GDF10 promotes rodent cardiomyocyte maturation during the postnatal period.

Cardiomyocytes and cardiac fibroblasts undergo coordinated maturation after birth, and cardiac fibroblasts are required for postnatal cardiomyocyte maturation in mice. Here, we investigate the role of cardiac fibroblast-expressed Growth Differentiation Factor 10 (GDF10) in postnatal heart development. In neonatal mice, Gdf10 is expressed specifically in cardiac fibroblasts, with its highest expression coincident with the onset of cardiomyocyte cell cycle arrest and transition to hypertrophic growth. In neonatal rat ventricular myocyte (NRVM) cultures, GDF10 treatment promotes cardiomyocyte maturation indicated by increased binucleation, downregulation of cell cycle progression genes, and upregulation of cell cycle inhibitor genes. GDF10 treatment leads to an increase in cardiomyocyte cell size, together with increased expression of mature sarcomeric protein isoforms and decreased expression of fetal cardiac genes. RNAsequencing of GDF10-treated NRVM shows an increase in the expression of genes related to myocardial maturation, including upregulation of sodium and potassium channel genes. In vivo, loss of Gdf10 leads to a delay in myocardial maturation indicated by decreased cardiomyocyte cell size and binucleation, as well as increased mitotic activity, at postnatal (P) day 7. Further, induction of mature sarcomeric protein isoform gene expression is delayed, and expression of cell cycle progression genes is prolonged. However, by P10, indicators of cardiomyocyte maturation and mitotic activity are normalized in Gdf10-null hearts relative to controls. Together, these results implicate GDF10 as a novel crosstalk mediator between cardiomyocytes and cardiac fibroblasts, which is required for appropriate timing of cardiomyocyte maturation steps including binucleation, hypertrophy, mature sarcomeric isoform gene expression, and cell cycle arrest in the postnatal period.