Circulating p53-responsive microRNAs are predictive indicators of heart failure after acute myocardial infarction

Exosomes: Therapy delivery tools and biomarkers of diseases

Virtually all cells in the organism secrete extracellular vesicles (EVs), a heterogeneous population of lipid bilayer membrane-enclosed vesicles that transport and deliver payloads of proteins and nucleic acids to recipient cells, thus playing central roles in cell-cell communications. Exosomes, nanosized EVs of endosomal origin, regulate many pathophysiological processes including immune responses and inflammation, tumour growth, and infection. Healthy subjects and patients with different diseases release exosomes with different RNA and protein contents into the circulation, which can be measured as biomarkers. The discovery of exosomes as natural carriers of functional small RNA and proteins has raised great interest in the drug delivery field, as it may be possible to harness these vesicles for therapeutic delivery of miRNA, siRNA, mRNA, lncRNA, peptides, and synthetic drugs. However, systemically delivered exosomes accumulate in liver, kidney, and spleen. Targeted exosomes can be obtained by displaying targeting molecules, such as peptides or antibody fragments recognizing target antigens, on the outer surface of exosomes. Display of glycosylphosphatidylinositol (GPI)-anchored nanobodies on EVs is a novel technique that enables EV display of a variety of proteins including antibodies, reporter proteins, and signaling molecules. However, naturally secreted exosomes show limited pharmaceutical acceptability. Engineered exosome mimetics that incorporate desirable components of natural exosomes into synthetic liposomes or nanoparticles, and are assembled using controllable procedures may be more acceptable pharmaceutically. In this communication, we review the current understanding of physiological and pathophysiological roles of exosomes, their potential applications as diagnostic markers, and current efforts to develop improved exosome-based drug delivery systems.

Extracellular vesicles in coronary artery disease

Membrane vesicles released in the extracellular space are composed of a lipid bilayer enclosing soluble cytosolic material and nuclear components. Extracellular vesicles include apoptotic bodies, exosomes, and microvesicles (also known previously as microparticles). Originating from different subcellular compartments, the role of extracellular vesicles as regulators of transfer of biological information, acting locally and remotely, is now acknowledged. Circulating vesicles released from platelets, erythrocytes, leukocytes, and endothelial cells contain potential valuable biological information for biomarker discovery in primary and secondary prevention of coronary artery disease. Extracellular vesicles also accumulate in human atherosclerotic plaques, where they affect major biological pathways, including inflammation, proliferation, thrombosis, calcification, and vasoactive responses. Extracellular vesicles also recapitulate the beneficial effect of stem cells to treat cardiac consequences of acute myocardial infarction, and now emerge as an attractive alternative to cell therapy, opening new avenues to vectorize biological information to target tissues. Although interest in microvesicles in the cardiovascular field emerged about 2 decades ago, that for extracellular vesicles, in particular exosomes, started to unfold a decade ago, opening new research and therapeutic avenues. This Review summarizes current knowledge on the role of extracellular vesicles in coronary artery disease, and their emerging potential as biomarkers and therapeutic agents.

Exosomal miRNAs in Heart Disease

Micro-RNAs (miRNAs) are small noncoding RNAs involved in the posttranscriptional regulation of gene expression. Exosomes have recently emerged as novel elements of intercellular communication in the cardiovascular system. Exosomal miRNAs could be key players in intercellular cross-talk, particularly during different diseases such as myocardial infarction (MI) and heart failure (HF). This review addresses the functional role played by exosomal miRNAs in heart disease and their potential use as new biomarkers.

Exosomes Mediate the Beneficial Effects of Exercise

It is known that moderate exercise can prevent the development of cardiovascular diseases, but the exact molecular mechanisms mediating cardioprotective effect of exercise remain unknown. Emerging evidence suggests that exercise has great impact on the biogenesis of exosomes, which have been found in both interstitial fluid and circulation, and play important roles in cellular communication. Exosomes carry functional molecules such as mRNAs, microRNA, and specific proteins, which can be used in the early diagnosis and targeted therapy of a variety of diseases. Our review focus on the current knowledge on exosome production, secretion, uptake and how exercise influence exosome content. We also highlight recent research development in exosome based approach for cardiac repair.

Exosomes-Based Biomarkers for the Prognosis of Cardiovascular Diseases

Cardiovascular diseases (CVDs) have a high prevalence and annually increasing incidence with high mortality and morbidity. Identification of biomarkers with high sensitivity and specificity for assessing the prognosis of CVDs is necessary for optimizing personalized treatment and reducing mortality. Exosomes have been proved to be accessible in nearly all body fluids and they can reflect disease stage or progression. Here we summarized exosomes-based biomarkers for the prognosis of coronary artery diseases, heart failure, stroke, hypertension, cardiac arrhythmia, cardiomyopathy, valvular heart diseases and pulmonary arterial hypertension. If exosome-based biomarkers can achieve additionally benefits as compared to the present prognostic biomarkers remains to be determined and multicenter studies with large cohorts of patients are highly needed.

The Multifaceted Functions of Exosomes in Health and Disease: An Overview

Exosomes are extracellular vesicles of 50-150 nm in diameter secreted by basically all cell types. They mediate micro-communication among cells, tissues, and organs under both healthy and disease conditions by virtue of their ability to deliver macromolecules to target cells. Research on exosomes is a rapidly growing field, however many aspects of their biogenesis and functions still await a complete clarification. In our review we summarize most recent findings regarding biogenesis, structure, and functions of exosomes. In addition, an overview regarding the role of exosomes in both infectious and non-infectious diseases is provided. Finally, the use of exosomes as biomarkers and delivery tools for therapeutic molecules is addressed. Considering the body of literature data, exosomes have to be considered key components of the intercellular communication in both health and disease.

Stem cell therapy for ischemic heart diseases

INTRODUCTION

Ischemic heart diseases, especially the myocardial infarction, is a major hazard problem to human health. Despite substantial advances in control of risk factors and therapies with drugs and interventions including bypass surgery and stent placement, the ischemic heart diseases usually result in heart failure (HF), which could aggravate social burden and increase the mortality rate. The current therapeutic methods to treat HF stay at delaying the disease progression without repair and regeneration of the damaged myocardium. While heart transplantation is the only effective therapy for end-stage patients, limited supply of donor heart makes it impossible to meet the substantial demand from patients with HF. Stem cell-based transplantation is one of the most promising treatment for the damaged myocardial tissue.

SOURCES OF DATA

Key recent published literatures and ClinicalTrials.gov.

AREAS OF AGREEMENT

Stem cell-based therapy is a promising strategy for the damaged myocardial tissue. Different kinds of stem cells have their advantages for treatment of Ischemic heart diseases.

AREAS OF CONTROVERSY

The efficacy and potency of cell therapies vary significantly from trial to trial; some clinical trials did not show benefit. Diverged effects of cell therapy could be affected by cell types, sources, delivery methods, dose and their mechanisms by which delivered cells exert their effects.

