Selective transfer of exosomes from oligodendrocytes to microglia by macropinocytosis

Role of Extracellular Vesicle-Based Cell-to-Cell Communication in Multiple Myeloma Progression

Multiple myeloma (MM) progression closely depends on the bidirectional crosstalk between tumor cells and the surrounding microenvironment, which leads to the creation of a tumor supportive niche. Extracellular vesicles (EVs) have emerged as key players in the pathological interplay between the malignant clone and near/distal bone marrow (BM) cells through their biologically active cargo. Here, we describe the role of EVs derived from MM and BM cells in reprogramming the tumor microenvironment and in fostering bone disease, angiogenesis, immunosuppression, drug resistance, and, ultimately, tumor progression. We also examine the emerging role of EVs as new therapeutic agents for the treatment of MM, and their potential use as clinical biomarkers for early diagnosis, disease classification, and therapy monitoring.

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

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

Effects of exosomal miRNAs in the diagnosis and treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Exosomes are extracellular vesicles secreted by a variety of cells, and they participate in intercellular communication by transferring microRNA (miRNA) and other substances. Among the various internal and external factors involved in the occurrence and development of AD, exosome-derived miRNAs have become essential in the pathogenesis and treatment of AD. As nanocarriers of miRNA, exosomes are expected to become an important tool in the pathogenesis, diagnosis, and treatment of AD. This article reviews the roles of exosomal miRNAs in the pathophysiological process, diagnostic biomarkers and treatment of AD.

Mitochondrial Extracellular Vesicles - Origins and Roles

Extracellular vesicles (EVs) have emerged in the last decade as critical cell-to-cell communication devices used to carry nucleic acids and proteins between cells. EV cargo includes plasma membrane and endosomal proteins, but EVs also contain material from other cellular compartments, including mitochondria. Within cells, mitochondria are responsible for a large range of metabolic reactions, but they can also produce damaging levels of reactive oxygen species and induce inflammation when damaged. Consistent with this, recent evidence suggests that EV-mediated transfer of mitochondrial content alters metabolic and inflammatory responses of recipient cells. As EV mitochondrial content is also altered in some pathologies, this could have important implications for their diagnosis and treatment. In this review, we will discuss the nature and roles of mitochondrial EVs, with a special emphasis on the nervous system.

Formation, contents, functions of exosomes and their potential in lung cancer diagnostics and therapeutics

Lung cancer is the leading cause of cancer-related death worldwide due to diagnosis in the advanced stage and drug resistance in the subsequent treatments. Development of novel diagnostic and therapeutic methods is urged to improve the disease outcome. Exosomes are nano-sized vehicles which transport different types of biomolecules intercellularly, including DNA, RNA and proteins, and are implicated in cross-talk between cells and their surrounding microenvironment. Tumor-derived exosomes (TEXs) have been revealed to strongly influence the tumor microenvironment, antitumor immunoregulatory activities, tumor progression and metastasis. Potential of TEXs as biomarkers for lung cancer diagnosis, prognosis and treatment prediction is supported by numerous studies. Moreover, exosomes have been proposed to be promising drug carriers. Here, we review the mechanisms of exosomal formation and uptake, the functions of exosomes in carcinogenesis, and potential clinical utility of exosomes as biomarkers, tumor vaccine and drug delivery vehicles in the diagnosis and therapeutics of lung cancer.

Effects of oral milk extracellular vesicles on the gut microbiome and serum metabolome in mice

Milk extracellular vesicles (EVs) are rich in abundant bioactive macromolecules, such as glycoconjugates, proteins, lipids and nucleic acids, and these vesicles might transmit signals to human consumers. However, it remains to be determined whether milk EVs import new pathogens to humans or are beneficial for human health. Here, C57BL/6 female and male mice were randomly divided into 4 EV dose levels (0, 1.5 × 10⁹ p g^-1, 1.0 × 10¹⁰ p g^-1 and 1.5 × 10¹⁰ p g^-1). Based on the alterations in body weight, the control group (0 p g^-1, PBS) and the middle treatment group (1.0 × 10¹⁰ p g^-1) were chosen for further analysis of the effects of EVs on the gut microbiota and blood metabolites in mice, by 16S rRNA gene sequencing and untargeted metabolomics, respectively. We found that milk EVs increased the abundance of "beneficial" microbes such as Akkermansia, Muribaculum and Turicibacter, while decreased the level of "harmful" bacteria Desulfovibrio. Serum metabolites showed that EVs mainly changed the lipid and amino acid metabolism, and especially increased several serum anti-inflammatory factors, which might be beneficial for inflammation and other metabolic diseases. The results of KEGG analysis suggested that the enriched pathways were the intestinal immune network for IgA production, retinol metabolism, and D-glutamine and D-glutamate metabolism. Taken together, the positive effect of milk EVs on serum nutrient metabolism without promoting "harmful" bacterial colonization in female and male mice may indicate that they are safe bioactive molecules, and some of the changes they induce may provide protection against certain diseases.

Role of Extracellular Vesicle-Derived Biomarkers in Drug Metabolism and Disposition

Extracellular vesicles (EVs) are small, nonreplicating, lipid-encapsulated particles that contain a myriad of protein and nucleic acid cargo derived from their tissue of origin. The potential role of EV-derived biomarkers to the study of drug metabolism and disposition (DMD) has gained attention in recent years. The key trait that makes EVs an attractive biomarker source is their capacity to provide comparable insights to solid organ biopsy through an appreciably less invasive collection procedure. Blood-derived EVs exist as a heterogenous milieu of biologically distinct particles originating from different sources through different biogenesis pathways. Furthermore, blood (plasma and serum) contains an array of vesicular and nonvesicular contaminants, such as apoptotic bodies, plasma proteins, and lipoproteins that are routinely coisolated with EVs, albeit to a different extent depending on the isolation technique. The following minireview summarizes current studies reporting DMD biomarkers and addresses elements of EV isolation and quantification relevant to the application of EV-derived DMD biomarkers. Evidence based-best practice guidance aligned to Minimum Information for the Study of Extracellular Vesicles and EV-TRACK reporting standards are summarized in the context of DMD studies. SIGNIFICANCE STATEMENT: Extracellular vesicle (EV)-derived protein and nucleic acid cargo represent a potentially game-changing source of novel DMD biomarkers with the capacity to define within- and between-individual variability in drug exposure irrespective of etiology. However, robust translation of EV-derived biomarkers requires the generation of transparent reproducible evidence. This review outlines the critical elements of data generation and reporting relevant to achieving this evidence in a drug metabolism and disposition context.

Exosomes in Ageing and Motor Neurone Disease: Biogenesis, Uptake Mechanisms, Modifications in Disease and Uses in the Development of Biomarkers and Therapeutics

Intercellular communication between neurons and their surrounding cells occurs through the secretion of soluble molecules or release of vesicles such as exosomes into the extracellular space, participating in brain homeostasis. Under neuro-degenerative conditions associated with ageing, such as amyotrophic lateral sclerosis (ALS), Alzheimer's or Parkinson's disease, exosomes are suspected to propagate toxic proteins. The topic of this review is the role of exosomes in ageing conditions and more specifically in ALS. Our current understanding of exosomes and exosome-related mechanisms is first summarized in a general sense, including their biogenesis and secretion, heterogeneity, cellular interaction and intracellular fate. Their role in the Central Nervous System (CNS) and ageing of the neuromotor system is then considered in the context of exosome-induced signaling. The review then focuses on exosomes in age-associated neurodegenerative disease. The role of exosomes in ALS is highlighted, and their use as potential biomarkers to diagnose and prognose ALS is presented. The therapeutic implications of exosomes for ALS are considered, whether as delivery vehicles, neurotoxic targets or as corrective drugs in and of themselves. A diverse set of mechanisms underpin the functional roles, both confirmed and potential, of exosomes, generally in ageing and specifically in motor neurone disease. Aspects of their contents, biogenesis, uptake and modifications offer many plausible routes towards the development of novel biomarkers and therapeutics.

