Investigation of procoagulant activity in extracellular vesicles isolated by differential ultracentrifugation

Extracellular Vesicle-Inspired Therapeutic Strategies for the COVID-19

Emerging infectious diseases like coronavirus pneumonia (COVID-19) present significant challenges to global health, extensively affecting both human society and the economy. Extracellular vesicles (EVs) have demonstrated remarkable potential as crucial biomedical tools for COVID-19 diagnosis and treatment. However, due to limitations in the performance and titer of natural vesicles, their clinical use remains limited. Nonetheless, EV-inspired strategies are gaining increasing attention. Notably, biomimetic vesicles, inspired by EVs, possess specific receptors that can act as "Trojan horses," preventing the virus from infecting host cells. Genetic engineering can enhance these vesicles by enabling them to carry more receptors, significantly increasing their specificity for absorbing the novel coronavirus. Additionally, biomimetic vesicles inherit numerous cytokine receptors from parent cells, allowing them to effectively mitigate the "cytokine storm" by adsorbing pro-inflammatory cytokines. Overall, this EV-inspired strategy offers new avenues for the treatment of emerging infectious diseases. Herein, this review systematically summarizes the current applications of EV-inspired strategies in the diagnosis and treatment of COVID-19. The current status and challenges associated with the clinical implementation of EV-inspired strategies are also discussed. The goal of this review is to provide new insights into the design of EV-inspired strategies and expand their application in combating emerging infectious diseases.

Impact of production methods and storage conditions on extracellular vesicles in packed red blood cells and platelet concentrates

The use of blood and blood products can be life-saving, but there are also certain risks associated with their administration and use. Packed red blood cells (pRBCs) and platelet concentrates are the most commonly used blood products in transfusion medicine to treat anemia or acute and chronic bleeding disorders, respectively. During the production and storage of blood products, red blood cells and platelets release extracellular vesicles (EVs) as a result of the storage lesion, which may affect product quality. EVs are subcellular structures enclosed by a lipid bilayer and originate from the endosomal system or from the plasma membrane. They play a pivotal role in intercellular communication and are emerging as important regulators of inflammation and coagulation. Their cargo and their functional characteristics depend on the cell type from which they originate, as well as on their microenvironment, influencing their capacity to promote coagulation and inflammatory responses. Hence, the potential involvement of EVs in transfusion-related adverse events is increasingly recognized and studied. Here, we review the knowledge regarding the effect of production and storage conditions of pRBCs and platelet concentrates on the release of EVs. In this context, the mode of processing and anticoagulation, the influence of additive solutions and leukoreduction, as well as the storage duration will be addressed, and we discuss potential implications of EVs for the clinical outcome of transfusion.

Dynamic cultivation of human mesenchymal stem/stromal cells for the production of extracellular vesicles in a 3D bioreactor system

PURPOSE

3D cell culture and hypoxia have been demonstrated to increase the therapeutic effects of mesenchymal stem/stromal cells (MSCs)-derived extracellular vesicles (EVs). In this study, a process for the production of MSC-EVs in a novel 3D bioreactor system under normoxic and hypoxic conditions was established and the resulting EVs were characterized.

METHODS

Human adipose-derived MSCs were seeded and cultured on a 3D membrane in the VITVO® bioreactor system for 7 days. Afterwards, MSC-EVs were isolated and characterized via fluorescence nanoparticle tracking analysis, flow cytometry with staining against annexin V (Anx5) as a marker for EVs exposing phosphatidylserine, as well as CD73 and CD90 as MSC surface markers.

RESULTS

Cultivation of MSC in the VITVO® bioreactor system demonstrated a higher concentration of MSC-EVs from the 3D bioreactor (9.1 × 109 ± 1.5 × 109 and 9.7 × 109 ± 3.1 × 109 particles/mL) compared to static 2D culture (4.2 × 109 ± 7.5 × 108 and 3.9 × 109 ± 3.0 × 108 particles/mL) under normoxic and hypoxic conditions, respectively. Also, the particle-to-protein ratio as a measure for the purity of EVs increased from 3.3 × 107 ± 1.1 × 107 particles/µg protein in 2D to 1.6 × 108 ± 8.3 × 106 particles/µg protein in 3D. Total MSC-EVs as well as CD73-CD90+ MSC-EVs were elevated in 2D normoxic conditions. The EV concentration and size did not differ significantly between normoxic and hypoxic conditions.

CONCLUSION

The production of MSC-EVs in a 3D bioreactor system under hypoxic conditions resulted in increased EV concentration and purity. This system could be especially useful in screening culture conditions for the production of 3D-derived MSC-EVs.

Expanding applications of allogeneic platelets, platelet lysates, and platelet extracellular vesicles in cell therapy, regenerative medicine, and targeted drug delivery

Platelets are small anucleated blood cells primarily known for their vital hemostatic role. Allogeneic platelet concentrates (PCs) collected from healthy donors are an essential cellular product transfused by hospitals to control or prevent bleeding in patients affected by thrombocytopenia or platelet dysfunctions. Platelets fulfill additional essential functions in innate and adaptive immunity and inflammation, as well as in wound-healing and tissue-repair mechanisms. Platelets contain mitochondria, lysosomes, dense granules, and alpha-granules, which collectively are a remarkable reservoir of multiple trophic factors, enzymes, and signaling molecules. In addition, platelets are prone to release in the blood circulation a unique set of extracellular vesicles (p-EVs), which carry a rich biomolecular cargo influential in cell-cell communications. The exceptional functional roles played by platelets and p-EVs explain the recent interest in exploring the use of allogeneic PCs as source material to develop new biotherapies that could address needs in cell therapy, regenerative medicine, and targeted drug delivery. Pooled human platelet lysates (HPLs) can be produced from allogeneic PCs that have reached their expiration date and are no longer suitable for transfusion but remain valuable source materials for other applications. These HPLs can substitute for fetal bovine serum as a clinical grade xeno-free supplement of growth media used in the in vitro expansion of human cells for transplantation purposes. The use of expired allogeneic platelet concentrates has opened the way for small-pool or large-pool allogeneic HPLs and HPL-derived p-EVs as biotherapy for ocular surface disorders, wound care and, potentially, neurodegenerative diseases, osteoarthritis, and others. Additionally, allogeneic platelets are now seen as a readily available source of cells and EVs that can be exploited for targeted drug delivery vehicles. This article aims to offer an in-depth update on emerging translational applications of allogeneic platelet biotherapies while also highlighting their advantages and limitations as a clinical modality in regenerative medicine and cell therapies.

A sensitive tissue factor activity assay determined by an optimized thrombin generation method

BACKGROUND

Tissue factor (TF) is the principal activator of the coagulation system, but an increased concentration in the blood in cancer and inflammatory diseases has been suggested to play a role increasing the risk of venous thromboembolism. However, measurement of the TF concentration is difficult, and quantitation of activity is the most valid estimation. The objective of this study was to establish a sensitive method to measure TF activity based on thrombin generation.

