London, June 23 : As part of their efforts to document the heart's earliest origins, researchers at Children's Hospital Boston have identified a previously unrecognised group of stem cells that give rise to heart muscle cells, known as cardiomyocytes.
The researchers say that the stem cells they have identified are located in the surface of the heart, epicardium.
They believe that their discovery gives new hope that it may soon be possible to regenerate injured heart tissues.
"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," Nature magazine quoted Dr. William Pu, a pediatric cardiologist at Children's who was the study's senior investigator, as saying.
The researcher say that epicardial cells, though are known to give rise to smooth muscle and endothelial cells during coronary vessel formation, were not previously thought to be able to turn into cardiomyocytes.
"I couldn't believe it at first, myself," said Dr. Bin Zhou, a research fellow in Pu's laboratory and the study's first author.
The findings got more force when a team of researchers from the University of California, San Diego independently showed that cardiomyocytes could be derived from the epicardium, though using a different genetic marker.
Pu and Zhou say that the cells they have identified in the epicardium not only differentiate into cardiomyocytes, but also smooth muscle cells, endothelial cells and fibroblasts (found in connective tissue).
"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," said Pu.
The researchers now want to determine 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.
The group also wants to see whether the newly-discovered group stem cells is truly multi-potent (able to turn into all other cell types), how multi-potency is controlled, and whether this can be used therapeutically to benefit adults with heart failure.
The fact that such cells can also differentiate into fibroblasts in the developing heart suggests that they can contribute to scar formation in the adult heart after injury, Pu says.
"But if we can turn the progenitors away from making scars, and instead turn them towards making cardiomyocytes, that would be pretty exciting," the researcher adds.
The researchers say that they want to learn what controls a progenitor's choice to become a fibroblast, a smooth muscle cell, or a cardiomyocyte.
They say that they also wish to develop ways of "biasing progenitors to make the choice or choices we want."
"We still don't know how we can manipulate these progenitors, and there's no way to predict which ones will be useful. But I think having more choices is good, because then hopefully one of them will work," Pu says.