Gene-edited pig-to-human liver transplant probes on clinical use feasibility

A breakthrough in medical research is made as researchers in China successfully used a gene-edited pig liver to transplant into a human, as published in Nature this March.

According to the study that took place at Xijing Hospital of the Air Force Military Medical University, the liver was transplanted into a brain-dead patient, and closely monitored over the course of 10 days — showing no signs of rejection, and producing bile as hoped.

The operation aimed to assess whether pig livers could serve as temporary replacements or even long-term solutions for human patients in need of transplants.

“It is our dream to make this achievement,” trial leader Prof. Lin Wang proclaimed in an article by The Guardian.

As of September 2024, more than nine thousand Americans are waiting for a liver transplant—about nine percent of the national transplant list—and seventeen people die each day while waiting for organs, according to the Health Resources & Services Administration (HRSA).

The situation is even more dire for the Philippines. 

An article by St. Luke’s Medical Center states that as of 2017, there have only been a total of 59 liver transplants in the country, despite the 2020 World Health Organization global health estimates stating that over 7,000 Filipinos die of liver cirrhosis — or permanent scarring of the liver that can interfere with its function.

To address this gap, scientists are exploring xenotransplantation, or the transplant of animal organs into humans.

Previous experiments, such as pig heart transplants conducted at the University of Maryland, showed promise, with two patients surviving up to two months without immediate organ rejection.

The pig liver used in the Chinese study had six genetic edits—aimed at removing sugars that typically trigger immune attacks and adding human-compatible genes to reduce rejection risks.

The procedure was a heterotopic auxiliary transplantation, which means the liver was placed in an alternate location in the body rather than replacing the existing organ.

In this case, the pig liver was attached to the inferior vena cava and abdominal aorta — the body's largest vein and artery — allowing it to function in parallel with the human liver.

“They basically slot the liver into the main artery that runs from the leg towards the heart,” explained Professor Peter Friend, a transplant specialist at the University of Oxford. 

“That makes it safer and much less prone to complications and something that can be removed as and when it’s not needed.”

Despite promising results, researchers caution that the study had limitations.

The monitoring period lasted only ten days, at the request of the patient’s family, making long-term evaluation impossible.

“The study was terminated on day ten, which made the follow-up period insufficient to analyse alterations in xenograft function over a long period,” the paper stated.

Furthermore, as patients selected for such trials are typically already critically ill, it remains difficult to determine whether future failures would be due to the organ or the patient’s condition.

“We could not see whether the pig liver could support a patient with severe liver failure,” Prof. Wang noted.

Still, the experiment marks a significant step toward potentially resolving the global organ donor crisis and pushes xenotransplantation research closer to clinical application.