The ESCRT-III pathway facilitates cardiomyocyte release of cBIN1-containing microparticles

Extracellular vesicles as tools and targets in therapy for diseases

Extracellular vesicles (EVs) are nano-sized, membranous structures secreted into the extracellular space. They exhibit diverse sizes, contents, and surface markers and are ubiquitously released from cells under normal and pathological conditions. Human serum is a rich source of these EVs, though their isolation from serum proteins and non-EV lipid particles poses challenges. These vesicles transport various cellular components such as proteins, mRNAs, miRNAs, DNA, and lipids across distances, influencing numerous physiological and pathological events, including those within the tumor microenvironment (TME). Their pivotal roles in cellular communication make EVs promising candidates for therapeutic agents, drug delivery systems, and disease biomarkers. Especially in cancer diagnostics, EV detection can pave the way for early identification and offers potential as diagnostic biomarkers. Moreover, various EV subtypes are emerging as targeted drug delivery tools, highlighting their potential clinical significance. The need for non-invasive biomarkers to monitor biological processes for diagnostic and therapeutic purposes remains unfulfilled. Tapping into the unique composition of EVs could unlock advanced diagnostic and therapeutic avenues in the future. In this review, we discuss in detail the roles of EVs across various conditions, including cancers (encompassing head and neck, lung, gastric, breast, and hepatocellular carcinoma), neurodegenerative disorders, diabetes, viral infections, autoimmune and renal diseases, emphasizing the potential advancements in molecular diagnostics and drug delivery.

Cardiac gene therapy treats diabetic cardiomyopathy and lowers blood glucose

Diabetic cardiomyopathy, an increasingly global epidemic and a major cause of heart failure with preserved ejection fraction (HFpEF), is associated with hyperglycemia, insulin resistance, and intracardiomyocyte calcium mishandling. Here we identify that, in db/db mice with type 2 diabetes-induced HFpEF, abnormal remodeling of cardiomyocyte transverse-tubule microdomains occurs with downregulation of the membrane scaffolding protein cardiac bridging integrator 1 (cBIN1). Transduction of cBIN1 by AAV9 gene therapy can restore transverse-tubule microdomains to normalize intracellular distribution of calcium-handling proteins and, surprisingly, glucose transporter 4 (GLUT4). Cardiac proteomics revealed that AAV9-cBIN1 normalized components of calcium handling and GLUT4 translocation machineries. Functional studies further identified that AAV9-cBIN1 normalized insulin-dependent glucose uptake in diabetic cardiomyocytes. Phenotypically, AAV9-cBIN1 rescued cardiac lusitropy, improved exercise intolerance, and ameliorated hyperglycemia in diabetic mice. Restoration of transverse-tubule microdomains can improve cardiac function in the setting of diabetic cardiomyopathy and can also improve systemic glycemic control.

Extracellular vesicles highlight many cases of photoreceptor degeneration

The release of extracellular vesicles is observed across numerous cell types and serves a range of biological functions including intercellular communication and waste disposal. One cell type which stands out for its robust capacity to release extracellular vesicles is the vertebrate photoreceptor cell. For decades, the release of extracellular vesicles by photoreceptors has been documented in many different animal models of photoreceptor degeneration and, more recently, in wild type photoreceptors. Here, I review all studies describing extracellular vesicle release by photoreceptors and discuss the most unifying theme among them-a photoreceptor cell fully, or partially, diverts its light sensitive membrane material to extracellular vesicles when it has defects in the delivery or morphing of this material into the photoreceptor's highly organized light sensing organelle. Because photoreceptors generate an enormous amount of light sensitive membrane every day, the diversion of this material to extracellular vesicles can cause a massive accumulation of these membranes within the retina. Little is known about the uptake of photoreceptor derived extracellular vesicles, although in some cases the retinal pigment epithelial cells, microglia, Müller glia, and/or photoreceptor cells themselves have been shown to phagocytize them.

The impact of obesity on adipocyte-derived extracellular vesicles

Recently, the emerging roles of adipocyte-derived extracellular vesicles (EVs) linking obesity and its comorbidities have been recognized. In obese subjects, adipocytes are having hypertrophic growth and are under stressed. The dysfunction adipocytes dysregulate the assembly of the biological components in the EVs including exosomes. This article critically reviews the current findings on the impact of obesity on the exosomal cargo contents that induce the pathophysiological changes. Besides, this review also summarizes the understanding on how obesity affects the biogenesis of adipocyte-derived exosomes and the exosome secretion. Furthermore, the differences of the exosomal contents in different adipose depots, and the impact of obesity on the exosomes that are derived from the stromal vascular fraction such as the adipose tissue macrophages and adipocyte-derived stem cells will also be discussed. The current development and potential application of exosome-based therapy will be summarized. This review provides crucial information for the design of novel exosome-based therapy for the treatment of obesity and its comorbidities.

