The release of microparticles by apoptotic cells and their effects on macrophages

A guide to the expanding field of extracellular vesicles and their release in regulated cell death programs

Homeostasis disruption is visible at the molecular and cellular levels and may often lead to cell death. This vital process allows us to maintain the more extensive system's integrity by keeping the different features (genetic, metabolic, physiologic, and individual) intact. Interestingly, while cells can die in different manners, dying cells still communicate with their environment. This communication was, for a long time, perceived as only driven by the release of soluble factors. However, it has now been reconsidered with the increasing interest in extracellular vesicles (EVs), which are discovered to be released during different regulated cell death programs, with the observation of specific effects. EVs are game changers in the paradigm of cell-cell communication with tremendous implications in fundamental research with regard to noncell autonomous functions, as well as in biomarkers research, all of which are geared toward diagnostic and therapeutic purposes. This review is composed of two main parts. The first is a comprehensive presentation of the state of the art of the EV field at large. In the second part, we focus on EVs discovered to be released during different regulated cell death programs, also known as cell death EVs (cdEVs), and EV-associated specific effects on recipient cells in the context of cell death and inflammation/inflammatory responses.

Impact of microparticles released during murine systemic inflammation on macrophage activity and reactive nitrogen species regulation

Microparticles (MPs) packaged with numerous bioactive molecules are essential vehicles in cellular communication in various pathological conditions, including systemic inflammation, Whereas MPs are studied mostly upon isolation, their detection in vivo is limited. Impact of MPs might depend on target cell type and cargo they carry; thus herein, we aimed at verifying MPs' impact on macrophages. Unlike neutrophils, monocytes/macrophages are rather inactive during sepsis, and we hypothesized this might be at least partially controlled by MPs. For the above reasons, we focused on the detection of MPs with intravital microscopy (IVM) and report the presence of putative neutrophil-derived MPs in the vasculature of cremaster muscle of endotoxemic mice. Subsequently, we characterized MPs isolated not only from their blood but also from the peritoneal cavity and observed differences in their size, concentration, and cargo. Such MPs were then used to study their impact on RAW 264.7 macrophage cell line performance (cell viability/activity, cytokines, oxygen, and nitrogen reactive species). Addition of MPs to macrophages with or without co-stimulation with lipopolysaccharide did not affect respiratory burst, somewhat decreased mitochondrial activity but increased inducible nitric oxide synthase (iNOS) expression, and NO production especially in case of plasma-derived MPs. The latter MPs carried more iNOS-controlling ceruloplasmin than those discharged into the peritoneal cavity. We conclude that MPs can be detected in vivo with IVM and their cellular origin identified. They are heterogeneous in nature depending on the site of their release. Consequently, microparticles released during systemic inflammation to various body compartments differentially affect macrophages.

Extracellular vesicles arising from apoptosis: forms, functions, and applications

Extracellular vesicles (EVs) are lipid bilayer-enclosed subcellular bodies produced by most, if not all cells. Research over the last two decades has recognised the importance of EVs in intercellular communication and horizontal transfer of biological material. EVs range in diameter from tens of nanometres up to several micrometres and are able to transfer a spectrum of biologically active cargoes - from whole organelles, through macromolecules including nucleic acids and proteins, to metabolites and small molecules - from their cells of origin to recipient cells, which may consequently become physiologically or pathologically altered. Based on their modes of biogenesis, the most renowned EV classes are (1) microvesicles, (2) exosomes (both produced by healthy cells), and (3) EVs from cells undergoing regulated death by apoptosis (ApoEVs). Microvesicles bud directly from the plasma membrane, while exosomes are derived from endosomal compartments. Current knowledge of the formation and functional properties of ApoEVs lags behind that of microvesicles and exosomes, but burgeoning evidence indicates that ApoEVs carry manifold cargoes, including mitochondria, ribosomes, DNA, RNAs, and proteins, and perform diverse functions in health and disease. Here we review this evidence, which demonstrates substantial diversity in the luminal and surface membrane cargoes of ApoEVs, permitted by their very broad size range (from around 50 nm to >5 μm; the larger often termed apoptotic bodies), strongly suggests their origins through both microvesicle- and exosome-like biogenesis pathways, and indicates routes through which they interact with recipient cells. We discuss the capacity of ApoEVs to recycle cargoes and modulate inflammatory, immunological, and cell fate programmes in normal physiology and in pathological scenarios such as cancer and atherosclerosis. Finally, we provide a perspective on clinical applications of ApoEVs in diagnostics and therapeutics. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Apoptotic Cell-Derived CD14(+) Microparticles Promote the Phagocytic Activity of Neutrophilic Precursor Cells in the Phagocytosis of Apoptotic Cells

Membranous CD14 is crucial in the phagocytic activity of neutrophils. However, the role of CD14(+) microparticles (MPs) derived from apoptotic neutrophils (apo-MP) during the phagocytic process is not clear. All trans-retinoic acid (ATRA) induces acute promyelocytic leukemic NB4 cells along granulocytic differentiation. In this study, we investigated the role of CD14(+)apo-MP in the cell-cell interaction during the phagocytic process of apoptotic cells by viable ATRA-NB4 cells. We firstly demonstrate that CD14 expression and phagocytic activity of NB4 cells were upregulated simultaneously after ATRA treatment in a time-dependent manner, and both were significantly enhanced via concurrent lipopolysaccharide treatment. The phagocytic activity of ATRA-NB4 cells and lipopolysaccharide-treated ATRA-NB4 cells were both significantly attenuated by pre-treating cells with an antibody specific to either CD14 or TLR4. Further flow cytometric analysis demonstrates that apoptotic ATRA-NB4 cells release CD14(+)apo-MP in an idarubicin dosage-dependent manner. Both CD14 expression and the phagocytic activity of viable ATRA-NB4 cells were significantly enhanced after incubation with apo-MP harvested from apoptotic ATRA-NB4 cells, and the apo-MP-enhanced phagocytic activity was significantly attenuated by pre-treating apo-MP with an anti-CD14 antibody before incubation with viable cells. We conclude that CD14(+)apo-MP derived from apoptotic ATRA-NB4 cells promotes the phagocytic activity of viable ATRA-NB4 cells in engulfing apoptotic cells.

Apoptotic bodies: bioactive treasure left behind by the dying cells with robust diagnostic and therapeutic application potentials

Apoptosis, a form of programmed cell death, is essential for growth and tissue homeostasis. Apoptotic bodies (ApoBDs) are a form of extracellular vesicles (EVs) released by dying cells in the last stage of apoptosis and were previously regarded as debris of dead cells. Recent studies unraveled that ApoBDs are not cell debris but the bioactive treasure left behind by the dying cells with an important role in intercellular communications related to human health and various diseases. Defective clearance of ApoBDs and infected-cells-derived ApoBDs are possible etiology of some diseases. Therefore, it is necessary to explore the function and mechanism of the action of ApoBDs in different physiological and pathological conditions. Recent advances in ApoBDs have elucidated the immunomodulatory, virus removal, vascular protection, tissue regenerative, and disease diagnostic potential of ApoBDs. Moreover, ApoBDs can be used as drug carriers enhancing drug stability, cellular uptake, and targeted therapy efficacy. These reports from the literature indicate that ApoBDs hold promising potential for diagnosis, prognosis, and treatment of various diseases, including cancer, systemic inflammatory diseases, cardiovascular diseases, and tissue regeneration. This review summarizes the recent advances in ApoBDs-related research and discusses the role of ApoBDs in health and diseases as well as the challenges and prospects of ApoBDs-based diagnostic and therapeutic applications.

