Identification of therapeutic covariant microRNA clusters in hypoxia-treated cardiac progenitor cell exosomes using systems biology

Roles of exosomes in cardioprotection

Exosomes are extracellular vesicles of endosomal origin which have emerged as key mediators of intercellular communication. All major cardiac cell types-including cardiomyocytes, endothelial cells, and fibroblasts-release exosomes that modulate cellular functions. Exosomes released from human cardiac progenitor cells (CPCs) are cardioprotective and improve cardiac function after myocardial infarction to an extent comparable with that achieved by their parent cells. Cardiac progenitor cell-derived exosomes are enriched in cardioprotective microRNAs, particularly miR-146a-3p. Circulating exosomes mediate remote ischaemic preconditioning. Moreover, they currently are being investigated as diagnostic markers. The discovery that cell-derived extracellular signalling organelles mediate the paracrine effects of stem cells suggests that cell-free strategies could supplant cell transplantation. This review discusses emerging roles of exosomes in cardiovascular physiology, with a focus on cardioprotective activities of CPC-derived exosomes.

Do platelets promote cardiac recovery after myocardial infarction: roles beyond occlusive ischemic damage

Our understanding of platelet function has traditionally focused on their roles in physiological hemostasis and pathological thrombosis, with the latter being causative of vessel occlusion and subsequent ischemic damage to various tissues. In particular, numerous in vivo studies have implicated causative roles for platelets in the pathogenesis of ischemia-reperfusion (I/R) injury to the myocardium. However, platelets clearly have more complex pathophysiological roles, particularly as a result of the heterogeneous nature of biologically active cargo secreted from their granules or contained within released microparticles or exosomes. While some of these released mediators amplify platelet activation and thrombosis through autocrine or paracrine amplification pathways, they can also regulate diverse cellular functions within the localized microenvironment and recruit progenitor cells to the damage site to facilitate repair processes. Notably, there is evidence to support cardioprotective roles for platelet mediators during I/R injury. As such, it is becoming more widely appreciated that platelets fulfill a host of physiological and pathological roles beyond our basic understanding. Therefore, the purpose of this perspective is to consider whether platelets, through their released mediators, can assume a paradoxically beneficial role to promote cardiac recovery after I/R injury.

The Potential of Stem Cells and Stem Cell-Derived Exosomes in Treating Cardiovascular Diseases

In recent years, the cardiac protective mechanisms of stem cells have become a research focus. Increasing evidence has suggested that stem cells release vesicles, including exosomes and micro-vesicles. The content of these vesicles relies on an extracellular stimulus, and active ingredients are extensively being studied. Previous studies have confirmed that stem cell-derived exosomes have a cardiac protective function similar to that of stem cells, and promote angiogenesis, decrease apoptosis, and respond to stress. Compared to stem cells, exosomes are more stable without aneuploidy and immune rejection, and may be a promising and effective therapy for cardiovascular diseases. In this review, the biological functions and molecular mechanisms of stem cells and stem cell-derived exosomes are discussed.

The Mingle-Mangle of Wnt Signaling and Extracellular Vesicles: Functional Implications for Heart Research

Wnt signaling is an important pathway in health and disease and a key regulator of stem cell maintenance, differentiation, and proliferation. During heart development, Wnt signaling controls specification, proliferation and differentiation of cardiovascular cells. In this regard, the role of activated Wnt signaling in cardiogenesis is well defined. However, the knowledge about signaling transmission has been challenged. Recently, the packaging of hydrophobic Wnt proteins on extracellular vesicles (EVs) has emerged as a mechanism to facilitate their extracellular spreading and their functioning as morphogens. EVs spread systemically and therefore can have pleiotropic effects on very different cell types. They are heavily studied in tumor biology where they affect tumor growth and vascularization and can serve as biomarkers in liquid biopsies. In this review we will highlight recent discoveries of factors involved in the release of Wnts on EVs and its potential implications in the communication between physiological and pathological heart cells.

New strategies for improving stem cell therapy in ischemic heart disease

Stem cell therapy is a promising approach to the treatment of ischemic heart disease via replenishing cell loss after myocardial infarction. Both preclinical studies and clinical trials have indicated that cardiac function improved consistently, but very modestly after cell-based therapy. This mainly attributed to low cell survival rate, engraftment and functional integration, which became the major challenges to regenerative medicine. In recent years, several new cell types have been developed to regenerate cardiomyocytes and novel delivery approaches helped to increase local cell retention. New strategies, such as cell pretreatment, gene-based therapy, tissue engineering, extracellular vesicles application and immunologic regulation, have surged and brought about improved cell survival and functional integration leading to better therapeutic effects after cell transplantation. In this review, we summarize these new strategies targeting at challenges of cardiac regenerative medicine and discuss recent evidences that may hint their effectiveness in the future clinical settings.

Exosomal microRNA-21-5p Mediates Mesenchymal Stem Cell Paracrine Effects on Human Cardiac Tissue Contractility

RATIONALE

The promising clinical benefits of delivering human mesenchymal stem cells (hMSCs) for treating heart disease warrant a better understanding of underlying mechanisms of action. hMSC exosomes increase myocardial contractility; however, the exosomal cargo responsible for these effects remains unresolved.

OBJECTIVE

This study aims to identify lead cardioactive hMSC exosomal microRNAs to provide a mechanistic basis for optimizing future stem cell-based cardiotherapies.

METHODS AND RESULTS

Integrating systems biology and human engineered cardiac tissue (hECT) technologies, partial least squares regression analysis of exosomal microRNA profiling data predicted microRNA-21-5p (miR-21-5p) levels positively correlate with contractile force and calcium handling gene expression responses in hECTs treated with conditioned media from multiple cell types. Furthermore, miR-21-5p levels were significantly elevated in hECTs treated with the exosome-enriched fraction of the hMSC secretome (hMSC-exo) versus untreated controls. This motivated experimentally testing the human-specific role of miR-21-5p in hMSC-exo-mediated increases of cardiac tissue contractility. Treating hECTs with miR-21-5p alone was sufficient to recapitulate effects observed with hMSC-exo on hECT developed force and expression of associated calcium handling genes (eg, SERCA2a and L-type calcium channel). Conversely, knockdown of miR-21-5p in hMSCs significantly diminished exosomal procontractile and associated calcium handling gene expression effects on hECTs. Western blots supported miR-21-5p effects on calcium handling gene expression at the protein level, corresponding to significantly increased calcium transient amplitude and decreased decay time constant in comparison to miR-scramble control. Mechanistically, cotreating with miR-21-5p and LY294002, a PI3K inhibitor, suppressed these effects. Finally, mathematical simulations predicted the translational capacity for miR-21-5p treatment to restore calcium handling in mature ischemic adult human cardiomyocytes.

CONCLUSIONS

miR-21-5p plays a key role in hMSC-exo-mediated effects on cardiac contractility and calcium handling, likely via PI3K signaling. These findings may open new avenues of research to harness the role of miR-21-5p in optimizing future stem cell-based cardiotherapies.

