How does temperature play a role in the storage of extracellular vesicles?

Assessment of urine sample collection and processing variables for extracellular vesicle-based proteomics

Extracellular vesicles (EVs) in urine are a promising source for developing non-invasive biomarkers. However, urine concentration and content are highly variable and dynamic, and actual urine collection and handling often is nonideal. Furthermore, patients such as those with prostate diseases have challenges in sample collection due to difficulties in holding urine at designated time points. Here, we simulated the actual situation of clinical sample collection to examine the stability of EVs in urine under different circumstances, including urine collection time and temporary storage temperature, as well as daily urine sampling under different diet conditions. EVs were isolated using functionalized EVtrap magnetic beads and characterized by nanoparticle tracking analysis (NTA), western blotting, electron microscopy, and mass spectrometry (MS). EVs in urine remained relatively stable during temporary storage for 6 hours at room temperature and for 12 hours at 4 °C, while significant fluctuations were observed in EV amounts from urine samples collected at different time points from the same individuals, especially under certain diets. Sample normalization with creatinine reduced the coefficient of variation (CV) values among EV samples from 17% to approximately 6% and facilitated downstream MS analyses. Finally, based on the results, we applied them to evaluate potential biomarker panels in prostate cancer by data-independent acquisition (DIA) MS, presenting the recommendation that can facilitate biomarker discovery with nonideal handling conditions.

Platelet-derived extracellular vesicles: a new-generation nanostructured tool for chronic wound healing

Chronic nonhealing wounds pose a serious challenge to regaining skin function and integrity. Platelet-derived extracellular vesicles (PEVs) are nanostructured particles with the potential to promote wound healing since they can enhance neovascularization and cell migration and reduce inflammation and scarring. This work provides an innovative overview of the technical laboratory issues in PEV production, PEVs' role in chronic wound healing and the benefits and challenges in its clinical translation. The article also explores the challenges of proper sourcing, extraction techniques and storage conditions, and discusses the necessity of further evaluations and combinational therapeutics, including dressing biomaterials, M2-derived exosomes, mesenchymal stem cells-derived extracellular vesicles and microneedle technology, to boost their therapeutic efficacy as advanced strategies for wound healing.

Circulating exosomal miR-16-5p and let-7e-5p are associated with bladder fibrosis of diabetic cystopathy

Diabetic cystopathy (DCP) is a prevalent etiology of bladder dysfunction in individuals with longstanding diabetes, frequently leading to bladder interstitial fibrosis. Research investigating the initial pathological alterations of DCP is notably scarce. To comprehend the development of fibrosis and find effective biomarkers for its diagnosis, we prepared streptozotocin-induced long-term diabetic SD rats exhibiting a type 1 diabetes phenotype and bladder fibrosis in histology detection. After observing myofibroblast differentiation from rats' primary bladder fibroblasts with immunofluorescence, we isolated fibroblasts derived exosomes and performed exosomal miRNA sequencing. The co-differentially expressed miRNAs (DEMis) (miR-16-5p and let-7e-5p) were screened through a joint analysis of diabetic rats and long-term patients' plasma data (GES97123) downloaded from the GEO database. Then two co-DEMis were validated by quantitative PCR on exosomes derived from diabetic rats' plasma. Following with a series of analysis, including target mRNAs and transcription factors (TFs) prediction, hubgenes identification, protein-protein interaction (PPI) network construction and gene enrichment analysis, a miRNA-mediated genetic regulatory network consisting of two miRNAs, nine TFs, and thirty target mRNAs were identified in relation to fibrotic processes. Thus, circulating exosomal miR-16-5p and let-7e-5p are associated with bladder fibrosis of DCP, and the crucial genes in regulatory network might hold immense significance in studying the pathogenesis and molecular mechanisms of fibrosis, which deserves further exploration.

A New Paradigm in Spinal Cord Injury Therapy: from Cell-free Treatment to Engineering Modifications

Spinal cord injury (SCI) is an intractable and poorly prognostic neurological disease, and current treatments are still unable to cure it completely and avoid sequelae. Extracellular vesicles (EVs), as important carriers of intercellular communication and pharmacological effects, are considered to be the most promising candidates for SCI therapy because of their low toxicity and immunogenicity, their ability to encapsulate endogenous bioactive molecules (e.g., proteins, lipids, and nucleic acids), and their ability to cross the blood-brain/cerebrospinal barriers. However, poor targeting, low retention rate, and limited therapeutic efficacy of natural EVs have bottlenecked EVs-based SCI therapy. A new paradigm for SCI treatment will be provided by engineering modified EVs. Furthermore, our limited understanding of the role of EVs in SCI pathology hinders the rational design of novel EVbased therapeutic approaches. In this study, we review the pathophysiology after SCI, especially the multicellular EVs-mediated crosstalk; briefly describe the shift from cellular to cell-free therapies for SCI treatment; discuss and analyze the issues related to the route and dose of EVs administration; summarize and present the common strategies for EVs drug loading in the treatment of SCI and point out the shortcomings of these drug loading methods; finally, we analyze and highlight the feasibility and advantages of bio-scaffold-encapsulated EVs for SCI treatment, providing scalable insights into cell-free therapy for SCI.