GROWING POINTS

Understanding the origin of the regenerated cardiomyocytes, exploring the therapeutic effects of stem cell-derived exosomes and using the cell reprogram technology to improve the efficacy of cell therapy for cardiovascular diseases.

AREAS TIMELY FOR DEVELOPING RESEARCH

Recently, stem cell-derived exosomes emerge as a critical player in paracrine mechanism of stem cell-based therapy. It is promising to exploit exosomes-based cell-free therapy for ischemic heart diseases in the future.

Exosomes as Diagnostic Biomarkers in Cardiovascular Diseases

Exosomes play important roles in the development and progression of cardiovascular diseases by modulating intercellular communication. Contents and quantities of exosomes are variable under different pathological cardiovascular conditions. Based on these concepts, exosomes have been proposed as novel diagnostic biomarkers in cardiovascular diseases. However, many issues related with clinically applicable biomarkers remain unresolved. Within this chapter, we discuss the potential value, but also the current challenges using exosome numbers and contents as diagnostic and prognostic biomarker in diverse cardiovascular pathologies.

Circulating Exosomes in Cardiovascular Diseases

Circulating exosomes could arrive in distant tissues via blood circulation, thus directly communicating with target cells and rapidly regulating intracellular signalings. Circulating exosomes and exosomal cargos are critically involved in cardiovascular pathophysiology, such as cardiomyocyte hypertrophy, apoptosis, and angiogenesis. Circulating exosomes enriched with various types of biological molecules can be changed not only in the number but also in the composite cargos upon cardiac injury, such as myocardial infarction, myocardial ischemia reperfusion injury, atherosclerosis, hypertension, and sepsis cardiomyopathy, which may further influence cardiomyocyte function and contribute to the pathogenesis of cardiovascular diseases. Thus, exosome-based therapeutic strategy may be used to attenuate myocardial injury and promote cardiac regeneration and repair. Also, more preclinical and clinical studies would be needed to investigate the potential of circulating exosomes as biomarkers for the diagnosis, risk stratification, and prognosis of cardiovascular diseases.

Implications of dynamic changes in miR-192 expression in ischemic acute kidney injury

Purpose

Ischemia–reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) with poor outcomes. While many important functions of microRNAs (miRNAs) have been identified in various diseases, few studies reported miRNAs in acute kidney IRI, especially the dynamic changes in their expression and their implications during disease progression.

Methods

The expression of miR-192, a specific kidney-enriched miRNA, was assessed in both the plasma and kidney of IRI rats at different time points after kidney injury and compared to renal function and kidney histological changes. The results were validated in the plasma of the selected patients with AKI after cardiac surgery compared with those matched patients without AKI. The performance characteristics of miR-192 were summarized using area under the receiver operator characteristic (ROC) curves (AUC-ROC).

Results

MiRNA profiling in plasma led to the identification of 42 differentially expressed miRNAs in the IRI group compared to the sham group. MiR-192 was kidney-enriched and chosen for further validation. Real-time PCR showed that miR-192 levels increased by fourfold in the plasma and decreased by about 40% in the kidney of IRI rats. Plasma miR-192 expression started increasing at 3 h and peaked at 12 h, while kidney miR-192 expression started decreasing at 6 h and remained at a low level for 7 days after reperfusion. Plasma miR-192 level in patients with AKI increased at the time of ICU admission, was stable for 2 h and decreased after 24 h. AUC-ROC was 0.673 (95% CI: 0.540–0.806, p = 0.014).

Conclusions

Plasma miR-192 expression was induced in a time-dependent manner after IRI in rats and patients with AKI after cardiac surgery, comparably to the kidney injury development and recovery process, and may be useful for the detection of AKI.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

Novel Biomarker MicroRNAs for Subtyping of Acute Coronary Syndrome: A Bioinformatics Approach

Acute coronary syndrome (ACS) is a life-threatening disease that affects more than half a million people in United States. We currently lack molecular biomarkers to distinguish the unstable angina (UA) and acute myocardial infarction (AMI), which are the two subtypes of ACS. MicroRNAs play significant roles in biological processes and serve as good candidates for biomarkers. In this work, we collected microRNA datasets from the Gene Expression Omnibus database and identified specific microRNAs in different subtypes and universal microRNAs in all subtypes based on our novel network-based bioinformatics approach. These microRNAs were studied for ACS association by pathway enrichment analysis of their target genes. AMI and UA were associated with 27 and 26 microRNAs, respectively, nine of them were detected for both AMI and UA, and five from each subtype had been reported previously. The remaining 22 and 21 microRNAs are novel microRNA biomarkers for AMI and UA, respectively. The findings are then supported by pathway enrichment analysis of the targets of these microRNAs. These novel microRNAs deserve further validation and will be helpful for personalized ACS diagnosis.

Screening of circulating microRNA biomarkers for prevalence of abdominal aortic aneurysm and aneurysm growth

BACKGROUND AND AIMS

MicroRNA (miR) are important regulators of gene expression and biological processes and have recently been suggested as possible biomarkers for abdominal aortic aneurysm (AAA) disease. The aim of the present study was to assess the role of miR as biomarkers for initiation and progression of AAA disease, through evaluation of a wide range of miRs in a large population-based cohort, with AAA patients with linked clinical data regarding risk factors, AAA size and growth, as well as controls.

METHODS

The expression of the 172 most commonly expressed miRs in plasma was analyzed by real-time PCR in samples from 169 screening-detected AAA patients and 48 age-matched controls.

RESULTS

For 103 miRs, there was a significant difference in expression between AAA and controls. Of these, 20 miRs were differently expressed between fast and slow growing aneurysms. These miRs target genes known to be involved in AAA disease as well as novel genes and pathways. By combining the top altered miRs together with clinical variables, strong predictive values, determining growth of AAA, were obtained (area under curve = 0.86, p < 0.001).

CONCLUSIONS

This large cohort study identified several novel miRs with altered expression in AAA patients when compared to controls. Assessment of miR expression may offer an opportunity to predict disease progression and aneurysm growth.

Aberrant Expression of miR-323a-5p in Patients with Refractory Epilepsy Caused by Focal Cortical Dysplasia

BACKGROUND

Epilepsy remains one of the most common clinical neurological disorders. About a third of patients with epilepsy are refractory to drug treatment, mainly as a result of focal cortical dysplasia (FCD). In this study, we analyzed the aberrant expression of microRNAs (miRNAs) in the cortex and plasma of FCD patients.

METHODS

Cortical samples were collected from nine patients with refractory epilepsy caused by FCD who underwent surgery, and from eight volunteers (control group) undergoing emergency surgery for hypertensive cerebral hemorrhage. miRNA expression in the cortex was detected by microarray analysis and miR-323a-5p expression levels in the cortex were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). We also collected plasma samples from 30 patients with refractory epilepsy caused by FCD and from 23 healthy controls, and compared differential expression of miR-323a-5p in the plasma using qRT-PCR.

