Wednesday, November 29, 2023

Xenotransplantation – Monkey lives for two years with transplanted pig kidney

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Animal organs could be a saving grace for people waiting for organ donation. A US research group has come one step closer. They inserted a genetically modified pig kidney into monkeys. One lived with it for over two years.

Could you imagine living with a pig’s heart? That’s exactly what a 58-year-old man from Baltimore is currently doing. He had a pig heart transplant a few weeks ago. He is the second patient in the world with such a heart. The first patient received one in early 2022. However, he died almost two months later due to an infection with a porcine virus that was transplanted with the heart.

When pigs become kidney donors

In addition to the problem of infections, the big problem with such pig organ transplants is our immune system. It attacks everything foreign, including the organs of another human being – and even more so the organs of a pig.

How to humanize a pig kidney

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The researchers from the US company eGenesis have modified 69 genes using the genetic scissors called CRISPR. They pursued two goals: to protect the kidneys from attacks by the human immune system. And to protect people from dormant pig retroviruses. To do this, the research team inactivated all 59 retroviruses in this pig species.

The remaining ten modified genes make the pig organs more human-like. The research team cut out three of these genes from the genome of all pigs. And in some pigs they also incorporated seven human genes. This is how they achieved the best results. Among other things, these so-called knockins prevent clots from forming when monkey blood flows through the blood vessels of pig kidneys. They were able to publish their study in the specialist magazine Nature.

A research group from the USA wants to prevent such attacks and infections. To do this, she doesn’t transplant hearts, but rather kidneys. Because this is the organ that most people need worldwide. In Switzerland there are over 1,000 people and their waiting time lasts on average over two and a half years.

Record: A monkey lives for two years with pig kidneys

In order to trick our immune system and protect people from retroviruses, the 60 researchers from the USA have achieved great things: They have switched off an incredible 62 genes in the pigs and inserted seven human genes into the pigs’ genome. This makes the pig kidney more human-like. The researchers transplanted one of these genetically modified pig kidneys into 21 cynomolgus monkeys.

One of these monkeys lived with the donated kidney for 758 days, i.e. two years and 28 days. A new record – more than five months longer than previous experiments. The research group’s goal is to ensure that such pig kidneys will also function in humans in the near future.

Is there no longer anything standing in the way of pig kidneys for humans?

Even though nine of the test monkeys lived for over three months, the other twelve animals died after just a few days to weeks. “Obviously we don’t have all the factors under control yet,” says biotechnologist Eckhard Wolf. He is conducting very similar experiments with pigs and monkeys in Germany. But it doesn’t interfere that much with the pigs’ genetic makeup. This makes breeding easier. The disadvantage: The monkeys need more medication after the transplant. The goal remains the same: to find the optimal transplant organ for humans.


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Xenos means foreign and that means alien here. Accordingly, a so-called xenotransplantation involves the transfer of organs, tissue or even just a few cells across species boundaries. An example: A pig’s heart is inserted into a human. The pig is particularly suitable as an organ donor for humans. Because it is closely related to us and its organs fit us well in terms of appearance and function.

Pig heart valves and skin surfaces have been used in humans for years. In research, successful transplants from pigs to monkeys include hearts and kidneys, livers, lungs and various cell types.

Back to the initial question of whether you would accept such a pig organ or not. You may also consider ethical reasons. So considerations about the question of what kind of world we want to live in: for example, aspects of animal welfare and considerations of the medical and social risks and opportunities of such transplants. And if you were concerned that only people in rich countries could benefit from this, then this would be less an argument for or against, but rather a mandate for us, as a society, to provide equitable access.

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