How an injured heart heals itself
It might seem like something from science fiction, but researchers at The University of Texas South-Western Medical Centre have discovered that if the heart of a newborn mammal gets damaged it can completely heal itself.
Previous research had shown that following injury, lower organisms like some fish and amphibians could regrow fins and tails as well as portions of their hearts, but this was new research with respect to mammals.
In a study funded jointly by the US National Health and Medical Research Council, the National Heart Foundation of Australia and the American Heart Association, researchers working with mice found that if a portion of the heart was removed during the first week after birth, within a matter of weeks it grew back wholly and correctly as if nothing had ever happened.
Since heart disease is the number one killer in the developed world, this is an important step in the search for a cure. Dr Hesham Sadek, assistant professor of internal medicine - cardiology and senior author of a study recently published in Science said that, ''…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.''
''The hearts of adult mammals lack the ability to regrow lost or damaged tissue,'' Dr Sadek continued, ''and as a result when the heart is injured, for example after a heart attack, it gets weaker and this eventually leads to heart failure.''The researchers discovered that if 15% of a newborn mouse heart was removed, after three weeks the heart had been able to completely regrow the lost tissue and as a result it looked and functioned exactly like a normal heart. The indication was that uninjured beating heart cells called cardiomyocytes are a major source of the new cells. They stop beating for just long enough to divide and provide the heart with fresh cardiomyocytes.
Professor Eric Olson, chairman of molecular biology in the Graduate School of Biomedical Sciences at South-Western Medical Centre and co-senior author of the study is fascinated by this work, since the heart’s inability to regenerate following an injury presents a major barrier in cardiovascular medicine.
''This work demonstrates that cardiac regeneration is possible in the mammalian heart during a window of time after birth,'' he said, ''although this regenerative ability is then lost. Armed with is knowledge we can next work to discover methods to reawaken cardiac regeneration in adulthood.''
The researchers are now turning their attention to studying this brief window when the heart is still capable of regeneration, hoping to solve the problem of how and why the heart ''turns off'' this remarkable ability to regenerate itself as it grows older.
If they are successful this would be an amazing breakthrough in reducing the numbers of premature deaths as a result of heart disease, which currently accounts for one in every eight deaths worldwide.
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