Scientists have created human embryonic stem cells using a technique that does not require the destruction of embryos -- a development that could break the political roadblock over the highly touted but controversial research.
The method, described today in the journal Nature, involves taking a normal 3-day-old embryo with eight to 10 cells and removing a single cell, which is then biochemically coaxed into producing embryonic stem cells.
The original embryo, despite missing one cell, is unharmed, thus avoiding concerns about destroying life.
Fertility clinics have been removing cells from embryos created in vitro since 1990 to screen them for genetic diseases and chromosomal abnormalities. Doctors estimate at least 2,500 children alive today had a cell or two removed when they were days-old embryos.
The Bush administration, which has restricted federal support for human embryonic stem cell research to prevent taxpayers from funding the destruction of embryos, said it was too soon to say whether the new approach could solve the issue's ethical dilemma.
But White House spokeswoman Emily A. Lawrimore said the work appeared to be a step in the right direction.
"Any use of human embryos for research purposes raises serious ethical concerns, but it is encouraging to see scientists at least making serious efforts to move away from research that involves the destruction of embryos," she said.
Dr. Robert Lanza, the study's senior author, said he believed the technique met reasonable ethical standards and should make the research palatable to social conservatives and the Bush administration.
If Bush warms to the new approach and opens the floodgates of federal funding, it would "give the field a badly needed jump-start," said Lanza, medical director of Advanced Cell Technology Inc. in Worcester, Mass., where the work was done.
Federal funding is limited to about 20 stem cell lines created before August 2001. Last month, despite broad bipartisan support, Bush vetoed a bill to expand funding to more than 100 newer cell lines.
Critics are already saying that the new technique falls short. They said the method injured nascent embryos, and they questioned whether the cell that's removed could itself develop into an embryo.
Richard M. Doerflinger, secretariat for pro-life activities for the U.S. Conference of Catholic Bishops in Washington, D.C., said the study "raises more ethical questions than answers."
The new technique relies on a procedure known as pre-implantation genetic diagnosis, or PGD.
An embryo created through in vitro fertilization is allowed to develop into a small ball of cells, each of which is known as a blastomere. Specialists use a tiny glass tube to remove one cell for genetic testing. If the tests come up clean, the embryo can be implanted in the womb.
The procedure seems to be safe and is routinely used, said Dr. Joe Leigh Simpson, an obstetrician and professor of molecular and human genetics at Houston's Baylor College of Medicine.
Between 20% and 25% of couples who use PGD end up with healthy babies, compared with a success rate of 28.3% for all in vitro fertilization patients, according to Simpson and the Centers for Disease Control and Prevention.
Lanza sought to piggyback on that safety record. If the removed blastomere were allowed to divide once, one cell could be used for genetic testing and the other to make stem cells.
The key was to find a way to get the cell to multiply in a lab dish long enough to produce stem cells. Embryonic stem cells, which are believed to be capable of becoming any cell in the body, are typically harvested from the inner cell mass of a more developed embryo that contains about 150 cells.
Scientists and doctors are intensely searching for ways to harness embryonic stem cells to grow healthy tissue and treat diseases such as Alzheimer's, Parkinson's and diabetes.
Lanza's team thawed 16 frozen embryos donated by fertility clinic patients. To maximize their chance for success, they dismantled the embryos into 91 separate blastomeres and placed them in culture dishes. More than half of them started to multiply, and about half of those began forming clumps.
In two cases, the cells continued to multiply and became embryonic stem cells.
Although the embryos were destroyed in this experiment, Lanza said it was not necessary to destroy the embryos for the procedure to work.
The approach avoids the ethical problem with the standard method of making stem cells, which destroys an embryo by removing its inner cell mass.
"It's extremely unusual for a scientific development to resolve an ethical problem, and this is one of those very rare occasions where that's happened," said Ronald M. Green, a Dartmouth College ethicist who chairs the ethics advisory board for Advanced Cell.
Stem cell researchers who have felt stymied by the lack of federal support for their work were buoyed by Lanza's feat.