Single cell analysis of murine fibroblasts identifies neonatal to adult switching that regulates cardiomyocyte maturation
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ABSTRACT: Cardiac maturation lays the foundation for postnatal heart development and disease, yet little is known about the contributions of the microenvironment to cardiomyocyte maturation. By integrating single-cell RNA-sequencing data of mouse hearts at multiple postnatal stages, we construct cellular interactomes and regulatory signaling networks. Here we report switching of fibroblast subtypes from a neonatal to adult state and this drives cardiomyocyte maturation. Molecular and functional maturation of neonatal mouse cardiomyocytes and human embryonic stem cell-derived cardiomyocytes are considerably enhanced upon coculture with corresponding adult cardiac fibroblasts. Further, single-cell analysis of in vivo and in vitro cardiomyocyte maturation trajectories identify highly conserved signaling pathways, pharmacological targeting of which substantially delays cardiomyocyte maturation in postnatal hearts, and markedly enhances cardiomyocyte proliferation and improves cardiac function in infarcted hearts. Together, we identify cardiac fibroblasts as a key constituent in the microenvironment promoting cardiomyocyte maturation, providing insights into how the manipulation of cardiomyocyte maturity may impact on disease development and regeneration.
Project description: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 Differentiating Factor 10 (GDF10) in postnatal heart development. In neonatal mice, Gdf10 is expressed specifically in cardiac fibroblasts, with its highest expression coincident with onset of cardiomyocytes cell cycle arrest and transition to hypertrophic growth. In neonatal rat ventricular myocyte 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 gene expression 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 a decrease in 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, required for appropriate timing of cardiomyocyte maturation steps including binucleation, hypertrophy, mature sarcomeric isoform switch and cell cycle arrest in the postnatal period.
Project description:Some cell type-specific gene expression is maintained in the maturation of cardiomyocytes, where DNA hypomethylation of gene body regions of a set of specific genes. We used microarrays to detail the global gene expression program underlying the maintenance of cardiomyocyte function and maturation and compared it with DNA methylation status. Cardiomyocytes and cardiac fibroblasts were carefully isolated from neonatal and adult hearts and used fresh for the analysis.
Project description:Mammalian cardiomyocytes rapidly mature after birth, with hallmarks such as cell-cycle exit, binucleation, and metabolic switch to oxidative phosphorylation of lipids. The causes and transcriptional programs regulating cardiomyocyte maturation are not fully understood yet. Thus, we performed single cell RNA-seq of neonatal and postnatal day 7 rat hearts to identify the key factors for this process and found AP-1 as a key factor to regulate cardiomyocyte maturation. To find the mechanism of AP-1 during cardiomyocyte maturation, we performed RNA-seq analysis of neonatal rat ventricular cardiomyocytes and found Ap-1 promote cardiomyocyte maturation by regulating cardiomyocyte metabolism.
Project description:Evaluate the change in transcription factors that have a role in human mesenchymal stem cell (hMSC) commitment to a cardiomyocyte lineage when co-cultured for 4 days with rat neonatal cardiomyocytes and before acquiring a recognizable cardiac phenotype. A myocardial microenvironment was generated by dissociating neonatal rat hearts and establishing cardiomyocyte primary cultures. HumanMSCs constitutively labeled with dsRed localized to the cell's mitochondria were either grown separately (control) or added to the cardiomyocyte primary cultures and grown for 4 days. dsRed fluorescent hMSCs were harvested from co-cultures at 4 days using a FACscan flow cytometer. The RNA for the microarray analysis was prepared from three biologically separate samples of hMSCs co-cultured for 4 days and from hMSCs grown separately for 4 days (control).
Project description:Background - 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. Methods - 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). Results - Profiling of cardiomyocyte and non-myocyte transcriptional programs uncovered several injury responsive genes across regenerative and non-regenerative time points. However, the majority of transcriptional changes in all cardiac cell types resulted from developmental maturation from neonatal stages to adulthood rather than activation of a distinct regeneration-specific gene program. Furthermore, adult leukocytes and fibroblasts reverted to a neonatal state and re-activated a neonatal proliferative network following infarction. In contrast, cardiomyocytes failed to re-activate the neonatal proliferative network following infarction, which was associated with loss of chromatin accessibility around cell cycle genes during post-natal maturation. Conclusions – 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.
Project description:Background - 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. Methods - 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). Results - Profiling of cardiomyocyte and non-myocyte transcriptional programs uncovered several injury responsive genes across regenerative and non-regenerative time points. However, the majority of transcriptional changes in all cardiac cell types resulted from developmental maturation from neonatal stages to adulthood rather than activation of a distinct regeneration-specific gene program. Furthermore, adult leukocytes and fibroblasts reverted to a neonatal state and re-activated a neonatal proliferative network following infarction. In contrast, cardiomyocytes failed to re-activate the neonatal proliferative network following infarction, which was associated with loss of chromatin accessibility around cell cycle genes during post-natal maturation. Conclusions – 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.
