In a groundbreaking experiment that could signal a new era in organ transplantation, Chinese scientists have successfully transplanted a genetically modified pig lung into a human recipient, with the organ functioning for nine days before the procedure was halted. The study, published in Nature Medicine on August 25, 2025, marks the first documented case of a pig lung being transplanted into a human—a significant milestone in the field of xenotransplantation, the process of transferring organs across species.
The recipient, a 39-year-old man who had been declared brain-dead following a brain hemorrhage, underwent the procedure at Guangzhou Medical University First Affiliated Hospital in China. With consent from the man's family, doctors transplanted the left lung of a six-gene-edited pig into the patient, aiming to test the feasibility and safety of such a cross-species transplant. The donor pig, a 22-month-old, 70-kilogram Chinese Bama Xiang breed, was raised in a meticulously controlled environment to minimize infection risk.
According to National Geographic, the main scientific goals of the experiment were to monitor for signs of organ rejection and uncontrolled infection. The researchers administered a cocktail of immunosuppressive drugs to the patient, hoping to stave off the body's instinctive response to reject foreign tissue. The initial results were promising: the pig lung maintained viability and functionality for 216 hours—just over nine days—without immediate signs of hyperacute rejection or infection. "The lung xenograft maintained viability and functionality over the course of the 216 hours of the monitoring period, without signs of hyperacute rejection or infection," the study noted.
However, the journey was far from smooth. Within 24 hours post-transplant, doctors observed widespread swelling and fluid buildup throughout the man's body, likely due to blood flow complications. By days three and six, antibody-mediated rejection began to emerge, damaging the transplanted lung. As the immune response intensified, the research team, honoring the family's wishes and after achieving their main scientific objectives, terminated the experiment on day nine.
Despite the short duration, the study's authors see the achievement as a crucial step forward. "Although this study demonstrates the feasibility of pig-to-human lung xenotransplantation, substantial challenges relating to organ rejection and infection remain, and further preclinical studies are necessary before clinical translation of this procedure," they wrote in Nature Medicine. Lead author Jianxing He told National Geographic, "We must remain cautious: current evidence does not support clinical use in living patients." He emphasized that longer trials on brain-dead patients are needed to reduce lung injury and better manage the immune response before considering clinical use.
The implications of this research are particularly significant given the ongoing global organ shortage. In the United States alone, more than 103,000 people were on waiting lists for organ transplants in 2023, while only about 48,000 transplants were performed. According to the Health Resources and Services Administration (HRSA), approximately 13 people in the U.S. die each day while waiting for a transplant. The demand for lungs is especially dire, with only about a fifth of donor lungs deemed viable for transplantation and wait times often stretching for months or even years.
For decades, pig heart valves have been used in humans, but whole organ transplants have proven more complex. Recent years have seen limited success with genetically modified pig hearts and kidneys. In January 2025, Tim Andrews of Massachusetts received a pig kidney transplant and continues to live with the organ, representing one of the most successful cases to date. Yet, as BBC and CNN report, lungs present unique challenges due to their size, their direct exposure to airborne pathogens, and their critical roles in blood filtration, immune defense, and metabolic functions.
Dr. Adam Griesemer, a senior member of the xenotransplantation team at NYU Langone’s Transplant Institute, who was not involved in the Chinese study, commented on the complexity of lung transplantation: "Nobody would sign up for a nine-day lung transplant." He added, "I think it is very important to do these studies since you can’t assume that the animal models are going to perfectly reflect what happens in human recipients." Griesemer also pointed out that research is underway to use pig lungs as scaffolds for growing human cells, potentially sidestepping some of the immune rejection issues inherent in xenotransplantation.
Dr. Ankit Bharat, chief of thoracic surgery at Northwestern Medicine, echoed the sentiment that lung transplants are particularly difficult. "Lungs are much more complicated to transplant than organs like kidneys," Bharat explained to CNN. "That’s a tough problem to solve. We haven’t really solved that, even in human organs. So you are just adding another layer of complexity with pig antigens that can become another problem." Bharat also suggested that advances in stem cell technology might offer a more promising path for lung replacement in the future.
While the Chinese team’s results are a major step, outside experts caution that the procedure is far from ready for clinical use in living patients. As National Geographic reports, the short observation period leaves unanswered questions about long-term viability and the risk of chronic rejection. Moreover, ethical considerations abound: raising animals for their organs and performing experimental procedures on brain-dead patients with only surrogate consent raise complex moral questions. Insoo Hyun, a bioethicist at Harvard Medical School, noted, "It’s a call that the institution makes, and the ethical reviewers have to make." He also warned about the potential for a future two-tiered system in which some patients receive animal organs while others get human ones, raising questions about fairness and quality of care.
Nevertheless, the study represents a vital advance in the quest to address the global organ shortage. The researchers remain optimistic that with further improvements in donor genetic modifications and immunosuppressive strategies, pig lungs could one day offer a viable alternative for patients in need. For now, as Dr. Bharat put it, "A short-term success, even if you have a lung that survives a day or two, does not necessarily translate into shorter or long-term success." But every step forward brings science closer to a future where no one dies waiting for a transplant.
