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Two research groups have successfully implanted genetically modified pig kidneys into human recipients. Richard Hamilton Smith/Getty Images
  • Two research groups have successfully implanted genetically modified pig kidneys into human recipients.
  • The University of Alabama at Birmingham’s Heersink School of Medicine found that transplanted pig kidneys produced urine and effectively performed life-sustaining kidney functions such as waste filtration.
  • A separate team at New York University Langone Health achieved a significant breakthrough by having a genetically engineered pig kidney function effectively for a record 32 days within a brain-dead human recipient.
  • These groundbreaking advancements in the field of xenotransplantation signal promising strides toward addressing the ongoing organ shortage crisis.

About 37 million American adults have chronic kidney disease (CKD) and some of them progress to end-stage kidney disease (ESKD) where their kidneys fail.

Kidney transplants are the best treatment for end-stage kidney disease, but only around 25,000 people receive transplants each year in the United States.

This scarcity of donor kidneys means that nearly 40% of individuals on transplant waiting lists die within five years.

To address this, scientists are exploring xenotransplantation, using organs from animals such as pigs for human transplants.

Two separate research teams have reported recent developments in the transplantation of pig kidneys into humans. These advancements are significant milestones in the field of xenotransplantation.

A research team from the University of Alabama at Birmingham’s Heersink School of Medicine discovered that transplanted pig kidneys produced urine and effectively filtered waste in a human recipient, providing crucial life-sustaining kidney function.

This breakthrough was detailed in a research letter published in JAMA Surgery.

In their study, researchers experimented by placing pig kidneys into a deceased human who had been declared brain dead. The pig kidneys had been genetically modified to be more compatible with human physiology.

The recipients of the pig kidneys were given drugs to prevent their immune systems from rejecting the organs. Remarkably, the pig kidneys started working in the human recipients.

The pig kidneys produced urine like human kidneys and helped filter waste from the blood, including a substance called creatinine that builds up when kidneys don’t work properly.

Before the transplant, the recipients had high levels of creatinine, but those levels dropped after the transplant, indicating the pig kidneys were functioning well.

Tissue samples taken from the pig kidneys showed normal structures under the microscope, suggesting they were working properly without significant issues.

Study co-author Dr. Jayme E. Locke, professor of surgery in the Division of Transplantation and Arnold G. Diethelm Endowed Chair in Transplantation Surgery at the University of Alabama at Birmingham Heersink School of Medicine, told Medical News Today:

“For the first time in history, we have shown that a pig kidney can provide life-sustaining kidney function in a human, meaning the kidney made urine as well as cleared toxic substances from the body. We believe strongly that it can alleviate the lethal organ shortage crisis and are hopeful we will be able to move into clinical trials in living persons in the near future.”

This research has ethical implications, however Dr. Locke and colleagues “worked very closely with their internal ethics review board as well as an external ethicist.”

“The biggest focus was to ensure the families were supported throughout and to honor the extraordinary gift,” Dr. Locke explained.

In a second study, researchers at New York University Langone Health achieved a significant breakthrough by successfully implanting a genetically modified pig kidney into another brain-dead recipient, according to an NYU news release.

This engineered pig kidney continued to function effectively for an impressive 32 days inside the recipient’s body, marking the longest duration of a genetically modified pig kidney working in a human.

The researchers are still monitoring the results and the study will continue until mid-September 2023.

This research demonstrates that a pig kidney, with only a single genetic modification and without experimental medications or devices, can replace a human kidney’s function for more than a month without being rejected by the recipient’s immune system.

Challenges faced in previous xenotransplantation attempts, such as immediate rejection due to mismatched biomolecules, have been addressed in this study through specific genetic alterations.

To ensure the pig kidney was the sole functioning organ, the patient’s original kidneys were surgically removed before the pig kidney was transplanted.

The pig kidney began producing urine immediately after the procedure and its performance was assessed through regular biopsies and kidney function tests.

Throughout the study, the pig kidney functioned well, maintaining healthy levels of creatinine in the blood.

The study obtained ethical approval and was conducted in consultation with the New York State Department of Health.

The involvement of the donor family, who donated the body of a 57-year-old man after brain death, was pivotal in enabling this study.

In addition, the non-profit organization LiveOnNY, which facilitates organ and tissue donation in New York City, played a crucial role in supporting and collaborating on this initiative.

The successful pig kidney transplants are significant, as they demonstrate the potential success of using pig kidneys for human transplants amid an ongoing organ donor shortage.

Dr. Toby Coates, professor of medicine at the University of Adelaide, Australia, and director of Transplantation at Royal Adelaide Hospital, spoke to the Science Media Centre, on the research findings:

“This case represents one of the first functional kidney transplants from a pig into a human, and shows proof of principle that organs from a genetically modified animal can replace human kidney function for 1 week without rejection and using conventional kidney transplant drug therapy,” he said.

As a single case, however, more research is needed to determine if this particular approach could be a long-term solution for people with kidney problems.

Dr. Sabrina Kong, a veterinarian in San Mateo, CA, not involved in either study, spoke to MNT about the research.

“This is a monumental step for modern medicine, especially considering the vast gap between the supply and demand for kidney transplants,” she said. “Many patients with end-stage kidney disease wait years for a transplant, and some unfortunately pass away while waiting.”

Dr. Cat Henstridge, a veterinary surgeon based in the United Kingdom, also not involved in the new research, told MNT:

“Although we clearly have some way to go before xenotransplants will be a routine option for living recipients, this research shows some very promising results and could well represent a huge stride forward for patients impacted by organ failure.”

Dr. Kong noted that “the use of pigs in this research is not taken lightly.”

“Pigs are intelligent, social animals, and their welfare is paramount. However, the potential to save or improve countless human lives through xenotransplantation is a compelling argument.”

“From my perspective as a veterinarian, I’ve always been an advocate for animal welfare. However, I also recognize the broader context of medical science and its progression,” Dr. Kong said.

“In the veterinary field, we often have to make difficult decisions for the greater good, whether it’s for the health of an individual animal or for the betterment of a species. Similarly, in the realm of medical research, there are tough choices to be made,” Dr. Kong added.

Dr. Henstridge agreed, noting that “there are obviously some very significant ethical implications of this technique, both for the humans and animals impacted.”

“From the perspective of animal welfare as a veterinary surgeon, my opinion and approach is very much the same as any other animal we use for human gain; as long as they have had a life where their welfare needs are met, where they have been able to express their normal behavior and have been free from pain, discomfort, and distress and then undergone surgery and subsequent euthanasia in a calm, kind and painless way, I have no objections at all to using them as organ donors for human patients.”

— Dr. Cat Henstridge, veterinary surgeon

Dr. Kong noted that “the pigs used in these studies are genetically modified to be compatible with human physiology, which does raise ethical questions about the boundaries of genetic engineering.”

“Yet, these modifications are done with a clear and noble purpose: to address the significant shortage of human organs available for transplantation,” Dr. Kong explained.

“If this research continues to show promise and addresses ethical concerns, it could revolutionize the field of transplantation, offering hope to countless patients awaiting life-saving transplants,” she concluded.