Self-renewal of the human gastric epithelium: new insights from expression profiling using laser microdissection.

The gastric mucosa is subject to continual bidirectional renewal by differentiation from stem and transit amplifying cells. It was the aim of this study to characterize the self-renewal of the human gastric mucosa and its two major types of glands in the fundus and antrum, respectively. Three characteristic regions (pit, proliferative, and lower neck regions) were isolated from fundic and antral units by the use of laser microdissection, and expression profiles concerning 15 marker genes were generated by RT-PCR analysis. The surface mucous cells (SMCs) of fundic and antral units differed in their expression of at least four secretory genes, i.e., gastric lipase, TFF3, FCGBP, and lysozyme. The maturation of mucous neck cells was shown to occur stepwise, first towards a mucous phenotype followed by a serous differentiation step. Also, a stepwise maturation of both the antral SMCs and antral gland cells was observed. Additionally, the presence of gastric lipase was also demonstrated for the first time in antral gland cells. In conclusion, the different expression profiles of SMCs of the fundic and antral units could be the basis for the different self-renewal rates of fundic and antral SMCs and could influence the spatial organization of the bacterial microbiota within the various parts of the gastric mucosa.

Expression analysis of human salivary glands by laser microdissection: differences between submandibular and labial glands.

Both the major and minor salivary glands are the sources of saliva, a fluid vital for the maintenance of a healthy oral cavity. Here, the expression profiles of human submandibular (SMG) and labial glands (LG) were compared by RT-PCR analysis of laser microdissected mucous and serous cells, respectively. The focus was on trefoil factor family (TFF) genes, but also other genes encoding secretory proteins (mucins, lysozyme, amylase, statherin, and histatins) or aquaporin 5 were included. Immunofluorescence studies concerning TFF1-3, FCGBP, amylase, and lysozyme are also presented. It was shown that LGs clearly contain serous cells and that these cells differ in their expression profiles from serous SMG cells. Furthermore, all three TFF peptides, together with MUC5B, MUC7, MUC19, and FCGBP, were clearly detectable in mucous acini of both LGs and SMGs. In contrast, lysozyme was differentially expressed in LGs and SMGs. It can be expected that labial saliva may play a particularly important role for protecting the teeth.

Down-regulation of ephrin-A5, a gene product of normal cartilage, in chondrosarcoma.

As ephrins have been associated with tumorigenesis and tumor progression, we investigated ephrin-A5 (EFNA5) expression in specimens of normal cartilage and chondrosarcomas of different grade by conventional and quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry. We detected a significant EFNA5 down-regulation in chondrosarcomas compared with normal cartilage using quantitative RT-PCR (P < .05). The results were confirmed by Western blot and immunohistochemistry. We did not detect any causative genetic or epigenetic alterations in EFNA5 promoter methylation, loss of heterozygosity, or mutation analyses. Apart from slight differences in EFNA5 transcript amounts, we detected no significant influence of hypoxia on EFNA5 expression in C3842 and SW1353 chondrosarcoma cells. As EFNA5 down-regulation is a consistent finding in chondrosarcomas, we presume that it represents another essential alteration in tumorigenesis and tumor progression associated with cell adhesion, in addition to a multitude of other partially unknown biologic functions mediated by bidirectional ephrin/Eph receptor signaling and cross talk.

pH control for enhanced reductive bioremediation of chlorinated solvent source zones.

Enhanced reductive dehalogenation is an attractive treatment technology for in situ remediation of chlorinated solvent DNAPL source areas. Reductive dehalogenation is an acid-forming process with hydrochloric acid and also organic acids from fermentation of the electron donors typically building up in the source zone during remediation. This can lead to groundwater acidification thereby inhibiting the activity of dehalogenating microorganisms. Where the soils' natural buffering capacity is likely to be exceeded, the addition of an external source of alkalinity is needed to ensure sustained dehalogenation. To assist in the design of bioremediation systems, an abiotic geochemical model was developed to provide insight into the processes influencing the groundwater acidity as dehalogenation proceeds, and to predict the amount of bicarbonate required to maintain the pH at a suitable level for dehalogenating bacteria (i.e., >6.5). The model accounts for the amount of chlorinated solvent degraded, site water chemistry, electron donor, alternative terminal electron-accepting processes, gas release and soil mineralogy. While calcite and iron oxides were shown to be the key minerals influencing the soil's buffering capacity, for the extensive dehalogenation likely to occur in a DNAPL source zone, significant bicarbonate addition may be necessary even in soils that are naturally well buffered. Results indicated that the bicarbonate requirement strongly depends on the electron donor used and availability of competing electron acceptors (e.g., sulfate, iron (III)). Based on understanding gained from this model, a simplified model was developed for calculating a preliminary design estimate of the bicarbonate addition required to control the pH for user-specified operating conditions.

Heterogeneity of angiogenesis and blood vessel maturation in cartilage tumors.

