In September, doctors at the University of Alabama at Birmingham implanted two pig kidneys into a brain-dead person, a step toward testing the procedure on humans.

The results of the surgery were not made public until Thursday, when they were published in a scientific paper.

It was the second time a pig kidney had been implanted in a brain-dead patient. The first occurred five days prior at NYU Langone Health in New York City.

A Maryland man recently received a pig heart as a last-ditch effort to save his life.

In all three cases, the pig donor’s genes had been altered so that the human body would be less likely to reject it. The experiments with deceased recipients were designed to demonstrate that the body would not immediately reject the organ, as it would in an animal without such genetic changes.

Jim Parsons, 57, was declared brain dead at UAB Hospital but was kept alive by a ventilator. Parsons, of Huntsville, Alabama, was in a dirt bike accident in late September that left him paralyzed.

His organs could not be donated, but his family agreed to let his body be used in the study.

The procedure was approved by Parsons’ children and ex-wife, with whom he remained close. “She said it would have meant a lot to Mr. Parsons to know he was able to do something completely different that could potentially benefit so many,” Alan Spriggs, program manager with Legacy of Hope, Alabama’s organ procurement organization, said.

He had just celebrated his 57th birthday and had recently returned from a trip riding motorcycles to and from the mountains of Colorado with one of his three children.

Jeff Parsons’ kidneys were replaced on September 30 by two from a gene-edited pig raised in a pathogen-free facility established by UAB. They remained in place for about 77 hours before “brain death won the game” and Parsons’ body became too unstable to continue, according to Dr. Jayme Locke, director of the Comprehensive Transplant Institute in UAB’s Department of Surgery and the study’s lead investigator, during a news conference on Tuesday.

The pig underwent ten gene edits to prevent rejection after being implanted, to avoid growing too large inside the human body, and to prevent blood clots.

UAB plans to use the same edits on pigs in a clinical trial, which it hopes to begin later this year.

The goal of xeno-transplantation is to help solve the human organ shortage. Currently, people in need of a heart, kidney, or other organ must often wait years before receiving one at all. Their second chance comes at the expense of another person who had to die and donate their organs.

Over 100,000 Americans are currently on organ transplant waiting lists, with some never qualifying and approximately 6,000 dying each year. Experts predict that if pig organs can be obtained safely, demand will skyrocket.

Dr. Selwyn Vickers, dean of the UAB Heersink School of Medicine, said Tuesday that UAB has a special interest in resolving the organ crisis because it is located in the “stroke belt” and many of its patients are minorities. In the last 30 years, UAB has performed more organ transplants in Black Americans than any other institution, and the second highest number of transplants overall, he claims.

The procedure was approved by a hospital review board and subjected to an external ethics review before it was carried out.

UAB will continue to raise enough gene-edited pigs for clinical trials over the next year. An early-stage trial, which the hospital hopes will be approved by the Food and Drug Administration this year, would include 10-20 human transplants. Hundreds of patients would be included in later stages of trials.

UAB is starting with kidney and heart transplants and hopes to expand to lung and liver transplants in the future, according to Locke.

Others are also working to make pig organs transplantable.

If early trials can begin this year and all goes well, Locke believes xenotransplantation will become more common.