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Exosomes are small membrane-bound vesicles of endocytic origin that are actively secreted. The potential of exosomes as effective communicators of biological signaling in myocardial function has previously been investigated, and a recent explosion in exosome research not only underscores their significance in cardiac physiology and pathology, but also draws attention to methodological limitations of studying these extracellular vesicles. In this review, we discuss recent advances and challenges in exosome research with an emphasis on scientific innovations in isolation, identification, and characterization methodologies, and we provide a comprehensive summary of web-based resources available in the field. Importantly, we focus on the biology and function of exosomes, highlighting their fundamental role in cardiovascular pathophysiology to further support potential applications of exosomes as biomarkers and therapeutics for cardiovascular diseases.

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Background: Epigenetic mechanisms are critical in the pathogenesis of pulmonary arterial hypertension (PAH). Previous studies have suggested that hypermethylation of the BMPR2 (bone morphogenetic protein receptor type 2) promoter is associated with BMPR2 downregulation and progression of PAH. Here, we investigated for the first time the role of SIN3a (switch-independent 3a), a transcriptional regulator, in the epigenetic mechanisms underlying hypermethylation of BMPR2 in the pathogenesis of PAH. Methods: We used lung samples from PAH patients and non-PAH controls, preclinical mouse and rat PAH models, and human pulmonary arterial smooth muscle cells. Expression of SIN3a was modulated using a lentiviral vector or a siRNA in vitro and a specific adeno-associated virus serotype 1 or a lentivirus encoding for human SIN3a in vivo. Results: SIN3a is a known transcriptional regulator; however, its role in cardiovascular diseases, especially PAH, is unknown. It is interesting that we detected a dysregulation of SIN3 expression in patients and in rodent models, which is strongly associated with decreased BMPR2 expression. SIN3a is known to regulate epigenetic changes. Therefore, we tested its role in the regulation of BMPR2 and found that BMPR2 is regulated by SIN3a. It is interesting that SIN3a overexpression inhibited human pulmonary arterial smooth muscle cells proliferation and upregulated BMPR2 expression by preventing the methylation of the BMPR2 promoter region. RNA-sequencing analysis suggested that SIN3a downregulated the expression of DNA and histone methyltransferases such as DNMT1 (DNA methyltransferase 1) and EZH2 (enhancer of zeste 2 polycomb repressive complex 2) while promoting the expression of the DNA demethylase TET1 (ten-eleven translocation methylcytosine dioxygenase 1). Mechanistically, SIN3a promoted BMPR2 expression by decreasing CTCF (CCCTC-binding factor) binding to the BMPR2 promoter. Last, we identified intratracheal delivery of adeno-associated virus serotype human SIN3a to be a beneficial therapeutic approach in PAH by attenuating pulmonary vascular and right ventricle remodeling, decreasing right ventricle systolic pressure and mean pulmonary arterial pressure, and restoring BMPR2 expression in rodent models of PAH. Conclusions: All together, our study unveiled the protective and beneficial role of SIN3a in pulmonary hypertension. We also identified a novel and distinct molecular mechanism by which SIN3a regulates BMPR2 in human pulmonary arterial smooth muscle cells. Our study also identified lung-targeted SIN3a gene therapy using adeno-associated virus serotype 1 as a new promising therapeutic strategy for treating patients with PAH.

For therapeutic materials to be successfully delivered to the heart, several barriers need to be overcome, including the anatomical challenges of access, the mechanical force of the blood flow, the endothelial barrier, the cellular barrier and the immune response. Various vectors and delivery methods have been proposed to improve the cardiac-specific uptake of materials to modify gene expression. Viral and non-viral vectors are widely used to deliver genetic materials, but each has its respective advantages and shortcomings. Adeno-associated viruses have emerged as one of the best tools for heart-targeted gene delivery. In addition, extracellular vesicles, including exosomes, which are secreted by most cell types, have gained popularity for drug delivery to several organs, including the heart. Accumulating evidence suggests that extracellular vesicles can carry and transfer functional proteins and genetic materials into target cells and might be an attractive option for heart-targeted delivery. Extracellular vesicles or artificial carriers of non-viral and viral vectors can be bioengineered with immune-evasive and cardiotropic properties. In this Review, we discuss the latest strategies for targeting and delivering therapeutic materials to the heart and how the knowledge of different vectors and delivery methods could successfully translate cardiac gene therapy into the clinical setting.