Hitzeman T, Cook‐Wiens G, Pepine CJ, Handberg E, Anderson RD, Petersen J, Hong T, M. Shaw R, Bairey Merz CN. Association of coronary microvascular dysfunction and cardiac bridge integrator 1, a cardiomyocyte dysfunction biomarker

BACKGROUND

Coronary microvascular dysfunction (CMD) is associated with heart failure with preserved ejection fraction (HFpEF); however, pathophysiology is not well described.

HYPOTHESIS

We hypothesized that CMD in women with suspected ischemia with no obstructive coronary artery disease (INOCA) is associated with cardiomyocyte dysfunction reflected by plasma levels of a cardiomyocyte calcium handling protein, cardiac bridge integrator 1 (cBIN1).

METHODS

Women with suspected INOCA undergoing coronary function testing were included. Coronary flow reserve, vasodilation to nitroglycerin, change in coronary blood flow (ΔCBF), and vasodilation to acetylcholine (ΔAch) were evaluated. cBIN1 score (CS) levels in these women (n = 39) were compared to women with HFpEF (n = 20), heart failure with reduced ejection fraction (HFrEF) (n = 36), and reference controls (RC) (n = 50). Higher CS indicates cardiomyocyte tubule dysfunction.

RESULTS

INOCA, HFpEF, and HFrEF women were older than RC (p < .05). Higher CS was associated with vasoconstriction to acetylcholine (r = -0.43, p = .011) with a trend towards lower ΔCBF (r = 0.30, p = .086). Higher CS was specific for ΔAch and ΔCBF but had limited sensitivity. INOCA women had higher CS than RC, but lower CS than HFpEF/HFrEF groups (p < .001).

CONCLUSIONS

CS, a plasma biomarker indicating poor cardiomyocyte health, was higher in women with suspected INOCA as compared to RC, but lower than in women with HFpEF. Elevated CS in suspected INOCA patients represents an intermediate group between health and disease, supporting the hypothesis that CMD may progress to HFpEF. Larger prospective cohort studies are needed to confirm the pathophysiological relationship between cBIN1, CMD, and HFpEF.

Extracellular Vesicles in Blood: Sources, Effects, and Applications

Extracellular vesicles (EVs) are important players for intercellular communication. EVs are secreted by almost all cell types; they can transfer information between nearby or distant cells, and they are highly abundant in body fluids. In this review, we describe the general characteristics of EVs, as well as isolation and characterization approaches. Then, we focus on one of the most relevant sources of EVs: the blood. Indeed, apart from EVs secreted by blood cells, EVs of diverse origins travel in the bloodstream. We present the numerous types of EVs that have been found in circulation. Besides, the implications of blood-derived EVs in both physiological and pathological processes are summarized, highlighting their potential as biomarkers for the diagnosis, treatment monitoring, and prognosis of several diseases, and also as indicators of physiological modifications. Finally, the applications of EVs introduced in the circulatory system are discussed. We describe the use of EVs from distinct origins, naturally produced or engineered, autologous, allogeneic, or even from different species and the effects they have when introduced in circulation. Therefore, the present work provides a comprehensive overview of the components, effects, and applications of EVs in blood.

Cardiac T-Tubule cBIN1-Microdomain, a Diagnostic Marker and Therapeutic Target of Heart Failure

Since its first identification as a cardiac transverse tubule (t-tubule) protein, followed by the cloning of the cardiac isoform responsible for t-tubule membrane microdomain formation, cardiac bridging integrator 1 (cBIN1) and its organized microdomains have emerged as a key mechanism in maintaining normal beat-to-beat heart contraction and relaxation. The abnormal remodeling of cBIN1-microdomains occurs in stressed and diseased cardiomyocytes, contributing to the pathophysiology of heart failure. Due to the homeostatic turnover of t-tubule cBIN1-microdomains via microvesicle release into the peripheral circulation, plasma cBIN1 can be assayed as a liquid biopsy of cardiomyocyte health. A new blood test cBIN1 score (CS) has been developed as a dimensionless inverse index derived from plasma cBIN1 concentration with a diagnostic and prognostic power for clinical outcomes in stable ambulatory patients with heart failure with reduced or preserved ejection fraction (HFrEF or HFpEF). Recent evidence further indicates that exogenous cBIN1 introduced by adeno-associated virus 9-based gene therapy can rescue cardiac contraction and relaxation in failing hearts. The therapeutic potential of cBIN1 gene therapy is enormous given its ability to rescue cardiac inotropy and provide lusitropic protection in the meantime. These unprecedented capabilities of cBIN1 gene therapy are shifting the current paradigm of therapy development for heart failure, particularly HFpEF.