METHODS

The assay is based on thrombin generation (TG) measured on the Calibrated Automated Thrombogram (CAT). Various low concentrations of TF were prepared from reagents containing 1 pM TF and 4 μM phospholipid (PPL), and no TF and 4 μM PPL, and a calibration curve was produced from Lagtime vs TF concentration. TF in blood samples was measured after isolation and resuspension of extracellular vesicles (EVs) in a standard plasma from which EVs had been removed. The same standard plasma was used for the calibrators.

RESULTS

Contact activation of the coagulation system was avoided using CTI plasma samples in Monovette tubes. EVs contain procoagulant phospholipids but addition of PPL only reduced lagtime slightly at very low concentrations of TF resulting in overestimation to a lesser extent at 10 fM but no interference at 30 fM or higher. Addition of EVs to the TG analysis induced a small unspecific TF-independent activity (i.e., an activity not inhibited by antibodies against TF) which also may result in a smaller error in estimation of TF activity at very low levels but the effect was negligible at higher concentrations. It was possible to measure TF activity in healthy controls which was found to be 1-6 fM (EVs were concentrated, i.e. solubilized in a lower volume than the original volume plasma). Coefficient of variation (CV) was below 20% at the low level, and below 10% at a level around 100 fM TF. However, the step with isolation of EVs have a higher inherent CV.

CONCLUSION

A sensitive and rather precise one-stage TG-based method to measure TF activity has been established.

Involvement of monocyte-derived extracellular vesicle-associated tissue factor activity in convallatoxin-induced hypercoagulability

OBJECTIVES

Convallatoxin (CNT) is a natural cardiac glycoside extracted from lily of the valley ( Convallaria majalis ). Although it is empirically known to cause blood coagulation disorders, the underlying mechanism remains unclear. CNT exerts cytotoxicity and increases tissue factor (TF) expression in endothelial cells. However, the direct action of CNT on blood coagulation remains unclear. Therefore, herein, we investigated the effects of CNT on whole blood coagulation system and TF expression in monocytes.

METHODS

Blood samples were collected from healthy volunteers to measure plasma thrombin-antithrombin complex (TAT) concentration using ELISA and to perform rotational thromboelastometry (ROTEM) and whole-blood extracellular vesicle (EV)-associated TF (EV-TF) analysis. The effects of CNT were also investigated using the monocytic human cell line THP-1. Quantitative real-time PCR and western blotting were performed, and PD98059, a mitogen-activated protein kinase (MAPK) inhibitor, was used to elucidate the action mechanism of CNT-mediated TF production.

RESULTS

CNT treatment increased EV-TF activity, shortened the whole blood clotting time in rotational thromboelastometry analysis, and increased TAT levels, which is an index of thrombin generation. Furthermore, CNT increased TF mRNA expression in THP-1 cells and EV-TF activity in the cell culture supernatant. Therefore, CNT may induce a hypercoagulable state with thrombin generation, in which elevated EV-TF activity derived from monocytes might be involved. These procoagulant effects of CNT were reversed by PD98059, suggesting that CNT-induced TF production in monocytes might be mediated by the MAPK pathway.

CONCLUSIONS

The findings of the present study have further clarified the procoagulant properties of CNT.

Blood Donors with Thalassemic Trait, Glucose-6-Phosphate Dehydrogenase Deficiency Trait, and Sickle Cell Trait and Their Blood Products: Current Status and Future Perspective

The use of blood products for different medical purposes has increased in recent years. To meet increasing demand, some blood centers allow volunteer donors with thalassemic trait, glucose-6-phosphate dehydrogenase deficiency (G6PD) trait, and sickle cell trait (SCT) to donate blood if their hemoglobin values fall within acceptable ranges and show no signs of hemolysis. Currently, there are no standard guidelines or policies regarding the use or management of blood products obtained from these donors. However, in recent years, there has been advanced research on eligible donors who have these underlying conditions. In this review, we summarize the current knowledge from in vitro and in vivo studies regarding donor characteristics, changes in physical and biochemical parameters in blood products during processing and storage, and posttransfusion efficacy of blood products. In addition, we discuss some unresolved issues concerning blood products from thalassemic trait, G6PD-deficiency trait, and SCT donors.

Coagulation potential and the integrated omics of extracellular vesicles from COVID-19 positive patient plasma

Extracellular vesicles (EVs) participate in cell-to-cell communication and contribute toward homeostasis under physiological conditions. But EVs can also contribute toward a wide array of pathophysiology like cancer, sepsis, sickle cell disease, and thrombotic disorders. COVID-19 infected patients are at an increased risk of aberrant coagulation, consistent with elevated circulating levels of ultra-high molecular weight VWF multimers, D-dimer and procoagulant EVs. The role of EVs in COVID-19 related hemostasis may depend on cells of origin, vesicular cargo and size, however this is not well defined. We hypothesized that the procoagulant potential of EV isolates from COVID-19 (+) patient plasmas could be defined by thrombin generation assays. Here we isolated small EVs (SEVs) and large EVs (LEVs) from hospitalized COVID-19 (+) patient (n = 21) and healthy donor (n = 20) plasmas. EVs were characterized by flow cytometry, Transmission electron microscopy, nanoparticle tracking analysis, plasma thrombin generation and a multi-omics approach to define coagulation potential. These data were consistent with differences in EV metabolite, lipid, and protein content when compared to healthy donor plasma isolated SEVs and LEVs. Taken together, the effect of EVs on plasma procoagulant potential as defined by thrombin generation and supported by multi-omics is enhanced in COVID-19. Further, we observe that this effect is driven both by EV size and phosphatidyl serine.

Plasma levels of platelet-enriched microRNAs change during antiplatelet therapy in healthy subjects

Platelets are the main effectors of primary hemostasis but also cause thrombosis in pathological conditions. Antiplatelet drugs are the cornerstone for the prevention of adverse cardiovascular events. Monitoring the extent of platelet inhibition is essential. Currently available platelet function tests come with constraints, limiting use in antiplatelet drug development as well as in clinical routine. With this study, we aim to investigate whether plasma miRNAs might be suitable biomarkers for monitoring antiplatelet treatment. Platelet-poor plasma was obtained from a trial including 87 healthy male volunteers that either received ticagrelor (n = 44) or clopidogrel (n = 43). Blood was collected before drug intake and after 2 h, 6 h, and 24 h. We measured a panel of 11 platelet-enriched miRNAs (thrombomiRs) by RT-qPCR and selected four biomarker candidates (i.e., miR-223-3p, miR-150-5p, miR-126-3p, miR-24-3p). To further characterize those miRNAs, we performed correlation analyses with the number of extracellular vesicles and clotting time dependent on procoagulant vesicles (PPL assay). We show that platelet-enriched miRNAs in the circulation are significantly reduced upon P2Y12-mediated platelet inhibition. This effect occurred fast, reaching its peak after 2 h. Additionally, we demonstrate that higher baseline levels of thrombomiRs are linked to a stronger reduction upon antiplatelet therapy. Finally, we show that miRNAs from our panel might be the cargo of platelet-derived and procoagulant vesicles. In conclusion, we provide evidence that thrombomiR levels change within 2 h after pharmacological platelet inhibition and circulate the body within platelet-derived and procoagulant extracellular vesicles, rendering them potential biomarker candidates for the assessment of in vivo platelet function.