Background: Pulmonary arterial hypertension (PAH) is a fatal lung disease of multifactorial etiology, with no curative treatment. Several studies have previously suggested that hypermethylation of the BMPR2 promoter may be associated with gene repression and disease progression. However, the underlying mechanisms have yet to be discovered. Sin3A/B (Switch-Independent 3) plays a critical role in the transcriptional regulation of genes through various epigenetic mechanisms. Here, we investigated for the first time the role of SIN3a in the regulation of BMPR2 methylation and expression in PAH. Methods: Expression of SIN3a was analyzed by qRT-PCR and western blot in lung tissues from PAH patients and rodent models of PAH. Using a gain- and loss-of-function approach, we investigated the role of SIN3a on cell proliferation (BrdU assay) and migration (Boyden chamber assay), and BMPR2 levels in primary human pulmonary arterial smooth muscle cells (hPASMC) and endothelial cells (hPAEC). The methylation level was analyzed by MS-PCR. The therapeutic potential of SIN3a was tested in vivo in the Sugen/Hypoxia (SuHx) mouse and monocrotaline (MCT) rat models of PAH using an adeno-associated virus 1 encoding human SIN3a. Results: We found a significant downregulation of SIN3a expression in the lung samples from PAH patients, SuHx mice, and MCT rats. In hPASMC and hPAEC, our results showed that SIN3a inhibits cell proliferation, migration, and upregulates BMPR2 through two distinct pathways. In hPASMC, our data showed that SIN3a upregulates BMPR2 expression by inhibiting the methylation level of the BMPR2 promoter. In hPAEC, SIN3a restored BMPR2 expression independently of the methylation status by upregulating the FOXK2 transcription factor. In vivo , our results showed that restoring SIN3a expression by gene therapy significantly decreased MCT- and SuHx-induced PAH as illustrated by decreased vascular and RV remodeling, hypertrophy, PAP and RVSP. Conclusions: Altogether, our study revealed that SIN3a plays a critical role in the regulation of BMPR2 expression by modulating the lung epigenetic landscape. Additionally, our study identifies lung-targeted SIN3a gene therapy as a new promising therapeutic strategy for treating PAH patients.

Cardiovascular disease remains the leading cause of morbidity and mortality in the world. Thus, therapeutic interventions to circumvent this growing burden are of utmost importance. Extracellular vesicles (EVs) actively secreted by most living cells, play a key role in paracrine and endocrine intercellular communication via exchange of biological molecules. As the content of secreted EVs reflect the physiology and pathology of the cell of their origin, EVs play a significant role in cellular homeostasis, disease pathogenesis and diagnostics. Moreover, EVs are gaining popularity in clinics as therapeutic and drug delivery vehicles, transferring bioactive molecules such as proteins, genes, miRNAs and other therapeutic agents to target cells to treat diseases and deter disease progression. Despite our limited but growing knowledge of EV biology, it is imperative to understand the complex mechanisms of EV cargo sorting in pursuit of designing next generation EV-based therapeutic delivery systems. In this review, we highlight the mechanisms of EV cargo sorting and methods of EV bioengineering and discuss engineered EVs as a potential therapeutic delivery system to treat cardiovascular disease.