Extracellular Vesicles from Red Blood Cells and Their Evolving Roles in Health, Coagulopathy and Therapy

Red blood cells (RBCs) release extracellular vesicles (EVs) including both endosome-derived exosomes and plasma-membrane-derived microvesicles (MVs). RBC-derived EVs (RBCEVs) are secreted during erythropoiesis, physiological cellular aging, disease conditions, and in response to environmental stressors. RBCEVs are enriched in various bioactive molecules that facilitate cell to cell communication and can act as markers of disease. RBCEVs contribute towards physiological adaptive responses to hypoxia as well as pathophysiological progression of diabetes and genetic non-malignant hematologic disease. Moreover, a considerable number of studies focus on the role of EVs from stored RBCs and have evaluated post transfusion consequences associated with their exposure. Interestingly, RBCEVs are important contributors toward coagulopathy in hematological disorders, thus representing a unique evolving area of study that can provide insights into molecular mechanisms that contribute toward dysregulated hemostasis associated with several disease conditions. Relevant work to this point provides a foundation on which to build further studies focused on unraveling the potential roles of RBCEVs in health and disease. In this review, we provide an analysis and summary of RBCEVs biogenesis, composition, and their biological function with a special emphasis on RBCEV pathophysiological contribution to coagulopathy. Further, we consider potential therapeutic applications of RBCEVs.

Nanobar Array Assay Revealed Complementary Roles of BIN1 Splice Isoforms in Cardiac T-Tubule Morphogenesis

Bridging integrator-1 (BIN1) is a family of banana-shaped molecules implicated in cell membrane tubulation. To understand the curvature sensitivity and functional roles of BIN1 splicing isoforms, we engineered vertical nanobars on a cell culture substrate to create high and low curvatures. When expressed individually, BIN1 isoforms with phosphoinositide-binding motifs (pBIN1) appeared preferentially at high-curvature nanobar ends, agreeing well with their membrane tubulation in cardiomyocytes. In contrast, the ubiquitous BIN1 isoform without phosphoinositide-binding motif (uBIN1) exhibited no affinity to membranes around nanobars but accumulated along Z-lines in cardiomyocytes. Importantly, in pBIN1-uBIN1 coexpression, pBIN1 recruited uBIN1 to high-curvature membranes at nanobar ends, and uBIN1 attached the otherwise messy pBIN1 tubules to Z-lines. The complementary cooperation of BIN1 isoforms (comboBIN1) represents a novel mechanism of T-tubule formation along Z-lines in cardiomyocytes. Dysregulation of BIN1 splicing, e.g., during myocardial infarction, underlied T-tubule disorganization, and correction of uBIN1/pBIN1 stoichiometry rescued T-tubule morphology in heart disease.

Exogenous Cardiac Bridging Integrator 1 Benefits Mouse Hearts With Pre-existing Pressure Overload-Induced Heart Failure