Tissue factor in cancer-associated thromboembolism: possible mechanisms and clinical applications

Venous and arterial thromboses, called as cancer-associated thromboembolism (CAT), are common complications in cancer patients that are associated with high mortality. The cell-surface glycoprotein tissue factor (TF) initiates the extrinsic blood coagulation cascade. TF is overexpressed in cancer cells and is a component of extracellular vesicles (EVs). Shedding of TF⁺EVs from cancer cells followed by association with coagulation factor VII (fVII) can trigger the blood coagulation cascade, followed by cancer-associated venous thromboembolism in some cancer types. Secretion of TF is controlled by multiple mechanisms of TF⁺EV biogenesis. The procoagulant function of TF is regulated via its conformational change. Thus, multiple steps participate in the elevation of plasma procoagulant activity. Whether cancer cell-derived TF is maximally active in the blood is unclear. Numerous mechanisms other than TF⁺EVs have been proposed as possible causes of CAT. In this review, we focused on a wide variety of regulatory and shedding mechanisms for TF, including the effect of SARS-CoV-2, to provide a broad overview for its role in CAT. Furthermore, we present the current technical issues in studying the relationship between CAT and TF.

The Effect of Extracellular Vesicles on Thrombosis

The risk of cardiovascular events caused by acute thrombosis is high, including acute myocardial infarction, acute stroke, acute pulmonary embolism, and deep vein thrombosis. In this review, we summarize the roles of extracellular vesicles of different cellular origins in various cardiovascular events associated with acute thrombosis, as described in the current literature, to facilitate the future development of a precise therapy for thrombosis caused by such vesicles. We hope that our review will indicate a new horizon in the field of cardiovascular research with regard to the treatment of acute thrombosis, especially targeting thrombosis caused by extracellular vesicles secreted by individual cells. As more emerging technologies are being developed, new diagnostic and therapeutic strategies related to EVs are expected to be identified for related diseases in the future.

Exosomes as Novel Delivery Systems for Application in Traditional Chinese Medicine

Exosomes, as gifts of nature derived from various cell types with a size range from ~40 to 160 nm in diameter, have gained attention recently. They are composed of a lipid membrane bilayer structure containing different constituents, such as surface ligands and receptors, from the parental cells. Originating from a variety of sources, exosomes have the ability to participate in a diverse range of biological processes, including the regulation of cellular communication. On account of their ideal native structure and characteristics, exosomes are taken into account as drug delivery systems (DDSs). They can provide profound effects on conveying therapeutic agents with great advantages, including specific targeting, high biocompatibility, and non-toxicity. Further, they can also be considered to ameliorate natural compounds, the main constituents of traditional Chinese medicine (TCM), which are usually ignored due to the complexity of their structures, poor stability, and unclear mechanisms of action. This review summarizes the classification of exosomes as well as the research progress on exosome-based DDSs for the treatment of different diseases in TCM. Furthermore, this review discusses the advantages and challenges faced by exosomes to contribute to their further investigation and application.

The Role of Extracellular Vesicles in COVID-19 Pathology

Extracellular vesicles (EVs) have become a trending topic in recent years; they constitute a new intercellular communication paradigm. Extracellular vesicles are 30–4000 nanometers in diameter particles that are limited by a phospholipid bilayer and contain functional biomolecules, such as proteins, lipids, and nucleic acids. They are released by virtually all types of eukaryotic cells; through their cargoes, EVs are capable of triggering signaling in recipient cells. In addition to their functions in the homeostatic state, EVs have gained attention because of their roles in pathological contexts, eventually contributing to disease progression. In the Coronavirus disease 2019 (COVID-19) pandemic, aside from the scientific race for the development of preventive and therapeutic interventions, it is critical to understand the pathological mechanisms involved in SARS-CoV-2 infection. In this sense, EVs are key players in the main processes of COVID-19. Thus, in this review, we highlight the role of EVs in the establishment of the viral infection and in the procoagulant state, cytokine storm, and immunoregulation of innate and adaptive immune responses.

Exploring extracellular vesicles as mediators of clinical disease and vehicles for viral therapeutics: Insights from the COVID-19 pandemic

The COVID-19 pandemic has challenged researchers to rapidly understand the capabilities of the SARS-CoV-2 virus and investigate potential therapeutics for SARS-CoV-2 infection. COVID-19 has been associated with devastating lung and cardiac injury, profound inflammation, and a heightened coagulopathic state, which may, in part, be driven by cellular crosstalk facilitated by extracellular vesicles (EVs). In recent years, EVs have emerged as important biomarkers of disease, and while extracellular vesicles may contribute to the spread of COVID-19 infection from one cell to the next, they also may be engineered to play a protective or therapeutic role as decoys or "delivery drivers" for therapeutic agents. This review explores these roles and areas for future study.

Circulating tissue factor-positive extracellular vesicles and their association with thrombosis in different diseases

Tissue factor (TF) is a procoagulant protein released from activated host cells, such as monocytes, and tumor cells on extracellular vesicles (EVs). TF + EVs are observed in the circulation of patients with various types of diseases. In this review, we will summarize the association between TF + EVs and activation of coagulation and survival in different types of diseases, including cancer, sepsis, and infections with different viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We will also discuss the source of TF + EVs in various diseases. EVTF activity is associated with thrombosis in pancreatic cancer patients and coronavirus disease 2019 patients (COVID-19) and with disseminated intravascular coagulation in cancer patients. EVTF activity is also associated with worse survival in patients with cancer and COVID-19. Monocytes are the major sources of TF + EVs in sepsis, and viral infections, such as HIV, Ebola virus, and SARS-CoV-2. In contrast, alveolar epithelial cells are the major source of TF + EVs in bronchoalveolar lavage fluid in COVID-19 and influenza A patients. These studies indicate that EVTF activity could be used as a biomarker to identify patients that have an increased risk of coagulopathy and mortality.

Human and mouse PAR4 are functionally distinct receptors: Studies in novel humanized mice

BACKGROUND

Human and mouse platelets both express protease-activated receptor (PAR) 4 but sequence alignment reveals differences in several functional domains. These differences may result in functional disparities between the receptors which make it difficult to translate PAR4 studies using mice to human platelet physiology.

OBJECTIVES

To generate transgenic mice that express human, but not mouse, PAR4 and directly compare human and mouse PAR4 function in the same platelet environment.

METHODS

Transgenic mice were made using a genomic clone of the F2RL3 gene (encoding PAR4) and backcrossed with Par4 KO mice. For certain experiments, mice were bred with GRK6 KO mice. Tail bleeding time and platelet function in response to PAR4-activating peptide were assessed.

RESULTS

Human F2RL3 was successfully integrated into the mouse genome, transgenic mice were crossed to the mPar4 KO background (PAR4 tg/KO), and PAR4 was functionally expressed on platelets. Compared to WT, PAR4 tg/KO mice exhibited shortened tail bleeding time and their platelets were more responsive to PAR4-AP as assessed by α-granule release and integrin activation. The opposite was observed with thrombin. Knocking out GRK6 had no effect on human PAR4-expressing platelets, unlike mouse Par4-expressing platelets. PAR4 tg/KO platelets exhibited greater Ca2+ area under the curve and more robust extracellular vesicle release than WT stimulated with PAR4-AP.