Background: Despite its functional importance in various fundamental bioprocesses, studies of N 6 -methyladenosine (m6A) in the heart are lacking. Here, we show that the FTO (fat mass and obesity-associated protein), an m6A demethylase, plays a critical role in cardiac contractile function during homeostasis, remodeling, and regeneration. Methods: We used clinical human samples, preclinical pig and mouse models, and primary cardiomyocyte cell cultures to study the functional role of m6A and FTO in the heart and in cardiomyocytes. We modulated expression of FTO by using adeno-associated virus serotype 9 (in vivo), adenovirus (both in vivo and in vitro), and small interfering RNAs (in vitro) to study its function in regulating cardiomyocyte m6A, calcium dynamics and contractility, and cardiac function postischemia. We performed methylated (m6A) RNA immunoprecipitation sequencing to map transcriptome-wide m6A, and methylated (m6A) RNA immunoprecipitation quantitative polymerase chain reaction assays to map and validate m6A in individual transcripts, in healthy and failing hearts, and in myocytes. Results: We discovered that FTO has decreased expression in failing mammalian hearts and hypoxic cardiomyocytes, thereby increasing m6A in RNA and decreasing cardiomyocyte contractile function. Improving expression of FTO in failing mouse hearts attenuated the ischemia-induced increase in m6A and decrease in cardiac contractile function. This is performed by the demethylation activity of FTO, which selectively demethylates cardiac contractile transcripts, thus preventing their degradation and improving their protein expression under ischemia. In addition, we demonstrate that FTO overexpression in mouse models of myocardial infarction decreased fibrosis and enhanced angiogenesis. Conclusions: Collectively, our study demonstrates the functional importance of the FTO-dependent cardiac m6A methylome in cardiac contraction during heart failure and provides a novel mechanistic insight into the therapeutic mechanisms of FTO.

Adeno-associated viruses (AAVs) are promising therapeutic tools for gene delivery to the heart. However, pre-existing antibodies (NAbs) to many cardiotropic AAV serotypes naturally present in humans pose a critical challenge for the translation of gene therapies to clinical applications. Here, we describe the use of exosomal AAVs (eAAV) as a robust heart gene delivery system that improves transduction efficiency while protecting from pre-existing immunity to the viral capsid. To obtain eAAV specimens from conditioned medium from AAV-producing HEK-293T cells, we have developed a state-of-the-art multi-step ultracentrifugation strategy. We demonstrated through electron microscopy-based visualization, size distribution measurements and distribution of AAV genomes in post-centrifugation iodixanol gradients, that our purification process enables isolation of eAAVs with high purity and minimal contamination with standard AAVs. Efficiency of heart targeting was then evaluated for eAAV9 or eAAV6 and standard AAV9 or AAV6 in human cardiomyocytes (hCMs) in vitro and in passive immunity nude mouse model in vivo . Regardless of the presence or absence of NAbs, we demonstrated that eAAVs are more efficient in transduction of cells in the same titer ranges as standard AAVs. To test the therapeutic efficacy, eAAV9-SERCA2a or AAV9-SERCA2a were injected intramyocardially in post-myocardial infarction (MI) mice preinjected with NAbs. Remarkably, eAAV9-SERCA2a outperformed standard AAVs 6 weeks post-MI, significantly improving cardiac function in the presence of NAbs (%EF 55.14 ± 3.50 vs. 27.31 ± 1.63, respectively). Additionally, we demonstrated in vivo that eAAV9-mediated gene delivery is more specific to CMs than to other cell types present in the heart, which suggests that eAAVs preserve cardiotropic properties of AAV9 serotype. With examination of colocalization of eAAVs and markers specific for endosomes (Rab5 and Rab7) in hCMs in vitro , our preliminary data indicated that eAAV infectious entry potentially involves trafficking via endocytic compartments. In conclusion, these results underline the therapeutic potential of eAAVs to evade NAbs, and to facilitate the clinical translation of AAV-based gene therapies to a larger human population.

Heart failure (HF) remains a major cause of morbidity and mortality worldwide. One of the risk factors for HF is cardiac hypertrophy (CH), which is frequently accompanied by cardiac fibrosis (CF). CH and CF are controlled by master regulators mTORC1 and TGF‐β, respectively. Type‐2‐phosphatidylinositol‐5‐phosphate‐4‐kinase‐gamma (Pip4k2c) is a known mTORC1 regulator. It is shown that Pip4k2c is significantly downregulated in the hearts of CH and HF patients as compared to non‐injured hearts. The role of Pip4k2c in the heart during development and disease is unknown. It is shown that deleting Pip4k2c does not affect normal embryonic cardiac development; however, three weeks after TAC, adult Pip4k2c−/− mice has higher rates of CH, CF, and sudden death than wild‐type mice. In a gain‐of‐function study using a TAC mouse model, Pip4k2c is transiently upregulated using a modified mRNA (modRNA) gene delivery platform, which significantly improve heart function, reverse CH and CF, and lead to increased survival. Mechanistically, it is shown that Pip4k2c inhibits TGFβ1 via its N‐terminal motif, Pip5k1α, phospho‐AKT 1/2/3, and phospho‐Smad3. In sum, loss‐and‐gain‐of‐function studies in a TAC mouse model are used to identify Pip4k2c as a potential therapeutic target for CF, CH, and HF, for which modRNA is a highly translatable gene therapy approach., Heart failure remains a major cause of morbidity and mortality worldwide. One of the risk factors for HF is cardiac hypertrophy (CH), which is frequently accompanied by cardiac fibrosis (CF). Here, gain‐ and loss‐of‐function studies are used to identify the therapeutic role of Pip4k2c in preventing CH and CF via inhibition of mTOR and TGFβ1 pathways, respectively.

