heart attacks kill because they are strangling the heart muscle cell destruction and preventing the body to pump properly. Now, researchers reveal they have nudged cells in mouse hearts to repair some of the damage, a finding that could lead to new treatments for heart attacks in humans.
The researchers are probing several ways to encourage the heart to settle. Last year, for example, cardiac stem cell biologist Deepak Srivastava of the Gladstone Institute of Cardiovascular Disease in San Francisco, California, and colleagues inserted extra copies of the three genes in the cells of scar tissue, trigger to turn into cardiomyocytes, or heart muscle cells. Another approach is to use so-called progenitor cells, non-resident cells in the heart that are similar to stem cells can mature into cardiomyocytes. The challenge was to identify progenitor cells in adults and to determine whether they could provide enough fresh muscle.
Paul Riley stem cell biologist at University College London and his colleagues measured the capacity of progenitor cells in the epicardium, outer layer of the heart. During embryonic development, progenitor cells there is an important source of cardiomyocytes. In adults, however, the cells seem to relax. To regain youthful vigor of cells, the researchers injected mice with thymosin β4, a compound already undergoing clinical trials as a treatment for heart attack because it helps cardiomyocytes survive and stimulates the growth of new blood vessels. The researchers then mimicked a heart attack in animals by ligating one of the arteries that supply blood to the heart, wounding some of the muscle.
Unlike control mice that do not seem to fashion new cardiomyocytes, animals given thymosin β4 is part of the cells, reports the online team today Nature . The cells infiltrated the area left damaged by simulated heart attack and engaged with other cardiomyocytes physically and electrically, allowing them to beat. They also appeared to prevent some of the damage that can result from a heart attack. Magnetic resonance imaging scans showed that the hearts of mice that had received thymosin β4 had smaller scars and were able to pump more blood with each contraction than were the hearts of untreated rodents. "Having a source of cells that could repair the muscles and blood vessels is important resident," said Riley.
Because thymosin β4 was not very effective, less than 1% of progenitor cells transformed into cardiomyocytes-researchers are trying to identify other more potent molecules. Drugs that prod progenitor cells to create new muscle could benefit patients who have suffered heart attacks. But they might work better if patients took the medication preventively to initiate action progenitor cells, said Riley. It provides that persons who are susceptible to heart attacks, perhaps because they have high cholesterol and other risk factors, take regular doses, keeping their progenitor cells in a state of readiness.
The study "provides strong evidence that there is a population of cells in the epicardium that can turn into new muscles," Srivastava said. "The real question is how robust is the process [of cell transformation] and how can it be improved. "he recommends that researchers are also investigating whether the cells can rebuild the heart muscle during heart failure, a condition that affects about 5 million US and causes the body weaken gradually.
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