Inter-Laboratory Comparison of Extracellular Vesicle Isolation Based on Ultracentrifugation

Si Microanemones Integrated Microfluidic Chip for Highly Efficient Isolation of Extracellular Vesicles

Liquid biopsy has emerged as a transformative approach for early cancer detection and treatment monitoring, offering significant potential to improve patient outcomes. However, isolating tumor-derived extracellular vesicles (EVs) from body fluids is often impeded by background noise, making subsequent analysis challenging. Herein, a bio-inspired 3D silicon microanemone (SMA) microfluidic chip is reported. This innovative structure is prepared by a two-step lithographic method combined with nanosphere lithography, achieving an impressive isolation efficiency of 89.4%. Simulation results reveal that the hierarchical structure not only provides more antibody binding sites but also synergizes with an integrated chaotic mixer to amplify fluid perturbations, while inducing a flow around circular cylinder phenomenon to enhance EV-antibody interactions. Finally, the SMA chip's performance is assessed with clinical samples and combined with RT-qPCR-based β-actin (ACTB) mRNA quantification in purified EVs. The results demonstrate its high sensitivity and specificity in isolating cancer-related EV subgroups, enabling non-invasive and precise detection of cancer biomarkers in blood samples.

Isolation of bovine milk-derived extracellular vesicles via a capillary-channeled polymer (C-CP) fiber stationary phase

Extracellular vesicles (EVs) are released by all cell types into the extracellular environment. A subset of EVs, known as exosomes, range in size from 30 to 200 nm and are of biochemical interest due to their function as vehicles of intercellular communication. Their ability to transport proteinaceous species and genetic material at the cellular level makes them prime candidates as vectors in gene therapies. Focusing on biotherapeutics, bovine milk-derived extracellular vesicles (MDEVs) hold particular promise as an alternative to other exosome sources for therapeutics delivery. Bovine milk poses unique challenges due to the complex colloidal matrix, composed predominantly of fats and proteins like casein, which form micelles that exhibit exosome-like characteristics, specifically size and density. When faced with complex matrices like milk, conventional size/density-based isolation methods including ultracentrifugation and size exclusion chromatography struggle to provide high purity yields on practical time and cost scales. When paired with a stepwise hydrophobic interaction chromatography (HIC) gradient, polyester (PET) capillary-channeled polymer (C-CP) fibers in column and spin-down tips formats have been used effectively to isolate exosomes from highly diverse sources. Here, PET C-CP fiber columns are demonstrated to isolate MDEVs from pre-treated raw milk, yielding concentrations of 1.5 × 1010 particles mL⁻1 with purities of ~2 × 1010 EVs µg-1 protein in less than 20 min. The efficacy of the isolation process is verified by a suite of characterization methods. Implementing PET C-CP fiber columns for MDEV isolation addresses the challenges associated with conventional isolation methods, holding promise for scale-up towards therapeutic applications.

Establishment of minimum protein standards for Mycobacterium tuberculosis-derived extracellular vesicles through comparison of EV enrichment methods

Mycobacterium tuberculosis extracellular vesicles (MEV) have been described as having potent immunological activities that are both beneficial and harmful to the host. Key to understanding this conflicting information is the proteomic characterization of MEVs. However, there is neither a standard for a purification method nor markers to assess relative purity and quality of MEVs. In this study, we purified MEVs by four different methods (simple ultracentrifugation, differential density gradient-based ultracentrifugation, qEV size exclusion chromatography, and Capto™Core size exclusion chromatography) and assessed the variability of MEV characteristics (size, concentration, appearance, purity, and protein content) amongst isolation methods. The vesicle appearance and size were consistent across all methods; however variability was found between and within all methods, with simple ultracentrifugation demonstrating the most variability both in reproducibility and purity. Protein concentration and content, and particle yield and purity, varied amongst all methods. The two size exclusion chromatography-based methods were more technically reproducible than either ultracentrifugation-based method, while qEV size exclusion chromatography and differential density gradient ultracentrifugation afforded MEV samples of the highest purity. Nonetheless, all methods had 7 proteins in common, the Sec-independent membrane bound twin-arginine translocase TatA (Rv2094c), the periplasmic phosphate-binding lipoprotein PstS3 (Rv0928), the heparin binding hemagglutinin HBHA (Rv0475), lipoprotein antigens LprG (Rv1411c) and LpqH (Rv3763), a member of the conserved 13E12 repeat protein family P95201 (Rv0393), and the tuberculin related peptide Rv0431 (P96277), suggesting the use of these proteins as qualitative markers of MEVs versus contaminants, in addition to size and appearance criteria, to benefit reproducibility and consensus for ongoing MEV studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s44350-025-00003-8.

Proteomics of Extracellular Vesicles: Recent Updates, Challenges and Limitations

Extracellular vesicles (EVs) are lipid-bound vesicles secreted by cells, including exosomes, microvesicles, and apoptotic bodies. Proteomic analyses of EVs, particularly in relation to cancer, reveal specific biomarkers crucial for diagnosis and therapy. However, isolation techniques such as ultracentrifugation, size-exclusion chromatography, and ultrafiltration face challenges regarding purity, contamination, and yield. Contamination from other proteins complicates downstream processing, leading to difficulties in identifying biomarkers and interpreting results. Future research will focus on refining EV characterization for diagnostic and therapeutic applications, improving proteomics tools for greater accuracy, and exploring the use of EVs in drug delivery and regenerative medicine. In this review, we provide a bird's eye view of various challenges, starting with EV isolation methods, yield, purity, and limitations in the proteome analysis of EVs for identifying protein targets.

