Esophageal subepithelial fibrosis and hyalinization are features of eosinophilic esophagitis

Amphiregulin-producing TH2 cells facilitate esophageal fibrosis of eosinophilic esophagitis

Background

Massive eosinophil infiltration into the esophagus is associated with subepithelial fibrosis and esophageal stricture in patients with eosinophilic esophagitis (EoE). However, the pathogenesis of esophageal fibrosis remains unclear.

Objective

We sought to elucidate the cellular and molecular mechanisms underlying the induction of esophageal fibrosis.

Methods

We established a murine model of EoE accompanied by fibrotic responses following long-term intranasal administration of house dust mite antigen. Using this murine model, we investigated the characteristics of immune cells infiltrating the fibrotic region of the inflamed esophagus using flow cytometry and histological analyses. We also analyzed the local inflammatory sites in the esophagus of patients with EoE using single-cell RNA sequencing, flow cytometry, and immunohistochemistry.

Results

Enhanced infiltration of both amphiregulin-producing and IL-5-producing TH2 cells was detected in the fibrotic area of the esophagus in mice subjected to repeated house dust mite exposure. Deletion of amphiregulin in CD4+ T cells ameliorates esophageal fibrosis. An analysis of human esophageal biopsy samples showed that the infiltration of amphiregulin-producing CD4+ T cells was higher in patients with EoE than in control patients. Furthermore, the number of infiltrated amphiregulin-producing CD4+ T cells was associated with the degree of esophageal fibrosis in patients with EoE.

Conclusions

Amphiregulin, produced by TH2 cells, contributes to esophageal fibrosis in EoE and may be a therapeutic target.

Making Research Flourish Through ESPGHAN: A Position Paper From the ESPGHAN Special Interest Group for Basic and Translational Research

ABSTRACT

Recent research breakthroughs have emerged from applied basic research throughout all scientific areas, including adult and paediatric gastroenterology, hepatology and nutrition (PGHAN). The research landscape within the European Society of Paediatric Gastroenterology and Nutrition (ESPGHAN) is also inevitably changing from clinical research to studies involving applied laboratory research. This position paper aims to depict the current status quo of basic science and translational research within ESPGHAN, and to delineate how the society could invest in research in the present and future time. The paper also explores which research areas in the field of PGHAN represent the current and future priorities, and what type of support is needed across the ESPGHAN working groups (WGs) and special interest groups (SIGs) to fulfil their research goals.

Type 2 Inflammation in Eosinophilic Esophagitis: From Pathophysiology to Therapeutic Targets

Eosinophilic esophagitis (EoE) is a chronic immune-mediated disease of the esophagus characterized clinically by symptoms related to esophageal dysfunction and histologically by eosinophil-predominant inflammation, whose incidence is rising. It significantly affects patients’ quality of life and, if left untreated, results in fibrotic complications. Although broad consensus has been achieved on first-line therapy, a subset of patients remains non-responder to standard therapy. The pathogenesis of EoE is multifactorial and results from the complex, still mostly undefined, interaction between genetics and intrinsic factors, environment, and antigenic stimuli. A deep understanding of the pathophysiology of this disease is pivotal for the development of new therapies. This review provides a comprehensive description of the pathophysiology of EoE, starting from major pathogenic mechanisms (genetics, type 2 inflammation, epithelial barrier dysfunction, gastroesophageal reflux, allergens, infections and microbiota) and subsequently focusing on the single protagonists of type 2 inflammation (involved cells, cytokines, soluble effectors, surface proteins and transcription factors) that could represent present and future therapeutic targets, while summarizing previous therapeutic approaches in literature.

Pathophysiology of Dysphagia in Eosinophilic Esophagitis: Causes, Consequences, and Management

Eosinophilic esophagitis (EoE) is a leading cause of food bolus impaction in children and adults. The mechanism of dysphagia in EoE, particularly non-obstructive dysphagia, remains incompletely understood. While fibrostenotic processes appear to be critical in the development of dysphagia, somatosensory dysfunction and dysmotility also contribute. This review considers potential mechanisms of dysphagia and evaluates the utility of current and future treatment strategies in this context.

Development and technical validation of an artificial intelligence model for quantitative analysis of histopathologic features of eosinophilic esophagitis

Background

In an attempt to provide quantitative, reproducible, and standardized analyses in cases of eosinophilic esophagitis (EoE), we have developed an artificial intelligence (AI) digital pathology model for the evaluation of histologic features in the EoE/esophageal eosinophilia spectrum. Here, we describe the development and technical validation of this novel AI tool.

Methods

A total of 10 726 objects and 56.2 mm² of semantic segmentation areas were annotated on whole-slide images, utilizing a cloud-based, deep learning artificial intelligence platform (Aiforia Technologies, Helsinki, Finland). Our training set consisted of 40 carefully selected digitized esophageal biopsy slides which contained the full spectrum of changes typically seen in the setting of esophageal eosinophilia, ranging from normal mucosa to severe abnormalities with regard to each specific features included in our model. A subset of cases was reserved as independent “test sets” in order to assess the validity of the AI model outside the training set. Five specialized experienced gastrointestinal pathologists scored each feature blindly and independently of each other and of AI model results.

