Unraveling the mystery of the gastroesophageal junction: a pathologist's perspective

Untangling immune cell contributions in the progression from GERD to Barrett's esophagus and esophageal cancer: Insights from genetic causal analysis

BACKGROUND

Esophageal adenocarcinoma (EAC) is a rapidly increasing malignancy with significant morbidity and mortality. The progression from gastroesophageal reflux disease (GERD) to Barrett's esophagus (BE) and ultimately to EAC is thought to be influenced by chronic inflammation and immune cell dynamics. Despite the observed correlations in observational studies, the causal relationships between immune cell phenotypes and this disease continuum remain unclear.

METHODS

This study utilized a two-sample Mendelian Randomization (MR) approach to investigate the causal roles of 731 distinct immune cell phenotypes in the GERD-BE-EAC continuum. The analysis leveraged genome-wide association study (GWAS) data for immune phenotypes from a Sardinian cohort and data for GERD, BE, and EAC from the FinnGen and Open GWAS databases. A comprehensive set of MR methods, including inverse variance weighted (IVW), MR-Egger, and weighted median estimators, was employed to assess causality. Sensitivity analyses were conducted to evaluate heterogeneity and pleiotropy, ensuring the robustness of the findings.

RESULTS

The study revealed complex and multifaceted roles of immune cells across the GERD-BE-EAC continuum. In GERD, 34 immune phenotypes were found to be causally associated with either increased or decreased risk. Protective effects were observed in phenotypes such as Unswitched Memory B cells, while others like CD45RA- CD4+ T cells were linked to an elevated risk. In the context of BE, 28 immune phenotypes demonstrated significant causal associations, with the majority being protective, including Unswitched Memory B cells and CD62L on Granulocytes. Conversely, certain phenotypes, such as CD24 on Transitional B cells, were identified as risk factors for BE. For EAC, 34 immune phenotypes were implicated, with various B cell subsets, particularly those expressing BAFF-R and CD24, associated with an increased risk, while Switched Memory B cells and specific myeloid cell phenotypes showed protective effects.

CONCLUSIONS

This study provides novel insights into the complex role of immune cells in the pathogenesis of EAC, revealing a dynamic interplay where certain immune phenotypes may be protective in early stages but become risk-enhancing in later stages of disease progression. These findings highlight the potential of immune cell phenotypes to serve as biomarkers for early detection and targeted therapeutic interventions across the GERD-BE-EAC continuum. Further research is warranted to validate these findings in diverse populations and to explore the underlying mechanisms driving these immune-mediated effects.

Gastro-Esophageal Junction Precancerosis: Histological Diagnostic Approach and Pathogenetic Insights

Barrett's esophagus (BE) was initially defined in the 1950s as the visualization of gastric-like mucosa in the esophagus. Over time, the definition has evolved to include the identification of goblet cells, which confirm the presence of intestinal metaplasia within the esophagus. Chronic gastro-esophageal reflux disease (GERD) is a significant risk factor for adenocarcinoma of the esophagus, as intestinal metaplasia can develop due to GERD. The development of adenocarcinomas related to BE progresses in sequence from inflammation to metaplasia, dysplasia, and ultimately carcinoma. In the presence of GERD, the squamous epithelium changes to columnar epithelium, which initially lacks goblet cells, but later develops goblet cell metaplasia and eventually dysplasia. The accumulation of multiple genetic and epigenetic alterations leads to the development and progression of dysplasia. The diagnosis of BE requires the identification of intestinal metaplasia on histologic examination, which has thus become an essential tool both in the diagnosis and in the assessment of dysplasia's presence and degree. The histologic diagnosis of BE dysplasia can be challenging due to sampling error, pathologists' experience, interobserver variation, and difficulty in histologic interpretation: all these problems complicate patient management. The development and progression of Barrett's esophagus (BE) depend on various molecular events that involve changes in cell-cycle regulatory genes, apoptosis, cell signaling, and adhesion pathways. In advanced stages, there are widespread genomic abnormalities with losses and gains in chromosome function, and DNA instability. This review aims to provide an updated and comprehensible diagnostic approach to BE based on the most recent guidelines available in the literature, and an overview of the pathogenetic and molecular mechanisms of its development.

Kyoto international consensus report on anatomy, pathophysiology and clinical significance of the gastro-oesophageal junction

OBJECTIVE

An international meeting was organised to develop consensus on (1) the landmarks to define the gastro-oesophageal junction (GOJ), (2) the occurrence and pathophysiological significance of the cardiac gland, (3) the definition of the gastro-oesophageal junctional zone (GOJZ) and (4) the causes of inflammation, metaplasia and neoplasia occurring in the GOJZ.

DESIGN

Clinical questions relevant to the afore-mentioned major issues were drafted for which expert panels formulated relevant statements and textural explanations.A Delphi method using an anonymous system was employed to develop the consensus, the level of which was predefined as ≥80% of agreement. Two rounds of voting and amendments were completed before the meeting at which clinical questions and consensus were finalised.

RESULTS

Twenty eight clinical questions and statements were finalised after extensive amendments. Critical consensus was achieved: (1) definition for the GOJ, (2) definition of the GOJZ spanning 1 cm proximal and distal to the GOJ as defined by the end of palisade vessels was accepted based on the anatomical distribution of cardiac type gland, (3) chemical and bacterial (Helicobacter pylori) factors as the primary causes of inflammation, metaplasia and neoplasia occurring in the GOJZ, (4) a new definition of Barrett's oesophagus (BO).

CONCLUSIONS

This international consensus on the new definitions of BO, GOJ and the GOJZ will be instrumental in future studies aiming to resolve many issues on this important anatomic area and hopefully will lead to better classification and management of the diseases surrounding the GOJ.

Intestinal Metaplasia of the "Cardia": Accurate Differentiation of Gastric or Esophageal Origin With an Expanded Biopsy Protocol

Whether intestinal metaplasia (IM) distal to the endoscopic gastroesophageal junction (GEJ), that is, the cardia, is gastric or esophageal or both is controversial. Biopsies from this region are believed to be unreliable in resolving this issue and are not recommended. Our objective was to develop an accurate method of histologic diagnosis for IM of the cardia. An expanded biopsy protocol was employed in 986 patients irrespective of indication for endoscopy. This sampled columnar lined esophagus (CLE) when present, the endoscopic GEJ defined by the proximal limit of rugal folds, the area 1 cm distal to the GEJ, and distal stomach. The prevalence and associations of IM in these 4 locations were evaluated. IM was found in 79/91 patients with CLE above the GEJ. This was significantly associated with IM at the GEJ in 40/79 patients (P<0.001). The biopsy taken distal to the endoscopic GEJ had IM in 21/79 patients. No patient with CLE had IM in the distal stomach. In patients without CLE, IM was present at or distal to the endoscopic GEJ in 221 patients. In 32 patients, this was significantly associated with IM in the distal stomach (P<0.001). The remaining 189/986 (19.2%) patients had IM limited to the GEJ region. These data, in association with recent evidence, indicate that IM limited to the area distal to the GEJ in patients without distal gastric IM represents microscopic Barrett esophagus in a dilated distal esophagus. This is presently mistaken for IM of the proximal stomach because of a flawed endoscopic definition of the GEJ.