Targeting regenerative exosomes to myocardial infarction using cardiac homing peptide

Rationale: Cardiac stem cell-derived exosomes have been demonstrated to promote cardiac regeneration following myocardial infarction in preclinical studies. Recent studies have used intramyocardial injection in order to concentrate exosomes in the infarct. Though effective in a research setting, this method is not clinically appealing due to its invasive nature. We propose the use of a targeting peptide, cardiac homing peptide (CHP), to target intravenously-infused exosomes to the infarcted heart. Methods: Exosomes were conjugated with CHP through a DOPE-NHS linker. Ex vivo targeting was analyzed by incubating organ sections with the CHP exosomes and analyzing with fluorescence microscopy. In vitro assays were performed on neonatal rat cardiomyocytes and H9C2 cells. For the animal study, we utilized an ischemia/reperfusion rat model. Animals were treated with either saline, scramble peptide exosomes, or CHP exosomes 24 h after surgery. Echocardiography was performed 4 h after surgery and 21 d after surgery. At 21 d, animals were sacrificed, and organs were collected for analysis. Results: By conjugating the exosomes with CHP, we demonstrate increased retention of the exosomes within heart sections ex vivo and in vitro with neonatal rat cardiomyocytes. In vitro studies showed improved viability, reduced apoptosis and increased exosome uptake when using CHP-XOs. Using an animal model of ischemia/reperfusion injury, we measured the heart function, infarct size, cellular proliferation, and angiogenesis, with improved outcomes with the CHP exosomes. Conclusions: Our results demonstrate a novel method for increasing delivery of for treatment of myocardial infarction. By targeting exosomes to the infarcted heart, there was a significant improvement in outcomes with reduced fibrosis and scar size, and increased cellular proliferation and angiogenesis.

Mitochondrial pathways to cardiac recovery: TFAM

Mitochondrial dysfunction underlines a multitude of pathologies; however, studies are scarce that rescue the mitochondria for cellular resuscitation. Exploration into the protective role of mitochondrial transcription factor A (TFAM) and its mitochondrial functions respective to cardiomyocyte death are in need of further investigation. TFAM is a gene regulator that acts to mitigate calcium mishandling and ROS production by wrapping around mitochondrial DNA (mtDNA) complexes. TFAM's regulatory functions over serca2a, NFAT, and Lon protease contribute to cardiomyocyte stability. Calcium- and ROS-dependent proteases, calpains, and matrix metalloproteinases (MMPs) are abundantly found upregulated in the failing heart. TFAM's regulatory role over ROS production and calcium mishandling leads to further investigation into the cardioprotective role of exogenous TFAM. In an effort to restabilize physiological and contractile activity of cardiomyocytes in HF models, we propose that TFAM-packed exosomes (TFAM-PE) will act therapeutically by mitigating mitochondrial dysfunction. Notably, this is the first mention of exosomal delivery of transcription factors in the literature. Here we elucidate the role of TFAM in mitochondrial rescue and focus on its therapeutic potential.

Concise Review: Optimized Strategies for Stem Cell-Based Therapy in Myocardial Repair: Clinical Translatability and Potential Limitation

Ischemic heart diseases (IHDs) remain major public health problems with high rates of morbidity and mortality worldwide. Despite significant advances, current therapeutic approaches are unable to rescue the extensive and irreversible loss of cardiomyocytes caused by severe ischemia. Over the past 16 years, stem cell-based therapy has been recognized as an innovative strategy for cardiac repair/regeneration and functional recovery after IHDs. Although substantial preclinical animal studies using a variety of stem/progenitor cells have shown promising results, there is a tremendous degree of skepticism in the clinical community as many stem cell trials do not confer any beneficial effects. How to accelerate stem cell-based therapy toward successful clinical application attracts considerate attention. However, many important issues need to be fully addressed. In this Review, we have described and compared the effects of different types of stem cells with their dose, delivery routes, and timing that have been routinely tested in recent preclinical and clinical findings. We have also discussed the potential mechanisms of action of stem cells, and explored the role and underlying regulatory components of stem cell-derived secretomes/exosomes in myocardial repair. Furthermore, we have critically reviewed the different strategies for optimizing both donor stem cells and the target cardiac microenvironments to enhance the engraftment and efficacy of stem cells, highlighting their clinical translatability and potential limitation. Stem Cells 2018;36:482-500.

Biologically active constituents of the secretome of human W8B2+ cardiac stem cells

The benefits of adult stem cells for repair of the heart have been attributed to the repertoire of salutary paracrine activities they appear to exert. We previously isolated human W8B2⁺ cardiac stem cells (CSCs) and found they powerfully influence cardiomyocytes and endothelial cells to collectively promote cardiac repair and regeneration. Here, the complexity of the W8B2⁺ CSC secretomes was characterised and examined in more detail. Using ion exchange chromatography to separate soluble proteins based on their net surface charge, the secreted factors responsible for the pro-survival activity of W8B2⁺ CSCs were found within the low and medium cation fractions. In addition to the soluble proteins, extracellular vesicles generated from W8B2⁺ CSCs not only exhibited pro-survival and pro-angiogenic activities, but also promoted proliferation of neonatal cardiomyocytes. These extracellular vesicles contain a cargo of proteins, mRNA and primary microRNA precursors that are enriched in exosomes and are capable of modulating collectively many of the cellular pathways involved in protein metabolism, cell growth, as well as cellular responses to stress and organisation of the extracellular matrix. Thus the W8B2⁺ CSC secretome contains a multitude of bioactive paracrine factors we have now characterised, that might well be harnessed for therapeutic application for cardiac repair and regeneration.

Exosomes secreted by hypoxic cardiosphere-derived cells enhance tube formation and increase pro-angiogenic miRNA

Exosomes are required for the regenerative effects of human cardiosphere-derived cells (CDCs). Studies show that they mimic the cardioprotective benefits of CDCs in rodents and porcine myocardial infarction (MI) models. Hypoxic preconditioning of stem cells increases the cardioprotective effects of exosomes in MI models by enhancing angiogenesis. Several exosomal microRNAs (miRNAs) up-regulate in response to hypoxia and play a role in cardioprotective and pro-angiogenic effects. In this study, we have demonstrated that human CDCs secreted exosomes under hypoxic conditions (1% O₂ for 2 days) enhanced tube formation by human umbilical vein endothelial cells (HUVECs) at a concentration of 25 µg/mL. Pro-angiogenic exosomal miRNAs including miR-126, miR-130a, and miR-210 showed a substantial increase (>2-, >2-, and >4-fold, respectively) in the hypoxic exosomes compared to normoxic CDC-derived exosomes. Our study suggested a significant benefit of hypoxic CDC exosomes for the treatment of cardiac diseases by induction of angiogenesis via enrichment of pro-angiogenic exosomal miRNAs.

Exosomes derived from hypoxia-preconditioned mesenchymal stromal cells ameliorate cognitive decline by rescuing synaptic dysfunction and regulating inflammatory responses in APP/PS1 mice

Administration of exosomes derived from mesenchymal stromal cells (MSCs) could improve some neurologic conditions by transferring functional biomolecules to recipient cells. Furthermore, exosomes from hypoxic progenitor cells exerted better therapeutic effects in organ injury through specific cargoes. However, there are no related reports about whether exosomes derived from MSCs or hypoxia-preconditioned MSCs (PC-MSCs) could prevent memory deficits in Alzheimer disease (AD). In this study, the exosomes derived from MSCs or PC-MSCs were systemically administered to transgenic APP/PS1 mice. The expression of miR-21 in MSCs was significantly increased after hypoxic treatment. Injection of exosomes from normoxic MSCs could rescue cognition and memory impairment according to results of the Morris water maze test, reduced plaque deposition, and Aβ levels in the brain; could decrease the activation of astrocytes and microglia; could down-regulate proinflammatory cytokines (TNF-α and IL-1β); and could up-regulate anti-inflammatory cytokines (IL-4 and -10) in AD mice, as well as reduce the activation of signal transducer and activator of transcription 3 (STAT3) and NF-κB. Compared to the group administered exosomes from normoxic MSCs, in the group administered exosomes from PC-MSCs, learning and memory capabilities were significantly improved; the plaque deposition and Aβ levels were lower, and expression of growth-associated protein 43, synapsin 1, and IL-10 was increased; and the levels of glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1, TNF-α, IL-1β, and activation of STAT3 and NF-κB were sharply decreased. More importantly, exosomes from PC-MSCs effectively increased the level of miR-21 in the brain of AD mice. Additionally, replenishment of miR-21 restored the cognitive deficits in APP/PS1 mice and prevented pathologic features. Taken together, these findings suggest that exosomes from PC-MSCs could improve the learning and memory capabilities of APP/PS1 mice, and that the underlying mechanism may lie in the restoration of synaptic dysfunction and regulation of inflammatory responses through regulation of miR-21.-Cui, G.-H., Wu, J., Mou, F.-F., Xie, W.-H., Wang, F.-B., Wang, Q.-L., Fang, J., Xu, Y.-W., Dong, Y.-R., Liu, J.-R., Guo, H.-D. Exosomes derived from hypoxia-preconditioned mesenchymal stromal cells ameliorate cognitive decline by rescuing synaptic dysfunction and regulating inflammatory responses in APP/PS1 mice.

