New Method Makes Embryo-Safe Stem Cells
Thursday, August 24, 2006
Scientists have for the first time grown colonies of prized human embryonic stem cells using a technique that does not require the destruction of embryos, an advance that could significantly reshape the ethical and political debates that have long entangled the research.
The new work, described in today's issue of the journal Nature, shows that even a single cell plucked from an early human embryo can be coaxed to divide repeatedly in a laboratory dish and grow into a colony of stem cells, coveted for their potential to mend failing organs.
It is already common for fertility doctors to remove a single cell from a days-old embryo before transferring that embryo into a woman's womb -- part of a test to screen out embryos bearing genetic defects. Although the safety of the cell-removal process is still under study, there is no evidence that the procedure puts embryos at significant risk or that babies born from such "biopsied" embryos are abnormal in any way.
If scientists were to grow stem cell colonies from some of the single cells already being removed for genetic testing, scientists said, they could vastly increase the number of colonies for research without putting any embryos at added risk. Until now, researchers have isolated stem cells only from older embryos, which are inevitably destroyed in the process.
"I hope this will solve the political impasse and allow scientists to move on," said Robert Lanza, who led the research at Advanced Cell Technology (ACT) in Worcester, Mass.
Several experts said they, too, hope that Congress and President Bush will accept the approach as worthy of funding with taxpayer money, a source of support off-limits to research that harms embryos.
"You can honestly say this cell line is from an embryo that was in no way harmed or destroyed," said Ronald M. Green, director of Dartmouth College's Ethics Institute and chief of an ethics panel that ACT convened to assess the experiment before it was done.
But early reactions from others suggest it will not be that simple. Bush offered little encouragement yesterday and, if anything, raised the bar higher, suggesting he would not be comfortable unless embryos were not involved at all.
"Any use of human embryos for research purposes raises serious ethical concerns," said a statement released by the White House. ". . . The President is hopeful that with time scientists can find ways of deriving cells like those now derived from human embryos but without the need for using embryos."
Lanza and his team started eight months ago with 16 embryos donated by fertility clinic patients. Each embryo consisted of about eight cells. The researchers took not just one cell from each, but as many as they could get -- destroying some of the embryos and ending up with 91 cells.
Kept in their own dishes with special nutrients, 53 of the cells began to divide and two formed robust colonies of what appear to be, by all tests, embryonic stem cells. ACT scientists have since turned some of the cells into blood vessels, retinal (eye) cells and other potentially useful tissues.
The process is inefficient, Lanza acknowledged -- and would probably be even more so if researchers were limited to taking just one cell per embryo. Moreover, the colonies were grown in mixtures containing animal ingredients, which can leave human stem cells too contaminated for use in medical therapies. The team is now developing non-animal nutrients.
But some experts raised more daunting concerns. Several questioned whether using an embryo's single biopsied cell for stem cell cultivation before doing the genetic testing -- a kind of testing that always destroys the cell, so it cannot be done first -- might put that cell at risk of dying before the crucial gene test is done.
Others expressed concern that the single cell removed from an eight-cell embryo might, under certain conditions, itself be capable of becoming an embryo and eventually a baby. If so, the destruction of the cell might violate the president's insistence that scientists not take what some consider a life to save a life.
Experiments have shown that some mammals can develop from a single cell taken from a four-cell embryo. But several scientists yesterday said no mammal has ever been grown from a single cell taken from an eight-cell embryo -- a more advanced stage of development in which each cell has already become somewhat specialized.
Richard Doerflinger of the U.S. Conference of Catholic Bishops said he is concerned that such a feat may nonetheless be possible. The new work, he said, "raises more ethical questions than it answers."
James F. Battey, chief of the stem cells task force at the National Institutes of Health, said that if a scientist were to apply for grant money to conduct studies like Lanza's, the agency would ask for a legal opinion from the general counsel for the Department of Health and Human Services.
Two issues would have to be considered. The first is whether the work would violate a 10-year-old rider on HHS appropriations that precludes the use of agency funding for research "in which a human embryo or embryos are destroyed, discarded or knowingly subjected to risk of injury or death."
Battey asked: "Where is the bar going to be set? I really don't know, but it's not a scientific call. It's a legal call."
The second question is whether the work violates Bush's ban on federal funding of research on any embryonic stem cells created after Aug. 9, 2001 -- a ban based on the presumption, true at the time, that all such research would require the destruction of embryos.
"Here it's a different derivation process, so it's unclear to me where the president's policy stands," Battey said.
John Gearhart, a stem cell researcher at Johns Hopkins Medical Institutions in Baltimore, said he was hopeful that Lanza's approach would prove fruitful. But he was frustrated, he said, by the fact that Bush's order and the congressional appropriations rider continue to keep federal researchers from a more immediately promising resource: embryos slated for destruction at fertility clinics.
"You have to remember that all this talk of protecting embryos is being done against the background of the routine throwing away of embryos" at clinics, Gearhart said.
Last month, Bush vetoed legislation that would have allowed federally funded scientists to study discarded embryos.