Intestinal metaplasia at the gastroesophageal junction is associated with gastroesophageal reflux but not with Helicobacter pylori infection

OBJECTIVE

Studies of the etiology of intestinal metaplasia (IM) at a normal appearing gastroesophageal junction (GEJ) are conflicting as associations with both H. Pylori (HP) infection and gastroesophageal reflux has been reported. The aim of this study was to investigate whether IM at the GEJ is associated with gastroesophageal reflux or HP infection.

MATERIAL AND METHODS

Fifty asymptomatic volunteers and 149 patients with reflux symptoms underwent endoscopy with biopsies obtained from the gastric antrum and the squamocolumnar junction (SCJ). All subjects underwent wireless 48 h pH monitoring with the electrode placed immediately above the SCJ and a fecal antigen test for HP infection. Clinical characteristics and the pattern of reflux were compared in subjects with and without IM.

RESULTS

Three asymptomatic volunteers and 35 patients who had clearly irregular SCJs with short extensions of columnar mucosa were excluded from the study. In the remaining 47 asymptomatic volunteers and 114 patients, variables that reached a significance level of 0.1 or less on univariate analyses were used in a binomial regression analysis to assess their relative importance for the finding of IM. IM at the GEJ was significantly associated with abnormal distal esophageal acid exposure (5.5 (1.2-24.6), p = .026), the frequency of reflux episodes/hour (1.5 (1.1-2.2), p = .031), and an endoscopic appearance of the SCJ corresponding to ZAP grade I (4.6 (1.4-15.6), p = .013). There was no association with HP infection.

CONCLUSION

The finding of IM at an endoscopically normal-appearing GEJ is associated with gastroesophageal reflux but not with HP infection.

What Is the Best Operation for Proximal Gastric Cancer and Distal Esophageal Cancer?

Cancer of the gastroesophageal junction (GEJ) is increasing in incidence, likely as a result of rising obesity and gastroesophageal reflux disease rates. The tumors that arise here share features of esophageal and gastric cancer, and are classified based on their location in relationship to the GEJ. The definition of the GEJ itself, as well as optimal resection strategy, extent of lymph node dissection, resection margin length, and reconstruction methods are still very much a subject of debate. This article summarizes the available evidence on this topic, and highlights specific areas for further research.

Acid and the basis for cellular plasticity and reprogramming in gastric repair and cancer

Subjected to countless daily injuries, the stomach still functions as a remarkably efficient digestive organ and microbial filter. In this Review, we follow the lead of the earliest gastroenterologists who were fascinated by the antiseptic and digestive powers of gastric secretions. We propose that it is easiest to understand how the stomach responds to injury by stressing the central role of the most important gastric secretion, acid. The stomach follows two basic patterns of adaptation. The superficial response is a pattern whereby the surface epithelial cells migrate and rapidly proliferate to repair erosions induced by acid or other irritants. The stomach can also adapt through a glandular response when the source of acid is lost or compromised (that is, the process of oxyntic atrophy). We primarily review the mechanisms governing the glandular response, which is characterized by a metaplastic change in cellular differentiation known as spasmolytic polypeptide-expressing metaplasia (SPEM). We propose that the stomach, like other organs, exhibits marked cellular plasticity: the glandular response involves reprogramming mature cells to serve as auxiliary stem cells that replace lost cells. Unfortunately, such plasticity might mean that the gastric epithelium undergoes cycles of differentiation and de-differentiation that increase the risk of accumulating cancer-predisposing mutations.

Circular stripes were more common in Barrett's esophagus after acetic acid staining

BACKGROUND

The diagnosis of Barrett's esophagus (BE) is disturbed by numerous factors, including correct gastroesophageal junction judgment, the initial location of the Z-line and the biopsy result above it. The acetic acid (AA) could help to diagnose BE better than high resolution imaging technology or magnifying endoscopy, by providing enhanced contrast of different epithelium. We have noticed AA could produce multiple white circular lines, forming circular stripes (CS), at lower esophagus, which hasn't been reported by others. This study aimed to investigate whether the CS is a special marker in BE patients.

METHODS

A total of 47 BE patients and 63 healthy people were enrolled from March 2016 to October 2016, and 2% AA staining had been operated routinely at lower esophagus under high resolution gastroscopy. We observed whether there were CS after AA staining and the images were compared between the two groups.

RESULTS

CS were confirmed in 42 patients (89.36%) in the BE group and 5 (7.94) in the control group ((χ2 = 72.931, P < 0.001)). The average width of CS was 0.76 ± 0.25 cm in BE group, which was similar to that in the control group (0.88 ± 0.11 cm). Villous or punctate or reticular pattern usually existed above or below the CS.

CONCLUSIONS

CS could be found at lower esophagus in most BE patients with AA staining, and this special feature might be valuable in diagnosing, evaluating and following up of BE patients.

Unique Cellular Lineage Composition of the First Gland of the Mouse Gastric Corpus

The glandular stomach has two major zones: the acid secreting corpus and the gastrin cell-containing antrum. Nevertheless, a single gland lies at the transition between the forestomach and corpus in the mouse stomach. We have sought to define the lineages that make up this gland unit at the squamocolumnar junction. The first gland in mice showed a notable absence of characteristic corpus lineages, including parietal cells and chief cells. In contrast, the gland showed strong staining of Griffonia simplicifolia-II (GSII)-lectin-positive mucous cells at the bases of glands, which were also positive for CD44 variant 9 and Clusterin. Prominent numbers of doublecortin-like kinase 1 (DCLK1) positive tuft cells were present in the first gland. The first gland contained Lgr5-expressing putative progenitor cells, and a large proportion of the cells were positive for Sox2. The cells of the first gland stained strongly for MUC4 and EpCAM, but both were absent in the normal corpus mucosa. The present studies indicate that the first gland in the corpus represents a unique anatomic entity. The presence of a concentration of progenitor cells and sensory tuft cells in this gland suggests that it may represent a source of reserve reparative cells for adapting to severe mucosal damage.

