Immunocytochemistry and in situ hybridization studies of pepsinogen C-producing cells in developing rat fundic glands

Neonatal- maternal separation primes zymogenic cells in the rat gastric mucosa through glucocorticoid receptor activity

Neonatal- Maternal Separation (NMS) deprives mammals from breastfeeding and maternal care, influencing growth during suckling- weaning transition. In the gastric mucosa, Mist1 (encoded by Bhlha15 gene) and moesin organize the secretory apparatus for pepsinogen C in zymogenic cells. Our current hypothesis was that NMS would change corticosterone activity through receptors (GR), which would modify molecules involved in zymogenic cell differentiation in rats. We found that NMS increased corticosterone levels from 18 days onwards, as GR decreased in the gastric mucosa. However, as nuclear GR was detected, we investigated receptor binding to responsive elements (GRE) and observed an augment in NMS groups. Next, we demonstrated that NMS increased zymogenic population (18 and and 30 days), and targeted Mist1 and moesin. Finally, we searched for evolutionarily conserved sequences that contained GRE in genes involved in pepsinogen C secretion, and found that the genomic regions of Bhlha15 and PgC contained sites highly likely to be responsive to glucocorticoids. We suggest that NMS triggers GR- GRE to enhance the expression and to prime genes that organize cellular architecture in zymogenic population for PgC function. As pepsinogen C- pepsin is essential for digestion, disturbance of parenting through NMS might alter functions of gastric mucosa in a permanent manner.

Corticosterone activity during early weaning reprograms molecular markers in rat gastric secretory cells

Gastric epithelial cells differentiate throughout the third postnatal week in rats, and become completely functional by weaning time. When suckling is interrupted by early weaning (EW), cell proliferation and differentiation change in the gastric mucosa, and regulatory mechanisms might involve corticosterone activity. Here we used EW and RU486 (glucocorticoid receptor antagonist) to investigate the roles of corticosterone on differentiation of mucous neck (MNC) and zymogenic cells (ZC) in rats, and to evaluate whether effects persisted in young adults. MNC give rise to ZC, and mucin 6, Mist1, pepsinogen a5 and pepsinogen C are produced to characterize these cells. We found that in pups, EW augmented the expression of mucins, Mist1 and pepsinogen C at mRNA and protein levels, and it changed the number of MNC and ZC. Corticosterone regulated pepsinogen C expression, and MNC and ZC distributions. Further, the changes on MNC population and pepsinogen C were maintained until early- adult life. Therefore, by using EW as a model for altered corticosterone activity in rats, we demonstrated that the differentiation of secretory epithelial cells is sensitive to the type of nutrient in the lumen. Moreover, this environmental perception activates corticosterone to change maturation and reprogram cellular functions in adulthood.

Spatial distribution of osteoblast activating peptide in the rat stomach

Osteoblast activating peptide (OBAP) was previously reported to be expressed in the rat stomach and to have a vital role in osteogenesis, but its distribution in rat stomach has not been determined. Thus, the aim of the present study was to identify the cell types expressing OBAP in the rat stomach. The stomachs of twelve 10-to-11-week-old male Jc1:SD rats were used. Samples were collected for immunohistochemistry, immunoelectron microscopy and dot blot assay. Immunohistochemical investigation revealed that OBAP was distributed mainly in parietal cells without any expression in chief cells, X/A-like cells or enterochromaffin-like cells. Moreover, OBAP-immunopositive cells were observed mainly in the upper and lower parts of the gastric gland. Significantly high optical density of immunopositive cells was observed in the upper and lower gastric gland regions. The dot blot assay confirmed that OBAP is secreted by parietal cells and that it is present in the gastric gland lumen. Immunoelectron microscopy demonstrated that OBAP was confined to the mitochondrial inner membrane within parietal cells and that the number of mitochondria in the upper and lower parts of the gastric epithelium was significantly larger than the number in the middle part of the gastric epithelium. Based on the results, it was concluded that OBAP is mainly produced by mitochondria of parietal cells in the upper and lower parts of the gastric epithelium. Moreover, the presence of OBAP in the gastric gland lumen suggests an exocrine mechanism of release.