RESULTS

miRNA microarray analysis showed that expression of miR-323a-5p was upregulated in the FCD group compared with the control group, and miR-323a-5p expression levels in the cortex analyzed by qRT-PCR supported those obtained by microarray analysis. Plasma levels of miR-323a-5p were significantly higher in patient plasma compared with the healthy controls, as determined by qRT-PCR. Furthermore, expression of miR-323a-5p was positively correlated with the duration of epilepsy (p = 0.014) and seizure frequency (p = 0.043). The effectiveness of surgery in patients with FCD was significantly poorer in patients with high plasma levels of miR-323a-5p compared with those with low levels.

CONCLUSIONS

The expression of miR-323a-5p was significantly elevated in the cortex and plasma of FCD patients. These results suggest that abnormal expression of miR-323a-5p could be used for improving the current diagnosis of FCD and monitoring treatment responses in patients with FCD.

Thyroid hormones and cardiovascular disease

Myocardial and vascular endothelial tissues have receptors for thyroid hormones and are sensitive to changes in the concentrations of circulating thyroid hormones. The importance of thyroid hormones in maintaining cardiovascular homeostasis can be deduced from clinical and experimental data showing that even subtle changes in thyroid hormone concentrations - such as those observed in subclinical hypothyroidism or hyperthyroidism, and low triiodothyronine syndrome - adversely influence the cardiovascular system. Some potential mechanisms linking the two conditions are dyslipidaemia, endothelial dysfunction, blood pressure changes, and direct effects of thyroid hormones on the myocardium. Several interventional trials showed that treatment of subclinical thyroid diseases improves cardiovascular risk factors, which implies potential benefits for reducing cardiovascular events. Over the past 2 decades, accumulating evidence supports the association between abnormal thyroid function at the time of an acute myocardial infarction (MI) and subsequent adverse cardiovascular outcomes. Furthermore, experimental studies showed that thyroid hormones can have an important therapeutic role in reducing infarct size and improving myocardial function after acute MI. In this Review, we summarize the literature on thyroid function in cardiovascular diseases, both as a risk factor as well as in the setting of cardiovascular diseases such as heart failure or acute MI, and outline the effect of thyroid hormone replacement therapy for reducing the risk of cardiovascular disease.

MicroRNAs in Coronary Heart Disease: Ready to Enter the Clinical Arena?

Coronary artery disease (CAD) and its complication remain the leading cause of mortality in industrialized countries despite great advances in terms of diagnosis, prognosis, and treatment options. MicroRNAs (miRNAs), small noncoding RNAs, act as posttranscriptional gene expression modulators and have been implicated as key regulators in several physiological and pathological processes linked to CAD. Circulating miRNAs have been evaluated as promising novel biomarkers of CAD, acute coronary syndromes, and acute myocardial infarction, with prognostic implications. Several challenges related to technical aspects, miRNAs normalization, drugs interaction, and quality reporting of statistical multivariable analysis of the miRNAs observational studies remain unresolved. MicroRNA-based therapies in cardiovascular diseases are not ready yet for human trials but definitely appealing. Through this review we will provide clinicians with a concise overview of the pros and cons of microRNAs.

miR-192-5p mediates hypoxia/reoxygenation-induced apoptosis in H9c2 cardiomyocytes via targeting of FABP3

Myocardial ischemia/reperfusion (I/R) injury is a leading cause of morbidity and mortality. In this study, we investigated the role of miR-192-5p in hypoxia/reoxygenation (H/R)-induced cardiomyocyte apoptosis. H9c2 cardiomyocytes were subjected to H/R and tested for miR-192-5p expression. Overexpression and knockdown experiments were performed to determine the effects of manipulating miR-192-5p on apoptotic responses. H/R-treated H9c2 cells exhibited a 2.2-fold increase in miR-192-5p levels. Overexpression of miR-192-5p significantly augmented apoptosis in H9c2 cells after H/R, which was accompanied by a significant increase in the ratio of Bax/Bcl-2. In contrast, delivery of anti-miR-192-5p inhibitors significantly reduced apoptosis induced by H/R. FABP3 was identified to be a functional target of miR-192-5p. Restoration of FABP3 prevented apoptosis in miR-192-5p-transfected H9c2 cells, whereas downregulation of FABP3 enhanced apoptosis in H/R-exposed H9c2 cells. In conclusion, miR-192-5p mediates H/R-induced apoptosis in cardiomyocytes by targeting FABP3 and represents a potential target for prevention of myocardial I/R injury.

Circulating miR-122-5p/miR-133b Ratio Is a Specific Early Prognostic Biomarker in Acute Myocardial Infarction

BACKGROUND

MicroRNAs (miRNAs) are key players in cardiovascular development and disease. However, not only miRNAs of a cardiac origin have a critical role in heart function. Recent studies have demonstrated that miR-122-5p, a hepatic miRNA, increases in the bloodstream during ischemic cardiogenic shock and it is upregulated in the infarcted myocardium. The aim of the present study was to determine the potential of circulating miR-122-5p as a biomarker for early prognostic stratification of ST-segment elevation acute myocardial infarction (STEMI) patients.

METHODS AND RESULTS

One hundred and forty-two consecutive STEMI patients treated with primary angioplasty were included in the study. Serum levels of miR-1-3p, -122-5p, -133a-3p, -133b, -208b-3p and -499a-5p were measured at the time of cardiac catheterization by quantitative polymerase chain reaction and related to in-hospital and long-term outcome. During a follow up of 20.8 months, 9 patients died, 6 had recurrence of myocardial infarction, and 26 patients suffered an adverse cardiovascular event. Event-free survival was significantly worse in patients with a higher miR-122-5p/133b ratio (3rd tertile distribution, above 1.42 Log(10)), having almost a 9-fold higher risk of death or myocardial infarction and a 4-fold higher risk of adverse cardiovascular events.

CONCLUSIONS

This study showed that the miR-122-5p/133b ratio is a new prognostic biomarker for the early identification of STEMI patients at a higher risk of developing major adverse events after undergoing primary percutaneous coronary intervention. (Circ J 2016; 80: 2183-2191).

Natriuretic peptides as biomarkers of cardiac endocrine function in heart failure: new challenges and perspectives

Several studies indicated that B-type natriuretic peptide (BNP) assay is able to detect patients even in the early phases of heart failure (HF), when the myocardial remodeling process may be still reversible. BNP assay may assist the physician to initiate appropriate and prompt pharmacological treatments. However, clinical relevance and result interpretation of BNP assay for the guide of therapy or in particular clinical conditions, such as renal failure or treatment with inhibitors of enzymes degrading BNP in HF patients, are still debated. The aim of this article is to discuss some still controversial issues concerning the clinical use of measurement of cardiac natriuretic peptides, and also to provide a general overview and some perspectives related to pathophysiological mechanisms of HF.