CONCLUSION

These data suggest that (1) human PAR4- and mouse Par4-mediated signaling are different and (2) the feedback regulation mechanisms of human and mouse PAR4 are different. These functional differences are important to consider when interpreting PAR4 studies done with mice.

Extracellular Vesicles Derived from 3T3-L1 Adipocytes Enhance Procoagulant Activity

Obesity is associated with the risk of venous thromboembolism. Thrombi are constantly formed via the coagulation cascade and degraded by the fibrinolytic system, so they tend to form in obese individuals. Adipocytes are involved in thrombus formation in obesity, but it is not clear whether bioactive factors from adipocytes directly initiate or enhance coagulation and thrombosis. In this study, we confirmed that adipocyte-derived extracellular vesicles (ADEVs) enhance procoagulant activity in vitro. ADEVs prepared from the culture supernatant of mature 3T3-L1 adipocytes shortened plasma clotting times. Moreover, the effect of ADEVs on clotting time was weakened when using plasma lacking factors of the extrinsic pathway, but not the intrinsic pathway. ADEVs contain tissue factors and phosphatidylserine, which are involved in the extrinsic pathway, and blockade of these molecules diminished the effects of ADEVs on plasma clotting time. Additionally, the effect of ADEVs on plasma clotting time was further enhanced when cells were stimulated with the proinflammatory cytokine tumor necrosis factor-α. Thus, ADEVs may be a factor in thrombus formation in obesity.

Stem cells or their exosomes: which is preferred in COVID-19 treatment?

It only took 8 months for the pneumonia caused by a previously unknown coronavirus to turn into a global pandemic of unprecedentedly far-reaching implications. Failure of the already discovered treatment measures opened up a new opportunity to evaluate the potentials of mesenchymal stem cells and their extracellular vesicles (EVs), exosomes in particular. Eventually, the initial success experienced after the use of MSCs in treating the new pneumonia by Lnge and his team backed up the idea of MSC-based therapies and pushed them closer to becoming a reality. However, MSC-related concerns regarding safety such as abnormal differentiation, spontaneous malignant and the formation of ectopic tissues have triggered the replacement of MSCs by their secreted exosomes. The issue has been further strengthened by the fact that the exosomes leave similar treatment impacts when compared to their parental cells. In recent years, much attention has been paid to the use of MSC-derived exosomes in the treatment of a variety of diseases. With a primary focus on COVID-19 and its current treatment methods, the present review looks into the potentials of MSCs and MSC-derived exosomes in battling the ongoing pandemic. Finally, the research will draw an analogy between exosomes and their parental cells, when it comes to the progresses and challenges in using exosomes as a large-scale treatment method.

Exosomes: Emerging implementation of nanotechnology for detecting and managing novel corona virus- SARS-CoV-2

The spread of SARS-CoV-2 as an emerging novel coronavirus disease (COVID-19) had progressed as a worldwide pandemic since the end of 2019. COVID-19 affects firstly lungs tissues which are known for their very slow regeneration. Afterwards, enormous cytokine stimulation occurs in the infected cells immediately after a lung infection which necessitates good management to save patients. Exosomes are extracellular vesicles of nanometric size released by reticulocytes on maturation and are known to mediate intercellular communications. The exosomal cargo serves as biomarkers in diagnosing various diseases; moreover, exosomes could be employed as nanocarriers in drug delivery systems. Exosomes look promising to combat the current pandemic since they contribute to the immune response against several viral pathogens. Many studies have proved the potential of using exosomes either as viral elements or host systems that acquire immune-stimulatory effects and could be used as a vaccine or drug delivery tool. It is essential to stop viral replication, prevent and reverse the massive storm of cytokine that worsens the infected patients' situations for the management of COVID-19. The main benefits of exosomes could be; no cells will be introduced, no chance of mutation, lack of immunogenicity and the damaged genetic material that could negatively affect the recipient is avoided. Additionally, it was found that exosomes are static with no ability for in vivo reproduction. The current review article discusses the possibilities of using exosomes for detecting novel coronavirus and summarizes state of the art concerning the clinical trials initiated for examining the use of COVID-19 specific T cells derived exosomes and mesenchymal stem cells derived exosomes in managing COVID-19.

Extracellular Vesicles Physiological Role and the Particular Case of Disease-Spreading Mechanisms in Polyglutamine Diseases

Recent research demonstrated pathological spreading of the disease-causing proteins from one focal point across other brain regions for some neurodegenerative diseases, such as Parkinson's and Alzheimer's disease. Spreading mediated by extracellular vesicles is one of the proposed disease-spreading mechanisms. Extracellular vesicles are cell membrane-derived vesicles, used by cells for cell-to-cell communication and excretion of toxic components. Importantly, extracellular vesicles carrying pathological molecules, when internalized by "healthy" cells, may trigger pathological pathways and, consequently, promote disease spreading to neighboring cells. Polyglutamine diseases are a group of genetic neurodegenerative disorders characterized by the accumulation of mutant misfolded proteins carrying an expanded tract of glutamines, including Huntington's and Machado-Joseph disease. The pathological spread of the misfolded proteins or the corresponding mutant mRNA has been explored. The understanding of the disease-spreading mechanism that plays a key role in the pathology progression of these diseases can result in the development of effective therapeutic approaches to stop disease progression, arresting the spread of the toxic components and disease aggravation. Therefore, the present review's main focus is the disease-spreading mechanisms with emphasis on polyglutamine diseases and the putative role played by extracellular vesicles in this process.

Blood derived extracellular vesicles as regenerative medicine therapeutics

The regenerative promise of nanosized extracellular vesicles (EVs) secreted by cells is widely explored. Recently, the capacity of EVs purified from blood to elicit regenerative effect has begun to be evaluated. Blood might be a readily available source of EVs, avoiding need for extensive cell culturing, but there are specific issues that complicate use of the biofluid in this area. We assess the evidence for blood containing regenerative material, progress made towards delivering blood derived EVs as regenerative therapeutics, difficulties that relate to the complexity of blood and the promise of hydrogel-based delivery of EVs.

Procoagulant Extracellular Vesicles Alter Trophoblast Differentiation in Mice by a Thrombo-Inflammatory Mechanism

Procoagulant extracellular vesicles (EV) and platelet activation have been associated with gestational vascular complications. EV-induced platelet-mediated placental inflammasome activation has been shown to cause preeclampsia-like symptoms in mice. However, the effect of EV-mediated placental thrombo-inflammation on trophoblast differentiation remains unknown. Here, we identify that the EV-induced thrombo-inflammatory pathway modulates trophoblast morphology and differentiation. EVs and platelets reduce syncytiotrophoblast differentiation while increasing giant trophoblast and spongiotrophoblast including the glycogen-rich cells. These effects are platelet-dependent and mediated by the NLRP3 inflammasome. In humans, inflammasome activation was negatively correlated with trophoblast differentiation marker GCM1 and positively correlated with blood pressure. These data identify a crucial role of EV-induced placental thrombo-inflammation on altering trophoblast differentiation and suggest platelet activation or inflammasome activation as a therapeutic target in order to achieve successful placentation.

