Mesenchymal stromal cell-derived extracellular vesicles modulate microglia/macrophage polarization and protect the brain against hypoxia-ischemic injury in neonatal mice by targeting delivery of miR-21a-5p

Microglia Morphological Response to Mesenchymal Stromal Cell Extracellular Vesicles Demonstrates EV Therapeutic Potential for Modulating Neuroinflammation

Background

Mesenchymal stromal cell derived extracellular vesicles (MSC-EVs) are a promising therapeutic for neuroinflammation. MSC-EVs can interact with microglia, the resident immune cells of the brain, to exert their immunomodulatory effects. In response to inflammatory cues, such as cytokines, microglia undergo phenotypic changes indicative of their function e.g. morphology and secretion. However, these changes in response to MSC-EVs are not well understood. Additionally, no disease-relevant screening tools to assess MSC-EV bioactivity exist, which has further impeded clinical translation. Here, we developed a quantitative, high throughput morphological profiling approach to assess the response of microglia to neuroinflammation-relevant signals and whether this morphological response can be used to indicate the bioactivity of MSC-EVs.

Results

Using an immortalized human microglia cell-line, we observed increased size (perimeter, major axis length) and complexity (form factor) upon stimulation with interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α). Upon treatment with MSC-EVs, the overall morphological score (determined using principal component analysis) shifted towards the unstimulated morphology, indicating that MSC-EVs are bioactive and modulate microglia. The morphological effects of MSC-EVs in TNF-γ/IFN-α stimulated cells were concomitant with reduced secretion of 14 chemokines/cytokines (e.g. CXCL6, CXCL9) and increased secretion of 12 chemokines/cytokines (e.g. CXCL8, CXCL10). Proteomic analysis of cell lysates revealed significant increases in 192 proteins (e.g. HIBADH, MEAK7, LAMC1) and decreases in 257 proteins (e.g. PTEN, TOM1, MFF) with MSC-EV treatment. Of note, many of these proteins are involved in regulation of cell morphology and migration. Gene Set Variation Analysis revealed upregulation of pathways associated with immune response, such as regulation of cytokine production, immune cell infiltration (e.g. T cells, NK cells) and morphological changes (e.g. Semaphorin, RHO/Rac signaling). Additionally, changes in microglia mitochondrial morphology were measured suggesting that MSC-EV modulate mitochondrial metabolism.

Conclusion

This study comprehensively demonstrates the effects of MSC-EVs on human microglial morphology, cytokine secretion, cellular proteome, and mitochondrial content. Our high-throughput, rapid, low-cost morphological approach enables screening of MSC-EV batches and manufacturing conditions to enhance EV function and mitigate EV functional heterogeneity in a disease relevant manner. This approach is highly generalizable and can be further adapted and refined based on selection of the disease-relevant signal, target cell, and therapeutic product.

All but Small: miRNAs from Wharton's Jelly-Mesenchymal Stromal Cell Small Extracellular Vesicles Rescue Premature White Matter Injury after Intranasal Administration

White matter injury (WMI) is a common neurological issue in premature-born neonates, often causing long-term disabilities. We recently demonstrated a key beneficial role of Wharton's jelly mesenchymal stromal cell-derived small extracellular vesicles (WJ-MSC-sEVs) microRNAs (miRNAs) in WMI-related processes in vitro. Here, we studied the functions of WJ-MSC-sEV miRNAs in vivo using a preclinical rat model of premature WMI. Premature WMI was induced in rat pups through inflammation and hypoxia-ischemia. Small EVs were purified from the culture supernatant of human WJ-MSCs. The capacity of WJ-MSC-sEV-derived miRNAs to decrease microglia activation and promote oligodendrocyte maturation was evaluated by knocking down (k.d) DROSHA in WJ-MSCs, releasing sEVs containing significantly less mature miRNAs. Wharton's jelly MSC-sEVs intranasally administrated 24 h upon injury reached the brain within 1 h, remained detectable for at least 24 h, significantly reduced microglial activation, and promoted oligodendrocyte maturation. The DROSHA k.d in WJ-MSCs lowered the therapeutic capabilities of sEVs in experimental premature WMI. Our results strongly indicate the relevance of miRNAs in the therapeutic abilities of WJ-MSC-sEVs in premature WMI in vivo, opening the path to clinical application.

BMSCs-derived exosomes inhibit macrophage/microglia pyroptosis by increasing autophagy through the miR-21a-5p/PELI1 axis in spinal cord injury

Spinal cord injury (SCI) results in a diverse range of disabilities and lacks effective treatment options. In recent years, exosomes derived from bone mesenchymal stem cells (BMSCs) have emerged as a promising cell-free therapeutic approach for treating ischemic brain injury and other inflammatory conditions. Macrophage/microglial pyroptosis has been identified as a contributing factor to neuroinflammation following SCI. The therapeutic potential of BMSC-derived exosomes in macrophage/microglia pyroptosis-induced neuroinflammation, however, has to be determined. Our findings demonstrate that exosomes derived from BMSCs can enhance motor function recovery and mitigate neuroinflammation subsequent to SCI by upregulating the expression of autophagy-related proteins and inhibiting the activation of NLRP3 inflammasomes in macrophage/microglia. Moreover, miR-21a-5p is markedly increased in BMSCs-derived exosomes, and knocking down miR-21a-5p in BMSCs-derived exosomes eliminates the beneficial effects of administration; upregulation of miR-21a-5p in BMSCs-derived exosomes enhances the beneficial effects of administration. Mechanistically, miR-21a-5p positively regulates the autophagy of macrophage/microglia by reducing PELI1 expression, which in turn inhibits their pyroptosis. This research provides novel evidence that exosomes derived from BMSCs can effectively suppress macrophage/microglia pyroptosis through the miR-21a-5p/PELI1 axis-mediated autophagy pathway, ultimately facilitating functional restoration following SCI. In particular, our constructed miR-21a-5p overexpression exosomes greatly improved the efficacy of BMSCs-derived exosomes in treating spinal cord injury. These results establish a foundation for the prospective utilization of exosomes derived from BMSCs as a novel biological intervention for spinal cord injury.

Microglia-derived extracellular vesicles in homeostasis and demyelination/remyelination processes

Microglia (MG) play a crucial role as the predominant myeloid cells in the central nervous system and are commonly activated in multiple sclerosis. They perform essential functions under normal conditions, such as actively surveying the surrounding parenchyma, facilitating synaptic remodeling, engulfing dead cells and debris, and protecting the brain against infectious pathogens and harmful self-proteins. Extracellular vesicles (EVs) are diverse structures enclosed by a lipid bilayer that originate from intracellular endocytic trafficking or the plasma membrane. They are released by cells into the extracellular space and can be found in various bodily fluids. EVs have recently emerged as a communication mechanism between cells, enabling the transfer of functional proteins, lipids, different RNA species, and even fragments of DNA from donor cells. MG act as both source and recipient of EVs. Consequently, MG-derived EVs are involved in regulating synapse development and maintaining homeostasis. These EVs also directly influence astrocytes, significantly increasing the release of inflammatory cytokines like IL-1β, IL-6, and TNF-α, resulting in a robust inflammatory response. Furthermore, EVs derived from inflammatory MG have been found to inhibit remyelination, whereas Evs produced by pro-regenerative MG effectively promote myelin repair. This review aims to provide an overview of the current understanding of MG-derived Evs, their impact on neighboring cells, and the cellular microenvironment in normal conditions and pathological states, specifically focusing on demyelination and remyelination processes.