Extracellular vesicles as biomarkers and modulators of atherosclerosis pathogenesis

Extracellular vesicles (EVs) are small, lipid bilayer-enclosed structures released by various cell types that play a critical role in intercellular communication. In atherosclerosis, EVs have been implicated in multiple pathophysiological processes, including endothelial dysfunction, inflammation, and thrombosis. This review provides an up-to-date overview of our current understanding of the roles of EVs in atherosclerosis, emphasizing their potential as diagnostic biomarkers and their roles in disease pathogenesis. We discuss the different types of EVs involved in atherosclerosis, the diverse cargoes they carry, their mechanisms of action, and the various methods employed for their isolation and analysis. Moreover, we underscore the importance of using relevant animal models and human samples to elucidate the role of EVs in disease pathogenesis. Overall, this review consolidates our current knowledge of EVs in atherosclerosis and highlights their potential as promising targets for disease diagnosis and therapy.

Caspases help to spread the message via extracellular vesicles

Cell-cell communication is an essential aspect of multicellular life, key for coordinating cell proliferation, growth, and death in response to environmental changes. Whilst caspases are well-known for facilitating apoptotic and pyroptotic cell death, several recent investigations are uncovering new roles for these enzymes in biological scenarios requiring long-range intercellular signalling mediated by extracellular vesicles (EVs). EVs are small membrane-bound nanoparticles released from cells that may carry and deliver cargo between distant cells, thus helping to coordinate their behaviour. Intriguingly, there is emerging evidence indicating a key contribution of caspases in the biogenesis of EVs, the selection of their cargo content, and EV uptake/function in recipient cells. Here, we discuss the latest findings supporting the interplay between caspases and EVs, and the biological relevance of this molecular convergence for cellular signalling, principally in non-apoptotic scenarios.

Extracellular Vesicles and Vascular Inflammation

Vascular inflammation is the most common pathological feature in the pathogenesis of human disease. It is a complex immune process involved with many different types of cells including platelet, monocytes, macrophages, endothelial cells, and others. It is widely accepted that both innate and adaptive immune responses are important for the initiation and progression of vascular inflammation. The cell-cell interaction constitutes an important aspect of those immune responses in the vascular inflammation. Extracellular vesicles (EVs) are nanometer-sized double-layer lipid membrane vesicles released from most types of cells. They have been proved to play critical roles in intercellular communication in the occurrence and development of multisystem diseases. With the advancement of basal medical science, the biological roles of EVs in vascular inflammation have been clearer today. In this chapter, we will summarize the advance progress of extracellular vesicles in regulating vascular inflammation and its potential application in the clinical.

The Role of Platelet-Derived Extracellular Vesicles in Immune-Mediated Thrombosis

Platelet-derived extracellular vesicles (PEVs) play important roles in hemostasis and thrombosis. There are three major types of PEVs described based on their size and characteristics, but newer types may continue to emerge owing to the ongoing improvement in the methodologies and terms used to define various types of EVs. As the literature on EVs is growing, there are continuing attempts to standardize protocols for EV isolation and reach consensus in the field. This review provides information on mechanisms of PEV production, characteristics, cellular interaction, and their pathological role, especially in autoimmune and infectious diseases. We also highlight the mechanisms through which PEVs can activate parent cells in a feedback loop.

Extracellular Vesicles as Drivers of Immunoinflammation in Atherothrombosis

Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality all over the world. Extracellular vesicles (EVs), small lipid-bilayer membrane vesicles released by most cellular types, exert pivotal and multifaceted roles in physiology and disease. Emerging evidence emphasizes the importance of EVs in intercellular communication processes with key effects on cell survival, endothelial homeostasis, inflammation, neoangiogenesis, and thrombosis. This review focuses on EVs as effective signaling molecules able to both derail vascular homeostasis and induce vascular dysfunction, inflammation, plaque progression, and thrombus formation as well as drive anti-inflammation, vascular repair, and atheroprotection. We provide a comprehensive and updated summary of the role of EVs in the development or regression of atherosclerotic lesions, highlighting the link between thrombosis and inflammation. Importantly, we also critically describe their potential clinical use as disease biomarkers or therapeutic agents in atherothrombosis.

Microparticles in Autoimmunity: Cause or Consequence of Disease?

Microparticles (MPs) are small (100 nm - 1 um) extracellular vesicles derived from the plasma membrane of dying or activated cells. MPs are important mediators of intercellular communication, transporting proteins, nucleic acids and lipids from the parent cell to other cells. MPs resemble the state of their parent cells and are easily accessible when released into the blood or urine. MPs also play a role in the pathogenesis of different diseases and are considered as potential biomarkers. MP isolation and characterization is technically challenging and results in different studies are contradictory. Therefore, uniform guidelines to isolate and characterize MPs should be developed. Our understanding of MP biology and how MPs play a role in different pathological mechanisms has greatly advanced in recent years. MPs, especially if derived from apoptotic cells, possess strong immunogenic properties due to the presence of modified proteins and nucleic acids. MPs are often found in patients with autoimmune diseases where MPs for example play a role in the break of immunological tolerance and/or induction of inflammatory conditions. In this review, we describe the main techniques to isolate and characterize MPs, define the characteristics of MPs generated during cell death, illustrate different mechanism of intercellular communication via MPs and summarize the role of MPs in pathological mechanisms with a particular focus on autoimmune diseases.

Microparticles: biogenesis, characteristics and intervention therapy for cancers in preclinical and clinical research

Extracellular vesicles (EVs), spherical biological vesicles, mainly contain nucleic acids, proteins, lipids and metabolites for biological information transfer between cells. Microparticles (MPs), a subtype of EVs, directly emerge from plasma membranes, and have gained interest in recent years. Specific cell stimulation conditions, such as ultraviolet and X-rays irradiation, can induce the release of MPs, which are endowed with unique antitumor functionalities, either for therapeutic vaccines or as direct antitumor agents. Moreover, the size of MPs (100–1000 nm) and their spherical structures surrounded by a lipid bilayer membrane allow MPs to function as delivery vectors for bioactive antitumor compounds, with favorable phamacokinetic behavior, immunostimulatory activity and biological function, without inherent carrier-specific toxic side effects. In this review, the mechanisms underlying MP biogenesis, factors that influence MP production, properties of MP membranes, size, composition and isolation methods of MPs are discussed. Additionally, the applications and mechanisms of action of MPs, as well as the main hurdles for their applications in cancer management, are introduced.