Barrett's esophagus: recent insights into pathogenesis and cellular ontogeny

Esophageal adenocarcinoma (EAC) has increased 6-fold in its incidence in the last 2 decades. Evidence supports the hypothesis of stepwise progression from normal squamous epithelium → reflux esophagitis → metaplasia (Barrett's esophagus, BE) → dysplasia → adenocarcinoma. The precursor, BE, stands as the bridge connecting the widespread but naive reflux disease and the rare but fatal EAC. The step of metaplasia from squamous to intestine-like columnar phenotype is perhaps pivotal in promoting dysplastic vulnerability. It is widely accepted that chronic inflammation because of gastroesophageal reflux disease leads to the development of metaplasia, however the precise molecular mechanism is yet to be discovered. Additionally, how this seemingly adaptive change in the cellular phenotype promotes dysplasia remains a mystery. This conceptual void is deterring further translational research and clouding clinical decision making. This article critically reviews theories on the pathogenesis of Barrett's esophagus and the various controversies surrounding its diagnosis. We further discuss unanswered questions and future directions, which are vital in formulating effective preventive and therapeutic guidelines for Barrett's esophagus.

Differential nucleobase protection against 5-fluorouracil toxicity for squamous and columnar cells: implication for tissue function and oncogenesis

Purpose The goal of these studies was to test if local excess of a normal nucleobase substrate prevents the toxicity of protracted 5FU exposure used in human cancer treatment. Methods Messenger RNA expression studies were performed of 5FU activating enzymes in human colon cancer cells lines (CaCo-2, HT-29), primary human gingival cells (HEGP), and normal esophageal and gastric clinical tissue samples. Excess nucleobase was then used in vitro to protect cells from 5FU toxicity. Results Pyrimidine salvage pathways predominate in squamous cells of the gingiva (HEGP) and esophageal tissue. Excess salvage nucleobase uracil but not adenine prevented 5FU toxicity in HEGP cells. Pyrimidine de novo synthesis predominates in columnar Caco-2, HT-29 and gastric tissue. Excess nucleobase adenine but not uracil prevented 5FU toxicity to Caco-2 and HT-29 cells. Conclusion The directed application of the normal nucleobase uracil to the squamous cells of the oral mucosa and palms and soles together with the delivery of the normal nucleobase adenine to the columnar cells of the GI tract may enable the safe delivery of higher 5FU dose intensity. These results also suggest a feature of tissue function where squamous cells grow largely by recycling overlying tissue cell components. Columnar cells use absorbed surface nutrients for de novo growth. A disruption of this tissue function can result in growth derived from an underlying nutrient source. That change would also cause the loss of the region of cell turnover at the tissue surface. Subsequent cell proliferation with limiting nutrient availability could promote oncogenesis in such initiated tissue.

Microanatomy of the cervical and anorectal squamocolumnar junctions: a proposed model for anatomical differences in HPV-related cancer risk

Human papilloma virus (HPV) infection causes cancers and their precursors (high-grade squamous intraepithelial lesions) near cervical and anal squamocolumnar junctions. Recently described cervical squamocolumnar junction cells are putative residual embryonic cells near the cervical transformation zone. These cells appear multipotential and share an identical immunophenotype (strongly CK7-positive) with over 90% of high-grade squamous intraepithelial lesions and cervical carcinomas. However, because the number of new cervical cancers discovered yearly world wide is 17-fold that of anal cancer, we posed the hypothesis that this difference in cancer risk reflects differences in the transition zones at the two sites. The microanatomy of the normal anal transformation zone (n=37) and topography and immunophenotype of anal squamous neoplasms (n=97) were studied. A discrete anal transition zone was composed of multilayered CK7-positive/p63-negative superficial columnar cells and an uninterrupted layer of CK7-negative/p63-positive basal cells. The CK7-negative/p63-positive basal cells were continuous with-and identical in appearance to-the basal cells of the mature squamous epithelium. This was in contrast to the cervical squamocolumnar junction, which harbored a single-layered CK7-positive/p63-negative squamocolumnar junction cell population. Of the 97 anal intraepithelial neoplasia/squamous cell carcinomas evaluated, only 27% (26/97) appeared to originate near the anal transition zone and only 23% (22/97) were CK7-positive. This study thus reveals two fundamental differences between the anus and the cervix: (1) the anal transition zone does not harbor a single monolayer of residual undifferentiated embryonic cells and (2) the dominant tumor immunophenotype is in keeping with an origin in metaplastic (CK7-negative) squamous rather than squamocolumnar junction (CK7-positive) epithelium. The implication is that, at birth, the embryonic cells in the anal transition zone have already begun to differentiate, presenting a metaplasia that-similar to vaginal and vulvar epithelium-is less prone to HPV-directed carcinogenesis. This in turn underscores the link between cancer risk and a very small and discrete population of vulnerable squamocolumnar junction cells in the cervix.

Molecular pathogenesis of Barrett esophagus: current evidence

This article focuses on recent findings on the molecular mechanisms involved in esophageal columnar metaplasia. Signaling pathways and their downstream targets activate specific transcription factors leading to the expression of columnar and the more specific intestinal-type of genes, which gives rise to Barrett metaplasia. Several animal models have been generated to validate and study these distinct molecular pathways but also to identify the Barrett progenitor cell. Currently, the many aspects involved in the development of esophageal metaplasia that have been elucidated can serve to develop novel molecular therapies to improve treatment or prevent metaplasia. Nevertheless, several key events are still poorly understood and require further investigation.

Stem cells in gastric cancer

Gastric cancer (GC) is one of the leading causes of cancer-related mortality worldwide. Cancer stem cells (CSCs), which were first identified in acute myeloid leukemia and subsequently in a large array of solid tumors, play important roles in cancer initiation, dissemination and recurrence. CSCs are often transformed tissue-specific stem cells or de-differentiated transit amplifying progenitor cells. Several populations of multipotent gastric stem cells (GSCs) that reside in the stomach have been determined to regulate physiological tissue renewal and injury repair. These populations include the Villin+ and Lgr5+ GSCs in the antrum, the Troy+ chief cells in the corpus, and the Sox2+ GSCs that are found in both the antrum and the corpus. The disruption of tumor suppressors in Villin+ or Lgr5+ GSCs leads to GC in mouse models. In addition to residing GSCs, bone marrow-derived cells can initiate GC in a mouse model of chronic Helicobacter infection. Furthermore, expression of the cell surface markers CD133 or CD44 defines gastric CSCs in mouse models and in human primary GC tissues and cell lines. Targeted elimination of CSCs effectively reduces tumor size and grade in mouse models. In summary, the recent identification of normal GSCs and gastric CSCs has greatly improved our understanding of the molecular and cellular etiology of GC and will aid in the development of effective therapies to treat patients.

