These findings disclose a novel regulatory pathway that is composed of HRCR, miR-223, and ARC. Modulation of their levels provides an attractive therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Rationale: Sustained cardiac hypertrophy is often accompanied by maladaptive cardiac remodeling leading to decreased compliance and increased risk for heart failure. Maladaptive hypertrophy is considered to be a therapeutic target for heart failure. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) have various biological functions and have been extensively investigated in past years.Objective: We identified miR-489 and lncRNAs (cardiac hypertrophy related factor, CHRF) from hypertrophic cardiomyocytes. Here, we tested the hypothesis that miR-489 and CHRF can participate in the regulation of cardiac hypertrophy in vivo and in vitro. Methods and Results:A microarray was performed to analyze miRNAs in response to angiotensin II treatment, and we found miR-489 was substantially reduced. Enforced expression of miR-489 in cardiomyocytes and transgenic overexpression of miR-489 both exhibited reduced hypertrophic response on angiotensin II treatment. We identified myeloid differentiation primary response gene 88 (Myd88) as a miR-489 target to mediate the function of miR-489 in cardiac hypertrophy. Knockdown of Myd88 in cardiomyocytes and Myd88-knockout mice both showed attenuated hypertrophic responses. Furthermore, we explored the molecular mechanism by which miR-489 expression is regulated and found that an lncRNA that we named CHRF acts as an endogenous sponge of miR-489, which downregulates miR-489 expression levels. CHRF is able to directly bind to miR-489 and regulate Myd88 expression and hypertrophy. Conclusions:

The abnormal autophagy is associated with a variety of cardiovascular diseases. Long noncoding RNAs (lncRNAs) are emerging as new factors in gene regulation, but how lncRNAs operate in the regulation of autophagy in the heart is unclear. Here we report that a long noncoding RNA, named autophagy promoting factor (APF), can regulate autophagic cell death by targeting miR-188-3p and ATG7. The results show that miR-188-3p suppresses autophagy and myocardial infarction by targeting ATG7. Further, we find that APF lncRNA regulates miR-188-3p, and thus affects ATG7 expression, autophagic cell death and myocardial infarction. Our present study reveals a novel regulating model of autophagic programme, which comprises APF, miR-188-3p and ATG7 in the heart. Modulation of their levels may serve as potential targets and diagnostic tools for novel therapeutic strategies of myocardial infarction and heart failure.

Abnormal mitochondrial fission participates in the pathogenesis of many diseases. Long non-coding RNAs (lncRNAs) are emerging as new players in gene regulation, but how lncRNAs operate in the regulation of mitochondrial network is unclear. Here we report that a lncRNA, named cardiac apoptosis-related lncRNA (CARL), can suppress mitochondrial fission and apoptosis by targeting miR-539 and PHB2. The results show that PHB2 is able to inhibit mitochondrial fission and apoptosis. miR-539 is responsible for the dysfunction of PHB2 and regulates mitochondrial fission and apoptosis by targeting PHB2. Further, we show that CARL can act as an endogenous miR-539 sponge that regulates PHB2 expression, mitochondrial fission and apoptosis. Our present study reveals a model of mitochondrial fission regulation that is composed of CARL, miR-539 and PHB2. Modulation of their levels may provide a new approach for tackling apoptosis and myocardial infarction.

Circular RNAs (circRNAs) have important roles in several cellular processes. No study has established the pathophysiological role for circRNAs in the heart. Here, we show that a circRNA (mitochondrial fission and apoptosis-related circRNA (MFACR)) regulates mitochondrial fission and apoptosis in the heart by directly targeting and downregulating miR-652-3p; this in turn blocks mitochondrial fission and cardiomyocyte cell death by suppressing MTP18 translation. MTP18 deficiency reduces mitochondrial fission and suppresses cardiomyocyte apoptosis and MI. miR-652-3p directly downregulates MTP18 and attenuates mitochondrial fission, cardiomyocyte apoptosis, and MI in vitro and in vivo. MFACR directly sequesters miR-652-3p in the cytoplasm and inhibits its activity. MFACR knockdown in cardiomyocytes and mice attenuates mitochondrial fission and MI. Our results reveal a crucial role for circRNA in regulating mitochondrial dynamics and apoptosis in the heart; as such, circRNAs may serve as a potential therapeutic avenue for cardiovascular diseases.

