Upscaling human mesenchymal stromal cell production in a novel vertical-wheel bioreactor enhances extracellular vesicle secretion and cargo profile

Quantifying extracellular vesicle heterogeneity: the effect of process conditions on protein cargo for skin therapy

Extracellular vesicles (EVs) contain a variety of proteins with anti-inflammatory and immunomodulatory properties that offer promising benefits in skin therapy applications. An influx of EV proteomic studies in recent years has created the opportunity for a detailed comparison of EV heterogeneity between studies in the context of therapeutic applications. Although several process conditions are known to cause variability in EVs, little has been done to quantify the impact of these factors on the nature of EV protein cargo. This review aims to both compile publicly available EV proteomics data and quantitatively estimate. the impact of process conditions on protein cargo-particularly in the context of skin therapy applications. Of roughly 400 articles, 52 relevant proteomic studies were identified within the last 15 years. Across studies, 40% of the 13,000 observed proteins were identified in only a single study. EVs in general were found to be highly variable, with mixed effects models only able to account for 25-60% of variance when considering factors such as EV source, medium, isolation method, LC-MS ionization, and protein search algorithm. Overall, MSC-derived EVs contained a greater fraction of proteins within pathways associated with wound healing and skin therapy (immune system, hemostasis, extracellular matrix organization, and cellular response to stress) as well as the most number of unique proteins when compared to all other analysed EVs. Although EVs are a promising tool within skin therapeutics, the overall variability in protein cargo underscores the need for standardized methodologies to fully elucidate the impact of process conditions on EV cargo.

Microenvironmental Modulation for Therapeutic Efficacy of Extracellular Vesicles

Extracellular vesicles (EVs) hold significant promise for the prevention and treatment of various diseases. However, the translation of EV-based therapies into clinical practice faces considerable challenges, particularly in terms of production yield and therapeutic efficacy. Recent studies have emphasized the heterogeneity of EVs and the influence of parental cell microenvironmental signals on their biogenesis, cargo composition, and therapeutic outcomes. This review offers a comprehensive overview of strategies to optimize the therapeutic efficacy of EVs through physical, biochemical, and mechanical modulation. Additionally, it explores how microenvironmental signals affect EV cargoes and the mechanisms by which these signals can improve therapeutic efficacy. The review also addresses current challenges and potential solutions to accelerate the clinical translation of EV therapies. Ultimately, it highlights the potential of microenvironmental modulation in unlocking the full therapeutic capacity of EVs, providing key insights into their production and clinical use for treating various diseases.

Scalability of spheroid-derived small extracellular vesicles production in stirred systems

Introduction

Small extracellular vesicle (sEV)-based therapies have gained widespread interest, but challenges persist to ensure standardization and high-scale production. Implementing upstream processes in a chemically defined media in stirred-tank bioreactors (STBr) is mandatory to closely control the cell environment, and to scale-up production, but it remains a significant challenge for anchorage-dependent cells.

Methods

We used a human β cell line, grown as monolayer or in suspension as spheroid in stirred systems. We assessed the consequences of culturing these cells in 3D with, or without fetal bovine serum in a chemically defined medium, for cell growth, viability and metabolism. We next explored how different scale-up strategies might influence cell and spheroid formation in spinner flask, with the aim to transfer the process in instrumented Ambr®250 STBr. Lastly, we analyzed and characterized sEV production in monolayer, spinner flask and STBr.

Results and discussion

Generation of spheroids in a chemically defined medium allowed the culture of highly viable cells in suspension in stirred systems. Spheroid size depended on the system's volumetric power input (P/V), and maintaining this parameter constant during scale-up proved to be the optimal strategy for standardizing the process. However, transferring the spinner flask (SpF) process to the Ambr®250 STBr at constant P/V modified spheroid size, due to important geometric differences and impeller design. Compared to a monolayer reference process, sEV yield decreased two-fold in SpF, but increased two-fold in STBr. Additionally, a lower expression of the CD63 tetraspanin was observed in sEV produced in both stirred systems, suggesting a reduced release of exosomes compared to ectosomes. This study addresses the main issues encountered in spheroid culture scale-up in stirred systems, rather conducive for the production of ectosomes.

Biomanufacturing and lipidomics analysis of extracellular vesicles secreted by human blood vessel organoids in a vertical wheel bioreactor

BACKGROUND

Extracellular vesicles (EVs) derived from human organoids are phospholipid bilayer-bound nanoparticles that carry therapeutic cargo. However, the low yield of EVs remains a critical bottleneck for clinical translation. Vertical-Wheel bioreactors (VWBRs), with unique design features, facilitate the scalable production of EVs secreted by human blood vessel organoids (BVOs) under controlled shear stress, using aggregate- and microcarrier-based culture systems.

METHODS

Human induced pluripotent stem cell-derived BVOs cultured as aggregates or on Synthemax II microcarriers within VWBRs (40 and 80 rpm) were compared to static controls. The organoids were characterized by metabolite profiling, flow cytometry, and gene expression of EV biogenesis markers. EVs were characterized by nanoparticle tracking analysis, electron microscopy, and Western blotting. Lipidomics provided insights into EV lipid composition, while functional assays assessed the impact of EVs in a D-galactose-induced senescence model.

RESULTS

VWBR cultures showed more aerobic metabolism and higher expression of EV biogenesis genes compared to the static control. EVs from different conditions were comparable in size, but the yields were significantly higher for microcarrier and dynamic cultures than static aggregates. Lipidomic profiling revealed minimal variation (< 0.36%) in total lipid content; however, distinct differences were identified in lipid chain lengths and saturation levels, affecting key pathways such as sphingolipid and neurotrophin signaling. Human BVO EVs demonstrated the abilities of reducing oxidative stress and increasing cell proliferation in vitro.

CONCLUSIONS

Human BVOs differentiated in VWBRs (in particular 40 rpm) produce 2-3 fold higher yield of EVs (per mL) than static control. The bio manufactured EVs from VWBRs have exosomal characteristics and therapeutic cargo, showing functional properties in in vitro assays. This innovative approach establishes VWBRs as a scalable platform for producing functional EVs with defined lipid profiles and therapeutic potential, paving the way for future in vivo studies.

Continuous collection of human mesenchymal-stromal-cell-derived extracellular vesicles from a stirred tank reactor operated under xenogeneic-free conditions for therapeutic applications

BACKGROUND

Mesenchymal-stromal-cell-derived extracellular vesicles (MSC-EVs) play a key role in the paracrine effects of MSC and have demonstrated therapeutic potential in various preclinical models. However, clinical translation is hindered by manufacturing practices relying on planar culture systems, fetal bovine serum (FBS)-supplemented media, and non-scalable, low-purity EV isolation methods that fail to meet dose and safety requirements, underscoring the need for innovative approaches. In this study, we developed a scalable platform to manufacture human MSC-EVs at clinically relevant numbers, integrating continuous collection of EV-enriched conditioned media (CM) using a stirred-tank reactor (STR) under xenogeneic-free conditions and a scalable downstream process.

METHODS

Wharton's jelly-derived MSC (MSC(WJ)) were expanded using microcarriers in a controlled STR using human platelet lysate (hPL)-supplemented medium. Then, a 3-day EV production stage, featuring continuous harvesting of the CM, was established using a novel serum-/xeno(geneic)-free exosome depleted-hPL supplement. For the isolation of MSC-EVs, a scalable process was implemented by pairing tangential flow filtration and anion exchange chromatography. Isolated MSC-EVs were characterised using nanoparticle tracking analysis, protein and zeta potential quantification, western blot analysis of EV protein markers, transmission electron microscopy and uptake studies of fluorescently labelled-EVs.

RESULTS

The system sustained the efficient expansion of MSC(WJ), reaching a total of (6.03 ± 0.181) x 107 cells after 7 days, which corresponds to a 30.1 ± 0.740-fold expansion. Upon a 3-day continuous CM harvesting, a total of (2.13 ± 0.301) x 1012 EVs were isolated corresponding to a particle yield factor of (1.26 ± 0.186) x 104 EVs/cell/day. MSC-EVs presented high purity levels ((5.53 ± 1.55) x 109 particles/µg), a homogeneous small size distribution (mean diameter of 115 ± 4.88 nm), a surface charge of -23.4 ± 6.23 mV, positive detection of tetraspanins CD9 and CD63 and syntenin-1 and displayed a typical cup-shaped morphology. MSC-EVs were readily incorporated by endothelial cells and two human breast cancer cell lines.

CONCLUSIONS

Overall, the scalable and Good Manufacturing Practices (GMP)-compliant platform established herein enabled the reproducible manufacturing of MSC-EVs with high purity and generally accepted characteristics concerning size, protein markers, surface charge, morphology, and cellular internalization, validating its potential for future clinical applications.

