Fetal rat glandular stomach epithelial cells differentiate into surface mucous cells which express cathepsin E in the absence of mesenchymal cells in primary culture

Malabaricone C Attenuates Nonsteroidal Anti-Inflammatory Drug-Induced Gastric Ulceration by Decreasing Oxidative/Nitrative Stress and Inflammation and Promoting Angiogenic Autohealing

Aims: Nonsteroidal anti-inflammatory drugs (NSAIDs), among the most commonly used drugs worldwide, are associated with gastrointestinal (GI) complications that severely limit the clinical utility of this essential class of pain medications. Here, we mechanistically dissect the protective impact of a natural product, malabaricone C (Mal C), on NSAID-induced gastropathy. Results: Mal C dose dependently diminished erosion of the stomach lining and inflammation in mice treated with NSAIDs with the protective impact translating to improvement in survival. By decreasing oxidative and nitrative stress, Mal C treatment prevented NSAID-induced mitochondrial dysfunction and cell death; nuclear factor κ-light-chain enhancer of activated B cell induction, release of proinflammatory cytokines and neutrophil infiltration; and disruptions in the vascular endothelial growth factor/endostatin balance that contributes to mucosal autohealing. Importantly, Mal C failed to impact the therapeutic anti-inflammatory properties of multiple NSAIDs in a model of acute inflammation. In all assays tested, Mal C proved as or more efficacious than the current first-line therapy for NSAID-dependent GI complications, the proton pump inhibitor omeprazole. Innovation: Given that omeprazole-mediated prophylaxis is, itself, associated with a shift in NSAID-driven GI complications from the upper GI to the lower GI system, there is a clear and present need for novel therapeutics aimed at ameliorating NSAID-induced gastropathy. Mal C provided significant protection against NSAID-induced gastric ulcerations impacting multiple critical signaling cascades contributing to inflammation, cell loss, extracellular matrix degradation, and angiogenic autohealing. Conclusion: Thus, Mal C represents a viable lead compound for the development of novel gastroprotective agents.

Isolation and functional studies of human fetal gastric epithelium in primary culture

Our understanding of gastric epithelial physiology in man is limited by the absence of normal or appropriate cancer cell lines that could serve as an in vitro model. Research mostly relied on primary culture of gastric epithelial cells of animal species, enriched with surface mucous cells, and devoid of glandular zymogenic chief cells. We successfully applied a new nonenzymatic procedure using Matrisperse Cell Recovery Solution to dissociate the entire epithelium from human fetal stomach. Cultures were generated by seeding multicellular aggregates prepared by mechanical fragmentation. We further demonstrate that this simple and convenient technique allows for the maintenance of heterogenous gastric epithelial primary cultures on plastic without a biological matrix as well as the persistence of viable chief cells able to synthesize and secrete gastric digestive enzymes, i.e., pepsinogen and gastric lipase. In wounding experiments, epithelial restitution occurred in serum-reduced conditions and was modulated by exogenous agents. This culture system is thus representative of the foveolus-gland axis and offers new perspectives to establish the influence of individual growth factors and extracellular matrix components as well as their combinatory effects on gastric epithelium homeostasis.

Impaired gastric gland differentiation in Peutz-Jeghers syndrome

Gastrointestinal hamartomatous polyps in the Peutz-Jeghers cancer predisposition syndrome and its mouse model (Lkb1(+/-)) are presumed to contain all cell types native to the site of their occurrence. This study aimed to explore the pathogenesis of Peutz-Jeghers syndrome polyposis by characterizing cell types and differentiation of the epithelium of gastric polyps and predisposed mucosa. Both antral and fundic polyps were characterized by a deficit of pepsinogen C-expressing differentiated gland cells (antral gland, mucopeptic, and chief cells); in large fundic polyps, parietal cells were also absent. Gland cell loss was associated with an increase in precursor neck cells, an expansion of the proliferative zone, and an increase in smooth muscle alpha-actin expressing myofibroblasts in the polyp stroma. Lack of pepsinogen C-positive gland cells identified incipient polyps, and even the unaffected mucosa of young predisposed mice displayed an increase in pepsinogen C negative glands (25%; P = 0045). In addition, in small intestinal polyps, gland cell differentiation was defective, with the absence of Paneth cells. There were no signs of metaplastic differentiation in any of the tissues studied, and both the gastric and small intestinal defects were seen in Lkb1(+/-) mice, as well as polyps from patients with Peutz-Jeghers syndrome. These results identify impaired epithelial differentiation as the earliest pathological sign likely to contribute to tumorigenesis in individuals with inherited Lkb1 mutations.

