TRURO, N.S. – Specialized pig herds might become the source of human “spare parts” in the future.
A transplant surgeon at Dalhousie University in Halifax is working with researchers at the Nova Scotia Agricultural College in Truro to find ways to use hog organs in humans.
Dr. Vivian McAlister said he started the research because of what he saw in his medical practice.
“I’ve seen people die waiting for organs. I’ve seen people come to us who are not suitable for transplants and we have to reject.”
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Chimpanzees would make better non-human organ donors than pigs because they are more closely related, but because of this kinship the medical community believes the public would reject “farming” primates for organs.
Pigs, on the other hand, are already intensively farmed for human use. Also, man and pig have lived in close quarters for thousands of years and rarely has there been transmission of disease between the two.
The big drawback to using pig organs is the certainty that the human body will reject them.
“Rejection of an animal organ is going to be more vigorous by many factors than rejection of a human organ,” he said.
Rejection is a significant problem in human to human transplants and doctors treat it by administering drugs to suppress the immune system. But with animal to human transplants, the drug dose would be so high that the risk of dying from infection or cancer would be unreasonable.
Scientists must either change the pig so it is less likely to be rejected or change the donor to be more tolerant to the pig organ.
The latter is the more hopeful area of research, he said.
“The techniques used to develop tolerance involve the transfer of bone marrow, or what are called stem cells, to the recipient.
“It is our bone marrow that fights the transplant, so if we trick the body into accepting the bone marrow of the donor, that marrow won’t recognize the organ that comes later as being different.”
Mix the marrow
The solution might be to remove some of the patient’s bone marrow and then destroy the rest. Temporarily defenseless, the patient would have to be in a isolated, disease-free unit.
“Then you’d give them back bone marrow of themselves and the pig and the period of risk for infection would pass and they’d go back to a normal life, but they’d be able to get a kidney.”
Scientists elsewhere have already used pig organs as temporary substitutes while the patient waits for a human donor. They found that some pigs provided organs with fewer rejection problems than others.
Researchers led by Leslie MacLaren at the agricultural college are trying to find a way to identify these animals and use them to breed a herd that uniformly has the trait.
