Chapter 36 - Stem Cells in the Gastrointestinal Tract

Abstract

The cells of the gastrointestinal tract undergo constant renewal and respond to damages by regeneration and repopulation. Although the stem cells are the most important cells of the gastrointestinal tract, responsible for the production of every other cell type in the gastrointestinal mucosa, they have not yet been closely characterized. This chapter reviews evidence that the multipotential stem cells generate all gastrointestinal epithelial cell lineages through committed precursor cells housed in the proliferative compartments of intestinal crypts and gastric glands. The gastrointestinal stem cells remain elusive and unidentified, mainly because of a lack of accepted morphological and functional markers at the single-cell level. Concepts of stem cell number, location, and fate, and the ability of gastrointestinal stem cells to regenerate cell lineages of whole intestinal crypts and villi after damage is also explored. There is a single stem cell in every intestinal crypt or gastric gland that indirectly generates a clone containing further stem cells, transit amplifying, and differentiated cells, through the production of committed progenitor cells. This cell also produces new crypts by crypt fission, repairs entire crypts and villi when damaged, and generates gastrointestinal tumors. The stem cell or cells occupy a niche, formed by mesenchymal cells, such as the intestinal subepithelial myofibroblasts, and extracellular matrix molecules, which regulate epithelial stem cells through mesenchymalepithelial crosstalk. Finally, it is concluded that the colonic stem cell is pivotal in understanding mechanisms of tumorigenesis in the colon. The isolation and characterization of gastrointestinal stem cells are a priority in gut biology.