Exosomes Secreted by Normoxic and Hypoxic Cardiosphere-derived Cells Have Anti-apoptotic Effect

Cardiosphere-derived cells (CDCs) have emerged as one of the most promising stem cell types for cardiac protection and repair. Exosomes are required for the regenerative effects of human CDCs and mimic the cardioprotective benefits of CDCs such as anti-apoptotic effect in animal myocardial infarction (MI) models. Here we aimed to investigate the anti-apoptotic effect of the hypoxic and normoxic human CDCs-derived exosomes on induced apoptosis in human embryonic stem cell-derived cardiomyocytes (hESC-CMs). In this study, CDCs were cultured under normoxic (18% O₂) and hypoxic (1% O₂) conditions and CDC-exosomes were isolated from conditioned media by differential ultracentrifugation. Cobalt chloride as hypoxia-mimetic agents at a high concentration was used to induce apoptosis in hESC-CMs. The caspase-3/7 activity was determined in apoptosis-induced hESC-CMs. The results indicated that the caspase-positive hESC-CMs were significantly decreased from 30.63 ± 1.44% (normalized against untreated cardiomyocytes) to 1.65 ± 0.1 and 1.1 ± 1.09 in the presence of normoxic exosomes (N-exo) at concentration of 25 and 50 μg/mL, respectively. Furthermore, hypoxic exosomes (H-exo) at concentration of 25 and 50 μg/mL led to 8.75 and 12.86 % reduction in caspase-positive cells, respectively. The anti-apoptotic activity of N-exo at the concentrations of 25 and 50 μg/mL was significantly higher than H-exo. These results could provide insights into optimal preparation of CDCs which would greatly influence the anti-apoptotic effect of CDC-exosomes. Totally, CDC-secreted exosomes have the potential to increase the survival of cardiomyocytes by inhibiting apoptosis. Therefore, CDC-exosomes can be developed as therapeutic strategy in ischemic cardiac disease.

Therapeutic angiogenesis of exosomes for ischemic stroke

Angiogenesis is the process through which new blood vessels are formed, while therapeutic angiogenesis aims to promote and control the angiogenic response. Ischemia results from the lack of blood flow with oxygen and nutrients. Therapeutic angiogenesis is crucial in preserving brain tissue and bodily functions after ischemic stroke. Various approaches have been proposed to promote angiogenesis in ischemic diseases. Traditional protein/gene and subsequent stem/progenitor cell approaches have not shown consistent efficacy for ischemic diseases in clinical trials. Exosomes are microparticles secreted from cells and conduct cell-cell communication including stem cell or cancer cell induced pro-angiogenesis. Utilization of exogenous exosomes for the treatment of ischemic diseases is an emerging approach which may prevent certain disadvantages such as easy degradation and tumor formation happened in other strategies. This review highlights recent reports on the use of exosomes as a therapeutic agent to promote angiogenesis in ischemic stroke.

Thy-1 dependent uptake of mesenchymal stem cell-derived extracellular vesicles blocks myofibroblastic differentiation

Bone marrow-derived mesenchymal stem cells (MSC) have been promoted for multiple therapeutic applications. Many beneficial effects of MSCs are paracrine, dependent on extracellular vesicles (EVs). Although MSC-derived EVs (mEVs) are beneficial for acute lung injury and pulmonary fibrosis, mechanisms of mEV uptake by lung fibroblasts and their effects on myofibroblastic differentiation have not been established. We demonstrate that mEVs, but not fibroblast EVs (fEVs), suppress TGFβ1-induced myofibroblastic differentiation of normal and idiopathic pulmonary fibrosis (IPF) lung fibroblasts. MEVs display increased time- and dose-dependent cellular uptake compared to fEVs. Removal or blocking of Thy-1, or blocking Thy-1-beta integrin interactions, decreased mEV uptake and prevented suppression of myofibroblastic differentiation. MicroRNAs (miRs) 199a/b-3p, 21-5p, 630, 22-3p, 196a-5p, 199b-5p, 34a-5p and 148a-3p are selectively packaged in mEVs. In silico analyses indicated that IPF lung fibroblasts have increased expression of genes that are targets of mEV-enriched miRs. MiR-630 mimics blocked TGFβ1 induction of CDH2 in normal and IPF fibroblasts, and antagomiR-630 abrogated the effect of mEV on CDH2 expression. These data suggest that the interaction of Thy-1 with beta integrins mediates mEV uptake by lung fibroblasts, which blocks myofibroblastic differentiation, and that mEVs are enriched for miRs that target profibrotic genes up-regulated in IPF fibroblasts.

Myocardial Regeneration via Progenitor Cell-Derived Exosomes

In the past 20 years, a variety of cell products has been evaluated in terms of their capacity to treat patients with acute myocardial infarction and chronic heart failure. Despite initial enthusiasm, therapeutic efficacy has overall been disappointing, and clinical application is costly and complex. Recently, a subset of small extracellular vesicles (EVs), commonly referred to as "exosomes," was shown to confer cardioprotective and regenerative signals at a magnitude similar to that of their donor cells. The conceptual advantage is that they may be produced in industrial quantities and stored at the point-of-care for off-the-shelf application, ideally without eliciting a relevant recipient immune response or other adverse effects associated with viable cells. The body of evidence on beneficial exosome-mediated effects in animal models of heart diseases is rapidly growing. However, there is significant heterogeneity in terms of exosome source cells, isolation process, therapeutic dosage, and delivery mode. This review summarizes the current state of research on exosomes as experimental therapy of heart diseases and seeks to identify roadblocks that need to be overcome prior to clinical application.

Beneficial effects of exosomes secreted by cardiac-derived progenitor cells and other cell types in myocardial ischemia

When injected into acutely infarcted rodent or pig hearts, naturally secreted nanovesicles known as exosomes from cardiac-derived progenitor cells (CPCs) reduce scar size and improve cardiac function. In this regard, exosomes fully mimic the benefits of injecting their parent cells. This recognition paves the way to the development of exosome-based, cell-free treatments for heart disease that could possibly supplant cell-based therapies. Mechanisms of benefit of these vesicles are incompletely understood but cytoprotection, stimulation of angiogenesis, induction of antifibrotic cardiac fibroblasts, and modulation of M1/M2 polarization of macrophages infiltrating the infarcted region can all play important roles. Accordingly, the beneficial molecules carried by CPC-secreted exosomes have been identified only in part but cytoprotective and proangiogenic microRNAs (miRNA) and proteins have been described. Besides CPC-secreted exosomes, vesicles released from other cell types including mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iSPCs) have also been associated with cardioprotection. This review aims to discuss recent advances in our understanding of the role of secreted vesicles in cardiac repair, with a focus on CPC-derived exosomes.

