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Variability of the cardiomyocyte ploidy in normal human hearts
Brodsky VYa1, A L Chernyaev, I A Vasilyeva
1Institute of Developmental Biology, USSR Academy of Sciences, Moscow.
Insights
Myocyte ploidy, a measure of DNA content in heart cells, varies significantly between individuals and even within different heart regions. This variation in DNA content and the proportion of binuclear cells may influence cardiac disease outcomes.
Area of Science:
- Cardiovascular Biology
- Cell Biology
- Genetics
Background:
- Myocyte ploidy, representing the DNA content within heart muscle cells, is a critical factor in cardiac function.
- Understanding variations in myocyte ploidy is essential for interpreting cardiac health and disease.
- Previous studies have not fully elucidated the extent of ploidy variation within the human ventricle.
Purpose of the Study:
- To investigate the variability of DNA content (ploidy) in isolated human left ventricular myocytes.
- To examine the relationship between myocyte ploidy and the percentage of binuclear cells.
- To explore potential implications of myocyte ploidy variation on cardiac pathology.
Main Methods:
- Cytophotometry was used to measure DNA content in isolated left ventricular myocytes from 16 adult males.
- Feulgen staining was employed to quantify DNA in myocyte preparations.
- Analysis included different layers of the anterior and posterior ventricular walls.
Main Results:
- Significant variation in mean myocyte ploidy (ranging from 3.2-3.9 c to 6.6-7.3 c) was observed within the left ventricle.
- The percentage of binuclear cells (25-86%) strongly correlated with mean ploidy values in each layer.
- Myocyte ploidy in the posterior wall was consistently higher than in corresponding layers of the anterior wall.
Conclusions:
- Individual differences in myocyte ploidy and the proportion of mono- and binucleate cells are significant.
- These variations, stable characteristics of an individual, may represent a factor influencing the course and outcome of cardiac pathology.
- Myocyte ploidy variation is independent of early developmental genomic changes.
Abstract:
We have performed cytophotometry for DNA in isolated myocytes of the left ventricle from 16 men, aged 19-39 years, who died from various non-cardiac or pulmonary causes. The mean ploidy of myocytes varied from 3.2-3.9 c to 6.6-7.3 c in different layers of the anterior wall of the left ventricle (where c is the haploid DNA content measured by cytophotometry in Feulgen-stained preparations). There was no correlation between the layers. The percentage of binuclear cells varied from 25 to 86% and correlated in every layer with the mean ploidy value of the whole myocyte population. Approximate calculation of total ploidy revealed low values in the ventricles of some individuals, and high values in others. Averaging the values for all the hearts studied obscures this variation. Mean myocyte ploidy in different layers of the anterior wall was similar: in the external layer it was 5.1 +/- 0.3 c, in the middle layer 5.5 +/- 0.3 c and in the inner layer 4.8 +/- 0.4 c. The mean percentage of binuclear myocytes in these three layers was also similar, being 61 +/- 3%, 63 +/- 4% and 54 +/- 5%, respectively. Myocyte ploidy in tissue from the posterior wall of the left ventricle also varied, but was always higher than for the same layer of the anterior wall in the same ventricle. We propose that high or low myocyte ploidy, as well as different proportions of mono- and binucleate cells, can be a factor affecting the course and result of cardiac pathology in the absence of any changes of myocyte genome determined during early ontogenesis and representing a stable characteristic of the individual.