In vitro differentiation of Runx3-/- p53-/- gastric epithelial cells into intestinal type cells

We have reported that a lack of RUNX3 function is causally associated with gastric carcinogenesis. We have also presented evidence that loss of Runx3 may be related to the genesis of intestinal metaplasia because expression of RUNX3 is reduced in some intestinal metaplasias, and some Runx3(-/-)p53(-/-) gastric epithelial cells differentiate into intestinal type cells in vivo. Recently several reports have indicated that blood cells play important roles in the gastric carcinogenesis. In the present study, we therefore examined whether Runx3(-/-)p53(-/-) gastric epithelial cells differentiate autonomously into intestinal type cells, or whether the presence of other cells is necessary for the differentiation in vitro. When Runx3(-/-)p53(-/-) gastric epithelial cells were cultured with collagen gels, they did not exhibit any morphogenesis and differentiated poorly. When cultured with fetal mouse gastric mesenchymes, the cells formed glandular structures and differentiated into surface mucous cells, but differentiation of intestinal type cells was never observed. When cultured with Matrigel, the cells formed glandular structures, and some cells differentiated into intestinal type cells in vitro. Reverse transcription-polymerase chain reaction analysis showed that the cells expressed stomach-specific genes, and their levels decreased gradually during the culture. The cells expressed some intestine-specific genes weakly at the start of culture, and their levels were increased with time in culture. We therefore conclude that Runx3(-/-)p53(-/-) gastric epithelial cells differentiate into intestinal type cells in combination with Matrigel in the absence of other cell types. Extracellular matrix, not blood cells, may play a role in the genesis of intestinal metaplasia.

Endothelin-3 controls growth of colonic epithelial cells by mediating epithelial-mesenchymal interaction

It has been repeatedly reported that endothelin-3 (ET-3) is expressed by gastrointestinal mesenchymes, and that paracrine signaling between ET-3 and its receptor plays an essential role in controlling differentiation of the enteric nervous system in the gut, especially in the colon. However it remains to be solved whether ET-3 plays a role in regulating the growth of gastrointestinal epithelial cells. We have previously reported culture systems for forestomach, glandular stomach and duodenal epithelial cells, but a system for colonic epithelial cells has not been established. In the present study, we examined optimal culture conditions for colonic epithelial cells, and examined whether ET-3 affects the growth of gastrointestinal epithelial cells, with special reference to colonic cells. We found that ET-3 dose-dependently and region-specifically stimulated their growth in primary culture: colonic epithelial cells were most responsive, followed by duodenal and glandular stomach epithelial cells. Reverse transcription-polymerase chain reaction analysis showed that ET-3 and a receptor for ET-3 were expressed by both colonic mesenchymes and epithelia, but the levels were much higher in mesenchymes than in epithelia. These results suggest that ET-3 plays an important role in the growth control of colonic epithelial cells, possibly by mediating epithelial-mesenchymal interactions.

