Altered expression of a putative progenitor cell marker DCAMKL1 in the rat gastric mucosa in regeneration, metaplasia and dysplasia

Helicobacter pylori plays a key role in gastric adenocarcinoma induced by spasmolytic polypeptide-expressing metaplasia

Heliobacter pylori (H. pylori), a group 1 human gastric carcinogen, is significantly associated with chronic gastritis, gastric mucosal atrophy, and gastric cancer. Approximately 20% of patients infected with H. pylori develop precancerous lesions, among which metaplasia is the most critical. Except for intestinal metaplasia (IM), which is characterized by goblet cells appearing in the stomach glands, one type of mucous cell metaplasia, spasmolytic polypeptide-expressing metaplasia (SPEM), has attracted much attention. Epidemiological and clinicopathological studies suggest that SPEM may be more strongly linked to gastric adenocarcinoma than IM. SPEM, characterized by abnormal expression of trefoil factor 2, mucin 6, and Griffonia simplicifolia lectin II in the deep glands of the stomach, is caused by acute injury or inflammation. Although it is generally believed that the loss of parietal cells alone is a sufficient and direct cause of SPEM, further in-depth studies have revealed the critical role of immunosignals. There is controversy regarding whether SPEM cells originate from the transdifferentiation of mature chief cells or professional progenitors. SPEM plays a functional role in the repair of gastric epithelial injury. However, chronic inflammation and immune responses caused by H. pylori infection can induce further progression of SPEM to IM, dysplasia, and adenocarcinoma. SPEM cells upregulate the expression of whey acidic protein 4-disulfide core domain protein 2 and CD44 variant 9, which recruit M2 macrophages to the wound. Studies have revealed that interleukin-33, the most significantly upregulated cytokine in macrophages, promotes SPEM toward more advanced metaplasia. Overall, more effort is needed to reveal the specific mechanism of SPEM malignant progression driven by H. pylori infection.

Mist1+ gastric isthmus stem cells are regulated by Wnt5a and expand in response to injury and inflammation in mice

BACKGROUND AND AIMS

The gastric epithelium undergoes continuous turnover. Corpus epithelial stem cells located in the gastric isthmus serve as a source of tissue self-renewal. We recently identified the transcription factor Mist1 as a marker for this corpus stem cell population that can give rise to cancer. The aim here was to investigate the regulation of the Mist1+ stem cells in the response to gastric injury and inflammation.

METHODS

We used Mist1CreERT;R26-Tdtomato mice in two models of injury and inflammation: the acetic acid-induced ulcer and infection with Helicobacter felis. We analysed lineage tracing at both early (7 to 30 days) and late (30 to 90 days) time points. Mist1CreERT;R26-Tdtomato;Lgr5DTR-eGFP mice were used to ablate the corpus basal Lgr5+ cell population. Constitutional and conditional Wnt5a knockout mice were used to investigate the role of Wnt5a in wound repair and lineage tracing from the Mist1+ stem cells.

RESULTS

In both models of gastric injury, Mist1+ isthmus stem cells more rapidly proliferate and trace entire gastric glands compared with the normal state. In regenerating tissue, the number of traced gastric chief cells was significantly reduced, and ablation of Lgr5+ chief cells did not affect Mist1-derived lineage tracing and tissue regeneration. Genetic deletion of Wnt5a impaired proliferation in the gastric isthmus and lineage tracing from Mist1+ stem cells. Similarly, depletion of innate lymphoid cells, the main source of Wnt5a, also resulted in reduced proliferation and Mist1+ isthmus cell tracing.

CONCLUSION

Gastric Mist1+ isthmus cells are the main supplier of regenerated glands and are activated in part through Wnt5a pathway.

