Though sufferers of heart attacks may survive the initial event, they cause permanent damage to the organ in the form of scar tissue, which affects its ability to pump blood. Scientists around the world are working on this problem, with hydrogels, human stem cells and even bioengineered tissue that sticks together like Velcro all offering possible solutions. But the latest promising advance comes from a team of researchers that has developed a simple protein patch that restores animal hearts almost to normal function.

The team's work was guided by earlier research indicating that the outside layer of the heart, called the epicardium, may be responsible for producing the compounds that regenerate heart muscle in fish. The effort was led by Professor Pilar Ruiz-Lozano at Stanford University and involved scientists from the University of California, San Diego.

In studying the epicardial cells themselves, the team was able to demonstrate that they did indeed cause existing heart muscle cells, called cardiomyocytes, to multiply. But the team then sought to narrow things down even further and determine whether a single compound might be driving the process. Using mass spectrometry, the team uncovered more than 300 proteins as possible candidates, and eventually whittled this down to one using high-throughput assays.

Once the researchers identified Follistatin-like 1 (FSTL1) as the protein they had been searching for, they then went on to develop a therapeutic patch made from collagen that incorporated this compound. The patch was designed to have the same elasticity as fetal heart tissue and gradually release the protein over time. It was applied to the surface of mouse and pig hearts that had suffered from attacks and was found to drive tissue regeneration.

In pigs that had suffered from a heart attack, blood pumped out of the left ventricle was reduced from the normal 50 percent to 30 percent. But surgically applying the patch on the surface of the heart a week after the event saw this restored to 40 percent, where it remained stable. The patch was also found to considerably reduce scarring of the pig's heart tissue.

The team hopes to move to human clinical trials as soon as 2017.

The research was published in the journal Nature.

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