Runx3-/- gastric epithelial cells differentiate into intestinal type cells

We have previously reported that Runx3, a runt domain transcription factor, is a major growth regulator of gastric epithelial cells, that a lack of RUNX3 function is causally related to the genesis and progression of human gastric cancer, and that expression of RUNX3 is greatly reduced in intestinal metaplasias in human stomachs. Here we examined the differentiation of Runx3-/- mouse gastric epithelial cells and found that some cells differentiated into intestinal type cells, which expressed Cdx2, a transcription factor that has been shown to induce intestinal metaplasia in transgenic mice. Differentiation of intestinal type cells was not found in culture of Runx3+/+ gastric epithelial cells. These results suggest that gastric epithelial cells can differentiate into intestinal type cells, probably due to expression of Cdx2 in them when the function of Runx3 is impaired. The relationship between loss of function of Runx3, formation of intestinal metaplasia, and gastric cancer was discussed.

Mice deficient in protein tyrosine phosphatase receptor type Z are resistant to gastric ulcer induction by VacA of Helicobacter pylori

The vacuolating cytotoxin VacA produced by Helicobacter pylori causes massive cellular vacuolation in vitro and gastric tissue damage in vivo, leading to gastric ulcers, when administered intragastrically. Here we report that mice deficient in protein tyrosine phosphatase receptor type Z (Ptprz, also called PTP-zeta or RPTP-beta, encoded by Ptprz) do not show mucosal damage by VacA, although VacA is incorporated into the gastric epithelial cells to the same extent as in wild-type mice. Primary cultures of gastric epithelial cells from Ptprz+/+ and Ptprz-/- mice also showed similar incorporation of VacA, cellular vacuolation and reduction in cellular proliferation, but only Ptprz+/+ cells showed marked detachment from a reconstituted basement membrane 24 h after treatment with VacA. VacA bound to Ptprz, and the levels of tyrosine phosphorylation of the G protein-coupled receptor kinase-interactor 1 (Git1), a Ptprz substrate, were higher after treatment with VacA, indicating that VacA behaves as a ligand for Ptprz. Furthermore, pleiotrophin (PTN), an endogenous ligand of Ptprz, also induced gastritis specifically in Ptprz+/+ mice when administered orally. Taken together, these data indicate that erroneous Ptprz signaling induces gastric ulcers.

Causal relationship between the loss of RUNX3 expression and gastric cancer

Runx3/Pebp2alphaC null mouse gastric mucosa exhibits hyperplasias due to stimulated proliferation and suppressed apoptosis in epithelial cells, and the cells are resistant to growth-inhibitory and apoptosis-inducing action of TGF-beta, indicating that Runx3 is a major growth regulator of gastric epithelial cells. Between 45% and 60% of human gastric cancer cells do not significantly express RUNX3 due to hemizygous deletion and hypermethylation of the RUNX3 promoter region. Tumorigenicity of human gastric cancer cell lines in nude mice was inversely related to their level of RUNX3 expression, and a mutation (R122C) occurring within the conserved Runt domain abolished the tumor-suppressive effect of RUNX3, suggesting that a lack of RUNX3 function is causally related to the genesis and progression of human gastric cancer.

Specific localization of an inwardly rectifying K(+) channel, Kir4.1, at the apical membrane of rat gastric parietal cells; its possible involvement in K(+) recycling for the H(+)-K(+)-pump

Hydrochloric acid (HCl) is produced in parietal cells of gastric epithelium by a H(+)-K(+) pump. Protons are secreted into the gastric lumen in exchange for K(+) by the action of the H(+)-K(+)-ATPase. Luminal K(+) is essential for the operation of the pump and is thought to be supplied by unidentified K(+) channels localized at the apical membrane of parietal cells. In this study, we showed that histamine- and carbachol-induced acid secretion from isolated parietal cells monitored by intracellular accumulation of aminopyrine was depressed by Ba(2+), an inhibitor of inwardly rectifying K(+) channels. Among members of the inwardly rectifying K(+) channel family, we found with reverse transcriptase-polymerase chain reaction analyses that Kir4.1, Kir4.2 and Kir7.1 were expressed in rat gastric mucosa. With immunohistochemical analyses, Kir4.1 was found to be expressed in gastric parietal cells and localized specifically at their apical membrane. The current flowing through Kir4.1 channel expressed in HEK293T cells was not affected by reduction of extracellular pH from 7.4 to 3. These results suggest that Kir4.1 may be involved in the K(+) recycling pathway in the apical membrane which is required for activation of the H(+)-K(+) pump in gastric parietal cells.

