Circulating microparticles: challenges and perspectives of flow cytometric assessment

Systemic Inflammatory Patterns in Ovarian Cancer Patients: Analysis of Cytokines, Chemokines, and Microparticles

OBJECTIVE

 To compare the patterns of systemic inflammatory response in women with epithelial ovarian cancer (EOC) or no evidence of malignant disease, as well as to evaluate the profile of systemic inflammatory responses in type-1 and type-2 tumors. This is a non-invasive and indirect way to assess both tumor activity and the role of the inflammatory pattern during pro- and antitumor responses.

MATERIALS AND METHODS

 We performed a prospective evaluation of 56 patients: 30 women without evidence of malignant disease and 26 women with EOC. The plasma quantification of cytokines, chemokines, and microparticles (MPs) was performed using flow cytometry.

RESULTS

 Plasma levels of proinflammatory cytokines interleukin-12 (IL12), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α) interleukin-1 beta (IL-1β), and interleukin-10 (IL-10), and C-X-C motif chemokine ligand 9 (CXCL-9) and C-X-C motif chemokine ligand 10 (CXCL-10) were significantly higher in patients with EOC than in those in the control group. Plasma levels of cytokine interleukin-17A (IL-17A) and MPs derived from endothelial cells were lower in patients with EOC than in the control group. The frequency of leukocytes and MPs derived from endothelial cells was higher in type-2 tumors than in those without malignancy. We observed an expressive number of inflammatory/regulatory cytokines and chemokines in the cases of EOC, as well as negative and positive correlations involving them, which leads to a higher complexity of these networks.

CONCLUSION

 The present study showed that, through the development of networks consisting of cytokines, chemokines, and MPs, there is a greater systemic inflammatory response in patients with EOC and a more complex correlation of these biomarkers in type-2 tumors.

Circulating microvesicles across a population with various degree of cardiovascular burden are associated with systolic blood pressure

Circulating microvesicles (MVs) have been studied in heterogeneous, divergent, and rather small patient populations with cardiovascular risk . Therefore, we measured endothelial (EMVs), platelet (PMVs) and erythrocyte (RMVs) MVs in patients with divergent cardiovascular risk. We then compared them to coronary artery disease (CAD) and healthy subjects and identified independent MVs' predictors. We enrolled consecutive patients from our Cardiology, Hypertension, Diabetic, Rheumatic, and Nephrology Outpatient Units with MVs measurements. Central blood pressure (BP) was measured by either applanation tonometry or Mobil-O-graph device, while MVs by a standardized flow cytometry protocol. We studied 369 participants with increased cardiovascular risk: 63 with high cardiovascular risk (47 diabetes mellitus type II/DM and 16 end-stage renal disease/ESRD), 92 with chronic inflammatory disorders and 73 with untreated essential hypertension/UEH. We further included 53 subjects with CAD and 87 otherwise healthy individuals. All MVs were lower in patients with increased cardiovascular risk compared to CAD, showing predictive value with high sensitivity and specificity. Furthermore, PMVs and EMVs were increased in patients with cardiovascular risk compared to healthy individuals. DM and ESRD patients had increased EMVs versus UEH and chronic inflammatory disorders. In the whole study population, RMVs were associated only with history of essential hypertension. In multivariate analysis, systolic BP predicted PMVs. Aage, systolic BP, and DM predicted EMVs. In a large population of patients with divergent cardiovascular risk, MVs are independently associated with systolic blood pressure.

Annexin V- and tissue factor+ microparticles as biomarkers for predicting deep vein thrombosis in patients after joint arthroplasty

OBJECTIVE

Venous thromboembolism (VTE) is a common and severe complication of joint arthroplasty. Microparticles (MPs) containing phosphatidylserine (PS) and tissue factor (TF) can trigger coagulation in VTE. This study aims to measure and compare MP levels in joint arthroplasty patients with and without VTE.

METHODS

This prospective cohort study enrolled 181 patients who underwent joint arthroplasty. Ultrasound examination was used to diagnose VTE on preoperative day 0 and postoperative day 6. MPs were analysed using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and flow cytometry. The levels of platelet-derived microparticles (PMPs), endothelial cell-derived microparticles (EMPs), granulocyte-derived microparticles (GMPs), red cell-derived microparticles (RMPs), monocyte-derived microparticles (MMPs), Annexin V⁺ MPs (AV⁺ MPs), and tissue factor⁺ MPs (TF⁺ MPs) derived from five kinds of MPs were measured on day 0 (before surgery), 1, 2, 3, 4, 5, and 6 after surgery.

RESULTS

The levels of AV^-TF⁺ EMPs and AV^-TF⁺ MMPs were significantly increased in patients with VTE on postoperative day 5 compared to those without VTE (P=0.031 and P=0.031, respectively).

CONCLUSION

AV^-TF⁺ MPs may indicate the development of VTE and serve as predictive markers in joint arthroplasty patients.

An Integrated Approach of the Potential Underlying Molecular Mechanistic Paradigms of SARS-CoV-2-Mediated Coagulopathy

Coronavirus disease 2019 (Covid-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a pandemic disease which has affected more than 6.2 million people globally, with numbers mounting considerably daily. However, till date, no specific treatment modalities are available for Covid-19 and also not much information is known about this disease. Recent studies have revealed that SARS-CoV-2 infection is associated with the generation of thrombosis and coagulopathy. Fundamentally, it has been believed that a diverse array of signalling pathways might be responsible for the activation of coagulation cascade during SARS-CoV-2 infection. Henceforth, a detailed understanding of these probable underlying molecular mechanistic pathways causing thrombosis in Covid-19 disease deserves an urgent exploration. Therefore, in this review, the hypothetical crosstalk between distinct signalling pathways including apoptosis, inflammation, hypoxia and angiogenesis attributable for the commencement of thrombotic events during SARS-CoV-2 infection has been addressed which might further unravel promising therapeutic targets in Covid-19 disease.

Flow Cytometry Analysis of Circulating Extracellular Vesicle Subtypes from Fresh Peripheral Blood Samples

Extracellular vesicles (EVs) are released by shedding during different physiological processes and are increasingly thought to be new potential biomarkers. However, the impact of pre-analytical processing phases on the final measurement is not predictable and for this reason, the translation of basic research into clinical practice has been precluded. Here we have optimized a simple procedure in combination with polychromatic flow cytometry (PFC), to identify, classify, enumerate, and separate circulating EVs from different cell origins. This protocol takes advantage of a lipophilic cationic dye (LCD) able to probe EVs. Moreover, the application of the newly optimized PFC protocol here described allowed the obtainment of repeatable EVs counts. The translation of this PFC protocol to fluorescence-activated cell sorting allowed us to separate EVs from fresh peripheral blood samples. Sorted EVs preparations resulted particularly suitable for proteomic analyses, which we applied to study their protein cargo. Here we show that LCD staining allowed PFC detection and sorting of EVs from fresh body fluids, avoiding pre-analytical steps of enrichment that could impact final results. Therefore, LCD staining is an essential step towards the assessment of EVs clinical significance.

