Impact of collection, isolation and storage methodology of circulating microvesicles on flow cytometric analysis

Flow Cytometry Analysis of Blood Large Extracellular Vesicles in Patients with Multiple Sclerosis Experiencing Relapse of the Disease

The number of people living with multiple sclerosis (MS) in developed countries is increasing. The management of patients is hindered by the absence of reliable laboratory tests accurately reflecting the disease activity. Extracellular vesicles (EVs) of different cell origin were reportedly elevated in MS patients. We assessed the diagnostic potential, with flow cytometry analysis, of fresh large EVs (lEVs), which scattered more light than the 590 nm silica beads and were isolated from the blood plasma of relapsing remitting MS patients. Venous blood was collected from 15 patients and 16 healthy controls (HC). The lEVs were isolated from fresh platelet-free plasma by centrifugation, labelled with antibodies and the presence of platelet (CD41+, CD36+), endothelial (CD105+), erythrocyte (CD235a+), leukocyte (CD45+, CD19+, CD3+) and phosphatidylserine (Annexin V+) positive lEVs was analyzed using standard flow cytometry. Cryo-electron microscopy was used to verify the presence of EVs in the analyzed plasma fractions. MS patients experiencing acute relapse had slightly reduced relative levels (% of positive lEVs) of CD105+, CD45+, CD3+, CD45+CD3+ or CD19+ labelled lEVs in comparison to healthy controls. An analysis of other markers or a comparison of absolute lEV counts (count of lEVs/µL) did not yield any significant differences. Our data do not support the hypothesis that the exacerbation of the disease in RRMS patients leads to an increased numbers of circulating plasma lEVs which can be monitored by standard flow cytometry.

Microvesicles transfer mitochondria and increase mitochondrial function in brain endothelial cells

We have demonstrated, for the first time that microvesicles, a sub-type of extracellular vesicles (EVs) derived from hCMEC/D3: a human brain endothelial cell (BEC) line transfer polarized mitochondria to recipient BECs in culture and to neurons in mice acute brain cortical and hippocampal slices. This mitochondrial transfer increased ATP levels by 100 to 200-fold (relative to untreated cells) in the recipient BECs exposed to oxygen-glucose deprivation, an in vitro model of cerebral ischemia. We have also demonstrated that transfer of microvesicles, the larger EV fraction, but not exosomes resulted in increased mitochondrial function in hypoxic endothelial cultures. Gene ontology and pathway enrichment analysis of EVs revealed a very high association to glycolysis-related processes. In comparison to heterotypic macrophage-derived EVs, BEC-derived EVs demonstrated a greater selectivity to transfer mitochondria and increase endothelial cell survival under ischemic conditions.

Enumeration and phenotyping of circulating microvesicles by flow cytometry and nanoparticle tracking analysis: Plasma versus serum

INTRODUCTION

Microvesicles (MVs) are bioactive, submicron-sized (0.01-1000 nm) membrane vesicles released from various types of cells under normal physiological and pathophysiological conditions. MVs have emerged as important mediators of cell-to-cell communication in a diverse range of normal and pathological processes. MVs have been recognized as potential biomarkers in coagulation, inflammation, and cancer. However, for clinical use, minimizing factors which could affect enumeration and phenotypic characterization of MVs during pre-analytical steps is crucial. In this study, we used flow cytometry and nanoparticle tracking analysis (NTA) to investigate the impact of blood collection using with and without anticoagulant on the number and phenotype of MVs in blood samples.

METHODS

Blood from 30 healthy volunteers was collected by venipuncture into 3.2% sodium citrate and clot activator tubes. MV subpopulations and their concentrations were investigated using flow cytometry and NTA. MV morphology was examined by transmission electron microscopy.

RESULTS

Results showed that the concentration of MVs was significantly lower in serum than in plasma and that CD41⁺ MV, CD41⁺ /CD62P⁺ MV, CD45⁺ MV, and CD142⁺ MV levels from serum were significantly lower than those from plasma, whereas no significant differences in Annexin V (Anx V)⁺ MV, CD235a⁺ MV, and CD144⁺ MV levels were found. Interestingly, serum MVs had a higher proportion of small-sized MVs and lower proportion of large-sized MVs than did plasma MVs.

CONCLUSION

Although plasma samples are commonly used, our results suggest that serum can also be used in enumeration of MVs, but care must be taken if coagulation is an aspect of the research.

Effects of Cell-Derived Microparticles on Immune Cells and Potential Implications in Clinical Medicine

In the past few years, interest has increased in cell-derived microparticles (MPs), which are defined by their size of from 0.1 to 1 μm, and can be derived from various cell types, including endothelial cells, leukocytes, red blood cells (RBCs), and platelets. These MPs carry negatively charged phosphatidylserine (PS) on their surfaces and proteins packaged from numerous cellular components. MPs that have been shed by the body can play important roles in the pathophysiology of diseases and can affect various biological systems. Among these systems, the immune components have been shown to be modulated by MPs. Therefore, understanding the roles of MPs in the immune system is crucial to developing alternative therapeutic treatments for diseases. This review describes the effects of MPs on various immune cells and provides plausible potential applications of the immune-modulating properties of MPs in clinical medicine.

