Features of Cardiomyocyte Division During Rat Heart Development

In the present study, the division modalities and regularity of rat cardiomyocytes from different developing stages were investigated with immunohistochemistry, transmission electron microscopy and cell culture in vitro. The results showed that the cells with mitotic figure and binuclear cells exist in the normal cardiomyocytes in prenatal and postnatal life. There are two types of binuclear cardiomyocytes with juxtaposed binuclear cells and separated binuclear cells, and both types of cells gradually increase along with developing time. For example, the division index of separated binuclear cells in the cardiomyocytes is 2.54±0.01% in the 20-day rat fetus, 3.86±0.01% in the 6-day postnatal rat, and 6.78±0.03% in the 12-day postnatal, respectively. However, the division index of mitotic cells in the cardiomyocytes is gradually decreased along the developing stages, for example, 1.44±0.02% in the 20-day rat fetus, 1.15±0.04% in 6-day postnatal rat, and 1.00±0.02% in the 12-day rat after birth. These results suggest that both binuclear cells and mitotic cells in rat cardiomyocytes exist and are temporally regulated during prenatal and postnatal life, for instance, mitotic cells are decreased, while binuclear cells are gradually increased during developmental stages. Binuclear cells may come from amitosis which may be a main division pattern during adult stage.