After transplanting a genetically engineered pig kidney into a human, health professionals announced that the organ lived for more than a month in a brain-dead patient in the United States without signs of failure, as researchers investigate methods for successful cross-species organ donation.
“We have a genetically-edited pig kidney surviving in a human for over a month,” said Robert Montgomery, director of the NYU Langone Transplant Institute.
In September 2021, Montgomery performed the first genetically engineered pig kidney transplant on a person, followed by a similar treatment in November 2021.
“I think there’s a very compelling story that exists at this point that should give further assurances about starting some initial studies… in living humans,” he said.
There have now been a few more occurrences, with all of the studies lasting two or three days.
Unlike previous transplants, which needed up to ten genetic alterations, the latest involved only one: in the gene involved in “hyperacute rejection,” which occurs within minutes of an animal organ being attached to a human circulatory system.
The NYU Langone team was able to prevent instant rejection by “knocking out” the gene responsible for a biomolecule called alpha-gal, which is a prominent target for wandering human antibodies.
“We’ve now gathered more evidence to show that, at least in kidneys, just eliminating the gene that triggers a hyperacute rejection may be enough along with clinically approved immunosuppressive drugs to successfully manage the transplant in a human for optimal performance — potentially in the long-term,” said Montgomery.
They also embedded the pig’s thymus gland — which lies around the neck and is responsible for educating the immune system — in the kidney’s outer layer.
Adam Griesemer, of the NYU Grossman School of Medicine, added: “This allowed immune cells in the host’s body to learn to recognise the pig’s cells as its own, preventing a more delayed rejection.”
After removing both of the patient’s own kidneys, one pig kidney was implanted and began generating urine immediately.
Monitoring revealed that creatinine levels, a waste product, were ideal, and there was no evidence of rejection.
No organ failure detected
Importantly, no indication of porcine cytomegalovirus — which can cause organ failure — has been found, and the team plans to monitor the animals for another month.
Surgeons at the University of Maryland Medical School performed the world’s first pig-to-human transplant on a living patient in January 2022.
Two months later, he died, and the discovery of porcine cytomegalovirus in the organ was later attributed.
The donor pig was sourced from the Revivicor herd in Virginia.
The Food and Drug Administration authorised the herd as a source of meat for persons who are allergic to the alpha-gal molecule, which is caused by tick bites.
Because these pigs are bred rather than cloned, the technique may be scaled more simply.
Current efforts focus on pigs, which are thought to be ideal donors because of their organ size, their rapid growth and large litters, and the fact they are already raised as a food source.