Results

The performance of the AI model for all cell type features was similar/non-inferior to that of our group of GI pathologists (F1-scores: 94.5–94.8 for AI vs human and 92.6–96.0 for human vs human). Segmentation area features were rated for accuracy using the following scale: 1. “perfect or nearly perfect” (95%–100%, no significant errors), 2. “very good” (80%–95%, only minor errors), 3. “good” (70%–80%, significant errors but still captures the feature well), 4. “insufficient” (less than 70%, significant errors compromising feature recognition). Rating scores for tissue (1.01), spongiosis (1.15), basal layer (1.05), surface layer (1.04), lamina propria (1.15), and collagen (1.11) were in the “very good” to “perfect or nearly perfect” range, while degranulation (2.23) was rated between “good” and “very good”.

Conclusion

Our newly developed AI-based tool showed an excellent performance (non-inferior to a group of experienced GI pathologists) for the recognition of various histologic features in the EoE/esophageal mucosal eosinophilia spectrum. This tool represents an important step in creating an accurate and reproducible method for semi-automated quantitative analysis to be used in the evaluation of esophageal biopsies in this clinical context.

Antifibrotic Effects of the Thiazolidinediones in Eosinophilic Esophagitis Pathologic Remodeling: A Preclinical Evaluation

Eosinophilic esophagitis (EoE) is a T-helper 2 (Th2), eosinophilic disease associated with pathologic tissue remodeling that leads to end-organ dysfunction. During early-stage disease, inflammation and subepithelial fibrosis are coupled and reversible, but in late-stage or therapy-resistant disease, there can be uncoupling of these features with progressive esophageal rigidity and strictures contributing to clinical dysphagia and food impactions. No current pharmacotherapeutic interventions directly target esophageal fibrosis. Based on the ability of the thiazolidinediones (TZD) to regulate intestinal and hepatic fibrosis, we tested the antifibrotic effects of the TZDs, rosiglitazone and pioglitazone, in preclinical studies using primary human esophageal fibroblasts.

Intestinal eosinophils: multifaceted roles in tissue homeostasis and disease

Intestinal eosinophils are largely considered to be one of the central immune effector cells during helminth infection and disorders such as eosinophilic oesophagitis and food allergies. Given the abundance of these cells present in the gastrointestinal tract at homeostasis, emerging studies now reveal novel roles for eosinophils in the development and regulation of immunity, and during tissue repair. In addition, the identification of distinct eosinophil subsets indicates that we must consider the heterogeneity of these cells and how they differentially participate in mucosal immunity at steady state and during disease. Here, we summarise the literature on intestinal eosinophils, and how they contribute to mucosal homeostasis through immune regulation and interactions with the microbiome. We then explore the divergent roles of eosinophils in the context of eosinophilic gastrointestinal disorders and during helminth infection, whereby we discuss key observations and differences that have emerged from animal models and human studies. Lastly, we consider the possible interactions of eosinophils with the enteric nervous system, and how this represents an exciting area for future research which may inform future therapeutic targets.

Esophageal Fibrosis in Eosinophilic Gastrointestinal Diseases

OBJECTIVES

Eosinophilic esophagitis (EoE), the most common eosinophilic gastrointestinal disease (EGID), is associated with lamina propria (LP) fibrosis. The relationship of EoE to other EGIDs is still unclear. We frequently observe cases of concurrent esophageal eosinophilia and extra-esophageal mucosal eosinophilia. The purpose of this study was to compare clinical, endoscopic, and histologic features, as well as the prevalence of esophageal LP fibrosis in children with EGID and concurrent esophageal eosinophilia to children with EoE. We also examine the current practices of pathologists in evaluating fibrosis.

METHODS

We reviewed esophageal biopsies from index cases of EoE (N = 38), EGID with significant esophageal eosinophilia (≥15 eos/hpf) (EGID-SEE, N = 38), EGID with mild esophageal eosinophilia (1-14 eos/hpf) (EGID-MEE, N = 12), and EGID with no esophageal eosinophilia (EGID-NEE, N = 12) for LP presence, adequacy, and fibrosis.

RESULTS

EoE and EGID-SEE cases share similar demographics, esophageal endoscopic features, and symptoms. A majority of EGID-SEE cases (71%) had adequate LP for the evaluation of fibrosis, similar to EoE cases (87%). The prevalence of esophageal fibrosis in EoE (79%) and EGID-SEE (55%) cases were similar, whereas no fibrosis was detected in the EGID-MEE and EGID-NEE cases. The fibrosis was patchy and often detected in the distal esophagus. Fourteen cases were reclassified from their original clinical diagnosis as having fibrosis by the study pathologists.

CONCLUSIONS

Cases of EGID-SEE have overlapping features with EoE, suggesting that all EGIDs are part of a disease continuum. A consensus for the evaluation of LP fibrosis is needed.

