New Source of Stem Cells Discovered

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Unlike "true" stem cells, however, these cells were predestined to grow into only one type of cell, or a limited type of other cells.

"We wanted to see if there was a true stem cell population within this fluid, pluripotent stem cells which could give rise to multiple cell types," Atala explained. Pluripotent cells are capable of differentiating into many different types of cells.

After seven years of digging, Atala's team found that 1 percent of the amniotic fluid cells were pluripotent. The newly discovered cells seem to possess characteristics that rest halfway between embryonic stem cells and adult stem cells. Like other stem cells, they can self-renew and double in number every 36 hours. But unlike other stem cells, they do not produce tumors.

The stem cells could be harvested any time from the beginning of pregnancy until just after a baby is born, Atala said.

When nerve cells created from AFS cells were implanted into mice with a degenerative brain disease, the cells re-populated the diseased areas of the brain. Bone cells were also successfully grown into bony tissue in mice, and liver cells were grown that could secrete urea.

But it will be some time before any human benefit from these cells is seen -- if it is seen at all, the researchers said.

"It's a very nice paper, very good science," said Dr. Darwin Prockop, director of the Center for Gene Therapy at Tulane University Health Sciences Center in New Orleans. "But I can't quite put a circle around the potential of the cells. They may be useful for some kinds of therapy but I don't quite know where it's going to go."

Theoretically speaking, Atala said, a bank of 100,000 specimens could potentially supply 99 percent of the U.S. population with a perfect genetic match for transplantation.

But human studies haven't even begun yet.

"We don't know what the extent of therapy will be with these cells," Atala said. "Time will tell."

More information

The U.S. National Institutes of Health has more on stem cells, including current official policy.