Math1/Atoh1 contributes to intestinalization of esophageal keratinocytes by inducing the expression of Muc2 and Keratin-20

Aryl Hydrocarbon Receptor Activation Coordinates Mouse Small Intestinal Epithelial Cell Programming

In the face of mechanical, chemical, microbial, and immunologic pressure, intestinal homeostasis is maintained through balanced cellular turnover, proliferation, differentiation, and self-renewal. Here, we present evidence supporting the role of the aryl hydrocarbon receptor (AHR) in the adaptive reprogramming of small intestinal gene expression, leading to altered proliferation, lineage commitment, and remodeling of the cellular repertoire that comprises the intestinal epithelium to promote intestinal resilience. Ahr gene/protein expression and transcriptional activity exhibit marked proximal^HI to distal^LO and crypt^HI to villi^LO gradients. Genetic ablation of Ahr impairs commitment/differentiation of the secretory Paneth and goblet cell lineages and associated mucin production, restricts expression of secretory/enterocyte differentiation markers, and increases crypt-associated proliferation and villi-associated enterocyte luminal exfoliation. Ahr^-/- mice display a decrease in intestinal barrier function. Ahr^+/+ mice that maintain a diet devoid of AHR ligands intestinally phenocopy Ahr^-/- mice. In contrast, Ahr^+/+ mice exposed to AHR ligands reverse these phenotypes. Ligand-induced AHR transcriptional activity positively correlates with gene expression (Math1, Klf4, Tff3) associated with differentiation of the goblet cell secretory lineage. Math1 was identified as a direct target gene of AHR, a transcription factor critical to the development of goblet cells. These data suggest that dietary cues, relayed through the transcriptional activity of AHR, can reshape the cellular repertoire of the gastrointestinal tract.

The role of bile acid in intestinal metaplasia

A precancerous lesion of gastric cancer (GC), intestinal metaplasia (IM) is a pathological transformation of non-intestinal epithelium into an intestinal-like mucosa. It greatly raises the risk of developing the intestinal type of GC, which is frequently observed in the stomach and esophagus. It is understood that esophageal adenocarcinoma's precursor lesion, chronic gastroesophageal reflux disease (GERD), is what causes Barrett's esophagus (BE), an acquired condition. Recently, Bile acids (BAs), which are one of the compositions of gastric and duodenal contents, have been confirmed that it led to the occurrence and development of BE and gastric intestinal metaplasia (GIM). The objective of the current review is to discuss the mechanism of IM induced by bile acids. This review serves as a foundation for further research aimed at improving the way BE and GIM are currently managed.

Intestinal phenotype is maintained by Atoh1 in the cancer region of intraductal papillary mucinous neoplasm

Intraductal papillary mucinous neoplasm (IPMN) is a precancerous lesion of pancreatic cancer. Although there are 4 types of IPMN, among which intestinal-type IPMN is likely to progress into invasive cancer known as colloid carcinoma, no information regarding the involvement of the intestinal phenotype in the carcinogenesis of IPMN exists. The present study was conducted to explore how the intestinal differentiation system is maintained during the tumor progression of intestinal-type IPMN using surgical resection specimens. Results showed that Atoh1, a critical transcriptional factor for intestinal differentiation toward the secretory lineages of intestinal epithelial cells, was expressed in an invasive-grade IPMN. To determine the function of Atoh1 in pancreatic cancer, we generated a pancreatic ductal adenocarcinoma (PDAC) cell line overexpressing Atoh1. In a xenograft model, we successfully induced an IPMN phenotype in PDAC cells via Atoh1 induction. Finally, for the first time, we discovered that GPA33 is expressed in intestinal-type IPMN, thereby suggesting a novel target for cancer therapy. In conclusion, the intestinal differentiation system might be maintained during tumor progression of intestinal-type IPMN. Further analysis of the function of Atoh1 in IPMN might be useful for understanding the molecular mechanism underlying the malignant potential during the tumor progression of IPMN.

Modeling Esophagitis Using Human Three-Dimensional Organotypic Culture System

Esophagitis, whether caused by acid reflux, allergic responses, graft-versus-host disease, drugs, or infections, is a common condition of the gastrointestinal tract affecting nearly 20% of the US population. The instigating agent typically triggers an inflammatory response. The resulting inflammation is a risk factor for the development of esophageal strictures, Barrett esophagus, and esophageal adenocarcinoma. Research into the pathophysiology of these conditions has been limited by the availability of animal and human model systems. Three-dimensional organotypic tissue culture (OTC) is an innovative three-dimensional multicellular in vitro platform that recapitulates normal esophageal epithelial stratification and differentiation. We hypothesized that this platform can be used to model esophagitis to better understand the interactions between immune cells and the esophageal epithelium. We found that human immune cells remain viable and respond to cytokines when cultured under OTC conditions. The acute inflammatory environment induced in the OTC significantly affected the overlying epithelium, inducing a regenerative response marked by increased cell proliferation and epithelial hyperplasia. Moreover, oxidative stress from the acute inflammation induced DNA damage and strand breaks in epithelial cells, which could be reversed by antioxidant treatment. These findings support the importance of immune cell-mediated esophageal injury in esophagitis and confirms the utility of the OTC platform to characterize the underlying molecular events in esophagitis.