Tuft and Cancer Stem Cell Marker DCLK1: A New Target to Enhance Anti-Tumor Immunity in the Tumor Microenvironment

Simple Summary

Doublecortin-like kinase 1 (DCLK1) is a tumor stem cell marker in colon, pancreatic, and potentially other cancers that has received wide attention recently. Aside from its role as a tuft cell marker in normal tissue and as a tumor stem cell marker in cancer, previous studies have demonstrated that silencing DCLK1 functionally reduces stemness, epithelial mesenchymal transition (EMT), and tumorigenesis in cancers. More recently, DCLK1′s role in regulating the inflammatory, pre-cancer, and tumor microenvironment including its ability to modulate immune cell mechanisms has started to come into focus. Importantly, clinically viable therapeutic means of targeting DCLK1 have finally become available in the form of kinase inhibitors, monoclonal antibodies, and chimeric antigen receptor T cells (CAR-T). Herein, we comprehensively review the mechanistic role of DCLK1 in the tumor microenvironment, assess the potential for targeting DCLK1 in colon, pancreatic and renal cancer.

Abstract

Microtubule-associated doublecortin-like kinase 1 (DCLK1) is an accepted marker of tuft cells (TCs) and several kinds of cancer stem cells (CSCs), and emerging evidence suggests that DCLK1-positive TCs participate in the initiation and formation of inflammation-associated cancer. DCLK1-expressing CSCs regulate multiple biological processes in cancer, promote resistance to therapy, and are associated with metastasis. In solid tumor cancers, tumor epithelia, immune cells, cancer-associated fibroblasts, endothelial cells and blood vessels, extracellular matrix, and hypoxia all support a CSC phenotype characterized by drug resistance, recurrence, and metastasis. Recently, studies have shown that DCLK1-positive CSCs are associated with epithelial-mesenchymal transition, angiogenesis, and immune checkpoint. Emerging data concerning targeting DCLK1 with small molecular inhibitors, monoclonal antibodies, and chimeric antigen receptor T-cells shows promising effects on inhibiting tumor growth and regulating the tumor immune microenvironment. Overall, DCLK1 is reaching maturity as an anti-cancer target and therapies directed against it may have potential against CSCs directly, in remodeling the tumor microenvironment, and as immunotherapies.

Loss of Tight Junction Protein Claudin 18 Promotes Progressive Neoplasia Development in Mouse Stomach

BACKGROUND & AIMS

Loss of claudin 18 (CLDN18), a membrane-spanning tight junction protein, occurs during early stages of development of gastric cancer and associates with shorter survival times of patients. We investigated whether loss of CLDN18 occurs in mice that develop intraepithelial neoplasia with invasive glands due to infection with Helicobacter pylori, and whether loss is sufficient to promote the development of similar lesions in mice with or without H pylori infection.

METHODS

We performed immunohistochemical analyses in levels of CLDN18 in archived tissues from B6:129 mice infected with H pylori for 6 to 15 months. We analyzed gastric tissues from B6:129S5-Cldn18tm1Lex/Mmucd mice, in which the CLDN18 gene was disrupted in gastric tissues (CLDN18-knockout mice), or from control mice with a full-length CLDN18 gene (CLDN18+/+; B6:129S5/SvEvBrd) or heterozygous disruption of CLDN18 (CLDN18+/-; B6:129S5/SvEvBrd) that were infected with H pylori SS1 or PMSS1 at 6 weeks of age and tissues collected for analysis at 20 and 30 weeks after infection. Tissues from CLDN18-knockout mice and control mice with full-length CLDN18 gene expression were also analyzed without infection at 7 weeks and 2 years after birth. Tissues from control and CLDN18-knockout mice were analyzed by electron microscopy, stained by conventional methods and analyzed for histopathology, prepared by laser capture microdissection and analyzed by RNAseq, and immunostained for lineage markers, proliferation markers, and stem cell markers and analyzed by super-resolution or conventional confocal microscopy.