Project description:The heart undergoes significant structural, metabolic, gene expression and functional alterations during the perinatal to postnatal transition. While recent studies have identified multiple epigenetic and transcriptional regulators of cardiac maturation, post-transcriptional mechanisms regulating this process remain poorly understood. Neddylation is a post-translational modification that conjugates a small ubiquitin-like protein, NEDD8, to protein substrates via an E1-E2-E3 enzymatic cascade. The goal of this study was to define the role of neddylation in perinatal cardiac development and cardiac maturation. Neddylation was inhibited in adult mouse hearts by cardiac-specific deletion of NAE1 gene, a regulatory subunit of NEDD8 E1 enzyme, or in neonatal cardiomyocytes (CMs) with a pharmacological neddylation inhibitor, MLN4924. The impact on cardiac transcriptome, metabolism, maturation and function was assessed. Mosaic deletion of NAE1 in ~40% neonatal CMs disrupted aspects of maturation, including transverse-tubule formation, cellular hypertrophy and fetal/adult isoform switching, whereas deletion of NAE1 in over 80% CMs led to rapid development of cardiomyopathy and heart failure. Transcriptome analysis demonstrated an association of metabolic derangement with immature cardiomyocyte signature. Biochemical, ultrastructural and metabolomics analyses confirmed downregulation of fatty acid and oxidative phosphorylation genes, deficits in fatty acid utilization, mitochondrial dysfunction, and significantly altered metabolic profiles in NAE1-deficient hearts or MLN4924-treated neonatal CMs. Mechanistically, we found that HIF1α, a transcription factor known to promote glycolysis and suppress oxidative metabolism, is a putative NEDD8 target. Inhibition of neddylation resulted in HIF1α accumulation and activation, which contributed to diminished fatty acid utilization. Taken together, we conclude that neddylation plays a crucial role in CM maturation and postnatal cardiac development through sustaining the glycolytic to oxidative metabolic switch in perinatal hearts.
Project description:During reprogramming of fibroblasts into cardiomyocyte-like cells by overexpression of transcription factors, GATA4, Hand2, Mef2C and Tbx5 (GHMT), H3K4Me2, an active histone code, shifts from fibroblast-exclusive peaks to cardiomyocyte-exclusive peaks. Important cardiac genes are gradually marked by this active histone marker. Mouse embryonic fibroblasts (MEFs) and neonatal mouse ventricular cardiomyocytes (NMVMs) represent fibroblasts and cardiomyocytes, respectively. Chromatins harvested from MEFs infected with retroviruses carrying GHMT at day 3, day 5, day 7 post-viral infection were prepared for immunoprecipitation.
Project description:During the postnatal period in mammals, the cardiac muscle transitions from hyperplasic to hypertrophic growth, the extracellular matrix (ECM) undergoes remodeling, and the heart loses regenerative capacity. While ECM maturation and crosstalk between cardiac fibroblasts (CFs) and cardiomyocytes (CM) have been implicated in neonatal heart development, not much is known about specialized fibroblast heterogeneity and functions in the early postnatal period. In order to better understand CF functions in heart maturation and postnatal cardiomyocyte cell cycle arrest, we have performed gene expression profiling and ablation of postnatal CF subpopulations. Fibroblast lineages expressing Tcf21 or Periostin were traced in transgenic GFP reporter mice and their biological functions and transitions during the postnatal period were examined in sorted cells using RNAseq. A subpopulation of highly proliferative Periostin (Postn)+ CFs was found from postnatal day (P)1 to P11 but was not detected at P30. This population was less abundant and transcriptionally different from Tcf21+ resident CFs, which persist in the mature heart. The Postn+ subpopulation preferentially expresses genes related to cell proliferation and neuronal development, while Tcf21+ CFs differentially express genes related to ECM maturation at P7 and immune crosstalk at P30. Ablation of the Postn+ CFs from P0 to P6 led to altered cardiac sympathetic nerve patterning and a reduction in CM binucleation, maturation, and hypertrophic growth. Thus, postnatal CFs are heterogeneous and include a transient proliferative Postn+ subpopulation required for cardiac nerve development and cardiomyocyte maturation soon after birth.
Project description:Mitochondria play a crucial role in the differentiation and maturation of human cardiomyocytes (CMs). To identify mitochondrial pathways and regulators that are involved in cardiac differentiation and maturation, we examined human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Proteomic analysis was performed on enriched mitochondrial protein extracts isolated from hiPSC-CMs differentiated from dermal fibroblasts (dFCM) and cardiac fibroblasts (cFCM), at different days of differentiation (between 12 and 115 days), and also from adult and neonatal mouse hearts for comparison. Mitochondrial proteins with a ≥2-fold change between differentiation time points in dFCMs and cFCMs, and between adult versus neonatal mouse hearts, were subjected to Ingenuity Pathway Analysis (IPA), and some upregulated proteins were validated by immunoblotting. The highest significant upregulation was in metabolic pathways for fatty acid oxidation (FAO), the tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS) and branched chain amino acid (BCAA) catabolism. The top upstream regulators predicted by IPA were- peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1-a), the insulin receptor and the retinoblastoma protein (Rb) transcriptional repressor. In addition, IPA and immunoblotting showed substantial upregulation of the mitochondrial LonP1 protease, which regulates mitochondrial proteostasis, energetics and metabolism. Using this proteomics approach, we have identified key metabolic and intracellular signaling pathways that are up- and down- regulated during the biogenesis of mitochondria in differentiating and maturing cardiac myocytes.