47 - Stem Cells in the Gastrointestinal Tract

Abstract

The cells of the gastrointestinal tract undergo constant renewal and respond to damage by regeneration and repopulation. Each region of the gastrointestinal tract is morphologically distinct with its own repertoire of cell types. 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. There is, initially at any rate, a single stem cell in every intestinal crypt or gastric gland that indirectly generates a clone containing further stem cells, and transits 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 and extracellular matrix molecules, which regulate epithelial stem cells through mesenchymal–epithelial crosstalk. This chapter reviews evidence that these multipotential stem cells generate all gastrointestinal epithelial cell lineages through committed precursor cells housed in the proliferative compartments of intestinal crypts and gastric glands, a concept that has had a long and difficult gestation.