Isolation of Exosomes and Microvesicles from Cell Culture Systems to Study Prion Transmission

Extracellular Vesicles Derived from Auricular Chondrocytes Facilitate Cartilage Differentiation of Adipose-Derived Mesenchymal Stem Cells

PURPOSE

Adipose-derived mesenchymal stem cell (ADSC)-based therapies have been utilized for cartilage regeneration because of their multi-lineage differentiation ability. However, commonly used cartilage inducers such as the transforming growth factor beta-3 (TGF-β3) may be prone to cartilage dedifferentiation and hypertrophy. The directional differentiation of elastic cartilage is limited nowadays. Extracellular vesicles (EVs) have been reported to influence the specific differentiation of mesenchymal stem cells (MSCs) by reflecting the composition of the parental cells. However, the role of auricular chondrogenic-derived EVs (AC-EVs) in elastic chondrogenic differentiation of ADSCs has not yet been reported.

RESULTS

AC-EVs isolated from the external ears of swine exhibited a positive effect on cell proliferation and migration. Furthermore, AC-EVs efficiently promoted chondrogenic differentiation of ADSCs in pellet culture, as shown by the elevated levels of COL2A1, ACAN, and SOX-9 expression. Moreover, there was a significantly higher expression of elastin and a lower expression of the fibrotic marker COL1A1 in comparison with that achieved with TGF-β3. The staining results demonstrated that AC-EVs promoted the deposition of cartilage-specific matrix, which is in good concordance with the real-time polymerase chain reaction (RT-PCR) results.

CONCLUSIONS

Auricular chondrogenic-derived EVs are a crucial component in elastic chondrogenic differentiation and other biological behaviors of ADSCs, which may be a useful ingredient for cartilage tissue engineering and external ear reconstruction.

NO LEVEL ASSIGNED

This journal requires that authors 42 assign a level of evidence to each submission to which 43 Evidence-Based Medicine rankings are applicable. This 44 excludes Review Articles, Book Reviews, and manuscripts 45 that concern Basic Science, Animal Studies, Cadaver 46 Studies, and Experimental Studies. For a full description of 47 these Evidence-Based Medicine ratings, please refer to the 48 Table oôf Contents or the online Instructions to Authors 49 www.springer.com/00266 .

Tumor-Associated Extracellular Microvesicles with Fluorine-Modified Carbohydrate Antigens Trigger a Stronger Antitumor Immune Response

Abnormal glycosylation is a hallmark of tumor development, and tumor-associated carbohydrate antigens are potential immune targets for tumor therapy. Tumor-associated extracellular microvesicles are subcellular vesicles released from cell membranes that have immunogenicity similar to that of precursor cells. However, unmodified tumor-derived microvesicles have weaknesses, such as low immunogenicity, poor biostability, and short half-life in vivo. For the first time, we herein generated extracellular microvesicles containing modified tumor-associated carbohydrate antigens by constructing a cell line with highly expressed antigen-processing enzymes utilizing fluorine-modified monosaccharide substrates via a metabolic oligosaccharide engineering strategy. The microvesicles were applied to tumor immunity, achieving enhanced immunoprophylaxis and immunotherapy effects. Furthermore, the mechanisms of antitumor immunity were explored. Our findings may provide new insights into the adhibition of suitably modified extracellular microvesicles and the development of more effective carbohydrate-based anticancer vaccines.