Myocardial reparative functions of exosomes from mesenchymal stem cells are enhanced by hypoxia treatment of the cells via transferring microRNA-210 in an nSMase2-dependent way

Hypoxia treatment enhances paracrine effect of mesenchymal stem cells (MSCs). The aim of this study was to investigate whether exosomes from hypoxia-treated MSCs (Exo^H) are superior to those from normoxia-treated MSCs (Exo^N) for myocardial repair. Mouse bone marrow-derived MSCs were cultured under hypoxia or normoxia for 24 h, and exosomes from conditioned media were intramyocardially injected into infarcted heart of C57BL/6 mouse. Exo^H resulted in significantly higher survival, smaller scar size and better cardiac functions recovery. Exo^H conferred increased vascular density, lower cardiomyocytes (CMs) apoptosis, reduced fibrosis and increased recruitment of cardiac progenitor cells in the infarcted heart relative to Exo^N. MicroRNA analysis revealed significantly higher levels of microRNA-210 (miR-210) in Exo^H compared with Exo^N. Transfection of a miR-210 mimic into endothelial cells (ECs) and CMs conferred similar biological effects as Exo^H. Hypoxia treatment of MSCs increased the expression of neutral sphingomyelinase 2 (nSMase2) which is crucial for exosome secretion. Blocking the activity of nSMase2 resulted in reduced miR-210 secretion and abrogated the beneficial effects of Exo^H. In conclusion, hypoxic culture augments miR-210 and nSMase2 activities in MSCs and their secreted exosomes, and this is responsible at least in part for the enhanced cardioprotective actions of exosomes derived from hypoxia-treated cells.

Stem Cell-Derived Exosomes, Autophagy, Extracellular Matrix Turnover, and miRNAs in Cardiac Regeneration during Stem Cell Therapy

Stem cell therapy (SCT) raises the hope for cardiac regeneration in ischemic hearts. However, underlying molecular mechanisms for repair of dead myocardium by SCT in the ischemic heart is poorly understood. Growing evidences suggest that cardiac matrix stiffness and differential expressions of miRNAs play a crucial role in stem cell survival and differentiation. However, their roles on transplanted stem cells, for myocardial repair of the ischemic heart, remain unclear. Transplanted stem cells may act in an autocrine and/or paracrine manner to regenerate the dead myocardium. Paracrine mediators such as stem cell-derived exosomes are emerging as a novel therapeutic strategy to overcome some of the limitations of SCT. These exosomes carry microRNAs (miRNAs) that may regulate stem cell differentiation into a specific lineage. MicroRNAs may also contribute to stiffness of surrounding matrix by regulating extracellular matrix (ECM) turnover. The survival of transplanted stem cell depends on its autophagic process that maintains cellular homeostasis. Therefore, exosomes, miRNAs, extracellular matrix turnover, and autophagy may have an integral role in improving the efficacy of SCT. This review elaborates the specific roles of these regulatory components on cardiac regeneration in the ischemic heart during SCT.

Exosomes contribute to endothelial integrity and acute chest syndrome risk: Preliminary findings

BACKGROUND

Acute Chest Syndrome (ACS) is one of the leading causes of death among children with Sickle Cell Disease (SCD). Disruption of microvascular integrity is critical to the pathophysiology of ACS, but the factors governing its phenotypic variability are incompletely understood. Because circulating exosomes have been implicated in vascular dysfunction in various diseases, we hypothesized that exosomes induce endothelial dysfunction in patients who experience ACS.

PROCEDURE

Cross-sectional cohort study including 33 outpatients with SCD (without new health-related complaints or recent transfusions) and a cohort of control patients. Exosomes were isolated from platelet-free plasma.

RESULTS

ImageStream showed that exosome counts were greatly increased in patients with SCD compared with controls, but there were few differences in the concentrations of exosomes between patients who had experienced ACS (ACS(+)) and those who had not (ACS(-)). Exosomes were added to human microvascular endothelial cells, and the exosomal effects on monolayer integrity was determined using Electric Cell-substrate Impedance Sensing (ECIS). Exosomes from SCD patients without ACS differed minimally from control patients; however, exosomes from ACS(+) decreased endothelial cell resistance compared to ACS(-), (Relative resistance: ACS(+): 0.981 ± 0.055 vs ACS(-): 1.124 ± 0.042; P = 0.006). Treatment of endothelial cultures with exosomes from ACS(-) patients increased endothelial Nitric Oxide Synthase (eNOS) mRNA expression, while ACS(+)-derived exosomes were not able to increase eNOS expression above that of controls.

CONCLUSIONS

These findings demonstrate that patients with SCD have circulating exosomes that produce differential effects that may contribute to the pathophysiology of ACS and may serve as risk-related biomarkers.

Ethanol Induces Enhanced Vascularization Bioactivity of Endothelial Cell-Derived Extracellular Vesicles via Regulation of MicroRNAs and Long Non-Coding RNAs

Extracellular vesicles (EVs), such as exosomes, have been identified as regulators of vascular remodeling and have promise as therapeutics for vascularization applications. Towards development of EVs as therapeutics, it has been demonstrated that physiological stimuli of angiogenic phenotypes in EV-producing cells can enhance the potency of EVs for vascularization. The goal of this study was to assess whether ethanol, which induces angiogenic phenotypes in endothelial cells, could be employed to enhance endothelial-derived EV vascularization bioactivity. The results indicate that ethanol conditioning of endothelial cells increases the ability of endothelial EVs to induce a pro-vascularization response. This response is due in part to increased CD34 expression in recipient endothelial cells that may result from downregulation of microRNA-106b in EVs isolated from ethanol-conditioned producer endothelial cells. Further, ethanol-induced upregulation of long non-coding RNAs (lncRNAs) HOTAIR and MALAT1 in endothelial EVs was observed to play a significant role in mediating pro-angiogenic effects of these vesicles. Overall, these studies validate ethanol conditioning as a method to enhance the bioactivity of endothelial EVs via regulation of EV-associated microRNAs (miRNAs) and, especially, lncRNAs. Further, the results suggest that alcohol consumption may activate endothelial EVs towards a pro-vascularization phenotype, which could have implications for alcohol-induced tumor angiogenesis.

Human Endothelial Progenitor Cell-Derived Exosomes Increase Proliferation and Angiogenesis in Cardiac Fibroblasts by Promoting the Mesenchymal-Endothelial Transition and Reducing High Mobility Group Box 1 Protein B1 Expression

Myocardial fibrosis is a characteristic feature of cardiomyopathies. However, no effective strategies to attenuate cardiac fibrosis are currently available. Late-stage endothelial progenitor cells (EPCs) are precursors of endothelial cells (ECs) that repair the heart through a paracrine mechanism. In the present study, we tested whether EPC-derived exosomes regulate the differentiation of fibroblasts into ECs. We isolated late-stage EPCs from human peripheral blood (PB) and used immunofluorescence and flow cytometry to confirm their identity. Next, we isolated exosomes from the EPCs and characterized their morphology using electron microscopy and confirmed the expression of exosome-specific marker proteins using Western blots. We then investigated the in vitro effects of exosomes on the proliferation and angiogenesis of cardiac fibroblasts (CFs) and on the expression of the mesenchymal-endothelial transition (MEndT)-related genes and the myocardial fibrosis-regulated protein, high mobility group box 1 protein B1 (HMGB1). We found that human PB-EPC-derived exosomes enhanced the proliferation and angiogenesis of CFs in vitro. Furthermore, CFs stimulated with these exosomes showed increased expression of the EC-specific markers, like cluster of differentiation 31 and vascular endothelial growth factor receptor 2, and decreased expression of proteins involved in fibrosis, like alpha-smooth muscle actin, vimentin, collagen I, transforming growth factor-beta, and tumor necrosis factor-alpha. In addition, CFs stimulated with human PB-EPC-derived exosomes, inhibited the expression of HMGB1. Taken together, our study demonstrated that EPC-derived exosomes promote the proliferation and angiogenesis of CFs by inhibiting MEndT and decreasing the expression of HMGB1.

