When he was only 43, Peter Harrison had a severe heart attack that left him suffering from the symptoms of a damaged heart: shortness of breath, chest pain and increased risk of another heart attack. An otherwise healthy commercial real estate agent from Key Biscayne, Harrison was in and out of the hospital for 20 years treating his heart condition until last year when doctors at the University of Miami Miller School of Medicine injected his heart with stem cells as part of a study.

Three weeks later, he was hiking the steep hills of the U.S. Virgin Islands, keeping up with his wife.

There was no chest pain and I was not out of breath it was quite a revelation, he said. I was hoping that the damaged part of my heart would come back to life, and the indication is that it has.

The study, which was funded by the National Institutes of Health and published in the Journal of the American Medical Association this week, found that stem cell injections into the heart muscle reduced scar tissue by one third, built up healthy heart tissue and remodeled the spherical shape of the damaged heart to look more like a football-shaped healthy heart.

Dr. Joshua Hare, the director of the UM Interdisciplinary Stem Cell Institute and the lead author of the study, said the stem cells cells that are not fully formed and have the potential to become different kinds of cells internalize information from their milieu to know what to become.

We think the cells respond to environmental cues to determine how they divide and differentiate, he said. The stem cells used in this study were taken from bone marrow and have a limited repertoire of possibility, meaning they are more easily transformed into bone or muscle than blood or brain.

Half of the 30 men enrolled in this small pilot study at UM and Johns Hopkins University received injections of their own stem cells, while the other half got stem cells from a third party donor. Harrison was in the group that got donated stem cells. There are no compatibility requirements for stem cell donors as there is with blood and bone marrow, and one donor can provide enough stem cells for many, many people, Hare said.

This is an elegant treatment in that it doesnt transgress any ethical boundaries, Hare said, alluding to the controversy surrounding the use of stem cells from human embryos. You dont need to create a donor bank, its easy to implement and relatively inexpensive.

Stem cell therapy, a growing area of research, drew attention earlier this year when the Nobel Prize in Medicine went to John B. Gurdon of the University of Cambridge in England and Shinya Yamanaka of Kyoto University in Japan for their work in turning mature cells back into pluripotent stem cells that have the potential to become other types of cells. Hare said the UM study was essentially the opposite rather than reduce mature cells to stem cells, these injections of stem cells differentiated into healthy heart tissue.

Participants were injected with 10 doses of stem cells delivered by a catheter with a cork-screw tip that bored into the heart muscle between damaged and healthy tissue. The randomized trial found best results with the patients who received the smallest dosage 20 million total stem cells compared to other doses of 100 million or 200 million. Further studies are required to determine the ideal dosage for heart patients, and also to explore other applications for this kind of treatment.

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In University of Miami study, stem cell injections repair damaged heart