Microvesicles released from activated CD4+ T cells alter microvascular endothelial cell function.

BACKGROUND: Microvesicles are vesicles shed by plasma membranes following cell activation and apoptosis. The role of lymphocyte-derived microvesicles in endothelial function remains poorly understood. METHODS: CD4+ T cells isolated from peripheral blood of healthy human donors were stimulated using anti-CD3/anti-CD28-coated beads. Proteomic profiling of microvesicles was performed using linear discriminant analysis (LDA) from activated T cells (MV.Act) and nonactivated T cells (MV.NAct). In addition, data processing analysis was performed using MaxQUANT workflow. Differentially expressed proteins found in MV.Act or MV.NAct samples with identification frequency = 100%, which were selected by both LDA (p < .01) and MaxQUANT (p < .01) workflows, were defined as "high-confidence" differentially expressed proteins. Functional effects of MV.Act on human primary microvascular endothelial cells were analysed. RESULTS: T cells released large amounts of microvesicles upon stimulation. Proteomic profiling of microvesicles using LDA identified 2279 proteins (n = 2110 and n = 851 proteins in MV.Act and MV.NAct, respectively). Protein-protein interaction network models reconstructed from both differentially expressed proteins (n = 594; LDA p ≤ .01) and "high-confidence" differentially expressed proteins (n = 98; p ≤ .01) revealed that MV.Act were enriched with proteins related to immune responses, protein translation, cytoskeleton organisation and TNFα-induced apoptosis. For instance, MV.Act were highly enriched with IFN-γ, a key proinflammatory pathway related to effector CD4+ T cells. Endothelial cell incubation with MV.Act induced superoxide generation, apoptosis, endothelial wound healing impairment and endothelial monolayer barrier disruption. CONCLUSIONS: T cell receptor-mediated activation of CD4+ T cells stimulates the release of microvesicles enriched with proteins involved in immune responses, inflammation and apoptosis. T cell-derived microvesicles alter microvascular endothelial function and barrier permeability, potentially promoting tissue inflammation.

Extracellular Vesicle Surface Markers as a Diagnostic Tool in Transient Ischemic Attacks.

Background and Purpose: Extracellular vesicles (EVs) are promising biomarkers for cerebral ischemic diseases, but not systematically tested in patients with transient ischemic attacks (TIAs). We aimed at (1) investigating the profile of EV-surface antigens in patients with symptoms suspicious for TIA; (2) developing and validating a predictive model for TIA diagnosis based on a specific EV-surface antigen profile. Methods: We analyzed 40 subjects with symptoms suspicious for TIA and 20 healthy controls from a training cohort. An independent cohort of 28 subjects served as external validation. Patients were stratified according to likelihood of having a real ischemic event using the Precise Diagnostic Score, defined as: unlikely (score 0­1), possible-probable (score 2­3), or very likely (score 4­8). Serum vesicles were quantified by nanoparticle tracking analysis and EV-surface antigen profile characterized by multiplex flow cytometry. Results: EV concentration increased in patients with very likely or possible-probable TIA (P<0.05) compared with controls. Nanoparticle concentration was directly correlated with the Precise Diagnostic score (R=0.712; P<0.001). After EV immuno-capturing, CD8, CD2, CD62P, melanoma-associated chondroitin sulfate proteoglycan, CD42a, CD44, CD326, CD142, CD31, and CD14 were identified as discriminants between groups. Receiver operating characteristic curve analysis confirmed a reliable diagnostic performance for each of these markers taken individually and for a compound marker derived from their linear combinations (area under the curve, 0.851). Finally, a random forest model combining the expression levels of selected markers achieved an accuracy of 96% and 78.9% for discriminating patients with a very likely TIA, in the training and external validation cohort, respectively. Conclusions: The EV-surface antigen profile appears to be different in patients with transient symptoms adjudicated to be very likely caused by brain ischemia compared with patients whose symptoms were less likely to due to brain ischemia. We propose an algorithm based on an EV-surface-antigen specific signature that might aid in the recognition of TIA.

Exosomes: Beyond stem cells for cardiac protection and repair.

