A compound that is derived from the skin around bone and is abundant during fetal heart development has been found to stimulate the growth of heart cells, a new U.S. study says.

Researchers hope their findings, appearing in the July 15 online edition of Nature Medicine, will lead to a treatment for humans to replace tissue damaged during a heart attack. Typically, damaged cardiac tissue cannot regrow.

Researchers added the compound periostin to mature heart muscle cells known as cardiomyocytes in a Petri dish and found that some of the cells began dividing and replicating.

Dr. Bernhard Kuhn from the department of cardiology at Children's Hospital Boston worked with colleagues at Massachusetts General Hospital and the Mount Sinai School of Medicine in New York.

They created a special patch soaked in periostin and placed it on the damaged heart muscle of rats in which they had induced a heart attack to again stimulate an increase in cardiomyocytes. After 12 weeks, the rats treated with the patch experienced a 16 per cent improvement in cardiac function, the study says.

The researchers also reported a reduction in the size of the damaged area of the heart and a denser network of blood vessels feeding the area. In contrast, rats that received a patch without periostin showed no change in their heart function.

At the cellular level, the periostin-treated group had a 100-fold increase in the number of cardiomyocytes entering the cell cycle, and grew, on average, six million more cardiomyocytes, far exceeding the number of dying cells. The average rat heart has about 20 million cardiomyocytes.

Mature human hearts have only tiny amounts of periostin. Increased amounts are made after skeletal-muscle injury, bone fracture and blood vessel injury, stimulating mature, specialized cells to begin dividing again.