Developmental cardiac tissue is regenerative while operating under low oxygen. After birth, ambient oxygen is associated with cardiomyocyte cell cycle exit and regeneration. Likewise, cardiac metabolism undergoes a shift with cardiac maturation. Whether there are common regulators of cardiomyocyte cell cycle linking metabolism to oxygen tension remains unknown.The objective of the study is to determine whether mitochondrial UCP2 is a metabolic oxygen sensor regulating cardiomyocyte cell cycle. Neonatal rat ventricular myocytes (NRVMs) under moderate hypoxia showed increased cell cycle activity and UCP2 expression. NRVMs exhibited a metabolic shift towards glycolysis, reduced citrate synthase, mtDNA, ΔΨm and DNA damage/oxidative stress while loss of UCP2 reversed this phenotype. Next, WT and UCP2KO mice kept under hypoxia for 4 weeks showed significant decline in cardiac function that was more pronounced in UCP2KO animals. Cardiomyocyte cell cycle activity was reduced while fibrosis and DNA damage was significantly increased in UCP2KO animals compared to WT under hypoxia. Mechanistically, UCP2 increased acetyl-CoA levels, histone acetylation and altered chromatin modifiers linking metabolism to cardiomyocyte cell cycle under hypoxia. Here, we show a novel role for mitochondrial UCP2 as an oxygen sensor regulating cardiomyocyte cell cycle activity, acetyl-CoA levels and histone acetylation in response to moderate hypoxia.
Rationale Cell-based therapeutics have been extensively used for cardiac repair yet underperform due to inability of the donated cells to survive in near anoxia after cardiac injury. Cellular metabolism is linked to maintenance of cardiac stem cell (CSC) renewal, proliferation and survival. Ex vivo expansion alters (CSC) metabolism increasing reliance on oxygen dependent respiration. Whether promoting ‘metabolic flexibility’ in CSCs augments their ability to survive in near anoxia and repair the heart after injury remains untested. Objective Determine the effect of LIN28a induced metabolic flexibility on cardiac tissue derived stem like cell (CTSC) survival and repair after cardiac injury. Methods and results LIN28a expression coincides during heart development but is lost in adult CTSCs. Reintroduction of LIN28a in adult CTSC (CTSC- LIN ) increased proliferation, survival, expression of pluripotency genes and reduced senescence compared to control (CTSC- GFP ). Metabolomic analysis show glycolytic intermediates upregulated in CTSC- LIN together with increased lactate production, pyruvate kinase activity, glucose uptake, ECAR and expression of glycolytic enzymes compared to CTSC- GFP . Additionally, CTSC- LIN showed significantly reduced ROS generation and increase antioxidant markers. In response to H2O2 induced oxidative stress, CTSC- LIN showed increased survival and expression of glycolytic genes. LIN28a salutary effects on CTSCs were linked to PDK1/let-7 signaling pathway with loss of PDK1 or alteration of let-7 abrogating LIN28a effects. Following transplantation in the heart after myocardial infarction (MI), CTSC- LIN showed 6% survival rate at day 7 after injection compared to control cells together with increased proliferation and significant increase in cardiac structure and function 8 weeks after MI. Finally, CSTC-LIN showed enhanced ability to secrete paracrine factors under hypoxic conditions and ability to promote cardiomyocyte proliferation following ischemic cardiac injury. Conclusions LIN28a modification promotes metabolic flexibility in CTSCs enhancing proliferation and survival post transplantation including ability to repair the heart after myocardial injury.
Metabolism has emerged as a regulator of core stem cell properties such as proliferation, survival, self-renewal, and multilineage potential. Metabolites serve as secondary messengers, fine-tuning signaling pathways in response to microenvironment alterations. Studies show a role for central metabolite acetyl-CoA in the regulation of chromatin state through changes in histone acetylation. Nevertheless, metabolic regulators of chromatin remodeling in cardiac cells in response to increasing biological age remains unknown. Previously, we identified novel cardiac-derived stem-like cells (CTSCs) that exhibit increased functional properties in the neonatal heart (nCTSC). These cells are linked to a unique metabolism which is altered with CTSC aging (aCTSC). Here, we present an in-depth, RNA-sequencing-based (RNA-Seq) bioinformatic with cluster analysis that details a distinct epigenome present in nCTSCs but not in aCTSCs. Gene Ontology (GO) and pathway enrichment reveal biological processes, including metabolism, gene regulation enriched in nCTSCs, and STRING analysis that identifies a network of genes related to acetyl-CoA that can potentially influence chromatin remodeling. Additional validation by Western blot and qRT-PCR shows increased acetyl-CoA signaling and histone acetylation in nCTSCs compared to aCTSCs. In conclusion, our data reveal that the link between metabolism and histone acetylation in cardiac cells is altered with the aging of the cardiac tissue.