The adult human heart has limited regenerative capacity; hence, stem cell therapy has been investigated as a potential approach for cardiac repair. However, a large part of the benefit of the injection of stem and progenitor cells into injured hearts is mediated by secreted factors. Exosomes-nano-sized secreted extracellular vesicles of endosomal origin-have emerged as key signaling organelles in intercellular communication, and are now viewed as the key regenerative constituent of the secretome of stem and progenitor cells. Exosomes released from mesenchymal stem cells, cardiac-derived progenitor cells, embryonic stem cells, induced pluripotent stem cells (iPSCs), and iPSC-derived cardiomyocytes exhibit cardioprotective, immunomodulatory, and reparative abilities. This concise review discusses the therapeutic benefit of exosomes secreted by stem and progenitor cells in preclinical models of ischemic heart disease.

An extracellular vesicle epitope profile is associated with acute myocardial infarction.

The current standard biomarker for myocardial infarction (MI) is high-sensitive troponin. Although powerful in clinical setting, search for new markers is warranted as early diagnosis of MI is associated with improved outcomes. Extracellular vesicles (EVs) attracted considerable interest as new blood biomarkers. A training cohort used for diagnostic modelling included 30 patients with STEMI, 38 with stable angina (SA) and 30 matched-controls. Extracellular vesicle concentration was assessed by nanoparticle tracking analysis. Extracellular vesicle surface-epitopes were measured by flow cytometry. Diagnostic models were developed using machine learning algorithms and validated on an independent cohort of 80 patients. Serum EV concentration from STEMI patients was increased as compared to controls and SA. EV levels of CD62P, CD42a, CD41b, CD31 and CD40 increased in STEMI, and to a lesser extent in SA patients. An aggregate marker including EV concentration and CD62P/CD42a levels achieved non-inferiority to troponin, discriminating STEMI from controls (AUC = 0.969). A random forest model based on EV biomarkers discriminated the two groups with 100% accuracy. EV markers and RF model confirmed high diagnostic performance at validation. In conclusion, patients with acute MI or SA exhibit characteristic EV biomarker profiles. EV biomarkers hold great potential as early markers for the management of patients with MI.

Exosomal Expression of CXCR4 Targets Cardioprotective Vesicles to Myocardial Infarction and Improves Outcome after Systemic Administration.

Cell therapy has been evaluated to enhance heart function after injury. Delivered cells mostly act via paracrine mechanisms, including secreted growth factors, cytokines, and vesicles, such as exosomes (Exo). Intramyocardial injection of cardiac-resident progenitor cells (CPC)-derived Exo reduced scarring and improved cardiac function after myocardial infarction in rats. Here, we explore a clinically relevant approach to enhance the homing process to cardiomyocytes (CM), which is crucial for therapeutic efficacy upon systemic delivery of Exo. By overexpressing exosomal CXCR4, we increased the efficacy of plasmatic injection of cardioprotective Exo-CPC by increasing their bioavailability to ischemic hearts. Intravenous injection of ExoCXCR4 significantly reduced infarct size and improved left ventricle ejection fraction at 4 weeks compared to ExoCTRL (p < 0.01). Hemodynamic measurements showed that ExoCXCR4 improved dp/dt min, as compared to ExoCTRL and PBS group. In vitro, ExoCXCR4 was more bioactive than ExoCTRL in preventing CM death. This in vitro effect was independent from SDF-1α, as shown by using AMD3100 as specific CXCR4 antagonist. We showed, for the first time, that systemic administration of Exo derived from CXCR4-overexpressing CPC improves heart function in a rat model of ischemia reperfusion injury These data represent a substantial step toward clinical application of Exo-based therapeutics in cardiovascular disease.

Notch pathway activation enhances cardiosphere in vitro expansion.

