LOS ANGELES -- Researchers at the University of Texas Southwestern Medical Center have discovered that 1-day-old mice can regenerate working heart tissue, according to a study published online Thursday by the journal Science.
Enzo R. Porello and colleagues surgically removed 15 percent of the newborn mice's hearts and found that the hearts regrew completely within three weeks.
The regrown hearts looked and functioned normally, the team reported. By 7 days of age, however, the regenerative ability was gone.
Some fish and amphibians can regrow damaged heart tissue. Adult mammals can't. That's the reason heart disease is so deadly in people: Once your ticker is damaged in a heart attack, it can't rebuild the cardiac muscle and heal.
Scientists hope to someday change this -- to figure out ways to help the human heart regenerate. Understanding how newborn mice regrow their hearts could lead to therapies to make that happen.
"If we can understand the mechanisms whereby cardiomyocytes (heart muscle cells) retain or regain the ability to proliferate, we may be able to harness that potential to regrow healthy heart muscle," said Dr. Eduardo Marban, director of the Cedars-Sinai Heart Institute.
For now, those mechanisms remain mysterious. The authors of the Science paper determined that the new heart tissue in newborn mice appeared to have developed directly from cardiomyocytes, but they wrote that they could not "exclude the possibility that stem or progenitor cells also contribute to this process."
Marban, who is leading a clinical trial studying the use of cardiac stem cells to regenerate heart tissue in heart attack patients, thinks that both stem cells and cardiomyocytes might be involved. Some of his earlier work showed that mammalian heart cells can regain stem cell properties, he said.
Marban added that he "would not be surprised" if a similar type of heart regeneration were to occur in newborn humans.
"Intriguingly, there have been case reports of babies with large heart attacks who go on to recover completely," he said. "Perhaps the ability of the newborn heart to regrow is indeed enhanced."
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