Selective transfer of exosomes from oligodendrocytes to microglia by macropinocytosis

A CRISPR-Cas9-based reporter system for single-cell detection of extracellular vesicle-mediated functional transfer of RNA

Extracellular vesicles (EVs) form an endogenous transport system for intercellular transfer of biological cargo, including RNA, that plays a pivotal role in physiological and pathological processes. Unfortunately, whereas biological effects of EV-mediated RNA transfer are abundantly studied, regulatory pathways and mechanisms remain poorly defined due to a lack of suitable readout systems. Here, we describe a highly-sensitive CRISPR-Cas9-based reporter system that allows direct functional study of EV-mediated transfer of small non-coding RNA molecules at single-cell resolution. Using this CRISPR operated stoplight system for functional intercellular RNA exchange (CROSS-FIRE) we uncover various genes involved in EV subtype biogenesis that play a regulatory role in RNA transfer. Moreover we identify multiple genes involved in endocytosis and intracellular membrane trafficking that strongly regulate EV-mediated functional RNA delivery. Altogether, this approach allows the elucidation of regulatory mechanisms in EV-mediated RNA transfer at the level of EV biogenesis, endocytosis, intracellular trafficking, and RNA delivery.

The Role of Secretory Pathways in Candida albicans Pathogenesis

Candida albicans is a fungus that is a commensal organism and a member of the normal human microbiota. It has the ability to transition into an opportunistic invasive pathogen. Attributes that support pathogenesis include secretion of virulence-associated proteins, hyphal formation, and biofilm formation. These processes are supported by secretion, as defined in the broad context of membrane trafficking. In this review, we examine the role of secretory pathways in Candida virulence, with a focus on the model opportunistic fungal pathogen, Candida albicans.

Inside(sight) of tiny communicator: exosome biogenesis, secretion, and uptake

Discovered in the late 1980s as an extracellular vesicle of endosomal origin secreted from reticulocytes, exosomes recently gained scientific attention due to its role in intercellular communication. Exosomes have now been identified to carry cell-specific cargo of nucleic acids, proteins, lipids, and other biologically active molecules. Exosomes can be selectively taken up by neighboring or distant cells, which has shown to result in structural and functional responses in the recipient cells. Recent advances indicate the regulation of exosomes at various steps, including their biogenesis, selection of their cargo, as well as cell-specific uptake. This review will shed light on the differences between the type of extracellular vesicles. In this review, we discuss the recent progress in our understanding of the regulation of exosome biogenesis, secretion, and uptake.

Insights into the pathogenesis of multiple system atrophy: focus on glial cytoplasmic inclusions

Multiple system atrophy (MSA) is a debilitating and fatal neurodegenerative disorder. The disease severity warrants urgent development of disease-modifying therapy, but the disease pathogenesis is still enigmatic. Neurodegeneration in MSA brains is preceded by the emergence of glial cytoplasmic inclusions (GCIs), which are insoluble α-synuclein accumulations within oligodendrocytes (OLGs). Thus, preventive strategies against GCI formation may suppress disease progression. However, although numerous studies have tried to elucidate the molecular pathogenesis of GCI formation, difficulty remains in understanding the pathological interaction between the two pivotal aspects of GCIs; α-synuclein and OLGs. The difficulty originates from several enigmas: 1) what triggers the initial generation and possible propagation of pathogenic α-synuclein species? 2) what contributes to OLG-specific accumulation of α-synuclein, which is abundantly expressed in neurons but not in OLGs? and 3) how are OLGs and other glial cells affected and contribute to neurodegeneration? The primary pathogenesis of GCIs may involve myelin dysfunction and dyshomeostasis of the oligodendroglial cellular environment such as autophagy and iron metabolism. We have previously reported that oligodendrocyte precursor cells are more prone to develop intracellular inclusions in the presence of extracellular fibrillary α-synuclein. This finding implies a possibility that the propagation of GCI pathology in MSA brains is mediated through the internalization of pathological α-synuclein into oligodendrocyte precursor cells. In this review, in order to discuss the pathogenesis of GCIs, we will focus on the composition of neuronal and oligodendroglial inclusions in synucleinopathies. Furthermore, we will introduce some hypotheses on how α-synuclein pathology spreads among OLGs in MSA brains, in the light of our data from the experiments with primary oligodendrocyte lineage cell culture. While various reports have focused on the mysterious source of α-synuclein in GCIs, insights into the mechanism which regulates the uptake of pathological α-synuclein into oligodendroglial cells may yield the development of the disease-modifying therapy for MSA. The interaction between glial cells and α-synuclein is also highlighted with previous studies of post-mortem human brains, cultured cells, and animal models, which provide comprehensive insight into GCIs and the MSA pathomechanisms.

Chemoenzymatic Labeling of Extracellular Vesicles for Visualizing Their Cellular Internalization in Real Time

Extracellular vesicles (EVs) are intercellular communicators that are heavily implicated in diverse pathological processes. However, it is poorly understood how EVs interact with recipient cells due to the lack of appropriate tracking techniques. Here, we report a robust chemoenzymatic labeling technique for visualizing the internalization process of EVs into target cells in real time. This method uses phospholipase D (PLD) to catalyze the in situ exchange of choline by alkyne in the native EV phosphatidylcholine. Subsequent alkyne-azide click chemistry allows conjugation of Cy5 dyes for visualizing EVs internalization by confocal fluorescence microscopy. The fluorescent labeling of EVs was accomplished in an efficient and biocompatible way, without affecting both the morphology and biological activity of EVs. We applied this chemoenzymatic labeling strategy to monitor the cellular uptake of cancer cell-derived EVs in real time and to further reveal multiple internalization mechanisms. This robust, biocompatible labeling strategy provides an essential tool for EV-related studies ranging from chemical biology to drug delivery.

Communication in tiny packages: Exosomes as means of tumor-stroma communication

Tumor-derived exosomes are nano-sized vesicles acting as multi-signal devices influencing tumor growth at local and distant sites. Exosomes are derived from the endolysosomal compartment and can shuttle diverse biomolecules like nucleic acids (microRNAs and DNA fragments), lipids, proteins, and even pharmacological compounds from a donor cell to recipient cells. The transfer of cargo to recipient cells enables tumor-derived exosomes to influence diverse cellular functions like proliferation, cell survival, and migration in recipient cells, highlighting tumor-derived exosomes as important players in communication within the tumor microenvironment and at distant sites. In this review, we discuss the mechanisms associated with exosome biogenesis and cargo sorting. In addition, we highlight the communication of tumor-derived exosomes in the tumor microenvironment during different phases of tumor development, focusing on angiogenesis, immune escape mechanisms, drug resistance, and metastasis.

Infarct Zone: a Novel Platform for Exosome Trade in Cardiac Tissue Regeneration

The global incidence of coronary artery diseases (CADs), especially myocardial infarction (MI), has drastically increased in recent years. Even though the conventional therapies have improved the outcomes, the post-MI complications and the increased rate of recurrence among the survivors are still alarming. Molecular events associated with the pathogenesis and the adaptive responses of the surviving myocardium are largely unknown. Focus on exosome-mediated signaling for cell-cell/matrix communications at the infarct zone reflects an emerging opportunity in cardiac regeneration. Also, cardiac tissue engineering provides promising insights for the next generation of therapeutic approaches in the management of CADs. In this article, we critically reviewed the current understanding on the biology of cardiac exosomes, therapeutic potential of exosomes, and recent developments in cardiac tissue engineering and discussed novel translational approaches based on tissue engineering and exosomes for cardiac regeneration and CADs.