The Role of Viral Infections in Acute Kidney Injury and Mesenchymal Stem Cell-Based Therapy

Viruses may cause a wide range of renal problems. Furthermore, many kidney diseases may be brought on by viral infections. Both the primary cause and a contributing factor of acute kidney injury (AKI) may be viral infections. As an example, it is recommended that patients with dengue virus (DENV) infections undergo careful monitoring of their AKI levels. Also, researchers' data so far lend credence to the several hypothesized pathophysiological mechanisms via which AKI can develop in SARS-CoV- 2 infection. Thus, it is critical to comprehend how viral infections cause AKI. Finding an effective method of treating AKI caused by viruses is also vital. Thus, a potential cell-free method for treating AKI that uses regenerative and anti-inflammatory processes is mesenchymal stem cells (MSCs) and their exosomes (MSC-EXOs). MSCs alleviate tissue damage and enhance protective effects on damaged kidneys in AKI. Furthermore, MSC-EXOs have exhibited substantial regulatory impact on a range of immune cells and exhibit robust immune regulation in the therapy of AKI. Thus, in models of AKI caused by ischemia-reperfusion damage, nephrotoxins, or sepsis, MSCs and MSC-EXOs improved renal function, decreased inflammation, and improved healing. Therefore, MSCs and MSC-EXOs may help treat AKI caused by different viruses. Consequently, we have explored several innovative and significant processes in this work that pertain to the role of viruses in AKI and the significance of viral illness in the onset of AKI. After that, we assessed the key aspects of MSCs and MSC-EXOs for AKI therapy. We have concluded by outlining the current state of and plans for future research into MSC- and EXO-based therapeutic approaches for the treatment of AKI brought on by viruses.

Potential upscaling protocol establishment and wound healing bioactivity screening of exosomes isolated from canine adipose-derived mesenchymal stem cells

Mesenchymal stem cell-derived exosomes exhibit promising potential in tissue regeneration. Recent studies highlight its significant therapeutic potential in various stages of wound healing. However, the clinical translation of exosome-based therapy was hindered due to issues regarding low productivity and the lack of efficient production protocol to obtain a clinically relevant exosome quantity. Therefore, this study established a potential upscaling protocol to produce exosomes derived from canine adipose-derived mesenchymal stem cells (cAD-MSCs) and explored its potential for wound treatment. The potential upscaling protocol, termed VSCBIC-3-3D, was carried out using VSCBIC-3 in-house serum-free exosome-collecting solution in a three-dimensional (3D) culture system followed by the tangential flow filtration (TFF) isolation. Our findings suggest that culturing cAD-MSCs with VSCBIC-3 maintained cell morphology and viability. Compared to conventional two-dimensional (2D) protocols, The potential upscaling protocol increased exosome yield and concentration in conditioned medium by 2.4-fold and 3.2-fold, respectively. The quality assessment revealed enhanced purity and bioactivity of exosomes produced using the VSCBIC-3-3D protocol. In addition, the cAD-MSCs-derived exosomes were shown to significantly improve fibroblast migration, proliferation, and wound healing-related gene expression in vitro. This study collectively demonstrates that potential upscaling protocol establishment allowed robust production of exosomes from cAD-MSCs, which exhibit therapeutic potential for wound healing in vitro.

Engineering Extracellular Vesicles Secreted by Human Brain Organoids with Different Regional Identity

Extracellular vesicles (EVs) are membrane-bound nanovesicles that show significance in intercellular communications and high therapeutic potential. In this study, a novel type of EV subpopulation, matrix-bound nanovesicles (MBVs), was identified from a decellularized extracellular matrix of brain organoids that were derived from human pluripotent stem cells to compare with supernatant EVs (SuEVs) isolated from spent media. The organoids generated 10-fold more MBVs than did SuEVs. SuEVs contained more enriched microRNA cargo than MBVs, and the microRNA relative abundance changed during organoid maturation. The forebrain and hindbrain organoid SuEVs had a highly overlapped protein cargo based on proteomics analysis. More membrane proteins, including integrins, were identified in MBVs than SuEVs, which could contribute to MBV retention in matrices. Lipidomics data showed that MBVs were enriched in glycerophospholipids and sphingolipids, which affect the lipid membrane rigidity and recruitment of integral membrane proteins. To mimic ischemic stroke, in vitro oxygen and glucose deprivation model results revealed stronger recovery effects of MBVs than SuEVs at the same dose. The effects were exerted by regulating autophagy, reactive oxygen species scavenging, and anti-inflammatory ability. This study laid the foundation for advancing our knowledge of intercellular communication and for developing cell-free based therapies for treating neurological disorders such as ischemic stroke.

Static Topographical Cue Combined with Dynamic Fluid Stimulation Enhances the Macrophage Extracellular Vesicle Yield and Therapeutic Potential for Bone Defects

Extracellular vesicles (EVs) hold promise for tissue regeneration, but their low yield and limited therapeutic efficacy hinder clinical translation. Bioreactors provide a larger culture surface area and stable environment for large-scale EV production, yet their ability to enhance EV therapeutic efficacy is limited. Physical stimulation, by inducing cell differentiation and modulating EV cargo composition, offers a more efficient, cost-effective, and reproducible approach compared to the cargo loading of EVs and biochemical priming of parental cells. Herein, the effects of a 3D-printed perfusion bioreactor with a topographical cue on the macrophage EV yield and bioactivity were assessed. The results indicate that the bioreactor increased the EV yield 12.5-fold and enhanced bioactivity in promoting osteogenic differentiation and angiogenesis via upregulated miR-210-3p. Mechanistically, fluid shear stress activates Piezo1, triggering Ca2+ influx and Yes-associated protein (YAP) nuclear translocation, promoting EV secretion and enhancing macrophage M2 polarization in conjunction with morphological changes guided by aligned topography. Moreover, a porous electrospun membrane-hydrogel composite scaffold loaded with bioreactor-derived EVs exhibited outstanding efficacy in promoting osteogenic differentiation and angiogenesis in a rat cranial defect model. This study presents a scalable, cost-effective, and stable platform for the production of therapeutic EVs, potentially overcoming key challenges in translating EV-based therapies to the clinic.

Mesenchymal stem cell-derived exosomes as a plausible immunomodulatory therapeutic tool for inflammatory diseases

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs), especially, exosomes are considered to have diverse therapeutic effects for various significant diseases. MSC-derived exosomes (MSCex) offer substantial advantages over MSCs due to their long-term preservation, stability, absence of nuclei and fewer adverse effects such as infusion toxicity, thereby paving the way towards regenerative medicine and cell-free therapeutics. These exosomes harbor several cellular contents such as DNA, RNA, lipids, metabolites, and proteins, facilitating drug delivery and intercellular communication. MSCex have the ability to immunomodulate and trigger the anti-inflammatory process hence, playing a key role in alleviating inflammation and enhancing tissue regeneration. In this review, we addressed the anti-inflammatory effects of MSCex and the underlying immunomodulatory pathways. Moreover, we discussed the recent updates on MSCex in treating specific inflammatory diseases, including arthritis, inflammatory bowel disease, inflammatory eye diseases, and respiratory diseases such as asthma and acute respiratory distress syndrome (ARDS), as well as neurodegenerative and cardiac diseases. Finally, we highlighted the challenges in using MSCex as the successful therapeutic tool and discussed future perspectives.

Effects of Hydrogels on Mesenchymal Stem/Stromal Cells Paracrine Activity and Extracellular Vesicles Production

Mesenchymal stem/stromal cells (MSCs) are a valuable source of paracrine factors, as they have a remarkable secretory capacity, and there is a sizeable knowledge base to develop industrial and clinical production protocols. Promising cell-free approaches for tissue regeneration and immunomodulation are driving research towards secretome applications, among which extracellular vesicles (EVs) are steadily gaining attention. However, the manufacturing and application of EVs is limited by insufficient yields, knowledge gaps, and low standardization. Facing these limitations, hydrogels represent a versatile three-dimensional (3D) culture platform that can incorporate extracellular matrix (ECM) components to mimic the natural stem cell environment in vitro; via these niche-mimicking properties, hydrogels can regulate MSCs' morphology, adhesion, proliferation, differentiation and secretion capacities. However, the impact of the hydrogel's architectural, biochemical and biomechanical properties on the production of EVs remains poorly understood, as the field is still in its infancy and the interdependency of culture parameters compromises the comparability of the studies. Therefore, this review summarizes and discusses the reported effects of hydrogel encapsulation and culture on the secretion of MSC-EVs. Considering the effects of cell-material interactions on the overall paracrine activity of MSCs, we identify persistent challenges from low standardization and process control, and outline future paths of research, such as the synergic use of hydrogels and bioreactors to enhance MSC-EV generation.

