Now, one of the big questions is whether the improved heart function fades with time, Zeiher said. Repeat treatments may be necessary.
"In principle," Zeiher said, "that can be very easily performed, because the procedure itself is rather simple and -- most importantly -- safe."
Marban agreed that, based on years of research experience, bone marrow cell therapy does seem to be safe.
It's not clear, though, exactly how it works. Early on, some researchers suggested that transplanted bone marrow cells actually generate new heart muscle. But studies since then have failed to show that's true.
The "best guess," Marban said, is that the bone marrow cells secrete certain growth factors that improve the heart's ability to contract.
Right now, the standard treatments for heart failure include medications that lighten the heart's workload and moderate exercise. But researchers are looking for new ways to improve the heart's pumping ability, or even regenerate the damaged muscle.
Marban and his colleagues are studying the use of heart stem cells -- primitive cells within the heart that are, in theory, capable of generating new heart muscle.
The current study was funded by Goethe University. Zeiher and a co-researcher are founders of a company, t2cure, focused on regenerative therapies for heart disease.
Learn more about heart failure from the Heart Failure Society of America.
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