Light and electron microscopy of the European beaver (Castor fiber) stomach reveal unique morphological features with possible general biological significance

Anatomical, histological, and ultrastructural studies of the European beaver stomach revealed several unique morphological features. The prominent attribute of its gross morphology was the cardiogastric gland (CGG), located near the oesophageal entrance. Light microscopy showed that the CGG was formed by invaginations of the mucosa into the submucosa, which contained densely packed proper gastric glands comprised primarily of parietal and chief cells. Mucous neck cells represented <0.1% of cells in the CGG gastric glands and 22–32% of cells in the proper gastric glands of the mucosa lining the stomach lumen. These data suggest that chief cells in the CGG develop from undifferentiated cells that migrate through the gastric gland neck rather than from mucous neck cells. Classical chief cell formation (i.e., arising from mucous neck cells) occurred in the mucosa lining the stomach lumen, however. The muscularis around the CGG consisted primarily of skeletal muscle tissue. The cardiac region was rudimentary while the fundus/corpus and pyloric regions were equally developed. Another unusual feature of the beaver stomach was the presence of specific mucus with a thickness up to 950 µm (in frozen, unfixed sections) that coated the mucosa. Our observations suggest that the formation of this mucus is complex and includes the secretory granule accumulation in the cytoplasm of pit cells, the granule aggregation inside cells, and the incorporation of degenerating cells into the mucus.

The origin of pre-neoplastic metaplasia in the stomach: chief cells emerge from the Mist

The digestive-enzyme secreting, gastric epithelial chief (zymogenic) cell is remarkable and underappreciated. Here, we discuss how all available evidence suggests that mature chief cells in the adult, mammalian stomach are postmitotic, slowly turning over cells that arise via a relatively long-lived progenitor, the mucous neck cell, The differentiation of chief cells from neck cells does not involve cell division, and the neck cell has its own distinct pattern of gene expression and putative physiological function. Thus, the ontogeny of the normal chief cell lineage exemplifies transdifferentiation. Furthermore, under pathophysiogical loss of acid-secreting parietal cell, the chief cell lineage can itself trasndifferentiate into a mucous cell metaplasia designated Spasmolytic Polypeptide Expressing Metaplasia (SPEM). Especially in the presence of inflammation, this metaplastic lineage can regain proliferative capacity and, in humans may also further differentiate into intestinal metaplasia. The results indicate that gastric fundic lineages display remarkable plasticity in both physiological ontogeny and pathophysiological pre-neoplastic metaplasia.

The transcription factor MIST1 is a novel human gastric chief cell marker whose expression is lost in metaplasia, dysplasia, and carcinoma

The lack of reliable molecular markers for normal differentiated epithelial cells limits understanding of human gastric carcinogenesis. Recognized precursor lesions for gastric adenocarcinoma are intestinal metaplasia and spasmolytic polypeptide expressing metaplasia (SPEM), defined here by ectopic CDX2 and TFF2 expression, respectively. In mice, expression of the bHLH transcription factor MIST1, normally restricted to mature chief cells, is down-regulated as chief cells undergo experimentally induced metaplasia. Here, we show MIST1 expression is also a specific marker of human chief cells. SPEM, with and without MIST1, is present in human lesions and, akin to murine data, likely represents transitional (TFF2(+)/MIST1(+) = "hybrid"-SPEM) and established (TFF2(+)/MIST1(-) = SPEM) stages. Co-visualization of MIST1 and CDX2 shows similar progressive loss of MIST1 with a transitional, CDX2(+)/MIST1(-) hybrid-intestinal metaplasia stage. Interinstitutional analysis and comparison of findings in tissue microarrays, resection specimens, and biopsies (n > 400 samples), comprising the entire spectrum of recognized stages of gastric carcinogenesis, confirm MIST1 expression is restricted to the chief cell compartment in normal oxyntic mucosa, rare in established metaplastic lesions, and lost in intraepithelial neoplasia/dysplasia and carcinoma of various types with the exception of rare chief cell carcinoma ( approximately 1%). Our findings implicate MIST1 as a reliable marker of mature, healthy chief cells, and we provide the first evidence that metaplasia in humans arises at least in part from the chief cell lineage.