Cardiac progenitor cells application in cardiovascular disease

Stem cells (SCs) have special potency to differentiate into different types of cells, especially cardiomyocytes. In order to demonstrate the therapeutic applications of these cells, various investigations are recently being developed. Cardiac progenitor cells are endogenous cardiac SCs that found to express tyrosine kinase receptors, c-Kit and other stemness features in adult heart, contributing to the regeneration of cardiac tissue after injury. This lineage is able to efficiently trans-differentiate into different cell types such as cardiomyocytes, endothelial cells, and smooth muscle cells. Noticeably, several cardiac progenitor cells have been identified until yet. The therapeutic applications of cardiac SCs have been studied previously, which could introduce a novel therapeutic approach in the treatment of cardiac disorders. The current review enlightens the potency of cardiac progenitor cells features and differentiation capacity, with current applications in cardiovascular field.

Exosomes in Critical Illness

OBJECTIVE

Exosomes are small, cell-released vesicles (40-100 nm in size) with the potential to transfer proteins, lipids, small RNAs, messenger RNAs, or DNA between cells via interstitial fluids. Due to their role in tissue homeostasis, exosomes have emerged as a new type of therapeutic and diagnostic (theranostic) tool in the noninvasive assessment of organ response to injury or treatment and in the development of reliable organ-protective intensive therapy. Our review provides current insights into the role of exosomes in the personalized management of injury and repair responses in critical illness.

DATA SOURCE

Data were obtained from a PubMed search of the most recent medical literature, including the PubMed "related articles" search methodology.

STUDY SELECTION

Articles considered include original articles, review articles and conference proceedings.

DATA EXTRACTION

A detailed review of scientific, peer-reviewed data was performed. Relevant pre-clinical and clinical studies were included and summarized.

DATA SYNTHESIS

Current scientific evidence is focused on the following: 1) Frontiers in the management of critical illness; 2) Biogenesis, characterization, and function of circulating exosomes; 3) The role of exosomes in acute lung injury; 4) The role of exosomes in acute cardiac injury; 5) The role of exosomes in acute kidney injury; 6) The role of exosomes in sepsis; 7) Limitations of exosome isolation protocols; and 8) Perspectives in the theranostic use of exosomes.

CONCLUSIONS

Circulating levels of exosomes are associated with the onset and clinical course of critical illness. Exosomes released from cells with different phenotypes exert different functions in order to protect tissue and preserve organ function. Therefore, multifunctional exosomes with combined diagnostic and therapeutic functions show great promise in terms of personalized nanomedicine for patient-specific diagnosis and treatment of critical illness.

Exosomes as agents of change in the cardiovascular system

Exosomes have an evolving role in paracrine and autocrine signaling, which is enhanced because these lipid vesicles are quite stable and can deliver miRNA, DNA, protein and other molecules to cells throughout the body. Most cell types release exosomes, and exosomes are found in all biological fluids, making them accessible biomarkers. Significantly, exosomes can carry a biologically potent cargo, which can alter the phenotype of recipient cells. In the cardiovascular system exosomes have been primarily studied for their role in mediating the beneficial effects of mesenchymal stem cells after myocardial injury. Exosomes released by cardiac cells in disease states, such as myocardial ischemia, can potentially have important pathophysiologic effects on other cardiac cells as well as on distant organs.

Exosomes: A Rising Star in Falling Hearts

Although exosomes were previously recognized as a mechanism for discharging useless cellular components, growing evidence has elucidated their roles in conveying information between cells. They contribute to cell-cell communication by carrying nucleic acids, proteins and lipids that can, in turn, regulate behavior of the target cells. Recent research suggested that exosomes extensively participate in progression of diverse cardiovascular diseases (CVDs), such as myocardial infarction, cardiomyopathy, pulmonary arterial hypertension and others. Here, we summarize effects of exosome-derived molecules (mainly microRNAs and proteins) on cardiac function, to examine their potential applications as biomarkers or therapeutics in CVDs.

Concise Review: Challenges in Regenerating the Diabetic Heart: A Comprehensive Review

Stem cell therapy is one of the promising regenerative strategies developed to improve cardiac function in patients with ischemic heart diseases (IHD). However, this approach is limited in IHD patients with diabetes due to a progressive decline in the regenerative capacity of stem cells. This decline is mainly attributed to the metabolic memory incurred by diabetes on stem cell niche and their systemic cues. Understanding the molecular pathways involved in the diabetes-induced deterioration of stem cell function will be critical for developing new cardiac regeneration therapies. In this review, we first discuss the most common molecular alterations occurring in the diabetic stem cells/progenitor cells. Next, we highlight the key signaling pathways that can be dysregulated in a diabetic environment and impair the mobilization of stem/progenitor cells, which is essential for the transplanted/endogenous stem cells to reach the site of injury. We further discuss the possible methods of preconditioning the diabetic cardiac progenitor cell (CPC) with an aim to enrich the availability of efficient stem cells to regenerate the diseased diabetic heart. Finally, we propose new modalities for enriching the diabetic CPC through genetic or tissue engineering that would aid in developing autologous therapeutic strategies, improving the proliferative, angiogenic, and cardiogenic properties of diabetic stem/progenitor cells. Stem Cells 2017;35:2009-2026.

Exosomes: promising sacks for treating ischemic heart disease?

Ischemic heart disease(IHD) is the leading cause of death worldwide. Despite the development of continuously improving therapeutic strategies, morbidity and mortality of patients with IHD remain relatively high. Exosomes are a subpopulation of vesicles that are universally recognized as major mediators in intercellular communication. Numerous preclinical studies have shown that these tiny vesicles were protective in IHD, through such actions as alleviating myocardial ischemia-reperfusion injury, promoting angiogenesis, inhibiting fibrosis, and facilitating cardiac regeneration. Our review focused on these beneficial exosome-mediated processes. In addition, we discuss in detail how to fully exploit the therapeutic potentials of exosomes in the field of IHD. Topics include identifying robust sources of exosomes, loading protective agents into exosomes, developing heart-specific exosomes, optimizing isolation methods, and translating the cardioprotective effects of exosomes into clinical practice. Finally, both the advantages and disadvantages of utilizing exosomes in clinical settings are addressed.

Stem Cell Therapy: A New Therapeutic Option for Cardiovascular Diseases

Cardiovascular diseases are known as one of major causes of morbidity and mortality worldwide. Despite the many advancement in therapies are associated with cardiovascular diseases, it seems that finding of new therapeutic option is necessary. Cell therapy is one of attractive therapeutic platforms for treatment of a variety of diseases such as cardiovascular diseases. Among of various types of cell therapy, stem cell therapy has been emerged as an effective therapeutic approach in this area. Stem cells divided into multipotent stem cells and pluripotent stem cells. A large number studies indicated that utilization of each of them are associated with a variety of advantages and disadvantages. Multiple lines evidence indicated that stem cell therapy could be used as suitable therapeutic approach for treatment of cardiovascular diseases. Many clinical trials have been performed for assessing efficiency of stem cell therapies in human. However, stem cell therapy are associated with some challenges, but, it seems resolving of them could contribute to using of them as effective therapeutic approach for patients who suffering from cardiovascular diseases. In the current review, we summarized current therapeutic strategies based on stem cells for cardiovascular diseases. J. Cell. Biochem. 119: 95-104, 2018. © 2017 Wiley Periodicals, Inc.