Epigenetic methylation in Eosinophilic Esophagitis: Molecular ageing and novel biomarkers for treatment response

BACKGROUND

Treatment failure in eosinophilic esophagitis (EoE) is common. We hypothesize that DNA methylation differs between patients by treatment response to topical steroids (oral viscous budesonide), thus offering the potential to inform targeting therapies.

OBJECTIVE

We sought to identify differentially methylated sites and affiliated genes in pre-treatment oesophageal cells between responders and non-responders and test for accelerated epigenetic ageing in oesophageal cells of EoE patients.

METHODS

DNA was extracted from prospectively collected and biobanked oesophageal biopsies from 36 Caucasian treatment naïve EoE patients at diagnosis. Methylation assays were completed using the Infinium HumanMethylation450 BeadChip. Normalized β values for each CpG site were tested (t test) for differential methylation. Further, 353 CpG probes were used to estimate epigenetic age for each patient and a linear regression model tested whether chronologic age and epigenetic age differed. Epigenetic age results were confirmed in an independent cohort of healthy controls.

RESULTS

Eighteen CpG sites were differentially methylated by treatment response (P < .00001). The mean epigenetic age and chronological age were 56.1 ± 11.1 and 36.7 ± 12.3 years, a mean age difference of 19.3 ± 5.2 years (P < .0001); accelerated ageing was not observed in the oesophageal cells of healthy controls.

CONCLUSIONS AND CLINICAL RELEVANCE

EoE patients that respond versus do not respond to treatment have differences in their methylation profile, including enrichment of genes in pathways consistent with cellular injury and repair due to environmental stress and cell adhesion and barrier integrity. EoE also appears to accelerate cellular ageing. Whether treatment can arrest or reverse accelerated epigenetic ageing and the implications for long-term disease progression is important areas for future research.

The Role of MIF on Eosinophil Biology and Eosinophilic Inflammation

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine that participates in innate and adaptive immune responses. MIF contributes to the resistance against infection agents, but also to the cellular and tissue damage in infectious, autoimmune, and allergic diseases. In the past years, several studies demonstrated a critical role for MIF in the pathogenesis of type-2-mediated inflammation, including allergy and helminth infection. Atopic patients have increased MIF amounts in affected tissues, mainly produced by immune cells such as macrophages, Th2 cells, and eosinophils. Increased MIF mRNA and protein are found in activated Th2 cells, while eosinophils stock pre-formed MIF protein and secrete high amounts of MIF upon stimulation. In mouse models of allergic asthma, the lack of MIF causes an almost complete abrogation of the cardinal signs of the disease including mucus secretion, eosinophilic inflammation, and airway hyper-responsiveness. Additionally, blocking the expression of MIF in animal models leads to significant reduction of pathological signs of eosinophilic inflammation such as rhinitis, atopic dermatitis, eosinophilic esophagitis and helminth infection. A number of studies indicate that MIF is important in the effector phase of type-2 immune responses, while its contribution to Th2 differentiation and IgE production is not consensual. MIF has been found to intervene in different aspects of eosinophil physiology including differentiation, survival, activation, and migration. CD4+ T cells and eosinophils express CD74 and CXCR4, receptors able to signal upon MIF binding. Blockage of these receptors with neutralizing antibodies or small molecule antagonists also succeeds in reducing the signals of inflammation in experimental allergic models. Together, these studies demonstrate an important contribution of MIF on eosinophil biology and in the pathogenesis of allergic diseases and helminth infection.

Chronic restraint stress induces esophageal fibrosis with enhanced oxidative stress in a murine model

Although the underlying mechanism of stress remains unknown, it has been associated with the pathophysiology of gastroesophageal reflux diseases, the development of which appear to be accelerated by oxidative stress and fibrosis. The aim of the current study was to investigate the effect of chronic restraint stress on esophageal oxidative stress and fibrosis, as well as the impact of oxidative stress in a murine model whereby 8-week old C57BL/6J male mice were subjected to intermittent chronic restraint stress for a two-week period. The current study demonstrated that chronic restraint stress significantly reduced the body weight of mice compared with the control group. Although chronic restraint stress did not significantly alter the levels of triglycerides or cholesterol, free fatty acid concentration was significantly increased compared with the control group. Furthermore, chronic restraint stress significantly upregulated the expression levels of several fibrotic biomarkers including collagen type I, transforming growth factor β-1, α-smooth muscle actin and SMAD-3 compared with the control group. In addition, the expression levels of the reactive oxygen species (ROS) NADPH oxidase-4 and malondialdehyde were significantly increased, while the expression levels of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 were significantly decreased in esophageal tissue from mice in the chronic restraint stress group compared with the control group. In conclusion, chronic restraint stress may induce esophageal fibrosis by accumulating ROS and increasing fibrotic gene expression in a murine model.