The clinical role of host and bacterial-derived extracellular vesicles in pneumonia

Pneumonia is among the leading causes of morbidity and mortality worldwide. Due to constant evolution of respiratory bacteria and viruses, development of drug resistance and emerging pathogens, it constitutes a considerable health care threat. To enable development of novel strategies to control pneumonia, a better understanding of the complex mechanisms of interaction between host cells and infecting pathogens is vital. Here, we review the roles of host cell and bacterial-derived extracellular vesicles (EVs) in these interactions. We discuss clinical and experimental as well as pathogen-overarching and pathogen-specific evidence for common viral and bacterial elicitors of community- and hospital-acquired pneumonia. Finally, we highlight the potential of EVs for improved management of pneumonia patients and discuss the translational steps to be taken before they can be safely exploited as novel vaccines, biomarkers, or therapeutics in clinical practice.

Increased activity of procoagulant factors in patients with small cell lung cancer

Small cell lung cancer (SCLC) patients have augmented risk of developing venous thromboembolism, but the mechanisms triggering this burden on the coagulation system remain to be understood. Recently, cell-derived microparticles carrying procoagulant phospholipids (PPL) and tissue factor (TF) in their membrane have attracted attention as possible contributors to the thrombogenic processes in cancers. The aims of this study were to assess the coagulation activity of platelet-poor plasma from 38 SCLC patients and to provide a detailed procoagulant profiling of small and large extracellular vesicles (EVs) isolated from these patients at the time of diagnosis, during and after treatment compared to 20 healthy controls. Hypercoagulability testing was performed by thrombin generation (TG), procoagulant phospholipid (PPL), TF activity, Protein C, FVIII activity and cell-free deoxyribonucleic acid (cfDNA), a surrogate measure for neutrophil extracellular traps (NETs). Our results revealed a coagulation activity that is significantly increased in the plasma of SCLC patients when compared to age-related healthy controls, but no substantial changes in coagulation activity during treatment and at follow-up. Although EVs in the patients revealed an increased PPL and TF activity compared with the controls, the TG profiles of EVs added to a standard plasma were similar for patients and controls. Finally, we found no differences in the coagulation profile of patients who developed VTE to those who did not, i.e. the tests could not predict VTE. In conclusion, we found that SCLC patients display an overall increased coagulation activity at time of diagnosis and during the disease, which may contribute to their higher risk of VTE.

Extracellular vesicle-mediated endothelial apoptosis and EV-associated proteins correlate with COVID-19 disease severity

Coronavirus disease-2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has lead to a global pandemic with a rising toll in infections and deaths. Better understanding of its pathogenesis will greatly improve the outcomes and treatment of affected patients. Here we compared the inflammatory and cardiovascular disease-related protein cargo of circulating large and small extracellular vesicles (EVs) from 84 hospitalized patients infected with SARS-CoV-2 with different stages of disease severity. Our findings reveal significant enrichment of proinflammatory, procoagulation, immunoregulatory and tissue-remodelling protein signatures in EVs, which remarkably distinguished symptomatic COVID-19 patients from uninfected controls with matched comorbidities and delineated those with moderate disease from those who were critically ill. Specifically, EN-RAGE, followed by TF and IL-18R1, showed the strongest correlation with disease severity and length of hospitalization. Importantly, EVs from COVID-19 patients induced apoptosis of pulmonary microvascular endothelial cells in the order of disease severity. In conclusion, our findings support a role for EVs in the pathogenesis of COVID-19 disease and underpin the development of EV-based approaches to predicting disease severity, determining need for patient hospitalization and identifying new therapeutic targets.

The Cholesterol Metabolite 27HC Increases Secretion of Extracellular Vesicles Which Promote Breast Cancer Progression

Cholesterol has been implicated in the clinical progression of breast cancer, a disease that continues to be the most commonly diagnosed cancer in women. Previous work has identified the cholesterol metabolite 27-hydroxycholesterol (27HC) as a major mediator of the effects of cholesterol on breast tumor growth and progression. 27HC can act as an estrogen receptor (ER) modulator to promote the growth of ERα+ tumors, and as a liver X receptor (LXR) ligand in myeloid immune cells to establish an immune-suppressive program. In fact, the metastatic properties of 27HC require the presence of myeloid cells with neutrophils (polymorphonuclear neutrophils; PMNs) being essential for the increase in lung metastasis in murine models. In an effort to further elucidate the mechanisms by which 27HC alters breast cancer progression, we made the striking finding that 27HC promoted the secretion of extracellular vesicles (EVs), a diverse assortment of membrane bound particles that includes exosomes. The resulting EVs had a size distribution that was skewed slightly larger than EVs generated by treating cells with vehicle. The increase in EV secretion and size was consistent across 3 different subtypes: primary murine PMNs, RAW264.7 monocytic cells, and 4T1 murine mammary cancer cells. Label-free analysis of 27HC-EVs indicated that they had a different metabolite composition to those from vehicle-treated cells. Importantly, 27HC-EVs from primary PMNs promoted tumor growth and metastasis in 2 different syngeneic models, demonstrating the potential role of 27HC-induced EVs in the progression of breast cancer. EVs from PMNs were taken up by cancer cells, macrophages, and PMNs, but not T cells. Since EVs did not alter proliferation of cancer cells, it is likely that their protumor effects are mediated through interactions with myeloid cells. Interestingly, RNA-seq analysis of tumors from 27HC-EV-treated mice do not display significantly altered transcriptomes, suggesting that the effects of 27HC-EVs occur early on in tumor establishment and growth. Future work will be required to elucidate the mechanisms by which 27HC increases EV secretion, and how these EVs promote breast cancer progression. Collectively, however, our data indicate that EV secretion and content can be regulated by a cholesterol metabolite, which may have detrimental effects in terms of disease progression, important findings given the prevalence of both breast cancer and hypercholesterolemia.

Comparative Analysis of Platelet-Derived Extracellular Vesicles Using Flow Cytometry and Nanoparticle Tracking Analysis

Growing interest in extracellular vesicles (EVs) has prompted the advancements of protocols for improved EV characterization. As a high-throughput, multi-parameter, and single particle technique, flow cytometry is widely used for EV characterization. The comparison of data on EV concentration, however, is hindered by the lack of standardization between different protocols and instruments. Here, we quantified EV counts of platelet-derived EVs, using two flow cytometers (Gallios and CytoFLEX LX) and nanoparticle tracking analysis (NTA). Phosphatidylserine-exposing EVs were identified by labelling with lactadherin (LA). Calibration with silica-based fluorescent beads showed detection limits of 300 nm and 150 nm for Gallios and CytoFLEX LX, respectively. Accordingly, CytoFLEX LX yielded 40-fold higher EV counts and 13-fold higher counts of LA⁺CD41⁺ EVs compared to Gallios. NTA in fluorescence mode (F-NTA) demonstrated that only 9.5% of all vesicles detected in scatter mode exposed phosphatidylserine, resulting in good agreement of LA⁺ EVs for CytoFLEX LX and F-NTA. Since certain functional characteristics, such as the exposure of pro-coagulant phosphatidylserine, are not equally displayed across the entire EV size range, our study highlights the necessity of indicating the size range of EVs detected with a given approach along with the EV concentration to support the comparability between different studies.