Pulmonary microRNA profiling: implications in upper lobe predominant lung disease

Background

Numerous pulmonary diseases manifest with upper lobe predominance including cystic fibrosis, smoking-related chronic obstructive pulmonary disease, and tuberculosis. Zonal hypoxia, characteristic of these pulmonary maladies, and oxygen stress in general is known to exert profound effects on various important aspects of cell biology. Lung macrophages are major participants in the pulmonary innate immune response and regional differences in macrophage responsiveness to hypoxia may contribute in the development of lung disease. MicroRNAs are ubiquitous regulators of human biology and emerging evidence indicates altered microRNA expression modulates respiratory disease processes. The objective of this study is to gain insight into the epigenetic and cellular mechanisms influencing regional differences in lung disease by investigating effect of hypoxia on regional microRNA expression in the lung.

All studies were performed using primary alveolar macrophages (n = 10) or bronchoalveolar lavage fluid (n = 16) isolated from human subjects. MicroRNA was assayed via the NanoString nCounter microRNA assay.

Results

Divergent molecular patterns of microRNA expression were observed in alternate lung lobes, specifically noted was disparate expression of miR-93 and miR-4454 in alveolar macrophages along with altered expression of miR-451a and miR-663a in bronchoalveolar lavage fluid. Gene ontology was used to identify potential downstream targets of divergent microRNAs. Targets include cytokines and matrix metalloproteinases, molecules that could have a significant impact on pulmonary inflammation and fibrosis.

Conclusions

Our findings show variant regional microRNA expression associated with hypoxia in alveolar macrophages and BAL fluid in the lung—upper vs lower lobe. Future studies should address whether these specific microRNAs may act intracellularly, in a paracrine/endocrine manner to direct the innate immune response or may ultimately be involved in pulmonary host-to-pathogen trans-kingdom cross-talk.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0355-1) contains supplementary material, which is available to authorized users.

Exocytosis-Mediated Urinary Full-Length Megalin Excretion Is Linked With the Pathogenesis of Diabetic Nephropathy

Efficient biomarkers for diabetic nephropathy (DN) have not been established. Using ELISA, we found previously that urinary levels of full-length megalin (C-megalin), a multiligand endocytic receptor in proximal tubules, was positively correlated with DN progression in patients with type 2 diabetes mellitus (T2DM). Here, we found that urinary extracellular vesicle (UEV) excretion and C-megalin content in UEVs or in their exosomal fraction increased along with the progression of the albuminuric stages in patients with T2DM. Cultured immortalized rat proximal tubule cells (IRPTCs) treated with fatty acid-free BSA or advanced glycation end product-modified BSA (AGE-BSA), endocytic ligands of megalin, increased EV excretion, and their C-megalin content. C-megalin excretion from IRPTCs via extracellular vesicles was significantly blocked by an exosome-specific inhibitor, GW4869, indicating that this excretion is mainly exocytosis-mediated. AGE-BSA treatment of IRPTCs caused apparent lysosomal dysfunction, which stimulated multivesicular body formation, resulting in increased exosomal C-megalin excretion. In a high-fat diet-induced, megalin-mediated kidney injury model in mice, urinary C-megalin excretion also increased via UEVs. Collectively, exocytosis-mediated urinary C-megalin excretion is associated with the development and progression of DN in patients with T2DM, particularly due to megalin-mediated lysosomal dysfunction in proximal tubules, and hence it could be a candidate biomarker linked with DN pathogenesis.

Exosomal MicroRNA Transfer Into Macrophages Mediates Cellular Postconditioning

BACKGROUND

Cardiosphere-derived cells (CDCs) confer cardioprotection in acute myocardial infarction by distinctive macrophage (Mϕ) polarization. Here we demonstrate that CDC-secreted exosomes (CDC_exo) recapitulate the cardioprotective effects of CDC therapy known as cellular postconditioning.

METHODS

Rats and pigs underwent myocardial infarction induced by ischemia/reperfusion before intracoronary infusion of CDC_exo, inert fibroblast exosomes (Fb_exo; control), or vehicle. Two days later, infarct size was quantified. Macrophages were isolated from cardiac tissue or bone marrow for downstream analyses. RNA sequencing was used to determine exosome content and alterations in gene expression profiles in Mϕ.

RESULTS

Administration of CDC_exo but not Fb_exo after reperfusion reduces infarct size in rat and pig models of myocardial infarction. Furthermore, CDC_exo reduce the number of CD68+ Mϕ within infarcted tissue and modify the polarization state of Mϕ so as to mimic that induced by CDCs. CDC_exo are enriched in several miRNAs (including miR-146a, miR-181b, and miR-126) relative to Fb_exo. Reverse pathway analysis of whole-transcriptome data from CDC_exo-primed Mϕ implicated miR-181b as a significant (P=1.3x10^-21) candidate mediator of CDC-induced Mϕ polarization, and PKCδ (protein kinase C δ) as a downstream target. Otherwise inert Fb_exo loaded selectively with miR-181b alter Mϕ phenotype and confer cardioprotective efficacy in a rat model of myocardial infarction. Adoptive transfer of PKCδ-suppressed Mϕ recapitulates cardioprotection.

CONCLUSIONS

Our data support the hypothesis that exosomal transfer of miR-181b from CDCs into Mϕ reduces PKCδ transcript levels and underlies the cardioprotective effects of CDCs administered after reperfusion.

Overexpression of Exosomal Cardioprotective miRNAs Mitigates Hypoxia-Induced H9c2 Cells Apoptosis

Recent evidence suggests that hypoxia caused by acute myocardial infarction can induce cardiomyocyte apoptosis. Exosomes are signalling mediators that contribute to intercellular communication by transporting cytosolic components including miRNAs, mRNAs, and proteins. However, the systemic regulation and function of exosomal miRNAs in hypoxic cardiomyocytes are currently not well understood. Here, we used small RNA sequencing to investigate the effects of hypoxia stress on miRNAome of rat cardiomyoblast cells (H9c2) and corresponding exosomes. We identified 92 and 62 miRNAs in cells and exosomes, respectively, that were differentially expressed between hypoxia and normoxia. Hypoxia strongly modulated expression of hypoxia-associated miRNAs in H9c2 cells, and altered the miRNAome of H9c2 cells-derived exosomes. Functional enrichment analysis revealed extensive roles of differentially expressed exosomal miRNAs in the HIF-1 signalling pathway and in apoptosis-related pathways including the TNF, MAPK, and mTOR pathways. Furthermore, gain- and loss-of-function analysis demonstrated potential anti-apoptotic effects of the hypoxia-induced exosomal miRNAs, including miR-21-5p, miR-378-3p, miR-152-3p, and let-7i-5p; luciferase reporter assay confirmed that Atg12 and Faslg are targets of miR-152-3p and let-7i-5p, respectively. To summarize, this study revealed that hypoxia-induced exosomes derived from H9c2 cells loaded cardioprotective miRNAs, which mitigate hypoxia-induced H9c2 cells apoptosis.

