Morphological characterization of the squamocolumnar junction of the esophagus in patients with and without Barrett's epithelium

Signaling Pathways in the Pathogenesis of Barrett's Esophagus and Esophageal Adenocarcinoma

Barrett's esophagus (BE) is a premalignant lesion that can develop into esophageal adenocarcinoma (EAC). The development of Barrett's esophagus is caused by biliary reflux, which causes extensive mutagenesis in the stem cells of the epithelium in the distal esophagus and gastro-esophageal junction. Other possible cellular origins of BE include the stem cells of the mucosal esophageal glands and their ducts, the stem cells of the stomach, residual embryonic cells and circulating bone marrow stem cells. The classical concept of healing a caustic lesion has been replaced by the concept of a cytokine storm, which forms an inflammatory microenvironment eliciting a phenotypic shift toward intestinal metaplasia of the distal esophagus. This review describes the roles of the NOTCH, hedgehog, NF-κB and IL6/STAT3 molecular pathways in the pathogenesis of BE and EAC.

Pathogenesis and Cells of Origin of Barrett's Esophagus

In patients with Barrett's esophagus (BE), metaplastic columnar mucosa containing epithelial cells with gastric and intestinal features replaces esophageal squamous mucosa damaged by gastroesophageal reflux disease. This condition is estimated to affect 5.6% of adults in the United States, and is a major risk factor for esophageal adenocarcinoma. Despite the prevalence and importance of BE, its pathogenesis is incompletely understood and there are disagreements over the cells of origin. We review mechanisms of BE pathogenesis, including transdifferentiation and transcommitment, and discuss potential cells of origin, including basal cells of the squamous epithelium, cells of esophageal submucosal glands and their ducts, cells of the proximal stomach, and specialized populations of cells at the esophagogastric junction (residual embryonic cells and transitional basal cells). We discuss the concept of metaplasia as a wound-healing response, and how cardiac mucosa might be the precursor of the intestinal metaplasia of BE. Finally, we discuss shortcomings in current diagnostic criteria for BE that have important clinical implications.

Cellular Origins of Barrett's Esophagus: the Search Continues

PURPOSE OF REVIEW

The cellular origins of Barrett's esophagus remain elusive. In this review, we discuss the potential cellular mechanisms behind squamous to columnar metaplasia as well as the limitations of these proposed mechanisms.

RECENT FINDINGS

Several theories have been proposed, including the reprogramming of native squamous cells, repopulation from submucosal glands, contributions from circulating bone marrow-derived cells, and direct extension of gastric cells. Most recent data support an innate progenitor cell unique to the squamocolumnar junction that can expand into metaplastic glands. Active investigation to clarify each of these potential cells of origin is being pursued, but ultimately each could contribute to the pathogenesis of Barrett's esophagus depending on the clinical context. Nonetheless, identifying cells of origin is critical to understand the molecular mechanisms behind Barrett's esophagus and developing strategies to better treat (and possibly prevent) this increasingly significant premalignant disease.

The characterization of an intestine-like genomic signature maintained during Barrett's-associated adenocarcinogenesis reveals an NR5A2-mediated promotion of cancer cell survival

Barrett’s oesophagus (BO), an intestinal-type metaplasia (IM), typically arising in conjunction with gastro-oesophageal reflux disease, is a prominent risk factor for the development of oesophageal adenocarcinoma (OAC). The molecular similarities between IM and normal intestinal tissues are ill-defined. Consequently, the contribution of intestine-enriched factors expressed within BO to oncogenesis is unclear. Herein, using transcriptomics we define the intestine-enriched genes expressed in meta-profiles of BO and OAC. Interestingly, 77% of the genes differentially expressed in a meta-profile of BO were similarly expressed in intestinal tissues. Furthermore, 85% of this intestine-like signature was maintained upon transition to OAC. Gene networking analysis of transcription factors within this signature revealed a network centred upon NR5A2, GATA6 and FOXA2, whose over-expression was determined in a cohort of BO and OAC patients. Simulated acid reflux was observed to induce the expression of both NR5A2 and GATA6. Using siRNA-mediated silencing and an NR5A2 antagonist we demonstrate that NR5A2-mediated cancer cell survival is facilitated through augmentation of GATA6 and anti-apoptotic factor BCL-XL levels. Abrogation of NR5A2-GATA6 expression in conjunction with BCL-XL co-silencing resulted in synergistically increased sensitivity to chemotherapeutics and photo-dynamic therapeutics. These findings characterize the intestine-like signature associated with IM which may have important consequences to adenocarcinogenesis.

