Mouse Brain Now Self Repairing

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The Associated Press

Scientists have managed to make new neurons grow in an area of the brain once
thought to lack the ability to regenerate, raising hopes of developing new ways of treating neurological diseases and head injuries.

The researchers induced the creation of the neurons in the neocortex of lab mice by triggering stem cells, or precursor cells, that already exist in the brain. Other research has shown that under specific conditions, transplanted stem cells can form new neurons. The new study indicates that transplantation may not be needed.

Instead, a combination of molecular signals can accomplish the same thing, said Dr. Jeffrey Macklis, a neuroscience professor at Harvard Medical School and Children's Hospital who led the study. It was published in Thursday's issue of the journal Nature.

The researchers were encouraged to find that the new cells showed evidence
that they were incorporated into the brain circuitry. The cells migrated to areas populated by the dead neurons and sprouted axons, or connections, into the proper tissue.

Macklis and fellow researchers Sanjay Magavi and Blair Leavitt triggered the
new growth by killing specific neurons - a procedure that the scientists do not envision as part of any future treatments. Future experiments will focus on understanding exactly what triggers the creations of neurons and developing drugs or molecular manipulations that do not involve killing cells to create new ones, Macklis said.

Any new treatments for neurological disorders like Alzheimer's and Parkinson's disease or nervous system injuries are many years and experiments away.

"We just have to keep in mind that you can do things in the brain of a mouse that you can't necessarily do in people," said Bruce Dobkin, director of the neurologic rehabilitation and research program at the University of California at Los Angeles. And the fact that a connection sprouted does not mean it functions like the neuron it replaced.

"It's a little bit like you're wiring a switch on your door to the bell in the hallway," Dobkin said. "You can do some things to know that there seems to be a connection there, but you still haven't pressed the button and seen the bell go off."