ADULT stem cells may be able to perform many of the same tricks as embryonic stem cells. If so, the ethical debates about the use of human embryos could be avoided.
Adult mammals have about 20 types of stem cell. It was thought these cells gave rise to only specific cell lines-for example, that blood stem cells could only turn into blood cells-but scientists are now discovering how versatile these cells are.
Angelo Vescovi of Italy’s National Neurological Institute in Milan showed in 1999 that mouse brain stem cells could produce blood cells when injected into mice whose bone marrow-the normal blood-making tissue-had been largely destroyed.…
