Five baboons were able to survive for more than two years with an extra heart connected to their circulatory system – donated by a pig – with the help of immune-suppressing drug therapy.
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In the new study, researchers at the National Institutes of Health and colleagues, tweaked the approach; they engineered the gal-knock out pigs to have extra anti-clotting genetic features and used an antibody to selectively shut down the part of the primate’s immune system that responds to pig organs. To overcome this problem, researchers have explored a variety of strategies to prevent or minimize rejection, including modifying the organ donor’s genes and developing novel immune-suppressing drugs for the organ recipients.
In a statement provided to Washingtonpost News, “To get around that, scientists are using genetic engineering to create pig organs that come just a hair closer to human-like – then testing them in baboons”. The donor pigs were also genetically modified so that their organs would be more compatible with the biology of humans.
As for the baboons, they were given a series of drugs and antibodies so its immune system would not show any overreactions to the transplant.
The study involved transplanting pig hearts into baboons.
“Xenotransplants-organ transplants between different species-could potentially save thousands of lives each year that are lost due to a shortage of human organs for transplantation”, study coauthor Muhammad Mohiuddin, a transplant surgeon at the National Heart, Lung, and Blood Institute, told the Agence France-Presse. The longest a pig heart kept beating was 945 days or almost three years. The finding, published today in Nature Communications, is an important step toward using pig organs to replace ailing human parts.
But through genetic changes, the scientists have added several human genes to the pig genome as well as removing genes which trigger a risky immune response in humans. (The pig is thought to be an ideal candidate for animal-to-human transplants because of its size, its short breeding cycle and its DNA, which has been researched extensively.) In 2002, that work began to pay off; two biotechnology companies announced that they had produced pigs whose organs wouldn’t prompt an immediate rejection when placed in the human body.
The long term goal of the cross-special organ transplants, known as xenotransplantion (foreign transplant), is to provide a solution for the 22 people who die in the USA daily while waiting for an organ transplant.
Science magazine reports that four of the five baboon hosts (one died of an infection) were doing well until the researchers tried to wean them off the drugs.
But organ rejection has stood stubbornly in the way.
However, pigs’ hearts are quite similar to our own and can be farmed easily.
Spending your life on an immune-suppressing drug cocktail isn’t great, but it’s a choice that many organ recipients must make. But having achieved some success, the researchers are now planning to perform heart replacement surgeries on another group of baboons.
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Mohiuddin said the tapering experiments suggest that a lower “maintenance dose” might be effective.