In oesophageal squamous cells, nitric oxide causes S-nitrosylation of Akt and blocks SOX2 (sex determining region Y-box 2) expression

OBJECTIVE

Barrett's metaplasia might develop if GORD causes oesophageal squamous cells to convert into columnar cells. Acid and bile exposures upregulate columnar differentiation genes like CDX2 in oesophageal squamous cells, but it is not known if such exposures downregulate squamous differentiation genes like SOX2. In addition to acid and bile, patients with GORD also have high oesophageal concentrations of nitric oxide (NO). This study aims to determine how acid, bile salts and NO affect genes that influence oesophageal cell phenotype.

DESIGN

Oesophageal squamous cells from patients with Barrett's oesophagus were exposed to acidic bile salts or NOC-9 (an NO donor). SOX2, p63 (squamous transcription factor) and CDX2 mRNAs were measured by quantitative RT-PCR. SOX2 and its regulatory Akt pathway proteins were evaluated by western blotting. S-nitrosylation by NO was blocked by dithiothreitol. Immunohistochemistry for SOX2 was performed on the oesophagus of rats with surgically induced GORD which were fed diets with and without nitrite supplementation.

RESULTS

In oesophageal squamous cells, NO profoundly decreased SOX2 protein and caused a significantly greater decrease in SOX2 mRNA than did acidic bile salts. NO also decreased p63 and increased CDX2 expression. NO caused S-nitrosylation of Akt, blocking its phosphorylation. Akt pathway inhibition by LY294002 or Akt siRNA reduced SOX2 mRNA. Rats fed with nitrite-supplemented diets exhibited weaker SOX2 oesophageal staining than rats fed with normal diets.

CONCLUSIONS

In oesophageal squamous cells, NO blocks SOX2 expression through Akt S-nitrosylation. NO also increases CDX2 and decreases p63 expression. By triggering molecular events preventing squamous differentiation while promoting intestinal differentiation, NO might contribute to Barrett's pathogenesis.

Transcommitment: Paving the Way to Barrett's Metaplasia

Barrett's esophagus is the condition in which metaplastic columnar epithelium that predisposes to cancer development replaces stratified squamous epithelium in the distal esophagus. Potential sources for the cell or tissue of origin for metaplastic Barrett's epithelium are reviewed including native esophageal differentiated squamous cells, progenitor cells native to the esophagus located within the squamous epithelium or in the submucosal glands or ducts, circulating bone marrow-derived stem cells, and columnar progenitor cells from the squamocolumnar junction or the gastric cardia that proximally shift into the esophagus to fill voids left by damaged squamous epithelium. Wherever its source the original cell must undergo molecular reprogramming (i.e., either transdifferentiation or transcommitment) to give rise to specialized intestinal metaplasia. Transcription factors that specify squamous, columnar, intestinal, and mucus-secreting epithelial differentiation are discussed. An improved understanding of how esophageal columnar metaplasia forms could lead to development of effective treatment or prevention strategies for Barrett's esophagus. It could also more broadly inform upon normal tissue development and differentiation, wound healing, and stem cell biology.

Mechanisms of Barrett's oesophagus: intestinal differentiation, stem cells, and tissue models

Barrett's oesophagus (BE) is defined as any metaplastic columnar epithelium in the distal oesophagus which replaces normal squamous epithelium and which predisposes to cancer development. It is this second requirement, the predisposition to cancer, which makes this condition both clinically highly relevant and an important area for ongoing research. While BE has been defined pathologically since the 1950's (Allison and Johnstone, Thorax 1955), and identified as a risk factor for esophageal adenocarcinoma since the 1970's (Naef A.P., et al J Thorac Cardiovasc Surg. 1975), our understanding of the molecular events giving rise to this condition remains limited. Herein we will examine what is known about the intestinal features of BE and how well it recapitulates the intestinal epithelium, including stem identity and function. Finally, we will explore laboratory models of this condition presently in use and under development, to identify new insights they may provide into this important clinical condition.

