Adult stem cells: their scientific interest and therapeutic future

Fascinating and provocative findings have shaken the stem cell field during these past years, which may be exploited in the future in cell replacement therapies. Continuous renewal of blood, skin, and gut cells, has long be attributed to stem cells, but it was more unexpected to identify cells that fulfil the requirements for stem-progenitor cells in many tissues with a slow turnover such as heart, kidney, muscle and brain. However, despite their lack of risk and immunological barrier, adult stem cells are yet of poor therapeutic value in many diseases, because they are available in scarce number, are poorly amplified, and loose potential with ageing, among many obstacles. Thus, the identification in adult, and more recently fetal tissues, of cells with a high proliferative capacity and multi-lineage differentiation potential has been wellcome, although their existence is still a matter of controversy. An alternative would be to activate stem cells in situ, by acting on components of the niche as recently exemplified in the hematopoetic system. Finally, as fiction meets reality, it may become possible to reprogram human adult cells in pluripotent ES cells-like, as recently demonstrated in mice. (C) 2007 Elsevier Masson SAS. Tous droits reserves.