Multicellular Transcriptional Analysis of Mammalian Heart Regeneration. Mus musculus

The inability of the adult mammalian heart to regenerate following injury represents a major barrier in cardiovascular medicine. In contrast, the neonatal mammalian heart retains a transient capacity for regeneration, which is lost shortly after birth. Defining the molecular mechanisms that govern regenerative capacity in the neonatal period remains a central goal in cardiac biology. Here, we construct a transcriptional atlas of multiple cardiac cell populations, which enables comparative analyses of the regenerative (neonatal) versus non-regenerative (adult) state for the first time. This work provides a comprehensive transcriptional resource of multiple cardiac cell populations during cardiac development, repair and regeneration. Our findings define a transcriptional program underpinning the neonatal regenerative state and identifies an epigenetic barrier to re-induction of the regenerative program in adult cardiomyocytes. Overall design: Cardiomyocytes, fibroblasts, leukocytes and endothelial cells from infarcted and non-infarcted neonatal (P1) and adult (P56) hearts were isolated by enzymatic dissociation and FACS. RNA sequencing (RNA-seq) was performed on these cell populations to generate a transcriptomic atlas of the major cardiac cell populations during cardiac development, repair and regeneration. In addition, we surveyed the epigenetic landscape of cardiomyocytes during post-natal maturation by performing deep sequencing of accessible chromatin regions using the Assay for Transposase-Accessible Chromatin (ATAC-seq) from purified cardiomyocyte nuclei (P1, P14 and P56).