Nkx2.5+\u2009Cardiomyoblasts Contribute to Cardiomyogenesis in the Neonatal Heart

Vahid Serpooshan,Xiaojing Huang,Daniël A Pijnappels,Sharon Paige,David R Rawnsley,Anusha Kumar,Orlando Chirikian,Sneha Venkatraman,Yuan-Hung Liu,Jan W Buikema,Francisco X Galdos,Sean M Wu

doi:10.1038/s41598-017-12869-4

Abstract

During normal lifespan, the mammalian heart undergoes limited renewal of cardiomyocytes. While the exact mechanism for this renewal remains unclear, two possibilities have been proposed: differentiated myocyte replication and progenitor/immature cell differentiation. This study aimed to characterize a population of cardiomyocyte precursors in the neonatal heart and to determine their requirement for cardiac development. By tracking the expression of an embryonic Nkx2.5 cardiac enhancer, we identified cardiomyoblasts capable of differentiation into striated cardiomyocytes in vitro. Genome-wide expression profile of neonatal Nkx2.5+ cardiomyoblasts showed the absence of sarcomeric gene and the presence of cardiac transcription factors. To determine the lineage contribution of the Nkx2.5+ cardiomyoblasts, we generated a doxycycline suppressible Cre transgenic mouse under the regulation of the Nkx2.5 enhancer and showed that neonatal Nkx2.5+ cardiomyoblasts mature into cardiomyocytes in vivo. Ablation of neonatal cardiomyoblasts resulted in ventricular hypertrophy and dilation, supporting a functional requirement of the Nkx2.5+ cardiomyoblasts. This study provides direct lineage tracing evidence that a cardiomyoblast population contributes to cardiogenesis in the neonatal heart. The cell population identified here may serve as a promising therapeutic for pediatric cardiac regeneration.

Highlights

The mammalian heart possesses a limited capacity for new cardiomyocyte (CM) formation after embryonic development[1,2]
While retrospective labeling studies confirm that cardiac stem/progenitor cells may contribute to endogenous cardiac renewal after injury[9], this approach does not allow the identification of the precise cell population and the phenotypic characteristics
By prospective lineage tracing using a doxycycline suppressible Nkx2.5 enhancer-Cre transgenic mouse line, that Nkx2.5 enh-eGFP+ cardiomyoblasts reside in the subepicardium and contribute directly to cardiomyogenesis in vivo

Summary

Introduction

The mammalian heart possesses a limited capacity for new cardiomyocyte (CM) formation after embryonic development[1,2]. While retrospective labeling studies confirm that cardiac stem/progenitor cells may contribute to endogenous cardiac renewal after injury[9], this approach does not allow the identification of the precise cell population and the phenotypic characteristics www.nature.com/scientificreports/. Nkx2.5 enh-eGFP+ cells represent cardiac progenitor cells in the early fetal heart and we postulate that it may label a population of cardiomyogenic precursors in the postnatal heart. The ablation of neonatal Nkx2.5 enh-eGFP+ cardiomyoblasts led to early heart failure phenotypes, including ventricular dilation and hypertrophy, consistent with a requirement for these cells in normal neonatal heart development

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