NEW YORK (AP) _ Challenging decades of medical dogma, researchers have discovered that damaged hearts can repair themselves by growing brand-new muscle cells.
With this discovery, researchers hope to eventually find ways to boost the heart's ability to mend itself after a heart attack or heart failure.
``The recognition that this mechanism exists and, in the future, the ability to recruit this mechanism, opens up entirely new prospects for novel kinds of therapy for heart attacks,'' said Dr. Eduardo Marban of Johns Hopkins University, chairman of the American Heart Association's council on basic cardiovascular sciences.
Until now, experts had assumed that the heart _ unlike other body parts, such as skin and bone _ could not form new cells. It was thought that once the heart was damaged, the damage was irreversible.
``The bottom line: We didn't know before. Now we know that heart cells divide. It's obviously highly significant,'' said David Finkelstein of the National Institute on Aging, which helped fund the research. ``If one could find a way to turn on this division, it would be very important.''
For example, Marban said, heart attack patients in a matter of just a few years might routinely be given injections of their own laboratory-grown stem cells to stimulate the growth of new heart muscle.
The researchers examined 13 hearts after fatal heart attacks and found a significant amount of new cardiac muscle being formed in two areas of the heart. Their findings are reported in Thursday's New England Journal of Medicine.
``This is probably the most compelling demonstration that heart muscle cells can regenerate and therefore repair damage,'' said Dr. Piero Anversa, who conducted the research at New York Medical College in Valhalla, New York.
The damaged hearts were from patients who had died four to 12 days after suffering a heart attack. During a heart attack, blockage of a coronary artery cuts off the blood supply to the heart, killing off part of the heart muscle. The damaged hearts were compared with 10 hearts from people who died from injuries or other ailments.
The researchers focused on two areas of the heart _ one next to the damaged portion and one more remote. They checked for evidence of cell division by looking for a protein present when cells are dividing. Compared with the normal hearts, the number of multiplying muscle cells was 70 times higher next to the damage and 24 times higher in the remote area.
``So the heart is not so unusual like everybody believed, and the dogma has no basis to exist,'' Anversa said.
He said the next step is to identify the dividing cells and to find ways to target the damaged area of the heart for new cell growth.
Anversa said the source of the new growth could be existing heart muscle cells or a primitive cell _ called a stem cell _ in the heart. He noted that the brain was once thought to lack stem cells and the ability to regenerate, but that is no longer true.
``We believe in the heart the same phenomenon is occurring, although we still have to prove it unequivocally,'' he said.