High miR-133a levels in the circulation anticipates presentation of clinical events in familial hypercholesterolaemia patients

AIMS

Presentation of acute events in patients with atherosclerosis remains unpredictable even after controlling for classical risk factors. MicroRNAs (miRNAs) measured in liquid biopsies could be good candidate biomarkers to improve risk prediction. Here, we hypothesized that miRNAs could predict atherosclerotic plaque progression and clinical event presentation in familial hypercholesterolaemia (FH) patients.

METHODS AND RESULTS

Circulating miRNAs (plasma, exosomes, and microvesicles) were investigated by TaqMan Array and RT-qPCR assays. Patients with genetic diagnosis of FH and healthy relatives from the SAFEHEART cohort were included. A differential signature of 10 miRNA was obtained by comparing two extreme phenotypes consisting of FH patients suffering a cardiovascular event (CVE) within a 8-year follow-up period (FH-CVE, N = 42) and non-FH hypercholesterolaemic relatives from the same cohort, matched for age and treatment, without CVE during the same period (nFH-nCVE, N = 30). The validation studies included two independent groups of patients with FH background (discovery group, N = 89, validation group N = 196), developing a future CVE (FH-CVE) or not (FH-nCVE) within the same time period of follow-up. Of the 10 miRNAs initially selected, miR-133a was significantly higher in FH-CVE than in FH-nCVE patients. Receiver operating characteristic analysis confirmed miR-133a as the best microRNA for predicting CVE in FH patients (0.76 ± 0.054; P < 0.001). Furthermore, Kaplan-Meier and COX analysis showed that high plasma miR-133a levels associated to the higher risk of presenting a CVE within the next 8 years (hazard ratio 3.89, 95% confidence interval 1.88-8.07; P < 0.001). In silico analysis of curate biological interactions related miR-133a with target genes involved in regulation of the cell-membrane lipid-receptor LRP6 and inflammatory cytokines (CXCL8, IL6, and TNF). These predictions were experimentally proven in human macrophages and endothelial cells transfected with agomiR-133a.

CONCLUSION

Elevated levels of miR-133a in the circulation anticipate those FH patients that are going to present a clinical CVE within the next 2 years (average). Mechanistically, miR-133a is directly related with lipid- and inflammatory signalling in key cells for atherosclerosis progression.

Liquid Biopsy of Extracellular Microvesicles Predicts Future Major Ischemic Events in Genetically Characterized Familial Hypercholesterolemia Patients

Objective—

Circulating microvesicles (cMVs) exert regulatory roles in atherothrombosis. Patients with familial hypercholesterolemia (FH) that are at high risk for premature cardiovascular events (CVEs) have previously shown high levels of cMVs related to disease severity. However, much remains unknown about their value as markers of CVE. We sought to investigate the prognostic cMV signature for future major CVE presentation in patients with FH.

Approach and Results—

Liquid biopsies from genetically characterized patients with FH from the SAFEHEART (Spanish Familial Hypercholesterolemia Cohort Study)-cohort without clinical manifestation of disease at entry that were going to suffer a CVE within a mean period of 3.3±2.6 years postsampling (CVE, N=92) and from age/cardiovascular risk factor/treatment-matched patients with FH that did not suffer an event within the same time-period (non-CVE, N=48) were investigated. cMVs were phenotyped by flow cytometry to identify activated parental cells. Patients with CVE had higher number of overall procoagulant annexin V + -cMVs than non-CVE ( P <0.05). Pan-leukocyte-derived and neutrophil-derived cMVs, as well as activated platelet-derived cMVs, were significantly higher in patients with CVE. Baseline number of cMVs derived from lymphocytes, neutrophils, and activated platelets were positively associated with mortality at follow-up ( P <0.05). Patient-risk calculated by classical cardiovascular risk-factor scores did not correlate with cMVs. Inclusion of the cMV signature into the SAFEHEART risk model for patients with FH for the prediction of ischemic events increased the area under the curve from 0.603±0.050 to 0.768±0.042 ( P <0.005).

Conclusions—

Patients with FH who are going to suffer a CVE within a mean period of 3.3 years, despite being treated according to guidelines, have ongoing innate immune cell and platelet activation. The proposed cMV signature is a prognostic marker for accelerated atherosclerosis and clinical event presentation in patients with FH.