Mitochondria-targeted cerium vanadate nanozyme suppressed hypoxia-ischemia injury in neonatal mice via intranasal administration

Oxidative stress is a major obstacle for neurological functional recovery after hypoxia-ischemia (HI) brain damage. Nanozymes with robust anti-oxidative stress properties offer a therapeutic option for HI injury. However, insufficiency of nanozyme accumulation in the HI brain by noninvasive administration hinders their application. Herein, we reported a cerium vanadate (CeVO4) nanozyme to realize a noninvasive therapy for HI brain in neonatal mice by targeting brain neuron mitochondria. CeVO4 nanozyme with superoxide dismutase activity mainly co-located with neuronal mitochondria 1 h after administration. Pre- and post-HI administrations of CeVO4 nanozyme were able to attenuate acute brain injury, by inhibiting caspase-3 activation, microglia activation, and proinflammation cytokine production in the lesioned cortex 2 d after HI injury. Moreover, CeVO4 nanozyme administration led to short- and long-term functional recovery following HI insult without any potential toxicities in peripheral organs of mice even after prolonged delivery for 4 weeks. These beneficial effects of CeVO4 nanozyme were associated with suppressed oxidative stress and up-regulated nuclear factor erythroid-2-related factor 2 (Nrf2) expression. Finally, we found that Nrf2 inhibition with ML385 abolished the protective effects of CeVO4 nanozyme on HI injury. Collectively, this strategy may provide an applicative perspective for CeVO4 nanozyme therapy in HI brain damage via noninvasive delivery.

Pulsed ultrasound promotes secretion of anti-inflammatory extracellular vesicles from skeletal myotubes via elevation of intracellular calcium level

The regulation of inflammatory responses is an important intervention in biological function and macrophages play an essential role during inflammation. Skeletal muscle is the largest organ in the human body and releases various factors which mediate anti-inflammatory/immune modulatory effects. Recently, the roles of extracellular vesicles (EVs) from a large variety of cells are reported. In particular, EVs released from skeletal muscle are attracting attention due to their therapeutic effects on dysfunctional organs and tissues. Also, ultrasound (US) promotes release of EVs from skeletal muscle. In this study, we investigated the output parameters and mechanisms of US-induced EV release enhancement and the potential of US-treated skeletal muscle-derived EVs in the regulation of inflammatory responses in macrophages. High-intensity US (3.0 W/cm2) irradiation increased EV secretion from C2C12 murine muscle cells via elevating intracellular Ca2+ level without negative effects. Moreover, US-induced EVs suppressed expression levels of pro-inflammatory factors in macrophages. miRNA sequencing analysis revealed that miR-206-3p and miR-378a-3p were especially abundant in skeletal myotube-derived EVs. In this study we demonstrated that high-intensity US promotes the release of anti-inflammatory EVs from skeletal myotubes and exert anti-inflammatory effects on macrophages.

Therapeutic role of mesenchymal stem cell-derived extracellular vesicles in neuroinflammation and cognitive dysfunctions induced by binge-like ethanol treatment in adolescent mice

BACKGROUND

Extracellular vesicles (EVs) are heterogeneous membrane vesicles secreted by cells in extracellular spaces that play an important role in intercellular communication under both normal and pathological conditions. Mesenchymal stem cells (MSC) are anti-inflammatory and immunoregulatory cells capable of secreting EVs, which are considered promising molecules for treating immune, inflammatory, and degenerative diseases. Our previous studies demonstrate that, by activating innate immune receptors TLR4 (Toll-like receptor 4), binge-like ethanol exposure in adolescence causes neuroinflammation and neural damage.

AIMS

To evaluate whether the intravenous administration of MSC-derived EVs is capable of reducing neuroinflammation, myelin and synaptic alterations, and the cognitive dysfunction induced by binge-like ethanol treatment in adolescent mice.

MATERIALS & METHODS

MSC-derived EVs obtained from adipose tissue were administered in the tail vein (50 microg/dose, one weekly dose) to female WT adolescent mice treated intermittently with ethanol (3.0 g/kg) during two weeks.

RESULTS

MSC-derived EVs from adipose tissue ameliorate ethanol-induced up-regulation of inflammatory genes (e.g., COX-2, iNOS, MIP-1α, NF-κB, CX3CL1, and MCP-1) in the prefrontal cortex of adolescent mice. Notably, MSC-derived EVs also restore the myelin and synaptic derangements, and the memory and learning impairments, induced by ethanol treatment. Using cortical astroglial cells in culture, our results further confirm that MSC-derived EVs decrease inflammatory genes in ethanol-treated astroglial cells. This, in turn, confirms in vivo findings.

CONCLUSION

Taken together, these results provide the first evidence for the therapeutic potential of the MSC-derived EVs in the neuroimmune response and cognitive dysfunction induced by binge alcohol drinking in adolescence.

Mesenchymal stem cell-derived exosomes: Shaping the next era of stroke treatment

Exosome-based treatments are gaining traction as a viable approach to addressing the various issues faced by an ischemic stroke. These extracellular vesicles, mainly produced by Mesenchymal Stem Cells (MSCs), exhibit many properties with substantial therapeutic potential. Exosomes are particularly appealing for stroke therapy because of their low immunogenicity, effective cargo transport, and ability to cross the blood-brain barrier. Their diverse effects include neuroprotection, angiogenesis stimulation, inflammatory response modulation, and cell death pathway attenuation, synergistically promoting neuronal survival, tissue regeneration, and functional recovery. Exosomes also show potential as diagnostic indicators for early stroke identification and customized treatment options. Despite these promising qualities, current exosome-based therapeutics have some limitations. The heterogeneity of exosome release among cell types, difficulty in standardization and isolation techniques, and complications linked to dosage and targeted administration necessitates extensive investigation. It is critical to thoroughly understand exosomal processes and their complicated interactions within the cellular milieu. To improve the practicality and efficacy of exosome-based medicines, research efforts must focus on improving production processes, developing robust evaluation criteria, and developing large-scale isolation techniques. Altogether, exosomes' multifunctional properties offer a new route for transforming stroke treatment and significantly improving patient outcomes.

Small extracellular vesicles administered directly in the brain promote neuroprotection and decreased microglia reactivity in a stroke mouse model

Herein, we investigate the bioactivity of small extracellular vesicles (sEVs), focusing on their local effect in the brain. sEVs from mononuclear cells (MNCs) showed superior effects in vitro to sEVs from mesenchymal stem cells (MSCs) and were able to promote neuroprotection and decrease microglia reactivity in a stroke mouse model.

Anti-inflammatory effects of antenatal administration of stem cell derived extracellular vesicles in the brain of rat fetuses with congenital diaphragmatic hernia

PURPOSE

Congenital diaphragmatic hernia (CDH) survivors may experience neurodevelopmental impairment, whose etiology remains elusive. Preclinical evidence indicates that amniotic fluid stem cell extracellular vesicle (AFSC-EV) administration promotes lung development but their effects on other organs are unknown. Herein, we investigated the brain of rat fetuses with CDH for signs of inflammation and response to AFSC-EVs.

