Part of a Pig Liver was Transplanted into a Human

Pig Liver Surgery Moves Us Closer to Transplants from Other Species

By Humberto Basilio edited by Tanya Lewis

Chinese scientists have performed what is thought 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 supported the patient’s metabolic functions properly for 38 days, at which point it had to be removed because of complications. The patient lived another 133 days and died from gastrointestinal bleeding. 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 strides in recent years. The pig liver transplant “demonstrates that xenogeneic organs can not only survive 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 conducted the study with his colleagues This “creates a bridge to give a patient more time” to recover or to receive a donor organ in case their liver must be completely replaced.

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

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The genetically engineered pig liver began functioning immediately after the surgery, secreting golden-yellow bile and synthesizing pig-derived albumin protein, clotting factors and bile acids. “This provided critical support to the patient, stabilizing his vital signs,” Sun says.

Complications appeared in 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 day 38.

Afterward, the man’s remaining liver took over, and his condition remained stable for more than three months. One day 171, he died from gastrointestinal bleeding, unrelated to the transplant itself, the authors reported in the study.

The core principle of auxiliary transplantation, Sun says, is to avoid removing all of the patient’s own liver. With temporary support from the pig liver, the patient’s own left lobe was able to recover and regenerate. “This enabled the patient to survive on his regenerated native liver after the pig liver was removed,” he says.

The surgery “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 xenotransplant. And earlier this year the U.S. Food and Drug Administration approved the first clinical trial of pig kidney transplantation.

Currently, patients in the U.S. are waiting for Food and Drug Administration approval for ex vivo pig 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 that a similar outcome might be achieved through surgery. “The 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 the pig liver extract truly benefited the regeneration of the human liver, says surgeon Parsia Vagefi of UT Southwestern Medical Center, who was not involved in the new study. After these types of surgeries, “there’s always the question of how much the pig liver is actually doing and how much the human liver is functioning,” he says.

When surgeons move to studies where the native liver is completely failing and a pig liver rescues the patient, Vagefi says, “we’ll be able to really see if the pig liver provides enough support to actually bridge someone” to a human liver transplant.

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