Esophageal submucosal glands: structure and function

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

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

Development of Test Programs for the Biorelevant Characterization of Esophageal-Applied Dosage Forms

In the local treatment of the esophageal mucosa, the retention time of the different dosage forms, such as tablets, films or liquids, is of high relevance for the effective treatment of diseases. Unfortunately, there are only few in vitro models describing the esophageal route of administration. To predict the behaviour of an esophageal-applied dosage form, it is necessary to simulate the site of application in a biorelevant way. The aim of this work was to develop two test setups for an esophageal peristalsis model which was described in a previous study. Different parameters such as flow rate, peristalsis, angle of inclination or mucous membrane were varied or introduced into the model. A stimulated and unstimulated modus were developed and tested with two different dosage forms. The time until the dosage form was cleared from the in vitro model was shorter with the stimulated than with the unstimulated modus. Also, esophageal-applied films had a prolonged transit time compared to a viscous syrup. The modification of the simulated esophageal surface made it possible to estimate the retention time of the dosage forms. It could be demonstrated that the residence time of a dosage form depends on different parameters affecting each other.

Anatomy and embryology of tracheo-esophageal fistula

Anomalies in tracheo-esophageal development result in a spectrum of congenital malformations ranging from, most commonly, esophageal atresia with or without trachea-esophageal fistula (EA+/-TEF) to esophageal web, duplication, stricture, tracheomalacia and tracheal agenesis. Despite the relative frequency of EA, however, the underlying etiology remains unknown and is likely due to a combination of genetic, epigenetic and environmental factors. In recent years, animal models have dramatically increased our understanding of the molecular and morphological processes involved in normal esophageal development during the key stages of anterior-posterior regionalization, dorsal-ventral patterning and morphogenic separation. Moreover, the use of animal models in conjunction with increasingly advanced techniques such as genomic sequencing, sophisticated live imaging studies and organoid models have more recently cast light on potential mechanisms involved in EA pathogenesis. This article aims to unravel some of the mysteries behind the anatomy and embryology of EA whilst providing insights into future directions for research.

A new murine esophageal organoid culture method and organoid-based model of esophageal squamous cell neoplasia

Organoids mimic the physiologic and pathologic events of organs. However, no consensus on esophageal organoid (EO) culture methods has been reached. Moreover, organoid models reproducing esophageal squamous cell carcinoma (ESCC) initiation have been unavailable. Herein, we sought to develop an esophageal minimum essential organoid culture medium (E-MEOM) for culturing murine EOs and establishing an early ESCC model. We formulated E-MEOM to grow EOs from a single cell with clonal expansion, maintenance, and passage. We found that EOs cultured in E-MEOM were equivalent to the esophageal epithelium by histological analysis and transcriptomic study. Trp53 knockout and Kras^G12D expression in EOs induced the development of esophageal squamous neoplasia, an early lesion of ESCC. Here we propose the new formula for EO culture with minimum components and the organoid model recapitulating ESCC initiation, laying the foundation for ESCC research and drug discovery.

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Identification of minimal components for murine EO growth and maintenance

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Mouse EOs morphologically and transcriptionally recapitulate the human esophagus

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Trp53 KO and KrasG12D induced esophageal neoplasia mimicking early ESCC

3D Organoids: An Untapped Platform for Studying Host-Microbiome Interactions in Esophageal Cancers

The microbiome is an emerging key co-factor in the development of esophageal cancer, the sixth leading cause of cancer death worldwide. However, there is a paucity of data delineating how the microbiome contributes to the pathobiology of the two histological subtypes of esophageal cancer: esophageal squamous cell carcinoma and esophageal adenocarcinoma. This critical knowledge gap is partially due to inadequate modeling of host-microbiome interactions in the etiology of esophageal cancers. Recent advances have enabled progress in this field. Three dimensional (3D) organoids faithfully recapitulate the structure and function of the normal, preneoplastic, and neoplastic epithelia of the esophagus ex vivo and serve as a platform translatable for applications in precision medicine. Elsewhere in the gastrointestinal (GI) tract, the co-culture of 3D organoids with the bacterial microbiome has fostered insight into the pathogenic role of the microbiome in other GI cancers. Herein, we will summarize our current understanding of the relationship between the microbiome and esophageal cancer, discuss 3D organoid models of esophageal homeostasis, review analogous models of host-microbiome interactions in other GI cancers, and advocate for the application of these models to esophageal cancers. Together, we present a promising, novel approach with the potential to ameliorate the burden of esophageal cancer-related morbidity and mortality via improved prevention and therapeutic interventions.

Development of Epidermoid Metaplasia of the Mucosa in Association with Esophageal Intramural Pseudodiverticulosis and Candidiasis

We report a case of epidermoid metaplasia of the esophageal mucosa that developed in a patient with a long history of esophageal intramural pseudodiverticulosis (EIPD) complicated by candidiasis. The patient, a 69-year-old man, had been treated for about 3 years for EIPD with candidiasis. After candidiasis improved, the development of epidermoid metaplasia of the esophageal mucosa was observed. It comprised longitudinally arranged, multiple, small, whitish flecks with a scaly appearance on the mucosa of the middle to lower esophagus, and pathological examination demonstrated several fine keratohyalin granules in superficial layers of the squamous epithelium. Six months later, candidiasis was almost cured, but these small flecks had slightly increased in size, and pathological examination demonstrated epidermoid metaplasia consisting of a thick, acellular keratin layer and well-developed granular layer beneath it. We considered that chronic candida esophagitis played the principal pathogenetic role in the development of epidermoid metaplasia. EIPD may have provided an environment suitable for the growth of fungi, and mucinous material contaminated by Candida and excreted from the orifices of EIPD may have irritated the mucosa and induced epidermoid metaplasia.

Extension of early esophageal squamous cell neoplasia into ducts and submucosal glands and the role of endoscopic ablation therapy

BACKGROUND AND AIMS

Early esophageal squamous cell neoplasia (ESCN) is preferably treated with en-bloc endoscopic resection. Ablation might be an alternative for flat ESCN, but ESCN extension along the epithelial lining of ducts and submucosal glands (SMGs) might jeopardize ablation efficacy. Clinical studies suggest that local recurrence might arise from such buried ESCN niches after ablation. We studied human endoscopic resection specimens of ESCN to quantify ESCN extension into ducts/SMGs and performed a prospective porcine study to evaluate the depth of radiofrequency ablation (RFA) and CryoBalloon ablation (CBA) into ducts/SMGs.

