Ciliated Surface in the Esophagogastric Junction Zone

Xenopus epidermal and endodermal epithelia as models for mucociliary epithelial evolution, disease, and metaplasia

The Xenopus embryonic epidermis is a powerful model to study mucociliary biology, development, and disease. Particularly, the Xenopus system is being used to elucidate signaling pathways, transcription factor functions, and morphogenetic mechanisms regulating cell fate specification, differentiation and cell function. Thereby, Xenopus research has provided significant insights into potential underlying molecular mechanisms for ciliopathies and chronic airway diseases. Recent studies have also established the embryonic epidermis as a model for mucociliary epithelial remodeling, multiciliated cell trans-differentiation, cilia loss, and mucus secretion. Additionally, the tadpole foregut epithelium is lined by a mucociliary epithelium, which shows remarkable features resembling mammalian airway epithelia, including its endodermal origin and a variable cell type composition along the proximal-distal axis. This review aims to summarize the advantages of the Xenopus epidermis for mucociliary epithelial biology and disease modeling. Furthermore, the potential of the foregut epithelium as novel mucociliary model system is being highlighted. Additional perspectives are presented on how to expand the range of diseases that can be modeled in the frog system, including proton pump inhibitor-associated pneumonia as well as metaplasia in epithelial cells of the airway and the gastroesophageal region.

Ciliated columnar epithelium in the esophagus and gastroesophageal junction: A different perspective from study of a North American population

An index case of ciliated columnar epithelium in a gastroesophageal (GE) junction biopsy identified in routine surgical pathology practice struck us as highly unusual. However, pathology literature, mainly from Asian populations, reports ciliated columnar epithelium in up to 40% of tissue samples from the upper GI tract. This was inconsistent with our pathology practice experience, so we initiated a local review of cases at our Canadian centre. 1048 consecutive tissue samples from the esophagus and GE junction were reviewed retrospectively and no ciliated epithelium was identified. This review included 1000× oil immersion microscopy of 22 cases with "multilayered epithelium". In 971 cases verified in prospective surgical pathology practice following identification of the index case, 3 additional cases of ciliated columnar epithelium were identified. The index case had ciliated pseudostratified columnar epithelium, resembling respiratory epithelium, and had strong, diffuse expression of TTF-1 by immunohistochemistry. In the other 3 cases, the cilia were located on the surface of a pseudostratified columnar epithelium, a multilayered epithelium, or a low columnar epithelium, all TTF-1 negative. Over a year later, the index case proved to have arisen from a bronchial-esophageal fistula. The other cases were not associated with a fistula. Our conclusion is that ciliated columnar epithelium is rare in Canadian adults (<0.5% of patients). Ciliated epithelium due to a bronchial-esophageal fistula is exceptional, but something to consider if there is a suspicious clinical picture and TTF-1 expression. Other cases might represent a rare metaplastic phenomenon or remnant from fetal development.

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.

A renewed insight into Barrett's esophagus: comparative histopathological analysis of esophageal columnar metaplasia

Specialized intestinal metaplasia (SIM) is considered as a premalignant condition of the esophagus, but other types of esophageal metaplasia are commonly neglected. A standardized histopathological analysis was focused not only on SIM but also on the presence of metaplastic processes typical of additional glands. A morphological study using standardized histopathological tests was carried out between 2004 and 2007, with biopsies taken from esophageal mucosa of 826 consecutive patients. Mean age and male : female ratio of patients were 55.6 ± 14.7 and 1.1 : 1, respectively. Only 4.1% (n = 34) of all cases proved to have SIM. The remainder of the cases (n = 615; 74.4%) contained cardiac-fundic mucosa without SIM. Some samples exhibited superficial mucous glands, pancreatic acinar metaplasia (PAM), and ciliated metaplasia accounting for 24% (n = 198), 14.9% (n = 123), and 0.2% (n = 2), respectively. SIM was colocalized with superficial mucous glands (103/198 superficial mucous gland cases; P < 0.001). Low-grade dysplasia (n = 51; 6.2%) and high-grade dysplasia (n = 9; 1.1%) were found mainly in SIM (37/51; 9/9; P = 0.071) with male preponderance (3 : 1 at low-grade and 2 : 1 at high-grade dysplasia). PAM was found mainly in cases without dysplasia (103 of 123 pancreatic metaplasias; P < 0.001). SIM alone in the esophagus is rare, and its frequent association with cardiac mucosa-type metaplasia testifies to transition of mucinous-goblet cell through pseudogoblet cells. PAM rather indicates absence of dysplasia, but superficial mucous glands predicts that SIM follows dysplasia.

