Surgeons carried out the world's first successful transplant of a pig's kidney into a 62-year-old man.
The patient Rick Slayman, who had been living with end-stage kidney disease, is expected to be discharged soon. The four-hour-long surgery took place on March 16.
“The success of this transplant is the culmination of efforts by thousands of scientists and physicians over several decades. We are privileged to have played a significant role in this milestone," said Tatsuo Kawai, Chair of Transplant Surgery at Massachusetts General Hospital and the surgeon who performed the transplant.
"Our hope is that this transplant approach will offer a lifeline to millions of patients worldwide who are suffering from kidney failure".
Slayman previously received a kidney transplant from a human donor in 2018 after being on dialysis for seven years.
Dialysis helps to clear waste from patients' bloodstream, a function typically carried about by the kidneys.
But five years after his human kidney transplant, it showed signs of failure and he had to resume dialysis but had complications that required frequent trips to the hospital.
'Provide hope'
Slayman said in a statement that he saw the pig kidney transplant "not only as a way to help me, but a way to provide hope for the thousands of people who need a transplant to survive".
The pig kidney had been genetically edited using CRISPR-Cas9 technology to "remove harmful pig genes and add certain human genes to improve its compatibility with humans," the hospital said.
Demand for human organs is higher than the number that are available for transplant. More than 150,000 Europeans were on a waiting list for organ transplants in 2018.
Kidneys are the most frequently transplanted organ, according to the European Commission.
This was a milestone for xenotransplantation - the process of transplanting animal organs into humans - which is hoped to be a possible solution for the lack of organs.
It comes with risks, however, including transferring an unknown pathogen from the animal or triggering a serious immune response.
Two men who received successful pig heart transplants in the US both died after receiving the transplant. Both had been ineligible for human heart transplants.
The procedure was performed under a special US regulator authorisation granted to patients with serious illnesses to access an experimental treatment.
"The continued success of this groundbreaking kidney transplant represents a true milestone in the field of transplantation," said Dr Winfred Williams, Slayman's nephrologist.
"It also represents a potential breakthrough in solving one of the more intractable problems in our field, that being unequal access for ethnic minority patients to the opportunity for kidney transplants due to the extreme donor organ shortage and other system-based barriers," he added.
