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Heart helper. The hearts of mice treated with protein thymosin b4 (right panels) before a simulated heart attack have less scar tissue (blue) and more healthy muscle (red) than the hearts of untreated mice (left panels).

Protein Mends Broken Hearts

Beer and whiskey might help country singers get over their broken hearts, but new research may point to a more effective medicine. A protein that normally plays a role in heart development shows early promise in mice for helping the heart heal after a heart attack.

About a million people have heart attacks in the United States every year. Trouble begins when chunks of plaques that accumulate in the arteries break off and block the flow of blood to the heart muscle. This starves the muscle for oxygen and kills cells. Physicians minimize the damage to the muscle cells with clot-busting drugs and stents, but 5 million people are living with partially dead hearts. Experimental therapies that treat heart attacks have so far improved blood pumping by less than 10%.

Pediatric cardiologist Deepak Srivastava of the University of Texas Southwestern Medical Center in Dallas found the new protein, called thymosin b4, while searching for proteins that could help children with malformed hearts. Biochemical tests revealed that thymosin b4 causes cells to turn on genes that help them survive adverse conditions, such as lack of oxygen. To determine whether thymosin b4 has broader talents, the team simulated heart attacks by tying off an artery that feeds part of the heart muscle in 58 mice. Then they injected either saline or thymosin b4 into the bloodstream or directly into the heart.

Four weeks later, the hearts of mice treated with thymosin b4--with either method--pumped nearly twice as much blood as the hearts of untreated mice. Heart cross-sections showed that treated mice also had only half as much scar tissue as untreated mice, indicating that fewer cells had died in the treated mice, the researchers report in the 25 November issue of Nature. Srivastava says they are already gearing up to test thymosin b4 in humans.

"This compound is one of the best leads for how one might reduce the size of heart attacks," says molecular cardiologist Michael Schneider of Baylor College of Medicine in Houston, Texas. He adds that thymosin b4 works five times better than stem cells--the next best experimental option--at keeping heart cells alive. If the compound works as well in humans as in mice, Schneider says, eventually emergency personnel might give it to people who have just had a heart attack.

Related sites
Deepak Srivastava's site
More about heart attacks from the American Heart Association