Role of Extracellular Vesicles in Epithelial Ovarian Cancer: A Systematic Review

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived submicron vesicles released under physiological or pathological conditions. EVs mediate the cellular crosstalk, thus contributing to defining the tumor microenvironment, including in epithelial ovarian cancer (EOC). The available literature investigating the role of EVs in EOC has been reviewed following PRISMA guidelines, focusing on the role of EVs in early disease diagnosis, metastatic spread, and the development of chemoresistance in EOC. Data were identified from searches of Medline, Current Contents, PubMed, and from references in relevant articles from 2010 to 1 April 2020. The research yielded 194 results. Of these, a total of 36 papers, 9 reviews, and 27 original types of research were retained and analyzed. The literature findings demonstrate that a panel of EV-derived circulating miRNAs may be useful for early diagnosis of EOC. Furthermore, it appears clear that EVs are involved in mediating two crucial processes for metastatic and chemoresistance development: the epithelial–mesenchymal transition, and tumor escape from the immune system response. Further studies, more focused on in vivo evidence, are urgently needed to clarify the role of EV assessment in the clinical management of EOC patients.

Platelet microvesicles are associated with the severity of coronary artery disease: comparison between peripheral and coronary circulation

Microvesicles (MVs) have recently emerged as markers of thrombosis. Furthermore, there is an unexplained residual thrombotic risk is observed in patients with acute coronary syndrome (ACS) and/or stable coronary artery disease (CAD), despite treatment. We measured platelet (PMVs) and erythrocyte (ErMVs) in patients with ACS and stable CAD, both in the peripheral and coronary circulation. We studied consecutive eligible patients during a coronary angiography. Blood samples were collected from the stem of the left coronary artery and femoral artery. PMVs were significantly increased in CAD patients compared to controls. ACS patients had also increased PMVs in coronary and peripheral circulation, compared to controls. Furthermore, ACS patients exhibited increased PMVs in coronary compared to peripheral circulation. Lastly, coronary PMVs were associated with the severity of CAD based on the SYNTAX score. No significant differences were observed in the levels of ErMVs among groups. Therefore, PMVs emerge as novel markers of thrombosis in CAD, further augmenting the vicious cycle of inflammation and thrombosis during ACS. Importantly, coronary PMVs may reflect the severity of CAD in this population.

Extracellular Vesicles in Feto-Maternal Crosstalk and Pregnancy Disorders

Extracellular vesicles (EVs) actively participate in inter-cellular crosstalk and have progressively emerged as key players of organized communities of cells within multicellular organisms in health and disease. For these reasons, EVs are attracting the attention of many investigators across different biomedical fields. In this scenario, the possibility to study specific placental-derived EVs in the maternal peripheral blood may open novel perspectives in the development of new early biomarkers for major obstetric pathological conditions. Here we reviewed the involvement of EVs in feto–maternal crosstalk mechanisms, both in physiological and pathological conditions (preeclampsia, fetal growth restriction, preterm labor, gestational diabetes mellitus), also underlining the usefulness of EV characterization in maternal–fetal medicine.

Endothelial Microvesicles Circulating in Peripheral and Coronary Circulation Are Associated With Central Blood Pressure in Coronary Artery Disease

BACKGROUND

Endothelial microvesicles (EMVs) have emerged as markers of endothelial injury. However, little is known about their levels in the coronary circulation of acute coronary syndrome (ACS) and stable coronary artery disease (CAD). We hypothesized that ACS patients exhibit a more pronounced increase of EMVs both in the peripheral and coronary circulation when compared with CAD. We also investigated possible associations of EMVs with markers preclinical target organ damage.

METHODS

We enrolled consecutive eligible patients undergoing coronary angiography. Blood samples were collected from the stem of the left coronary artery and the femoral artery. ΕMVs were measured by a standardized flow cytometry protocol. Central systolic blood pressure (cSBP) was measured invasively and patients' history was recorded.

RESULTS

CAD patients exhibited increased levels of EMVs compared with controls. When patients with ACS and stable CAD were compared, the former had significantly increased EMVs in both coronary and peripheral circulation. Importantly, both ACS and CAD patients exhibited increased levels of EMVs in the coronary circulation compared with periphery. In addition, EMVs were associated with cSBP.

CONCLUSIONS

EMVs emerge as novel markers of ongoing underlying vascular damage, further augmenting the vicious cycle of inflammation and thrombosis mainly in ACS but also in stable CAD.

Cell-derived microparticles and von Willebrand factor in Brazilian renal transplant recipients

AIM

This study was aimed at investigating platelet-derived microparticles (PMP), endothelium cell-derived microparticles (EMP) and von Willebrand factor (VWF) according to renal function and time post-transplant. We found this study relevant because unusual biomarkers seem to be a promising tool to evaluate chronic renal disease and post-transplant monitoring.

METHODS

Ninety-one renal transplant recipients (RTx) were allocated into groups according to creatinine plasma levels (C1 < 1.4 and C2 ≥ 1.4 mg/dL), estimated glomerular filtration rates (R1 < 60 and R2 ≥ 60 mL/min per 1.73 m² ) and time post-transplant (T1: 3-24; T2: 25-60; T3: 61-120; and T4 > 120 months). EMP and PMP levels were assessed by flow cytometry and VWF levels were evaluated by enzyme-linked immunosorbent assay.

RESULTS

Platelet-derived microparticle levels were higher in C1 group compared with C2 (P = 0.00). According to diameter, small PMP and EMP (≤0.7 μm) were also higher in C1 group, all values of P less than 0.05. T1 and T2 groups have shown high EMP levels and a predominance of big microparticle (>0.7 μm) compared with T4 group, all values of P less than 0.05. Higher VWF levels were observed among RTx with creatinine ≥1.4 mg/dL compared with other RTx, P = 0.01.

CONCLUSION

The results showed that PMP, EMP and VWF are promising markers to evaluate endothelial function in RTx. These biomarkers could play a major role in monitoring patients after renal transplant.