Cardiospheres (CSps) are self-assembling clusters of a heterogeneous population of poorly differentiated cells outgrowing from in vitro cultured cardiac explants. Scanty information is available on the molecular pathways regulating CSp growth and their differentiation potential towards cardiac and vascular lineages. Here we report that Notch1 stimulates a massive increase in both CSp number and size, inducing a peculiar gene expression programme leading to a cardiovascular molecular signature. These effects were further enhanced using Adeno-Associated Virus (AAV)-based gene transfer of activated Notch1-intracellular domain (N1-ICD) or soluble-Jagged1 (sJ1) ligand to CSp-forming cells. A peculiar effect was exploited by selected pro-proliferating miRNAs: hsa-miR-590-3p induced a cardiovascular gene expression programme, while hsa-miR-199a-3p acted as the most potent stimulus for the activation of the Notch pathway, thus showing that, unlike in adult cardiomyocytes, these miRNAs involve Notch signalling activation in CSps. Our results identify Notch1 as a crucial regulator of CSp growth and differentiation along the vascular lineage, raising the attracting possibility that forced activation of this pathway might be exploited to promote in vitro CSp expansion as a tool for toxicology screening and cell-free therapeutic strategies.

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.

Sildenafil attenuates hypoxic pulmonary remodelling by inhibiting bone marrow progenitor cells.

The recruitment of bone marrow (BM)-derived progenitor cells to the lung is related to pulmonary remodelling and the pathogenesis of pulmonary hypertension (PH). Although sildenafil is a known target in PH treatment, the underlying molecular mechanism is still elusive. To test the hypothesis that the therapeutic effect of sildenafil is linked to the reduced recruitment of BM-derived progenitor cells, we induced pulmonary remodelling in rats by two-week exposure to chronic hypoxia (CH, 10% oxygen), a trigger of BM-derived progenitor cells. Rats were treated with either placebo (saline) or sildenafil (1.4 mg/kg/day ip) during CH. Control rats were kept in room air (21% oxygen) with no treatment. As expected, sildenafil attenuated the CH-induced increase in right ventricular systolic pressure and right ventricular hypertrophy. However, sildenafil suppressed the CH-induced increase in c-kit+ cells in the adventitia of pulmonary arteries. Moreover, sildenafil reduced the number of c-kit+ cells that colocalize with tyrosine kinase receptor 2 (VEGF-R2) and CD68 (a marker for macrophages), indicating a positive effect on moderating hypoxia-induced smooth muscle cell proliferation and inflammation without affecting the pulmonary levels of hypoxia-inducible factor (HIF)-1α. Furthermore, sildenafil depressed the number of CXCR4+ cells. Collectively, these findings indicate that the improvement in pulmonary haemodynamic by sildenafil is linked to decreased recruitment of BM-derived c-kit+ cells in the pulmonary tissue. The attenuation of the recruitment of BM-derived c-kit+ cells by sildenafil may provide novel therapeutic insights into the control of pulmonary remodelling.

Can the optimal type of stent be predicted based on clinical risk factors? A subgroup analysis of the randomized BASKET-PROVE trial.

BACKGROUND: The randomized BASKET-PROVE study showed no significant differences between sirolimus-eluting stents (SES), everolimus-eluting stents (EES), and bare-metal stents (BMS) with respect to the primary end point, rates of death from cardiac causes, or myocardial infarction (MI) at 2 years of follow-up, in patients requiring stenting of a large coronary artery. Clinical risk factors may affect clinical outcomes after percutaneous coronary interventions. We present a retrospective analysis of the BASKET-PROVE data addressing the question as to whether the optimal type of stent can be predicted based on a cumulative clinical risk score. METHODS: A total of 2,314 patients (mean age 66 years) who underwent coronary angioplasty and implantation of ≥1 stents that were ≥3.0 mm in diameter were randomly assigned to receive SES, EES, or BMS. A cumulative clinical risk score was derived using a Cox model that included age, gender, cardiovascular risk factors (hypercholesterolemia, hypertension, family history of cardiovascular disease, diabetes, smoking), presence of ≥2 comorbidities (stroke, peripheral artery disease, chronic kidney disease, chronic rheumatic disease), a history of MI or coronary revascularization, and clinical presentation (stable angina, unstable angina, ST-segment elevation MI). RESULTS: An aggregate drug-eluting stent (DES) group (n = 1,549) comprising 775 patients receiving SES and 774 patients receiving EES was compared to 765 patients receiving BMS. Rates of death from cardiac causes or nonfatal MI at 2 years of follow-up were significantly increased in patients who were in the high tertile of risk stratification for the clinical risk score compared to those who were in the aggregate low-mid tertiles. In patients with a high clinical risk score, rates of death from cardiac causes or nonfatal MI were lower in patients receiving DES (2.4 per 100 person-years, 95% CI 1.6-3.6) compared with BMS (5.5 per 100 person-years, 95% CI 3.7-8.2, hazard ratio 0.45, 95% CI 0.26-0.80, P = .007). However, they were not significantly different between receivers of DES and BMS in patients in the low-mid risk tertiles. CONCLUSIONS: This exploratory analysis suggests that, in patients who require stenting of a large coronary artery, use of a clinical risk score may identify those patients for whom DES use may confer a clinical advantage over BMS, beyond lower restenosis rates.