Angiogenic Mechanisms of Human CD34+ Stem Cell Exosomes in the Repair of Ischemic Hindlimb

RATIONALE

Paracrine secretions seem to mediate therapeutic effects of human CD34⁺ stem cells locally transplanted in patients with myocardial and critical limb ischemia and in animal models. Earlier, we had discovered that paracrine secretion from human CD34⁺ cells contains proangiogenic, membrane-bound nanovesicles called exosomes (CD34Exo).

OBJECTIVE

Here, we investigated the mechanisms of CD34Exo-mediated ischemic tissue repair and therapeutic angiogenesis by studying their miRNA content and uptake.

METHODS AND RESULTS

When injected into mouse ischemic hindlimb tissue, CD34Exo, but not the CD34Exo-depleted conditioned media, mimicked the beneficial activity of their parent cells by improving ischemic limb perfusion, capillary density, motor function, and their amputation. CD34Exo were found to be enriched with proangiogenic miRNAs such as miR-126-3p. Knocking down miR-126-3p from CD34Exo abolished their angiogenic activity and beneficial function both in vitro and in vivo. Interestingly, injection of CD34Exo increased miR-126-3p levels in mouse ischemic limb but did not affect the endogenous synthesis of miR-126-3p, suggesting a direct transfer of stable and functional exosomal miR-126-3p. miR-126-3p enhanced angiogenesis by suppressing the expression of its known target, SPRED1, simultaneously modulating the expression of genes involved in angiogenic pathways such as VEGF (vascular endothelial growth factor), ANG1 (angiopoietin 1), ANG2 (angiopoietin 2), MMP9 (matrix metallopeptidase 9), TSP1 (thrombospondin 1), etc. Interestingly, CD34Exo, when treated to ischemic hindlimbs, were most efficiently internalized by endothelial cells relative to smooth muscle cells and fibroblasts, demonstrating a direct role of stem cell-derived exosomes on mouse endothelium at the cellular level.

CONCLUSIONS

Collectively, our results have demonstrated a novel mechanism by which cell-free CD34Exo mediates ischemic tissue repair via beneficial angiogenesis. Exosome-shuttled proangiogenic miRNAs may signify amplification of stem cell function and may explain the angiogenic and therapeutic benefits associated with CD34⁺ stem cell therapy.

Fabrication of Synthetic Mesenchymal Stem Cells for the Treatment of Acute Myocardial Infarction in Mice

RATIONALE

Stem cell therapy faces several challenges. It is difficult to grow, preserve, and transport stem cells before they are administered to the patient. Synthetic analogs for stem cells represent a new approach to overcome these hurdles and hold the potential to revolutionize regenerative medicine.

OBJECTIVE

We aim to fabricate synthetic analogs of stem cells and test their therapeutic potential for treatment of acute myocardial infarction in mice.

METHODS AND RESULTS

We packaged secreted factors from human bone marrow-derived mesenchymal stem cells (MSC) into poly(lactic-co-glycolic acid) microparticles and then coated them with MSC membranes. We named these therapeutic particles synthetic MSC (or synMSC). synMSC exhibited a factor release profile and surface antigens similar to those of genuine MSC. synMSC promoted cardiomyocyte functions and displayed cryopreservation and lyophilization stability in vitro and in vivo. In a mouse model of acute myocardial infarction, direct injection of synMSC promoted angiogenesis and mitigated left ventricle remodeling.

CONCLUSIONS

We successfully fabricated a synMSC therapeutic particle and demonstrated its regenerative potential in mice with acute myocardial infarction. The synMSC strategy may provide novel insight into tissue engineering for treating multiple diseases.

First Characterization of Human Amniotic Fluid Stem Cell Extracellular Vesicles as a Powerful Paracrine Tool Endowed with Regenerative Potential

Human amniotic fluid stem cells (hAFS) have shown a distinct secretory profile and significant regenerative potential in several preclinical models of disease. Nevertheless, little is known about the detailed characterization of their secretome. Herein we show for the first time that hAFS actively release extracellular vesicles (EV) endowed with significant paracrine potential and regenerative effect. c‐KIT⁺ hAFS were isolated from leftover samples of amniotic fluid from prenatal screening and stimulated to enhance EV release (24 hours 20% O₂ versus 1% O₂ preconditioning). The capacity of the c‐KIT⁺ hAFS‐derived EV (hAFS‐EV) to induce proliferation, survival, immunomodulation, and angiogenesis were investigated in vitro and in vivo. The hAFS‐EV regenerative potential was also assessed in a model of skeletal muscle atrophy (HSA‐Cre, Smn^F7/F7 mice), in which mouse AFS transplantation was previously shown to enhance muscle strength and survival. hAFS secreted EV ranged from 50 up to 1,000 nm in size. In vitro analysis defined their role as biological mediators of regenerative, paracrine effects while their modulatory role in decreasing skeletal muscle inflammation in vivo was shown for the first time. Hypoxic preconditioning significantly induced the enrichment of exosomes endowed with regenerative microRNAs within the hAFS‐EV. In conclusion, this is the first study showing that c‐KIT⁺ hAFS dynamically release EV endowed with remarkable paracrine potential, thus representing an appealing tool for future regenerative therapy. Stem Cells Translational Medicine2017;6:1340–1355

Vesicle miR-195 derived from Endothelial Cells Inhibits Expression of Serotonin Transporter in Vessel Smooth Muscle Cells

Serotonin or 5-hydroxytryptamine (5-HT) has been shown to be essential in lots of physiological and pathological processes. It is well known that 5-HT and 5-HT transporter (5-HTT) play important roles in the pulmonary artery in pulmonary hypertension. However, little is known about the function of 5-HTT in other arteries. In this study we found that the expression of 5-HTT was elevated in injured carotid arteries and over-expression of 5-HTT induced proliferation of smooth muscle cells (SMCs); however, this phenotype could be reversed by knocking-down of 5-HTT or endothelial cells conditional medium (EC-CM). A 5-HTT inhibitor, fluoxetine, treated animals also exhibited reduced restenosis after injury. We identified that miR-195 was packaged in the extracellular vesicles from EC-CM. We further confirmed that extracellular vesicles could transfer miR-195 from ECs to SMCs to inhibit the expression of 5-HTT in SMCs and the proliferation of SMCs. These results provide the first evidence that ECs communicate with SMCs via micro-RNA195 in the regulation of the proliferation of SMCs through 5-HTT, which will contribute to a better understanding of communications between ECs and SMCs via micro-RNA. Our findings suggest a potential target for the control of vessel restenosis.

Obstacles and opportunities in the functional analysis of extracellular vesicle RNA - an ISEV position paper

The release of RNA-containing extracellular vesicles (EV) into the extracellular milieu has been demonstrated in a multitude of different in vitro cell systems and in a variety of body fluids. RNA-containing EV are in the limelight for their capacity to communicate genetically encoded messages to other cells, their suitability as candidate biomarkers for diseases, and their use as therapeutic agents. Although EV-RNA has attracted enormous interest from basic researchers, clinicians, and industry, we currently have limited knowledge on which mechanisms drive and regulate RNA incorporation into EV and on how RNA-encoded messages affect signalling processes in EV-targeted cells. Moreover, EV-RNA research faces various technical challenges, such as standardisation of EV isolation methods, optimisation of methodologies to isolate and characterise minute quantities of RNA found in EV, and development of approaches to demonstrate functional transfer of EV-RNA in vivo. These topics were discussed at the 2015 EV-RNA workshop of the International Society for Extracellular Vesicles. This position paper was written by the participants of the workshop not only to give an overview of the current state of knowledge in the field, but also to clarify that our incomplete knowledge – of the nature of EV(-RNA)s and of how to effectively and reliably study them – currently prohibits the implementation of gold standards in EV-RNA research. In addition, this paper creates awareness of possibilities and limitations of currently used strategies to investigate EV-RNA and calls for caution in interpretation of the obtained data.

