Depleting extracellular vesicles from fetal bovine serum alters proliferation and differentiation of skeletal muscle cells in vitro

Profiling of Extracellular Small RNAs Highlights a Strong Bias towards Non-Vesicular Secretion

The extracellular environment consists of a plethora of molecules, including extracellular miRNA that can be secreted in association with extracellular vesicles (EVs) or soluble protein complexes (non-EVs). Yet, interest in therapeutic short RNA carriers lies mainly in EVs, the vehicles conveying the great majority of the biological activity. Here, by overexpressing miRNA and shRNA sequences in parent cells and using size exclusion liquid chromatography (SEC) to separate the secretome into EV and non-EV fractions, we saw that >98% of overexpressed miRNA was secreted within the non-EV fraction. Furthermore, small RNA sequencing studies of native miRNA transcripts revealed that although the abundance of miRNAs in EVs, non-EVs and parent cells correlated well (R2 = 0.69-0.87), quantitatively an outstanding 96.2-99.9% of total miRNA was secreted in the non-EV fraction. Nevertheless, though EVs contained only a fraction of secreted miRNAs, these molecules were stable at 37 °C in a serum-containing environment, indicating that if sufficient miRNA loading is achieved, EVs can remain delivery-competent for a prolonged period of time. This study suggests that the passive endogenous EV loading strategy might be a relatively wasteful way of loading miRNA to EVs, and active miRNA loading approaches are needed for developing advanced EV miRNA therapies in the future.

The Regulation of Staphylococcus aureus-Induced Inflammatory Responses in Bovine Mammary Epithelial Cells

Mastitis, an inflammatory disease, causes severe economic loss in the dairy industry, which is mainly infected by bacteria. Staphylococcus aureus (S. aureus), the major pathogenic microorganism, derived from lipoteichoic acid (LTA) has been identified to activate inflammatory responses, but the cellular or intercellular regulatory mechanism is unclear. This study mainly focused on the effects of LTA in bovine mammary epithelial cells (Mac-T) and elaborated the regulation of microRNAs (miRNAs). The results showed that LTA enhanced the messenger RNA (mRNA) expression and production of tumor necrosis factor α (TNF-α) and interleukin (IL)-6. Furthermore, LTA could activate Toll-like receptor (TLR)2/MyD88-mediated phosphoinositide 3-kinase (PI3K)/AKT pathway, and TLR2 plays a pivotal role in LTA-induced inflammatory responses. The results of qRT-PCR showed that miRNA levels increased and reached the highest at 3 h and then gradually decreased over time in Mac-T cells. In exosomes, the levels of 11 and three miRNAs were upregulated and downregulated at 24 h, respectively. In addition, miR-23a showed the highest increase in Mac-T cells treated with LTA and targeted PI3K to regulate inflammatory responses. Furthermore, Mac-T cell-derived exosomes were identified to play a cell–cell communication by promoting M1 polarization of bovine macrophages. In summary, our study demonstrated that LTA could activate inflammatory responses via TLR2/MyD88/PI3K/AKT signaling pathway, and miR-23a inhibited it by targeting PI3K. Furthermore, we found that Mac-T cell-derived exosomes might be associated with inflammatory responses by promoting M1 polarization of bovine macrophages.

Nanoparticles from culture media are internalized by in vitro-produced bovine embryos and its depletion affect expression of pluripotency genes

Extracellular vesicles are nanoparticles secreted by cell and have been proposed as suitable markers to identify competent embryos produced in vitro. Characterizing EVs secreted by individual embryos is challenging because culture medium itself contributes to the pool of nanoparticles that are co-isolated. To avoid this, culture medium must be depleted of nanoparticles that are present in natural protein source. The aim of this study was to evaluate if the culture medium subjected to nanoparticle depletion can support the proper in vitro development of bovine embryos. Zygotes were cultured in groups on depleted or control medium for 8 days. Nanoparticles from the medium were characterized by their morphology, size and expression of EVs surface markers. Isolated nanoparticles were labelled and added to depleted medium containing embryos at different developmental stages and evaluated after 24 hours at 2, 8-16 cells, morula and blastocyst stages. There were no statistical differences on blastocyst rate at day 7 and 8, total cell count neither blastocyst diameter between groups. However, morphological quality was better in blastocysts cultured in non-depleted medium and the expression of SOX2 was significantly lower whereas NANOG expression was significantly higher. Few nanoparticles from medium had a typical morphology of EVs but were positive to specific surface markers. Punctuated green fluorescence near the nuclei of embryonic cells was observed in embryos from all developmental stages. In summary, nanoparticles from culture medium are internalized by in vitro cultured bovine embryos and their depletion affects the capacity of medium to support the proper embryo development.

