A GENETICALLY-MODIFIED pig kidney is continuing to function well a record-breaking 32 days after it was transplanted into a brain dead patient, a US medical centre said today.

The experimental procedure is part of a growing field of research aimed at advancing cross-species organ donation and thus reducing transplant waiting lists.

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

“This work demonstrates a pig kidney – with only one genetic modification and without experimental medications or devices – can replace the function of a human kidney for at least 32 days without being rejected,” said surgeon Robert Montgomery, director of the NYU Langone Transplant Institute.

Researchers have reached a new milestone in the future of organ transplantation: a modified pig kidney transplanted into a human has been successfully functioning for 32 consecutive days.

Learn more about Dr. Robert Montgomery’s research: https://t.co/x8iQ2I4LTH pic.twitter.com/TCmCUf2msL

— NYU Langone Health (@nyulangone) August 16, 2023

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.

While previous such transplants have involved up to 10 modifications, the latest experiment involved just one: the gene involved in the so-called “hyperacute rejection,” which would otherwise occur within minutes of an animal organ being connected to a human circulatory system.

Researchers at NYU Langone Health examine cells from a pig kidney biopsy after the transplant of the pig's kidney into a brain-dead man in New York on 28 July. Alamy Stock Photo Alamy Stock Photo

By “knocking out” the gene responsible for a biomolecule called alpha-gal – which otherwise would be a prime target for 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.

They also embedded the pig’s thymus gland – responsible for educating the immune system – in the kidney’s outer layer, in order to prevent a more delayed host rejection.

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

Monitoring showed that levels of creatinine, a waste product, were at optimal levels, and there was no evidence of rejection.

Surgeons at NYU Langone Health prepare to transplant a pig's kidney into a brain-dead man in New York on 14 July. Alamy Stock Photo Alamy Stock Photo

Crucially, no evidence of porcine cytomegalovirus – which may trigger organ failure – have been detected, and the team plan to continue monitoring for another month.

The research was made possible by the family of the 57-year-old male patient who had elected to make his body available for science.

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.

He died two months after the milestone, with the presence of porcine cytomegalovirus in the organ later blamed for his death.