Functional screening identifies miRNAs inducing cardiac regeneration. Nature. 2012;492:376-381. [PMID: 23222520 DOI: 10.1038/nature11739]

Exploring the role of pericardial miRNAs and exosomes in modulating cardiac fibrosis

The potential of the pericardial space as a therapeutic delivery tool for cardiac fibrosis and heart failure (HF) treatment has yet to be elucidated. Recently, miRNAs and exosomes have been discovered to be present in human pericardial fluid (PF). Novel studies have shown characteristic human PF miRNA compositions associated with cardiac diseases and higher miRNA expressions in PF compared to peripheral blood. Five key studies found differentially expressed miRNAs in HF, angina pectoris, aortic stenosis, ventricular tachycardia, and congenital heart diseases with either atrial fibrillation or sinus rhythm. As miRNA-based therapeutics for cardiac fibrosis and HF showed promising results in several in vivo studies for multiple miRNAs, we hypothesize a potential role of miRNA-based therapeutics delivered through the pericardial cavity. This is underlined by the favorable results of the first phase 1b clinical trial in this emerging field. Presenting the first human miRNA antisense drug trial, inhibition of miR-132 by intravenous administration of a novel antisense oligonucleotide, CDR132L, established efficacy in reducing miR-132 in plasma samples in a dose-dependent manner. We screened the literature, provided an overview of the miRNAs and exosomes present in PF, and drew a connection to those miRNAs previously elucidated in cardiac fibrosis and HF. Further, we speculate about clinical implications and potential delivery methods.

Adducin Regulates Sarcomere Disassembly During Cardiomyocyte Mitosis

BACKGROUND

Recent interest in understanding cardiomyocyte cell cycle has been driven by potential therapeutic applications in cardiomyopathy. However, despite recent advances, cardiomyocyte mitosis remains a poorly understood process. For example, it is unclear how sarcomeres are disassembled during mitosis to allow the abscission of daughter cardiomyocytes.

METHODS

Here, we use a proteomics screen to identify adducin, an actin capping protein previously not studied in cardiomyocytes, as a regulator of sarcomere disassembly. We generated many adeno-associated viruses and cardiomyocyte-specific genetic gain-of-function models to examine the role of adducin in neonatal and adult cardiomyocytes in vitro and in vivo.

RESULTS

We identify adducin as a regulator of sarcomere disassembly during mammalian cardiomyocyte mitosis. α/γ-adducins are selectively expressed in neonatal mitotic cardiomyocytes, and their levels decline precipitously thereafter. Cardiomyocyte-specific overexpression of various splice isoforms and phospho-isoforms of α-adducin in vitro and in vivo identified Thr445/Thr480 phosphorylation of a short isoform of α-adducin as a potent inducer of neonatal cardiomyocyte sarcomere disassembly. Concomitant overexpression of this α-adducin variant along with γ-adducin resulted in stabilization of the adducin complex and persistent sarcomere disassembly in adult mice, which is mediated by interaction with α-actinin.

CONCLUSIONS

These results highlight an important mechanism for coordinating cytoskeletal morphological changes during cardiomyocyte mitosis.

Endothelial-to-mesenchymal transition enhances permissiveness to AAV vectors in cardiac endothelial cells

A major obstacle in inducing therapeutic angiogenesis in the heart is inefficient gene transfer to endothelial cells (ECs). Here, we identify compounds able to enhance the permissiveness of cardiac ECs to adeno-associated virus (AAV) vectors, which stand as ideal tools for in vivo gene delivery. We screened a library of >1,500 US Food and Drug Administration (FDA)-approved drugs, in combination with AAV vectors, in cardiac ECs. Among the top drugs increasing AAV-mediated transduction, we found vatalanib, an inhibitor of multiple tyrosine kinase receptors. The increased AAV transduction efficiency by vatalanib was paralleled by induction of the endothelial-to-mesenchymal transition, as documented by decreased endothelial and increased mesenchymal marker expression. Induction of the endothelial-to-mesenchymal transition by other strategies similarly increased EC permissiveness to AAV vectors. In vivo injection of AAV vectors in the heart after myocardial infarction resulted in the selective transduction of cells undergoing the endothelial-to-mesenchymal transition, which is known to happen transiently after cardiac ischemia. Collectively, these results point to the endothelial-to-mesenchymal transition as a mechanism for improving AAV transduction in cardiac ECs, with implications for both basic research and the induction of therapeutic angiogenesis in the heart.

Multi-omic analysis reveals VEGFR2, PI3K, and JNK mediate the small molecule induction of human iPSC-derived cardiomyocyte proliferation

Mammalian hearts lose their regenerative potential shortly after birth. Stimulating the proliferation of preexisting cardiomyocytes is a potential therapeutic strategy for cardiac damage. In a previous study, we identified 30 compounds that induced the bona-fide proliferation of human iPSC-derived cardiomyocytes (hiPSC-CM). Here, we selected five active compounds with diverse targets, including ALK5 and CB1R, and performed multi-omic analyses to identify common mechanisms mediating the cell cycle progression of hiPSC-CM. Transcriptome profiling revealed the top enriched pathways for all compounds including cell cycle, DNA repair, and kinesin pathways. Functional proteomic arrays found that the compounds collectively activated multiple receptor tyrosine kinases including ErbB2, IGF1R, and VEGFR2. Network analysis integrating common transcriptomic and proteomic signatures predicted that MAPK/PI3K pathways mediated compound responses. Furthermore, VEGFR2 negatively regulated endoreplication, enabling the completion of cell division. Thus, in this study, we applied high-content imaging and molecular profiling to establish mechanisms linking pro-proliferative agents to mechanisms of cardiomyocyte cell cycling.

CircNCX1 modulates cardiomyocyte proliferation through promoting ubiquitination of BRG1

In mammal, the myocardium loss cannot be recovered spontaneously due to the negligible proliferation ability of mature mammalian cardiomyocyte. However, accumulated evidence has shown that terminally differentiated mammalian cardiomyocyte also has proliferation potency, which can be mediated by several mechanisms. Here, we reported that circNCX1, the most abundant circular RNA in mammalian hearts, can affect the proliferation of murine cardiomyocytes. The level of circNCX1 is significantly elevated during heart development. Forced expression of circNCX1 inhibits cardiomyocyte proliferation, while silencing of endogenous circNCX1 in cardiomyocyte shows reversed effect in vitro. Mechanistically, circNCX1 functions via negatively regulating transcription activator BRG1. It bridges BRG1 and FBXW7 to enhance the ubiquitination and degradation of BRG1, decreasing the expression of BMP10 to lead cell cycle arrest. In summary, our study first revealed that circNCX1 is a modulator of cardiomyocyte proliferation.

Non-coding RNAs as therapeutic targets and biomarkers in ischaemic heart disease

The adult heart is a complex, multicellular organ that is subjected to a series of regulatory stimuli and circuits and has poor reparative potential. Despite progress in our understanding of disease mechanisms and in the quality of health care, ischaemic heart disease remains the leading cause of death globally, owing to adverse cardiac remodelling, leading to ischaemic cardiomyopathy and heart failure. Therapeutic targets are urgently required for the protection and repair of the ischaemic heart. Moreover, personalized clinical biomarkers are necessary for clinical diagnosis, medical management and to inform the individual response to treatment. Non-coding RNAs (ncRNAs) deeply influence cardiovascular functions and contribute to communication between cells in the cardiac microenvironment and between the heart and other organs. As such, ncRNAs are candidates for translation into clinical practice. However, ncRNA biology has not yet been completely deciphered, given that classes and modes of action have emerged only in the past 5 years. In this Review, we discuss the latest discoveries from basic research on ncRNAs and highlight both the clinical value and the challenges underscoring the translation of these molecules as biomarkers and therapeutic regulators of the processes contributing to the initiation, progression and potentially the prevention or resolution of ischaemic heart disease and heart failure.