METHODS

CDH was induced by maternal nitrofen administration at E9.5. At E18.5, fetuses were injected intra-amniotically with saline or AFSC-EVs (isolated by ultracentrifugation, characterized as per MISEV guidelines). Fetuses from vehicle-gavaged dams served as controls. Groups were compared for: lung hypoplasia, TNFa and IL-1B brain expression, and activated microglia (Iba1) density in the subgranular zone (SGZ).

RESULTS

CDH lungs had fewer airspaces compared to controls, whereas AFSC-EV-treated lungs had rescued branching morphogenesis. Fluorescently labeled AFSC-EVs injected intra-amniotically into CDH fetuses had fluorescent signal in the brain. Compared to controls, the brain of CDH fetuses had higher TNFa and IL-1B levels, and increased activated microglia density. Conversely, the brain of AFSC-EV treated fetuses had inflammatory marker expression levels and microglia density similar to controls.

CONCLUSION

This study shows that the brain of rat fetuses with CDH has signs of inflammation that are abated by the intra-amniotic administration of AFSC-EVs.

Exosomes derived from mesenchymal stem cells primed with disease-condition-serum improved therapeutic efficacy in a mouse rheumatoid arthritis model via enhanced TGF-β1 production

BACKGROUNDS

Rheumatoid arthritis (RA) is a chronic and systemic autoimmune disease characterized by synovial inflammation-mediated progressive destruction of the cartilage and bone, resulting in reduced quality of life. We primed human telomerase reverse transcriptase-overexpressing immortalized human adipose tissue-derived mesenchymal stem cells (iMSCs) with serum derived from a non-human primate RA model and studied the immunomodulatory ability of exosomes obtained from primed iMSCs.

METHODS

After immunophenotyping, nanoparticle tracking analysis, and in vitro functional tests, Dulbecco's phosphate-buffered saline (dPBS, Group C), exosomes derived from the supernatant of iMSCs (Exo-FBS, Group E), exosomes derived from the supernatant of iMSCs primed with RA serum (Exo-RA, Group F), and methotrexate (Group M) were administered in collagen-induced arthritis (CIA) model mice. dPBS was administered to the normal (N) group for comparison (n = 10/group).

RESULTS

Exo-RA had a significantly higher number of exosomes compared to Exo-FBS when measured with nanoparticle tracking analysis or exosome marker CD81, and Transforming growth factor-β1 amounts were significantly higher in Exo-RA than in Exo-FBS. When Exo-FBS or Exo-RA was administered to the collagen-induced arthritis model, serum interleukin (IL)-4 and the proportion of Th2 (CD4+CD25+GATA3+) and M2 (CD11c - CD206+ of CD45+CD64+) cells were significantly increased compared to the control group. Furthermore, Exo-RA could alleviate cartilage damage by significantly lowering the concentrations of proinflammatory cytokines such as tumor necrosis factor-α, keratinocyte chemoattractant, and IL-12p70.

CONCLUSION

Exosomes derived from disease-condition-serum-primed iMSCs ameliorated cartilage damage in a RA model by enhancing TGF-β1 production, inducing Th2 and M2 polarization and lowering proinflammatory cytokines, TNF-α, KC, and IL-12p70 in the host. Patient-derived serum can be used as an iMSC priming strategy in iMSC-derived exosome treatment of RA.

MicroRNA Cargo in Wharton's Jelly MSC Small Extracellular Vesicles: Key Functionality to In Vitro Prevention and Treatment of Premature White Matter Injury

Preterm birth is the leading cause of childhood morbidity and mortality and can result in white matter injury (WMI), leading to long-term neurological disabilities with global health burden. Mesenchymal stromal cell-derived small extracellular vesicles (MSC-sEV) are a promising therapeutic agent for treating perinatal neurological injury. They carry microRNAs (miRNAs) predicted to be involved in the onset of premature WMI. We hypothesize that miRNAs have a key function in the beneficial effects of MSC-sEV. We isolated MSC from umbilical cord tissue, the Wharton's jelly (WJ), and purified small extracellular vesicles (sEV) from WJ-MSC culture supernatant by ultracentrifugation and size exclusion chromatography. The miRNA content was quantified by real-time polymerase chain reaction. A luciferase gene assay validated silencing of TP53 and TAOK1, which we previously identified as predicted target genes of MSC-sEV miRNAs by Next Generation Sequencing and pathway enrichment analysis. The impact of sEV miRNAs on oligodendroglial maturation and neuronal apoptosis was evaluated using an in vitro oxygen-glucose deprivation model (OGD/R) by knocking-down DROSHA in WJ-MSC, which initiates miRNA processing. WJ-MSC-sEV contained miRNAs involved in WMI, namely hsa-miR-22-3p, hsa-miR-21-5p, hsa-miR-27b-3p, and the hsa-let-7 family. The luciferase assay strongly indicated an inhibitory effect of sEV miRNAs on the gene expression of TP53 and TAOK1. Small EV initiated oligodendrocyte maturation and reduced OGD/R-mediated neuronal apoptosis. Knocking-down DROSHA in WJ-MSC reduced the expression of sEV miRNAs and led to the loss of their beneficial effects. Our in vitro study strongly indicates the key function of miRNAs in the therapeutic potential of WJ-MSC-sEV in premature WMI.

Pathological role of inflammation in ocular disease progress and its targeting by mesenchymal stem cells (MSCs) and their exosome; current status and prospect

Because of their unique capacity for differentiation to a diversity of cell lineages and immunosuppressive properties, mesenchymal stem cells (MSC) are being looked at as a potential new treatment option in ophthalmology. The MSCs derived from all tissue sources possess immunomodulatory attributes through cell-to-cell contact and releasing a myriad of immunomodulatory factors (IL-10, TGF-β, growth-related oncogene (GRO), indoleamine 2,3 dioxygenase (IDO), nitric oxide (NO), interleukin 1 receptor antagonist (IL-1Ra), prostaglandin E2 (PGE2)). Such mediators, in turn, alter both the phenotype and action of all immune cells that serve a pathogenic role in the progression of inflammation in eye diseases. Exosomes from MSCs, as natural nano-particles, contain the majority of the bioactive components of parental MSCs and can easily by-pass all biological barriers to reach the target epithelial and immune cells in the eye without interfering with nearby parenchymal cells, thus having no serious side effects. We outlined the most recent research on the molecular mechanisms underlying the therapeutic benefits of MSC and MSC-exosome in the treatment of inflammatory eye diseases in the current article.

Harnessing the therapeutic potential of the stem cell secretome in neonatal diseases

Preterm birth and intrapartum related complications account for a substantial amount of mortality and morbidity in the neonatal period despite significant advancements in neonatal-perinatal care. Currently, there is a noticeable lack of curative or preventative therapies available for any of the most common complications of prematurity including bronchopulmonary dysplasia, necrotizing enterocolitis, intraventricular hemorrhage, periventricular leukomalacia and retinopathy of prematurity or hypoxic-ischemic encephalopathy, the main cause of perinatal brain injury in term infants. Mesenchymal stem/stromal cell-derived therapy has been an active area of investigation for the past decade and has demonstrated encouraging results in multiple experimental models of neonatal disease. It is now widely acknowledged that mesenchymal stem/stromal cells exert their therapeutic effects via their secretome, with the principal vector identified as extracellular vesicles. This review will focus on summarizing the current literature and investigations on mesenchymal stem/stromal cell-derived extracellular vesicles as a treatment for neonatal diseases and examine the considerations to their application in the clinical setting.

