Pro-Inflammatory Priming of Umbilical Cord Mesenchymal Stromal Cells Alters the Protein Cargo of Their Extracellular Vesicles

Mesenchymal stromal cell derived extracellular vesicles as a therapeutic tool: immune regulation, MSC priming, and applications to SLE

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by a dysfunction of the immune system. Mesenchymal stromal cell (MSCs) derived extracellular vesicles (EVs) are nanometer-sized particles carrying a diverse range of bioactive molecules, such as proteins, miRNAs, and lipids. Despite the methodological disparities, recent works on MSC-EVs have highlighted their broad immunosuppressive effect, thus driving forwards the potential of MSC-EVs in the treatment of chronic diseases. Nonetheless, their mechanism of action is still unclear, and better understanding is needed for clinical application. Therefore, we describe in this review the diverse range of bioactive molecules mediating their immunomodulatory effect, the techniques and possibilities for enhancing their immune activity, and finally the potential application to SLE.

ST2-Conditioned Medium Fosters Dorsal Horn Cell Excitability and Synaptic Transmission in Cultured Mouse Spinal Cord

Conditioned medium obtained from bone marrow-derived stem cells has been proposed as a novel cell-free therapy in spinal cord injury and neuropathic pain, yet the direct effect on spinal neuron function has never been investigated. Here, we adopted spinal cord organotypic cultures (SCOCs) as an experimental model to probe the effect of ST2 murine mesenchymal stem cells-conditioned medium (ST2-CM) on dorsal horn (DH) neuron functional properties. Three days of SCOC exposure to ST2-CM increased neuronal activity measured by Fos expression, as well as spontaneous or induced firing. We showed that the increase in neuronal excitability was associated with changes in both intrinsic membrane properties and an enhanced excitatory drive. The increased excitability at the single-cell level was substantiated at the network level by detecting synchronous bursts of calcium waves across DH neurons. Altogether, SCOCs represent a viable tool to probe mesenchymal cells' effect on intact neuronal networks. Our findings indicate that ST2-CM enhances neuronal activity and synaptic wiring in the spinal dorsal horn. Our data also support the trophic role of mesenchymal cells CM in maintaining network activity in spinal circuits.

Extracellular vesicles derived from umbilical cord mesenchymal stromal cells show enhanced anti-inflammatory properties via upregulation of miRNAs after pro-inflammatory priming

Autoimmune conditions, such as rheumatoid arthritis, are characterised by a loss of immune tolerance, whereby the immune cells attack self-antigens causing pain and inflammation. These conditions can be brought into remission using pharmaceutical treatments, but often have adverse side effects and some patients do not respond favourably to them. Human umbilical cord mesenchymal stromal cells (UCMSCs) present a promising alternative therapeutic due to their innate anti-inflammatory properties which can be strengthened using pro-inflammatory conditions. Their therapeutic mechanism of action has been attributed to paracrine signalling, by which nanosized acellular particles called 'extracellular vesicles' (EVs) are one of the essential components. Therefore, this research analysed the anti-inflammatory properties of UCMSC-EVs 'primed' with pro-inflammatory cytokines and at baseline with no inflammatory cytokines (control). Both control and primed EVs were co-cultured with un-pooled peripheral blood mononuclear cells (PBMCs; n = 6) from healthy donors. Neither control nor primed EVs exerted a pro-inflammatory effect on PBMCs. Instead, the primed EVs showed the immunosuppressive potential by increasing the expression of the anti-inflammatory protein FoxP3 in PBMCs. This may be attributed to the upregulated miRNAs identified in primed EVs in comparison to control EVs (miR-139-5p, miR-140-5p, miR-214-5p). These findings aid in understanding how UCMSC-EVs mediate immunosuppression and support their potential use in treating autoimmune conditions.

