Typical and atypical neural stem cell niches

The adult central nervous system (CNS) is a tissue with a low rate of renewal and can be seriously affected by injuries and diseases. The generation o f new neural cells, such as neurons and glia, is prevalently restricted to specific CNS areas ( niches ) deriving from embryonic germinative layers. Continual neurogenesis is sustained by multipotent astro/radial glia-like neural stem/precursor cells (NPCs), which persist within adult CNS niches endowed with molecular/cellular signals capable of regulating their biological features. Multipotent NPCs have less typically been identified in the mor e spread mammalian CNS parenchyma. Due to their inherent plasticity, NPCs from typical and non- typical CNS germinal areas might therefore concur to nervous system repair upon injury and/or disease . In parallel, the transplantation of NPCs promotes remarkable CNS repair via both cell replacement as well as intrinsic bystander neuroprotective capacities. Strictly depending on when injected int o a live host suffering from a CNS disease (e.g., inflammatory vs. degenerative), transplanted NPCs display an extraordinary capacity of finding in viv o the proper way(s) towards certain favourable perivascular sites ( atypical niches) , where they survive and act as therapeutic weapons trough the interaction with the (micro)environment. The next challenge for the future of (endogenous vs transplanted) stem cell-based therapies will be the development of new protocols for carefully weighting and tightly regulating the different therapeutic alternative mechanisms NPCs may instruct in vivo.