Inhibition of neutral sphingomyelinase 2 reduces extracellular vesicle release from neurons, oligodendrocytes, and activated microglial cells following acute brain injury

Extracellular Vesicles (EVs) are implicated in the spread of pathogenic proteinsin a growing number of neurological diseases. Given this, there is rising interest in developing inhibitors of Neutral Sphingomyelinase 2 (nSMase2), an enzyme critical in EV biogenesis. Our group recently discovered phenyl(R)-(1-(3-(3,4-dimethoxyphenyl)-2,6-dimethylimidazo[1,2-b]pyridazin-8-yl)pyrrolidin-3-yl)carbamate (PDDC), the first potent, selective, orally-available, and brain-penetrable nSMase2 inhibitor, capable of dose-dependently reducing EVs release in vitro and in vivo. Herein, using multiplexed Surface Plasmon Resonance imaging (SPRi), we evaluated which brain cell-derived EVs were affected by PDDC following acute brain injury. Mice were fed PDDC-containing chow at doses which gave steady PDDC brain exposures exceeding its nSMase2 IC₅₀. Mice were then administered an intra-striatal IL-1β injection and two hours later plasma and brain were collected. IL-1β injection significantly increased striatal nSMase2 activity which was completely normalized by PDDC. Using SPRi, we found that IL-1β-induced injury selectively increased plasma levels of CD171 + and PLP1 + EVs; this EV increase was normalized by PDDC. In contrast, GLAST1 + EVs were unchanged by IL-1β or PDDC. IL-1β injection selectively increased EVs released from activated versus non-activated microglia, indicated by the CD11b+/IB4 + ratio. The increase in EVs from CD11b + microglia was dramatically attenuated with PDDC. Taken together, our data demonstrate that following acute injury, brain nSMase2 activity is elevated. EVs released from neurons, oligodendrocytes, and activated microglial are increased in plasma and inhibition of nSMase2 with PDDC reduced these IL-1β-induced changes implicating nSMase2 inhibition as a therapeutic target for acute brain injury.

DAL-1/4.1B promotes the uptake of exosomes in lung cancer cells via Heparan Sulfate Proteoglycan 2 (HSPG2)

DAL-1/4.1B is frequently absent in lung cancer tissues, which is significantly related to the occurrence and development of lung cancer. In this research, we found that DAL-1/4.1B affected the uptake of exosomes by lung cancer cells. When the expression of DAL-1/4.1B increased and decreased, the ability of exosome uptake enhanced and attenuated correspondingly. And we found that when cells were treated with different vesicles uptake inhibitors (chlorpromazine, methyl-β-cyclodextrin (MβCD), cytochalasin D, chloroquine and heparin) and heparinase (HSPE), only heparin and HSPE counteracted the uptake enhancement effect caused by DAL-1/4.1B. Therefore, we speculated that DAL-1/4.1B might promote the uptake of exosomes through the heparan sulfate proteoglycans (HSPGs) pathway. After screening the expression of HSPGs and HSPE in H292 cells, the expression of heparan sulfate proteoglycan 2 (HSPG2) increased with overexpression of DAL-1/4.1B and decreased with knockdown of DAL-1/4.1B. Meanwhile, exosome uptake decreased with HSPG2 knockdown in H292 and DAL-1/4.1B-overexpressing H292 cells. Moreover, knockdown of DAL-1/4.1B and HSPG2 in lung cancer A549 cells resulted in a similar decrease in exosome uptake, and the expression of HSPG2 was also decreased with DAL-1/4.1B knockdown. These results indicated that HSPG2 directly affected the uptake of exosomes, while DAL-1/4.1B positively affected the expression of HSPG2. Therefore, DAL-1/4.1B may promote cellular adhesion and inhibit migration in cancer cells.

Extracellular Vesicles in Bone Tumors: How to Seed in the Surroundings Molecular Information for Malignant Transformation and Progression

Bone is a very dynamic tissue hosting different cell types whose functions are regulated by a plethora of membrane-bound and soluble molecules. Intercellular communication was recently demonstrated to be also sustained by the exchange of extracellular vesicles (EVs). These are cell-derived nanosized structures shuttling biologically active molecules, such as nucleic acids and proteins. The bone microenvironment is a preferential site of primary and metastatic tumors, in which cancer cells find a fertile soil to “seed and blossom”. Nowadays, many oncogenic processes are recognized to be sustained by EVs. For example, EVs can directly fuel the vicious cycle in the bone/bone marrow microenvironment. EVs create a favourable environment for tumor growth by affecting osteoblasts, osteoclasts, osteocytes, adipocytes, leukocytes, and endothelial cells. At the same time other crucial tumor-mediated events, such as the premetastatic niche formation, tumor cell dormancy, as well as drug resistance, have been described to be fostered by tumor-derived EVs. In this review, we will discuss the main body of literature describing how the cancer cells use the EVs for their growth into the bone and for educating the bone microenvironment to host metastases.

Therapeutic Drugs and Devices for Tackling Ocular Hypertension and Glaucoma, and Need for Neuroprotection and Cytoprotective Therapies

Damage to the optic nerve and the death of associated retinal ganglion cells (RGCs) by elevated intraocular pressure (IOP), also known as glaucoma, is responsible for visual impairment and blindness in millions of people worldwide. The ocular hypertension (OHT) and the deleterious mechanical forces it exerts at the back of the eye, at the level of the optic nerve head/optic disc and lamina cribosa, is the only modifiable risk factor associated with glaucoma that can be treated. The elevated IOP occurs due to the inability of accumulated aqueous humor (AQH) to egress from the anterior chamber of the eye due to occlusion of the major outflow pathway, the trabecular meshwork (TM) and Schlemm’s canal (SC). Several different classes of pharmaceutical agents, surgical techniques and implantable devices have been developed to lower and control IOP. First-line drugs to promote AQH outflow via the uveoscleral outflow pathway include FP-receptor prostaglandin (PG) agonists (e.g., latanoprost, travoprost and tafluprost) and a novel non-PG EP2-receptor agonist (omidenepag isopropyl, Eybelis^®). TM/SC outflow enhancing drugs are also effective ocular hypotensive agents (e.g., rho kinase inhibitors like ripasudil and netarsudil; and latanoprostene bunod, a conjugate of a nitric oxide donor and latanoprost). One of the most effective anterior chamber AQH microshunt devices is the Preserflo^® microshunt which can lower IOP down to 10–13 mmHg. Other IOP-lowering drugs and devices on the horizon will be also discussed. Additionally, since elevated IOP is only one of many risk factors for development of glaucomatous optic neuropathy, a treatise of the role of inflammatory neurodegeneration of the optic nerve and retinal ganglion cells and appropriate neuroprotective strategies to mitigate this disease will also be reviewed and discussed.

Azurocidin is loaded into small extracellular vesicles via its N-linked glycosylation and promotes intravasation of renal cell carcinoma cells

Azurocidin (AZU1) is an antimicrobial protein secreted by neutrophils that acts as a chemoattractant for monocytes and macrophages and a permeabilizer of vascular endothelial cells. We previously identified AZU1 to be specifically present in extracellular vesicles (EVs) obtained from renal cell carcinoma (RCC) tissues. Here, we examined the relationship between N-linked glycosylation and AZU1 loading into small EVs (SEVs). Inhibition of N-linked glycosylation by introducing mutations in three glycosylation sites inhibited AZU1 loading into SEVs. Furthermore, SEVs released from AZU1-wild-type cells increased the Ca2+ concentration in endothelial cells and the endothelial permeability, whereas SEVs released from AZU1-mutant cells had no significant effect. Anti-AZU1 antibodies diminished the effect of SEVs on endothelial cell sheets. Collectively, we found that N-linked glycosylation of AZU1 directs its loading into SEVs, thereby enabling AZU1-positive SEVs to function as potent permeabilizers of endothelial cells and leading to enhanced transendothelial migration of RCC cells.