Small Extracellular Vesicles: A Novel Avenue for Cancer Management

Extracellular vesicles are small membrane particles derived from various cell types. EVs are broadly classified as ectosomes or small extracellular vesicles, depending on their biogenesis and cargoes. Numerous studies have shown that EVs regulate multiple physiological and pathophysiological processes. The roles of small extracellular vesicles in cancer growth and metastasis remain to be fully elucidated. As endogenous products, small extracellular vesicles are an ideal drug delivery platform for anticancer agents. However, several aspects of small extracellular vesicle biology remain unclear, hindering the clinical implementation of small extracellular vesicles as biomarkers or anticancer agents. In this review, we summarize the utility of cancer-related small extracellular vesicles as biomarkers to detect early-stage cancers and predict treatment outcomes. We also review findings from preclinical and clinical studies of small extracellular vesicle-based cancer therapies and summarize interventional clinical trials registered in the United States Food and Drug Administration and the Chinese Clinical Trials Registry. Finally, we discuss the main challenges limiting the clinical implementation of small extracellular vesicles and recommend possible approaches to address these challenges.

Extracellular vesicles in cancer diagnostics and therapeutics

Cancer promotion, development, and malignant transformation is greatly influenced by cell-to-cell interactions in a complex tissue microenvironment. Cancer and stromal cells secrete soluble factors, as well as deport membrane-encapsulated structures, which actively contribute and mediate cell-to-cell interaction within a tumor microenvironment (TME). These membrane structures are recognized as extracellular vesicles (EVs), which include exosomes and microvesicles. They can carry and transport regulatory molecules such as oncogenic proteins, coding and non-coding RNAs, DNA, and lipids between neighboring cells and to distant sites. EVs mediate crucial pathophysiological effects such as the formation of premetastatic niches and the progression of malignancies. There is compelling evidence that cancer cells exhibit a significant amount of EVs, which can be released into the surrounding body fluids, compared with nonmalignant cells. EVs therefore have the potential to be used as disease indicator for the diagnosis and prognosis of cancers, as well as for facilitating research into the underlying mechanism and biomolecular basis of these diseases. Because of their ability to transport substances, followed by their distinct immunogenicity and biocompatibility, EVs have been used to carry therapeutically-active molecules such as RNAs, proteins, short and long peptides, and various forms of drugs. In this paper, we summarize new advancement in the biogenesis and physiological roles of EVs, and underpin their functional impacts in the process of cancer growth and metastasis. We further highlight the therapeutic roles of EVs in the treatment, prevention, and diagnosis of human malignancies.

Quantitative Proteomic Analysis of Biogenesis-Based Classification for Extracellular Vesicles

Extracellular vesicles (EVs) are traditionally divided into two major groups: (i) large vesicles originating from plasma membrane and called microvesicles, and (ii) small vesicles originating from the endoplasmic membrane and called exosomes. However, it is increasingly clear that the actual composition of a particular EV preparation cannot be adequately described with these two simple terms and is much more complex. Since the cell membrane origin of EVs predetermines their biological functions, the understanding of EV biogenesis is important for accurate interpretation of observed results. In the present study, we propose to take advantage of selective expression of some proteins in plasma or endosomal membranes and to use these proteins as plasma membrane-specific or endosomal membrane-specific markers. We have demonstrated that a quantitative mass spectrometry analysis allows simultaneous measurement of plasma membrane-specific and endosomal membrane-specific proteins in microvesicles and exosomes obtained after differential ultracentrifugation. Before mass spectrometry analysis, we also used sonicated platelets as a model of mixed EVs and multidetector asymmetrical-flow field-flow fractionation as an analytical method to verify a possible cross contamination of obtained microvesicles and exosomes. Based on the quantitative appearance of membrane-specific protein markers in EV preparations from human plasma and from human ARPE-19 cell medium, we concluded that there is no actual size limitation and both microvesicles and exosomes can be represented by large and small vesicles.

Extracellular vesicles from organoids and 3D culture systems

When discovered, extracellular vesicles (EVs) such as exosomes were thought of as junk carriers and a means by which the cell disposed of its waste material. Over the years, the role of EVs in cell communication has become apparent with the discovery that the nano-scale vesicles also transport RNA, DNA, and other bioactive components to and from the cells. These findings were originally made in EVs from body fluids of organisms and from in vitro two-dimensional (2D) cell culture models. Recently, organoids and other 3D multicellular in vitro models are being used to study EVs in the context of both physiologic and pathological states. However, standard, reproducible methods are lacking for EV analysis using these models. As a step toward understanding the implications of these platforms, this review provides a comprehensive picture of the progress using 3D in vitro culture models for EV analysis. Translational efforts and regulatory considerations for EV therapeutics are also briefly overviewed to understand what is needed for scale-up and, ultimately, commercialization.

The Role and Impact of Extracellular Vesicles in the Modulation and Delivery of Cytokines during Autoimmunity

Cytokines and extracellular vesicles are two methods of initiating and maintaining cellular crosstalk. The role of cytokines in the initiation, progression, and resolution of inflammation has been well studied and more so, their pathophysiological role in the development of autoimmune disease. In recent years, the impact of extracellular vesicles on the progression of autoimmunity has become more widely appreciated. In this review, we discuss the mechanisms that allow extracellular vesicles of various sources to modulate cytokine production, and release, and how extracellular vesicles might be involved in the direct delivery and modulation of cytokine levels. Moreover, we explore what challenges are faced by current therapies and the promising future for extracellular vesicles as therapeutic agents in conditions driven by immune dysregulation.

The Potential Role of Extracellular Vesicles in COVID-19 Associated Endothelial injury and Pro-inflammation

COVID-19 infection caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has resulted in a global pandemic with the number of deaths growing exponentially. Early evidence points to significant endothelial dysfunction, micro-thromboses, pro-inflammation as well as a dysregulated immune response in the pathogenesis of this disease. In this study, we analyzed the cargo of EVs isolated from the plasma of patients with COVID-19 for the identification of potential biomarkers of disease severity and to explore their role in disease pathogenesis. Plasma-derived EVs were isolated from 53 hospitalized patients with COVID infection and compared according to the severity of the disease. Analysis of inflammatory and cardiovascular protein cargo of large EVs revealed significantly differentially expressed proteins for each disease sub-group. Notably, members of the TNF superfamily and IL-6 family were up-regulated in patients on oxygen support with severe and moderate disease. EVs from the severe group were also enhanced with pro-thrombotic/endothelial injury factors (TF, t-PA, vWF) and proteins associated with cardiovascular pathology (MB, PRSS8, REN, HGF). Significantly higher levels of TF, CD163, and EN-RAGE were observed in EVs from severe patients when compared to patients with a moderate disease requiring supplemental O2. Importantly, we also observed increased caspase 3/7 activity and decreased cell survival in human pulmonary microvascular endothelial cells exposed to EVs from the plasma of patients with severe disease compared to healthy controls. In conclusion, our findings indicate alterations in pro-inflammatory, coagulopathy, and endothelial injury protein cargo in large EVs in response to SARS-CoV-2 infection that may be a causative agent in severe illness.

