Doctors in China have transplanted a genetically modified pig liver to a 71-year-old man, who lived 171 days after the procedure.
Scientists have already achieved promising results in transplanting genetically modified pig kidneys and hearts to humans, but the pig liver had only been transplanted to individuals in a state of brain death until now.
Experts in xenotransplantation - the use of animal organs in humans - have doubts about the liver being a suitable candidate for such a procedure.
"Everyone was saying that the liver is too complicated for transplantation, especially compared to the heart or kidneys, but after this case, I think people will change their minds. If we can introduce enough human genes into pigs, the liver becomes a good option," said Dr. Beicheng Sun, president of the First Affiliated Hospital of Anhui Medical University and co-author of a study in this field, as cited by CNN.
Why the liver is the most complex organ to replace
Unlike the heart or kidneys, the liver is a much more complex organ - it has large dimensions, dual blood supply, and performs numerous functions. It filters the blood, eliminates toxins and waste, processes nutrients, detoxifies substances such as alcohol or drugs, produces bile for digestion, synthesizes essential proteins for blood clotting, and helps regulate blood sugar.
Last year, doctors at Penn Medicine successfully conducted the first external perfusion experiment on a genetically modified pig liver. The blood of a patient in a state of brain death was passed through a pig liver outside the human body. The organ showed no signs of inflammation for 72 hours, and the patient's body remained stable.
In another case, in March 2024, doctors in China transplanted a pig liver to a person in a state of brain death. The organ was removed at the family's request after 10 days, without signs of immune rejection.
A possible "bridge" between liver failure and human transplantation
According to a study published Thursday in the Journal of Hepatology, pig liver transplantation in humans could be used in the future as a temporary solution - a "bridge" to keep the patient alive until their own liver regenerates or a compatible human donor becomes available.
In the USA, over 100,000 people are on waiting lists for transplants, with over 9,000 waiting for a liver - the second-highest need after kidneys, according to the American Health Resources and Services Administration.
The acute organ shortage has led researchers to seek alternatives, including the use of pig organs, which are anatomically and physiologically similar to human organs.
In May 2024, doctors at the First Affiliated Hospital of Anhui Medical University transplanted a liver from an 11-month-old cloned pig to a 71-year-old man. The pig had 10 genetic modifications aimed at reducing the risk of infections or rejection. The patient also received immunosuppressive treatment to prevent his body's reaction.
The man was suffering from cirrhosis caused by hepatitis B, and his liver was severely affected and contained a large tumor in the right lobe, which could not be reduced through localized chemotherapy.
A courageous decision by the patient and his family
After three weeks of hospitalization, the patient developed severe abdominal pain, and tests showed that the tumor was at risk of rupturing. No family member was a match for donation, so the pig liver remained the only option. The patient and his daughter were informed about the experimental nature of the procedure and agreed to it.
"We must have profound respect for this patient and his family. His contribution to science is enormous, and the field of xenotransplantation owes a lot to these people who are willing to take risks for medical progress," said Dr. Sun.
Doctors removed the tumor and attached the pig liver to the remaining functional human liver.
First days: positive signs, no rejection
The transplant initially seemed successful. The pig liver immediately reddened, and bile - essential for digestion - began to flow through the external bile duct, with a constant increase in secretion. Significant improvements in liver function were observed within the first 24 hours, without signs of inflammation or rejection.
After 10 days, analyses showed no acute rejection, and the left part of the human liver seemed to function even better. Ultrasounds confirmed normal blood flow through the hepatic veins and arteries.
Complications and end of the experiment
After 25 days, the patient's heart began to show signs of stress. At 28 and 33 days, tests revealed inflammatory changes associated with the transplant, and doctors adjusted the immunosuppressive treatment. Subsequently, there were indications that the man was developing a rare condition, thrombotic microangiopathy associated with xenotransplantation, characterized by the formation of microscopic clots affecting vessels and organs.
On day 37, the patient experienced a sudden drop in blood pressure and episodes of loss of consciousness. As his own liver seemed sufficient to support his body, doctors removed the pig organ on day 38. The human liver continued to function well.
On day 135, the patient developed gastrointestinal bleeding and died 171 days after the transplant.
G.P.