CircSorbs1 regulates myocardial regeneration and reduces cancer therapy-related cardiovascular toxicity through the Mir-99/GATA4 pathway

Due to the cancer therapy-related cardiovascular toxicity, heart failure following cancer therapy has a significant mortality rate. Gene-targeted therapy promotes the re-entry of existing cardiomyocytes into the cell cycle to achieve myocardial regeneration, which is a promising strategy for preventing and treating heart failure after myocardial infarction. Circular RNAs (circRNAs) are considered as potential targets for myocardial regeneration due to their strong stability, resistance to degradation, and potential role in heart development and cardiovascular diseases. By comparing the myocardial tissue of mice in the sham operation group and the Doxorubicin therapy group (DOX), we observed a significant decrease in Cirsorbs expression in the DOX group. Cirsorbs was predominantly localized in cardiomyocytes and exhibited high conservation. Subsequent investigations revealed that Cirsorbs could promote myocardial proliferation and inhibit myocardial apoptosis. Mechanistic studies further demonstrated that Cirsorbs could bind to miR99 and reduce its expression level. Meanwhile, miR99 was found to bind to GATA4 mRNA and decrease its expression level. The binding of Cirsorbs to miR99 alleviated the repression of miR99, thereby enhancing GATA4 expression and the transcription of downstream cyclin A2 and cyclin E1. This, in turn, increased cardiomyocyte proliferation and reduced apoptosis. In conclusion, Cirsorbs holds promise as an effective target for myocardial regeneration in reducing cancer therapy-related cardiovascular toxicity.

LncRNAs in the Dlk1-Dio3 Domain Are Essential for Mid-Embryonic Heart Development

The Dlk1-Dio3 domain is important for normal embryonic growth and development. The heart is the earliest developing and functioning organ of the embryo. In this study, we constructed a transcriptional termination model by inserting termination sequences and clarified that the lack of long non-coding RNA (lncRNA) expression in the Dlk1-Dio3 domain caused the death of maternal insertion mutant (MKI) and homozygous mutant (HOMO) mice starting from E13.5. Parental insertion mutants (PKI) can be born and grow normally. Macroscopically, dying MKI and HOMO embryos showed phenomena such as embryonic edema and reduced heart rate. Hematoxylin and eosin (H.E.) staining showed thinning of the myocardium in MKI and HOMO embryos. In situ hybridization (IHC) and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) showed downregulation of lncGtl2, Rian, and Mirg expression in MKI and HOMO hearts. The results of single-cell RNA sequencing (scRNA-Seq) analysis indicated that the lack of lncRNA expression in the Dlk1-Dio3 domain led to reduced proliferation of epicardial cells and may be an important cause of cardiac dysplasia. In conclusion, this study demonstrates that Dlk1-Dio3 domain lncRNAs play an integral role in ventricular development.

Therapeutic Potential of Natural Compounds Acting through Epigenetic Mechanisms in Cardiovascular Diseases: Current Findings and Future Directions

Cardiovascular diseases (CVDs) remain a leading global cause of morbidity and mortality. These diseases have a multifaceted nature being influenced by a multitude of biochemical, genetic, environmental, and behavioral factors. Epigenetic modifications have a crucial role in the onset and progression of CVD. Epigenetics, which regulates gene activity without altering the DNA's primary structure, can modulate cardiovascular homeostasis through DNA methylation, histone modification, and non-coding RNA regulation. The effects of environmental stimuli on CVD are mediated by epigenetic changes, which can be reversible and, hence, are susceptible to pharmacological interventions. This represents an opportunity to prevent diseases by targeting harmful epigenetic modifications. Factors such as high-fat diets or nutrient deficiencies can influence epigenetic enzymes, affecting fetal growth, metabolism, oxidative stress, inflammation, and atherosclerosis. Recent studies have shown that plant-derived bioactive compounds can modulate epigenetic regulators and inflammatory responses, contributing to the cardioprotective effects of diets. Understanding these nutriepigenetic effects and their reversibility is crucial for developing effective interventions to combat CVD. This review delves into the general mechanisms of epigenetics, its regulatory roles in CVD, and the potential of epigenetics as a CVD therapeutic strategy. It also examines the role of epigenetic natural compounds (ENCs) in CVD and their potential as intervention tools for prevention and therapy.

Nanoparticle-Patch System for Localized, Effective, and Sustained miRNA Administration into Infarcted Myocardium to Alleviate Myocardial Ischemia-Reperfusion Injury

Timely blood reperfusion after myocardial infarction (MI) paradoxically triggers ischemia-reperfusion injury (I/RI), which currently has not been conquered by clinical treatments. Among innovative repair strategies for myocardial I/RI, microRNAs (miRNAs) are expected as genetic tools to rescue damaged myocardium. Our previous study identified that miR-30d can provide protection against myocardial apoptosis and fibrosis to alleviate myocardial injury. Although common methods such as liposomes and viral vectors have been used for miRNA transfection, their therapeutic efficiencies have struggled with inefficient in vivo delivery, susceptible inactivation, and immunogenicity. Here, we establish a nanoparticle-patch system for miR-30d delivery in a murine myocardial I/RI model, which contains ZIF-8 nanoparticles and a conductive microneedle patch. Loaded with miR-30d, ZIF-8 nanoparticles leveraging the proton sponge effect enable miR-30d to escape the endocytic pathway, thus avoiding premature degradation in lysosomes. Meanwhile, the conductive microneedle patch offers a distinct advantage by intramyocardial administration for localized, effective, and sustained miR-30d delivery, and it simultaneously releases Au nanoparticles to reconstruct electrical impulses within the infarcted myocardium. Consequently, the nanoparticle-patch system supports the consistent and robust expression of miR-30d in cardiomyocytes. Results from echocardiography and electrocardiogram (ECG) revealed improved heart functions and standard ECG wave patterns in myocardial I/RI mice after implantation of a nanoparticle-patch system for 3 and 6 weeks. In summary, our work incorporated conductive microneedle patch and miR-30d nanodelivery systems to synergistically transcend the limitations of common RNA transfection methods, thus mitigating myocardial I/RI.

Single dose of intravenous miR199a-5p delivery targeting ischemic heart for long-term repair of myocardial infarction

Long-term treatment of myocardial infarction is challenging despite medical advances. Tissue engineering shows promise for MI repair, but implantation complexity and uncertain outcomes pose obstacles. microRNAs regulate genes involved in apoptosis, angiogenesis, and myocardial contraction, making them valuable for long-term repair. In this study, we find downregulated miR-199a-5p expression in MI. Intramyocardial injection of miR-199a-5p into the infarcted region of male rats revealed its dual protective effects on the heart. Specifically, miR-199a-5p targets AGTR1, diminishing early oxidative damage post-myocardial infarction, and MARK4, which influences long-term myocardial contractility and enhances cardiac function. To deliver miR-199a-5p efficiently and specifically to ischemic myocardial tissue, we use CSTSMLKAC peptide to construct P-MSN/miR199a-5p nanoparticles. Intravenous administration of these nanoparticles reduces myocardial injury and protects cardiac function. Our findings demonstrate the effectiveness of P-MSN/miR199a-5p nanoparticles in repairing MI through enhanced contraction and anti-apoptosis. miR199a-5p holds significant therapeutic potential for long-term repair of myocardial infarction.

Exosomes based strategies for cardiovascular diseases: Opportunities and challenges

Exosomes, as nanoscale extracellular vesicles (EVs), are secreted by all types of cells to facilitate intercellular communication in living organisms. After being taken up by neighboring or distant cells, exosomes can alter the expression levels of target genes in recipient cells and thereby affect their pathophysiological outcomes depending on payloads encapsulated therein. The functions and mechanisms of exosomes in cardiovascular diseases have attracted much attention in recent years and are thought to have cardioprotective and regenerative potential. This review summarizes the biogenesis and molecular contents of exosomes and details the roles played by exosomes released from various cells in the progression and recovery of cardiovascular disease. The review also discusses the current status of traditional exosomes in cardiovascular tissue engineering and regenerative medicine, pointing out several limitations in their application. It emphasizes that some of the existing emerging industrial or bioengineering technologies are promising to compensate for these shortcomings, and the combined application of exosomes and biomaterials provides an opportunity for mutual enhancement of their performance. The integration of exosome-based cell-free diagnostic and therapeutic options will contribute to the further development of cardiovascular regenerative medicine.

