12-14-06

SAN FRANCISCO (AFP) - A US study has found that neural stem cells repair damaged brain tissue in laboratory mice far better than previously believed, a finding that could translate into treatment for stroke and other trauma.

Researchers from the University of California at San Francisco wrote in the journal Cell Thursday that neural stem cells in the brain's subventricular zone can effectively fix damaged cerebral tissue.

"The results were very surprising," said Chay Kuo, a member of the research team.

"If we can figure out how this happens, and determine that it occurs in human neural stem cells, we may be able to increase the effect and harness it for therapeutic uses."

The researchers found that within six weeks of birth mice whose brains were purposely damaged by the loss of certain proteins were unexpectedly repaired.

The scientists focused on the postnatal neural stem cells in the subventricular zone, a region next to the lining of the brain's lateral cavity.

Previous studies had identified this part of the brain as a rich source of neural stem cells in newborn mice and humans.

Scientists genetically engineered the neural stem cells in newborn mice so they lacked two critical proteins, dubbed Numb and Numblike.

In the first weeks without the key proteins the mice developed big holes in that part of their brains, and researchers thought they would die.

But as the mice grew the holes were mostly repaired -- evidently by neural stem cells that had "escaped" and wielded regenerative power, the study's authors reported.

"These adolescent mice looked quite good," said researcher Yuh-Nung Jan. "The findings show that the brain has the ability to repair itself and that it is more plastic than previously appreciated."

Scientists have known that neural stem cells drive the growth of specialized brain cells such as neurons in fetal and postnatal mice, but it was unclear how these cells might respond to tissue damage in newborn mice.

Neural stem cells in the brain's subventricular zone may be key to developing therapies to Parkinson's disease, amyotrophic lateral sclerosis -- better known as Lou Gehrig's disease -- and epilepsy, said Arnold Kriegstein, director of the university's Institute for Regenerative Medicine.

The study was funded in part by the California Institute for Regenerative Medicine, the state's three-billion-dollar stem cell agency created by voter initiative in 2004.