A novel approach for large-scale manufacturing of small extracellular vesicles from bone marrow-derived mesenchymal stromal cells using a hollow fiber bioreactor

Mesenchymal stromal cells (MSCs) are promising therapeutic candidates in a variety of diseases due to having immunomodulatory and pro-regenerative properties. In recent years, MSC-derived small extracellular vesicles (sEVs) have attracted increasing interest as a possible alternative to conventional cell therapy. However, translational processes of sEVs for clinical applications are still impeded by inconsistencies regarding isolation procedures and culture conditions. We systematically compared different methods for sEV isolation from conditioned media of ex vivo expanded bone marrow-derived MSCs and demonstrated considerable variability of quantity, purity, and characteristics of sEV preparations obtained by these methods. The combination of cross flow filtration with ultracentrifugation for sEV isolation resulted in sEVs with similar properties as compared to isolation by differential centrifugation combined with ultracentrifugation, the latter is still considered as gold standard for sEV isolation. In contrast, sEV isolation by a combination of precipitation with polyethylene glycol and ultracentrifugation as well as cross flow filtration and size exclusion chromatography resulted in sEVs with different characteristics, as shown by surface antigen expression patterns. The MSC culture requires a growth-promoting supplement, such as platelet lysate, which contains sEVs itself. We demonstrated that MSC culture with EV-depleted platelet lysate does not alter MSC characteristics, and conditioned media of such MSC cultures provide sEV preparations enriched for MSC-derived sEVs. The results from the systematic stepwise evaluation of various aspects were combined with culture of MSCs in a hollow fiber bioreactor. This resulted in a strategy using cross flow filtration with subsequent ultracentrifugation for sEV isolation. In conclusion, this workflow provides a semi-automated, efficient, large-scale-applicable, and good manufacturing practice (GMP)-grade approach for the generation of sEVs for clinical use. The use of EV-depleted platelet lysate is an option to further increase the purity of MSC-derived sEVs.

Usage of celery root exosome as an immune suppressant; Lipidomic characterization of apium graveolens originated exosomes and its suppressive effect on PMA/ionomycin mediated CD4+ T lymphocyte activation

Diseases such as autoimmune, cancer, neurodegenerative diseases or obesity have a serious impact on the lives of patients all rise from a common point; the immune system. Various in vitro and in vivo studies on regulating the immune system have been made to correct these diseases. As one of the key effector cells of the immune system, T lymphocytes are the focus of many of these studies. In this study, exosomes isolated from a known anti-inflammatory plant, celery, were used to suppress the inflammatory response of T lymphocytes. Celery-derived exosomes (C-Exo) were isolated using an aqueous two-phase isolation method. The size distribution, morphology, particle concentration, and GC-FAME-based lipidomic analysis were determined for the isolated C-Exo. T lymphocytes were stimulated using Phorbol 12-myristate 13-acetate (PMA)/ionomycin, and treated with various doses of C-Exo. T lymphocyte responses were measured using qPCR and capillary Western blots. According to the results, C-Exo suppressed T lymphocytes in a dose-dependent manner in in vitro conditions. These findings show the potential of C-Exo as a therapeutic agent for immune disorders. PRACTICAL APPLICATION: Excessive immune response in the body adversely affects the treatment mechanism and process of many diseases such as autoimmune disorders, neurodegenerative diseases and GDHV. In this preliminary study, the role of extracellular vesicles obtained from celery roots in suppressing this high immune response was investigated. The suppressive effect of celery exosome was observed by creating an immune response in T cells and PBMC cells, which play a leading role in the immune response. The role of these vesicles in immune suppression, obtained from the root part of the celery plant and characterized, was determined by measuring both mRNA, intracellular protein and extracellular cytokine levels. Celery exosome suppressed activated T lymphocyte cells and PBMC cells in a dose-dependent manner. These vesicles, which can be used as an edible, can be used in many areas as immunosuppressants.