Gastrin stimulates the growth of gastric pit cell precursors by inducing its own receptors

Gastrin/CCK-B receptors (CCKB-Rs) are present on parietal and enterochromaffin-like cells in the gastric mucosa but not on pit cells in the proliferative zone. Because serum gastrin levels are well correlated with the growth of the gastric pit, we examined whether pit precursor cells express CCKB-Rs using hypergastrinemic transgenic mice and a mouse pit precursor cell line, GSM06. In situ hybridization indicated that CCKB-R mRNA was limited to the lower one-third of the mucosa in control mice, whereas it was faintly distributed along the mid- to low glandular region in the hypergastrinemic transgenic mouse mucosa. CCKB-R-positive midglandular cells appear to have a pit cell lineage; therefore, GSM06 cells were used for an [(125)I]gastrin binding study. [(125)I]gastrin bound to the membrane fraction of the GSM06 cells when precultured with gastrin. Gastrin dose dependently induced CCKB-R expression in GSM06 cells and stimulated their growth. Thus these findings suggest that gastrin directly stimulates the growth of the pit cell lineage by inducing its own receptor in pit cell precursors.

Pre-gut endoderm of chick embryos is regionalized by 1.5 days of development

In this study, we set out to test the ability of endoderm from 1.5-day-old chick embryos (just before digestive tube formation) to develop region-specific characteristics when cultured heterotopically. Various parts of the 1.5-day endoderm were cultured in combination with the flank somatic mesoderm of 3- to 3.5-day chick embryos, and these cultures were analyzed for the expression of several transcription factors and the differentiation of the endoderm. By 1.5 days of normal development, the transcription factors, which are expressed in specific digestive organs, cSox2, CdxA, and cHoxb9/a13 were already expressed in the endodermal cells of the presumptive areas of their later expression domains. When 1.5-day pre-gut endoderm was cultured for 14-15 days, it showed specific differentiation into appropriate organ structures. In general, the more anterior part of the pre-gut endoderm formed the more rostral digestive organ structures while the posterior part became the caudal gut. The differentiation of these regions of endoderm matches their normal fate as recently elucidated (Matsushita [1996a] Rouxs Arch. Dev. Biol. 205:225-231; Matsushita [1999] Dev. Growth Differ. 41:313-319). Expression of cSox2, CdxA, and cHoxb9/a13 in endoderm cultured for 4-5 days is also consistent with their normal fate. Thus, each part of the pre-gut endoderm appears to be already regionally committed to some extent, in accordance with its fate by 1.5 days of development.

Establishment of culture systems of human gastric epithelium for the study of pepsinogen and gastric lipase synthesis and secretion

A main purpose of gastric secretion pertains to the digestion of dietary proteins and involves the release of pepsinogens by the fundic and antral mucosa. Over the last decade, data on human gastric physiology has expanded to equally include a significant role in fat digestion. Characteristics of human gastric lipase (HGL) such as optimum acid pH, resistance to proteolysis and non requirement of bile salts or cofactors, are advantageous in gastric lipolysis. Furthermore, the importance of HGL increases in the context of perinatal physiology and pathological situations where secretion of HGL could compensate, to some extent the depressed pancreatic activities. It is therefore important to understand the regulatory mechanisms involved in the synthesis and secretion of human gastric digestive enzymes. The establishment of an organ culture technique as well as a novel primary culture system of human gastric epithelium permitted us to demonstrate that Pg5 and HGL are colocalized in human chief cells and both digestive enzymes are efficiently synthesized and secreted in explants and primary cultures. Pepsin activity rises at the cellular level while its secretion remains constant. In contrast, cellular lipase activity drastically diminishes while being preferentially secreted. This nonparallelism supports the concept that Pg5 and HGL are differently regulated in culture. Furthermore, EGF downregulates HGL expression at the mRNA level via the p42/44(MAPK) pathway without affecting Pg5. Future studies should be designed to fully understand the cellular and molecular mechanisms involved in regulating HGL activity in normal and pathological conditions.

