(CBS News) There is no greater threat to this country than heart disease. It is the leading cause of death, killing 600,000 Americans a year.
But Doctors Rich Lee and Amy Wagers may have discovered a new way of treating old, sick hearts make them young again.
"The heart experiences a decline in function as people age. And we wanted to understand how that decline in function arose and whether we might be able to intervene to stop it or reverse it," Wagers said.
During age-related heart failure, the heart grows larger as the muscle thickens and becomes stiff. That can cause fluid to back up into the lungs, which can make it hard to breathe.
"There has been a suspicion that there is a circulating hormone or some material that can reverse some of the aging process," Lee said.
The Harvard team honed in on a hormone called GDF-11, which declines with age in mice. The scientists took GDF-11 from young, healthy mice and gave it to old mice with heart failure.
"The heart is not known for being a regenerative organ. So I actually secretly suspected that we would not see any effect in these experiments," Wagers said.
The results took Wagers and Lee by surprise.
"When old mouse hearts are exposed to this hormone at the levels the young mice have, then their hearts go back quite dramatically to the appearance of the young mouse heart in just a few weeks," Lee said.
At left is the heart of a young mouse, compared to the enlarged heart of an old mouse with heart failure. The next image shows the heart of a young mouse compared to an old mouse's heart after receiving GDF-11 -- it's returned to a normal size.
The team's next step is to see if this hormone has the same effect in humans.