Exploring the role of polymers to overcome ongoing challenges in the field of extracellular vesicles

Extracellular vesicles (EVs) are naturally occurring nanoparticles released from all eucaryotic and procaryotic cells. While their role was formerly largely underestimated, EVs are now clearly established as key mediators of intercellular communication. Therefore, these vesicles constitute an attractive topic of study for both basic and applied research with great potential, for example, as a new class of biomarkers, as cell-free therapeutics or as drug delivery systems. However, the complexity and biological origin of EVs sometimes complicate their identification and therapeutic use. Thus, this rapidly expanding research field requires new methods and tools for the production, enrichment, detection, and therapeutic application of EVs. In this review, we have sought to explain how polymer materials actively contributed to overcome some of the limitations associated to EVs. Indeed, thanks to their infinite diversity of composition and properties, polymers can act through a variety of strategies and at different stages of EVs development. Overall, we would like to emphasize the importance of multidisciplinary research involving polymers to address persistent limitations in the field of EVs.

Comparative Studies of Different Preservation Methods and Relative Freeze-Drying Formulations for Extracellular Vesicle Pharmaceutical Applications

Extracellular vesicles (EVs) have been studied for years for their role as effectors and mediators of cell-to-cell communication and their potential application to develop new and increasingly performing nanotechnological systems for the diagnosis and/or treatment of many diseases. Given all the EVs applications as just isolated, functionalized, or even engineered cellular-derived pharmaceuticals, the standardization of reliable and reproducible methods for their preservation is urgently needed. In this study, we isolated EVs from a healthy blood cell line, B lymphocytes, and compared the effectiveness of different storage methods and relative freeze-drying formulations to preserve some of the most important EVs' key features, i.e., concentration, mean size, protein content, and surface antigen's expression. To develop a preservation method that minimally affects the EVs' integrity and functionality, we applied the freeze-drying process in combination with different excipients. Since EVs are isolated not only from body fluids but also from culture media conditioned by the cells growing there, we decided to test both the effects of the traditional pharmaceutical excipient and of biological media to develop EVs solidified products with desirable appearance and performance properties. Results showed that some of the tested excipients, i.e., sugars in combination with dextran and glycine, successfully maintained the stability and integrity of EVs upon lyophilization. In addition, to evaluate the preservation of the EVs' biological activity, we assessed the cytotoxicity and internalization ability of the reconstituted EVs in healthy (B lymphocytes) and tumoral (Burkitt's lymphoma) cells. Reconstituted EVs demonstrated toxicity only toward the cancerous cells, opening new therapeutic opportunities for the oncological field. Furthermore, our study showed how some biological or cellular-conditioned fluids, commonly used in the field of cell cultures, can act not only as cryoprotectants but also as active pharmaceutical ingredients, significantly tuning the therapeutic effect of EVs, even increasing their cellular internalization.

Effect of pro-inflammatory cytokine priming and storage temperature of the mesenchymal stromal cell (MSC) secretome on equine articular chondrocytes

Context: Osteoarthritis (OA) is an invalidating articular disease characterized by cartilage degradation and inflammatory events. In horses, OA is associated with up to 60% of lameness and leads to reduced animal welfare along with extensive economic losses; currently, there are no curative therapies to treat OA. The mesenchymal stromal cell (MSC) secretome exhibits anti-inflammatory properties, making it an attractive candidate for improving the management of OA. In this study, we determined the best storage conditions for conditioned media (CMs) and tested whether priming MSCs with cytokines can enhance the properties of the MSC secretome. Methods: First, properties of CMs collected from bone-marrow MSC cultures and stored at -80°C, -20°C, 4°C, 20°C or 37°C were assessed on 3D cultures of equine articular chondrocytes (eACs). Second, we primed MSCs with IL-1β, TNF-α or IFN-γ, and evaluated the MSC transcript levels of immunomodulatory effectors and growth factors. The primed CMs were also harvested for subsequent treatment of eACs, either cultured in monolayers or as 3D cell cultures. Finally, we evaluated the effect of CMs on the proliferation and the phenotype of eACs and the quality of the extracellular matrix of the neosynthesized cartilage. Results: CM storage at -80°C, -20°C, and 4°C improved collagen protein accumulation, cell proliferation and the downregulation of inflammation. The three cytokines chosen for the MSC priming influenced MSC immunomodulator gene expression, although each cytokine led to a different pattern of MSC immunomodulation. The cytokine-primed CM had no major effect on eAC proliferation, with IL-1β and TNF-α slightly increasing collagen (types IIB and I) accumulation in eAC 3D cultures (particularly with the CM derived from MSCs primed with IL-1β), and IFN-γ leading to a marked decrease. IL-1β-primed CMs resulted in increased eAC transcript levels of MMP1, MMP13 and HTRA1, whereas IFNγ-primed CMs decreased the levels of HTRA1 and MMP13. Conclusion: Although the three cytokines differentially affected the expression of immunomodulatory molecules, primed CMs induced a distinct effect on eACs according to the cytokine used for MSC priming. Different mechanisms seemed to be triggered by each priming cytokine, highlighting the need for further investigation. Nevertheless, this study demonstrates the potential of MSC-CMs for improving equine OA management.