A Reproducible Protocol for the Isolation of Malaria-Derived Extracellular Vesicles by Differential Centrifugation

Over the last few decades, malaria-derived extracellular vesicles (EVs) have gained increasing interest due to their role in disease pathophysiology and parasite biology. Unlike other EV research fields, the isolation of malaria EVs is not standardized, hampering inter-study comparisons. Most malaria EV studies isolate vesicles by the "gold-standard" technique of differential (ultra)centrifugation (DC). Here, we describe in detail an optimized and reproducible protocol for the isolation of malaria-derived EVs by DC. The protocol begins with a description of cultivating high-parasitemia, synchronous P. falciparum cultures that are the source of EV-containing conditioned culture media. The isolation protocol generates two EV subtypes, and we provide details of characterizing these distinct subtypes by analyzing human and parasite proteins by Western blot analysis. We identify some of these proteins as suitable markers for malaria EV subpopulations and subtypes.

Bacterial Extracellular Vesicles: Potential Therapeutic Applications, Challenges, and Future Prospects

Almost all cell types naturally secret extracellular vesicles (EVs) in the extracellular space with variable metabolic cargo facilitating intracellular communication, posing immune-modulation capacity. Thus, "bacterial extracellular vesicles" (BEVs), with their great immunoregulatory, immune response stimulation and disease condition-altering potential, have gained importance in the medical and therapeutic industry. Various subtypes of BEVs were observed and reported in the literature, such as exosomes (30-150 nm), microvesicles (100-1000 nm), apoptotic bodies (1000-5000 nm), and oncosomes (1000-10,000 nm). As biological systems are complex entities, inserting BEVs requires extra high purity. Various techniques for BEV isolation have been employed alone or with other strategies, such as ultracentrifugation, precipitation, size-exclusion chromatography, affinity-based separation, ultrafiltration, and field-flow fractionation. But to date, no BEV isolation method is considered perfect as the lack of standard protocols limits their scale-up. Medical research has focused on BEVs to explore their diverse therapeutic potential. This review particularly focused on the recent advancements in the potential medical application of BEVs, current challenges, and prospects associated with their scale-up.

Development of a Sampling and Storage Protocol of Extracellular Vesicles (EVs)-Establishment of the First EV Biobank for Polytraumatized Patients

In the last few years, several studies have emphasized the existence of injury-specific EV "barcodes" that could have significant importance for the precise diagnosis of different organ injuries in polytrauma patients. To expand the research potential of the NTF (network trauma research) biobank of polytraumatized patients, the NTF research group decided to further establish a biobank for EVs. However, until now, the protocols for the isolation, characterization, and storage of EVs for biobank purposes have not been conceptualized. Plasma and serum samples from healthy volunteers (n = 10) were used. Three EV isolation methods of high relevance for the work with patients' samples (ultracentrifugation, size exclusion chromatography, and immune magnetic bead-based isolation) were compared. EVs were quantified using nanoparticle tracking analysis, EV proteins, and miRNAs. The effects of different isolation solutions; the long storage of samples (up to 3 years); and the sensibility of EVs to serial freezing-thawing cycles and different storage conditions (RT, 4/-20/-80 °C, dry ice) were evaluated. The SEC isolation method was considered the most suitable for EV biobanking. We did not find any difference in the quantity of EVs between serum and plasma-EVs. The importance of particle-free PBS as an isolation solution was confirmed. Plasma that has been frozen for a long time can also be used as a source of EVs. Serial freezing-thawing cycles were found to affect the mean size of EVs but not their amount. The storage of EV samples for 5 days on dry ice significantly reduced the EV protein concentration.

Extracellular vesicles in heart failure

Physiologically, extracellular vesicles (EVs) have been implicated as crucial mediators of immune response, cell homeostasis, angiogenesis, cell differentiation and growth, and tissue repair. In heart failure (HF) they may act as regulators of cardiac remodeling, microvascular inflammation, micro environmental changes, tissue fibrosis, atherosclerosis, neovascularization of plaques, endothelial dysfunction, thrombosis, and reciprocal heart-remote organ interaction. The chapter summaries the nomenclature, isolation, detection of EVs, their biologic role and function physiologically as well as in the pathogenesis of HF. Current challenges to the utilization of EVs as diagnostic and predictive biomarkers in HF are also discussed.

Emerging role of mesenchymal stem cells-derived extracellular vesicles in vascular dementia

Vascular dementia (VD) is a prevalent cognitive disorder among the elderly. Its pathological mechanism encompasses neuronal damage, synaptic dysfunction, vascular abnormalities, neuroinflammation, and oxidative stress, among others. In recent years, extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have garnered significant attention as an emerging therapeutic strategy. Current research indicates that MSC-derived extracellular vesicles (MSC-EVs) play a pivotal role in both the diagnosis and treatment of VD. Thus, this article delves into the recent advancements of MSC-EVs in VD, discussing the mechanisms by which EVs influence the pathophysiological processes of VD. These mechanisms form the theoretical foundation for their neuroprotective effect in VD treatment. Additionally, the article highlights the potential applications of EVs in VD diagnosis. In conclusion, MSC-EVs present a promising innovative treatment strategy for VD. With rigorous research and ongoing innovation, this concept can transition into practical clinical treatment, providing more effective options for VD patients.