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.

Rationale: Abnormal SUMOylation has emerged as a characteristic of heart failure (HF) pathology. Previously, we found reduced SUMO1 (small ubiquitin-like modifier 1) expression and SERCA2a (sarcoplasmic reticulum Ca 2+ -ATPase) SUMOylation in human and animal HF models. SUMO1 gene delivery or small molecule activation of SUMOylation restored SERCA2a SUMOylation and cardiac function in HF models. Despite the critical role of SUMO1 in HF, the regulatory mechanisms underlying SUMO1 expression are largely unknown. Objective: To examine miR-146a–mediated SUMO1 regulation and its consequent effects on cardiac morphology and function. Methods and Results: In this study, miR-146a was identified as a SUMO1-targeting microRNA in the heart. A strong correlation was observed between miR-146a and SUMO1 expression in failing mouse and human hearts. miR-146a was manipulated in cardiomyocytes through AAV9 (adeno-associated virus serotype 9)-mediated gene delivery, and cardiac morphology and function were analyzed by echocardiography and hemodynamics. Overexpression of miR-146a reduced SUMO1 expression, SERCA2a SUMOylation, and cardiac contractility in vitro and in vivo. The effects of miR-146a inhibition on HF pathophysiology were examined by transducing a tough decoy of miR-146a into mice subjected to transverse aortic constriction. miR-146a inhibition improved cardiac contractile function and normalized SUMO1 expression. The regulatory mechanisms of miR-146a upregulation were elucidated by examining the major miR-146a–producing cell types and transfer mechanisms. Notably, transdifferentiation of fibroblasts triggered miR-146a overexpression and secretion through extracellular vesicles, and the extracellular vesicle–associated miR-146a transfer was identified as the causative mechanism of miR-146a upregulation in failing cardiomyocytes. Finally, extracellular vesicles isolated from failing hearts were shown to contain high levels of miR-146a and exerted negative effects on the SUMO1/SERCA2a signaling axis and hence cardiomyocyte contractility. Conclusions: Taken together, our results show that miR-146a is a novel regulator of the SUMOylation machinery in the heart, which can be targeted for therapeutic intervention.

Background: Despite its functional importance in various fundamental bioprocesses, the studies of N6-methyladenosine (m6A) in the heart are lacking. In this study, we investigated the role of fat mass and obesity-associated (FTO), an m6A demethylase, in cardiac contractile function during homeostasis and remodeling. Methods: We used clinical human samples, preclinical pig and mouse models and primary cardiomyocyte cell cultures to study the functional role of m6A and FTO in the heart and in cardiomyocytes. We modulated expression of FTO using AAV9 (in vivo), adenovirus (both in vivo and in vitro) and siRNAs (in vitro). We performed methylated (m6A) RNA immunoprecipitation sequencing (MeRIP-seq) to map transcriptome-wide m6A, and MeRIP qPCR assays to map and validate m6A in individual transcripts, in healthy and failing hearts and myocytes. We performed proteomics analysis using stable isotope labeling with amino acids in cell culture to study m6A role in mRNA to protein translation. Results: We discovered that FTO has decreased expression in failing mammalian hearts and hypoxic cardiomyocytes, thereby increasing m6A in RNA and decreasing cardiomyocyte contractile function. Improving expression of FTO in failing mouse hearts attenuated the ischemia-induced increase in m6A and decrease in cardiac contractile function. This is carried out by the demethylation activity of FTO, which selectively demethylates cardiac contractile transcripts, thus preventing their degradation and improving their protein expression under ischemia. Conclusion: Collectively, our study demonstrates the functional importance of FTO-dependent cardiac m6A methylome in cardiac contraction during heart failure and provides a novel mechanistic insight into the therapeutic mechanisms of FTO.

