Stem Cells Discovered in Surface of Heart

Nature, June 22, 2008

Cardiomyocytes are the fundamental cells of heart muscle, and as such they are critical to the regeneration of damaged heart tissue. Now scientists at Children's Hospital in Boston have discovered cardiac progenitor cells that are located inside the epicardium, which is the outer layer of the heart.

Some of these progenitor cells were found to express the gene Nkx2-5, while others express the gene lsl1, and a third type was found to express the Wt1 gene. In all cases the cells were shown to be capable of differentiating into heart muscle, vascular smooth muscle cells and endothelial cells. Similar studies conducted at UC-San Diego have yielded the same results with the genetic marker Tbx18. Known as epicardial cells, these stem cells were already proven to be capable of differentiating into endothelial cells and smooth muscle during coronary vessel formation, but this is the first evidence demonstrating that they can also differentiate into cardiomyocytes. According to William Pu, M.D., a pediatric cardiologist at Children's Hospital, "If you're going to regenerate a tissue, you need to regenerate the whole tissue, not just the cardiomyocytes. This progenitor population contains all the potential to regenerate multiple tissue types within the heart."

The discovery is expected to have vast implications in the field of heart tissue regeneration following damage from heart attacks and other types of cardiac injury.