A new primary culture system representative of the human gastric epithelium

The gastric pit-gland unit is a highly dynamic and compartimentalized structure which assumes important key functions such as acid secretion, digestion of dietary proteins and triglycerides, protection, and epithelial restitution following injury. However, in vitro models representative of the intact gastric epithelium are still lacking. The current study was undertaken to investigate the possibility of generating such primary cultures from human fetal stomach. The use of Matrisperse, a nonenzymatic solution, allowed complete dissociation of the epithelial layer and the maintenance for at least 7 days of all gastric epithelial cell types in primary culture on plastic. Indirect immunofluorescence and Western blot analyses confirmed the purity of epithelial cultures, composed of 60% mucus-secreting cells, 25% zymogenic chief cells, 5% parietal cells, and a small proportion of mitotic precursors. Their functionality was demonstrated by the presence of zonulae occludens and adherens at cell to cell contacts, [(3)H]thymidine incorporation, Periodic acid Schiff staining, and expression of growth factor receptors (EGF/TGFalpha, IGF1, HGF, KGF), gastric H(+)/K(+)-ATPase, pepsinogen (Pg5), and human gastric lipase (HGL). Chief cells were able to produce and secrete both Pg5 and HGL and to respond to EGF treatment. In conclusion, we developed a new primary culture system of human gastric epithelium characterized for the first time by the absence of added matrix and the maintenance of functional chief cells. It represents an experimental breakthrough that will serve applications in investigating the actions of hormones, mesenchymal growth factors, and basement membrane proteins on human gastric functions in vitro.

In vitro analysis of mesenchymal influences on the differentiation of stomach epithelial cells of the chicken embryo

It is well established that epithelial-mesenchymal interactions play important roles in the differentiation of stomach epithelial cells in the chicken embryo. To analyze mesenchymal influences on the differentiation of the epithelial cells, we developed a tissue culture system for stomach (proventriculus and gizzard) epithelia of chicken embryo, and examined their differentiation in the presence or absence of mesenchyme. Stomach epithelium from 6-day chicken embryo did not express embryonic chicken pepsinogen (ECPg), a marker molecule of glandular epithelial cells of proventriculus, while it expressed marker molecules of epithelial cells of the luminal surface of stomach, when cultured alone on the Millipore filter, covered with the gel consisting of extracellular matrix components. When the epithelium was recombined with mesenchyme separated by the filter, differentiation of the epithelium was affected by the recombined mesenchyme. Proventricular and lung mesenchymes induced the expression of ECPg in epithelial cells, and the expression was extensive when the gel contained basement membrane components. Proventricular and gizzard epithelia showed different responses to the mesenchymal action. We tested the effects of some growth factors on the differentiation of epithelial cells using this culture system. Furthermore we devised a "conditioned semi-solid medium experiment" for analysis of the inductive properties of proventricular and lung mesenchymes. The results of this experiment clearly demonstrated for the first time that diffusible factors from mesenchyme induce the differentiation of glandular epithelial cells in the absence of mesenchymal cells.

Tissue interaction regulates expression of a spasmolytic polypeptide gene in chicken stomach epithelium