Isolation of Extracellular Vesicles Using Formulas to Adapt Centrifugation to Different Centrifuges

Extracellular vesicles (EVs) are small lipid bilayer vesicles released by cells to facilitate cell-to-cell communication. To study their biological roles and functions, they need to be isolated and purified, which can be achieved through a variety of methods. Here, we describe different methods for isolating and purifying EVs, with a focus on calculating the required g-force and centrifugation time with different centrifuges and rotors. We have compiled key formulas and tested predicted parameters for EV acquisitions to provide a comprehensive guide for EV isolation.

Rigorous Comparison of Extracellular Vesicle Processing to Enhance Downstream Analysis for Glioblastoma Characterization

Extracellular vesicles (EVs) are highly sought after as a source of biomarkers for disease detection and monitoring. Tumor EV isolation, processing, and evaluation from biofluids is convoluted by EV heterogeneity and biological contaminants and is limited by technical processing efficacy. This study rigorously compares common bulk EV isolation workflows (size exclusion chromatography, SEC; membrane affinity, MA) alongside downstream RNA extraction protocols to investigate molecular analyte recovery. EV integrity and recovery is evaluated using a variety of technologies to quantify total intact EVs, total and surface proteins, and RNA purity and recovery. A comprehensive evaluation of each analyte is performed, with a specific emphasis on maintaining user (n = 2), biological (n = 3), and technical replicates (n≥3) under in vitro conditions. Subsequent study of tumor EV spike-in into healthy donor plasma samples is performed to further validate biofluid-derived EV purity and isolation for clinical application. Results show that EV surface integrity is considerably preserved in eluates from SEC-derived EVs, but RNA recovery and purity, as well as bulk protein isolation, is significantly improved in MA-isolated EVs. This study concludes that EV isolation and RNA extraction pipelines govern recovered analyte integrity, necessitating careful selection of processing modality to enhance recovery of the analyte of interest.

Effects of Co-Culture EBV-miR-BART1-3p on Proliferation and Invasion of Gastric Cancer Cells Based on Exosomes

AIM

EBV encodes at least 44 miRNAs involved in immune regulation and disease progression. Exosomes can be used as carriers of EBV-miRNA-BART intercellular transmission and affect the biological behavior of cells. We characterized exosomes and established a co-culture experiment of exosomes to explore the mechanism of miR-BART1-3p transmission through the exosome pathway and its influence on tumor cell proliferation and invasion.

MATERIALS AND METHODS

Exosomes of EBV-positive and EBV-negative gastric cancer cells were characterized by transmission electron microscopy. NanoSight and Western blotting, and miRNA expression profiles in exosomes were sequenced with high throughput. Exosomes with high or low expression of miR-BART1-3p were co-cultured with AGS cells to study the effects on proliferation, invasion, and migration of gastric cancer cells. The target genes of EBV-miR-BART1-3p were screened and predicted by PITA, miRanda, RNAhybrid, virBase, and DIANA-TarBase v.8 databases, and the expression of the target genes after co-culture was detected by qPCR.

RESULTS

The exosomes secreted by EBV-positive and negative gastric cancer cells range in diameter from 30 nm to 150 nm and express the exosomal signature proteins CD9 and CD63. Small RNA sequencing showed that exosomes expressed some human miRNAs, among which hsa-miR-23b-3p, hsa-miR-320a-3p, and hsa-miR-4521 were highly expressed in AGS-exo; hsa-miR-21-5p, hsa-miR-148a-3p, and hsa-miR-7-5p were highly expressed in SNU-719-exo. All EBV miRNAs were expressed in SNU-719 cells and their exosomes, among which EBV-miR-BART1-5p, EBV-miR-BART22, and EBV-miR-BART16 were the highest in SNU-719 cells; EBV-miR-BART1-5p, EBV-miR-BART10-3p, and EBV-miR-BART16 were the highest in SNU-719-exo. After miR-BART1-3p silencing in gastric cancer cells, the proliferation, healing, migration, and invasion of tumor cells were significantly improved. Laser confocal microscopy showed that exosomes could carry miRNA into recipient cells. After co-culture with miR-BART1-3p silenced exosomes, the proliferation, healing, migration, and invasion of gastric cancer cells were significantly improved. The target gene of miR-BART1-3p was FAM168A, MACC1, CPEB3, ANKRD28, and USP37 after screening by a targeted database. CPEB3 was not expressed in all exosome co-cultured cells, while ANKRD28, USP37, MACC1, and FAM168A were all expressed to varying degrees. USP37 and MACC1 were down-regulated after up-regulation of miR-BART1-3p, which may be the key target genes for miR-BART1-3p to regulate the proliferation of gastric cancer cells through exosomes.

CONCLUSIONS

miR-BART1-3p can affect the growth of tumor cells through the exosome pathway. The proliferation, healing, migration, and invasion of gastric cancer cells were significantly improved after co-culture with exosomes of miR-BART1-3p silenced expression. USP37 and MACC1 may be potential target genes of miR-BART1-3p in regulating cell proliferation.

