinophil counts between both groups. Mast cell tryptase-positive areas were significantly higher in EoE than in aEE (4.9 [3.5-6.2] vs. 2.0 [1.2-3.4] %, p < 0.01). The number of PAR-2-positive cells was significantly higher in EoE than in aEE (14 [8.8-20.0] vs. 4 [2.8-8.0] cells/high-power field [HPF], p < 0.01). The number of VPAC-1-positive cells was significantly higher in the EoE group than in the aEE group (13 [8.8-16.0] vs. 6 [3.0-9.3] cells/HPF, p < 0.01). A positive correlation was observed between the numbers of PAR-2-positive cells and VPAC-1-positive cells (r = 0.851, p < 0.01). Moreover, mast cell tryptase-positive areas positively correlated with the number of PAR-2- and VPAC-1-positive cells (r = 0.352, p < 0.01; r = 0.355, p < 0.01, respectively).

CONCLUSIONS

Esophageal mast cells and their receptors, PAR-2 and VPAC-1, may contribute to the perception of symptoms in patients with EoE.

Eosinophilic Esophagitis beyond Eosinophils - an Emerging Phenomenon Overlapping with Eosinophilic Esophagitis: Collegium Internationale Allergologicum (CIA) Update 2023

Having long been considered the mainstay in eosinophilic esophagitis (EoE) diagnosis and pathogenesis, the role of eosinophils has been questioned and might be less important than previously thought. It is well known now that EoE is a Th2-mediated disease with many more disease features than eosinophilic infiltration. With more knowledge on EoE, less pronounced phenotypes or nuances of the disease have become apparent. In fact, EoE might be only the tip of the iceberg (and the most extreme phenotype) with several variant forms, at least three, lying on a disease spectrum. Although a common (food induced) pathogenesis has yet to be confirmed, gastroenterologists and allergologists should be aware of these new phenomena in order to further characterize these patients. In the following review, we discuss the pathogenesis of EoE, particularly those mechanisms beyond eosinophilic infiltration of the esophageal mucosa, non-eosinophilic inflammatory cell populations, the new disease entity EoE-like disease, variant forms of EoE, and the recently coined term mast cell esophagitis.

Breaking down the complex pathophysiology of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic and progressive immune-mediated disease of the esophagus associated with antigen-driven type 2 inflammation and symptoms of esophageal dysfunction. Our understanding of EoE pathophysiology has evolved since its initial recognition more than 20 years ago and has translated into diagnostic and novel therapeutic approaches that are affecting patient care. The mechanisms underlying disease development and progression are influenced by diverse factors, such as genetics, age, allergic comorbidities, and allergen exposures. Central to EoE pathophysiology is a dysregulated feed-forward cycle that develops between the esophageal epithelium and the immune system. Allergen-induced, type 2-biased immune activation by the esophageal epithelium propagates a cycle of impaired mucosal barrier integrity and allergic inflammation, eventually leading to tissue remodeling and progressive organ dysfunction. Herein, we review the current understanding of fundamental pathophysiological mechanisms contributing to EoE pathogenesis.

Role of mast cells in eosinophilic esophagitis

PURPOSE OF REVIEW

This review will present what is known from recent research on the involvement of mast cells in eosinophilic esophagitis and identify questions requiring further investigation.

RECENT FINDINGS

In the adults and children with eosinophilic esophagitis, there is increasing evidence that mastocytosis can persist, despite resolution of eosinophilia and is associated with persistent mucosal abnormalities and symptoms. Despite, treatment mast cells have an activated transcriptome. Mast cells likely contribute to epithelial barrier dysfunction, smooth muscle hypertrophy and contraction, and subepithelial fibrosis. It remains unclear whether targeting MCs alone has therapeutic efficacy to improve tissue damage.

SUMMARY

Mast cells appear to play a key role in eosinophilic esophagitis and serve as a biomarker of mucosal healing in conjunction with eosinophils. Excessive mast cell activation likely contributes to tissue damage in eosinophilic esophagitis and need to be considered as a target of therapy along with eosinophils.