Defined MSC exosome with high yield and purity to improve regenerative activity

Exosomes derived from mesenchymal stem cells (MSCs) have been studied as vital components of regenerative medicine. Typically, various isolation methods of exosomes from cell culture medium have been developed to increase the isolation yield of exosomes. Moreover, the exosome-depletion process of serum has been considered to result in clinically active and highly purified exosomes from the cell culture medium. Our aim was to compare isolation methods, ultracentrifuge (UC)-based conventional method, and tangential flow filtration (TFF) system-based method for separation with high yield, and the bioactivity of the exosome according to the purity of MSC-derived exosome was determined by the ratio of Fetal bovine serum (FBS)-derived exosome to MSC-derived exosome depending on exosome depletion processes of FBS. The TFF-based isolation yield of exosome derived from human umbilical cord MSC (UCMSC) increased two orders (92.5 times) compared to UC-based isolation method. Moreover, by optimizing the process of depleting FBS-derived exosome, the purity of UCMSC-derived exosome, evaluated using the expression level of MSC exosome surface marker (CD73), was about 15.6 times enhanced and the concentration of low-density lipoprotein-cholesterol (LDL-c), known as impurities resulting from FBS, proved to be negligibly detected. The wound healing and angiogenic effects of highly purified UCMSC-derived exosomes were improved about 23.1% and 71.4%, respectively, with human coronary artery endothelial cells (HCAEC). It suggests that the defined MSC exosome with high yield and purity could increase regenerative activity.

Extracellular vesicles and female reproduction

Extracellular vesicles (EVs) are nano-sized membrane bound complexes that have been identified as a mean for intercellular communication between cells and tissues both in physiological and pathological conditions. These vesicles contain numerous molecules involved in signal transduction including microRNAs, mRNAs, DNA, proteins, lipids, and cytokines and can affect the behavior of recipient cells. Female reproduction is dependent on extremely fine-tuned endocrine regulation, and EVs may represent an added layer that contributes to this regulation. This narrative review article provides an update on the research of the role of EVs in female reproduction including folliculogenesis, fertilization, embryo quality, and implantation. We also highlight potential pitfalls in typical EV studies and discuss gaps in the current literature.

FBS-Derived Exosomes as a Natural Nano-Scale Carrier for Icariin Promote Osteoblast Proliferation

Icariin is a class IV drug of low solubility, permeability, and poor bioavailability. Synthetic nanomaterials have developed rapidly. However, some literatures point out that synthetic nanomaterials such as liposomes, aptamers, metal nanoparticles, and nanogels have high toxicity and are affected by the reticuloendothelial system or mononuclear phagocyte system. It is known that exosomes could be used as an ideal clinical drug delivery vehicle to avoid the above-mentioned problems to a certain extent. Studies have shown that drugs can be loaded into exosomes by passive and active loading. We used Fetal bovine serum (FBS) exosomes to carry Icariin for the first time in this experiment, FBS exosomes-Icariin (FBS EXO-ICA) more effectively promoted the proliferation of osteoblasts and bone regeneration than Icariin alone. FBS EXO-ICA could become a new nano scale drug formulation for treating diseases associated with bone loss.

Expression and secretion of apoE isoforms in astrocytes and microglia during inflammation

Neuroinflammation is a common feature in neurodegenerative diseases, modulated by the Alzheimer's disease risk factor, apolipoprotein E (APOE). In the brain, apoE protein is synthesized by astrocytes and microglia. We examined primary cultures of astrocytes and microglia from human APOE (E2, E3, and E4) targeted-replacement mice. Astrocytes secreted two species of apoE, whereas cellular apoE consisted of only one. Both forms of secreted astrocytic apoE were bound during glycoprotein isolation, and enzymatic removal of glycans produced a convergence of the two forms of apoE to a single form; thus, the two species of astrocyte-secreted apoE are differentially glycosylated. Microglia released only a single species of apoE, while cellular apoE consisted of two forms; the secreted apoE and one of the two forms of cellular apoE were glycosylated. We treated the primary glia with either endogenous (TNFα) or exogenous (LPS) pro-inflammatory stimuli. While LPS had no effect on astrocytic apoE, APOE2, and APOE3 microglia increased release of apoE; APOE4 microglia showed no effect. APOE4 microglia showed higher baseline secretion of TNFα compared to APOE2 and APOE3 microglia. TNFα treatment reduced the secretion and cellular expression of apoE only in APOE4 astrocytes. The patterns of apoE species produced by astrocytes and microglia were not affected by inflammation. No changes in APOE mRNA were observed in astrocytes after both treatments. Together, our data demonstrate that astrocytes and microglia differentially express and secrete glycosylated forms of apoE and that APOE4 astrocytes and microglia are deficient in immunomodulation compared to APOE2 and APOE3.

