Neural progenitor and stem cells in the adult central nervous system

Neurogenesis occurs in the adult brain, and neural stem cells (NSCs) reside in the adult central nervous system (CNS). In the adult brain, newly generated neuronal cells would originate from a population of glial cells with stem cells properties, and be involved in processes such as learning and memory, depression, and in regenerative attempts in the diseased brain and after injuries. In human, a recent study reported no evidence of migrating neural progenitor cells along the subventricular zone (SVZ) to the olfactory bulb (OB), contrary to other species, highlighting the particularity of adult neurogenesis in human. Though the origin and contribution of newly generated neuronal cells to CNS pathophysiology remain to be fully understood, the discovery that NSCs reside in the adult CNS force us to re-evaluate our knowledge and understanding of brain functioning, and suggest that the adult CNS may be amenable to repair. In this manuscript,we will review the recent data, debates and controversies on the identification, origin and function of newly generated neuronal cells in the adult brain, in human and in other species. We will discuss their contribution and significance to CNS pathophysiology, and for cellular therapy.