The finding by researchers at Children's Hospital Boston follows studies that found a specific stem cell or progenitor, marked by expression of a gene called Nkx2-5 can form many components of the heart, including heart muscle cells.

In the new finding, Children's Hospital scientists showed heart muscle cells can also be derived from a third type of cardiac progenitor located within the epicardium, or the heart's surface, and identifiable through its expression of a gene called Wt1.

"There's a lot of interest in finding places to obtain new cardiomyocytes, because in heart failure you lose cardiomyocytes, so the only way to reverse heart failure is to make more of these cells," said Dr. William Pu, who led the research.

Although epicardial cells are known to give rise to smooth muscle and endothelial cells during coronary vessel formation, nobody previously thought epicardial cells might turn into cardiomyocytes. The results were independently corroborated by researchers from the University of California-San Diego.

The findings are reported online in the journal Nature.