Bacterial Membrane Vesicles as Smart Drug Delivery and Carrier Systems: A New Nanosystems Tool for Current Anticancer and Antimicrobial Therapy

Bacterial membrane vesicles (BMVs) are known to be critical communication tools in several pathophysiological processes between bacteria and host cells. Given this situation, BMVs for transporting and delivering exogenous therapeutic cargoes have been inspiring as promising platforms for developing smart drug delivery systems (SDDSs). In the first section of this review paper, starting with an introduction to pharmaceutical technology and nanotechnology, we delve into the design and classification of SDDSs. We discuss the characteristics of BMVs including their size, shape, charge, effective production and purification techniques, and the different methods used for cargo loading and drug encapsulation. We also shed light on the drug release mechanism, the design of BMVs as smart carriers, and recent remarkable findings on the potential of BMVs for anticancer and antimicrobial therapy. Furthermore, this review covers the safety of BMVs and the challenges that need to be overcome for clinical use. Finally, we discuss the recent advancements and prospects for BMVs as SDDSs and highlight their potential in revolutionizing the fields of nanomedicine and drug delivery. In conclusion, this review paper aims to provide a comprehensive overview of the state-of-the-art field of BMVs as SDDSs, encompassing their design, composition, fabrication, purification, and characterization, as well as the various strategies used for targeted delivery. Considering this information, the aim of this review is to provide researchers in the field with a comprehensive understanding of the current state of BMVs as SDDSs, enabling them to identify critical gaps and formulate new hypotheses to accelerate the progress of the field.

Impact of Experimental Conditions on Extracellular Vesicles' Proteome: A Comparative Study

Extracellular vesicle (EV) research is a rapidly developing field, mainly due to the key role of EVs in intercellular communication and pathophysiological processes. However, the heterogeneity of EVs challenges their exploration and the establishment of gold-standard methods. Here, we aimed to reveal the influence of technical changes on EV biology and the reliability of experimental data. We used B16F1 melanoma cells as a model and applied nanoparticle tracking analysis, mass spectrometry (LC-MS/MS) and pathway enrichment analysis to analyze the quantity, size distribution, proteome and function of their small EVs (sEVs) produced in sEV-depleted fetal bovine serum (FBS)-containing medium or serum-free medium. Additionally, we investigated the effects of minor technical variances on the quality of sEV preparations. We found that storage of the isolates at -80 °C has no adverse effect on LC-MS/MS analysis, and an additional washing step after differential ultracentrifugation has a minor influence on the sEV proteome. In contrast, FBS starvation affects the production and proteome of sEVs; moreover, these vesicles may have a greater impact on protein metabolism, but a smaller impact on cell adhesion and membrane raft assembly, than the control sEVs. As we demonstrated that FBS starvation has a strong influence on sEV biology, applying serum-free conditions might be considered in in vitro sEV studies.

Production and purification of bacterial membrane vesicles for biotechnology applications: Challenges and opportunities

Bacterial membrane vesicles (BMVs) are bi-layered nanostructures derived from Gram-negative and Gram-positive bacteria. Among other pathophysiological roles, BMVs are critical messengers in intercellular communication. As a result, BMVs are emerging as a promising technology for the development of numerous therapeutic applications. Despite the remarkable progress in unveiling BMV biology and functions in recent years, their successful isolation and purification have been limited. Several challenges related to vesicle purity, yield, and scalability severely hamper the further development of BMVs for biotechnology and clinical applications. This review focuses on the current technologies and methodologies used in BMV production and purification, such as ultracentrifugation, density-gradient centrifugation, size-exclusion chromatography, ultrafiltration, and precipitation. We also discuss the current challenges related to BMV isolation, large-scale production, storage, and stability that limit their application. More importantly, the present work explains the most recent strategies proposed for overcoming those challenges. Finally, we summarize the ongoing applications of BMVs in the biotechnological field.

Microfluidic Strategies for Extracellular Vesicle Isolation: Towards Clinical Applications

Extracellular vesicles (EVs) are double-layered lipid membrane vesicles released by cells. Currently, EVs are attracting a lot of attention in the biological and medical fields due to their role as natural carriers of proteins, lipids, and nucleic acids. Thus, they can transport useful genomic information from their parental cell through body fluids, promoting cell-to-cell communication even between different organs. Due to their functionality as cargo carriers and their protein expression, they can play an important role as possible diagnostic and prognostic biomarkers in various types of diseases, e.g., cancers, neurodegenerative, and autoimmune diseases. Today, given the invaluable importance of EVs, there are some pivotal challenges to overcome in terms of their isolation. Conventional methods have some limitations: they are influenced by the starting sample, might present low throughput and low purity, and sometimes a lack of reproducibility, being operator dependent. During the past few years, several microfluidic approaches have been proposed to address these issues. In this review, we summarize the most important microfluidic-based devices for EV isolation, highlighting their advantages and disadvantages compared to existing technology, as well as the current state of the art from the perspective of the use of these devices in clinical applications.

