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Molecule Promotes Growth of Heart Muscle

Helps repair heart attack damage in mice

TUESDAY, Nov. 23, 2004 (HealthDayNews) -- A molecule that promotes the growth of the young heart shows promise as a treatment for heart attack in animal studies and is being readied for human trials, researchers report.

Studies to see whether the molecule, thymosin beta-4, can help people recover from a heart attack could begin "by middle to late next year," said study lead researcher Dr. Deepak Srivastava, a professor of pediatrics and molecular biology at the University of Texas Southwestern Medical, in Dallas. His group describe their results in the Nov. 25 issue of Nature.

"Our original interest was in trying to understand how the heart forms," Srivastava said. "We found that thymosin beta-4 induced cells to migrate and also made them survive longer."

He and his colleagues began a series of studies in mice induced to have heart attacks. In mice treated with thymosin beta-4, more heart muscle survived and that muscle was better able to pump blood, compared with mice given a placebo.

Srivastava's group is continuing studies in larger animals and is working "to try to understand what are the exact mechanisms by which the heart is protected," he said. "But we are at the point where we are designing the first human trials."

Approval by the U.S. Food and Drug Administration is needed to conduct those trials, in which thymosin beta-4 will be infused into people in the early hours of a heart attack. Srivastava anticipates getting that approval within a matter of months.

If thymosin beta-4 works as hoped, it could resolve ongoing controversies surrounding the use of stem cells to repair the damage of a heart attack, added Dr. Michael D. Schneider, M.D. co-director of the Center for Cardiovascular Development at Baylor College of Medicine, Houston, and the author of an accompanying editorial.

Some critics have objected to the use of stem cells from embryos, citing ethical concerns. Use of adult cells has started a totally different controversy within the scientific community, where there are doubts about their effectiveness.

"There are roughly half a dozen trials, mostly in Europe," of human stem cell treatment for heart attacks, Schneider said. Several use bone marrow stem cells delivered to the heart in hopes that they will help form new heart muscle or new blood vessels.

The newly reported trial "makes a wonderful leap of imagination from the fact that this protein is highly expressed in the early heart," Schneider said.

Srivastava's group is using a laboratory-made protein produced by recombinant technology, Schneider noted. The group is working with Regenerx, a biotechnology company based in Washington, D.C., that has had experience with thymosin beta-4, Srivastava said.

"If it works, it will be phenomenal," he said.

More information

The warning signs and treatment of heart attack can be found at the National Heart, Lung and Blood Institute.

SOURCES: Deepak Srivastava, M.D., professor of pediatrics and molecular biology, University of Texas Southwestern Medical Center, Dallas; Michael D. Schneider, M.D., co-director, Center for Cardiovascular Development, Baylor College of Medicine, Houston; Nov. 25, 2004 Nature
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