Eosinophilic Esophagitis

Eosinophilic esophagitis is an immune-mediated chronic disease of the esophagus. It is clinically characterized by symptoms related to esophageal dysfunction and histologically by eosinophil-rich inflammation with a peak intraepithelial eosinophil count of at least 15 eosinophils per high-power field. Both children and adults can be affected with a strong male predominance. Food appears to be the key trigger, although the exact mechanisms remain unclear. Treatment for eosinophilic esophagitis can be summarized as the 3 D's: dietary, drugs, and dilatation. The differential diagnosis includes gastroesophageal reflux disease, eosinophilic gastroenteritis, drug hypersensitivity, hypereosinophilic syndrome, infection, Crohn disease, connective tissue diseases, and vasculitis.

Eosinophilic Esophagitis and the Eosinophilic Gastrointestinal Diseases: Approach to Diagnosis and Management

The eosinophilic gastrointestinal diseases (EGIDs) represent disorders of the gastrointestinal (GI) tract that result from the local infiltration and aberrant activity of eosinophils and other immune cells. Eosinophilic esophagitis (EoE) is the most well-characterized EGID and is defined by the presence of intraepithelial eosinophils in the esophagus (≥15 eosinophils per high-powered field) and clinical symptoms associated with esophageal dysfunction. The other EGIDs are rare and lack strong data regarding pathogenesis and management. The incidence and prevalence of EoE are increasing, and EoE is now a major cause of upper GI morbidity. Management is multidisciplinary, with collaboration between gastroenterologists, allergists, pathologists, and dieticians, and is aimed at amelioration of symptoms and prevention of long-term complications such as esophageal stricture. Treatment options for EoE include proton pump inhibitors, swallowed topical corticosteroids, and elimination diets. Esophageal dilation is used when esophageal strictures or fibrostenotic changes are present. Additional therapies targeting eosinophils and other mediators of Th2 inflammation are under development and are promising. Treatment options for other EGIDs typically involve corticosteroids or dietary elimination.

Obtaining adequate lamina propria for subepithelial fibrosis evaluation in pediatric eosinophilic esophagitis

BACKGROUND AND AIMS

Subepithelial fibrosis in eosinophilic esophagitis (EoE) can be detected only in esophageal biopsy specimens with adequate amounts of lamina propria (LP). We investigated how often pediatric esophageal biopsy specimens contain adequate LP, and whether esophageal eosinophilia influences the acquisition rates.

METHODS

We evaluated 284 esophageal biopsy specimens from 39 patients with EoE, and 87 biopsy specimens from 32 patients without esophageal eosinophilia or other esophageal abnormalities for the presence of adequate LP and fibrosis.

RESULTS

On a per biopsy specimen basis, there was no significant difference in the rate of procuring adequate amounts of LP between patients with EoE and patients without esophageal eosinophilia (43% vs 31%, P = .14). Eighty-five percent of patients with EoE had fibrosis. Fibrosis in patients with EoE was patchy and more likely to be detected in the middle or distal esophagus (odds ratio, 19.93; 95% confidence interval, 4.12-91.52). Among patients with fibrosis, the probability of its detection reached >95% with 7 middle-distal esophageal biopsy specimens. Most children with newly diagnosed EoE already had subepithelial fibrosis despite exhibiting only inflammatory endoscopic features.

CONCLUSIONS

Most individual esophageal biopsy specimens in children are inadequate for assessing subepithelial fibrosis, and the rates of procuring adequate LP per biopsy specimen are similar in patients with and without EoE. To reliably detect fibrosis in patients with EoE, at least 7 biopsy specimens should be taken from the middle-distal esophagus. The finding of fibrosis in children with newly diagnosed EoE and only inflammatory endoscopic features suggests that fibrosis can occur early in this disease.

Eosinophilic Esophagitis: Pathophysiology and Definition

Eosinophilic esophagitis is an adaptive immune response to patient-specific antigens, mostly foods. Eosinophilic esophagitis is not solely IgE-mediated and is likely characterized by Th2 lymphocytes with an impaired esophageal barrier function. The key cytokines and chemokines are thymic stromal lymphopoeitin, interleukin-13, CCL26/eotaxin-3, and transforming growth factor-β, all involved in eosinophil recruitment and remodeling. Chronic food dysphagia and food impactions, the feared late complications, are related in part to dense subepithelial fibrosis, likely induced by interleukin-13 and transforming growth factor-β.

Other Forms of Esophagitis: It Is Not Gastroesophageal Reflux Disease, So Now What Do I Do?

Esophagitis results from diverse causes, including gastroesophageal reflux, immune-mediated or allergic reactions, therapeutic complications, and infections. The appropriate clinical management differs in each of these situations and is often guided by pathologic interpretation of endoscopic mucosal biopsy specimens. This review summarizes the diagnostic features of unusual forms of esophagitis, including eosinophilic esophagitis, lymphocytic esophagitis, esophagitis dissecans superficialis, drug-induced esophageal injury, and bullous disorders. Differential diagnoses and distinguishing features are emphasized.