Glia-Derived Extracellular Vesicles: Role in Central Nervous System Communication in Health and Disease

Glial cells are crucial for the maintenance of correct neuronal functionality in a physiological state and intervene to restore the equilibrium when environmental or pathological conditions challenge central nervous system homeostasis. The communication between glial cells and neurons is essential and extracellular vesicles (EVs) take part in this function by transporting a plethora of molecules with the capacity to influence the function of the recipient cells. EVs, including exosomes and microvesicles, are a heterogeneous group of biogenetically distinct double membrane-enclosed vesicles. Once released from the cell, these two types of vesicles are difficult to discern, thus we will call them with the general term of EVs. This review is focused on the EVs secreted by astrocytes, oligodendrocytes and microglia, aiming to shed light on their influence on neurons and on the overall homeostasis of the central nervous system functions. We collect evidence on neuroprotective and homeostatic effects of glial EVs, including neuronal plasticity. On the other hand, current knowledge of the detrimental effects of the EVs in pathological conditions is addressed. Finally, we propose directions for future studies and we evaluate the potential of EVs as a therapeutic treatment for neurological disorders.

Mononuclear phagocyte system blockade improves therapeutic exosome delivery to the myocardium

Rationale: Exosomes are emerging as a promising drug delivery carrier. However, rapid uptake of exosomes by the mononuclear phagocyte system (MPS) remains an obstacle for drug delivery into other targeted organs, including the heart. We hypothesized that prior blocking of uptake of exosomes by the MPS would improve their delivery to the targeted organs.

Methods: Exosomes were isolated from the cell culture medium. Fluorescence-labeled exosomes were tracked in vitro and in vivo by fluorescence imaging. The expression of clathrin heavy chain (Cltc), cavolin1, Pak1 and Rhoa, known genes for endocytosis, were profiled in various cell lines and organs by qPCR. The knockdown efficiency of siRNA against Cltc was analyzed by Western blotting. Exosome^control and exosome^blocking were constructed by encapsulating isolated exosomes with siControl or siClathrin via electroporation, while exosome^therapeutic was constructed by encapsulating isolated exosomes with miR-21a. Doxorubicin-induced cardiotoxicity model was used to verify the therapeutic efficiency of the exosome-based miR-21a delivery by echocardiography.

Results: Exosomes were preferentially accumulated in the liver and spleen, mainly due to the presence of abundant macrophages. Besides the well-known phagocytic effect, efficient endocytosis also contributes to the uptake of exosomes by macrophages. Cltc was found to be highly expressed in the macrophages compared with other endocytosis-associated genes. Accordingly, knockdown of Cltc significantly decreased the uptake of exosomes by macrophages in vitro and in vivo. Moreover, prior injection of exosome^blocking strikingly improved the delivery efficiency of exosomes to organs other than spleen and liver. Consistently, compared with the direct injection of exosome^therapeutic, prior injection of exosome^blocking produced a much better therapeutic effect on cardiac function in the doxorubicin-induced cardiotoxicity mouse model.

Conclusions: Prior blocking of endocytosis of exosomes by macrophages with exosome^blocking successfully and efficiently improves the distribution of following exosome^therapeutic in targeted organs, like the heart. The established two-step exosome delivery strategy (blocking the uptake of exosomes first followed by delivery of therapeutic exosomes) would be a promising method for gene therapy.

Nanogel hybrid assembly for exosome intracellular delivery: effects on endocytosis and fusion by exosome surface polymer engineering

Surface polymer engineering was applied with a carrier of exosomes, namely, the amphiphilic cationic CHP (cCHP) nanogel, to improve the delivery of exosome content by forming complexes with the exosomes.

Cell-to-Cell Communication in Learning and Memory: From Neuro- and Glio-Transmission to Information Exchange Mediated by Extracellular Vesicles

Most aspects of nervous system development and function rely on the continuous crosstalk between neurons and the variegated universe of non-neuronal cells surrounding them. The most extraordinary property of this cellular community is its ability to undergo adaptive modifications in response to environmental cues originating from inside or outside the body. Such ability, known as neuronal plasticity, allows long-lasting modifications of the strength, composition and efficacy of the connections between neurons, which constitutes the biochemical base for learning and memory. Nerve cells communicate with each other through both wiring (synaptic) and volume transmission of signals. It is by now clear that glial cells, and in particular astrocytes, also play critical roles in both modes by releasing different kinds of molecules (e.g., D-serine secreted by astrocytes). On the other hand, neurons produce factors that can regulate the activity of glial cells, including their ability to release regulatory molecules. In the last fifteen years it has been demonstrated that both neurons and glial cells release extracellular vesicles (EVs) of different kinds, both in physiologic and pathological conditions. Here we discuss the possible involvement of EVs in the events underlying learning and memory, in both physiologic and pathological conditions.

Intranasally Administered Human MSC-Derived Extracellular Vesicles Pervasively Incorporate into Neurons and Microglia in both Intact and Status Epilepticus Injured Forebrain

Extracellular vesicles (EVs) derived from human bone marrow mesenchymal stem cells (hMSCs) have great promise as biologics to treat neurological and neurodegenerative conditions due to their robust antiinflammatory and neuroprotective properties. Besides, intranasal (IN) administration of EVs has caught much attention because the procedure is noninvasive, amenable for repetitive dispensation, and leads to a quick penetration of EVs into multiple regions of the forebrain. Nonetheless, it is unknown whether brain injury-induced signals are essential for the entry of IN-administered EVs into different brain regions. Therefore, in this study, we investigated the distribution of IN-administered hMSC-derived EVs into neurons and microglia in the intact and status epilepticus (SE) injured rat forebrain. Ten billion EVs labeled with PKH26 were dispensed unilaterally into the left nostril of naïve rats, and rats that experienced two hours of kainate-induced SE. Six hours later, PKH26 + EVs were quantified from multiple forebrain regions using serial brain sections processed for different neural cell markers and confocal microscopy. Remarkably, EVs were seen bilaterally in virtually all regions of intact and SE-injured forebrain. The percentage of neurons incorporating EVs were comparable for most forebrain regions. However, in animals that underwent SE, a higher percentage of neurons incorporated EVs in the hippocampal CA1 subfield and the entorhinal cortex, the regions that typically display neurodegeneration after SE. In contrast, the incorporation of EVs by microglia was highly comparable in every region of the forebrain measured. Thus, unilateral IN administration of EVs is efficient for delivering EVs bilaterally into neurons and microglia in multiple regions in the intact or injured forebrain. Furthermore, incorporation of EVs by neurons is higher in areas of brain injury, implying that injury-related signals likely play a role in targeting of EVs into neurons, which may be beneficial for EV therapy in various neurodegenerative conditions including traumatic brain injury, stroke, multiple sclerosis, and Alzheimer's disease.