Role of Circulating Microparticles in Type 2 Diabetes Mellitus: Implications for Pathological Clotting

Type 2 diabetes mellitus (T2DM) is a multifactorial chronic metabolic disease characterized by chronic hyperglycemia due to insulin resistance and a deficiency in insulin secretion. The global diabetes pandemic relates primarily to T2DM, which is the most prevalent form of diabetes, accounting for over 90% of all cases. Chronic low-grade inflammation, triggered by numerous risk factors, and the chronic activation of the immune system are prominent features of T2DM. Here we highlight the role of blood cells (platelets, and red and white blood cells) and vascular endothelial cells as drivers of systemic inflammation in T2DM. In addition, we discuss the role of microparticles (MPs) in systemic inflammation and hypercoagulation. Although once seen as inert by-products of cell activation or destruction, MPs are now considered to be a disseminated storage pool of bioactive effectors of thrombosis, inflammation, and vascular function. They have been identified to circulate at elevated levels in the bloodstream of individuals with increased risk of atherothrombosis or cardiovascular disease, two significant hallmark conditions of T2DM. There is also general evidence that MPs activate blood cells, express proinflammatory and coagulant effects, interact directly with cell receptors, and transfer biological material. MPs are considered major players in the pathogenesis of many systemic inflammatory diseases and may be potentially useful biomarkers of disease activity and may not only be of prognostic value but may act as novel therapeutic targets.

Extracellular Vesicles and Their Relationship with the Heart-Kidney Axis, Uremia and Peritoneal Dialysis

Cardiorenal syndrome (CRS) is described as primary dysfunction in the heart culminating in renal injury or vice versa. CRS can be classified into five groups, and uremic toxin (UT) accumulation is observed in all types of CRS. Protein-bound uremic toxin (PBUT) accumulation is responsible for permanent damage to the renal tissue, and mainly occurs in CRS types 3 and 4, thus compromising renal function directly leading to a reduction in the glomerular filtration rate (GFR) and/or subsequent proteinuria. With this decrease in GFR, patients may need renal replacement therapy (RRT), such as peritoneal dialysis (PD). PD is a high-quality and home-based dialysis therapy for patients with end-stage renal disease (ESRD) and is based on the semi-permeable characteristics of the peritoneum. These patients are exposed to factors which may cause several modifications on the peritoneal membrane. The presence of UT may harm the peritoneum membrane, which in turn can lead to the formation of extracellular vesicles (EVs). EVs are released by almost all cell types and contain lipids, nucleic acids, metabolites, membrane proteins, and cytosolic components from their cell origin. Our research group previously demonstrated that the EVs can be related to endothelial dysfunction and are formed when UTs are in contact with the endothelial monolayer. In this scenario, this review explores the mechanisms of EV formation in CRS, uremia, the peritoneum, and as potential biomarkers in peritoneal dialysis.

Role of extracellular vesicles in atherosclerosis: An update

Extracellular vesicles (EVs) are membrane particles released by most cell types in response to different stimuli. They are composed of a lipid bilayer that encloses a wide range of bioactive material, including proteins and nucleic acids. EVs have garnered increasing attention over recent years, as their role in intercellular communication has been brought to light. As such, they have been found to regulate pathophysiologic pathways like inflammation, angiogenesis, or senescence, and are therefore implicated in key aspects atherosclerosis initiation and progression. Interestingly, EVs appear to have a multifaceted role; depending on their cargo, they can either facilitate or hamper the development of atherosclerotic lesions. In this review, we examine how EVs of varying origins may be implicated in the different phases of atherosclerotic lesion development. We also discuss the need to standardize isolation and analysis procedures to fully fulfil their potential as biomarkers and therapeutics for cardiovascular diseases.

Communication is key: Extracellular vesicles as mediators of infection and defence during host-microbe interactions in animals and plants

Extracellular vesicles (EVs) are now understood to be ubiquitous mediators of cellular communication. In this review, we suggest that EVs have evolved into a highly regulated system of communication with complex functions including export of wastes, toxins and nutrients, targeted delivery of immune effectors and vectors of RNA silencing. Eukaryotic EVs come in different shapes and sizes and have been classified according to their biogenesis and size distributions. Small EVs (or exosomes) are released through fusion of endosome-derived multivesicular bodies with the plasma membrane. Medium EVs (or microvesicles) bud off the plasma membrane as a form of exocytosis. Finally, large EVs (or apoptotic bodies) are produced as a result of the apoptotic process. This review considers EV secretion and uptake in four eukaryotic kingdoms, three of which produce cell walls. The impacts cell walls have on EVs in plants and fungi are discussed, as are roles of fungal EVs in virulence. Contributions of plant EVs to development and innate immunity are presented. Compelling cases are sporophytic self-incompatibility and cellular invasion by haustorium-forming filamentous pathogens. The involvement of EVs in all of these eukaryotic processes is reconciled considering their evolutionary history.

Extracellular vesicles in atherothrombosis and cardiovascular disease: Friends and foes

Extracellular vesicles (EV, exosomes and microvesicles -MV-) are 30-1000 nm particles surrounded by a phospholipid bilayer membrane that are released from almost all cell types through several pathways. EV encapsulate bioactive molecules, and the molecular cargo is determined by the trigger stimulating its release, reflecting its cell origin and biological functions. This review is primarily focused on the latest evidence of the roles of EV, released from cells involved in the different stages of atherothrombosis. The potential translation of this information to the clinical arena is also discussed. EV can have both pro- and anti-atherothrombotic effects depending on several factors, such as the type of vesicle (MV/exosome), its molecular cargo, its cell of origin, and the context in which are generated, i.e., the stimulus triggering its release. In fact, EV actively participate in every step of atherosclerosis onset and progression, and also in thrombus formation leading to a major adverse cardiovascular event. Moreover, EV have a determinant role in fibrous cap stability, thus determining the propensity of the plaque to rupture. On the other hand, and again, conditioned by the context and stimulus instigating its secretion, some EV may have protective biological functions, perhaps as a compensatory mechanism or even with reparative or regenerative potential. Therefore, the study of the implication of EV in atherothrombosis might be of relevance to unveil new therapeutic targets, vectors and biomarkers of cardiovascular disease (CVD).