The multiple functions of PrPC in physiological, cancer, and neurodegenerative contexts

Cellular prion protein (PrP^C) is a highly conserved glycoprotein, present both anchored in the cell membrane and soluble in the extracellular medium. It has a diversity of ligands and is variably expressed in numerous tissues and cell subtypes, most notably in the central nervous system (CNS). Its importance has been brought to light over the years both under physiological conditions, such as embryogenesis and immune system homeostasis, and in pathologies, such as cancer and neurodegenerative diseases. During development, PrP^C plays an important role in CNS, participating in axonal growth and guidance and differentiation of glial cells, but also in other organs such as the heart, lung, and digestive system. In diseases, PrP^C has been related to several types of tumors, modulating cancer stem cells, enhancing malignant properties, and inducing drug resistance. Also, in non-neoplastic diseases, such as Alzheimer's and Parkinson's diseases, PrP^C seems to alter the dynamics of neurotoxic aggregate formation and, consequently, the progression of the disease. In this review, we explore in detail the multiple functions of this protein, which proved to be relevant for understanding the dynamics of organism homeostasis, as well as a promising target in the treatment of both neoplastic and degenerative diseases.

Prion Protein: The Molecule of Many Forms and Faces

Cellular prion protein (PrP^C) is a glycosylphosphatidylinositol (GPI)-anchored protein most abundantly found in the outer membrane of neurons. Due to structural characteristics (a flexible tail and structured core), PrP^C interacts with a wide range of partners. Although PrP^C has been proposed to be involved in many physiological functions, only peripheral nerve myelination homeostasis has been confirmed as a bona fide function thus far. PrP^C misfolding causes prion diseases and PrP^C has been shown to mediate β-rich oligomer-induced neurotoxicity in Alzheimer’s and Parkinson’s disease as well as neuroprotection in ischemia. Upon proteolytic cleavage, PrP^C is transformed into released and attached forms of PrP that can, depending on the contained structural characteristics of PrP^C, display protective or toxic properties. In this review, we will outline prion protein and prion protein fragment properties as well as overview their involvement with interacting partners and signal pathways in myelination, neuroprotection and neurodegenerative diseases.

Isolation of Microvesicles from Human Circulating Neutrophils

Neutrophil-derived microvesicles (NDMVs) are liberated by neutrophils upon cell activation by molecules. Once activated, neutrophils are primarily involved in acute inflammation; however, the microvesicles they produce are largely anti-inflammatory. NDMVs have been shown to protect cartilage during inflammatory arthritis. They exert these effects by inhibiting or affecting the function of target cells, including macrophages. NDMVs have the potential to act as disease-modifying agents, especially for inflammatory diseases. This protocol describes a method using differential centrifugation to separate neutrophils from whole human blood. Subsequently, neutrophils are identified by cytospin and Wright's staining, and then the NDMVs are isolated using differential centrifugation.

Role of Exosomes in Brain Diseases

Exosomes are a subset of extracellular vesicles that act as messengers to facilitate communication between cells. Non-coding RNAs, proteins, lipids, and microRNAs are delivered by the exosomes to target molecules (such as proteins, mRNAs, or DNA) of host cells, thereby playing a key role in the maintenance of normal brain function. However, exosomes are also involved in the occurrence, prognosis, and clinical treatment of brain diseases, such as Alzheimer's disease, Parkinson's disease, stroke, and traumatic brain injury. In this review, we have summarized novel findings that elucidate the role of exosomes in the occurrence, prognosis, and treatment of brain diseases.

Influence of Anti-Glaucoma Drugs on Uptake of Extracellular Vesicles by Trabecular Meshwork Cells

Background

Extracellular vesicles (EVs) are capable of manipulating cellular functions for the maintenance of biological homeostasis and disease progression, such as in glaucoma disease. These nano-particles carry a net negative surface charge under physiological conditions that can contribute to EVs:EVs interaction and their uptake by target cells.

Purpose

To investigate the effect of glaucoma drugs on EVs physicochemical characters and the implications for their uptake by trabecular meshwork (TM) cells.

Methods

TM or non-pigmented ciliary epithelium (NPCE) cells derived EVs were incubated with commercial anti-glaucoma formulation, Timolol maleate, Brinzolamide or Benzalkonium Cl and their size and zeta potential (ZP) and physical interactions of EVs derived from NPCE cells and TM cells were evaluated. The contribution of EVs interactions to up-take by TM cells was examined using fluorescence-activated cell sorting.