Background: Developmental cardiac tissue holds remarkable capacity to regenerate after injury and consists of regenerative mononuclear and diploid cardiomyocytes (MNDCMs). Upon maturation, MNDCMs become binucleated or polyploid and exit the cell cycle. Interestingly, cardiomyocyte (CM) metabolism undergoes a profound shift that coincides with cessation of regeneration in the postnatal heart. However, whether reprogramming metabolism promotes persistence of regenerative MNDCMs enhancing cardiac function and repair after injury is unknown. Here, we identify a novel role for RNA-binding protein LIN28a, a master regulator of cellular metabolism, in cardiac repair following injury. Methods: LIN28a overexpression was tested using mouse transgenesis on postnatal CM numbers, cell cycle and response to apical resection (AR) injury. Using, neonatal and adult cell culture system and adult and MADM myocardial injury models in mice, effect of LIN28a overexpression on cardiomyocyte cell cycle and metabolism was tested. Finally, isolated adult CMs from LIN28a and wildtype mice 4 days after myocardial injury, were used for RNA-immunoprecipitation sequencing (RIP-seq). Results: LIN28a was found as primarily active during cardiac development and rapidly decreases after birth. LIN28a reintroduction at P1, P3, P5, and P7 decreased maturation-associated polyploidization, nucleation, and cell size, enhancing CM cell cycle activity in LIN28a transgenic pups compared to WT littermates. Moreover, LIN28a overexpression extended CM cell cycle activity beyond P7 concurrent with increased cardiac function 30 days after AR. In the adult heart, LIN28a overexpression attenuated CM apoptosis, enhanced cell cycle activity, cardiac function, and survival in mice 12 weeks after myocardial infarction compared to WT littermate controls. Alternatively, LIN28a small molecule inhibitor attenuated pro-reparative effects of LIN28a on the heart. Mechanistically, Neonatal rat ventricular myocytes (NRVMs) overexpressing LIN28a showed increased glycolysis, ATP production and levels of metabolic enzymes compared to control. LIN28a immunoprecipitation followed by RNA sequencing (RIPseq) in CMs isolated from LIN28a-overexpressing hearts after injury identified lncRNA-H19 as its most significantly altered target. Ablation of lncRNA-H19 blunted LIN28a-induced enhancement on CM metabolism and cell cycle activity. Conclusions: Collectively, LIN28a reprograms CM metabolism and promotes persistence of MNDCMs in the injured heart enhancing pro-reparative processes thereby linking CM metabolism to regulation of ploidy/nucleation and repair in the heart.
Developmental cardiac tissue holds a remarkable capacity to regenerate after injury and consists of regenerative mononuclear and diploid cardiomyocytes (MNDCMs). Upon maturation, MNDCMs become binucleated or polyploid and exit the cell cycle. Interestingly, CM metabolism undergoes a profound shift that coincides with the cessation of regeneration in the postnatal heart. However, whether reprogramming metabolism promotes persistence of regenerative MNDCMs enhancing cardiac function and regeneration after injury is unknown. Here, we identify a novel role for RNA-binding protein LIN28a, a master regulator of cellular metabolism, in cardiac regeneration following injury. LIN28a was found as primarily active during cardiac developmental stages and rapidly decreases after birth. LIN28a reintroduction at P0, P3, P5, and P7 decreased maturation-associated polyploidization, nucleation, and cell size enhancing CM cell cycle activity (Ki67+, pHH3+, and AurB+ cells) in LIN28a transgenic pups compared to WT littermates. Moreover, LIN28a overexpression extended CM cell cycle activity beyond P7 concurrent with increased cardiac function 30 days after apical resection. In the adult heart, LIN28a overexpression attenuated CM apoptosis, enhanced CM cell cycle activity, cardiac function, and survival in mice 12 weeks after myocardial infarction compared to WT littermate controls. Alternatively, LIN28a small molecule inhibitor attenuated the pro-regenerative effects of LIN28a on the heart. Mechanistically, Neonatal rat ventricular myocytes (NRVMs) overexpressing LIN28a showed increased glycolysis, ATP production, and activity of metabolic enzymes compared to control. Collectively, LIN28a reprograms CM metabolism and promotes persistence of regenerative MNDCMs in the injured heart enhancing pro-regenerative processes thereby linking CM metabolism to the regulation of ploidy/nucleation and regeneration in the heart.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.