Mesenchymal Stromal Cells as a Driver of Inflammaging

Life expectancy and age-related diseases burden increased significantly over the past few decades. Age-related conditions are commonly discussed in a very limited paradigm of depleted cellular proliferation and maturation with exponential accumulation of senescent cells. However, most recent evidence showed that the majority of age-associated ailments, i.e., diabetes mellitus, cardiovascular diseases and neurodegeneration. These diseases are closely associated with tissue nonspecific inflammation triggered and controlled by mesenchymal stromal cell secretion. Mesenchymal stromal cells (MSCs) are known as the most common type of cells for therapeutic approaches in clinical practice. Side effects and complications of MSC-based treatments increased interest in the MSCs secretome as an alternative concept for validation tests in regenerative medicine. The most recent data also proposed it as an ideal tool for cell-free regenerative therapy and tissue engineering. However, senescent MSCs secretome was shown to hold the role of ‘key-driver’ in inflammaging. We aimed to review the immunomodulatory effects of the MSCs-secretome during cell senescence and provide eventual insight into the interpretation of its beneficial biological actions in inflammaging-associated diseases.

Mesenchymal Stem Cells and Their Exocytotic Vesicles

Mesenchymal stem cells (MSCs), as a kind of pluripotent stem cells, have attracted much attention in orthopedic diseases, geriatric diseases, metabolic diseases, and sports functions due to their osteogenic potential, chondrogenic differentiation ability, and adipocyte differentiation. Anti-inflammation, anti-fibrosis, angiogenesis promotion, neurogenesis, immune regulation, and secreted growth factors, proteases, hormones, cytokines, and chemokines of MSCs have been widely studied in liver and kidney diseases, cardiovascular and cerebrovascular diseases. In recent years, many studies have shown that the extracellular vesicles of MSCs have similar functions to MSCs transplantation in all the above aspects. Here we review the research progress of MSCs and their exocrine vesicles in recent years.

Infiltrating circulating monocytes provide an important source of BMP4 at the early stage of spinal cord injury

Bone morphogenetic protein (BMP)4 plays a critical role in regulating neuronal and glial activity in the course of spinal cord injury (SCI). The underlying cause and cellular source of BMP4 accumulation at the injured spinal cord remain unclear. Here, we observed that plasma BMP4 levels are statistically higher in SCI patients than in healthy donors. When comparing rats in the sham group (T9 laminectomy without SCI) with rats in the SCI group, we found a persistent decline in BBB scores, together with necrosis and mononuclear cell accumulation at the contusion site. Moreover, during 2 weeks after SCI both plasma and cerebrospinal fluid levels of BMP4 displayed notable elevation, and a positive correlation. Importantly, percentages of circulating BMP4-positive (BMP4+) monocytes and infiltrating MDMs were higher in the SCI group than in the sham group. Finally, in the SCI+clodronate liposome group, depletion of monocytes effectively attenuated the accumulation of both BMP4+ MDMs and BMP4 in the injured spinal cord. Our results indicated that, following SCI, infiltrating MDMs provide an important source of BMP4 in the injured spinal cord and, therefore, might serve as a potential therapeutic target.

Dynamic release of neuronal extracellular vesicles containing miR-21a-5p is induced by hypoxia

Hypoxia induces changes in the secretion of extracellular vesicles (EVs) in several non-neuronal cells and pathological conditions. EVs are packed with biomolecules, such as microRNA(miR)-21-5p, which respond to hypoxia. However, the true EV association of miR-21-5p, and its functional or biomarker relevance, are inadequately characterised. Neurons are extremely sensitive cells, and it is not known whether the secretion of neuronal EVs and miR-21-5p are altered upon hypoxia. Here, we characterised the temporal EV secretion profile and cell viability of neurons under hypoxia. Hypoxia induced a rapid increase of miR-21a-5p secretion in the EVs, which preceded the elevation of hypoxia-induced tissue or cellular miR-21a-5p. Prolonged hypoxia induced cell death and the release of morphologically distinct EVs. The EVs protected miR-21a-5p from enzymatic degradation but a remarkable fraction of miR-21a-5p remained fragile and non-EV associated. The increase in miR-21a-5p secretion may have biomarker potential, as high blood levels of miR-21-5p in stroke patients were associated with significant disability at hospital discharge. Our data provides an understanding of the dynamic regulation of EV secretion from neurons under hypoxia and provides a candidate for the prediction of recovery from ischemic stroke.

Mesenchymal Stromal/Stem Cell Extracellular Vesicles and Perinatal Injury: One Formula for Many Diseases

Over the past decades, substantial advances in neonatal medical care have increased the survival of extremely premature infants. However, there continues to be significant morbidity associated with preterm birth with common complications including bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), neuronal injury such as intraventricular hemorrhage (IVH) or hypoxic ischemic encephalopathy (HIE), as well as retinopathy of prematurity (ROP). Common developmental immune and inflammatory pathways underlie the pathophysiology of such complications providing the opportunity for multisystem therapeutic approaches. To date, no single therapy has proven to be effective enough to prevent or treat the sequelae of prematurity. In the past decade mesenchymal stem/stromal cell (MSC)-based therapeutic approaches have shown promising results in numerous experimental models of neonatal diseases. It is now accepted that the therapeutic potential of MSCs is comprised of their secretome, and several studies have recognized the small extracellular vesicles (sEVs) as the paracrine vector. Herein, we review the current literature on the MSC-EVs as potential therapeutic agents in neonatal diseases and comment on the progress and challenges of their translation to the clinical setting.

Extracellular vesicles in neurodegenerative diseases: A systematic review

Introduction

Extracellular vesicles (EVs) are known to have a significant role in the central nervous system (CNS) and neurodegenerative disease.

Methods

PubMed, Scopus, ISI Web of Science, EMBASE, and Google Scholar were used to identify published articles about EV modifications (2012 to Feb 2022).

Results

In total, 1,435 published papers were identified among the searched articles, with 1,128 non-duplicate publications being identified. Following the screening of titles and abstracts, 214 publications were excluded; following the full-text screening of 93 published articles, another 33 publications were excluded. The remaining 60 studies were considered. The kappa statistic of 0.868 indicated that the raters were highly reliable. Furthermore, the inter-reliability and intra-reliability coefficients were found to be 0.931 and 0.908, respectively, indicating strong reliability and consistency between the eligible studies identified by the raters. A total of 27 relevant studies demonstrated the role of EVs as therapeutic and diagnostic biomarkers in neurodegenerative diseases. Of note, 19 and 14 studies, respectively, found EVs to be pioneering in diagnostic and therapeutic roles.

Discussion

EVs play an important role in the central nervous system (CNS), aiding in cell-to-cell communication and serving as a diagnostic marker and therapeutic target in a variety of neurodegenerative diseases. EVs are the home of several proteins [including-synuclein (-syn) and tau proteins], lipids, and genetic materials such as DNA and RNA. The presence of novel miRNAs in EVs suggests biomarkers for the diagnosis and screening of neurodegenerative disorders. Furthermore, EVs play an important role in the pathogenesis of such disorders. This systematic review discussed the current state of EVs' role in neurological diseases, as well as some preclinical studies on the therapeutic and diagnostic potential of EVs.