METHODS

Endoscopic submucosal dissection specimens of flat-type ESCN from a Japanese (n = 65) and Dutch cohort (n = 14) were evaluated for presence and neoplastic involvement of ducts/SMGs. Twenty-seven pigs were treated with circumferential RFA (c-RFA; n = 4), focal CBA (n = 20), and focal RFA (n = 3) with 4, 60, and 9 treatment areas, respectively. After prespecified survival periods (0 hours, 8 hours, 2 days, 5 days, and 28 days), treatment areas were evaluated for uniformity and depth of ablation and affected SMGs.

RESULTS

Neoplastic extension in ducts/SMGs was observed in most lesions: 58% (38/65) in the Japanese and 64% (9/14) in the Dutch cohort. In the animal study, 33% of SMGs (95% confidence interval, 28-50) were not affected after c-RFA, although the overlying epithelium was ablated. Focal RFA and CBA resulted in uniform ablations with effective treatment of all SMGs.

CONCLUSIONS

ESCN extends into ducts/SMGs in most patients. In an animal model, focal RFA and CBA effectively ablated SMGs, whereas c-RFA inadequately ablated SMGs. Given this potential reason for recurrence, endoscopic resection should remain the standard of care.

Assessment of tumor extension to the ductal system of submucosal glands in patients with superficial esophageal squamous neoplasms: Implications for endoscopic resection

BACKGROUND

Endoscopic submucosal dissection (ESD) has become the standard treatment for superficial esophageal squamous cell neoplasia (SESCN); however, local recurrence still occurs occasionally even in patients who meet the current curative criteria. Esophageal ducts of the submucosal gland may serve as a pathway for the spread of SESCN to a deeper layer. However, the clinical impact of ductal involvement (DI) in patients undergoing ESD has yet to be investigated.

METHODS

We consecutively enrolled patients with SESCN who were treated with ESD. The resected specimens were meticulously reviewed in multiple section slices for the presence and resected margins of DI, and their correlations with clinical factors were evaluated.

RESULTS

A total of 210 lesions were analyzed, of which 78 (37.1%) presented with DI. The presence of submucosal invasion, lymphovascular invasion (LVI), and DI were indicators of worse prognosis (P < .05). Deep extended DIs were misdiagnosed as deep submucosal invasive cancer in 4 cases (2%). Of the 185 patients who met the criteria for curative ESD (ie, R0 resection and no deep submucosal invasion or LVI), 11 (5.9%) developed local recurrence/metastasis during a mean follow-up of 55.2 months (range, 6 to 140) months. Compared with patients with without DI, patients with DI had worse recurrence-free survival (P = .008, log-rank test) and a higher local risk of recurrence (12.7% vs 2.5%) after curative ESD (hazard ratio, 4.20; P = .038).

CONCLUSIONS

A precise histological assessment of DI in SESCN is crucial after ESD, given that DI is common and associated with worse outcome. Whether total removal of esophageal glands/ducts can improve outcome requires future study.

Genetically engineered mouse models of esophageal cancer

BACKGROUND

Esophageal cancer is the most common cause of cancer-related death worldwide with a diverse geographical distribution, poor prognosis, and diagnosis in advanced stages of the disease. Identification of the mechanisms involved in esophageal cancer development is evaluative to improve outcomes for patients. Genetically engineered mouse models (GEMMs) of cancer provide the physiologic, molecular, and histologic features of the human tumors to determine the pathogenesis and treatments for cancer, hence exhibiting a source of tremendous potential for oncology research. The advancement of cancer modeling in mice has improved to the extent that researchers can observe and manipulate the disease process in a specific manner. Despite the significant differences between mice and humans, mice can be great models for human oncology researches due to similarities between them at the molecular and physiological levels. Due to most of the existing esophageal cancer GEMMs do not propose an ideal system for pathogenesis of the disease, genetic risks, and microenvironment exposure, so identification of challenges in GEM modeling and well-developed technologies are required to obtain the most value for patients. In this review, we describe the biology of human and mouse, followed by the exciting esophageal cancer mouse models with a discussion of applicability and challenges of these models for generating new GEMMs in future studies.

Immune system and microbiome in the esophagus: implications for understanding inflammatory diseases

The gastrointestinal tract is the largest compartment of the body's immune system exposed to microorganisms, structural components and metabolites, antigens derived from the diet, and pathogens. Most studies have focused on immune responses in the stomach, the small intestine, and the colon, but the esophagus has remained an understudied anatomic immune segment. Here, we discuss the esophagus' anatomical and physiological distinctions that may account for inflammatory esophageal diseases.

The development and stem cells of the esophagus

The esophagus is derived from the anterior portion of the foregut endoderm, which also gives rise to the respiratory system. As it develops, the esophageal lining is transformed from a simple columnar epithelium into a stratified squamous cell layer, accompanied by the replacement of unspecified mesenchyme with layers of muscle cells. Studies in animal models have provided significant insights into the roles of various signaling pathways in esophageal development. More recent studies using human pluripotent stem cells (hPSCs) further demonstrate that some of these signaling pathways are conserved in human esophageal development. In addition, a combination of mouse genetics and hPSC differentiation approaches have uncovered new players that control esophageal morphogenesis. In this Review, we summarize these new findings and discuss how the esophagus is established and matures throughout different stages, including its initial specification, respiratory-esophageal separation, epithelial morphogenesis and maintenance. We also discuss esophageal muscular development and enteric nervous system innervation, which are essential for esophageal structure and function.