Human Microglia Respond to Malaria-Induced Extracellular Vesicles

Microglia are the chief immune cells of the brain and have been reported to be activated in severe malaria. Their activation may drive towards neuroinflammation in cerebral malaria. Malaria-infected red blood cell derived-extracellular vesicles (MiREVs) are produced during the blood stage of malaria infection. They mediate intercellular communication and immune regulation, among other functions. During cerebral malaria, the breakdown of the blood–brain barrier can promote the migration of substances such as MiREVs from the periphery into the brain, targeting cells such as microglia. Microglia and extracellular vesicle interactions in different pathological conditions have been reported to induce neuroinflammation. Unlike in astrocytes, microglia–extracellular vesicle interaction has not yet been described in malaria infection. Therefore, in this study, we aimed to investigate the uptake of MiREVs by human microglia cells and their cytokine response. Human blood monocyte-derived microglia (MoMi) were generated from buffy coats of anonymous healthy donors using Ficoll-Paque density gradient centrifugation. The MiREVs were isolated from the Plasmodium falciparum cultures. They were purified by ultracentrifugation and labeled with PKH67 green fluorescent dye. The internalization of MiREVs by MoMi was observed after 4 h of co-incubation on coverslips placed in a 24-well plate at 37 °C using confocal microscopy. Cytokine-gene expression was investigated using rt-qPCR, following the stimulation of the MoMi cells with supernatants from the parasite cultures at 2, 4, and 24 h, respectively. MiREVs were internalized by the microglia and accumulated in the perinuclear region. MiREVs-treated cells increased gene expression of the inflammatory cytokine TNFα and reduced gene expression of the immune suppressive IL-10. Overall, the results indicate that MiREVs may act on microglia, which would contribute to enhanced inflammation in cerebral malaria.

Bone marrow mesenchymal stem cell-derived exosome uptake and retrograde transport can occur at peripheral nerve endings

We investigated the occurrence of mesenchymal stem cell (MSC)-derived exosome uptake and retrograde transport at peripheral nerve endings using bone marrow MSCs (bMSCs) transduced with recombinant CD63-green fluorescent protein (GFP) lentiviral plasmid. GFP was used to track the release of bMSC-derived exosomes and the uptake and transport at peripheral nerve terminals, the dorsal root ganglion (DRG), and the spinal cord. In vitro cell culture and injection of a CD63-GFP exosome suspension into the right gastrocnemius muscle of an in vivo rat model were also performed. Fluorescence microscopy of co-cultured CD63-GFP exosomes and SH-SY5Y or BV2 cell lines and primary cultured DRG cells in a separate experiment demonstrated exosome uptake into DRG neurons and glia. Moreover, we observed both retrograde axoplasmic transport and hematogenous transport of exosomes injected into rat models at the DRG and the ipsilateral side of the anterior horn of the spinal cord using fluorescence microscopy, immunohistochemistry, and Western blot analyses. In conclusion, we showed that exosome uptake at peripheral nerve endings and retrograde transport of exosomes to DRG neurons and spinal cord motor neurons in the anterior horn can occur. In addition, our findings propose a novel drug delivery approach for treating neuronal diseases.

Effects of Pseudomonas aeruginosa on Microglial-Derived Extracellular Vesicle Biogenesis and Composition

The packaging of molecular constituents inside extracellular vesicles (EVs) allows them to participate in intercellular communication and the transfer of biological molecules, however the role of EVs during bacterial infection is poorly understood. The goal of this study was to examine the effects of Pseudomonas aeruginosa (P. aeruginosa) infection on the biogenesis and composition of EVs derived from the mouse microglia cell line, BV-2. BV-2 cells were cultured in exosome-free media and infected with 0, 1.3 × 10⁴, or 2.6 × 10⁴ colony forming units per milliliter P. aeruginosa for 72 h. The results indicated that compared with the control group, BV-2 cell viability significantly decreased after P. aeruginosa infection and BV-2-derived EVs concentration decreased significantly in the P. aeruginosa-infected group. P. aeruginosa infection significantly decreased chemokine ligand 4 messenger RNA in BV-2-derived infected EVs, compared with the control group (p ≤ 0.05). This study also revealed that heat shock protein 70 (p ≤ 0.05) and heat shock protein 90β (p ≤ 0.001) levels of expression within EVs increased after P. aeruginosa infection. EV treatment with EVs derived from P. aeruginosa infection reduced cell viability of BV-2 cells. P. aeruginosa infection alters the expression of specific proteins and mRNA in EVs. Our study suggests that P. aeruginosa infection modulates EV biogenesis and composition, which may influence bacterial pathogenesis and infection.

Exosome Production Is Key to Neuronal Endosomal Pathway Integrity in Neurodegenerative Diseases

Dysfunction of the endosomal–lysosomal system is a prominent pathogenic factor in Alzheimer’s disease (AD) and other neurodevelopmental and neurodegenerative disorders. We and others have extensively characterized the neuronal endosomal pathway pathology that results from either triplication of the amyloid-β precursor protein (APP) gene in Down syndrome (DS) or from expression of the apolipoprotein E ε4 allele (APOE4), the greatest genetic risk factor for late-onset AD. More recently brain exosomes, extracellular vesicles that are generated within and released from endosomal compartments, have been shown to be altered in DS and by APOE4 expression. In this review, we discuss the emerging data arguing for an interdependence between exosome production and endosomal pathway integrity in the brain. In vitro and in vivo studies indicate that altered trafficking through the endosomal pathway or compromised cargo turnover within lysosomes can affect the production, secretion, and content of exosomes. Conversely, exosome biogenesis can affect the endosomal–lysosomal system. Indeed, we propose that efficient exosome release helps to modulate flux through the neuronal endosomal pathway by decompressing potential “traffic jams.” Exosome secretion may have the added benefit of unburdening the neuron’s lysosomal system by delivering endosomal–lysosomal material into the extracellular space, where other cell types may contribute to the degradation of neuronal debris. Thus, maintaining robust neuronal exosome production may prevent or mitigate endosomal and lysosomal abnormalities linked to aging and neurodegenerative diseases. While the current evidence suggests that the exosomal system in the brain can be modulated both by membrane lipid composition and the expression of key proteins that contribute to the formation and secretion of exosomes, how exosomal pathway-regulatory elements sense and respond to perturbations in the endosomal pathway is not well understood. Based upon findings from the extensively studied DS and APOE4 models, we propose that enhanced neuronal exosome secretion can be a protective response, reducing pathological disruption of the endosomal–lysosomal system in disease-vulnerable neurons. Developing therapeutic approaches that help to maintain or enhance neuronal exosome biogenesis and release may be beneficial in a range of disorders of the central nervous system.

Exosomes in Cancer: Circulating Immune-Related Biomarkers

Exosomes, the smallest vesicles (30–100 nm) among multivesicular bodies, are released by all body cells including tumor cells. The cargo they transfer plays an important role in intercellular communication. Tumor-derived exosomes (TEXs) maintain interactions between cancer cells and the microenvironment. Emerging evidence suggests that tumor cells release a large number of exosomes, which may not only influence proximal tumor cells and stromal cells in the local microenvironment but can also exert systemic effects as they are circulating in the blood. TEXs have been shown to boost tumor growth promote progression and metastatic spread via suppression or modification of the immune response towards cancer cells, regulation of tumor neo-angiogenesis, pre-metastatic niche formation, and therapy resistance. In addition, recent studies in patients with cancer suggest that TEXs could serve as tumor biomarker reflecting partially the genetic and molecular content of the parent cancer cell (i.e., as a so-called “liquid biopsy”). Furthermore, recent studies have demonstrated that exosomes may have immunotherapeutic applications, or can act as a drug delivery system for targeted therapies with drugs and biomolecules.