Extracellularly secreted membrane vesicles (EMVs) including exosomes were first discovered 30 years ago and were considered to be garbage bags comprised of unwanted cellular components [(1)][1]. Exosomes are relatively homogenous in size (about 30 to 100 nm) and are different from other secreted

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.

Bioinformatics tools are imperative for the in depth analysis of heterogeneous high-throughput data. Most of the software tools are developed by specific laboratories or groups or companies wherein they are designed to perform the required analysis for the group. However, such software tools may fail to capture "what the community needs in a tool". Here, we describe a novel community-driven approach to build a comprehensive functional enrichment analysis tool. Using the existing FunRich tool as a template, we invited researchers to request additional features and/or changes. Remarkably, with the enthusiastic participation of the community, we were able to implement 90% of the requested features. FunRich enables plugin for extracellular vesicles wherein users can download and analyse data from Vesiclepedia database. By involving researchers early through community needs software development, we believe that comprehensive analysis tools can be developed in various scientific disciplines. We would like to thank Tejaswee P. Shah for her valuable input in the development of FunRich. We would like to thank Jan Lotvall for helping us in this effort by circulating the email within his group. We thanks many other users who requested for features/changes in FunRich though the e-mail and the online forum. Suresh Mathivanan is supported by Australian Research Council DECRA (DE150101777) and Award U54- DA036134 supported by the NIH Common Fund through the Office of Strategic Coordination/Office of the NIH Director.The funders had no role in study design, data collection andanalysis, decision to publish, or preparation of the manuscript. Sí

We argue that the field of extracellular vesicle (EV) biology needs more transparent reporting to facilitate interpretation and replication of experiments. To achieve this, we describe EV-TRACK, a crowdsourcing knowledgebase (http://evtrack.org) that centralizes EV biology and methodology with the goal of stimulating authors, reviewers, editors and funders to put experimental guidelines into practice.

Rationale: Ischemic cardiovascular disease represents one of the largest epidemics currently facing the aging population. Current literature has illustrated the efficacy of autologous, stem cell therapies as novel strategies for treating these disorders. The CD34+ hematopoetic stem cell has shown significant promise in addressing myocardial ischemia by promoting angiogenesis that helps preserve the functionality of ischemic myocardium. Unfortunately, both viability and angiogenic quality of autologous CD34+ cells decline with advanced age and diminished cardiovascular health. Objective: To offset age- and health-related angiogenic declines in CD34+ cells, we explored whether the therapeutic efficacy of human CD34+ cells could be enhanced by augmenting their secretion of the known angiogenic factor, sonic hedgehog (Shh). Methods and Results: When injected into the border zone of mice after acute myocardial infarction, Shh-modified CD34+ cells (CD34 Shh ) protected against ventricular dilation and cardiac functional declines associated with acute myocardial infarction. Treatment with CD34 Shh also reduced infarct size and increased border zone capillary density compared with unmodified CD34 cells or cells transfected with the empty vector. CD34 Shh primarily store and secrete Shh protein in exosomes and this storage process appears to be cell-type specific. In vitro analysis of exosomes derived from CD34 Shh revealed that (1) exosomes transfer Shh protein to other cell types, and (2) exosomal transfer of functional Shh elicits induction of the canonical Shh signaling pathway in recipient cells. Conclusions: Exosome-mediated delivery of Shh to ischemic myocardium represents a major mechanism explaining the observed preservation of cardiac function in mice treated with CD34 Shh cells.

Recent studies using exosomes as a therapeutic platform for the treatment of vascular diseases have led to very encouraging responses.1–3 To date, exosomes secreted by stem and progenitor cells in the myocardium have shown promising therapeutic benefits, although their precise cellular origin and mechanism(s) of action remain poorly characterized. In this issue of Molecular Therapy, Beltrami et al.4 report that exosomes present in the pericardial fluid (PF) of patients undergoing aortic valve replacement (AVR) are enriched with microRNAs (miRNAs) co-expressed in patients’ myocardium and vasculature.

