Both eukaryotic and prokaryotic cells release small, phospholipid-enclosed vesicles into their environment. Why do cells release vesicles? Initial studies showed that eukaryotic vesicles are used to ...remove obsolete cellular molecules. Although this release of vesicles is beneficial to the cell, the vesicles can also be a danger to their environment, for instance in blood, where vesicles can provide a surface supporting coagulation. Evidence is accumulating that vesicles are cargo containers used by eukaryotic cells to exchange biomolecules as transmembrane receptors and genetic information. Because also bacteria communicate to each other via extracellular vesicles, the intercellular communication via extracellular cargo carriers seems to be conserved throughout evolution, and therefore vesicles are likely to be a highly efficient, robust, and economic manner of exchanging information between cells. Furthermore, vesicles protect cells from accumulation of waste or drugs, they contribute to physiology and pathology, and they have a myriad of potential clinical applications, ranging from biomarkers to anticancer therapy. Because vesicles may pass the blood-brain barrier, they can perhaps even be considered naturally occurring liposomes. Unfortunately, pathways of vesicle release and vesicles themselves are also being used by tumors and infectious diseases to facilitate spreading, and to escape from immune surveillance. In this review, the different types, nomenclature, functions, and clinical relevance of vesicles will be discussed.
Summary
Background
Enumeration of extracellular vesicles has clinical potential as a biomarker for disease. In biological samples, the smallest and largest vesicles typically differ 25‐fold in size, ...300 000‐fold in concentration, 20 000‐fold in volume, and 10 000 000‐fold in scattered light. Because of this heterogeneity, the currently employed techniques detect concentrations ranging from 104 to 1012 vesicles mL–1.
Objectives
To investigate whether the large variation in the detected concentration of vesicles is caused by the minimum detectable vesicle size of five widely used techniques.
Methods
The size and concentration of vesicles and reference beads were measured with transmission electron microscopy (TEM), a conventional flow cytometer, a flow cytometer dedicated to detecting submicrometer particles, nanoparticle tracking analysis (NTA), and resistive pulse sensing (RPS).
Results
Each technique gave a different size distribution and a different concentration for the same vesicle sample.
Conclusion
Differences between the detected vesicle concentrations are primarily caused by differences between the minimum detectable vesicle sizes. The minimum detectable vesicle sizes were 70–90 nm for NTA, 70–100 nm for RPS, 150–190 nm for dedicated flow cytometry, and 270–600 nm for conventional flow cytometry. TEM could detect the smallest vesicles present, albeit after adhesion on a surface. Dedicated flow cytometry was most accurate in determining the size of reference beads, but is expected to be less accurate on vesicles, owing to heterogeneity of the refractive index of vesicles. Nevertheless, dedicated flow cytometry is relatively fast and allows multiplex fluorescence detection, making it most applicable to clinical research.
Cell-derived vesicles are recognized as essential components of intercellular communication, and many disease processes are associated with their aberrant composition and release. Circulating ...tumor-derived vesicles have major potential as biomarkers; however, the diagnostic use of exosomes is limited by the technology available for their objective characterization and measurement. In this study, we compare nanoparticle tracking analysis (NTA) with submicron particle analysis (SPA), dynamic light scattering (DLS), and electron microscopy (EM) to objectively define size distribution, number, and phenotype of circulating cell-derived vesicles from ovarian cancer patients. Using the NanoSight LM10 instrument, cell-derived vesicles were visualized by laser light scattering and analyzing Brownian motion of these vesicles captured by video. The NTA software calculates the size and total concentration of the vesicles in solution. Using vesicles isolated from ovarian cancer patients, we demonstrate that NTA can measure the size distributions of cell-derived vesicles comparable to other analysis instrumentation. Size determinations by NTA, SPA, and DLS were more objective and complete than that obtained with the commonly used EM approach. NTA can also define the total vesicle concentration. Furthermore, the use of fluorescent-labeled antibodies against specific markers with NTA allows the determination of the “phenotype” of the cell-derived vesicles.