Human-induced pluripotent stem cell-derived cardiomyocytes from cardiac progenitor cells: effects of selective ion channel blockade.

AIM: Human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes are likely to revolutionize electrophysiological approaches to arrhythmias. Recent evidence suggests the somatic cell origin of hiPSCs may influence their differentiation potential. Owing to their cardiomyogenic potential, cardiac-stromal progenitor cells (CPCs) are an interesting cellular source for generation of hiPSC-derived cardiomyocytes. The effect of ionic current blockade in hiPSC-derived cardiomyocytes generated from CPCs has not been characterized yet. METHODS AND RESULTS: Human-induced pluripotent stem cell-derived cardiomyocytes were generated from adult CPCs and skin fibroblasts from the same individuals. The effect of selective ionic current blockade on spontaneously beating hiPSC-derived cardiomyocytes was assessed using multi-electrode arrays. Cardiac-stromal progenitor cells could be reprogrammed into hiPSCs, then differentiated into hiPSC-derived cardiomyocytes. Human-induced pluripotent stem cell-derived cardiomyocytes of cardiac origin showed higher upregulation of cardiac-specific genes compared with those of fibroblastic origin. Human-induced pluripotent stem cell-derived cardiomyocytes of both somatic cell origins exhibited sensitivity to tetrodotoxin, a blocker of Na+ current (INa), nifedipine, a blocker of L-type Ca2+ current (ICaL), and E4031, a blocker of the rapid component of delayed rectifier K+ current (IKr). Human-induced pluripotent stem cell-derived cardiomyocytes of cardiac origin exhibited sensitivity to JNJ303, a blocker of the slow component of delayed rectifier K+ current (IKs). CONCLUSION: In hiPSC-derived cardiomyocytes of cardiac origin, INa, ICaL, IKr, and IKs were present as tetrodotoxin-, nifedipine-, E4031-, and JNJ303-sensitive currents, respectively. Although cardiac differentiation efficiency was improved in hiPSCs of cardiac vs. non-cardiac origin, no major functional differences were observed between hiPSC-derived cardiomyocytes of different somatic cell origins. Further studies are warranted to characterize electrophysiological properties of hiPSC-derived cardiomyocytes generated from CPCs.

Additive effects of rapamycin and aspirin on dendritic cell allostimulatory capacity.

Acting as antigen presenting cells, mature dendritic cells (DCs) initiate both innate and adaptive alloimmune responses. However, immature DCs are weak immunostimulators and mediate tolerogenic effects under certain conditions. Tolerogenic activities of immature DCs can be enhanced by pharmacological agents. Here, we compared pharmacological DC preconditioning with rapamycin and aspirin, applied alone or in combination, on LPS-induced DC maturation and T-cell allostimulatory capacity. Preconditioning with aspirin but not rapamycin tended to reduce the number of mouse bone marrow-derived immature DCs expressing CD40 and major histocompatibility complex class II molecules upon LPS stimulation. Conversely, DC preconditioning with rapamycin, but not aspirin, reduced T-cell alloproliferative responses. A combination of rapamycin and aspirin was more effective than either drug applied alone with respect to inhibition of T-cell alloproliferation. The two agents in combination reduced numbers of CD4(+)IFN-γ(+) Th1 and CD4(+)IL-17(+) Th17 effector cells while maintaining Foxp3(+) regulatory T cells. These results suggest aspirin may moderately enhance rapamycin-mediated inhibition of DC allostimulatory capacity.