Lubiprostone protects esophageal mucosa from acid injury in porcine esophagus

Esophageal injury from acid exposure related to gastroesophageal reflux disease is a common problem and a risk factor for development of Barrett's esophagus and esophageal adenocarcinoma. Our previous work highlights the benefits of using porcine esophagus to study human esophageal disease because of the similarities between porcine and human esophagus. In particular, esophageal submucosal glands (ESMGs) are present in human esophagus and proximal porcine esophagus but not in rodent esophagus. Although CFTR is expressed in the ducts of ESMGs, very little is known about CFTR and alternate anion channels, including ClC-2, in the setting of acid-related esophageal injury. After finding evidence of CFTR and ClC-2 in the basal layers of the squamous epithelium, and in the ducts of the ESMGs, we developed an ex vivo porcine model of esophageal acid injury. In this model, esophageal tissue was placed in Ussing chambers to determine the effect of pretreatment with the ClC-2 agonist lubiprostone on tissue damage related to acid exposure. Pretreatment with lubiprostone significantly reduced the level of acid injury and significantly augmented the recovery of the injured tissue (P < 0.05). Evaluation of the interepithelial tight junctions showed well-defined membrane localization of occludin in lubiprostone-treated injured tissues. Pretreatment of tissues with the Na⁺-K⁺-2Cl^- cotransporter inhibitor bumetanide blocked lubiprostone-induced increases in short-circuit current and inhibited the reparative effect of lubiprostone. Furthermore, inhibition of ClC-2 with ZnCl₂ blocked the effects of lubiprostone. We conclude that ClC-2 contributes to esophageal protection from acid exposure, potentially offering a new therapeutic target.NEW & NOTEWORTHY This research is the first to describe the presence of anion channels ClC-2 and CFTR localized to the basal epithelia of porcine esophageal mucosa and the esophageal submucosal glands. In the setting of ex vivo acid exposure, the ClC-2 agonist lubiprostone reduced acid-related injury and enhanced recovery of the epithelial barrier. This work may ultimately provide an alternate mechanism for treating gastroesophageal reflux disease.

Role of submucosal glands in the development and progression of carcinoma in Barrett's oesophagus

Oesophageal submucosal glands secrete mucins and other chemicals that are believed to serve as protectants of the mucosal surface from luminal noxious agents, either ingested or refluxed. Changes in the type, distribution or number of submucosal glands may contribute to, or be associated with, the development of Barrett's oesophagus and progression to cancer. The aim of this study was to investigate the anatomical, morphological and immunohistochemical characteristics of submucosal glands in Barrett's oesophagus-associated neoplasia in 64 oesophageal resections for Barrett's oesophagus-associated adenocarcinoma and 32 squamous cell carcinomas (as a control group). Gland density was not significantly different between the oesophageal adenocarcinoma (0.91/cm) and squamous cell carcinoma (0.81/cm) groups (p=0.7). In the oesophageal adenocarcinoma group, glands underlying Barrett's oesophagus-associated neoplastic epithelium showed a significant decrease in the percentage of mucinous acini and a significant increase in the percentage of atrophic acini compared to glands underlying epithelium without dysplasia or carcinoma (74% vs 83%, p=0.03; and 24% vs 14%, p=0.01). There was also an increase in the percentage of glands with moderate to severe inflammation underlying neoplastic epithelium compared to glands underlying epithelium without dysplasia or carcinoma (53% vs 33%, p=0.001). None of these differences was seen in the squamous cell carcinoma group. The immunohistochemical characteristics of the different histological subtypes were also distinct. Atrophic and oncocytic acini were diffusely and strongly positive for CK7, SOX2, SOX9 and CK5/6 (a progenitor cell phenotype) while mucinous acini showed weak or moderate staining for those markers. Our results suggest that submucosal glands play a role in the progression of neoplasia, possibly by offering less protection to the mucosal surface of the oesophageal epithelium from chemical injury.

Submucosal gland neoplasms of the esophagus: an update and review

Submucosal glands (SMGs) present throughout human esophagus with clusters at either the upper third or lower third of the organ. SMGs tend to atrophy with age, and neoplasms arising in these glands are rare. In order to bring convenience to diagnosis, we summarize the histopathologic characteristics of all esophageal submucosal gland tumors (SGTs). Due to the morphological similarity, the nomenclature of salivary tumors is adopted for SGTs. However, there is great confusion about the definition and histogenesis of these tumors, especially the malignant subtypes. In the literature, esophageal mucoepidermoid carcinoma and adenoid cystic carcinoma usually adjoin the surface squamous epithelium and coexist with intraepithelial neoplasia or invasive squamous cell carcinoma (SCC). In addition, the typical gene alterations of salivary tumors have not been reported in these SGTs. Therefore, we propose to apply stringent diagnostic criteria to esophageal SGTs so as to exclude mimickers that are SCCs with various degree of SMG differentiation.

Glyco-conjugated bile acids drive the initial metaplastic gland formation from multi-layered glands through crypt-fission in a murine model

Bile acid reflux is known to be associated with the development of Barrett’s esophagus and esophageal adenocarcinoma (EAC), yet the role of specific bile acids and the mechanism behind the metaplastic changes is unclear. Here, we demonstrate that multi-layered glandular structures at the squamo-columnar junction in mice contain multiple cell lineages, which resemble the human esophageal submucosal gland ducts. Exposing mice to patient’s refluxates induced expansion of multi-layered glandular structures and development of columnar metaplasia at the squamo-columnar junction. The glycine conjugated bile acids induced an intestinal type of metaplasia more typical for Barrett’s esophagus. Through lineage tracing, we excluded the involvement of K5⁺, DCLK1⁺, and LGR5⁺ progenitor cells as the primary source in the development of the glandular metaplastic epithelium. We show that the mechanism behind development of metaplasia involves crypt fission and may be independent of stem cell proliferation. Our findings support the hypothesis that in humans, BE arises from non-squamous cells residing in submucosal gland ducts and that induction of intestinal type of metaplasia is most effectively induced by glycine-conjugated bile acids. These novel insights may lead to more effective strategies to prevent development of Barrett’s esophagus and esophageal adenocarcinoma.

Comparison of esophageal submucosal glands in experimental models for esophagus tissue engineering applications

OBJECTIVE

Esophagus tissue engineering holds promises to overcome the limitations of the presently employed esophageal replacement procedures. This study investigated 5 animal models for esophageal submucosal glands (ESMG) to identify models appropriate for regenerative medicine applications. Furthermore, this study aimed to measure geometric parameters of ESMG that could be utilized for fabrication of ESMG-specific scaffolds for esophagus tissue engineering applications.

METHODS

Ovine, avian, bovine, murine, and porcine esophagus were investigated using Hematoxylin-Eosin (HE), Periodic Acid Schiff (PAS), and Alcian Blue (AB), with AB applied in 3 pH levels (0.2, 1.0, and 2.5) to detect sulphated mucous. Celleye^® (version F) was employed to gain parametric data on ESMGs (size, perimeter, distance to lumen, and acini concentration) necessary for scaffold fabrication.