Roles of Skeletal Muscle-Derived Exosomes in Organ Metabolic and Immunological Communication

Skeletal muscles secrete various factors, such as proteins/peptides, nucleotides, and metabolites, which are referred to as myokines. Many of these factors are transported into extracellular bodily fluids in a free or protein-bound form. Furthermore, several secretory factors have been shown to be wrapped up by small vesicles, particularly exosomes, secreted into circulation, and subsequently regulate recipient cells. Thus, exosome contents can be recognized as myokines. In recipient cells, proteins, microRNAs, and metabolites in exosomes can regulate the expression and activity of target proteins associated with nutrient metabolism and immune function. The levels of circulating exosomes and their contents are altered in muscle disorders and metabolic-related states, such as metabolic dysfunction, sarcopenia, and physical fitness. Therefore, such circulating factors could mediate various interactions between skeletal muscle and other organs and may be useful as biomarkers reflecting physiological and pathological states associated with muscular function. Here, this review summarizes secretory regulation of muscle-derived exosomes. Their metabolic and immunological roles and the significance of their circulating levels are also discussed.

Therapeutic application of extracellular vesicles for musculoskeletal repair & regeneration

Traumatic musculoskeletal injuries are common in both the civilian and combat care settings. Significant barriers exist to repairing these injuries including fracture nonunion, muscle fibrosis, re-innervation, and compartment syndrome, as well as infection and inflammation. Recently, extracellular vesicles (EVs), including exosomes and microvesicles, have attracted attention in the field of musculoskeletal regeneration. These vesicles are released by different cell types and play a vital role in cell communication by delivering functional cargoes such as proteins and RNAs. Many of these cargo molecules can be utilized for repair purposes in skeletal disorders such as osteoporosis, osteogenesis imperfecta, sarcopenia, and fracture healing. There are, however, some challenges to overcome in order to advance the successful application of these vesicles in the therapeutic setting. These include large-scale production and isolation of exosomes, long-term storage, in vivo stability, and strategies for tissue-specific targeting and delivery. This paper reviews the general characteristics of exosomes along with their physiological roles and contribution to the pathogenesis of musculoskeletal diseases. We also highlight new findings on the use of synthetic exosomes to overcome the limitations of native exosomes in treating musculoskeletal injuries and disorders.

Progress in exosome associated tumor markers and their detection methods

Exosomes are secreted by cells and are widely present in body fluids. Exosomes contain various molecular constituents of their cells of origin such as proteins, mRNA, miRNAs, DNA, lipid and glycans which are very similar as the content in tumor cells. These contents play an important role in various stages of tumor development, and make the tumor-derived exosome as a hot and emerging biomarker for various cancers diagnosis and management in non-invasive manner. The present problems of exosome isolation and detection hinder the application of exosomes. With the development of exosome isolation and detection technology, the contents of exosomes can be exploited for early cancer diagnosis. This review summarizes the recent progress on exosome-associated tumor biomarkers and some new technologies for exosome isolation and detection. Furthermore, we have also discussed the future development direction in exosome analysis methods.

Fetal bovine serum-derived exosomes regulate the adipogenic differentiation of human bone marrow mesenchymal stromal cells in a cross-species manner

Fetal bovine serum (FBS) contains a large number of exosomes which may disturb the analysis of exosomes derived from cultured cells. We investigated the effect of FBS-derived exosomes (FBS-Exos) on the adipogenic differentiation of human bone marrow mesenchymal stromal cells (hBM-MSCs) and the underlying molecular mechanism. The uptake of FBS-Exos by hBM-MSCs could be detected by the laser confocal microscopy, and the treatment of exosomes resulted in the decreased lipid droplet formation and reduced expression of genes associated with adipogenic differentiation of hBM-MSCs. miR-1246 was identified as an abundant microRNA in FBS-Exos by public sequencing data identification and RT-qPCR validation. Moreover, miR-1246 overexpression in hBM-MSCs led to decreased adipogenic differentiation level, while miR-1246 knockdown in FBS-Exos attenuated the inhibitory effect on the adipogenic differentiation. Our results indicate that FBS-Exos inhibit the adipogenic differentiation of hBM-MSCs in a cross-species manner and miR-1246 transferred by FBS-Exos partly contributes to this effect.