Significance of wastewater surveillance in detecting the prevalence of SARS-CoV-2 variants and other respiratory viruses in the community - A multi-site evaluation

Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral genome in wastewater has proven to be useful for tracking the trends of virus prevalence within the community. The surveillance also provides precise and early detection of any new and circulating variants, which aids in response to viral outbreaks. Site-specific monitoring of SARS-CoV-2 variants provides valuable information on the prevalence of new or emerging variants in the community. We sequenced the genomic RNA of viruses present in the wastewater samples and analyzed for the prevalence of SARS-CoV-2 variants as well as other respiratory viruses for a period of one year to account for seasonal variations. The samples were collected from the Reno-Sparks metropolitan area on a weekly basis between November 2021 to November 2022. Samples were analyzed to detect the levels of SARS-CoV-2 genomic copies and variants identification. This study confirmed that wastewater monitoring of SARS-CoV-2 variants can be used for community surveillance and early detection of circulating variants and supports wastewater-based epidemiology (WBE) as a complement to clinical respiratory virus testing as a healthcare response effort. Our study showed the persistence of the SARS-CoV-2 virus throughout the year compared to a seasonal presence of other respiratory viruses, implicating SARS-CoV-2's broad genetic diversity and strength to persist and infect susceptible hosts. Through secondary analysis, we further identified antimicrobial resistance (AMR) genes in the same wastewater samples and found WBE to be a feasible tool for community AMR detection and monitoring.

Impact of storage conditions and duration on function of native and cargo-loaded mesenchymal stromal cell extracellular vesicles

BACKGROUND AIMS

As evidenced by ongoing clinical trials and increased activity in the commercial sector, extracellular vesicle (EV)-based therapies have begun the transition from bench to bedside. As this progression continues, one critical aspect of EV clinical translation is understanding the effects of storage and transport conditions. Several studies have assessed the impact of storage on EV characteristics such as morphology, uptake and component content, but effects of storage duration and temperature on EV functional bioactivity and, especially, loaded cargo are rarely reported.

METHODS

The authors assessed EV outcomes following storage at different temperatures (room temperature, 4°C, -20°C, -80°C) for various durations as well as after lyophilization.

RESULTS

Mesenchymal stromal cell (MSC) EVs were observed to retain key aspects of their bioactivity (pro-vascularization, anti-inflammation) for up to 4-6 weeks at -20°C and -80°C and after lyophilization. Furthermore, via in vitro assays and an in vivo wound healing model, these same storage conditions were also demonstrated to enable preservation of the functionality of loaded microRNA and long non-coding RNA cargo in MSC EVs.

CONCLUSIONS

These findings extend the current understanding of how EV therapeutic potential is impacted by storage conditions and may inform best practices for handling and storing MSC EVs for both basic research and translational purposes.

Biophysical Parameters of Plasma-Derived Extracellular Vesicles as Potential Biomarkers of Bone Disturbances in Breast Cancer Patients Receiving an Individualized Nutrition Intervention

Extracellular vesicles (EVs) are implicated in several biological conditions, including bone metabolism disturbances in breast cancer patients (BCPs). These disorders hinder the adjustment of nutrition interventions due to changes in bone mineral density (BMD). The biophysical properties of EVs (e.g., size or electrostatic repulsion) affect their cellular uptake, however, their clinical relevance is unclear. In this study, we aimed to investigate the association between the biophysical properties of the plasma-derived EVs and BMDs in BCPs who received an individualized nutrition intervention during the first six months of antineoplastic treatment. As part of the nutritional assessment before and after the intervention, body composition including bone densitometry and plasma samples were obtained. In 16 BCPs, EVs were isolated using ExoQuick^® and their biophysical properties were analyzed using light-scattering techniques. We found that the average hydrodynamic diameter of large EVs was associated with femoral neck bone mineral content, lumbar spine BMD, and neoplasms' molecular subtypes. These results provide evidence that EVs play a role in BCPs' bone disorders and suggest that the biophysical properties of EVs may serve as potential nutritional biomarkers. Further studies are needed to evaluate EVs' biophysical properties as potential nutritional biomarkers in a clinical context.

