In healthy volunteers, immunohistochemistry supports squamous to columnar metaplasia as mechanism of expansion of cardia, aggravated by central obesity.

INTRODUCTION: Recently, we showed that the length of cardiac mucosa in healthy volunteers correlated with age and obesity. We have now examined the immunohistological characteristics of this expanded cardia to determine whether it may be due to columnar metaplasia of the distal oesophagus. METHODS: We used the squamocolumnar junction (SCJ), antral and body biopsies from the 52 Helicobacter pylori-negative healthy volunteers who had participated in our earlier physiological study and did not have hiatus hernia, transsphincteric acid reflux, Barrett's oesophagus or intestinal metaplasia (IM) at cardia. The densities of inflammatory cells and reactive atypia were scored at squamous, cardiac and oxyntocardiac mucosa of SCJ, antrum and body. Slides were stained for caudal type homeobox 2 (CDX-2), villin, trefoil factor family 3 (TFF-3) and liver-intestine (LI)-cadherin, mucin MUC1, Muc-2 and Muc-5ac. In addition, biopsies from 15 Barrett's patients with/without IM were stained and scored as comparison. Immunohistological characteristics were correlated with parameters of obesity and high-resolution pH metry recording. RESULTS: Cardiac mucosa had a similar intensity of inflammatory infiltrate to non-IM Barrett's and greater than any of the other upper GI mucosae. The immunostaining pattern of cardiac mucosa most closely resembled non-IM Barrett's showing only slightly weaker CDX-2 immunostaining. In distal oesophageal squamous mucosa, expression of markers of columnar differentiation (TFF-3 and LI-cadherin) was apparent and these correlated with central obesity (correlation coefficient (CC)=0.604, p=0.001 and CC=0.462, p=0.002, respectively). In addition, expression of TFF-3 in distal oesophageal squamous mucosa correlated with proximal extension of gastric acidity within the region of the lower oesophageal sphincter (CC=-0.538, p=0.001). CONCLUSIONS: These findings are consistent with expansion of cardia in healthy volunteers occurring by squamo columnar metaplasia of distal oesophagus and aggravated by central obesity. This metaplastic origin of expanded cardia may be relevant to the substantial proportion of cardia adenocarcinomas unattributable to H. pylori or transsphincteric acid reflux.

Gastrokine 1 is abundantly and specifically expressed in superficial gastric epithelium, down-regulated in gastric carcinoma, and shows high evolutionary conservation.

Through previous large-scale gene expression profiling we identified a transcript that was abundant in normal stomach and down-regulated in gastric cancer. Genes expressed at similar levels included gastrin, MUC5 and pS2, which are important in gastric function. We aimed to characterise this candidate, gastrokine 1 (GKN1), at mRNA, DNA, protein and tissue levels. The gene was studied in human, mouse, rat and cow, and was highly conserved across these species. The mRNA transcripts averaged 750 bp in length. The human, mouse and rat genes all contained six exons spanning 6 kb, and were located on chromosomes 2, 6 and 4 respectively. The full-length translation products were 183-185 amino acids long, reducing to the mature protein of 18 kDa following signal peptide cleavage; these predictions were confirmed by Western blotting. Tagged gastrokine 1 yielded granular cytoplasmic staining with perinuclear accentuation, representing the Golgi apparatus, in keeping with secretion or expression on the extracellular surface. Gene expression in tissues was profiled extensively by Northern blotting, in situ hybridisation and immunohistochemistry. Gastrokine 1 was highly expressed in normal stomach, where it was located in the superficial/foveolar gastric epithelium, but was absent from gastric carcinomas. Outwith the stomach, gastrokine 1 was found only in epithelia showing gastric metaplasia eg Barrett's oesophagus, the ulcer-associated cell lineage and ovarian mucinous neoplasms. In conclusion, we have characterised gastrokine 1, previously known as CA11, AMP-18 or foveolin. Its abundance in, and specificity for, native or metaplastic gastric epithelium, down-regulation in gastric carcinoma and evolutionary conservation suggest that this gene is physiologically important in the stomach. The function of gastrokine 1 is unknown but a role in mucosal protection is postulated.