Researchers at Wake Forest University School of Medicine and Harvard Medical School discovered the novel source of amniotic fluid-derived stem (AFS) cells.
"Our hope is that these cells will provide a valuable resource for tissue repair and for engineered organs as well," said Dr Anthony Atala, director of the Institute for Regenerative Medicine.
He continued: "It has been known for decades that both the placenta and amniotic fluid contain multiple progenitor cell types from the developing embryo, including fat, bone, and muscle. We asked the question, 'Is there a possibility that within this cell population we can capture true stem cells?' The answer is yes."
Stem cells can be grown into any tissue in the body and are widely touted as a potential cure for a huge array of disorders, including diabetes, Alzheimer's disease and stroke. But their use is currently restricted on ethical grounds: they are often harvested from human embryos that then have to be destroyed.
However, AFS cells avoid that ethical debate and are easy to collect either while a baby is in the womb or directly from the placenta after birth. People could, if needed, then use their own stem cells from infancy to treat a disease or grow new tissue. The cells could also be collected and stored for existing patients, having come from an ethical source.
It has taken the team seven years to verify the research and the scientists now believe that the new stem cells represent an intermediate stage between embryonic stem cells and adult stem cells.
As well as being easy to obtain, AFS cells grow fast, doubling in number every 36 hours and do not require feeder guidance to grow and do not produce tumours, a drawback often seen with embryonic stem cells.
Atala said that a bank with 100,000 specimens could theoretically supply 99 per cent if the US with perfect genetic matches for transplantation.
"The full range of cells that AFS cells can give rise to remains to be determined," said Atala. "So far, we've been successful with every cell type we've attempted to produce from these stem cells. The AFS cells can also produce mature cells that meet tests of function, which suggests their therapeutic value."
When injected into mice, the AFS cells grew and repaired damage caused but a degenerative brain disease. Also, bone tissue was successfully grown and liver cells produced from stem cells were successfully able to secrete urea,
In 2005, Atala used stem cells garnered from circumcised foreskin to generate bone, fat and muscle tissue.