Optimized operation of a controlled stirred tank reactor system for the production of mesenchymal stromal cells and their extracellular vesicles

The therapeutic effects of human mesenchymal stromal cells (MSC) have been attributed mostly to their paracrine activity, exerted through small-secreted extracellular vesicles (EVs) rather than their engraftment into injured tissues. Currently, the production of MSC-derived EVs (MSC-EVs) is performed in laborious static culture systems with limited manufacturing capacity using serum-containing media. In this work, a serum-/xenogeneic-free microcarrier-based culture system was successfully established for bone marrow-derived MSC cultivation and MSC-EV production using a 2  l-scale controlled stirred tank reactor (STR) operated under fed-batch (FB) or fed-batch combined with continuous perfusion (FB/CP). Overall, maximal cell numbers of (3.0 ± 0.12) × 108 and (5.3 ± 0.32) × 108 were attained at Days 8 and 12 for FB and FB/CP cultures, respectively, and MSC(M) expanded under both conditions retained their immunophenotype. MSC-EVs were identified in the conditioned medium collected from all STR cultures by transmission electron microscopy, and EV protein markers were successfully identified by Western blot analysis. Overall, no significant differences were observed between EVs isolated from MSC expanded in STR operated under the two feeding approaches. EV mean sizes of 163 ± 5.27 nm and 162 ± 4.44 nm (p > 0.05) and concentrations of (2.4 ± 0.35) × 1011  EVs/mL and (3.0 ± 0.48) × 1011  EVs/mL (p > 0.05) were estimated by nanoparticle tracking analysis for FB and FB/CP cultures, respectively. The STR-based platform optimized herein represents a major contribution toward the development of human MSC- and MSC-EV-based products as promising therapeutic agents for Regenerative Medicine settings.

Menstrual blood-derived mesenchymal stromal cells: impact of preconditioning on the cargo of extracellular vesicles as potential therapeutics

BACKGROUND

Mesenchymal stromal cells (MSCs) have been shown to exert their therapeutic effects through the secretion of broad spectrum of paracrine factors, including extracellular vesicles (EVs). Accordingly, EVs are being pursued as a promising alternative to cell-based therapies. Menstrual blood-derived stromal cells (MenSCs) are a type of MSC that, due to their immunomodulatory and regenerative properties, have emerged as an innovative source. Additionally, new strategies of cell priming may potentially alter the concentration and cargo of released EVs, leading to modification of their biological properties. In this study, we aimed to characterize the EVs released by MenSCs and compare their therapeutic potential under three different preconditioning conditions (proinflammatory stimuli, physioxia, and acute hypoxia).

METHODS

MenSCs were isolated from five healthy women. Following culturing to 80% confluence, MenSCs were exposed to different priming conditions: basal (21% O₂), proinflammatory stimuli (IFNγ and TNFα, 21% O₂), physioxia (1-2% O₂), and acute hypoxia (< 1% O₂) for 48-72 h. Conditioned media from MenSCs was collected after 48 h and EVs were isolated by a combination of ultra-filtration and differential centrifugation. An extensive characterization ranging from nano-flow cytometry (nFC) to quantitative high-throughput shotgun proteomics was performed. Bioinformatics analyses were used to derive hypotheses on their biological properties.

RESULTS

No differences in the morphology, size, or number of EVs released were detected between priming conditions. The proteome analysis associated with basal MenSC-EVs prominently revealed their immunomodulatory and regenerative capabilities. Furthermore, quantitative proteomic analysis of differentially produced MenSC-EVs provided sufficient evidence for the utility of the differential preconditioning in purpose-tailoring EVs for their therapeutic application: proinflammatory priming enhanced the anti-inflammatory, regenerative and immunomodulatory capacity in the innate response of EVs, physioxia priming also improves tissue regeneration, angiogenesis and their immunomodulatory capacity targeting on the adaptive response, while acute hypoxia priming, increased hemostasis and apoptotic processes regulation in MenSC-EVs, also by stimulating immunomodulation mainly through the adaptive response.

CONCLUSIONS

Priming of MenSCs under proinflammatory and hypoxic conditions affected the cargo proteome of EVs released, resulting in different therapeutic potential, and thus warrants experimental exploration with the aim to generate better-defined MSC-derived bioproducts.

