For the first time in the world, a pig's liver transplanted into a human has shown normal function. There was also little immune rejection. Xenotransplantation is expected to be utilized for chronic patients to maintain health while waiting for human organs for transplantation.
Researchers from the Fourth Military Medical University of the People's Liberation Army of China and Xijing University School of Medicine announced the results of a 10-day observation after transplanting a genetically modified pig's liver into a brain-dead person in the international journal 'Nature' on the 27th. The pig liver transplant experiment conducted in March of last year attracted attention as the world's first xenogeneic liver transplant.
The number of patients needing organ transplants is gradually increasing, but it is difficult to obtain organs for transplantation. According to the National Organ and Tissue Blood Management Center, the number of patients waiting for organ transplantation in the country is 51,876 as of 2023, a 29% increase compared to 40,253 five years ago in 2019. In contrast, the number of organ donors has remained stagnant at around 400 annually. By June 2023, an average of 8.3 people died each day while waiting for organ transplants.
Xenotransplantation has emerged as an alternative to solve the problem of organ shortage for transplantation. In particular, pigs are considered the most suitable animals for xenotransplantation due to their similarity in organ size and anatomical structure to humans. The problem is that the human body recognizes pig organs as invaders and mounts an immune rejection response. Scientists are researching gene editing to humanize pig genes to prevent this.
Researchers in China transplanted a pig's liver into the body of a brain-dead man in his 50s in March of last year. The experiment was conducted with the consent of the patient's family and successfully connected all functions of the pig's liver for the first time in the world. Previous attempts to transplant pig livers into humans were limited to connecting them outside the body. This was due to the anatomical differences between the liver of a quadrupedal pig and that of a human, which made transplantation difficult.
The research team successfully transplanted the pig's liver into the brain-dead person's body after a 9-hour surgery. Prior to this, they edited six pig genes to prevent immune rejection. They observed whether the liver functioned normally for 10 days after the transplant. The experiment was terminated after 10 days at the request of the brain-dead person's family.
According to the paper published by the research team, the pig's liver began secreting bile and functioning normally two hours after transplantation. They confirmed that albumin, a protein synthesized by the liver, was also secreted normally. The secretion of bile and albumin is one of the key indicators used to evaluate liver function.
The blood vessels connecting the human body and the liver also worked normally, although temporary drops in platelet counts and coagulation ability were observed. However, the research team noted that the vascular-related side effects were not serious and returned to normal following temporary abnormal reactions.
The greatest challenge of xenotransplantation, the immune response, could also be regulated using immunosuppressants. Immune cells called B cells, which produce antibodies, increased three days after surgery, but returned to normal levels with the administration of the immunosuppressant rituximab. The researchers said, “After observing the transplant patient for 10 days, we confirmed that liver function was normal and there were no significant rejection responses,” adding, “We have confirmed that pig livers can be transplanted to patients requiring liver transplants.”
This experiment is the first to prove that even if humans transplant pig livers, they can function normally for up to 10 days. Although this experiment was conducted on a brain-dead person, it is expected that if safety is further confirmed, pig livers could also be transplanted into patients with liver diseases who are not brain-dead. For example, it could be used as 'bridge therapy' to sustain life for patients urgently needing liver transplants while waiting for available organs.
The researchers noted, “With immunosuppressive drugs and gene manipulation, xenotransplantation is becoming feasible,” but added, “Since this experiment was only conducted for 10 days, further research on long-term safety must be conducted.”
References
Nature(2025), DOI: https://doi.org/10.1038/s41586-025-08799-1