Mesenchymal Stem Cells and MSCs-Derived Extracellular Vesicles in Infectious Diseases: From Basic Research to Clinical Practice

Mesenchymal stem cells (MSCs) are attractive in various fields of regenerative medicine due to their therapeutic potential and complex unique properties. Basic stem cell research and the global COVID-19 pandemic have given impetus to the development of cell therapy for infectious diseases. The aim of this review was to systematize scientific data on the applications of mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) in the combined treatment of infectious diseases. Application of MSCs and MSC-EVs in the treatment of infectious diseases has immunomodulatory, anti-inflammatory, and antibacterial effects, and also promotes the restoration of the epithelium and stimulates tissue regeneration. The use of MSC-EVs is a promising cell-free treatment strategy that allows solving the problems associated with the safety of cell therapy and increasing its effectiveness. In this review, experimental data and clinical trials based on MSCs and MSC-EVs for the treatment of infectious diseases are presented. MSCs and MSC-EVs can be a promising tool for the treatment of various infectious diseases, particularly in combination with antiviral drugs. Employment of MSC-derived EVs represents a more promising strategy for cell-free treatment, demonstrating a high therapeutic potential in preclinical studies.

Bone marrow mesenchymal stem cell-derived exosomal miR-21a-5p alleviates renal fibrosis by attenuating glycolysis by targeting PFKM

Renal fibrosis is a common pathological feature and outcome of almost all chronic kidney diseases, and it is characterized by metabolic reprogramming toward aerobic glycolysis. Mesenchymal stem cell-derived exosomes (MSC-Exos) have been proposed as a promising therapeutic approach for renal fibrosis. In this study, we investigated the effect of MSC-Exos on glycolysis and the underlying mechanisms. We demonstrated that MSC-Exos significantly ameliorated unilateral ureter obstruction (UUO)-induced renal fibrosis by inhibiting glycolysis in tubular epithelial cells (TECs). miRNA sequencing showed that miR-21a-5p was highly enriched in MSC-Exos. Mechanistically, miR-21a-5p repressed the expression of phosphofructokinase muscle isoform (PFKM), a rate-limiting enzyme of glycolysis, thereby attenuating glycolysis in TECs. Additionally, knockdown of miR-21a-5p abolished the renoprotective effect of MSC-Exos. These findings revealed a novel role for MSC-Exos in the suppression of glycolysis, providing a new insight into the treatment of renal fibrosis.

Quantitative and Noninvasive Detection of SAH-Related MiRNA in Cerebrospinal Fluids In Vivo Using SERS Sensors Based on Acupuncture-Based Technology

Quantitative analysis of microRNAs (miRNAs) in a noninvasive manner is of vital importance for disease diagnosis and prognosis evaluation. However, conventional strategies for realizing accurate, simple, and sensitive detection of target molecules are still a challenge, especially for miRNAs due to their low abundance and susceptibility in the complex biological environment. Here, a novel surface-enhanced Raman scattering (SERS) strategy was established for quantitative detection and monitoring of miRNA-21-5p (miR-21-5p) in living cells and in vivo cerebrospinal fluid (CSF) by applying hairpin DNA (hpDNA)-conjugated gold nanostars (GNSs) SERS probes combined with acupuncture-based technology. This strategy enabled ultrasensitive exploration toward miR-21-5p in a wide range from 1 fM to 100 pM in cell lysates. Moreover, SERS analysis facilitated the detection and long-term monitoring for in vivo miR-21-5p noninvasively. This developed strategy promises to offer a powerful method for the analysis of multiple biomolecules in single cells and living bodies.

Bioengineering exosomes for treatment of organ ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a leading cause of death worldwide. It arises from blood reflowing after tissue hypoxia induced by ischemia that causes severe damages due to the accumulation of reactive oxygen species and the activation of inflammatory responses. Exosomes are the smallest members of the extracellular vesicles' family, which originate from nearly all eukaryotic cells. Exosomes have a great potential in the treatment of I/R injury either in native or modified forms. Native exosomes are secreted by different cell types, such as stem cells, and contain components such as specific miRNA molecules with tissue protective properties. On the other hand, exosome bioengineering has recently received increased attention in context of current advances in the purification, manipulation, biological characterization, and pharmacological applications. There are various pre-isolation and post-isolation manipulation approaches that can be utilized to increase the circulation half-life of exosomes or the availability of their bioactive cargos in the target site. In this review, the various therapeutic actions of native exosomes in different I/R injury will be discussed first. Exosome bioengineering approaches will then be explained, including pre- and post-isolation manipulation methods, applicability for delivery of bioactive agents to injured tissue, clinical translation issues, and future perspectives.

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.

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

Current Status of Mesenchymal Stem/Stromal Cells for Treatment of Neurological Diseases

Neurological disorders include a wide spectrum of clinical conditions affecting the central and peripheral nervous systems. For these conditions, which affect hundreds of millions of people worldwide, generally limited or no treatments are available, and cell-based therapies have been intensively investigated in preclinical and clinical studies. Among the available cell types, mesenchymal stem/stromal cells (MSCs) have been widely studied but as yet no cell-based treatment exists for neurological disease. We review current knowledge of the therapeutic potential of MSC-based therapies for neurological diseases, as well as possible mechanisms of action that may be explored to hasten the development of new and effective treatments. We also discuss the challenges for culture conditions, quality control, and the development of potency tests, aiming to generate more efficient cell therapy products for neurological disorders.

The human dental apical papilla promotes spinal cord repair through a paracrine mechanism

Traumatic spinal cord injury is an overwhelming condition that strongly and suddenly impacts the patient's life and her/his entourage. There are currently no predictable treatments to repair the spinal cord, while many strategies are proposed and evaluated by researchers throughout the world. One of the most promising avenues is the transplantation of stem cells, although its therapeutic efficiency is limited by several factors, among which cell survival at the lesion site. In our previous study, we showed that the implantation of a human dental apical papilla, residence of stem cells of the apical papilla (SCAP), supported functional recovery in a rat model of spinal cord hemisection. In this study, we employed protein multiplex, immunohistochemistry, cytokine arrays, RT- qPCR, and RNAseq technology to decipher the mechanism by which the dental papilla promotes repair of the injured spinal cord. We found that the apical papilla reduced inflammation at the lesion site, had a neuroprotective effect on motoneurons, and increased the apoptosis of activated macrophages/ microglia. This therapeutic effect is likely driven by the secretome of the implanted papilla since it is known to secrete an entourage of immunomodulatory or pro-angiogenic factors. Therefore, we hypothesize that the secreted molecules were mainly produced by SCAP, and that by anchoring and protecting them, the human papilla provides a protective niche ensuring that SCAP could exert their therapeutic actions. Therapeutic abilities of the papilla were demonstrated in the scope of spinal cord injury but could very well be beneficial to other types of tissue.