Viscoelasticity of Hyaluronic Acid Hydrogels Regulates Human Pluripotent Stem Cell-derived Spinal Cord Organoid Patterning and Vascularization

Recently, it has been recognized that natural extracellular matrix (ECM) and tissues are viscoelastic, while only elastic properties have been investigated in the past. How the viscoelastic matrix regulates stem cell patterning is critical for cell-ECM mechano-transduction. Here, this study fabricated different methacrylated hyaluronic acid (HA) hydrogels using covalent cross-linking, consisting of two gels with similar elasticity (stiffness) but different viscoelasticity, and two gels with similar viscoelasticity but different elasticity (stiffness). Meanwhile, a second set of dual network hydrogels are fabricated containing both covalent and coordinated cross-links. Human spinal cord organoid (hSCO) patterning in HA hydrogels and co-culture with isogenic human blood vessel organoids (hBVOs) are investigated. The viscoelastic hydrogels promote regional hSCO patterning compared to the elastic hydrogels. More viscoelastic hydrogels can promote dorsal marker expression, while softer hydrogels result in higher interneuron marker expression. The effects of viscoelastic properties of the hydrogels become more dominant than the stiffness effects in the co-culture of hSCOs and hBVOs. In addition, more viscoelastic hydrogels can lead to more Yes-associated protein nuclear translocation, revealing the mechanism of cell-ECM mechano-transduction. This research provides insights into viscoelastic behaviors of the hydrogels during human organoid patterning with ECM-mimicking in vitro microenvironments for applications in regenerative medicine.

Identifying and optimizing critical process parameters for large-scale manufacturing of iPSC derived insulin-producing β-cells

BACKGROUND

Type 1 diabetes, an autoimmune disorder leading to the destruction of pancreatic β-cells, requires lifelong insulin therapy. Islet transplantation offers a promising solution but faces challenges such as limited availability and the need for immunosuppression. Induced pluripotent stem cells (iPSCs) provide a potential alternative source of functional β-cells and have the capability for large-scale production. However, current differentiation protocols, predominantly conducted in hybrid or 2D settings, lack scalability and optimal conditions for suspension culture.

METHODS

We examined a range of bioreactor scaleup process parameters and quality target product profiles that might affect the differentiation process. This investigation was conducted using an optimized High Dimensional Design of Experiments (HD-DoE) protocol designed for scalability and implemented in 0.5L (PBS-0.5 Mini) vertical wheel bioreactors.

RESULTS

A three stage suspension manufacturing process is developed, transitioning from adherent to suspension culture, with TB2 media supporting iPSC growth during scaling. Stage-wise optimization approaches and extended differentiation times are used to enhance marker expression and maturation of iPSC-derived islet-like clusters. Continuous bioreactor runs were used to study nutrient and growth limitations and impact on differentiation. The continuous bioreactors were compared to a Control media change bioreactor showing metabolic shifts and a more β-cell-like differentiation profile. Cryopreserved aggregates harvested from the runs were recovered and showed maintenance of viability and insulin secretion capacity post-recovery, indicating their potential for storage and future transplantation therapies.

CONCLUSION

This study demonstrated that stage time increase and limited media replenishing with lactate accumulation can increase the differentiation capacity of insulin producing cells cultured in a large-scale suspension environment.

Stimulative piezoelectric nanofibrous scaffolds for enhanced small extracellular vesicle production in 3D cultures

Small extracellular vesicles (sEVs) have great promise as effective carriers for drug delivery. However, the challenges associated with the efficient production of sEVs hinder their clinical applications. Herein, we report a stimulative 3D culture platform for enhanced sEV production. The proposed platform consists of a piezoelectric nanofibrous scaffold (PES) coupled with acoustic stimulation to enhance sEV production of cells in a 3D biomimetic microenvironment. Combining cell stimulation with a 3D culture platform in this stimulative PES enables a 15.7-fold increase in the production rate per cell with minimal deviations in particle size and protein composition compared with standard 2D cultures. We find that the enhanced sEV production is attributable to the activation and upregulation of crucial sEV production steps through the synergistic effect of stimulation and the 3D microenvironment. Moreover, changes in cell morphology lead to cytoskeleton redistribution through cell-matrix interactions in the 3D cultures. This in turn facilitates intracellular EV trafficking, which impacts the production rate. Overall, our work provides a promising 3D cell culture platform based on piezoelectric biomaterials for enhanced sEV production. This platform is expected to accelerate the potential use of sEVs for drug delivery and broad biomedical applications.

Tumor Microenvironment-Derived Exosomes: A Double-Edged Sword for Advanced T Cell-Based Immunotherapy

The tumor microenvironment (TME) plays a crucial role in cancer progression and immune evasion, partially mediated by the activity of the TME-derived exosomes. These extracellular vesicles are pivotal in shaping immune responses through the transfer of proteins, lipids, and nucleic acids between cells, facilitating a complex interplay that promotes tumor growth and metastasis. This review delves into the dual roles of exosomes in the TME, highlighting both their immunosuppressive functions and their emerging therapeutic potential. Exosomes can inhibit T cell function and promote tumor immune escape by carrying immune-modulatory molecules, such as PD-L1, yet they also hold promise for cancer therapy as vehicles for delivering tumor antigens and costimulatory signals. Additionally, the review discusses the intricate crosstalk mediated by exosomes among various cell types within the TME, influencing both cancer progression and responses to immunotherapies. Moreover, this highlights current challenges and future directions. Collectively, elucidating the detailed mechanisms by which TME-derived exosomes mediate T cell function offers a promising avenue for revolutionizing cancer treatment. Understanding these interactions allows for the development of targeted therapies that manipulate exosomal pathways to enhance the immune system's response to tumors.

Basic Guide for Approaching Drug Delivery with Extracellular Vesicles

Extracellular vesicles (EVs) are natural carriers of biomolecules that play a crucial role in cell-to-cell communication and tissue homeostasis under normal and pathological conditions, including inflammatory diseases and cancer. Since the discovery of the pro-regenerative and immune-modulating properties of EVs, EV-based therapeutics have entered clinical trials for conditions such as myocardial infarction and autoimmune diseases, among others. Due to their unique advantages-such as superior bioavailability, substantial packaging capacity, and the ability to traverse biological barriers-EVs are regarded as a promising platform for targeted drug delivery. However, achieving a sufficient accumulation of therapeutic agents at the target site necessitates a larger quantity of EVs per dose compared to using EVs as standalone drugs. This challenge can be addressed by administering larger doses of EVs, increasing the drug dosage per administration, or enhancing the selective accumulation of EVs at target cells. In this review, we will discuss methods to improve the isolation and purification of EVs, approaches to enhance cargo packaging-including proteins, RNAs, and small-molecule drugs-and technologies for displaying targeting ligands on the surface of EVs to facilitate improved targeting. Ultimately, this guide can be applied to the development of novel classes of EV-based therapeutics and to overcoming existing technological challenges.

Profiling biomanufactured extracellular vesicles of human forebrain spheroids in a Vertical-Wheel Bioreactor

Extracellular vesicles (EVs) secreted by human brain cells have great potential as cell-free therapies in various diseases, including stroke. However, because of the significant amount of EVs needed in preclinical and clinical trials, EV application is still challenging. Vertical-Wheel Bioreactors (VWBRs) have designed features that allow for scaling up the generation of human forebrain spheroid EVs under low shear stress. In this study, EV secretion by human forebrain spheroids derived from induced pluripotent stem cells as 3D aggregates and on Synthemax II microcarriers in VWBRs were investigated with static aggregate culture as a control. The spheroids were characterized by metabolite and transcriptome analysis. The isolated EVs were characterized by nanoparticle tracking analysis, electron microscopy, and Western blot. The EV cargo was analyzed using proteomics and miRNA sequencing. The in vitro functional assays of an oxygen and glucose-deprived stroke model were conducted. Proof of concept in vivo study was performed, too. Human forebrain spheroid differentiated on microcarriers showed a higher growth rate than 3D aggregates. Microcarrier culture had lower glucose consumption per million cells and lower glycolysis gene expression but higher EV biogenesis genes. EVs from the three culture conditions showed no differences in size, but the yields from high to low were microcarrier cultures, dynamic aggregates, and static aggregates. The cargo is enriched with proteins (proteomics) and miRNAs (miRNA-seq), promoting axon guidance, reducing apoptosis, scavenging reactive oxygen species, and regulating immune responses. Human forebrain spheroid EVs demonstrated the ability to improve recovery in an in vitro stroke model and in vivo. Human forebrain spheroid differentiation in VWBR significantly increased the EV yields (up to 240-750 fold) and EV biogenesis compared to static differentiation due to the dynamic microenvironment and metabolism change. The biomanufactured EVs from VWBRs have exosomal characteristics and more therapeutic cargo and are functional in in vitro assays, which paves the way for future in vivo stroke studies.

