Part of a pig’s liver was transplanted into a human

Pig liver surgery brings us closer to transplants of other species

By Humberto Basilio edited by Tanya Lewis

Chinese scientists have carried out what is believed to be the first transplant of a genetically modified pig liver segment into a person with cancer. Surgeons reported that the transplanted section of the pig organ adequately supported the patient’s metabolic functions for 38 days, after which it had to be removed due to complications. The patient lived another 133 days and died of gastrointestinal hemorrhage. The results were published on October 8 in the Journal of Hepatology.

Transplanting organs from other animals into humans – known as xenotransplantation – has made notable progress in recent years. Pig liver transplantation “demonstrates that xenogeneic organs can not only survive in the short term but also perform physiological functions in the complex environment of a living body,” says Beicheng Sun, president of the First Affiliated Hospital of Anhui Medical University in China, who led the study with his colleagues. This “creates a bridge to give the patient more time” to recover or receive an organ from a donor in case their liver needs to be completely replaced.

The patient was at risk of liver rupture due to a tumor on the right side of the organ. His remaining left lobe was insufficient to survive, according to the doctors who treated him. Sun and his team implanted a section of pig liver as an “auxiliary” graft. In this way, part of the man’s liver remained in place, allowing him to regenerate while the pig’s organ temporarily supported his metabolism. The liver is the only human organ capable of regenerating after injury.

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The genetically modified pig liver began to function immediately after surgery, secreting golden yellow bile and synthesizing albumin proteins, clotting factors and bile acids derived from pigs. “This provided essential support to the patient, stabilizing his vital signs,” says Sun.

Complications arose as early as the second month, when the patient developed thrombotic microangiopathy, a dangerous clotting disorder linked to immune activation. Doctors treated him with immunosuppressive drugs and a blood-filtering procedure called plasma exchange. When tests showed the condition was worsening, the team removed the pig liver on the 38th day.

Subsequently, the man’s remaining liver took over and his condition remained stable for more than three months. On day 171, he died of a gastrointestinal hemorrhage, unrelated to the transplant itself, the authors reported in the study.

According to Sun, the basic principle of auxiliary transplantation is to avoid removing the patient’s entire liver. With the temporary support of the pig liver, the patient’s left lobe was able to recover and regenerate. “This allowed the patient to survive thanks to his regenerated native liver after the removal of the pig liver,” he explains.

The operation “is a step in the right direction,” says Muhammad Mohiuddin, a surgeon at the University of Maryland and president of the International Xenotransplantation Association, who was not involved in the experiment.

In August, a team of researchers in China performed the first-ever pig-to-human lung xenotransplantation. And earlier this year, the U.S. Food and Drug Administration approved the first kidney transplant clinical trial in pigs.

Currently, patients in the United States are awaiting approval from the Food and Drug Administration for ex vivo porcine liver perfusion, a procedure that allows doctors to use pig organs outside the body to temporarily replace the functions of a damaged human liver, giving patients more time to wait for a suitable donor. Mohiuddin says the new study shows a similar result could be achieved through surgery. “Pig liver was not a substitute but a bridge to support the human liver,” he says.

Although the procedure was “technically successful,” more studies are needed to confirm that pig liver extract actually benefited human liver regeneration, says surgeon Parsia Vagefi of UT Southwestern Medical Center, who was not involved in the new study. After these types of surgeries, “the question always arises of how well the pig liver actually works and how well the human liver works,” he says.

When surgeons turn to studies where the native liver completely fails and a pig liver saves the patient, Vagefi says, “we’ll really be able to see if the pig liver provides enough support to actually connect someone” to a human liver transplant.

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