A team of surgeons externally connected a pig liver to a brain-dead human body and watched it successfully filter blood. This is a step towards the possibility of applying the technique in patients who have liver failure.

The University of Pennsylvania announced the groundbreaking experiment Thursday, which employs a new strategy for animal-to-human transplants. In this case, the pig’s liver was used outside the donated body and not internally, creating a “bridge” that might help diseased livers do the work of cleaning blood externally, like a kind of dialysis.

Transplants from animals to humans, called xenotransplants, have failed for decades because the human immune system rejects the foreign tissue. Now scientists are trying once more with pigs whose organs have been genetically modified to be more like humans.

In recent years, kidneys from genetically modified pigs have been temporarily transplanted into brain-dead donors to test their function, and two men received pig heart transplants, although both died within months.

The U.S. Food and Drug Administration is considering allowing a small number of Americans in need of a new organ to volunteer in rigorous studies involving pig hearts or kidneys.

Some researchers also want to use pig livers. The liver has different complexities than the kidneys or the heart: it filters blood, eliminates waste, and produces substances necessary for other bodily functions. In the United States, regarding 10,000 people are currently on the waiting list for a liver transplant.

In the University of Pennsylvania experiment, researchers connected a pig liver—genetically modified by eGenesis—to a device made by OrganOx that typically helps preserve donated human livers before transplantation.

The family of the deceased person, whose organs were not suitable for donation, offered the body for research. With the help of machines they kept the body’s blood in circulation.

In the experiment, which took place last month, blood was filtered through the device made from pig liver for 72 hours. In a statement, the university team reported that the donor’s body had remained stable and that the pig liver showed no signs of deterioration.

Much work is being done to develop equipment that works like liver dialysis, and experiments with pig livers were attempted years ago, before the advanced genetic techniques that exist today, explained Dr. Parsia Vagefi of UT Southwestern Medical Center, who does not He participated in the new experiment but closely follows research on xenotransplantations.

“I applaud them for promoting this project,” said Vagefi, who called this combination of pig and device an interesting step toward better care for liver failure.

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