Scientists have been able to grow human heart tissue that contracts spontaneously in a petri dish.
A team from the University of Pittsburgh, Pennsylvania, used induced pluripotent stem (iPS) cells generated from human skin cells to create precursor heart cells called MCPs.
iPS cells are mature human cells "reprogrammed" into a versatile, primitive state from which they can be prompted to develop into any kind of cell of the body.
The primitive heart cells created in this way were attached to a mouse heart "scaffold" from which the researchers had removed all mouse heart cells, they wrote in the journal Nature Communications.
The scaffold is a network of non-living tissue composed of proteins and carbohydrates to which cells adhere and grow on.
Placed on the 3D scaffold, the precursor cells grew and developed into heart muscle, and after 20 days of blood supply the reconstructed mouse organ "began contracting again at the rate of 40 to 50 beats per minute," said a University of Pittsburgh statement.
"It is still far from making a whole human heart," added senior researcher Lei Yang.
Ways have to be found to make the heart contract strongly enough to pump blood effectively and to rebuild the heart's electrical conduction system.
"However, we provide a novel resource of cells -- iPS cell-derived MCPs -- for future heart tissue engineering," Yang told AFP by email.
"We hope our study would be used in the future to replace a piece of tissue damaged by a heart attack, or perhaps an entire organ, in patients with heart disease."
According to the World Health Organisation, an estimated 17 million people die of cardiovascular ailments every year, most of them from heart disease.
Due to a shortage of donor organs, "end-stage heart failure is irreversible," said the study.
More than half of patients with heart disease do not benefit from drugs.
"Heart tissue engineering holds a great promise... based on the reconstruction of patient-specific cardiac muscle," the researchers wrote.
Last month, scientists in Japan said they had grown functional human liver tissue from stem cells in a similar process.
Creating lab-grown tissue to replenish organs damaged by accident or disease is a Holy Grail for the pioneering field of stem cell research.
Until a few years ago, when iPS cells were created, the only way to obtain stem cells was to harvest them from human embryos.
This was controversial because it required the destruction of the embryo, a process to which religious conservatives and others object.