Therapeutic Potential of Mesenchymal Stromal Cells and Extracellular Vesicles in the Treatment of Radiation Lesions-A Review

Ionising radiation-induced normal tissue damage is a major concern in clinic and public health. It is the most limiting factor in radiotherapy treatment of malignant diseases. It can also cause a serious harm to populations exposed to accidental radiation exposure or nuclear warfare. With regard to the clinical use of radiation, there has been a number of modalities used in the field of radiotherapy. These includes physical modalities such modified collimators or fractionation schedules in radiotherapy. In addition, there are a number of pharmacological agents such as essential fatty acids, vasoactive drugs, enzyme inhibitors, antioxidants, and growth factors for the prevention or treatment of radiation lesions in general. However, at present, there is no standard procedure for the treatment of radiation-induced normal tissue lesions. Stem cells and their role in tissue regeneration have been known to biologists, in particular to radiobiologists, for many years. It was only recently that the potential of stem cells was studied in the treatment of radiation lesions. Stem cells, immediately after their successful isolation from a variety of animal and human tissues, demonstrated their likely application in the treatment of various diseases. This paper describes the types and origin of stem cells, their characteristics, current research, and reviews their potential in the treatment and regeneration of radiation induced normal tissue lesions. Adult stem cells, among those mesenchymal stem cells (MSCs), are the most extensively studied of stem cells. This review focuses on the effects of MSCs in the treatment of radiation lesions.

Production of erythrocyte microparticles in a sub-hemolytic environment

Microparticles are produced by various cells due to a number of different stimuli in the circulatory system. Shear stress has been shown to injure red blood cells resulting in hemolysis or non-reversible sub-hemolytic damage. We hypothesized that, in the sub-hemolytic shear range, there exist sufficient mechanical stimuli for red blood cells to respond with production of microparticles. Red blood cells isolated from blood of healthy volunteers were exposed to high shear stress in a microfluidic channel to mimic mechanical trauma similar to that occurring in ventricular assist devices. Utilizing flow cytometry techniques, both an increase of shear rate and exposure time showed higher concentrations of red blood cell microparticles. Controlled shear rate exposure shows that red blood cell microparticle concentration may be indicative of sub-hemolytic damage to red blood cells. In addition, properties of these red blood cell microparticles produced by shear suggest that mechanical trauma may underlie some complications for cardiovascular patients.

Tumor-derived microparticles in tumor immunology and immunotherapy

Microvesicles or microparticles, a type of cytoplasm membrane-derived extracellular vesicles, can be released by cancer cells or normal cell types. Alteration of F-actin cytoskeleton by various signals may lead to the cytoplasm membrane encapsulating cellular contents to form microparticles, which contain various messenger molecules, including enzymes, RNAs and even DNA fragments, and are released to extracellular space. The release of microparticles by tumor cells (T-MPs) is a very common event in tumor microenvironments. As a result, T-MPs not only influence tumor cell biology but also profoundly forge tumor immunology. Moreover, T-MPs can act as a natural vehicle that delivers therapeutic drugs to tumor cells and immune cells, thus, remodeling tumor microenvironments and resetting antitumor immune responses, thus, conferring T-MPs a potential role in tumor immunotherapies and tumor vaccines. In this review, we focus on the double-edged sword role of T-MPs in tumor immunology, specifically in TAMs and DCs, and emphasize the application of drug-packaging T-MPs in cancer patients. We aim to provide a new angle to understand immuno-oncology and new strategies for cancer immunotherapy.

Extracellular vesicle signalling in atherosclerosis

Atherosclerosis is a major cardiovascular disease and in 2016, the World Health Organisation (WHO) estimated 17.5 million global deaths, corresponding to 31% of all global deaths, were driven by inflammation and deposition of lipids into the arterial wall. This leads to the development of plaques which narrow the vessel lumen, particularly in the coronary and carotid arteries. Atherosclerotic plaques can become unstable and rupture, leading to myocardial infarction or stroke. Extracellular vesicles (EVs) are a heterogeneous population of vesicles secreted from cells with a wide range of biological functions. EVs participate in cell-cell communication and signalling via transport of cargo including enzymes, DNA, RNA and microRNA in both physiological and patholophysiological settings. EVs are present in atherosclerotic plaques and have been implicated in cellular signalling processes in atherosclerosis development, including immune responses, inflammation, cell proliferation and migration, cell death and vascular remodeling during progression of the disease. In this review, we summarise the current knowledge regarding EV signalling in atherosclerosis progression and the potential of utilising EV signatures as biomarkers of disease.

MSC-Derived Extracellular Vesicles: New Emergency Treatment to Limit the Development of Radiation-Induced Hematopoietic Syndrome?

Nuclear accidents or acts of terrorism involving radioactive sources might lead to mass casualties irradiation. The hematopoietic system is one of the most critical and radiation-sensitive tissues because the limited life span of blood cells requires the continuous division of hematopoietic stem cells (HSCs) into the bone marrow. The radiation-induced hematopoietic syndrome, RI-HS, is an impairment of the hematopoiesis that will result in pancytopenia of various degrees. In fact, treatment with granulocyte-colony stimulating factor (G-CSF) is considered as a valuable adjunct to treatment controls in some irradiated patients. Nevertheless, these overexposed patients with bone marrow suppression have minimal medullary territories that do not allow complete recovery of hematopoiesis but lead to significant immunoreactivity following allogeneic hematopoietic stem cell transplantation (HSCT). The high morbidity and mortality of these overexposed patients is a reminder of the lack of effective treatment for hematopoietic syndrome. During the last 20 y, a therapeutic approach for mesenchymal stem cells (MSC) has been proposed for the management of accidentally irradiated victims. Many preclinical animal studies have shown that MSC, mainly by their secretory activity, in particular extracellular vesicles (EVs), contribute to the control of inflammation and promote regeneration of tissues by accelerating angiogenesis and re-epithelialization processes. Therefore, we investigated the potential effect of EVs on the reduction of early bone marrow ionization toxicity, early anti-apoptotic therapy, and vascular protection in the RI-HS model. The main purpose is to propose an innovative treatment of non-patient-specific RI-HS emergency treatment in order to limit allogeneic HSC.

Ca2+ mediates extracellular vesicle biogenesis through alternate pathways in malignancy

Extracellular vesicles (EVs) are small membrane vesicles that serve as important intercellular signalling intermediaries in both malignant and non-malignant cells. For EVs formed by the plasma membrane, their biogenesis is characterized by an increase in intracellular calcium followed by successive membrane and cytoskeletal changes. EV-production is significantly higher in malignant cells relative to non-malignant cells and previous work suggests this is dependent on increased calcium mobilization and activity of calpain. However, calcium-signalling pathways involved in malignant and non-malignant EV biogenesis remain unexplored. Here we demonstrate; malignant cells have high basal production of plasma membrane EVs compared to non-malignant cells and this is driven by a calcium–calpain dependent pathway. Resting vesiculation in malignant cells occurs via mobilization of calcium from endoplasmic reticulum (ER) stores rather than from the activity of plasma membrane calcium channels. In the event of ER store depletion however, the store-operated calcium entry (SOCE) pathway is activated to restore ER calcium stores. Depleting both ER calcium stores and blocking SOCE, inhibits EV biogenesis. In contrast, calcium signalling pathways are not activated in resting non-malignant cells. Consequently, these cells are relatively low vesiculators in the resting state. Following cellular activation however, an increase in cytosolic calcium and activation of calpain increase in EV biogenesis. These findings contribute to furthering our understanding of extracellular vesicle biogenesis. As EVs are key mediators in the intercellular transfer of deleterious cancer traits such as cancer multidrug resistance (MDR), understanding the molecular mechanisms governing their biogenesis in cancer is the crucial first step in finding novel therapeutic targets that circumvent EV-mediated MDR.

