Scientists in China say they’ve achieved a human pregnancy through a new technique that may one day help some infertile women.
The work, which experts said couldn’t be done in the United States because of regulatory concerns, did not create any live babies.
One ethicist called the experiment “proof of principle” for human cloning, but other experts disagreed. The work is not aimed at producing genetic copies of people.
Results are to be reported Tuesday in San Antonio, Texas, at the annual meeting of the American Society for Reproductive Medicine. The research was done by scientists at the Sun Yat-Sen University of Medical Science in Guangzhou, China.
They were advised by Drs. John Zhang and Jamie Grifo of New York University Medical Center, whose earlier work had laid the foundation for the new research. Grifo said the Food and Drug Administration indicated that work he was doing might be subject to government regulation, and he stopped his experiments in 1998 because of the energy and money required to comply.
The 30-year-old Chinese woman involved in the experiment had an unusual fertility problem in which embryos stopped developing when they contained only two cells.
Eggs, like other cells, basically consist of a nucleus, which holds most of their DNA, and a surrounding material called the cytoplasm. For the experiment, the researchers removed the nucleus DNA from fertilized eggs and transferred it to the cytoplasm of donor eggs. The idea was to surround the transferred DNA with a new cytoplasm, in hopes that such reconstituted eggs would fare better than the woman’s previous attempts at pregnancy.
They did develop much farther. The researchers say they achieved pregnancy with triplets. One embryo was later terminated at the request of the woman to reduce the medical risk of the overall pregnancy, Grifo said. The other two died at 24 and 29 weeks from complications that did not appear connected to the experimental procedure.
Dr. Joe Massey, a fertility specialist at Reproductive Biology Associates in Atlanta, said a big question about the experimental procedure is how safe it is. If it does prove safe, he said, it would be a big advance for women with the unusual problem in which their own embryos stop developing very early.
It’s possible that such a procedure could also help some older women who can’t use their own eggs, because it would replace the cytoplasm that might be causing the problem, he said.
Dr. David Sable, director of the division of reproductive endocrinology at the St. Barnabas Medical Center in Livingston, N.J., stressed that most age-related infertility in women is not due to problems in cytoplasm. So providing a new cytoplasm could be only “one small tool in the tool kit” for age-related infertility, he said.
Jeffrey Kahn, director of the Center for Bioethics at the University of Minnesota, said the procedure raises concern because it is “akin to cloning technology... I think this is proof of principle for cloning.”
In cloning, the DNA-containing nucleus of a cell from an animal is transplanted into the cytoplasm of an egg. The resulting reconstituted egg is implanted and grown to a genetic copy of the original animal.
R. Alta Charo, professor of bioethics at the University of Wisconsin at Madison, said the Chinese work is not a direct analogy to cloning. A key difference is that the transferred DNA does not have to be reprogrammed to act properly in an egg as it does in cloning, she said.
So the study result doesn’t offer a direct indication of the outcome of attempts to clone humans, she said.
Massey and Sable said the experiment was not cloning, with Massey stressing that it wasn’t aimed at copying an individual. “This is not a pathway to cloning. It’s not about that,” Massey said.