Pig liver transplant into a living person edges it closer to the norm

Transplanting organs from non-human animals into people could revolutionize medicine, potentially saving thousands of lives lost while people wait for organs. Scientists have previously experimented with feeding pigs to people. hearts And kidneysand have now reported the transplantation of an animal liver into a living person.

“This is truly revolutionary,” says Heiner Wedemeyer at Hannover Medical School in Germany, who was not involved in the procedure. “The patient was close to death, but thanks to the transplant he lived for six months.”

The complexity of the liver meant that such operations were only performed tested on brain dead peoplewith signs of success. “The heart is just a muscle that pumps blood,” Wedemeyer says. “The kidneys are also simple because they only need to cleanse the body. But the liver is different because it produces so many different proteins that are involved in many metabolic processes.”

Transplantation of hearts and kidneys into living people also showed early signs of success, but later complications arose. It was related to a heart transplant possible transmission of swine virus.

Now, Beicheng Sun from Anhui Medical University in China and colleagues reported porcine liver transplantation in a 71-year-old man. The recipient's liver function was deemed too poor for a traditional transplant to have a good chance of success due to the large tumor and severe scarring caused by hepatitis B infection. Thousands of people die every year while waiting for a liver transplant, so each procedure must be carefully considered, Sun says.

However, the man still needed some kind of transplant because his tumor could rupture at any time, Sun said. With the recipient's permission, in May 2024, Sun and his team replaced the right part of his liver containing the tumor with part from an 11-month-old miniature pig. In a five-hour operation, they connected the pig's liver blood vessels to those on the left side of his own organ.

To prevent liver rejection immune systemIn the pig, three genes were deactivated and seven genes were introduced, so the organ functioned more like a human. The man was also taking immunosuppressive drugs, and the team carefully checked whether the liver was infected with pig viruses.

Almost immediately, the liver began secreting bile, a fluid the organ produces to help break down fat from food. Within a few weeks, the recipient's bile and albumin levels (a protein produced by the liver that prevents too much fluid from leaking from the blood vessels) increased to healthy levels, Sun said.

But about a month after the procedure, he developed life-threatening blood clots in his blood vessels, forcing the team to remove the graft. This was likely caused in part by the overactivation of part of the recipient's immune system and the production of abnormal levels of certain blood clotting proteins that a healthy liver also produces. This is likely more common in pig transplants because the animal is different from humans, Sun says.

The man lived for about five more months, retaining only the left side of his liver, and then died from stomach bleeding. often occurs with scarring of the liver– says San. Both Sun and Wedemeyer said the bleeding was likely not related to the transplant.

Despite the man's death, the procedure can still be considered a partial success, since he would otherwise likely have died soon after the tumor was removed, Wedemeyer said. What's more, the recipient's own liver partially regenerated while the graft functioned well, which is likely why he lived for several months after it was removed, he says.

This procedure has advanced our understanding of xenotransplantation, raising the possibility that pig liver could buy time for those awaiting human transplantation. transplants” says Wedemeyer. They may even allow the remaining liver tissue to regenerate enough that people no longer need the procedure, Sun said.

But it will likely be at least a decade before pig liver can be used as a permanent replacement for human liver, Sun says. “We first need to significantly reduce the risk of complications, for example through further genetic modifications,” Sun says.