Detailed Histologic Evaluation of Eosinophilic Esophagitis in Pediatric Patients Presenting with Dysphagia or Abdominal Pain and Comparison of the Histology between the Two Groups

EoE in children presents with four main symptoms. Most common symptoms exhibited by our clinic population are dysphagia (D) and abdominal pain (AP). Despite similar treatments, we found in an earlier study that the outcomes between these two groups were different. Therefore, we investigated if there exist any histological differences between these groups that could further our knowledge of EoE. Aim. To compare esophageal histology in detail, apart from the eosinophil count, between EoE-D and EoE-AP. Method. Biopsies of patients with EoE-D and EoE-AP were reevaluated for 10 additional histological criteria, in addition to the eosinophil count. Results. Both groups had 67 patients; peak mean eosinophil was 33.9 and 31.55 for EoE-D and EoE-AP (p < 0.05). Eosinophilic microabscesses, superficial layering of eosinophils, and epithelial desquamation were twice as common and significant in EoE-D group than EoE-AP. Eosinophil distribution around rete pegs was also significantly higher in EoE-D group. The remaining criteria were numerically higher in EoE-D, but not significant, with the exception of rete peg elongation. Conclusion. EoE-D patients have significantly higher eosinophils compared to EoE-AP, and the level of inflammation as seen from eosinophil microabscesses, superficial layering, desquamation, and the distribution around rete pegs is significantly higher.

Specific locations of linear furrows in patients with esophageal eosinophilia

BACKGROUND AND AIM

Linear furrows are the most frequently found endoscopic abnormality in patients with esophageal eosinophilia (EE); however, the precise endoscopic features remain to be fully elucidated. Here, we aimed to clarify the endoscopic features of EE, essential for the diagnosis of eosinophilic esophagitis (EoE), by focusing on the specific locations of linear furrows in a Japanese population.

METHODS

We enrolled 70 cases with EE (≥15 eosinophils/high-power field) who were diagnosed at our hospital and related facilities. Information regarding endoscopic findings and clinical parameters was retrospectively reviewed. Next, the position of linear furrows in relation to esophageal longitudinal folds (ridge or valley) was evaluated in each case and compared with the position of mucosal breaks in patients with reflux esophagitis. Finally, the relationship between linear furrows and eosinophilic infiltration was evaluated.

RESULTS

Of the 70 EE patients, 63 (90%) had linear furrows. Those occurred in a radial pattern and were widespread throughout the lower to upper esophagus, and exclusively found in esophageal longitudinal mucosal fold valleys, not on ridges, which was different from the position of mucosal breaks in patients with reflux esophagitis. Increased eosinophilic infiltration was significantly more frequent in linear furrows in the valleys (93%) as compared to mucosa on adjacent ridges (60%) (P < 0.05).

CONCLUSION

Investigation of these endoscopic characteristics, especially by focusing on linear furrows in esophageal mucosal fold valleys, may provide important clues for more accurate diagnosis of EoE.

Macrophage migration inhibitory factor promotes eosinophil accumulation and tissue remodeling in eosinophilic esophagitis

Macrophage migration inhibitory factor (MIF) is involved in eosinophil biology and in type 2 inflammation, contributing to allergic and helminthic diseases. We hypothesized that MIF participates in the pathogenesis of eosinophilic esophagitis (EoE), an allergic condition characterized by esophageal eosinophilic inflammation. MIF is highly expressed in esophageal mucosa of patients with EoE, compared with gastro-esophageal reflux disease and control patients, where it co-localizes predominantly with eosinophils. In vitro, recombinant MIF promotes human eosinophil chemotaxis, while MIF antagonist and CXCR4 antagonist, AMD3100, revert this effect. In a model of EoE induced by ovalbumin, Mif-deficient mice have reduced inflammation and collagen deposition compared with wild-type (WT) mice. Importantly, treatment of WT mice with anti-MIF or with AMD3100 during the challenge phase prevents accumulation of eosinophils and tissue remodeling. Conversely, recombinant MIF promoted tissue eosinophil inflammation in allergic mice. Together, these results implicate MIF in the pathogenesis of esophageal inflammation and suggest that targeting MIF might represent a novel therapy for EoE.

Eosinophils in the GI tract: how many is too many and what do they mean?

Eosinophils are commonly detected in normal mucosal biopsies from all sites within the gastrointestinal tract where they are dispersed in the lamina propria and, to a lesser extent, in the epithelium. The distinction between the upper limit of normal and abnormally increased tissue eosinophils is not well defined. However, eosinophils that infiltrate the epithelium in more than occasional numbers, coalesce to form aggregates, or show extensive degranulation are always abnormal and raise a broad differential diagnosis. Although the differential diagnosis of purely eosinophilic inflammation is largely limited to hypersensitivity reactions and some infections, they are increased in several gastrointestinal conditions, including gastroesophageal reflux disease, autoimmune gastritis, infections, drug reactions, inflammatory bowel disease, radiation enteritis, and collagen vascular disease. These disorders feature eosinophils as one component of a mixed inflammatory infiltrate that can, in some instances, be prominent enough to cause diagnostic confusion. The purpose of this review is to discuss the normal distribution of eosinophils in the gastrointestinal tract and the differential diagnosis of inflammatory conditions that feature prominent eosinophilia.

