Newborn mouse’s heart can heal itself

WASHINGTON - A mammalian newborn’s heart can heal itself completely — a discovery that looks more like science fiction than a reality.

Researchers working with mice found that a portion of the heart removed during the first week after birth grew back wholly and correctly, as if nothing had happened.

“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,” said Hesham Sadek, assistant professor of internal medicine at the University of Texas Southwestern (UTS).

Previous research has demonstrated that the lower organisms, like some fish and amphibians, that can regrow fins and tails, can also regrow portions of their hearts after injury, the journal Science reports.

“In contrast, the hearts of adult mammals lack the ability to regrow lost or damaged tissue, and as a result, when the heart is injured, for example, after a heart attack, it gets weaker, which eventually leads to heart failure,” said Sadek, who led the study.

Researchers found that within three weeks of removing 15 percent of the newborn mouse heart, it was able to completely grow back the lost tissue, and as a result looked and functioned just like a normal heart, according to an UTS statement.

They 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.

Eric Olson, UTS chairman of molecular biology and senior study co-author, said: “The inability of the adult heart to regenerate following injury represents a major barrier in cardiovascular medicine.”

The next step, the researchers said, is to study this brief window when the heart is still capable of regeneration, and to find out how, and why, the heart “turns off” this remarkable ability to regenerate as it grows older.