RESULTS

Murine, bovine, and ovine esophagus were devoid of ESMG. Avian esophagus demonstrated sulphated acid mucous producing ESMGs with a holocrine secretion pattern, whereas sulphated acid and neutral mucous producing ESMGs with a merocrine secretion pattern were observed in porcine esophagus. Distance of ESMGs to lumen ranged from 127-340 μm (avian) to 916-983 μm (porcine). ESMGs comprised 35% (avian) to 45% (porcine) area of the submucosa. ESMG had an area of 125000 μm² (avian) to 580000 μm² (porcine).

CONCLUSION

Avian and porcine esophagus possesses ESMGs. However, porcine esophagus correlates with data available on human ESMGs. Geometric and parametric data obtained from ESMG are valuable for the fabrication of ESMG-specific scaffolds for esophagus tissue engineering using the hybrid construct approach.

Single cell RNA-seq reveals profound transcriptional similarity between Barrett's oesophagus and oesophageal submucosal glands

Barrett's oesophagus is a precursor of oesophageal adenocarcinoma. In this common condition, squamous epithelium in the oesophagus is replaced by columnar epithelium in response to acid reflux. Barrett's oesophagus is highly heterogeneous and its relationships to normal tissues are unclear. Here we investigate the cellular complexity of Barrett's oesophagus and the upper gastrointestinal tract using RNA-sequencing of single cells from multiple biopsies from six patients with Barrett's oesophagus and two patients without oesophageal pathology. We find that cell populations in Barrett's oesophagus, marked by LEFTY1 and OLFM4, exhibit a profound transcriptional overlap with oesophageal submucosal gland cells, but not with gastric or duodenal cells. Additionally, SPINK4 and ITLN1 mark cells that precede morphologically identifiable goblet cells in colon and Barrett's oesophagus, potentially aiding the identification of metaplasia. Our findings reveal striking transcriptional relationships between normal tissue populations and cells in a premalignant condition, with implications for clinical practice.

The Esophageal Epithelial Barrier in Health and Disease

Dysfunction in the esophageal epithelial barrier function is a major source for morbidity. To better understand the pathophysiologic pathways of the diseases associated with barrier dysfunction, including gastroesophageal reflux disease, eosinophilic esophagitis, Barrett's esophagus, and obesity, it is important to understand the esophageal epithelial embryologic development, microscopic anatomy with a special focus on the barrier structure and function, extraepithelial defense mechanisms, and how these change in the diseased state. In recent years, significant progress has been made in elucidating the esophageal barrier structure and function both in vitro and in vivo. This has enhanced the understanding of mechanisms of disease, and may also allow identification of therapeutic targets that can help in the management of these diseases. This review provides a detailed discussion regarding the esophageal epithelial barrier structure and function, the current and historical techniques used to study the barrier, and how it is affected by common esophageal diseases.

A slippery slope: On the origin, role and physiology of mucus

The mucosa of the gastrointestinal tract, eyes, nose, lungs, cervix and vagina is lined by epithelium interspersed with mucus-secreting goblet cells, all of which contribute to their unique functions. This mucus provides an integral defence to the epithelium against noxious agents and pathogens. However, it can equally act as a barrier to drugs and delivery systems targeting epithelial passive and active transport mechanisms. This review highlights the various mucins expressed at different mucosal surfaces on the human body, and their role in creating a mucoid architecture to protect epithelia with specialized functions. Various factors compromising the barrier properties of mucus have been discussed, with an emphasis on how disease states and microbiota can alter the physical properties of mucus. For instance, Akkermansia muciniphila, a bacterium found in higher levels in the gut of lean individuals induces the production of a thickened gut mucus layer. The aims of this article are to elucidate the different physiological, biochemical and physical properties of bodily mucus, a keen appreciation of which will help circumvent the slippery slope of challenges faced in achieving effective mucosal drug and gene delivery.

Ductular and proliferative response of esophageal submucosal glands in a porcine model of esophageal injury and repair

Esophageal injury is a risk factor for diseases such as Barrett's esophagus (BE) and esophageal adenocarcinoma. To improve understanding of signaling pathways associated with both normal and abnormal repair, animal models are needed. Traditional rodent models of esophageal repair are limited by the absence of esophageal submucosal glands (ESMGs), which are present in the human esophagus. Previously, we identified acinar ductal metaplasia in human ESMGs in association with both esophageal injury and cancer. In addition, the SOX9 transcription factor has been associated with generation of columnar epithelium and the pathogenesis of BE and is present in ESMGs. To test our hypothesis that ESMGs activate after esophageal injury with an increase in proliferation, generation of a ductal phenotype, and expression of SOX9, we developed a porcine model of esophageal injury and repair using radiofrequency ablation (RFA). The porcine esophagus contains ESMGs, and RFA produces a consistent and reproducible mucosal injury in the esophagus. Here we present a temporal assessment of this model of esophageal repair. Porcine esophagus was evaluated at 0, 6, 18, 24, 48, and 72 h and 5 and 7 days following RFA and compared with control uninjured esophagus. Following RFA, ESMGs demonstrated an increase in ductal phenotype, echoing our prior studies in humans. Proliferation increased in both squamous epithelium and ESMGs postinjury with a prominent population of SOX9-positive cells in ESMGs postinjury. This model promises to be useful in future experiments evaluating mechanisms of esophageal repair.NEW & NOTEWORTHY A novel porcine model of injury and repair using radiofrequency ablation has been developed, allowing for reproducible injury to the esophagus to study repair in an animal model with esophageal submucosal glands, a key anatomical feature and missing in rodent models but possibly harboring progenitor cells. There is a strong translational component to this porcine model given the anatomical and physiological similarities between pigs and humans.

Effects of estrogen on esophageal function through regulation of Ca2+-related proteins

BACKGROUND

The calcium ion is important for physiological functions in all tissues and organs and essential to many vital functions, including hormone secretion and muscle contraction. The intracellular concentration of calcium is regulated by calcium related proteins such as CaBP-9k, PMCA1, and NCX1. In this study, we investigated the relationship between calcium regulation and esophageal functions such as mucin secretion and smooth muscle contraction.

METHODS

To evaluate the influence of sex steroid hormones, immature rats were treated for 3 days with estradiol (E2), progesterone (P4), and their antagonists (ICI 182,780, and RU486). Esophageal function, transcription level, and localization of CaBP-9k, PMCA1, NCX1, ERα, and MUC2 were examined in the esophagus.