Telocytes in human oesophagus

Telocytes (TCs), a new type of interstitial cells, were identified in many different organs and tissues of mammalians and humans. In this study, we show the presence, in human oesophagus, of cells having the typical features of TCs in lamina propria of the mucosa, as well as in muscular layers. We used transmission electron microscopy (TEM), immunohistochemistry (IHC) and primary cell culture. Human oesophageal TCs present a small cell body with 2–3 very long Telopodes (Tps). Tps consist of an alternation of thin segments (podomers) and thick segments (podoms) and have a labyrinthine spatial arrangement. Tps establish close contacts (‘stromal synapses’) with other neighbouring cells (e.g. lymphocytes, macrophages). The ELISA testing of the supernatant of primary culture of TCs indicated that the concentrations of VEGF and EGF increased progressively. In conclusion, our study shows the existence of typical TCs at the level of oesophagus (mucosa, submucosa and muscular layer) and suggests their possible role in tissue repair.

Prevalence and pathogenesis of Barrett's esophagus in Luoyang, China

BACKGROUND

Prevalence of Barrett's esophagus (BE) in Luoyang, China, has not been reported, and its pathogenesis is controversial. The aim of this study was therefore to investigate the prevalence of BE and its underlying factors in the city of Luoyang.

METHOD

This was a prospective study in one center. Many patients were analyzed using endoscopy who showed upper gastrointestinal symptoms between August 2006 and June 2007. In addition, the effect of apoptosis-related proteins and heat shock proteins upon BE's pathogenesis were also investigated by an immunohistochemical protocol.

RESULTS

Prevalence of BE was at 4.55% and the mean age of those affected was about 10 years older than for esophagitis. Typical reflux symptoms were significantly lower than with esophagitis, whereas signs of caspase-3 and HSP105 elevation were significantly higher. Expression of TERT, HSP70 and HSP90α in BE cases was significantly lower than in esophagitis. However, there was no statistical difference between the two groups in expression of HSP27.

CONCLUSIONS

The prevalence of BE is high in Luoyang, which could result from esophagitis despite typical reflux symptoms being relatively uncommon. Initiation and development of BE might be the result of accelerated proliferation, apoptosis and differentiation of original cells to intestinal epithelium.

Ectopic Cdx2 expression in murine esophagus models an intermediate stage in the emergence of Barrett's esophagus

Barrett's esophagus (BE) is an intestinal metaplasia that occurs in the setting of chronic acid and bile reflux and is associated with a risk for adenocarcinoma. Expression of intestine-specific transcription factors in the esophagus likely contributes to metaplasia development. Our objective was to explore the effects of an intestine-specific transcription factor when expressed in the mouse esophageal epithelium. Transgenic mice were derived in which the transcription factor Cdx2 is expressed in squamous epithelium using the murine Keratin-14 gene promoter. Effects of the transgene upon cell proliferation and differentiation, gene expression, and barrier integrity were explored. K14-Cdx2 mice express the Cdx2 transgene in esophageal squamous tissues. Cdx2 expression was associated with reduced basal epithelial cell proliferation and altered cell morphology. Ultrastructurally two changes were noted. Cdx2 expression was associated with dilated space between the basal cells and diminished cell-cell adhesion caused by reduced Desmocollin-3 mRNA and protein expression. This compromised epithelial barrier function, as the measured trans-epithelial electrical resistance (TEER) of the K14-Cdx2 epithelium was significantly reduced compared to controls (1189 Ohm*cm(2) ±343.5 to 508 Ohm*cm(2)±92.48, p = 0.0532). Secondly, basal cells with features of a transitional cell type, intermediate between keratinocytes and columnar Barrett's epithelial cells, were observed. These cells had reduced keratin bundles and increased endoplasmic reticulum levels, suggesting the adoption of secretory-cell features. Moreover, at the ultrastructural level they resembled "Distinctive" cells associated with multilayered epithelium. Treatment of the K14-Cdx2 mice with 5'-Azacytidine elicited expression of BE-associated genes including Cdx1, Krt18, and Slc26a3/Dra, suggesting the phenotype could be advanced under certain conditions. We conclude that ectopic Cdx2 expression in keratinocytes alters cell proliferation, barrier function, and differentiation. These altered cells represent a transitional cell type between normal squamous and columnar BE cells. The K14-Cdx2 mice represent a useful model to study progression from squamous epithelium to BE.

Biology of Barrett's esophagus and esophageal adenocarcinoma

The past few years have brought new advances in our understanding of the molecular mechanisms underlying the development of Barrett's esophagus and esophageal adenocarcinoma. Although knowledge of the genetic basis for these conditions has not yet translated into clinically useful biomarkers, the current pace of biomedical discovery holds endless possibilities for molecular medicine to improve the diagnosis and management of patients with these conditions. This article provides a useful conceptual basis for understanding the molecular events involved in the making of Barrett metaplasia and in its neoplastic progression, and provides a rationale for evaluating studies on the application of molecular medicine to the diagnosis and management of patients with Barrett's esophagus and esophageal adenocarcinoma.