Abstract
Extracellular vesicles (EVs)-particularly exosomes and microvesicles (MVs)-are attracting considerable interest in the cardiovascular field as the wide range of their functions is ...recognized. These capabilities include transporting regulatory molecules including different RNA species, lipids, and proteins through the extracellular space including blood and delivering these cargos to recipient cells to modify cellular activity. EVs powerfully stimulate angiogenesis, and can protect the heart against myocardial infarction. They also appear to mediate some of the paracrine effects of cells, and have therefore been proposed as a potential alternative to cell-based regenerative therapies. Moreover, EVs of different sources may be useful biomarkers of cardiovascular disease identities. However, the methods used for the detection and isolation of EVs have several limitations and vary widely between studies, leading to uncertainties regarding the exact population of EVs studied and how to interpret the data. The number of publications in the exosome and MV field has been increasing exponentially in recent years and, therefore, in this ESC Working Group Position Paper, the overall objective is to provide a set of recommendations for the analysis and translational application of EVs focussing on the diagnosis and therapy of the ischaemic heart. This should help to ensure that the data from emerging studies are robust and repeatable, and optimize the pathway towards the diagnostic and therapeutic use of EVs in clinical studies for patient benefit.
Tumor-derived extracellular vesicles are important mediators of cell-to-cell communication during tumorigenesis. Here, we demonstrated that hepatocellular carcinoma (HCC)-derived ectosomes remodel ...the tumor microenvironment to facilitate HCC progression in an ectosomal PKM2-dependent manner. HCC-derived ectosomal PKM2 induced not only metabolic reprogramming in monocytes but also STAT3 phosphorylation in the nucleus to upregulate differentiation-associated transcription factors, leading to monocyte-to-macrophage differentiation and tumor microenvironment remodeling. In HCC cells, sumoylation of PKM2 induced its plasma membrane targeting and subsequent ectosomal excretion via interactions with ARRDC1. The PKM2-ARRDC1 association in HCC was reinforced by macrophage-secreted cytokines/chemokines in a CCL1-CCR8 axis-dependent manner, further facilitating PKM2 excretion from HCC cells to form a feedforward regulatory loop for tumorigenesis. In the clinic, ectosomal PKM2 was clearly detected in the plasma of HCC patients. This study highlights a mechanism by which ectosomal PKM2 remodels the tumor microenvironment and reveals ectosomal PKM2 as a potential diagnostic marker for HCC.
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•HCC-cell-derived ectosomal PKM2 induces monocyte-to-macrophage differentiation•Remodeling tumor microenvironment by ectosomal PKM2 promotes HCC progression•Sumoylation facilitates PKM2 sorting into ectosomes in an ARRDC1-dependent manner•Macrophage-secreted CCL1 reinforces PKM2 ectosomal excretion in a feedforward loop
Hou et al. demonstrate that sumoylation facilitates ectosomal excretion of PKM2 from HCC cells, which remodels the tumor microenvironment to promote HCC progression through inducing monocyte-to-macrophage differentiation. Macrophage-secreted CCL1 in tumor microenvironment further enhances ectosomal excretion of PKM2. The plasma ectosomal PKM2 is a potential early diagnostic marker for HCC.
Sepsis is associated with dysfunctional coagulation. Recent data suggest that platelets play a role in sepsis by promoting neutrophil accumulation. Herein, we show that cecal ligation and puncture ...(CLP) triggered systemic inflammation, which is characterized by formation of IL‐6 and CXC chemokines as well as neutrophil accumulation in the lung. Platelet depletion decreased neutrophil accumulation, IL‐6, and CXC chemokines formation in septic lungs. Depletion of platelets increased peak thrombin formation and total thrombin generation (TG) in plasma from septic animals. CLP elevated circulating levels of platelet‐derived microparticles (PMPs). In vitro generated PMPs were a potent inducer of TG. Interestingly, in vitro wild‐type recombinant annexin V abolished PMP‐induced thrombin formation whereas a mutant annexin V protein, which does not bind to phosphatidylserine (PS), had no effect. Administration of wild‐type, but not mutant annexin V, significantly inhibited thrombin formation in septic animals. Moreover, CLP‐induced formation of thrombin‐antithrombin complexes were reduced in platelet‐depleted mice and in animals pretreated with annexin V. PMP‐induced TG attenuated in FXII‐ and FVII‐deficient plasma. These findings suggest that sepsis‐induced TG is dependent on platelets. Moreover, PMPs formed in sepsis are a potent inducer of TG via PS exposure, and activation of both the intrinsic and extrinsic pathway of coagulation. In conclusion, these observations suggest that PMPs and PS play an important role in dysfunctional coagulation in abdominal sepsis.