Apoptotic Bodies: Particular Extracellular Vesicles Involved in Intercellular Communication

In the last decade, a new method of cell-cell communication mediated by membranous extracellular vesicles (EVs) has emerged. EVs, including exosomes, microvesicles, and apoptotic bodies (ApoBDs), represent a new and important topic, because they are a means of communication between cells and they can also be involved in removing cellular contents. EVs are characterized by differences in size, origin, and content and different types have different functions. They appear as membranous sacs released by a variety of cells, in different physiological and patho-physiological conditions. Intringuingly, exosomes and microvesicles are a potent source of genetic information carriers between different cell types both within a species and even across a species barrier. New, and therefore still relatively poorly known vesicles are apoptotic bodies, on which numerous in-depth studies are needed in order to understand their role and possible function. In this review we would like to analyze their morpho-functional characteristics.

Apoptotic cell-derived exosomes: messages from dying cells

Apoptosis, a type of programmed cell death that plays a key role in both healthy and pathological conditions, releases extracellular vesicles such as apoptotic bodies and microvesicles, but exosome release due to apoptosis is not yet commonly accepted. Here, the reports demonstrating the presence of apoptotic exosomes and their roles in inflammation and immune responses are summarized, together with a general summary of apoptosis and extracellular vesicles. In conclusion, apoptosis is not just a 'silent' type of cell death but an active form of communication from dying cells to live cells through exosomes.

Regulation of Apoptotic Cell Clearance During Resolution of Inflammation

Programmed cell death (apoptosis) has an important role in the maintenance of tissue homeostasis as well as the progression and ultimate resolution of inflammation. During apoptosis, the cell undergoes morphological and biochemical changes [e.g., phosphatidylserine (PtdSer) exposure, caspase activation, changes in mitochondrial membrane potential and DNA cleavage] that act to shut down cellular function and mark the cell for phagocytic clearance. Tissue phagocytes bind and internalize apoptotic cells, bodies, and vesicles, providing a mechanism for the safe disposal of apoptotic material. Phagocytic removal of apoptotic cells before they undergo secondary necrosis reduces the potential for bystander damage to adjacent tissue and importantly initiates signaling pathways within the phagocytic cell that act to dampen inflammation. In a pathological context, excessive apoptosis or failure to clear apoptotic material results in secondary necrosis with the release of pro-inflammatory intracellular contents. In this review, we consider some of the mechanisms by which phagocytosis of apoptotic cells can be controlled. We suggest that matching apoptotic cell load with the capacity for apoptotic cell clearance within tissues may be important for therapeutic strategies that target the apoptotic process for treatment of inflammatory disease.

The association of P2Y12 inhibitors with pro-coagulatory extracellular vesicles and microRNAs in stable coronary artery disease

Extracellular vesicles (EV) act as a cellular communication tool by carrying lipids, proteins and micro RNA (miR) between cells, thereby playing a pivotal role in thromboembolic processes. The effect of P2Y₁₂ inhibitors on pro-coagulatory, phosphatidylserine (PS)-expressing EV has been investigated previously, but only in vitro or during confounding clinical conditions, such as acute coronary syndrome. Hence, we enrolled 62 consecutive patients 12 month after percutaneous coronary intervention and stent implantation and consequent treatment with dual-antiplatelet therapy consisting of low-dose aspirin and P2Y₁₂ inhibitors. Blood for platelet function testing and EV and miR measurements was taken on the last day of P2Y₁₂ inhibitor intake (baseline, on-treatment) and 10, 30 and 180 days thereafter (off-treatment). We did not observe any influence of P2Y₁₂ inhibitors on the levels of PS-EV or EV sub-population from platelets, erythrocytes, monocytes or endothelial cells, respectively. There was no relationship between platelet function and EV levels in plasma. However, the association of miR-21 and miR-150 with platelet EVs was significantly different between on- and off-treatment measurements. Hence, our study suggests no influence of P2Y₁₂ inhibition on the count of EVs in plasma, but on the potential cargo of platelet-derived EV.

Microparticulate Caspase 1 Regulates Gasdermin D and Pulmonary Vascular Endothelial Cell Injury

Lung endothelial cell apoptosis and injury occur throughout all stages of acute lung injury/acute respiratory distress syndrome and impact disease progression. Caspases 1, 4, and 5 are essential for completion of the apoptotic program known as pyroptosis that also involves proinflammatory cytokines. Because gasdermin D (GSDMD) mediates pyroptotic death and is essential for pore formation, we hypothesized that it might direct caspase 1-encapsulated microparticle (MP) release and mediate endothelial cell death. Our present work provides evidence that GSDMD is released by LPS-stimulated THP-1 monocytic cells, where it is packaged into microparticles together with active caspase 1. Furthermore, only MP released from stimulated monocytic cells that contain both cleaved GSDMD and active caspase 1 induce endothelial cell apoptosis. MPs pretreated with caspase 1 inhibitor Y-VAD or pan-caspase inhibitor Z-VAD do not contain cleaved GSDMD. MPs from caspase 1-knockout cells are also deficient in p30 active GSDMD, further confirming that caspase 1 regulates GSDMD function. Although control MPs contained cleaved GSDMD without caspase 1, these fractions were unable to induce cell death, suggesting that encapsulation of both caspase 1 and GSDMD is essential for cell death induction. Release of microparticulate active caspase 1 was abrogated in GSDMD knockout cells, although cytosolic caspase 1 activation was not impaired. Last, higher concentrations of microparticulate GSDMD were detected in the plasma of septic patients with acute respiratory distress syndrome than in that of healthy donors. Taken together, these findings suggest that GSDMD regulates the release of microparticulate active caspase 1 from monocytes essential for induction of cell death and thereby may play a critical role in sepsis-induced endothelial cell injury.

Extracellular Vesicles from Apoptotic Cells Promote TGFβ Production in Macrophages and Suppress Experimental Colitis

The clearance of apoptotic cells is an essential process to maintain homeostasis of immune system, which is regulated by immunoregulatory cytokines such as TGFβ. We show here that Extracellular Vesicles (EVs) were highly released from apoptotic cells, and contributed to macrophage production of TGFβ in vitro and in vivo. We further elucidated mechanistically that phosphatidylserine in EVs was a key triggering-factor, and transcription factor FOXO3 was a critical mediator for apoptotic EV-induced TGFβ in macrophages. Importantly, we found that macrophages pre-exposed to EVs exhibited an anti-inflammatory phenotype. More strikingly, administration of EVs in vivo promotes Tregs differentiation and suppresses Th1 cell response, and ameliorates experimental colitis. Thus, apoptotic-EV-based treatment might be a promising therapeutic approach for human autoimmune disease.

