US researchers say they will redouble their efforts to create human
sperm from stem cells following the success of a Japanese study involving mice.
A Kyoto University team used mice stem cells to create eggs, which were
fertilised to produce baby mice. Dr Renee Pera, of Stanford University in
California, aims to create human sperm to use for reproduction within two
years, and eggs within five years. Infertility affects up to 15% of
reproductive-aged couples worldwide.
"I know people think it's Frankenstein medicine, but I think it's
not an imagined or lessened health problem - infertility affects your whole
life," Dr Pera says. "To have sex and have a baby would be a super
simple decision, but not everybody can do it." But using embryonic stem
cells for research - as Dr Pera's lab at the Institute for Stem Cell Biology
and Regenerative Medicine does - is controversial because the embryos are
destroyed in order to use them. Dr Pera's lab uses embryos left over from IVF
treatments.
Laboratory generation?
Stem cells have the potential to grow into any cell in the body.
Creating eggs in a lab could become mainstream, much like IVF is viewed today. Dr
Pera says there are about one million or 1.5 million embryos made each year in
America using IVF - and about 500,000 of those embryos are discarded. About 500
of those embryos are used for research, she said. "And people worry about
those 500 instead of the 500,000 discarded," Dr Pera says. The Japanese
study marks the first time a mammal has been created from stem cells. It is
being hailed as the Holy Grail of reproductive stem cell research.
The researchers at Kyoto University say they have demonstrated how to
grow eggs and sperm in a lab and combine them to produce seemingly healthy
offspring. "We are reinvigorated again. It seems that something every two
years comes out that gets everyone reinvigorated," Dr Pera said of the
Japanese study. "We've been mostly working on the human system to do the
same things - to make mature eggs and mature sperm in a dish."
Pregnancy age limits
By creating sperm and eggs from embryonic stem cells, scientists hope to
better understand the reproductive process and embryos. Clinically, this could
eventually give new options to infertile couples who want to have biological
children. Dr Pera's lab has successfully made "primitive" sperm and
eggs in the past, but have not yet mastered creating cells good enough to
actually use in human reproduction. "The cells have some errors. When you
think about stem cell biology and regenerative medicine, most applications are
about making large batches or large sets of cells for, say, cardiac
repair," she says. "Here, we are trying to make one cell that's
perfect.
"One mistake in a genome can lead to devastating disease in a
child. And so I would guess if we were not so careful we could inject the cells
we make into an egg and see what happens. "But you can do that in mice.
You can't do that in women." If successful, the technology could
significantly wind back the time on a woman's biological clock. That is great
news for many women who have put off having babies to pursue careers and for
women who cannot get pregnant due to cancer treatments.
But it raises a slew of new ethical issues: who would decide when a
woman is too old to become pregnant? "That is one of the major worries of
technologies like this - what age should women be allowed to reproduce,"
Dr Pera says. "In most countries there is an age limit - mainly based on
health of being able to carry a pregnancy. It can be dangerous to the heart. It's
hard to carry a baby."
BBC News
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