RESULTS

Transcriptional level of Cabp-9k and Muc2 was increased by E2, but not by P4. CaBP-9k, PMCA1, and MUC2 were mainly localized in the mucosal layer. Acidic mucosubstances in the esophagus were increased by E2 and recovered by ICI treatment. Unlike the expression of Cabp-9k, mRNA levels of Pmca1, Ncx1, and Erα were only decreased in response to E2, and recovered by ICI co-treatment group. The contraction of the esophagus and mRNA level of Mylk were reduced by E2. Overall, E2 upregulated mucus secretion, but downregulated muscle contraction in the esophagus through regulation of the expression of calcium related genes and the resultant intracellular calcium level.

CONCLUSIONS

The regulation of E2 in the function of esophagus may be applied to treat esophageal diseases such as reflux esophagitis, achalasia, and esophageal cancer.

The prevalence of gastric heterotopia of the proximal esophagus is underestimated, but preneoplasia is rare - correlation with Barrett's esophagus

BACKGROUND

The previously reported prevalence of gastric heterotopia in the cervical esophagus, also termed inlet patch (IP), varies substantially, ranging from 0.18 to 14%. Regarding cases with adenocarcinoma within IP, some experts recommend to routinely obtain biopsies from IP for histopathology. Another concern is the reported relation to Barrett's esophagus. The objectives of the study were to prospectively determine the prevalence of IP and of preneoplasia within IP, and to investigate the association between IP and Barrett's esophagus.

METHODS

372 consecutive patients undergoing esophagogastroduodenoscopy were carefully searched for the presence of IP. Biopsies for histopathology were targeted to the IP, columnar metaplasia of the lower esophagus, gastric corpus and antrum. Different definitions of Barrett's esophagus were tested for an association with IP.

RESULTS

At least one IP was endoscopically identified in 53 patients (14.5%). Histopathology, performed in 46 patients, confirmed columnar epithelium in 87% of cases, which essentially presented corpus and/or cardia-type mucosa. Intestinal metaplasia was detected in two cases, but no neoplasia. A previously reported association of IP with Barrett's esophagus was weak, statistically significant only when short segments of cardia-type mucosa of the lower esophagus were included in the definition of Barrett's esophagus.

CONCLUSIONS

The prevalence of IP seems to be underestimated, but preneoplasia within IP is rare, which does not support the recommendation to regularly obtain biopsies for histopathology. Biopsies should be targeted to any irregularities within the heterotopic mucosa. The correlation of IP with Barrett's esophagus hints to a partly common pathogenesis.

Development and stem cells of the esophagus

The esophagus is derived from the anterior portion of the developmental intermediate foregut, a structure that also gives rise to other organs including the trachea, lung, and stomach. Genetic studies have shown that multiple signaling pathways (e.g. Bmp) and transcription factors (e.g. SOX2) are required for the separation of the esophagus from the neighboring respiratory system. Notably, some of these signaling pathways and transcription factors continue to play essential roles in the subsequent morphogenesis of the esophageal epithelium which undergoes a simple columnar-to-stratified squamous conversion. Reactivation of the relevant signaling pathways has also been associated with pathogenesis of esophageal diseases that affect the epithelium and its stem cells in adults. In this review we will summarize these findings. We will also discuss new data regarding the cell-of-origin for the striated and smooth muscles surrounding the esophagus and how they are differentiated from the mesenchyme during development.

Esophageal submucosal gland duct adenoma: a clinicopathological and immunohistochemical study with a review of the literature

Esophageal submucosal gland duct adenoma (ESGDA) is a rare tumor. The clinicopathological features of the ESGDA and its precursor lesion have not been comprehensively evaluated. In this study, we aimed at delineating the clinicopathological features of the ESGDA and cyst formation of the esophageal submucosal gland duct (ESGD), as well as their correlations and clinical implications. We identified three cases of ESGDA and 16 cases of cyst formation of the ESGD among 786 endoscopic mucosal resection specimens over a 7-year period. The median patient age was 58 years with a male predominance. These lesions were small submucosal bulges locating at the lower esophagus with a size no more than 1 cm. The main microscopic changes of these lesions included content retention, multilayered epithelium or papillary folds of the ESGD and inflammatory cell infiltration, acidophilic degeneration, hyperplasia or atrophy of the acini. The included cases generally showed moderate to severe microscopic esophagitis. The ESGDA was mainly consisted by multiple glandular cysts covered by two layers of cells. Immunohistochemical results showed that the luminal duct lining cells and basal cells were positive for CK7 and p63, respectively. Both of the two layer cells were positive for HMWCK and negative for CK20, p53, CDX2, MUC5AC, MUC6, MUC2 and MUC1. The proliferation index was very low (1%). The diagnostic criteria of the ESGDA were proposed and, the differential diagnosis was discussed. Cyst formation of the ESGD is considered to be the precursor lesion of the ESGDA, because they have overlapping clinicopathological features with progressive relationship. In addition, the ESGDA have close connection with advance of the GERD and, probably, an increased risk of carcinoma.

Esophageal intramural pseudodiverticulosis as a diagnostic and therapeutic problem

The article presents the case of a 68-year-old patient with alcohol dependence syndrome, who was admitted, in serious condition, to the Department of Surgery due to esophageal intramural lesions of unclear etiology. The imaging studies showed no signs of transmural perforation of the esophageal wall. Esophagogastroscopy revealed intramural fluid reservoirs and small oval cavities with smooth edges in the esophageal mucosa. The patient was treated conservatively with parenteral nutrition and rehabilitation. Subsequently, the patient was transferred to the intensive care unit because of cardiorespiratory failure. Despite adequate pharmacological treatment, the patient died.

Large Animal Models: The Key to Translational Discovery in Digestive Disease Research

Gastrointestinal disease is a prevalent cause of morbidity and mortality and the use of animal models have been instrumental in studying mechanisms of digestive pathophysiology. As investigators attempt to translate the wealth of basic science information developed from rodent, models, large animal models provide a number of translational advantages. The pig, in particular, is arguably one of the most powerful models of human organ systems, including the gastrointestinal tract. The pig has provided important tools and insight into intestinal ischemia/reperfusion injury, intestinal mucosal repair, as well as new insights into esophageal injury and repair. Porcine model development has taken advantage of the size of the animal, allowing increased surgical and endoscopic access. In addition, cellular tools such as the intestinal porcine epithelial cell line and porcine enteroids are providing the methodology to translate basic science findings using in-depth mechanistic analyses. Further opportunities in porcine digestive disease modeling include developing additional transgenic pig strains. Collectively, porcine models hold great promise for the future of clinically relevant digestive disease research.