The Role of Circulating MicroRNAs in Cardiovascular Diseases: A Novel Biomarker for Diagnosis and Potential Therapeutic Targets?

MicroRNAs, involved in a large variety of pathological conditions, tend to be potential specific biomarkers in cardiovascular diseases. Moreover, these short, non-coding RNAs, regulate post-transcriptional gene expression and protein synthesis, making them ideal for therapeutic targets. Down-regulation and up-regulation of specific microRNAs are currently studied as a novel approach to the diagnosis and treatment of cardiovascular diseases, such as chronic and acute coronary syndromes, atherosclerosis, heart failure, and arrhythmia. MicroRNAs are interesting and attractive targets for cardiovascular-associated therapeutics because of their stability, tissue-specific expression pattern, and secretion of body fluids. Extended research on their isolation, detection, and function will provide the standardization needed for using microRNAs as biomarkers and potential therapeutic targets. This review will summarize recent data on the implication of microRNAs in cardiovascular diseases, their potential role as biomarkers for diagnosis, and also the challenges of using microRNAs as future therapeutic targets.

The potential mechanisms and treatment effects of stem cell-derived exosomes in cardiac reengineering

Exosomes are extracellular vesicles of diverse compositions that are secreted by numerous cell types. Exosomes contain significant bioactive components, including lipids, proteins, mRNA, and miRNA. Exosomes play an important role in regulating cellular signaling and trafficking under both normal physiological and pathological circumstances. A multitude of factors, including thermal stress, ribosomal stress, endoplasmic reticulum stress, and oxidative stress influence the concentrations of exosomal mRNA, miRNA, proteins, and lipids. It has been stated that exosomes derived from stem cells (SCs) modulate a range of stresses by preventing or fostering cell balance. Exosomes derived from SCs facilitate recovery by facilitating cross-cellular communication via the transmission of information in the form of proteins, lipids, and other components. For this reason, exosomes are used as biomarkers to diagnose a wide variety of diseases. The focus of this review is the bioengineering of artificial exosomal cargoes. This process encompasses the control and transportation of particular exosomal cargoes, including but not limited to small molecules, recombinant proteins, immune modulators, and therapeutic medications. Therapeutic approaches of this nature have the potential to deliver therapeutic medications precisely to the intended site for the cure of a variety of disorders. Notably, our attention has been directed towards the therapeutic implementations of exosomes derived from SCs in the cure of cardiovascular ailments, including but not limited to ischemic heart disease, myocardial infarction, sepsis, heart failure, cardiomyopathy, and cardiac fibrosis. In general, researchers employ two methodologies when it comes to exosomal bioengineering. This review aims to explain the function of exosomes derived from SCs in the regulation of stress and present a novel therapeutic approach for cardiovascular disorders.

Pharmacological inhibition of RUNX1 reduces infarct size after acute myocardial infarction in rats and underlying mechanism revealed by proteomics implicates repressed cathepsin levels

Myocardial infarction (MI) results in prolonged ischemia and the subsequent cell death leads to heart failure which is linked to increased deaths or hospitalizations. New therapeutic targets are urgently needed to prevent cell death and reduce infarct size among patients with MI. Runt-related transcription factor-1 (RUNX1) is a master-regulator transcription factor intensively studied in the hematopoietic field. Recent evidence showed that RUNX1 has a critical role in cardiomyocytes post-MI. The increased RUNX1 expression in the border zone of the infarct heart contributes to decreased cardiac contractile function and can be therapeutically targeted to protect against adverse cardiac remodelling. This study sought to investigate whether pharmacological inhibition of RUNX1 function has an impact on infarct size following MI. In this work we demonstrate that inhibiting RUNX1 with a small molecule inhibitor (Ro5-3335) reduces infarct size in an in vivo rat model of acute MI. Proteomics study using data-independent acquisition method identified increased cathepsin levels in the border zone myocardium following MI, whereas heart samples treated by RUNX1 inhibitor present decreased cathepsin levels. Cathepsins are lysosomal proteases which have been shown to orchestrate multiple cell death pathways. Our data illustrate that inhibition of RUNX1 leads to reduced infarct size which is associated with the suppression of cathepsin expression. This study demonstrates that pharmacologically antagonizing RUNX1 reduces infarct size in a rat model of acute MI and unveils a link between RUNX1 and cathepsin-mediated cell death, suggesting that RUNX1 is a novel therapeutic target that could be exploited clinically to limit infarct size after an acute MI.

Targeting cardiomyocyte cell cycle regulation in heart failure

Heart failure continues to be a significant global health concern, causing substantial morbidity and mortality. The limited ability of the adult heart to regenerate has posed challenges in finding effective treatments for cardiac pathologies. While various medications and surgical interventions have been used to improve cardiac function, they are not able to address the extensive loss of functioning cardiomyocytes that occurs during cardiac injury. As a result, there is growing interest in understanding how the cell cycle is regulated and exploring the potential for stimulating cardiomyocyte proliferation as a means of promoting heart regeneration. This review aims to provide an overview of current knowledge on cell cycle regulation and mechanisms underlying cardiomyocyte proliferation in cases of heart failure, while also highlighting established and novel therapeutic strategies targeting this area for treatment purposes.

Discovery platforms for RNA therapeutics

RNA therapeutics are emerging as a unique opportunity to drug currently "undruggable" molecules and diseases. While their advantages over conventional, small molecule drugs, their therapeutic implications and the tools for their effective in vivo delivery have been extensively reviewed, little attention has been so far paid to the technological platforms exploited for the discovery of RNA therapeutics. Here, we provide an overview of the existing platforms and ex vivo assays for RNA discovery, their advantages and disadvantages, as well as their main fields of application, with specific focus on RNA therapies that have reached either phase 3 or market approval.

Leveraging chromatin state transitions for the identification of regulatory networks orchestrating heart regeneration

The limited regenerative capacity of the human heart contributes to high morbidity and mortality worldwide. In contrast, zebrafish exhibit robust regenerative capacity, providing a powerful model for studying how to overcome intrinsic epigenetic barriers maintaining cardiac homeostasis and initiate regeneration. Here, we present a comprehensive analysis of the histone modifications H3K4me1, H3K4me3, H3K27me3 and H3K27ac during various stages of zebrafish heart regeneration. We found a vast gain of repressive chromatin marks one day after myocardial injury, followed by the acquisition of active chromatin characteristics on day four and a transition to a repressive state on day 14, and identified distinct transcription factor ensembles associated with these events. The rapid transcriptional response involves the engagement of super-enhancers at genes implicated in extracellular matrix reorganization and TOR signaling, while H3K4me3 breadth highly correlates with transcriptional activity and dynamic changes at genes involved in proteolysis, cell cycle activity, and cell differentiation. Using loss- and gain-of-function approaches, we identified transcription factors in cardiomyocytes and endothelial cells influencing cardiomyocyte dedifferentiation or proliferation. Finally, we detected significant evolutionary conservation between regulatory regions that drive zebrafish and neonatal mouse heart regeneration, suggesting that reactivating transcriptional and epigenetic networks converging on these regulatory elements might unlock the regenerative potential of adult human hearts.

miR-590-3p Overexpression Improves the Efficacy of hiPSC-CMs for Myocardial Repair

Recent evidence demonstrates that low engraftment rates limit the efficacy of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for cardiac repair after myocardial infarction. In this study, we attempted to overcome this limitation by enhancing the proliferative capacity of transplanted hiPSC-CMs. We found that miR-590-3p overexpression increased the proliferative capacity of hiPSC-CMs. miR-590-3p overexpression increased the number of engrafted cells and had a higher efficacy for myocardial repair than control cells. Moreover, we confirmed the safety of using miR-590-3p-overexpressing hiPSC-CMs in pig hearts. These results indicated that miR-590-3p overexpression stimulated hiPSC-CM cell cycle re-entry to induce cell proliferation and increased the therapeutic efficacy in MI.

