The brain and spinal cord were once considered mitotic dead ends, a division of neurons dwindling with toddlerhood, with memory and learning the consequence of synaptic plasticity, not new neurons. But the discovery of neural stem cells (NSCs) in the human adult central nervous system (CNS) has raised the possibility of reawakening neurogenesis in the adult to treat neurodegenerative diseases, such as Parkinson, Alzheimer, and Huntington diseases, and spinal cord injuries.
"Does the human CNS self-repair? Of course it does! We live 90 years. It is unreasonable to think that there is no turnover, like in every other organ," says Fred Gage, of Salk Institute for Biological Studies, La Jolla, Calif., who led the team that discovered neural stem cells in the human brain in 1998. "Can we turn endogenous cells into neurons in a disease setting? Can we activate our own systems? We are beginning to unravel cell fates ...
