Cardiac master cells discovered

Heart is made up of three main tissues

Scientists have discovered what they believe could be cardiac master cells, capable of developing into different tissues in the heart.

Groups of US scientists, working independently, have discovered two separate candidates.

One has the capacity to produce all three major tissues in the heart, the other two of the three.

The breakthrough, published in the journal Cell, raises hopes for new treatments for heart disease.

The findings challenge the notion that the heart's different cell types are so diverse they must have come from separate sources.

In one study, a team from Massachusetts General Hospital identified a type of progenitor cell in mice, and showed that it could go on to form cardiac muscle, smooth muscle or endothelial cells.

The second type of cardiac progenitor cell, identified by a team from the Children's Hospital Boston, was shown to be capable of forming cardiac and smooth muscle.

HEART TISSUE Cardiac muscle: Makes up the heart itself, and contracts to pump blood around the heart Smooth muscle: Found in the heart's blood vessel walls Endothelial cells: Line the heart's blood vessels

Dr Stuart Orkin, from the Children's Hospital team, said: "Previously, it had been thought that each cell type in the heart had a different origin. Now, it's pretty clear that some have common origins.

"Instead of multiple different cell types migrating and coming together to form the heart, the heart comes from stem cells that give rise to multiple cell types in the same local environment - a simpler way of building the organ.

"And because these cells can make multiple cell types, they could be more useful in repairing the heart than any single kind of cell."

Relationship unclear

The researchers do not know the precise relationship between the two types of master cells that have been identified.

One appears to generate structures on the left-hand side of the heart, and the other on the right-hand side.

These are early steps in the long road to discovering how to repair a damaged heart Professor Peter Weissberg British Heart Foundation

However, they are hopeful that they could be harnessed to carry out repairs to damaged hearts.

At present, scientists are trying to perfect the use of embryonic stem cells for this purpose, but this carries the risk of cancer resulting from uncontrolled growth of the cells.

Dr Kenneth Chien, leader of the Massachusetts General Hospital team, said: "If we can get around that threat by cloning master cardiovascular stem cells, that would be a major advance."

The heart is the earliest organ in the body to develop, and the one most susceptible to congenital defects.

Professor Peter Weissberg, medical director of the British Heart Foundation, said until recently it was thought that the heart had no means of regenerating itself if it became damaged.

"But these studies, coupled with other recent discoveries, suggest that there may be certain cells within the heart which have the capacity to become new heart and blood vessel cells.

"Such findings are very promising, but preliminary studies in people have suggested that there are very few such cells in the hearts of relatively elderly people with advanced heart disease, who most need a repair mechanism.

"Nevertheless, by studying how these cells change into mature, functioning heart cells we will ultimately understand the molecular mechanisms required to form new heart cells.

"These are early steps in the long road to discovering how to repair a damaged heart."