Circulating microparticles as biomarkers of stroke: A focus on the value of endothelial- and platelet-derived microparticles

Stroke is one of the leading causes of mortality and disability worldwide. Numerous pathophysiological mechanisms involving blood vessels, coagulation and inflammation contribute to the vascular occlusion. Perturbations in these pathways can be detected by numerous methods including changes in endoplasmic membrane remodeling and rearrangement leading to the shedding of microparticles (MPs) from various cellular origins in the blood. MPs are small membrane-derived vesicles that are shed from nearly all cells in the body in resting state or upon stimulation. MPs act as biological messengers to transfer information to adjacent and distant cells thus regulating various biological processes. MPs may be important biomarkers and tools for the identification of the risk and diagnosis of cerebrovascular diseases. Endothelial activation and dysfunction and altered thrombotic responses are two of the main features predisposing to stroke. Endothelial MPs (EMPs) have been recognized as both biomarkers and effectors of endothelial cell activation and injury while platelet-derived MPs (PMPs) carry a strong procoagulant potential and are activated in thrombotic states. Therefore, we reviewed here the role of EMPs and PMPs as biomarkers of stroke. Most studies reported high circulating levels of EMPs and PMPs in addition to other cell origins in stroke patients and have been linked to stroke severity, the size of infarction, and prognosis. The identification and quantification of EMPs and PMPs may thus be useful for the diagnosis and management of stroke.

Extracellular vesicles in lung health, disease, and therapy

Both physiological homeostasis and pathological disease processes in the lung typically result from complex, yet coordinated multicellular responses that are synchronized via paracrine and endocrine intercellular communication pathways. Of late, extracellular vesicles have emerged as important information shuttles that can coordinate and disseminate homeostatic and disease signals. In parallel, extracellular vesicles in biological fluids such as sputum, mucus, epithelial lining fluid, edema fluid, the pulmonary circulation, pleural fluid, and lymphatics have emerged as promising candidate biomarkers for diagnosis and prognosis in lung disease. Extracellular vesicles are small, subcellular, membrane-bound vesicles containing cargos from parent cells such as lipids, proteins, genetic information, or entire organelles. These cargos endow extracellular vesicles with biologically active information or functions by which they can reprogram their respective target cells. Recent studies show that extracellular vesicles found in lung-associated biological fluids play key roles as biomarkers and effectors of disease. Conversely, administration of naïve or engineered extracellular vesicles with homeostatic or reparative effects may provide a promising novel protective and regenerative strategy to treat lung disease. To highlight this rapidly developing field, the American Journal of Physiology-Lung Cellular and Molecular Physiology is now launching a special Call for Papers on extracellular vesicles in lung health, disease, and therapy. This review aims to set the stage for this call by introducing extracellular vesicles and their emerging roles in lung physiology and pathobiology.

BloodSurf 2017: News from the blood-biomaterial frontier

From stents and large-diameter vascular grafts, to mechanical heart valves and blood pumps, blood-contacting devices are enjoying significant clinical success owing to the application of systemic antiplatelet and anticoagulation therapies. On the contrary, research into material and device hemocompatibility aimed at alleviating the need for systemic therapies has suffered a decline. This research area is undergoing a renaissance fueled by recent fundamental insights into coagulation and inflammation that are offering new avenues of investigation, the growing recognition of the limitations facing existing therapeutic approaches, and the severity of the cardiovascular disorders epidemic. This Opinion article discusses clinical needs for hemocompatible materials and the emerging research directions for fulfilling those needs. Based on the 2017 BloodSurf conference that brought together clinicians, scientists, and engineers from academia, industry, and regulatory bodies, its purpose is to draw the attention of the wider clinical and scientific community to stimulate further growth. STATEMENT OF SIGNIFICANCE: The article highlights recent fundamental insights into coagulation, inflammation, and blood-biomaterial interactions that are fueling a renaissance in the field of material hemocompatibility. It will be useful for clinicians, scientists, engineers, representatives of industry and regulatory bodies working on the problem of developing hemocompatible materials and devices for treating cardiovascular disorders.

Circulating small-sized endothelial microparticles as predictors of clinical outcome after chemotherapy for breast cancer: an exploratory analysis

PURPOSE

Therapeutic exploitation of angiogenesis in breast cancer has been limited by the lack of reliable biomarkers. Circulating small-sized endothelial microparticles (sEMP) are likely to play a significant role as messengers of angiogenesis. Higher levels of EMP have been observed in cancer patients, but their prognostic value in breast cancer is unknown. Our aim was to determine the value of circulating sEMP as a marker of response to chemotherapy in breast cancer.

METHODS

We included patients with breast cancer treated with neoadjuvant or first-line chemotherapy. Baseline and post-treatment circulating sEMP (CD144+) were quantified using a flow cytometer approach specifically designed for analysis of small-sized particles (0.1-0.5 μm). Small-sized EMP response was defined as a post-treatment decrease of sEMP larger than the median decrease of sEMP after chemotherapy. Baseline and post-chemotherapy VEGFA levels were determined with ELISA.

RESULTS

Forty-four breast cancer patients were included (19 with metastatic and 25 with locally advanced disease). Median levels of sEMP decreased after chemotherapy (P = 0.005). Response to chemotherapy showed a non-significant trend to associate with sEMP response (P = 0.056). A sEMP response was observed in 51% of patients and was associated with better overall survival (HR 0.18; 95% CI 0.04-0.87; P = 0.02) and progression free survival (HR 0.30; 95% CI 0.09-0.99; P = 0.04) in the group of women with metastatic disease. Post-chemotherapy decrease of VEGFA levels was not associated with breast cancer prognosis.

CONCLUSIONS

Our results did not support sEMP as a marker of response to chemotherapy. However, our exploratory analysis suggests that in patients with metastatic breast cancer, the decrease of sEMP levels after chemotherapy is associated with better overall and disease free survival and might be superior to VEGFA levels as an angiogenesis-related prognostic marker.

Standardization of a fast and effective method for the generation and detection of platelet-derived microparticles by a flow cytometer

The Flow Cytometry is the principal method used to measure platelet-derived microparticles (PDMPs), by fluorescent properties analysis. PDMPs (0.1-1.0 μm) are abundant in circulation, accounting for approximately 90% of the microparticles and are associated with Cardiovascular Disease, the leading cause of death in the world.

