Brain, heal thyself

Adding to the growing evidence that the brains of mammals can produce new nerve cells, a Medical School research team reports that adult rats with strokes caused by blood-vessel blockage are able to grow new brain cells.

The findings presented April 23 at the annual meeting of the Neurosurgical Society of America. The investigators, led by Robert Dempsey, chair of neurosurgery, were trying to determine if the brain of stroke victims could be stimulated to form new nerve cells.

The researchers conducted their study on a group of adult male rats with ischemic strokes (those caused by a blocked blood vessel). As in humans, such strokes kill and damage nerve cells by depriving them of nutrients. The researchers then injected a chemical that incorporates into the DNA of dividing cells. Using specific antibodies, the researchers were able to see that some of the divided cells matured into nerve cells.

One week after the stroke occurred, the researchers found a significant increase in the number of dividing cells in the dentate gyrus, one of several small structures deep in the brain. The dentate gyrus is part of the hippocampus, a region important in memory, learning and the regulation of emotions.

The rats without stroke showed normal rates of cell division in the dentate gyrus, but a very low rate of maturing into nerve cells. “The cell growth took place in a location separate from where the stroke damaged the brain,” notes Dempsey. “This represents a natural healing response of adult brain to a remote ischemic insult. If we come to understand what is happening at the molecular level when the brain is damaged, we will have great potential to replace nerve cells lost during a stroke.”

The finding builds upon recent discoveries that the brains of adult mammals can, under certain circumstances, produce new cells. That was believed to be impossible until about three years ago, when Elizabeth Gould of Princeton documented that the primate brain could create new nerve cells.

The current work at Wisconsin demonstrates that the brain can produce new cells in response to serious injury. A great deal more work, however, must be done before it will be possible to repair human brains by stimulating them to grow new cells.

Dempsey’s lab is now working to identify the mix of brain chemicals necessary to stimulate cell growth in response to stress on the brain. The Dempsey team’s research was funded by a grant from the American Heart Association. Co-authors of the study are Kurt Sailor and Rao Vemuganti of the Medical School Department of Neurosurgery.