Transmigration of Tetraspanin 2 (Tspan2) siRNA Via Microglia Derived Exosomes across the Blood Brain Barrier Modifies the Production of Immune Mediators by Microglia Cells

Microglia are implicated in the neuropathogenesis of HIV. Tetraspanin 2 (Tspan2) is closely related to CD9 and CD81 proteins, and are expressed on microglia cells. They have been implicated in cell fusion and adhesion and in the immune response, and neuroinflammation. Developing therapeutics that target microglia remains a challenge as these therapeutics must cross the Blood-Brain Barrier (BBB). Our goal was to use microglia derived exosomes as a vehicle to deliver siRNA across the BBB to target human telomerase reverse transcriptase immortalized human microglial cells (HTHU) latently infected by HIV (HTHU-HIV) and to evaluate if the knockdown of Tspan2 gene expression in changes the activation state of microglia cells, thereby modulating the neuroinflammatory response. A blood brain barrier (BBB) model that closely mimics and accurately reflects the characteristics and functional properties of the in vivo BBB was used to examine HTHU microglia exosome effects on BBB permeability, and their ability to migrate across the and delivery small interfering RNA (siRNA) to cells on the CNS side of the BBB model. Exosomes were loaded with Texas-Red control siRNA (20 pmol) or Cy5-Tspan2 siRNA and then placed in the apical side of the BBB model, 24 h after incubation, HTHU-HIV cells microglial cells on the lower chamber were either imaged for siRNA uptake or analyzed for gene expression induced modifications. HTHU exosomes transmigrate from the apical side of the BBB to deliver Texas-Red control siRNA or Cy5-Tspan2 siRNA to HTHU-HIV microglia cells on the CNS side of the BBB model. A dose dependent (5-40 pmol) increase in Cy5-Tspan2 uptake with a corresponding decrease in gene expression for Tspan2 occurred in HTHU-HIV microglia. A decrease in Tspan2 gene expression as a consequence of knockdown with Tspan2 siRNA at both 20 and 40 pmol concentrations resulted in a significant decrease in C-X-C motif chemokine 12 (CXCL12) and C-X-C chemokine receptor type 4 (CXCR4) gene expression in HTHU-HIV microglia. Furthermore, a decrease in the gene expression levels of the Interleukins, IL-13 and IL-10 and an increase in the gene expression levels for the Fc gamma receptor 2A(FCGR2A) and TNF-α occurred in HTHU-HIV microglial cells These data demonstrate that HTHU exosomes cross the BBB and are efficient delivery vehicles to the CNS. Moreover, modifying the expression levels of Tspan2, has downstream consequences that includes alterations in cytokines and microglia biomarkers. Graphical Abstract Microglia-derived exosomes loaded with Tspan2 siRNA transmigrate across the BBB and knockdown Tspan2 gene expression in human microglial cells latently infected by HIV. This knockdown increases CXCL12, CXCR4, FCGR2A and TNF-α while decreasing IL-13 and IL-10 gene expression in HTHU-HIV microglial cells. Modulating Tspan2 modulates microglia cytokines and phenotype biomarkers.

Decoding the Biology of Exosomes in Metastasis

Metastasis is the leading cause of cancer mortality. Cancer cells must adapt to colonize and thrive at the metastatic site. The modulation of the receptive organ microenvironment is a key event in the adaptation process and is partially accomplished at a distance by the primary tumor. Exosomes, a subclass of extracellular vesicles (EVs), are distal mediators of communication that carry genetic and molecular information to neighboring and distant cells. Cancer exosomes have been involved in restructuring metastatic sites to support cancer cell colonization. In this article, we discuss the role of exosomes in the metastatic process.

Theoretical Investigation of Perylene Diimide derivatives as Acceptors to Match with Benzodithiophene based Donors for Organic Photovoltaic Devices

Optoelectronic properties of PDI derivatives (PDI-1–PDI-28) have been studied by inserting functional groups (–CN, –NO2 and –SO2) at different positions, by using DFT and TD-DFT functional at CAM-B3LYP/6-31 (d) level of theory. Absorption spectra of investigated PDI derivatives cover whole UV-Visible region which indicate that studied molecules could be used efficiently for photovoltaics. The R*(λmax – λmin) value of PDI derivatives is red shifted due to CN substitution while it resulted in slightly blue shift due to NO2 substitution. In addition, reorganization energy (λ) values found to be lowered by all substituents but more efficiently by SO2 and CN substituents. Molecular electrostatic potential surfaces and chemical reactivity indices have also been calculated to verify results. Furthermore, investigated acceptor molecules have been matched with suitable donors (based on benzo [2.1-b:3.4-b′] dithiophene derivatives D1–D5) to verify their practical efficiency. The calculated open circuit voltage (Voc) of investigated PDI derivatives is fairly high with donors D1 (0.95–1.34) and D2 (0.54–0.92). This study can be beneficial in future investigations of donor-acceptor materials for organic photovoltaic devices.

Noninvasive Assessment of Exosome Pharmacokinetics In Vivo: A Review

Exosomes, intraluminal vesicles that contain informative DNA, RNA, proteins, and lipid membranes derived from the original donor cells, have recently been introduced to therapy and diagnosis. With their emergence as an alternative to cell therapy and having undergone clinical trials, proper analytical standards for evaluating their pharmacokinetics must now be established. Molecular imaging techniques such as fluorescence imaging, magnetic resonance imaging, and positron emission tomography (PET) are helpful to visualizing the absorption, distribution, metabolism, and excretion of exosomes. After exosomes labelled with a fluorescer or radioisotope are administered in vivo, they are differentially distributed according to the characteristics of each tissue or lesion, and real-time biodistribution of exosomes can be noninvasively monitored. Quantitative analysis of exosome concentration in biological fluid or tissue samples is also needed for the clinical application and industrialization of exosomes. In this review, we will discuss recent pharmacokinetic applications to exosomes, including labelling methods for in vivo imaging and analytical methods for quantifying exosomes, which will be helpful for evaluating pharmacokinetics of exosomes and improving exosome development and therapy.

Exosomes From Astrocyte Processes: Signaling to Neurons

It is widely recognized that extracellular vesicles subserve non-classical signal transmission in the central nervous system. Here we assess if the astrocyte processes, that are recognized to play crucial roles in intercellular communication at the synapses and in neuron-astrocyte networks, could convey messages through extracellular vesicles. Our findings indicate, for the first time that freshly isolated astrocyte processes prepared from adult rat cerebral cortex, can indeed participate to signal transmission in central nervous system by releasing exosomes that by volume transmission might target near or long-distance sites. It is noteworthy that the exosomes released from the astrocyte processes proved ability to selectively target neurons. The astrocyte-derived exosomes were proven positive for neuroglobin, a protein functioning as neuroprotectant against cell insult; the possibility that exosomes might transfer neuroglobin to neurons would add a mechanism to the potential astrocytic neuroprotectant activity. Notably, the exosomes released from the processes of astrocytes maintained markers, which prove their parental astrocytic origin. This potentially allows the assessment of the cellular origin of exosomes that might be recovered from body fluids.

The Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes in Treatment of Neurodegenerative Diseases

Neurologic complications are commonly regarded as irreversible impairments that stem from limited potential of regeneration of the central nervous system (CNS). On the other side, the regenerative potential of stem cells has been evaluated in basic research, as well as in preclinical studies. Mesenchymal stem cells (MSCs) have been regarded as candidate cell sources for therapeutic purposes of various neurological disorders, because of their self-renewal ability, plasticity in differentiation, neurotrophic characteristics, and immunomodulatory properties. Exosomes are extracellular vesicles which can deliver biological information over long distances and thereby influencing normal and abnormal processes in cells and tissues. The therapeutic capacity of exosomes relies on the type of cell, as well as on the physiological condition of a given cell. Therefore, based on tissue type and physiological condition of CNS, exosomes may function as contributors or suppressors of pathological conditions in this tissue. When it comes to the therapeutic viewpoint, the most promising cellular source of exosomes is considered to be MSCs. The aim of this review article is to discuss the current knowledge around the potential of stem cells and MSC-derived exosomes in the treatment of neurodegenerative diseases.

Extracellular Vesicles in Cancer Immune Microenvironment and Cancer Immunotherapy

Extracellular vesicles (EVs) are secreted by almost all cells. They contain proteins, lipids, and nucleic acids which are delivered from the parent cells to the recipient cells. Thereby, they function as mediators of intercellular communication and molecular transfer. Recent evidences suggest that exosomes, a small subset of EVs, are involved in numerous physiological and pathological processes and play essential roles in remodeling the tumor immune microenvironment even before the occurrence and metastasis of cancer. Exosomes derived from tumor cells and host cells mediate their mutual regulation locally or remotely, thereby determining the responsiveness of cancer therapies. As such, tumor-derived circulating exosomes are considered as noninvasive biomarkers for early detection and diagnosis of tumor. Exosome-based therapies are also emerging as cutting-edge and promising strategies that could be applied to suppress tumor progression or enhance anti-tumor immunity. Herein, the current understanding of exosomes and their key roles in modulating immune responses, as well as their potential therapeutic applications are outlined. The limitations of current studies are also presented and directions for future research are described.

The Role of Vesicle Trafficking and Release in Oligodendrocyte Biology

Oligodendrocytes are a subtype of glial cells found within the central nervous system (CNS), responsible for the formation and maintenance of specialized myelin membranes which wrap neuronal axons. The development of myelin requires tight coordination for the cell to deliver lipid and protein building blocks to specific myelin segments at the right time. Both internal and external cues control myelination, thus the reception of these signals also requires precise regulation. In late years, a growing body of evidence indicates that oligodendrocytes, like many other cell types, may use extracellular vesicles (EVs) as a medium for transferring information. The field of EV research has expanded rapidly over the past decade, with new contributions that suggest EVs might have direct involvement in communications with neurons and other glial cells to fine tune oligodendroglial function. This functional role of EVs might also be maladaptive, as it has likewise been implicated in the spreading of toxic molecules within the brain during disease. In this review we will discuss the field's current understanding of extracellular vesicle biology within oligodendrocytes, and their contribution to physiologic and pathologic conditions.

Systemic Immune Response to Traumatic CNS Injuries-Are Extracellular Vesicles the Missing Link?

Inflammation following traumatic injury to the central nervous system (CNS) persists long after the primary insult and is known to exacerbate cell death and worsen functional outcomes. Therapeutic interventions targeting this inflammation have been unsuccessful, which has been attributed to poor bioavailability owing to the presence of blood-CNS barrier. Recent studies have shown that the magnitude of the CNS inflammatory response is dependent on systemic inflammatory events. The acute phase response (APR) to CNS injury presents an alternative strategy to modulating the secondary phase of injury. However, the communication pathways between the CNS and the periphery remain poorly understood. Extracellular vesicles (EVs) are membrane bound nanoparticles that are regulators of intercellular communication. They are shed from cells of the CNS including microglia, astrocytes, neurons and endothelial cells, and are able to cross the blood-CNS barrier, thus providing an attractive candidate for initiating the APR after acute CNS injury. The purpose of this review is to summarize the current evidence that EVs play a critical role in the APR following CNS injuries.

Neurons can upregulate Cav-1 to increase intake of endothelial cells-derived extracellular vesicles that attenuate apoptosis via miR-1290

Extracellular vesicles (EVs) including exosomes can serve as mediators of cell–cell communication under physiological and pathological conditions. However, cargo molecules carried by EVs to exert their functions, as well as mechanisms for their regulated release and intake, have been poorly understood. In this study, we examined the effects of endothelial cells-derived EVs on neurons suffering from oxygen-glucose deprivation (OGD), which mimics neuronal ischemia-reperfusion injury in human diseases. In a human umbilical endothelial cell (HUVEC)–neuron coculture assay, we found that HUVECs reduced apoptosis of neurons under OGD, and this effect was compromised by GW4869, a blocker of exosome release. Purified EVs could be internalized by neurons and alleviate neuronal apoptosis under OGD. A miRNA, miR-1290, was highly enriched in HUVECs-derived EVs and was responsible for EV-mediated neuronal protection under OGD. Interestingly, we found that OGD enhanced intake of EVs by neurons cultured in vitro. We examined the expression of several potential receptors for EV intake and found that caveolin-1 (Cav-1) was upregulated in OGD-treated neurons and mice suffering from middle cerebral artery occlusion (MCAO). Knock-down of Cav-1 in neurons reduced EV intake, and canceled EV-mediated neuronal protection under OGD. HUVEC-derived EVs alleviated MCAO-induced neuronal apoptosis in vivo. These findings suggested that ischemia likely upregulates Cav-1 expression in neurons to increase EV intake, which protects neurons by attenuating apoptosis via miR-1290.

Immune cell modulation of oligodendrocyte lineage cells

Chronic demyelination and the concomitant loss of trophic support and increased energy demands in axons are thought to contribute to neurodegeneration in a number of neurological diseases such as multiple sclerosis (MS). Adult oligodendrocyte precursor cells (OPCs) play an important role in these demyelinating diseases by generating new myelinating oligodendrocytes that may help limit axonal degeneration. Thus, promoting the differentiation of OPCs and functional integration of newly generated oligodendrocytes is a crucial avenue for the next generation of therapies. Evidence to date suggests that the immune system may both positively and negatively impact OPC differentiation and endogenous remyelination in disease. Inflammatory cytokines not only suppress OPC differentiation but may also directly affect other functions of OPCs. Recent studies have demonstrated that OPCs and oligodendrocytes in both human multiple sclerosis lesions and mouse models of demyelination can express an immunogenic transcriptional signature and upregulate antigen presenting genes. In inflammatory demyelinating mouse models OPCs are capable of presenting antigen and activating CD8 + T cells. Here we review the evidence for this new role of oligodendroglia as antigen presenting cells and how these inflammatory OPCs (iOPCs) and inflammatory oligodendrocytes (iOLs) may influence myelin repair and other disease processes.

