Key Takeaways
A gene-edited pig liver functioned for 10 days in a brain-dead human without signs of rejection.
The study tested basic liver functions but didn’t assess full metabolic support.
Pig livers may one day serve as short-term support for patients awaiting human transplants.
Gene-modified Pig Credit: Nature
It wasn’t a typical transplant, and it wasn’t meant to save a life. In March 2024, at a hospital in Xi’an, China, doctors connected a genetically modified pig liver to a brain-dead human patient. The goal wasn’t treatment. It was a test to see if a pig liver, altered to reduce immune rejection, actually functions inside a human body.
Over the next 10 days, the liver did exactly that. It made bile, produced albumin, kept its blood vessels open, and showed no immediate signs of rejection or infection. The patient remained stable throughout the experiment, which ended at the family’s request.
The Setup: Not a Full Transplant, but a Test
The case was carried out at Xijing Hospital, part of the Fourth Military Medical University. The liver came from a gene-edited Bama miniature pig, modified in six places — three genes removed to silence rejection triggers, three added to help control inflammation and clotting.
Published in Nature, the study adds a new data point to a growing area of transplant research: xenotransplantation. The work is still early. But it raises a serious question: could organs from pigs become a real tool for managing the growing shortage of human donors?
Rather than replacing the patient’s own liver, the team used a heterotopic auxiliary approach, meaning the pig liver was added alongside the native one. It was connected to the patient’s blood supply but left the original organ untouched. This allowed the graft to function without disrupting other systems and gave the team the option to remove it safely when the study ended.
How the Liver Performed
Two hours after the liver was connected to blood flow, it began producing bile — an early marker of organ activity. By day ten, output had reached just over 66 milliliters. The liver also generated albumin, a protein that plays a critical role in blood volume and fluid balance.
Blood tests showed normal ALT levels, and although AST spiked shortly after surgery, it fell quickly. The researchers attributed this to transient stress, not graft failure. Biopsy results showed encouraging signs: the liver had no evidence of rejection, and cell samples indicated regeneration, not damage.
Importantly, viral monitoring throughout the study found no traces of pig viruses such as PERV or PCMV — a key safety concern in cross-species transplants.
A Carefully Controlled Environment
This was not an emergency case, and it wasn’t rushed. The patient had been declared brain-dead through a multi-physician process, and the transplant was conducted under full ethical approval. The recipient’s family gave informed consent, and the study followed national medical guidelines.
To prevent rejection, the research team used a combination of immunosuppressive drugs, including tacrolimus, steroids, rituximab, and anti-thymocyte globulin. Clotting factors and immune markers were tracked daily. There were no significant bleeding issues, and the liver remained stable until it was removed at the end of the study, as planned.
What the Researchers Took Away
The team didn’t set out to cure liver disease or propose pig organs as replacements, at least not yet. Their focus was on understanding whether a pig liver, when modified and monitored closely, could carry out basic functions in a human environment. The answer appears to be yes, at least over a short period.
Dr. Lin Wang, one of the lead researchers, said the study provides early evidence that a pig liver might serve as a temporary support — a bridge — for patients in acute liver failure who are waiting for a donor.
Other transplant specialists agree the findings are promising but stress that much more work is needed before this approach could be used in living patients. There are still unanswered questions about immune memory, long-term metabolic performance, and how conscious patients would respond to a xenograft.
Not a Replacement Yet
This type of auxiliary transplant isn’t meant to replace standard liver transplants. Rather, it could one day serve as a stopgap in emergency cases. Acute liver failure can develop in just days, and not every patient can get a human donor in time. If a pig liver can offer temporary function — even for a week or two — it might give doctors the time they need to save a life.
That said, the field is still early. This case involved a brain-dead patient, and while the short-term results are encouraging, trials in living recipients will bring new challenges. For now, researchers are cautious in their conclusions, but quietly optimistic that this approach could become part of liver failure care in the future.
Related Reading:
Cambridge Scientists Make a Discovery That Could Increase the Number of Kidneys Available for Transplantation
Beyond Transplants: How RNF41’s Discovery Could Revolutionize Liver Fibrosis Treatment and Eliminate the Need for Organ Replacement
Organ Transplantation: Researchers Change Blood Type A Donor Lungs to Universal Type O Blood Lungs
Blood Test to Detect Zombie Cells May Expand Use of Older Donor Hearts and Reduce Transplant Wait Times
Frequently Asked Questions
What is xenotransplantation?
It’s the transplantation of organs or tissues from one species to another — in this case, from a pig to a human.
Why use a pig liver?
Pig organs are similar in size and function to human organs and can be genetically modified for better compatibility.
What was the goal of this study?
To test whether a pig liver could function safely in a human body, even temporarily.
Was the pig liver replacing the human liver?
No. It was connected as a second liver. The patient’s own liver stayed in place.
How was the pig liver modified?
Scientists removed three pig genes that trigger rejection and added three human genes that reduce inflammation and clotting risk.
What did the liver actually do?
It made bile, produced albumin (a key protein), and maintained blood flow for 10 days.
Why only 10 days?
The study ended at the request of the patient’s family — not because the liver failed.
Was the patient alive?
No. The recipient was brain-dead and on life support. This was a non-survival study.
Did the liver show signs of rejection?
No. Biopsies showed normal structure, and no immune attack was observed.
Were viruses from the pig transmitted?
No. Tests for porcine viruses like PERV and PCMV were negative.
Can this be used in living patients now?
Not yet. It hasn’t been tested in living recipients. More safety and function data are needed.
What’s the difference between bile and albumin?
Bile helps digest fats; albumin keeps fluid in the bloodstream and transports hormones and drugs.
What parts of liver function weren’t tested?
Detoxification, clotting factor production, and full metabolism were not fully evaluated.
What happens next in this research?
Future trials may involve living patients and test long-term function and safety.
Are there other ways to increase donor organs?
Yes. Studies are evaluating older human donor organs and using machine perfusion to improve organ quality before transplant.
Bottom Line
This study shows that a genetically modified pig liver can function inside the human body for at least 10 days, producing bile, synthesizing proteins, and maintaining stable circulation. But that time frame reflects the study design, not the liver’s limit. The experiment ended at the family’s request, not because the organ failed. We still don’t know how long it could have lasted.
More importantly, this wasn’t a full test of liver function. Detoxification, clotting regulation, and full metabolic support weren’t thoroughly evaluated. And the patient was brain-dead. How the liver might perform in a living, unstable patient with active inflammation, infection, or multi-organ stress is still unknown.
There’s also the question of use case. Would pig livers be viable for long-term support? Or are they destined to be niche, last-resort bridges for patients waiting hours or days for a human donor?
For now, it’s a controlled success not a clinical solution. But it moves the field one step closer to giving patients more time when time is all they have.
References
Tao, K.-S., Yang, Z.-X., Zhang, X., Zhang, H.-T., Yue, S.-Q., Yang, Y.-L., Song, W.-J., Wang, D.-S., Liu, Z.-C., Li, H.-M., Chen, Y., Ding, R., Sun, S.-R., Yu, M., Li, J.-P., Duan, W.-X., Wang, Z., Wang, J.-W., Liu, J.-Y., Zheng, M.-W., Zhang, X.-J., Yin, W., Qin, W.-J., Bian, D.-M., … Dou, K.-F. (2025). Gene-modified pig-to-human liver xenotransplantation. Nature. https://doi.org/10.1038/s41586-025-08799-1