Head-to-head comparison of relevant cell sources of small extracellular vesicles for cardiac repair: Superiority of embryonic stem cells

Small extracellular vesicles (sEV) derived from various cell sources have been demonstrated to enhance cardiac function in preclinical models of myocardial infarction (MI). The aim of this study was to compare different sources of sEV for cardiac repair and determine the most effective one, which nowadays remains limited. We comprehensively assessed the efficacy of sEV obtained from human primary bone marrow mesenchymal stromal cells (BM-MSC), human immortalized MSC (hTERT-MSC), human embryonic stem cells (ESC), ESC-derived cardiac progenitor cells (CPC), human ESC-derived cardiomyocytes (CM), and human primary ventricular cardiac fibroblasts (VCF), in in vitro models of cardiac repair. ESC-derived sEV (ESC-sEV) exhibited the best pro-angiogenic and anti-fibrotic effects in vitro. Then, we evaluated the functionality of the sEV with the most promising performances in vitro, in a murine model of MI-reperfusion injury (IRI) and analysed their RNA and protein compositions. In vivo, ESC-sEV provided the most favourable outcome after MI by reducing adverse cardiac remodelling through down-regulating fibrosis and increasing angiogenesis. Furthermore, transcriptomic, and proteomic characterizations of sEV derived from hTERT-MSC, ESC, and CPC revealed factors in ESC-sEV that potentially drove the observed functions. In conclusion, ESC-sEV holds great promise as a cell-free treatment for promoting cardiac repair following MI.

Hydrogel-based cardiac repair and regeneration function in the treatment of myocardial infarction

A life-threatening illness that poses a serious threat to human health is myocardial infarction. It may result in a significant number of myocardial cells dying, dilated left ventricles, dysfunctional heart function, and ultimately cardiac failure. Based on the development of emerging biomaterials and the lack of clinical treatment methods and cardiac donors for myocardial infarction, hydrogels with good compatibility have been gradually applied to the treatment of myocardial infarction. Specifically, based on the three processes of pathophysiology of myocardial infarction, we summarized various types of hydrogels designed for myocardial tissue engineering in recent years, including natural hydrogels, intelligent hydrogels, growth factors, stem cells, and microRNA-loaded hydrogels. In addition, we also describe the heart patch and preparation techniques that promote the repair of MI heart function. Although most of these hydrogels are still in the preclinical research stage and lack of clinical trials, they have great potential for further application in the future. It is expected that this review will improve our knowledge of and offer fresh approaches to treating myocardial infarction.

Extracellular vesicles purified from serum-converted human platelet lysates offer strong protection after cardiac ischaemia/reperfusion injury

Extracellular vesicles (EVs) from cultured cells or bodily fluids have been demonstrated to show therapeutic value following myocardial infarction. However, challenges in donor variation, EV generation and isolation methods, and material availability have hindered their therapeutic use. Here, we show that human clinical-grade platelet concentrates from a blood establishment can be used to rapidly generate high concentrations of high purity EVs from sero-converted platelet lysate (SCPL-EVs) with minimal processing, using size-exclusion chromatography. Processing removed serum carrier proteins, coagulation factors and complement proteins from the original platelet lysate and the resultant SCPL-EVs carried a range of trophic factors and multiple recognised cardioprotective miRNAs. As such, SCPL-EVs protected rodent and human cardiomyocytes from hypoxia/re-oxygenation injury and stimulated angiogenesis of human cardiac microvessel endothelial cells. In a mouse model of myocardial infarction with reperfusion, SCPL-EV delivery using echo-guided intracavitary percutaneous injection produced large improvements in cardiac function, reduced scar formation and promoted angiogenesis. Since platelet-based biomaterials are already widely used clinically, we believe that this therapy could be rapidly suitable for a human clinical trial.

Tailoring Treatment in Cardiovascular Diseases: The Role of Targeted Therapies

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality around the globe. To address this public health burden, innovative therapeutic agents are being developed to specifically target molecular and genetic markers. Various therapeutic modalities have been implemented, including vaccines, monoclonal or bispecific antibodies, and gene-based therapies. Such drugs precisely target the underlying disease pathophysiology, aiming at notable molecules such as lipid metabolism regulators, proinflammatory cytokines, and growth factors. This review focuses on the latest advancements in different targeted therapies. It provides an insightful overview of the current landscape of targeted cardiovascular therapies, highlighting promising strategies with potential to transform the treatment of CVDs into an era of precision medicine.

Non-Coding RNA-Targeted Therapy: A State-of-the-Art Review

The use of non-coding RNAs (ncRNAs) as drug targets is being researched due to their discovery and their role in disease. Targeting ncRNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), is an attractive approach for treating various diseases, such as cardiovascular disease and cancer. This seminar discusses the current status of ncRNAs as therapeutic targets in different pathological conditions. Regarding miRNA-based drugs, this approach has made significant progress in preclinical and clinical testing for cardiovascular diseases, where the limitations of conventional pharmacotherapy are evident. The challenges of miRNA-based drugs, including specificity, delivery, and tolerability, will be discussed. New approaches to improve their success will be explored. Furthermore, it extensively discusses the potential development of targeted therapies for cardiovascular disease. Finally, this document reports on the recent advances in identifying and characterizing microRNAs, manipulating them, and translating them into clinical applications. It also addresses the challenges and perspectives towards clinical application.

MiR-181a protects the heart against myocardial infarction by regulating mitochondrial fission via targeting programmed cell death protein 4

Worldwide, myocardial infarction (MI) is the leading cause of death and disability-adjusted life years lost. Recent researches explored new methods of detecting biomarkers that can predict the risk of developing myocardial infarction, which includes identifying genetic markers associated with increased risk. We induced myocardial infarction in mice by occluding the left anterior descending coronary artery and performed TTC staining to assess cell death. Next, we performed ChIP assays to measure the enrichment of histone modifications at the promoter regions of key genes involved in mitochondrial fission. We used qPCR and western blot to measure expression levels of relative apoptotic indicators. We report that miR-181a inhibits myocardial ischemia-induced apoptosis and preserves left ventricular function after MI. We show that programmed cell death protein 4 (PDCD4) is the target gene involved in miR-181a-mediated anti-ischemic injury, which enhanced BID recruitment to the mitochondria. In addition, we discovered that p53 inhibits the expression of miR-181a via transcriptional regulation. Here, we discovered for the first time a mitochondrial fission and apoptosis pathway which is controlled by miR-181a and involves PDCD4 and BID. This pathway may be controlled by p53 transcriptionally, and we presume that miR-181a may lead to the discovery of new therapeutic and preventive targets for ischemic heart diseases.

Current RNA strategies in treating cardiovascular diseases

Cardiovascular disease (CVD) continues to impose a significant global health burden, necessitating the exploration of innovative treatment strategies. Ribonucleic acid (RNA)-based therapeutics have emerged as a promising avenue to address the complex molecular mechanisms underlying CVD pathogenesis. We present a comprehensive review of the current state of RNA therapeutics in the context of CVD, focusing on the diverse modalities that bring about transient or permanent modifications by targeting the different stages of the molecular biology central dogma. Considering the immense potential of RNA therapeutics, we have identified common gene targets that could serve as potential interventions for prevalent Mendelian CVD caused by single gene mutations, as well as acquired CVDs developed over time due to various factors. These gene targets offer opportunities to develop RNA-based treatments tailored to specific genetic and molecular pathways, presenting a novel and precise approach to address the complex pathogenesis of both types of cardiovascular conditions. Additionally, we discuss the challenges and opportunities associated with delivery strategies to achieve targeted delivery of RNA therapeutics to the cardiovascular system. This review highlights the immense potential of RNA-based interventions as a novel and precise approach to combat CVD, paving the way for future advancements in cardiovascular therapeutics.