Transcriptomic Profile of Primary Culture of Skeletal Muscle Cells Isolated from Semitendinosus Muscle of Beef and Dairy Bulls

The aim of the study was to identify differences in the transcriptomic profiles of primary muscle cell cultures derived from the semitendinosus muscle of bulls of beef breeds (Limousin (LIM) and Hereford (HER)) and a dairy breed (Holstein-Friesian (HF)) (n = 4 for each breed). Finding a common expression pattern for proliferating cells may point to such an early orientation of the cattle beef phenotype at the transcriptome level of unfused myogenic cells. To check this hypothesis, microarray analyses were performed. The analysis revealed 825 upregulated and 1300 downregulated transcripts similar in both beef breeds (LIM and HER) and significantly different when compared with the dairy breed (HF) used as a reference. Ontological analyses showed that the largest group of genes were involved in muscle organ development. Muscle cells of beef breeds showed higher expression of genes involved in myogenesis (including erbb-3, myf5, myog, des, igf-1, tgfb2) and those encoding proteins comprising the contractile apparatus (acta1, actc1, myh3, myh11, myl1, myl2, myl4, tpm1, tnnt2, tnnc1). The obtained results confirmed our hypothesis that the expression profile of several groups of genes is common in beef breeds at the level of proliferating satellite cells but differs from that observed in typical dairy breeds.

Exosome biogenesis, secretion and function of exosomal miRNAs in skeletal muscle myogenesis

Exosomes are membrane-bound extracellular vesicles that are produced in the endosomal compartment of most mammalian cell types and then released. Exosomes are effective carriers for the intercellular material transfer of material that can influence a series of physiological and pathological processes in recipient cells. Among loaded cargoes, non-coding RNAs (ncRNAs) vary for the exosome-producing cell and its homeostatic state, and characterization of the biogenesis and secretion of exosomal ncRNAs and the functions of these ncRNAs in skeletal muscle myogenesis remain preliminary. In this review, we will describe what is currently known of exosome biogenesis, release and uptake of exosomal ncRNAs, as well as the varied functions of exosomal miRNAs in skeletal muscle myogenesis.

Nanofiltration of growth media supplemented with human platelet lysates for pathogen-safe xeno-free expansion of mesenchymal stromal cells

Background aims

Human platelet lysate can replace fetal bovine serum (FBS) for xeno-free ex vivo expansion of mesenchymal stromal cells (MSCs), but pooling of platelet concentrates (PCs) increases risks of pathogen transmission. We evaluated the feasibility of performing nanofiltration of platelet lysates and determined the impact on expansion of bone marrow–derived MSCs.

Methods

Platelet lysates were prepared by freeze-thawing of pathogen-reduced (Intercept) PCs suspended in 65% storage solution (SPP+) and 35% plasma, and by serum-conversion of PCs suspended in 100% plasma. Lysates were added to the MSC growth media at 10% (v/v), filtered and subjected to cascade nanofiltration on 35- and 19-nm Planova filters. Media supplemented with 10% starting platelet lysates or FBS were used as the controls. Impacts of nanofiltration on the growth media composition, removal of platelet extracellular vesicles (PEVs) and MSC expansion were evaluated.

Results

Nanofiltration did not detrimentally affect contents of total protein and growth factors or the biochemical composition. The clearance factor of PEVs was >3 log values. Expansion, proliferation, membrane markers, differentiation potential and immunosuppressive properties of cells in nanofiltered media were consistently better than those expanded in FBS-supplemented media. Compared with FBS, chondrogenesis and osteogenesis genes were expressed more in nanofiltered media, and there were fewer senescent cells over six passages.

Conclusions

Nanofiltration of growth media supplemented with two types of platelet lysates, including one prepared from pathogen-reduced PCs, is technically feasible. These data support the possibility of developing pathogen-reduced xeno-free growth media for clinical-grade propagation of human cells.

Mechanisms regulating myoblast fusion: A multilevel interplay

Myoblast fusion into myotubes is one of the crucial steps of skeletal muscle development (myogenesis). The fusion is preceded by specification of a myogenic lineage (mesodermal progenitors) differentiating into myoblasts and is followed by myofiber-type specification and neuromuscular junction formation. Similarly to other processes of myogenesis, the fusion requires a very precise spatial and temporal regulation occuring both during embryonic development as well as regeneration and repair of the muscle. A plethora of genes and their products is involved in regulation of myoblast fusion and a precise multilevel interplay between them is crucial for myogenic cells to fuse. In this review, we describe both cellular events taking place during myoblast fusion (migration, adhesion, elongation, cell-cell recognition, alignment, and fusion of myoblast membranes enabling formation of myotubes) as well as recent findings on mechanisms regulating this process. Also, we present muscle disorders in humans that have been associated with defects in genes involved in regulation of myoblast fusion.

