A promising stem cell therapy approach could soon provide a way to regenerate heart muscle damaged by heart attacks.

Researchers at Cedars-Sinai Heart Institute and The Johns Hopkins University harvested stem cells from the hearts of 17 heart attack patients and after prepping the cells, infused them back into the patients' hearts. Their study is published in the current issue of The Lancet.

The patients received the stem cell infusions about three months after their heart attacks.

Researchers found that six months after treatment, patients had significantly less scarring of the heart muscle and also showed a considerable increase the amount of healthy heart muscle, compared to eight post-heart attack patients studied who did not receive the stem cell infusions. One year after, scar size was reduced by about 50 percent.

"The damaged tissue of the heart was replaced by what looks like healthy myocardium," said Dr. Peter Johnston, a study co-author and an assistant professor of medicine at The Johns Hopkins University School of Medicine. "It's functioning better than the damaged myocardium in the control subjects, and there's evidence it's starting to contract and generate electrical signals the way healthy heart tissue does."

While this research is an early study designed to demonstrate that this stem cell therapy is safe, cardiologists say it's an approach that could potentially benefit millions of people who have suffered heart attacks. Damage to the heart muscle is permanent and irreparable, and little can be done to compensate for loss of heart function.

"In the U.S., six million patients have heart failure, and the vast majority have it because of a prior heart attack," said Johnston.

The damaged scar tissue that results from a heart attack diminishes heart function, which can ultimately lead to enlargement of the heart.

At best, Johnston said, there are measures doctors can try to reduce or compensate for the damage, but in many cases, heart failure ultimately sets in, often requiring mechanical support or a transplant.

"This type of therapy can save people's lives and reduce the chances of developing heart failure," he said.

Cardiac Regeneration A Promising Field

Other researchers have also had positive early results in experiments with stem cell therapy using different types of cells, including bone marrow cells and a combination of bone marrow and heart cells.

"It's exciting that studies using a number of different cell types are yielding similar results," said Dr. Joshua Hare, professor of cardiology and director of the University of Miami Interdisciplinary Stem Cell Institute.

The next steps, he said, include determining what the optimal cell types are and how much of the cells are needed to regenerate damaged tissue.

"We also need to move to larger clinical trials and measure whether patients are improving clinically and exhibiting a better quality of life after the therapy."

In an accompanying comment, Drs. Chung-Wah Siu amd Hung-Fat Tse of the University of Hong Kong wrote that given the promising results of these studies, health care providers will hopefully recognize the benefits that cardiac regeneration can offer.

And Hare added that someday, this type of regeneration can possibly offer hope to others who suffered other types of organ damage.

"This stategy might work in other organs," he said. "Maybe this can work in the brain, perhaps for people who had strokes."

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Stem Cells May Help Regenerate Heart Muscle