Implications of exosomes derived from cholesterol-accumulated astrocytes in Alzheimer's disease pathology

Amyloid β (Aβ) peptides generated from the amyloid precursor protein (APP) play a critical role in the development of Alzheimer's disease (AD) pathology. Aβ-containing neuronal exosomes, which represent a novel form of intercellular communication, have been shown to influence the function/vulnerability of neurons in AD. Unlike neurons, the significance of exosomes derived from astrocytes remains unclear. In this study, we evaluated the significance of exosomes derived from U18666A-induced cholesterol-accumulated astrocytes in the development of AD pathology. Our results show that cholesterol accumulation decreases exosome secretion, whereas lowering cholesterol increases exosome secretion, from cultured astrocytes. Interestingly, exosomes secreted from U18666A-treated astrocytes contain higher levels of APP, APP-C-terminal fragments, soluble APP, APP secretases and Aβ1-40 than exosomes secreted from control astrocytes. Furthermore, we show that exosomes derived from U18666A-treated astrocytes can lead to neurodegeneration, which is attenuated by decreasing Aβ production or by neutralizing exosomal Aβ peptide with an anti-Aβ antibody. These results, taken together, suggest that exosomes derived from cholesterol-accumulated astrocytes can play an important role in trafficking APP/Aβ peptides and influencing neuronal viability in the affected regions of the AD brain.

Maternal high-fat diet modifies myelin organization, microglial interactions, and results in social memory and sensorimotor gating deficits in adolescent mouse offspring

Prenatal exposure to maternal high-fat diet (mHFD) acts as a risk factor for various neurodevelopmental alterations in the progeny. Recent studies in mice revealed that mHFD results in both neuroinflammation and hypomyelination in the exposed offspring. Microglia, the brain-resident macrophages, play crucial roles during brain development, notably by modulating oligodendrocyte populations and performing phagocytosis of myelin sheaths. Previously, we reported that mHFD modifies microglial phenotype (i.e., morphology, interactions with their microenvironment, transcripts) in the hippocampus of male and female offspring. In the current study, we further explored whether mHFD may induce myelination changes among the hippocampal-corpus callosum-prefrontal cortex pathway, and result in behavioral outcomes in adolescent offspring of the two sexes. To this end, female mice were fed with control chow or HFD for 4 weeks before mating, during gestation, and until weaning of their litter. Histological and ultrastructural analyses revealed an increased density of myelin associated with a reduced area of cytosolic myelin channels in the corpus callosum of mHFD-exposed male compared to female offspring. Transcripts of myelination-associated genes including Igf1 -a growth factor released by microglia- were also lower, specifically in the hippocampus (without changes in the prefrontal cortex) of adolescent male mouse offspring. These changes in myelin were not related to an altered density, distribution, or maturation of oligodendrocytes, instead we found that microglia within the corpus callosum of mHFD-exposed offspring showed reduced numbers of mature lysosomes and increased synaptic contacts, suggesting microglial implication in the modified myelination. At the behavioral level, both male and female mHFD-exposed adolescent offspring presented loss of social memory and sensorimotor gating deficits. These results together highlight the importance of studying oligodendrocyte-microglia crosstalk and its involvement in the long-term brain alterations that result from prenatal mHFD in offspring across sexes.

Extracellular Vesicles Taken up by Astrocytes

Extracellular vesicles (EVs) are composed of lipid bilayer membranes and contain various molecules, such as mRNA and microRNA (miRNA), that regulate the functions of the recipient cell. Recent studies have reported the importance of EV-mediated intercellular communication in the brain. The brain contains several types of cells, including neurons and glial cells. Among them, astrocytes are the most abundant glial cells in the mammalian brain and play a wide range of roles, from structural maintenance of the brain to regulation of neurotransmission. Furthermore, since astrocytes can take up EVs, it is possible that EVs originating from inside and outside the brain affect astrocyte function, which in turn affects brain function. However, it has not been fully clarified whether the specific targeting mechanism of EVs to astrocytes as recipient cells exists. In recent years, EVs have attracted attention as a cell-targeted therapeutic approach in various organs, and elucidation of the targeting mechanism of EVs to astrocytes may pave the way for new therapies for brain diseases. In this review, we focus on EVs in the brain that affect astrocyte function and discuss the targeting mechanism of EVs to astrocytes.

Delivery of Oligonucleotide Therapeutics: Chemical Modifications, Lipid Nanoparticles, and Extracellular Vesicles

Oligonucleotides (ONs) comprise a rapidly growing class of therapeutics. In recent years, the list of FDA-approved ON therapies has rapidly expanded. ONs are small (15-30 bp) nucleotide-based therapeutics which are capable of targeting DNA and RNA as well as other biomolecules. ONs can be subdivided into several classes based on their chemical modifications and on the mechanisms of their target interactions. Historically, the largest hindrance to the widespread usage of ON therapeutics has been their inability to effectively internalize into cells and escape from endosomes to reach their molecular targets in the cytosol or nucleus. While cell uptake has been improved, "endosomal escape" remains a significant problem. There are a range of approaches to overcome this, and in this review, we focus on three: altering the chemical structure of the ONs, formulating synthetic, lipid-based nanoparticles to encapsulate the ONs, or biologically loading the ONs into extracellular vesicles. This review provides a background to the design and mode of action of existing FDA-approved ONs. It presents the most common ON classifications and chemical modifications from a fundamental scientific perspective and provides a roadmap of the cellular uptake pathways by which ONs are trafficked. Finally, this review delves into each of the above-mentioned approaches to ON delivery, highlighting the scientific principles behind each and covering recent advances.

Nanosystems and exosomes as future approaches in treating multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system which leads to neurological dysfunctions and severe disabilities. MS pathology is characterised by damage of the blood-brain barrier and infiltration of autoreactive T cells that overactivate glial cells, thereby initiating neuroinflammation accompanied by the formation of demyelinating plaques and neurodegeneration. Clinical deficits in this multifactorial disease depend on the progression of myelin loss, the stage of inflammation, the status of axons and the activity of oligodendrocyte precursor cells (OPCs). Despite significant progress in the treatment of MS, current therapies remain limited and new approaches are highly desirable. Nanosystems based on liposomes and nanoparticles are among some of the more noteworthy therapeutic strategies being investigated. Applications of nanosystems alone or as drug carriers in animal models of MS have been found to successfully alleviate the symptoms of the disease and exert anti-inflammatory potential. Exosomes are a specific type of nanosystem based on nanometre-sized extracellular vesicles released by different cells which exhibit important healing features. Exosomes contain an array of anti-inflammatory and neuroprotective agents which may contribute to modulation of the immune system as well as promoting remyelination and tissue repair. In this review, opportunities to use nanosystems against progression of MS will be discussed in context of cell-specific pathologies associated with MS.