Harnessing Engineered Extracellular Vesicles from Mesenchymal Stem Cells as Therapeutic Scaffolds for Bone‐Related Diseases

Mesenchymal stem cells (MSCs) play a crucial role in maintaining bone homeostasis and are extensively explored for cell therapy in various bone‐related diseases. In addition to direct cell therapy, the secretion of extracellular vesicles (EVs) by MSCs has emerged as a promising alternative approach. MSC‐derived EVs (MSC‐EVs) offer equivalent therapeutic efficacy to MSCs while mitigating potential risks. These EVs possess unique properties that enable them to traverse biological barriers and deliver bioactive cargos to target cells. Furthermore, by employing modification and engineering strategies, the therapeutic effects and tissue targeting specificity of MSC‐EVs can be further enhanced to meet specific therapeutic needs. In this review, the mechanisms and advantages of MSC‐EV therapy in diseased bone tissues are highlighted. Through simple isolation and modification techniques, MSC‐EV‐based biomaterials have demonstrated great promise for bone regeneration. Finally, future perspectives on MSC‐EV therapy are presented, envisioning the development of next‐generation regenerative materials and bioactive agents for clinical translation in the field of bone regeneration.

Four sides to the story: A proteomic comparison of liquid-phase and matrix-bound extracellular vesicles in 2D and 3D cell cultures

Multipotent mesenchymal stromal cells (MSCs)-derived extracellular vesicles (EVs) play important roles in cellular communication and are extensively studied as promising therapeutic agents. While there is a substantial pool of studies on liquid-phase EVs, data on EVs bound to the extracellular matrix (ECM) is lacking. There is also an emerging trend of accumulating and comparing data on characteristics of EVs obtained in different culturing conditions. Aiming to reveal proteomic signatures of EVs obtained from conditioned media and ECM of MSCs cultured in 2D and 3D conditions, we performed liquid chromatography with tandem mass spectrometry. Bioinformatic analysis revealed common patterns in proteomic composition of liquid-phase EVs and matrix-bound vesicles (MBVs), namely extracellular environment organization, immune, and transport pathways enrichment. However, extracellular environmental organization pathways are more enriched in liquid-phase EVs than in MBVs, while MBVs proteins noticeably enrich enzymatic pathways. Furthermore, each type of EVs from 2D and 3D cultures has a unique differential abundance profile. We have also performed comparative functional assays, namely scratch assay to assess EVs effect on cell migration and tubulogenesis assay to evaluate EVs angiogenic potential. We found that both liquid-phase EVs and MBVs enhance cell migration, while angiogenic potential is higher in MBVs. Results of the present study suggest that while both liquid-phase EVs and MBVs have therapeutic potential, some unique features of each subgroup may determine optimal areas of their application.

High-Throughput 3D Imaging Flow Cytometry of Suspended Adherent 3D Cell Cultures

3D cell cultures are indispensable in recapitulating in vivo environments. Among the many 3D culture methods, culturing adherent cells on hydrogel beads to form spheroid-like structures is a powerful strategy for maintaining high cell viability and functions in the adherent states. However, high-throughput, scalable technologies for 3D imaging of individual cells cultured on the hydrogel scaffolds are lacking. This study reports the development of a high throughput, scalable 3D imaging flow cytometry platform for analyzing spheroid models. This platform is realized by integrating a single objective fluorescence light-sheet microscopy with a microfluidic device that combines hydrodynamic and acoustofluidic focusing techniques. This integration enabled unprecedentedly high-throughput and scalable optofluidic 3D imaging, processing 1310 spheroids consisting of 28 117 cells min-1. The large dataset obtained enables precise quantification and comparison of the nuclear morphology of adhering and suspended cells, revealing that the adhering cells have smaller nuclei with less rounded surfaces. This platform's high throughput, robustness, and precision for analyzing the morphology of subcellular structures in 3D culture models hold promising potential for various biomedical analyses, including image-based phenotypic screening of drugs with spheroids or organoids.

Robust bioprocess design and evaluation of commercial media for the serial expansion of human induced pluripotent stem cell aggregate cultures in vertical-wheel bioreactors

BACKGROUND

While pluripotent stem cell (PSC) therapies move toward clinical and commercial applications at a rapid rate, manufacturing reproducibility and robustness are notable bottlenecks in regulatory approval. Therapeutic applications of PSCs require large cell quantities to be generated under highly robust, well-defined, and economically viable conditions. Small-scale and short-term process optimization, however, is often performed in a linear fashion that does not account for time needed to verify the bioprocess protocols and analysis methods used. Design of a reproducible and robust bioprocess should be dynamic and include a continuous effort to understand how the process will respond over time and to different stresses before transitioning into large-scale production where stresses will be amplified.

METHODS

This study utilizes a baseline protocol, developed for the short-term culture of PSC aggregates in Vertical-Wheel® bioreactors, to evaluate key process attributes through long-term (serial passage) suspension culture. This was done to access overall process robustness when performed with various commercially available media and cell lines. Process output variables including growth kinetics, aggregate morphology, harvest efficiency, genomic stability, and functional pluripotency were assessed through short and long-term culture.

RESULTS

The robust nature of the expansion protocol was demonstrated over a six-day culture period where spherical aggregate formation and expansion were observed with high-fold expansions for all five commercial media tested. Profound differences in cell growth and quality were revealed only through long-term serial expansion and in-vessel dissociation operations. Some commercial media formulations tested demonstrated maintenance of cell growth rates, aggregate morphology, and high harvest recovery efficiencies through three bioreactor serial passages using multiple PSC lines. Exceptional bioprocess robustness was even demonstrated with sustained growth and quality maintenance over 10 serial bioreactor passages. However, some commercial media tested proved less equipped for serial passage cultures in bioreactors as cultures led to cell lysis during dissociation, reduction in growth rates, and a loss of aggregate morphology.

CONCLUSIONS

This study demonstrates the importance of systematic selection and testing of bioprocess input variables, with multiple bioprocess output variables through serial passages to create a truly reproducible and robust protocol for clinical and commercial PSC production using scalable bioreactor systems.

Advancing stroke therapy: innovative approaches with stem cell-derived extracellular vesicles

Stroke is a leading cause of mortality and long-term disability globally, with acute ischemic stroke (AIS) being the most common subtype. Despite significant advances in reperfusion therapies, their limited time window and associated risks underscore the necessity for novel treatment strategies. Stem cell-derived extracellular vesicles (EVs) have emerged as a promising therapeutic approach due to their ability to modulate the post-stroke microenvironment and facilitate neuroprotection and neurorestoration. This review synthesizes current research on the therapeutic potential of stem cell-derived EVs in AIS, focusing on their origin, biogenesis, mechanisms of action, and strategies for enhancing their targeting capacity and therapeutic efficacy. Additionally, we explore innovative combination therapies and discuss both the challenges and prospects of EV-based treatments. Our findings reveal that stem cell-derived EVs exhibit diverse therapeutic effects in AIS, such as promoting neuronal survival, diminishing neuroinflammation, protecting the blood-brain barrier, and enhancing angiogenesis and neurogenesis. Various strategies, including targeting modifications and cargo modifications, have been developed to improve the efficacy of EVs. Combining EVs with other treatments, such as reperfusion therapy, stem cell transplantation, nanomedicine, and gut microbiome modulation, holds great promise for improving stroke outcomes. However, challenges such as the heterogeneity of EVs and the need for standardized protocols for EV production and quality control remain to be addressed. Stem cell-derived EVs represent a novel therapeutic avenue for AIS, offering the potential to address the limitations of current treatments. Further research is needed to optimize EV-based therapies and translate their benefits to clinical practice, with an emphasis on ensuring safety, overcoming regulatory hurdles, and enhancing the specificity and efficacy of EV delivery to target tissues.

Equine mesenchymal stem cell-derived extracellular vesicle productivity but not overall yield is improved via 3-D culture with chemically defined media

OBJECTIVE

Mesenchymal stem cell (MSC) extracellular vesicles (EVs) have emerged as a biotherapeutic for osteoarthritis; however, manufacturing large quantities is not practical using traditional monolayer (2-D) culture. We aimed to examine the effects of 3-D and 2-D culture 2 types of media: Dulbecco modified Eagle medium and a commercially available medium (CM) on EV yield.

