British scientists say human hearts could be repairable in 10 years.
Researchers at University College London studied stem cells that line the hearts of mice. In the embryo, these cells are able to form into heart tissue but they are dormant in adults.
However, the research team has found a chemical - thymosin beta 4 - that can wake the cells up so that they start forming new heart tissue.
Head of the research team, Professor Paul Riley says the results was repair to damaged heart muscle.
"The adult epicardial cells that line the outside of the muscle of the heart muscle can be activated, move inward and give rise to new heart muscle."
He says there was an 25% improvement in the heart's ability to pump blood.
The technique, if it is successful in humans, would mean the increasing number of people who survive heart attacks would no longer have to live with damaged hearts.