Introduction: Clinical application of human CD34+ stem cells is associated with improved exercise tolerance and therapeutic angiogenesis in patients with myocardial ischemia. We reported the first description of independent therapeutic potential of CD34+ stem cell-derived exosomes (CD34Exo) to that of parent cell by mechanisms that still remain poorly understood. Hypothesis: Herein, we tested the hypothesis that CD34Exo may selectively carry non-coding RNA (ncRNA) cargo targeted for pro-angiogenic signaling and ischemic tissue repair. Methods and Results: Murine models of myocardial ischemia employed throughout the study. Cell-free CD34Exo replicated the therapeutic activity of their parent cells by significantly improving myocardial ischemia (ejection fraction, 42±4 v 22±6%; capillary density, 113±7 v 66±6/HPF; fibrosis, 27±2 v 48±7%; p Conclusion: Our results reveal specific CD34Exo-shuttled microRNAs and pathways regulated in the ischemic myocardium. Our work presents a molecular framework for CD34Exo mechanism and function in therapeutic angiogenesis. Precise understanding of CD34Exo mechanisms could significantly amplify the therapeutic benefits of CD34Exo in ischemic tissue regeneration and repair.

Previous studies in our lab have revealed a novel mechanism that therapeutically important human CD34+ stem cells secrete exosomes (Exo) to extracellular milieu that induce angiogenic activity independent of the cells. Further studies demonstrated that CD34+ exosomes (CD34Exo) carry and transfer of proangiogenic miRNAs, such as miR-126, which affect the therapeutic function of the exosomes. Herein we hypothesized that hypoxic treatment of CD34+ stem cells can modulate the miRNA content and regenerative efficacy of CD34Exo. Methods and Results: Exosomes from human CD34+ cells cultured under hypoxia (H-Exo) were more proliferative, anti-apoptotic and angiogenic in vitro, as compared to exosomes from cells under normoxia (N-Exo). In a mouse model of hind limb ischemia, H-Exo treatment significantly enhanced perfusion (ratio: 0.93±0.05 v 0.77±0.02), increased capillary density (1.6±0.2 v 1.1±0.1/HPF) and prevented ischemic limb amputation (0% v 37.5%) as compared to N-Exo (p Conclusion: Hypoxia induced miR-126 expression in CD34 cell-derived exosomes stimulating exosomes-mediated angiogenesis and therapeutic recovery via ETS-transcriptional pathway. Our work has important clinical implications for therapeutic angiogenesis, especially in diabetic and cardiovascular patients who have stem cells with diminished angiogenic potential.

Myocardial infarction is a leading cause of death among all cardiovascular diseases. The analysis of molecular mechanisms by which the ischemic myocardium initiates repair and remodeling indicates that secreted soluble factors are key players in communication to local and distant tissues, such as bone marrow. Recently, actively secreted membrane vesicles, including exosomes, are being recognized as new candidates with important roles in intercellular and tissue-level communication. In this review, we critically examine the emerging role of exosomes in local and distant microcommunication mechanisms after myocardial infarction. A comprehensive understanding of the role of exosomes in cardiac repair after myocardial infarction could bridge a major gap in knowledge of the repair mechanism after myocardial injury.

Introduction: Locally transplanted human CD34 + stem cells have been shown to improve exercise tolerance in patients with myocardial ischemia and promote angiogenesis in animal models. Recently we have demonstrated that CD34 + cells secrete exosomes, membrane bound nano-vesicles, as a major component of their paracrine secretion which induces angiogenesis. We hypothesize that cell-free exosomes from CD34 + cells (CD34 Exo) mimic the beneficial effects of cells, and promote myocardial revascularization and repair via transfer of pro-angiogenic microRNAs, possibly to endothelial cells. Methods and Results: Therapeutic potential of CD34 Exo isolated from equal number of adult human peripheral blood-derived CD34 + cells was evaluated in a murine model of myocardial ischemia (MI). Similar to cells, treatment with CD34 Exo resulted in significant improvement in ischemia compared to treatment with PBS (ejection fraction, 42±4 v 22±6%; capillary density, 113±7 v 66±6/HPF; fibrosis 27±2 v 48±7%, p Conclusion: CD34 + exosomes transfer miR126 to endothelial cells to induce angiogenesis and myocardial repair. The functional benefits associated with CD34 + cell therapy may be mediated by exosomes-mediated transfer of angiogenic microRNAs to endothelial cells.