Esophageal epithelial resistance

Besides its important role of digestion and absorption, esophageal tissue has an essential role as a major barrier against intraluminal pathogens like hostile microorganisms and toxins. This barrier function is achieved via various mechanical, chemical, and immunological mechanisms which are typically altered in inflammatory diseases, thereby causing subsequent damage of the mucosa. In this review we will focus on the main structural and functional barriers of host defense within the esophageal mucosa, including the epithelial layer, membrane-bound and secretory mucins, and different types of defensins. In addition, we will discuss the relevance of biofilm on esophageal tissue and will illustrate the importance of different regulators of intestinal permeability like zonulin and desmosomal components.

Characteristics of cardiac epithelium at the esophagogastric junction of a pediatric population with gastroesophageal reflux

Cardiac mucosa (CM) of the adult, regardless its location, shares phenotypic characteristics with Barrett's epithelium, namely villin expression and a Barrett's pattern of cytokeratins 7 and 20 expression. As far as we know, the phenotypic profile of CM in children has not been studied. The objective was to evaluate the phenotypic profile of cardiac mucosa from the esophagogastric junction of children with reflux symptoms. Biopsies routinely performed at the esophagogastric junction of children submitted to upper-gastrointestinal endoscopy for complaints suggestive of reflux were retrieved from the archive and used for the purposes of this study. Biopsies were assessed for the presence of squamous epithelium, cardiac and oxyntic mucosa and intestinal metaplasia. Samples displaying both squamous and columnar epithelia were immunohistochemically evaluated for the presence of villin and sucrase-isomaltae and for the expression of cytokeratins 7 and 20. From the 42 biopsies samples retrieved, 30 had simultaneously squamous and columnar epithelia. Cardiac mucosa was present in 86.7% of the cases, and intestinal metaplasia was observed only in one (3.3%). Villin expression in cardiac mucosa was observed in 96% of the cases and a cytokeratins 7 and 20 Barrett's pattern in 73%. Sucrase-isomaltase and MUC2 were only expressed in the case with intestinal metaplasia. Cardiac mucosa was high prevalent in biopsies from the esophagogastric junction of children with reflux. As in adults, cardiac mucosa in children has an immunoprofile similar to Barrett's esophagus. For the first time, it was shown that pediatric cardiac mucosa frequently expresses villin.

Barrett Esophagus: Evolving Concepts in Diagnosis and Neoplastic Progression

Surgical pathologists need to answer 2 questions when evaluating biopsies from the distal esophagus or gastroesophageal junction in patients with a history of gastroesophageal reflux disease: Are the findings consistent with Barrett esophagus? and Is there any evidence of dysplasia? Pathologists should be well informed about the controversy around the definition of Barrett esophagus and the common pitfalls that lead to a false-positive diagnosis of Barrett esophagus or Barrett esophagus-associated dysplasia. A concise description of distinct morphologic types of dysplasia in Barrett esophagus and a summary of recent data on the natural history of BE are provided in this review.

Expression of CDX2 and villin in gastric cardiac intestinal metaplasia and the relation with gastric cardiac carcinogenesis

OBJECTIVE

To determine whether CDX2 and villin protein expression are associated with intestinal metaplasia (IM) in gastric cardiac mucosa and to explore the relationship with evolution of gastric cardiac adenocarcinoma (GCA).

METHODS

We studied 143 gastric cardiac biopsy or resection specimens from Henan province China, including 25 cardiac gastritis specimens with IM, 65 dysplasia specimens with IM and 35 gastric cardiac adenocarcinoma specimens and stained them for CDX2 and villin by the immunohistochemical SP method. 15 normal gastric cardiac biopsy specimens were also collected as control.

RESULTS

(1) Normal gastric mucosa presented no CDX2 and villin expression. The positive rates of CDX2 protein in cardiac gastritis with IM, dysplasia with IM, and carcinoma tissues were 84.0% (21/25), 66.7% (32/48) and 36.4% (20/55), respectively. While the positive rates of villin protein in cardiac gastritis with IM, dysplasia with IM, and carcinoma tissues were 76.0% (19/25), 70.8% (34/48) and 45.5% (25/55), respectively.There were significant differences among the three groups for both CDX2 and villin (P<0.01). Spearman's rank correlation coefficient(rho) showed a close correlation between the two proteins (r=0.843, P<0.01) and both were positively related with tumor differentiation (both P<0.05), but not associated with age, sex, invasion and metastasis of lymph node (P>0.05).

CONCLUSION

Our results suggest that ectopic expression of CDX2 and villin may be involved in early-stage IM and tumorigenesis in gastric cardia and the expression of villin may be regulated by CDX2.

Gastro-oesophageal reflux disease is associated with up-regulation of desmosomal components in oesophageal mucosa

AIMS

Gastro-oesophageal reflux disease (GERD) is associated with impaired epithelial barrier function. This study was aimed at investigating the role of desmosomal proteins in relation to GERD.

METHODS AND RESULTS

Ninety-five patients with GERD-related symptoms (erosive, n = 51; non-erosive, n = 44) and 27 patients lacking those symptoms were included. Endoscopic and histological characterization of oesophagitis was performed according to the Los Angeles and Ismeil-Beigi criteria, respectively. Multiple biopsies were taken from the oesophageal mucosa of each patient. Gene expression analysis of plakoglobin, desmoglein-1, desmoglein-2 and desmoglein-3 was performed by quantitative real time (RT)-polymerase chain reaction and immunohistochemistry in the oesophageal mucosa. Routine histology revealed specific GERD-related alterations, such as dilatation of intercellular spaces (DIS), basal cell hyperplasia (BCH), and elongation of the papillae, in the oesophageal mucosa of patients with GERD, as compared with controls (all parameters: P < 0.05). All four genes and corresponding proteins were found to be up-regulated by between 1.7 and 8.1-fold (transcript level, P < 0.05; protein level, P < 0.05). Induced gene expression levels of plakoglobin, desmoglein-1 and desmoglein-2 correlated significantly with DIS and BCH.