The pathophysiology of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is an emerging disease characterized by esophageal eosinophilia (>15eos/hpf), lack of responsiveness to acid-suppressive medication and is managed by allergen elimination and anti-allergy therapy. Although the pathophysiology of EoE is currently unsubstantiated, evidence implicates food and aeroallergen hypersensitivity in genetically predisposed individuals as contributory factors. Genome-wide expression analyses have isolated a remarkably conserved gene-expression profile irrespective of age and gender, suggesting a genetic contribution. EoE has characteristics of mainly TH2 type immune responses but also some TH1 cytokines, which appear to strongly contribute to tissue fibrosis, with esophageal epithelial cells providing a hospitable environment for this inflammatory process. Eosinophil-degranulation products appear to play a central role in tissue remodeling in EoE. This remodeling and dysregulation predisposes to fibrosis. Mast-cell-derived molecules such as histamine may have an effect on enteric nerves and may also act in concert with transforming growth factor-β to interfere with esophageal musculature. Additionally, the esophageal epithelium may facilitate the inflammatory process under pathogenic contexts such as in EoE. This article aims to discuss the contributory factors in the pathophysiology of EoE.

Remodeling and fibrosis in chronic eosinophil inflammation

Chronic eosinophilic inflammation has been associated with tissue remodeling in a number of disease states including the hypereosinophilic syndrome (HES), asthma, and, more recently, eosinophilic esophagitis (EoE). Remodeling occurs in the epithelial and subepithelial esophageal tissue, and includes basal zone hyperplasia, epithelial mesenchymal transition, fibrosis, angiogenesis, and smooth muscle hypertrophy/hyperplasia. Previously, research on the clinical impacts of tissue remodeling has been limited by a paucity of human tissue. However, in EoE, recurrent biopsies are required for diagnosis and management. As such, investigators are able to study the associations between tissue changes and clinical disease features. A number of profibrotic and proangiogenic factors are elevated in EoE, including TGF-β1, CCL-18, FGF-9, VEGF, and VCAM-1. Both eosinophils and mast cells produce a number of these factors. TGF-β1 appears to be a master regulator of end-organ dysfunction in EoE and can cause esophageal epithelial mesenchymal transition, fibrosis, and smooth muscle contraction. The requirement for eosinophils, the eosinophilopoietic interleukin, IL-5, and the canonical TGF-β1 signaling pathway for EoE-associated fibrosis, has been invoked using gene-deficient mice. The clinical consequences of eosinophil-associated tissue fibrosis can be devastating, such as endomyocardial fibrosis and heart failure in HES. In EoE, tissue remodeling appears to be the mechanism for multiple cardinal disease complications including esophageal rigidity, strictures, narrowing, and food impactions, as well as the clinical hallmark of dysphagia. Therapies that may be able to reduce or reverse EoE-associated remodeling include topical corticosteroids, anti-IL-5, and food antigen avoidance.

Validation of methods to assess potential biomarkers in pediatric patients with esophageal eosinophilia

AIM: To validate methods for determining mast cell density, extracellular major basic protein content, and presence of fibrosis in esophageal eosinophilia.

METHODS: Twenty specimens with > 20 eosinophils/high-power field (hpf) classified as high eosinophil density (HE) and 20 specimens with < 5 eosinophils/hpf classified as low esophageal density (LE) were identified. All 40 specimens underwent immunohistochemical staining and trichrome staining. Mast cell density, extracellular major basic protein (MBP) density, and presence of subepithelial fibrosis were assessed in a standardized manner. All specimens were evaluated by two separate observers and by a single observer on two separate occasions to evaluate reproducibility of the methods.

RESULTS: A strong inter-observer correlation was noted for both peak and mean mast cell counts (r = 0.725, P < 0.0001 and r = 0.823, P < 0.0001). A strong intra-observer correlation also was noted for both peak and mean mast cell counts (r = 0.752, P < 0.0001 and r = 0.878, P < 0.0001). A very strong inter-observer correlation was noted for both peak (τ = 0.867, P < 0.0001) and mean extracellular MBP densities (r = 0.925, P < 0.0001). A very strong intra-observer correlation was noted for both peak (τ = 0.875; P < 0.0001) and mean extracellular MBP densities (r = 0.956, P < 0.0001). Excellent inter-rater reliability was found for fibrosis (κ = 0.887). Mast cell and MBP densities, as well as presence of fibrosis, were significantly increased in HE vs LE. The HE group had significantly higher intraepithelial mast cell peak (29.35 ± 21.61 vs 12.45 ± 8.26, P = 0.002) and mean (19.84 ± 15.81 vs 6.35 ± 4.5, P = 0.001) densities than the LE group. The HE group had significantly higher peak extracellular MBP (2.35 ± 0.67 vs 0.45 ± 0.61, P < 0.001) and mean extracellular MBP (1.95 ± 0.76 vs 0.20 ± 0.29, P < 0.0001) densities than the LE group. Seventy-three percent of patients with HE (11/15) had fibrosis, whereas only 10% of patients with LE (1/10) had fibrosis (P < 0.01). MBP performed the best in predicting classification of HE vs LE, with mean MBP demonstrating 100% sensitivity and 95% specificity at the optimal cut point.