Characterization of oncocytes in deep esophageal glands

Deep esophageal glands play a vital role in the protection and regeneration of the esophageal mucosa. Conditions such as gastroesophageal reflux disease and Barrett's esophagus have been associated with a change in the usual glands by oncocytic metaplasia. However, little is known regarding the function of oncocytes or the relevance of this metaplastic change in the human esophagus. We hypothesized that oncocytes of deep esophageal glands also express markers characteristic of a ductal epithelial phenotype because similar oncocytes have been described as part of large ductal epithelial cells in salivary glands. We used immunohistochemical stains to define structural, functional, proliferative, and potential stem/progenitor characteristics of oncocytes. Oncocytes did not express mucins or lysozyme C, two molecules found in mucous cells and used for antimicrobial defense. Oncocytes did not express CK5, a cytokeratin found in myoepithelial cells and basal epithelial cells, but expressed CK7, a cytokeratin found in intralobular ductal epithelial cells and luminal epithelial cells of the main duct. Oncocytes expressed cystic fibrosis transmembrane conductance regulator and sodium/potassium ATPase, ion channels that play a role in bicarbonate secretion. Membrane-bound beta-catenin was detected in oncocytes, but these cells did not express the proliferative marker Ki67. Approximately, a third of oncocytes expressed SOX9 and p63, transcription factors expressed in epithelial progenitor cells in multiple organs. Moreover, oncocytes expressed CD44, a transmembrane Glycoprotein expressed in cancer stem cells. Taken together, our data show that oncocytes express markers of intralobular ductal epithelial cells and luminal epithelial cells of the main duct. Additionally, our observations suggest that oncocytes act as epithelial progenitor cells and play a role in bicarbonate secretion. Since oncocytic metaplasia is associated with conditions of chronic acid injury, it is possible that oncocytes replace the mucous cells in deep esophageal glands (dEG) as an adaptive change to counteract injury from acid reflux. The marker characterization suggests that oncocytes may originate from transdifferentiation of myoepithelial and mucous cells. This transdifferentiation might lead to an overall decrease of mucins production and secretion by the dEG and a subsequent reduction of the protection conferred by the viscoelastic mucous layer.

Integrative Physiology of Fasting

Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting-induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting.

Fundamentals of Neurogastroenterology: Physiology/Motility - Sensation

The fundamental gastrointestinal functions include motility, sensation, absorption, secretion, digestion and intestinal barrier function. Digestion of food and absorption of nutrients normally occurs without conscious perception. Symptoms of functional gastrointestinal disorders are often triggered by meal intake suggesting abnormalities in the physiological processes are involved in the generation of symptoms. In this manuscript, normal physiology and pathophysiology of gastrointestinal function, and the processes underlying symptom generation are critically reviewed. The functions of each anatomical region of the digestive tract are summarized. The pathophysiology of perception, motility, mucosal barrier, and secretion in functional gastrointestinal disorders as well as effects of food, meal intake and microbiota on gastrointestinal motility and sensation are discussed. Genetic mechanisms associated with visceral pain and motor functions in health and functional gastrointestinal disorders are reviewed. Understanding the basis for digestive tract functions is essential to understand dysfunctions in the functional gastrointestinal disorders.

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.

Esophageal development and epithelial homeostasis

The esophagus is a relatively simple organ that evolved to transport food and liquids through the thoracic cavity. It is the only part of the gastrointestinal tract that lacks any metabolic, digestive, or absorptive function. The mucosa of the adult esophagus is covered by a multilayered squamous epithelium with a remarkable similarity to the epithelium of the skin despite the fact that these tissues originate from two different germ layers. Here we review the developmental pathways involved in the establishment of the esophagus and the way these pathways regulate gut-airway separation. We summarize current knowledge of the mechanisms that maintain homeostasis in esophageal epithelial renewal in the adult and the molecular mechanism of the development of Barrett's metaplasia, the precursor lesion to esophageal adenocarcinoma. Finally, we examine the ongoing debate on the hierarchy of esophageal epithelial precursor cells and on the presence or absence of a specific esophageal stem cell population. Together the recent insights into esophageal development and homeostasis suggest that the pathways that establish the esophagus during development also play a role in the maintenance of the adult epithelium. We are beginning to understand how reflux of gastric content and the resulting chronic inflammation can transform the squamous esophageal epithelium to columnar intestinal type metaplasia in Barrett's esophagus.

The immunophenotypic relationship between the submucosal gland unit, columnar metaplasia and squamous islands in the columnar-lined oesophagus

AIMS

To characterize the immunophenotypic relationship between the squamous and the glandular compartments in the oesophagus of patients with columnar-lined oesophagus (CLO).

METHODS AND RESULTS

Eight tissue blocks from three oesophageal resection specimens from patients who underwent oesophagectomy for adenocarcinoma of the oesophagus were selected for immunohistochemical analysis. The markers of intestinal differentiation [CK20, CDX2 and MUC2] were all expressed in the expected pattern, solely in the glandular compartment of the resection specimens. CK4, CK17 and lysozyme were expressed in both the glandular and the squamous compartments. In addition, CK17 expression was found on both the squamous and glandular margins of the squamocolumnar transformation zones and in the submucosal gland (SMG) intraglandular and excretory ducts.

CONCLUSIONS

There is an immunophenotypic relationship between the squamous and the glandular compartments of the CLO, with expression of lysozyme, CK4 and CK17 in both squamous and columnar cells. These overlapping immunophenotypes indicate similar differentiation paths, and link the SMG unit with the columnar metaplasia and the neosquamous islands in CLO. Our findings support the theory of a cellular origin of CLO and neosquamous islands from the SMG unit.

Ductal metaplasia in oesophageal submucosal glands is associated with inflammation and oesophageal adenocarcinoma

AIMS

Recent studies have suggested that oesophageal submucosal gland (ESMG) ducts harbour progenitor cells that may contribute to oesophageal metaplasia. Our objective was to determine whether histological differences exist between the ESMGs of individuals with and without oesophageal adenocarcinoma (EAC).