CONCLUSIONS

Taken together, the uniform up-regulation of desmosomal genes/proteins in the oesophageal mucosa of patients with GERD supports the concept of architectural and molecular changes in the desmosomal compartment in the pathogenesis of GERD.

The dilated distal esophagus: a new entity that is the pathologic basis of early gastroesophageal reflux disease

Present management algorithms for patients with gastroesophageal reflux disease (GERD) limit endoscopy to patients with advanced disease. When endoscopy is performed, biopsy is limited to patients who have a visible columnar-lined esophagus. Biopsy is not recommended for patients whose endoscopy is normal. This algorithm results in the failure to evaluate patients with early stages of GERD at a pathologic level. We report 714 patients with normal endoscopic findings irrespective of symptoms who had adequate biopsies taken from the squamocolumnar junction and the area 1-cm distal to this from mucosa that had rugal folds. Concurrent biopsies were also taken from the gastric body and/or antrum. All patients had a gap between their esophageal squamous epithelium and gastric oxyntic mucosa in the junctional region composed of oxyntocardiac ± cardiac ± intestinal epithelia. A total of 643 (90.1%) patients had no significant pathology in the gastric antrum and/or body, indicating that the squamooxyntic gap was an isolated abnormality in this region in all but 71 (9.9%) patients. The gap contained only oxyntocardiac epithelium in 71 (9.9%) patients, cardiac mucosa without intestinal metaplasia in 482 (67.5%) patients, and intestinal metaplasia in 161 (22.6%) patients. The pathologic interpretation of biopsies taken from the gastroesophageal junction is confusing and has significant interobserver variation. This results from lack of agreement as to whether these biopsies originate in the proximal stomach ("gastric cardia") or in the esophagus. We provide evidence that the presence of oxyntocardiac ± cardiac ± intestinal epithelia in biopsies from patients who are endoscopically normal is diagnostic of a dilated GERD-damaged distal esophagus. The dilated distal esophagus is the pathologic manifestation of destruction of the abdominal segment of the lower esophageal sphincter. Its presence is the pathologic basis of early GERD, which is missed if patients who are endoscopically normal are not biopsied, as is the present recommendation. Its recognition allows for accurate and evidence-based interpretation of biopsies from this region and removes the present confusion and permits the development of a reproducible pathologic diagnostic method.

Hepatocyte paraffin 1 antigen as a biomarker for early diagnosis of Barrett esophagus

We evaluated hepatocyte paraffin 1 (HepPar1) antigen expression, a sensitive marker of small intestinal differentiation, in combination with morphologic features to demonstrate intestinal differentiation in cases equivocal for Barrett esophagus (BE). Clinicopathologic features and HepPar1 expression were recorded for 54 BE cases, 45 consistent with reflux esophagitis (RE) cases, and 65 "suspicious" for BE (SBE) cases. The SBE category included RE cases with 2 or more morphologic changes associated with BE or metaplastic reaction to injury (eg, multilayered epithelium, squamous islands, goblet cell mimickers, pancreatic metaplasia). HepPar1 was expressed in all 54 BE cases, 4 of 45 RE cases, and 24 of 65 SBE cases. In SBE cases, 2 or more morphologic changes were associated with HepPar1 expression in 37% of cases (24/65), 3 or more features in 59% (13/22), and 4 or more features in 100% (4/4) (P ≤ .004). The combination of certain morphologic changes and HepPar1 expression in clinically suspicious distal esophageal biopsy cases without goblet cells supports the presence of evolving intestinal metaplasia.

Gastroesophageal reflux disease--from reflux episodes to mucosal inflammation

Gastroesophageal reflux disease (GERD) affects 20-30% of the population in Western countries, and is one of the most common clinical problems in daily practice. GERD-associated functional and structural abnormalities are caused by recurrent exposure of the esophagus to acidic and nonacidic refluxate of gastric contents (containing duodenal and intestinal proteases as well as acid and gastric pepsin) from the stomach. Major progress has been made in the understanding of the molecular pathogenesis of GERD-associated mucosal inflammation, suggesting a complex and multifactorial pathogenesis and immune-mediated effects. This Review summarizes the complexity of mucosal pathogenesis, including microscopic changes, mucosal inflammation and GERD-specific molecular mediators, in the context of the clinical features and pathophysiological characteristics of GERD. The abnormal exposure of the esophagus to luminal contents leads to chronic mucosal inflammation that is characterized by the release of IL-8 specifically, as well as other proinflammatory mediators, from the esophageal mucosa. Evidence from animal studies indicates a stepwise inflammatory response by the epithelium, which attracts immune effector cells to infiltrate the mucosa. From bench to bedside, these novel molecular findings might provide new treatment options beyond current acid-suppressive therapy and the principle of inhibition of transient lower esophageal sphincter relaxation.

The gene expression profile of cardia intestinal metaplasia is similar to that of Barrett's esophagus, not gastric intestinal metaplasia

The etiology and significance of cardia intestinal metaplasia (CIM) is disputed. CIM may represent a form of Barrett's esophagus due to reflux or could reflect generalized gastric intestinal metaplasia due to Helicobacter pylori. The aim of this study was to utilize gene expression data to compare CIM to Barrett's and gastric intestinal metaplasia. Endoscopic biopsies were classified by endoscopic and histologic criteria as CIM (n= 33), Barrett's (n= 25), or gastric intestinal metaplasia of the antrum or body (n= 18). The squamocolumnar and gastroesophageal junctions were aligned in CIM patients and patients with diffuse gastric intestinal metaplasia were excluded. H. pylori was tested for in the biopsies of all patients. After laser-capture microdissection, quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to measure the mRNA expression of a panel of nine genes that has been shown to differentiate Barrett's from other foregut mucosa. Cluster analysis with linear discriminant analysis of the expression data was used to classify each sample into groups based solely on similarity of gene expression. Cluster analysis was performed for three groups (CIM vs. Barrett's vs. gastric intestinal metaplasia) and two groups (CIM + Barrett's vs. gastric intestinal metaplasia). There was no difference in H. pylori infection among groups (P= 0.66). Clustering into three groups resulted in frequent misclassification between CIM and Barrett's while misclassification of gastric intestinal metaplasia was uncommon. The CIM and Barrett's groups were then combined for two group clustering and linear discriminant analysis correctly predicted 95% of CIM and Barrett's samples and 83% of gastric intestinal metaplasia samples based on gene expression alone. In conclusion, the gene expression profiles of CIM and Barrett's esophagus were similar in 95% of biopsies and differed significantly from that of gastric intestinal metaplasia. The indistinguishable gene expression profile of CIM and BE suggests that they may share a common etiology in the majority of patients with a similar biology, and calls into question the perception that CIM is an innocuous process.