Mesenchymal Stem Cell-Derived Extracellular Vesicles as Non-Coding RNA Therapeutic Vehicles in Autoimmune Diseases

Autoimmune diseases (ADs) are characterized by the activation of the immune system against self-antigens. More common in women than in men and with an early onset, their incidence is increasing worldwide, and this, combined with their chronic nature, is contributing to an enlarged medical and economic burden. Conventional immunosuppressive agents are designed to alleviate symptoms but do not constitute an effective therapy, highlighting a need to develop new alternatives. In this regard, mesenchymal stem cells (MSCs) have demonstrated powerful immunosuppressive and regenerative effects. MSC-derived extracellular vesicles (MSC-EVs) have shown some advantages, such as less immunogenicity, and are proposed as novel therapies for ADs. In this review, we summarize current perspectives on therapeutic options for ADs based on MSCs and MSC-EVs, focusing particularly on their mechanism of action exerted through their non-coding RNA (ncRNA) cargo. A complete state-of-the-art review was performed, centralized on some of the most severe ADs (rheumatoid arthritis, autoimmune type 1 diabetes mellitus, and systemic lupus erythematosus), giving evidence that a promising field is evolving to overcome the current knowledge and provide new therapeutic possibilities centered on MSC-EVs and their role as ncRNA delivery vehicles for AD gene therapy.

The delivery of miR-21a-5p by extracellular vesicles induces microglial polarization via the STAT3 pathway following hypoxia-ischemia in neonatal mice

Extracellular vesicles (EVs) from mesenchymal stromal cells (MSCs) have previously been shown to protect against brain injury caused by hypoxia-ischemia (HI). The neuroprotective effects have been found to relate to the anti-inflammatory effects of EVs. However, the underlying mechanisms have not previously been determined. In this study, we induced oxygen-glucose deprivation in BV-2 cells (a microglia cell line), which mimics HI in vitro, and found that treatment with MSCs-EVs increased the cell viability. The treatment was also found to reduce the expression of pro-inflammatory cytokines, induce the polarization of microglia towards the M2 phenotype, and suppress the phosphorylation of selective signal transducer and activator of transcription 3 (STAT3) in the microglia. These results were also obtained in vivo using neonatal mice with induced HI. We investigated the potential role of miR-21a-5p in mediating these effects, as it is the most highly expressed miRNA in MSCs-EVs and interacts with the STAT3 pathway. We found that treatment with MSCs-EVs increased the levels of miR-21a-5p in BV-2 cells, which had been lowered following oxygen-glucose deprivation. When the level of miR-21a-5p in the MSCs-EVs was reduced, the effects on microglial polarization and STAT3 phosphorylation were reduced, for both the in vitro and in vivo HI models. These results indicate that MSCs-EVs attenuate HI brain injury in neonatal mice by shuttling miR-21a-5p, which induces microglial M2 polarization by targeting STAT3.

Human amniotic fluid derived-exosomes alleviate hypoxic encephalopathy by enhancing angiogenesis in neonatal mice after hypoxia

Neonatal hypoxic encephalopathy is a type of central nervous system dysfunction manifested by high mortality and morbidity. Exosomes play a crucial role in neuroprotection by enhancing angiogenesis. The objective of this study was to investigate the effect of human amniotic fluid-derived exosomes (hAFEXOs) on functional recovery in neonatal hypoxic encephalopathy. The transwell assay, scratch wound healing assay, and tube formation assay were used to evaluate the effect of hAFEXOs on the angiogenesis of human umbilical vein endothelial cells (HUVECs) after oxygen and glucose deprivation (OGD). The angiogenesis of microvascular endothelial cells (MECs) in the cortex was tested in neonatal mice treated with hAFEXOs or phosphate-buffered saline (PBS) after hypoxia. Expressions of hypoxia-inducible factor 1 α (HIF-1α) and vascular endothelial growth factor (VEGF) in the cerebral cortex were also tested by western blot. The Morris Water Maze Test (MWM) was carried out to detect the performance of spatial memory after processing with hAFEXOs or PBS. The results indicated that hAFEXOs favored tubing formation and migration of HUVECs after in vitro OGD. The hAFEXOs also favored the expression of CD31 in neonatal mice following hypoxia. The expressions of both HIF-1α and VEGF were significantly augmented in the cerebral cortex of neonatal mice which were treated with hAFEXOs. Moreover, the MWM test results showed that the performance of the spatial memory was better in the hAFEXO-treated group than in the PBS-treated group. Our study indicates that hAFEXOs alleviated hypoxic encephalopathy and enhanced angiogenesis in neonatal mice after hypoxia. In addition, hAFEXOs  promoted migration and tube formation of HUVECs after OGD in vitro. These findings confirm that hAFEXOs show great potential for further studies aimed at developing therapeutic agents for hypoxic encephalopathy.

Brain Tissue-Derived Extracellular Vesicle Mediated Therapy in the Neonatal Ischemic Brain

Hypoxic-Ischemic Encephalopathy (HIE) in the brain is the leading cause of morbidity and mortality in neonates and can lead to irreparable tissue damage and cognition. Thus, investigating key mediators of the HI response to identify points of therapeutic intervention has significant clinical potential. Brain repair after HI requires highly coordinated injury responses mediated by cell-derived extracellular vesicles (EVs). Studies show that stem cell-derived EVs attenuate the injury response in ischemic models by releasing neuroprotective, neurogenic, and anti-inflammatory factors. In contrast to 2D cell cultures, we successfully isolated and characterized EVs from whole brain rat tissue (BEV) to study the therapeutic potential of endogenous EVs. We showed that BEVs decrease cytotoxicity in an ex vivo oxygen glucose deprivation (OGD) brain slice model of HI in a dose- and time-dependent manner. The minimum therapeutic dosage was determined to be 25 μg BEVs with a therapeutic application time window of 4-24 h post-injury. At this therapeutic dosage, BEV treatment increased anti-inflammatory cytokine expression. The morphology of microglia was also observed to shift from an amoeboid, inflammatory phenotype to a restorative, anti-inflammatory phenotype between 24-48 h of BEV exposure after OGD injury, indicating a shift in phenotype following BEV treatment. These results demonstrate the use of OWH brain slices to facilitate understanding of BEV activity and therapeutic potential in complex brain pathologies for treating neurological injury in neonates.

Distinct Polarization Dynamics of Microglia and Infiltrating Macrophages: A Novel Mechanism of Spinal Cord Ischemia/Reperfusion Injury

Purpose

Recent studies indicate that microglia and monocyte-derived macrophages (MDMs) have different roles in diseases such as stroke and spinal cord injury, yet their respective polarized phenotypes and roles remain unclear in spinal cord ischemia/reperfusion injury (SCIRI).

Methods

We established a mouse model of SCIRI by transient aortic occlusion followed by reperfusion. Basso mouse scale (BMS) scores were used to test the locomotor functions. The histopathological changes in spinal cord were assessed by hematoxylin-eosin staining and NF-200 immunohistochemistry. Real-time PCR, immunofluorescence and flow cytometry were employed to analyze the polarized phenotypes of the microglia and infiltrating MDMs, and the resulting inflammatory responses. Furthermore, the role of infiltrating MDMs were investigated by MDMs depletion using systemic administration of clodronate-liposomes.

Results

SCIRI significantly impaired locomotor function of mice, accompanied with progressed necrosis, infiltration of inflammatory cells and neuron loss in the spinal cord. M1-related pro-inflammatory markers (iNOS, CD16, CD86 and TNF-α) increased dramatically in the early phase following SCIRI. In contrast, M2-related anti-inflammatory markers (CD204 and CD206) elevated at later stage. Besides, the invading MDMs were principally pro-inflammatory M1 type, transiently restricted to the first week after SCIRI. In contrast, microglia were the main source of anti-inflammatory M2 type. Furthermore, depletion of MDMs by clodronate-liposomes significantly preserved neurological functions and relieved neuronal damage caused by SCIRI.