Cardiac regeneration: Pre-existing cardiomyocyte as the hub of novel signaling pathway

In the mammalian heart, cardiomyocytes are forced to withdraw from the cell cycle shortly after birth, limiting the ability of the heart to regenerate and repair. The development of multimodal regulation of cardiac proliferation has verified that pre-existing cardiomyocyte proliferation is an essential driver of cardiac renewal. With the continuous development of genetic lineage tracking technology, it has been revealed that cell cycle activity produces polyploid cardiomyocytes during the embryonic, juvenile, and adult stages of cardiogenesis, but newly formed mononucleated diploid cardiomyocytes also elevated sporadically during myocardial infarction. It implied that adult cardiomyocytes have a weak regenerative capacity under the condition of ischemia injury, which offers hope for the clinical treatment of myocardial infarction. However, the regeneration frequency and source of cardiomyocytes are still low, and the mechanism of regulating cardiomyocyte proliferation remains further explained. It is noteworthy to explore what force triggers endogenous cardiomyocyte proliferation and heart regeneration. Here, we focused on summarizing the recent research progress of emerging endogenous key modulators and crosstalk with other signaling pathways and furnished valuable insights into the internal mechanism of heart regeneration. In addition, myocardial transcription factors, non-coding RNAs, cyclins, and cell cycle-dependent kinases are involved in the multimodal regulation of pre-existing cardiomyocyte proliferation. Ultimately, awakening the myocardial proliferation endogenous modulator and regeneration pathways may be the final battlefield for the regenerative therapy of cardiovascular diseases.

Identification of FDA-approved drugs that induce heart regeneration in mammals

Targeting Meis1 and Hoxb13 transcriptional activity could be a viable therapeutic strategy for heart regeneration. In this study, we performd an in silico screening to identify FDA-approved drugs that can inhibit Meis1 and Hoxb13 transcriptional activity based on the resolved crystal structure of Meis1 and Hoxb13 bound to DNA. Paromomycin (Paro) and neomycin (Neo) induced proliferation of neonatal rat ventricular myocytes in vitro and displayed dose-dependent inhibition of Meis1 and Hoxb13 transcriptional activity by luciferase assay and disruption of DNA binding by electromobility shift assay. X-ray crystal structure revealed that both Paro and Neo bind to Meis1 near the Hoxb13-interacting domain. Administration of Paro-Neo combination in adult mice and in pigs after cardiac ischemia/reperfusion injury induced cardiomyocyte proliferation, improved left ventricular systolic function and decreased scar formation. Collectively, we identified FDA-approved drugs with therapeutic potential for induction of heart regeneration in mammals.

Discovery of novel microRNA mimic repressors of ribosome biogenesis

While microRNAs and other non-coding RNAs are the next frontier of novel regulators of mammalian ribosome biogenesis (RB), a systematic exploration of microRNA-mediated RB regulation has not yet been undertaken. We carried out a high-content screen in MCF10A cells for changes in nucleolar number using a library of 2603 mature human microRNA mimics. Following a secondary screen for nucleolar rRNA biogenesis inhibition, we identified 72 novel microRNA negative regulators of RB after stringent hit calling. Hits included 27 well-conserved microRNAs present in MirGeneDB, and were enriched for mRNA targets encoding proteins with nucleolar localization or functions in cell cycle regulation. Rigorous selection and validation of a subset of 15 microRNA hits unexpectedly revealed that most of them caused dysregulated pre-rRNA processing, elucidating a novel role for microRNAs in RB regulation. Almost all hits impaired global protein synthesis and upregulated CDKN1A (p21) levels, while causing diverse effects on RNA Polymerase 1 (RNAP1) transcription and TP53 protein levels. We provide evidence that the MIR-28 siblings, hsa-miR-28-5p and hsa-miR-708-5p, potently target the ribosomal protein mRNA RPS28 via tandem primate-specific 3' UTR binding sites, causing a severe pre-18S pre-rRNA processing defect. Our work illuminates novel microRNA attenuators of RB, forging a promising new path for microRNA mimic chemotherapeutics.

Engineered bone marrow mesenchymal stem cell-derived exosomes loaded with miR302 through the cardiomyocyte specific peptide can reduce myocardial ischemia and reperfusion (I/R) injury

BACKGROUND

MicroRNA (miRNA)-based therapies have shown great potential in myocardial repair following myocardial infarction (MI). MicroRNA-302 (miR302) has been reported to exert a protective effect on MI. However, miRNAs are easily degraded and ineffective in penetrating cells, which limit their clinical applications. Exosomes, which are small bioactive molecules, have been considered as an ideal vehicle for miRNAs delivery due to their cell penetration, low immunogenicity and excellent stability potential. Herein, we explored cardiomyocyte-targeting exosomes as vehicles for delivery of miR302 into cardiomyocyte to potentially treat MI.

METHODS

To generate an efficient exosomal delivery system that can target cardiomyocytes, we engineered exosomes with cardiomyocyte specific peptide (CMP, WLSEAGPVVTVRALRGTGSW). Afterwards, the engineered exosomes were characterized and identified using transmission electron microscope (TEM) and Nanoparticle Tracking Analysis (NTA). Later on, the miR302 mimics were loaded into the engineered exosomes via electroporation technique. Subsequently, the effect of the engineered exosomes on myocardial ischemia and reperfusion (I/R) injury was evaluated in vitro and in vivo, including MTT, ELISA, real-time quantitative polymerase chain reaction (PCR), western blot, TUNNEL staining, echocardiogram and hematoxylin and eosin (HE) staining.

RESULTS

Results of in vitro experimentation showed that DSPE-PEG-CMP-EXO could be more efficiently internalized by H9C2 cells than unmodified exosomes (blank-exosomes). Importantly, compared with the DSPE-PEG-CMP-EXO group, DSPE-PEG-CMP-miR302-EXO significantly upregulated the expression of miR302, while exosomes loaded with miR302 could enhance proliferation of H9C2 cells. Western blot results showed that the DSPE-PEG-CMP-miR302-EXO significantly increased the protein level of Ki67 and Yap, which suggests that DSPE-PEG-CMP-miR302-EXO enhanced the activity of Yap, the principal downstream effector of Hippo pathway. In vivo, DSPE-PEG-CMP-miR302-EXO improved cardiac function, attenuated myocardial apoptosis and inflammatory response, as well as reduced infarct size significantly.

CONCLUSION

In conclusion, our findings suggest that CMP-engineered exosomes loaded with miR302 was internalized by H9C2 cells, an in vitro model for cardiomyocytes coupled with potential enhancement of the therapeutic effects on myocardial I/R injury.

MicroRNA205: A Key Regulator of Cardiomyocyte Transition from Proliferative to Hypertrophic Growth in the Neonatal Heart

The mammalian myocardium grows rapidly during early development due to cardiomyocyte proliferation, which later transitions to cell hypertrophy to sustain the heart's postnatal growth. Although this cell transition in the postnatal heart is consistently preserved in mammalian biology, little is known about the regulatory mechanisms that link proliferation suppression with hypertrophy induction. We reasoned that the production of a micro-RNA(s) could serve as a key bridge to permit changes in gene expression that control the changed cell fate of postnatal cardiomyocytes. We used sequential expression analysis to identify miR205 as a micro-RNA that was uniquely expressed at the cessation of cardiomyocyte growth. Cardiomyocyte-specific miR205 deletion animals showed a 35% increase in heart mass by 3 months of age, with commensurate changes in cell cycle and Hippo pathway activity, confirming miR205's potential role in controlling cardiomyocyte proliferation. In contrast, overexpression of miR205 in newborn hearts had little effect on heart size or function, indicating a complex, probably redundant regulatory system. These findings highlight miR205's role in controlling the shift from cardiomyocyte proliferation to hypertrophic development in the postnatal period.

