Posted by Madeline Ellis
Experts claim that once a heart is damaged, it is nearly impossible to fix. Surgical techniques can repair blood vessels and heart valves can be replaced, but once the heart muscle is damaged, there is no known way for it to heal on its own, in part because the cells called cardiomyocytes that are responsible for the development of heart muscle stop dividing and proliferating shortly after birth. However, researchers at Children’s Hospital in Boston say they have been able to restart that cell cycle and reverse heart damage in mice—without using stem cells.
What they used is known as neuregulin 1 (NRG1), a protein which is essential for the initial development of the nervous system and the heart. Beginning a week after experiencing laboratory-induced heart attacks, live mice were given daily injections of NRG1 for 12 weeks, after which they showed evidence of improved pumping function, reductions in heart muscle scar size, and an increase in heart muscle cells. They also showed no signs of heart failure, such as dilation of the heart chambers and thickening of the heart muscle. “Most of the (heart attack) related cell death had already occurred,” said lead researcher Dr. Bernhard Kuhn. “When we began the injections we saw replacement of a significant number of cardiomyocytes resulting in significant structural and functional improvements in the heart muscle.”
The ultimate goal will be to one day use NRG1 as a therapy for heart attack patients, those with heart failure or children with congenital heart defects. It may also be used in conjunction with another protein, periostin, which is found in the developing fetal heart and in injured skeletal muscle but scarce in adult hearts, identified by Dr. Kuhn and colleagues in 2007. Periostin also promoted heart muscle cell growth and improved heart function in rats, but it cannot be injected. So the researchers developed sponge-like patches that they soaked in the compound and then placed directly on the damaged area of the heart of rats. “During initial treatment, patients might receive neuregulin injections, and once they are stable and out of the ICU, they might be taken to the cath lab for the periostin patch,” Dr. Kuhn said.
But first, both treatments must be proven safe and effective in large animal and human studies. The researchers recently completed a study of periostin in pigs, which have more in common with humans than rodents do, and the protein is now in preclinical development at Children’s Hospital for future application in human patients with heart failure.
Many other researchers are also looking for ways to repair damaged heart muscle, but most of these efforts have focused on the use of stem cells. However, Dr. Kuhn says these proteins could provide another option. “Collectively, we have identified the major elements of a new approach to promote myocardial regeneration,” he said. “Many efforts and important advances have been made toward the goal of developing stem-cell based strategies to regenerate damaged tissues in the heart as well as in other organs. The work presented here suggests that stimulating differentiated cardiomyocytes to proliferate may be a viable alternative that could be developed into a simple strategy to promote myocardial regeneration in mammals.”
Professor Jeremy Pearson, British Heart Foundation (BHF) Associate Medical Director, called the new study “fascinating” and said “if the same mechanisms identified by the researchers can be shown to work in the human heart, it opens up real possibilities for new and more efficient ways to treat people with heart disease.” He added that “up until now, adult heart cells have been widely believed to be incapable of replication.”
Resources: http://www.healthnews.com/medical-updates/healing-a-damaged-heart-without-need-stem-cells-3493.html
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