ANIMALS

Banked bone marrow-derived MSCs (BM-MSCs) from 6 healthy, young horses were used.

METHODS

4 microcarriers (collagen-coated polystyrene, uncoated polystyrene, collagen-coated dextran, and uncoated dextran) were tested in static and bioreactor cultures, and the optimal microcarrier was chosen. The BM-MSCs were inoculated into a bioreactor with collagen-coated dextran microcarriers at 5,000 cells/cm2 or onto culture dishes at 4,000 cells/cm2 in either Dulbecco modified Eagle medium or CM media. Supernatants were obtained for metabolite and pH analysis. The BM-MSCs were expanded until confluent (2-D) or for 7 days (3-D) when the 48-hour EV collection period commenced using EV-depleted media. Extracellular vesicles were isolated and characterized via nanoparticle tracking analysis, Western blot, transmission electron microscopy, and protein quantification. The BM-MSCs were harvested, quantified, and immunophenotyped.

RESULTS

The number of EVs isolated was not improved by 3-D culture or CM media, however, the CM 3-D condition improved the number of EVs produced per BM-MSC over the CM 2-D condition (mean ± SD: 306 ± 99 vs 37 ± 22, respectively). Glucose decreased and lactate and ammonium accumulated in 3-D culture. Surface markers of stemness exhibited reduced expression in 3-D culture.

CLINICAL RELEVANCE

Optimization of our 3-D culture methods could improve BM-MSC expansion and thus EV yield.

Transitioning from static to suspension culture system for large-scale production of xeno-free extracellular vesicles derived from mesenchymal stromal cells

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) have shown increasing therapeutic potential in the last years. However, large production of EV is required for therapeutic purposes. Thereby, scaling up MSC cultivation in bioreactors is essential to allow culture parameters monitoring. In this study, we reported the establishment of a scalable bioprocess to produce MSC-EV in suspension cultures using spinner flasks and human collagen-coated microcarriers (3D culture system). We compared the EV production in this 3D culture system with the standard static culture using T-flasks (2D culture system). The EV produced in both systems were characterized and quantify by western blotting and nanoparticle tracking analysis. The presence of the typical protein markers CD9, CD63, and CD81 was confirmed by western blotting analyses for EV produced in both culture systems. The cell fold-increase was 5.7-fold for the 3D culture system and 4.6-fold for the 2D culture system, signifying a fold-change of 1.2 (calculated as the ratio of fold-increase 3D to fold-increase 2D). Furthermore, it should be noted that the total cell production in the spinner flask cultures was 4.8 times higher than that in T-flask cultures. The total cell production in the spinner flask cultures was 5.2-fold higher than that in T-flask cultures. While the EV specific production (particles/cell) in T-flask cultures (4.40 ± 1.21 × 108 particles/mL, p < 0.05) was higher compared to spinner flask cultures (2.10 ± 0.04 × 108 particles/mL, p < 0.05), the spinner flask culture system offers scalability, making it capable of producing enough MSC-EV at a large scale for clinical applications. Therefore, we concluded that 3D culture system evaluated here serves as an efficient transitional platform that enables the scaling up of MSC-EV production for therapeutic purposes by utilizing stirred tank bioreactors and maintaining xeno-free conditions.

Advances in the application of extracellular vesicles derived from three-dimensional culture of stem cells

Stem cells (SCs) have been used therapeutically for decades, yet their applications are limited by factors such as the risk of immune rejection and potential tumorigenicity. Extracellular vesicles (EVs), a key paracrine component of stem cell potency, overcome the drawbacks of stem cell applications as a cell-free therapeutic agent and play an important role in treating various diseases. However, EVs derived from two-dimensional (2D) planar culture of SCs have low yield and face challenges in large-scale production, which hinders the clinical translation of EVs. Three-dimensional (3D) culture, given its ability to more realistically simulate the in vivo environment, can not only expand SCs in large quantities, but also improve the yield and activity of EVs, changing the content of EVs and improving their therapeutic effects. In this review, we briefly describe the advantages of EVs and EV-related clinical applications, provide an overview of 3D cell culture, and finally focus on specific applications and future perspectives of EVs derived from 3D culture of different SCs.

Peripheral extracellular vesicles in neurodegeneration: pathogenic influencers and therapeutic vehicles

Neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis epitomize a class of insidious and relentless neurological conditions that are difficult to cure. Conventional therapeutic regimens often fail due to the late onset of symptoms, which occurs well after irreversible neurodegeneration has begun. The integrity of the blood-brain barrier (BBB) further impedes efficacious drug delivery to the central nervous system, presenting a formidable challenge in the pharmacological treatment of NDDs. Recent scientific inquiries have shifted focus toward the peripheral biological systems, investigating their influence on central neuropathology through the lens of extracellular vesicles (EVs). These vesicles, distinguished by their ability to breach the BBB, are emerging as dual operatives in the context of NDDs, both as conveyors of pathogenic entities and as prospective vectors for therapeutic agents. This review critically summarizes the burgeoning evidence on the role of extracerebral EVs, particularly those originating from bone, adipose tissue, and gut microbiota, in modulating brain pathophysiology. It underscores the duplicity potential of peripheral EVs as modulators of disease progression and suggests their potential as novel vehicles for targeted therapeutic delivery, positing a transformative impact on the future landscape of NDD treatment strategies. Search strategy A comprehensive literature search was conducted using PubMed, Web of Science, and Scopus from January 2000 to December 2023. The search combined the following terms using Boolean operators: "neurodegenerative disease" OR "Alzheimer's disease" OR "Parkinson's disease" OR "Amyotrophic lateral sclerosis" AND "extracellular vesicles" OR "exosomes" OR "outer membrane vesicles" AND "drug delivery systems" AND "blood-brain barrier". MeSH terms were employed when searching PubMed to refine the results. Studies were included if they were published in English, involved human subjects, and focused on the peripheral origins of EVs, specifically from bone, adipose tissue, and gut microbiota, and their association with related diseases such as osteoporosis, metabolic syndrome, and gut dysbiosis. Articles were excluded if they did not address the role of EVs in the context of NDDs or did not discuss therapeutic applications. The titles and abstracts of retrieved articles were screened using a dual-review process to ensure relevance and accuracy. The reference lists of selected articles were also examined to identify additional relevant studies.

Mesenchymal Stem Cell-based Scaffolds in Regenerative Medicine of Dental Diseases

Biomedical engineering breakthroughs and increased patient expectations and requests for more comprehensive care are propelling the field of regenerative dentistry forward at a fast pace. Stem cells (SCs), bioactive compounds, and scaffolds are the mainstays of tissue engineering, the backbone of regenerative dentistry. Repairing damaged teeth and gums is a significant scientific problem at present. Novel therapeutic approaches for tooth and periodontal healing have been inspired by tissue engineering based on mesenchymal stem cells (MSCs). Furthermore, as a component of the MSC secretome, extracellular vesicles (EVs) have been shown to contribute to periodontal tissue repair and regeneration. The scaffold, made of an artificial extracellular matrix (ECM), acts as a supporting structure for new cell development and tissue formation. To effectively promote cell development, a scaffold must be non-toxic, biodegradable, biologically compatible, low in immunogenicity, and safe. Due to its promising biological characteristics for cell regeneration, dental tissue engineering has recently received much attention for its use of natural or synthetic polymer scaffolds with excellent mechanical properties, such as small pore size and a high surface-to-volume ratio, as a matrix. Moreover, as a bioactive material for carrying MSC-EVs, the combined application of scaffolds and MSC-EVs has a better regenerative effect on dental diseases. In this paper, we discuss how MSCs and MSC-derived EV treatment may be used to regenerate damaged teeth, and we highlight the role of various scaffolds in this process.

Effects of tension on mitochondrial autophagy and osteogenic differentiation of periodontal ligament stem cells

This study aimed to explore the osteogenic ability and mitochondrial autophagy of periodontal ligament stem cells (PDLSCs) under cyclic tensile stress (CTS). Primary PDLSCs were isolated from the periodontal membrane and cultured by passage. Alizarin red staining, alkaline phosphatase detection, reverse transcription polymerase chain reaction (RT-PCR), and Western blotting were used to detect the osteogenic differentiation level of PDLSCs. Mitochondrial autophagy in PDLSCs after CTS was measured using a mitochondrial autophagy detection kit, and the expression levels of autophagy-related proteins LC3B, LAMP1 and Beclin1 were measured using cellular immunofluorescence technology, RT-PCR and Western blot. After applying CTS, the osteogenic differentiation ability of PDLSCs was significantly improved, and the expression of alkaline phosphatase on the surface of the cell membrane and the formation of calcium nodules in PDLSCs were significantly increased respectively. We also studied the relevant mechanism of action and found that applying CTS can promote the osteogenic differentiation of PDLSCs and is related to the activation of mitochondrial autophagy. This study provides new insights into the mechanism of increased osteogenic differentiation on the tension side of orthodontic teeth and provides new experimental evidence for the involvement of mitochondrial autophagy in the regulation of osteogenic differentiation.

