2023-09-14 20:54:49
The dramatic experience ended that day when surgeons at New York University (NYU) Langone Health removed the pig kidney and returned the donated body of Maurice “Mo” Miller to his family for cremation.
This marked the longest time a genetically modified pig kidney has ever functioned inside a human being, even if it was a deceased one. By pushing the boundaries of cadaver research, scientists have learned crucial lessons that they are preparing to share with the Food and Drug Administration (FDA), in hopes of eventually testing pig kidneys on living beings .
“It’s a mixture of excitement and relief,” Dr. Robert Montgomery, the transplant surgeon who led the experiment, told the Associated Press.
“Two months is a long time for a pig kidney to be in such a state. This gives a lot of confidence for the next attempts.”
– Le Dr Robert Montgomery
Montgomery, himself a heart transplant recipient, sees animal-to-human transplants as crucial to relieving 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.
Attempts at xenografting, in other words transplanting animal organs into humans, have failed for decades – with the human immune system immediately destroying the foreign animal tissue. What’s new: the use of genetically modified pigs to make their organs more closely resemble those of humans.
Some short experiments on cadavers avoided an immediate immune attack, but did not shed light on a more common type of rejection that can take a month to develop. Last year, surgeons at the University of Maryland tried to save a dying man with a pig’s heart – but he survived only two months because the organ failed for reasons that aren’t completely clear.
And the FDA asked Montgomery’s team a list of questions about how pig organs actually perform their functions compared to those of humans.
SEE ALSO | Increase in organ donations from patients who receive medical assistance in dying
A calculated risk
Montgomery took the risk of keeping Miller’s body on a ventilator for two months to see how the pig kidney worked, hoping to answer some of these questions.
“I’m so proud of you,” Mary Miller-Duffy, Miller’s sister, said during an emotional farewell at her brother’s bedside this week.
Miller had collapsed and was declared brain dead, unable to donate his organs due to cancer. After hesitation, Miller-Duffy donated the Newburgh, New York, man’s body for the pig experiment. She recently received a card from a stranger in California waiting for 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 embraced 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 forms immune cells. For the first month, the kidney functioned without any signs of problems.
However, soon after, doctors noticed a slight decrease in the amount of urine produced. A biopsy confirmed a subtle sign that rejection was beginning – giving doctors the opportunity to see if it was treatable. And indeed, the kidney’s performance has rebounded thanks to a change in standard immunosuppression medications used by patients today.
“We’re learning that it’s actually feasible,” said Massimo Mangiola, a transplant immunologist at NYU.
The researchers answered further questions from the FDA, including finding that there was no difference in the pig kidney’s response to human hormones, its elimination from antibiotics, or drug-related side effects.
“It looks beautiful, it’s just like normal kidneys,” 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, digestive tract – to check for possible signs of problems due to the xenograft.
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 xenograft clinical trials.
But they can provide other valuable information, she said. This includes helping identify differences between pigs with up to 10 genetic modifications that some research teams prefer – and those like those used by Montgomery that have only one modification, the deletion of one gene that triggers an immediate immune attack.
“We do this because there are a lot of people who unfortunately die before they have the opportunity for a second chance at life,” said Mangiola, the immunologist.
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