Dead Brains Get Smart.

Wrap your brain around this: the newest and most promising hope to repair brain damage comes from dead brains! Too bizarre to believe? Neuroscientist (brain scientist) Fred Gage at the Salk Institute in La Jolla, Calif., doesn't think so.

Last November, Gage plucked fresh cells from human cadaver brains (10 hours to three days after death), stewed them in a lab dish, then grew them into brain cells called neurons (nerve cells that transmit electrical signals). "It's amazing," says Gage. "No one dreamed it would be possible to grow new brain cells."

The experiment marks a major medical breakthrough--normally the brain doesn't replenish neurons that die, and their number gradually decreases with age. Neuron loss can lead to fatal brain diseases such as Alzheimer's, which destroys memory, and Parkinson's, which damages the brain's ability to control muscle movement.

So how do you coax new neurons out of dead brains? The answer: stem cells. In the early stages of embryos (unborn babies in their first eight weeks of development), stem cells give rise to all the body's organs, tissues, and body parts (see diagram, above).

HOW SCIENTISTS GROW STEM CELLS

Stem cells can give rise to many types of cells, including brain, muscle, nerve, and liver cells.

1. FERTILIZATION In a lab dish, an egg and a sperm are fused to form an embryo.

2. 1 TO 5 DAYS The embryo repeatedly divides and takes shape as a hollow ball of cells called a blastocyst.

3. 5 TO 7 DAYS Stem cells are removed from the blastocyst.

4. STEM CELLS Once the cells have been removed, the embryo can't survive to become a fetus.

5. SPECIALIZATION Stem cells are bathed in nutrient-rich fluids that direct their growth into advanced cell types.

Once the body has formed, embryonic stem cells vanish and leave behind adult stem cells, which conduct cell repair throughout life. Your skin, for example, relies on adult stem cells in the epidermis (outermost skin layer) to replace the millions of cells that die and slough off each day.

Scientists have discovered the human brain is equipped with adult stem cells as well, and depends on them for rejuvenation. But for reasons still not understood, certain cells, like neurons or heart-muscle cells, may not regenerate. Although Gage has yet to determine if new neurons created from dead brains will be functional in humans, he has good reason to believe they will. Scientists have already injected burn victims with adult stem cells that grew new skin cells to replace damaged ones.

Although adult stem cells divide slower than embryonic stem cells--and are ordinarily limited in what they can become--new research holds promise for their "morphing power."