Getting closer to humans.
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Researchers get stem cells from cloned monkeys
By Maggie Fox, Health and Science EditorWed Nov 14, 3:31 PM ET
U.S. researchers have cloned monkeys and used the resulting embryos to
get embryonic stem cells, an important step towards being able to do the
same thing in humans, they reported on Wednesday.
Shoukhrat Mitalipov and colleagues at Oregon Health & Science University
said they used skin cells from monkeys to create cloned embryos, and
then extracted embryonic stem cells from these days-old embryos.
This had only been done in mice before, they reported in the journal
Nature. Mitalipov had given sketchy details of his work at a conference
in Australia in June, but the work has now been independently verified
by another team of experts.
They said their work shows it is possible, in principle, to clone humans
and get stem cells from the embryos. "The efficiency is still low but I
am quite sure that it will work in humans," Mitalipov told reporters in
a telephone briefing.
Embryonic stem cells are the source of every cell, tissue and organ in
the body. Scientists study them to understand the biology of disease and
want to use them to transform medicine.
The idea would be to take a small piece of skin from a patient and grow
tissue or even organ transplants perfectly matched to the patient.
But their use is controversial, with opponents saying it is wrong to use
a human embryo in this way. President George W. Bush has repeatedly
blocked legislation that would expand federal funding of such research.
OVERCOMING BARRIERS
Many species of animals have been cloned, and experts have taken stem
cells from a variety of embryos, including human embryos. But it has
been very difficult to both clone and then get embryonic stem cells from
any animal.
Mitalipov's team overcame two barriers -- first cloning a primate, the
group of mammals that includes monkeys, apes and humans, and then
getting embryonic stem cells from the clone.
Mitalipov said the dyes used in cloning some animals apparently are
toxic to primate cells.
They used somatic cell nuclear transfer, which involves taking the
nucleus from an adult cell, in this case fibroblasts, a type of skin
cell, taken from nine adult males.
Then an egg cell is hollowed out and the nucleus from the adult cell
inserted. This programs the egg into behaving as if it had been
fertilized and it can grow into a embryo.
It was not easy. The researchers used 304 eggs from 14 rhesus macaque
monkeys and ended up with just two stem cell lines.
This means a lot more work before this would be useful for humans, they
said -- especially given how hard human eggs are to come by.
Tests show the embryonic stem cells are truly pluripotent, Mitalipov
said, meaning they can develop into any kind of cell found in the body.
"We have been able to develop them into heart cells," he said. They also
grew nerve cells.
It was important to confirm the work. A rival journal, Science, was
forced to withdraw papers published by South Korean scientist Hwang
Woo-suk in 2004 and 2005 after his claims to have cloned a human embryo
proved false.
Mitalipov said the team has tried, and failed, to produce cloned monkeys
that could grow into live baby monkeys.
"We have a goal also of producing live monkeys using the somatic cell
nuclear transfer technique," he said. "One reason is to generate
genetically modified macaques that, for example, carry a specific
disease that is a model of human disease."
His team will not try to clone humans, he said.
"However we hope the techniques we develop will be useful for other labs
which are working ... with human eggs," he said.
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http://news.yahoo.com/s/nm/20071114/sc_nm/cloning_monkeys_dc
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John #1782
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