Platelets, Protean Cells with All-Around Functions and Multifaceted Pharmacological Applications

Platelets, traditionally known for their roles in hemostasis and coagulation, are the most prevalent blood component after erythrocytes (150,000-400,000 platelets/μL in healthy humans). However, only 10,000 platelets/μL are needed for vessel wall repair and wound healing. Increased knowledge of the platelet's role in hemostasis has led to many advances in understanding that they are crucial mediators in many other physiological processes, such as innate and adaptive immunity. Due to their multiple functions, platelet dysfunction is involved not only in thrombosis, mediating myocardial infarction, stroke, and venous thromboembolism, but also in several other disorders, such as tumors, autoimmune diseases, and neurodegenerative diseases. On the other hand, thanks to their multiple functions, nowadays platelets are therapeutic targets in different pathologies, in addition to atherothrombotic diseases; they can be used as an innovative drug delivery system, and their derivatives, such as platelet lysates and platelet extracellular vesicles (pEVs), can be useful in regenerative medicine and many other fields. The protean role of platelets, from the name of Proteus, a Greek mythological divinity who could take on different shapes or aspects, is precisely the focus of this review.

Unraveling multilayered extracellular vesicles: Speculation on cause

Extracellular vesicles (EVs) are cell-released, heterogenous nanoparticles that play important roles in (patho)physiological processes through intercellular communication. EVs are often depicted as having a single lipid bilayer, but many studies have demonstrated the existence of multilayered EVs. There has been minimal inquiry into differences between unilamellar and multilamellar EVs in terms of biogenesis mechanisms and functional effects. This commentary speculates on potential causes and roles of multilamellar EVs and serves as a call to action for the research community to unravel the complex layers of EVs.

A survey to evaluate parameters governing the selection and application of extracellular vesicle isolation methods

Extracellular vesicles (EVs) continue to gain interest across the scientific community for diagnostic and therapeutic applications. As EV applications diversify, it is essential that researchers are aware of challenges, in particular the compatibility of EV isolation methods with downstream applications and their clinical translation. We report outcomes of the first cross-comparison study looking to determine parameters (EV source, starting volume, operator experience, application and implementation parameters such as cost and scalability) governing the selection of popular EV isolation methods across disciplines. Our findings highlighted an increased clinical focus, with 36% of respondents applying EVs in therapeutics and diagnostics. Data indicated preferential selection of ultracentrifugation for therapeutic applications, precipitation reagents in clinical settings and size exclusion chromatography for diagnostic applications utilising biofluids. Method selection was influenced by operator experience, with increased method diversity when EV research was not the respondents primary focus. Application and implementation criteria were indicated to be major influencers in method selection, with UC and SEC chosen for their abilities to process large and small volumes, respectively. Overall, we identified parameters influencing method selection across the breadth of EV science, providing a valuable overview of practical considerations for the effective translation of research outcomes.

Comparison of extracellular vesicle isolation processes for therapeutic applications

While extracellular vesicles (EVs) continue to gain interest for therapeutic applications, their clinical translation is limited by a lack of optimal isolation methods. We sought to determine how universally applied isolation methods impact EV purity and yield. EVs were isolated by ultracentrifugation (UC), polyethylene glycol precipitation, Total Exosome Isolation Reagent, an aqueous two-phase system with and without repeat washes or size exclusion chromatography (SEC). EV-like particles could be detected for all isolation methods but varied in their purity and relative expression of surface markers (Alix, Annexin A2, CD9, CD63 and CD81). Assessments of sample purity were dependent on the specificity of characterisation method applied, with total particle counts and particle to protein (PtP) ratios often not aligning with quantitative measures of tetraspanin surface markers obtained using high-resolution nano-flow cytometry. While SEC resulted in the isolation of fewer particles with a relatively low PtP ratio (1.12 × 107 ± 1.43 × 106 vs highest recorded; ATPS/R 2.01 × 108 ± 1.15 × 109, p ⩽ 0.05), EVs isolated using this method displayed a comparatively high level of tetraspanin positivity (e.g. ExoELISA CD63⁺ particles; 1.36 × 1011 ± 1.18 × 1010 vs ATPS/R 2.58 × 1010 ± 1.92 × 109, p ⩽ 0.001). Results originating from an accompanying survey designed to evaluate pragmatic considerations surrounding method implementation (e.g. scalability and cost) identified that SEC and UC were favoured for overall efficiency. However, reservations were highlighted in the scalability of these methods, which could potentially hinder downstream therapeutic applications. In conclusion, variations in sample purity and yield were evident between isolation methods, while standard non-specific assessments of sample purity did not align with advanced quantitative high-resolution analysis of EV surface markers. Reproducible and specific assessments of EV purity will be critical for informing therapeutic 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.

