Xenotransplantation is back

It was an ingenious idea… put aside. Its controversy was the main cause of this decision. But no longer. Xenotransplantation is back. A kidney from a pig was transplanted into the leg of a woman declared brain dead. The organ appears to have functioned for 54 hours.

Xenotransplantation is back. A pig kidney was implanted into a human body.
Xenotransplants are back. A pig kidney was implanted into a human body.

This xenotransplantation was carried out in the United States (the Greek xenosmeaning strange, foreign). These are organ transplants between different species. For example, between pigs and humans. They were proposed more than 30 years ago. It was hoped to make up for the lack of organs required by people on waiting lists.

They do not replace organs from living donors or clinically dead patients. They just provide extra survival time. It is not at all straightforward. The recipient animal’s immune system usually rejects the intruder. The immune system must be tricked. How? By genetically modifying the donor animal’s cells. By making them human-like, the body will believe that these cells are its own.

There are even pigs created with genetic modifications for the purpose of xenotransplantation. Preclinical experiments of transplanting pigs into baboons have been done successfully. They endured more than 6 months with kidneys. And in a few cases, up to almost 3 years with hearts.

Some pigs are genetically modified to favor transplantation.
Some pigs are genetically modified to favor transplantation.
Pig in the leg

In this case, we chose to place the kidney in the leg. Why? To have better direct access and to monitor the process in more detail. We had 54 hours with no apparent rejection of the transplanted organ. The life-support system that kept the patient alive was then disconnected.

This is an experiment with a possible ethical controversy. Consent was obtained from her relatives. It could be interpreted as a donation of the body to science. And it brings us closer to the future reality of xenotransplantation.

The National Transplant Organization indicate that in Spain there were 1,777 donors in 2020. Spain is the second country in transplants performed per million people, very close to the United States. But it is still insufficient.

However, the organs available are still totally insufficient.

In 2017 there were more than 87,000 people waiting for a transplant in Europe. But there were only 10,500 annual donors available. That is why, perhaps, xenotransplantation is back. However, they will never cease to be controversial.

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