Stem Cells in the Adult Brain

This chapter reviews the evidence that neural stem cells exist in adult brain and describes the factors that determine whether these cells divide and, in that case, the fate of their progeny. The adult mammalian brain has vastly reduced regenerative potential compared to the developing brain. Nevertheless, cell proliferation occurs in the adult brain, as does neurogenesis, and cells that generate neurons and glia in vivo and in vitro have been identified in the adult central nervous system (CNS). Although studies dating to the 1960s have documented neurogenesis in the adult mammalian brain, the isolation of cells with stem cell properties, that is, multipotent and self-renewing, from adult neural tissue did not occur until much later. Since that time, numerous reports have identified cells from adult animals with the potential to produce neurons and glia when grown in culture or transplanted into other brain regions. These cells have been isolated from a variety of locations in the CNS, including the spinal cord, the hippocampus, the neocortex, and the striatum. Adult-generated neurons appear to use radial glia processes as migratory guides to their final destination in the rostral forebrain.