Towards Brain Regeneration
It may be possible to direct stem cells lying dormant in the brain to set forth and repair damage: scientists "have identified specific molecules in the brain that are responsible for awakening and putting to sleep brain stem cells, which, when activated, can transform into neurons (nerve cells) and repair damaged brain tissue. ... Chen believes that tapping the brain's dormant, but intrinsic, ability to regenerate itself is the best hope for people suffering from brain-ravaging diseases such as Parkinson's or Alzheimer's disease or traumatic brain or spinal cord injuries. Until these studies, which were conducted in the adult brains of mice, scientists assumed that only two parts of the brain contained neural stem cells and could turn them on to regenerate brain tissue ... Chen's team learned that stem cells existed everywhere in the brain by testing tissue from different parts of adult mice brains in cultures containing support cells (known as astrocytes) from the hippocampus, where stem cells do regenerate. ... In the [second] study, the team went on to discover the exact nature of those different chemical signals. They learned that in the areas where stem cells were sleeping, astrocytes were producing high levels of two related molecules ... They also found that removing these molecules (with a genetic tool) activated the sleeping stem cells."
Link: http://www.eurekalert.org/pub_releases/2008-06/seri-b060608.php