The conventional wisdom has been that cell division in heart muscle cells (cardiomyocytes) stops at or shortly after birth and that the cardiomyocytes of an 80 year-old are the same ones he started out with. The technology of radioactive carbon-dating has been recently applied to study this issue and shows that this conventional wisdom is wrong. Heart muscle cells are slowly but constantly renewing throughout life.
Radioactive carbon-dating has long been used as the primary technology for establishing the age of archeological artifacts. A recent study applied radioactive carbon-dating based on carbon-14, generated by nuclear bomb tests during the Cold War to analyzing the issue of heart muscle renewal. The study looked at the integration of carbon-14 into human cardiomyocyte DNA to establish the age of cardiomyocytes. Nuclear bombs were tested above-ground between 1955 and 1963. So, looking at the carbon-14 content in cardiomyocyte DNA from people born before 1955 it is possible to tell how many are original and the rate of cardiomycyte renewal.. “We report that cardiomyocytes renew, with a gradual decrease from 1% turning over annually at the age of 25 to 0.45% at the age of 75. Fewer than 50% of cardiomyocytes are exchanged during a normal life span.” So, when someone reaches the age of 50, about 55% of his or her heart muscle cells date back to birth and the rest are newer(ref).
The study is interested in that it opens the possibility for interventions that greatly accelerate the rate of renewal of heart muscle cells. Such could be useful for treating a number of cardiac pathologies and for helping extend the working lifetimes of hearts.