Cell-Specific mRNA Therapeutics for Cardiovascular Diseases and Regeneration

Cardiovascular diseases (CVDs) represent a significant global health burden, demanding innovative therapeutic approaches. In recent years, mRNA therapeutics have emerged as a promising strategy to combat CVDs effectively. Unlike conventional small-molecule drugs, mRNA therapeutics enable the direct modulation of cellular functions by delivering specific mRNA molecules to target cells. This approach offers unprecedented advantages, including the ability to harness endogenous cellular machinery for protein synthesis, thus allowing precise control over gene expression without insertion into the genome. This review summarizes the current status of the potential of cell-specific mRNA therapeutics in the context of cardiovascular diseases. First, it outlines the challenges associated with traditional CVD treatments and emphasizes the need for targeted therapies. Subsequently, it elucidates the underlying principles of mRNA therapeutics and the development of advanced delivery systems to ensure cell-specificity and enhanced efficacy. Notably, innovative delivery methods such as lipid nanoparticles and exosomes have shown promise in improving the targeted delivery of mRNA to cardiac cells, activated fibroblasts, and other relevant cell types. Furthermore, the review highlights the diverse applications of cell-specific mRNA therapeutics in addressing various aspects of cardiovascular diseases, including atherosclerosis, myocardial infarction, heart failure, and arrhythmias. By modulating key regulatory genes involved in cardiomyocyte proliferation, inflammation, angiogenesis, tissue repair, and cell survival, mRNA therapeutics hold the potential to intervene at multiple stages of CVD pathogenesis. Despite its immense potential, this abstract acknowledges the challenges in translating cell-specific mRNA therapeutics from preclinical studies to clinical applications like off-target effects and delivery. In conclusion, cell-specific mRNA therapeutics have emerged as a revolutionary gene therapy approach for CVD, offering targeted interventions with the potential to significantly improve patient outcomes.

Myocardial ischemia/reperfusion: Translational pathophysiology of ischemic heart disease

Ischemic heart disease is the greatest health burden and most frequent cause of death worldwide. Myocardial ischemia/reperfusion is the pathophysiological substrate of ischemic heart disease. Improvements in prevention and treatment of ischemic heart disease have reduced mortality in developed countries over the last decades, but further progress is now stagnant, and morbidity and mortality from ischemic heart disease in developing countries are increasing. Significant problems remain to be resolved and require a better pathophysiological understanding. The present review attempts to briefly summarize the state of the art in myocardial ischemia/reperfusion research, with a view on both its coronary vascular and myocardial aspects, and to define the cutting edges where further mechanistic knowledge is needed to facilitate translation to clinical practice.

HOPX-associated molecular programs control cardiomyocyte cell states underpinning cardiac structure and function

Genomic regulation of cardiomyocyte differentiation is central to heart development and function. This study uses genetic loss-of-function human-induced pluripotent stem cell-derived cardiomyocytes to evaluate the genomic regulatory basis of the non-DNA-binding homeodomain protein HOPX. We show that HOPX interacts with and controls cardiac genes and enhancer networks associated with diverse aspects of heart development. Using perturbation studies in vitro, we define how upstream cell growth and proliferation control HOPX transcription to regulate cardiac gene programs. We then use cell, organoid, and zebrafish regeneration models to demonstrate that HOPX-regulated gene programs control cardiomyocyte function in development and disease. Collectively, this study mechanistically links cell signaling pathways as upstream regulators of HOPX transcription to control gene programs underpinning cardiomyocyte identity and function.

MiR-431 promotes cardiomyocyte proliferation by targeting FBXO32 expression

BACKGROUND

The induction of cardiomyocyte (CM) proliferation is a promising approach for cardiac regeneration following myocardial injury. MicroRNAs (miRNAs) have been reported to regulate CM proliferation. In particular, miR-431 expression decreases during cardiac development, according to Gene Expression Omnibus (GEO) microarray data. However, whether miR-431 regulates CM proliferation has not been thoroughly investigated.

METHODS

We used integrated bioinformatics analysis of GEO datasets to identify the most significantly differentially expressed miRNAs. Real-time quantitative PCR and fluorescence in situ hybridization were performed to determine the miRNA expression patterns in hearts. Gain- and loss-of-function assays were conducted to detect the role of miRNA in CM proliferation. Additionally, we detected whether miR-431 affected CM proliferation in a myocardial infarction model. The TargetScan, miRDB and miRWalk online databases were used to predict the potential target genes of miRNAs. Luciferase reporter assays were used to study miRNA interactions with the targeting mRNA.

RESULTS

First, we found a significant reduction in miR-431 levels during cardiac development. Then, by overexpression and inhibition of miR-431, we demonstrated that miR-431 promotes CM proliferation in vitro and in vivo, as determined by immunofluorescence assays of 5-ethynyl-2'-deoxyuridine (EdU), pH3, Aurora B and CM count, whereas miR-431 inhibition suppresses CM proliferation. Then, we found that miR-431 improved cardiac function post-myocardial infarction. In addition, we identified FBXO32 as a direct target gene of miR-431, with FBXO32 mRNA and protein expression being suppressed by miR-431. FBXO32 inhibited CM proliferation. Overexpression of FBXO32 blocks the enhanced effect of miR-431 on CM proliferation, suggesting that FBXO32 is a functional target of miR-431 during CM proliferation.

CONCLUSION

In summary, miR-431 promotes CM proliferation by targeting FBXO32, providing a potential molecular target for preventing myocardial injury.

The miR-17-92 cluster in cardiac health and disease

MicroRNAs (miRs) are small noncoding RNAs that play important roles in both physiological and pathological processes through post-transcriptional regulation. The miR-17-92 cluster includes six individual members: miR-17, miR-18a, miR-19a, miR-19b-1, miR-20a, and miR-92a-1. The miR-17-92 cluster has been extensively studied and reported to broadly function in cancer biology, immunology, neurology, pulmonology, and cardiology. This review focuses on its roles in heart development and cardiac diseases. We briefly introduce the nature of the miR-17-92 cluster and its crucial roles in both normal development and the pathogenesis of various diseases. We summarize the recent progress in understanding the versatile roles of miR-17-92 during cardiac development, regeneration, and aging. Additionally, we highlight the indispensable roles of the miR-17-92 cluster in pathogenesis and therapeutic potential in cardiac birth defects and adult cardiac diseases.

Cardiomyocyte maturation and its reversal during cardiac regeneration

Cardiovascular disease is a leading cause of death worldwide. Due to the limited proliferative and regenerative capacity of adult cardiomyocytes, the lost myocardium is not replenished efficiently and is replaced by a fibrotic scar, which eventually leads to heart failure. Current therapies to cure or delay the progression of heart failure are limited; hence, there is a pressing need for regenerative approaches to support the failing heart. Cardiomyocytes undergo a series of transcriptional, structural, and metabolic changes after birth (collectively termed maturation), which is critical for their contractile function but limits the regenerative capacity of the heart. In regenerative organisms, cardiomyocytes revert from their terminally differentiated state into a less mature state (ie, dedifferentiation) to allow for proliferation and regeneration to occur. Importantly, stimulating adult cardiomyocyte dedifferentiation has been shown to promote morphological and functional improvement after myocardial infarction, further highlighting the importance of cardiomyocyte dedifferentiation in heart regeneration. Here, we review several hallmarks of cardiomyocyte maturation, and summarize how their reversal facilitates cardiomyocyte proliferation and heart regeneration. A detailed understanding of how cardiomyocyte dedifferentiation is regulated will provide insights into therapeutic options to promote cardiomyocyte de-maturation and proliferation, and ultimately heart regeneration in mammals.

Mesenchymal Stem Cell-Derived Exosomal microRNAs in Cardiac Regeneration

Mesenchymal stem cell (MSC)-based therapy is one of the most promising modalities for cardiac repair. Accumulated evidence suggests that the therapeutic value of MSCs is mainly attributable to exosomes. MSC-derived exosomes (MSC-Exos) replicate the beneficial effects of MSCs by regulating various cellular responses and signaling pathways implicated in cardiac regeneration and repair. miRNAs constitute an important fraction of exosome content and are key contributors to the biological function of MSC-Exo. MSC-Exo carrying specific miRNAs provides anti-apoptotic, anti-inflammatory, anti-fibrotic, and angiogenic effects within the infarcted heart. Studying exosomal miRNAs will provide an important insight into the molecular mechanisms of MSC-Exo in cardiac regeneration and repair. This significant information can help optimize cell-free treatment and overcome the challenges associated with MSC-Exo therapeutic application. In this review, we summarize the characteristics and the potential mechanisms of MSC-derived exosomal miRNAs in cardiac repair and regeneration.

