Stem cell plasticity - building the brain of our dreams

Many recent studies indicate that adult-derived stem cells are much more plastic than was previously thought, and that they can cross lineage boundaries and produce progeny of widely diverse types. This would increase the number of routes available for generating new cells for tissue repair, and would make patient-donated autografts more feasible. Beyond the attention-grabbing headlines that have appeared in the press, scientists working in the stem cell field have to evaluate critically the evidence that adult stem cells can make other cell types, using traditional techniques combined with new technologies for determining cell fates. Focusing on the nervous system, the evidence that adult neural stem cells are highly plastic, and that other types of adult non neural stem cells can generate neural progeny, is reviewed. The aim is to provide a balanced view of the evidence and to highlight some important experiments that should be done before we can conclude that adult stem cells are potent enough to replace the wealth of neural cell types.