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Affairs of the Heart
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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.


Photo of baby fae
  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.

Photo of pigs
  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.


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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