Platelet‐derived microparticles regulates thrombin generation via phophatidylserine in abdominal sepsis Thrombin generation triggered by PMPs is mediated via both intrinsic and extrinsic pathway of coagulation.
Release of membrane vesicles, a process conserved in both prokaryotes and eukaryotes, represents an evolutionary link, and suggests essential functions of a dynamic extracellular vesicular ...compartment (including exosomes, microparticles or microvesicles and apoptotic bodies). Compelling evidence supports the significance of this compartment in a broad range of physiological and pathological processes. However, classification of membrane vesicles, protocols of their isolation and detection, molecular details of vesicular release, clearance and biological functions are still under intense investigation. Here, we give a comprehensive overview of extracellular vesicles. After discussing the technical pitfalls and potential artifacts of the rapidly emerging field, we compare results from meta-analyses of published proteomic studies on membrane vesicles. We also summarize clinical implications of membrane vesicles. Lessons from this compartment challenge current paradigms concerning the mechanisms of intercellular communication and immune regulation. Furthermore, its clinical implementation may open new perspectives in translational medicine both in diagnostics and therapy.
Summary
Platelets are known to play a central role in primary hemostasis as well as in the pathophysiology of thrombotic disorders. However, in addition to hemostasis, platelets are involved in a ...variety of pathophysiological responses including immune responses, inflammation, angiogenesis, tissue regeneration, and cancer metastasis. Recent studies revealed a significant role for platelet‐derived microparticles (PMP), in these responses. PMP communicate with, and deliver signals to, other cells, induce signals, and change their phenotype during inflammation, angiogenesis, and tumor metastasis. The current report describes the recent development in this field with a focus on the role of platelets and PMP in all of the above responses.
Membrane bound vesicles, including microvesicles and exosomes, are secreted by both normal and cancerous cells into the extracellular space and in blood circulation. These circulating extracellular ...vesicles (cirEVs) and exosomes in particular are recognized as a potential source of disease biomarkers. However, to exploit the use of circulatory exosomes as a biomarker, a rapid, high-throughput and reproducible method is required for their isolation and molecular analysis. We have developed a simple, low cost microfluidic-based platform to isolate cirEVs enriched in exosomes directly from blood serum allowing simultaneous capture and quantification of exosomes in a single device. To capture specific exosomes, we employed "ExoChip", a microfluidic device fabricated in polydimethylsiloxane (PDMS) and functionalized with antibodies against CD63, an antigen commonly overexpressed in exosomes. Subsequent staining with a fluorescent carbocyanine dye (DiO) that specifically labels the exosomes, we quantitated exosomes using a standard plate-reader. Ten independent ExoChip experiments performed using serum obtained from five pancreatic cancer patients and five healthy individuals revealed a statistically significant increase (2.34 ± 0.31 fold, p < 0.001) in exosomes captured in cancer patients when compared to healthy individuals. Exosomal origins of ExoChip immobilized vesicles were further confirmed using immuno-electron-microscopy and Western blotting. In addition, we demonstrate the ability of ExoChip to recover exosomes with intact RNA enabling profiling of exosomal-microRNAs through openarray analysis, which has potential applications in biomarker discovery. Based on our findings, ExoChip is a well suited platform to be used as an exosome-based diagnostic and research tool for molecular screening of human cancers.
Microvesicles are generated by the outward budding and fission of membrane vesicles from the cell surface. Recent studies suggest that microvesicle shedding is a highly regulated process that occurs ...in a spectrum of cell types and, more frequently, in tumor cells. Microvesicles have been widely detected in various biological fluids including peripheral blood, urine and ascitic fluids, and their function and composition depend on the cells from which they originate. By facilitating the horizontal transfer of bioactive molecules such as proteins, RNAs and microRNAs, they are now thought to have vital roles in tumor invasion and metastases, inflammation, coagulation, and stem-cell renewal and expansion. This Commentary summarizes recent literature on the properties and biogenesis of microvesicles and their potential role in cancer progression.
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