MUC2 is a highly specific marker of goblet cell metaplasia in the distal esophagus and gastroesophageal junction

Currently, the American College of Gastroenterology requires identification of goblet cells in mucosal biopsies from the esophagus to diagnose Barrett esophagus (BE). Identification of goblet cells in mucosal biopsies is fraught with limitations such as sampling and interpretation error. One previous study by our group suggested that MUC2 expression in esophageal nongoblet columnar cells represents a late biochemical reaction in the conversion of mucinous columnar cells to goblet cells in BE. We conducted this study to evaluate the prevalence, sensitivity, and specificity of MUC2 positivity in nongoblet columnar epithelium for detection of goblet cells in the distal esophagus and gastroesophageal junction (GEJ) region. We also sought to identify associations between MUC2 positivity and clinical and endoscopic risk factors for BE. This analysis utilized mucosal biopsies of the distal esophagus or GEJ from 100 patients who participated in a community clinic-based study of patients with chronic gastroesophageal reflux disease evaluated prospectively in the western part of Washington state. We randomly selected 50 patients who had columnar epithelium with goblet cells, representing the study group and 50 patients without goblet cells, representing the comparison group. Immunohistochemistry for MUC2 was performed on samples in a blinded manner without knowledge of the clinical or endoscopic features of the patients. The presence of staining was noted in both goblet and nongoblet epithelium, both close to and distant from the mucosa with goblet cells, when the latter were present. All study patients showed MUC2 positivity in goblet cells. MUC2 was present in nongoblet columnar epithelium in 78% of study patients with goblet cells, but in only 4% of controls without goblet cells (P<0.0001) (sensitivity, 78%; specificity, 96% for goblet cell metaplasia). MUC2 was significantly more common in nongoblet columnar cells close to, rather than distant from, the mucosa with goblet cells (P<0.00001). Finally, MUC2 was significantly associated with endoscopic evidence of columnar metaplasia in the distal esophagus, and with known risk factors for BE, such as older age, white race, frequent heartburn, and elevated body mass index. We conclude that goblet cells likely develop from a field of MUC2-positive mucinous columnar cells, and as such, MUC2 represents a late event in the development of goblet cells. MUC2 staining in nongoblet columnar cells is a reasonably sensitive and highly specific marker for goblet cells in the distal esophagus and GEJ, and its presence is predictive of endoscopic columnar metaplasia of the esophagus, even in patients without goblet cells.

Comparison of intestinal metaplasia in gastric cardia and Barrett's esophagus

OBJECTIVE

To evaluate and compare the pathological features and immunostaining pattern (cytokeratin 7 (CK-7), mucin core peptide 1 (Muc-1)) in Barrett's esophagus (BE) and cardiac intestinal metaplasia (CIM).

METHODS

According to endoscopic diagnosis, patients with gastric cardiac inflammation and BE were selected from March 2008 to February 2009 in Renji Hospital, Shanghai Jiaotong University School of Medicine. Those patients who had histological findings of intestinal metaplasia (82 cases of CIM and 64 special type BE) were enrolled in our study. Hematoxylin-eosin, periodic acid-Schiff and Alcian blue staining and an immunohistochemical examination (CK-7, Muc-1) were undertaken in all of them.

RESULTS

Squamous mucosa overlying the columnar crypts with intestinal metaplasia, also called buried metaplasia, was often found in the BE group (56.2%), mainly as an incomplete type (85.9%). Inflammation in the gastric antrum was more severe in the CIM group (45.1% vs 26.6%), in contrast, esophagitis was more severe in the BE group (53.1% vs 35.4%). CK-7 was highly expressed in the BE group (84.4%) in contrast to the CIM group (37.8%). There was no difference in the expression of Muc-1 in these two kinds of intestinal metaplasia (14.1% vs 19.5%).

CONCLUSIONS

Buried intestinal metaplasia, mainly as an incomplete type, is the major predominant type of BE. The degree of inflammation in the gastric antrum and esophagus can differentiate BE from CIM to some extent. CK-7 immunohistochemical staining can help identify BE and CIM but Muc-1 cannot.

Does short-segment columnar-lined esophagus elongate during a mean follow-up period of 5.7 years?

BACKGROUND

The length of Barrett's esophagus is considered to be important because it is associated with the risk of neoplasia. In Japan, there is a high prevalence of short-segment columnar-lined esophagus (SS-CLE). The natural history of SS-CLE is not fully understood, so the aim of the present study was to investigate the chronological changes of SS-CLE.

METHODS

The subjects were 500 consecutive patients with SS-CLE (327 men and 173 women; mean age: 64.0 years) diagnosed between January 2001 and July 2002 at our hospital based on the definition of SS-CLE proposed by the Japanese Society for Esophageal Diseases. Follow-up endoscopy was carried out annually for a mean period of 5.7 ± 1.2 years. The cumulative probability of SS-CLE showing elongation was estimated by the Kaplan-Meier method, and factors related to endoscopic findings making an independent contribution to elongation were determined with Cox's proportional hazard model.

RESULTS

Elongation of SS-CLE occurred in 29 patients (5.8%) during the follow-up period and the cumulative 5-year probability of elongation was 16.6%. There was no progression of SS-CLE to Barrett's adenocarcinoma. The absence of atrophic gastritis (adjusted odds ratio (aOR): 23.4; 95%CI [6.5, 83.8]), the presence of reflux esophagitis (aOR: 4.53; 95%CI [1.2, 16.4]), and the flame-shaped type of SS-CLE (aOR: 22.4; 95%CI [7.8, 64.0]) were found to be independent contributors to the elongation of SS-CLE.

CONCLUSIONS

The present study demonstrated that SS-CLE remains stable in length over time, especially in patients without atrophic gastritis, as well as in those with reflux esophagitis and/or flame-shaped SS-CLE at initial examination.