Effects of Physical Cues on Stem Cell-Derived Extracellular Vesicles toward Neuropathy Applications

The peripheral nervous system undergoes sufficient stress when affected by diabetic conditions, chemotherapeutic drugs, and personal injury. Consequently, peripheral neuropathy arises as the most common complication, leading to debilitating symptoms that significantly alter the quality and way of life. The resulting chronic pain requires a treatment approach that does not simply mask the accompanying symptoms but provides the necessary external environment and neurotrophic factors that will effectively facilitate nerve regeneration. Under normal conditions, the peripheral nervous system self-regenerates very slowly. The rate of progression is further hindered by the development of fibrosis and scar tissue formation, which does not allow sufficient neurite outgrowth to the target site. By incorporating scaffolding supplemented with secretome derived from human mesenchymal stem cells, it is hypothesized that neurotrophic factors and cellular signaling can facilitate the optimal microenvironment for nerve reinnervation. However, conventional methods of secretory vesicle production are low yield, thus requiring improved methods to enhance paracrine secretions. This report highlights the state-of-the-art methods of neuropathy treatment as well as methods to optimize the clinical application of stem cells and derived secretory vesicles for nerve regeneration.

A large-scale production of mesenchymal stem cells and their exosomes for an efficient treatment against lung inflammation

Mesenchymal stem cells (MSCs) and their produced exosomes have demonstrated inherent capabilities of inflammation-guided targeting and inflammatory modulation, inspiring their potential applications as biologic agents for inflammatory treatments. However, the clinical applications of stem cell therapies are currently restricted by several challenges, and one of them is the mass production of stem cells to satisfy the therapeutic demands in the clinical bench. Herein, a production of human amnion-derived MSCs (hMSCs) at a scale of over 1 × 109 cells per batch was reported using a three-dimensional (3D) culture technology based on microcarriers coupled with a spinner bioreactor system. The present study revealed that this large-scale production technology improved the inflammation-guided migration and the inflammatory suppression of hMSCs, without altering their major properties as stem cells. Moreover, these large-scale produced hMSCs showed an efficient treatment against the lipopolysaccharide (LPS)-induced lung inflammation in mice models. Notably, exosomes collected from these large-scale produced hMSCs were observed to inherit the efficient inflammatory suppression capability of hMSCs. The present study showed that 3D culture technology using microcarriers coupled with a spinner bioreactor system can be a promising strategy for the large-scale expansion of hMSCs with improved anti-inflammation capability, as well as their secreted exosomes.

Engineered Extracellular Vesicles in Wound Healing: Design, Paradigms, and Clinical Application

The severe quality of life and economic burden imposed by non-healing skin wounds, infection risks, and treatment costs are affecting millions of patients worldwide. To mitigate these challenges, scientists are relentlessly seeking effective treatment measures. In recent years, extracellular vesicles (EVs) have emerged as a promising cell-free therapy strategy, attracting extensive attention from researchers. EVs mediate intercellular communication, possessing excellent biocompatibility and stability. These features make EVs a potential tool for treating a plethora of diseases, including those related to wound repair. However, there is a growing focus on the engineering of EVs to overcome inherent limitations such as low production, relatively fixed content, and targeting capabilities of natural EVs. This engineering could improve both the effectiveness and specificity of EVs in wound repair treatments. In light of this, the present review will introduce the latest progress in the design methods and experimental paradigms of engineered EVs applied in wound repair. Furthermore, it will comprehensively analyze the current clinical research status and prospects of engineered EVs within this field.

Extracellular vesicle biogenesis of three-dimensional human pluripotent stem cells in a novel Vertical-Wheel bioreactor

Extracellular vesicles (EVs) secreted by human-induced pluripotent stem cells (hiPSCs) have great potential as cell-free therapies in various diseases, including prevention of blood-brain barrier senescence and stroke. However, there are still challenges in pre-clinical and clinical use of hiPSC-EVs due to the need for large-scale production of a large quantity. Vertical-Wheel bioreactors (VWBRs) have design features that allow the biomanufacturing of hiPSC-EVs using a scalable aggregate or microcarrier-based culture system under low shear stress. EV secretion by undifferentiated hiPSCs expanded as 3-D aggregates and on Synthemax II microcarriers in VWBRs were investigated. Additionally, two types of EV collection media, mTeSR and HBM, were compared. The hiPSCs were characterized by metabolite and transcriptome analysis as well as EV biogenesis markers. Protein and microRNA cargo were analysed by proteomics and microRNA-seq, respectively. The in vitro functional assays of microglia stimulation and proliferation were conducted. HiPSCs expanded as 3-D aggregates and on microcarriers had comparable cell number, while microcarrier culture had higher glucose consumption, higher glycolysis and lower autophagy gene expression based on mRNA-seq. The microcarrier cultures had at least 17-23 fold higher EV secretion, and EV collection in mTeSR had 2.7-3.7 fold higher yield than HBM medium. Microcarrier culture with mTeSR EV collection had a smaller EV size than other groups, and the cargo was enriched with proteins (proteomics) and miRNAs (microRNA-seq) reducing apoptosis and promoting cell proliferation (e.g. Wnt-related pathways). hiPSC-EVs demonstrated the ability of stimulating proliferation and M2 polarization of microglia in vitro. HiPSC expansion on microcarriers produces much higher yields of EVs than hiPSC aggregates in VWBRs. EV collection in mTeSR increases yield compared to HBM. The biomanufactured EVs from microcarrier culture in mTeSR have exosomal characteristics and are functional in microglia stimulation, which paves the ways for future in vivo anti-aging study.

Current optimized strategies for stem cell-derived extracellular vesicle/exosomes in cardiac repair

Ischemic heart diseases remain the leading cause of death globally, and stem cell-based therapy has been investigated as a potential approach for cardiac repair. Due to poor survival and engraftment in the cardiac ischemic milieu post transplantation, the predominant therapeutic effects of stem cells act via paracrine actions, by secreting extracellular vesicles (EVs) and/or other factors. Exosomes are nano-sized EVs of endosomal origin, and now viewed as a major contributor in facilitating myocardial repair and regeneration. However, EV/exosome therapy has major obstacles before entering clinical settings, such as limited production yield, unstable biological activity, poor homing efficiency, and low tissue retention. This review aims to provide an overview of the biogenesis and mechanisms of stem cell-derived EV/exosomes in the process of cardiac repair and discuss the current advancements in different optimized strategies to produce high-yield EV/exosomes with higher bioactivity, or engineer them with improved homing efficiency and therapeutic potency. In particular, we outline recent findings toward preclinical and clinical translation of EV/exosome therapy in ischemic heart diseases, and discuss the potential barriers in regard to clinical translation of EV/exosome therapy.

Computer controlled expansion of equine cord blood mesenchymal stromal cells on microcarriers in 3 L vertical-wheel® bioreactors

Mesenchymal stromal cells (MSCs) are an ideal cell source for allogenic cell therapy due to their immunomodulatory and differentiation properties. Equine MSCs (eMSCs) have been found to be a promising treatment for equine joint injuries including meniscal injuries, cartilage degradation, and osteoarthritis. Although the use of eMSCs has shown efficacy in preliminary studies, challenges associated with biomanufacturing remain. To achieve the required cell numbers for clinical application, bioreactor-based processes are required. Initial studies have shown that eMSCs can be cultivated in microcarrier-based, stirred suspension bioreactor culture at the laboratory 0.1 L scale using a Vertical-Wheel® (VW) bioreactor. However, investigations regarding scale up of these processes to the required biomanufacturing scales are required. This study investigated the scale-up of a equine cord blood MSC (eCB-MSC) bioprocess in VW bioreactors at three scales. This included scale-up from the 0.1-0.5 L bioreactor, scale-up from static culture to the 3 L computer-controlled bioreactor, and scale-up into the 3 L computer-controlled bioreactor using a mock clinical trial process. Results from the various scale-up experiments demonstrated similar cell expansion at the various tested scales. The 3 L computer-controlled system resulted in a final cell densities of 1.5 × 105 cells/cm2 on average, achieving 1.5 × 109 harvested cells. Biological testing of the cells showed that cell phenotype and functionality were maintained after scale-up. These findings demonstrate the scalability of an eCB-MSC bioprocess using microcarriers in VW bioreactors to achieve clinically relevant cell numbers, a critical step to translate MSC treatments from research to clinical applications. This study also represents the first known published study expanding any cell type in the 3 L VW bioreactor.

