Kidneys grown in pigs pave way for transplants

It is the first time they have been able to start growing solid organs made from mostly human cells inside an animal.

Liangxue Lai from the Guangzhou Institutes of Biomedicine and Health, and lead author of the study, with his colleague Miguel Esteban, who said transplants might be possible in a decade

Scientists have taken a big step towards growing “unlimited” organs for transplant after creating the first “humanised” kidneys in pigs.

It is the first time they have been able to start growing solid organs made from mostly human cells inside an animal.

The kidneys were allowed to develop for only four weeks within embryos implanted into surrogate pigs but scientists reviewing the research said it was a “major achievement on the road to unlimited organ production”.

Researchers in China hope to be able to use the process to create organs for human transplant within a decade.

Kidneys are the most sought-after organs for transplant, with 5564 people on the waiting list in Britain – more than three times the number waiting for all other organs combined – with an average wait of two to three years.

A study in the journal Cell Stem Cell says: “The results indicate that it might be possible to generate a functional human kidney inside newborn pigs, offering an attractive alternative to overcome the shortage of human organs for transplantation.”

Scientists at Guangzhou Institutes of Biomedicine and Health implanted human stem cells into pig embryos in a new way to ensure they would develop human rather than pig kidneys.

The embryos were implanted into sows and allowed to develop for 25 to 28 days.

The researchers found that kidneys had started growing that were “structurally normal for their stage of development” and were made up of about 60 per cent human cells.

The humanised kidney cells are shown in red inside the embryo

The rest of the embryo was composed almost entirely of pig cells, with only a small number of human cells found in the brain and spinal cord of the embryonic pig.

Researchers around the world have hailed the importance of the development.

Rafael Matesanz, a neurologist who founded the National Transplant Organisation in Spain, said it had “greatly increased the efficiency of the procedure”. He added: “The authors themselves acknowledge that the clinical use of this technology is years away but it is a major achievement on the road to unlimited organ production for transplantation.”

Dusko Ilic, from King’s College London, said the research demonstrated “pioneering steps in a new approach to organ bio­engineering using pigs as incubators for growing and cultivating human organs”.

Professor Ilic added that there were still “plenty of challenges to overcome” but asked: “Will this approach prove to be the ultimate solution? Only time holds the ­answer. Nevertheless, this captivating strategy warrants further exploration.”

In 2017, the first chimeric embryos, those with genetic material from two or more species, with both human and pig material, were implanted into sows in Spain and grown for three weeks. No organs were grown but it showed that it was possible to integrate human cells into non-human embryos.

Only a fraction of the embryos implanted were successful and scientists have been unsure about how to prevent the human cells within the hybrid embryos from being crowded out by pig cells. Researchers have been able to create human skeletal muscle using a similar process but never solid organs.

In order for the hybrid embryos to develop human kidneys, scientists needed to ensure that the embryo did not also develop pig kidneys.

Scientists in China used gene-editing technology to remove the genes from pig cells that trigger kidney development. This allowed humanised kidneys to develop without competition.

The law in China permits the embryos to be grown for longer, allowing scientists to stop the development after four weeks rather than three. They found that the kidneys had reached the second of three stages of development, known as the mesonephros stage, having formed tubules and the buds that would develop into ureters to connect the kidney to the bladder. The study said that “obstacles still need to be solved” in growing fully human organs.

The Times