Cartilage tumors have a special angiogenic phenotype, with blood vessels arranged predominantly in pericartilage fibrous septa and relatively low microvessel density (MVD), except in dedifferentiated chondrosarcomas. To further elucidate angiogenesis in cartilage tumors, we used double-labeling immunohistochemistry to determine microvessel pericyte coverage index (MPI) and proliferating capillary index (PCI), referring to blood vessel maturation and angiogenic activity in enchondromas, conventional chondrosarcomas, and dedifferentiated chondrosarcomas. Altogether, we found high MPIs (>70%) especially in dedifferentiated chondrosarcomas but without a correlation to the grade of malignancy. PCI was significantly higher in conventional chondrosarcomas grades II and III than in enchondromas, chondrosarcomas grade I, and dedifferentiated chondrosarcomas. Thus, PCI positively correlated with the previously reported differential expression of vascular endothelial growth factor (VEGF)-A in cartilage tumors. Altogether, cartilage tumors exhibit a heterogeneous but predominantly mature angiogenic phenotype with differential proliferative activity.

Biosynthesis of gastrokine-2 in the human gastric mucosa: restricted spatial expression along the antral gland axis and differential interaction with TFF1, TFF2 and mucins.

UNLABELLED: Gastrokine-2 (GKN2) is a secretory peptide of human gastric surface mucous cells (SMCs). It forms disulfide-linked heterodimers with the trefoil factor family (TFF) peptide TFF1. Binding with TFF2 was also reported. Antral SMCs differ from those of the corpus by their TFF3 expression. The aim of this study was to localize GKN2 expression along the antral gland axis, to characterize the continuous regeneration of antral glands, and to investigate the interactions of GKN2 with TFF1, TFF2 and mucins. METHODS: The spatial expression of GKN1, GKN2, TFF1-3, MUC5AC and MUC6 was determined using laser microdissection and RT-PCR analysis. Furthermore, antral extracts were separated by gel chromatography and the association of GKN2 with TFF1, TFF2, and mucins was investigated. RESULTS: Differential GKN2 expression was localized along the rostro-caudal axis of the stomach. Laser microdissection revealed characteristic differential expression profiles of GKN1, GKN2, TFF1-3, MUC5AC and MUC6 along the antral gland axis. Both GKN2 and TFF1 were expressed in superficial SMCs. Surprisingly, the TFF1-GKN2 heterodimer did not associate with the mucin fraction; whereas TFF2 showed exclusive association with mucins. CONCLUSIONS: Maturation of antral SMCs occurs stepwise via trans-differentiation of TFF3 expressing progenitor cells. The TFF1-GKN2 heterodimer and TFF2 differ characteristically by their binding to gastric mucins. This points to different physiological functions of TFF1 and TFF2, the latter maybe acting as a 'link peptide' for stabilization of the gastric mucus.

Localization of TFF3 peptide in human esophageal submucosal glands and gastric cardia: differentiation of two types of gastric pit cells along the rostro-caudal axis.

TFF3 (trefoil factor family 3), which is a major secretory product of the gastric antrum and the intestine, but which is nearly absent in the gastric corpus, plays a key role in the maintenance of mucosal integrity. Here, we have systematically investigated TFF3 expression in the esophagus and gastric cardia by the use of reverse transcription/polymerase chain reaction (RT-PCR) analysis and immunohistochemistry. Synthesis of TFF3, but not TFF1 or TFF2, is detectable in esophageal submucosal glands. The stratified squamous epithelium is devoid of TFF synthesis. Prominent TFF3 expression starts at the Z-line with a sharply decreasing gradient toward the cardia. Immunohistochemistry has localized TFF3 to surface mucous cells of the proximal cardia. TFF3 distribution differs characteristically from that of TFF1 (secreted primarily by superficial surface mucous cells), whereas TFF3, together with the mucin MUC5AC, is also found in deeper lying cells toward the isthmus. This is the first report of TFF3 as a typical secretory peptide of esophageal submucosal glands and gastric cardia. The different expression patterns of TFF3 and TFF1 in the cardia suggest a stepwise maturation of surface mucous cells from TFF3/MUC5AC-positive cells close to the isthmus to TFF1/TFF3/MUC5AC-positive cells at the pit. The gradient of TFF3 expression along the gastric rostro-caudal axis defines two types of gastric pit cells: those secreting TFF3 in the cardia and the antrum and those nearly devoid of TFF3 synthesis in the corpus. This indicates the special requirement, particularly of the esophagogastric junction, for TFF3-triggered protection and repair.

Induced trefoil factor family 1 expression by trans-differentiating Clara cells in a murine asthma model.