The pathogenesis of Barrett's metaplasia and the progression to esophageal adenocarcinoma

The most important risk factor for the development of Barrett's esophagus is the reflux of both gastric and duodenal contents into the esophagus. The reason why Barrett's metaplasia develops only in a minority of patients suffering from gastroesophageal reflux disease remains unknown.The exact mechanism behind the transition of normal squamous epithelium into specialized columnar epithelium is also unclear. It is likely that stem cells are involved in this metaplastic change, as they are the only permanent residents of the epithelium. Several tumorigenic steps that lead to the underlying genetic instability, which is indispensable in the progression from columnar metaplasia to esophageal adenocarcinoma have been described. This review outlines the process of pathogenesis of Barrett's metaplasia and its progression to esophageal adenocarcinoma.

Multilayered epithelium in mucosal biopsy specimens from the gastroesophageal junction region is a histologic marker of gastroesophageal reflux disease

Barrett esophagus (BE) is defined as a columnar metaplasia of the distal esophagus that develops as a result of chronic gastroesophageal reflux disease (GERD). A distinctive type of multilayered epithelium (ME) that exhibits features of both squamous and columnar epithelium has been hypothesized to represent an early, or intermediate, phase in the development of BE. The aim of this prospective study was to evaluate the prevalence and specificity of ME in mucosal biopsies of the squamocolumnar junction (SCJ) from patients who had GERD, either with or without BE. During endoscopic examination of the esophagus, 2 biopsy specimens were obtained from across the SCJ from 27 patients with BE, 12 patients who had GERD without BE, and 14 controls who had no symptoms or endoscopic or histologic signs of GERD. ME was present at the SCJ in 33%, 33%, and 0% of BE, GERD, and control patients, respectively. Compared with control subjects, the prevalence of ME was significantly higher in both GERD and BE patients (P<0.05). In GERD patients without BE, ME was always detected adjacent to areas of cardia-type mucosa composed of mucous glands. ME from GERD patients and BE patients had a similar immunophenotype, showing expression of the intestinal markers MUC2 and cdx-2 in 38% and 77% of cases, respectively. The prevalence of expression of these markers in ME was significantly different from nongoblet epithelium in control patients. Our results provide further evidence that ME may represent an early, transitional form of columnar metaplasia, and that ME may be used as a histologic marker of reflux disease in mucosal biopsies from the gastroesophageal junction region.

Repeated exposure to acid and bile selectively induces colonic phenotype expression in a heterogeneous Barrett's epithelial cell line

Barrett's epithelium is a precancerous, specialized columnar metaplasia in the distal esophagus. We demonstrate the changes in cellular phenotype in a non-neoplastic Barrett's cell line (BAR-T), following exposure to acid and bile salt, the two important components of gastroesophageal refluxate. Cell phenotypes in BAR-T cell line were quantified by fluorescence-activated cell sorting (FACS) using monoclonal antibodies against markers: cytokeratin 8/18 (CK8/18) for columnar, CK4 for squamous, mAbDas-1 for colonic epithelial cell phenotype and p75NTR for esophageal progenitors. Cells were exposed for 5 min each day to 200 microM glycochenodeoxycholic acid at pH 4, pH 6 and pH 7.4 or only to acid (pH 4) for up to 6 weeks. The BAR-T cell line comprised 35+/-5.2% CK8/18, 32+/-3.5% mAbDas-1, 9.5+/-3% CK4 and 4+/-2.5% p75NTR-positive cells. Single exposure to acid and or bile did not change cell phenotypes. However, chronic treatment for at least 2 weeks significantly enhanced (P<0.05) the expression of colonic phenotype and CK8/18-positive cells, as evidenced by FACS analysis. Bile salt at pH 4 and bile salt followed by acid (pH 4) in succession were the strongest stimulators (P<0.01) for induction of colonic phenotype cells. Squamous (CK4(+)) phenotype did not change by the treatments. Cox-2 expression was induced after acute treatment and increased to twofold during chronic treatment, particularly in response to acidic pH. We conclude that BAR-T cells can be utilized as an 'in vitro' model to study the effect of environmental factors and their influence on the cellular phenotype and molecular changes in the pathogenesis of esophageal cancer.

