Scientists at the Victor Chang Cardiac Research Institute, in collaboration with colleagues at Emory University in the United States, have discovered for the first time that heart muscle cells retain the ability to replicate long after birth.
In a study published in Cell, the scientists have overturned more than a century of scientific theory, which proposed that heart muscle cells in mammals stopped replicating just after birth, limiting the organ’s ability to repair itself after injury. The study, carried out on mice, also showed that in response to a surge in thyroid hormone, heart muscle cells undergo an intense 24 hour ‘burst’ of division in preadolescence. During this burst, the number of heart muscle cells increase by more than 40 per cent, or half a million cells, and compared with later in development, the ability of the heart to recover after injury was enhanced. This response is essential for the heart to meet the increased circulatory needs of the body during a period of rapid growth in preadolescence, in which the heart increases almost four-fold in size.
Professor Bob Graham, Executive Director, Victor Chang Cardiac Research Institute and Des Renford Professor of Medicine, University of NSW, with colleague Professor Ahsan Husain at Emory University, led the study.
“For over one hundred years it has been thought that the heart, much like the brain, stops being able to make new muscle cells soon after birth. In this study, we have overturned the dogma and shown this is not the case.The implications of our findings could be huge, as it may give us a significant window of opportunity in which to repair the hearts of babies born with heart defects, or even to reactivate heart muscle cells damaged after a heart attack in adults,” Professor Graham said.
“I think this research has given us some really important and significant insights, including that the heart is not as static as we previously thought. It is actually a very dynamic organ, which is something we may be able to use to our advantage as we continue the fight against heart disease,” Professor Graham concluded.
Commenting on the significance of this work, Stem Cells Australia’s Professor Martin Pera said, “This stunning finding from Bob Graham and his colleagues completely changes our thinking about how the adult heart might undergo repair and remodelling in disease. The study shows that in striking contrast to scientific dogma, cardiac muscle cells undergo proliferation long after birth. Heart cells in mice multiply rapidly in a narrow time window around puberty in response to thyroid hormone. These findings open up new approaches to the management of congenital heart disorders in children, and provide hope that appropriate stimuli might enable the heart to repair damage caused by disease or myocardial infarction in adults. Moreover the new results offer insight into how cardiac stem cell therapy might be enhanced.
“Another Australian scientist, Dr James Chong, recently showed that grafts of cardiac muscle made from stem cells in the laboratory can help repair damage from a heart attack, but the experimental therapy had complications. Studies of how newly formed cardiac cells integrate into the mouse heart in puberty might help us to use stem cell derived grafts more effectively."
Professor Bob Graham is a Chief Investigator in the Stem Cells Australia initiative.
Publication: Naqui et al (2014) A Proliferative Burst during Preadolescence Establishes the Final Cardiomyocyte Number. Cell 157(4):795-807. Click here for more information.
Heart cells have 'preteen' growth spurt [ABC Science] 9 May 2014
Sydney scientists show young hearts can mend [SHM] 10 May 2014