Intestinal stem cell resurgence by enterocyte precursors

The adult intestinal epithelium has a remarkable capacity for renewal that is driven by the activity of stem cells located in the intestinal crypts. Until now two major types of the intestinal stem cells have been identified: (I) actively proliferating intestinal stem cells (aISC), expressing Lgr5, that reside at the bottom of the crypts and are fast-cycling and sensitive to injury, e.g., irradiation (1), and (II) quiescent or reserve intestinal stem cells (qISC or rISC), characterized by expression of Bmi1, mTert, and Hopx, that reside at +4 position of the crypt and are slow-cycling and have been shown to facilitate the regeneration of the intestinal epithelium upon injury.