How to make a Barrett esophagus: pathophysiology of columnar metaplasia of the esophagus

Barrett esophagus is defined as a specialized intestinal replacing the squamous epithelium of the esophageal mucosa in response to gastroesophageal reflux. Barrett metaplasia is a healing process that develops to protect the esophagus from further damage. Although mechanisms by which Barrett metaplasia evolves toward dysplasia and adenocarcinoma have been extensively studied, the process by which squamous epithelium is replaced by specialized intestinal metaplasia is poorly understood. Barrett esophagus develops when defense mechanisms in the esophageal mucosa (luminal secretion of mucus, bicarbonate, growth factors, etc.) are overwhelmed by an ongoing cycle of mucosal injury and repair. Hydrogen ion, pepsin, trypsin, and bile acids are considered harmful agents that synergistically invade the esophageal mucosa. Areas of destroyed squamous epithelium are then progressively reepithelized by a columnar epithelium that may originate from multipotent stem cells located within the basal layer of the normal esophageal mucosa or in the ducts of submucosal glands.

Pathologic features of reflux and Helicobacter pylori-associated carditis: a comparative study

Inflammation of the gastric cardia, which is the most proximal portion of the stomach, in most instances is the result of either gastroesophageal reflux disease or H. pylori infection. Histologic distinction between these two entities is important because the treatment, natural history, and risk of malignancy are different. Moreover, multilayered epithelium, a possible precursor to Barrett's esophagus, has only recently been described in the gastric cardia, and its relationship to gastroesophageal reflux disease is unknown. The aim of this study was to compare the histologic features of the gastric cardia and the prevalence of multilayered epithelium in patients with reflux versus H. pylori-associated carditis. Routinely processed hematoxylin and eosin-stained mucosal biopsies of the gastric cardia from 30 patients with reflux-associated carditis, 25 with H. pylori-associated carditis, and 30 control patients (no reflux, no H. pylori) were evaluated for a wide variety of histologic features such as goblet cell metaplasia, presence of multilayered epithelium, type of glandular epithelium (mucous, oxyntic, mixed mucous/oxyntic), pancreatic metaplasia, overall degree of inflammation, and the quantity of individual types of inflammatory cells. The clinical and histologic features were compared between the two study groups and controls. Clinically, the reflux carditis group (male/female ratio: 21/9, mean age 56 years) had a significantly higher male/female ratio (p <0.01) and a slightly higher mean age in comparison with the H. pylori group (male/female ratio: 9/16, mean age 50 years). Histologically, the reflux group had significantly less overall inflammation (p <0.05), with fewer plasma cells (p <0.04) and neutrophils (p <0.006), but a higher prevalence of multilayered epithelium [9 of 30 (30%) vs 1 of 25 (4%) in the H. pylori group, p = 0.01]. In the reflux carditis group, multilayered epithelium was significantly associated with neutrophilic inflammation (p <0.05), but not any other features of chronic carditis or with any of the specific epithelial cell types. The control group showed less inflammatory activity in comparison with the H. pylori group and a lower prevalence of multilayered epithelium and eosinophilic inflammation in comparison with the reflux group. The clinical and pathologic features of reflux carditis are distinct from H. pylori carditis and are characterized by less overall inflammation and fewer neutrophils and plasma cells. Multilayered epithelium not uncommonly occurs in the cardia of patients with gastroesophageal reflux disease but without Barrett's esophagus, further supporting our hypothesis that multilayered epithelium may represent an early precursor in the development of columnar metaplasia in Barrett's esophagus.

Barrett's esophagus: an update

Barrett's esophagus (BE) is a complication observed in a small subset of patients with chronic gastroesophageal reflux. It is characterized by the presence of intestinal-type goblet cells in biopsies from the lower esophagus. The prevalence of BE increases with age, affecting 1% of the population older than 60 years. A genetic predisposition to reflux disease has been proposed. In a twin study of reflux disease, concordance was greater in monozygotic than dizygotic twins. An association between BE and esophageal adenocarcinoma, the incidence of which has increased remarkably in the last few decades, has been established. Esophagogastric junction cancers can arise from small areas of cardia intestinal metaplasia (CIM). Regular endoscopic and histologic follow-up of BE patients is recommended. Surveillance of patients with CIM is not advised. Chromoendoscopy may help to detect areas of high-grade dysplasia (HGD). The ablation of BE, e.g. by PDT or argon plasma coagulation, is not yet proven to reduce the cancer risk. Esophagectomy is still the standard management of HGD. Endoscopic mucosal resection may be used for visible, localized lesions with HGD, and this technique may be combined with thermal ablation for areas of HGD without visible abnormality.

