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THE
NEXT GENERATION OF ARTIFICIAL HEARTS
As
in every other arena, advances in technology pave the way
for smaller, sleeker, more efficient artificial hearts. Today,
teams of scientists from various disciplines- including NASA
engineers- race to design the next generation of artificial
hearts.
PIG
PARTS
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In
1984, "Baby Fae's" baboon-heart transplant sparked public
debate |
While
some researchers have been seeking a mechanical means of replacing
or repairing ailing hearts, other scientists are looking to
a more home grown alternative. Natural as it may seem, xenotransplantation
is equally fraught with scientific quandaries, ethical dilemmas
and bad publicity.
Xenotransplantation
is the use of animal organs in humans. In 1964, doctors first
placed a chimpanzee's heart into a human being. The organ
functioned for only two hours before the recipient's immune
system rejected it, a complication even in human to human
transplants. But recent developments in genetic engineering
might present the solution scientists have been looking for
since 1905.
Primates
like chimpanzees and baboons are the animals most closely
related to humans. That makes them the best and the worst
possible organ donors. Their size and blood types mean primate
organs are most compatible with our own and are least likely
to be rejected; however, primate viruses could also take advantage
of the similarities between chimps and humans and make the
leap into human populations. Add to that the endangered status
of chimpanzees, and it's clear why scientists are looking
to a less cherished species as organ donors.
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Bioengineered
pigs could one day provide thousands of suitable hearts
and other organs. |
Each
year, more than 90 million pigs are slaughtered for food in
the United States. Since they are less closely related to
humans, pig organs are more likely to be rejected, but less
likely to transmit viruses. Today, bioengineers are working
to make pig organs more acceptable to the human immune system
by altering the pig's genetic make up. By adding human immunity
genes to and removing certain pig genes from the cells of
fetal pigs, researchers hope to breed a strain of pigs whose
organs would go unnoticed by a human recipient's immune system.
The
dilemma is forcing scientists to choose between the health
of an individual and the health of society at large.
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But
scientists are in a bind. Bioengineering pigs could provide
more than enough compatible organs each year, but the greater
the usage, the greater the risk of transmitting viruses between
species. Scientists can't yet agree on which poses the bigger
threat to society- the risk of virus transmission or the loss
of hundred's of thousands of people with AIDS, Parkinson's
Disease, spinal cord injuries, diabetes, liver failure, muscular
dystrophy or even psoriasis who could benefit from animal
tissue transplants. The dilemma is an ethical one, forcing
scientists to choose between the health of an individual and
the health of society at large. As with the artificial heart,
public opinion and allocation of funds will have much to do
with its resolution.
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Photos:
LLUMC (Loma Linda University Med. Ctr.); USDA
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