Chinese doctors transplanted a genetically modified pig liver into a 71-year-old man who lived 171 days after surgery, with the pig organ in place for 38 of those days. This is the first publication in a peer-reviewed journal.
Scientists have had initial success transplanting genetically modified pig kidneys and hearts into humans, and pig livers have been transplanted into brain-dead human beings. But experts in xenotransplantation, the use of animal organs in humans, have concerns about whether livers are suitable candidates for such procedures.
“Everyone says, ‘Oh, the liver is too complicated to transplant compared to the heart or kidney,’ but I think people will think differently after this. I think the liver is good if we can get enough human genes from pigs,” said Dr. Beicheng Sun, co-author of the study and director of the First Affiliated Hospital of Anhui Medical University.
Unlike the heart or kidneys, which have narrower functions, the liver is large, has a dual blood supply and multiple functions, making it more complex to replace with pig organs. The liver filters blood, removes toxins and waste, processes nutrients, detoxifies harmful substances such as alcohol and drugs, produces bile to aid digestion, produces proteins that help blood clot, and plays an important role in regulating blood sugar.
Last year, doctors pen medicine The world’s first successful external liver perfusion using gene-edited pig organs. The brain-dead patient’s blood was circulated out of the human body through the pig’s liver. In this case, the pig’s liver showed no signs of inflammation during the 72-hour test, and the patient’s body remained stable.
A pig liver transplanted to a brain-dead patient in China in March 2024 was removed at the request of the family 10 days after the surgery. There were no signs of immune rejection or inflammatory buildup.
Experts say a new study published Thursday in the Journal of Hepatology suggests that liver transplantation from pigs to humans has the potential to serve as a bridge to help humans with serious liver disease recover sufficiently from their own livers or live long enough for a donor human liver to be used.
“In the future, we may possibly have a real chance of the left side regenerating. In that case, removing the graft would be enough to sustain life. Or at least we know we could wait a month or two for a human graft that could be life-saving. I think this is a very important discovery,” Sun said.
There are more than 100,000 people on the organ transplant waiting list. Only in the US There are more than 9,000 people waiting for a liver transplant, and demand for human organs far exceeds supply. The liver is the second most needed organ after the kidneys. According to the U.S. Health Resources and Services Administration. Scientists have been exploring alternatives for decades, including using pig organs because of their similarity to human organs.
In the case described in the new paper, doctors at the First Affiliated Hospital of Anhu Medical University in China transplanted the liver of an 11-month-old pig into a 71-year-old man in May 2024. The cloned pig underwent 10 gene edits to reduce the chance of infection or rejection of the organ. Doctors also gave the man drugs to suppress his immune system to prevent his body from rejecting foreign organs.
The man was initially admitted to hospital with hepatitis B-related cirrhosis. This is a condition in which scar tissue replaces healthy tissue, impairing liver function and sometimes leading to liver failure. He also had a large tumor in the right lobe of his liver, but efforts to shrink the tumor with high-dose chemotherapy targeting the blood supply were unsuccessful.
In some cases like this, surgeons can surgically remove part of the liver, but researchers leading the new study said there is something left of the liver. The human liver was probably too small to meet metabolic demands.
Nearly three weeks after being admitted to hospital, the man began experiencing severe abdominal pain and tests showed the tumor was at risk of rupturing. Doctors ran tests on family members to see if they could donate liver tissue, but with no matches, gene-edited pig liver was considered the only remaining option to save the man’s life. He and his daughter discussed the experiment with doctors and agreed to continue.
“We must have great respect for this patient and his family,” Sun said. “Patients have made a special contribution to this field of science. We must thank all patients for their great contribution to this field.”
Doctors removed the tumor and transplanted a genetically modified pig liver. What’s left of a man’s liver.
The transplant seemed successful. Immediately, the pig’s liver became red, and bile, which helps remove waste and absorb fat, began to be discharged through the external bile duct, and the amount secreted gradually increased over time. On the first day, other liver function markers increased significantly and there were no early signs of inflammation or rejection.
The researchers said that 10 days after surgery, there were no signs of acute rejection in the man’s body. In fact, the man’s left liver seemed to function better than before surgery. Ultrasound results showed that the portal vein, hepatic artery, and hepatic vein blood flow in the transplanted pig liver were functioning normally.
But by day 25, the patient’s heart began to show signs of progressive stress. Examinations on days 28 and 33 showed inflammatory changes associated with the transplant, and doctors switched some of the immunocompromising medications. But there were other signs that the transplant was not working as well as it initially did, suggesting the man had developed a condition called xenograft-related thrombotic microangiopathy, in which microscopic blood clots damage small blood vessels and organs.
By day 37, the man’s blood pressure plummeted, his heart rate increased, and he fell in and out of consciousness. At that point, the man’s liver was deemed functional enough to support the body, so doctors removed the pig’s organ on day 38. The man’s liver continued to function well thereafter.
On day 135, the man developed an upper gastrointestinal hemorrhage, from which he died 171 days after transplantation.
The study authors said the study gave them important insight into the challenges and feasibility of such transplants. It has been shown that liver transplantation from pigs to humans “can provide effective liver support while preserving part of the native liver and confirms its clinical feasibility as a bridging strategy.”
Dr. Co-author of the editorial published Thursday accompanying the study is professor and chair of the Department of Gastroenterology, Hepatology, Infectious Diseases and Endocrinology at the Medical School of Hannover, Germany. Heiner Wedemeyer wrote that the experiment is “a cause for cautious optimism” as well as “a reminder of how far the field still has to go.”
“It’s truly groundbreaking,” Wedemeyer told CNN. “For me, as a transplant hepatologist, this opens up completely new perspectives and ideas.”
Wedemeyer said Wednesday morning he saw a patient suffering from acute liver failure and ineligible for a human organ transplant due to some cancer issues.
“If we had used pig liver to hook her up at this stage – because she may need three, four, five, six, seven weeks for her liver to recover – we would have done that,” he said. “Porcine liver offers us a completely new opportunity, which could be really promising for patients.”