RESULTS

CLDN18 had a basolateral rather than apical tight junction localization in gastric epithelial cells. B6:129 mice infected with H pylori, which developed intraepithelial neoplasia with invasive glands, had increasing levels of CLDN18 loss over time compared with uninfected mice. In B6:129 mice infected with H pylori compared with uninfected mice, CLDN18 was first lost from most gastric glands followed by disrupted and reduced expression in the gastric neck and in surface cells. Gastric tissues from CLDN18-knockout mice had low levels of inflammation but increased cell proliferation, expressed markers of intestinalized proliferative spasmolytic polypeptide-expressing metaplasia, and had defects in signal transduction pathways including p53 and STAT signaling by 7 weeks after birth compared with full-length CLDN18 gene control mice. By 20 to 30 weeks after birth, gastric tissues from uninfected CLDN18-knockout mice developed intraepithelial neoplasia that invaded the submucosa; by 2 years, gastric tissues contained large and focally dysplastic polypoid tumors with invasive glands that invaded the serosa.

CONCLUSIONS

H pylori infection of B6:129 mice reduced the expression of CLDN18 early in gastric cancer progression, similar to previous observations from human gastric tissues. CLDN18 regulates cell lineage differentiation and cellular signaling in mouse stomach; CLDN18-knockout mice develop intraepithelial neoplasia and then large and focally dysplastic polypoid tumors in the absence of H pylori infection.

Dclk1-expressing tuft cells: critical modulators of the intestinal niche?

Dclk1-expressing tuft cells constitute a unique intestinal epithelial lineage that is distinct from enterocytes, Paneth cells, goblet cells, and enteroendocrine cells. Tuft cells express taste-related receptors and distinct transcription factors and interact closely with the enteric nervous system, suggesting a chemosensory cell lineage. In addition, recent work has shown that tuft cells interact closely with cells of the immune system, with a critical role in the cellular regulatory network governing responses to luminal parasites. Importantly, ablation of tuft cells severely impairs epithelial proliferation and tissue regeneration after injury, implicating tuft cells in the modulation of epithelial stem/progenitor function. Finally, tuft cells expand during chronic inflammation and in preneoplastic tissues, suggesting a possible early role in inflammation-associated tumorigenesis. Hence, we outline and discuss emerging evidence that strongly supports tuft cells as key regulatory cells in the complex network of the intestinal microenvironment.

Trefoil Factor Peptides and Gastrointestinal Function

Trefoil factor (TFF) peptides, with a 40-amino acid motif and including six conserved cysteine residues that form intramolecular disulfide bonds, are a family of mucin-associated secretory molecules mediating many physiological roles that maintain and restore gastrointestinal (GI) mucosal homeostasis. TFF peptides play important roles in response to GI mucosal injury and inflammation. In response to acute GI mucosal injury, TFF peptides accelerate cell migration to seal the damaged area from luminal contents, whereas chronic inflammation leads to increased TFF expression to prevent further progression of disease. Although much evidence supports the physiological significance of TFF peptides in mucosal defenses, the molecular and cellular mechanisms of TFF peptides in the GI epithelium remain largely unknown. In this review, we summarize the functional roles of TFF1, 2, and 3 and illustrate their action mechanisms, focusing on defense mechanisms in the GI tract.

The Development of Spasmolytic Polypeptide/TFF2-Expressing Metaplasia (SPEM) During Gastric Repair Is Absent in the Aged Stomach

BACKGROUND & AIMS

During aging, physiological changes in the stomach result in more tenuous gastric tissue that is less capable of repairing injury, leading to increased susceptibility to chronic ulceration. Spasmolytic polypeptide/trefoil factor 2-expressing metaplasia (SPEM) is known to emerge after parietal cell loss and during Helicobacter pylori infection, however, its role in gastric ulcer repair is unknown. Therefore, we sought to investigate if SPEM plays a role in epithelial regeneration.

METHODS

Acetic acid ulcers were induced in young (2-3 mo) and aged (18-24 mo) C57BL/6 mice to determine the quality of ulcer repair with advancing age. Yellow chameleon 3.0 mice were used to generate yellow fluorescent protein-expressing organoids for transplantation. Yellow fluorescent protein-positive gastric organoids were transplanted into the submucosa and lumen of the stomach immediately after ulcer induction. Gastric tissue was collected and analyzed to determine the engraftment of organoid-derived cells within the regenerating epithelium.