Circulating microparticles are associated with clinical severity of persistent ST-segment elevation myocardial infarction complicated with cardiogenic shock

BACKGROUND

Cardiogenic shock (CS) is the leading cause of death in patients admitted for acute myocardial infarction (MI). Despite the recent advances in reperfusion and medical treatment mortality remains unacceptably high. Whether cells of the blood compartment in CS-patients are activated and release microparticles (cMPs) that may be both messengers and biomarkers of cell damage is not known. We aimed to investigate the cMP subtypes and parental activated cells of ST-elevation MI (STEMI)-patients complicated by CS and that of non-CS STEMI-patients (non-CS) in order to identify a cMP signature that could aid CS patient's risk stratification.

METHODS

Clinically-characterized STEMI-patients with and without CS (36/group) were included. Treatment was delivered according to guidelines and included primary percutaneous coronary intervention. cMPs were characterized by triple-labeling flow cytometry using Annexin V and cell surface-specific monoclonal antibodies.

RESULTS

Increased levels of leukocyte-derived (neutrophil and granulocyte origin) and platelet-derived cMPs were detected in CS compared to non-CS patients. A signature of cMPs derived from platelets, leukocytes, and endothelium discriminated CS-patients (AUC of 0.743±0.059 [95% CI: 0.628-0.859], P<0.0001) and predicted mortality in CS (AUC of 0.869±0.06 [95% CI: 0.750-0.988], P<0.0001). In CS-patients, a higher number of platelet- and monocyte-cMPs and of tissue factor-rich cMPs associated to worse myocardial blush grade and thrombolysis in myocardial infarction flow.

CONCLUSIONS

cMPs derived from proinflammatory and prothrombotic cells were found to be elevated in CS-patients. In treated as per guidelines CS patients, granulocytes and neutrophils remained activated and actively shed cMPs. These cMPs were biomarkers of adverse prognosis in CS.

TRANSLATIONAL ASPECT

Increased levels of leukocyte and platelet-derived circulating microparticles (cMPs) are found in cardiogenic shock (CS) patients as compared to non-CS patients. In CS-patients, a higher number of platelet- and monocyte-cMPs and a higher number of tissue factor-rich cMPs were associated to worse myocardial reperfusion. A specific prothrombotic and proinflammatory cMPs signature in cardiogenic shock (CS) patients is a potential discriminator and survival prognostic biomarker for CS, which could aid management and improve clinical outcomes.

Platelet-Derived Microvesicles in Cardiovascular Diseases

Microvesicles (MVs) circulating in the blood are small vesicles (100–1,000 nm in diameter) derived from membrane blebs of cells such as activated platelets, endothelial cells, and leukocytes. A growing body of evidence now supports the concept that platelet-derived microvesicles (PMVs), the most abundant MVs in the circulation, are important regulators of hemostasis, inflammation, and angiogenesis. Compared with healthy individuals, a large increase of circulating PMVs has been observed, particularly in patients with cardiovascular diseases. As observed in MVs from other parent cells, PMVs exert their biological effects in multiple ways, such as triggering various intercellular signaling cascades and by participating in transcellular communication by the transfer of their “cargo” of cytoplasmic components and surface receptors to other cell types. This review describes our current understanding of the potential role of PMVs in mediating hemostasis, inflammation, and angiogenesis and their consequences on the pathogenesis of cardiovascular diseases, such as atherosclerosis, myocardial infarction, and venous thrombosis. Furthermore, new developments of the therapeutic potential of PMVs for the treatment of cardiovascular diseases will be discussed.

Tumor Cell-Derived Microvesicles Induced Not Epithelial-Mesenchymal Transition but Apoptosis in Human Proximal Tubular (HK-2) Cells: Implications for Renal Impairment in Multiple Myeloma

Renal impairment (RI) is one of the hallmarks of multiple myeloma (MM) and carries a poor prognosis. Microvesicles (MVs) are membrane vesicles and play an important role in disease progression. Here, we investigated the role of MVs derived from MM cells (MM-MVs) in RI of MM. We found that MM-MVs significantly inhibited viability and induced apoptosis, but not epithelial-mesenchymal transition in human kidney-2 (HK-2), a human renal tubular epithelial cell line. The protein levels of cleaved caspase-3, 8, and 9, and E-cadherin, were increased, but vementin levels were decreased in the HK-2 cells treated with MM-MVs. Through a comparative sequencing and analysis of RNA content between the MVs from RPMI8226 MM cells (RPMI8226-MVs) and K562 leukemia cells, RPMI8226-MVs were enriched with more renal-pathogenic miRNAs, in which the selective miRNAs may participate in the up-regulation of the levels of cleaved caspase-3. Furthermore, the levels of CD138+ circulating MVs (cirMVs) in the peripheral blood were positively correlated with the severity of RI in newly-diagnosed MM. Our study supports MM-MVs representing a previously undescribed factor and playing a potential role in the development of RI of MM patients, and sheds light on the potential application of CD138+ cirMV counts in precise diagnosis of RI in MM and exploring MM-MVs as a therapeutic target.