Systematic review of extracellular vesicle-based treatments for lung injury: are EVs a potential therapy for COVID-19?

Severe COVID-19 infection results in bilateral interstitial pneumonia, often leading to acute respiratory distress syndrome (ARDS) and pulmonary fibrosis in survivors. Most patients with severe COVID-19 infections who died had developed ARDS. Currently, ARDS is treated with supportive measures, but regenerative medicine approaches including extracellular vesicle (EV)-based therapies have shown promise. Herein, we aimed to analyse whether EV-based therapies could be effective in treating severe pulmonary conditions that affect COVID-19 patients and to understand their relevance for an eventual therapeutic application to human patients. Using a defined search strategy, we conducted a systematic review of the literature and found 39 articles (2014–2020) that reported effects of EVs, mainly derived from stem cells, in lung injury models (one large animal study, none in human). EV treatment resulted in: (1) attenuation of inflammation (reduction of pro-inflammatory cytokines and neutrophil infiltration, M2 macrophage polarization); (2) regeneration of alveolar epithelium (decreased apoptosis and stimulation of surfactant production); (3) repair of microvascular permeability (increased endothelial cell junction proteins); (4) prevention of fibrosis (reduced fibrin production). These effects were mediated by the release of EV cargo and identified factors including miRs-126, −30b-3p, −145, −27a-3p, syndecan-1, hepatocyte growth factor and angiopoietin-1. This review indicates that EV-based therapies hold great potential for COVID-19 related lung injuries as they target multiple pathways and enhance tissue regeneration. However, before translating EV therapies into human clinical trials, efforts should be directed at developing good manufacturing practice solutions for EVs and testing optimal dosage and administration route in large animal models.

Microparticles (Exosomes) and Atherosclerosis

PURPOSE OF REVIEW

This review summarizes the effects of microparticles and exosomes in the progression of atherosclerosis and the prospect for their diagnostic and therapeutic potentials.

RECENT FINDINGS

Microparticles and exosomes can induce endothelial dysfunction, vascular inflammation, coagulation, thrombosis, and calcification via their components of proteins and noncoding RNAs, which may promote the progression of atherosclerosis. The applications of microparticles and exosomes become the spotlight of clinical diagnosis and therapy. Microparticles and exosomes are members of extracellular vesicles, which are generated in various cell types by different mechanisms of cell membrane budding and multivesicular body secretion, respectively. They are important physiologic pathways of cell-to-cell communication in vivo and act as messengers accelerating or alleviating the process of atherosclerosis. Microparticles and exosomes may become diagnostic biomarkers and therapeutic approaches of atherosclerosis.

Advances in extracellular vesicles analysis

Extracellular vesicles (EVs) play an important role in intercellular communication in normal cellular process and pathological conditions by facilitating the transport of cellular content from one cell to another. EVs as conveyors of various biological molecules with their ability to redirect effects on a target cell physiological function in cell type-specific manner makes EVs an excellent candidate for drug delivery vehicle in disease therapy. Moreover, unique characteristics and contents of EVs which differ depends on cellular origin and physiological state make them a valuable source of diagnostic biomarker. Herein, we review the current progress in extracellular vesicle (EV) analysis, its transition from biomedical research to advancing therapy, and recent pioneered approaches to characterize and quantify EVs' subclasses with an emphasis on the integration of advanced technologies for both qualitative and quantitative analysis of EVs in different clinical tissue/body fluid samples.

Adipose-Derived Biogenic Nanoparticles for Suppression of Inflammation

Extracellular vesicles secreted from adipose-derived mesenchymal stem cells (ADSCs) have therapeutic effects in inflammatory diseases. However, production of extracellular vesicles (EVs) from ADSCs is costly, inefficient, and time consuming. The anti-inflammatory properties of adipose tissue-derived EVs and other biogenic nanoparticles have not been explored. In this study, biogenic nanoparticles are obtained directly from lipoaspirate, an easily accessible and abundant source of biological material. Compared to ADSC-EVs, lipoaspirate nanoparticles (Lipo-NPs) take less time to process (hours compared to months) and cost less to produce (clinical-grade cell culture facilities are not required). The physicochemical characteristics and anti-inflammatory properties of Lipo-NPs are evaluated and compared to those of patient-matched ADSC-EVs. Moreover, guanabenz loading in Lipo-NPs is evaluated for enhanced anti-inflammatory effects. Apolipoprotein E and glycerolipids are enriched in Lipo-NPs compared to ADSC-EVs. Additionally, the uptake of Lipo-NPs in hepatocytes and macrophages is higher. Lipo-NPs and ADSC-EVs have comparable protective and anti-inflammatory effects. Specifically, Lipo-NPs reduce toll-like receptor 4-induced secretion of inflammatory cytokines in macrophages. Guanabenz-loaded Lipo-NPs further suppress inflammatory pathways, suggesting that this combination therapy can have promising applications for inflammatory diseases.

Plasma mEV levels in Ghanain malaria patients with low parasitaemia are higher than those of healthy controls, raising the potential for parasite markers in mEVs as diagnostic targets

This study sought to measure medium-sized extracellular vesicles (mEVs) in plasma, when patients have low Plasmodium falciparum early in infection. We aimed to define the relationship between plasma mEVs and: (i) parasitaemia, (ii) period from onset of malaria symptoms until seeking medical care (patient delay, PD), (iii) age and (iv) gender. In this cross-sectional study, n = 434 patients were analysed and Nanosight Tracking Analysis (NTA) used to quantify mEVs (vesicles of 150–500 nm diameter, isolated at 15,000 × g, β-tubulin-positive and staining for annexin V, but weak or negative for CD81). Overall plasma mEV levels (1.69 × 10¹⁰ mEVs mL⁻¹) were 2.3-fold higher than for uninfected controls (0.51 × 10¹⁰ mEVs mL⁻¹). Divided into four age groups, we found a bimodal distribution with 2.5- and 2.1-fold higher mEVs in infected children (<11 years old [yo]) (median:2.11 × 10¹⁰ mEVs mL⁻¹) and the elderly (>45 yo) (median:1.92 × 10¹⁰ mEVs mL⁻¹), respectively, compared to uninfected controls; parasite density varied similarly with age groups. There was a positive association between mEVs and parasite density (r = 0.587, p < 0.0001) and mEVs were strongly associated with PD (r = 0.919, p < 0.0001), but gender had no effect on plasma mEV levels (p = 0.667). Parasite density was also exponentially related to patient delay. Gender (p = 0.667) had no effect on plasma mEV levels. During periods of low parasitaemia (PD = 72h), mEVs were 0.93-fold greater than in uninfected controls. As 75% (49/65) of patients had low parasitaemia levels (20–500 parasites µL⁻¹), close to the detection limits of microscopy of Giemsa-stained thick blood films (5–150 parasites µL⁻¹), mEV quantification by NTA could potentially have early diagnostic value, and raises the potential of Pf markers in mEVs as early diagnostic targets.

