MicroRNA signatures in Helicobacter pylori‐infected gastric mucosa

The study was conducted to determine expression patterns of microRNA (miRNA), a non‐coding RNA that controls gene expression mainly through translational repression, in gastric mucosa infected with Helicobacter pylori. Using endoscopic biopsy specimens, miRNA expression patterns in H. pylori‐infected gastric mucosa were determined by microarray. The differentially expressed miRNAs were quantitated by real‐time reverse‐transcriptase polymerase chain reaction (RT‐PCR). An in vitro infection model was assessed to monitor the regulation of miRNAs in gastric epithelium in response to H. pylori. The comprehensive method unraveled the expression profiles; among 470 human miRNAs loaded, 55 were differentially expressed between H. pylori‐positive and ‐negative subjects. The expression levels were significantly decreased in 30 miRNAs, whereas hsa‐miRNA‐223 was the only miRNA to be overexpressed on quantitative RT‐PCR. Eight miRNAs enabled discrimination of H. pylori status with acceptable accuracy. Gastritis scores of activity and chronic inflammation according to the updated Sydney system correlated significantly with the expression levels of diverse miRNAs. Cure of the infection with an anti‐H. pylori regimen restored decreased expression in 14 of the 30 miRNAs. Expression levels of some miRNAs, including let‐7 family members, were significantly altered following infection with a virulent H. pylori strain carrying intact cag pathogenicity island including cagA but not isogenic mutants. These results provide insights into miRNA involvement in the pathogenesis of H. pylori‐associated gastritis. cagA may be involved in cellular regulation of certain miRNAs in the gastric epithelium.