Novel insights of the gastric gland organization revealed by chief cell specific expression of moesin

ERM (ezrin, radixin, and moesin) proteins play critical roles in epithelial and endothelial cell polarity, among other functions. In gastric glands, ezrin is mainly expressed in acid-secreting parietal cells, but not in mucous neck cells or zymogenic chief cells. In looking for other ERM proteins, moesin was found lining the lumen of much of the gastric gland, but it was not expressed in parietal cells. No significant radixin expression was detected in the gastric glands. Moesin showed an increased gradient of expression from the neck to the base of the glands. In addition, the staining pattern of moesin revealed a branched morphology for the gastric lumen. This pattern of short branches extending from the glandular lumen was confirmed by using antibody against zonula occludens-1 (ZO-1) to stain tight junctions. With a mucous neck cell probe (lectin GSII, from Griffonia simplicifolia) and a chief cell marker (pepsinogen C), immunohistochemistry revealed that the mucous neck cells at the top of the glands do not express moesin, but, progressing toward the base, mucous cells showing decreased GSII staining had low or moderate level of moesin expression. The level of moesin expression continued to increase toward the base of the glands and reached a plateau in the base where chief cells and parietal cells abound. The level of pepsinogen expression also increased toward the base. Pepsinogen C was located on cytoplasmic granules and/or more generally distributed in chief cells, whereas moesin was exclusively expressed on the apical membrane. This is a clear demonstration of distinctive cellular expression of two ERM family members in the same tissue. The results provide the first evidence that moesin is involved in the cell biology of chief cells. Novel insights on gastric gland morphology revealed by the moesin and ZO-1 staining provide the basis for a model of cell maturation and migration within the gland.

The maturation of mucus-secreting gastric epithelial progenitors into digestive-enzyme secreting zymogenic cells requires Mist1

Continuous regeneration of digestive enzyme (zymogen)-secreting chief cells is a normal aspect of stomach function that is disrupted in precancerous lesions (e.g. metaplasias, chronic atrophy). The cellular and genetic pathways that underlie zymogenic cell (ZC) differentiation are poorly understood. Here, we describe a gene expression analysis of laser capture microdissection purified gastric cell populations that identified the bHLH transcription factor Mist1 as a potential ZC regulatory factor. Our molecular and ultrastructural analysis of proliferation, migration and differentiation of the gastric unit in Mist1(-/-) and control mice supports a model whereby wild-type ZC progenitors arise as neck cells in the proliferative (isthmal) zone of the gastric unit and become transitional cells (TCs) with molecular and ultrastructural characteristics of both enzyme-secreting ZCs and mucus-secreting neck cells as they migrate to the neck-base zone interface. Thereafter, they rapidly differentiate into mature ZCs as they enter the base. By contrast, Mist1(-/-) neck cells differentiate normally, but ZCs in the mature, basal portion of the gastric unit uniformly exhibit multiple apical cytoplasmic structural abnormalities. This defect in terminal ZC differentiation is also associated with markedly increased abundance of TCs, especially in late-stage TCs that predominantly have features of immature ZCs. Thus, we present an in vivo system for analysis of ZC differentiation, present molecular evidence that ZCs differentiate from neck cell progenitors and identify Mist1 as the first gene with a role in this clinically important process.

