Scientists took the first steps toward pig-to-human kidney transplants

For the first time, surgeons successfully attached a kidney from a genetically modified pig to a human patient — a major scientific breakthrough, and one that could open up a new way to provide organs to sick people.

Scientists got the kidney from a pig genetically engineered so that it wouldn’t produce a sugar called alpha-gal, which the human immune system attacks and would trigger the body to reject the organ. Surgeons at NYU attached the organ to a brain-dead patient on a ventilator whose family agreed to the experimental procedure. It was connected outside of her body to blood vessels on her leg, and observed over a period of 54 hours.

The recipient’s body didn’t immediately reject the kidney, and the kidney functioned normally for the hours it was attached. “There didn’t seem to be any kind of incompatibility between the pig kidney and the human that would make it not work,” said Robert Montgomery the director of the NYU Langone Transplant Institute, according to The New York Times. “There wasn’t immediate rejection of the kidney.”

There are still many open questions: it’s not clear if the organ would last over an extended period of time inside the body. While the kidney worked for the time it was attached, organ rejection can happen over years — and can happen even if the donor and the recipient are perfect matches. The details of the procedure haven’t been reviewed or published in a medical journal.

Experts are also considering the ethical implications of this type of animal-to-human procedure. Karen Maschke, a research scholar at the Hastings Center, has a grant to develop ethics and policy recommendations for clinical trials of these transplants.

But the procedure was still a landmark step in efforts to perform animal-to-human transplants, called xenotransplantation. Animal heart valves have been used in human procedures for decades, but those can be chemically treated to kill living cells and prevent rejections. Organs, made of living tissue, are more complicated. Proponents of the efforts envision a steady supply of organs from animals, which could help the thousands of people on waitlists for transplants. They could be a lifeline for the hundreds of thousands of people with kidney failure who rely on dialysis.

The kidney used in this procedure was produced by the company Revivicor. The Food and Drug Administration (FDA) approved its genetically altered pigs for therapeutic uses and for human consumption in December 2020. (Some people have an allergy to the alpha-gal sugar, and meat from these pigs might be safe for them to eat.) The FDA would still need to review any medical products — like organs — before they could be used in medicine. The company said in April that it hoped to launch clinical trials using its animal organs for transplants “within the next year or two.”