Skeletal Muscle-Released Extracellular Vesicles: State of the Art

All cells export part of their intracellular content into the extracellular space through the release of various types of extracellular vesicles (EVs). They are synthetized either from the budding of the plasma membrane [i.e., microparticles (MPs, 150–300 nm size)] or from the late endosomes in which intraluminal vesicles progressively (ILVs) accumulate during their maturation into multivesicular bodies (MVBs). ILVs are then released into the extracellular space through MVB fusion with the plasma membrane [i.e., exosomes (50–100 nm size)]. In the context of metabolic diseases, recent data have highlighted the role of EVs in inflammation associated with pancreas dysfunction, adipose tissue homeostasis, liver steatosis, inflammation, and skeletal muscle (SkM) insulin resistance (IR). Among these insulin-sensitive tissues, SkM is the largest organ in human and is responsible for whole-body glucose disposal and locomotion. Therefore, understanding the contribution of SkM-EVs in the development of diabetes/obesity/dystrophy/,-related diseases is a hot topic. In this review, we have summarized the role of SkM-EVs in muscle physiology and in the development of metabolic diseases and identify important gaps that have to be filled in order to have more precise information on SkM-EVs biological actions and to understand the functions of the different subpopulations of SkM-EVs on the whole-body homeostasis.

Nanoformulation properties, characterization, and behavior in complex biological matrices: Challenges and opportunities for brain-targeted drug delivery applications and enhanced translational potential

Nanocarriers (synthetic/cell-based have attracted enormous interest for various therapeutic indications, including neurodegenerative disorders. A broader understanding of the impact of nanomedicines design is now required to enhance their translational potential. Nanoformulations in vivo journey is significantly affected by their physicochemical properties including the size, shape, hydrophobicity, elasticity, and surface charge/chemistry/morphology, which play a role as an interface with the biological environment. Understanding protein corona formation is crucial in characterizing nanocarriers and evaluating their interactions with biological systems. In this review, the types and properties of the brain-targeted nanocarriers are discussed. The biological factors and nanocarriers properties affecting their in vivo behavior are elaborated. The compositional description of cell culture and biological matrices, including proteins potentially relevant to protein corona built-up on nanoformulation especially for brain administration, is provided. Analytical techniques of characterizing nanocarriers in complex matrices, their advantages, limitations, and implementation challenges in industrial GMP environment are discussed. The uses of orthogonal complementary characterization approaches of nanocarriers are also covered.

Efficient isolation, biophysical characterisation and molecular composition of extracellular vesicles secreted by primary and immortalised cells of reproductive origin

Effective communication between the maternal reproductive tract, gametes and the pre-implantation embryo is essential for the successful establishment of pregnancy. Recent studies have recognised extracellular vesicles (EVs) as potent vehicles for intercellular communication, potentially via their transport of microRNAs (miRNAs). The aim of the current investigation was to determine the size, concentration and electrical surface properties (zeta potential) of EVs secreted by; (1) primary cultures of porcine oviductal epithelial cells (POECs) from the isthmus and ampullary regions of the female reproductive tract; (2) Ishikawa and RL95-2 human endometrial epithelial cell line cultures; and (3) the non-reproductive epithelial cell line HEK293T. In addition, this study investigated whether EVs secreted by POECs contained miRNAs. All cell types were cultured in EV-depleted medium for 24 or 48 h. EVs were successfully isolated from conditioned culture media using size exclusion chromatography. Nanoparticle tracking analysis (NTA) was performed to evaluate EV size, concentration and zeta potential. QRT-PCR was performed to quantify the expression of candidate miRNAs (miR-103, let-7a, miR-19a, miR-203, miR-126, miR-19b, RNU44, miR-92, miR-196a, miR-326 and miR-23a). NTA confirmed the presence of EVs with diameters of 50-150 nm in all cell types. EV size distribution was significantly different between cell types after 24 and 48 h of cell culture and the concentration of EVs secreted by POECs and Ishikawa cells was also time dependent. The distribution of EVs with specific electrokinetic potential measurements varied between cell types, indicating that EVs of differing cellular origin have varied membrane components. In addition, EVs secreted by POECs exhibited significantly different time dependant changes in zeta potential. QRT-PCR confirmed the presence of miR-103, let-7a, miR-19a, miR-203, miR-126, and miR-19b in EVs secreted by POECs (C_T ≥ 29). Bioinformatics analysis suggests that these miRNAs are involved in cell proliferation, innate immune responses, apoptosis and cellular migration. In conclusion, reproductive epithelial cells secrete distinct populations of EVs containing miRNAs, which potentially act in intercellular communication in order to modulate the periconception events leading to successful establishment of pregnancy.

