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- BLACKSBURG, Virginia (ENS)
- The same company that in 1996 produced the world's first cloned mammal,
the sheep Dolly, says that on March 5, five piglets were born as a result
of cloning using adult cells, raising hopes for a new source of organ transplants
for humans.
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- This is the first time cloned pigs have been successfully
produced from adult cells.
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- The cloned piglets were produced by the Blacksburg, Virginia
facility of PPL Therapeutics which has its headquarters near Edinburgh,
Scotland.
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- The five cloned piglets (Photos courtesy PPL Therapeutics)
They were delivered by Caesarean section at the Virginia-Maryland College
of Veterinary Medicine. Tests by an independent laboratory confirmed the
piglets are clones of the sow.
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- The cloning of these pigs opens the door to "making
modified pigs whose organs and cells can be successfully transplanted into
humans - the only near term solution to solving the worldwide organ shortage
crisis," the company said in a statement today.
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- Clinical trials could start in as little as four years
and analysts believe the market could be worth $6 billion for organs alone.
A similar sized market exists for cellular therapies, such as transplantable
cells that produce insulin for treatment of diabetes, the company said.
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- The British Medical Association's head of ethics, science
and health policy, Dr. Vivienne Nathanson, said the cloning of pigs raises
serious issues. "The issues that need to be understood include the
fact that what we are talking about is a technique that carries risks for
the population at large, as well as the potential to save lives,"
she said.
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- Dr. Nathanson said there is huge public sympathy with
people who die while waiting for transplants, but people are sceptical
about the safety of new techniques.
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- But PPL Therapeutics said the possibility of so-called
"silent viruses" being transferred from pigs was "hypothetical."
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- Xenotransplantation is the transfer of organs from one
species to another. The fundamental problem with transferring organs between
species is rejection by the recipient,s immune system. PPL,s clonin program
aims to overcome the causes of rejection and develop transgenic animals
containing genetic modifications which can be used as organ donors for
humans.
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- The method used to produce the five female piglets, to
be named Millie, Christa, Alexis, Carrel and Dotcom, was different from
that used to produce the world's first cloned sheep, Dolly, in that it
used additional inventive steps for which a patent application has been
filed.
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- The work was carried out by PPL,s U.S. staff in Blacksburg,
Virginia, partly supported by funding from the U.S. government,s National
Institute of Standards and Technology. This particular award has as its
objective the production of a "knock-out" pig - a pig which has
a specific gene inactivated. The ability to clone pigs is the first essential
step in achieving this objective.
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- The gene to be inactivated is alpha 1-3 gal transferase.
This gene is responsible for adding to pig cells a particular sugar group
recognised by the human immune system as foreign. When the human system
detects this sugar group, an immune response is triggered that makes the
human system reject the transplanted organ.
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- Ron James, managing director of PPL, said, "An end
to the chronic organ shortage is now in sight. The next step for PPL is
to repeat the pig cloning experiment to produce knock-out pigs."
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- "We are unaware of any other group that has as comprehensive
an approach to xenotransplantation as PPL. All the known technical hurdles
have been overcome. It is now a case of combining the various strategies
into one male and one female pig, and breeding from these," said James.
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