Can these specialized stem cells help aging hearts turn back the clock?

Heart disease is the leading cause of death in the United States, according to the Atlanta-based Centers for Disease Control and Prevention.

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And it disproportionately affects the elderly population. In fact, approximately 66 percent of cardiovascular disease deaths occur in people aged 75 and older.

But new research from scientists at the Cedars-Sinai Heart Institute in Los Angeles, California, suggests specialized stem cells could potentially reverse the aging process in the heart — and possibly reverse other signs of aging.

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The study, published Monday in the "European Heart Journal," involved injecting cardiosphere-derived cells from newborn rats bred in the lab into aging hearts of elderly rats approximately 22 months old.

According to Medical News Today, cardiosphere-derived cells are still immature, meaning they can mature into any of the three major types of heart cells: cardiomyocytes, endothelial cells and smooth muscle cells.

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By comparing the injected rats to a control group of rats injected with saline as well as before and after tests of both groups, the scientists found evidence of improvement in heart function.

Aging hearts tend to experience the shortening of telomeres, the end caps on our chromosomes, which is associated with heart dysfunction and hypertrophy among other impairments.

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But once injected, the heart cells in the older rats had longer telomeres and when compared to the control group, they not only improved their exercise capacity by 20 percent, but they could also regrow their hair more quickly.

While the team’s previous studies have shown promising evidence in using cardiac stem cells to treat heart failure, the findings from this research are especially groundbreaking, authors said.

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"It's extremely exciting," Eduardo Marbán, lead researcher and director of Cedars-Sinai, told CNN. Witnessing "the systemic rejuvenating effects," he said, is "kind of like an unexpected fountain of youth."

According to Marbán, the cardiosphere-derived cells likely secreted vesicles with signaling molecules (RNA and proteins, for example) that contained “all the needed instructions to turn back the clock.”

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Future researchers, Marbán suggested, should focus on more extensive studies to find out whether these cardiosphere-derived cells actually increase lifespan, whether donors have to be young and more.

The company that grows the cardiosphere-derived cells primarily focuses on treating heart failure and muscular dystrophy, CNN reported.

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But the cells have been proven “completely safe” in “over 100 human patients,” Marban said. “I can't tell you that there are any plans to do that, but it could easily be done from a safety viewpoint.”

Read the full study in the “European Heart Journal.”