Scientists reported Sunday they had found a plentiful source of stem cells in the fluid that cushions babies in the womb and produced a variety of tissue types from these cells _ sidestepping the controversy over destroying embryos for research.

Researchers at Wake Forest University and Harvard University reported the stem cells they drew from amniotic fluid donated by pregnant women hold much the same promise as embryonic stem cells. They reported they were able to extract the stem cells without harm to mother or fetus and turn their discovery into several different tissue cell types, including brain, liver and bone.

"Our hope is that these cells will provide a valuable resource for tissue repair and for engineered organs as well," said Dr. Anthony Atala, head of Wake Forest's regenerative medicine institute and senior researcher on the project.

It took Atala's team some seven years of research to determine the cells they found were truly stem cells that "can be used to produce a broad range of cells that may be valuable for therapy."

However, the scientists noted they still don't know exactly how many different cell types can be made from the stem cells found in amniotic fluid. They also said that even preliminary tests in patients are years away.

Still, Atala said the research reported in the scientific journal Nature Biotechnology expands far beyond similar work discussed at a heart research conference in November. There, Swiss researcher Simon Hoerstrup said he managed to turn amniotic fluid stem cells into heart cells that could be grown into replacement valves. Hoerstrup has yet to publish his work in a scientific journal.

Atala said the new research has found even more promising stem cells with the potential to turn into many more medically useful replacement parts.

"We have other cell lines cooking," Atala said.