Scientists have regrown a monkey's heart using human stem cells

Australian researchers have become the first in the world to regenerate primates' heart muscles using human embryonic stem cells. The breakthrough could lead to a cure for heart failure and could be trialled in humans within a few years. The team, led by cardiologist James Chong from the University of Sydney and the Westmead Millennium Institute, injected about a billion heart muscle cells grown from human embryonic stem cells onto the hearts of seven pigtail macaque monkeys to repair damage caused by a heart attack.  As a result, 40 percent of the damaged region of the heart regenerated, and the grafted muscle cells started to be supplied by the blood vessels of the host heart. Scientists have previously succeeded in growing embryonic stem cells into heart cells, but this is the first time these cells have been successfully translated into a large animal. The research was published in Nature. "We were able to show for the first time that from two weeks after transplantation these human heart muscle cells were beating synchronously with the host heart of a large animal," Chong told Nikki Phillips for the Sydney Morning Herald. To monitor the injected heart cells that had been differentiated from human embryonic stem cells, the researchers tagged them with a marker that glowed green when they beat. The breakthrough, if successful in humans, could potentially replace the need for heart transplants in humans. Chong said that with further research and funding he hoped to start clinical trials in humans in a few years.  However, some of the monkeys did develop abnormal heart rhythms after the procedure, although they did appear healthy, and this will require further investigation before human trials begin.