For the first time in scientific history, researchers have grown the structural blueprint of a human organ inside another animal. A team at the Guangzhou Institute of Biomedicine and Health in China successfully generated rudimentary human kidneys within pig embryos — a milestone that edges the medical world closer to solving one of its most stubborn problems: there are never enough organs to transplant.
At a glance
- Pig-human chimeras: Researchers inserted reprogrammed human cells into genetically modified pig embryos, where the cells filled the developmental niche left by the deleted porcine kidney genes.
- Mesonephros stage: The human cells organized into a mesonephros — an intermediate, structured stage of kidney development — with roughly half of the kidney cells being human.
- Organ transplant crisis: Around 150,000 organs are transplanted worldwide each year, yet in the U.S. alone, 100,000 people sit on waiting lists and approximately 17 die every day waiting for a match.
How the experiment worked
The team, led by scientist Liangxue Lai and Spanish researcher Miguel Ángel Esteban, began by reprogramming adult human cells back into a pluripotent state — meaning the cells regained the ability to develop into virtually any tissue in the body.
Those cells were then injected into pig embryos that had been genetically edited to block the development of porcine kidneys. With that biological space left open, the human cells moved in and self-organized into kidney tissue. The embryos were gestated in sows for up to 28 days, roughly a quarter of a pig’s normal pregnancy. The results were published in the journal Cell Stem Cell.
What makes this different from earlier chimera experiments is the degree of organization the human cells achieved. Spanish researcher Juan Carlos Izpisua, who pioneered pig-human chimera work in 2017 C.E. at the University of Murcia, noted the significance. “It goes a step further and shows that cells can be organized in space and give rise to organized tissue structures,” Izpisua said. “It has not yet been possible to develop mature humanized organs in pigs, but this study brings us one step closer.”
A long road to transplantable organs
This is not a kidney ready for transplant. Nephrologist Rafael Matesanz, founder of Spain’s National Transplant Organization, put it plainly: “Conceptually, it is a very important and significant step, but it is not a prelude to producing kidneys, far from it.”
The researchers themselves are working toward the next goal: a fully mature, humanized kidney. That means overcoming a series of technical and ethical hurdles, not least of which is ensuring that human cells stay confined to the kidney and do not migrate into the pig’s brain or reproductive organs. The study found that “very few” human cells were dispersed in the brain and spinal cord of the embryos — a finding the team takes seriously. “To eliminate any kind of ethical problem, we are further modifying the human cells so that they cannot go to the pig’s central nervous system in any way,” Esteban said.
Matesanz raised a pointed concern about regulatory context, noting it is “doubtful” a similar trial would be approved in Europe given the risk of human cells colonizing the pig brain. He also pointed to what he considers a more immediately promising path: genetically modifying pigs so their organs do not trigger immune rejection in humans. That route has already produced early real-world results — in September 2021 C.E., surgeons at New York University successfully transplanted a pig kidney into a brain-dead patient, and in January 2022 C.E., David Bennett became the first living person to receive a genetically modified pig heart. Bennett died two months later from heart failure, though there were no apparent signs of organ rejection.
What researchers say about the future
The chimera approach and the xenotransplantation approach are not competing — they are parallel bets on the same urgent problem. Marc Güell, a Spanish chemist and co-founder of eGenesis, a U.S. company editing pig DNA for human-compatible organs, said the new results “may help to better understand where the current limits of interspecies chimerism are.”
Josep Maria Campistol, general director of the Hospital Clínic de Barcelona and a co-author on Izpisua’s 2017 C.E. research, sees another practical use for chimeric pig models even before transplantation becomes possible. “These pig models allow you to test different therapeutic strategies to prove their usefulness before moving on to a human patient,” he said.
Campistol also believes regenerative medicine will eventually reduce the need for transplants altogether. “I am convinced that, in the near future, we will be able to regenerate chronically diseased kidneys, livers and hearts, to fully or partially restore their function and avoid transplantation,” he said.
The ethical questions around chimera research are real and unresolved. The boundaries around which experiments are permissible — and in which countries — remain contested, and no international consensus governs this kind of work. Growing a fully mature humanized organ inside a living animal, and doing so safely for both species, remains a distant goal.
But the image of half-human kidney cells organizing themselves inside a pig embryo, for the first time, is hard to dismiss. For the roughly 100,000 Americans waiting for a kidney right now, every step forward carries real weight.
Read more
For more on this story, see: El País
For more from Good News for Humankind, see:
- U.K. cancer death rates fall to their lowest level on record
- Alzheimer’s risk cut in half by drug in landmark prevention trial
- The Good News for Humankind archive on global health
About this article
- 🤖 This article is AI-generated, based on a framework created by Peter Schulte.
- 🌍 It aims to be inspirational but clear-eyed, accurate, and evidence-based, and grounded in care for the Earth, peace and belonging for all, and human evolution.
- 💬 Leave your notes and suggestions in the comments below — I will do my best to review and implement where appropriate.
- ✉️ One verified piece of good news, one insight from Antihero Project, every weekday morning. Subscribe free.
