Monkeys With Transplanted Pig Kidneys Survive for Up to Two Years

Results from a new study published this week give hope to the goal of solving the world's kidney crisis. In the United States alone, 92,000 people are awaiting a new kidney on the national transplant waiting list, according to the American Kidney Fund. Donated kidneys cannot meet support the demand—as of 2020, 5,000 people were dying each year while waiting for a kidney transplant, per the University of Pennsylvania.

One strategy for addressing this organ shortage is using kidneys from pigs, whose organs are of a similar size to human organs.

“The global burden of kidney disease is staggering,” Mike Curtis, CEO of eGenesis, tells Wired’s Emily Mullin. “Cross species transplantation offers the most sustainable, scalable, and feasible approach for delivering new sources of organs.”

The new study, published Wednesday in the journal Nature, reported that a new experiment transplanting kidneys from genetically engineered pigs into monkeys showed that the primates could survive up to two years. Researchers used the gene editing technology CRISPR to make tweaks to Yucatan miniature pig genes, then removed the kidneys from 21 crab-eating macaques and transplanted the pigs' organs into the monkeys.

Some of the monkeys received kidneys just with three edits to prevent their immune systems from attacking the donated organ, per Wired. The monkeys that received the kidneys that were only designed to evade rejection survived for only between four and 50 days, with a median of 24 days. Others received kidneys with seven additional edits to “make the pig cells behave a little bit more like human cells,” Qin tells Scientific American’s Shi En Kim. Those monkeys survived times longer for a median of 176 days, with one surviving for 758 days.

The results bring researchers closer to testing pig kidney transplants in human trials, the study authors write.

The study is a “proof of principle in non-human primates to say our [genetically engineered] organ is safe and supports life,” Wenning Qin, a co-author of the study and a molecular biologist at eGenesis, a biotech company that conducted the research, tells Nature News’ Max Kozlov.

The research is a “groundbreaking achievement,” but “there is still a long way to go before this strategy could be used in clinical trials,” Dusko Ilic, a stem cell scientist at King’s College London who did not contribute to the findings, tells the Guardian’s Ian Sample and Anna Bawden.

A number of transplants involving pig organs have taken place in recent years. Last April, scientists reported transplanting a genetically edited pig kidneys into a brain-dead human patient, and the kidneys remained viable for the duration of the 74-hour experiment. Two other brain-dead human patients received pig kidneys that remained functional during a 54-hour experiment. And a human patient with no treatment options remaining received a pig heart transplant that functioned normally for 49 days.

Adam Griesemer, a transplant surgeon at New York University who contributed to research on transplants in brain-dead humans, tells Wired that the studies and brain-dead humans together demonstrate that pig kidneys can be tested in clinical trials. But these trials will be different from the monkey experiments in part because humans weigh much more and have higher blood pressure than the monkeys, Jayme Locke, a transplant surgeon at the University of Alabama at Birmingham, says to Nature News.

“If ultimately proved successful in human organ recipients—which is still years away at this point—this could be one of the key advances needed to make xenotransplantation a reality in clinical practice,” Josh Levitsky, who was not involved in the study and is the president of the American Society of Transplantation, tells ABC News’ Sony Salzman.

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.