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Researchers repair injured heart muscle with novel stem cells

November 15, 2017

The research team - led by Johnny Huard, PhD - transplanted stem cells purified from human muscle-derived blood vessels into the hearts of mice that had heart damage similar to that which would occur in people who had suffered a heart attack.

These transplanted myoendothelial cells repaired the injured muscle, stimulated the growth of new blood vessels in the heart and reduced scar tissue from the injury, thereby dramatically improving the function of the injured left ventricle, said Dr. Huard, director of the Stem Cell Research Center at Children's Hospital's John G. Rangos Sr. Research Center.

"This study confirms our belief that this novel population of stem cells discovered in our laboratory holds tremendous promise for the future of regenerative medicine. Specifically, myoendothelial cells show potential as a therapy for people who have suffered a myocardial infarction," said Dr. Huard, also the Henry J. Mankin Professor and vice chair for research in the Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine. "The important benefit of our approach is that as a therapy, it would be an autologous transplant. This means that for a patient who suffers a heart attack, we would take a muscle biopsy from his or her muscle, isolate and purify the myoendothelial cells, and re-inject them into the injured heart muscle, thereby avoiding any risk of rejection by introducing foreign cells."

Results of this study are published in the Dec. 2 issue of the Journal of the American College of Cardiology .

The myoendothelial cells used in this study were more effective at repairing the injured cardiac muscle and reducing scar tissue than previous approaches that have used muscle cells known as myoblasts, according to Dr. Huard. At six weeks after injection, the myoendothelial cell-injected hearts functioned at 40 to 50 percent more effectively compared with hearts that had been injected with myogenic cells (myoblasts).

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"CT technology has come a long way in the last decade," says Miller, the leader of angiographic research and an assistant professor at Hopkins. She cites improvements that cut the average amount of radiation exposure and time required for a CT scan to less than 20 millisieverts with 16-CT scanners (which took about 12 seconds to perform), on average, to less than 15 millisieverts with 64-CT devices (at close to 6 seconds), and less than 6 millisieverts with the 320-CT (at less than a second.)

She says the cost of the newer CT scans ?? approximately $700 ?? compares favorably with that of current nuclear stress testing for reduced blood flow, in which radioactive dyes are used to detect arterial clogs, at nearly $1,000.

In cardiac catheterization, a thin tube is threaded into a blood vessel in the groin area to the heart's arteries, where a dye is released to produce a clear X-ray image of the beating heart and its arterial blood supply. The procedure usually costs in excess of $1,500.

In CT imaging, computer-driven machinery passes X-rays through the body, producing digitized signals from multiple angles that are detected and reconstructed for a precise picture.

Miller points out that early detection of blockages is critical to preempting a heart attack, allowing time for drug therapy, angioplasty or heart bypass surgery to be used to keep arteries open. In coronary artery disease, hardened bits of fat and dead tissue, called plaque, build up along the inside wall of the blood vessels, impeding the body's natural blood flow and leaving the narrowed opening more vulnerable to formation of blood clots.

Lima says the team's next steps are head-to-head comparison studies using either CT or nuclear stress testing, which gauges reduced blood flow in parts of the heart to reveal clogging arteries. Included in the next analysis will be scans performed using an even more advanced scanner, the 320-CT. The latest imaging device was also tested at Johns Hopkins in 2006, and it can obtain images in less than a second, with significant reductions in radiation exposure.

According to researchers, nearly 5,000 64-CT scanners are installed worldwide, but not all of the centers are equipped to perform and read cardiac CTs. Miller notes that special training and certification are required by technicians and physicians to accurately perform, read and interpret the scanned images. The American Heart Association and the American College of Cardiology Foundation in 2005 jointly established training guidelines.

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