Injectable Supramolecular Hybrid Hydrogel Delivers IL-1β-Stimulated Exosomes to Target Neuroinflammation

Long-term neuroinflammation is a major barrier to neurological recovery after cerebral ischemia-reperfusion injury (CIRI). Here, a thermosensitive injectable supramolecular hybrid hydrogel is developed to sustainably deliver exosomes derived from interleukin-1β-stimulated bone marrow stromal cells (BMSCs) (βExos) with improved exosome production and anti-inflammatory capacity for neuroinflammation inhibition and neurological recovery. The supramolecular hydrogel displays self-healing and injectable features, along with high biocompatibility and tissue-like softness. The βExos effectively reduce the lipopolysaccharide-induced inflammatory responses in the immortalized mouse microglia (BV2) cell line, and the in situ formed hydrogel improves the exosome retention in the ischemic core area. More remarkably, in the middle cerebral artery occlusion in vivo model, glial scar formation and neuronal loss are significantly reduced by regulating neuroinflammation using the released βExos. Therefore, the combination of interleukin-1β-stimulated exosomes with injectable supramolecular hydrogel provides an appealing strategy for treating central nervous system diseases.

Strategies of Macrophages to Maintain Bone Homeostasis and Promote Bone Repair: A Narrative Review

Bone homeostasis (a healthy bone mass) is regulated by maintaining a delicate balance between bone resorption and bone formation. The regulation of physiological bone remodeling by a complex system that involves multiple cells in the skeleton is closely related to bone homeostasis. Loss of bone mass or repair of bone is always accompanied by changes in bone homeostasis. However, due to the complexity of bone homeostasis, we are currently unable to identify all the mechanisms that affect bone homeostasis. To date, bone macrophages have been considered a third cellular component in addition to osteogenic spectrum cells and osteoclasts. As confirmed by co-culture models or in vivo experiments, polarized or unpolarized macrophages interact with multiple components within the bone to ensure bone homeostasis. Different macrophage phenotypes are prone to resorption and formation of bone differently. This review comprehensively summarizes the mechanisms by which macrophages regulate bone homeostasis and concludes that macrophages can control bone homeostasis from osteoclasts, mesenchymal cells, osteoblasts, osteocytes, and the blood/vasculature system. The elaboration of these mechanisms in this narrative review facilitates the development of macrophage-based strategies for the treatment of bone metabolic diseases and bone defects.

Heterogeneity of mesenchymal stem cell-derived extracellular vesicles is highly impacted by the tissue/cell source and culture conditions

Extracellular vesicles (EVs) are cell-derived membrane structures exerting major effects in physiological as well as pathological processes by functioning as vehicles for the delivery of biomolecules to their target cells. An increasing number of effects previously attributed to cell-based therapies have been recognized to be actually mediated by EVs derived from the respective cells, suggesting the administration of purified EVs instead of living cells for cell-based therapies. In this review, we focus on the heterogeneity of EVs derived from mesenchymal stem/stromal cells (MSC) and summarize upstream process parameters that crucially affect the resulting therapeutic properties and biological functions. Hereby, we discuss the effects of the cell source, medium composition, 3D culture, bioreactor culture and hypoxia. Furthermore, aspects of the isolation and storage strategies influences EVs are described. Conclusively, optimization of upstream process parameters should focus on controlling MSC-derived EV heterogeneity for specific therapeutic applications.