Extracellular vesicles and coagulation in blood from healthy humans revisited

Background: In 2001, we studied the presence and coagulant properties of “microparticles” in the blood of healthy humans. Since then, multiple improvements in detection, isolation and functional characterization of the now called “extracellular vesicles” (EVs) have been made, and shortcomings were identified. Aim: To revisit the presence and function of EVs in blood from healthy humans. Methods: Blood was collected from 20 healthy donors. EV-containing plasma was prepared according to new guidelines, and plasma was diluted to prevent swarm detection. Single EVs were measured by flow cytometry with known sensitivity of fluorescence and light scatter. The haemostatic properties of EVs were measured by thrombin-, fibrin-, and plasmin generation. Plasma concentrations of thrombin-antithrombin complexes and prothrombin fragment 1 + 2 were measured to assess the coagulation status in vivo. Results: Compared to 2001, the total concentrations of detected EVs increased from 190- to 264-fold. In contrast to 2001, however, EVs are non-coagulant which we show can be attributed to improvements in blood collection and plasma preparation. No relation is present between the plasma concentrations of EVs and either TAT or F1 + 2. Finally, we show that EVs support plasmin generation. Discussion: Improvements in blood collection, plasma preparation and detection of EVs reveal that results from earlier studies have to be interpreted with care. Compared to 2001, higher concentrations of EVs are detected in blood of healthy humans which promote fibrinolysis rather than coagulation.

Complement mediated Klebsiella pneumoniae capsule changes

The Gram-negative bacterium Klebsiella pneumoniae is an opportunistic pathogen, which can cause life-threatening infections such as sepsis. Worldwide, emerging multidrug resistant K. pneumoniae infections are challenging to treat, hence leading to increased mortality. Therefore, understanding the interactions between K. pneumoniae and the immune system is important to develop new treatment options. We characterized ten clinical K. pneumoniae isolates obtained from blood of bacteremia patients. The interaction of the isolates with human serum was investigated to elucidate how K. pneumoniae escapes the host immune system, and how complement activation by K. pneumoniae changed the capsule structure. All K. pneumoniae isolates activated the alternative complement pathway despite serum resistance of seven isolates. One serum sensitive isolate activated two or all three pathways, and this isolate was lysed and had numerous membrane attack complexes in the outer membrane. However, we also found deposition of complement components in the capsule of serum resistant isolates resulting in morphological capsule changes and capsule shedding. These bacteria did not lyse, and no membrane attack complex was observed despite deposition of C5b-9 within the capsule, indicating that the capsule of serum resistant K. pneumoniae isolates is a defense mechanism against complement-mediated lysis.

Increasing the sensitivity of the human microvesicle tissue factor activity assay

INTRODUCTION

The TF-FVIIa complex is the primary activator of coagulation. Elevated levels of microvesicle (MV) bearing tissue factor (TF)-dependent procoagulant activity are detectable in patients with an increased risk of thrombosis. Several methods have been described to measure MV TF activity but they are hampered by limited sensitivity and specificity. The aim of this work was to increase the sensitivity of the MV TF activity assay (called Chapel Hill assay).

MATERIAL AND METHODS

Improvements of the MV TF activity assay included i/ speed and time of centrifugation, ii/ use of a more potent inhibitory anti-TF antibody iii/ use of FVII and a fluorogenic substrate to increase specificity.

RESULTS

The specificity of the MV TF activity assay was demonstrated by the absence of activity on MV derived from a knock-out-TF cell line using an anti-human TF monoclonal antibody called SBTF-1, which shows a higher TF inhibitory effect than the anti-human TF monoclonal antibody called HTF-1. Experiments using blood from healthy individuals, stimulated or not by LPS, or plasma spiked with 3 different levels of MV, demonstrated that the new assay was more sensitive and this allowed detection of MV TF activity in platelet free plasma (PFP) samples from healthy individuals. However, the assay was limited by an inter-assay variability, mainly due to the centrifugation step.

CONCLUSIONS

We have improved the sensitivity of the MV TF activity assay without losing specificity. This new assay could be used to evaluate levels of TF-positive MV as a potential biomarker of thrombotic risk in patients.

Involvement of Extracellular Vesicles in Vascular-Related Functions in Cancer Progression and Metastasis

The primary cause of mortality among patients with cancer is the progression of the tumor, better known as cancer invasion and metastasis. Cancer progression involves a series of biologically important steps in which the cross-talk between cancer cells and the cells in the surrounding environment is positioned as an important issue. Notably, angiogenesis is a key tumorigenic phenomenon for cancer progression. Cancer-related extracellular vesicles (EVs) commonly contribute to the modulation of a microenvironment favorable to cancer cells through their function of cell-to-cell communication. Vascular-related cells such as endothelial cells (ECs) and platelets activated by cancer cells and cancer-derived EVs develop procoagulant and proinflammatory statuses, which help excite the tumor environment, and play major roles in tumor progression, including in tumor extravasation, tumor cell microthrombi formation, platelet aggregation, and metastasis. In particular, cancer-derived EVs influence ECs, which then play multiple roles such as contributing to tumor angiogenesis, loss of endothelial vascular barrier by binding to ECs, and the subsequent endothelial-to-mesenchymal transition, i.e., extracellular matrix remodeling. Thus, cell-to-cell communication between cancer cells and ECs via EVs may be an important target for controlling cancer progression. This review describes the current knowledge regarding the involvement of EVs, especially exosomes derived from cancer cells, in EC-related cancer progression.

Extracellular vesicle-associated procoagulant phospholipid and tissue factor activity in multiple myeloma

Multiple myeloma (MM) patients have increased risk of developing venous thromboembolism, but the underlying mechanisms and the effect on the coagulation system of the disease and the current cancer therapies are not known. It is possible that cancer-associated extracellular vesicles (EV), carrying tissue factor (TF) and procoagulant phospholipids (PPL) may play a role in thrombogenesis. The aim of this study was to perform an in-depth analysis of procoagulant activity of small and large EVs isolated from 20 MM patients at diagnosis and after receiving first-line treatment compared with 20 healthy control subjects. Differential ultracentrifugation at 20,000 × g and 100,000 × g were used to isolate EVs for quantitative and phenotypical analysis through nanoparticle tracking analysis, Western blotting and transmission electron microscopy. The isolated EVs were analyzed for procoagulant activity using the calibrated automated thrombogram technique, a factor Xa-based activity assay, and the STA Procoag-PPL assay. In general, MM patients contained more EVs, and immunoelectron microscopy confirmed the presence of CD9- and CD38-positive EVs. EVs in the 20,000 × g pellets from MM patients exerted procoagulant activity visualized by increased thrombin generation and both TF and PPL activity. This effect diminished during treatment, with the most prominent effect observed in the high-dose chemotherapy eligible patients after induction therapy with bortezomib, cyclophosphamide, and dexamethasone. In conclusion, the EVs in patients with MM carrying TF and PPL are thus capable of exerting procoagulant activity.