The beagle dog MicroRNA tissue atlas: identifying translatable biomarkers of organ toxicity

Background

MicroRNAs (miRNA) are varied in length, under 25 nucleotides, single-stranded noncoding RNA that regulate post-transcriptional gene expression via translational repression or mRNA degradation. Elevated levels of miRNAs can be detected in systemic circulation after tissue injury, suggesting that miRNAs are released following cellular damage. Because of their remarkable stability, ease of detection in biofluids, and tissue specific expression patterns, miRNAs have the potential to be specific biomarkers of organ injury. The identification of miRNA biomarkers requires a systematic approach: 1) determine the miRNA tissue expression profiles within a mammalian species via next generation sequencing; 2) identify enriched and/or specific miRNA expression within organs of toxicologic interest, and 3) in vivo validation with tissue-specific toxicants. While miRNA tissue expression has been reported in rodents and humans, little data exists on miRNA tissue expression in the dog, a relevant toxicology species. The generation and evaluation of the first dog miRNA tissue atlas is described here.

Results

Analysis of 16 tissues from five male beagle dogs identified 106 tissue enriched miRNAs, 60 of which were highly enriched in a single organ, and thus may serve as biomarkers of organ injury. A proof of concept study in dogs dosed with hepatotoxicants evaluated a qPCR panel of 15 tissue enriched miRNAs specific to liver, heart, skeletal muscle, pancreas, testes, and brain. Dogs with elevated serum levels of miR-122 and miR-885 had a correlative increase of alanine aminotransferase, and microscopic analysis confirmed liver damage. Other non-liver enriched miRNAs included in the screening panel were unaffected. Eli Lilly authors created a complimentary Sprague Dawely rat miRNA tissue atlas and demonstrated increased pancreas enriched miRNA levels in circulation, following caerulein administration in rat and dog.

Conclusion

The dog miRNA tissue atlas provides a resource for biomarker discovery and can be further mined with refinement of dog genome annotation. The 60 highly enriched tissue miRNAs identified within the dog miRNA tissue atlas could serve as diagnostic biomarkers and will require further validation by in vivo correlation to histopathology. Once validated, these tissue enriched miRNAs could be combined into a powerful qPCR screening panel to identify organ toxicity during early drug development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2958-x) contains supplementary material, which is available to authorized users.

Sex differences in response to miRNA-34a therapy in mouse models of cardiac disease: identification of sex-, disease- and treatment-regulated miRNAs

KEY POINTS

MicroRNA (miRNA)-based therapies are in development for numerous diseases, including heart disease. Currently, very limited basic information is available on the regulation of specific miRNAs in male and female hearts in settings of disease. The identification of sex-specific miRNA signatures has implications for translation into the clinic and suggests the need for customised therapy. In the present study, we found that a miRNA-based treatment inhibiting miRNA-34a (miR-34a) was more effective in females in a setting of moderate dilated cardiomyopathy than in males. Furthermore, the treatment showed little benefit for either sex in a setting of more severe dilated cardiomyopathy associated with atrial fibrillation. The results highlight the importance of understanding the effect of miRNA-based therapies in cardiac disease settings in males and females.

ABSTRACT

MicroRNA (miRNA)-34a (miR-34a) is elevated in the diseased heart in mice and humans. Previous studies have shown that inhibiting miR-34a in male mice in settings of pathological cardiac hypertrophy or ischaemia protects the heart against progression to heart failure. Whether inhibition of miR-34a protects the female heart is unknown. Furthermore, the therapeutic potential of silencing miR-34a in settings of dilated cardiomyopathy (DCM) and atrial fibrillation (AF) has not been assessed previously. In the present study, we examined the effect of silencing miR-34a in males and females in (1) a model of moderate DCM and (2) a model of severe DCM with AF. The cardiac disease models were administered with a locked nucleic acid-modified oligonucleotide (LNA-antimiR-34a) at 6-7 weeks of age when the models display cardiac dysfunction and conduction abnormalities. Cardiac function and morphology were measured 6 weeks after treatment. In the present study, we show that inhibition of miR-34a provides more protection in the DCM model in females than males. Disease prevention in LNA-antimiR-34a treated DCM female mice was characterized by attenuated heart enlargement and lung congestion, lower expression of cardiac stress genes (B-type natriuretic peptide, collagen gene expression), less cardiac fibrosis and better cardiac function. There was no evidence of significant protection in the severe DCM and AF model in either sex. Sex- and treatment-dependent regulation of miRNAs was also identified in the diseased heart, and may explain the differential response of males and females. These studies highlight the importance of examining the impact of miRNA-based drugs in both sexes and under different disease conditions.

Genes and miRNA expression signatures in peripheral blood mononuclear cells in healthy subjects and patients with metabolic syndrome after acute intake of extra virgin olive oil

Extra virgin olive oil (EVOO) consumption has been associated with reduced cardiovascular risk but molecular mechanisms underlying its beneficial effects are not fully understood. Here we aimed to identify genes and miRNAs expression changes mediated by acute high- and low-polyphenols EVOO intake. Pre- and post-challenge gene and miRNAs expression analysis was performed on the peripheral blood mononuclear cells (PBMCs) of 12 healthy subjects and 12 patients with metabolic syndrome (MS) by using microarray and RT-qPCR. In healthy subjects, acute intake of EVOO rich in polyphenols was able to ameliorate glycaemia and insulin sensitivity, and to modulate the transcription of genes and miRNAs involved in metabolism, inflammation and cancer, switching PBMCs to a less deleterious inflammatory phenotype; weaker effects were observed in patients with MS as well as in healthy subjects following low-polyphenol EVOO challenge. Concluding, our study shows that acute high-polyphenols EVOO intake is able to modify the transcriptome of PBMCs through the modulation of different pathways associated with the pathophysiology of cardio-metabolic disease and cancer. These beneficial effects are maximized in healthy subjects, and by the use of EVOO cultivars rich in polyphenols. Nutrigenomic changes induced by EVOO thus legitimate the well-known beneficial effects of EVOO in promoting human health and, potentially, preventing the onset of cardiovascular disease and cancer.