Sucrose-based cryoprotective storage of extracellular vesicles

Advancements in extracellular vesicle (EV) studies necessitate the development of optimized storage conditions to ensure preservation of physical and biochemical characteristics. In this study, the most common buffer for EV storage (phosphate-buffered saline/PBS) was compared to a cryoprotective 5% sucrose solution. The size distribution and concentration of EVs from two different sources changed to a greater extent after -80 °C storage in PBS compared to the sucrose solution. Additionally, molecular surface protrusions and transmembrane proteins were more prevalent in EVs stored in the sucrose solution compared to those stored in PBS. This study demonstrates, for the first time, that distinct ring-like molecular complexes and cristae-like folded membranous structures are visible upon EV degradation. Taken together, the size, concentration, molecular surface extensions, and transmembrane proteins of EVs varied substantially based on the buffer used for -80 °C storage, suggesting that biocompatible cryoprotectants, such as sucrose, should be considered for EV studies.

Exosomes from prostate cancer cell lines: Isolation optimisation and characterisation

Exosomes are considered to be a rich source of biomarkers, hence in this article we examine the best procedure for their isolation. We examine several isolation procedures, exosome storage conditions and other conditions affecting exosome production by prostate cell lines. We selected four different commercially available kits based on different principles to achieve exosome isolation, the best being magnetic-based. In addition, we found storage at - 20 °C to be good for storing isolated exosomes and that exosomes were produced from the cancerous prostate cell line 22Rv1 in much greater amounts than the non-cancerous prostate cell line RWPE1. We also found differences in the response of both cell lines in the production of exosomes as a result of stress, i.e. exposure to hydrogen peroxide and starvation. The effect of Triton X-100 on exosome lysis was examined using two different surfactant concentrations by analysis of the exosome count and change in the exosome size. The final part of the article details the advantages of the use of a 2D biochip prepared in-house over a commercially available 3D biochip for monitoring the interaction of exosomes via its surface receptors (CD63) with an immobilised ligand (anti-CD63 antibodies) using surface plasmon resonance. The final experiment shows the potential of lectin fluorescent microarrays for the analysis of glycans present in lysed exosomes.

Identification of storage conditions stabilizing extracellular vesicles preparations

Extracellular vesicles (EVs) play a key role in many physiological and pathophysiological processes and hold great potential for therapeutic and diagnostic use. Despite significant advances within the last decade, the key issue of EV storage stability remains unresolved and under investigated. Here, we aimed to identify storage conditions stabilizing EVs and comprehensively compared the impact of various storage buffer formulations at different temperatures on EVs derived from different cellular sources for up to 2 years. EV features including concentration, diameter, surface protein profile and nucleic acid contents were assessed by complementary methods, and engineered EVs containing fluorophores or functionalized surface proteins were utilized to compare cellular uptake and ligand binding. We show that storing EVs in PBS over time leads to drastically reduced recovery particularly for pure EV samples at all temperatures tested, starting already within days. We further report that using PBS as diluent was found to result in severely reduced EV recovery rates already within minutes. Several of the tested new buffer conditions largely prevented the observed effects, the lead candidate being PBS supplemented with human albumin and trehalose (PBS-HAT). We report that PBS-HAT buffer facilitates clearly improved short-term and long-term EV preservation for samples stored at -80°C, stability throughout several freeze-thaw cycles, and drastically improved EV recovery when using a diluent for EV samples for downstream applications.

Impact of Storage Conditions on EV Integrity/Surface Markers and Cargos

Extracellular vesicles (EVs) are small biological particles released into biofluids by every cell. Based on their size, they are classified into small EVs (<100 nm or <200 nm) and medium or large EVs (>200 nm). In recent years, EVs have garnered interest for their potential medical applications, including disease diagnosis, cell-based biotherapies, targeted drug delivery systems, and others. Currently, the long-term and short-term storage temperatures for biofluids and EVs are −80 °C and 4 °C, respectively. The storage capacity of EVs can depend on their number, size, function, temperature, duration, and freeze−thaw cycles. While these parameters are increasingly studied, the effects of preservation and storage conditions of EVs on their integrity remain to be understood. Knowledge gaps in these areas may ultimately impede the widespread applicability of EVs. Therefore, this review summarizes the current knowledge on the effect of storage conditions on EVs and their stability and critically explores prospective ways for improving long-term storage conditions to ensure EV stability.