Apoptotic cell-derived extracellular vesicles: structure–function relationships

Apoptosis is an essential process for normal physiology and plays a key role in the resolution of inflammation. Clearance of apoptotic cells (ACs) involves complex signalling between phagocytic cells, ACs, and the extracellular vesicles (EVs) they produce. Here, we discuss apoptotic cell-derived extracellular vesicles (ACdEVs) and how their structure relates to their function in AC clearance and the control of inflammation, focussing on the ACdEV proteome. We review the current knowledge, ongoing work and future directions for research in this field.

Proteins Regulating Microvesicle Biogenesis and Multidrug Resistance in Cancer

Microvesicles (MV) are emerging as important mediators of intercellular communication. While MVs are important signaling vectors for many physiological processes, they are also implicated in cancer pathology and progression. Cellular activation is perhaps the most widely reported initiator of MV biogenesis, however, the precise mechanism remains undefined. Uncovering the proteins involved in regulating MV biogenesis is of interest given their role in the dissemination of deleterious cancer traits. MVs shed from drug-resistant cancer cells transfer multidrug resistance (MDR) proteins to drug-sensitive cells and confer the MDR phenotype in a matter of hours. MDR is attributed to the overexpression of ABC transporters, primarily P-glycoprotein and MRP1. Their expression and functionality is dependent on a number of proteins. In particular, FERM domain proteins have been implicated in supporting the functionality of efflux transporters in drug-resistant cells and in recipient cells during intercellular transfer by vesicles. Herein, the most recent research on the proteins involved in MV biogenesis and in the dissemination of MV-mediated MDR are discussed. Attention is drawn to unanswered questions in the literature that may prove to be of benefit in ongoing efforts to improve clinical response to chemotherapy and circumventing MDR.

Vesicles bearing gifts: the functional importance of micro-RNA transfer in extracellular vesicles in chronic kidney disease

Extracellular vesicles (EVs), including microparticles (MPs) and exosomes (EXOs), are derived from a wide range of mammalian cells including blood platelets, endothelial cells, and kidney cells and can be detected in body fluids including blood and urine. While EVs are well established as diagnostic markers under pathophysiological and stress conditions, there is also mounting evidence of their functional significance as vehicles for communication between cells mediated by the presence of nucleic acids, especially microRNAs (miRs), encapsulated in the EVs. miRs regulate gene expression, are transported both in MPs and EXOs, and exert profound effects in the kidney. Here we review current understanding of the links between EVs and miRs, discuss the importance of miRs in kidney disease, and shed light on the role of EVs in transferring miRs through the circulation among the renal, vascular, and inflammatory cell populations that are functionally important in patients with chronic kidney disease.

The Impact of Vascular Disease Treatment on Platelet-Derived Microvesicles

Platelet-derived microvesicles (pMVs) are small, heterogeneous vesicles released from platelet membranes as a result of activation. These microvesicles possess a wide range of properties, including prothrombotic, proatherogenic, proinflammatory, immunomodulatory, and even anticoagulant activity. The elevated release of these microvesicles has been observed in various metabolic, inflammatory, thrombotic, and vascular diseases, including ischemic heart disease, stroke, hypertension, diabetes, and connective tissue disease. Modulation of both pMV generation and the expression of their surface molecules may have beneficial clinical implications and could become a novel therapeutic target. However, mechanisms by which pharmacological agents can modify pMV formation are elusive. The purpose of this review is to discuss the effects of drugs routinely used in primary and secondary prevention of vascular disease on the release of pMV and expression of their surface procoagulant and proinflammatory molecules.

Apoptotic Cell-Derived Extracellular Vesicles: More Than Just Debris

The many functions of extracellular vesicles (EVs) like exosomes and microvesicles released from healthy cells have been well characterized, particularly in relation to their roles in immune modulation. Apoptotic bodies, a major class of EV released as a product of apoptotic cell disassembly, and other types of EVs released from dying cells are also becoming recognized as key players in this emerging field. There is now increasing evidence to suggest that EVs produced during apoptosis have important immune regulatory roles, a concept relevant across different disease settings including autoimmunity, cancer, and infection. Therefore, this review focuses on how the formation of EVs during apoptosis could be a key mechanism of immune modulation by dying cells.

Microparticles as new markers of cardiovascular risk in diabetes and beyond

The term microparticle (MP) identifies a heterogeneous population of vesicles playing a relevant role in the pathogenesis of vascular diseases, cancer and metabolic diseases such as diabetes mellitus. MPs are released by virtually all cell types by shedding during cell growth, proliferation, activation, apoptosis or senescence processes. MPs, in particular platelet- and endothelial-derived MPs (PMPs and EMPs), are increased in a wide range of thrombotic disorders, with an interesting relationship between their levels and disease pathophysiology, activity or progression. EMP plasma levels have been associated with several cardiovascular diseases and risk factors. PMPs are also shown to be involved in the progressive formation of atherosclerotic plaque and development of arterial thrombosis, especially in diabetic patients. Indeed, diabetes is characterised by an increased procoagulant state and by a hyperreactive platelet phenotype, with enhanced adhesion, aggregation, and activation. Elevated MP levels, such as TF+ MPs, have been shown to be one of the procoagulant determinants in patients with type 2 diabetes mellitus. Atherosclerotic plaque constitutes an opulent source of sequestered MPs, called “plaque” MPs. Otherwise, circulating MPs represent a TF reservoir, named “blood-borne” TF, challenging the dogma that TF is a constitutive protein expressed in minute amounts. “Blood-borne” TF is mainly harboured by PMPs, and it can be trapped within the developing thrombus. MP detection and enumeration by polychromatic flow cytometry (PFC) have opened interesting perspectives in clinical settings, particularly for the evaluation of MP numbers and phenotypes as independent marker of cardiovascular risk, disease and outcome in diabetic patients.

Message in a Microbottle: Modulation of Vascular Inflammation and Atherosclerosis by Extracellular Vesicles

Extracellular vesicles (EVs) have emerged as a novel intercellular communication system. By carrying bioactive lipids, miRNAs and proteins they can modulate target cell functions and phenotype. Circulating levels of EVs are increased in inflammatory conditions, e.g., cardiovascular disease patients, and their functional contribution to atherosclerotic disease development is currently heavily studied. This review will describe how EVs can modulate vascular cell functions relevant to vascular inflammation and atherosclerosis, particularly highlighting the role of EV-associated proteolytic activity and effector proteins involved. Furthermore, we will discuss key questions and challenges, especially for EV-based therapeutics.

Loading of Extracellular Vesicles with Hydrophobically Modified siRNAs

Delivery represents a significant barrier to the clinical advancement of oligonucleotide therapeutics. Small, endogenous extracellular vesicles (EVs) have the potential to act as oligonucleotide delivery vehicles, but robust and scalable methods for loading RNA therapeutic cargo into vesicles are lacking. Here we describe the efficient loading of hydrophobically modified siRNAs (hsiRNAs) into EVs upon co-incubation, without altering vesicle size distribution or integrity. This method is expected to advance the development of EV-based therapies for the treatment of a broad range of disorders.

