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.
