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In a medical first, scientists in Haifa, Israel, took skin cells from two heart failure patients and reprogrammed them into stem cells that generated healthy, beating heart muscle cells in the lab. Though human testing is likely a decade off, the hope is that such cells can be used to help people with heart failure repair their damaged hearts with their own skin cells.

In the current study, scientists first mixed the newly developed heart cells with pre-existing heart tissue — within days, the cells were beating together. The heart tissue was then transplanted into rats, where it integrated with the rats’ healthy heart cells.

“What is new and exciting about our research is that we have shown that it’s possible to take skin cells from an elderly patient with advanced heart failure and end up with his own beating cells in a laboratory dish that are healthy and young — the equivalent to the stage of his heart cells when he was just born,” says lead researcher Dr. Lior Gepstein, a senior clinical electrophysiologist at Rambam Medical Center in Israel, said in a statement.

The researchers were pleased to find that the cells made from the two heart failure patients, ages 51 and 61, generated heart muscle cells that were just as effective as those developed from healthy, young controls.

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If the technology works in human hearts, it could potentially prevent problems of immune rejection, since the cells would be the patient’s own. It would also avoid the moral issues surrounding the use of embryonic stem cells, since such reprogrammed stem cells — or human induced pluripotent stem (iPS) cells — do not use embryos.

But it’s still too early to predict whether the procedure could be successful humans. The new study involved cells from only two patients and were transplanted only into healthy animals. The authors note that human clinical trials are likely at least five or 10 years away. Further, creating iPS cells is not an easy or efficient process; it’s not clear whether enough cells could be made quickly enough to repair the broad-scale damage that occurs after a heart attack.

Reprogramming skin cells to become stem cells also introduces the potential for the cells to grow out of control and become cancerous. The Israeli researchers took additional steps — removing certain transcription factors and viral factors — to reduce the risk of cancer. But these hurdles would have to be revisited if the technique is tested in human patients.

“This is an interesting paper, but very early and it’s really important for patients that the promise of such a technique is not oversold,” John Martin, a professor of cardiovascular medicine at University College London, told Reuters. “The chances of translation are slim and if it does work it would take around 15 years to come to clinic.”

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Still, observers say the research brings scientists one step closer to a potential treatment for heart damage. The human heart has only a limited capacity to repair itself, so any treatment that can help regenerate heart tissue after a heart attack would be crucial. With more people surviving heart attacks these days, that means more patients are living with damaged heart tissue or developing heart failure, a debilitating condition that renders the heart unable to pump enough blood; many patients require either mechanical assistance or a transplant.

In February, in another medical first, researchers at Cedars Sinai Heart Institute used patients’ own heart stem cells to heal scarred heart tissue after a heart attack.

The current study is published in the European Heart Journal.