Exosomal Micro-RNAs as Intercellular Communicators in Idiopathic Pulmonary Fibrosis

Communication between neighboring or distant cells is made through a complex network that includes extracellular vesicles (EVs). Exosomes, which are a subgroup of EVs, are released from most cell types and have been found in biological fluids such as urine, plasma, and airway secretions like bronchoalveolar lavage (BAL), nasal lavage, saliva, and sputum. Mainly, the cargo exosomes are enriched with mRNAs and microRNAs (miRNAs), which can be transferred to a recipient cell consequently modifying and redirecting its biological function. The effects of miRNAs derive from their role as gene expression regulators by repressing or degrading their target mRNAs. Nowadays, various types of research are focused on evaluating the potential of exosomal miRNAs as biomarkers for the prognosis and diagnosis of different pathologies. Nevertheless, there are few reports on their role in the pathophysiology of idiopathic pulmonary fibrosis (IPF), a chronic lung disease characterized by progressive lung scarring with no cure. In this review, we focus on the role and effect of exosomal miRNAs as intercellular communicators in the onset and progression of IPF, as well as discussing their potential utility as therapeutic agents for the treatment of this disease.

Biomaterials and Extracellular Vesicle Delivery: Current Status, Applications and Challenges

In this review, we will discuss the current status of extracellular vesicle (EV) delivery via biopolymeric scaffolds for therapeutic applications and the challenges associated with the development of these functionalized scaffolds. EVs are cell-derived membranous structures and are involved in many physiological processes. Naïve and engineered EVs have much therapeutic potential, but proper delivery systems are required to prevent non-specific and off-target effects. Targeted and site-specific delivery using polymeric scaffolds can address these limitations. EV delivery with scaffolds has shown improvements in tissue remodeling, wound healing, bone healing, immunomodulation, and vascular performance. Thus, EV delivery via biopolymeric scaffolds is becoming an increasingly popular approach to tissue engineering. Although there are many types of natural and synthetic biopolymers, the overarching goal for many tissue engineers is to utilize biopolymers to restore defects and function as well as support host regeneration. Functionalizing biopolymers by incorporating EVs works toward this goal. Throughout this review, we will characterize extracellular vesicles, examine various biopolymers as a vehicle for EV delivery for therapeutic purposes, potential mechanisms by which EVs exert their effects, EV delivery for tissue repair and immunomodulation, and the challenges associated with the use of EVs in scaffolds.

Recommendations for extracellular vesicle miRNA biomarker research in the endometrial cancer context

Endometrial cancer (EC) is the most common gynaecological malignancy in the developed world, and concerningly incidence is rising, particularly in younger people. Therefore, there is increased interest in novel diagnostic and prognostic biomarkers. Extracellular vesicles (EVs) are membrane-bound particles present in bodily fluids that have the potential to facilitate non-invasive, early diagnosis of EC and could aid with monitoring of recurrence and treatment response. EV cargo provides molecular insight into the tumor, with the lipid bilayer providing stability for RNA species usually prone to degradation. miRNAs have recently become a focus for EV biomarker research due to their ability to regulate cancer related pathways and influence cancer development and progression. This review evaluates the current literature on EV miRNA biomarkers with a focus on EC, and discusses the challenges facing this research. This review finally highlights areas of focus for EV miRNA biomarker research going forward, such as standardization of normalization approaches, sample storage and processing, extensive reporting of methodologies and moving away from single miRNA biomarkers.

Extracellular Vesicle Measurements with Nanoparticle Tracking Analysis: A Different Appreciation of Up and Down Secretion

As is the case with most eucaryotic cells, cancer cells are able to secrete extracellular vesicles (EVs) as a communication means towards their environment and surrounding cells. EVs are represented by microvesicles and smaller vesicles called exosomes, which are known for their involvement in cancer aggressiveness. The release of such EVs requires the intervention of trafficking-associated proteins, mostly represented by the RAB-GTPases family. In particular, RAB27A is known for its role in addressing EVs-to-be secreted towards the the plasma membrane. In this study, shRNAs targeting RAB27A were used in colorectal (CRC) and glioblastoma (GB) cell lines in order to alter EVs secretion. To study and monitor EVs secretion in cell lines’ supernatants, nanoparticle tracking analysis (NTA) was used through the NanoSight NS300 device. Since it appeared that NanoSight failed to detect the decrease in the EVs secretion, we performed another approach to drop EVs secretion (RAB27A-siRNA, indomethacin, Nexihnib20). Similar results were obtained i.e., no variation in EVs concentration. Conversely, NTA allowed us to monitor EVs up-secretion following rotenone treatment or hypoxia conditions. Therefore, our data seemed to point out the insufficiency of using only this technique for the assessment of EVs secretion decrease.

Heterotopic ossification vs. fracture healing: Extracellular vesicle cargo proteins shed new light on bone formation

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare disease in which bone tissue forms in extraskeletal sites, which is known as heterotopic ossification (HO). Extracellular vesicles (EVs) are small phospholipid-enclosed particles released by various cells which have an emerging, but not completely understood role in various (patho)physiological processes. In order to further study the pathophysiology of FOP we conducted a small observational study comparing the proteomic profiles of EV cargo, derived from pooled plasma of four patient groups: FOP patient (N = 1) during active disease phase (flare-up), FOP patients during remission (N = 2), patients after long bone fracture (N = 20) and healthy controls (N = 10). After isolation of EVs – their protein cargo was determined using liquid chromatography / mass spectrometry, after which a functional gene enrichment analysis was performed. Our results show a sizeable difference of the proteomics profiles in which EVs from the bone fracture group show significant activity of integrin interactions, Wnt, VEGF, IGF-1 and PDGF pathways; conversely, FOP patients' EVs indicate that HO occurs via processes of innate immunity and the Ephrin B signaling pathway. We hypothesize that the Ephrin B signaling (expressed in EVs) contributes to HO by aiding in mesenchymal stem cell recruitment and osteogenic differentiation, as well as by contributing to the inflammatory response, including macrophage chemotaxis and activation. This is, to our knowledge, the first published analysis of EV protein cargo in FOP.