CONCLUSION: This study provides methodology and proof-of-concept for future evaluation of these biomarkers for differentiating esophageal eosinophilic diseases such as reflux esophagitis and eosinophilic esophagitis.

CD14+CD33+ myeloid cell-CCL11-eosinophil signature in ulcerative colitis

This study tested the hypothesis that eotaxins (CCL11, CCL24, and CCL26) and IL-5 contribute to eosinophil recruitment to the intestine in UC and that intestinal macrophages are important producers of CCL11 in this disease. Peripheral blood and rectal biopsy samples were obtained from patients with active (n=18) and quiescent UC (n=9), and control patients (n=7). Eosinophil and macrophage levels and activation were analyzed by flow cytometry. Rectal mRNA levels of CCL11, CCL24, CCL26, and IL-5 were determined by qRT-PCR. The cellular source of CCL11 was visualized by immunofluorescence analyses. Eosinophil numbers were elevated in the blood and rectum of active and quiescent UC patients compared with controls. Levels of activated eosinophils (CD66b(high)) correlated with disease severity. Rectal CCL11, CCL24, and CCL26 mRNA levels were increased in active UC, whereas only CCL11 was elevated in quiescent UC. Levels of CCL11, but not CCL24 and CCL26, positively correlated with eosinophil numbers. Numbers of CD14(+)CD33(+) cells correlated with CCL11 and eosinophil levels. Immunofluorescence analyses revealed the presence of CD14(+)CCL11(+) mononuclear cells in colonic biopsies in UC. These results support the hypothesis that CCL11 contributes to eosinophil recruitment in UC and that intestinal myeloid cells are a source of CCL11. Interestingly, rectal levels of CCL24, CCL26, and IL-5 only increase during active UC, coinciding with further elevation of eosinophil numbers and with the activation of rectal eosinophils. In conclusion, there is a link among CD14(+)CD33(+) myeloid cells, CCL11, and eosinophils in adult UC.

T cell co-stimulatory molecules: a co-conspirator in the pathogenesis of eosinophilic esophagitis?

Eosinophilic esophagitis (EoE) has become a common gastrointestinal disease. It is characterized by severe eosinophil infiltration in the esophagus. EoE is strongly associated with food allergy, asthma, atopic dermatitis, and other allergic diseases. T lymphocytes, especially Th2 cells, play an instrumental role in the development of allergic inflammation. Recent studies have shown that the ligation of co-stimulatory molecules contributes to the activation, differentiation, and proliferation of T cells. In this review, we will discuss the growing evidence of co-stimulatory molecules including OX40, Light, and HVEM in the pathogenesis of Th2-driven EoE. Our goal is to provide the rationale for the development of novel therapy therapies that target co-stimulatory molecules.

Eosinophils in infection and intestinal immunity

PURPOSE OF REVIEW

Inflammatory bowel diseases (IBDs, e.g., Crohn's disease and ulcerative colitis) are thought to be a consequence of an uncontrolled inflammatory response against luminal antigens, including commensal bacteria. The observed link between eosinophil levels and severity and remission rates in IBD has led to speculation that eosinophils may contribute to the antimicrobial inflammatory response in IBD.

RECENT FINDINGS

Eosinophils express the necessary cellular machinery (innate immune receptors, proinflammatory cytokines, antibacterial proteins, and DNA traps) to mount an efficient antibacterial response; however, the rapid decline in eosinophil numbers following acute systemic bacterial infection suggests a very limited role for eosinophils in bacterial responses.

SUMMARY

We describe the clinical evidence of eosinophil involvement in IBD, summarize the in-vitro and in-vivo evidence of eosinophil antibacterial activity and the biology of eosinophils focusing on eosinophil-mediated bactericidal mechanisms and the involvement of eosinophil-derived granule proteins in this response, and conceptualize the contribution of eosinophils to a response against commensal bacteria in IBD.

Dietary therapy can reverse esophageal subepithelial fibrosis in patients with eosinophilic esophagitis: a historical cohort

BACKGROUND

Fibrosis of the esophageal lamina propria is a known complication of eosinophilic esophagitis (EoE). To date, therapy with topical corticosteroids has been shown to reverse esophageal fibrosis in some patients; however, there is little evidence to suggest that dietary therapy can also reverse it. Our aim was to examine whether dietary therapy alone can reverse esophageal fibrosis in children with EoE.

METHODS

We performed a historical cohort study based on children with EoE who had esophageal fibrosis on pretreatment biopsies using trichrome staining. Post-treatment biopsies were analyzed for fibrosis reversal, and results were compared between patients treated with dietary restriction and those that received topical steroids. Clinical characteristics (age, symptoms, duration of symptoms prior to therapy, treatment type, and duration of therapy) were recorded. Histological markers (eosinophil numbers and eosinophilic degranulation in both epithelium and lamina propria, basal zone hyperplasia, and the presence of eosinophilic microabscesses in the epithelium) were examined by reviewing hematoxylin and eosin-stained biopsies and by immunohistochemical staining. These were examined as potential predictors for fibrosis reversal.

