Aberrant expression of TTF-1 and forkhead factor HFH-4 in atrophic gastritis and ciliated metaplasia suggests gastric broncho-pulmonary transdetermination

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.

Sonic hedgehog signaling in epithelial tissue development

The Sonic hedgehog (SHH) signaling pathway is essential for embryonic development and tissue regeneration. The dysfunction of SHH pathway is involved in a variety of diseases, including cancer, birth defects, and other diseases. Here we reviewed recent studies on main molecules involved in the SHH signaling pathway, specifically focused on their function in epithelial tissue and appendages development, including epidermis, touch dome, hair, sebaceous gland, mammary gland, tooth, nail, gastric epithelium, and intestinal epithelium. The advance in understanding the SHH signaling pathway will give us more clues to the mechanisms of tissue repair and regeneration, as well as the development of new treatment for diseases related to dysregulation of SHH signaling pathway.

A high-fat diet regulates gastrin and acid secretion through primary cilia

The role of primary cilia in the gastrointestinal tract has not been examined. Here we report the presence of primary cilia on gastric endocrine cells producing gastrin, ghrelin, and somatostatin (Sst), hormones regulated by food intake. During eating, cilia in the gastric antrum decreased, whereas gastric acid and circulating gastrin increased. Mice fed high-fat chow showed a delayed decrease in antral cilia, increased plasma gastrin, and gastric acidity. Mice fed high-fat chow for 3 wk showed lower cilia numbers and acid but higher gastrin levels than mice fed a standard diet, suggesting that fat affects gastric physiology. Ex vivo experiments showed that cilia in the corpus responded to acid and distension, whereas cilia in the antrum responded to food. To analyze the role of gastric cilia, we conditionally deleted the intraflagellar transport protein Ift88 (Ift88(-/fl)). In fed Ift88(-/fl) mice, gastrin levels were higher, and gastric acidity was lower. Moreover, gastrin and Sst gene expression did not change in response to food as in controls. At 8 mo, Ift88(-/fl) mice developed foveolar hyperplasia, hypergastrinemia, and hypochlorhydria associated with endocrine dysfunction. Our results show that components of food (fat) are sensed by antral cilia on endocrine cells, which modulates gastrin secretion and gastric acidity.

Gastric tuft cells express DCLK1 and are expanded in hyperplasia

Epithelial tuft cells are named after their characteristic microtubule bundles located at the cell apex where these are exposed to the luminal environment. As such, tuft cells are found in multiple organs, including the gastrointestinal (GI) tract where the apical "tuft" is hypothesized to detect and transmit environmental signals. Thus, the goal of our study was to characterize gastric tuft cells during GI tract development, then subsequently in the normal and metaplastic adult stomach. GI tracts from mouse embryos, and newborn and postnatal mice were analyzed. Tuft cells were identified by immunohistochemistry using acetylated-α-tubulin (acTub) antibody to detect the microtubule bundle. Additional tuft cell markers, e.g., doublecortin-like kinase 1 (DCLK1), were used to co-localize with acTub. Tuft cells were quantified in human gastric tissue arrays and in mouse stomachs with or without inflammation. In the developing intestine, tuft cells in both the crypts and villi expressed all markers by E18.5. In the stomach, acTub co-localized with DCLK1 and other established tuft cell markers by E18.5 in the antrum, but not until postnatal day 7 in the corpus, with the highest density of tuft cells clustered at the forestomach ridge. Tuft cell numbers increased in hyperplastic human and mouse stomachs. In the adult GI tract, the tuft cell marker acTub co-expressed with DCKL1 and chemosensory markers, e.g.,TRPM5. In summary, tuft cells appear in the gastric antrum and intestine at E18.5, but their maximal numbers in the corpus are not achieved until after weaning. Tuft cell numbers increase with inflammation, hyperplasia, and metaplasia.

Biphasic low-grade nasopharyngeal papillary adenocarcinoma with a prominent spindle cell component: report of a case localized to the posterior nasal septum

A case (female, 39 years of) of thyroid-like nasopharyngeal low-grade papillary adenocarcinoma with a significant spindle cell component is presented. The tumor was located on the posterior nasal septum. The spindle cells displayed nuclear features very much similar to the epithelial component and the two cell types merged imperceptibly. Immunohistochemically, the neoplastic cells (including the spindle cell component) were strongly and diffusely positive for TTF-1, cytokeratins (AE1-3), cytokeratin 19 and vimentin. C-kit immunohistochemistry showed diffuse mild to moderate membranous positivity with focal areas displaying moderate to strong immunoreactivity. EMA was strongly positive in the epithelial component with membranous and cytoplasmic reactivity whereas the spindle cell component was weakly although diffusely positive. Carcinoembryonic antigen, calcitonin, chromogranin A, S100-protein, thyroglobulin, cdx2 and p63 were negative. The proliferative activity (Mib-1/Ki-67) was low; 3-4%. In the molecular genetic study we found no mutations at position 1799 (exon 15) in the BRAF-gene, (BRAFV600E) or in exons 9 and 11 of the KIT-gene.