Inhibition of miR-199a-3p in a murine hypertrophic cardiomyopathy (HCM) model attenuates fibrotic remodeling

Background

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant genetic disorder, characterized by cardiomyocyte hypertrophy, cardiomyocyte disarray and fibrosis, which has a prevalence of ∼1: 200-500 and predisposes individuals to heart failure and sudden death. The mechanisms through which diverse HCM-causing mutations cause cardiac dysfunction remain mostly unknown and their identification may reveal new therapeutic avenues. MicroRNAs (miRNAs) have emerged as critical regulators of gene expression and disease phenotype in various pathologies. We explored whether miRNAs could play a role in HCM pathogenesis and offer potential therapeutic targets.

Methods and results

Using high-throughput miRNA expression profiling and qPCR analysis in two distinct mouse models of HCM, we found that miR-199a-3p expression levels are upregulated in mutant mice compared to age- and treatment-matched wild-type mice. We also found that miR-199a-3p expression is enriched in cardiac non-myocytes compared to cardiomyocytes. When we expressed miR-199a-3p mimic in cultured murine primary cardiac fibroblasts and analyzed the conditioned media by proteomics, we found that several extracellular matrix (ECM) proteins (e.g., TSP2, FBLN3, COL11A1, LYOX) were differentially secreted (data are available via ProteomeXchange with identifier PXD042904). We confirmed our proteomics findings by qPCR analysis of selected mRNAs and demonstrated that miR-199a-3p mimic expression in cardiac fibroblasts drives upregulation of ECM gene expression, including Tsp2, Fbln3, Pcoc1, Col1a1 and Col3a1. To examine the role of miR-199a-3p in vivo, we inhibited its function using lock-nucleic acid (LNA)-based inhibitors (antimiR-199a-3p) in an HCM mouse model. Our results revealed that progression of cardiac fibrosis is attenuated when miR-199a-3p function is inhibited in mild-to-moderate HCM. Finally, guided by computational target prediction algorithms, we identified mRNAs Cd151 and Itga3 as direct targets of miR-199a-3p and have shown that miR-199a-3p mimic expression negatively regulates AKT activation in cardiac fibroblasts.

Conclusions

Altogether, our results suggest that miR-199a-3p may contribute to cardiac fibrosis in HCM through its actions in cardiac fibroblasts. Thus, inhibition of miR-199a-3p in mild-to-moderate HCM may offer therapeutic benefit in combination with complementary approaches that target the primary defect in cardiac myocytes.

The characteristics of proliferative cardiomyocytes in mammals

Better understanding of the mechanisms regulating the proliferation of pre-existing cardiomyocyte (CM) should lead to better options for regenerating injured myocardium. The absence of a perfect research model to definitively identify newly formed mammalian CMs is lacking. However, methodologies are being developed to identify and enrich proliferative CMs. These methods take advantages of the different proliferative states of CMs during postnatal development, before and after injury in the neonatal heart. New approaches use CMs labeled in lineage tracing animals or single cell technique-based CM clusters. This review aims to provide a timely update on the characteristics of the proliferative CMs, including their structural, functional, genetic, epigenetic and metabolic characteristics versus non-proliferative CMs. A better understanding of the characteristics of proliferative CMs should lead to the mechanisms for inducing endogenous CMs to self-renew, which is a promising therapeutic strategy to treat cardiac diseases that cause CM death in humans.

Crafting a Blueprint for MicroRNA in Cardiovascular Diseases (CVDs)

Cardiovascular diseases (CVDs) encompass a range of disorders, from congenital heart malformation, cardiac valve, peripheral artery, coronary artery, cardiac muscle diseases, and arrhythmias, ultimately leading to heart failure. Despite therapeutic advancements, CVDs remain the primary cause of global mortality, highlighting the need for a thorough knowledge of CVDs at the level of molecular structure. Gene and microRNA (miRNA) expression variations significantly influence cellular pathways, impacting an organism's physiology. MiRNAs, in particular, serve as regulators of gene expression, playing critical roles in essential cellular pathways and influencing the development of various diseases, including CVD. A wealth of evidence supports the involvement of miRNAs in CVD progression. These findings highlight the potential of miRNAs as valuable diagnostic biomarkers and open new avenues for their therapeutic application in CVDs. This study focuses on the latest advancements in identifying and characterizing microRNAs, exploring their manipulation and clinical application, and discussing future perspectives.

Whole-genome doubling in tissues and tumors

The overwhelming majority of proliferating somatic human cells are diploid, and this genomic state is typically maintained across successive cell divisions. However, failures in cell division can induce a whole-genome doubling (WGD) event, in which diploid cells transition to a tetraploid state. While some WGDs are developmentally programmed to produce nonproliferative tetraploid cells with specific cellular functions, unscheduled WGDs can be catastrophic: erroneously arising tetraploid cells are ill-equipped to cope with their doubled cellular and chromosomal content and quickly become genomically unstable and tumorigenic. Deciphering the genetics that underlie the genesis, physiology, and evolution of whole-genome doubled (WGD+) cells may therefore reveal therapeutic avenues to selectively eliminate pathological WGD+ cells.

Drug Discovery for Adult Cardiomyocyte Regeneration: Opportunities and Challenges

Significance: Cardiovascular disease is a major contributor to human mortality and morbidity. The cardiac tissue undergoes fibrotic healing after injury because of the limited regenerative capacity of adult mammalian cardiomyocyte (CM). Extensive research has been performed to identify therapeutic targets for CM regeneration, as the success of promoting adult human CM regeneration to repair the injured heart is considered the Holy Grail in the field. Recent Advances: To date, more than 30 target genes have been shown to regulate adult mammalian CM proliferation. More than 20 targets have been validated in adult mouse myocardial infarction (MI) model in a therapeutic setting. In this review, the translational efficacy readouts from 17 selected pharmaceutical targets are summarized, among which the Hippo-yes-associated protein (Yap) pathway is the most extensively investigated and fits the criteria for a promising target for pro-CM-regeneration therapy development. Critical Issues and Future Directions: As the pro-CM-regeneration potential of current drug treatment for cardiovascular patients is limited, to help identify and fill the gap between basic research and drug discovery in this specific field, details regarding target identification, validation in mouse MI models, high-throughput screening assay development, and preclinical in vivo efficacy model optimization are discussed. Finally, suggestions and recommendations are also provided to help establish a common guideline for in vivo translational studies for drug discovery focusing on CM regeneration. Antioxid. Redox Signal. 39, 1070-1087.

Hippo pathway-manipulating neutrophil-mimic hybrid nanoparticles for cardiac ischemic injury via modulation of local immunity and cardiac regeneration

The promise of regeneration therapy for restoration of damaged myocardium after cardiac ischemic injury relies on targeted delivery of proliferative molecules into cardiomyocytes whose healing benefits are still limited owing to severe immune microenvironment due to local high concentration of proinflammatory cytokines. Optimal therapeutic strategies are therefore in urgent need to both modulate local immunity and deliver proliferative molecules. Here, we addressed this unmet need by developing neutrophil-mimic nanoparticles NM@miR, fabricated by coating hybrid neutrophil membranes with artificial lipids onto mesoporous silica nanoparticles (MSNs) loaded with microRNA-10b. The hybrid membrane could endow nanoparticles with strong capacity to migrate into inflammatory sites and neutralize proinflammatory cytokines and increase the delivery efficiency of microRNA-10b into adult mammalian cardiomyocytes (CMs) by fusing with cell membranes and leading to the release of MSNs-miR into cytosol. Upon NM@miR administration, this nanoparticle could home to the injured myocardium, restore the local immunity, and efficiently deliver microRNA-10b to cardiomyocytes, which could reduce the activation of Hippo-YAP pathway mediated by excessive cytokines and exert the best proliferative effect of miR-10b. This combination therapy could finally improve cardiac function and mitigate ventricular remodeling. Consequently, this work offers a combination strategy of immunity modulation and proliferative molecule delivery to boost cardiac regeneration after injury.