The primitive epithelium of embryonic chicken proventriculus (glandular stomach) differentiates, after day 6 of incubation, into luminal epithelium, which faces the lumen and abundantly secretes mucus, and glandular epithelium, which invaginates into mesenchyme and later expresses embryonic chicken pepsinogen (ECPg). So far it is not well understood how undifferentiated epithelial cells differentiate into these two distinct cell populations. Spasmolytic polypeptide (SP) is known to be expressed in surface mucous cells of mammalian stomach. In order to obtain the differentiation marker for proventricular luminal epithelial cells, we cloned a cDNA encoding chicken SP (cSP). Sequence analysis indicated that cSP has the duplicated cysteine-rich domain characteristic of SP. Examination of the spatial and temporal expression pattern of cSP gene revealed that, during embryogenesis, cSP was expressed in lumina epithelial cells of the proventriculus, gizzard, small intestine, and lung, but not the esophagus. In the proventriculus, cSP mRNA was first detected on day 8 of incubation and was localized to differentiated luminal epithelial cells. By using cSP as a molecular marker, the effects of mesenchyme on the differentiation of epithelium were analyzed in vitro. On the basis of these data, a model is presented concerning the differentiation of proventricular epithelium.

Thyroid hormone-induced apoptosis of larval cells and differentiation of pepsinogen-producing cells in the stomach of Xenopus laevis in vitro

It is generally known that the anuran stomach begins to express pepsinogens (Pg) during metamorphosis. To clarify the mechanisms of differentiation of Pg-producing cells, we examined immunohistochemically the epithelial transformation from larval to adult form in Xenopus laevis stomach at the cellular level. At the beginning of metamorphic climax, concomitantly with the modification of the basement membrane, apoptotic cells labelled by TUNEL suddenly increased in number in the entire epithelium except for the primordia of adult epithelial cells in the basal region of larval glands. Subsequently, with the development of connective tissue, the adult epithelial cells actively proliferated and replaced the larval cells from the basal to the luminal region. Following the start of morphogenesis of adult glands, Pg-producing cells became differentiated in newly formed adult glands, but not in the adult surface epithelium. We then developed an organ culture system and examined effects of thyroid hormone (TH) on the differentiation of Pg-producing cells in X. laevis stomach in vitro. In the presence of TH, just as in spontaneous metamorphosis, Pg-producing cells differentiated from the adult epithelial primordia after the apoptosis of larval epithelial cells. In contrast, in the absence of TH, neither apoptotic larval cells no Pg-producing cells were detected. Therefore, we conclude that TH triggers organ-autonomously the entire process leading to the differentiation of Pg-producing cells in X. laevis stomach. In addition, the strict localization of Pg-producing cells in the adult glands both in vivo and in vitro suggests the correlation between the differentiation of Pg-producing cells and morphogenesis of the glands surrounded by the developed connective tissue.

Establishment and characterization of two cell lines from N-methyl-N-nitrosourea-induced mouse glandular stomach carcinomas

We previously reported the induction with N-methyl-N-nitrosourea (MNU) of mouse glandular stomach carcinomas showing a gastric phenotype but variation in histologic appearance, as with human gastric carcinomas. In the present study, we established two cell lines, designated MGT-40 and MGT-93, from MNU-induced mouse glandular stomach carcinomas. These cell lines are keratin-positive and grow as epithelial monolayers in culture, requiring transforming growth factor alpha, epidermal growth factor or insulin/transferrin for optimal growth in addition to 10% fetal bovine serum. Retention of the differentiated phenotype for gastric surface mucous cells has been confirmed by cathepsin E immunohistochemistry and reverse transcriptase-polymerase chain reaction for mouse spasmolytic polypeptide. Neither transplantability in nude mice nor colony formation on soft agar was observed, except in one subline. Chromosome analysis revealed aneuploidy with modal chromosome numbers ranging from 58 to 78 and no specific structural abnormalities. This is the first report of cell lines derived from mouse glandular stomach carcinomas. They should prove useful for studies of the mechanisms of regulation of growth and differentiation.