RESULTS

Wound healing in young mice coincided with the emergence of SPEM within the ulcerated region, a response that was absent in the aged stomach. Although aged mice showed less metaplasia surrounding the ulcerated tissue, organoid-transplanted aged mice showed regenerated gastric glands containing organoid-derived cells. Organoid transplantation in the aged mice led to the emergence of SPEM and gastric regeneration.

CONCLUSIONS

These data show the development of SPEM during gastric repair in response to injury that is absent in the aged stomach. In addition, gastric organoids in an injury/transplantation mouse model promoted gastric regeneration.

Epithelial Regeneration After Gastric Ulceration Causes Prolonged Cell-Type Alterations

BACKGROUND & AIMS

The peptic ulcer heals through a complex process, although the ulcer relapse often occurs several years later after healing. Our hypothesis is that even after visual evidence of healing of gastric ulceration, the regenerated epithelium is aberrant for an extended interval, increasing susceptibility of the regenerated epithelium to damage and further diseases.

METHODS

Gastric ulcers were induced in mice by serosal topical application of acetic acid.

RESULTS

Gastric ulcers induced by acetic acid visually healed within 30 days. However, regenerated epithelial architecture was poor. The gene profile of regenerated tissue was abnormal, indicating increased stem/progenitor cells, deficient differentiated gastric cell types, and deranged cell homeostasis. Despite up-regulation of PDX1 in the regenerated epithelium, no mature antral cell type was observed. Four months after healing, the regenerated epithelium lacks parietal cells, trefoil factor 2 (TFF2) and (sex-determining region Y)-box 9 (SOX9) remain up-regulated deep in the gastric gland, and the Na/H exchanger 2 (a TFF2 effector in gastric healing) remains down-regulated. Gastric ulcer healing was strongly delayed in TFF2 knockout mice, and re-epithelialization was accompanied with mucous metaplasia. After Helicobacter pylori inoculum 30 days after ulceration, we observed that the gastric ulcer selectively relapses at the same site where it originally was induced. Follow-up evaluation at 8 months showed that the relapsed ulcer was not healed in H pylori-infected tissues.

CONCLUSIONS

These findings show that this macroscopically regenerated epithelium has prolonged abnormal cell distribution and is differentially susceptible to subsequent damage by H pylori.

Selective and reversible suppression of intestinal stem cell differentiation by pharmacological inhibition of BET bromodomains

Absorptive and secretory cells of the small intestine are derived from a single population of Lgr5-expressing stem cells. While key genetic pathways required for differentiation into specific lineages have been defined, epigenetic programs contributing to this process remain poorly characterized. Members of the BET family of chromatin adaptors contain tandem bromodomains that mediate binding to acetylated lysines on target proteins to regulate gene expression. In this study, we demonstrate that mice treated with a small molecule inhibitor of BET bromodomains, CPI203, exhibit greater than 90% decrease in tuft and enteroendocrine cells in both crypts and villi of the small intestine, with no changes observed in goblet or Paneth cells. BET bromodomain inhibition did not alter the abundance of Lgr5-expressing stem cells in crypts, but rather exerted its effects on intermediate progenitors, in part through regulation of Ngn3 expression. When BET bromodomain inhibition was combined with the chemotherapeutic gemcitabine, pervasive apoptosis was observed in intestinal crypts, revealing an important role for BET bromodomain activity in intestinal homeostasis. Pharmacological targeting of BET bromodomains defines a novel pathway required for tuft and enteroendocrine differentiation and provides an important tool to further dissect the progression from stem cell to terminally differentiated secretory cell.