Progress in bioprinting technology for tissue regeneration

In recent years, due to the increase in diseases that require organ/tissue transplantation and the limited donor, on the other hand, patients have lost hope of recovery and organ transplantation. Regenerative medicine is one of the new sciences that promises a bright future for these patients by providing solutions to repair, improve function, and replace tissue. One of the technologies used in regenerative medicine is three-dimensional (3D) bioprinters. Bioprinting is a new strategy that is the basis for starting a global revolution in the field of medical sciences and has attracted much attention. 3D bioprinters use a combination of advanced biology and cell science, computer science, and materials science to create complex bio-hybrid structures for various applications. The capacity to use this technology can be demonstrated in regenerative medicine to make various connective tissues, such as skin, cartilage, and bone. One of the essential parts of a 3D bioprinter is the bio-ink. Bio-ink is a combination of biologically active molecules, cells, and biomaterials that make the printed product. In this review, we examine the main bioprinting strategies, such as inkjet printing, laser, and extrusion-based bioprinting, as well as some of their applications.

Integrated small RNA, mRNA and protein omics reveal a miRNA network orchestrating metabolic maturation of the developing human heart

BACKGROUND

As the fetal heart develops, cardiomyocyte proliferation potential decreases while fatty acid oxidative capacity increases in a highly regulated transition known as cardiac maturation. Small noncoding RNAs, such as microRNAs (miRNAs), contribute to the establishment and control of tissue-specific transcriptional programs. However, small RNA expression dynamics and genome-wide miRNA regulatory networks controlling maturation of the human fetal heart remain poorly understood.

RESULTS

Transcriptome profiling of small RNAs revealed the temporal expression patterns of miRNA, piRNA, circRNA, snoRNA, snRNA and tRNA in the developing human heart between 8 and 19 weeks of gestation. Our analysis demonstrated that miRNAs were the most dynamically expressed small RNA species throughout mid-gestation. Cross-referencing differentially expressed miRNAs and mRNAs predicted 6200 mRNA targets, 2134 of which were upregulated and 4066 downregulated as gestation progressed. Moreover, we found that downregulated targets of upregulated miRNAs, including hsa-let-7b, miR-1-3p, miR-133a-3p, miR-143-3p, miR-499a-5p, and miR-30a-5p predominantly control cell cycle progression. In contrast, upregulated targets of downregulated miRNAs, including hsa-miR-1276, miR-183-5p, miR-1229-3p, miR-615-3p, miR-421, miR-200b-3p and miR-18a-3p, are linked to energy sensing and oxidative metabolism. Furthermore, integrating miRNA and mRNA profiles with proteomes and reporter metabolites revealed that proteins encoded in mRNA targets and their associated metabolites mediate fatty acid oxidation and are enriched as the heart develops.

CONCLUSIONS

This study presents the first comprehensive analysis of the small RNAome of the maturing human fetal heart. Our findings suggest that coordinated activation and repression of miRNA expression throughout mid-gestation is essential to establish a dynamic miRNA-mRNA-protein network that decreases cardiomyocyte proliferation potential while increasing the oxidative capacity of the maturing human fetal heart. Our results provide novel insights into the molecular control of metabolic maturation of the human fetal heart.

Age-related promoter-switch regulates Runx1 expression in adult rat hearts

BACKGROUND

Runt-related transcription factor-1 (RUNX1), a key member of the core-binding factor family of transcription factors, has emerged as a novel therapeutic target for cardiovascular disease. There is an urgent need to fully understand the expression pattern of Runx1 in the heart and the mechanisms by which it is controlled under normal conditions and in response to disease. The expression of Runx1 is regulated at the transcriptional level by two promoters designated P1 and P2. Alternative usage of these two promoters creates differential mRNA transcripts diversified in distribution and translational potential. While the significance of P1/P2 promoter-switch in the transcriptional control of Runx1 has been highlighted in the embryogenic process, very little is known about the level of P1- and P2-specific transcripts in adult hearts, and the underlying mechanisms controlling the promoter-switch.

METHODS

To amplify P1/P2 specific sequences in the heart, we used two different sense primers complementary to either P1 or P2 5'-regions to monitor the expression of P1/P2 transcripts. DNA methylation levels were assessed at the Runx1 promoter regions. Rats were grouped by age.

RESULTS

The expression levels of both P1- and P2-derived Runx1 transcripts were decreased in older rats when compared with that in young adults, paralleled with an age-dependent decline in Runx1 protein level. Furthermore, older rats demonstrated a higher degree of DNA methylation at Runx1 promoter regions. Alternative promoter usage was observed in hearts with increased age, as reflected by altered P1:P2 mRNA ratio.

CONCLUSION

Our data demonstrate that the expression of Runx1 in the heart is age-dependent and underscore the importance of gene methylation in the promoter-mediated transcriptional control of Runx1, thereby providing new insights to the role of epigenetic regulation in the heart.

Extracellular vesicles and microRNAs in the regulation of cardiomyocyte differentiation and proliferation

Cardiomyocyte differentiation and proliferation are essential processes for the regeneration of an injured heart. In recent years, there have been several reports highlighting the involvement of extracellular vesicles (EVs) in cardiomyocyte differentiation and proliferation. These EVs originate from mesenchymal stem cells, pluripotent stem cells, and heart constituting cells (cardiomyocytes, cardiac fibroblasts, cardiac progenitor cells, epicardium). Numerous reports also indicate the involvement of microRNAs (miRNAs) in cardiomyocyte differentiation and proliferation. Among them, miRNA-1, miRNA-133, and miRNA-499, recently demonstrated to promote cardiomyocyte differentiation, and miRNA-199, shown to promote cardiomyocyte proliferation, were found effective in various studies. MiRNA-132 and miRNA-133 have been identified as cargo in EVs and are reported to induce cardiomyocyte differentiation. Similarly, miRNA-30a, miRNA-100, miRNA-27a, miRNA-30e, miRNA-294 and miRNA-590 have also been identified as cargo in EVs and are shown to have a role in the promotion of cardiomyocyte proliferation. Regeneration of the heart by EVs or artificial nanoparticles containing functional miRNAs is expected in the future. In this review, we outline recent advancements in understanding the roles of EVs and miRNAs in cardiomyocyte differentiation and proliferation. Additionally, we explore the related challenges when utilizing EVs and miRNAs as a less risky approach to cardiac regeneration compared to cell transplantation.

Discovery of novel microRNA mimic repressors of ribosome biogenesis

While microRNAs and other non-coding RNAs are the next frontier of novel regulators of mammalian ribosome biogenesis (RB), a systematic exploration of microRNA-mediated RB regulation has not yet been undertaken. We carried out a high-content screen in MCF10A cells for changes in nucleolar number using a library of 2,603 mature human microRNA mimics. Following a secondary screen for nucleolar rRNA biogenesis inhibition, we identified 72 novel microRNA negative regulators of RB after stringent hit calling. Hits included 27 well-conserved microRNAs present in MirGeneDB, and were enriched for mRNA targets encoding proteins with nucleolar localization or functions in cell cycle regulation. Rigorous selection and validation of a subset of 15 microRNA hits unexpectedly revealed that most of them caused dysregulated pre-rRNA processing, elucidating a novel role for microRNAs in RB regulation. Almost all hits impaired global protein synthesis and upregulated CDKN1A ( p21 ) levels, while causing diverse effects on RNA Polymerase 1 (RNAP1) transcription and TP53 protein levels. We discovered that the MIR-28 siblings, hsa-miR-28-5p and hsa-miR-708-5p, directly and potently target the ribosomal protein mRNA RPS28 via tandem primate-specific 3' UTR binding sites, causing a severe pre-18S pre-rRNA processing defect. Our work illuminates novel microRNA attenuators of RB, forging a promising new path for microRNA mimic chemotherapeutics.