Scientists have succeeded in using gene therapy to repair damage to human heart cells in the laboratory.
Gene therapy holds great promise
The researchers, from Thomas Jefferson University, hope it will not be long before the technique is tested on patients with failing hearts.
The journal Circulation reports how they used a virus to insert a gene into cells taken from people with congestive heart failure.
After treatment, the cells were able to contract once again at full strength.
The Jefferson team are confident that their work represents the first time that gene therapy has been successfully used to repair human heart cells - other work has focused on animal cells
The gene works by blocking activity of an enzyme called beta-adrenergic kinase.
The enzyme plays a key role in helping to regulate the beating of the heart.
But it can cause problems when found, as it is in people with heart failure, at higher than normal levels.
In this instance, too many receptors in the heart are de-activated, and the organ is unable to pump as hard as it would normally do.
The therapy gene produced a peptide called beta-Arkct which blocked the
Lead researcher Professor Walter Koch said: "This is the first work in actual human hearts to show efficacy of beta-Arkct as a potential therapy, and more importantly, proves that the enzyme beta-Ark1 is a target for heart failure treatment."
Professor Sir Charles George, medical director of the British Heart Foundation, warned that there was a big difference between lab experiments and treating patients.
He said: "Although interesting in terms of unravelling some of the changes which occur in the failing heart, all of this work was done in cells isolated in the laboratory.
"The implications for treatment of patients are uncertain, because gene therapy has often produced only short term benefits in living animals and humans."
Professor Eric Alton, of the National Heart and Lung Institute at Imperial College London, told BBC News Online: "It is an important step in a series of studies that will be needed to develop a new treatment for patients with heart failure.
"The key will be to see if these interesting laboratory studies can be translated into benefit in living human patients."