RESULTS

Fibrosis resolved following both dietary restriction and topical steroids (3/17 and 5/9 patients respectively, P = 0.078). Post-treatment symptom resolution and decreased intraepithelial eosinophil numbers were found to be the only significant predictors of fibrosis resolution.

CONCLUSIONS

Dietary restriction alone, similar to topical steroids, can reverse fibrosis in children with EoE.

The prevalence and diagnostic utility of endoscopic features of eosinophilic esophagitis: a meta-analysis

BACKGROUND & AIMS

Endoscopic findings such as esophageal rings, strictures, narrow-caliber esophagus, linear furrows, white plaques, and pallor or decreased vasculature might indicate the presence of eosinophilic esophagitis (EoE). We aimed to determine the prevalence and diagnostic utility of endoscopic features of EoE.

METHODS

We conducted a systematic review and meta-analysis. PubMed, EMBASE, and gastrointestinal meeting abstracts were searched to identify studies that included more than 10 patients with EoE and reported endoscopic findings. Pooled prevalence, sensitivity, specificity, and predictive values were calculated using random- and mixed-effects models.

RESULTS

The search yielded 100 articles and abstracts on 4678 patients with EoE and 2742 without (controls). In subjects with EoE, the overall pooled prevalence was as follows: esophageal rings, 44%; strictures, 21%; narrow-caliber esophagus, 9%; linear furrows, 48%; white plaques, 27%; and pallor/decreased vasculature, 41%. Substantial heterogeneity existed among studies. Results from endoscopy examinations were normal in 17% of patients, but this number decreased to 7% when the analysis was limited to prospective studies (P < .05). Overall levels of sensitivity were modest, ranging from 15% to 48%, whereas levels of specificity were greater, ranging from 90% to 95%. Positive predictive values ranged from 51% to 73% and negative predictive values ranged from 74% to 84%.

CONCLUSIONS

There is heterogeneity among studies in the reported prevalence of endoscopic findings in patients with EoE, but in prospective studies at least 1 abnormality was detected by endoscopy in 93% of patients. The operating characteristics of endoscopic findings alone are inadequate for diagnosis of EoE. Esophageal biopsy specimens should be obtained from all patients with clinical features of EoE, regardless of the endoscopic appearance of the esophagus.

Update on clinical and immunological features of eosinophilic gastrointestinal diseases

PURPOSE OF REVIEW

Eosinophilic gastrointestinal diseases (EGIDs) are an increasingly common heterogeneous group of intestinal diseases. The purpose of this review is to present the latest developments in the care of patients with EGIDs and to summarize a growing literature defining the clinical features and mechanistic elements of eosinophils and their complex relationships with the gastrointestinal tract.

RECENT FINDINGS

Recent studies continue to define what constitutes 'normal' and 'abnormal' numbers of eosinophils in the different sections of the gastrointestinal tract. Symptom complexes of EGIDs appear to be related primarily to the mucosal, as opposed to the muscular or serosal, forms of EGIDs. Dissection of the mucosal microenvironment is uncovering a complex array of cells, other than eosinophils, that likely contribute to the inflammatory response associated with EGIDs. Mechanistic studies have identified genetic perturbations (eotaxin-3, thymic stromal lymphopoietin, IL-13, and filaggrin) that may also contribute to the development of the most often encountered and well studied EGID, eosinophilic esophagitis.

SUMMARY

Clinicians should remain aware of EGIDs as a diagnostic possibility for patients with common gastrointestinal symptoms. Additional research is needed to determine mechanistic processes leading to dysfunction associated with eosinophilic gastrointestinal inflammation.

Eosinophilic Esophagitis in Pediatrics: The Worst of all Possible Allergy Worlds?

Eosinophilic esophagitis (EoE) is a relatively uncommon allergic disease. Presenting with variable gastrointestinal symptoms, the definitive diagnosis is made after esophageal visualization and histological confirmation of excessive esophageal eosinophils. The scientific discovery of the pathophysiology of EoE has been aided by its relationship to other common and well-recognized allergic diseases. Similarities and important differences have emerged to distinguish EoE as a significant pediatric allergic disease with unique medical care requirements.

Genetic dissection of eosinophilic esophagitis provides insight into disease pathogenesis and treatment strategies

Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder of the esophagus that is compounded by both genetic predisposition and aberrant responses to environmental antigens, particularly those that are food derived. Data have indicated a unique transcriptional response in vivo that defines EoE and that appears to be partially attributable to the T(H)2 cytokine IL-13. Moreover, a number of genetic risk variants in proinflammatory and epithelial cell genes associate with EoE susceptibility, demonstrating novel heritable mechanisms that contribute to disease risk. Here we discuss recent advances in our understanding of the intrinsic (genetic) and extrinsic (environmental) components that illustrate the complex nature of EoE.