Damaged hearts can be repaired using genetic "master switches" that convert scar tissue into muscle, research has shown.
The technique, demonstrated in mice, could lead to new treatments for heart attack survivors in the next decade, say scientists.
Scar tissue left by a heart attack can weaken the heart, making it incapable of pumping blood efficiently and leading to heart failure.
The debilitating condition, suffered by 900,000 people in the UK and 23m worldwide, causes exhaustion with even the slightest physical effort and may ultimately contribute to death.
Several groups of scientists are investigating the use of stem cells, immature cells with more than one development pathway, to rebuild scar-ridden hearts. But the new research points to a simpler method of turning scar tissue into functioning heart muscle without stem cell transplants.
Scientists in the US used microRNAs, small genetic molecules that serve as master regulators controlling the activity of multiple genes.
They identified a particular combination of three microRNAs that appeared to convert scar tissue cells called fibroblasts into heart muscle cells.
When the microRNAs were delivered into fibroblasts in the laboratory, the reprogrammed cells began to transform into the cardiomyocytes that make up heart muscle.
The same conversion was achieved in living mice, indicating that it had therapeutic potential.
Lead scientist Professor Victor Dzau, from Duke University Medical Centre in Durham, North Carolina, said: "Researchers have tried various approaches, including the use of stem cells, to regenerate damaged heart muscle tissue.
"This is the first study to use microRNA, which are small molecules that control gene expression, to reprogramme fibroblasts into heart muscle cells. We have not only shown evidence of this tissue regeneration in cell cultures, but also in mice."
He added: "This is a significant finding with many therapeutic implications.
"If you can do this in the heart, you can do it in the brain, the kidneys and other tissues. This is a whole new way of regenerating tissue."
The team, whose results are reported in the journal Circulation Research, now plans to see whether microRNAs can repair damaged hearts in larger animals. If these studies prove successful, human trials will follow.
Prof Dzau believes microRNA injections could prove a viable treatment for heart attack patients in years to come.
"If everything comes to fruition, I think we will see this as a therapy in the next decade," he said. "Conceivably, we'll use it to regenerate hearts damaged by heart attacks, avoiding heart failure and saving lives."
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