As the size of transistor is decreasing, more number of functionalities are integrated onto a single chip, so the interconnect length is ever increasing. Signal rise time is decreasing as compared to the time of flight. Hence, the interconnect can no longer be modelled as RC tree, rather it must be modelled as a transmission line by taking the inductance into account. With the increase in frequency, the dynamic power dissipation associated with interconnect is also increasing. Hence, an efficient method to estimate the interconnect power dissipation is necessary. In this paper, a simple yet accurate method has been proposed to estimate dynamic power dissipation of on-chip interconnect. A reduced order model is derived. The proposed model is directly derived from total resistance, inductance and capacitance of interconnects. Through the analysis made in this paper, it is shown that the dynamic power dissipation for the interconnects can be accurately estimated. The results of the proposed method applied to various RLC networks show that maximum relative error is within 4 to 6% compared to the SPICE results.

With the increase in the levels of on-chip integration, the number of functional units integrated onto a single chip is rapidly increasing and as a result, the logic delays are decreasing due to faster transistors. At the same time, the local interconnect delays improve because the physical size of the circuit blocks decrease and the local interconnect spans shorter distances. On the other hand, the global interconnect delay increases with the technology scaling. Multiple design criteria are considered during the interconnect design process, such as delay, power, bandwidth and noise. Performance of any VLSI circuit depends on the bandwidth, as it decreases with the increase in the length of interconnects. Depending on the frequency range of operation, on-chip interconnect can be modelled as lumped and/or distributed RC line for low frequency and as a distributed RLC segments for high frequency. At even higher frequency, of the order of above 10GHz, the shunt conductance needs to be considered for accurate interconnect modelling. In this paper, on-chip interconnect has been modelled as distributed RLCG transmission lines, based on which a crosstalk aware bandwidth estimation method has been proposed in the transform domain in the presence of both inductive as well as capacitive coupling. First, the amount of crosstalk noise that would be induced on the victim line due to the transiting aggressor line has been analytically derived and then from the crosstalk noise voltage, a closed form expression for bandwidth has been proposed for distributed RLCG VLSI interconnects. The calculated bandwidth has been compared with the results obtained from that of SPICE simulation. The simulation shows that the proposed model could result an average error of as low as 15% when compared to the SPICE simulation.

Extracellular vesicles (EVs) are a heterogeneous group of natural particles that are relevant to the treatment of cardiovascular diseases. These endogenous vesicles have certain properties that allow them to survive in the extracellular space, bypass biological barriers and deliver their biologically active molecular cargo to recipient cells. Moreover, EVs can be bioengineered to increase their stability, bioactivity, presentation to acceptor cells and capacity for on-target binding at both cell-type-specific and tissue-specific levels. Bioengineering of EVs involves the modification of the donor cell before EV isolation or direct modification of the EV properties after isolation. The therapeutic potential of native EVs and bioengineered EVs has been only minimally explored in the context of cardiovascular diseases. Efforts to harness the therapeutic potential of EVs will require innovative approaches and a comprehensive integration of knowledge gathered from decades of research into molecular-compound delivery. In this Review, we outline the endogenous properties of EVs that make them natural delivery agents as well as the features that can be improved by bioengineering. We also discuss the therapeutic applications of native and bioengineered EVs to cardiovascular diseases and examine the opportunities and challenges that need to be addressed to advance this research area, with an emphasis on clinical translation. Extracellular vesicles are a heterogeneous group of natural particles that can deliver their biologically active molecular cargo to recipient cells. In this Review, the authors outline the endogenous properties of extracellular vesicles that make them natural delivery agents and the features that can be improved by bioengineering for the treatment of cardiovascular diseases.