The study investigates whether cardiomyocytes in humans are renewed throughout life, a question that has been difficult to answer due to the lack of suitable methods. The researchers used carbon-14 (14C) levels in genomic DNA to determine the age of cardiomyocytes, which were incorporated into the atmosphere during the Cold War through nuclear bomb tests. By analyzing 14C levels in DNA from human myocardial cells, they found that cardiomyocytes do renew, with an annual turnover rate of about 1% at age 20 and 0.3% at age 75. This suggests that less than 50% of cardiomyocytes are replaced during a normal lifespan. The findings indicate that the adult human heart has the capacity to generate new cardiomyocytes, which could be a rational target for therapeutic strategies aimed at treating cardiac pathologies. The study also highlights the potential for non-invasive and immunosuppression-free approaches to stimulate endogenous regenerative processes in the heart.The study investigates whether cardiomyocytes in humans are renewed throughout life, a question that has been difficult to answer due to the lack of suitable methods. The researchers used carbon-14 (14C) levels in genomic DNA to determine the age of cardiomyocytes, which were incorporated into the atmosphere during the Cold War through nuclear bomb tests. By analyzing 14C levels in DNA from human myocardial cells, they found that cardiomyocytes do renew, with an annual turnover rate of about 1% at age 20 and 0.3% at age 75. This suggests that less than 50% of cardiomyocytes are replaced during a normal lifespan. The findings indicate that the adult human heart has the capacity to generate new cardiomyocytes, which could be a rational target for therapeutic strategies aimed at treating cardiac pathologies. The study also highlights the potential for non-invasive and immunosuppression-free approaches to stimulate endogenous regenerative processes in the heart.