Circulating microparticles and the risk of thrombosis in inherited deficiencies of antithrombin, protein C and protein S

Many subjects carrying inherited thrombophilic defects will never experience venous thromboembolism (VTE) while other individuals developed recurrent VTE with no known additional risk factors. High levels of circulating microparticles (MP) have been associated with increased risk of VTE in patients with factor V Leiden and prothrombin G20210A mutation, suggesting a possible contribution of MP in the hypercoagulability of mild genetic thrombophilia. The role of MP as additional risk factor of VTE in carriers of natural clotting inhibitors defects (severe thrombophilia) has never been assessed. Plasma levels of annexin V-MP, endothelial-derived MP (EMP), platelet-derived MP (PMP), tissue factor-bearing MP (TF+) and the MP procoagulant activity (PPL) were measured in 132 carriers of natural anticoagulant deficiencies (25 antithrombin, 63 protein C and 64 protein S defect) and in 132 age and gender-matched healthy controls. Carriers of natural anticoagulant deficiencies, overall and separately considered, presented with higher median levels of annexin V-MP, EMP, PMP, TF+MP and PPL activity than healthy controls (p< 0.001, < 0.001, < 0.01, 0.025 and 0.03, respectively). Symptomatic carriers with a previous episode of VTE had significantly higher median levels of annexin-V MP than those without VTE (p=0.027). Carriers with high levels of annexin V-MP, EMP and PMP had an adjusted OR for VTE of 3.36 (95 % CI, 1.59 to 7.11), 9.26 (95 % CI, 3.55 to 24.1) and 2.72 (95 %CI, 1.16 to 6.38), respectively. Elevated levels of circulating MP can play a role in carriers of mild and severe inherited thrombophilia. The clinical implications of this association remain to be defined.

The Emerging Roles of Microparticles in Diabetic Nephropathy

Microparticles (MPs) are a type of extracellular vesicles (EVs) shed from the outward budding of plasma membranes during cell apoptosis and/or activation. These microsized particles then release specific contents (e.g., lipids, proteins, microRNAs) which are active participants in a wide range of both physiological and pathological processes at the molecular level, e.g., coagulation and angiogenesis, inflammation, immune responses. Research limitations, such as confusing nomenclature and overlapping classification, have impeded our comprehension of these tiny molecules. Diabetic nephropathy (DN) is currently the greatest contributor to end-stage renal diseases (ESRD) worldwide, and its public health impact will continue to grow due to the persistent increase in the prevalence of diabetes mellitus (DM). MPs have recently been considered as potentially involved in DN onset and progression, and this review juxtaposes some of the research updates about the possible mechanisms from several relevant aspects and insights into the therapeutic perspectives of MPs in clinical management and pharmacological treatment of DN patients.

Modulating thrombotic diathesis in hereditary thrombophilia and antiphospholipid antibody syndrome: a role for circulating microparticles?

Over the past decades, there have been great advances in the understanding of the pathogenesis of venous thromboembolism (VTE) in patients with inherited and acquired thrombophilia [mainly antiphospholipid antibody syndrome (APS)]. However, a number of questions remain unanswered. Prognostic markers capable of estimating the individual VTE risk would be of great use. Microparticles (MPs) are sub-micron membrane vesicles constitutively released from the surface of cells after cellular activation and apoptosis. The effects of MPs on thrombogenesis include the exposure of phopshatidylserine and the expression of tissue factor and MPs have been described in clinical studies as possible diagnostic and prognostic biomarkers for VTE. This review will provide a novel perspective on the current knowledge and research trends on the possible role of MPs in hereditary thrombophilia and APS. Basically, the published data show that circulating MPs may contribute to the development of VTE in thrombophilic carriers, both in mild and severe states. Moreover, the presence of endothelial-MPs and platelet-MPs has been described in antiphospholipid syndrome and seems to be directly linked to antiphospholipid antibodies and not to other underlying autoimmune disorders or the thrombotic event itself. In conclusion, circulating MPs may constitute an epiphenomenon of thrombophilia itself and could be up-regulated in acute particular conditions, promoting a global prothrombotic state up to the threshold of the clinical relevant thrombotic event.

Relationship between renal function and circulating microparticles, soluble P-selectin and E-selectin levels in atrial fibrillation

Atrial fibrillation (AF) and chronic kidney disease are closely related, and any associated risk of stroke and thromboembolism due to AF is increased by concurrent renal dysfunction. The mechanism(s) for this include abnormalities in platelets and endothelial cells. We hypothesized relationships between levels of circulating platelet microparticles (PMPs, defined by CD42b), soluble P selectin (both reflecting platelet activation), soluble E-selectin (reflecting endothelial activation) and endothelial/platelet microparticles (EPMPs, defined by CD31) with progressive renal dysfunction. Blood samples were obtained from 160 anticoagulated AF patients. Microparticles were measured by flow cytometry, soluble E and P selectin levels by ELISA. Renal function was determined by estimated glomerular filtration rate (eGFR). EPMP levels demonstrated a linear increased trend across quartiles of eGFR (p = 0.034) and CKD stage (p < 0.001), and correlated with eGFR and serum creatinine (p < 0.01). PMPs, P-selectin and E-selectin levels were not significantly different across groupings of renal dysfunction, and no significant correlations with eGFR were evident (p = 0.186, p = 0.561, p = 0.746 respectively). Stepwise multivariable regression analysis demonstrated that worsening renal function was an independent predictor of EPMP levels (p < 0.001). In well-anticoagulated AF patients, there is potential relationship between endothelial function (as judged by elevated EPMP levels, with no change in PMPs) and renal function. Other markers of prothombotic state or cellular activation (PMP, P-selectin and E-selectin levels) were not significantly different across the various degree of renal dysfunction. Renal function must be addressed when measuring EPMP levels.

Association of ficolin-3 with abdominal aortic aneurysm presence and progression

Essentials Abdominal aortic aneurysm (AAA) is asymptomatic and its evolution unpredictable. To find novel potential biomarkers of AAA, microvesicles are an excellent source of biomarkers. Ficolin-3 is increased in microvesicles obtained from activated platelets and AAA tissue. Increased ficolin-3 plasma levels are associated with AAA presence and progression.

