Gastric epithelial stem cells.

Advances in our understanding of stem cells in the gastrointestinal tract include the identification of molecular markers of stem and early progenitor cells in the small intestine. Although gastric epithelial stem cells have been localized, little is known about their molecular biology. Recent reports describe the use of inducible Cre recombinase activity to indelibly label candidate stem cells and their progeny in the distal stomach, (ie, the antrum and pylorus). No such lineage labeling of epithelial stem cells has been reported in the gastric body (corpus). Among stem cells in the alimentary canal, those of the adult corpus are unique in that they lie close to the lumen and increase proliferation following loss of a single mature progeny lineage, the acid-secreting parietal cell. They are also unique in that they neither depend on Wnt signaling nor express the surface marker Lgr5. Because pathogenesis of gastric adenocarcinoma has been associated with abnormal patterns of gastric differentiation and with chronic tissue injury, there has been much research on the response of stomach epithelial stem cells to inflammation. Chronic inflammation, as induced by infection with Helicobacter pylori, affects differentiation and promotes metaplasias. Several studies have identified cellular and molecular mechanisms in spasmolytic polypeptide-expressing (pseudopyloric) metaplasia. Researchers have also begun to identify signaling pathways and events that take place during embryonic development that eventually establish the adult stem cells to maintain the specific features and functions of the stomach mucosa. We review the cytologic, molecular, functional, and developmental properties of gastric epithelial stem cells.