Adipose stromal cells bioproducts as cell-free therapies: manufacturing and therapeutic dose determine in vitro functionality

BACKGROUND

Extracellular vesicles (EV) are considered a cell-free alternative to mesenchymal stromal cell (MSC) therapy. Numerous reports describe the efficacy of EV in conferring immunomodulation and promoting angiogenesis, yet others report these activities to be conveyed in EV-free bioproducts. We hypothesized that this discrepancy may depend either on the method of isolation or rather the relative impact of the individual bioactive components within the MSC secretome.

METHODS

To answer this question, we performed an inter-laboratory study evaluating EV generated from adipose stromal cells (ASC) by either sequential ultracentrifugation (UC) or size-exclusion chromatography (SEC). The effect of both EV preparations on immunomodulation and angiogenesis in vitro was compared to that of the whole secretome and of the EV-free protein fraction after SEC isolation.

RESULTS

In the current study, neither the EV preparations, the secretome or the protein fraction were efficacious in inhibiting mitogen-driven T cell proliferation. However, EV generated by SEC stimulated macrophage phagocytic activity to a similar extent as the secretome. In turn, tube formation and wound healing were strongly promoted by the ASC secretome and protein fraction, but not by EV. Within the secretome/protein fraction, VEGF was identified as a potential driver of angiogenesis, and was absent in both EV preparations.

CONCLUSIONS

Our data indicate that the effects of ASC on immunomodulation and angiogenesis are EV-independent. Specific ASC-EV effects need to be dissected for their use as cell-free therapeutics.

Engineering Extracellular Matrix-Bound Nanovesicles Secreted by Three-Dimensional Human Mesenchymal Stem Cells

Extracellular matrix (ECM) in the human tissue contains vesicles, which are defined as matrix-bound nanovesicles (MBVs). MBVs serve as one of the functional components in ECM, recapitulating part of the regulatory roles and in vivo microenvironment. In this study, extracellular vesicles from culture supernatants (SuEVs) and MBVs are isolated from the conditioned medium or ECM, respectively, of 3D human mesenchymal stem cells. Nanoparticle tracking analysis shows that MBVs are smaller than SuEVs (100-150 nm). Transmission electron microscopy captures the typical cup shape morphology for both SuEVs and MBVs. Western blot reveals that MBVs have low detection of some SuEV markers such as syntenin-1. miRNA analysis of MBVs shows that 3D microenvironment enhances the expression of miRNAs such as miR-19a and miR-21. In vitro functional analysis shows that MBVs can facilitate human pluripotent stem cell-derived forebrain organoid recovery after starvation and promote high passage fibroblast proliferation. In macrophage polarization, 2D MBVs tend to suppress the pro-inflammatory cytokine IL-12β, while 3D MBVs tend to enhance the anti-inflammatory cytokine IL-10. This study has the significance in advancing the understanding of the bio-interface of nanovesicles with human tissue and the design of cell-free therapy for treating neurological disorders such as ischemic stroke.

Emerging Roles of Using Small Extracellular Vesicles as an Anti-Cancer Drug

Small extracellular vesicles (sEVs) are emerging as a novel therapeutic strategy for cancer therapy. Tumor-cell-derived sEVs contain biomolecules that can be utilized for cancer diagnosis. sEVs can directly exert tumor-killing effects or modulate the tumor microenvironment, leading to anti-cancer effects. In this review, the application of sEVs as a diagnostic tool, drug delivery system, and active pharmaceutical ingredient for cancer therapy will be highlighted. The therapeutic efficacies of sEVs will be compared to conventional immune checkpoint inhibitors. Additionally, this review will provide strategies for sEV engineering to enhance the therapeutic efficacies of sEVs. As a bench-to-bedside application, we will discuss approaches to encourage good-manufacturing-practice-compliant industrial-scale manufacturing and purification of sEVs.

Enhanced bioprocess control to advance the manufacture of mesenchymal stromal cell-derived extracellular vesicles in stirred-tank bioreactors

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) act as signaling mediators of cellular responses. However, despite representing a promising alternative to cell-based therapies, clinical translation of EVs is currently limited by their lack of scalability and standardized bioprocessing. Herein, we integrated scalable downstream processing protocols with standardized expansion of large numbers of viable cells in stirred-tank bioreactors to improve EV production. Higher EV yields were linked to EV isolation by tangential flow filtration followed by size exclusion chromatography, rendering 5 times higher number of EVs comparatively to density gradient ultracentrifugation protocols. Additionally, when compared to static culture, EV manufacture in bioreactors resulted in 2.2 higher yields. Highlighting the role of operating under optimal cell culture conditions to maximize the number of EVs secreted per cell, MSCs cultured at lower glucose concentration favored EV secretion. While offline measurements of metabolites concentration can be performed, in this work, Raman spectroscopy was also applied to continuously track glucose levels in stirred-tank bioreactors, contributing to streamline the selection of optimal EV collection timepoints. Importantly, MSC-derived EVs retained their quality attributes and were able to stimulate angiogenesis in vitro, therefore highlighting their promising therapeutic potential.

Inflammatory Response and Exosome Biogenesis of Choroid Plexus Organoids Derived from Human Pluripotent Stem Cells

The choroid plexus (ChP) is a complex structure in the human brain that is responsible for the secretion of cerebrospinal fluid (CSF) and forming the blood-CSF barrier (B-CSF-B). Human-induced pluripotent stem cells (hiPSCs) have shown promising results in the formation of brain organoids in vitro; however, very few studies to date have generated ChP organoids. In particular, no study has assessed the inflammatory response and the extracellular vesicle (EV) biogenesis of hiPSC-derived ChP organoids. In this study, the impacts of Wnt signaling on the inflammatory response and EV biogenesis of ChP organoids derived from hiPSCs was investigated. During days 10-15, bone morphogenetic protein 4 was added along with (+/-) CHIR99021 (CHIR, a small molecule GSK-3β inhibitor that acts as a Wnt agonist). At day 30, the ChP organoids were characterized by immunocytochemistry and flow cytometry for TTR (~72%) and CLIC6 (~20%) expression. Compared to the -CHIR group, the +CHIR group showed an upregulation of 6 out of 10 tested ChP genes, including CLIC6 (2-fold), PLEC (4-fold), PLTP (2-4-fold), DCN (~7-fold), DLK1 (2-4-fold), and AQP1 (1.4-fold), and a downregulation of TTR (0.1-fold), IGFBP7 (0.8-fold), MSX1 (0.4-fold), and LUM (0.2-0.4-fold). When exposed to amyloid beta 42 oligomers, the +CHIR group had a more sensitive response as evidenced by the upregulation of inflammation-related genes such as TNFα, IL-6, and MMP2/9 when compared to the -CHIR group. Developmentally, the EV biogenesis markers of ChP organoids showed an increase over time from day 19 to day 38. This study is significant in that it provides a model of the human B-CSF-B and ChP tissue for the purpose of drug screening and designing drug delivery systems to treat neurological disorders such as Alzheimer's disease and ischemic stroke.

Assessment of anti-inflammatory bioactivity of extracellular vesicles is susceptible to error via media component contamination

Extracellular vesicles (EVs) are widely implicated as novel diagnostic and therapeutic modalities for a wide range of diseases. Thus, optimization of EV biomanufacturing is of high interest. In the course of developing parameters for a human embryonic kidney cells (HEK293T) EV production platform, we examined the combinatorial effects of cell culture conditions (i.e., static versus dynamic) and isolation techniques (i.e., ultracentrifugation versus tangential flow filtration versus size-exclusion chromatography) on functional characteristics of HEK293T EVs, including anti-inflammatory bioactivity using a well-established lipopolysaccharide-stimulated mouse macrophage model. We unexpectedly found that, depending on culture condition and isolation strategy, HEK293T EVs appeared to significantly suppress the secretion of pro-inflammatory cytokines (i.e., interleukin-6, RANTES [regulated upon activation, normal T cell expressed and secreted]) in the stimulated mouse macrophages. Further examination revealed that these results were most likely due to non-EV fetal bovine serum components in HEK293T EV preparations. Thus, future research assessing the anti-inflammatory effects of EVs should be designed to account for this phenomenon.

