Team shows newborn heart muscle can grow back by itself

Researchers at UT Southwestern Medical Center have discovered that the mammalian newborn heart can grow back when damaged, just as a lizard can grow a new tail.

Working with mice, they found that a portion of the heart removed during the first week after birth grew back as if nothing had happened. Within three weeks of removing 15 percent of the newborn mouse heart, it once again looked and functioned just like a normal heart.

“This is an important step in our search for a cure for heart disease, the number one killer in the developed world,” says Dr Hesham Sadek, assistant professor of internal medicine.

“We found that the heart of newborn mammals can fix itself; it just forgets how as it gets older. The challenge now is to find a way to remind the adult heart how to fix itself again.”

Lower organisms, such as some fish and amphibians, have been shown to be capable of regrowing heart tissue as well as fins and tails. Adult humans, however, can’t.

The researchers believe that uninjured beating heart cells, called cardiomyocytes, are a major source of the new cells. They stop beating long enough to divide and provide the heart with fresh cardiomyocytes.

The work could have major implications for the treatment of heart disease.

“The inability of the adult heart to regenerate following injury represents a major barrier in cardiovascular medicine,” says Dr Eric Olson, chairman of molecular biology.

“This work demonstrates that cardiac regeneration is possible in the mammalian heart during a window of time after birth, but this regenerative ability is then lost. Armed with this knowledge, we can next work to discover methods to reawaken cardiac regeneration in adulthood.”

The next step is to try and understand why the heart ‘turns off’ this ability to regenerate as it grows older.