Increasing evidence suggests that long noncoding RNAs (lncRNAs) play crucial roles in various biological processes. However, little is known about the effects of lncRNAs on autophagy. Here we report that a lncRNA, termed cardiac autophagy inhibitory factor (CAIF), suppresses cardiac autophagy and attenuates myocardial infarction by targeting p53-mediated myocardin transcription. Myocardin expression is upregulated upon H2O2 and ischemia/reperfusion, and knockdown of myocardin inhibits autophagy and attenuates myocardial infarction. p53 regulates cardiomyocytes autophagy and myocardial ischemia/reperfusion injury by regulating myocardin expression. CAIF directly binds to p53 protein and blocks p53-mediated myocardin transcription, which results in the decrease of myocardin expression. Collectively, our data reveal a novel CAIF-p53-myocardin axis as a critical regulator in cardiomyocyte autophagy, which will be potential therapeutic targets in treatment of defective autophagy-associated cardiovascular diseases.

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Background: The adult mammalian cardiomyocytes lose their proliferative capacity, which is responsible for cardiac dysfunction and heart failure following injury. The molecular mechanisms underlying the attenuation of adult cardiomyocyte proliferation remain largely unknown. Because long noncoding RNAs (lncRNAs) have a critical role in the development of cardiovascular problems, we investigated whether lncRNAs have any role in the regulation of cardiomyocyte proliferation and cardiac repair. Methods: Using bioinformatics and initial analysis, we identified an lncRNA, named CPR (cardiomyocyte proliferation regulator), that has a potential regulatory role in cardiomyocyte proliferation. For in vivo experiments, we generated CPR knockout and cardiac-specific CPR-overexpressing mice. In isolated cardiomyocytes, we used adenovirus for silencing (CPR–small interfering RNA) or overexpressing CPR. To investigate the mechanisms of CPR function in cardiomyocyte proliferation, we performed various analyses including quantitative reverse transcription–polymerase chain reaction, Western blot, histology, cardiac function (by echocardiography), transcriptome analyses (microarray assay), RNA pull-down assay, and chromatin immunoprecipitation assay. Results: CPR level is comparatively higher in the adult heart than in the fetal stage. The silencing of CPR significantly increased cardiomyocyte proliferation in postnatal and adult hearts. Moreover, CPR deletion restored the heart function after myocardial injury, which was evident from increased cardiomyocyte proliferation, improvement of myocardial function, and reduced scar formation. In contrast, the neonatal cardiomyocyte proliferation and cardiac regeneration were remarkably suppressed in CPR-overexpressing mice or adeno-associated virus serotype 9–CPR—overexpressing heart. These results indicate that CPR acts as a negative regulator of cardiomyocyte proliferation and regeneration. Next, we found that CPR targets minichromosome maintenance 3, an initiator of DNA replication and cell cycle progression, to suppress cardiomyocyte proliferation. CPR silenced minichromosome maintenance 3 expression through directly interacting and recruiting DNMT3A to its promoter cysteine-phosphate-guanine sites, as evident from decreased minichromosome maintenance 3 promoter methylation and increased minichromosome maintenance 3 expression in CPR knocked-down cardiomyocytes and CPR knockout mouse heart. These results were confirmed in CPR-overexpressing cardiomyocytes and CPR-overexpressing mouse heart. Conclusions: Together, our findings identified that CPR is a suppressor of cardiomyocyte proliferation and indicated that lncRNAs take part in the regulation of cardiomyocyte proliferation and cardiac repair. Our study provides an lncRNA-based therapeutic strategy for effective cardiac repair and regeneration.