Neutrophil-Derived Microvesicle Induced Dysfunction of Brain Microvascular Endothelial Cells In Vitro

The blood-brain barrier (BBB), composed of brain microvascular endothelial cells (BMEC) that are tightly linked by tight junction (TJ) proteins, restricts the movement of molecules between the periphery and the central nervous system. Elevated systemic levels of neutrophils have been detected in patients with altered BBB function, but the role of neutrophils in BMEC dysfunction is unknown. Neutrophils are key players of the immune response and, when activated, produce neutrophil-derived microvesicles (NMV). NMV have been shown to impact the integrity of endothelial cells throughout the body and we hypothesize that NMV released from circulating neutrophils interact with BMEC and induce endothelial cell dysfunction. Therefore, the current study investigated the interaction of NMV with human BMEC and determined whether they altered gene expression and function in vitro. Using flow cytometry and confocal imaging, NMV were shown to be internalized by the human cerebral microvascular endothelial cell line hCMEC/D3 via a variety of energy-dependent mechanisms, including endocytosis and macropinocytosis. The internalization of NMV significantly altered the transcriptomic profile of hCMEC/D3, specifically inducing the dysregulation of genes associated with TJ, ubiquitin-mediated proteolysis and vesicular transport. Functional studies confirmed NMV significantly increased permeability and decreased the transendothelial electrical resistance (TEER) of a confluent monolayer of hCMEC/D3. These findings indicate that NMV interact with and affect gene expression of BMEC as well as impacting their integrity. We conclude that NMV may play an important role in modulating the permeability of BBB during an infection.

Glia-derived exosomes: Promising therapeutic targets

Glia is an important component of the nervous system that is involved in neurotransmitter uptake, signal transduction, myelin synthesis, neurodevelopment, and immune response. Exosomes are extracellular vesicles that are secreted from certain types of cells, and are known to mediate glia function. Glia-derived exosomes (GDEs) can transport proteins, nucleotides and cellular waste, and exert both protective and toxic effects on the nervous system. GDEs promote glia-neuron communication, anti-stress responses, anti-inflammation and neurite outgrowth, and may also be involved in neurological disease such as glioma, glioblastoma, Alzheimer's disease, Parkinson disease and neuronal HIV infections. This review summarizes the current research on GDEs and their functions, with emphasis on their therapeutic potential.

Exosomes and Ectosomes in Intercellular Communication

Exosomes and ectosomes, two distinct types of extracellular vesicles generated by all types of cell, play key roles in intercellular communication. The formation of these vesicles depends on local microdomains assembled in endocytic membranes for exosomes and in the plasma membrane for ectosomes. These microdomains govern the accumulation of proteins and various types of RNA associated with their cytosolic surface, followed by membrane budding inward for exosome precursors and outward for ectosomes. A fraction of endocytic cisternae filled with vesicles - multivesicular bodies - are later destined to undergo regulated exocytosis, leading to the extracellular release of exosomes. In contrast, the regulated release of ectosomes follows promptly after their generation. These two types of vesicle differ in size - 50-150 nm for exosomes and 100-500 nm for ectosomes - and in the mechanisms of assembly, composition, and regulation of release, albeit only partially. For both exosomes and ectosomes, the surface and luminal cargoes are heterogeneous when comparing vesicles released by different cell types or by single cells in different functional states. Upon release, the two types of vesicle navigate through extracellular fluid for varying times and distances. Subsequently, they interact with recognized target cells and undergo fusion with endocytic or plasma membranes, followed by integration of vesicle membranes into their fusion membranes and discharge of luminal cargoes into the cytosol, resulting in changes to cellular physiology. After fusion, exosome/ectosome components can be reassembled in new vesicles that are then recycled to other cells, activating effector networks. Extracellular vesicles also play critical roles in brain and heart diseases and in cancer, and are useful as biomarkers and in the development of innovative therapeutic approaches.

Extracellular miRNAs: From Biomarkers to Mediators of Physiology and Disease

miRNAs can be found in serum and other body fluids and serve as biomarkers for disease. More importantly, secreted miRNAs, especially those in extracellular vesicles (EVs) such as exosomes, may mediate paracrine and endocrine communication between different tissues and thus modulate gene expression and the function of distal cells. When impaired, these processes can lead to tissue dysfunction, aging, and disease. Adipose tissue is an especially important contributor to the pool of circulating exosomal miRNAs. As a result, alterations in adipose tissue mass or function, which occur in many metabolic conditions, can lead to changes in circulating miRNAs, which then function systemically. Here we review the findings that led to these conclusions and discuss how this sets the stage for new lines of investigation in which extracellular miRNAs are recognized as important mediators of intercellular communication and potential candidates for therapy of disease.

Exosomes: Revisiting their role as "garbage bags"

In recent years, the term "extracellular vesicle" (EV) has been used to define different types of vesicles released by various cells. It includes plasma membrane-derived vesicles (ectosomes/microvesicles) and endosome-derived vesicles (exosomes). Although it remains difficult to evaluate the compartment of origin of the two kinds of vesicles once released, it is critical to discriminate these vesicles because their mode of biogenesis is probably directly related to their physiologic function and/or to the physio-pathologic state of the producing cell. The purpose of this review is to specifically consider exosome secretion and its consequences in terms of a material loss for producing cells, rather than on the effects of exosomes once they are taken up by recipient cells. I especially describe one putative basic function of exosomes, that is, to convey material out of cells for off-site degradation by recipient cells. As illustrated by some examples, these components could be evacuated from cells for various reasons, for example, to promote "differentiation" or enhance homeostatic responses. This basic function might explain why so many diseases have made use of the exosomal pathway during pathogenesis.

Characteristics and roles of extracellular vesicles released by epidermal keratinocytes

Keratinocytes, which constitute 90% of the cells in the epidermis of the skin, have been demonstrated to communicate with other skin cells such as fibroblasts, melanocytes and immune cells through extracellular vesicles (EVs). This communication is facilitated by the enriched EV biomolecular cargo which regulates multiple biological processes within skin tissue, including cell proliferation, cell migration, anti-apoptosis, pigmentation transfer and extracellular matrix remodelling. This review will provide an overview of the current literature and advances in the field of keratinocyte-derived EV research with particular regard to the interactions and communication between keratinocytes and other skin cells, mediated by EVs and EV components. Importantly, this information may shed some light on the potential for keratinocyte-derived EVs in future biomedical studies.

Neonatal Subventricular Zone Neural Stem Cells Release Extracellular Vesicles that Act as a Microglial Morphogen

Subventricular zone (SVZ) neural stem cells (NSCs) are the cornerstone of the perinatal neurogenic niche. Microglia are immune cells of the nervous system that are enriched in the neonatal SVZ. Although microglia regulate NSCs, the extent to which this interaction is bi-directional is unclear. Extracellular vesicles (EVs) are cell-derived particles that encase miRNA and proteins. Here, we demonstrate that SVZ NSCs generate and release EVs. Neonatal electroporated fluorescent EV fusion proteins were released by NSCs and subsequently cleared from the SVZ. EVs were preferentially targeted to microglia. Small RNA sequencing identified miRNAs within the EVs that regulate microglia physiology and morphology. EVs induced a transition to a CD11b/Iba1 non-stellate microglial morphology. The transition accompanied a microglial transcriptional state characterized by Let-7-regulated cytokine release and a negative feedback loop that controlled NSC proliferation. These findings implicate an NSC-EV-microglia axis and provide insight to normal and pathophysiological brain development.

The Role of Extracellular Vesicles in Viral Infection and Transmission

Extracellular vesicles (EVs) have been found to be released by any type of cell and can be retrieved in every circulating body fluid, namely blood (plasma, serum), saliva, milk, and urine. EVs were initially considered a cellular garbage disposal tool, but later it became evident that they are involved in intercellular signaling. There is evidence that viruses can use EV endocytic routes to enter uninfected cells and hijack the EV secretory pathway to exit infected cells, thus illustrating that EVs and viruses share common cell entry and biogenesis mechanisms. Moreover, EVs play a role in immune response against viral pathogens. EVs incorporate and spread both viral and host factors, thereby prompting or inhibiting immune responses towards them via a multiplicity of mechanisms. The involvement of EVs in immune responses, and their potential use as agents modulating viral infection, will be examined. Although further studies are needed, the engineering of EVs could package viral elements or host factors selected for their immunostimulatory properties, to be used as vaccines or tolerogenic tools in autoimmune diseases.