Multiparametric Biosensors for Characterizing Extracellular Vesicle Subpopulations

Extracellular vesicles (EVs) are an important intercellular communication conduit for cells that have applications in precision therapy and targeted drug delivery. Small EVs, or exosomes, are a 30-150 nm phospholipid-encased subpopulation of EVs that are particularly difficult to characterize due to their small size and because they are difficult to isolate using conventional methods. In this review, we discuss some recent advances in exosome isolation, purification, and sensing platforms using microfluidics, acoustics, and size exclusion chromatography. We discuss some of the challenges and unanswered questions with respect to understanding exosome size heterogeneity and how modern biosensor technology can be applied to exosome isolation. In addition, we discuss how some advancements in sensing platforms such as colorimetric, fluorescent, electronic, surface plasmon resonance (SPR), and Raman spectroscopy may be applied to exosome detection in multiparametric systems. The application of cryogenic electron tomography and microscopy to understanding exosome ultrastructure will become vital as this field progresses. In conclusion, we speculate on some future needs in the exosome research field and how these technologies could be applied.

Immunocyte Derived Exosomes: Insight into the Potential Chemo-immunotherapeutic Nanocarrier Targeting the Tumor Microenvironment

"Cancer" is a dreadful immune-pathological condition that is characterized by anti-inflammatory and tumorigenic responses, elicited by the infiltrating immune cells in the vicinity of an uncontrollably proliferative tumor in the tumor microenvironment (TME). The TME offers a conducive microenvironment that supports cancer cell survival by modulating the host immune defense. Recent advancement in exosomal research has shown exosomes, originating from immune cells as well as the cancer cells, have immense potential for suppressing cancer progression and survival in the TME. Additionally, exosomes, irrespective of their diverse sources, have been reported to be efficient nanocarriers for cancer therapeutics with the ability for targeted delivery due to their biogenic nature, ease of cellular uptake, and scope for functionalization with biomolecules like peptides, aptamers, targeting ligands, etc. Immune cell-derived exosomes per se have been found efficacious against cancer owing to their immune-stimulant properties (in either naive or antigen primed form) even without loading any of cancer therapeutics or targeting ligand conjugation. Nevertheless, exosomes are being primarily explored as nanovesicular carriers for therapeutic molecules with different loading and targeting strategies, and the synergism between immunotherapeutic behavior of exosomes and the anticancer effect of the therapeutic molecules is yet to be explored. Hence, this review focuses specifically on the possible strategies to modulate the immunological nature of the source immune cells to obtain immune stimulant exosomes and bring these into the spotlight as chemo-immunotherapeutic nanovesicles, that can easily target and modulate the TME.

Cancer Exosomes: An Overview and the Applications of Flow

Cancer is one of the most prevalent and disruptive diseases affecting the population, and as such, is the subject of major research efforts. Recently, these efforts have been put towards understanding the role that exosomes can play in the progression of cancer. Exosomes are small extracellular vesicles ranging from 40–150 nm in size that carry bioactive molecules like proteins, DNA, RNA, miRNA, and surface receptors. One of the most important features of exosomes is their ability to easily travel throughout the body, extending the reach of parent cell’s signaling capabilities. Cancer derived exosomes (CDEs) carry dangerous cargo that can aid in the metastasis, and disease progression through angiogenesis, promoting epithelial to mesenchymal transition, and immune suppression. Exosomes can transport these molecules to cells in the tumor environment as well as distant premetastatic locations making them an extremely versatile tool in the toolbelt of cancer. This review aims to compile the present knowledge and understanding of the involvement of exosomes in the progression of cancer as well as current production, isolation, and purification methods, with particular interest on flow perfusion bioreactor and microfluidics systems, which allow for accurate modeling and production of exosomes.

Bioreactor Expansion Reconfigures Metabolism and Extracellular Vesicle Biogenesis of Human Adipose-derived Stem Cells In Vitro

Human mesenchymal stem cells (hMSCs), including human adipose tissue-derived stem cells (hASCs), as well as the secreted extracellular vesicles (EVs), are promising therapeutics in treating inflammatory and neural degenerative diseases. However, prolonged expansion can lead to cellular senescence characterized by a gradual loss of self-renewal ability while altering secretome composition and EV generation. Additionally, hMSCs are highly sensitive to biophysical microenvironment in bioreactor systems utilized in scaling production. In this study, hASCs grown on Plastic Plus or Synthemax II microcarriers in a spinner flask bioreactor (SFB) system were compared to traditional 2D culture. The SFB microenvironment was found to increase the expression of genes associated with hASC stemness, nicotinamide adenine dinucleotide (NAD+) metabolism, glycolysis, and the pentose phosphate pathway as well as alter cytokine secretion (e.g., PGE2 and CXCL10). Elevated reactive oxidative species levels in hASCs of SFB culture were observed without increasing rates of cellular senescence. Expression levels of Sirtuins responsible for preventing cellular senescence through anti-oxidant and DNA repair mechanisms were also elevated in SFB cultures. In particular, the EV biogenesis genes were significantly upregulated (3-10 fold) and the EV production increased 40% per cell in SFB cultures of hASCs. This study provides advanced understanding of hASC sensitivity to the bioreactor microenvironment for EV production and bio-manufacturing towards the applications in treating inflammatory and neural degenerative diseases.

Engineering Human Mesenchymal Bodies in a Novel 3D-Printed Microchannel Bioreactor for Extracellular Vesicle Biogenesis

Human Mesenchymal Stem Cells (hMSCs) and their derived products hold potential in tissue engineering and as therapeutics in a wide range of diseases. hMSCs possess the ability to aggregate into "spheroids", which has been used as a preconditioning technique to enhance their therapeutic potential by upregulating stemness, immunomodulatory capacity, and anti-inflammatory and pro-angiogenic secretome. Few studies have investigated the impact on hMSC aggregate properties stemming from dynamic and static aggregation techniques. hMSCs' main mechanistic mode of action occur through their secretome, including extracellular vesicles (EVs)/exosomes, which contain therapeutically relevant proteins and nucleic acids. In this study, a 3D printed microchannel bioreactor was developed to dynamically form hMSC spheroids and promote hMSC condensation. In particular, the manner in which dynamic microenvironment conditions alter hMSC properties and EV biogenesis in relation to static cultures was assessed. Dynamic aggregation was found to promote autophagy activity, alter metabolism toward glycolysis, and promote exosome/EV production. This study advances our knowledge on a commonly used preconditioning technique that could be beneficial in wound healing, tissue regeneration, and autoimmune disorders.

Exosomal MicroRNAs as Novel Cell-Free Therapeutics in Tissue Engineering and Regenerative Medicine

Extracellular vesicles (EVs) are membrane-bound vesicles (50-1000 nm) that can be secreted by all cell types. Microvesicles and exosomes are the major subsets of EVs that exhibit the cell-cell communications and pathological functions of human tissues, and their therapeutic potentials. To further understand and engineer EVs for cell-free therapy, current developments in EV biogenesis and secretion pathways are discussed to illustrate the remaining gaps in EV biology. Specifically, microRNAs (miRs), as a major EV cargo that exert promising therapeutic results, are discussed in the context of biological origins, sorting and packing, and preclinical applications in disease progression and treatments. Moreover, advanced detection and engineering strategies for exosomal miRs are also reviewed. This article provides sufficient information and knowledge for the future design of EVs with specific miRs or protein cargos in tissue repair and regeneration.

Investigating the consistency of extracellular vesicle production from breast cancer subtypes using CELLine adherent bioreactors

Extracellular vesicle (EV) research has grown rapidly in recent years, largely due to the potential use of EVs as liquid biopsy biomarkers or therapeutics. However, in-depth characterisation and validation of EVs produced using conventional in vitro cultures can be challenging due to the large area of cell monolayers and volumes of culture media required. To overcome this obstacle, multiple bioreactor designs have been tested for EV production with varying success, but the consistency of EVs produced over time in these systems has not been reported previously. In this study, we demonstrate that several breast cancer cell lines of different subtypes can be cultured simultaneously in space, resource, and time efficient manner using CELLine AD 1000 systems, allowing the consistent production of vast amounts of EVs for downstream experimentation. We report an improved workflow used for inoculating, maintaining, and monitoring the bioreactors, their EV production, and the characterisation of the EVs produced. Lastly, our proteomic analyses of the EVs produced throughout the lifetime of the bioreactors show that core EV-associated proteins are relatively consistent, with few minor variations over time, but that tracking the production of EVs is a convenient method to indirectly monitor the bioreactor and consistency of the yielded EVs. These findings will aid future studies requiring the simultaneous production of large amounts of EVs from several cell lines of different subtypes of a disease and other EV biomanufacturing applications.