Induction of precocious pepsinogen synthesis by glucocorticoids in fetal rat gastric epithelium in organ culture: importance of mesenchyme for epithelial differentiation

Glucocorticoids significantly affect both proliferation and differentiation of gastric epithelial cells in vivo. Here we examined the mechanism of action of glucocorticoids on the cells in vitro, with special reference to the epithelial-mesenchymal interaction. When 16.5-day fetal rat gastric explants were maintained in organ culture, the epithelial cells began to invaginate into mesenchyme on days 3 to 4, and formed glandular structures on days 5 to 6 in culture. Immunohistochemical analysis with specific antibodies revealed that pepsinogen-synthesizing cells first appeared on day 2, and they increased in number with epithelial morphogenesis to about 20%-30% of total epithelial cells on days 4 to 6, and that these cells were localized at the base of glandular structures in control media. When the explants were treated with hydrocortisone (1 microgram/ml), epithelial morphogenesis was mostly suppressed, but epithelial cytodifferentiation was significantly stimulated, indicating that epithelial morphogenesis is not necessary for their cytodifferentiation. In glucocorticoid-treated explants, pepsinogen-synthesizing cells first appeared on day 1, and more than 90% of the cells were positively stained with the antibodies from days 3 to 5 in culture. Biochemical analysis showed that much higher acid protease activity could be detected in glucocorticoid-treated explants than in controls from days 2 to 6 in culture, and analysis by zymography indicated that the synthesis of pepsinogen 1 but not cathepsin E was stimulated by the hormone. Northern blotting analysis showed that the level of pepsinogen 1 mRNA was greatly increased by glucocorticoids. Examination of the effect of the hormone on the epithelial proliferation showed that hydrocortisone (1 microgram/ml) significantly inhibited the epithelial growth from days 1 to 3 in culture. To investigate the role of epithelial-mesenchymal interaction in the glucocorticoid-induced differentiation of the gastric epithelial cells, effects of the hormone on the proliferation and differentiation of the cells in the absence of mesenchyme were examined, using a recently established primary culture system. The epithelial cells synthesized cathepsin E but not pepsinogen in cell culture, irrespective of glucocorticoid treatment, and the level of acid protease activity was not affected by the hormone, indicating that mesenchyme is necessary for the hormone to induce pepsinogen gene expression in the epithelial cells. In the cell culture system, glucocorticoids did not inhibit but significantly stimulated epithelial proliferation. This suggests that the hormone indirectly inhibited epithelial proliferation in organ culture, probably via mesenchyme. The mechanism of action of glucocorticoids on the epithelial-mesenchymal interaction in the fetal glandular stomach is discussed.

Proprotein-processing endoprotease furin controls the growth and differentiation of gastric surface mucous cells

Gastric surface mucous cells originate from progenitor cells at the isthmus of the gastric gland, from where the cells migrate to the luminal surface. With migration they form secretory granules and express TGF alpha. We found that proprotein-processing endoprotease furin-positive cells were layered around the upper one fourth of the gastric glands of adult rats, whereas they were distributed along an outer epithelial layer in fetal rats. Because the furin-positive cell layer was localized from the upper cell proliferating zone to the less proliferating pit-cell region in the gastric gland unit, we examined the role of furin in the growth and differentiation of surface mucous cells by using the cell line, GSM06. This cell line is derived from the gastric surface mucous cells of transgenic mice harboring the temperature-sensitive simian virus 40 T antigen. At T antigen-active temperature (33 degrees C), the cells grew to confluency, whereas at T antigen-inactive temperature (39 degrees C), the cells ceased growing. At 33 degrees C, the cells exhibited a high level of furin expression with a negligible level of periodic acid Schiff (PAS)-positive materials and a low level of TGF alpha. In contrast, at 39 degrees C the cells produced a high level of PAS-positive materials, TGF alpha, and secretory granules, with a negligible level of furin expression. To further examine the role of furin, we established a GSM06 cell line introduced with either a sense or an antisense furin cDNA. The cells with sense furin expression produced fewer PAS-positive materials and a low level of TGF alpha even at 39 degrees C, whereas the cells with antisense furin expression exhibited more PAS-positive materials and TGF alpha even at 33 degrees C. When furin expression was suppressed by its antisense oligonucleotide, the cell growth was retarded with enhanced expression of the differentiated characteristics. Thus, we conclude that furin is instrumental in controlling the growth of the surface mucous cells.