SUMMARY

Background Abdominal aortic aneurysm (AAA) patients are usually asymptomatic and AAA evolution is unpredictable. Ficolin-3, mainly synthesized by the liver, is a molecule of the lectin complement-activation pathway involved in AAA pathophysiology. Objectives To define extra-hepatic sources of ficolin-3 in AAA and investigate the role of ficolin-3 as a biomarker of the presence and progression of AAA. Methods Microvesicles (exosomes and microparticles) were isolated from culture-conditioned medium of ADP-activated platelets, as well as from AAA tissue-conditioned medium (thrombus and wall). Ficolin-3 levels were analyzed by western-blot, real-time PCR, immunohistochemistry and ELISA. Results Increased ficolin-3 levels were observed in microvesicles isolated from activated platelets. Similarly, microvesicles released from AAA tissue display increased ficolin-3 levels as compared with those from healthy tissue. Moreover, ficolin-3 mRNA levels in the AAA wall were greatly increased compared with healthy aortic walls. Immunohistochemistry of AAA tissue demonstrated increased ficolin-3, whereas little staining was present in healthy walls. Finally, increased ficolin-3 levels were observed in AAA patients' plasma (n = 478) compared with control plasma (n = 176), which persisted after adjustment for risk factors (adjusted odds ratio [OR], 5.29; 95% confidence interval [CI], 3.27, 8.57)]. Moreover, a positive association of ficolin-3 with aortic diameter (Rho, 0.25) and need for surgical repair was observed, also after adjustment for potential confounding factors (adjusted hazard ratio, 1.55; 95% CI, 1.11, 2.15). Conclusions In addition to its hepatic expression, ficolin-3 may be released into the extracellular medium via microvesicles, by both activated cells and pathological AAA tissue. Ficolin-3 plasma levels are associated with the presence and progression of AAA, suggesting its potential role as a biomarker of AAA.

Microparticles in Chronic Heart Failure

Heart failure (HF) continues to have a sufficient impact on morbidity, mortality, and disability in developed countries. Growing evidence supports the hypothesis that microparticles (MPs) might contribute to the pathogenesis of the HF development playing a pivotal role in the regulation of the endogenous repair system, thrombosis, coagulation, inflammation, immunity, and metabolic memory phenomenon. Therefore, there is a large body of data clarifying the predictive value of MP numerous in circulation among subjects with HF. Although the determination of MP signature is better than measurement of single MP circulating level, there is not yet close confirmation that immune phenotype of cells produced MPs are important for HF prediction and development. The aim of the chapter is to summarize knowledge regarding the role of various MPs in diagnosis and prognosis of HF. The role of MPs as a delivery vehicle for drugs attenuated cardiac remodeling is considered.

A simple clot based assay for detection of procoagulant cell-derived microparticles

BACKGROUND

Cell-derived microparticles (MPs) are important biomarkers in many facets of medicine. However, the MP detection methods used till date are costly and time consuming. The main aim of this study was to standardize an in-house clot based screening method for MP detection which would not only be specific and sensitive, but also inexpensive.

METHODS

Four different methods of MP assessment were performed and the results correlated. Using the flow cytometry technique as the gold standard, 25 samples with normal phosphatidylserine (PS) expressing MP levels and 25 samples with elevated levels were selected, which was cross checked by the commercial STA Procoag PPL clotting time (CT) assay. A simple recalcification time and an in-house clot assay were the remaining two tests. The in-house test measures the CT after the addition of calcium chloride to MP rich plasma, following incubation with Russell viper venom and phospholipid free plasma.

RESULTS

The CT obtained by the in-house assay significantly correlated with the results obtained by flow cytometry (R2=0.87, p<0.01).

CONCLUSIONS

Though preliminary, the in-house assay seems to be efficient, inexpensive and promising. It could definitely be utilized routinely for procoagulant MP assessment in various clinical settings.

Neutrophil-derived microparticles are released into the coronary circulation following percutaneous coronary intervention in acute coronary syndrome patients

To evaluate (i) local coronary and systemic levels of microparticles (MP) in acute coronary syndrome (ACS) and stable angina pectoris (SAP) patients and (ii) their release after plaque disruption with percutaneous coronary intervention (PCI). MP are small vesicles originating from plasma membranes of cells after activation or apoptosis and are implicated in the pathogenesis of atherosclerosis. Neutrophils play a role in plaque destabilization and shed neutrophil-derived MP that have the potential to drive significant proinflammatory and thrombotic downstream effects. Eight ACS and eight SAP patients were included. Coronary sinus (CS) samples pre-intervention (CS1), 45 s following balloon angioplasty (CS2) and at 45 s intervals following stent deployment (CS3, CS4 and CS5), together with peripheral vein samples, pre- and post-PCI were analysed for neutrophil-derived (CD66b+), endothelial-derived (CD144+), platelet-derived (CD41a+), monocyte-derived (CD14+) and apoptotic (Annexin V+) MP. ELISA for interleukin (IL)-6, myeloperoxidase (MPO) and P-selectin was also performed. CD66b+ MP levels were similar in both groups pre-intervention. Post-PCI, CS levels rose significantly in ACS but not SAP patients (ACS area under the curve (AUC): 549 ± 83, SAP AUC: 24 ± 29, P<0.01). CS CD41a+, CD144+, CD14+ and Annexin V+ MP levels did not differ between groups. Acute neutrophil-derived MP release post-PCI occurs in ACS compared with stable patients, likely to be reflective of plaque MP content in vulnerable lesions.

Imaging flow cytometry for the characterization of extracellular vesicles

Extracellular Vesicles (EVs) are potent bio-activators and inter-cellular communicators that play an important role in both health and disease. It is for this reason there is a strong interest in understanding their composition and origin, with the hope of using them as important biomarkers or therapeutics. Due to their very small size, heterogeneity, and large numbers there has been a need for better tools to measure them in an accurate and high throughput manner. While traditional flow cytometry has been widely used for this purpose, there are inherent problems with this approach, as these instruments have traditionally been developed to measure whole cells, which are orders of magnitude larger and express many more molecules of identifying epitopes. Imaging flow cytometry, as performed with the ImagestreamX MKII, with its combination of increased fluorescence sensitivity, low background, image confirmation ability and powerful data analysis tools, provides a great tool to accurately evaluate EVs. We present here a comprehensive approach in applying this technology to the study of EVs.

Platelet function testing: from routine to specialist testing

Platelets have many functions within the haemostatic system, and when these actions are diminished for whatever reason, a bleeding tendency can manifest. Unravelling the reason(s) for this bleeding can be complex due to the multiple roles platelets perform. This review seeks to explain each level of platelet testing moving from those performed at local hospital laboratories to those performed by specialist centres and university research departments. It will examine the testing available and discuss when to move on to additional testing.