Identification and Evaluation of Novel MicroRNA Biomarkers in Plasma and Feces Associated with Drug-induced Intestinal Toxicity

Gastrointestinal toxicity is dose limiting with many therapeutic and anticancer agents. Real-time, noninvasive detection of markers of toxicity in biofluids is advantageous. Ongoing research has revealed microRNAs as potential diagnostic and predictive biomarkers for the detection of select organ toxicities. To study the potential utility of microRNA biomarkers of intestinal injury in a preclinical toxicology species, we evaluated 3 rodent models of drug-induced intestinal toxicity, each with a distinct mechanism of toxicity. MiR-215 and miR-194 were identified as putative intestinal toxicity biomarkers. Both were evaluated in plasma and feces and compared to plasma citrulline, an established intestinal injury biomarker. Following intestinal toxicant dosing, microRNA changes in feces and plasma were detected noninvasively and correlated with histologic evidence of intestinal injury. Fecal miR-215 and miR-194 levels increased, and plasma miR-215 decreased in a dose- and time-dependent manner. Dose-dependent decreases in plasma miR-215 levels also preceded and correlated positively with plasma citrulline modulation, suggesting miR-215 is a more sensitive biomarker. Moreover, during the drug-free recovery phase, plasma miR-215 returned to predose levels, supporting a corresponding recovery of histologic lesions. Despite limitations, this study provides preliminary evidence that select microRNAs have the potential to act as noninvasive, sensitive, and quantitative biomarkers of intestinal injury.

Advanced research on the microRNA mechanism in heart failure

Heart failure is the end stage of most cardiac diseases and also an important cardiovascular disease. Ventricular remodeling, a complicated pathophysiological process involving multiple molecular pathways, is a crucial mechanism for the occurrence and development of heart failure. A microRNA (miRNA) is a highly conservative noncoding molecule containing 18-25 nucleotides. miRNA is different from other RNAs. It mainly serves as an endogenous gene-regulating factor, and is a member of the complex regulatory network. It induces gene repression of target transcripts by affecting mRNA at the post-transcriptional level Vasudevan et al. (2007) . This study aimed at determining the mechanism of miRNA action in heart failure.

Diagnostic, Prognostic, and Therapeutic Value of Circulating miRNAs in Heart Failure Patients Associated with Oxidative Stress

Heart failure is a major public health problem especially in the aging population (≥65 years old), affecting nearly 5 million Americans and 15 million European people. Effective management of heart failure (HF) depends on a correct and rapid diagnosis. Presently, BNP (brain natriuretic peptide) or N-terminal pro-brain natriuretic peptide (NT-proBNP) assay is generally accepted by the international community for diagnostic evaluation and risk stratification of patients with HF. However, regardless of its widespread clinical use, BNP is still encumbered by reduced specificity. As a result, diagnosis of heart failure remains challenging. Although significant improvement happened in the clinical management of HF over the last 2 decades, traditional treatments are ultimately ineffective in many patients who progress to advanced HF. Therefore, a novel diagnostic, prognostic biomarker and new therapeutic approach are required for clinical management of HF patients. Circulating miRNAs seem to be the right choice for novel noninvasive biomarkers as well as new treatment strategies for HF. In this review, we briefly discuss the diagnostic, prognostic, and therapeutic role of circulating miRNAs in heart failure patients. We also mentioned our own technique of extraction of RNA and detection of circulating miRNAs from human plasma and oxidative stress associated miRNAs with HF.

Tiny Shuttles for Information Transfer: Exosomes in Cardiac Health and Disease

Intercellular communication mediated by exosomes, nano-sized extracellular vesicles, is crucial for preserving vascular integrity and in the development of cardiovascular and other diseases. As natural carriers of signal molecules, exosomes released from sources such as blood cells, endothelial cells, immune cells, smooth muscle cells, etc., can modify a multitude of cellular bioactivities. They do so by shuttling lipids, proteins, and nucleic acids between donor and recipient cells while circulating in body fluids and in the extracellular space. A recent surge of interest in the field of exosomal biology is in part due to the recognition that the molecules they carry can act as facilitators of both pathogenesis but can also initiate protective and rescue signaling. This mini-review describes current knowledge on exosome function in health and disease including cardiovascular disease.

Extracellular vesicle microRNAs: biomarker discovery in various diseases based on RT-qPCR

In recent years, biomarker discovery based on extracellular microRNAs (miRNAs), especially exosome miRNAs, has drawn wide attention. While exosome isolation and identification technologies are increasingly sophisticated, the preanalytical process of exosome miRNAs seems to be no longer a crucial problem. Though next-generation sequencing, microarray and digital PCR have been recommended as good downstream analytical platforms for exosome miRNA quantification, they are still more constrained in clinical utility compared with RT-qPCR method at present. In this review, we will trace back to the origin and summarize current studies of biomarker discovery based on extracellular vesicle miRNAs, and provide an overview and latest developments of RT-qPCR-based data normalization, in order to further assist the development of translational medicine.

Overview of MicroRNAs in Cardiac Hypertrophy, Fibrosis, and Apoptosis

MicroRNAs (miRNAs) are non-coding RNAs that play essential roles in modulating the gene expression in almost all biological events. In the past decade, the involvement of miRNAs in various cardiovascular disorders has been explored in numerous in vitro and in vivo studies. In this paper, studies focused upon the discovery of miRNAs, their target genes, and functionality are reviewed. The selected miRNAs discussed herein have regulatory effects on target gene expression as demonstrated by miRNA/3′ end untranslated region (3′UTR) interaction assay and/or gain/loss-of-function approaches. The listed miRNA entities are categorized according to the biological relevance of their target genes in relation to three cardiovascular pathologies, namely cardiac hypertrophy, fibrosis, and apoptosis. Furthermore, comparison across 86 studies identified several candidate miRNAs that might be of particular importance in the ontogenesis of cardiovascular diseases as they modulate the expression of clusters of target genes involved in the progression of multiple adverse cardiovascular events. This review illustrates the involvement of miRNAs in diverse biological signaling pathways and provides an overview of current understanding of, and progress of research into, of the roles of miRNAs in cardiovascular health and disease.

Coronary Artery-Bypass-Graft Surgery Increases the Plasma Concentration of Exosomes Carrying a Cargo of Cardiac MicroRNAs: An Example of Exosome Trafficking Out of the Human Heart with Potential for Cardiac Biomarker Discovery

Introduction

Exosome nanoparticles carry a composite cargo, including microRNAs (miRs). Cultured cardiovascular cells release miR-containing exosomes. The exosomal trafficking of miRNAs from the heart is largely unexplored. Working on clinical samples from coronary-artery by-pass graft (CABG) surgery, we investigated if: 1) exosomes containing cardiac miRs and hence putatively released by cardiac cells increase in the circulation after surgery; 2) circulating exosomes and exosomal cardiac miRs correlate with cardiac troponin (cTn), the current “gold standard” surrogate biomarker of myocardial damage.

Methods and Results

The concentration of exosome-sized nanoparticles was determined in serial plasma samples. Cardiac-expressed (miR-1, miR-24, miR-133a/b, miR-208a/b, miR-210), non-cardiovascular (miR-122) and quality control miRs were measured in whole plasma and in plasma exosomes. Linear regression analyses were employed to establish the extent to which the circulating individual miRs, exosomes and exosomal cardiac miR correlated with cTn-I. Cardiac-expressed miRs and the nanoparticle number increased in the plasma on completion of surgery for up to 48 hours. The exosomal concentration of cardiac miRs also increased after CABG. Cardiac miRs in the whole plasma did not correlate significantly with cTn-I. By contrast cTn-I was positively correlated with the plasma exosome level and the exosomal cardiac miRs.