Expression and localization of galectin 4 in rat stomach during postnatal development

Galectins are lectins implicated in cell-cell or cell-matrix adhesion, cell growth, the cell cycle, transcription processes, and apoptosis, and some of them are differentially regulated during pre- or post-natal development. The purpose of the present study was to determine whether the expression of galectin 4 is relevant to developmental processes during postnatal development in the rat stomach. Galectin 4 expression in the rat gastric mucosa, between birth and adulthood, was studied at the protein and mRNA levels by western and northern blotting, respectively. This lectin was localized precisely by immunoelectron microscopy. In the gastric mucosa, galectin 4 protein was present at lower levels in suckling than in weaned rats, but mRNA levels did not change significantly during postnatal development. This suggests possible differences in mRNA stability or in the translation regulation. Immunocytochemical examination of galectin 4 confirmed more highly elevated levels of the protein in endocrine, parietal, and chief cells in weaned rats than in suckling rats. Galectin 4 was more strongly localized in weaned rats than in suckling rats in the nuclei of all cell types and in or over secretory granules in endocrine and chief cells, suggesting that galectin 4 is implicated in nuclear events and perhaps in secretory processes.

Cellular expression of gut chitinase mRNA in the gastrointestinal tract of mice and chickens

Recently, the second mammalian chitinase, designated acidic mammalian chitinase (AMCase), has been identified in human, mouse, and cow. In contrast to the earlier identified macrophage-derived chitinase (chitotriosidase), this chitinase is richly expressed in the gastrointestinal (GI) tract, suggesting its role in digestion of chitin-containing foods as well as defense against chitin-coated microorganisms and parasites. This in situ hybridization study first revealed cellular localization of the gut-type chitinase in the mouse and chicken. In adult mice, the parotid gland, von Ebner's gland, and gastric chief cells, all of which are exocrine cells of the serous type, expressed the gut chitinase mRNA. In the chicken, oxyntico-peptic cells in glandular stomach (proventriculus) and hepatocytes expressed the chitinase mRNA. Because cattle produce the gut chitinase (chitin-binding protein b04) only in the liver, the gut chitinases in mammals and birds have three major sources of production, i.e., the salivary gland, stomach, and liver. During ontogenetic development, the expression level in the parotid gland and stomach of mice increased to the adult level before weaning, whereas in the stomach of chickens intense signals were detectable in embryos from incubation day 7.

Cellular immunolocalization of gastric and pancreatic lipase in various tissues obtained from dogs

OBJECTIVE

To determine cellular immunolocalization of canine gastric lipase (cGL) and canine pancreatic lipase (cPL) in various tissues obtained from clinically healthy dogs.

SAMPLE POPULATION

Samples of 38 tissues collected from 2 climically healthy dogs.

PROCEDURES

The cGL and cPL were purified from gastric and pancreatic tissue, respectively, obtained from dogs. Antisera against both proteins were developed, using rabbits, and polyclonal antibodies were purified by use of affinity chromatography. Various tissues were collected from 2 healthy dogs. Primary antibodies were used to evaluate histologic specificity. Replicate sections from the collected tissues were immunolabeled for cGL and cPL and examined by use of light microscopy.

RESULTS

Mucous neck cells and mucous pit cells of gastric glands had positive labeling for cGL, whereas other tissues did not immunoreact with cGL. Pancreatic acinar cells had positive labeling for cPL, whereas other tissues did not immunoreact with cPL.

CONCLUSIONS AND CLINICAL RELEVANCE

We concluded that cGL and cPL are exclusively expressed in gastric glands and pancreatic acinar cells, respectively. Also, evidence for cross-immunoreactivity with other lipases or related proteins expressed by other tissues was not found for either protein. Analysis of these data suggests that gastric lipase is a specific marker for gastric glands and that pancreatic lipase is a specific marker for pancreatic acinar cells. These markers may have clinical use in the diagnosis of gastric and exocrine pancreatic disorders, respectively.

