TFF3 expression at the esophagogastric junction is increased in gastro-esophageal reflux disease (GERD)
Introduction
The esophagogastric junction is a site with a high prevalence of inflammation and intestinal metaplasia, and a rapidly increasing incidence of adenocarcinoma [6]. Beside representing the border between esophageal squamous and gastric columnar epithelium, it is a transitional zone between two organs with different causes of inflammation. In the esophagus, gastro-esophageal reflux disease (GERD) is the predominant cause, whereas Helicobacter pylori infection is the leading pathogen responsible for gastritis. In both organs, a temporal sequence of inflammation, intestinal metaplasia, and eventually adenocarcinoma is observed. In the stomach, the risk of carcinoma is related to the anatomical distribution of gastritis. Pangastritis and corpus-predominant gastritis are linked with hypoaciditiy and pose a considerably higher risk for adenocarcinoma than does antrum-predominant gastritis. The underlying molecular mechanisms for the development of intestinal metaplasia are incompletely understood [9], [17]. The risk of cancer arising from intestinal metaplasia differs between esophagus and stomach: Intestinal metaplasia in the esophagus, called specialized intestinal metaplasia or Barrett’s mucosa, increases the risk by a factor of around 30 [8], [30], whereas gastric intestinal metaplasia implicates a risk of adenocarcinoma that is only about two- to six-fold [20], [24]. While esophageal specialized intestinal metaplasia is considered a premalignant lesion, some authors regard gastric intestinal metaplasia merely as a marker of an underlying still undefined premalignant condition [24]. The prognostic significance of intestinal metaplasia at the gastric cardia, adjacent to the esophagogastric junction, is not defined. Epidemiological and clinical data have yielded conflicting results on the interference of GERD and H. pylori infection as causes of inflammation and metaplasia at the cardia, [12], [25], [32], [33], [36].
To elucidate the pathway from inflammation towards intestinal metaplasia at the esophagogastric junction, markers of intestinal differentiation are of particular interest. By histopathology, mucin-containing goblet cells are the hallmark of intestinal metaplasia. These cells are interspersed among columnar mucous cells. The glandular structure of Barrett’s esophagus has morphological similarities with the mucosa found in the normal gastric cardia. Cardia-type mucosa is a foveologlandular epithelium consisting of columnar mucous cells, but devoid of parietal cells. Some authors suggest that cardia-type mucosa precedes the development of Barrett’s esophagus [4].
TFF peptides are mucin-associated molecules known to be involved in protection and repair of gastric and intestinal mucosa (for reviews, see [15], [16], [40]). Under physiological conditions, the three currently known human TFF peptides are secreted in a cell-specific manner [15], [16], [22], [40]. There are data on TFF gene expression in the normal esophagus, in Barrett’s esophagus and in the stomach, but no data regarding the gastric cardia. The stomach is the major source of human TFF1 and TFF2 [16]. TFF1 is secreted by foveolar cells in antrum and corpus. TFF2 is released predominantly from mucous neck and pyloric gland cells; whereas TFF3 is present in the human stomach in limited amounts only [14]. Intestinal metaplasia, however, is a recognized source of gastric TTF3 [21], [34]. TFF peptides are also expressed in a wide variety of chronic inflammatory diseases [15], [16], [40], [41].
In the normal esophageal squamous mucosa, none of the three TFF peptides have been detected at the mRNA or protein level, neither in squamous epithelium nor in esophageal glands [13], [19], [35], [37]. In Barrett’s esophagus, the localization of TFF1 and TFF2 expression by immunohistochemistry and in situ hybridization was found to be similar with antral mucosa: TFF1 is localized at the surface epithelium, TFF2 in glandular structures, but in part also in superficial epithelium [13], [35], [37]. TFF3 was found in virtually all Barrett’s esophagus cells, but primarily deeper in the glands [35], [37]. In the small intestine, the localization of TFF peptides is coordinated with different secreted mucins [22]. In Barrett’s esophagus, this coordination was reported to be altered [35], [37]. The pattern of mucin expression shares common features with the stomach and the intestine as well [1].
The aim of our study was to assess the mRNA expression of three TFF genes at the gastric cardia in relation to the main causes of inflammation, H. pylori infection and GERD, and in relation to the expression of tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8) [31]. The TFF expression values in the cardia and corpus of patients without intestinal metaplasia were compared with those of patients with histologically confirmed Barrett’s mucosa. The hypothesis was that different causes of inflammation lead to distinctive patterns of TFF transcription.
Section snippets
Human tissue
Patients undergoing upper gastrointestinal endoscopy in the department of gastroenterology of the Otto-von-Guericke University, Magdeburg, were included in the study when meeting the following criteria:
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age at least 18 years;
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indication for endoscopy: dyspepsia or reflux symptoms;
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no endoscopic pathology except of reflux esophagitis, columnar epithelium metaplasia in the lower esophagus, or minimal gastric erosions;
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no major concomitant disease;
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written informed consent.
The investigations followed
Results
RNA extraction and cDNA synthesis were successful in 26 samples from corpus and 24 samples from cardia of group 1, and in all 10 samples from the esophagus of group 2. The results of TFF RT-PCR are shown in Table 1. TFF1 and TFF2 transcripts were clearly detectable in all patients of group 1 in corpus and cardia, as well in Barrett’s mucosa of group 2. In contrast, TFF3 transcripts were found in only 2 of the 26 corpus samples, but in 9 of the 24 cardia samples of group 1. The difference
Discussion
This is the first report on TFF expression at the gastric cardia. It sheds some light on the pathophysiological role of these peptides, TFF3 in particular, in GERD. GERD seems to be responsible for the induction of TFF3 at the cardia also in cases without intestinal metaplasia.
The expression of TFF3 at the cardia was shown to take an intermediate position between the normal gastric corpus and Barrett’s mucosa. Previous studies [14], [21], [27], [34], [43] and the data presented indicate that,
Acknowledgements
This work was supported by grants NBL3/01ZZ0107/PP12 and PP13 from the “Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie” (BMBF; to P.M. and W.H., respectively) and grants 0163615 and 0500058 from the “Fonds der Chemischen Industrie” (to W.H.).
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