Is therapeutic cloning on the skids?
Monday, 16 June 2008
By Michael Cook
Is the juggernaut of therapeutic cloning grinding slowly to a halt?
Recently (Tuesday, May 6) a bill authorising it in Western Australia
failed on a conscience vote in the upper house by a vote of 18 to 15.
WA Premier Alan Carpenter may use it a trigger for an early poll. For
local supporters of the controversial technique, it was a bitter
blow. Similar acts were preceded by impassioned debate in Canberra
and in Victoria, Tasmania, New South Wales, Queensland and the ACT -
but in the end therapeutic cloning always cruised through.
The decisive factor seems to have been a brilliant new technique in
stem cell science that matches the promise of therapeutic cloning
without its heavy ethical baggage. The creation of "induced
pluripotent stem cells" (iPS cells) was announced by Japanese
researcher Shinya Yamanaka last November - and overnight both the
medical and political landscape changed dramatically.
The WA vote marked the first time that cloning has been put to the
vote since this discovery. It will hearten opponents in the UK, where
the issue is threatening to tear Gordon Brown's government apart.
Therapeutic cloning involves creating a human embryo by injecting a
patient's DNA into a woman's egg, allowing it to develop, killing it,
and extracting "pluripotent" embryonic stem cells. These can develop,
at least theoretically, into any cell in the body. By contrast,
Yamanaka's technique begins with a patient's skin cell. By
introducing a clever combination of precisely targeted retroviruses,
he alters key genes which "reprogram" the skin cell to a pluripotent
state. No need to beg or pay women for their eggs. No destruction of
embryos. No ugly battles with politicians. It is a development so
simple, so clever and so momentous that Yamanaka is being mentioned
as a candidate for a Nobel Prize.
The political consequences are obvious. Some politicians care nothing
for the dignity of embryos; some care passionately. But most feel
that creating and sacrificing embryos for the sake of cures for dread
diseases is a necessary evil. Yamanaka's breakthrough gives these
fence-sitters a way out - cures without ethical controversy.
Significantly, induced pluripotent stem cells featured in the
speeches of at least three Western Australian MLCs. The new
development might persuade South Australian MPs to balk at endorsing
cloning, too, when they debate their own bill.
Yamanaka's achievement is not the sort of good news that withers
under the glare of peer review from hostile colleagues. On the
contrary, according to the authoritative journal Nature Reports Stem
Cells, "The enthusiasm with which the highest-tier ES cell [embryonic
stem cell] scientists have turned to reprogramming speaks volumes".
The scientist who first isolated human embryonic stem cells, James
Thomson, of the University of Wisconsin, calls it the end of an
era. "If you can't tell the difference between iPS cells and
embryonic stem cells [ESC], the embryonic stem cells will turn out to
be an historical anomaly," he says. Ian Wilmut, the Scot who cloned
Dolly the sheep, has also jumped ship.
The switch in Thomson and Wilmut's allegiance has little to do with
ethics. They see only one thing wrong with embryonic stem cells: they
don't work too well. Much like a new computer operating system which
displaces a clunkier rival, iPS cells are rapidly making cloned stem
cells obsolete.
One important advantage is that iPS cells are a 100 per cent match
for the patient. Cloned cells, on the other hand, contain
mitochondrial DNA from a woman's egg. This makes quality control very
difficult and will lead to problems with rejection. Therapeutic
cloning also requires an abundant supply of eggs. This could
eventually entail exploiting poor women, a possibility which cast
another shadow over the bill for WA MLCs.
Of course, iPS cells have problems. Japanese researcher Shinya
Yamanaka developed them by using retroviruses and gene factors which
could cause cancers. But scientists are very confident that the
cancer hurdle will disappear.
"It's going to happen sooner than people think," says Richard Young,
of the Whitehead Institute, one of America's leading stem cell
research centres. And Nature Reports Stem Cells is optimistic: "A
cadre of talented young investigators trained on ES cells and ready
to surpass their mentors is chafing at the bit. As a result of this
ferment, the convergent view of numerous leaders in the field is that
the retroviral delivery problem will be solved within a year or so."
Despite the bubbling interest in iPS cells, most stem cell scientists
still insist that research on embryos must not be stopped. As a
recent editorial in New Scientist puts it, "ESCs remain the gold
standard for pluripotent class, and cloning remains the gold standard
for developmental reprogramming.
journals is bound to continue.
But now that the purpose of creating and destroying cloned embryos
has shrunk from cures for dread diseases to blue sky research and
drug testing for multinational pharmaceutical companies, politicians
everywhere will be having second thoughts about the wisdom of casting
a vote for cloning.
Michael Cook edits the Internet magazine MercatorNet and the
bioethics newsletter BioEdge.
http://www.sciencea
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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