Loss of Renewal of Extracellular Vesicles: Harmful Effects on Embryo Development in vitro

Background

Methods

Results

Conclusion

Mesenchymal Stromal Cell-Derived Extracellular Vesicles as Biological Carriers for Drug Delivery in Cancer Therapy

Cancer is the second leading cause of death worldwide, with 10.0 million cancer deaths in 2020. Despite advances in targeted therapies, some pharmacological drawbacks associated with anticancer chemo and immunotherapeutic agents include high toxicities, low bioavailability, and drug resistance. In recent years, extracellular vesicles emerged as a new promising platform for drug delivery, with the advantage of their inherent biocompatibility and specific targeting compared to artificial nanocarriers, such as liposomes. Particularly, mesenchymal stem/stromal cells were proposed as a source of extracellular vesicles for cancer therapy because of their intrinsic properties: high in vitro self-renewal and proliferation, regenerative and immunomodulatory capacities, and secretion of extracellular vesicles that mediate most of their paracrine functions. Moreover, extracellular vesicles are static and safer in comparison with mesenchymal stem/stromal cells, which can undergo genetic/epigenetic or phenotypic changes after their administration to patients. In this review, we summarize currently reported information regarding mesenchymal stem/stromal cell-derived extracellular vesicles, their proper isolation and purification techniques - from either naive or engineered mesenchymal stem/stromal cells - for their application in cancer therapy, as well as available downstream modification methods to improve their therapeutic properties. Additionally, we discuss the challenges associated with extracellular vesicles for cancer therapy, and we review some preclinical and clinical data available in the literature.

The impact of storage on extracellular vesicles: A systematic study

Mounting evidence suggests that storage has an impact on extracellular vesicles (EVs) properties. While -80°C storage is a widespread approach, some authors proposed improved storage strategies with conflicting results. Here, we designed a systematic study to assess the impact of -80°C storage and freeze-thaw cycles on EVs. We tested the differences among eight storage strategies and investigated the possible fusion phenomena occurring during storage. EVs were collected from human plasma and murine microglia culture by size exclusion chromatography and ultracentrifugation, respectively. The analysis included: concentration, size and zeta potential (tunable resistive pulse sensing), contaminant protein assessment; flow cytometry for the analysis of two single fluorescent-tagged EVs populations (GFP and mCherry), mixed before preservation. We found that -80°C storage reduces EVs concentration and sample purity in a time-dependent manner. Furthermore, it increases the particle size and size variability and modifies EVs zeta potential, with a shift of EVs in size-charge plots. None of the tested conditions prevented the observed effects. Freeze-thaw cycles lead to an EVs reduction after the first cycle and to a cycle-dependent increase in particle size. With flow cytometry, after storage, we observed a significant population of double-positive EVs (GFP+ -mCherry+ ). This observation may suggest the occurrence of fusion phenomena during storage. Our findings show a significant impact of storage on EVs samples in terms of particle loss, purity reduction and fusion phenomena leading to artefactual particles. Depending on downstream analyses and experimental settings, EVs should probably be processed from fresh, non-archival, samples in majority of cases.

A scalable coaxial bioprinting technology for mesenchymal stem cell microfiber fabrication and high extracellular vesicle yield

Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) are promising candidates for regenerative medicine; however, the lack of scalable methods for high quantity EV production limits their application. In addition, signature EV-derived proteins shared in 3D environments and 2D surfaces, remain mostly unknown. Herein, we present a platform combining MSC microfiber culture with ultracentrifugation purification for high EV yield. Within this platform, a high quantity MSC solution (∼3 × 10⁸total cells) is encapsulated in a meter-long hollow hydrogel-microfiber via coaxial bioprinting technology. In this 3D core-shell microfiber environment, MSCs express higher levels of stemness markers (Oct4, Nanog, Sox2) than in 2D culture, and maintain their differentiation capacity. Moreover, this platform enriches particles by ∼1009-fold compared to conventional 2D culture, while preserving their pro-angiogenic properties. Liquid chromatography-mass spectrometry characterization results demonstrate that EVs derived from our platform and conventional 2D culturing have unique protein profiles with 3D-EVs having a greater variety of proteins (1023 vs 605), however, they also share certain proteins (536) and signature MSC-EV proteins (10). This platform, therefore, provides a new tool for EV production using microfibers in one culture dish, thereby reducing space, labor, time, and cost.

New hope for intervertebral disc degeneration: bone marrow mesenchymal stem cells and exosomes derived from bone marrow mesenchymal stem cell transplantation

Bone marrow mesenchymal stem cells (BMSCs), multidirectional cells with self-renewal capacity, can differentiate into many cell types and play essential roles in tissue healing and regenerative medicine. Cell experiments and in vivo research in animal models have shown that BMSCs can repair degenerative discs by promoting cell proliferation and expressing extracellular matrix (ECM) components, such as type II collagen and protein-polysaccharides. Delaying or reversing the intervertebral disc (IVD) degeneration (IDD) process at an etiological level may be an effective strategy. However, despite increasingly in-depth research, some deficiencies in cell transplantation timing and strategy remain, preventing the clinical application of cell transplantation. Exosomes exhibit the characteristics of the mother cells from which they were secreted and can inhibit nucleus pulposus (NP) cell (NPC) apoptosis and delay IDD through intercellular communication. Furthermore, the use of exosomes effectively avoids problems associated with cell transplantation, such as immune rejection. This manuscript introduces almost all of the BMSCs and exosomes derived from BMSCs (BMSCs-Exos) described in the IDD literature. Many challenges regarding the use of cell transplantation and therapeutic exosome intervention for IDD remain to be overcome.