Effect of Hath1 on the proliferation and apoptosis of cutaneous squamous cell carcinoma in vitro

Increasing evidence has demonstrated that the tumor suppressor gene Hath1 is implicated in the development and progression of tumors and is verified to be downregulated in several types of tumor. However, the roles and precise molecular mechanisms of Hath1 in cutaneous squamous cell carcinoma (SCC) remain to be elucidated. In the present study, two approaches were used to investigate the tumor-suppressing effect of Hath1 in cutaneous SCC. Firstly, the effect of inhibiting Hath1 expression with short hairpin RNA (shRNA) on tumor growth and apoptosis was investigated. KUMA5 cells were stably transfected with a plasmid expressing Hath1 shRNA (pGenesil-1-Hath1). Secondly, the anti-tumor effect of Hath1 was investigated in KUMA5 cells following transfection with pcDNA3.1-Hath1. The mRNA and protein expression of Hath1 was detected by reverse transcription quantitative polymerase chain reaction and western blot analysis, respectively. Cell proliferation in vitro was assessed using an MTT assay. Flow cytometry was used to detect cell apoptosis. The results demonstrated that compared with the control groups, the expression of Hath1 was significantly reduced in the KUMA5/pGenesil-1-Hath1 cells and markedly increased in the KUMA5/pcDNA3.1-Hath1 cells. Cell proliferation was markedly increased in the KUMA5/pGen-esil-1-Hath1 cells in a time-dependent manner; however, it was markedly inhibited in the KUMA5/pcDNA3.1-Hath1 cells. Flow cytometry revealed that apoptosis decreased in KUMA5/pGenesil-1-Hath1 cells and increased in KUMA5/pcDNA3.1-Hath1 cells. Downregulation of Hath1 expression promoted the proliferation and reduced the apoptosis of KUMA5 cells. By contrast, overexpression of Hath1 inhibited proliferation and induced the apoptosis of KUMA5 cells. These findings provide possible new strategies and therapeutic targets for the treatment and diagnosis of cutaneous SCC.

Molecular pathogenesis of Barrett esophagus: current evidence

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

Nonviral Reprogramming of Human Wharton's Jelly Cells Reveals Differences Between ATOH1 Homologues

The transcription factor atonal homolog 1 (ATOH1) has multiple homologues that are functionally conserved across species and is responsible for the generation of sensory hair cells. To evaluate potential functional differences between homologues, human and mouse ATOH1 (HATH1 and MATH-1, respectively) were nonvirally delivered to human Wharton's jelly cells (hWJCs) for the first time. Delivery of HATH1 to hWJCs demonstrated superior expression of inner ear hair cell markers and characteristics than delivery of MATH-1. Inhibition of HES1 and HES5 signaling further increased the atonal effect. Transfection of hWJCs with HATH1 DNA, HES1 siRNA, and HES5 siRNA displayed positive identification of key hair cell and support cell markers found in the cochlea, as well as a variety of cell shapes, sizes, and features not native to hair cells, suggesting the need for further examination of other cell types induced by HATH1 expression. In the first side-by-side evaluation of HATH1 and MATH-1 in human cells, substantial differences were observed, suggesting that the two atonal homologues may not be interchangeable in human cells, and artificial expression of HATH1 in hWJCs requires further study. In the future, this line of research may lead to engineered systems that would allow for evaluation of drug ototoxicity or potentially even direct therapeutic use.

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.

Sox9 drives columnar differentiation of esophageal squamous epithelium: a possible role in the pathogenesis of Barrett's esophagus

The molecular mechanism underlying the development of Barrett's esophagus (BE), the precursor to esophageal adenocarcinoma, remains unknown. Our previous work implicated sonic hedgehog (Shh) signaling as a possible driver of BE and suggested that bone morphogenetic protein 4 (Bmp4) and Sox9 were downstream mediators. We have utilized a novel in vivo tissue reconstitution model to investigate the relative roles of Bmp4 and Sox9 in driving metaplasia. Epithelia reconstituted from squamous epithelial cells or empty vector-transduced cells had a stratified squamous phenotype, reminiscent of normal esophagus. Expression of Bmp4 in the stromal compartment activated signaling in the epithelium but did not alter the squamous phenotype. In contrast, expression of Sox9 in squamous epithelial cells induced formation of columnar-like epithelium with expression of the columnar differentiation marker cytokeratin 8 and the intestinal-specific glycoprotein A33. In patient tissue, A33 protein was expressed specifically in BE, but not in normal esophagus. Expression of Cdx2, another putative driver of BE, alone had no effect on reconstitution of a squamous epithelium. Furthermore, epithelium coexpressing Cdx2 and Sox9 had a phenotype similar to epithelium expressing Sox9 alone. Our results demonstrate that Sox9 is sufficient to drive columnar differentiation of squamous epithelium and expression of an intestinal differentiation marker, reminiscent of BE. These data suggest that Shh-mediated expression of Sox9 may be an important early event in the development of BE and that the potential for inhibitors of the hedgehog pathway to be used in the treatment of BE and/or esophageal adenocarcinoma could be tested in the near future.

Notch in the intestine: regulation of homeostasis and pathogenesis

The small and large intestines are tubular organs composed of several tissue types. The columnar epithelium that lines the inner surface of the intestines distinguishes the digestive physiology of each region of the intestine and consists of several distinct cell types that are rapidly and continually renewed by intestinal stem cells that reside near the base of the crypts of Lieberkühn. Notch signaling controls the fate of intestinal stem cells by regulating the expression of Hes genes and by repressing Atoh1. Alternate models of Notch pathway control of cell fate determination are presented. Roles for Notch signaling in development of the intestine, including mesenchymal and neural cells, are discussed. The oncogenic activities of Notch in colorectal cancer, as well as the tumor suppressive activities of Atoh1, are reviewed. Therapeutic targeting of the Notch pathway in colorectal cancers is discussed, along with potential caveats.