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Proteomics-based analysis of extracellular vesicles’ protein cargo in FOP patients, bone fracture healing and controls.

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Marked differences in signaling pathways expressed in extracellular vesicles in FOP vs. patients with bone fractures.

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Ephrin B signaling pathway expressed in extracellular vesicles identified as a likely cogwheel in heterotopic ossification.

Extracellular vesicles carry miR-27a-3p to promote drug resistance of glioblastoma to temozolomide by targeting BTG2

OBJECTIVE

Glioblastoma (GBM) is the most common central nervous system tumor. Temozolomide (TMZ) is a commonly used drug for GBM management. This study explored the mechanism of extracellular vesicles (EVs) regulating TMZ-resistance in GBM.

METHODS

LN229 cells were inducted into TMZ-resistant LN229r strain by stepwise induction. After the intervention of miR-27a-3p expression, cell viability of GBM cells treated with different concentrations of TMZ was detected by MTT and IC50 value was calculated. Cell proliferation and apoptosis were detected by colony formation and flow cytometry. EVs extracted from LN18 cells were identified and the internalization of EVs by LN229r cells was evaluated. The 100 μmol/L TMZ-treated LN229r cells were treated with EVs or EVs with downregulated miR-27a-3p to verify the effect of EVs-carried miR-27a-3p on TMZ resistance. The binding relation between BTG2 and miR-27a-3p was verified. miR-27a-3p and BTG2 expressions in GBM cells and EVs were detected by RT-qPCR. The BTG2 effect on TMZ-resistance in GBM was verified. The xenograft tumor nude mouse model was established by injecting LN229r cells and treated with EVs and 100 μmol/L TMZ.

RESULTS

miR-27a-3p was highly expressed in LN229r cells. IC50 value and proliferation of LN229r cells with silenced miR-27a-3p were decreased and apoptosis was increased, indicating that miR-27a-3p silencing reduced the drug-resistant cell LN229r resistance to TMZ. LN18-derived EVs could be internalized by LN229r cells, and release its encapsulated miR-27a-3p into LN229r cells and increase miR-27a-3p expression. EV treatment increased LN229r cell proliferation and reduced apoptosis, while EVs with silenced miR-27a-3p showed the opposite trend. miR-27a-3p targeted BTG2. BTG2 overexpression reduced LN229r cell resistance to TMZ. In vivo, after EVs treatment, tumor volume and weight, Ki67-positive rate, and miR-27a-3p were increased, while BTG2 expression was decreased.

CONCLUSION

GBM-derived EVs were internalized by GBM cells, released miR-27a-3p into GBM cells, upregulated miR-27a-3p expression, and targeted BTG2, thus promoting TMZ resistance.

NKG2D Ligands in Liquid Biopsy: The Importance of Soluble and Vesicle-Bound Proteins for Immune Modulation

The identification of biomarkers allowing diagnostics, prognostics and patient classification is still a challenge in oncological research for patient management. Improvements in patient survival achieved with immunotherapies substantiate that biomarker studies rely not only on cellular pathways contributing to the pathology, but also on the immune competence of the patient. If these immune molecules can be studied in a non-invasive manner, the benefit for patients and clinicians is obvious. The immune receptor Natural Killer Group 2 Member D (NKG2D) represents one of the main systems involved in direct recognition of tumor cells by effector lymphocytes (T and Natural Killer cells), and in immune evasion. The biology of NKG2D and its ligands comprises a complex network of cellular pathways leading to the expression of these tumor-associated ligands on the cell surface or to their release either as soluble proteins, or in extracellular vesicles that potently inhibit NKG2D-mediated responses. Increased levels of NKG2D-ligands in patient serum correlate with tumor progression and poor prognosis; however, most studies did not test the biochemical form of these molecules. Here we review the biology of the NKG2D receptor and ligands, their role in cancer and in patient response to immunotherapies, as well as the changes provoked in this system by non-immune cancer therapies. Further, we discuss the use of NKG2D-L in liquid biopsy, including methods to analyse vesicle-associated proteins. We propose that the evaluation in cancer patients of the whole NKG2D system can provide crucial information about patient immune competence and risk of tumor progression.

