Amniotic Fluid Seen as Alternative Source for Stem Cells

WINSTON-SALEM, N.C., Jan. 8 -- Cells harvested from amniotic fluid express embryonic and adult stem cells markers, researchers here reported.

If the findings are confirmed, amniotic fluid may be an amble and viable alternative source for stem cells without the ethical baggage attached to embryonic stem cells derived from an aborted fetus. Stem cells, the investigators believe, amount to about 1% of all cells in amniotic fluid.

The undifferentiated amniotic fluid-derived stem cells "expand extensively without feeders, double in 36 hours, and are not tumerigenic," said Anthony Atala, M.D., of the Institute for Regenerative Medicine at Wake Forest, and colleagues.

"Our hope is that these cells will provide a valuable resource for tissue repair and for engineered organs as well," said Dr, Atala, who reported the findings online in Nature Biotechnology.

"We have demonstrated that stem cells can be obtained routinely from human amniotic fluid, using back-up cells from amniocentesis specimens that would otherwise be discarded," he and colleagues said. "The amniotic fluid-derived stem cells grow easily in culture and appear phenotypically and genetically stable. They are capable of extensive self-renewal, a defining property of stem cells."

Cell lines, which were maintained for over 250 population doublings, retained long telomeres and a normal karyotype. Moreover, the amniotic fluid-derived stem cells are broadly multipotent, as demonstrated by differentiation into adipogenic, osteogenic, myogenic, endothelial, neuronal and hepatic lineages.

His team has used the cells, taken from amniotic fluid of 19 pregnant women, to create muscle, bone, fat, blood vessel, nerve and liver cells in the laboratory. "We tested lines obtained from 19 different amniocentesis donors and found that amniotic fluid-derived stem cells were able to differentiate along adipogenic, osteogenic, myogenic, endothelial, neurogenic and hepatic pathways," they wrote.

In some cases the differentiated cells displayed specialized functions, for example neuronal lineage cells secreted either the neurotransmitter L-glutamate or expressed G-protein-gated inwardly rectifying potassium channels, while liver hepatic lineage cells produced urea, and osteogenic lineage cells formed tissue-engineered bone, Dr. Atala said.

Dr. Atala said he and his colleagues also conducted tests on mice with neurodegenterative. In those tests, murine amniotic fluid-derived stem cells homed in on damaged regions of the brain repopulated the areas with fresh neurons.

He noted that researchers have known for decades that both the placenta and amniotic fluid contain multiple progenitor cell types form the developing embryo.

He and his colleagues where intrigued by the possibility that "within this cell population we could capture true stem cells and the answer is yes."

"We asked the question, 'Is there a possibility that within this cell population we can capture true stem cells?' The answer is yes."

He predicted that a tissue bank with 100,000 such specimens theoretically could supply 99% of the U.S. population with perfect genetic matches for transplantation.