Characterization of mononuclear cardiomyocytes in adult murine hearts
【Background and Objective】
Mammalian adult hearts have poor regenerative ability and the injured hearts scarcely recover. However, in adult mice, mononuclear cardiomyocytes (mnCMs), which account for about 10% of total cardiomyocytes, are relatively more proliferative than polynuclear cardiomyocytes (pnCMs). Therefore, we focused on mnCMs and examined their properties.
【Methods and Results】
We tried to analyze genes that are highly expressed in mnCM group. Cardiomyocytes from adult mice were separated into mnCM and pnCM groups by single cell handling device, followed by RNA-sequence analysis. As a result, about 480 genes, whose expression was markedly increased by more than 5 folds in the mnCM group as compared with the pnCM group, were extracted. These extracted genes included 4 marker genes characteristic of immature cardiomyocytes, such as Myl7 and Nppa. Next, focusing on Myl7, fluorescent immunostaining was performed, and the expression of Myl7 was observed in small myocyte population.
It could be concluded that mnCMs population includes subpopulation that expresses marker genes characteristic of immature cardiomyocytes, such as Myl7. Further studies would be required to elucidate the biological function of these immature cardiomyocytes.

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