Histology of Barrett's esophagus and dysplasia

This article explores issues related to the diagnosis of Barrett's esophagus (BE) in endoscopic biopsies and dysplasia in Barrett's epithelium. The definitions of BE, including long- and short-segment BE, are reviewed, with an emphasis on the significance of intestinal metaplasia (IM). IM of the gastroesophageal junction and cardia is reviewed and problems in its distinction from short-segment BE are discussed. In addition, the article reviews the classification of dysplasia in Barrett's mucosa, with reference to problematic areas, such as sampling error and interobserver variability. Biomarkers and their role in the diagnosis of dysplasia and stratification of risk are summarized.

Nonsurgical management of Barrett's esophagus with high-grade dysplasia

Endoscopic management options for BE with high-grade dysplasia consist of either surveillance methods or endoscopic mucosal ablative therapies. Intensive surveillance once a person is diagnosed with high-grade dysplasia may avoid an unneeded esophagectomy because it appears that most patients with high-grade dysplasia may not progress to esophageal adenocarcinoma. Only a single study has been presented that demonstrates that this approach does not lead to missed opportunities for intervention before progression to advanced stage disease [20]. This study excluded patients with cancer detected within 1 year of diagnosis of high-grade dysplasia; thus, patients who wish to proceed with an observation approach should be aware that the rate of missed esophageal adenocarcinomas ranges from 38% to 73%. The ability to observe a patient with high-grade dysplasia, however, does have appeal because a number of these patients appear to lose the high-grade dysplasia over time. The other endoscopic management option for Barrett's esophagus with high-grade dysplasia is endoscopic mucosal ablative therapies. These include the KTP:YAG laser, the Nd:YAG laser, photodynamic therapy, and endoscopic mucosal resection. All ablative therapies are used in combination with control of gastroesophageal reflux. This allows the esophageal tissue to heal in an environment that is conducive to squamous mucosa. Although most are relatively small series with short durations of observation, they all have shown some promise in treating BE with high-grade dysplasia. These approaches have the advantage of eliminating the problem. The patient who is being observed must live with the thought of developing cancer. Patients who undergo successful ablation are returned to a normal life. The combination of therapies such as EMR with PDT may be the most promising approach to BE with high-grade dysplasia; however, the long-term effects of ablative therapy are not known and continued surveillance is still advised for this group of patients. The choice of a nonsurgical approach for the management of BE with high-grade dysplasia is ultimately up to the individual patient. All patients must be carefully informed of the treatment effects, possible outcomes, and the surgical alternative. Most patients who select nonsurgical approaches are either elderly or are not good surgical candidates. The choice is often affected by local expertise, as surgical procedures should be performed in centers with surgeons expert in esophagectomy. Nonsurgical approaches should also be performed by physicians who are familiar with their application. Future advances in nonsurgical techniques such as new photosensitizers in PDT and improvements in diagnostic techniques may allow patients a greater opportunity to preserve their esophagus.

Experimental Barrett's esophagus and the origin of intestinal metaplasia

Many questions remain unanswered regarding the pathogenesis and the cell origin of Barrett's esophagus. Recent studies suggest that progenitor cell populations, which are presumed to reside at the basal layer in the squamous epithelium and at the esophageal glands duct epithelium, may differentiate into a glandular phenotype leading to the development of columnar epithelium in the distal esophagus. Other studies also support the hypothesis that cardiac epithelium may precede the occurrence of specialized intestinal metaplasia. It remains unclear whether cardiac-type epithelium in Barrett's esophagus arises from squamous epithelium or from migration of native cardiac epithelium at the EGJ into the distal esophagus. Experimental animal models of chronic reflux esophagitis, although with some shortcomings when researchers extrapolate the study data to the human situation, have provided interesting insights into possible mechanisms associated with the occurrence of Barrett's esophagus. A better understanding of the molecular mechanisms regulating the development of Barrett's esophagus is necessary for developing new strategies directed toward prevention and treatment of this metaplastic condition with a potential risk for malignant transformation.

Prospective evaluation of multilayered epithelium in Barrett's esophagus

OBJECTIVE

We recently identified a distinctive type of multilayered epithelium in two patients with Barrett's esophagus, which shows morphological characteristics of both squamous and columnar epithelium. This study was performed to prospectively evaluate the prevalence of multilayered epithelium in patients with Barrett's esophagus.