The histologic squamo-oxyntic gap: an accurate and reproducible diagnostic marker of gastroesophageal reflux disease

The present definition of gastroesophageal reflux disease (GERD) is based on clinical criteria that are difficult to reproduce accurately. This study provides a method to develop a histologic definition of GERD based on biopsies obtained from the affected esophagus. Pathology reports from 1655 patients who had upper gastrointestinal endoscopy and biopsy according to a systematic protocol were reviewed. Biopsies were obtained from the esophagus, around the gastroesophageal junction and the stomach: proximal, body, and antrum. Patients who had oxyntocardiac±cardiac±intestinal epithelia between the squamous epithelium proximally and the proximal limit of gastric oxyntic mucosa distally were defined as having a squamo-oxyntic gap. The length of the squamo-oxyntic gap varied from less than 1 cm in 1399 (84.5%) patients to greater than 5 cm in 80 (4.8%) of the patients. Only oxyntocardiac epithelium was seen in 190 (11.5%) of the patients, oxyntocardiac and cardiac epithelia in 898 (54.3%), and intestinal metaplasia in addition to the other 2 epithelial types in 567 (34.2%). The prevalence of intestinal metaplasia was directly proportional to length of the squamo-oxyntic gap, being 24.3% (340/1399) when the length was <1 cm, and 83.5% (147/176) with length 1 to 5 cm. All patients with a length more than 5 cm had intestinal metaplasia. The distribution of the 3 epithelia was constant irrespective of the length of the squamocolumnar gap; intestinal metaplasia, when present, was seen maximally in the proximal region of the gap, cardiac epithelium intermediate and oxyntocardiac epithelium in the most distal segment of the gap. The squamo-oxyntic gap started in a dilated region distal to the end of the tubular esophagus and distal to the proximal limit of the rugal folds and extended into the tubular esophagus. Distal gastric biopsies showed no evidence of significant inflammation, intestinal metaplasia or Helicobacter pylori infection in 1543 (93.2%) of the patients, indicating that the squamo-oxyntic gap was largely independent of gastric pathology. We provide evidence that the squamo-oxyntic gap is equivalent to the columnar-lined esophagus. Its presence is a specific and sensitive indicator of reflux and can be used as a cellular criterion to define GERD. The length of the squamo-oxyntic gap provides an accurate assessment of the severity of chronic GERD. The distal limit of the squamo-oxyntic gap, which is the junction between oxyntocardiac and gastric oxyntic epithelium is the true gastroesophageal junction. The presence of intestinal metaplasia within the squamo-oxyntic gap is the most accurate risk indicator for esophageal adenocarcinoma and defines Barrett esophagus.

CD44+ slow-cycling tumor cell expansion is triggered by cooperative actions of Wnt and prostaglandin E2 in gastric tumorigenesis

Similar to normal tissue stem cells, cancer stem cells (CSCs) are thought to be quiescent or slow-cycling and, thereby, insensitive to chemo- and radiotherapies. CD44, a cell surface component that interacts with the extracellular matrix, has been found to be highly expressed in CSCs of several solid tumors. However, the relevancy between CD44(+) cells and slow-cycling cells and the underlying mechanisms for the emergence of CD44(+) CSCs during tumorigenesis have not been elucidated. Here we show that a gastric gland residing at the squamo-columnar junction (SCJ) in normal mouse stomach contains CD44(+) stem cell-like slow-cycling cells and that this characteristic CD44(+) gland was expanded by prostaglandin E2 (PGE(2)) and Wnt signaling in K19-Wnt1/C2mE mouse, a genetic mouse model for gastric tumorigenesis. The analysis of three transgenic mouse lines, K19-Wnt1, K19-C2mE and K19-Wnt1/C2mE, revealed that the expansion of CD44(+) SCJ cells is triggered by PGE(2)-mediated signaling and is prominently enhanced by the addition of Wnt activation. Furthermore, each expanded CD44(+) gland in gastric tumor of K19-Wnt1/C2mE mouse contains a few BrdU label-retaining quiescent or slow-cycling cells, suggesting that the CD44(+) SCJ cells in normal mouse are candidates for the cell-of-origin of gastric CSCs. These observations suggest that PGE(2)-mediated inflammatory signaling and Wnt signaling cooperatively trigger the expansion of CD44(+) slow-cycling stem-like cells in SCJ, leading to development of lethal gastric tumors in mice.

Intestinal differentiation in metaplastic, nongoblet columnar epithelium in the esophagus

Barrett esophagus (BE) is defined by the presence of metaplastic esophageal columnar epithelium with goblet cells within endoscopically recognizable areas of the esophagus. However, some carcinomas in BE, or from the gastroesophageal junction region, develop within mucosa devoid of goblet cells. However, the biologic properties, pathogenesis, and risk of malignancy of metaplastic, esophageal nongoblet columnar epithelium, is, essentially, unknown. In this study, 89 patients with metaplastic esophageal columnar epithelium were evaluated immunohistochemically for markers of intestinal differentiation, such as MUC2, DAS-1, Villin, and CDX2, a marker of gastric differentiation (MUC5AC), and Ki67, a marker of cell proliferation. Of the 89 patients, 59 had columnar metaplasia with goblet cells (BE), which were further separated into low-density goblet cell and high-density goblet cell groups based on the percentage of crypts with goblet cells, and 30 patients had columnar metaplasia of the esophagus without goblet cells. As controls, gastric biopsies from 19 age and sex matched patients without esophageal or gastric pathology were used. The rate of positivity of the markers and the location of Ki67 staining was evaluated only in non-goblet columnar epithelium from all patient groups. Patients with metaplastic esophageal columnar epithelium without goblet cells showed positivity for MUC5AC, MUC2, DAS-1, Villin, and CDX2 in 100%, 0%, 30%, 17%, and 43% of cases, respectively. 17% of cases showed aberrant surface Ki67 positivity. These values were significantly higher than gastric controls, which showed absence of staining for all markers except MUC5AC (100%). In patients with metaplastic esophageal columnar epithelium with goblet cells (BE) a significant increased rate of staining was observed for all markers, except MUC5AC. In addition, both MUC2 and surface Ki67 staining were significantly increased in BE patients with high-density goblet cells versus those with low-density goblet cells. In a separate analysis in which metaplastic esophageal nongoblet epithelium was evaluated in areas of mucosa devoid of goblet cells compared with areas of mucosa with goblet cells, from patients who had goblet cells elsewhere in the mucosa (N=59), no significant differences were observed with regard to the percentage of cases that stained with any of the markers in the nongoblet epithelium in areas devoid of goblet cells, similar to the patient group with metaplastic esophageal epithelium without goblet cells (N=30). Similar to above, in all cases, expression of intestinal markers increased in areas of mucosa adjacent to goblet cells. This study provides evidence that metaplastic esophageal columnar epithelium without goblet cells shows phenotypic evidence of intestinal differentiation and supports the theory that squamous epithelium converts initially to nongoblet columnar epithelium before goblet cell metaplasia. Further prospective studies are needed to evaluate the pathogenetic sequence, natural history, and risk of malignancy of metaplastic esophageal nongoblet epithelium.

