Early kidney structures made of mostly human cells have been grown in pig embryos for up to 28 days as part of efforts to grow human organs in other animals for transplants

By Alice Klein

A normal pig embryo (top row) and one with human kidney cells, labelled in red (below)

Wang, Xie, Li, Li, and Zhang et al./Cell Stem Cell

Kidneys that are more than 50 per cent human have started to grow in pigs for the first time after scientists created embryos made of human and pig cells and implanted them in sows for up to four weeks.

The research, conducted by Miguel Esteban at Guangzhou Institutes of Biomedicine and Health in China and his colleagues, brings us a step closer to being able to grow human kidneys in other animals to address the shortage of organ donors.

Over 100,000 people in the US alone are currently waiting for a kidney transplant, with 13 dying per day.

To get around the need for donors, it may be possible to grow human kidneys in other species like pigs that have similar organ sizes and physiology to us.

Esteban and his colleagues explored this idea by creating pig embryos that couldn’t form kidneys of their own, by disabling two key genes responsible for development of the organs.

Next, they introduced human stem cells into the pig embryos, hoping they would transform into kidney cells in the pigs and assemble into the relevant organs. The human cells were genetically engineered to help them integrate in the foreign environment by increasing the expression of two pro-survival genes.