Graphical Abstract

Cytokine-primed umbilical cord mesenchymal stem cells enhanced therapeutic effects of extracellular vesicles on osteoarthritic chondrocytes

In recent years, extracellular vesicles (EVs) secreted by mesenchymal stem cells (MSCs) have emerged as a potential cell-free therapy against osteoarthritis (OA). Thus, we investigated the therapeutic effects of EVs released by cytokine-primed umbilical cord-derived MSCs (UCMSCs) on osteoarthritic chondrocyte physiology. Priming UCMSCs individually with transforming growth factor beta (TGFβ), interferon alpha (IFNα), or tumor necrosis factor alpha (TNFα) significantly reduced the sorting of miR-181b-3p but not miR-320a-3p; two negative regulators of chondrocyte regeneration, into EVs. However, the EV treatment did not show any significant effect on chondrocyte proliferation. Meanwhile, EVs from both non-priming and cytokine-primed UCMSCs induced migration at later time points of measurement. Moreover, TGFβ-primed UCMSCs secreted EVs that could upregulate the expression of chondrogenesis markers (COL2 and ACAN) and downregulate fibrotic markers (COL1 and RUNX2) in chondrocytes. Hence, priming UCMSCs with cytokines can deliver selective therapeutic effects of EV treatment in OA and chondrocyte-related disorders.

Mesenchymal stromal cells as a tool to unravel the developmental origins of disease

The intrauterine environment can induce alterations of the epigenome that have a lasting impact on disease risk. Current human studies in the field focus on a single epigenetic mark, DNA methylation, measured in blood. For in-depth mechanistic insight into the developmental origins of disease, it will be crucial to consider innovative tissue types. Mesenchymal stromal cells (MSCs) may serve as a novel tool to investigate the full epigenome beyond DNA methylation, to explore other omics levels, and to perform functional assays. Moreover, MSCs can be differentiated into multiple cell types and thereby mimic otherwise inaccessible cell types. A first wave of studies supports the potential of MSCs and illustrates how the innovative use of this cell type may be incorporated in birth cohorts.

Mesenchymal Stem Cell-Derived Secretome: A Potential Therapeutic Option for Autoimmune and Immune-Mediated Inflammatory Diseases

Immune-mediated inflammatory diseases (IMIDs) encompass several entities such as "classic" autoimmune disorders or immune-mediated diseases with autoinflammatory characteristics. Adult stem cells including mesenchymal stem cells (MSCs) are by far the most commonly used type in clinical practice. However, due to the possible side effects of MSC-based treatments, there is an increase in interest in the MSC-secretome (containing large extracellular vesicles, microvesicles, and exosomes) as an alternative therapeutic option in IMIDs. A wide spectrum of MSC-secretome-related biological activities has been proven thus far including anti-inflammatory, anti-apoptotic, and immunomodulatory properties. In comparison with MSCs, the secretome is less immunogenic but exerts similar biological actions, so it can be considered as an ideal cell-free therapeutic alternative. Additionally, since the composition of the MSC-secretome can be engineered, for a future perspective, it could also be viewed as part of a potential delivery system within nanomedicine, allowing us to specifically target dysfunctional cells or tissues. Although many encouraging results from pre-clinical studies have recently been obtained that strongly support the application of the MSC-secretome in IMIDs, human studies with MSC-secretome administration are still in their infancy. This article reviews the immunomodulatory effects of the MSC-secretome in IMIDs and provides insight into the interpretation of its beneficial biological actions.

Therapeutic Effects of Hypoxic and Pro-Inflammatory Priming of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Inflammatory Arthritis

Mesenchymal stem cells (MSCs) immunomodulate inflammatory responses through paracrine signalling, including via secretion of extracellular vesicles (EVs) in the cell secretome. We evaluated the therapeutic potential of MSCs-derived small EVs in an antigen-induced model of arthritis (AIA). EVs isolated from MSCs cultured normoxically (21% O₂, 5% CO₂), hypoxically (2% O₂, 5% CO₂) or with a pro-inflammatory cytokine cocktail were applied into the AIA model. Disease pathology was assessed post-arthritis induction through swelling and histopathological analysis of synovial joint structure. Activated CD4+ T cells from healthy mice were cultured with EVs or MSCs to assess deactivation capabilities prior to application of standard EVs in vivo to assess T cell polarisation within the immune response to AIA. All EVs treatments reduced knee-joint swelling whilst only normoxic and pro-inflammatory primed EVs improved histopathological outcomes. In vitro culture with EVs did not achieve T cell deactivation. Polarisation towards CD4+ helper cells expressing IL17a (Th17) was reduced when normoxic and hypoxic EV treatments were applied in vitro. Normoxic EVs applied into the AIA model reduced Th17 polarisation and improved Regulatory T cell (Treg):Th17 homeostatic balance. Normoxic EVs present the optimal strategy for broad therapeutic benefit. EVs present an effective novel technology with the potential for cell-free therapeutic translation.