Exposure to both radiation and chemotherapy increases the risk of Barrett's and multilayered epithelium

The relationship between radiation and/or chemotherapy and the development of Barrett's and/or multilayered epithelium has not been investigated before. We ascertained a group of patients exposed to radiation and/or chemotherapy and an unexposed group to compare the prevalence rates of Barrett's epithelium and multilayered epithelium at the time of endoscopy in these two groups. Barrett's epithelium was found in ten of the 19 (53%) exposed patients, compared to eight of 38 (21%) unexposed subjects (P = 0.02). Six of 19 (32%) exposed patients had multilayered epithelium, compared to four of 38 (11%) unexposed subjects (P = 0.06). Twelve of the 19 exposed patients (63%) had either Barrett's or multilayered epithelium, in contrast to ten of 38 (26%) unexposed subjects (P = 0.01). Those with exposure to both chemotherapy and radiation had a significant increase in the risk for Barrett's and/or multilayered epithelium (P = 0.003). This study suggests a relationship between exposure to a combination of radiation and chemotherapy and the development of Barrett's and/or multilayered epithelium.

Advances in the diagnosis of Barrett's esophagus

Barrett's esophagus is a metaplastic change in esophageal lining, characterized by the replacement of normal squamous epithelium with columnar epithelium. Barrett's esophagus is associated with a high risk of esophageal adenocarcinoma. As the incidence of esophageal adenocarcinoma has risen dramatically in developed countries, the research on Barrett's esophagus is attracting increasing attention. In this article, we will review the recent advances in the diagnosis of Barrett's esophagus.

Inhibition of nucleostemin upregulates CDX2 expression in HT29 cells in response to bile acid exposure: implications in the pathogenesis of Barrett's esophagus

BACKGROUND

Barrett's esophagus (BE), a squamous-to-columnar metaplasia, may originate from growth-promoting mutations in metaplastic stem cells. Nucleostemin is a protein highly expressed in undifferentiated embryonic stem cells. The objectives of this study were to explore the potential role of nucleostemin in the pathogenesis of BE METHODS: The expression profiles of 30,968 genes were compared between BE and normal esophageal tissues (n = 6 in each group) by using oligo microarray. Three siRNA plasmid expression vectors against nucleostemin, pRNAi-1, pRNAi-2, and pRNAi-3, were constructed and transfected into HT29 cells. In addition, HT29 cells were exposed to 100-1,000 microM chenodeoxycholic acid (CDC), a bile acid, for 2, 12, and 24 h, and then messenger RNA and protein expressions of nucleostemin and CDX2 were determined by reverse-transcriptase polymerase chain reaction and Western blotting.

RESULTS

Four hundred and twenty-six differentially expressed genes were detected in BE; 142 were upregulated and 284 downregulated. Nucleostemin was downregulated while CDX2 was upregulated. In vitro, all the recombinant plasmids inhibited the nucleostemin expression in transfected HT29 cells, with pRNAi-1 being the most effective. CDX2 expression was significantly increased in pRNAi-1-transfected HT29 cells, compared with that in the empty plasmid (pRNAT-U6.1/Neo) transfected or untransfected HT29 cells. In addition, CDX2 expression was increased whereas nucleostemin expression was decreased in a dose- and time-dependent manner in HT29 cells treated with CDC.

CONCLUSION

These findings suggest that the inhibition of nucleostemin expression in "esophageal stem cells" in response to bile acid exposure may be involved in the pathogenesis of BE through upregulating CDX2 expression.

Barrett esophagus: histology and pathology for the clinician

The incidence of adenocarcinoma of the esophagus and gastroesophageal junction has increased dramatically over the past 30 years. The major precursor to this type of adenocarcinoma is Barrett esophagus, which is defined as the conversion of normal squamous epithelium into metaplastic columnar epithelium. Abundant evidence suggests that adenocarcinoma in the setting of Barrett esophagus develops via a progressive sequence of histological and molecular events. Consequently, patients with Barrett esophagus routinely undergo endoscopic surveillance for early detection of neoplasia. Histological evaluation of mucosal biopsy samples from the esophagus and gastroesophageal junction for identification of goblet cells and evaluation of the presence, grade and extent of dysplasia is the mainstay of risk assessment for these patients. This Review provides physicians with a summary of the pertinent, clinically relevant histological features of Barrett esophagus and its neoplastic complications. The histology of Barrett esophagus and the gastroesophageal junction is summarized, and an overview of information necessary to interpret pathology reports from patients either with or without endoscopic evidence of Barrett esophagus is provided to appropriately guide management of patients. Close interaction between the clinician and the pathologist is essential for proper interpretation of biopsy results and to provide optimal surveillance or treatment strategies.

Paracrine Hedgehog signaling in stomach and intestine: new roles for hedgehog in gastrointestinal patterning

BACKGROUND & AIMS

Hedgehog signaling is critical in gastrointestinal patterning. Mice deficient in Hedgehog signaling exhibit abnormalities that mirror deformities seen in the human VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association. However, the direction of Hedgehog signal flow is controversial and the cellular targets of Hedgehog signaling change with time during development. We profiled cellular Hedgehog response patterns from embryonic day 10.5 (E10.5) to adult in murine antrum, pyloric region, small intestine, and colon.

METHODS

Hedgehog signaling was profiled using Hedgehog pathway reporter mice and in situ hybridization. Cellular targets were identified by immunostaining. Ihh-overexpressing transgenic animals were generated and analyzed.

RESULTS

Hedgehog signaling is strictly paracrine from antrum to colon throughout embryonic and adult life. Novel findings include the following: mesothelial cells of the serosa transduce Hedgehog signals in fetal life; the hindgut epithelium expresses Ptch but not Gli1 at E10.5; the 2 layers of the muscularis externa respond differently to Hedgehog signals; organogenesis of the pyloric sphincter is associated with robust Hedgehog signaling; dramatically different Hedgehog responses characterize stomach and intestine at E16; and after birth, the muscularis mucosa and villus smooth muscle consist primarily of Hedgehog-responsive cells and Hh levels actively modulate villus core smooth muscle.

CONCLUSIONS

These studies reveal a previously unrecognized association of paracrine Hedgehog signaling with several gastrointestinal patterning events involving the serosa, pylorus, and villus smooth muscle. The results may have implications for several human anomalies and could potentially expand the spectrum of the human VACTERL association.