Asthma is a chronic inflammatory disease of the airways that is accompanied by goblet cell metaplasia and mucus hypersecretion. Trefoil factor family (TFF) peptides represent major secretory products of the respiratory tract and are synthesized together with mucins. In the murine lung, TFF2 is mainly expressed, whereas TFF1 transcripts represent only a minor species. TFF peptides are well known for their motogenic and anti-apoptotic effects, and they modulate the inflammatory response of bronchial epithelial cells. Here, an established mouse model of asthma was investigated (i.e., exposure to Aspergillus fumigatus [AF] antigens). RT-PCR analysis of lung tissue showed elevated levels particularly of TFF1 transcripts in AF-sensitized/challenged animals. In contrast, transcripts encoding Clara cell secretory protein (CCSP/CC10) were strongly diminished in these animals. For comparison, the expression of the goblet cell secretory granule marker mCLCA3/Gob-5, the mucins Muc1-Muc6 and Muc19, and the secretoglobins ScgB3A1 and ScgB3A2, as well as the mammalian ependymin-related gene MERP2, were monitored. Immunohistochemistry localized TFF1 mainly in cells with a mixed phenotype (e.g., TFF1-positive cells stain with the lectin wheat germ agglutinin (WGA), which recognizes mucins characteristic of goblet cells). In addition, these cells express CCSP/CC10, a Clara cell marker. When compared with mucins or CCSP/CC10, TFF1 was stored in a different population of secretory granules localized at the more basolateral portion of these cells. Thus, the results presented indicate for the first time that allergen exposure leads to the trans-differentiation of Clara cells toward a TFF1-expressing mucous phenotype.

Modelling the long-term performance of zero-valent iron using a spatio-temporal approach for iron aging.

Zero-valent iron (ZVI) permeable reactive barriers (PRBs) have become popular for the degradation of chlorinated ethenes (CEs) in groundwater. However, a knowledge gap exists pertaining to the longevity of ZVI. The present investigation addresses this situation by suggesting a numerical simulation model that is intended to be used in conjunction with field or column tests in order to describe long-term ZVI performance at individual sites. As ZVI aging processes are not yet completely understood and are still subject to research, we propose a phenomenological modelling technique instead of a common process-based approach. We describe ZVI aging by parameters that characterise the extent and rate of ZVI reactivity change depending on the propagation of the precipitation front through ZVI. We approximate degradation of CEs by pseudo-first order kinetics accounting for the formation of partially dechlorinated products, and describe ZVI reactivity change by scaling the degradation rate constants. Three independent modelling studies were carried out to test the suitability of the conceptual and numerical model to describe the observations of accelerated column tests. All three tests indicated that ZVI reactivity declined with an increasing number of exchanged pore volumes. Measured and modelled concentrations showed good agreement, thereby proving that resolving spatial as well as temporal changes in ZVI reactivity is reasonable.

TFF3 expression at the esophagogastric junction is increased in gastro-esophageal reflux disease (GERD).

At the gastric cardia, the molecular mechanisms of inflammation and metaplasia are incompletely understood. Thus, the aim of this study was to determine the expression of TFF1, TFF2 and TFF3 at this site and correlate these data with Helicobacter pylori infection or gastro-esophageal reflux disease (GERD). In 27 patients without intestinal metaplasia at the cardia, endoscopic biopsies were obtained for histology and RT-PCR. TFF1 and TFF2 were expressed in all cardia samples. TFF3 expression was significantly more frequent at the cardia (n = 15/24) than in the corpus (n = 2/26). TFF3 expression at the cardia was mainly observed in GERD patients, and there was a clear tendency towards higher interleukin-8 (IL-8) transcription levels; whereas TFF3 expression was not correlated with the H. pylori status or to tumor necrosis factor-alpha (TNF-alpha) expression. The expression of TFF3 at the cardia may represent an adaptation to GERD and precede the development of Barrett's esophagus.

A gradient of TFF3 (trefoil factor family 3) peptide synthesis within the normal human gastric mucosa.

TFF3 is a member of the trefoil factor family (TFF) peptides, which enhance the surface integrity of mucous epithelia, and is typically secreted by intestinal goblet cells together with the mucin MUC2. Reports of the expression of TFF3 within the normal human stomach are contradictory and the precise localisation of TFF3 is unknown. We have mapped the human gastric mucosa by reverse transcription/polymerase chain reaction and Western blot analysis and by immunohistochemistry. Small amounts of TFF3 were detectable in the oxyntic mucosa of the corpus, whereas TFF3 synthesis increased sharply distal to the corpus-antrum transitional zone. TFF3 secretion was demonstrated in the antrum, the pyloric region and the proximal duodenum. High TFF1 levels were present in all regions of the gastric mucosa including the corpus, whereas the proximal duodenum was nearly devoid of TFF1. Immunohistochemistry localised TFF3 to antral and pyloric surface mucous cells. In the antrum, an increasing concentration gradient was found towards cells deeper in the isthmus. TFF1 was confined to superficial pit cells in the antrum. TFF3 was also present in specific layers of the laminated mucous gel of the antral and pyloric regions and variable concentrations of TFF3 (2-62 nmol/l) were measured in gastric juice. Here, a probably N-terminally shortened variant is present that forms disulphide-linked dimers. Thus, TFF3 is a typical secretory peptide of the normal human antral and pyloric gastric mucosa and has a gastric expression pattern different from that of TFF1 and TFF2. TFF3 might therefore have important physiological functions in the stomach, e.g. as a luminal surveillance peptide maintaining particularly the integrity of the antral and pyloric mucosa.