Mesenchymal Stromal Cell Secretome for the Treatment of Immune-Mediated Inflammatory Diseases: Latest Trends in Isolation, Content Optimization and Delivery Avenues

Considering the high prevalence and the complex pharmacological management of immune-mediated inflammatory diseases (IMIDs), the search for new therapeutic approaches for their treatment is vital. Although the immunomodulatory and anti-inflammatory effects of mesenchymal stromal cells (MSCs) have been extensively studied as a potential therapy in this field, direct MSC implantation presents some limitations that could slow down the clinical translation. Since the beneficial effects of MSCs have been mainly attributed to their ability to secrete a plethora of bioactive factors, their secretome has been proposed as a new and promising pathway for the treatment of IMIDs. Formed from soluble factors and extracellular vesicles (EVs), the MSC-derived secretome has been proven to elicit immunomodulatory effects that control the inflammatory processes that occur in IMIDs. This article aims to review the available knowledge on the MSC secretome, evaluating the advances in this field in terms of its composition, production and application, as well as analyzing the pending challenges in the field. Moreover, the latest research involving secretome administration in IMIDs is discussed to provide an updated state-of-the-art for this field. Finally, novel secretome delivery alternatives are reviewed, paying special attention to hydrogel encapsulation as one of the most convenient and promising strategies.

Synthesized nanoparticles, biomimetic nanoparticles and extracellular vesicles for treatment of autoimmune disease: Comparison and prospect

An emerging strategy is needed to treat autoimmune diseases, many of which are chronic with no definitive cure. Current treatments only alleviate symptoms and have many side effects affecting patient quality of life. Recently, nanoparticle drug delivery systems, an emerging method in medicine, has been used to target cells or organs, without damaging normal tissue. This approach has led to fewer side effects, along with a strong immunosuppressive capacity. Therefore, a nanotechnology approach may help to improve the treatment of autoimmune diseases. In this review, we separated nanoparticles into three categories: synthesized nanoparticles, biomimetic nanoparticles, and extracellular vesicles. This review firstly compares the typical mechanism of action of these three nanoparticle categories respectively in terms of active targeting, camouflage effect, and similarity to parent cells. Then their immunomodulation properties are discussed. Finally, the challenges faced by all these nanoparticles are described.

Urinary Extracellular Vesicles: Uncovering the Basis of the Pathological Processes in Kidney-Related Diseases

Intercellular communication governs multicellular interactions in complex organisms. A variety of mechanisms exist through which cells can communicate, e.g., cell-cell contact, the release of paracrine/autocrine soluble molecules, or the transfer of extracellular vesicles (EVs). EVs are membrane-surrounded structures released by almost all cell types, acting both nearby and distant from their tissue/organ of origin. In the kidney, EVs are potent intercellular messengers released by all urinary system cells and are involved in cell crosstalk, contributing to physiology and pathogenesis. Moreover, urine is a reservoir of EVs coming from the circulation after crossing the glomerular filtration barrier—or originating in the kidney. Thus, urine represents an alternative source for biomarkers in kidney-related diseases, potentially replacing standard diagnostic techniques, including kidney biopsy. This review will present an overview of EV biogenesis and classification and the leading procedures for isolating EVs from body fluids. Furthermore, their role in intra-nephron communication and their use as a diagnostic tool for precision medicine in kidney-related disorders will be discussed.

Extracellular Vesicles and Hematopoietic Stem Cell Aging

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