Brain, heal thyself.

Can scientists prompt the brain to grow new nerve cells to replace ones felled by strokes or neurodegenerative diseases such as Alzheimer's? That's a recurring dream, reinvigorated by data published in the June 22 NATURE.

In 1998, countering decades of dogma, scientists obtained convincing evidence that an adult's brain can grow new nerve cells. These newborn cells derive from neural stem cells, rare precursor cells within the human brain. Two years ago, scientists isolated these versatile cells and grew them in the laboratory. That bolstered the possibility that neural--stem cell transplants could heal damaged brains (SN: 11/7/98, p. 293).

Jeffrey Macklis of Children's Hospital in Boston and his colleagues wonder whether there's another option. Perhaps the stem cells already within a stricken brain can be stimulated to do a better repair job than they normally do.

In mouse experiments exploring that idea, Macklis' team first induced mouse nerve cells to commit suicide in a brain region known as the neocortex. This indeed triggered the growth of new nerve cells over the following weeks. Physicians would never deliberately kill brain cells in a person, notes Macklis, but such animal experiments may help reveal the natural signals the brain uses to turn on its in-house repair machinery.