Scarring in damaged hearts can be reversed by the injection of three vital genes, a ground-breaking study has shown.
The research holds out the hope of helping heart attack patients recover naturally.
Scientists used a virus to carry the genes directly into the scar tissue of mice that had suffered heart attacks. Tests showed that the fibroblast cells responsible for scarring began to transform into beating heart cells.
Evidence suggests the same technique could be used to combat scarring in other parts of the body. It might then be possible to regenerate nerve cells in patients with spinal cord injuries, and pancreatic cells in diabetics, say the scientists.
Healthy hearts consist of different kinds of cells, including beating muscle cardiomyocytes and fibroblasts which provide structural support. When a person suffers a heart attack, fibroblast cells migrate to the site of damage and form a scar.
"The process at first can be considered beneficial since without fibroblasts adding structural support damaged hearts would rupture," said study leader Dr Deepak Srivastava, director of the Gladstone Institute of Cardiovascular Diseases in San Francisco, US.
"But later difficulties arise when the fibrotic scar doesn't contract like the muscle it has replaced. Reduced global contractility means the heart has to work much harder, and the extra stress can ultimately lead to heart failure and even death."
One of the holy grails of heart research has been to repair heart attack damage by replacing lost cardiomyocytes. Implanted stem cells offer a potential solution, but it is hard to get them to integrate with neighbouring heart cells. Experts also worry that some rogue stem cells might produce tumours.
The latest work, presented at the Frontiers in CardioVascular Biology (FCVB) meeting at Imperial College London, emerged from research on the genetic factors that drive heart development in embryos.
More work was needed to test the approach on a larger animal, such as the pig, whose heart is similar in size to that of a human, said Dr Srivastava.