Doctors transplanted a pig's kidney into a brain-dead man’s body. Then this happened

A pig’s kidney transplanted into a brain-dead man has continued to function normally for over a month, marking a critical step in medical research aimed at advancing cross-species transplants.

Dr Robert Montgomery, director of NYU Langone’s transplant institute, prepares a pig kidney for transplant into a brain-dead man in New York on 14 July 2023. Source: AAP / Shelby Lum/AP

Key Points

• The pig's kidney was genetically edited and survived over a month in a human.
• Similar transplants have previously failed due to human immune systems attacking the foreign tissue.
• There are more than 103,000 people waiting for organs in the United States, 88,000 of whom need kidneys.

US surgeons who transplanted a genetically modified pig kidney into a brain-dead patient said the organ was still working well after a record 32 days making a significant step in the quest to close the organ donation gap.

The latest experimental procedure is part of a growing field of research aimed at advancing cross-species transplants, testing the technique on bodies donated for science.

Medical researchers collect a kidney biopsy during the transplant. Credit: Steve Wood/AP

There are more than 103,000 people waiting for organs in the United States, 88,000 of whom need kidneys.

"We have a genetically edited pig kidney surviving for over a month in a human," Robert Montgomery, director of the New York University Langone Transplant Institute, told reporters.

"I think there's a very compelling story that exists at this point that I think should give further assurances about starting some initial studies... in living humans."

Montgomery carried out the first genetically modified pig kidney transplant to a human in September 2021, followed by a similar procedure in November 2021. There have since been a handful of other cases, with all the experiments running for two or three days.

Surgeons at NYU Langone Health prepare to transplant a pig's kidney into a brain-dead man in New York on 14 July 2023. Source: AP / Shelby Lum/AP

While previous transplants have involved body parts with up to 10 genetic modifications, the latest had just one: in the gene involved in so-called "hyperacute rejection," which would otherwise occur within minutes of an animal organ being connected to a human circulatory system.

By ‘knocking out’ the gene responsible for a biomolecule called alpha-gal, a prime target for roving human antibodies, the NYU Langone team were able to stop immediate rejection.

"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.

Adam Griesemer, of the NYU Grossman School of Medicine, added that this practice allowed immune cells in the host's body to learn to recognize the pig's cells as its own, preventing a delayed rejection.

Both of the patient's own kidneys were removed, then one pig kidney was transplanted and started immediately producing urine.

Medical researchers at the University of Alabama prepare for the transplant. Credit: Steve Wood/AP

The research was made possible by the family of the 57-year-old male patient, Maurice "Mo" Miller, who was found unresponsive in his bathroom in July. Doctors determined he had an aggressive form of brain cancer and would not wake up.

In January 2022, surgeons at the University of Maryland Medical School carried out the world's first pig-to-human transplant on a living patient, this time involving a heart however he died two months after the milestone.

Current ‘xenotransplantation’ research efforts focus on pigs, which are thought to be ideal donors for humans because of their organ size, their rapid growth and large litter, and the fact they are already raised as a food source.