Bone marrow-derived cells for cardiovascular cell therapy: an optimized GMP method based on low-density gradient improves cell purity and function.

BACKGROUND: Cardiovascular cell therapy represents a promising field, with several approaches currently being tested. The advanced therapy medicinal product (ATMP) for the ongoing METHOD clinical study ("Bone marrow derived cell therapy in the stable phase of chronic ischemic heart disease") consists of fresh mononuclear cells (MNC) isolated from autologous bone marrow (BM) through density gradient centrifugation on standard Ficoll-Paque. Cells are tested for safety (sterility, endotoxin), identity/potency (cell count, CD45/CD34/CD133, viability) and purity (contaminant granulocytes and platelets). METHODS: BM-MNC were isolated by density gradient centrifugation on Ficoll-Paque. The following process parameters were optimized throughout the study: gradient medium density; gradient centrifugation speed and duration; washing conditions. RESULTS: A new manufacturing method was set up, based on gradient centrifugation on low density Ficoll-Paque, followed by 2 washing steps, of which the second one at low speed. It led to significantly higher removal of contaminant granulocytes and platelets, improving product purity; the frequencies of CD34+ cells, CD133+ cells and functional hematopoietic and mesenchymal precursors were significantly increased. CONCLUSIONS: The methodological optimization described here resulted in a significant improvement of ATMP quality, a crucial issue to clinical applications in cardiovascular cell therapy.

Impact of Isolation Methods on Extracellular Vesicle Functionality In Vitro and In Vivo.

This study compares the impact of two isolation methods, ultracentrifugation (UC) and size exclusion chromatography (SEC), on small extracellular vesicles (sEVs) from primary human cardiac mesenchymal-derived progenitor cells (CPCs). sEV_UC and sEV_SEC exhibit similar size, marker expression, and miRNA cargo, but sEV_UC contains notably higher total protein levels. In vitro assays show that sEV_UC, despite an equal particle count, induces more robust ERK phosphorylation, cytoprotection, and proliferation in iPS-derived cardiomyocytes (iPS-CMs) compared to sEV_SEC. sEV_UC also contains elevated periostin (POSTN) protein levels, resulting in enhanced focal adhesion kinase (FAK) phosphorylation in iPS-CMs. Importantly, this effect persists with treatment with soluble free-sEV protein fraction from SEC (Prote_SEC), indicating that free proteins like POSTN in sEV_UC enhance FAK phosphorylation. In vivo, sEV contamination with soluble proteins doesn't affect cardiac targeting or FAK phosphorylation, underscoring the intrinsic tissue targeting properties of sEV. These findings emphasize the need for standardized sEV isolation methods, as the choice of method can impact experimental outcomes, particularly in vitro.

Plasma-derived extracellular vesicles released after endurance exercise exert cardioprotective activity through the activation of antioxidant pathways.

Cardiovascular diseases (CVD) can cause various conditions, including an increase in reactive oxygen species (ROS) levels that can decrease nitric oxide (NO) availability and promote vasoconstriction, leading to arterial hypertension. Physical exercise (PE) has been found to be protective against CVD by helping to maintain redox homeostasis through a decrease in ROS levels, achieved by increased expression of antioxidant enzymes (AOEs) and modulation of heat shock proteins (HSPs). Extracellular vesicles (EVs) circulating in the body are a major source of regulatory signals, including proteins and nucleic acids. Interestingly, the cardioprotective role of EVs released after PE has not been fully described. The aim of this study was to investigate the role of circulating EVs, obtained through Size Exclusion Chromatography (SEC) of plasma samples from healthy young males (age: 26.95 ± 3.07; estimated maximum oxygen consumption rate (VO2max): 51.22 ± 4.85 (mL/kg/min)) at basal level (Pre_EVs) and immediately after a single bout of endurance exercise (30' treadmill, 70% heart rate (HR) -Post_EVs). Gene ontology (GO) analysis of proteomic data from isolated EVs, revealed enrichment in proteins endowed with catalytic activity in Post_EVs, compare to Pre_EVs, with MAP2K1 being the most significantly upregulated protein. Enzymatic assays on EVs derived from Pre and Post samples showed increment in Glutathione Reductase (GR) and Catalase (CAT) activity in Post_EVs. At functional level, Post_EVs, but not Pre_EVs, enhanced the activity of antioxidant enzymes (AOEs) and reduced oxidative damage accumulation in treated human iPS-derived cardiomyocytes (hCM) at basal level and under stress conditions (Hydrogen Peroxide (H2O2) treatment), resulting in a global cardioprotective effect. In conclusion, our data demonstrated, for the first time, that a single 30-min endurance exercise is able to alter the cargo of circulating EVs, resulting in cardioprotective effect through antioxidant activity.