The normal anatomy around the oesophagogastric junction: a histopathologic view and its correlation with endoscopy

The incidence of primary oesophageal adenocarcinoma in Caucasian men has recently been increasing rapidly. Therefore, primary oesophageal adenocarcinoma, columnar-lined oesophagus (CLO) or Barrett's oesophagus and the normal condition of the lower segment of the oesophagus are currently receiving worldwide attention in the medical field. Precise definitions of the anatomical features of the oesophagogastric junction (OGJ) are essential before accurate assessment of CLO can be made. This article reviews the normal morphological features in the OGJ zone to give a closer insight into the histopathology and endoscopic appearance of the OGJ and CLO. We review definitions of the OGJ, the pattern of the squamocolumnar junction (SCJ), oesophageal cardiac-type glands beneath the squamous epithelium, the normal squamous epithelium, columnar islands in squamous-lined mucosa, squamous islands in CLO and newly reported metaplastic changes in the OGJ zone. The nature of the OGJ is clarified in detail through comparison between endoscopically evident and histological features.

Expression of CDX2 and MUC2 in Barrett's mucosa

Barrett's mucosa is a risk factor for esophageal adenocarcinoma and should be detected at an early stage. It is defined by the presence of columnar epithelium with goblet cells in the lower esophagus, but histologic diagnosis can be uncertain in the absence of distinct goblet cells. We investigated 55 biopsies from 48 patients with endoscopically plain Barrett's esophagus and performed immunohistochemistry for CDX2 and MUC2. In addition, alcian blue (pH 2,5)/PAS staining was done. In histologically unequivocal Barrett's mucosa, nuclear expression of CDX2 in goblet cells and many columnar cells, as well as cytoplasmic positivity for MUC2 in goblet cells, could be observed. Alcian blue (pH 2,5)/PAS stained acidic mucins in goblet cells and in some non-goblet columnar cells. In six cases, no definite Barrett's mucosa was present, and no expression of MUC2 could be observed. In these biopsies, there was granular cytoplasmic and/or focal nuclear staining for CDX2 in non-goblet columnar epithelial cells, indicating their intestinal differentiation. We suggest that this peculiar mucosa is the precursor of unequivocal Barrett's mucosa and would designate it early Barrett's mucosa. Alcian blue for acidic mucins is inconsistent in this epithelium and does not reliably indicate early intestinal differentiation.

On the histogenesis of Barrett's oesophagus and its associated squamous islands: a three-dimensional study of their morphological relationship with native oesophageal gland ducts

Current hypotheses concerning the histogenesis and regression of Barrett's oesophagus are based predominantly on animal models. Our study was formulated to assess, in human tissue, the morphological relationship between oesophageal gland ducts and both Barrett's oesophagus and their associated squamous islands. Serial sections were cut through a total of 46 blocks of archived oesophageal resection tissue containing oesophageal gland ducts underlying Barrett's epithelium. Serial sections were also taken through 15 squamous islands, taken from the same archived tissue, to assess their underlying histology: 21 of the ducts opened onto overlying Barrett's epithelium; in 17 there was a relatively sharp distinction between the two cell types, at the junction, whereas in four there was continuity and a gradual morphological change between the cells of the oesophageal gland ducts and the Barrett's epithelium. All 15 squamous islands sectioned were found to be continuous with an underlying gland duct. This study suggests an interrelationship between Barrett's epithelium and oesophageal gland ducts. More definitively we confirm that squamous islands are universally associated with oesophageal gland duct epithelium. These findings are of fundamental importance for the development of more targeted management strategies for Barrett's oesophagus.