[Adult stem cells: who are they, what do they do?]

Fascinating and provocative findings have shaken the stem cell research field in recent years. One unexpected discovery is the identification of stem/progenitor-like cells in many tissues with slow cellular turnover, such as heart, kidney, muscle and brain. Cells with high proliferative capacity and multilineage differentiation potential have also been described in bone marrow, although their existence needs to be confirmed. Both cell types may prove to have therapeutic potential, but research on their use for tissue repair has been rather disappointing. In addition, serious doubts have been raised concerning the transdifferentiation potential of hematopoietic stem cells, underlining the need for care when interpreting findings that question long-established concepts.