Epigenetic changes and alternate promoter usage by human colon cancers for expressing DCLK1-isoforms: Clinical Implications

DCLK1 specifically marks colon/pancreatic cancers in mice, and is expressed by human colon adenocarcinomas (hCRCs). Down-regulation of DCLK1 results in loss of cancer-stem-cells (CSCs), and inhibits spheroidal/xenograft growths from hCRC-cells. The 5'-promoter of DCLK1-gene is reportedly hypermethylated in hCRCs, resulting in loss of expression of DCLK1-transcripts, originating from 5'(α)-promoter (termed DCLK1-L, in here). However, in mouse colon-tumors, 5'-promoter of DCLK1-gene remains unchanged, and DCLK1-L, originating from 5'(α)-promoter, is expressed. We hypothesized that elevated levels of DCLK1-protein in hCRC-cells, may be transcribed/translated from an alternate-promoter. Several in silico and molecular biology approaches were used to test our hypothesis. We report for the first time that majority of hCRCs express short-transcripts of DCLK1 (termed DCLK1-S, in here) from an alternate β-promoter in IntronV of the gene, while normal-colons mainly express DCLK1-L from 5'(α)-promoter. We additionally report an important role of β-catenin and TCF4/LEF binding-sites for activating (α)-promoter, while activated NF-κBp65 (bound to NF-κB-cis-element), activates (β)-promoter in cancer-cells. DCLK1-S expression was examined in a cohort of 92 CRC patients; high-expressors had significantly worse overall-survival compared to low-expressors. Our novel findings' regarding usage of alternate (β)-promoter by hCRCs, suggests that DCLK1-S may represent an important target for preventing/inhibiting colon-cancers, and for eliminating colon-CSCs.

The use of murine-derived fundic organoids in studies of gastric physiology

KEY POINTS

An in vitro approach to study gastric development is primary mouse-derived epithelium cultured as three-dimensional spheroids known as organoids. We have devised two unique gastric fundic-derived organoid cultures: model 1 for the expansion of gastric fundic stem cells, and model 2 for the maintenance of mature cell lineages. Organoids maintained in co-culture with immortalized stomach mesenchymal cells express robust numbers of surface pit, mucous neck, chief, endocrine and parietal cells. Histamine induced a significant decrease in intraluminal pH that was reversed by omeprazole in fundic organoids and indicated functional activity and regulation of parietal cells. Localized photodamage resulted in rapid cell exfoliation coincident with migration of neighbouring cells to the damaged area, sustaining epithelial continuity. We report the use of these models for studies of epithelial cell biology and cell damage and repair.

ABSTRACT

Studies of gastric function and disease have been limited by the lack of extended primary cultures of the epithelium. An in vitro approach to study gastric development is primary mouse-derived antral epithelium cultured as three-dimensional spheroids known as organoids. There have been no reports on the use of organoids for gastric function. We have devised two unique gastric fundic-derived organoid cultures: model 1 for the expansion of gastric fundic stem cells, and model 2 for the maintenance of mature cell lineages. Both models were generated from single glands dissociated from whole fundic tissue and grown in basement membrane matrix (Matrigel) and organoid growth medium. Model 1 enriches for a stem cell-like niche via simple passage of the organoids. Maintained in Matrigel and growth medium, proliferating organoids expressed high levels of stem cell markers CD44 and Lgr5. Model 2 is a system of gastric organoids co-cultured with immortalized stomach mesenchymal cells (ISMCs). Organoids maintained in co-culture with ISMCs express robust numbers of surface pit, mucous neck, chief, endocrine and parietal cells. Histamine induced a significant decrease in intraluminal pH that was reversed by omeprazole in fundic organoids and indicated functional activity and regulation of parietal cells. Localized photodamage resulted in rapid cell exfoliation coincident with migration of neighbouring cells to the damaged area, sustaining epithelial continuity. Thus, we report the use of these models for studies of epithelial cell biology and cell damage and repair.