Extracellular small non-coding RNA contaminants in fetal bovine serum and serum-free media

In the research field of extracellular vesicles (EVs), the use of fetal bovine serum (FBS) depleted of EVs for in vitro studies is advocated to eliminate the confounding effects of media derived EVs. EV-depleted FBS may either be prepared by ultracentrifugation or purchased commercially. Nevertheless, these preparations do not guarantee an RNA-free FBS for in vitro use. In this study we address the RNA contamination issue, of small non-coding (nc)RNA in vesicular or non-vesicular fractions of FBS, ultracentrifugation EV-depleted FBS, commercial EV-depleted FBS, and in our recently developed filtration based EV-depleted FBS. Commercially available serum- and xeno-free defined media were also screened for small ncRNA contamination. Our small ncRNA sequencing data showed that all EV-depleted media and commercially available defined media contained small ncRNA contaminants. Out of the different FBS preparations studied, our ultrafiltration-based method for EV depletion performed the best in depleting miRNAs. Certain miRNAs such miR-122 and miR-203a proved difficult to remove completely and were found in all media. Compared to miRNAs, other small ncRNA (snRNA, Y RNA, snoRNA, and piRNA) were difficult to eliminate from all the studied media. Additionally, our tested defined media contained miRNAs and other small ncRNAs, albeit at a much lower level than in serum preparations. Our study showed that no media is free of small ncRNA contaminants. Therefore, in order to screen for baseline RNA contamination in culturing media, RNA sequencing data should be carefully controlled by adding a media sample as a control. This should be a mandatory step before performing cell culture experiments in order to eliminate the confounding effects of media.

A novel serum free primary astrocyte culture method that mimic quiescent astrocyte phenotype

BACKGROUND

Primary astrocyte cultures have been used for decades to study astrocyte functions in health and disease. The current primary astrocyte cultures are mostly maintained in serum-containing medium which produces astrocytes with a reactive phenotype as compared to in vivo quiescent astrocytes. The aim of this study was to establish a serum-free astrocyte culture medium that maintains primary astrocytes in a quiescent state.

NEW METHOD

Serum free astrocyte base medium (ABM) supplemented with basic fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) (ABM-FGF2-EGF) or serum supplemented DMEM (MD-10%FBS) was used to culture primary astrocytes isolated from cerebral cortex of postnatal day 1 C57BL/6 mice.

RESULTS

Compared to astrocytes cultured in MD-10%FBS medium, astrocytes in ABM-FGF2-EGF had higher process bearing morphologies similar to in vivo astrocytes. Western blot, immunostaining, quantitative polymerase chain reaction and metabolic assays revealed that astrocytes maintained in ABM-FGF2-EGF had enhanced glycolytic metabolism, higher glycogen content, lower GFAP expression, increased glutamine synthase, and glutamate transporter-1 mRNA levels as compared to astrocytes cultured in MD-10% FBS medium.

COMPARISON TO EXISTING METHODS

These observations suggest that astrocytes cultured in ABM-FGF2-EGF media compared to the usual FBS media promote quiescent and biosynthetic phenotype similar to in vivo astrocytes.

CONCLUSION

This media provides a novel method for studying astrocytes functions in vitro under physiological and pathological conditions.

Towards rationally designed biomanufacturing of therapeutic extracellular vesicles: impact of the bioproduction microenvironment

Extracellular vesicles (EVs), including exosomes, microvesicles, and others, have emerged as potential therapeutics for a variety of applications. Pre-clinical reports of EV efficacy in treatment of non-healing wounds, myocardial infarction, osteoarthritis, traumatic brain injury, spinal cord injury, and many other injuries and diseases demonstrate the versatility of this nascent therapeutic modality. EVs have also been demonstrated to be effective in humans, and clinical trials are underway to further explore their potential. However, for EVs to become a new class of clinical therapeutics, issues related to translation must be addressed. For example, approaches originally developed for cell biomanufacturing, such as hollow fiber bioreactor culture, have been adapted for EV production, but limited knowledge of how the cell culture microenvironment specifically impacts EVs restricts the possibility for rational design and optimization of EV production and potency. In this review, we discuss current knowledge of this issue and delineate potential focus areas for future research towards enabling translation and widespread application of EV-based therapeutics.

