Pig kidney transplanted into human body is still working one month later

Surgeons transplanted a pig's kidney into a brain-dead man over a month ago, and it is still working normally.

The successful experiment, carried out at an academic medical centre in New York City on July 14, is hoped to be a critical step towards animal animal-human transplants in living patients.

It is the longest period that a gene-edited pig kidney has worked inside a human body, with researchers at NYU Langone Health now tracking its performance for a second month.

Dr Robert Montgomery, director of NYU Langone’s transplant institute, said the procedure wasn't that different from thousands he's performed over the course of his career.

“But somewhere in the back of your mind is the enormity of what you're doing... recognising that this could have a huge impact on the future of transplantation," he added.

The operation took careful timing. Early that morning, Drs Adam Griesemer and Jeffrey Stern flew hundreds of miles to a facility where Virginia-based Revivicor Inc. houses genetically modified pigs.

From there, they retrieved kidneys lacking a gene that would trigger immediate destruction by the human immune system.

As they raced back to NYU, Montgomery was removing both kidneys from the donated body so there'd be no doubt if the soon-to-arrive pig version was working.

One pig kidney was transplanted, the other stored for comparison when the experiment ends. Dr Griesemer said people in his profession are "always nervous" during a transplant.

He said “there was a lot of thrill and lot of sense of relief”, to see the organ kickstart so rapidly.

The University of Maryland’s Dr Muhammad Mohiuddin cautions that it’s not clear how closely a deceased body will mimic a live patient's reactions to a pig organ.

However, striking an optimistic tone, Dr Montgomery said: "Is this organ really going to work like a human organ? So far it’s looking like it is.”

He added that it looks "even better than a human kidney" and that he watched it immediately start producing urine.

Whatever the longer-term results of this experiment, the research is an opportunity to educate the public about xenotransplantation so “people will not be shocked” when it’s time to try again in the living.

The possibility that pig kidneys might one day help ease a dire shortage of transplantable organs persuaded the family of the 57-year-old Maurice “Mo” Miller from upstate New York to donate his body for the experiment.

His sister, Mary Miller-Duffy, said she "struggled" with the idea at first, but said her brother liked helping others.

She added: “I think this is what my brother would want. So I offered my brother to them. He’s going to be in the medical books, and he will live on forever.”

Last year, University of Maryland surgeons made history by transplanting a gene-edited pig heart into a dying man who was out of other options.

He survived only two months before the organ failed for reasons that aren’t fully understood, but that offer lessons for future attempts.

Now, the Food and Drug Administration is considering whether to allow some small but rigorous studies of pig heart or kidney transplants in volunteer patients.

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And it’s critical to answer some remaining questions “in a setting where we’re not putting someone’s life in jeopardy”, said Dr Montgomery.

As someone who received a heart transplant of his own, the surgeon is acutely aware of the need for a new source of organs.

More than 100,000 patients are on the nation's transplant list and thousands die each year waiting.

Previously, NYU and a team at the University of Alabama at Birmingham had tested pig kidney transplants in deceased recipients for just two or three days.

An NYU team also had transplanted pig hearts into donated bodies for three days of intense testing.

While the latest procedure is a big step forward in the field, unanswered questions remain.

For example, whether a pig organ could withstand a more common human immune attack that takes about a month to form - only a longer period of testing can tell.