Background: Cardiac bridging integrator 1 (cBIN1) organizes transverse tubule (t-tubule) membrane calcium handling microdomains required for normal beat-to-beat contractility. cBIN1 is transcriptionally reduced in heart failure (HF). We recently found that cBIN1 pretreatment can limit HF development in stressed mice. Here, we aim to explore whether cBIN1 replacement therapy can improve myocardial function in continuously stressed hearts with pre-existing HF. Methods: Adult male mice were subjected to sham or transverse aortic constriction (TAC) surgery at the age of 8-10 weeks old. Adeno-associated virus 9 (AAV9) transducing cBIN1-V5 or GFP-V5 (3 × 1010 vg) was administered through retro-orbital injection at 5 weeks post-TAC. Mice were followed by echocardiography to monitor cardiac function until 20 weeks after TAC. Overall survival, heart and lung weight (LW), and HF incidence were determined. In a second set of animals in which AAV9-cBIN1 pretreatment prevents HF, we recorded cardiac pressure-volume (PV) loops and obtained myocardial immunofluorescence imaging. Results: The overall Kaplan-Meir survival of AAV9-cBIN1 mice was 77.8%, indicating a significant partial rescue between AAV9-GFP (58.8%) and sham (100%) treated mice. In mice with ejection fraction (EF) ≥30% prior to AAV9 injection at 5 weeks post-TAC, AAV9-cBIN1 significantly increased survival to 93.3%, compared to 62.5% survival for AAV9-GFP treated mice. The effect of exogenous cBIN1 was to attenuate TAC-induced left ventricular (LV) dilation and prevent further HF development. Recovery of EF also occurs in AAV9-cBIN1-treated mice. We found that EF increases to a peak at 6-8 weeks post-viral injection. Furthermore, PV loop analysis identified that AAV9-cBIN1 increases both systolic and diastolic function of the post-TAC hearts. At the myocyte level, AAV9-cBIN1 normalizes cBIN1 expression, t-tubule membrane intensity, and intracellular distribution of Cav1.2 and ryanodine receptors (RyRs). Conclusions: In mice with pre-existing HF, exogenous cBIN1 can normalize t-tubule calcium handling microdomains, limit HF progression, rescue cardiac function, and improve survival.

cBIN1 Score (CS) Identifies Ambulatory HFrEF Patients and Predicts Cardiovascular Events

BACKGROUND

Cardiac Bridging Integrator 1 (cBIN1) is a membrane deformation protein that generates calcium microdomains at cardiomyocyte t-tubules, whose transcription is reduced in heart failure, and is released into blood. cBIN1 score (CS), an inverse index of plasma cBIN1, measures cellular myocardial remodeling. In patients with heart failure with preserved ejection fraction (HFpEF), CS diagnoses ambulatory heart failure and prognosticates hospitalization. The performance of CS has not been tested in patients with heart failure with reduced ejection fraction (HFrEF).

METHODS AND RESULTS

CS was determined from plasma of patients recruited in a prospective study. Two comparative cohorts consisted of 158 ambulatory HFrEF patients (left ventricular ejection fraction (LVEF) ≤ 40%, 57 ± 10 years, 80% men) and 115 age and sex matched volunteers with no known history of HF. N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations were also analyzed for comparison. CS follows a normal distribution with a median of 0 in the controls, which increases to a median of 1.9 (p < 0.0001) in HFrEF patients. CS correlates with clinically assessed New York Heart Association Class (p = 0.007). During 1-year follow-up, a high CS (≥ 1.9) in patients predicts increased cardiovascular events (43% vs. 26%, p = 0.01, hazard ratio 1.9). Compared to a model with demographics, clinical risk factors, and NT-proBNP, adding CS to the model improved the overall continuous net reclassification improvement (NRI 0.64; 95% CI 0.18-1.10; p = 0.006). Although performance for diagnosis and prognosis was similar to CS, NT-proBNP did not prognosticate between patients whose NT-proBNP values were > 400 pg/ml.

CONCLUSION

CS, which is mechanistically distinct from NT-proBNP, successfully differentiates myocardial health between patients with HFrEF and matched controls. A high CS reflects advanced NYHA stage, pathologic cardiac muscle remodeling, and predicts 1-year risk of cardiovascular events in ambulatory HFrEF patients. CS is a marker of myocardial remodeling in HFrEF patients, independent of volume status.

Effect of BIN1 on cardiac dysfunction and malignant arrhythmias

Heart failure (HF) is the end-stage syndrome for most cardiac diseases, and the 5-year morbidity and mortality of HF remain high. Malignant arrhythmia is the main cause of sudden death in the progression of HF. Recently, bridging integrator 1 (BIN1) was discovered as a regulator of transverse tubule function and calcium signalling in cardiomyocytes. BIN1 downregulation is linked to abnormal cardiac contraction, and it increases the possibility of malignant arrhythmias preceding HF. Because of the detectability of cardiac BIN1 in peripheral blood, BIN1 may serve as a predictor of HF and may be useful in therapy development. However, the mechanism of BIN1 downregulation in HF and how BIN1 regulates normal cardiac function under physiological conditions remain unclear. In this review, recent progress in the biological studies of BIN1-related cardiomyocytes and the effect of cardiac dysfunction and malignant arrhythmia will be discussed.

