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Mitochondria regulate proliferation in adult cardiac myocytes

ABSTRACT: Newborn mammalian cardiomyocytes quickly transition from a fetal to an adult phenotype that utilizes mitochondrial oxidative phosphorylation but loses mitotic capacity. We tested whether forced reversal of adult cardiomyocytes back to a fetal glycolytic phenotype would restore proliferative capacity. We deleted Uqcrfs1 (mitochondrial Rieske Iron-Sulfur protein, RISP) in hearts of adult mice. As RISP protein decreased, heart mitochondrial function declined and glucose utilization increased. Simultaneously, they underwent hyperplastic remodeling during which cardiomyocyte number doubled without cellular hypertrophy. Cellular energy supply was preserved, AMPK activation was absent, and mTOR activation was evident. In ischemic hearts with RISP deletion, new cardiomyocytes migrated into the infarcted region, suggesting the potential for therapeutic cardiac regeneration. RNA-seq revealed upregulation of genes associated with cardiac development and proliferation. Metabolomic analysis revealed a decrease in alpha-ketoglutarate (required for TET-mediated demethylation) and an increase in S-adenosylmethionine (required for methyltransferase activity). Analysis revealed an increase in methylated CpGs near gene transcriptional start sites. Genes that were both differentially expressed and differentially methylated were linked to upregulated cardiac developmental pathways. We conclude that decreased mitochondrial function and increased glucose utilization can restore mitotic capacity in adult cardiomyocytes resulting in the generation of new heart cells, potentially through the modification of substrates that regulate epigenetic modification of genes required for proliferation.

ORGANISM(S): Mus musculus

PROVIDER: GSE264439 | GEO | 2024/04/30

REPOSITORIES: GEO

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Project description:Cardiomyocytes exhibit differential growth patterns throughout development. In fetal life the increase in cardiac mass is associated with hyperplastic growth and cardiomyocyte proliferation. The majority of fetal cardiomyocytes are also mononucleated. During the early neonatal period in mice there is a switch from hyperplastic to hypertrophic growth of cardiomyocytes. This period is characterized by bi-nucleation and polyploidization of cardiomyocyte nuclei and a decreased capacity for cardiomyocytes to proliferate and complete cytokinesis. Increases in myocardial mass occur predominantly via hypertrophic growth. Adult mammalian cardiomyocytes are generally accepted to have little or no proliferative capacity and to be terminally withdrawn from the cell cycle. The vast majority of adult murine cardiomyocytes are bi-nucleated. The present study sought to accurately establish the growth pattern of cardiomyocytes throughout development in mice and identify genes associated with the switch from hyperplastic to hypertrophic growth. These cell cycle associated genes are crucial to the understanding of the mechanisms of bi-nucleation, polyploidization and hypertrophy in the neonatal period. Cardiomyocytes were FACS sorted from the hearts of ED11-12 embryos, neonatal day 3-4 and adult (10 week) eGFP ?-MHC mice whereby GFP expression is driven constitutively by the ?-MHC promoter. Gene analyses identified genes whose expression was predicted to be particular to day 3 -4 neonatal cardiomyocytes, compared to embryonic or adult cells. Cell cycle associated genes are crucial to the understanding of the mechanisms of bi-nucleation and hypertrophy in the neonatal period, and offer attractive candidates for manipulation. Total RNA obtained from isolated cardiomyocytes from ED11-12; Neonatal day 3-4 and adult timepoints compared with each other. Several hearts per sample, RNA was pooled within samples. FACS samples were prepared in the following manner: embryonic, neonatal and adult hearts were dissected and dissociated to single cell solution with Liberase Blendzyme 3 (0.1 mg/ml) (Roche Diagnostics), washed and spun down and resuspended in cardiomyocyte isolation buffer (130 mM NaCl; 5 mM KCl; 1.2 mM KH2PO4; 6 mM HEPES; 5 mM NaHCO3; 1 mM MgCl2; 5 mM Glucose).

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.

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Mitochondria regulate proliferation in adult cardiac myocytes

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