The Role of Extracellular Vesicles in the Developing Brain: Current Perspective and Promising Source of Biomarkers and Therapy for Perinatal Brain Injury

This comprehensive review focuses on our current understanding of the proposed physiological and pathological functions of extracellular vesicles (EVs) in the developing brain. Furthermore, since EVs have attracted great interest as potential novel cell-free therapeutics, we discuss advances in the knowledge of stem cell- and astrocyte-derived EVs in relation to their potential for protection and repair following perinatal brain injury. This review identified 13 peer-reviewed studies evaluating the efficacy of EVs in animal models of perinatal brain injury; 12/13 utilized mesenchymal stem cell-derived EVs (MSC-EVs) and 1/13 utilized astrocyte-derived EVs. Animal model, method of EV isolation and size, route, timing, and dose administered varied between studies. Notwithstanding, EV treatment either improved and/or preserved perinatal brain structures both macroscopically and microscopically. Additionally, EV treatment modulated inflammatory responses and improved brain function. Collectively this suggests EVs can ameliorate, or repair damage associated with perinatal brain injury. These findings warrant further investigation to identify the optimal cell numbers, source, and dosage regimens of EVs, including long-term effects on functional outcomes.

Extracellular heat shock proteins in cancer: From early diagnosis to new therapeutic approach

In cancer, human cells lose the ability to properly control the series of events that occur constantly during cell growth and division, including protein expression, stability, and dynamics. Heat shock proteins (Hsps) are key molecules in these events, constitutively expressed at high levels and could furthermore be induced by the response to cancer-induced stress. In tumor cells, Hsps have been shown to be implicated in the regulation of apoptosis, immune responses, angiogenesis and metastasis; in some cases, they can be overexpressed and dysregulated, representing important cancer hallmarks. In the past few years, it has been demonstrated that Hsps can be released by tumor cells through several secreting pathways, including the extracellular vesicles (EVs), thus modulating the tumor microenvironment as well as long-distance intercellular communication and metastatization. In this review, we discuss the role of extracellular Hsps in cancer, with a particular interest in Hsps in EVs. We would also like to highlight the importance of fully understanding of the role of extracellular Hsps released by EVs and encourage further research in this field the use of Hsps as early cancer biomarkers and therapeutic targets.

The Emerging Role of Neural Cell-Derived Exosomes in Intercellular Communication in Health and Neurodegenerative Diseases

Intercellular communication in the central nervous system (CNS) is essential for brain growth, development, and homeostasis maintenance and, when dysfunctional, is involved in the occurrence and development of neurodegenerative diseases. Increasing evidence indicates that extracellular vesicles, especially exosomes, are critical mediators of intercellular signal transduction. Under physiological and pathological conditions, neural cells secret exosomes with the influence of many factors. These exosomes can carry specific proteins, lipids, nucleic acids, and other bioactive substances to the recipient cells to regulate their function. Depending on the CNS environment, as well as the origin and physiological or pathological status of parental cells, exosomes can mediate a variety of different effects, including synaptic plasticity, nutritional metabolic support, nerve regeneration, inflammatory response, anti-stress effect, cellular waste disposal, and the propagation of toxic components, playing an important role in health and neurodegenerative diseases. This review will discuss the possible roles of exosomes in CNS intercellular communication in both physiologic and neurodegenerative conditions.

The pathogenic, therapeutic and diagnostic role of exosomal microRNA in the autoimmune diseases

Exosomes are a nano-vesicle surrounded by a bilipid layer that can release from almost all cells and could be detected in tissues and biological liquids. These vesicles contain lipids, proteins, and nucleic acids (including DNA, mRNA, and miRNA) inside and on the exosomes' surface constitute their content. Exosomes can transfer their cargo into the recipient cell, which can modify recipient cells' biological activities. Recently it has been deciphering that the miRNA pattern of exosomes reveals the cellular pathophysiological situation and modifies various biological processes. Increasing data regarding exosomes highlights that the exosomes and their cargo, especially miRNAs, are implicated in the pathophysiology of various disorders, such as autoimmune disease. The current evidence on the deciphering of mechanisms in which exosomal miRNAs contributed to autoimmunity was indicated that exosomal miRNA might hold information that can reprogram the function of many of the immune cells involved in autoimmune diseases' pathogenesis. In the present study, we summarized the pathogenic role of exosomal miRNAs in several autoimmune diseases, including myasthenia gravis (MG), psoriasis, inflammatory bowel disease (IBD), type 1 diabetes (T1D), multiple sclerosis (MS), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjogren's Syndrome (SS), systemic sclerosis (SSc), vitiligo, and autoimmune thyroid diseases (AITD). Moreover, in this work, we present evidence of the potential role of exosomal miRNAs as therapeutic and diagnostic agents in autoimmune diseases.

What we know on the potential use of exosomes for nanodelivery

Antitumor therapy is taking into consideration the possibility to use natural nanovesicles, called exosomes, as an ideal delivery for both old and new anti-cancer molecules. This with the attempt to improve the efficacy, at the same time reducing the systemic toxicity of physical, chemical, and biological molecules. Exosomes may in fact increase the level of biomimetism, through simulating what really occurs in nature. Although extracellularly released vesicles include both microvesicles (MVs) and exosomes, only exosomes have the size that may be considered suitable for potential use to this purpose, also by analogy with the diffusely used artificial nanoparticles, such as lyposomes. In fact, recent reports have shown that exosomes are able to interact with target cells within an organ or at a distance using different mechanisms. Much is yet to be understood about exosomes, and currently, we are looking at the visible top of an iceberg, with most of what we have to understand on these nanovesicles still under the sea. In fact, we know that exosomes released by normal cells always trigger positive effects, while those released by cells in pathological condition, such as tumors may induce undesired, dangerous, and mostly unknown effects. To date we have many pre-clinical data available and possibly useful to think about a strategic use of exosomes as a delivery nanodevice in cancer treatment. However, this review wants to critically emphasize two important points actually hampering further discussion in the field : (i) the clinical data are virtually absent at the moment ; (ii) the best cellular source of exosomes to be used to deliver drugs is really far to be defined. Facing off these two points may well facilitate the attempt to figure out this very important issue for improving at the best future anti-cancer treatments.

Astrocytes in Neurodegenerative Diseases: A Perspective from Tauopathy and α-Synucleinopathy

Neurodegenerative diseases are aging-associated chronic pathological conditions affecting primarily neurons in humans. Inclusion bodies containing misfolded proteins have emerged as a common pathologic feature for these diseases. In many cases, misfolded proteins produced by a neuron can be transmitted to another neuron or a non-neuronal cell, leading to the propagation of disease-associated pathology. While undergoing intercellular transmission, misfolded proteins released from donor cells can often change the physiological state of recipient cells. Accumulating evidence suggests that astrocytes are highly sensitive to neuron-originated proteotoxic insults, which convert them into an active inflammatory state. Conversely, activated astrocytes can release a plethora of factors to impact neuronal functions. This review summarizes our current understanding of the complex molecular interplays between astrocyte and neuron, emphasizing on Tau and α-synuclein (α-syn), the disease-driving proteins for Alzheimer's and Parkinson's diseases, respectively.

Exosomes as mediators of intercellular crosstalk in metabolism

Exosomes are nanoparticles secreted by all cell types and are a large component of the broader class of nanoparticles termed extracellular vesicles (EVs). Once secreted, exosomes gain access to the interstitial space and ultimately the circulation, where they exert local paracrine or distal systemic effects. Because of this, exosomes are important components of an intercellular and intraorgan communication system capable of carrying biologic signals from one cell type or tissue to another. The exosomal cargo consists of proteins, lipids, miRNAs, and other RNA species, and many of the biologic effects of exosomes have been attributed to miRNAs. Exosomal miRNAs have also been used as disease biomarkers. The field of exosome biology and metabolism is rapidly expanding, with new discoveries and reports appearing on a regular basis, and it is possible that potential therapeutic approaches for the use of exosomes or miRNAs in metabolic diseases will be initiated in the near future.