Association of a Novel Diagnostic Biomarker, the Plasma Cardiac Bridging Integrator 1 Score, With Heart Failure With Preserved Ejection Fraction and Cardiovascular Hospitalization

Importance

Transverse tubule remodeling is a hallmark of heart failure. Cardiac bridging integrator 1 (cBIN1) is a circulating membrane scaffolding protein that is essential for transverse tubule health, and its plasma level declines with disease.

Objective

To determine if a cBIN1-derived score can serve as a diagnostic biomarker of heart failure with preserved ejection fraction (HFpEF).

Design, Setting, and Participants

In this cohort study, the cBIN1 score (CS) was determined from enzyme-linked immunoabsorbent assay-measured plasma cBIN1 concentrations from study participants in an ambulatory heart failure clinic at Cedars-Sinai Medical Center. Consecutive patients with a confirmed diagnosis of heart failure with preserved ejection fraction (HFpEF; defined by a left ventricular ejection fraction ≥50%) were recruited from July 2014 to November 2015 and compared with age-matched and sex-matched healthy volunteers with no known cardiovascular diagnoses and participants with risk factors for heart failure but no known HFpEF. Baseline characteristics and 1-year longitudinal clinical information were obtained through electronic medical records. Data analysis occurred from November 2016 to November 2017.

Main Outcomes and Measures

The analysis examined the ability of the CS and N-terminal pro-B-type natriuretic peptide (NT-proBNP) results to differentiate among patients with HFpEF, healthy control participants, and control participants with risk factors for heart failure. We further explored the association of the CS with future cardiovascular hospitalizations.

Results

A total of 52 consecutive patients with a confirmed diagnosis of HFpEF were enrolled (mean [SD] age, 57 [15] years; 33 [63%] male). The CS values are significantly higher in the patients with HFpEF (median [interquartile range (IQR)], 1.85 [1.51-2.28]) than in the 2 control cohorts (healthy control participants: median [IQR], -0.03 [-0.48 to 0.41]; control participants with risk factors only: median [IQR], -0.08 [-0.75 to 0.42]; P < .001). For patients with HFpEF, the CS outperforms NT-proBNP when the comparator group was either healthy control participants (CS: area under curve [AUC], 0.98 [95% CI, 0.96-1.00]; NT-proBNP level: AUC, 0.93 [95% CI, 0.88-0.99]; P < .001) or those with risk factors (CS: AUC, 0.98 [95% CI, 0.97-1.00]; NT-proBNP: AUC, 0.93 [95% CI, 0.88-0.99]; P < .001). Kaplan-Meier analysis of 1-year cardiovascular hospitalizations adjusted for age, sex, body mass index, and NT-proBNP levels reveals that patients with HFpEF with CS greater than or equal to 1.80 have a hazard ratio of 3.8 (95% CI, 1.3-11.2; P = .02) for hospitalizations compared with those with scores less than 1.80.

Conclusions and Relevance

If further validated, the plasma CS, a marker of transverse tubule dysfunction, may serve as a biomarker of cardiomyocyte remodeling that has the potential to aide in the diagnosis of HFpEF.

Species differences in the morphology of transverse tubule openings in cardiomyocytes

Aims

The ultrastructure of ventricular cardiomyocyte T-tubule connections with the outer cell surface ('mouth' regions) has been reported to differ between mice and rabbits. In mice, T-tubule mouths form convoluted narrow spaces filled with electron-dense matter that impedes diffusion between T-tubular lumen and bulk extracellular space. Here, we explore whether T-tubule mouths are also constricted in rat (another murine model used frequently for cardiac research) and whether pig and human T-tubule mouth configurations are structurally more similar to mice or rabbits.

Methods and results

We used chemically-fixed tissue and high-pressure frozen isolated cardiomyocytes to compare T-tubule mouth architecture using transmission electron microscopy and three-dimensional electron tomography. We find that rat T-tubular mouth architecture is more similar to that of rabbits than mice, lacking the marked tortuosity and electron-dense ground substance that obstructs access to deeper portions of the T-tubular system in mice. Pilot observations in larger mammals (pig, human) suggest that mouse may be the least representative animal model of T-tubule connectivity with the outer cell surface in larger mammals.

Conclusion

Rat T-tubular system architecture appears to be more similar in size and topology to larger mammals than mice. T-tubular mouth topology may contribute to differences in experimental model behaviour, underscoring the challenge of appropriate model selection for research into cell and tissue function.

