A study led by researchers in Sweden discovered that our heart muscle cells are renewed over our lifetime and we are not limited to those we are born with. They believe the discovery opens a door to treatments that could replace damaged heart tissue with new cells.

The research was led by Professor Jonas Frisén of the Karolinska Institutet, in Stockholm, Sweden, and several of his colleagues worked with him. This study is published online in the 3 April issue of Science.
Carbon-14 which was generated by nuclear bomb tests during the Cold War enters into the DNA, as well as in heart muscle cells, called ‘Cardiomyocytes’. Scientists can then use this to date the age of the heart muscle cells in humans.
Using this approach, Frisén and colleagues found that heart muscle cells renew gradually over our lifetime. However, the rate at which they renew themselves declines as we get older. They estimate that 1 per cent of our heart cells are replaced per year at age 25 and this rate of renewal falls to 0.45 per cent at age 75.

They also found that fewer than 50 per cent of the heart’s muscle cells are replaced over a normal lifespan.
Frisén and colleagues suggested this could lead to research in new heart disease treatments that replace damaged tissue by stimulating the process of heart cell renewal.
Dr Charles Murry, a heart researcher at the University of Washington in Seattle, commented that this was one of the most important studies in cardiovascular medicine in years. Murry said he was especially impressed by the rigour of the study, as Frisén and colleagues had to deal with a number of technical problems. For example, heart muscle cells have two nuclei, which may mean that the DNA could be in there twice, so this could screw up the carbon 14 dating.
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