Neonatal stroke enhances interaction of microglia-derived extracellular vesicles with microglial cells

Microglial cells support brain homeostasis under physiological conditions and modulate brain injury in a context-dependent and brain maturation-dependent manner. Microglial cells protect neonatal brain from acute stroke. While microglial signaling via direct cell-cell interaction and release of variety of molecules is intensely studied, less is known about microglial signaling via release and uptake of extracellular vesicles (EVs). We asked whether neonatal stroke alters release of microglial EVs (MEV) and MEV communication with activated microglia. We pulled down and plated microglia from ischemic-reperfused and contralateral cortex 24 h after transient middle cerebral artery occlusion (tMCAO) in postnatal day 9 mice, isolated and characterized microglia-derived microvesicles (P3-MEV) and exosomes (P4-MEV), and determined uptake of fluorescently labeled P3-MEV and P4-MEV by plated microglia derived from ischemic-reperfused and contralateral cortex. We then examined how reducing EVs release in neonatal brain-by intra-cortical injection of CRISPR-Cas9-Smpd3/KO (Smpd3/KD) to downregulate Smpd3 gene to disrupt neutral sphingomyelinase-2 (N-SMase2)-impacts P3-MEV and P4-MEV release and stroke injury. Both size and protein composition differed between P3-MEV and P4-MEV. tMCAO further altered protein composition of P3-MEV and P4-MEV and significantly, up to 5-fold, increased uptake of both vesicle subtypes by microglia from ischemic-reperfused regions. Under physiological conditions neurons were the predominant cell type expressing N-SMase-2, an enzyme involved in lipid signaling and EVs release. After tMCAO N-SMase-2 expression was diminished in injured neurons but increased in activated microglia/macrophages, leading to overall reduced N-SMase-2 activity. Compared to intracerebral injection of control plasmid, CRISPR-Cas9-Smpd3/Ct, Smpd3/KD injection further reduced N-SMase-2 activity and significantly reduced injury. Smpd3 downregulation decreased MEV release from injured regions, reduced Smpd3/KD-P3-MEV uptake and abolished Smpd3/KD-P4-MEV uptake by microglia from ischemic-reperfused region. Cumulatively, these data demonstrate that microglial cells release both microvesicles and exosomes in naïve neonatal brain, that the state of microglial activation determines both properties of released EVs and their recognition/uptake by microglia in ischemic-reperfused and control regions, suggesting a modulatory role of MEV in neonatal stroke, and that sphingosine/N-SMase-2 signaling contributes both to EVs release and uptake (predominantly P4-MEV) after neonatal stroke.

Small Neuron-Derived Extracellular Vesicles from Individuals with Down Syndrome Propagate Tau Pathology in the Wildtype Mouse Brain

Individuals with Down syndrome (DS) exhibit Alzheimer's disease (AD) pathology at a young age, including amyloid plaques and neurofibrillary tangles (NFTs). Tau pathology can spread via extracellular vesicles, such as exosomes. The cargo of neuron-derived small extracellular vesicles (NDEVs) from individuals with DS contains p-Tau at an early age. The goal of the study was to investigate whether NDEVs isolated from the blood of individuals with DS can spread Tau pathology in the brain of wildtype mice. We purified NDEVs from the plasma of patients with DS-AD and controls and injected small quantities using stereotaxic surgery into the dorsal hippocampus of adult wildtype mice. Seeding competent Tau conformers were amplified in vitro from DS-AD NDEVs but not NDEVs from controls. One month or 4 months post-injection, we examined Tau pathology in mouse brains. We found abundant p-Tau immunostaining in the hippocampus of the mice injected with DS-AD NDEVs compared to injections of age-matched control NDEVs. Double labeling with neuronal and glial markers showed that p-Tau staining was largely found in neurons and, to a lesser extent, in glial cells and that p-Tau immunostaining was spreading along the corpus callosum and the medio-lateral axis of the hippocampus. These studies demonstrate that NDEVs from DS-AD patients exhibit Tau seeding capacity and give rise to tangle-like intracellular inclusions.

Engineered exosomes: desirable target-tracking characteristics for cerebrovascular and neurodegenerative disease therapies

As extracellular vesicles secreted by cells, exosomes are intercellular signalosomes for cell communication and pharmacological effectors. Because of their special properties, including low toxicity and immunogenicity, biodegradability, ability to encapsulate endogenous biologically active molecules and cross the blood-brain barrier (BBB), exosomes have great therapeutic potential in cerebrovascular and neurodegenerative diseases. However, the poor targeting ability of natural exosomes greatly reduces the therapeutic effect. Using engineering technology, exosomes can obtain active targeting ability to accumulate in specific cell types and tissues by attaching targeting units to the membrane surface or loading them into cavities. In this review, we outline the improved targeting functions of bioengineered exosomes, tracing and imaging techniques, administration methods, internalization in the BBB, and therapeutic effects of exosomes in cerebrovascular and neurodegenerative diseases and further evaluate the clinical opportunities and challenges in this research field.

Stem Cell-Derived Exosomes Potential Therapeutic Roles in Cardiovascular Diseases

Owing to myocardial abnormalities, cardiac ailments are considered to be the major cause of morbidity and mortality worldwide. According to a recent study, membranous vesicles that are produced naturally, termed as "exosomes", have emerged as the potential candidate in the field of cardiac regenerative medicine. A wide spectrum of stem cells has also been investigated in the treatment of cardiovascular diseases (CVD). Exosomes obtained from the stem cells are found to be cardioprotective and offer great hope in the treatment of CVD. The basic nature of exosomes is to deal with the intracellular delivery of both proteins and nucleic acids. This activity of exosomes helps us to rely on them as the attractive pharmaceutical delivery agents. Most importantly, exosomes derived from microRNAs (miRNAs) hold great promise in assessing the risk of CVD, as they serve as notable biomarkers of the disease. Exosomes are small, less immunogenic, and lack toxicity. These nanovesicles harbor immense potential as a therapeutic entity and would provide fruitful benefits if consequential research were focused on their upbringing and development as a useful diagnostic and therapeutic tool in the field of medicine.

Extracellular Vesicles in neural cell interaction and CNS homeostasis

Central nervous system (CNS) homeostasis critically depends on the interaction between neurons and glia cells. Extracellular vesicles (EVs) recently emerged as versatile messengers in CNS cell communication. EVs are released by neurons and glia in activity-dependent manner and address multiple target cells within and outside the nervous system. Here, we summarize the recent advances in understanding the physiological roles of EVs in the nervous system and their ability to deliver signals across the CNS barriers. In addition to the disposal of cellular components via EVs and clearance by phagocytic cells, EVs are involved in plasticity-associated processes, mediate trophic support and neuroprotection, promote axonal maintenance, and modulate neuroinflammation. While individual functional components of the EV cargo are becoming progressively identified, the role of neural EVs as compound multimodal signaling entities remains to be elucidated. Novel transgenic models and imaging technologies allow EV tracking in vivo and provide further insight into EV targeting and their mode of action. Overall, EVs represent key players in the maintenance of CNS homeostasis essential for the lifelong performance of neural networks and thus provide a wide spectrum of biomedical applications.

Trends in the biological functions and medical applications of extracellular vesicles and analogues

Natural extracellular vesicles (EVs) play important roles in many life processes such as in the intermolecular transfer of substances and genetic information exchanges. Investigating the origins and working mechanisms of natural EVs may provide an understanding of life activities, especially regarding the occurrence and development of diseases. Additionally, due to their vesicular structure, EVs (in small molecules, nucleic acids, proteins, etc.) could act as efficient drug-delivery carriers. Herein, we describe the sources and biological functions of various EVs, summarize the roles of EVs in disease diagnosis and treatment, and review the application of EVs as drug-delivery carriers. We also assess the challenges and perspectives of EVs in biomedical applications.

