Nearly 40 years after the
world was jolted by the birth of the first test-tube baby, a new revolution in
reproductive technology is on the horizon — and it promises to be far more
controversial than in vitro fertilization ever was.
Within a decade or two, researchers
say, scientists will likely be able to create a baby from human skin cells that
have been coaxed to grow into eggs and sperm and used to create embryos to
implant in a womb.
The process, in vitro
gametogenesis, or I.V.G., so far has been used only in mice. But stem cell
biologists say it is only a matter of time before it could be used in human
reproduction — opening up mind-boggling possibilities.
With I.V.G., two men could
have a baby that was biologically related to both of them, by using skin cells
from one to make an egg that would be fertilized by sperm from the other. Women
with fertility problems could have eggs made from their skin cells, rather than
go through the lengthy and expensive process of stimulating their ovaries to
retrieve their eggs.
“It gives me an unsettled feeling because we
don’t know what this could lead to,” said Paul Knoepfler, a stem cell
researcher at the University of California, Davis. “You can imagine one man
providing both the eggs and the sperm, almost like cloning himself. You can
imagine that eggs becoming so easily available would lead to designer babies.”
Some scientists even talk
about what they call the “Brad Pitt scenario” when someone retrieves a
celebrity’s skin cells from a hotel bed or bathtub. Or a baby might have what
one law professor called “multiplex” parents.
“There are groups out
there that want to reproduce among themselves,” said Sonia Suter, a George
Washington University law professor who began writing about I.V.G. even before
it had been achieved in mice. “You could have two pairs who would each create an
embryo, and then take an egg from one embryo and sperm from the other, and
create a baby with four parents.”
Three prominent academics
in medicine and law sounded an alarm about the possible consequences in a paper
published this year.
“I.V.G. may raise the
specter of ‘embryo farming’ on a scale currently unimagined, which might
exacerbate concerns about the devaluation of human life,” Dr. Eli Y. Adashi, a
medical science professor at Brown; I. Glenn Cohen, a Harvard Law School
professor; and Dr. George Q. Daley, dean of Harvard Medical School, wrote in
the journal Science Translational
Medicine.
Still, how soon I.V.G.
might become a reality in human reproduction is open to debate.
“I wouldn’t be surprised
if it was five years, and I wouldn’t be surprised if it was 25 years,” said
Jeanne Loring, a researcher at the Scripps Research Institute, who, with the
San Diego Zoo, hopes to use I.V.G. to increase the population of the nearly
extinct northern white rhino.
Dr. Loring said that when
she discussed I.V.G. with colleagues who initially said it would never be used
with humans, their skepticism often melted away as the talk continued. But not
everyone is convinced that I.V.G. will ever become a regularly used process in
human reproduction — even if the ethical issues are resolved.
“People are a lot more
complicated than mice,” said Susan Solomon, chief executive of the New York
Stem Cell Foundation. “And we’ve often seen that the closer you get to something,
the more obstacles you discover.”
I.V.G. is not the first
reproductive technology to challenge the basic paradigm of baby-making. Back
when in vitro fertilization was beginning, many people were horrified by the
idea of creating babies outside the human body. And yet, I.V.F. and related
procedures have become so commonplace that they now account for about 70,000,
or almost 2 percent, of the babies born in the United States each year.
According to the latest
estimate, there have been more than 6.5 million babies born worldwide through
I.V.F. and related technologies.
Of course, even I.V.F. is
not universally accepted. The Catholic Church remains firm in its opposition to
in vitro fertilization, in part because it so often leads to the creation of extra
embryos that are frozen or discarded.
I.V.G. requires layers of
complicated bioengineering. Scientists must first take adult skin cells — other
cells would work as well or better, but skin cells are the easiest to get — and
reprogram them to become embryonic stem cells capable of growing into different
kinds of cells.
Then, the same kind of
signaling factors that occur in nature are used to guide those stem cells to
become eggs or sperm. (Cells taken from women could be made to produce sperm,
the researchers say, but the sperm, lacking a Y chromosome, would produce only
female babies.)
Last year, researchers in
Japan, led by Katsuhiko Hayashi, used
I.V.G. to make
viable eggs from the skin cells of adult female mice, and produced embryos that
were implanted into female mice, who then gave birth to healthy babies.
The process strikes some
people as inherently repugnant.
“There is a yuck factor
here,” said Arthur Caplan, a bioethicist at New York University. “It strikes
many people as intuitively yucky to have three parents, or to make a baby
without starting from an egg and sperm. But then again, it used to be that
people thought blood transfusions were yucky, or putting pig valves in human
hearts.”
Whatever the social norms,
there are questions about the wisdom of tinkering with basic biological
processes. And there is general agreement that reproductive technology is
progressing faster than consideration of the legal and ethical questions it
raises.
“We have come to realize
that scientific developments are outpacing our ability to think them through,”
Dr. Adashi said. “It’s a challenge for which we are not fully prepared. It
would be good to be having the conversation before we are actually confronting
the challenges.”
Some bioethicists take the
position that while research on early stages of human life can deepen the
understanding of our genetic code, tinkering with biological mechanisms that
have evolved over thousands of years is inherently wrongheaded.
“Basic research is
paramount, but it’s not clear that we need new methods for creating viable
embryos,” said David Lemberg, a bioethicist at National University in
California. “Attempting to apply what we’ve learned to create a human zygote is
dangerous, because we have no idea what we’re doing, we have no idea what the
outcomes are going to be.”
Source: NYTimes
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