METHODS AND RESULTS

We performed histological assessment of 343 unique ESMGs from 30 control patients, 24 patients with treatment-naïve high-grade columnar dysplasia (HGD) or EAC, and 23 non-EAC oesophagectomy cases. A gastrointestinal pathologist assessed haematoxylin and eosin-stained ESMG images by using a scoring system that assigns individual ESMG acini to five histological types (mucous, serous, oncocytic, dilated, or ductal metaplastic). In our model, ductal metaplastic acini were more common in patients with HGD/EAC (12.7%) than in controls (3.5%) (P = 0.006). We also identified greater proportions of acini with dilation (21.9%, P < 0.001) and, to a lesser extent, ductal metaplasia (4.3%, P = 0.001) in non-EAC oesophagectomy cases than in controls. Ductal metaplasia tended to occur in areas of mucosal ulceration or tumour.

CONCLUSIONS

We found a clear association between ductal metaplastic ESMG acini and HGD/EAC. Non-EAC cases had dilated acini and some ductal dilation. Because ESMGs and ducts harbour putative progenitor cells, these associations could have significance for understanding the pathogenesis of EAC.

CDX2 protein expression compared to alcian blue staining in the evaluation of esophageal intestinal metaplasia

AIM: To compare the sensitivity and specificity of CDX2 and alcian blue (AB) pH 2.5 staining in identifying esophageal intestinal metaplasia.

METHODS: One hundred and ninty-nine biopsies from 186 patients were retrospectively reviewed and categorized as Barrett’s esophagus (BE) (n = 108); non-Barrett’s esophagus (NBE) (n = 48); columnar blue cells (CB) and esophageal glands (EG) (n = 43). The biopsies were stained with AB and immunostained for CDX2 using a mouse monoclonal antibody from Biogenex (clone CDX2-88) and the Ventana Discovery X automated immunostainer. The positive and negative predictive value of each group was used to determine the predictive power of CDX2 and AB in diagnosing intestinal metaplasia.

RESULTS: All of the 108 BE biopsies (100%) were positive for AB and 102 of them (94.4%) were positive for CDX2. The six BE patients (5.6%) who failed to stain with CDX2 were found to have lost the focus of intestinal metaplasia upon deeper sectioning for immunostaining. Both AB and CDX2 were negative in 43 out of 48 (89.6%) NBE cases. Five NBE patients (10.4%) were falsely positive for AB due to the presence of EG and CB in these biopsies. These cases were all CDX2 negative. In addition, 5 AB negative NBE were found to be CDX2 positive. Based on these results the CDX2 immunostain had similar sensitivity but higher specificity (100% vs about 91%) than AB in detecting intestinal type metaplasia in these samples. Our data shows that CDX2 has a better PPV in detecting intestinal metaplasia as compared to AB (95.6% vs 71.5%, respectively).

CONCLUSION: CDX2 has a better positive predictive value than AB in detecting intestinal metaplasia. CDX2 may be useful when challenged by gastro-esophageal biopsies containing mimikers of BE.

The initial establishment and epithelial morphogenesis of the esophagus: a new model of tracheal-esophageal separation and transition of simple columnar into stratified squamous epithelium in the developing esophagus

The esophagus and trachea are tubular organs that initially share a single common lumen in the anterior foregut. Several models have been proposed to explain how this single-lumen developmental intermediate generates two tubular organs. However, new evidence suggests that these models are not comprehensive. I will first briefly review these models and then propose a novel 'splitting and extension' model based on our in vitro modeling of the foregut separation process. Signaling molecules (e.g., SHHs, WNTs, BMPs) and transcription factors (e.g., NKX2.1 and SOX2) are critical for the separation of the foregut. Intriguingly, some of these molecules continue to play essential roles during the transition of simple columnar into stratified squamous epithelium in the developing esophagus, and they are also closely involved in epithelial maintenance in the adults. Alterations in the levels of these molecules have been associated with the initiation and progression of several esophageal diseases and cancer in adults.

Excitatory and inhibitory enteric innervation of horse lower esophageal sphincter

The lower esophageal sphincter (LES) is a specialized, thickened muscle region with a high resting tone mediated by myogenic and neurogenic mechanisms. During swallowing or belching, the LES undergoes strong inhibitory innervation. In the horse, the LES seems to be organized as a "one-way" structure, enabling only the oral-anal progression of food. We characterized the esophageal and gastric pericardial inhibitory and excitatory intramural neurons immunoreactive (IR) for the enzymes neuronal nitric oxide synthase (nNOS) and choline acetyltransferase. Large percentages of myenteric plexus (MP) and submucosal (SMP) plexus nNOS-IR neurons were observed in the esophagus (72 ± 9 and 69 ± 8 %, respectively) and stomach (57 ± 17 and 45 ± 3 %, respectively). In the esophagus, cholinergic MP and SMP neurons were 29 ± 14 and 65 ± 24 vs. 36 ± 8 and 38 ± 20 % in the stomach, respectively. The high percentage of nitrergic inhibitory motor neurons observed in the caudal esophagus reinforces the role of the enteric nervous system in the horse LES relaxation. These findings might allow an evaluation of whether selective groups of enteric neurons are involved in horse neurological disorders such as megaesophagus, equine dysautonomia, and white lethal foal syndrome.

Necrotizing sialometaplasia-like change of the esophageal submucosal glands is associated with Barrett's esophagus

The esophageal submucosal glands (SMG) protect the squamous epithelium from insults such as gastroesophageal reflux disease by secreting mucins and bicarbonate. We have observed metaplastic changes within the SMG acini that we have termed oncocytic glandular metaplasia (OGM), and necrotizing sialometaplasia-like change (NSMLC). The aim of this study is to evaluate the associated clinicopathological parameters of, and to phenotypically characterize the SMG metaplasias. Esophagectomy specimens were retrospectively assessed on hematoxylin and eosin sections and assigned to either a Barrett's esophagus (BE) or non-BE control group. Clinicopathologic data was collected, and univariate analysis and multivariate logistic regression models were performed to assess the adjusted associations with NSMLC and OGM. Selected cases of SMG metaplasia were characterized. SMG were present in 82 esophagi that met inclusion criteria. On univariate analysis, NSMLC was associated with BE (p = 0.002). There was no relationship between NSMLC and patient age, sex, tumor size, or treatment history. OGM was associated with BE (p = 0.031). No relationship was found between OGM and patient age, sex, or tumor size. On multivariate analysis, BE was independently associated with NSMLC (odds ratio [OR] 4.95, p = 0.003). Treatment history was also independently associated with OGM (p = 0.029), but not NSMLC. Both NSMLC and OGM were non-mucinous ductal type epithelia retaining a p63-smooth muscle actin co-positive myoepithelial cell layer. NSMLC and OGM were present in endoscopic mucosal resection specimens. Our study suggests that SMG metaplasia is primarily a reflux-induced pathology. NSMLC may pose diagnostic dilemmas in resection specimens or when only partially represented in mucosal biopsies or endoscopic resection specimens.

