In this month's issue of Nature Reviews Neuroscience, Italian scientists G. Martino and S. Pluchino review the therapeutic potential of neural precursor stem cells. The paper provides an excellent overview of the advances that have been made with adult neural progenitor/precursor cells (aNPCs). The authors noted that in chronic neurodegenerative diseases, whereby there are multifocal lesions in the brain, chronic inflammation leads to recruitment of aNPCs to the damaged tissue sites. However, the wound-healing response usually leads to scar formation and permanent damage of the tissues in the CNS. Furthermore, the authors cited in vivo results in which aNPCs implanted at the diseased sites were not able to regenerate the damaged tissues back to a fully functional state. It was noted, however, that the implanted aNPCs demonstrated a neuroprotective effect, but the implanted cells were incapable of terminally differentiating into the appropriate neural phenotypes when the tissues were examined histologically. Therefore, the authors suggested that therapeutic efficacy reported by others may be attributed to bystander mechanism(s) in which the implanted cells form an atypical ecotopic (perivascular) niche by providing neurotrophic and immunomodulation support to the neural stem cells within the germinal centers of the subventricular zone in the lateral ventricles and the subgranular zone in the hippocampal dentate gyrus of the brain during the tissue remodeling process. The authors noted that immunomodulation by the transplanted aNPCs may occur from the cells secreting soluble molecules such as certain cytokines, chemokines, and various surface receptors that may downregulate inflammatory T cells and macrophages at the targeted tissues. (Another hypothesis is that the aNPCs may not be the correct cells for remodeling the damaged tissues. We have observed that in order to obtain good tissue integration, one needs to implant a more primitive lineage of uncommitted stem cells within target tissues such as brain, heart, or skeletal muscle.)