Techniques for increasing the yield of stem cell-derived exosomes: what factors may be involved?

Exosomes are nano-scale extracellular vesicles secreted by cells and constitute an important part in the cell-cell communication. The main contents of the exosomes include proteins, microRNAs, and lipids. The mechanism and safety of stem cell-derived exosomes have rendered them a promising therapeutic strategy for regenerative medicine. Nevertheless, limited yield has restrained full explication of their functions and clinical applications To address this, various attempts have been made to explore the up- and down-stream manipulations in a bid to increase the production of exosomes. This review has recapitulated factors which may influence the yield of stem cell-derived exosomes, including selection and culture of stem cells, isolation and preservation of the exosomes, and development of artificial exosomes.

Cryo-self-assembled silk fibroin sponge as a biodegradable platform for enzyme-responsive delivery of exosomes

Although advances in protein assembly preparation have provided a new platform for drug delivery during tissue engineering, achieving long-term controlled exosome delivery remains a significant challenge. Diffusion-dominated exosome release using protein hydrogels results in burst release of exosomes. Here, a fibroin-based cryo-sponge was developed to provide controlled exosome release. Fibroin chains can self-assemble into silk I structures under ice-cold conditions when annealed above the glass transition temperature. Exosome release is enzyme-responsive, with rates primarily determined by enzymatic degradation of the scaffolds. In vivo experiments have demonstrated that exosomes remain in undigested sponge material for two months, superior to their retention in fibrin glue, a commonly used biomaterial in clinical practice. Fibroin cryo-sponges were implanted subcutaneously in nude mice. The exosome-containing sponge group exhibited better neovascularization and tissue ingrowth effects, demonstrating the efficacy of this exosome-encapsulating strategy by realizing sustained release and maintaining exosome bioactivity. These silk fibroin cryo-sponges containing exosomes provide a new platform for future studies of exosome therapy.

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The glass transition temperature of fibroin solution is affected by ions.

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Silk fibroin could self-assembly into silk I structure when annealed below 0 °C.

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Encapsulation of exosomes into the fibroin cryo-sponge would not destroy the integrity of exosomes.

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The release of exosomes from fibroin cryo-sponges is dominated by scaffold degradation.

Tissue-derived extracellular vesicles: Research progress from isolation to application

Extracellular vesicles (EVs) are the structures that all cells release into the environment. They are separated by a lipid bilayer and contain the cellular components that release them. To date, most studies have been performed on EVs derived from cell supernatants or different body fluids, while the number of studies on EV isolation directly from tissues is still limited. Studies of EV isolation directly from tissues may provide us with better information. This review summarizes the role of EV in the extracellular matrix, the protocol for isolation of EV in the tissue interstitium, and the application of the protocol in different tissues.

Platelet-Derived Extracellular Vesicles for Regenerative Medicine

Extracellular vesicles (EVs) present a great potential for the development of new treatments in the biomedical field. To be used as therapeutics, many different sources have been used for EVs obtention, while only a few studies have addressed the use of platelet-derived EVs (pEVs). In fact, pEVs have been shown to intervene in different healing responses, thus some studies have evaluated their regenerative capability in wound healing or hemorrhagic shock. Even more, pEVs have proven to induce cellular differentiation, enhancing musculoskeletal or neural regeneration. However, the obtention and characterization of pEVs is widely heterogeneous and differs from the recommendations of the International Society for Extracellular Vesicles. Therefore, in this review, we aim to present the main advances in the therapeutical use of pEVs in the regenerative medicine field while highlighting the isolation and characterization steps followed. The main goal of this review is to portray the studies performed in order to enhance the translation of the pEVs research into feasible therapeutical applications.

Urinary Extracellular Vesicles and Their miRNA Cargo in Patients with Fabry Nephropathy

