[Where intestinal epithelial stem cells are localized? About molecular markers]

Using stem cells as an example the review considers a new history and methodology of search for stem cells (SC), found in tissues of adult Homo sapiens and Drosophila melanogaster organisms. These studies of SC resulted in several original hypotheses explaining their unusual features. Impressive progress recently achieved in this direction (2008-2010) is associated with employment of new methods of somatic recombination for long-term registration of various strains of differentiated cells, early and distant SC progeny. 1) Although anatomic localization of intestinal epithelium cells lacking marked morphological and biochemical differentiation markers (the lower third of intestinal and colon crypts) is known for about 40 years results of their experimental identification, isolation and detection of their functional characteristics still represent the subject for discussions. Particularly, it remains unclear, which SC are involved in crypt regeneration: the same as those involved into homeostatic renewal or their various subpopulations or early SC progenies acquired stem features by reprogramming? 2) In addition, most detected biochemical markers of potential SC are common for SC from other tissues of embryonic and mature organisms so it is possible to apply method developed for intestinal epithelium for their isolation. 3) Data on induction of intestinal epithelium polyps and neoplasias by mutations in genes encoding SC markers and identification of biochemical characteristics of potential SC in these tumors support the hypothesis of stem tumor cell origination from normal SC or their earliest progeny. In general, facts considered in this review may be useful for both development of optimal methods for the use of SC in cell therapy (as the source of humoral factors), regenerative medicine (as the source of differentiated cells for restoration of injured tissue), and also for targeted search of antitumor drugs (SC as the target) and preparations modifying genetic and epigenetic reactions of SC to genotoxic and stress treatments.