Stem cell technology for basic science and clinical applications

In the adult mammalian central nervous system (CNS), most of the mechanisms responsible for cell proliferation and migration are shut off; thus, the c apacities for self-repair and cellular replacement are greatly diminished. Observations that cell division continues in some regions of the adult brai n and some resulting cells become neurons prompted attempts to identify the progenitor cells responsible for both embryonic and postnatal neural devel opments. The term stem cells refers to a population of cells that is capabl e of extended self-renewal and the ability to generate multilineage (neuron s and glia) cell types (Figure). The growing interest in the isolation and propagation of stem cells and studying stem cell biology is driven by 2 goa ls. The first goal is to establish an in vitro system to ellucidate the fat e pathways of individual neural progenitors. Such a system can be used to d etermine signaling molecules controlling the generation of specific neural cell lineages and to dissect cellular mechanisms underlying the progressive processes of commitment, fate determination, and differentiation during ne ural development. The second goal is to use such cultured, well-characteriz ed cells for therapeutic applications in the treatment of neurologic and ne urodegenerative diseases.