UEG Week 2014 Oral Presentations

INTRODUCTION:Helicobater pylori (Hp) is a bacterial pathogen that colonizes the human stomach, and is the main risk factor for gastro-duodenal ulcers and gastric cancer. Hp are found in close proximity to the surface of the stomach epithelium either as a free-swimming population in the gastric mucus or adhered to epithelial cells. The attached bacteria are known to alter cell signalling and behavior though different virulence factors. AIMS & METHODS: While the effects of attachment have been studied extensively in vitro, we aimed to study the localization and pathological relevance of the direct interaction of bacteria with the gastric epithelum, and in particular with gastric stem cells, in vivo. We utilized a murine model ofHp infection using a mouse adapted Hp strain PMSS1. We developed a novel technique to visualize Hp in mouse stomachs using 3D confocal microscopy. In addition, full thickness stomach surgical specimens were used to visualize bacteria in human stomachs. Lgr5eGFP mice were used to study the interaction of Hp with stem cells. Lgr5eGFPCreER RosadtTomato compound heterozygous mice were used for lineage tracing experiments. RESULTS: We discovered that Hp colonize the epithelial surface deep in the gastric glands where they grow as distinct microcolonies associated with the epithelial junctions. In addition, using EdU or mitosis labeling, we find that the gland-associated H. pylori directly colonize the surface of progenitor cells. In addition to the data obtained in our murine model, we document glandassociated Hp microcolonies deep in the human gastric glands in association with the epithelial junctions and with dividing precursor cells. We hypothesized that direct colonization of precursor/stem cells may drive pathological responses. Using quantitative microscopy we mapped the distribution of bacteria in the glands of the antrum vs the corpus. We found that the location of bacteria in the glands correlates with hyperplastic and metaplastic lesions. Using Lgr5eGFP mice, we observerd a direct interaction of Hp with gastric Lgr5 expressing stem cells. Infection induced an expansion of the stem cell number. In addition, lineage tracing experiments revelaed a significantly higher number of cells being generated from Lgr5 expressing stem cell in infected animals compared to uninfected controls. The acclerated tracing tightly correlated with the bacteria in the gastric glands. CONCLUSION: Taken together our data reveals that bacteria directly interact with progenitor and stem cells in the stomach, induce hyper-proliferation and alter the stem cell homeostasis of the colonized glands. Disclosure of Interest: None declared