Dynamics of circulating microparticles in obesity after weight loss

A definitive relationship between adiposity and MP production is yet to be demonstrated. The aim of our study was to prospectively evaluate the levels of microparticles (MP) in a group of 20 III degree obese patients before and after weight loss. Plasma levels of annexin V-MP, endothelial-derived MP, platelet-derived MP (CD61+ and P-Selectin+), leukocyte-derived MP, tissue factor-bearing (TF+) and CD36+MP were prospectively measured in 20 patients with III degree obesity (BMI ≥ 40 kg/m(2)) before (T0) and 3 (T3) and 12 (T12) months after sleeve gastrectomy (SLG). Obese patients had lost 18 % of their body weight at T3 and 41 % at T12. We find that considering all MP, except for endothelial-derived MP, which had significantly decreased at T3, all MP subtypes had significantly decreased at T12. At T12, subjects showed a higher median level of all types of MP, except endothelial-derived MP, compared to T3, but without a statistically significant difference. The percentages of reduction of all the MP were significantly correlated with the percentage of reduction of BMI. The reductions of leukocyte-derived, TF+ and CD36+MP were significantly correlated with the reduction of leptin. Moreover, the reductions of leukocyte-derived and CD36+MP were significantly correlated with hs-CRP decrease. The decrease of BMI post-SLG in morbid obesity was matched with a decrease of circulating MP of endothelial, platelet, leukocyte origin, TF+ and CD36+. A trend of slight increase in all MP subtypes, except endothelial-derived, was detected 12 months after gastrectomy, indicating a possible underlying slow low-grade inflammatory/hypercoagulability state from adipose tissue before the potential overt weight gain.

Stirred, shaken, or stagnant: What goes on at the blood-biomaterial interface

There is a widely recognized need to improve the performance of vascular implants and external medical devices that come into contact with blood by reducing adverse reactions they cause, such as thrombosis and inflammation. These reactions lead to major adverse cardiovascular events such as heart attacks and strokes. Currently, they are managed therapeutically. This need remains unmet by the biomaterials research community. Recognized stagnation of the blood-biomaterial interface research translates into waning interest from clinicians, funding agencies, and practitioners of adjacent fields. The purpose of this contribution is to stir things up. It follows the 2014 BloodSurf meeting (74th International IUVSTA Workshop on Blood-Biomaterial Interactions), offers reflections on the situation in the field, and a three-pronged strategy integrating different perspectives on the biological mechanisms underlying blood-biomaterial interactions. The success of this strategy depends on reengaging clinicians and on the renewed cooperation of the funding agencies to support long-term efforts.

Microparticles as biomarkers of venous thromboembolic events

Microparticles (MPs) are small (0.1–1.0 μm) membrane vesicles constitutively released from the surface of cells after activation and apoptosis. The clinical research on MPs is hampered by the limitations of the currently available detection methods. A correlation between MPs and venous thromboembolism (VTE) has been observed. The effects of MPs on thrombogenesis involve the exposure of phosphatidylserine, the vehiculation of tissue factor, and MP-induced intercellular cross-talk between inflammation and coagulation. This review will focus on the potential role of plasma MPs as biomarkers in detecting acute unprovoked VTE, predicting VTE occurrence in high-risk situations (mainly cancer), and ultimately, we will discuss currently available studies on the prognostic role of MPs to guide primary and secondary VTE prevention protocols.

Microparticles as biomarkers of lung disease: enumeration in biological fluids using lipid bilayer microspheres

Extracellular vesicles, specifically microparticles (MPs), are rapidly gaining attention for their capacity to act as biomarkers for diagnosis, prognosis, or responsiveness to therapy in lung disease, in keeping with the concept of precision medicine. However, MP analysis by high-sensitivity flow cytometry (FCM) is complicated by a lack of accurate means for MP enumeration. To address this gap, we report here an enhanced FCM MP gating and enumeration technique based on the use of novel engineered lipid bilayer microspheres (LBMs). By comparison of LBM-based MP enumeration with conventional bead- or fluorescent-based FCM enumeration techniques and a gravimetric consumption gold standard, we found LBMs to be superior to commercial bead preparations, showing the smallest fixed bias and limits of agreement in Bland Altman analyses. LBMs had simultaneous capacity to aid FCM enumeration of MPs in plasma, BAL, and cell culture supernatants. LBM enumeration detected differences in MP counts in mice exposed to intraperitoneal lipopolysaccharide or saline. LBMs provided for 1) higher sensitivity for gating MPs populations, 2) reduced background within MP gates, 3) more appropriate size, and 4) an inexpensive alternative amenable to different fluorescent tags. LBM-based MP enumeration was useful for a series of different FCM systems assessed, whereas LBM gating benefited high- but not low-sensitivity FCM systems compared with fluorescence gating. By offering exclusive advantages over current means of gating and enumerating MPs, LBMs are uniquely suited to realizing the potential of MPs as biomarkers in biological lung fluids and facilitating precision medicine in lung disease.

Use of flow cytometry for characterization of human cytomegalovirus vaccine particles

Despite a 40-year effort, an effective vaccine against human cytomegalovirus (HCMV) remains an unmet medical need. The discovery of potent neutralizing epitopes on the pentameric gH complex (gH/gL/UL128/130/131) has reenergized HCMV vaccine development. Our whole-virus vaccine candidate, currently in a Phase I clinical trial, is based on the attenuated AD169 strain with restored expression of the pentameric gH complex. Given the complexity of a whole-virus vaccine, improved analytical methods have been developed to better characterize heterogeneous viral particles released from infected cells during vaccine production. Here we show the utility of a commercial flow cytometer for the detection of individual HCMV particles, either via light scattering or using fluorescence after labeling of specific antigens. Rapid measurements requiring minimal material provide near real-time information on particle concentration, distributions of different particle types, and product purity. Additionally, utilizing immunoreagents has allowed us to characterize the distribution of key antigens across individual particles and particle types.

Measurement of microvesicle levels in human blood using flow cytometry

Microvesicles are fragments of cells released when the cells are activated, injured, or apoptotic. Analysis of microvesicle levels in blood has the potential to shed new light on the pathophysiology of many diseases. Flow cytometry is currently the only method that can simultaneously separate true lipid microvesicles from other microparticles in blood, determine the cell of origin and other microvesicle characteristics, and handle large numbers of clinical samples with a reasonable effort, but expanded use of flow cytometric measurement of microvesicle levels as a clinical and research tool requires improved, standardized assays. The goal of this review is to aid investigators in applying current best practices to microvesicle measurements. First pre-analytical factors are evaluated and data summarized for anticoagulant effects, sample transport and centrifugation. Next flow cytometer optimization is reviewed including interference from background in buffers and reagents, accurate microvesicle counting, swarm interference, and other types of coincidence errors, size calibration, and detection limits using light scattering, impedance and fluorescence. Finally current progress on method standardization is discussed and a summary of current best practices provided. © 2016 Clinical Cytometry Society.