Results

EVs size and ZP were affected by the ionic strength of the buffer rather than EVs type. Commercial glaucoma eye drops, including β-blocker, α-2-agonist and prostaglandin analogs, reduced NPCE EVs ZP, whereas exposure of EVs to carbonic anhydrase inhibitor caused an increase in the ZP. A correlation was found between increased ZP values and increased NPCE EVs uptake by TM cells. We were able to show that Benzalkonium chloride stands behind this ZP effect and not Timolol or Brinzolamide.

Conclusion

Altogether, our findings demonstrate that EVs size, surface membrane charge, and ionic strength of the surrounding have an impact on EVs:EVs interactions, which affect the uptake of NPCE EVs by TM cells.

Ultrasonics-Assisted Effective Isolation and Characterization of Exosomes from Whole Organs

Exosomes, natural and nanovesicular structures surrounded by a lipid membrane, tend to be secreted toward extracellular environments by almost all cell types. Late studies have shown them to be effective in several complex biological processes like cancer development and metastasis, immune system regulation, cellular signal transduction, stem cell differentiation, and regeneration of damaged tissues. Although there are many studies dealing with the role of exosomes in the aforementioned fields, the mechanisms remained largely unknown. There is therefore a need for further study on exosome isolation from different sources. While researchers mostly use serum, plasma, urine, and cell culture media as a source for exosome isolation, there are no studies dealing with direct isolation of exosomes from whole organs in literature. In this study, we propose a protocol for effective isolation of exosomes from whole organs. Mouse brain, heart, and liver were chosen as the sources of exosomes in this study. Isolated exosomes were successfully characterized with BCA test, western blot, transmission electron microscopy and ELISA.

Multi-Omics Data Integration in Extracellular Vesicle Biology-Utopia or Future Reality?

Extracellular vesicles (EVs) are membranous structures derived from the endosomal system or generated by plasma membrane shedding. Due to their composition of DNA, RNA, proteins, and lipids, EVs have garnered a lot of attention as an essential mechanism of cell-to-cell communication, with various implications in physiological and pathological processes. EVs are not only a highly heterogeneous population by means of size and biogenesis, but they are also a source of diverse, functionally rich biomolecules. Recent advances in high-throughput processing of biological samples have facilitated the development of databases comprised of characteristic genomic, transcriptomic, proteomic, metabolomic, and lipidomic profiles for EV cargo. Despite the in-depth approach used to map functional molecules in EV-mediated cellular cross-talk, few integrative methods have been applied to analyze the molecular interplay in these targeted delivery systems. New perspectives arise from the field of systems biology, where accounting for heterogeneity may lead to finding patterns in an apparently random pool of data. In this review, we map the biological and methodological causes of heterogeneity in EV multi-omics data and present current applications or possible statistical methods for integrating such data while keeping track of the current bottlenecks in the field.

Quantitative changes in the secretion of exosomes from keratinocytes homeostatically regulate skin pigmentation in a paracrine manner

The content and distribution of melanin in the epidermis determines the wide variety of skin colors associated with ethnic/racial diversity. Although it was previously reported that qualitative changes in keratinocyte-derived exosomes regulate melanocyte pigmentation in vitro, their practical involvement, especially in skin color development in vivo, has remained unclear. To address this unexplained scientific concern, the correlation of epidermal exosomes isolated from human skin tissues with melanosomal protein expression levels was demonstrated in this study for the first time. After confirming the quantitative effect of human keratinocyte-derived exosomes on human melanocyte activation, even in the absence of ultraviolet B (UV-B) exposure, the impact of exosomes secreted from UV-B-irradiated keratinocytes on melanogenesis was consistently detected, which suggests their constitutive role in regulating cutaneous pigmentation. Additionally, both a specific exosome secretion inducer and a suppressor were consistently found to significantly control melanin synthesis in a co-culture system composed of keratinocytes and melanocytes as well as in an ex vivo skin culture system. These results suggest that quantitative changes, in addition to already known qualitative changes, in exosomes secreted from human epidermal keratinocytes homeostatically regulate melanogenic activity in a paracrine manner, which leads to skin color determination.