GM crops and the rat digestive tract: a critical review

The aim of this review is to examine the relationship between genetically modified (GM) crops and health, based on histopathological investigations of the digestive tract in rats. We reviewed published long-term feeding studies of crops containing one or more of three specific traits: herbicide tolerance via the EPSPS gene and insect resistance via cry1Ab or cry3Bb1 genes. These genes are commonly found in commercialised GM crops. Our search found 21 studies for nine (19%) out of the 47 crops approved for human and/or animal consumption. We could find no studies on the other 38 (81%) approved crops. Fourteen out of the 21 studies (67%) were general health assessments of the GM crop on rat health. Most of these studies (76%) were performed after the crop had been approved for human and/or animal consumption, with half of these being published at least nine years after approval. Our review also discovered an inconsistency in methodology and a lack of defined criteria for outcomes that would be considered toxicologically or pathologically significant. In addition, there was a lack of transparency in the methods and results, which made comparisons between the studies difficult. The evidence reviewed here demonstrates an incomplete picture regarding the toxicity (and safety) of GM products consumed by humans and animals. Therefore, each GM product should be assessed on merit, with appropriate studies performed to indicate the level of safety associated with them. Detailed guidelines should be developed which will allow for the generation of comparable and reproducible studies. This will establish a foundation for evidence-based guidelines, to better determine if GM food is safe for human and animal consumption.

Ectopic tissue consisting of a mixture of glandular gastric, intestinal, and exocrine pancreatic tissue in the forestomach of a rat

The development of ectopic gastric, intestinal, or pancreatic tissue in the gastrointestinal tract is extremely rare in rats, although it is fairly common in humans. In this report, we describe an unusual case in which a mixture of different types of ectopic tissue was found in the forestomach of a rat. A solitary white nodular/polypoid structure, which measured 5 mm in size, was detected on the luminal surface of the greater curvature of the forestomach in an 8-week-old female Crl:CD(SD) rat. A histological examination revealed that the lesion contained ectopic glandular gastric tissue, including gastric surface mucous cells, parietal cells, and pyloric gland cells, which was confirmed by immunohistochemistry. Moreover, the lesion also contained villin-positive columnar intestinal absorptive cells and chymotrypsin-positive pancreatic exocrine tissue. To the best of our knowledge, this is the first study to detect a mixture of ectopic glandular gastric, intestinal, and exocrine pancreatic tissue in a rat.

The hyaluronic acid receptor CD44 coordinates normal and metaplastic gastric epithelial progenitor cell proliferation

The stem cell in the isthmus of gastric units continually replenishes the epithelium. Atrophy of acid-secreting parietal cells (PCs) frequently occurs during infection with Helicobacter pylori, predisposing patients to cancer. Atrophy causes increased proliferation of stem cells, yet little is known about how this process is regulated. Here we show that CD44 labels a population of small, undifferentiated cells in the gastric unit isthmus where stem cells are known to reside. Loss of CD44 in vivo results in decreased proliferation of the gastric epithelium. When we induce PC atrophy by Helicobacter infection or tamoxifen treatment, this CD44(+) population expands from the isthmus toward the base of the unit. CD44 blockade during PC atrophy abrogates the expansion. We find that CD44 binds STAT3, and inhibition of either CD44 or STAT3 signaling causes decreased proliferation. Atrophy-induced CD44 expansion depends on pERK, which labels isthmal cells in mice and humans. Our studies delineate an in vivo signaling pathway, ERK → CD44 → STAT3, that regulates normal and atrophy-induced gastric stem/progenitor-cell proliferation. We further show that we can intervene pharmacologically at each signaling step in vivo to modulate proliferation.

Gastric cancer stem cells: a novel therapeutic target

Gastric cancer remains one of the leading causes of global cancer mortality. Multipotent gastric stem cells have been identified in both mouse and human stomachs, and they play an essential role in the self-renewal and homeostasis of gastric mucosa. There are several environmental and genetic factors known to promote gastric cancer. In recent years, numerous in vitro and in vivo studies suggest that gastric cancer may originate from normal stem cells or bone marrow-derived mesenchymal cells, and that gastric tumors contain cancer stem cells. Cancer stem cells are believed to share a common microenvironment with normal niche, which play an important role in gastric cancer and tumor growth. This mini-review presents a brief overview of the recent developments in gastric cancer stem cell research. The knowledge gained by studying cancer stem cells in gastric mucosa will support the development of novel therapeutic strategies for gastric cancer.