Comparison of thyroid transcription factor-1 expression by 2 monoclonal antibodies in pulmonary and nonpulmonary primary tumors

Thyroid transcription factor-1 (TTF-1) is a transcription factor that plays a role in the development and physiology of the thyroid and lungs. Expression of TTF-1 is used as a marker of lung and thyroid clinically. Commercially available clones of TTF-1 monoclonal antibodies, 8G7G3/1 and SPT24, have been reported to have different sensitivities for the detection of neoplasms of different origins. Although they are used extensively in daily practice, a comprehensive comparative study of these antibodies in a wide variety of neoplasms is lacking. We examined TTF-1 expression in primary tumors of the lung, prostrate, pancreas, stomach, salivary glands, breast, bladder, colon, and squamous cell carcinoma of the head and neck and compared the results obtained with both TTF-1 clones. The SPT24 clone detected more primary lung tumors of all histologic subtypes. Importantly, the SPT24 clone detected a significantly higher number of squamous cell carcinomas and carcinoid tumors of the lung. Among nonpulmonary primary tumors, a significant number of invasive urothelial carcinoma of the bladder (5.1%) was TTF-1 positive. In addition, a small proportion of prostate (1.2%), stomach (0.9%), salivary gland (1.8%), and colon (2.5%) carcinomas were positive with both clones. Of note, both clones stained the same nonpulmonary tumors with similar intensity and distribution. Carcinomas of the pancreas, breast, and squamous cell carcinomas of the head and neck were negative with both clones. In summary, the SPT24 clone detected a higher number of pulmonary non-small cell tumors of all histologic subtypes whereas both clones stained a similar proportion of nonpulmonary tumors.

Minireview: beta-cell replacement therapy for diabetes in the 21st century: manipulation of cell fate by directed differentiation

Pancreatic beta-cell failure underlies type 1 diabetes; it also contributes in an essential way to type 2 diabetes. beta-Cell replacement is an important component of any cure for diabetes. The current options of islet and pancreas transplantation are not satisfactory as definitive forms of therapy. Here, we review strategies for induced de novo pancreatic beta-cell formation, which depend on the targeted differentiation of cells into pancreatic beta-cells. With this objective in mind, one can manipulate the fate of three different types of cells: 1) from terminally differentiated cells, e.g. exocrine pancreatic cells, into beta-cells; 2) from multipotent adult stem cells, e.g. hepatic oval cells, into pancreatic islets; and 3) from pluripotent stem cells, e.g. embryonic stem cells and induced pluripotent stem cells, into beta-cells. We will examine the pros and cons of each strategy as well as the hurdles that must be overcome before these approaches to generate new beta-cells will be ready for clinical application.

Neurogenin3 is sufficient for transdetermination of hepatic progenitor cells into neo-islets in vivo but not transdifferentiation of hepatocytes

The transcription factor Neurogenin3 (Ngn3) is required for islet-cell type specification. Here, we show that hepatic gene transfer of Ngn3 transiently induces insulin in terminally differentiated hepatocytes but fails to transdifferentiate them, i.e., switch their lineage into islet cells. However, Ngn3 leads to long-term diabetes reversal in mice due to the emergence of periportal islet-like cell clusters. These neo-islets display glycemia-regulated insulin, beta-cell-specific transcripts, and an islet-specific transcription cascade, and they produce all four major islet hormones. They appear to arise from hepatic progenitor cells, most likely endoderm-derived oval cells. Thus, transfer of a single lineage-defining transcription factor, Ngn3, is sufficient to induce cell-lineage switching from a hepatic to an islet lineage in these progenitor cells, a process consistent with transdetermination, i.e, lineage switching in lineage-determined, but not terminally differentiated, cells. This paradigm of induced transdetermination of receptive progenitor cells in vivo may be generally applicable to therapeutic organogenesis for multiple diseases, including diabetes.

Signaling meets chromatin during tissue regeneration in Drosophila

As transcription programs become stabilized in fate-determined cells by progressive patterning of chromatin structures, cells lose their plasticity and the ability to freely modify their identity in response to changing developmental cues. By contrast, stem cells maintain this flexibility, enabling them to embark on different determination pathways. However, regeneration of tissue requires an exception because determined cells are forced to switch their transcription programs to reconstruct the missing tissue. In Drosophila, proliferating cells in the regenerating imaginal discs can even switch to a new disc identity. New studies show that the increased plasticity observed during regeneration results from the action of multiple signaling pathways on chromatin malleability, cell-cycle profiles, and expression of 'stemness' genes. Understanding how signaling pathways can integrate to switch determined cells into multipotent cells has a great medical potential, especially in the field of tissue engineering and remodeling.

Ciliated hepatic cyst without smooth muscle layer: a variant of ciliated hepatic foregut cyst?

The ciliated hepatic foregut cyst (CHFC) is a rare lesion that may arise from remnants of the embryonic foregut. Its wall is lined by pseudostratified ciliated columnar epithelium, and is characterized by the presence of bundles of smooth muscle. Herein is presented two cases of ciliated hepatic cyst without smooth muscle layer. One case was an incidental autopsy finding, and the other was a surgically resected cystic lesion of the liver. Both cysts were <2.0 cm in diameter, and were located subcapusularly in the medial segment (S4) of the liver. The histological appearance of the two cases was identical. They had an epithelial lining of ciliated pseudostratified cells with occasional goblet cells, and lacked a smooth muscle layer, as shown by the actin immunostaining. The lining epithelium contained cells positive for immunohistochemical staining of surfactant apoprotein A, suggesting the embryonic foregut origin of the cysts and differentiation toward bronchiolar structures, rather than ciliated metaplasia of the epithelium of the simple (cholangiogenic) cyst. It is considered that ciliated hepatic cysts of the present case are a rare histological variant of CHFC where the smooth muscle layer is inconspicuous or absent.