Pig-organ transplants could soon be reality

Gene-editing leap removes viruses that would harm humans

In a striking advance that helps open the door to organ transplants from animals, researchers have created gene-edited piglets cleansed of viruses that might cause disease in humans.

In a striking advance that helps open the door to organ transplants from animals, researchers have created gene-edited piglets cleansed of viruses that might cause disease in humans.

The experiments, reported Thursday in the journal Science, may make it possible one day to transplant livers, hearts and other organs from pigs into humans.

If pig organs were shown to be safe and effective, “they could be a real game changer,” said Dr. David Klassen, chief medical officer at the United Network for Organ Sharing, a private, nonprofit organization that manages the nation’s transplant system.

Animal exploitation?

There were 33,600 organ transplants last year and 116,800 patients on waiting lists, according to Klassen, who was not involved in the new study.

Dr. George Church, a geneticist at Harvard who led the experiments, said the first pig-to-human transplants could occur within two years.

The new research combines two great achievements in recent years — gene editing and cloning. But it may be years before enough is known about the safety of pig organ transplants to allow them to be used widely.

Porcine organs can be the right size for human transplantation, and in theory, similar enough to function in patients.

But the prospect also raises thorny questions about animal exploitation and welfare.

Scientists pursuing this goal argue that the few thousand pigs grown for their organs would represent just a small fraction of the estimated 100 million pigs killed in the U.S. each year for food and that they would be used to save human lives. The animals would be would be anesthetized and killed humanely.

Retrovirus-free piglets

Major religious groups have already weighed in, generally concluding that pig organs are acceptable for lifesaving transplants, noted Dr. Jay Fishman, co-director of the transplant program at Massachusetts General Hospital.

In 1998, Fishman and his colleagues discovered that hidden in pig DNA were genes for viruses that resembled those causing leukemia in monkeys. When researchers grew pig cells next to human embryonic kidney cells in the laboratory, these viruses — known as retroviruses — spread to the human cells.

Church and his colleagues thought the retrovirus question could be resolved with Crispr, the new gene-editing technology. They took cells from pigs and snipped the viral DNA from their genomes. Then the scientists cloned the edited cells.

Church and his colleagues ended up with 15 living piglets, the oldest now 4 months old. None have the retroviruses.