Scientists have just tried to transplant human kidneys into pigs

in the beginning, Researchers in China used pigs to grow early-stage kidneys made up mostly of human cells. This advance is a step closer to producing organs in animals that could one day be transplanted into humans.

More than 100,000 people in the United States are on the national transplant waiting list, and 17 people die across the country every day waiting for a donor organ, according to the Organ Procurement and Transplant Network. Kidneys are in greatest demand, with nearly 89,000 Americans needing one as of September.

“Being able to produce human organs in pigs would have a huge impact in reducing the number of patients on the waiting list in the United States and around the world,” says Mary Garry, a professor of medicine at the University of Minnesota who studies chemical composition. Organisms – those that contain cells of different types – but were not involved in the research. Gary’s team showed in 2020 and 2021 that it is possible to grow human blood vessels and skeletal muscle in pigs.

Attempts to create animal yeasts in the laboratory began decades ago. In 1984, researchers at the Institute of Animal Physiology in Cambridge, England, reported that they had created goat and sheep chimeras by mixing embryos of the two species. More recently, news leaked in 2019 that scientists had made the first part human, part monkey embryos. (They later destroyed it.) The work was eventually published in 2021. Led by Juan Carlos Izpisua Belmonte, then a professor at the Salk Institute for Biological Studies in California, the team conducted their experiments in China, where they said monkey embryos were located. Cheaper and easier to obtain.

In the current study, a team led by scientists at the Guangzhou Institutes of Biomedicine and Health injected more than 1,800 pig embryos with human stem cells and then transferred them into the wombs of 13 female pigs. They allowed the chimeric embryos to develop for up to 28 days, then stopped the pregnancy to remove the embryos for examination. They collected five of them, all of which were normally developing kidneys containing up to 65% of human cells. The research is published Sept. 7 in the journal stem cell. (The study authors did not respond to WIRED’s request for an interview.)

“Remarkably, about 60 percent of the primitive pig kidney contained human cells,” says John Wu, a stem cell biologist at the University of Texas Southwestern Medical Center who was not involved in the new study. Wu, Belmonte and their colleagues were the first to culture embryos containing mixed human and porcine tissue, a feat they reported in a 2017 study. In that paper, Wu and his team also described the development of the pancreas, heart and eyes of a developing mouse.

However, integrating cells from pigs and humans has proven more difficult than integrating cells from rats and mice, which are closer genetic relatives. Pig cells tend to outcompete human cells when transplanted into animal tissues, causing human cells to die rapidly. As a result, the contribution of human cells to the chimeric embryos produced by Wu’s group was low. He says this study is a huge improvement.