A first-ever experiment shows how pigs might one day help people who have liver failure

Researchers at the University of Pennsylvania have externally attached a pig liver to a brain-dead human body and watched it successfully filter blood

Surgeons externally attached a pig liver to a brain-dead human body and watched it successfully filter blood, a step toward eventually trying the technique in patients with liver failure.

The University of Pennsylvania announced the novel experiment Thursday, a different spin on animal-to-human organ transplants. In this case, the pig liver was used outside the donated body, not inside — a way to create a “bridge” to support failing livers by doing the organ's blood-cleansing work externally, much like dialysis for failing kidneys.

Animal-to-human transplants, called xenotransplants, have failed for decades because people's immune systems rejected the foreign tissue. Now scientists are trying again with pigs whose organs have been genetically modified to be more humanlike.

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

The U.S. Food and Drug Administration is considering whether to allow a small number of Americans who need a new organ to volunteer for rigorous studies of either pig hearts or kidneys.