The multiple roles of exosomes in Parkinson's disease: an overview

The extracellular vesicles (EVs) represent a relatively new field of research in neurodegenerative disease and they are thought to be one of the ways that neurodegenerative pathologies, such as Parkinson's Disease (PD), spread in the brain. EVs are membrane vesicles released from cells into the extracellular space and they are produced by all cells of the nervous tissue. The classification of the vesicle subtypes comprises exosomes, microvesicles/microparticles, apoptotic bodies. EVs change in number and content in response to environmental conditions and may function as shuttles for the delivery of cargo between cells. Recent data suggest that exosomes secreted by both activated microglia and neurons play an important role in α-synuclein (α-syn) spreading and increase of neuroinflammation, thus exacerbating neuronal dysfunction and disease progression. α-syn is a presynaptic protein secreted by neurons in small amounts, and it is the main component of Lewy bodies, one of the histopathological features of PD. Several factors have shown to induce and/or modulate α-syn structure and oligomerization in vitro. Under pathological conditions, progressive accumulation of α-syn and the formation of oligomers have been proposed to play a critical role in the pathogenesis of PD. This review gives an overview about the multiple roles of exosomes in PD, despite their role in the progression of neurodegeneration, exosomes could represent a specific drug delivery tool for a difficult target such as the brain, which poses an obstacle to most drugs and they could also represent new biomarkers to track the progression of PD.

Heterologous and cross-species tropism of cancer-derived extracellular vesicles

Extracellular vesicles (EVs) are naturally occurring cargo delivery vesicles that have recently received considerable attention for their roles in intercellular communication in many physiological and pathological processes, including tumourigenesis. EVs generated by different tissues demonstrated specific homing: in particular, cancer-derived EVs showed a selective tropism for the tumor tissue from which the vesicles originated. For this property, EVs have been proposed as drug delivery tools for anti-cancer therapies, although the limited knowledge about their in vivo tropism hinders their therapeutic applications. The current study aimed to characterize the targeting properties of cancer-derived EVs in vitro and their biodistribution in vivo, by using an imaging approach. Methods: EVs were generated from: i) murine lung (LL/2) and colon (MC-38) cancer lines, ii) human lung cancer cell line (A549) and iii) human liver biopsy samples from healthy individuals. EVs were loaded with fluorescent dyes alone or in combination with a biopharmaceutical agent, the oncolytic adenovirus (OV), characterized for charge and size and tested for their activity in cancer cell lines. Finally, optical imaging was extensively applied to study in vivo and ex vivo the biodistribution of EVs originated from different sources in different mouse models of cancer, including xenograft, syngeneic graft and the MMTV-NeuT genetically modified animal. Results: We initially demonstrated that even loading EVs even with a large biopharmaceutical oncolytic viruses (OVs) did not significantly change their charge and dimension properties, while increasing their anti-neoplastic activity compared to the virus or EVs alone. Interestingly, this activity was observed even if the EVs derived from lung cancer were applied to colon carcinoma cell lines and vice versa, suggesting that the EV uptake occurred in vitro without any specificity for the cancer cells from which the vesicles originated. When administered i.v (intravenously) to the mouse models of cancer, the tumour-derived EVs, but not the EVs derived from a healthy tissue, demonstrated a selective accumulation of the fluorescence at the tumour site 24 h after injection; adding OVs to the formulation did not change the tumour-specific tropism of the EVs also in vivo. Most interestingly, the in vivo experiments confirmed the in vitro observation of the generalized tropism of tumour-derived EVs for any neoplastic tissue, independent of the tumour type or even the species originating the vesicles. Conclusions: Taken together, our in vitro and in vivo data demonstrate for the first time a heterologous, cross-species tumour-tropism for cancer-derived EVs. This finding challenges our current view on the homing properties of EVs and opens new avenues for the selective delivery of diagnostic/therapeutic agents to solid tumours.

A pleiotropic role for exosomes loaded with the amyloid β precursor protein carboxyl-terminal fragments in the brain of Down syndrome patients

Down syndrome (DS) is characterized by cognitive deficits throughout the life span and with the development of aging-dependent Alzheimer's type neuropathology, which is related to the triplication of the amyloid β precursor protein (APP) gene. A dysfunctional endosomal system in neurons is an early characteristic of DS and APP metabolites accumulate in endosomes in DS neurons. We have previously shown enhanced release of exosomes in the brain of DS patients and the mouse model of DS Ts[Rb(12.17¹⁶)]2Cje (Ts2), and by DS fibroblasts, as compared with diploid controls. Here, we demonstrate that exosome-enriched extracellular vesicles (hereafter called EVs) isolated from DS and Ts2 brains, and from the culture media of human DS fibroblasts are enriched in APP carboxyl-terminal fragments (APP-CTFs) as compared with diploid controls. Moreover, APP-CTFs levels increase in an age-dependent manner in EVs isolated from the brain of Ts2 mice. The release of APP-CTFs-enriched exosomes may have a pathogenic role by transporting APP-CTFs into naïve neurons and propagating these neurotoxic metabolites, which are also a source of amyloid β, throughout the brain, but also provides a benefit to DS neurons by shedding APP-CTFs accumulated intracellularly.

Mesenchymal stromal cell-derived nanovesicles ameliorate bacterial outer membrane vesicle-induced sepsis via IL-10

Background

Sepsis remains a source of high mortality in hospitalized patients despite proper antibiotic approaches. Encouragingly, mesenchymal stromal cells (MSCs) and their produced extracellular vesicles (EVs) have been shown to elicit anti-inflammatory effects in multiple inflammatory conditions including sepsis. However, EVs are generally released from mammalian cells in relatively low amounts, and high-yield isolation of EVs is still challenging due to a complicated procedure. To get over these limitations, vesicles very similar to EVs can be produced by serial extrusions of cells, after which they are called nanovesicles (NVs). We hypothesized that MSC-derived NVs can attenuate the cytokine storm induced by bacterial outer membrane vesicles (OMVs) in mice, and we aimed to elucidate the mechanism involved.

Methods

NVs were produced from MSCs by the breakdown of cells through serial extrusions and were subsequently floated in a density gradient. Morphology and the number of NVs were analyzed by transmission electron microscopy and nanoparticle tracking analysis. Mice were intraperitoneally injected with Escherichia coli-derived OMVs to establish sepsis, and then injected with 2 × 10⁹ NVs. Innate inflammation was assessed in peritoneal fluid and blood through investigation of infiltration of cells and cytokine production. The biodistribution of NVs labeled with Cy7 dye was analyzed using near-infrared imaging.

Results

Electron microscopy showed that NVs have a nanometer-size spherical shape and harbor classical EV marker proteins. In mice, NVs inhibited eye exudates and hypothermia, signs of a systemic cytokine storm, induced by intraperitoneal injection of OMVs. Moreover, NVs significantly suppressed cytokine release into the systemic circulation, as well as neutrophil and monocyte infiltration in the peritoneum. The protective effect of NVs was significantly reduced by prior treatment with anti-interleukin (IL)-10 monoclonal antibody. In biodistribution study, NVs spread to the whole mouse body and localized in the lung, liver, and kidney at 6 h.

