World’s First Pig-to-Human Liver Transplant: A Major Step in Solving the Organ Shortage Crisis
A team of surgeons in China has achieved something that could change the future of organ transplantation — they successfully transplanted part of a genetically modified pig’s liver into a living human patient. The case, now published in the Journal of Hepatology, is the first documented instance where a pig liver graft functioned inside a human for a significant amount of time.
The recipient, a 71-year-old man suffering from hepatitis B-related cirrhosis and liver cancer (hepatocellular carcinoma), survived 171 days after the operation. For a field that has long struggled with the shortage of human donor organs, this breakthrough opens a new and potentially lifesaving path forward.
The Patient and the Problem
Every year, thousands of people around the world die while waiting for an organ transplant. The World Health Organization estimates that less than 10% of those who need transplants actually receive them. In China alone, hundreds of thousands develop end-stage liver failure each year, yet only about 6,000 patients underwent liver transplantation in 2022.
This patient had reached a point where no standard medical treatment could save him. He wasn’t eligible for liver resection (surgical removal of part of the liver) or for a human liver transplant, mainly due to his age and medical condition. Instead of giving up, his doctors decided to attempt an experimental xenotransplantation — a transplant between two different species.
What Is Xenotransplantation?
Xenotransplantation involves transferring organs or tissues from animals to humans. The idea isn’t new — scientists have experimented with it for decades — but immune rejection has always been the biggest barrier. The human body recognizes animal cells as foreign and attacks them almost instantly.
The breakthrough came with gene-editing technology. Using tools like CRISPR-Cas9, researchers can now modify animal genes to make their organs more compatible with the human immune system. Pigs are considered ideal donors because their organs are similar in size and function to those of humans, and they can be bred under controlled, virus-free conditions.
This particular case used a Diannan miniature pig, a breed commonly used in biomedical research due to its manageable size and physiological similarities to humans.
The Pig Liver: Designed for Human Compatibility
The pig used for the transplant was not an ordinary one. Scientists created it through 10 targeted genetic modifications designed to reduce the chances of rejection and other complications.
These genetic changes included:
- Removal of xenoantigens, the molecules that typically trigger a violent immune response in humans.
- Addition of human genes that regulate the immune and coagulation systems, allowing smoother blood interaction between the human body and the transplanted pig tissue.
- Modifications to minimize complement activation (a part of the immune system that can cause rapid graft destruction).
In addition, extensive testing confirmed that the pig was free from viruses such as porcine cytomegalovirus (PCMV) and porcine endogenous retroviruses (PERVs), both of which have previously raised concerns about possible cross-species infections.
How the Surgery Was Done
This wasn’t a full liver transplant. Instead, doctors performed what’s known as an auxiliary liver transplant. That means the pig liver was implanted alongside the patient’s existing, diseased liver rather than replacing it completely.
The idea behind this method is that the pig organ can temporarily take over essential liver functions — like producing bile, filtering toxins, and synthesizing clotting factors — giving the patient’s native liver a chance to rest, recover, or simply sustain life until a human organ becomes available.
The surgical team was led by Dr. Beicheng Sun, a hepatobiliary surgeon and president of the First Affiliated Hospital of Anhui Medical University in Hefei, China.
Early Success and Functioning of the Graft
In the first month after surgery, the pig liver graft performed exceptionally well. It produced bile, maintained normal metabolic and synthetic activity, and showed no signs of hyperacute or acute rejection — the two most feared complications in xenotransplantation.
Doctors were able to verify that the pig liver was actively producing coagulation factors (which help blood clot properly) and supporting metabolic functions vital for survival.
This period proved that a genetically engineered pig liver can indeed function inside a human body, at least temporarily.
Complications and Removal of the Graft
However, the success didn’t last indefinitely. After 38 days, the patient developed a complication called xenotransplantation-associated thrombotic microangiopathy (xTMA). This condition involves damage to the small blood vessels, leading to clot formation and endothelial injury (damage to the inner lining of blood vessels).
xTMA is one of the major risks in xenotransplantation, as it often arises from immune system activation and incompatibility between human and pig vascular systems.