Conclusions

The plasma concentrations of exosomes and their cargo of cardiac miRs increased in patients undergoing CABG and were positively correlated with hs-cTnI. These data provide evidence that CABG induces the trafficking of exosomes from the heart to the peripheral circulation. Future studies are necessary to investigate the potential of circulating exosomes as clinical biomarkers in cardiac patients.

Epidemiology of cardiovascular disease: recent novel outlooks on risk factors and clinical approaches

INTRODUCTION

Cardiovascular (CVD) risk assessment with traditional risk factors (age, sex, blood pressure, lipids, smoking and diabetes) has remained relatively invariant over the past decades despite some inaccuracies associated with this approach. However, the search for novel, robust and cost-effective risk markers of CVD risk is ongoing.

AREAS COVERED

A large share of the major developments in CVD risk prediction during the past five years has been made in large-scale biomarker discovery and the so called 'omics' - the rapidly growing fields of genomics, transcriptomics, epigenetics and metabolomics. This review focuses on how these new technologies are helping drive primary CVD risk estimation forward in recent years, and speculates on how they could be utilized more effectively for discovering novel risk factors in the future. Expert commentary: The search for new CVD risk factors is currently undergoing a significant revolution as the simple relationship between single risk factors and disease will have to be replaced by models that strive to integrate the whole field of omics into medicine.

MicroRNA and Heart Failure

Heart failure (HF) imposes significant economic and public health burdens upon modern society. It is known that disturbances in neurohormonal status play an important role in the pathogenesis of HF. Therapeutics that antagonize selected neurohormonal pathways, specifically the renin-angiotensin-aldosterone and sympathetic nervous systems, have significantly improved patient outcomes in HF. Nevertheless, mortality remains high with about 50% of HF patients dying within five years of diagnosis thus mandating ongoing efforts to improve HF management. The discovery of short noncoding microRNAs (miRNAs) and our increasing understanding of their functions, has presented potential therapeutic applications in complex diseases, including HF. Results from several genome-wide miRNA studies have identified miRNAs differentially expressed in HF cohorts suggesting their possible involvement in the pathogenesis of HF and their potential as both biomarkers and as therapeutic targets. Unravelling the functional relevance of miRNAs within pathogenic pathways is a major challenge in cardiovascular research. In this article, we provide an overview of the role of miRNAs in the cardiovascular system. We highlight several HF-related miRNAs reported from selected cohorts and review their putative roles in neurohormonal signaling.

The importance of p53 pathway genetics in inherited and somatic cancer genomes

Decades of research have shown that mutations in the p53 stress response pathway affect the incidence of diverse cancers more than mutations in other pathways. However, most evidence is limited to somatic mutations and rare inherited mutations. Using newly abundant genomic data, we demonstrate that commonly inherited genetic variants in the p53 pathway also affect the incidence of a broad range of cancers more than variants in other pathways. The cancer-associated single nucleotide polymorphisms (SNPs) of the p53 pathway have strikingly similar genetic characteristics to well-studied p53 pathway cancer-causing somatic mutations. Our results enable insights into p53-mediated tumour suppression in humans and into p53 pathway-based cancer surveillance and treatment strategies.

Loss of CEACAM1, a Tumor-Associated Factor, Attenuates Post-infarction Cardiac Remodeling by Inhibiting Apoptosis

Carcinoembryonic antigen-related cell adhesion molecule1 (CEACAM1) is a tumor-associated factor that is known to be involved in apoptosis, but the role of CEACAM1 in cardiovascular disease is unclear. We aims to investigate whether CEACAM1 influences cardiac remodeling in mice with myocardial infarction (MI) and hypoxia-induced cardiomyocyte injury. Both serum in patients and myocardial CEACAM1 levels in mice were significantly increased in response to MI, while levels were elevated in neonatal rat cardiomyocytes (NRCs) exposed to hypoxia. Eight weeks after MI, a lower mortality rate, improved cardiac function, and less cardiac remodeling in CEACAM1 knock-out (KO) mice than in their wild-type (WT) littermates were observed. Moreover, myocardial expression of mitochondrial Bax, cytosolic cytochrome C, and cleaved caspase-3 was significantly lower in CEACAM1 KO mice than in WT mice. In cultured NRCs exposed to hypoxia, recombinant human CEACAM1 (rhCEACAM1) reduced mitochondrial membrane potential, upregulated mitochondrial Bax, increased cytosolic cytochrome C and cleaved caspase-3, and consequently increased apoptosis. RhCEACAM1 also increased the levels of GRP78 and CHOP in NRCs with hypoxia. All of these effects were abolished by silencing CEACAM1. Our study indicates that CEACAM1 exacerbates hypoxic cardiomyocyte injury and post-infarction cardiac remodeling by enhancing cardiomyocyte mitochondrial dysfunction and endoplasmic reticulum stress-induced apoptosis.

MicroRNAs as a diagnostic tool for heart failure and atrial fibrillation

MicroRNAs (miRNAs) are small non-coding RNAs, which are directly involved in the regulation of post-transcriptional gene expression. Their biological function represents a repression of protein expression of the targeted messenger-RNA(s). Expression of several miRNAs is somehow tissue-specific or cell-specific and their expression pattern can reflect an underlying pathophysiological condition. Beyond this biological function their role as potential biomarkers has been emerged in the past years. This was based on the fact that miRNAs can be detected in blood samples (serum or plasma) in a surprisingly stable form, by contrast to mRNAs. This fact made miRNAs interesting candidates for biomarkers providing information with respect to a potentially ongoing pathophysiological condition and could thereby have an impact on specific treatment strategies in patients. In this review we try to provide an overview of the potential role of miRNAs as a diagnostic tool in atrial fibrillation and heart failure patients taken different methodological aspects and distinct type of patients into account.