Gastrointestinal HCO3- transport and epithelial protection in the gut: new techniques, transport pathways and regulatory pathways

The concept of a protective alkaline gastric and duodenal mucus layer is a century old, yet it is amazing how much new information on HCO3(-) transport pathways has emerged recently, made possible by the extensive utilization of gene-deleted and transgenic mice and novel techniques to study HCO3(-) transport. This review highlights recent findings regarding the importance of HCO3(-) for mucosal protection of duodenum and other gastrointestinal epithelia against luminal acid and other damaging factors. Recently, methods have been developed to visualize HCO3(-) transport in vivo by assessing the surface pH in the mucus layer, as well as the epithelial pH. New information about HCO3(-) transport pathways, and emerging concepts about the intricate regulatory network that governs duodenal HCO3(-) secretion are described, and new perspectives for drug therapy discussed.

Genetic and cellular mechanisms regulating anterior foregut and esophageal development

Separation of the single anterior foregut tube into the esophagus and trachea involves cell proliferation and differentiation, as well as dynamic changes in cell-cell adhesion and migration. These biological processes are regulated and coordinated at multiple levels through the interplay of the epithelium and mesenchyme. Genetic studies and in vitro modeling have shed light on relevant regulatory networks that include a number of transcription factors and signaling pathways. These signaling molecules exhibit unique expression patterns and play specific functions in their respective territories before the separation process occurs. Disruption of regulatory networks inevitably leads to defective separation and malformation of the trachea and esophagus and results in the formation of a relatively common birth defect, esophageal atresia with or without tracheoesophageal fistula (EA/TEF). Significantly, some of the signaling pathways and transcription factors involved in anterior foregut separation continue to play important roles in the morphogenesis of the individual organs. In this review, we will focus on new findings related to these different developmental processes and discuss them in the context of developmental disorders or birth defects commonly seen in clinics.

Review: Experimental models for Barrett's esophagus and esophageal adenocarcinoma

Several different cell culture systems and laboratory animal models have been used over the years to study Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC). Most of the existing models have key differences with the human esophagus and complex pathogenesis of disease. None of the models offers an ideal system for the complex study of environmental exposure, genetic risk, and prevention strategies. In fact, different model systems may be required to answer different specific research questions about the pathogenesis of BE and EAC. Given the high mortality associated with EAC and the fact that current screening strategies miss most cases of EAC, advances in basic and translational science related to esophageal injury, repair, and carcinogenesis are clearly needed. This review describes several of the existing and potential model systems for BE and EAC with their benefits and disadvantages.

Anatomy and physiology of the esophageal body

The primary role of the esophagus is to propel swallowed food or fluid into the stomach and to prevent or clear gastroesophageal reflux. This function is achieved by an organized pattern that involves a sensory pathway, neural reflexes, and a motor response that includes esophageal tone, peristalsis, and shortening. The motor function of the esophagus is controlled by highly complex voluntary and involuntary mechanisms. There are three different functional areas in the esophagus: the upper esophageal sphincter, the esophageal body, and the LES. This article focused on anatomy and physiology of the esophageal body.

Submucosal glands in the columnar-lined oesophagus: evidence of an association with metaplasia and neosquamous epithelium

AIM

A multipotential stem cell, possibly located in the submucosal gland ducts, has been suggested as the origin of metaplastic mucosa in the oesophagus. The topographic distribution of these glands and their excretory ducts (SMG) within the columnar lined oesophagus (CLO) is largely unknown. The aim of this study was to examine the distribution of SMG in relation to the type of overlying epithelium in patients with CLO.

METHODS AND RESULTS

Seven oesophageal resection specimens were examined histologically in toto. The median frequency of SMG was similar in the metaplastic segments (0.12 SMG/mm) and the normal squamous segments (0.10 SMG/mm). Within the metaplastic segments, the median frequency of SMG beneath the squamous islands was significantly higher than that observed under the columnar lined parts (0.22 versus 0.08 SMG/mm, P = 0.046), There was a strong accumulation of SMG at the squamo-columnar transition zones (0.53 SMG/mm), which was significantly greater than that found in the columnar and squamous parts (P = 0.001 and 0.002, respectively).

CONCLUSIONS

The relative accumulation of SMG beneath squamous islands and the squamo-columnar junctions within the metaplastic segment supports the hypothesis that both metaplastic columnar mucosa and neosquamous epithelium originate from a progenitor in the SMG.

Models for oral uptake of nanoparticles in consumer products

Presently, many consumer products contain nano-sized materials (NMs) to improve material properties, product quality and ease of use. NMs in food additives and in cosmetic articles (e.g., tooth paste) may be taken up by the oral route. As adverse effects of environmental nanoparticles, like ultrafine particles, have been reported, consumers worry about potential risks when using products containing NMs. The review focuses on metal and metal oxide NMs as common additives in tooth paste and in food industry and exposure by the oral route. Testing of NMs for oral exposure is very complex because differences in the diet, in mucus secretion and composition, in pH, in gastrointestinal transit time and in gastrointestinal flora influence NM uptake. Acellular (mucus, saliva) and epithelial layer of the orogastrointestinal barrier are described. Expected exposure doses, interaction of the NMs with mucus and permeation through the epithelium as well as in vivo data are mentioned. The role of in vitro models for the study of parameters relevant for ingested NMs is discussed.

Molecular aspects of esophageal development

The following on molecular aspects of esophageal development contains commentaries on esophageal striated myogenesis and transdifferentiation; conversion from columnar into stratified squamous epithelium in the mouse esophagus; the roles for BMP signaling in the developing esophagus and forestomach; and evidence of a direct conversion from columnar to stratified squamous cells in the developing esophagus.