Researchers have found stem cells in human amniotic fluid that appear to have many of the key benefits of embryonic stem cells while avoiding their knottiest ethical, medical and logistical drawbacks, according to a study published Sunday.
The stem cells – easy to harvest from the fluid left over from amniocentesis tests given to pregnant women – were able to transform into new bone, heart muscle, blood vessels, fat, nerve and liver tissues, the study said.
“So far, we’ve been successful with every cell type we’ve attempted to produce from these stem cells,” said Dr. Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine in Winston-Salem, N.C., and senior author of the report published online by the journal Nature Biotechnology.
The finding points to a promising avenue of research that sidesteps the hurdles facing embryonic stem-cell research, which has been stymied by moral objections to the destruction of embryos when cells are harvested.
Most of the work involving human embryonic stem cells is ineligible for the more than $25 billion that the federal government spends on research each year. But amniotic-fluid stem-cell studies are already being funded by the National Institutes of Health.
The study also suggests another advantage: Unlike embryonic cells, which can form tumors when implanted in lab animals, amniotic-fluid stem cells do not appear to do so.
“If everything that people think about them turns out to be true, they’ll be a powerful source for therapeutic cells,” said Alan Russell, director of the McGowan Institute for Regenerative Medicine at the University of Pittsburgh, who wasn’t involved in the study.
It is still unclear whether stem cells from amniotic fluid – the liquid that cushions babies in the womb – can give rise to the full range of cell types that embryonic stem cells can produce.
“They can clearly generate a broad range of important cell types, but they may not do as many tricks as embryonic stem cells,” said Dr. Robert Lanza, a prominent embryonic-stem-cell researcher and head of scientific development at Advanced Cell Technology in Worcester, Mass.
But even if the amniotic-fluid stem cells turn out to be less flexible, they still may be an important tool in the nascent field of regenerative medicine.
Dr. Dario Fauza, coordinator of the surgical-research laboratories at Children’s Hospital Boston, has used the cells to grow tissue to repair defective diaphragms and tracheas in sheep.
He has asked the Food and Drug Administration for permission to do the same for children born with herniated diaphragms. It would be the first human clinical trial involving amniotic-fluid stem cells, he said.
Two Swiss scientists, Dr. Dorthe Schmidt and Dr. Simon Hoerstrup of University Hospital Zurich, have used amniotic- fluid stem cells to grow heart valves. They are testing them in sheep.
The stem cells “may not be as earth-shattering a discovery as human embryonic stem cells, but these cells could prove to be equally important for medical therapy,” Lanza said. “This is an exciting breakthrough.”
Amniotic-fluid stem cells lie somewhere between the two major categories of stem cells: embryonic and adult.
Embryonic stem cells are derived from days-old embryos. Nearly all of the development is still to come, so those cells must be extremely flexible.
That trait, called “pluripotency,” is the reason researchers believe embryonic stem cells could offer cures for a range of ailments. They envision using them to replace the faulty islet cells that leave diabetes patients without enough insulin and to grow fresh brain tissue to treat stroke victims, among other things. But they don’t yet know how.
Adult stem cells are narrowly focused on replenishing specific types of tissue that wear out over the course of a lifetime, such as skin, hair and blood. Researchers all over the world are looking for ways to expand their range of capabilities.
Amniotic-fluid stem cells, which are sloughed off by the developing fetus, are “a different kind of a stem cell,” Atala said.
The researchers from Wake Forest and Harvard Medical School studied 10-milliliter samples of fluid extracted from pregnant women who had amniocentesis tests to screen their babies for genetic abnormalities. Those tests are routinely performed early in the second trimester.
The scientists biochemically prompted the cells to transform into all the main categories of embryonic tissue.
“You may be able to obtain the same medical benefits – and cure the same diseases – without the risks or controversy associated with embryonic stem cells,” said Lanza of Advanced Cell Technology.
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What’s new: Researchers are hoping that the stem cells discovered in human amniotic fluid, which are shed by a developing fetus, can as readily transform into new bone, muscle and nerves as embryonic stem cells. The latter, created in the first days after conception, can be turned into any of the more than 220 cell types that make up the human body.
The controversy: Many people oppose the destruction of embryos, necessary to harvest embryonic stem cells. The Bush administration has severely limited funding for embryo work. Amniotic stem-cell studies are funded by the National Institutes of Health.