Conclusion

These findings suggested distinct polarized status of resident microglia and MDMs following SCIRI. Inhibition of the invading MDMs may represent a novel approach for SCIRI treatment.

The Role of Extracellular Vesicles in the Developing Brain: Current Perspective and Promising Source of Biomarkers and Therapy for Perinatal Brain Injury

This comprehensive review focuses on our current understanding of the proposed physiological and pathological functions of extracellular vesicles (EVs) in the developing brain. Furthermore, since EVs have attracted great interest as potential novel cell-free therapeutics, we discuss advances in the knowledge of stem cell- and astrocyte-derived EVs in relation to their potential for protection and repair following perinatal brain injury. This review identified 13 peer-reviewed studies evaluating the efficacy of EVs in animal models of perinatal brain injury; 12/13 utilized mesenchymal stem cell-derived EVs (MSC-EVs) and 1/13 utilized astrocyte-derived EVs. Animal model, method of EV isolation and size, route, timing, and dose administered varied between studies. Notwithstanding, EV treatment either improved and/or preserved perinatal brain structures both macroscopically and microscopically. Additionally, EV treatment modulated inflammatory responses and improved brain function. Collectively this suggests EVs can ameliorate, or repair damage associated with perinatal brain injury. These findings warrant further investigation to identify the optimal cell numbers, source, and dosage regimens of EVs, including long-term effects on functional outcomes.

Immunomodulatory Effect of MSCs and MSCs-Derived Extracellular Vesicles in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a common autoimmune connective tissue disease with unclear etiology and pathogenesis. Mesenchymal stem cell (MSC) and MSC derived extracellular vesicles (EVs) play important roles in regulating innate and adaptive immunity, which are involved in many physiological and pathological processes and contribute to the immune homeostasis in SLE. The effects of MSCs and EVs on SLE have been drawing more and more attention during the past few years. This article reviews the immunomodulatory effects and underlying mechanisms of MSC/MSC-EVs in SLE, which provides novel insight into understanding SLE pathogenesis and guiding the biological therapy.

Mesenchymal stem cell-derived exosomal miR-21a-5p promotes M2 macrophage polarization and reduces macrophage infiltration to attenuate atherosclerosis

Atherosclerosis (AS) is the main pathological basis for ischemic cardiovascular and cerebrovascular diseases. Mesenchymal stem cell (MSC)-derived exosomes have the potential to alleviate AS, while the underlying mechanism remains unclear. Here, we aimed to investigate the mechanism of MSC-derived exosomes in AS. The AS mouse model was prepared by feeding ApoE-/- mice with high-fat diet. AS mice were administered with MSC-derived exosomes, and the atherosclerotic plaque area was analyzed by Oil Red O staining. Mouse RAW264.7 macrophages were incubated with MSC-derived exosomes. The macrophage infiltration, macrophage proportion, and cell migration were estimated by immunohistochemistry, flow cytometry, or Transwell assay. The relationship between miR-21a-5p and kruppel-like factor 6 (KLF6) or extracellular signal-regulated protein kinases 2 (ERK2) was verified by luciferase reporter assay. We found that MSC-derived exosomes promoted M2 polarization of macrophages and reduced plaque area and macrophage infiltration in AS mice. miR-21a-5p overexpression caused an increase of M2 macrophages in RAW264.7 cells and led to a decrease in migration of RAW264.7 cells. Moreover, both KLF6 and ERK2 are the targets of miR-21a-5p. MSC-derived exosomes containing miR-21a-5p promoted M2 polarization of RAW264.7 cells by suppressing KLF6 expression. MSC-derived exosomes containing miR-21a-5p inhibited migration of RAW264.7 cells through inhibiting the ERK1/2 signaling pathway. In conclusion, MSC-derived exosomes containing miR-21a-5p promote macrophage polarization and reduce macrophage infiltration by targeting KLF6 and ERK1/2 signaling pathways, thereby attenuating the development of AS. Thus, MSC-derived exosomes may be a promising treatment for AS.

Microglia and Stem-Cell Mediated Neuroprotection after Neonatal Hypoxia-Ischemia

Neonatal hypoxia-ischemia encephalopathy (HIE) refers to a brain injury in term infants that can lead to death or lifelong neurological deficits such as cerebral palsy (CP). The pathogenesis of this disease involves multiple cellular and molecular events, notably a neuroinflammatory response driven partly by microglia, the brain resident macrophages. Treatment options are currently very limited, but stem cell (SC) therapy holds promise, as beneficial outcomes are reported in animal studies and to a lesser degree in human trials. Among putative mechanisms of action, immunomodulation is considered a major contributor to SC associated benefits. The goal of this review is to examine whether microglia is a cellular target of SC-mediated immunomodulation and whether the recruitment of microglia is linked to brain repair. We will first provide an overview on microglial activation in the rodent model of neonatal HI, and highlight its sensitivity to developmental age. Two complementary questions are then addressed: (i) do immune-related treatments impact microglia and provide neuroprotection, (ii) does stem cell treatment modulates microglia? Finally, the immune-related findings in patients enrolled in SC based clinical trials are discussed. Our review points to an impact of SCs on the microglial phenotype, but heterogeneity in experimental designs and methodological limitations hamper our understanding of a potential contribution of microglia to SC associated benefits. Thorough analyses of the microglial phenotype are warranted to better address the relevance of the neuroimmune crosstalk in brain repair and improve or advance the development of SC protocols in humans.

Extracellular vesicle activities regulating macrophage- and tissue-mediated injury and repair responses

Macrophages are typically identified as classically activated (M1) macrophages and alternatively activated (M2) macrophages, which respectively exhibit pro- and anti-inflammatory phenotypes, and the balance between these two subtypes plays a critical role in the regulation of tissue inflammation, injury, and repair processes. Recent studies indicate that tissue cells and macrophages interact via the release of small extracellular vesicles (EVs) in processes where EVs released by stressed tissue cells can promote the activation and polarization of adjacent macrophages which can in turn release EVs and factors that can promote cell stress and tissue inflammation and injury, and vice versa. This review discusses the roles of such EVs in regulating such interactions to influence tissue inflammation and injury in a number of acute and chronic inflammatory disease conditions, and the potential applications, advantage and concerns for using EV-based therapeutic approaches to treat such conditions, including their potential role of drug carriers for the treatment of infectious diseases.

Mesenchymal Stem Cell Derived Extracellular Vesicles for Repairing the Neurovascular Unit after Ischemic Stroke

Ischemic stroke is a debilitating disease and one of the leading causes of long-term disability. During the early phase after ischemic stroke, the blood-brain barrier (BBB) exhibits increased permeability and disruption, leading to an influx of immune cells and inflammatory molecules that exacerbate the damage to the brain tissue. Mesenchymal stem cells have been investigated as a promising therapy to improve the recovery after ischemic stroke. The therapeutic effects imparted by MSCs are mostly paracrine. Recently, the role of extracellular vesicles released by these MSCs have been studied as possible carriers of information to the brain. This review focuses on the potential of MSC derived EVs to repair the components of the neurovascular unit (NVU) controlling the BBB, in order to promote overall recovery from stroke. Here, we review the techniques for increasing the effectiveness of MSC-based therapeutics, such as improved homing capabilities, bioengineering protein expression, modified culture conditions, and customizing the contents of EVs. Combining multiple techniques targeting NVU repair may provide the basis for improved future stroke treatment paradigms.