Erratum: Inflammatory extracellular vesicles prompt heart dysfunction via TLR4-dependent NF-κB activation: Erratum.

[This corrects the article DOI: 10.7150/thno.39072.].

Circulating GDF11 exacerbates myocardial injury in mice and associates with increased infarct size in humans.

AIMS: The heart rejuvenating effects of circulating growth differentiation factor 11 (GDF11), a transforming growth factor-ß superfamily member that shares 90% homology with myostatin (MSTN), remains controversial. Here, we aimed to probe the role of GDF11 in acute myocardial infarction (MI), a frequent cause of heart failure and premature death during ageing. METHODS AND RESULTS: In contrast to endogenous Mstn, myocardial Gdf11 declined during the course of ageing and was particularly reduced following ischaemia/reperfusion (I/R) injury, suggesting a therapeutic potential of GDF11 signalling in MI. Unexpectedly, boosting systemic Gdf11 by recombinant GDF11 delivery (0.1 mg/kg body weight over 30 days) prior to myocardial I/R augmented myocardial infarct size in C57BL/6 mice irrespective of their age, predominantly by accelerating pro-apoptotic signalling. While intrinsic cardioprotective signalling pathways remained unaffected by high circulating GDF11, targeted transcriptomics and immunomapping studies focusing on GDF11-associated downstream targets revealed attenuated Nkx2-5 expression confined to CD105-expressing cells, with pro-apoptotic activity, as assessed by caspase-3 levels, being particularly pronounced in adjacent cells, suggesting an indirect effect. By harnessing a highly specific and validated liquid chromatography-tandem mass spectrometry-based assay, we show that in prospectively recruited patients with MI circulating GDF11 but not MSTN levels incline with age. Moreover, GDF11 levels were particularly elevated in those at high risk for adverse outcomes following the acute event, with circulating GDF11 emerging as an independent predictor of myocardial infarct size, as estimated by standardized peak creatine kinase-MB levels. CONCLUSION: Our data challenge the initially reported heart rejuvenating effects of circulating GDF11 and suggest that high levels of systemic GDF11 exacerbate myocardial injury in mice and humans alike. Persistently high GDF11 levels during ageing may contribute to the age-dependent loss of cardioprotective mechanisms and thus poor outcomes of elderly patients following acute MI.

Ultrastructural evidence of exosome secretion by progenitor cells in adult mouse myocardium and adult human cardiospheres.

The demonstration of beneficial effects of cell therapy despite the persistence of only few transplanted cells in vivo suggests secreted factors may be the active component of this treatment. This so-called paracrine hypothesis is supported by observations that culture media conditioned by progenitor cells contain growth factors that mediate proangiogenic and cytoprotective effects. Cardiac progenitor cells in semi-suspension culture form spherical clusters (cardiospheres) that deliver paracrine signals to neighboring cells. A key component of paracrine secretion is exosomes, membrane vesicles that are stored intracellularly in endosomal compartments and are secreted when these structures fuse with the cell plasma membrane. Exosomes have been identified as the active component of proangiogenic effects of bone marrow CD34⁺ stem cells in mice and the regenerative effects of embryonic mesenchymal stem cells in infarcted hearts in pigs and mice. Here, we provide electron microscopic evidence of exosome secretion by progenitor cells in mouse myocardium and human cardiospheres. Exosomes are emerging as an attractive vector of paracrine signals delivered by progenitor cells. They can be stored as an "off-the-shelf" product. As such, exosomes have the potential for circumventing many of the limitations of viable cells for therapeutic applications in regenerative medicine.