Recent progress in histochemistry and cell biology

Studies published in Histochemistry and Cell Biology in the year 2011 represent once more a manifest of established and newly sophisticated techniques being exploited to put tissue- and cell type-specific molecules into a functional context. The review is therefore the Histochemistry and Cell Biology's yearly intention to provide interested readers appropriate summaries of investigations touching the areas of tissue biology, developmental biology, the biology of the immune system, stem cell research, the biology of subcellular compartments, in order to put the message of such studies into natural scientific-/human- and also pathological-relevant correlations.

Current molecular markers for gastric progenitor cells and gastric cancer stem cells

Gastric stem and progenitor cells (GPC) play key roles in the homeostatic renewal of gastric glands and are instrumental in epithelial repair after injury. Until very recently, the existence of GPC could only be inferred by indirect labeling strategies. The last few years have seen significant progress in the identification of biomarkers that allow prospective identification of GPC. The analysis of these unique cell populations is providing new insights into the molecular underpinnings of gastric epithelial homeostasis and repair. Of closely related interest is the potential to identify so-called cancer stem cells, a rare subpopulation of tumor-initiating cells. Here, we review the current useful biomarkers for GPC, including: (a) those that have been demonstrated by lineage tracing to give rise to all gastric cell lineages (e.g., the villin-transgene marker as well as Lgr5); (b) those that give rise to a subset of gastric lineages (e.g., TFF2); (c) markers that recognize cryptic progenitors for metaplasia (e.g., MIST1), and (d) markers that have not yet been analyzed by lineage tracing (e.g., DCKL1/DCAMKL1, CD133/PROM1, and CD44). The study of these markers has been mostly limited to the mouse model, but the hope is that the rapid pace of recent breakthroughs in this animal model will soon lead to a greater understanding of human gastric stem cell biology and to new insights into gastric cancer, the second leading cause of cancer-related death worldwide.

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.

Murine tissue-engineered stomach demonstrates epithelial differentiation

BACKGROUND

Gastric cancer remains the second largest cause of cancer-related mortality worldwide. Postgastrectomy morbidity is considerable and quality of life is poor. Tissue-engineered stomach is a potential replacement solution to restore adequate food reservoir and gastric physiology. In this study, we performed a detailed investigation of the development of tissue-engineered stomach in a mouse model, specifically evaluating epithelial differentiation, proliferation, and the presence of putative stem cell markers.

MATERIALS AND METHODS

Organoid units were isolated from <3 wk-old mouse glandular stomach and seeded onto biodegradable scaffolds. The constructs were implanted into the omentum of adult mice. Implants were harvested at designated time points and analyzed with histology and immunohistochemistry.

RESULTS

Tissue-engineered stomach grows as an expanding sphere with a simple columnar epithelium organized into gastric glands and an adjacent muscularis. The regenerated gastric epithelium demonstrates differentiation of all four cell types: mucous, enteroendocrine, chief, and parietal cells. Tissue-engineered stomach epithelium proliferates at a rate comparable to native glandular stomach and expresses two putative stem cell markers: DCAMKL-1 and Lgr5.

CONCLUSIONS

This study demonstrates the successful generation of tissue-engineered stomach in a mouse model for the first time. Regenerated gastric epithelium is able to appropriately proliferate and differentiate. The generation of murine tissue-engineered stomach is a necessary advance as it provides the transgenic tools required to investigate the molecular and cellular mechanisms of this regenerative process. Delineating the mechanism of how tissue-engineered stomach develops in vivo is an important precursor to its use as a human stomach replacement therapy.

