Stem cells as therapeutics for neurodegenerative disorders?

Aging is associated with a progressive increase in the risk of several prominent neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, stroke and amyotrophic lateral sclerosis. In each of these disorders specific populations of neurons become dysfunctional, then die and are not replaced. The adult brain and spinal cord contain populations of so-called neural stem cells (self-renewing and multipotent) and neural precursor cells (specified to a certain fate, but still mitotic) that may provide a continuing source of new neurons and glial cells during successful aging and after injury to the nervous system. Recent studies have shown that stem cells from embryos and adults can be transplanted into the nervous system, differentiate into neurons and glia and restore lost function in experimental models of neurodegenerative diseases. Embryonic stem cells may be a particularly effective donor cell type for transplantation-based therapies. Efficacy of stem cell therapies remains to be established in clinical trials in humans. Another approach is to mobilize endogenous neural stem cells. Animals studies have shown that dietary and behavioral modifications can indeed stimulate neurogenesis. Molecular and cellular mechanisms that regulate the proliferation, differentiation and survival of neural stem cells and neural precursor cells are being elucidated and are revealing novel targets for the development of pharmaceuticals that promote neurogenesis.