MicroRNAs as early toxicity signatures of doxorubicin in human-induced pluripotent stem cell-derived cardiomyocytes

An in depth investigation at the genomic level is needed to identify early human-relevant cardiotoxicity biomarkers that are induced by drugs and environmental toxicants. The main objective of this study was to investigate the role of microRNAs (miRNAs) as cardiotoxicity biomarkers using human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) that were exposed to doxorubicin (DOX) as a "gold standard" cardiotoxicant. hiPSC-CMs were exposed to 156 nM DOX for 2 days or for 6 days of repeated exposure, followed by drug washout and incubation in drug-free culture medium up to day 14 after the onset of exposure. The induced miRNAs were profiled using miRNA microarrays, and the analysis of the data was performed using the miRWalk 2.0 and DAVID bioinformatics tools. DOX induced early deregulation of 14 miRNAs (10 up-regulated and 4 down-regulated) and persistent up-regulation of 5 miRNAs during drug washout. Computational miRNA gene target predictions suggested that several DOX-responsive miRNAs might regulate the mRNA expression of genes involved in cardiac contractile function. The hiPSC-CMs exposed to DOX in a range from 39 to 156 nM did not show a significant release of the cytotoxicity marker lactate dehydrogenase (LDH) compared to controls. Quantitative real-time PCR analyses confirmed the early deregulation of miR-187-3p, miR-182-5p, miR-486-3p, miR-486-5p, miR-34a-3p, miR-4423-3p, miR-34c-3p, miR-34c-5p and miR-1303, and also the prolonged up-regulation of miR-182-5p, miR-4423-3p and miR-34c-5p. Thus, we identified and validated miRNAs showing differential DOX-responsive expression before the occurrence of cytotoxicity markers such as LDH, and these miRNAs also demonstrated the significant involvement in heart failure in patients and animal models. These results suggest that the DOX-induced deregulated miRNAs in human CMs may be used as early sensitive cardiotoxicity biomarkers for screening potential drugs and environmental cardiotoxicants with a similar mechanism of action.

Circulating miR-34a levels correlate with age-related hearing loss in mice and humans

Age-related hearing loss (AHL) is a progressive neurodegenerative disease that is largely silent in its initial stages. There is no sensitive blood biomarker for diagnosis or early detection of AHL. MicroRNAs (miRNAs or miRs) are abundant and highly stable in blood, and have been recently described as powerful circulating biomarkers in a wide range of diseases. In the present study, we identified concordant increases in miR-34a levels in the cochlea, auditory cortex, and plasma of C57BL/6 mice during aging. These increases were accompanied by elevated hearing thresholds and greater loss of hair cells. Levels of miR-34a targets, silent information regulator 1 (SIRT1), B-cell lymphoma-2 (Bcl-2), and E2F transcription factor 3 (E2F3), in the cochlea, auditory cortex, and plasma decreased with aging inversely to miR-34a. Moreover, plasma miR-34a levels were significantly higher in patients with AHL compared with controls who had normal hearing and had a receiver-operating characteristic curve that distinguished AHL patients from controls. However, SIRT1, Bcl-2, and E2F3 showed no correlation with AHL in humans. In summary, circulating miR-34a level may potentially serve as a useful biomarker for early detection of AHL.

Role of the Thyroid System in the Dynamic Complex Network of Cardioprotection

Cardioprotection is a common goal of new therapeutic strategies in patients with coronary artery disease and/or left ventricular dysfunction. Myocardial damage following ischaemia/reperfusion injury lead to left ventricular adverse remodelling through many mechanisms arising from different cell types in different myocardial districts, namely the border and remote zone. Cardioprotection must face this complex, dynamic network of cooperating units. In this scenario, thyroid hormones can represent an effective therapeutic strategy due to the numerous actions and regulating mechanisms carried out at the level of the myocytes, interstitium and the vasculature, as well as to the activation of different pro-survival intracellular pathways involved in cardioprotection.

Identification of General and Heart-Specific miRNAs in Sheep (Ovis aries)

MicroRNAs (miRNAs or miRs) are small regulatory RNAs crucial for modulation of signaling pathways in multiple organs. While the link between miRNAs and heart disease has grown more readily apparent over the past three years, these data are primarily limited to small animal models or cell-based systems. Here, we performed a high-throughput RNA sequencing (RNAseq) analysis of left ventricle and other tissue from a pre-clinical ovine model. We identified 172 novel miRNA precursors encoding a total of 264 mature miRNAs. Notably, 84 precursors were detected in both the left ventricle and other tissues. However, 10 precursors, encoding 11 mature sequences, were specific to the left ventricle. Moreover, the total 168 novel miRNA precursors included 22 non-conserved ovine-specific sequences. Our data identify and characterize novel miRNAs in the left ventricle of sheep, providing fundamental new information for our understanding of protein regulation in heart and other tissues.

miRNA-34a reduces neointima formation through inhibiting smooth muscle cell proliferation and migration

AIMS

We have recently reported that microRNA-34a (miR-34a) regulates vascular smooth muscle cell (VSMC) differentiation from stem cells in vitro and in vivo. However, little is known about the functional involvements of miR-34a in VSMC functions and vessel injury-induced neointima formation. In the current study, we aimed to establish the causal role of miR-34a and its target genes in VSMC proliferation, migration and neointima lesion formation.

METHODS AND RESULTS

Various pathological stimuli regulate miR-34a expression in VSMCs through a transcriptional mechanism, and the P53 binding site is required for miR-34a gene regulation by these stimuli. miR-34a over-expression in serum-starved VSMCs significantly inhibited VSMC proliferation and migration, while knockdown of miR-34a dramatically promoted VSMC proliferation and migration, respectively. Notch homolog 1 (Notch1), a well-reported regulator in VSMC functions and arterial remodeling, was predicted as one of the top targets of miR-34a by using several computational miRNA target prediction tools, and was negatively regulated by miR-34a in VSMCs. Luciferase assay showed miR-34a substantially repressed wild type Notch1-3'-UTR-luciferase activity in VSMCs, but not mutant Notch1-3'-UTR-luciferease reporter, confirming the Notch1 is the functional target of miR-34a in VSMCs. Data from co-transfection experiments also revealed that miR-34a inhibited VSMC proliferation and migration through modulating Notch gene expression levels. Importantly, the expression level of miR-34a was significantly down-regulated in injured arteries, and miR-34a perivascular over-expression significantly reduced Notch1 expression levels, decreased VSMC proliferation, and inhibited neointima formation in wire-injured femoral arteries.

CONCLUSION

Our data have demonstrated that miR-34a is an important regulator in VSMC functions and neointima hyperplasia, suggesting its potential therapeutic application for vascular diseases.

Roles of microRNA-34a targeting SIRT1 in mesenchymal stem cells

Introduction

Mesenchymal stem cell (MSC)-based therapies have had positive outcomes both in animal models of cardiovascular diseases and in clinical patients. However, the number and function of MSCs decline during hypoxia and serum deprivation (H/SD), reducing their ability to contribute to endogenous injury repair. MicroRNA-34a (miR-34a) is originally identified as a TP53-targeted miRNA that modulates cell functions, including apoptosis, proliferation, and senescence via several signaling pathways, and hence is an appealing target for MSC-based therapy for myocardial infarction.

Methods

Bone marrow-derived MSCs were isolated from 60–80 g male donor rats. Expression levels of miR-34a were determined by qRT-PCR. The roles of miR-34a in regulating cell vitality, apoptosis and senescence were investigated using the cell counting kit (CCK-8) assay, flow cytometric analysis of Annexin V-FITC/PI staining and senescence-associated β-galactosidase (SA-β-gal) staining, respectively. The expression of silent information regulator 1 (SIRT1) and forkhead box class O 3a (FOXO3a) and of apoptosis- and senescence-associated proteins in MSCs were analyzed by western blotting.