Fetal Bovine Serum-Derived Extracellular Vesicles Persist within Vesicle-Depleted Culture Media

It is known that culture media (CM) promotes cellular growth, adhesion, and protects explanted primary brain cells from in vitro stresses. The fetal bovine serum (FBS) supplement used in most CM, however, contains significant quantities of extracellular vesicles (EVs) that confound quantitative and qualitative analyses from the EVs produced by the cultured cells. We quantitatively tested the ability of common FBS EV-depletion protocols to remove exogenous EVs from FBS-supplemented CM and evaluated the influence such methods have on primary astrocyte culture growth and viability. We assessed two methodologies utilized for FBS EV removal prior to adding to CM: (1) an 18-h ultracentrifugation (UC); and (2) a commercial EV-depleted FBS (Exo-FBS™). Our analysis demonstrated that Exo-FBS™ CM provided the largest depletion (75%) of total FBS EVs, while still providing 6.92 × 10⁹ ± 1.39 × 10⁸ EVs/mL. In addition, both UC and Exo-FBS™ CM resulted in poor primary astrocyte cell growth and viability in culture. The two common FBS EV-depletion methods investigated, therefore, not only contaminate in vitro primary cell-derived EV analyses, but also provide a suboptimal environment for primary astrocyte cell growth and viability. It appears likely that future CM optimization, using a serum-free alternative, might be required to advance analyses of cell-specific EVs isolated in vitro.

Bringing cultured meat to market: Technical, socio-political, and regulatory challenges in cellular agriculture

BACKGROUND

Cultured meat forms part of the emerging field of cellular agriculture. Still an early stage field it seeks to deliver products traditionally made through livestock rearing in novel forms that require no, or significantly reduced, animal involvement. Key examples include cultured meat, milk, egg white and leather. Here, we focus upon cultured meat and its technical, socio-political and regulatory challenges and opportunities.

SCOPE AND APPROACH

The paper reports the thinking of an interdisciplinary team, all of whom have been active in the field for a number of years. It draws heavily upon the published literature, as well as our own professional experience. This includes ongoing laboratory work to produce cultured meat and over seventy interviews with experts in the area conducted in the social science work.

KEY FINDINGS AND CONCLUSIONS

Cultured meat is a promising, but early stage, technology with key technical challenges including cell source, culture media, mimicking the in-vivo myogenesis environment, animal-derived and synthetic materials, and bioprocessing for commercial-scale production. Analysis of the social context has too readily been reduced to ethics and consumer acceptance, and whilst these are key issues, the importance of the political and institutional forms a cultured meat industry might take must also be recognised, and how ambiguities shape any emergent regulatory system.

Isolation and Characterization of Extracellular Vesicles from Ex Vivo Cultured Human Placental Explants

Ex vivo culture of human placental explants has long allowed placentologists to study the milieu of soluble factors secreted by the human placenta throughout gestation while retaining the correct three-dimensional structure of the placental villi. Here, we detail the placental explant culture method employed in our laboratory to collect extracellular vesicles which are known to be released by the human placenta throughout pregnancy from 6 weeks of gestation. Using this method, at least three different populations of placental extracellular vesicles can be simultaneously collected from each placental sample, allowing for comparative analysis of the cargos and downstream effects of the different types of extracellular vesicles produced by the human placenta.

Isolation, cultivation, and characterization of human mesenchymal stem cells

Mesenchymal stem cells (MSC) exhibit a high self-renewal capacity, multilineage differentiation potential and immunomodulatory properties. This set of exceptional features makes them an attractive tool for research and clinical application. However, MSC are far from being a uniform cell type, which makes standardization difficult. The exact properties of human MSC (hMSC) can vary greatly depending on multiple parameters including tissue source, isolation method and medium composition. In this review we address the most important influence factors. We highlight variations in the differentiation potential of MSC from different tissue sources. Furthermore, we compare enzymatic isolation strategies with explants cultures focusing on adipose tissue and umbilical cords as two relevant examples. Additionally, we address effects of medium composition and serum supplementation on MSC expansion and differentiation. The lack of standardized methods for hMSC isolation and cultivation mandates careful evaluation of different protocols regarding efficiency and cell quality. MSC characterization based on a set of minimal criteria defined by the International Society for Cellular Therapy is a widely accepted practice, and additional testing for MSC functionality can provide valuable supplementary information. The MSC secretome has been identified as an important signaling mechanism to affect other cells. In this context, extracellular vesicles (EVs) are attracting increasing interest. The thorough characterization of MSC-derived EVs and their interaction with target cells is a crucial step toward a more complete understanding of MSC-derived EV functionality. Here, we focus on flow cytometric approaches to characterize free as well as cell bound EVs and address potential differences in the bioactivity of EVs derived from stem cells from different sources. © 2017 International Society for Advancement of Cytometry.

