"And This Little Piggy Went to the O.R."
by Jeffrey P. Kahn, Ph.D., M.P.H.
Director, Center for Bioethics
University of Minnesota
The idea of transplanting animal organs into humans is not entirely new--some of the first efforts at heart transplantation in the 1960s placed a sheep's heart in the chest of a man. And until breakthroughs in developmental biology allow us to grow entire organs in the laboratory, the shortage of human organs makes the prospect of transplanting animal organs into humans an attractive option.
The major obstacle to the success of efforts at cross-species transplantation (xenotransplantation) has been overcoming the human immune system's rejection of "foreign" organs. The advent of powerful drugs developed for human-to-human transplantation, and dramatic breakthroughs in genetic techniques promise the ability to create animals whose organs are human-compatible. Success would mean an ample supply of organs for all that need them.Organs for all?
If animal organs could be made human-compatible, or human immunology made indifferent to the presence of animal organs, then the shortage of human organs could be quickly overcome.
Take for instance the research being performed on pig organs for human transplantation. It so happens that a pig's anatomy, in terms of the size and shape of its internal organs, is relatively similar to a human's. If a pig liver, heart, kidney, or any number of other organs could be genetically altered so that it could be successfully transplanted into a human, hog farms and meat packing plants could do double duty-they'd be raising and collecting organs for transplant as well as meat for our tables.
The ethics of xenotransplantation
But the development of cross-species transplants raises a number of ethical issues, both for individuals and the public. Individual and public safety are real concerns when animal organs are placed into humans. Animals may transmit diseases to humans, which could then infect other humans. Careful screening of the animals from which organs would come, and an ongoing surveillance of those who receive animal organs should reduce the likelihood of infection.
But the long-term risk of animal to human infection is unknown, and it is possible that animal infections exist that we cannot detect or test--witness the only recently discovered infectious agent for so-called mad cow disease and its human counterpart, Cruezfeldt-Jacob disease.
In addition to assuring safety, the challenge of achieving informed consent from the recipients of animal organs will be daunting. There is precious little information about the physical risks as well as psychological impact of xenotransplantation. And the desperation of potential recipients--and therefore likely willingness to undertake even extreme risk--make understanding difficult and increase the potential for taking advantage of patients.
Making genetically-altered bacon
The genetic modification of food animals also raises issues for the public. Experience with other "altered" food products should tell us that society is not always willing to accept technological innovation in the things we eat. Milk from cows treated with bovine growth hormone was rejected in many areas where it was marketed, for instance.
So how would the public react to pork products that came from pigs genetically engineered so that their organs would be useful in human transplantation? Would the public be enticed by cheaper meat from genetically altered, organ donating animals? If so, xenotransplantation offers a way to more efficiently use food animals. If not, we have to ask ourselves the more difficult question of whether we should raise animals expressly for the purpose of harvesting their organs--effectively creating organ farms. Raising pigs or other traditional food animals for such a purpose would be one thing, but what if the most effective organ donor animals were dogs, porpoises or chimpanzees?
Providing organs and protecting the public
The prospect of creating a way to save the lives of the thousands waiting for donor organs is enticing, and research into its eventual realization ought to go forward. But the fact that xenotransplantation raises many new ethical issues argues for careful consideration and public debate as this research proceeds so that we are not solving the organ shortage crisis at the expense of creating another.
"Ethics Matters" Archive
where you'll find other columns from Jeffrey Kahn
on a wide range of bioethics topics.
Center for Bioethics and CNN Interactive.
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