Native and Bioengineered Exosomes for Ischemic Stroke Therapy

Exosomes are natural cells-derived vesicles, which are at the forefront toward clinical success for various diseases, including cerebral ischemia. Exosomes mediate cell-to-cell communication in different brain cells during both physiological and pathological conditions. Exosomes are an extensively studied type of extracellular vesicle, which are considered to be the best alternative for stem cell-based therapy. They can be secreted by various cell types and have unique biological properties. Even though native exosomes have potential for ischemic stroke therapy, some undesirable features prevent their success in clinical applications, including a short half-life, poor targeting property, low concentration at the target site, rapid clearance from the lesion region, and inefficient payload. In this review, we highlight exosome trafficking and cellular uptake and survey the latest discoveries in the context of exosome research as the best fit for brain targeting owing to its natural brain-homing abilities. Furthermore, we overview the methods by which researchers have bioengineered exosomes (BioEng-Exo) for stroke therapy. Finally, we summarize studies in which exosomes were bioengineered by a third party for stroke recovery. This review provides up-to-date knowledge about the versatile nature of exosomes with a special focus on BioEng-Exo for ischemic stroke. Standard exosome bioengineering techniques are mandatory for the future and will lead exosomes toward clinical success for stroke therapy.

L-Cysteine Provides Neuroprotection of Hypoxia-Ischemia Injury in Neonatal Mice via a PI3K/Akt-Dependent Mechanism

Background

Previous work within our laboratory has revealed that hydrogen sulfide (H₂S) can serve as neuroprotectant against brain damage caused by hypoxia-ischemia (HI) exposure in neonatal mice. After HI insult, activation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway has been shown to be implicated in neuro-restoration processes. The goal of the current study was to determine whether the neuroprotective effects of H₂S were mediated by the PI3K/Akt signaling pathway.

Methods

The mouse HI model was built at postnatal day 7 (P7), and the effects of L-Cysteine treatment on acute brain damage (72 h post-HI) and long-term neurological responses (28 days post-HI) were evaluated. Nissl staining and Transmission electron microscopy were used to evaluate the neuronal loss and apoptosis. Immunofluorescence imaging and dihydroethidium staining were utilized to determine glial cell activation and ROS content, respectively.

Results

Quantitative results revealed that L-Cysteine treatment significantly prevented the acute effects of HI on apoptosis, glial cell activation and oxidative injury as well as the long-term effects upon memory impairment in neonatal mice. This protective effect of L-Cysteine was found to be associated with the phosphorylation of Akt and phosphatase and a tensin homolog deletion on chromosome 10 (PTEN). Following treatment with the PI3K inhibitor, LY294002, the neuroprotective effects of L-Cysteine were attenuated.

Conclusion

PTEN/PI3K/Akt signaling was involved in mediating the neuroprotective effects of exogenous H₂S against HI exposure in neonatal mice.

MSCs-extracellular vesicles attenuated neuroinflammation, synapse damage and microglial phagocytosis after hypoxia-ischemia injury by preventing osteopontin expression

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) significantly suppressed hypoxia-ischemia (HI)-induced neuroinflammation in neonatal mice. However, its underlying mechanism is still unknown. Osteopontin (OPN) is one of the key molecules involved in neuroinflammation. We demonstrate here for the first time a key role of OPN in EVs-mediated neuroinflammation following HI. Firstly, HI exposure upregulated OPN expression in Iba-1+/ TMEM119+ microglia and Iba-1+/TMEM119- monocytes/macrophages. Blocking OPN mRNA expression with LV-shOPN attenuated edema, infarct volumes, and the levels of inflammatory cytokines following HI exposure. MSCs-EVs treatment remarkably restored synaptic reorganization and up-regulated synaptic protein expression post-HI, concomitant with reducing OPN levels. Moreover, MSCs-EVs treatment rescued microglial phagocytosis of viable neurons following HI, concomitant with decreasing OPN expression. In addition, blocking NF-κB activation with pyrrolidine dithiocarbamate (PDTC, NF-κB inhibitor) or MSCs-EVs attenuated HI-induced OPN expression in the ipsilateral cortex. This study demonstrates that upregulation of OPN expression in cerebral immune cells aggravated brain damage and inflammation following HI insult. MSCs-EVs suppressed neuroinflammation, synaptic damage and microglial phagocytosis after HI injury by preventing NF-κB-mediated OPN expression in neonate mice.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles Reduce Neuroinflammation, Promote Neural Cell Proliferation and Improve Oligodendrocyte Maturation in Neonatal Hypoxic-Ischemic Brain Injury

Background: Neonatal encephalopathy caused by hypoxia-ischemia (HI) is a major cause of childhood mortality and disability. Stem cell-based regenerative therapies seem promising to prevent long-term neurological deficits. Our previous work in neonatal HI revealed an unexpected interaction between mesenchymal stem/stromal cells (MSCs) and the brains' microenvironment leading to an altered therapeutic efficiency. MSCs are supposed to mediate most of their therapeutic effects in a paracrine mode via extracellular vesicles (EVs), which might be an alternative to cell therapy. In the present study, we investigated the impact of MSC-EVs on neonatal HI-induced brain injury.

Methods: Nine-day-old C57BL/6 mice were exposed to HI through ligation of the right common carotid artery followed by 1 h hypoxia (10% oxygen). MSC-EVs were injected intraperitoneally 1, 3, and 5 days after HI. One week after HI, brain injury was evaluated by regional neuropathological scoring, atrophy measurements and immunohistochemistry to assess effects on neuronal, oligodendrocyte and vessel densities, proliferation, oligodendrocyte maturation, myelination, astro-, and microglia activation. Immunohistochemistry analyses were complemented by mRNA expression analyses for a broad set of M1/M2- and A1/A2-associated molecules and neural growth factors.

Results: While total neuropathological scores and tissue atrophy were not changed, MSC-EVs significantly protected from HI-induced striatal tissue loss and decreased micro- and astroglia activation. MSC-EVs lead to a significant downregulation of the pro-inflammatory cytokine TNFa, accompanied by a significant upregulation of the M2 marker YM-1 and the anti-inflammatory cytokine TGFb. MSC-EVs significantly decreased astrocytic expression of the A1 marker C3, concomitant with an increased expression of neural growth factors (i.e., BDNF, VEGF, and EGF). These alterations were associated with an increased neuronal and vessel density, coinciding with a significant increase of proliferating cells in the neurogenic sub-ventricular zone juxtaposed to the striatum. MSC-EV-mediated neuroprotection went along with a significant improvement of oligodendrocyte maturation and myelination.

Conclusion: The present study demonstrates that MSC-EVs mediate anti-inflammatory effects, promote regenerative responses and improve key developmental processes in the injured neonatal brain. The present results suggest different cellular target mechanisms of MSC-EVs, preventing secondary HI-induced brain injury. MSC-EV treatment may be a promising alternative to risk-associated cell therapies in neonatal brain injury.