[Microenvironment directs the life of stem cells].

The regeneration of human tissues requires actively dividing tissue-specific stem cells. These cells are maintained and functionally regulated by a specific microenvironment, the stem cell niche. The niche provides protection and produces signals that guide stem cell division and differentiation. As a consequence, the niche plays a significant role in maintaining the tissue throughout life, and thus impaired tissue regeneration associated with aging may be partly due to the non-functional stem cell niche.