New Fertility Treatments Arising From Mouse Stem Cell Studies May Ease 'Biological Clock' Fears
NEW YORK -- Scientists have turned mouse skin cells into
eggs that produced baby mice – a technique that, if successfully applied
to humans, could someday allow women to stop worrying about the ticking
of their biological
clocks and perhaps even help couples create "designer babies."
For technical as well as ethical reasons, nobody expects doctors will
be making eggs from women's skin cells any time soon. But some see
possibilities and questions about its use.
Some experts say it could help millions of women who don't
have working eggs of their own, whether because of a medical condition
or cancer treatment, or because they are too old.
"It could mean the reproductive clock doesn't tick for women
anymore," said Hank Greely, a Stanford University law professor who
studies the implications of biomedical technologies.
"I think it's a pretty large advance in the next generation of
reproductive technologies for women," said Amander Clark, who studies
egg development at the University of California, Los Angeles. Discussion
about policy and regulation "needs to begin now."
The mice experiments were reported online Thursday in the journal
Science by scientists at Kyoto University in Japan. The same group had
previously reported work with male mouse cells that led to sperm.
In the new work, they began with genetically reprogrammed skin cells
from female fetal mice. The reprogramming technique, discovered several
years ago, makes an ordinary cell revert to a kind of blank slate, so it
can be chemically prodded to develop into any kind of cell.
The Japanese researchers turned these cells into an early-stage
version of eggs. Then they mixed them with mouse ovarian cells and
implanted them into mice. Four weeks later they collected immature eggs,
matured and fertilized them in the laboratory, and placed them into
surrogate mother mice. The result: three baby mice, which grew into
fertile adults.
That procedure is too cumbersome to be adapted directly for human
use, experts said, and study co-author Katsuhiko Hayashi said in an
email that it is also too inefficient. What's more, he and others said,
biological differences between mice and people would have to be overcome
before some version of the technique could be applied to women.
Starting
with an adult's cells rather than fetal cells would probably work,
experts said. But scientists would also have to learn more about how
women form eggs, which is largely a mystery, some said.
The hurdles are so big that some experts are skeptical about ever
using the approach in people. "I don't think there's a lot of clinical
potential here," said David Albertini, who has studies the development
of eggs at the University of Kansas.
Others are more optimistic but say it won't be easy. A human therapy
is in "the quite far future," Hayashi said. Clark said it would take at
least a decade.
Greely, the Stanford law professor, speculated that in 20 to 40
years, the technique might make couples more likely to go through
test-tube fertilization just so they could choose characteristics of
their babies. That is because donating skin cells to make eggs is a lot
easier than going through the medical and surgical procedure of having
one's own eggs harvested, which is what some women do now.
In the future, Greely said, couples could create eggs and then have
the resulting embryos analyzed genetically. Then they could choose which
embryos they wish to have implanted on the basis of that analysis,
which by that date might be able to indicate not only disease risk but
also a variety of normal traits such as eye color and or a propensity
for certain talents, he said.
Some others, however, said they doubt that practice would become widespread.
"I don't think there's a huge market for it," said Debra Mathews of
the Johns Hopkins Berman Institute of Bioethics. "And people are not
going to stop having sex."
The technique also raises a host of medical and ethical concerns.
"I would be worried about the safety of trying to make kids this
way," said Lawrence Goldstein, director of the stem cell program at the
University of California, San Diego. "It seems like an experiment on
those kids."
It would also be complicated and expensive, adding to the question of
whether it would really be a good way to treat infertility, he said.
He and others also said society will have to decide how much
government regulation would be needed, both for the initial research in
humans and its routine use by doctors.
For example, the new work moves scientists closer to the possibility
of tinkering with genes that would affect not only one person but also
be inherited by future generations, which has long been controversial,
said Dr. George Daley of the Harvard Stem Cell Institute. And basic
research with such eggs could mean making and destroying human embryos
in the lab, which many people oppose.
More controversy could arise over using the method for women who are infertile simply because of their age.
"Society is not clear about how it feels about older women having
children," said Josephine Johnston of the Hastings Center, a bioethics
research institute in Garrison, N.Y. She said there has been no
sustained public discussion of "how old is too old, and what does that
even mean."
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