Recent advances and challenges in the recovery and purification of cellular exosomes

Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome-based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.

High sensitivity detection of extracellular vesicles immune-captured from urine by conventional flow cytometry

Extracellular vesicles (EVs) provide an invaluable tool to analyse physiological processes because they transport, in biological fluids, biomolecules secreted from diverse tissues of an individual. EV biomarker detection requires highly sensitive techniques able to identify individual molecules. However, the lack of widespread, affordable methodologies for high-throughput EV analyses means that studies on biomarkers have not been done in large patient cohorts. To develop tools for EV analysis in biological samples, we evaluated here the critical parameters to optimise an assay based on immunocapture of EVs followed by flow cytometry. We describe a straightforward method for EV detection using general EV markers like the tetraspanins CD9, CD63 and CD81, that allowed highly sensitive detection of urinary EVs without prior enrichment. In proof-of-concept experiments, an epithelial marker enriched in carcinoma cells, EpCAM, was identified in EVs from cell lines and directly in urine samples. However, whereas EVs isolated from 5–10 ml of urine were required for western blot detection of EpCAM, only 500 μl of urine were sufficient to visualise EpCAM expression by flow cytometry. This method has the potential to allow any laboratory with access to conventional flow cytometry to identify surface markers on EVs, even non-abundant proteins, using minimally processed biological samples.

Extracellular micro/nanovesicles rescue kidney from ischemia-reperfusion injury

Acute renal failure (ARF) is a clinical challenge that is highly resistant to treatment, and its high rate of mortality is alarming. Ischemia-reperfusion injury (IRI) is the most common cause of ARF. Especially IRI is implicated in kidney transplantation and can determine graft survival. Although the exact pathophysiology of renal IRI is unknown, the role of inflammatory responses has been elucidated. Because mesenchymal stromal cells (MSCs) have strong immunomodulatory properties, they are under extensive investigation as a therapeutic modality for renal IRI. Extracellular vesicles (EVs) play an integral role in cell-to-cell communication. Because the regenerative potential of the MSCs can be recapitulated by their EVs, the therapeutic appeal of MSC-derived EVs has dramatically increased in the past decade. Higher safety profile and ease of preservation without losing function are other advantages of EVs compared with their producing cells. In the current review, the preliminary results and potential of MSC-derived EVs to alleviate kidney IRI are summarized. We might be heading toward a cell-free approach to treat renal IRI.

MSC exosome works through a protein-based mechanism of action. Biochem Soc Trans. 2018;46:843-853. [PMID: 29986939 PMCID: PMC6103455 DOI: 10.1042/bst20180079]

Mesenchymal stem cell (MSC) exosome specifically defines the 50–200 nm vesicles that are secreted into the extracellular space when multivesicular bodies in the MSC fuse with the plasma membrane. However, the exosome is just one of several 50–200 nm extracellular vesicles (EVs) known to be secreted by cells. Nevertheless, the term ‘MSC exosome’ is often used to describe populations of 50–200 nm EVs that are prepared from culture medium conditioned by MSCs on the basis that these populations collectively exhibited typical exosome-associated proteins such as endosomal proteins, TSG101 and Alix, and tetraspanin proteins, CD9, CD63 and CD81. They also carry a rich diverse RNA cargo. MSC exosomes are increasingly implicated as the mediator of many of the MSC-associated therapeutic potencies. They elicit therapeutic activity by delivering their cargo of potentially therapeutic proteins and RNAs to the recipient cells. The therapeutic potency of MSC exosomes is usually rationalized on the presence of a biologically relevant protein or RNA in the MSC exosome. In the present paper, we expanded this rationale beyond a physical presence to include biologically relevant concentration, biochemical functionality and the potential to elicit an appropriate timely biochemical response. Based on these, we propose that MSC exosomes most probably work through the protein rather than the RNA.

