Animal-human transplant breakthrough raises questions

In September, a surgical team at NYU Langone Health performed the first successful transplant of a genetically modified animal kidney to a human. Led by Dr. Robert Montgomery, the team attached a pig kidney to blood vessels on the exterior of a brain-dead patient’s leg. The animal biotechnology company Revivicor provided a genetically engineered pig for the experiment. The animal lacked the gene encoding the sugar molecule alpha-gal, known to trigger immediate organ rejection in humans.

The transplanted pig kidney started working immediately. It functioned normally over a 54-hour observation period, removing waste and producing urine. It also lowered high creatinine levels caused by the patient’s poor kidney function.

Animal-to-human transplants, or xenotransplants, have the potential to shorten organ transplant waiting lists. Over 100,000 people in the United States are on the kidney transplant waiting list, according to the National Kidney Foundation. But xenotransplantation technology is far from receiving U.S. Food and Drug Administration approval for use in human trials. Researchers still need to assess the long-term viability of pig organs in humans and the possibility of a deadly virus transferring from animal to person.

Solving those technical problems requires longer-term studies—but on whom? The success of xenotransplantation could depend on whether scientists find enough patients to participate in dangerous transplant trials, and that raises important ethical questions about consent.

The family of the brain-dead woman, who was an organ donor, consented to the experiment after her organs were deemed unfit for donation. The woman was taken off life support after the 54-hour observation period.

Dr. Jeffrey Barrows, a retired OB-GYN and senior vice president of bioethics and public policy at the Christian Medical and Dental Associations, said he sees an ethical problem with performing experimental research without direct consent from the patient even if he or she is a registered organ donor. He believes medical trials that have nothing to do with the patient’s care need consent from the patient, not just his or her family.

What about living patients? Some bioethicists are eager to perform xenotransplant studies on patients in a persistent vegetative state (PVS), arguing they should be considered dead because of their unconscious state. The 1981 Uniform Determination of Death Act, accepted in all 50 states, defines brain death as “irreversible cessation of all functions of the entire brain, including the brain stem.” PVS patients, while their brain function is severely limited, retain function in the lower brain stem. They can breathe on their own and can perform some involuntary actions such as blinking and smiling. There’s also the remote possibility that a PVS patient will regain consciousness. One French patient showed signs of consciousness while receiving nerve stimulation therapy after 15 years in a persistent vegetative state.

“When we start looking at bodies as raw material to be used in experimentation, I think we’re on a quick ethical downslide that is going to be quite dangerous,” said Barrows. He would consider use of PVS patients for xenotransplant trials ethical only if there was informed consent: For example, someone with a chronic neurological disease, who knows they will eventually deteriorate into an unconscious state but otherwise remain healthy, might give permission to use their body for later medical trials. Without such consent, he said, “we’ve lost the high view of what it means to be human.”

Still, consenting PVS patients would offer a very small population for xenotransplant trials. A better option would be to perform trials on willing organ-failure patients whose chances of receiving a human organ transplant are slim. Such people might view their disease as a way to advance science.

Using such patients for xenotransplantation would be ethical if the doctors conducting the clinical trials are transparent about the procedure and its risks and the patient is still willing to proceed, said Barrows.

But he worried that xenotransplantation research has already creeped into dangerous territory with the development of human-animal chimeras. For example, researchers at the State University of New York and Roswell Park Cancer Institute recently injected mouse embryos with human stem cells. Scientists hope chimeras will lead to better understanding of disease development and even one day serve as a source of transplant organs.

Barrows believes Christians should push back against research that mixes human and animal cells, given the Bible’s distinction between humans and animals: “Even though we have the technological ability to cross those barriers, we need to be very, very, very careful in doing that.”

—WORLD has corrected this story to reflect that the NYU Langone surgery was the first successful transplant of a genetically modified animal kidney to a human.