Analytical challenges of extracellular vesicle detection: A comparison of different techniques

The interest in extracellular vesicles (EVs) has grown exponentially over the last decade. Evolving evidence is demonstrating that these EVs are playing an important role in health and disease. They are involved in intercellular communication and have been shown to transfer proteins, lipids, and nucleic acids. This review focuses on the most commonly used techniques for detection of EVs, to include microparticles, 100-1,000 nm in size, and exosomes, 50-100 nm in size. Conventional flow cytometry is the most prevalent technique, but nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), and resistive pulse sensing have also been used to detect EVs. The accurate measurement of these vesicles is challenged by size heterogeneity, low refractive index, and the lack of dynamic measurement range for most of the available technologies. Sample handling during the preanalytical phase can also affect the accuracy of measurements. Currently, there is not one single method which allows phenotyping, sizing, and enumerating the whole range of EVs and, therefore, providing all the necessary information to truly understand the biology of these particles. A combination of methods is probably needed which might also include electron and atomic force microscopy and full RNA, lipid, and protein profiling.

Thrombotic Role of Blood and Endothelial Cells in Uremia through Phosphatidylserine Exposure and Microparticle Release

The mechanisms contributing to an increased risk of thrombosis in uremia are complex and require clarification. There is scant morphological evidence of membrane-dependent binding of factor Xa (FXa) and factor Va (FVa) on endothelial cells (EC) in vitro. Our objectives were to confirm that exposed phosphatidylserine (PS) on microparticle (MP), EC, and peripheral blood cell (PBC) has a prothrombotic role in uremic patients and to provide visible and morphological evidence of PS-dependent prothrombinase assembly in vitro. We found that uremic patients had more circulating MP (derived from PBC and EC) than controls. Additionally, patients had more exposed PS on their MPs and PBCs, especially in the hemodialysis group. In vitro, EC exposed more PS in uremic toxins or serum. Moreover, reconstitution experiments showed that at the early stages, PS exposure was partially reversible. Using confocal microscopy, we observed that PS-rich membranes of EC and MP provided binding sites for FVa and FXa. Further, exposure of PS in uremia resulted in increased generation of FXa, thrombin, and fibrin and significantly shortened coagulation time. Lactadherin, a protein that blocks PS, reduced 80% of procoagulant activity on PBC, EC, and MP. Our results suggest that PBC and EC in uremic milieu are easily injured or activated, which exposes PS and causes a release of MP, providing abundant procoagulant membrane surfaces and thus facilitating thrombus formation. Blocking PS binding sites could become a new therapeutic target for preventing thrombosis.

Indolic uremic solutes enhance procoagulant activity of red blood cells through phosphatidylserine exposure and microparticle release

Increased accumulation of indolic uremic solutes in the blood of uremic patients contributes to the risk of thrombotic events. Red blood cells (RBCs), the most abundant blood cells in circulation, may be a privileged target of these solutes. However, the effect of uremic solutes indoxyl sulfate (IS) and indole-3-acetic acid (IAA) on procoagulant activity (PCA) of erythrocyte is unclear. Here, RBCs from healthy adults were treated with IS and IAA (mean and maximal concentrations reported in uremic patients). Phosphatidylserine (PS) exposure of RBCs and their microparticles (MPs) release were labeled with Alexa Fluor 488-lactadherin and detected by flow cytometer. Cytosolic Ca(2+) ([Ca(2+)]) with Fluo 3/AM was analyzed by flow cytometer. PCA was assessed by clotting time and purified coagulation complex assays. We found that PS exposure, MPs generation, and consequent PCA of RBCs at mean concentrations of IS and IAA enhanced and peaked in maximal uremic concentrations. Moreover, 128 nM lactadherin, a PS inhibitor, inhibited over 90% PCA of RBCs and RMPs. Eryptosis or damage, by indolic uremic solutes was due to, at least partially, the increase of cytosolic [Ca(2+)]. Our results suggest that RBC eryptosis in uremic solutes IS and IAA plays an important role in thrombus formation through releasing RMPs and exposing PS. Lactadherin acts as an efficient anticoagulant in this process.

Microparticles as Biomarkers of Blood Coagulation in Cancer

Cancer is associated with hypercoagulopathy and increased risk of thrombosis. This negatively influences patient morbidity and mortality. Cancer is also frequently complicated by the development of venous thromboembolism (VTE). Tumor-derived tissue factor (TF)-bearing microparticles (MPs) are associated with VTE events in malignancy. MPs are small membrane vesicles released from many different cell types by exocytic budding of the plasma membrane in response to cellular activation or apoptosis. MPs may also be involved in clinical diseases through expression of procoagulative phospholipids. The detection of TF-expressing MPs in cancer patients may be clinically useful. In lung and breast cancer patients, MPs induce metastasis and angiogenesis and may be indicators of vascular complications. Additionally, MPs in patients with various types of cancer possess adhesion proteins and bind target cells to promoting cancer progression or metastasis. Overexpression of TF by cancer cells is closely associated with tumor progression, and shedding of TF-expressing MPs by cancer cells correlates with the genetic status of cancer. Consequently, TF-expressing MPs represent important markers to consider in the prevention of and therapy for VTE complications in cancer patients.

Microparticle and Atherothrombotic Diseases

Microparticles (MPs) are small membrane vesicles that are released from many different cell types by exocytotic budding of the plasma membrane in response to cellular activation or apoptosis. MPs may be involved in both physiological processes and clinical treatments because they express phospholipids, which function as procoagulants. Elevated levels of platelet-derived MPs, endothelial cell-derived MPs, and monocyte-derived MPs are observed in almost all thrombotic diseases occurring in venous and arterial beds. Several studies have shown that the quantity, cellular origin, and composition of circulating MPs depend on the type of disease, the disease state, and medical treatment. Although MPs were initially thought to be small particles with only procoagulant activity, they are now known to have many different functions. An increasing number of studies have identified new implications of elevated MPs in clinical disorders. On the basis of evidence available till date, the present review suggests that MPs may be a useful biomarker in identifying atherothrombosis.

Microvesicles from platelets: novel drivers of vascular inflammation

Microvesicles are receiving increased attention not only as biomarkers but also as mediators of cell communication and as integral effectors of disease. Platelets present a major source of microvesicles and release these microvesicles either spontaneously or upon activation. Platelet-derived microvesicles retain many features of their parent cells and have been shown to exert modulatory effects on vascular and immune cells. Accordingly, microvesicles from platelets can be measured at increased levels in patients with cardiovascular disease or individuals at risk. In addition, isolated microvesicles from platelets were shown to exert immunomodulatory actions on various cell types. In this review the various aspects of platelet-derived microvesicles including release, clearance, measurement, occurrence during disease and relevance for the pathophysiology of vascular inflammation will be discussed.