Endothelial miRNAs as Cellular Messengers in Cardiometabolic Diseases

Metabolic syndrome is a clustering of risk factors that increases susceptibility to serious cardiometabolic complications, including type 2 diabetes (T2D) and myocardial infarction. Understanding the underlying mechanisms will advance the development of diagnostic and therapeutic approaches. A prominent feature of cardiometabolic diseases is endothelial dysfunction. Endothelial cell (EC) homeostasis and response to pathological stimuli are controlled by gene regulatory networks in which miRNAs play a critical role. Recently, miRNAs have been implicated as cell-cell messengers that can influence cellular function. This review investigates the known and potential roles for miRNA-based cell-cell communication in the control of cardiovascular health and explores the value of identifying miRNA biomarkers and developing therapeutics that harness or antagonize miRNA-based communication.

Increased Circulating Exosomal miRNA-223 Is Associated with Acute Ischemic Stroke

Recent studies have demonstrated that exosomal microRNAs (miRNAs) are novel biomarkers and therapeutic targets for various diseases including vascular disease. However, specific exosomal miRNAs expression in stroke patients has not been reported yet. Here, we explored whether circulating exosomal miRNAs can serve as potential biomarkers for the diagnosis of acute ischemic stroke and discussed the potential for clinical application. Blood samples were collected from acute ischemic stroke patients within the first 72 h (n = 50). Circulating exosomes were exacted by Exoquick exosome isolation kit and characterized by transmission electron microscopy. Western blot was performed to assess the expression of exosomal protein makers. Exosomal miRNA-223 (miR-223) was detected by RT-PCR assay. The relationship between the expression levels of miR-223 and National Institutes of Health Stroke Scale (NIHSS) scores, brain infarct volume, and neurological outcomes were analyzed. Circulating exosomes were isolated and the size of vesicles ranged between 30 and 100 nm. The identification of exosomes was further confirmed by the detection of specific exosomal protein markers CD9, CD63, and Tsg101. Exosomal miR-223 in acute ischemic stroke patients was significantly upregulated compared to control group (p < 0.001). Exosomal miR-223 level was positively correlated with NIHSS scores (r = 0.31, p = 0.03). Exosomal miR-223 expression in stroke patients with poor outcomes was higher than those with good outcomes (p < 0.05). Increased exosomal miR-223 was associated with acute ischemic stroke occurrence, stroke severity, and short-term outcomes. Future studies with large sample are needed to assess the clinical application of exosomal miR-223 as a novel biomarker for ischemic stroke diagnosis.

Experimental, Systems, and Computational Approaches to Understanding the MicroRNA-Mediated Reparative Potential of Cardiac Progenitor Cell-Derived Exosomes From Pediatric Patients

RATIONALE

Studies have demonstrated that exosomes can repair cardiac tissue post-myocardial infarction and recapitulate the benefits of cellular therapy.

OBJECTIVE

We evaluated the role of donor age and hypoxia of human pediatric cardiac progenitor cell (CPC)-derived exosomes in a rat model of ischemia-reperfusion injury.

METHODS AND RESULTS

Human CPCs from the right atrial appendages from children of different ages undergoing cardiac surgery for congenital heart defects were isolated and cultured under hypoxic or normoxic conditions. Exosomes were isolated from the culture-conditioned media and delivered to athymic rats after ischemia-reperfusion injury. Echocardiography at day 3 post-myocardial infarction suggested statistically improved function in neonatal hypoxic and neonatal normoxic groups compared with saline-treated controls. At 28 days post-myocardial infarction, exosomes derived from neonatal normoxia, neonatal hypoxia, infant hypoxia, and child hypoxia significantly improved cardiac function compared with those from saline-treated controls. Staining showed decreased fibrosis and improved angiogenesis in hypoxic groups compared with controls. Finally, using sequencing data, a computational model was generated to link microRNA levels to specific outcomes.

CONCLUSIONS

CPC exosomes derived from neonates improved cardiac function independent of culture oxygen levels, whereas CPC exosomes from older children were not reparative unless subjected to hypoxic conditions. Cardiac functional improvements were associated with increased angiogenesis, reduced fibrosis, and improved hypertrophy, resulting in improved cardiac function; however, mechanisms for normoxic neonatal CPC exosomes improved function independent of those mechanisms. This is the first study of its kind demonstrating that donor age and oxygen content in the microenvironment significantly alter the efficacy of human CPC-derived exosomes.

Exosomes Generated From iPSC-Derivatives: New Direction for Stem Cell Therapy in Human Heart Diseases

Cardiovascular disease (CVD) is the leading cause of death in modern society. The adult heart innately lacks the capacity to repair and regenerate the damaged myocardium from ischemic injury. Limited understanding of cardiac tissue repair process hampers the development of effective therapeutic solutions to treat CVD such as ischemic cardiomyopathy. In recent years, rapid emergence of induced pluripotent stem cells (iPSC) and iPSC-derived cardiomyocytes presents a valuable opportunity to replenish the functional cells to the heart. The therapeutic effects of iPSC-derived cells have been investigated in many preclinical studies. However, the underlying mechanisms of iPSC-derived cell therapy are still unclear, and limited engraftment of iPSC-derived cardiomyocytes is well known. One facet of their mechanism is the paracrine effect of the transplanted cells. Microvesicles such as exosomes secreted from the iPSC-derived cardiomyocytes exert protective effects by transferring the endogenous molecules to salvage the injured neighboring cells by regulating apoptosis, inflammation, fibrosis, and angiogenesis. In this review, we will focus on the current advances in the exosomes from iPSC derivatives and discuss their therapeutic potential in the treatment of CVD.

Exosomes secreted by cardiosphere-derived cells reduce scarring, attenuate adverse remodelling, and improve function in acute and chronic porcine myocardial infarction

Aims

Naturally secreted nanovesicles known as exosomes are required for the regenerative effects of cardiosphere-derived cells (CDCs), and exosomes mimic the benefits of CDCs in rodents. Nevertheless, exosomes have not been studied in a translationally realistic large-animal model. We sought to optimize delivery and assess the efficacy of CDC-secreted exosomes in pig models of acute (AMI) and convalescent myocardial infarction (CMI).

Methods and Results

In AMI, pigs received human CDC exosomes (or vehicle) by intracoronary (IC) or open-chest intramyocardial (IM) delivery 30 min after reperfusion. No-reflow area and infarct size (IS) were assessed histologically at 48 h. Intracoronary exosomes were ineffective, but IM exosomes decreased IS from 80 ± 5% to 61 ± 12% (P= 0.001) and preserved left ventricular ejection fraction (LVEF). In a randomized placebo-controlled study of CMI, pigs 4 weeks post-myocardial infarction (MI) underwent percutaneous IM delivery of vehicle (n = 6) or CDC exosomes (n = 6). Magnetic resonance imaging (MRI) performed before and 1 month after treatment revealed that exosomes (but not vehicle) preserved LV volumes and LVEF (−0.1 ± 2.2% vs. −5.4 ± 3.6%, P= 0.01) while decreasing scar size. Histologically, exosomes decreased LV collagen content and cardiomyocyte hypertrophy while increasing vessel density.

Conclusion

Cardiosphere-derived cell exosomes delivered IM decrease scarring, halt adverse remodelling and improve LVEF in porcine AMI and CMI. While conceptually attractive as cell-free therapeutic agents for myocardial infarction, exosomes have the disadvantage that IM delivery is necessary.

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.