Epithelial Stem Cells, Self-renewal and Differentiation in the Intestine

The inner lining of the gut is a simple epithelium that completely selfrenews every five days because of the high mechanical and chemical stress. At the basis of the epithelial homeostasis are intestinal stem cells that are located at the bottom of crypts. Progeny is generated on a daily basis to compensate for the loss of differentiated cells that cover the villi. Under normal conditions, active cycling stem cells produce daughter cells that compete with each other for residency in the stem cell niche. Upon niche displacement, a daughter cell will lose stem cell characteristics, migrates out of the crypts and matures into a terminally specialized differentiated cell type. Here, we describe and summarize the recent developments in the identification and characterization of intestinal stem cells.