METHODS

Mucosal biopsies were obtained from the squamocolumnar junction (Z-line) of 58 patients with endoscopic evidence of esophageal columnar epithelium and from the gastroesophageal junction in 21 patients without endoscopic evidence of esophageal columnar epithelium. Specimens were evaluated for the presence of multilayered epithelium and goblet cells.

RESULTS

Twenty-four of 58 (41%) of the patients with endoscopic evidence of esophageal columnar epithelium had multilayered epithelium compared with only one of 21 patients (5%) in the control group (p = 0.005). Of the 58 patients in the study group, 43 had goblet cell metaplasia and 15 did not (p < 0.001). Only patients with goblet cell metaplasia had multilayered epithelium. Shorter lengths of columnar epithelium were noted in the 24 patients with goblet cells and multilayered epithelium compared with the 19 patients with goblet cells and no multilayered epithelium (p < 0.05).

CONCLUSIONS

Multilayered epithelium is strongly associated with goblet cell metaplasia in patients with endoscopic evidence of esophageal columnar epithelium. These data support the hypothesis that multilayered epithelium may represent a transitional stage in the development of Barrett's esophagus.

Expression of p53-related protein p63 in the gastrointestinal tract and in esophageal metaplastic and neoplastic disorders

p63 is a p53-related DNA-binding protein that helps regulate differentiation and proliferation in epithelial progenitor cells. Its expression has never been evaluated in the human gastrointestinal tract. The aim of this study was to evaluate the expression of p63 in the esophagus and related metaplastic and neoplastic disorders to gain insight into the pathogenesis of these processes. Of particular interest was the expression of p63 in Barrett esophagus (BE) and in BE-associated multilayered epithelium. Multilayered epithelium has been postulated to represent an early precursor to the development of BE primarily because it shares morphologic and immunophenotypic features of both squamous and columnar epithelium, and has been shown prospectively to be highly associated with BE. Routinely processed mucosal biopsy or resection specimens that contained normal esophageal squamous epithelium (n = 20), squamous dysplasia (n = 4), squamous cell carcinoma (n = 7), BE (n = 10), BE-associated multilayered epithelium (n = 13), esophageal mucosal gland ducts (n = 10), BE-associated dysplasia (n = 12), and BE-associated adenocarcinoma (n = 7) were immunostained for p63 to determine the extent and location of staining. p63 staining was compared with the staining patterns observed for p53, Ki 67 (proliferation marker), and cytokeratins (CKs) 13 (squamous marker), 14 (basal squamous marker), 8/18 (columnar marker), and 19 (basal/columnar marker). Expression of p63 messenger RNA (mRNA) isoforms was also analyzed by reverse-transcription polymerase chain reaction of freshly isolated tissues. In the normal esophagus, p63 was expressed in the basal and suprabasal layers of the squamous epithelium and in basal cells that line the mucosal gland ducts but was negative in all other epithelia of the gastrointestinal tract, including the stomach, small intestine, and colon. Similarly, p63 was not expressed in BE, but it, was present in the basal layer of multilayered epithelium in 9 of 13 cases (69%). p63-positive cells in multilayered epithelium and in the mucosal gland duct epithelium were positive for CK8/18 (100%) and CK13 (67% and 30%, respectively) and negative for CK14 (0%), in contrast to p63-positive cells in squamous epithelium, which were positive for CK14 and CK13 (100%) but negative for CK8/18. In neoplastic tissues, p63 was diffusely expressed in all cases of esophageal squamous cell dysplasia and carcinoma but was negative in all cases of esophageal and colorectal adenocarcinoma. The DeltaN isoform of p63 mRNA predominated in all benign and neoplastic squamous tissues examined. p63 may represent a marker of 2 distinct epithelial progenitor cells (basal squamous epithelium and gland duct epithelium) in the esophagus. P63 is upregulated in squamous neoplastic conditions and in this manner may play a role in squamous carcinogenesis. These data also indicate that multilayered epithelium is phenotypically similar to, and may share a lineage relationship with, mucosal gland duct epithelium.

