Scientists have identified a new, previously unrecognized group of stem cells that give rise to the different heart muscle cells. These stem cells, the third type of cardiac progenitor identified so far, is located on the surface of the heart (epicardium) and is identifiable through its expression of a gene called Wt1. In addition, these stem cells not only differentiated into cardiomyocytes, but also Smooth muscle cells, endothelial cells and fibroblasts (found in connective tissue).

Pu and Zhou now want to know whether the epicardium in an adult mouse could be induced to make cardiomyocytes. "If so, obviously this would be much more translatable to human studies," Pu said. Other ongoing questions are whether this newly-discovered progenitor is truly multipotent (able to turn into all other cell types), how multipotency is controlled, and whether this can be used therapeutically to benefit adults with heart failure.

Photo: Pu and Zhou tagged the Wt-1 expressing epicardial cells with a fluorescent red protein, then allowed the cells to differentiate. The image shows a descendent cardiomyocyte (green) that carries the same red marker, and another cell that arose from different origins. (The blue stain indicates cell nuclei).