Results

The results of the current study showed that miR-34a was significantly up-regulated under H/SD conditions in MSCs, while overexpression of miR-34a was significantly associated with increased apoptosis, impaired cell vitality and aggravated senescence. Moreover, we found that the mechanism underlying the proapoptotic function of miR-34a involves activation of the SIRT1/FOXO3a pathway, mitochondrial dysfunction and finally, activation of the intrinsic apoptosis pathway. Further study showed that miR-34a can also aggravate MSC senescence, an effect which was partly abolished by the reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC).

Conclusions

Our study demonstrates for the first time that miR-34a plays pro-apoptotic and pro-senescence roles in MSCs by targeting SIRT1. Thus, inhibition of miR-34a might have important therapeutic implications in MSC-based therapy for myocardial infarction.

The biology of circulating microRNAs in cardiovascular disease

BACKGROUND

Since their first description in mammalian cells, more than 2500 microRNA molecules have been predicted or verified within human cells. Recently, extracellular microRNAs have been described, protected from degradation by specialized packaging in extracellular vesicles or RNA-binding proteins.

MATERIALS AND METHODS

We will discuss recent data regarding circulating microRNAs, their potential role as novel biomarkers and intercellular communicators, as well as future challenges of studying and applying such novel biology, particularly in the cardiovascular system.

RESULTS

Circulating microRNAs have been proposed as attractive candidates as both diagnostic and prognostic biomarkers in various diseases, including a spectrum of cardiovascular conditions. Moreover, consistent with our evolving appreciation of the role of exosomes and microvesicles in intercellular communication, it has been proposed that delivery of active microRNAs to recipient tissues may serve as a primary mode of intercellular communication. Indeed, the transfer of functional microRNAs has been demonstrated in in vitro models and has been reported in a few in vivo contexts. In addition, therapeutic application of extracellular microRNAs has also been explored.

CONCLUSION

Over recent years, increasing attention has been paid to the role of circulating miRNAs in cardiovascular disease. As biomarkers and intercellular communicators, circulating miRNAs could play important roles in the prediction, diagnosis and tailored treatment of cardiovascular diseases in the near future.

Extracellular vesicles as new pharmacological targets to treat atherosclerosis

Extracellular vesicles released by most cell types, include apoptotic bodies (ABs), microvesicles (MVs) and exosomes. They play a crucial role in physiology and pathology, contributing to "cell-to-cell" communication by modifying the phenotype and the function of target cells. Thus, extracellular vesicles participate in the key processes of atherosclerosis from endothelial dysfunction, vascular wall inflammation to vascular remodeling. The purpose of this review is to summarize recent findings on extracellular vesicle formation, structure, release and clearance. We focus on the deleterious and beneficial effects of extracellular vesicles in the development of atherosclerosis. The potential role of extracellular vesicles as biomarkers and pharmacological targets, their innate therapeutic capacity, or their use for novel drug delivery devices in atherosclerotic cardiovascular diseases will also be discussed.

Extracellular vesicles and atherosclerotic disease

Circulating extracellular vesicles (EVs) comprise a heterogeneous population of vesicular structures. According to the current paradigm, there are three types of EVs, including exosomes, microvesicles and apoptotic bodies, that are differentiated in their size, formation, and release mechanisms. EVs were shown to act as a 'post service' that serves a long-distance delivery of complex cellular messages. The cargo of EVs consists of a variety of biomolecules including proteins, DNA, mRNA, and non-coding RNA. In normal or pathological conditions, EVs deliver various molecules to the recipient cells. Those molecules greatly vary depending on the microenvironmental stimuli. In proinflammatory conditions such as atherosclerosis and other cardiovascular diseases, EVs derived from vascular endothelial cells, vascular smooth muscle cells, macrophages, and other circulating immune cells mainly possess proinflammatory properties. However, the capacity of circulating EVs to stably maintain and deliver a variety of biomolecules makes these microparticles to be a promising therapeutic tool for treatment of cardiovascular pathology. To date, circulating EVs were evaluated to be as a source of valuable diagnostic and prognostic biomarkers such as microRNA. Circulating EVs keep a great therapeutic potential to serve as vehicles for targeted therapy of cardiovascular diseases.

Gene Expression Signatures and the Spectrum of Coronary Artery Disease

Over the past 10-15 years, developments in gene expression profiling have opened new arenas for the discovery of important factors in the pathogenesis of numerous disease processes, including coronary artery disease. Messenger RNA and microRNA are differentially expressed in patients with coronary plaques, acute plaque rupture, and response to well-established treatments for acute coronary syndromes. In this review, we will explore recent developments in messenger RNA and microRNA technology at each stage of a patient's progression through the natural history of cardiovascular disease, including evaluation of risk factors, prediction and detection of coronary artery disease and acute coronary syndromes, and finally, response to treatments for coronary artery disease and its sequelae including congestive heart failure.

MicroRNA-34a Plays a Key Role in Cardiac Repair and Regeneration Following Myocardial Infarction

RATIONALE

In response to injury, the rodent heart is capable of virtually full regeneration via cardiomyocyte proliferation early in life. This regenerative capacity, however, is diminished as early as 1 week postnatal and remains lost in adulthood. The mechanisms that dictate postinjury cardiomyocyte proliferation early in life remain unclear.

OBJECTIVE

To delineate the role of miR-34a, a regulator of age-associated physiology, in regulating cardiac regeneration secondary to myocardial infarction (MI) in neonatal and adult mouse hearts.

METHODS AND RESULTS

Cardiac injury was induced in neonatal and adult hearts through experimental MI via coronary ligation. Adult hearts demonstrated overt cardiac structural and functional remodeling, whereas neonatal hearts maintained full regenerative capacity and cardiomyocyte proliferation and recovered to normal levels within 1-week time. As early as 1 week postnatal, miR-34a expression was found to have increased and was maintained at high levels throughout the lifespan. Intriguingly, 7 days after MI, miR-34a levels further increased in the adult but not neonatal hearts. Delivery of a miR-34a mimic to neonatal hearts prohibited both cardiomyocyte proliferation and subsequent cardiac recovery post MI. Conversely, locked nucleic acid-based anti-miR-34a treatment diminished post-MI miR-34a upregulation in adult hearts and significantly improved post-MI remodeling. In isolated cardiomyocytes, we found that miR-34a directly regulated cell cycle activity and death via modulation of its targets, including Bcl2, Cyclin D1, and Sirt1.

CONCLUSIONS

miR-34a is a critical regulator of cardiac repair and regeneration post MI in neonatal hearts. Modulation of miR-34a may be harnessed for cardiac repair in adult myocardium.