PROLIFERATION AND DIFFERENTIATION OF THE SMALL-INTESTINAL EPITHELIUM - FROM PETRI-DISH TO BEDSIDE

The small intestinal epithelium is a continuously renewing cell system in which two main compartments can be defined: the crypt compartment and the villus compartment,The crypt compartment houses the proliferat ive cells (stem cells) that give birth to the four types of differenti ated enterocytes (absorptive enterocytes, goblet cells, enteroendocrin e cells, Paneth cells) that, with the exception of Paneth cells, popul ate the villus compartment, Enterocyte proliferation, differentiation and migration are regulated by a complex network of cell-cell and cell -matrix: information, and modulated by growth factors, luminal factors and, possibly, hormones, The intimate mechanisms underlying the fasci nating life of the enterocytes are the object of intensive investigati on although insights have come from studies ''in vitro'' and in transg enic animals, The enormous proliferative potential makes the small bow el an extremely plastic organ, able to adapt to various injuries and a dverse conditions and to completely recover even from extensive damage , Knowledge of the biologic mechanisms of adaptation has begun to affe ct therapeutic approaches to a number of intestinal diseases and the f uture will see a significant advancement in their management, More imp ortant, understanding the molecular mechanisms regulating the perfect equilibrium between proliferation and differentiation of the intestina l enterocytes will eventually help disclose the dark side of cancer.