Tiny Human Hearts Grown in Pig Embryos For the First Time

Scientists have successfully grown beating human hearts inside pig embryos for the first time, marking a significant advance in developing human-animal chimeras for potential organ transplantation. The hybrid embryos survived for 21 days, during which the fingertip-sized hearts began beating, according to findings presented at the International Society for Stem Cell Research meeting in Hong Kong.

Researchers — led by Lai Liangxue at the Guangzhou Institutes of Biomedicine and Health — reprogrammed human stem cells to survive in pigs and introduced them into pig embryos with two heart development genes knocked out. The human cells, tagged with luminescent biomarkers, were visible glowing within the developing hearts.