The specific linker phosphorylation of Smad2/3 indicates epithelial stem cells in stomach; particularly increasing in mucosae of Helicobacter-associated gastritis

BACKGROUND

The gastric corpus and antrum are believed to contain epithelial stem cells in the isthmus. However, the lack of useful markers has hindered studies of their origin. We explored whether Smad2/3, phosphorylated at specific linker threonine residues (pSmad2/3L-Thr), could serve as a marker for stem cells.

METHODS

Stomachs, small intestines, and colons from Helicobacter felis-infected and noninfected C57BL/6 mice were examined. Double immunofluorescent staining of pSmad2/3L-Thr with Ki67, cytokeratin 8, or doublecortin and calcium/calmodulin-dependent protein kinase-like-1 (DCAMKL1) was performed, and pSmad2/3L-Thr immunostaining-positive cells were counted. After immunofluorescent staining, we stained the same sections with hematoxylin-eosin and observed these cells under a light microscope.

RESULTS

In infected mice, pSmad2/3L-Thr immunostaining-positive cells were significantly increased in the corpus and antrum compared with those of noninfected mice (p < 0.0001). The number of Ki67 immunostaining-positive cells in the corpus and antrum of infected mice was also much greater than in the noninfected mice. Although pSmad2/3L-Thr immunostaining-positive cells were detected among the Ki67 cells, immunohistochemical co-localization of pSmad2/3L-Thr with Ki67 was never observed. pSmad2/3L-Thr immunostaining-positive cells showed immunohistochemical co-localization with cytokeratin 8, but some of them showed co-localization or adjacent localization with DCAMKL1 immunostaining-positive cells. Under a light microscope, pSmad2/3L-Thr immunostaining-positive cells indicated undifferentiated morphological features and were confirmed in the isthmus. In small intestines and colons, pSmad2/3L-Thr immunostaining-positive cells were detected in specific epithelial cells around crypt bases, where the respective putative stem cells are thought to exist.

CONCLUSIONS

We have identified the significant expression of pSmad2/3L-Thr in specific epithelial cells of the murine stomach and have suggested these cells to be epithelial stem cells.

Inhibition of gastric carcinogenesis by the hormone gastrin is mediated by suppression of TFF1 epigenetic silencing

BACKGROUND & AIMS

Epigenetic alterations have been correlated with field cancerization in human patients, but evidence from experimental models that specific epigenetic changes can initiate cancer has been lacking. Although hormones have been associated with cancer risk, the mechanisms have not been determined. The peptide hormone gastrin exerts a suppressive effect on antral gastric carcinogenesis.

METHODS

N-methyl-N-nitrosourea (MNU)-dependent gastric cancer was investigated in hypergastrinemic (INS-GAS), gastrin-deficient (GAS(-/-)), Tff1-deficient (Tff1(+/-)), and wild-type (WT) mice. Epigenetic alterations of the trefoil factor 1 (TFF1) tumor suppressor gene were evaluated in vitro and in vivo.

RESULTS

Human intestinal-type gastric cancers in the antrum exhibited progressive TFF1 repression and promoter hypermethylation. Mice treated with MNU exhibited a field defect characterized by widespread Tff1 repression associated with histone H3 lysine 9 methylation and H3 deacetylation at the Tff1 promoter in epithelial cells. In MNU-induced advanced cancers, DNA methylation at the Tff1 promoter was observed. Tumor induction and Tff1 repression were increased in MNU-treated mice by Helicobacter infection. Hypergastrinemia suppressed MNU-dependent tumor initiation and progression in a manner that correlated with gene silencing and epigenetic alterations of Tff1. In contrast, homozygous gastrin-deficient and heterozygous Tff1-deficient mice showed enhanced MNU-dependent field defects and cancer initiation compared with WT mice. In gastric cancer cells, gastrin stimulation partially reversed the epigenetic silencing in the TFF1 promoter.

CONCLUSIONS

Initiation of antral gastric cancer is associated with progressive epigenetic silencing of TFF1, which can be suppressed by the hormone gastrin.