A pig kidney functions for 2 months in a given body

NEW YORK — Dozens of doctors and nurses gathered silently in the hospital corridor in tribute: For two historic months, a pig kidney functioned normally inside the brain-dead man on the stretcher who passed in front of them.

The dramatic experiment ended Wednesday when surgeons at NYU Langone Health removed the pig kidney and returned the donated body of Maurice “Mo” Miller to his family for cremation.

This is the longest a genetically modified pig kidney has functioned in a human, even if they have died. And by pushing the boundaries of research on the dead, scientists have learned crucial lessons that they are preparing to share with the Food and Drug Administration – in hopes of eventually being able to test pig kidneys on living people .

“It’s a combination of excitement and relief,” Dr. Robert Montgomery, the transplant surgeon who led the experiment, told the Associated Press. “Two months is a long time to have a pig kidney in such good condition. This gives you a lot of confidence” for the next attempts.

Montgomery, himself a heart transplant recipient, sees animal-to-human transplants as crucial to alleviating the nation’s organ shortage. More than 100,000 people are on the national waiting list, most in need of a kidney, and thousands will die waiting.

So-called xenotransplantation attempts have failed for decades: the human immune system immediately destroyed foreign animal tissues. What’s new: Trying genetically modified pigs to make their organs more like those of humans.

Some short experiments on deceased bodies avoided an immediate immune attack, but failed to shed light on a more common form of rejection that can take a month to form. Last year, surgeons at the University of Maryland tried to save a dying man with a pig’s heart, but he only survived two months because the organ failed for reasons that are not entirely clear. And the FDA gave Montgomery’s team a list of questions about how pig organs actually perform their jobs compared to those of humans.

Montgomery bet that keeping Miller’s body on a ventilator for two months to see how the pig kidney worked could answer some of those questions.

“I’m so proud of you,” Miller’s sister, Mary Miller-Duffy, said through tears at her brother’s bedside this week.

Miller had collapsed and was declared brain dead, unable to donate his organs due to cancer. After struggling to choose, Miller-Duffy donated the Newburgh, New York, man’s body for the pig experiment. She recently received a card from a stranger in California who is awaiting a kidney transplant, thanking her for helping advance desperately needed research.

“It’s been quite a journey,” Miller-Duffy said as she and her wife Sue Duffy hugged the Montgomery team.

On July 14, shortly before his 58th birthday, surgeons replaced Miller’s kidneys with a pig kidney and the animal’s thymus, a gland that drives immune cells. For the first month, the kidney functioned without any signs of problems.

But soon after, doctors measured a slight decrease in the amount of urine produced. A biopsy confirmed a subtle sign that rejection was starting – giving doctors a chance to say if it was treatable. Sure enough, kidney performance has rebounded thanks to a change in the standard immunosuppressive medications that patients use today.

“We’re learning that this is actually achievable,” said Massimo Mangiola, a transplant immunologist at NYU.

The researchers ticked off other FDA questions, including finding no difference in how the pig kidney responded to human hormones, excreted antibiotics, or drug-related side effects.

“It’s beautiful, it’s exactly what normal kidneys look like,” Dr. Jeffrey Stern said Wednesday after removing the pig kidney after 61 days for further examination.

The next steps: The researchers took about 180 different tissue samples – from every major organ, lymph nodes and the digestive tract – to look for any signs of problems due to the xenotransplantation.

Experiments on the deceased cannot predict that organs will function the same way in the living, cautioned Karen Maschke, a researcher at the Hastings Center who helps develop ethical and policy recommendations for xenotransplantation clinical trials.

But they can provide other valuable information, she said. This includes helping to determine the differences between pigs with up to 10 genetic changes that some research teams prefer – and those like Montgomery uses that have only one change, the deletion of a gene that triggers a immediate immune attack.

“The reason we do this is because unfortunately there are a lot of people who die before they have the opportunity for a second chance at life,” said Mangiola, the immunologist. “And we have to do something about it.”

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Education Media Group. The AP is solely responsible for all content.