The functional role of soluble proteins acquired by extracellular vesicles

Extracellular vesicles (EVs) are lipid bilayer-enclosed nanosized particles released by all cell types during physiological as well as pathophysiological processes to carry out diverse biological functions, including acting as sources of cellular dumping, signalosomes and mineralisation nanoreactors. The ability of EVs to perform specific biological functions is due to their biochemical machinery. Among the components of the EVs' biochemical machinery, surface proteins are of critical functional significance as they mediate the interactions of EVs with components of the extracellular milieu, the extracellular matrix and neighbouring cells. Surface proteins are thought to be native, that is, pre-assembled on the EVs' surface by the parent cells before the vesicles are released. However, numerous pieces of evidence have suggested that soluble proteins are acquired by the EVs' surface from the extracellular milieu and further modulate the biological functions of EVs during innate and adaptive immune responses, autoimmune disorders, complement activation, coagulation, viral infection and biomineralisation. Herein, we will describe the methods currently used to identify the EVs' surface proteins and discuss recent knowledge on the functional relevance of the soluble proteins acquired by EVs.

Stability of Erythrocyte-Derived Nanovesicles Assessed by Light Scattering and Electron Microscopy

Extracellular vesicles (EVs) are gaining increasing amounts of attention due to their potential use in diagnostics and therapy, but the poor reproducibility of the studies that have been conducted on these structures hinders their breakthrough into routine practice. We believe that a better understanding of EVs stability and methods to control their integrity are the key to resolving this issue. In this work, erythrocyte EVs (hbEVs) were isolated by centrifugation from suspensions of human erythrocytes that had been aged in vitro. The isolate was characterised by scanning (SEM) and cryo-transmission electron microscopy (cryo-TEM), flow cytometry (FCM), dynamic/static light scattering (LS), protein electrophoresis, and UV-V spectrometry. The hbEVs were exposed to various conditions (pH (4–10), osmolarity (50–1000 mOsm/L), temperature (15–60 °C), and surfactant Triton X-100 (10–500 μM)). Their stability was evaluated by LS by considering the hydrodynamic radius (R_h), intensity of scattered light (I), and the shape parameter (ρ). The morphology of the hbEVs that had been stored in phosphate-buffered saline with citrate (PBS–citrate) at 4 °C remained consistent for more than 6 months. A change in the media properties (50–1000 mOsm/L, pH 4–10) had no significant effect on the R_h (=100–130 nm). At pH values below 6 and above 8, at temperatures above 45 °C, and in the presence of Triton X-100, hbEVs degradation was indicated by a decrease in I of more than 20%. Due to the simple preparation, homogeneous morphology, and stability of hbEVs under a wide range of conditions, they are considered to be a suitable option for EV reference material.

Acidic and Hypoxic Microenvironment in Melanoma: Impact of Tumour Exosomes on Disease Progression

The mechanisms of melanoma progression have been extensively studied in the last decade, and despite the diagnostic and therapeutic advancements pursued, malignant melanoma still accounts for 60% of skin cancer deaths. Therefore, research efforts are required to better define the intercellular molecular steps underlying the melanoma development. In an attempt to represent the complexity of the tumour microenvironment (TME), here we analysed the studies on melanoma in acidic and hypoxic microenvironments and the interactions with stromal and immune cells. Within TME, acidity and hypoxia force melanoma cells to adapt and to evolve into a malignant phenotype, through the cooperation of the tumour-surrounding stromal cells and the escape from the immune surveillance. The role of tumour exosomes in the intercellular crosstalk has been generally addressed, but less studied in acidic and hypoxic conditions. Thus, this review aims to summarize the role of acidic and hypoxic microenvironment in melanoma biology, as well as the role played by melanoma-derived exosomes (Mexo) under these conditions. We also present a perspective on the characteristics of acidic and hypoxic exosomes to disclose molecules, to be further considered as promising biomarkers for an early detection of the disease. An update on the use of exosomes in melanoma diagnosis, prognosis and response to treatment will be also provided and discussed.

Isolation and characterization of urine microvesicles from prostate cancer patients: different approaches, different visions

BACKGROUND

Because of their specific and biologically relevant cargo, urine extracellular vesicles (EVs) constitute a valuable source of potential non-invasive biomarkers that could support the clinical decision-making to improve the management of prostate cancer (PCa) patients. Different EV isolation methods differ in terms of complexity and yield, conditioning, as consequence, the analytical result.

METHODS

The aim of this study was to compare three different isolation methods for urine EVs: ultracentrifugation (UC), size exclusion chromatography (SEC), and a commercial kit (Exolute® Urine Kit). Urine samples were collected from 6 PCa patients and 4 healthy donors. After filtered through 0.22 µm filters, urine was divided in 3 equal volumes to perform EVs isolation with each of the three approaches. Isolated EVs were characterized by spectrophotometric protein quantification, nanoparticle tracking analysis, transmission electron microscopy, AlphaScreen Technology, and whole miRNA Transcriptome.

RESULTS

Our results showed that UC and SEC provided better results in terms of EVs yield and purity than Exolute®, non-significant differences were observed in terms of EV-size. Interestingly, luminescent AlphaScreen assay demonstrated a significant enrichment of CD9 and CD63 positive microvesicles in SEC and UC methods compared with Exolute®. This heterogeneity was also demonstrated in terms of miRNA content indicating that the best correlation was observed between UC and SEC.

CONCLUSIONS

Our study highlights the importance of standardizing the urine EV isolation methods to guaranty the analytical reproducibility necessary for their implementation in a clinical setting.