Promise of extracellular vesicles for diagnosis and treatment of epilepsy

Extracellular vesicles (EVs) released from cells play vital roles in intercellular communication. Moreover, EVs released from stem cells have therapeutic properties. This review confers the potential of brain-derived EVs in the cerebrospinal fluid (CSF) and the serum as sources of epilepsy-related biomarkers, and the promise of mesenchymal stem cell (MSC)-derived EVs for easing status epilepticus (SE)-induced adverse changes in the brain. Extracellular vesicles shed from neurons and glia in the brain can also be found in the circulating blood as EVs cross the blood-brain barrier (BBB). Evaluation of neuron and/or glia-derived EVs in the blood of patients who have epilepsy could help in identifying specific biomarkers for distinct types of epilepsies. Such a liquid biopsy approach is also amenable for repeated analysis in clinical trials for comprehending treatment efficacy, disease progression, and mechanisms of therapeutic interventions. Extracellular vesicle biomarker studies in animal prototypes of epilepsy, in addition, could help in identifying specific micro ribonucleic acid (miRNAs) contributing to epileptogenesis, seizures, or cognitive dysfunction in different types of epilepsy. Furthermore, intranasal (IN) administration of MSC-derived EVs after SE has shown efficacy for restraining SE-induced neuroinflammation, aberrant neurogenesis, and cognitive dysfunction in an animal prototype. Clinical translation of EV therapy as an adjunct to antiepileptic drugs appears attractive to counteract the progression of SE-induced epileptogenic changes, as the risk for thrombosis or tumor is minimal with nanosized EVs. Also, EVs can be engineered to deliver specific miRNAs, proteins, or antiepileptic drugs to the brain since they incorporate into neurons and glia throughout the brain after IN administration. This article is part of the Special Issue "NEWroscience 2018".

Mesenchymal Stem Cell-Derived Exosomes: Applications in Regenerative Medicine

Exosomes are a type of extracellular vesicles, produced within multivesicular bodies, that are then released into the extracellular space through a merging of the multivesicular body with the plasma membrane. These vesicles are secreted by almost all cell types to aid in a vast array of cellular functions, including intercellular communication, cell differentiation and proliferation, angiogenesis, stress response, and immune signaling. This ability to contribute to several distinct processes is due to the complexity of exosomes, as they carry a multitude of signaling moieties, including proteins, lipids, cell surface receptors, enzymes, cytokines, transcription factors, and nucleic acids. The favorable biological properties of exosomes including biocompatibility, stability, low toxicity, and proficient exchange of molecular cargos make exosomes prime candidates for tissue engineering and regenerative medicine. Exploring the functions and molecular payloads of exosomes can facilitate tissue regeneration therapies and provide mechanistic insight into paracrine modulation of cellular activities. In this review, we summarize the current knowledge of exosome biogenesis, composition, and isolation methods. We also discuss emerging healing properties of exosomes and exosomal cargos, such as microRNAs, in brain injuries, cardiovascular disease, and COVID-19 amongst others. Overall, this review highlights the burgeoning roles and potential applications of exosomes in regenerative medicine.

Secretome and Tunneling Nanotubes: A Multilevel Network for Long Range Intercellular Communication between Endothelial Cells and Distant Cells

As a cellular interface between the blood and tissues, the endothelial cell (EC) monolayer is involved in the control of key functions including vascular tone, permeability and homeostasis, leucocyte trafficking and hemostasis. EC regulatory functions require long-distance communications between ECs, circulating hematopoietic cells and other vascular cells for efficient adjusting thrombosis, angiogenesis, inflammation, infection and immunity. This intercellular crosstalk operates through the extracellular space and is orchestrated in part by the secretory pathway and the exocytosis of Weibel Palade Bodies (WPBs), secretory granules and extracellular vesicles (EVs). WPBs and secretory granules allow both immediate release and regulated exocytosis of messengers such as cytokines, chemokines, extracellular membrane proteins, coagulation or growth factors. The ectodomain shedding of transmembrane protein further provide the release of both receptor and ligands with key regulatory activities on target cells. Thin tubular membranous channels termed tunneling nanotubes (TNTs) may also connect EC with distant cells. EVs, in particular exosomes, and TNTs may contain and transfer different biomolecules (e.g., signaling mediators, proteins, lipids, and microRNAs) or pathogens and have emerged as a major triggers of horizontal intercellular transfer of information.

Current Understanding of Central Nervous System Drainage Systems: Implications in the Context of Neurodegenerative Diseases

Until recently, it was thought that there were no lymphatic vessels in the central nervous system (CNS). Therefore, all metabolic processes were assumed to take place only in the circulation of the cerebrospinal fluid (CSF) and through the blood-brain barrier's (BBB), which regulate ion transport and ensure the functioning of the CNS. However, recent findings yield a new perspective: There is an exchange of CSF with interstitial fluid (ISF), which is drained to the paravenous space and reaches lymphatic nodes at the end. This circulation is known as the glymphatic system. The glymphatic system is an extensive network of meningeal lymphatic vessels (MLV) in the basal area of the skull that provides another path for waste products from CNS to reach the bloodstream. MLV develop postnatally, initially appearing around the foramina in the basal part of the skull and the spinal cord, thereafter sprouting along the skull's blood vessels and spinal nerves in various areas of the meninges. VEGF-C protein (vascular endothelial growth factor), expressed mainly by vascular smooth cells, plays an important role in the development of the MLV. The regenerative potential and plasticity of MLV and the novel discoveries related to CNS drainage offer potential for the treatment of neurodegenerative diseases such as dementia, hydrocephalus, stroke, multiple sclerosis, and Alzheimer disease (AD). Herein, we present an overview of the structure and function of the glymphatic system and MLV, and their potential involvement in the pathology and progression of neurodegenerative diseases.

Trophoblast derived extracellular vesicles specifically alter the transcriptome of endometrial cells and may constitute a critical component of embryo-maternal communication

BACKGROUND

The period of time when the embryo and the endometrium undergo significant morphological alterations to facilitate a successful implantation-known as "window of implantation"-is a critical moment in human reproduction. Embryo and the endometrium communicate extensively during this period, and lipid bilayer bound nanoscale extracellular vesicles (EVs) are purported to be integral to this communication.

METHODS

To investigate the nature of the EV-mediated embryo-maternal communication, we have supplemented trophoblast analogue spheroid (JAr) derived EVs to an endometrial analogue (RL 95-2) cell layer and characterized the transcriptomic alterations using RNA sequencing. EVs derived from non-trophoblast cells (HEK293) were used as a negative control. The cargo of the EVs were also investigated through mRNA and miRNA sequencing.

RESULTS

Trophoblast spheroid derived EVs induced drastic transcriptomic alterations in the endometrial cells while the non-trophoblast cell derived EVs failed to induce such changes demonstrating functional specificity in terms of EV origin. Through gene set enrichment analysis (GSEA), we found that the response in endometrial cells was focused on extracellular matrix remodelling and G protein-coupled receptors' signalling, both of which are of known functional relevance to endometrial receptivity. Approximately 9% of genes downregulated in endometrial cells were high-confidence predicted targets of miRNAs detected exclusively in trophoblast analogue-derived EVs, suggesting that only a small proportion of reduced expression in endometrial cells can be attributed directly to gene silencing by miRNAs carried as cargo in the EVs.

CONCLUSION

Our study reveals that trophoblast derived EVs have the ability to modify the endometrial gene expression, potentially with functional importance for embryo-maternal communication during implantation, although the exact underlying signalling mechanisms remain to be elucidated.

Oligodendrocytes and Microglia: Key Players in Myelin Development, Damage and Repair

Oligodendrocytes, the myelin-making cells of the CNS, regulate the complex process of myelination under physiological and pathological conditions, significantly aided by other glial cell types such as microglia, the brain-resident, macrophage-like innate immune cells. In this review, we summarize how oligodendrocytes orchestrate myelination, and especially myelin repair after damage, and present novel aspects of oligodendroglial functions. We emphasize the contribution of microglia in the generation and regeneration of myelin by discussing their beneficial and detrimental roles, especially in remyelination, underlining the cellular and molecular components involved. Finally, we present recent findings towards human stem cell-derived preclinical models for the study of microglia in human pathologies and on the role of microbiome on glial cell functions.

