The brain is a singular organ - our selves are defined by its structure. The aging brain can't be replaced by the same near-future tissue engineering techniques that will give us new hearts and other organs grown fresh from our own stem cells. Thus we are going to have to become very good at repairing the brain in situ, cell by cell, aggregate by aggregate.
One of the biotechnologies needed to achieve this goal is mature regenerative medicine, specifically the ability to manipulate and reprogram stem cells within the brain. Those stem cells must first be found and categorized, and progress continues on that front:
Evidence strongly shows that the true stem cells in the mammalian brain are the ependymal cells that line the ventricles in the brain and spinal cord, rather than cells in the subventricular zone as biologists previously believed. Brain ventricles are hollow chambers filled with fluid that supports brain tissue, and a layer of ependymal cells lines these ventricles.
Knowing the cell source is crucial when developing stem cell-based therapies. Additionally, knowing that these normally dormant cells can be coaxed into dividing lays the groundwork for future therapies in which a patient's own stem cells produce new brain cells to treat neurological disorders and injuries such as Parkinson's disease, stroke or traumatic brain injury.
"With such a therapy, we would know which cells in the body to target for activation, and their offspring would have all the properties necessary to replace damaged or missing cells," said Darius Gleason, lead author of the study and a graduate student in the Department of Developmental and Cell Biology. "It is a very promising approach to stem cell therapy."
Replacing cells is only one part of repairing an age-damaged brain, however. You might take a look at the Strategies for Engineered Negligible Senescence to see the many other issues that accumulate in brain tissue over the course of a lifetime. A lot of work lies ahead.