Source: The Guardian
A pig’s kidney transplanted by surgeons into a brain-dead man has continued to function normally for more than a month – a critical step toward an operation the New York team hopes to eventually try in living patients.
The latest experiment, announced on Wednesday by New York University Langone Health, marks the longest a pig kidney has functioned in a person, albeit a deceased one, and it’s not over. Researchers will track the kidney’s performance for a second month.
“Is this organ really going to work like a human organ? So far it’s looking like it is,” Dr Robert Montgomery, director of NYU Langone’s transplant institute, told the Associated Press.
“It looks even better than a human kidney,” Montgomery said on 14 July as he replaced a deceased man’s own kidneys with a single kidney from a genetically modified pig – and watched it immediately start producing urine.
Scientists around the country are racing to learn how to use animal organs to save human lives, and bodies donated for research offer a remarkable rehearsal. More than 100,000 patients are on the nation’s transplant list and thousands die each year waiting.
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.
“I struggled with it,” his sister, Mary Miller-Duffy, told the AP. But he liked helping others and “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 for ever,” she added.
Attempts at animal-to-human transplants have failed for decades as people’s immune systems attacked the foreign tissue. Now researchers are using pigs genetically modified so their organs better match human bodies.
Last year, with special permission from regulators, University of Maryland surgeons transplanted a gene-edited pig heart as a last-ditch attempt to save a dying man. He survived only two months before the organ failed for reasons that are not 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.
The NYU experiment is one of a string of developments aimed at speeding the start of such clinical trials. Also on Wednesday, the University of Alabama at Birmingham (UAB) reported another important success – a pair of pig kidneys worked normally inside another donated body for seven days.
Kidneys perform a wide range of jobs in the body beyond making urine. In the journal Jama Surgery, the UAB transplant surgeon Dr Jayme Locke reported lab tests documenting the gene-modified pig organs’ performance. She said the weeklong experiment demonstrated they could “provide life-sustaining kidney function”.
These experiments are critical to answer more remaining questions “in a setting where we’re not putting someone’s life in jeopardy”, said Montgomery, the NYU kidney transplant surgeon, who also received his own heart transplant – and is acutely aware of the need for a new source of organs.
The surgery itself is not that different from thousands he has performed “but somewhere in the back of your mind is the enormity of what you’re doing … recognizing that this could have a huge impact on the future of transplantation”, Montgomery said.
The operation took careful timing. Early that morning doctors Adam Griesemer and Jeffrey Stern flew hundreds of miles to a facility where the Virginia-based Revivicor Inc houses genetically modified pigs – and 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 would 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.
“You’re always nervous,” Griesemer said. To see it so rapidly kickstart, “there was a lot of thrill and lot of sense of relief.”
How long should these experiments last? Alabama’s Locke said that was not clear – and among the ethical questions are how long a family is comfortable and whether it is adding to their grief. Because maintaining a brain-dead person on a ventilator is difficult, the decision is also dependent on how stable the donated body is.
In her own experiment, the donated body was stable enough that if the study was not required to end after a week, “I think we could have gone much longer, which I think offers great hope”, she said.
The University of Maryland’s Dr Muhammad Mohiuddin cautions that it is not clear how closely a deceased body will mimic a live patient’s reactions to a pig organ – but that this research educates the public about xenotransplantation so “people will not be shocked” when it’s time to try again in the living.