Stem cells: general aspects, biological and molecular events

Self-renewal capacity and differentiation are features of stem cells that vary among the different cellular types according to the tissue in which they reside and the surrounding microenvironment. Cellular cycle inhibitors, genes implied in chromosomal rearrangements, essential development proteins and specific signaling pathways intervene in these processes. Self-renewal is regulated by different mechanisms, the most important of which are the Wnt, Notch and Hedgehog pathways, and the factors BMI-1, p16(Ink4a), ARF, NANOG, OCT3/4, SOX2, HOXB4 and their paralogs. Advances in the knowledge of stem cells biology and of the molecular mechanisms that influence their self-renewal and differentiation have made these cells an important promise for both basic and applied research.