Figure 3. Cardiomyocyte turnover in adulthood.

(A) The ¹⁴C levels in cardiomyocyte DNA from individuals born before the time of the atmospheric radiocarbon increase correspond to time points after the birth of all individuals. The vertical bar indicates year of birth, with the correspondingly colored data point indicating the delta ¹⁴C value. (B) ¹⁴C levels in cardiomyocyte DNA from individuals born after the time of the nuclear bomb test. (C) Average DNA content (2n=100%) per cardiomyocyte nucleus from individuals (without severe heart enlargement, see figure S5) of different ages. Ploidy was measured by flow cytometry. Colored data points identify individuals analyzed for ¹⁴C (n=13). Black data points are from individuals only analyzed with regard to ploidy level (n=23) and white data points are taken from Adler et al. (n=26) (24, 26). The dashed lines indicate the 95% confidence interval for the regression curve. (D) ¹⁴C values corrected for the physiologically occurring polyploidization of cardiomyocytes during childhood for individuals born before and after the bomb spike, calculated based on the individual average DNA content per cardiomyocyte nucleus. The ¹⁴C content is not affected in individuals where the polyploidization occurred before the increase in atmospheric levels.