Cytochemical investigation of gastric gland component cells with high-pressure freezing followed by freeze-substitution and hydrophilic resin embedding

Gastric gland component cells were electron-microscopically and immunoelectronmicroscopically examined with high-pressure freezing followed by freeze substitution and a low-temperature embedding resin method and compared to that of the conventional chemical-fixation method. The rat gastric gland was high-pressure frozen, freeze-substituted with acetone-containing osmium or acrolein, and embedded in Epon 812 or Lowicryl K4M, respectively. Using the high-pressure freezing method, the vitreous freezing range reached the depth of 150 microns from the surface. The ultrathin sections from both procedures embedding in Epon 812 and Lowicryl K4M were doubly stained with uranyl acetate and lead acetate, and histochemically or immunohistochemically stained, respectively. In comparison to the conventional chemical fixation method, excellent results were obtained with respect to ultrastructural preservation. The stainings performed in this experiment included periodic acid-thiocarbohydrazide-silver proteinate staining, cationic colloidal cold at pH 2.5 staining, Helix pomatia lectin-staining, anti-alpha or -beta subunit antibodies of H+K(+)-ATPase immunostaining and pepsinogen immunostaining. The staining intensity of those was stronger than that of the conventional immersion-chemical fixation method. In addition to these results, the labels also showed good specific localization. In this paper, we provide a description of the high-pressure freezing followed by freeze substitution and low-temperature embedding resin method compared to the conventional chemical-fixation method. Our results suggest that this method is a suitable tool for ultrastructural and histochemical/immunohistochemical studies at high resolution.

The expression of gastric H+-K+-ATPase mRNA and protein in developing rat fundic gland

The proton pump H+-K+-ATPase is the final common pathway mediating the production and secretion of hydrochloric acid by gastric parietal cells. The present studies were undertaken to examine whether the expression of gastric H+-K+-ATPase mRNA and protein changes are associated with the development of H+-K+-ATPase activity in the rat fundic gland. H+-K+-ATPase activity was examined in rat fundic gland at different stages from gestational day 18.5 to postnatal 8 weeks. The expression of H+-K+-ATPase mRNA was detected by in situ hybridization using a digoxigenin-labelled RNA probe with a tyramide signal amplification system. The expression of H+-K+-ATPase protein was evaluated by immunoblotting and immunohistochemistry using antibodies against H+-K+-ATPase alpha- and beta-subunits. We found that H+-K+-ATPase enzyme activity was detectable from the onset of gland formation (day 19.5 of gestation) and increased with age in the developing rat fundic gland. Expression of mRNA and protein was also discernible at the same time, and a progressive increase in expressions was observed as rats developed. Our results suggested that in developing rat fundic gland, the expression of both mRNA and protein of H+-K+-ATPase increased with age in a manner that parallels the development of H+-K+-ATPase enzyme activity.

Analysis of gastrin receptor gene expression in proliferating cells in the neck zone of gastric fundic glands using laser capture microdissection

Gastrin stimulates proliferation of progenitor cells in the neck zone of gastric fundic mucosa. However, whether it directly enhances this proliferation through its receptors remains unclear. We investigated the expression of gastrin receptors in neck zone proliferating cells in rat gastric fundic glands using a reverse transcription polymerase chain reaction (RT-PCR) coupled with laser capture microdissection and in situ RT-PCR. Gastrin receptor expression was identified in c-fos-expressing cells located in the neck zone, and results of the RT-PCR analysis argued against contamination by other cells, such as enterochromaffin-like, parietal or D cells. Supporting this finding, gastrin receptor gene expression was identified in the neck zone as well as base glands by in situ RT-PCR. Therefore, it is suggested that proliferating cells in the neck zone are stimulated directly by gastrin via their gastrin receptors.

Expression of N-acetylglucosamine residues in developing rat fundic gland cells

The development of rat fundic gland was studied by immunohistochemistry using a recently developed monoclonal antibody, HIK 1083, at both light and electron microscope levels. Antibody HIK 1083 recognized oligosaccharides with a non-reducing terminal alpha-linked N-acetylglucosamine (GlcNAc) residue. In the developing rat fundic gland, cells expressing alpha-GlcNAc residues were discernible from day 19.5 of gestation and continued to exist till adult. The distribution of the alpha-GlcNAc expressing cells was consistent with that described previously for cells reacting to Griffonia simplicifolia lectin (GSA-II) in all developmental stages. These cells were located at the bottom of the fundic gland when they first appeared. With the elongation and maturation of the gland, these cells moved upwards and were finally restricted in the neck region of the gland. Combining previous reports and the present electron microscopical observations, HIK 1083-positive cells in the adult rat fundic gland are mucous neck cells. The interaction between antibody HIK 1083 and GSA-II lectin was investigated. GSA-II prevented the subsequent binding of HIK 1083, while HIK 1083 did not prevent GSA-II binding to mucous neck cells. Our results suggested that alpha-GlcNAc residues exist in rat fundic gland from day 19.5 of gestation and continue to exist till adult. Cells expressing alpha-GlcNAc residues appeared as typical mucous neck cells from postnatal four weeks.