Fostering "Education": Do Extracellular Vesicles Exploit Their Own Delivery Code?

Extracellular vesicles (EVs), comprising large microvesicles (MVs) and exosomes (EXs), play a key role in intercellular communication, both in physiological and in a wide variety of pathological conditions. However, the education of EV target cells has so far mainly been investigated as a function of EX cargo, while few studies have focused on the characterization of EV surface membrane molecules and the mechanisms that mediate the addressability of specific EVs to different cell types and tissues. Identifying these mechanisms will help fulfill the diagnostic, prognostic, and therapeutic promises fueled by our growing knowledge of EVs. In this review, we first discuss published studies on the presumed EV “delivery code” and on the combinations of the hypothesized EV surface membrane “sender” and “recipient” molecules that may mediate EV targeting in intercellular communication. Then we briefly review the main experimental approaches and techniques, and the bioinformatic tools that can be used to identify and characterize the structure and functional role of EV surface membrane molecules. In the final part, we present innovative techniques and directions for future research that would improve and deepen our understandings of EV-cell targeting.

Amiloride ameliorates muscle wasting in cancer cachexia through inhibiting tumor-derived exosome release

Background

Cancer cachexia (CAC) reduces patient survival and quality of life. Developments of efficient therapeutic strategies are required for the CAC treatments. This long-term process could be shortened by the drug-repositioning approach which exploits old drugs approved for non-cachexia disease. Amiloride, a diuretic drug, is clinically used for treatments of hypertension and edema due to heart failure. Here, we explored the effects of the amiloride treatment for ameliorating muscle wasting in murine models of cancer cachexia.

Methods

The CT26 and LLC tumor cells were subcutaneously injected into mice to induce colon cancer cachexia and lung cancer cachexia, respectively. Amiloride was intraperitoneally injected daily once tumors were formed. Cachexia features of the CT26 model and the LLC model were separately characterized by phenotypic, histopathologic and biochemical analyses. Plasma exosomes and muscle atrophy-related proteins were quantitatively analyzed. Integrative NMR-based metabolomic and transcriptomic analyses were conducted to identify significantly altered metabolic pathways and distinctly changed metabolism-related biological processes in gastrocnemius.

Results

The CT26 and LLC cachexia models displayed prominent cachexia features including decreases in body weight, skeletal muscle, adipose tissue, and muscle strength. The amiloride treatment in tumor-bearing mice distinctly alleviated muscle atrophy and relieved cachexia-related features without affecting tumor growth. Both the CT26 and LLC cachexia mice showed increased plasma exosome densities which were largely derived from tumors. Significantly, the amiloride treatment inhibited tumor-derived exosome release, which did not obviously affect exosome secretion from non-neoplastic tissues or induce observable systemic toxicities in normal healthy mice. Integrative-omics revealed significant metabolic impairments in cachectic gastrocnemius, including promoted muscular catabolism, inhibited muscular protein synthesis, blocked glycolysis, and impeded ketone body oxidation. The amiloride treatment evidently improved the metabolic impairments in cachectic gastrocnemius.

Conclusions

Amiloride ameliorates cachectic muscle wasting and alleviates cancer cachexia progression through inhibiting tumor-derived exosome release. Our results are beneficial to understanding the underlying molecular mechanisms, shedding light on the potentials of amiloride in cachexia therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13395-021-00274-5.

Applications of Exosomes in Targeted Drug Delivery for the Treatment of Parkinson's Disease: A Review of Recent Advances and Clinical Challenges

Parkinson's disease (PD) is one of the most prevalent and severe neurodegenerative disease affecting more than 6.1 million people globally. It is characterized by age-related progressive deterioration of neurological functions caused by neuronal damage or neuronal death. During PD, the dopamineproducing cells in the substantia nigra region of the brain degenerate, which leads to symptoms like resting tremors and rigidity. Treatment of PD is very challenging due to the blood-brain barrier, which restricts the drug from reaching the brain. Conventional drug delivery systems possess a limited capacity to cross the blood barrier, leading to low bioavailability and high toxicity (due to off-site drug release). Therefore, it becomes necessary to accelerate the development of novel drug delivery systems, including nanoparticles, microemulsions, matrix systems, solid dispersions, liposomes, and solid lipid nanoparticles for the treatment of PD. Exosomes are biological lipid bilayer membrane vesicles produced by nearly all mammalian cells. The characteristics of vesicles are unique to their cell of origin and are primarily involved in intracellular communication. Exosomes, due to their nanoscale size, could easily permeate across the central nervous system, which makes them ideal for targeting the neurons in the substantia nigra. Exosomes could be efficient drug carrier systems for brain targeting, which can increase the efficacy of the drug and minimize the side effects. The review aims at providing a broad updated view of exosomes and their application in the treatment of PD.

The emerging role of exosomes in Alzheimer's disease

Alzheimer's disease (AD), manifested by memory loss and a decline in cognitive functions, is the most prevalent neurodegenerative disease accounting for 60-80 % of dementia cases. But, to-date, there is no effective treatment available to slow or stop the progression of AD. Exosomes are small extracellular vesicles that carry constituents, such as functional messenger RNAs, non-coding RNAs, proteins, lipids, DNA, and other bioactive substances of their source cells. In the brain, exosomes are likely to be sourced by almost all cell types and involve in cell communication to regulate cellular functions. The yet, accumulated evidence on the roles of exosomes and their constituents in the AD pathological process suggests their significance as additional biomarkers and therapeutic targets for AD. This review summarizes the current reported research findings on exosomes roles in the pathogenesis, diagnosis, and treatment of AD.

Oligodendrocyte-derived extracellular vesicles as antigen-specific therapy for autoimmune neuroinflammation in mice

Autoimmune diseases such as multiple sclerosis (MS) develop because of failed peripheral immune tolerance for a specific self-antigen (Ag). Numerous approaches for Ag-specific suppression of autoimmune neuroinflammation have been proven effective in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. One such approach is intravenous tolerance induction by injecting a myelin Ag used for triggering EAE. However, the translation of this and similar experimental strategies into therapy for MS has been hampered by uncertainty regarding relevant myelin Ags in MS patients. To address this issue, we developed a therapeutic strategy that relies on oligodendrocyte (Ol)-derived extracellular vesicles (Ol-EVs), which naturally contain multiple myelin Ags. Intravenous Ol-EV injection reduced disease pathophysiology in a myelin Ag-dependent manner, both prophylactically and therapeutically, in several EAE models. The treatment was safe and restored immune tolerance by inducing immunosuppressive monocytes and apoptosis of autoreactive CD4⁺ T cells. Furthermore, we showed that human Ols also released EVs containing most relevant myelin Ags, providing a basis for their use in MS therapy. These findings introduce an approach for suppressing central nervous system (CNS) autoimmunity in a myelin Ag-specific manner, without the need to identify the target Ag.