De novo DNA methylation induced by circulating extracellular vesicles from acute coronary syndrome patients.

BACKGROUND AND AIMS: DNA methylation is associated with gene silencing, but its clinical role in cardiovascular diseases (CVDs) remains to be elucidated. We hypothesized that extracellular vesicles (EVs) may carry epigenetic changes, showing themselves as a potentially valuable non-invasive diagnostic liquid biopsy. We isolated and characterized circulating EVs of acute coronary syndrome (ACS) patients and assessed their role on DNA methylation in epigenetic modifications. METHODS: EVs were recovered from plasma of 19 ACS patients and 50 healthy subjects (HS). Flow cytometry, qRT-PCR, and Western blot (WB) were performed to evaluate both intra-vesicular and intra-cellular signals. ShinyGO, PANTHER, and STRING tools were used to perform GO and PPI network analyses. RESULTS: ACS-derived EVs showed increased levels of DNA methyltransferases (DNMTs) (p<0.001) and Ten-eleven translocation (TET) genes reduction. Specifically, de novo methylation transcripts, as DNMT3A and DNMT3B, were significantly increased in plasma ACS-EVs. DNA methylation analysis on PBMCs from healthy donors treated with HS- and ACS-derived EVs showed an important role of DNMTs carried by EVs. PPI network analysis evidenced that ACS-EVs induced changes in PBMC methylome. In the most enriched subnetwork, the hub gene SRC was connected to NOTCH1, FOXO3, CDC42, IKBKG, RXRA, DGKG, BAIAP2 genes that were showed to have many molecular effects on various cell types into onset of several CVDs. Modulation in gene expression after ACS-EVs treatment was confirmed for SRC, NOTCH1, FOXO3, RXRA, DGKG and BAIAP2 (p<0.05). CONCLUSIONS: Our data showed an important role for ACS-derived EVs in gene expression modulation through de novo DNA methylation signals, and modulating signalling pathways in target cells.

Stress-induced premature senescence is associated with a prolonged QT interval and recapitulates features of cardiac aging.

Rationale: Aging in the heart is a gradual process, involving continuous changes in cardiovascular cells, including cardiomyocytes (CMs), namely cellular senescence. These changes finally lead to adverse organ remodeling and resulting in heart failure. This study exploits CMs from human induced pluripotent stem cells (iCMs) as a tool to model and characterize mechanisms involved in aging. Methods and Results: Human somatic cells were reprogrammed into human induced pluripotent stem cells and subsequently differentiated in iCMs. A senescent-like phenotype (SenCMs) was induced by short exposure (3 hours) to doxorubicin (Dox) at the sub-lethal concentration of 0.2 µM. Dox treatment induced expression of cyclin-dependent kinase inhibitors p21 and p16, and increased positivity to senescence-associated beta-galactosidase when compared to untreated iCMs. SenCMs showed increased oxidative stress, alteration in mitochondrial morphology and depolarized mitochondrial membrane potential, which resulted in decreased ATP production. Functionally, when compared to iCMs, SenCMs showed, prolonged multicellular QTc and single cell APD, with increased APD variability and delayed afterdepolarizations (DADs) incidence, two well-known arrhythmogenic indexes. These effects were largely ascribable to augmented late sodium current (INaL) and reduced delayed rectifier potassium current (Ikr). Moreover sarcoplasmic reticulum (SR) Ca2+ content was reduced because of downregulated SERCA2 and increased RyR2-mediated Ca2+ leak. Electrical and intracellular Ca2+ alterations were mostly justified by increased CaMKII activity in SenCMs. Finally, SenCMs phenotype was furtherly confirmed by analyzing physiological aging in CMs isolated from old mice in comparison to young ones. Conclusions: Overall, we showed that SenCMs recapitulate the phenotype of aged primary CMs in terms of senescence markers, electrical and Ca2+ handling properties and metabolic features. Thus, Dox-induced SenCMs can be considered a novel in vitro platform to study aging mechanisms and to envision cardiac specific anti-aging approach in humans.