Physical exosome:exosome interactions

Exosomes are extracellular nanovesicles that mediate a number of cellular processes, including intracellular signalling. There are many published examples of exosome-exosome dimers; however, their relevance has not been explored. Here, we propose that cells release exosomes to physically interact with incoming exosomes, forming dimers that we hypothesize attenuate incoming exosome-mediated signalling. We discuss experiments to test this hypothesis and potential relevance in health and disease.

Extracellular vesicles as an efficient nanoplatform for the delivery of therapeutics

Extracellular vesicles (EVs) are membrane-derived vesicles that are enriched with RNAs, proteins and other functional molecules. We exploit the unique physical properties of EVs as a promising and advantageous nanoplatform for the delivery of therapeutic drugs and genetic materials. Early successes in the discovery of various disease-related characteristics of EVs have driven a new wave of innovation in developing nanoscale drug-delivery systems (DDSs). Nevertheless, there are several issues that need to be considered during the development of these alternative DDSs, such as standardized isolation and preservation methods, efficient drug encapsulation, mechanisms of drug release and so on. In this mini-review, we summarize the current status and progress of EV-based DDSs as an efficient nanoplatform for therapeutics delivery, followed by a discussion on their challenges and future prospects for clinical translation and applications.

Lysosomal Quality Control in Prion Diseases

Prion diseases are transmissible, familial or sporadic. The prion protein (PrP), a normal cell surface glycoprotein, is ubiquitously expressed throughout the body. While loss of function of PrP does not elicit apparent phenotypes, generation of misfolded forms of the protein or its aberrant metabolic isoforms has been implicated in a number of neurodegenerative disorders such as scrapie, kuru, Creutzfeldt-Jakob disease, fatal familial insomnia, Gerstmann-Sträussler-Scheinker and bovine spongiform encephalopathy. These diseases are all phenotypically characterised by spongiform vacuolation of the adult brain, hence collectively termed as late-onset spongiform neurodegeneration. Misfolded form of PrP (PrP^Sc) and one of its abnormal metabolic isoforms (the transmembrane ^CtmPrP) are known to be disease-causing agents that lead to progressive loss of structure or function of neurons culminating in neuronal death. The aberrant forms of PrP utilise and manipulate the various intracellular quality control mechanisms during pathogenesis of these diseases. Amongst these, the lysosomal quality control machinery emerges as one of the primary targets exploited by the disease-causing isoforms of PrP. The autophagosomal-lysosomal degradation pathway is adversely affected in multiple ways in prion diseases and may hence be regarded as an important modulator of neurodegeneration. Some of the ESCRT pathway proteins have also been shown to be involved in the manifestation of disease phenotype. This review discusses the significance of the lysosomal quality control pathway in affecting transmissible and familial types of prion diseases.

Exosomes and the Prion Protein: More than One Truth

Exosomes are involved in the progression of neurodegenerative diseases. The cellular prion protein (PrP^C) is highly expressed on exosomes. In neurodegenerative diseases, PrP^C has at least two functions: It is the substrate for the generation of pathological prion protein (PrP^Sc), a key player in the pathophysiology of prion diseases. On the other hand, it binds neurotoxic amyloid-beta (Aß) oligomers, which are associated with initiation and progression of Alzheimer's disease (AD). This has direct consequences for the role of exosomal expressed PrP^C. In prion diseases, exosomal PrP leads to efficient dissemination of pathological prion protein, thus promoting spreading and transmission of the disease. In AD, exosomal PrP^C can bind and detoxify Aß oligomers thus acting protective. In both scenarios, assessment of the state of PrP^C on exosomes derived from blood or cerebrospinal fluid (CSF) may be useful for diagnostic workup of these diseases. This review sums up current knowledge of the role of exosomal PrP^C on different aspects of Alzheimer's and prion disease.