Pressure Overload Greatly Promotes Neonatal Right Ventricular Cardiomyocyte Proliferation: A New Model for the Study of Heart Regeneration.

Background Current mammalian models for heart regeneration research are limited to neonatal apex amputation and myocardial infarction, both of which are controversial. RNAseq has demonstrated a very limited set of differentially expressed genes between sham and operated hearts in myocardial infarction models. Here, we investigated in rats whether pressure overload in the right ventricle, a common phenomenon in children with congenital heart disease, could be used as a better animal model for heart regeneration studies when considering cardiomyocyte proliferation as the most important index. Methods and Results In the rat model, pressure overload was induced by pulmonary artery banding on postnatal day 1 and confirmed by echocardiography and hemodynamic measurements at postnatal day 7. RNA sequencing analyses of purified right ventricular cardiomyocytes at postnatal day 7 from pulmonary artery banding and sham-operated rats revealed that there were 5469 differentially expressed genes between these 2 groups. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis showed that these genes mainly mediated mitosis and cell division. Cell proliferation assays indicated a continuous overproliferation of cardiomyocytes in the right ventricle after pulmonary artery banding, in particular for the first 3 postnatal days. We also validated the model using samples from overloaded right ventricles of human patients. There was an approximately 2-fold increase of Ki67/pHH3/aurora B-positive cardiomyocytes in human-overloaded right ventricles compared with nonoverloaded right ventricles. Other features of this animal model included cardiomyocyte hypotrophy with no fibrosis. Conclusions Pressure overload profoundly promotes cardiomyocyte proliferation in the neonatal stage in both rats and human beings. This activates a regeneration-specific gene program and may offer an alternative animal model for heart regeneration research.