Researchers in China have grown beating hearts made of human cells in pig embryos that survived for 21 days, providing new hope for the global shortage of organs for transplantation.  

Scientists from the Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, introduced human stem cells into pig embryos, immediately after fertilisation, which had lacked some of the genes necessary to form a heart. In the absence of pig heart cells, the human stem cells took over and led to the development of a human heart.  

To enhance these human stem cells’ ability to survive, the researchers genetically modified them to prevent cell death and stimulate growth. On day 21 of development, the now-beating hearts had the expected size of a human heart at the same stage of development.  

“Pigs are a suitable donor species because the size and anatomy of their organs are comparable with those of humans,” said Liangxue Lai, leader of the unpublished study that was presented last week at the meeting of the International Society for Stem Cell Research in Hong Kong. 

The current biggest challenge of growing human organs in animals is to achieve organs made completely of human cells. This is crucial for transplantation to avoid provoking a reaction from the body’s immune system.  

In 2023, in a previous work also led by Liangxue Lai, researchers were able to develop a human kidney in pig embryos. In that case, approximately 40-60% of the kidneys were made by human cells, and the rest comprised pig cells.