Pepsinogens: physiology, pharmacology pathophysiology and exercise

Human gastric mucosa contains aspartic proteinases that can be separated electrophoretically on the basis of their physical properties into two major groups: Pepsinogen I (PGA, PGI); and Pepsinogen II (PGC, PGII). Pepsinogens consist of a single polypeptide chain with molecular weight of approximately 42,000 Da. Pepsinogens are mainly synthesized and secreted by the gastric chief cells of the human stomach before being converted into the proteolytic enzyme pepsin, which is crucial for the digestive processes in the stomach. Pepsinogen synthesis and secretion are regulated by positive and negative feed-back mechanisms. In the resting state pepsinogens are stored in granules, which inhibit further synthesis. After appropriate physiological or external chemical stimuli, pepsinogens are secreted in the stomach lumen where hydrochloric acid, secreted by the parietal cells, converts them into the corresponding active enzyme pepsins. The stimulus-secreting coupling mechanisms of pepsinogens appear to include at least two major pathways: one involving cAMP as a mediator, the other involving modification of intracellular Ca(2+)concentration. Physiological or external chemical stimuli acting through the intracellular metabolic adenyl cyclase are more effective in inducing ' de novo ' pepsinogen synthesis than those acting through intracellular Ca(2+). The activation of protein kinase C (PK-C) would appear to be involved in regulatory processes. The measurement of pepsinogens A and C in the serum is considered to be one of the non-invasive biochemical markers for monitoring peptic secretion and obtaining information on the gastric mucosa status of healthy subjects. Recently, pepsinogen measurements have been used as an effective biochemical method for evaluating and monitoring patients with gastrointestinal diseases and for checking the effects of drug treatment. The level of PGA in the serum is always high in normal gastritis, while in atrophic gastritis it is always low. In both cases the PGC level in the serum is high. In most gastrointestinal pathologies the ratio between the PGA/PGC decreases. Various reports concerning hormone and/or enzyme modification as well as gastrointestinal distress in the case of long distance exercise have been reported. It has been suggested that the origin of the gastrointestinal distress experienced by long distance runners is a transient ischaemia of the gastric mucosa; it is also suggested that a hypobaric-hypoxic environment could contribute to induce gastric mucosa necrosis. Interrelation between gastrointestinal distress, hypobaric-hypoxic environment and modifications of PGA and PGC, gastrin and cortisol was evaluated in 13 athletes after a marathon performed at 4300 m. Gastrointestinal symptoms occurred in approximately 40% of the athletes. After the race the athletes showed a significant increase of gastrin and cortisol, while the ratio between PGA/PGC decreased. No relationship was observed between gastrointestinal symptoms and hormonal changes after the race. A control group of five subjects, who had been exposed to the same environmental conditions, showed no gastrointestinal or hormonal alteration. Conversely, control subjects presented a significant decrease of cortisol related to the circadian rhythm. The same incidence of gastrointestinal symptoms at high altitude and at sea level and the absence of pathological alteration of PGA and PGC in the serum of the athletes indicates that running a marathon and living for 6 days at 4300 m does not induce gastric mucosa necrosis. Cortisol and gastrin alteration observed in the athletes at this altitude would seem to be related to an activation of the mesopontine and forebrain structures involved in the behavioural and metabolic integration of the autonomic control and arousal and psychophysical-exercise stress. 2000 Academic Press@p$hr