Endothelial extracellular vesicles contain protective proteins and rescue ischemia-reperfusion injury in a human heart-on-chip

Extracellular vesicles (EVs) derived from various stem cell sources induce cardioprotective effects during ischemia-reperfusion injury (IRI). These have been attributed mainly to the antiapoptotic, proangiogenic, microRNA (miRNA) cargo within the stem cell-derived EVs. However, the mechanisms of EV-mediated endothelial signaling to cardiomyocytes, as well as their therapeutic potential toward ischemic myocardial injury, are not clear. EV content beyond miRNA that may contribute to cardioprotection has not been fully illuminated. This study characterized the protein cargo of human vascular endothelial EVs (EEVs) to identify lead cardioactive proteins and assessed the effect of EEVs on human laminar cardiac tissues (hlCTs) exposed to IRI. We mapped the protein content of human vascular EEVs and identified proteins that were previously associated with cellular metabolism, redox state, and calcium handling, among other processes. Analysis of the protein landscape of human cardiomyocytes revealed corresponding modifications induced by EEV treatment. To assess their human-specific cardioprotection in vitro, we developed a human heart-on-a-chip IRI assay using human stem cell-derived, engineered cardiac tissues. We found that EEVs alleviated cardiac cell death as well as the loss in contractile capacity during and after simulated IRI in an uptake- and dose-dependent manner. Moreover, we found that EEVs increased the respiratory capacity of normoxic cardiomyocytes. These results suggest that vascular EEVs rescue hlCTs exposed to IRI possibly by supplementing injured myocytes with cargo that supports multiple metabolic and salvage pathways and therefore may serve as a multitargeted therapy for IRI.

An Examination of the Putative Role of Melatonin in Exosome Biogenesis

During the last two decades, melatonin has been found to have pleiotropic effects via different mechanisms on its target cells. Data are abundant for some aspects of the signaling pathways within cells while other casual mechanisms have not been adequately addressed. From an evolutionary perspective, eukaryotic cells are equipped with a set of interrelated endomembrane systems consisting of intracellular organelles and secretory vesicles. Of these, exosomes are touted as cargo-laden secretory vesicles that originate from the endosomal multivesicular machinery which participate in a mutual cross-talk at different cellular interfaces. It has been documented that cells transfer various biomolecules and genetic elements through exosomes to sites remote from the original cell in a paracrine manner. Findings related to the molecular mechanisms between melatonin and exosomal biogenesis and cargo sorting are the subject of the current review. The clarification of the interplay between melatonin and exosome biogenesis and cargo sorting at the molecular level will help to define a cell's secretion capacity. This review precisely addresses the role and potential significance of melatonin in determining the efflux capacity of cells via the exosomal pathway. Certain cells, for example, stem cells actively increase exosome efflux in response to melatonin treatment which accelerates tissue regeneration after transplantation into the injured sites.

Activated microglia facilitate the transmission of α-synuclein in Parkinson's disease

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta and abnormal aggregates of α-synuclein protein called Lewy bodies. To date, there is no drug that can definitely slow down or stop the progression of this disease. The discovery of the cell-to-cell transmission of pathologic α-synuclein seeds offers the possibility to explore novel treatment strategies to prevent the spread of α-synuclein, with the purpose of slowing down the progression of PD in its tracks. Although recent studies have made tremendous progress in understanding how α-synuclein spreads throughout the brain, neuroinflammation seems to play a crucial role in the development of α-synuclein pathology in PD. The activation of microglia, one of the hallmarks of the neuroinflammatory process, is suggested to influence the neuron-to-neuron transmission of α-synuclein. This review summarizes how activated microglia facilitate this process, and focuses on the following mechanisms including the activation of microglia in PD, the reduced ability of activated microglia to clear α-synuclein and increased migratory capacity of microglia in PD, as well as the cooperation between microglia and exosomes in mediating α-synuclein release and propagation. In conclusion, this article help collate information on microglia in-relation to PD.

Extracellular vesicles in neuroinflammation: Pathogenesis, diagnosis, and therapy

Extracellular vesicles (EVs) are bilayer membrane vesicles and act as key messengers in intercellular communication. EVs can be secreted by both neurons and glial cells in the central nervous system (CNS). Under physiological conditions, EVs contribute to CNS homeostasis by facilitating omnidirectional communication among CNS cell populations. In response to CNS injury, EVs mediate neuroinflammatory responses and regulate tissue damage and repair, thereby influencing the pathogenesis, development, and/or recovery of neuroinflammatory diseases, including CNS autoimmune diseases, neurodegenerative diseases, stroke, CNS traumatic injury, and CNS infectious diseases. The unique ability of EVs to pass through the blood-brain barrier further confers them an important role in the bidirectional communication between the CNS and periphery, and application of EVs enables the diagnosis, prognosis, and therapy of neuroinflammatory diseases in a minimally invasive manner.

Latent HIV-Exosomes Induce Mitochondrial Hyperfusion Due to Loss of Phosphorylated Dynamin-Related Protein 1 in Brain Endothelium

Damage to the cerebral vascular endothelium is a critical initiating event in the development of HIV-1-associated neurocognitive disorders. To study the role of mitochondria in cerebral endothelial dysfunction, we investigated how exosomes, isolated from both cell lines with integrated provirus and HIV-1 infected primary cells (HIV-exosomes), accelerate the dysfunction of primary human brain microvascular endothelial cells (HBMVECs) by inducing mitochondrial hyperfusion, and reducing the expression of phosphorylated endothelial nitric oxide synthase (p-eNOS). The quantitative analysis of the extracellular vesicles (EVs) indicates that the isolated EVs were predominantly exosomes. It was further supported by the detection of exosomal markers, and the absence of large EV-related protein in the isolated EVs. The exosomes were readily taken up by primary HBMVECs. HIV-exosomes induce cellular and mitochondrial superoxide production but reduce mitochondrial membrane potential in HBMVECs. HIV-exosomes increase mitochondrial hyperfusion, possibly due to loss of phosphorylated dynamin-related protein 1 (p-DRP1). HIV-exosomes, containing the HIV-Tat protein, and viral Tat protein reduce the expression of p-DRP1 and p-eNOS, and accelerate brain endothelial dysfunction. Finally, exosomes isolated from HIV-1 infected primary human peripheral blood mononuclear cells (hPBMCs) produce more exosomes than uninfected controls and reduce both p-DRP1 and p-eNOS expressions in primary HBMVECs. Our novel findings reveal the significant role of HIV-exosomes on dysregulation of mitochondrial function, which induces adverse changes in the function of the brain microvascular endothelium.

Extracellular Vesicles as an Emerging Frontier in Spinal Cord Injury Pathobiology and Therapy

Extracellular vesicles (EVs) are membrane-delimited particles that are secreted by nearly all cell types. EVs mediate crucial physiological functions and pathophysiological processes in the CNS. As carriers of diverse bioactive cargoes (e.g., proteins, lipids, and nucleic acids) that can be modified in response to external stimuli, EVs have emerged as pathological mediators following neurotrauma such as spinal cord injury (SCI). We discuss the roles of endogenous EVs in the CNS as well as crosstalk with peripheral EVs in relation to neurotrauma, with a particular focus on SCI. We then summarize the status of EV-based therapeutic advances in preclinical animal models for these conditions. Finally, we discuss new bioengineering strategies that are poised to enhance CNS-specific therapeutic capabilities of EVs.

Exploring interactions between extracellular vesicles and cells for innovative drug delivery system design

Extracellular vesicles (EVs) are submicron cell-secreted structures containing proteins, nucleic acids and lipids. EVs can functionally transfer these cargoes from one cell to another to modulate physiological and pathological processes. Due to their presumed biocompatibility and capacity to circumvent canonical delivery barriers encountered by synthetic drug delivery systems, EVs have attracted considerable interest as drug delivery vehicles. However, it is unclear which mechanisms and molecules orchestrate EV-mediated cargo delivery to recipient cells. Here, we review how EV properties have been exploited to improve the efficacy of small molecule drugs. Furthermore, we explore which EV surface molecules could be directly or indirectly involved in EV-mediated cargo transfer to recipient cells and discuss the cellular reporter systems with which such transfer can be studied. Finally, we elaborate on currently identified cellular processes involved in EV cargo delivery. Through these topics, we provide insights in critical effectors in the EV-cell interface which may be exploited in nature-inspired drug delivery strategies.