Current biomarkers of Fabry nephropathy lack sensitivity in detecting early kidney damage and do not predict progression of nephropathy. Urinary extracellular vesicles (uEVs) and their molecular cargo could reflect early changes in renal impairment as they are secreted by the cells lining the urinary tract. We aimed to conduct a proof-of-concept study to investigate whether analysis of uEV characteristics and expression of uEV-derived microRNAs (miRNAs) could be applicable in studies to predict the development and progression of nephropathy in Fabry disease. A total of 20 Fabry patients were divided into two groups, depending on the presence of nephropathy. Chronological urine samples collected during 10-year follow-up were used for uEVs isolation with size exclusion chromatography. Nanoparticle tracking analysis was used to determine concentration and size of uEVs. We evaluated the expression of five uEV-derived miRNAs by qPCR (miR-23a-3p, miR-29a-3p, miR-30b-5p, miR-34a-5p, miR-200a-3p). There was no difference in the concentration and size of uEVs between patients with and without nephropathy at last follow-up or longitudinally. However, we found increased expression of miR-29a-3p and miR-200a-3p in uEVs isolated from chronological samples of patients with Fabry nephropathy. This may indicate an attempt by the organism to prevent the progression of renal damage leading to end-stage renal disease as previously reported in type 1 diabetes. In addition, we found an increased expression of miR-30b-5p in the 10-year period in uEVs of patients without renal dysfunction. miR-30b-5 was reported to have a protective role in podocyte injury and may possibly be important in Fabry nephropathy. These findings indicate that uEVs and their molecular cargo could be a promising target of studies focusing on elucidation of Fabry nephropathy. Nevertheless, total concentration and size of uEVs were neither indicative of the presence nor progression of Fabry nephropathy, while the role of the analyzed miRNAs in Fabry nephropathy progression was merely indicated and needs further in-depth studies.

Programmed cell death in stem cell-based therapy: Mechanisms and clinical applications

Stem cell-based therapy raises hopes for a better approach to promoting tissue repair and functional recovery. However, transplanted stem cells show a high death percentage, creating challenges to successful transplantation and prognosis. Thus, it is necessary to investigate the mechanisms underlying stem cell death, such as apoptotic cascade activation, excessive autophagy, inflammatory response, reactive oxygen species, excitotoxicity, and ischemia/hypoxia. Targeting the molecular pathways involved may be an efficient strategy to enhance stem cell viability and maximize transplantation success. Notably, a more complex network of cell death receives more attention than one crucial pathway in determining stem cell fate, highlighting the challenges in exploring mechanisms and therapeutic targets. In this review, we focus on programmed cell death in transplanted stem cells. We also discuss some promising strategies and challenges in promoting survival for further study.

Guidelines for Regulated Cell Death Assays: A Systematic Summary, A Categorical Comparison, A Prospective

Over the past few years, the field of regulated cell death continues to expand and novel mechanisms that orchestrate multiple regulated cell death pathways are being unveiled. Meanwhile, researchers are focused on targeting these regulated pathways which are closely associated with various diseases for diagnosis, treatment, and prognosis. However, the complexity of the mechanisms and the difficulties of distinguishing among various regulated types of cell death make it harder to carry out the work and delay its progression. Here, we provide a systematic guideline for the fundamental detection and distinction of the major regulated cell death pathways following morphological, biochemical, and functional perspectives. Moreover, a comprehensive evaluation of different assay methods is critically reviewed, helping researchers to make a reliable selection from among the cell death assays. Also, we highlight the recent events that have demonstrated some novel regulated cell death processes, including newly reported biomarkers (e.g., non-coding RNA, exosomes, and proteins) and detection techniques.

Extracellular vesicles derived from mesenchymal stem cells: A platform that can be engineered

Mesenchymal stem cells play an important role in tissue damage and repair. This role is mainly due to a paracrine mechanism, and extracellular vesicles (EVs) are an important part of the paracrine function. EVs play a vital role in many aspects of cell homeostasis, physiology, and pathology, and EVs can be used as clinical biomarkers, vaccines, or drug delivery vehicles. A large number of studies have shown that EVs derived from mesenchymal stem cells (MSC-EVs) play an important role in the treatment of various diseases. However, the problems of low production, low retention rate, and poor targeting of MSC-EVs are obstacles to current clinical applications. The engineering transformation of MSC-EVs can make up for those shortcomings, thereby improving treatment efficiency. This review summarizes the latest research progress of MSC-EV direct and indirect engineering transformation from the aspects of improving MSC-EV retention rate, yield, targeting, and MSC-EV visualization research, and proposes some feasible MSC-EV engineering methods of transformation.

Cancer therapy based on extracellular vesicles as drug delivery vehicles

Extracellular vesicles (EVs) are lipid bilayer vesicles of nanometric size secreted by cells to communicate with other cells, either nearby or remotely. Their physicochemical properties make them a promising nanomedicine for drug transport and release in cancer therapy. In this review, we present the different types and biogenesis of EVs and highlight the importance of adequately selecting the cell of origin in cancer therapy. Furthermore, the main methodologies followed for the isolation of EVs and drug loading, as well as the modification and functionalization of these vesicles to generate EV-based nanocarriers are discussed. Finally, we review some of the main studies using drug-loaded exosomes in tumor therapy both in in vitro and in vivo models (even in resistant tumors). These investigations show promising results, achieving significant improvement in the antitumor effect of drugs in most cases. However, the number of clinical trials and patents based on these nanoformulations is still low, thus further research is still warranted in this area.