Conclusions

Taken together, these data indicate that MSC-derived NVs have beneficial effects in a mouse model of sepsis by upregulating the IL-10 production, suggesting that artificial NVs may be novel EV-mimetics clinically applicable to septic patients.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1352-4) contains supplementary material, which is available to authorized users.

Development of a quantitative method to measure EV uptake

The outstanding potential of Extracellular Vesicles (EVs) in medicine, deserves a detailed study of the molecular aspects regulating their incorporation into target cells. However, because EV size lies below the limit of resolution of optical techniques, quantification together with discrimination between EV binding to the target cell and uptake is usually not completely achieved with current techniques. Human tetraspanins CD9 and CD63 were fused to a dual EGFP-Renilla-split tag. Subcellular localization and incorporation of these fusion proteins into EVs was assessed by western-blot and fluorescence microscopy. EV binding and uptake was measured using either a classical Renilla substrate or a cytopermeable one. Incubation of target cells expressing DSP2 with EVs containing the complementary DSP1 portion could not recover fluorescence or luciferase activity. However, using EVs carrying the fully reconstituted Dual-EGFP-Renilla protein and the cytopermeable Renilla luciferase substrate, we could distinguish EV binding from uptake. We provide proof of concept of the system by analysing the effect of different chemical inhibitors, demonstrating that this method is highly sensitive and quantitative, allowing a dynamic follow-up in a high-throughput scheme to unravel the molecular mechanisms of EV uptake in different biological systems.

α-Synuclein Trafficking in Parkinson's Disease: Insights From Fly and Mouse Models

Protein aggregation and accumulation are common pathological hallmarks in neurodegenerative diseases. To efficiently clear and eliminate such aggregation becomes an important cellular strategy for cell survival. Lewy bodies inclusion and aggregation of α-Synuclein (α-Syn) during the pathogenesis of Parkinson's disease (PD) serve as a good example and are potentially linked to other pathological PD features such as progressive dopaminergic neuron cell death, behavioral defects, and nonmotor symptoms like anosmia, cognitive impairment, and depression. Years of research have revealed a variety of mechanisms underlying α-Syn aggregation, clearance, and spread. Particularly, vesicular routes associated with the trafficking of α-Syn, leading to its aggregation and accumulation, have been shown to play vital roles in PD pathogenesis. How α-Syn proteins propagate among cells in a prion-like manner, either from or to neurons and glia, via means of uptake or secretion, are questions under active investigation and have been of central interest in the field of PD study. This review covers components and pathways of possible vesicular routes involved in α-Syn trafficking. Events including but not limited to exocytosis and endocytosis will be discussed within the context of an overall cellular trafficking theme. Recent advances on α-Syn trafficking mechanisms and their significance in mediating PD pathogenesis will be thoroughly reviewed, ending with a discussion on the advantages and limitations of different animal PD models.

Extracellular RNA in viral-host interactions: Thinking outside the cell

Small RNAs and their associated RNA interference (RNAi) pathways underpin diverse mechanisms of gene regulation and genome defense across all three kingdoms of life and are integral to virus-host interactions. In plants, fungi and many animals, an ancestral RNAi pathway exists as a host defense mechanism whereby viral double-stranded RNA is processed to small RNAs that enable recognition and degradation of the virus. While this antiviral RNAi pathway is not generally thought to be present in mammals, other RNAi mechanisms can influence infection through both viral- and host-derived small RNAs. Furthermore, a burgeoning body of data suggests that small RNAs in mammals can function in a non-cell autonomous manner to play various roles in cell-to-cell communication and disease through their transport in extracellular vesicles. While vesicular small RNAs have not been proposed as an antiviral defense pathway per se, there is increasing evidence that the export of host- or viral-derived RNAs from infected cells can influence various aspects of the infection process. This review discusses the current knowledge of extracellular RNA functions in viral infection and the technical challenges surrounding this field of research. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA in Disease and Development > RNA in Disease Regulatory RNAs/RNAi/Riboswitches > RNAi: Mechanisms of Action.

Mesenchymal stem cell exosomes as a cell-free therapy for nerve injury-induced pain in rats

Nerve injury-induced neuropathic pain is difficult to treat. In this study, we used exosomes derived from human umbilical cord mesenchymal stem cell (UCMSC) as a cell-free therapy for nerve injury-induced pain in rats. Isolated UCMSC exosomes range in size from 30 to 160 nm and contain CD63, HSP60, and CD81 exosome markers. After L5/6 spinal nerve ligation surgery, single intrathecal injection of exosomes reversed nerve ligation-induced mechanical and thermal hypersensitivities of right hindpaw of rats at initial and well-developed pain stages. Moreover, continuous intrathecal infusion of exosomes achieved excellent preventive and reversal effects for nerve ligation-induced pain. In immunofluorescent study, lots of Exo-green-labelled exosomes could be found majorly in the ipsilateral L5 spinal dorsal horn, dorsal root ganglion, and peripheral axons, suggesting the homing ability of UCMSC exosomes. They also appeared in the central terminals or cell bodies of IB4, CGRP, and NF200 sensory neurons. In addition, exosome treatment suppressed nerve ligation-induced upregulation of c-Fos, CNPase, GFAP, and Iba1. All these data suggest that the analgesic effects of exosomes may involve their actions on neuron and glial cells. Exosomes also inhibited the level of TNF-α and IL-1β, while enhanced the level of IL-10, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in the ipsilateral L5/6 dorsal root ganglion of nerve-ligated rats, indicating anti-inflammatory and proneurotrophic abilities. Protein analysis revealed the content of vascular endothelial growth factor C, angiopoietin-2, and fibroblast growth factor-2 in the exosomes. In summary, intrathecal infusion of exosomes from UCMSCs may be considered as a novel therapeutic approach for nerve injury-induced pain.

Emerging roles of extracellular vesicles in neurodegenerative disorders

Extracellular vesicles (EVs) are heterogeneous cell-derived membranous vesicles which carry a large diversity of molecules such as proteins and RNA species. They are now considered to be a general mode of intercellular communication by direct transfer of biomolecules. Emerging evidence demonstrates that EVs are involved in multiple pathological processes of brain diseases including neurodegenerative disorders. In this review, we investigate the current knowledge about EV biology. We also provide an overview of the roles of EVs in related brain diseases, particularly in neurodegenerative disorders. Finally, we discuss their potential applications as novel biomarkers as well as the developments of EV-based therapies.

Alcohol Modulates the Biogenesis and Composition of Microglia-Derived Exosomes

Exosomes are small extracellular vesicles that have emerged as an important tool for intercellular communication. In the central nervous system, exosomes can mediate glia and neuronal communication. Once released from the donor cell, exosomes can act as discrete vesicles and travel to distant and proximal recipient cells to alter cellular function. Microglia cells secrete exosomes due to stress stimuli of alcohol abuse. The goal of this study was to investigate the effects of alcohol exposure on the biogenesis and composition of exosomes derived from microglia cell line BV-2. The BV-2 cells were cultured in exosome-free media and were either mock treated (control) or treated with 50 mM or 100 mM of alcohol for 48 and 72 h. Our results demonstrated that alcohol significantly impacted BV-2 cell morphology, viability, and protein content. Most importantly, our studies revealed that exosome biogenesis and composition was affected by alcohol treatment.

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.