BIN1 favors the spreading of Tau via extracellular vesicles

Despite Bridging INtegrator 1 (BIN1) being the second most statistically-significant locus associated to Late Onset Alzheimer’s Disease, its role in disease pathogenesis remains to be clarified. As reports suggest a link between BIN1, Tau and extracellular vesicles, we investigated whether BIN1 could affect Tau spreading via exosomes secretion. We observed that BIN1-associated Tau-containing extracellular vesicles purified from cerebrospinal fluid of AD-affected individuals are seeding-competent. We showed that BIN1 over-expression promotes the release of Tau via extracellular vesicles in vitro as well as exacerbation of Tau pathology in vivo in PS19 mice. Genetic deletion of Bin1 from microglia resulted in reduction of Tau secretion via extracellular vesicles in vitro, and in decrease of Tau spreading in vivo in male, but not female, mice, in the context of PS19 background. Interestingly, ablation of Bin1 in microglia of male mice resulted in significant reduction in the expression of heat-shock proteins, previously implicated in Tau proteostasis. These observations suggest that BIN1 could contribute to the progression of AD-related Tau pathology by altering Tau clearance and promoting release of Tau-enriched extracellular vesicles by microglia.

Endo-lysosomal dysregulations and late-onset Alzheimer's disease: impact of genetic risk factors

Increasing evidence supports that cellular dysregulations in the degradative routes contribute to the initiation and progression of neurodegenerative diseases, including Alzheimer's disease. Autophagy and endolysosomal homeostasis need to be maintained throughout life as they are major cellular mechanisms involved in both the production of toxic amyloid peptides and the clearance of misfolded or aggregated proteins. As such, alterations in endolysosomal and autophagic flux, as a measure of degradation activity in these routes or compartments, may directly impact as well on disease-related mechanisms such as amyloid-β clearance through the blood-brain-barrier and the interneuronal spreading of amyloid-β and/or Tau seeds, affecting synaptic function, plasticity and metabolism. The emerging of several genetic risk factors for late-onset Alzheimer's disease that are functionally related to endocytic transport regulation, including cholesterol metabolism and clearance, supports the notion that in particular the autophagy/lysosomal flux might become more vulnerable during ageing thereby contributing to disease onset. In this review we discuss our current knowledge of the risk genes APOE4, BIN1, CD2AP, PICALM, PLD3 and TREM2 and their impact on endolysosomal (dys)regulations in the light of late-onset Alzheimer's disease pathology.

Message in a vesicle - trans-kingdom intercommunication at the vector-host interface

Vector-borne diseases cause over 700,000 deaths annually and represent 17% of all infectious illnesses worldwide. This public health menace highlights the importance of understanding how arthropod vectors, microbes and their mammalian hosts interact. Currently, an emphasis of the scientific enterprise is at the vector-host interface where human pathogens are acquired and transmitted. At this spatial junction, arthropod effector molecules are secreted, enabling microbial pathogenesis and disease. Extracellular vesicles manipulate signaling networks by carrying proteins, lipids, carbohydrates and regulatory nucleic acids. Therefore, they are well positioned to aid in cell-to-cell communication and mediate molecular interactions. This Review briefly discusses exosome and microvesicle biogenesis, their cargo, and the role that nanovesicles play during pathogen spread, host colonization and disease pathogenesis. We then focus on the role of extracellular vesicles in dictating microbial pathogenesis and host immunity during transmission of vector-borne pathogens.

The therapeutic and diagnostic role of exosomes in cardiovascular diseases

Exosomes are nano-sized membranous vesicles that are secreted by cells. They have an important role in transferring proteins, mRNA, miRNA and other bioactive molecules between cells and regulate gene expression in recipient cells. Therefore, exosomes are a mechanism by which communication between cells is achieved and they are involved in a wide range of physiological processes, especially those requiring cell-cell communication. In the cardiovascular system, exosomes are associated with endothelial cells, cardiac myocytes, vascular cells, stem and progenitor cells, and play an essential role in development, injury and disease of the cardiovascular system. In recent years, accumulating evidence implicates exosomes in the development and progression of cardiovascular disease. Additionally, exosomal microRNAs are considered to be key players in cardiac regeneration and confer cardioprotective and regenerative properties on both cardiac and non-cardiac cells and, additionally, stem and progenitor cells. Notably, miRNAs may be isolated from blood and offer a potential source of novel diagnostic and prognostic biomarkers for cardiovascular disease. In this review, we summarize and assess the functional roles of exosomes in cardiovascular physiology, cell-to-cell communication and cardio-protective effects in cardiovascular disease.