To treat the condition, doctors used eculizumab, a drug that inhibits the complement system (a part of the immune response that can cause inflammation and cell damage). They also performed plasma exchange therapy, which helped remove harmful antibodies and inflammatory molecules from the blood.
The treatment was successful in controlling xTMA, but the surgical team decided to remove the pig liver graft to prevent further complications.
The Patient’s Remaining Months
After the graft was removed, the patient’s own liver continued to function—though not perfectly—and he lived for another 133 days, reaching a total survival period of 171 days after the initial surgery.
In the following months, he suffered several episodes of upper gastrointestinal bleeding, which ultimately led to his death. Despite that, his case remains historic. It demonstrated that a pig liver can perform essential liver functions in a human body for over a month, which has never been achieved before.
Why This Matters
This experiment is a milestone for transplant medicine. It proves that genetically modified animal organs can temporarily sustain human life and that such organs may one day be used as “bridge therapy” — a temporary solution for patients waiting for human donor organs.
The achievement also highlights the scientific, ethical, and medical challenges that still need to be solved before xenotransplantation can become a routine medical option. These include:
- Managing coagulation and immune complications like xTMA.
- Preventing long-term rejection and inflammation.
- Ensuring complete viral safety of animal organs.
- Developing appropriate ethical and regulatory frameworks for human trials.
If these challenges can be overcome, xenotransplantation might revolutionize organ transplantation, potentially saving thousands of lives every year.
The Bigger Picture: The Rise of Xenotransplantation
This liver transplant follows several other recent breakthroughs in xenotransplantation. Over the past few years, scientists have successfully transplanted pig hearts and kidneys into both brain-dead human donors and living patients.
For instance:
- In 2022, U.S. surgeons transplanted a pig heart into a 57-year-old man who lived for two months after the procedure.
- In 2023, a pig kidney was successfully transplanted into a brain-dead patient who lived for over 60 days with the organ functioning properly.
These successes have given researchers confidence that with further genetic engineering and improved immunosuppressive drugs, animal-to-human transplants could eventually move from experimental to clinical practice.
How Gene Editing Is Changing Transplant Science
Modern CRISPR-based gene editing allows scientists to precisely modify animal DNA. In this case, 10 specific genetic edits were made to the pig to make its liver more human-compatible.
Some of these edits involved:
- Knocking out genes responsible for producing sugar molecules that the human immune system sees as foreign.
- Inserting human genes related to blood clot regulation, immune tolerance, and cellular communication.
- Eliminating viral elements from the pig’s genome to prevent infection risks.
These genetic modifications are performed in embryos, ensuring that the resulting pig carries all the desired traits. Once mature, these pigs can serve as donor animals for research and, eventually, clinical use.
This same approach is being explored for kidneys, hearts, lungs, and pancreases, each with unique challenges but shared principles: genetic modification, immune control, and safety assurance.
The Ethical and Safety Concerns
Despite the excitement, there are valid concerns. Ethicists and scientists alike worry about long-term risks, especially regarding cross-species virus transmission and genetic compatibility.
There’s also the question of how far humanity should go in modifying animals for human benefit. Regulatory bodies around the world are still developing guidelines for xenotransplantation, requiring rigorous ethical approval and public transparency.
Still, for patients facing certain death without a transplant, many experts argue that these procedures can be justified — provided the research meets the highest safety and ethical standards.
Looking Ahead
The Chinese research team’s success represents a turning point. It’s the first proof that a genetically modified pig liver can perform key metabolic functions in a living human — not for hours or days, but for weeks.
Future trials will likely refine the genetic edits, develop better ways to control immune and vascular responses, and possibly extend the survival of such grafts.
While routine pig-to-human liver transplants are still years away, this case shows that science is moving steadily toward making that possibility a reality.
If xenotransplantation eventually becomes safe, reliable, and ethical, it could end the global organ shortage that costs countless lives every year.
Research Reference:
Genetically engineered pig-to-human liver xenotransplantation — Journal of Hepatology (DOI: 10.1016/j.jhep.2025.08.044)