Methodological Guidelines to Study Extracellular Vesicles

Owing to the relationship between extracellular vesicles (EVs) and physiological and pathological conditions, the interest in EVs is exponentially growing. EVs hold high hopes for novel diagnostic and translational discoveries. This review provides an expert-based update of recent advances in the methods to study EVs and summarizes currently accepted considerations and recommendations from sample collection to isolation, detection, and characterization of EVs. Common misconceptions and methodological pitfalls are highlighted. Although EVs are found in all body fluids, in this review, we will focus on EVs from human blood, not only our most complex but also the most interesting body fluid for cardiovascular research.

Serum-derived extracellular vesicles (EVs) impact on vascular remodeling and prevent muscle damage in acute hind limb ischemia

Serum is an abundant and accessible source of circulating extracellular vesicles (EVs). Serum-EV (sEV) pro-angiogenic capability and mechanisms are herein analyzed using an in vitro assay which predicts sEV angiogenic potential in vivo. Effective sEVs (e-sEVs) also improved vascular remodeling and prevented muscle damage in a mouse model of acute hind limb ischemia. e-sEV angiogenic proteomic and transcriptomic analyses show a positive correlation with matrix-metalloproteinase activation and extracellular matrix organization, cytokine and chemokine signaling pathways, Insulin-like Growth Factor and platelet pathways, and Vascular Endothelial Growth Factor signaling. A discrete gene signature, which highlights differences in e-sEV and ineffective-EV biological activity, was identified using gene ontology (GO) functional analysis. An enrichment of genes associated with the Transforming Growth Factor beta 1 (TGFβ1) signaling cascade is associated with e-sEV administration but not with ineffective-EVs. Chromatin immunoprecipitation analysis on the inhibitor of DNA binding I (ID1) promoter region, and the knock-down of small mother against decapentaplegic (SMAD)1–5 proteins confirmed GO functional analyses. This study demonstrates sEV pro-angiogenic activity, validates a simple, sEV pro-angiogenic assay which predicts their biological activity in vivo, and identifies the TGFβ1 cascade as a relevant mediator. We propose serum as a readily available source of EVs for therapeutic purposes.

Secretome of in vitro cultured human embryos contains extracellular vesicles that are uptaken by the maternal side

Communication between embryo and maternal endometrium occurs during a specific time frame in which implantation is possible. Here we demonstrate for the first time that conditioned media from non-manipulated human embryos cultured in vitro for 3 days or up to the blastocyst stage contain extracellular vesicles (EVs) with a diameter of 50 to 200 nm and bearing the traditional microvesicle and exosome marker proteins CD63, CD9 and ALIX. The embryonic origin of these EVs has been confirmed by the presence of stemness gene transcripts and their enrichment in the non-classical HLA-G protein. NANOG and POU5F1 transcripts were shown to be contained in vesicles deriving from embryos at different stages of development. In line with a higher detection rate of the HLA-G protein in blastocysts compared to cleavage stage embryos, a significantly higher amount of HLA-G was found in vesicles accumulated in spent media from day 3 to day 5 of development compared to those isolated from the earlier stage. Uptake of dye-labeled embryo-derived EVs by human primary endometrial epithelial and stromal cells was also demonstrated with a fluorescence intensity signal significantly higher for cells treated with vesicles derived from blastocysts. Based on these findings, EV exchange may be suggested as an emerging way of communication at the maternal-fetal interface.

Muscle cell communication in development and repair

Under basal conditions, postnatal skeletal muscle displays little cell turnover. With injury, muscle initiates a rapid repair response to reseal damaged membrane, reactivating many developmental pathways to facilitate muscle regeneration and prevent tissue loss. Muscle precursor cells become activated accompanied by differentiation and fusion during both muscle growth and regeneration; inter-cellular communication is required for successful completion of these processes. Cellular communication is mediated by lipids, fusogenic membrane proteins, and exosomes. Muscle-derived exosomes carry proteins and micro RNAs as cargo. Secreted factors such as IGF-1, TGFβ, and myostatin are also released by muscle cells providing local signaling cues to modulate muscle fusion and regeneration. Proteins that regulate myoblast fusion also participate in membrane repair and regeneration. Here we will review methods of muscle cell communication focusing on proteins that mediate membrane fusion, exosomes, and autocrine factors.