Microvesicles in Atherosclerosis and Angiogenesis: From Bench to Bedside and Reverse

Atherosclerosis (AT) is a progressive chronic disease involving lipid accumulation, fibrosis, and inflammation in medium and large-sized arteries, and it is the main cause of cardiovascular disease (CVD). AT is caused by dyslipidemia and mediated by both innate and adaptive immune responses. Despite lipid-lowering drugs have shown to decrease the risk of cardiovascular events (CVEs), there is a significant burden of AT-related morbidity and mortality. Identification of subjects at increased risk for CVE as well as discovery of novel therapeutic targets for improved treatment strategies are still unmet clinical needs in CVD. Microvesicles (MVs), small extracellular plasma membrane particles shed by activated and apoptotic cells have been widely linked to the development of CVD. MVs from vascular and resident cells by facilitating exchange of biological information between neighboring cells serve as cellular effectors in the bloodstream and play a key role in all stages of disease progression. This article reviews the current knowledge on the role of MVs in AT and CVD. Attention is focused on novel aspects of MV-mediated regulatory mechanisms from endothelial dysfunction, vascular wall inflammation, oxidative stress, and apoptosis to coagulation and thrombosis in the progression and development of atherothrombosis. MV contribution to vascular remodeling is also discussed, with a particular emphasis on the effect of MVs on the crosstalk between endothelial cells and smooth muscle cells, and their role regulating the active process of AT-driven angiogenesis and neovascularization. This review also highlights the latest findings and main challenges on the potential prognostic, diagnostic, and therapeutic value of cell-derived MVs in CVD. In summary, MVs have emerged as new regulators of biological functions in atherothrombosis and might be instrumental in cardiovascular precision medicine; however, significant efforts are still needed to translate into clinics the latest findings on MV regulation and function.

Comparative study of macrophages in naked mole rats and ICR mice

The domestic and foreign scholars have studied naked mole rats more focused on the respect such as its long life, resistant to low oxygen, little spontaneous tumor, but the study of the immune system is little. In this study, we compared the anatomy and tissue morphology of NMR and ICR mouse spleens and found that the gross appearance of the NNMR spleen differed from ICR. There were more macrophages in NNMR spleens than in ICR spleens. Furthermore, we focused on the differences of macrophages. We compared their phagocytic capabilities and the data showed that NNMR macrophages are more phagocytic than ICR mouse macrophages. We also used polyI:C and LPS to stimulate the NMR and ICR macrophages and then measured the immune response as expression of certain TLR signaling molecules. After stimulation, there was a lower increase in apoptosis of NMR macrophages than ICR macrophages and a non-significant increased expression of TLRs in NMR macrophages than in ICR macrophages. In contrast, NF-κB proteins increased more significantly in NMR’s than in ICR’s and the expression of downstream cytokines in NMR macrophages also increased more than in ICR macrophages. Based on these results, we hypothesize that in addition to being able to eat foreign matter, NMR macrophages can activate the TLRs, start the NF-κB and produce a large number of cytokines to enhance immune response, so as to protect the body from outside interference when the virus or bacteria invading.

Effect of ATRA and ATO on the expression of tissue factor in NB4 acute promyelocytic leukemia cells and regulatory function of the inflammatory cytokines TNF and IL-1β

The characteristic hemorrhages of acute promyelocytic leukemia (APL) are caused in part by the high expression of tissue factor (TF) on leukemic cells, which also produce TNF and IL-1β, proinflammatory cytokines known to increase TF in various cell types. Exposure of NB4 cells, an APL cell line, to all-trans retinoic acid (ATRA) or arsenic trioxide (ATO) rapidly and strongly reduced TF mRNA. Both drugs also reduced TNF mRNA, but later, and moreover increased IL-1β mRNA. The effect on procoagulant activity of cells and microparticles, as measured with calibrated automated thrombography, was delayed and only partial at 24 h. TNF and IL-1β inhibition reduced TF mRNA and activity only partially. Inhibition of the inflammatory signaling intermediate p38 reduced TF mRNA by one third but increased TNF and IL-1β mRNA. NF-κB inhibition reduced, within 1 h, TF and TNF mRNA but did not change IL-1β mRNA, and rapidly and markedly reduced cell survival, with procoagulant properties still being present. In conclusion, although we provide evidence that TNF, IL-1β, and their signaling intermediates have a regulatory function on TF expression by NB4 APL cells, the effect of ATRA and ATO on TF can only partially be accounted for by their impact on these cytokines.

Microparticle Formation in Peritoneal Dialysis: A Proof of Concept Study

BACKGROUND

Injury to the mesothelial layer of the peritoneal membrane during peritoneal dialysis (PD) is implicated in loss of ultrafiltration capacity, but there are no validated biomarkers for mesothelial cell injury. Microparticles (MPs) are 0.1 to 1.0 µm membrane vesicles shed from the cell surface following injury and are sensitive markers of tissue damage. Formation of MPs in the peritoneal cavity during PD has not been reported to date.

METHODS

We designed a single-center, proof of concept study to assess whether peritoneal solution exposure induces formation of mesothelial MPs suggestive of PD membrane injury. We examined MP levels in PD effluents by electron microscopy, nanoparticle tracking analysis (NTA), flow cytometry, procoagulant activity, and Western blot.

RESULTS

NTA identified particles in the size range of 30 to 900 nm, with a mean of 240 (SE: 10 nm). MP levels increased in a progressive manner during a 4-hour PD dwell. Electron microscopy confirmed size and morphology of vesicles consistent with characteristics of MPs as well as the presence of mesothelin on the surface. Western blot analysis of the MP fraction also identified the presence of mesothelin after 4 hours, suggesting that MPs found in PD effluents may arise from mesothelial cells.

CONCLUSIONS

Our results suggest that MPs are formed and accumulate in the peritoneal cavity during PD, possibly as a stress response. Assessing levels of MPs in PD effluents may be useful as a biomarker for peritoneal membrane damage.

Extracellular vesicles in coronary artery disease

Membrane vesicles released in the extracellular space are composed of a lipid bilayer enclosing soluble cytosolic material and nuclear components. Extracellular vesicles include apoptotic bodies, exosomes, and microvesicles (also known previously as microparticles). Originating from different subcellular compartments, the role of extracellular vesicles as regulators of transfer of biological information, acting locally and remotely, is now acknowledged. Circulating vesicles released from platelets, erythrocytes, leukocytes, and endothelial cells contain potential valuable biological information for biomarker discovery in primary and secondary prevention of coronary artery disease. Extracellular vesicles also accumulate in human atherosclerotic plaques, where they affect major biological pathways, including inflammation, proliferation, thrombosis, calcification, and vasoactive responses. Extracellular vesicles also recapitulate the beneficial effect of stem cells to treat cardiac consequences of acute myocardial infarction, and now emerge as an attractive alternative to cell therapy, opening new avenues to vectorize biological information to target tissues. Although interest in microvesicles in the cardiovascular field emerged about 2 decades ago, that for extracellular vesicles, in particular exosomes, started to unfold a decade ago, opening new research and therapeutic avenues. This Review summarizes current knowledge on the role of extracellular vesicles in coronary artery disease, and their emerging potential as biomarkers and therapeutic agents.