Small-size Microparticles as Indicators of Acute Decompensated State in Ischemic Heart Failure

INTRODUCTION AND OBJECTIVES

Microparticles are markers for cell activation and apoptosis and could provide valuable information that is not available from clinical data. This study assesses the clinical and biological relationship of small-sized microparticles in different forms of ischemic systolic heart failure and their relation to markers of inflammation and repair.

METHODS

We compared 49 patients with acute heart failure, 39 with stable heart failure and 25 patients with stable coronary artery disease. Small-size microparticles counts were determined by high-resolution flow cytometry. Moreover, 3 different monocyte subpopulations and their expression of inflammatory and adhesive scavenger receptors were analyzed using a conventional flow cytometer.

RESULTS

Endothelial CD144+ microparticle counts were decreased in heart failure groups (P=.008). Annexin V-binding microparticle counts were found increased in heart failure (P=.024) and in patients with lower functional class (P=.013). Platelet CD42b+ microparticle counts positively correlated with left ventricular ejection fraction (P=.006), and annexin V-binding microparticle counts with interleukin-6 levels in stable heart failure (P=.034). Annexin V-binding microparticle counts in the acute status strongly correlated with toll-like receptor-4 expression on all monocyte subsets (all P<.01). Three months after admission with acute heart failure, annexin V-binding microparticle counts were positively correlated with receptors for interleukin-6, CD163 and CD204 (all P<.05).

CONCLUSIONS

Annexin V-binding microparticle counts constitute valuable hallmarks of acute decompensated state in systolic heart failure. The observed relationship between small-size annexin V-binding microparticles and scavenger receptors supports their involvement in the progression of the acute response to injury, and thus their contribution to the pathogenesis of acute decompensated heart failure.

Microparticle analysis in disorders of hemostasis and thrombosis

Microparticles (MPs) are submicron vesicles released from the plasma membrane of eukaryotic cells in response to activation or apoptosis. MPs are known to be involved in numerous biologic processes, including inflammation, the immune response, cancer metastasis, and angiogenesis. Their earliest recognized and most widely accepted role, however, is the ability to promote and support the process of blood coagulation. Consequently, there is ongoing interest in studying MPs in disorders of hemostasis and thrombosis. Both phosphatidylserine (PS) exposure and the presence of tissue factor (TF) in the MP membrane may account for their procoagulant properties, and elevated numbers of MPs in plasma have been reported in numerous prothrombotic conditions. To date, however, there are few data on true causality linking MPs to the genesis of thrombosis. A variety of methodologies have been employed to characterize and quantify MPs, although detection is challenging due to their submicron size. Flow cytometry (FCM) remains the most frequently utilized strategy for MP detection; however, it is associated with significant technological limitations. Additionally, preanalytical and analytical variables can influence the detection of MPs by FCM, rendering data interpretation difficult. Lack of methodologic standardization in MP analysis by FCM confounds the issue further, although efforts are currently underway to address this limitation. Moving forward, it will be important to address these technical challenges as a scientific community if we are to better understand the role that MPs play in disorders of hemostasis and thrombosis.

Clinical significance of procoagulant microparticles

Microparticles (MPs) are small membrane vesicles that are released from many different cell types by exocytic budding of the plasma membrane in response to cellular activation or apoptosis. MPs may also be involved in clinical diseases because they express phospholipids, which function as procoagulants. Although flow cytometry is the most widely used method for studying MPs, some novel assays, such as tissue factor-dependent procoagulant assay or the ELISA method, have been reported. However, the use of quantification of MP as a clinical tool is still controversial. Elevated platelet-derived MP, endothelial cell-derived MP, and monocyte-derived MP concentrations are documented in almost all thrombotic diseases occurring in venous and arterial beds. However, the significance of MPs in various clinical conditions remains controversial. An example of this controversy is that it is unknown if MPs found in peripheral blood vessels cause thrombosis or whether they are the result of thrombosis. Numerous studies have shown that not only the quantity, but also the cellular origin and composition of circulating MPs, are dependent on the type of disease, the disease state, and medical treatment. Additionally, many different functions have been attributed to MPs. Therefore, the number and type of clinical disorders associated with elevated MPs are currently increasing. However, MPs were initially thought to be small particles with procoagulant activity. Taken together, our review suggests that MPs may be a useful biomarker to identify thrombosis.

Toward routine detection of extracellular vesicles in clinical samples

The majority, if not all, of human cell types secrete extracellular vesicles (EVs) into their environment, at least partly as a means of intercellular communication. These secreted vesicles can be detected in most bodily fluids including blood, urine, and saliva. The number of secreted vesicles and their composition is altered in various pathological conditions, raising opportunities to exploit EVs as diagnostic and/or prognostic biomarkers. For this to become a reality, it is important to reach consensus regarding the standardization of protocols for sample collection, EV isolation, handling, and storage for valid comparison and interpretation of measurements. Depending on the information required, there are several detection options including EV number and size distribution, molecular surface markers, procoagulation activity, and RNA content. For these purposes, different techniques are currently utilized or under development. This review discusses the techniques that have the potential to become standard EV detection methods in a clinical diagnostic setting. In addition to the accuracy of the detection technique, other factors such as high-throughput, cost-effectiveness, time consumption, and required operator skill are important to consider. A combination of increasing fundamental knowledge, technological progress, standardization of sample collection, and processing protocols is required for EVs to become reliable predictors of altered physiology or development of disease suitable for routine clinical diagnostics. Cancer and (cardio)vascular disorders are examples of pathologies where EV detection may be applied in the near future for diagnosis and/or prognosis.

Cutting-edge analysis of extracellular microparticles using ImageStream(X) imaging flow cytometry

Interest in extracellular vesicle biology has exploded in the past decade, since these microstructures seem endowed with multiple roles, from blood coagulation to inter-cellular communication in pathophysiology. In order for microparticle research to evolve as a preclinical and clinical tool, accurate quantification of microparticle levels is a fundamental requirement, but their size and the complexity of sample fluids present major technical challenges. Flow cytometry is commonly used, but suffers from low sensitivity and accuracy. Use of Amnis ImageStream^X Mk II imaging flow cytometer afforded accurate analysis of calibration beads ranging from 1 μm to 20 nm; and microparticles, which could be observed and quantified in whole blood, platelet-rich and platelet-free plasma and in leukocyte supernatants. Another advantage was the minimal sample preparation and volume required. Use of this high throughput analyzer allowed simultaneous phenotypic definition of the parent cells and offspring microparticles along with real time microparticle generation kinetics. With the current paucity of reliable techniques for the analysis of microparticles, we propose that the ImageStream^X could be used effectively to advance this scientific field.