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Team of surgeons at NYU Langone Health in Manhatten
Photo: Joe Carrotta / NYU Langone Health / REUTERS
For the first time, a pig kidney was transplanted into a human without the new organ causing complications with the immune system.
The operation was carried out by doctors working with surgeon Robert Montgomery at the Langone Transplant Institute in New York.
The organ came from an animal whose genes had been modified so that its tissues no longer contained known molecules that would trigger immediate rejection.
The recipient was a brain-dead patient with signs of kidney dysfunction. The family agreed to the medical experiment. However, the patient's organ was not used surgically. Instead, the kidney was kept outside of her body and only attached to the blood vessels in the thigh. The scientists observed the function for around three days. The kidney test results looked pretty normal, Montgomery said. The life support measures were then switched off and the patient died.
According to the researchers, the kidney produced the amount of urine one would expect from a transplanted human kidney. The recipient's abnormal creatinine level - an indicator of poor kidney function - returned to normal after the transplant, Montgomery said. And there was no evidence of violent, early rejection. Such immune reactions of the body had previously been observed by transplant experts in non-genetically modified pig kidneys, some of which had been used in primates.
Some questions about the procedure are still open.
For example, the results of the experiment have not yet been published in a scientific study and examined by independent colleagues.
But, according to Montgomery, the fact that the kidney works outside the body is an important indication that it will do the same in the body.
Usually problems occurred with so-called xenotransplantations
So far, animals and humans first appeared at the interface between the human blood supply and the organ.
Researchers have been working on the possibility of using animal organs for transplants for decades.
Pig kidneys have so far been seen as promising candidates because they are similar in structure and size to the human kidney.
But so far there have been problems, for example due to immediate rejection reactions or animal pathogens.
Genetic engineering is supposed to remedy this.
Heart valves or skin grafts from genetic pigs
The kidney from the animal now used had also been genetically modified by the biotech company United Therapeutics Corporation. The process was approved for specific uses by the US Food and Drug Administration (FDA) in December 2020. Montgomery's team theorized that turning off a pig's gene for a carbohydrate that causes rejection reactions would prevent the problem. Heart valves or human skin grafts may also be obtained from pigs using the procedure.
If the technology were to establish itself at some point, it would be an enormous advance in transplant medicine. In Germany alone, more than 7,000 people are currently waiting for a donor kidney, in the USA the figure is 90,000. There the waiting time for a kidney is three to five years on average. For years, the demand has exceeded the available donor organs - many patients therefore die from a saving transplant.
The current kidney transplant experiment should pave the way for trials in end-stage kidney failure patients in the US, possibly over the next year or two, Montgomery said.
In these attempts, the approach could be tested as a short-term solution for severely ill patients until a human kidney is available, or perhaps even as a permanent transplant.
However, Montgomery also admits that future attempts are likely to face new obstacles that need to be overcome.
The researchers worked with medical ethicists as well as legal experts in their experiment to test the concept.
Only then did they want to address the families of brain-dead patients, said Montgomery.
joe / Reuters