If scientists could decode the complex series of biochemical signals used to command the cells, they could create any type of tissue.
Doctors could grow new nerve fibers to patch a severed spine. They could make new organs to replace damaged ones without fear of tissue rejections. They could grow brain cells to help patients with Alzheimer's disease.
At the National Institutes of Health, mouse embryonic stem cells were transformed into neurons that made the brain chemical dopamine. The new cells were used to treat symptoms of Parkinson's disease in rats.
At Stanford University, the same type of cells was used to make insulin-producing cells that kept diabetic mice alive.
At UC Irvine, human embryonic stem cells were transformed into nerve-wrapping cells known as oligodendrocytes, which helped rats with spinal cord injuries.
But scientists say the complex biochemistry of humans means that medical therapies are years, if not decades, away. Therapies could lead to cancer if the stem cells migrate to the wrong place.
There are currently no trials underway for human therapies using embryonic stem cells in the U.S.
"It's still in its infancy," said Gail Martin, a developmental biologist at UC San Francisco who was one of the first scientists to isolate embryonic stem cells in mice.
A CONFIDENT MAN, A CONFIDENT PATIENT
Valerie had never really noticed how life was balanced on a knife point, ready to topple her into darkness at any moment.
She was a 23-year-old stewardess for Delta Airlines when Tom spotted her at a wedding in 1973. Eleven months later they were married — and on the path to the good life they both wanted.
Over the next three decades, they built a house in one of the toniest Atlanta suburbs, bought a vacation home on nearby Lake Burton, joined a country club and took ski trips to Aspen. Their two children attended private schools. Tom pushed hard for these things.
He was always so sure. That was one of the things that had attracted Valerie. He had a smooth, confident voice that put people at ease.
His voice was the first thing to go.
Valerie noticed in the spring of 2002 that his speech had begun to slur ever so slightly sometimes, as if he were drunk. She hoped the doctors were right, that he was suffering from allergies or stress from his business.
In October, a doctor told her that Tom probably had no more than a few years to live. She let out a scream. The doctor put her on an antidepressant.
Tom had bulbar ALS. The disease starts in the cranial nerves that control the lower face, tongue and palate, reaching the vital organs more quickly than a slower-killing variety that starts in the limbs.
Tom approached his illness like another real estate deal.
SELLING SCIENTIFIC PROMISE