The age related changes in cell cycle of mice cardiomyocytes

Although rapid progress is being made in many areas of molecular cardiology, issues pertaining to the origins of heart-forming cells, the mechanisms responsible for cardiogenic induction, and the pathways that regulate cardiomyocyte proliferation during embryonic and adult life remain unanswered. The present study was performed to investigate the age related changes in cardiomyocytes' cell cycle in white mice. 18 white mice were used. The animals were distributed in three age groups: juveniles (2 months old), adults (10 months old) and senescents (18 months old). The animals were killed under ether narcosis. The heart was removed. Number of diploid, tetraploid, polyploid (octaploid, 16 n and 32 n), apoptotic nuclei and nuclei in S phase were counted by a Becton Dickinson (Mountain View, CA) FACScan flow cytometer. Statistical analyses were performed using Student t test. The heart of white mice contain diploid, tetraploid, octaploid, hexadecaploid (16 n) and 32 n cells. The amount of cardiomyocytes of different ploidy classes varies from one age group to another. The intensity of apoptosis increases with age. In all age groups the cardiomyocytes retain some capacity to synthesize DNA, which is not influenced by aging. However, the fact of DNA synthesis per se seems to be insufficient to drive adult cardiomyocytes through cell division.