Phenotypic characteristics of a distinctive multilayered epithelium suggests that it is a precursor in the development of Barrett's esophagus

A distinctive type of multilayered epithelium (ME) has been described at the neo-squamocolumnar junction and within columnar mucosa in patients with Barrett's esophagus (BE). This epithelium has morphologic and ultrastructural features of both squamous and columnar epithelium. Multilayered epithelium may represent an early or intermediate stage of columnar metaplasia; therefore, we performed this study to determine the morphologic and biologic characteristics of this epithelium and to gain insight into its derivation. Esophageal mucosal biopsies containing ME from 17 patients with BE were evaluated morphologically, stained with a variety of mucin histochemical stains; and also immunostained with antibodies against cytokeratins (CK) 13 (squamous epithelium marker); 14 (basal squamous epithelium marker) 7, 8/18, 19, and 20 (columnar epithelium markers), MIB-1 (proliferation marker); villin (intestinal brush border protein); and TGFalpha, EGFR, pS2, and hSP (enteric proliferation/differentiation regulatory peptides). The results were compared with normal esophageal squamous epithelium, normal gastric cardia epithelium, specialized-type intestinal epithelium (BE), and esophageal mucosal and submucosal gland duct epithelium. Multilayered epithelium expressed a pattern of mucin production (neutral mucin, sialomucin, and sulfomucin in 88%, 100%, and 71% of cases, respectively) and cytokeratin expression (CK 13 and 19 in the basal "squamoid" cells, CK 7, 8/18, 19, and 20 in the superficial "columnar" cells) similar to that of columnar epithelium in BE, and showed a high capacity for cellular proliferation (Ki-67-positive in 88% of cases) and differentiation (TGFalpha, EGFR, pS2 and villin-positive in 100%, 100%, 93%, and 66% of cases, respectively). The mucosal gland duct epithelium showed a similar phenotypic pattern and, in one case, was seen to give rise to ME at the surface of the mucosa. These data provide evidence in support of the hypothesis that ME represents an early or intermediate stage in the development of esophageal columnar metaplasia (BE). The mucosal gland duct epithelium may contain progenitor cells that can give rise to ME.

Barrett's esophagus: the long and the short of it

Specialized intestinal epithelium occurs more frequently at the gastroesophageal junction than previously anticipated. It can occur either within tongues of mucosa (short segment Barrett's) or just beneath a normal z-line (intestinal metaplasia at the gastroesophageal junction). Whether the etiopathogenesis and the natural history of these two conditions are the same is as yet unclear. The role of gastroesophageal reflux disease (GERD), Helicobacter pylori, and inflammation at the gastroesophageal junction in the pathogenesis of short segment Barrett's and intestinal metaplasia at the gastroesophageal junction needs to be carefully documented. Intestinal metaplasia at the gastroesophageal junction, short segment Barrett's, and Barrett's may represent a continuum of the same disease process. Recent evidence suggests, however, that short segment Barrett's shares similar characteristics with Barrett's but may be distinct from intestinal metaplasia at the gastroesophageal junction. It is conceivable that short segment Barrett's may remain steady or even regress if and when the noxious influence wanes but, with continuing stimulation, short segment Barrett's may lengthen further to become what we observe to be Barrett's. If correct, endogenous or exogenous factors that induce progression need to be identified. Acid and bile reflux and H. pylori are possible candidates acting either singly or synergistically. Finally, the true neoplastic potential of short segment Barrett's needs clarification.

Barrett's esophagus

The columnar replacement of squamous epithelium in the lower esophagus is the result of gastroesophageal reflux. Whether the squamous cells are replaced or undergo metaplasia is still conjectural. This neoepithelium is unstable in the presence of continued reflux and prone to complications of stricture, ulceration, and adenocarcinoma. Considerable evidence supports the hypothesis that duodenal contents play a role in the development of Barrett's esophagus and its complications. The increasing incidence of adenocarcinoma in Barrett's esophagus is of concern in the Western World. Surveillance programs in some centers have been successful in early diagnosis, and excellent survival periods have been reported following resection in these cases. Both medical and surgical antireflux treatment is successful in symptom relief, but even in the absence of symptoms, reflux may continue. Surgery offers better overall results than proton pump inhibition of gastric acid and has been more popular since less aggressive (minimally invasive) techniques have been popularized. Mucosal ablation and antireflux measures by medicine or surgery are still in the experimental stages but hold considerable promise for the future.

Morphology of Barrett's esophagus and Barrett's-associated dysplasia and adenocarcinoma

This article has reviewed the morphologic features of BE and its complications of dysplasia and adenocarcinoma in routinely processed endoscopic biopsy and resection specimens. In addition, the problems related to the diagnosis of dysplasia in tissue samples have been analyzed, and the role of esophageal brush cytology in the diagnosis of these lesions has been reviewed.