Exosomes: Potential Disease Biomarkers and New Therapeutic Targets

Exosomes are extracellular vesicles released by cells, both constitutively and after cell activation, and are present in different types of biological fluid. Exosomes are involved in the pathogenesis of diseases, such as cancer, neurodegenerative diseases, pregnancy disorders and cardiovascular diseases, and have emerged as potential non-invasive biomarkers for the detection, prognosis and therapeutics of a myriad of diseases. In this review, we describe recent advances related to the regulatory mechanisms of exosome biogenesis, release and molecular composition, as well as their role in health and disease, and their potential use as disease biomarkers and therapeutic targets. In addition, the advantages and disadvantages of their main isolation methods, characterization and cargo analysis, as well as the experimental methods used for exosome-mediated drug delivery, are discussed. Finally, we present potential perspectives for the use of exosomes in future clinical practice.

Novel Protocols for Scalable Production of High Quality Purified Small Extracellular Vesicles from Bovine Milk

Extracellular Vesicles (EVs) are cell-secreted nanovesicles that have unique potential for encapsulating and targeting "difficult-to-drug" therapeutic cargos. Milk provides an enriched source of EVs, and of particular interest to the drug delivery field, small EVs. Small EVs are distinguished from large EVs by membrane components, biogenesis mechanism and downstream functionality - in particular, small EVs are primarily composed of exosomes, which show high stability in vivo and naturally function in the targeted delivery of biological materials to cells. Moreover, bovine milk is abundantly produced by the dairy industry, widely consumed, and generally well tolerated by humans. Importantly, there is evidence that milk exosomes and small EVs are efficiently taken up into the circulation from the gut, providing the opportunity for their use in administration of therapeutics such as microRNAs or peptides not typically available via an oral route. Unfortunately, present methods for isolation do not efficiently separate EVs from milk proteins, resulting in contamination that is not desirable in a clinical-grade therapeutic. Herein, we present novel EV purification methods focused on optimized timing and levels of temperature and divalent cation chelation. Incorporation of these solubilization steps into centrifugation- and tangential flow filtration-based methods provide large amounts of purified small EVs at ultra-dense concentrations, which are substantially free from contaminating milk proteins. Remarkably, these ultra-dense isolates equal 10 to 15% of the starting volume of milk indicating a prodigious rate of small EV production by mammary glands. Our approach enables gentle, scalable production of ultrastructurally and functionally intact small EVs from milk, providing a path to their industrial scale purification for oral delivery of therapeutic biologics and small drugs.

Separation, characterization, and standardization of extracellular vesicles for drug delivery applications

Extracellular vesicles (EVs) are membranous nanovesicles secreted from living cells, shuttling macromolecules in intercellular communication and potentially possessing intrinsic therapeutic activity. Due to their stability, low immunogenicity, and inherent interaction with recipient cells, EVs also hold great promise as drug delivery vehicles. Indeed, they have been used to deliver nucleic acids, proteins, and small molecules in preclinical investigations. Furthermore, EV-based drugs have entered early clinical trials for cancer or neurodegenerative diseases. Despite their appeal as delivery vectors, however, EV-based drug delivery progress has been hampered by heterogeneity of sample types and methods as well as a persistent lack of standardization, validation, and comprehensive reporting. This review highlights specific requirements for EVs in drug delivery and describes the most pertinent approaches for separation and characterization. Despite residual uncertainties related to pharmacodynamics, pharmacokinetics, and potential off-target effects, clinical-grade, high-potency EV drugs might be achievable through GMP-compliant workflows in a highly standardized environment.

Human Adipose Tissue-Derived Stromal Cells Suppress Human, but Not Murine Lymphocyte Proliferation, via Indoleamine 2,3-Dioxygenase Activity

Over recent years, mesenchymal stromal cells (MSC) have gained immense attraction in immunotherapy, regenerative medicine and tissue engineering. MSC microenvironment modulation occurs through synergy of direct cell-cell contact, and secreted soluble factors and extracellular vesicles (EV). MSC-derived EV have been suggested as cell-free immunomodulatory alternative to MSC; however, previous findings have challenged this. Furthermore, recent data suggest that evaluating the mechanism of action of human MSC (hMSC) in animal models might promote adverse immune reactions or lack of functionality due to xeno-incompatibilities. In this study, we first assessed the immunomodulatory strength of different human MSC sources on in vitro stimulated T cells and compared this to interferon-gamma (IFNγ) primed MSC conditioned medium (CM) and EV. Second, we addressed the main molecular mechanisms, and third, we assessed the MSC in vitro immunosuppressive effect across interspecies barriers. We identified human adipose tissue-derived stromal cells (ASC) with strongest immunomodulatory strength, followed by bone marrow (BM) and cord blood-derived MSC (CB). Whilst CM from primed ASC managed to exert analogous effects as their cellular counterpart, EV derived thereof did not, reproducing previous findings. IFNγ-induced indoleamine 2,3-dioxygenase (IDO) activity was identified as key mechanism to suppress human lymphocyte proliferation, as in the presence of the IDO inhibitor epacadostat (Epac) a stimulation of proliferation was seen. In addition, we revealed MSC immunosuppressive effects to be species-specific, because human cells failed to suppress murine lymphocyte proliferation. In summary, ASC were the strongest immunomodulators with the IDO-kynurenine pathway being key within the human system. Importantly, the in vitro lack of interspecies immunomodulatory strength suggests that preclinical data need to be carefully interpreted especially when considering a possible translation to clinical field.