Victims of heart disease have had to live with the possibility that their heart muscle, once destroyed, can never be mended.
But scientists in the US have revealed that this may not always be the case.
Muscle cells taken from the legs of laboratory animals suffering from heart disease have been shown to take over some of the functions of heart tissue that was effectively dead.
The scientists have demonstrated that skeletal muscle - which is used to move arms and legs - can ''learn'' how to behave like heart muscle, which is uniquely adapted to perform the millions of regular contractions a heart carries out over the course of a lifetime.
Doris Taylor, a surgeon at the Duke University Medical Center in Durham, North Carolina, said the research marks an important turning point in attempts to repair the damage caused by heart disease, which can result from a poor blood supply to the heart. In research published in the current issue of the journal Nature Medicine, Dr Taylor and her colleagues found that cells of leg muscles became attached to the damaged heart and took up many of the characteristics of heart muscle.
The results on animals mean that the first attempts at transplanting cells from the leg muscles of patients with severe heart failure who are awaiting transplants could take place next year.
Doctors plan to take small plugs of muscle tissue from the thigh and grow the cells in the laboratory for two weeks before injecting them back into the damaged heart.
''Even if the cells boosted contractions by only 10 or 15 per cent, that could mean a significant difference in a patient's quality of life,'' Dr Taylor said.
''Our hope is that, as a first step to treating patients, transplanted cells may boost the heart's ability to contract, at least long enough for a new heart to become available.''
The research on laboratory animals is the first to show that it is feasible to use skeletal muscle cells as replacements for damaged heart tissue.
''We were excited to see that in many of our test animals, contractions began to approach that of a normal animal,'' Dr Taylor said.
''When we examined the treated hearts their heart tissue was less stiff than if we had not treated them, meaning the heart could stretch better. ''
In the experiments, the scientists injected each of 12 rabbits with 10 million muscle cells grown in the laboratory from tiny plugs of tissue from the animals' hindlimbs.
Between three and six weeks later, the scientists found that the injected cells had become organised into a pattern that resembled heart tissue, suggesting that the skeletal muscle had somehow ''learned'' how to act like heart muscle.
The scientists will try to work with German researchers who have been able to stimulate regrowth of blood vessels to the heart.
Dr Taylor added: ''If we could combine new blood vessel formation with new muscle formation, we could for the first time regenerate living heart muscle where there was only dead tissue.''Reuse content