Neutrophil derived microparticles increase mortality and the counter-inflammatory response in a murine model of sepsis

Although advances in medical care have significantly improved sepsis survival, sepsis remains the leading cause of death in the ICU. This is likely due to a lack of complete understanding of the pathophysiologic mechanisms that lead to dysfunctional immunity. Neutrophil derived microparticles (NDMPs) have been shown to be the predominant microparticle present at infectious and inflamed foci in human models, however their effect on the immune response to inflammation and infection is sepsis has not been fully elucidated. As NDMPs may be a potential diagnostic and therapeutic target, we sought to determine the impact NDMPs on the immune response to a murine polymicrobial sepsis. We found that peritoneal neutrophil numbers, bacterial loads, and NDMPs were increased in our abdominal sepsis model. When NDMPs were injected into septic mice, we observed increased bacterial load, decreased neutrophil recruitment, increased expression of IL-10 and worsened mortality. Furthermore, the NDMPs express phosphatidylserine and are ingested by F4/80 macrophages via a Tim-4 and MFG-E8 dependent mechanism. Finally, upon treatment, NDMPs decrease macrophage activation, increase IL-10 release and decrease macrophage numbers. Altogether, these data suggest that NDMPs enhance immune dysfunction in sepsis by blunting the function of neutrophils and macrophages, two key cell populations involved in the early immune response to infection. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

Loading of Extracellular Vesicles with Chemically Stabilized Hydrophobic siRNAs for the Treatment of Disease in the Central Nervous System

Efficient delivery of oligonucleotide therapeutics, i.e., siRNAs, to the central nervous system represents a significant barrier to their clinical advancement for the treatment of neurological disorders. Small, endogenous extracellular vesicles were shown to be able to transport lipids, proteins and RNA between cells, including neurons. This natural trafficking ability gives extracellular vesicles the potential to be used as delivery vehicles for oligonucleotides, i.e., siRNAs. However, robust and scalable methods for loading of extracellular vesicles with oligonucleotide cargo are lacking. We describe a detailed protocol for the loading of hydrophobically modified siRNAs into extracellular vesicles upon simple co-incubation. We detail methods of the workflow from purification of extracellular vesicles to data analysis. This method may advance extracellular vesicles-based therapies for the treatment of a broad range of neurological disorders.

Impact of microparticles derived from erythrocytes on fibrinolysis

It has long been known that negatively charged membranes of erythrocyte-derived microparticles display procoagulant activity. However, relatively little is known about the possible fibrinolytic activity of such microparticles. This issue becomes particularly important during red blood cell storage, which significantly increases the number of microparticles. Whole blood was collected from 30 healthy donors. Microparticles were isolated on days 7, 14, 21, and 28 of erythrocyte storage. The effect of microparticles on the fibrinolytic activity of the donor plasma was determined by coagulation and optical (chromogenic substrate) methods. We demonstrated that erythrocyte microparticles had a prominent fibrinolytic activity which cleaves not only fibrin but also chromogenic substrates. Microparticles present fibrinolytic activity mainly due to the presence of plasminogen on them. Microparticles derived from erythrocytes significantly enhance cleavage of the chromogenic substrate by the streptokinase-plasminogen complex, but to a lesser extent accelerate euglobulin clot lysis time. Erythrocyte-derived microparticles display prominent fibrinolytic activity, which significantly decreases during storage of red blood cells.

Exosome-mediated Delivery of Hydrophobically Modified siRNA for Huntingtin mRNA Silencing

Delivery represents a significant barrier to the clinical advancement of oligonucleotide therapeutics for the treatment of neurological disorders, such as Huntington's disease. Small, endogenous vesicles known as exosomes have the potential to act as oligonucleotide delivery vehicles, but robust and scalable methods for loading RNA therapeutic cargo into exosomes are lacking. Here, we show that hydrophobically modified small interfering RNAs (hsiRNAs) efficiently load into exosomes upon co-incubation, without altering vesicle size distribution or integrity. Exosomes loaded with hsiRNAs targeting Huntingtin mRNA were efficiently internalized by mouse primary cortical neurons and promoted dose-dependent silencing of Huntingtin mRNA and protein. Unilateral infusion of hsiRNA-loaded exosomes, but not hsiRNAs alone, into mouse striatum resulted in bilateral oligonucleotide distribution and statistically significant bilateral silencing of up to 35% of Huntingtin mRNA. The broad distribution and efficacy of hsiRNA-loaded exosomes delivered to brain is expected to advance the development of therapies for the treatment of Huntington's disease and other neurodegenerative disorders.

A Potential Inhibitory Profile of Liver CD68+ Cells during HCV Infection as Observed by an Increased CD80 and PD-L1 but Not CD86 Expression

Aim

The lack of potent innate immune responses during HCV infection might lead to a delay in initiating adaptive immune responses. Kupffer cells (KCs) and liver-infiltrating monocytes/macrophages (CD68⁺ cells) are essential to establish effective anti-HCV responses. They express co-stimulatory molecules, CD80 and CD86. CD86 upregulation induces activator responses that are then potentially regulated by CD80. The relative levels of expression of CD80, CD86 and the inhibitory molecule, PD-L1, on CD68⁺ cells modulate T cell activation. A few studies have explored CD80 and PD-L1 expression on KCs and infiltrating monocytes/macrophages in HCV-infected livers, and none investigated CD86 expression in these cells. These studies have identified these cells based on morphology only. We investigated the stimulatory/inhibitory profile of CD68⁺ cells in HCV-infected livers based on the balance of CD80, CD86 and PD-L1 expression.

Methods

CD80, CD86 and PD-L1 expression by CD68⁺ cells in the lobular and portal areas of the liver of chronic HCV-infected (n = 16) and control (n = 14) individuals was investigated using double staining immunohistochemistry.

Results

The count of CD68⁺ KCs in the lobular areas of the HCV-infected livers was lower than that in the control (p = 0.041). The frequencies of CD68⁺CD80⁺ cells and CD68⁺PD-L1⁺ cells in both lobular and total areas of the liver were higher in HCV-infected patients compared with those in the control group (p = 0.001, 0.031 and 0.007 respectively). Moreover, in the lobular areas of the HCV-infected livers, the frequency of CD68⁺CD80⁺ cells was higher than that of CD68⁺CD86⁺ and CD68⁺PD-L1⁺ cells. In addition, the frequencies of CD68⁺CD80⁺ and CD68⁺CD86⁺ cells were higher in the lobular areas than the portal areas.

Conclusions

Our results show that CD68⁺ cells have an inhibitory profile in the HCV-infected livers. This might help explain the delayed T cell response and viral persistence during HCV infection.