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Hope for infants with damaged hearts

Therapy could help babies regrow defective tissue

Amy Mcconnell Schaarsmith Tribune News Service

PITTSBURGH – A substance naturally produced by the human body has the potential to regrow tissue in the hearts of infants with congenital defects, possibly improving how well their hearts work, according to a study published Wednesday by researchers at Children’s Hospital of Pittsburgh of UPMC and other medical institutions.

The research, which was performed on mice and on pediatric heart tissue samples, showed that treatment with the substance neuregulin – a growth-inducing material also known as rNRG1 that is produced by cells in the lining of small arteries and in the nervous system – stimulated the growth of normal tissue in damaged hearts.

While scarring was somewhat reduced in the neuregulin-treated hearts, the primary benefit to the therapy seemed to be the growth of normal tissue around scarred areas, in many cases effectively enveloping scarred tissue and compensating for its lack of pumping power, said lead author Dr. Bernard Kuhn.

“Instead of a solid scar in the heart wall, now that scar has heart muscle behind it, so now it doesn’t flip-flop in the breeze anymore,” said Kuhn, research director of the cardiology division of Children’s and a scholar at the Richard King Mellon Foundation. “It has heart tissue that can contract and beat in synchronicity with the remainder of the heart.”

The study, published in the scientific journal Science Translational Medicine, also was conducted with researchers from Boston Children’s Hospital, Harvard Medical School, Beth Israel Deaconess Medical Center in Boston, The University of Sydney in Australia and the Austrian Academy of Sciences. The research was funded by Boston Children’s Hospital and a grant from the National Institutes of Health.

Congenital heart defects, which are found in slightly less than 1 percent of all live births and usually are first detected during prenatal ultrasounds by obstetricians, are relatively rare but nevertheless remain the most common birth defect in the country, according to the Children’s Heart Foundation. Such defects affect approximately 40,000 babies each year in the United States, with another 1 million affected children born worldwide, according to the foundation.

Congenital heart defects also are the leading cause of all infant deaths in the United States, with thousands of children dying before their first birthday and survivors facing a higher risk of chronic heart failure later in life, according to the foundation and researchers. More than half of all children born with a heart defect will require surgery in their lifetimes.

Undiagnosed children with a severe defect typically would display blue coloring and symptoms of shock and would need emergency care, Kuhn said.

Surgeries, however, have “really turned the tide” for infants with defective hearts, saving many children who otherwise would have died 50 or 60 years ago, Kuhn said.

In the process of repairing children’s hearts surgically, however, scar tissue made of collagen unavoidably forms as the heart heals. That tissue, which is more rigid and lacks the squeezing ability of normal tissue, often works against the other parts of the heart – the scarred tissue, in an extreme case, might balloon out as the rest of the heart squeezes in, Kuhn said.

“It steals away energy, steals away work from the heart, instead of that energy pushing blood through the heart and circulating blood through the body,” in such cases, he said.

Treatment with drugs such as diuretics and beta blockers that help treat chronic heart disease in adults do not seem to help children, researchers said.

When treated with neuregulin, however, damaged heart tissue in mice younger than 4 days was stimulated into growing fresh, undamaged heart tissue that compensated for tissue that was not functioning properly, the study found. Corresponding experiments on heart tissue obtained from pediatric patients younger than 6 months old who had undergone heart surgery found a similar response, according to the study.

Neuregulin does not seem to help rebuild tissue in children older than 6 months, or in adults, researchers found. Neuregulin is being used as an experimental treatment in adults, but clinical trials in children are years away, Kuhn said.

And while its use as a therapy is still being investigated and won’t be available for years, if ever, neuregulin someday could be a boon for the youngest heart patients, according to Dr. Brian Feingold, medical director for heart failure and transplantation programs at Children’s.

“It may open the door to some therapies to recover a heart that’s sick, where right now the patient would need a transplant but this would allow the patient’s own heart to recover,” Feingold said. “That would be the dream.”

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