Extracellular vesicles in mesenchymal stromal cells: A novel therapeutic strategy for stroke

Astrocytic Extracellular Vesicles Regulated by Microglial Inflammatory Responses Improve Stroke Recovery

There are no effective treatments for post-stroke glial scar formation, which inhibits axonal outgrowth and functional recovery after stroke. We investigated whether astrocytic extracellular vesicles (AEVs) regulated by microglia modulate glial scars and improve stroke recovery. We found that peri-infarct glial scars comprised reactive astrocytes with proliferating C3d and decreased S100A10 expression in chronic stroke. In cultured astrocytes, microglia-conditioned media and treatment with P2Y1 receptor antagonists increased and reduced the area of S100A10- and C3d-expressing reactive astrocytes, respectively, by suppressing mitogen-activated protein kinase/nuclear factor-κβ (NF-κB)/tumor necrosis factor-α (TNF-α)/interleukin-1β signaling after oxygen-glucose deprivation. Intracerebral administrations of AEVs enriched miR-146a-5p, downregulated NF-κB, and suppressed TNF-α expressions, by transforming reactive astrocytes to those with S100A10 preponderance, causing functional recovery in rats subjected to middle cerebral artery occlusion. Modulating neuroinflammation in post-stroke glial scars could permit axonal outgrowth, thus providing a basis for stroke recovery with neuroprotective AEVs.

Potential regulatory effects of stem cell exosomes on inflammatory response in ischemic stroke treatment

The high incidence and disability rates of stroke pose a heavy burden on society. Inflammation is a significant pathological reaction that occurs after an ischemic stroke. Currently, therapeutic methods, except for intravenous thrombolysis and vascular thrombectomy, have limited time windows. Mesenchymal stem cells (MSCs) can migrate, differentiate, and inhibit inflammatory immune responses. Exosomes (Exos), which are secretory vesicles, have the characteristics of the cells from which they are derived, making them attractive targets for research in recent years. MSC-derived exosomes can attenuate the inflammatory response caused by cerebral stroke by modulating damage-associated molecular patterns. In this review, research on the inflammatory response mechanisms associated with Exos therapy after an ischemic injury is discussed to provide a new approach to clinical treatment.

Comparative study of extracellular vesicles derived from mesenchymal stem cells and brain endothelial cells attenuating blood-brain barrier permeability via regulating Caveolin-1-dependent ZO-1 and Claudin-5 endocytosis in acute ischemic stroke

BACKGROUND

Blood-brain barrier (BBB) disruption is a major adverse event after ischemic stroke (IS). Caveolin-1 (Cav-1), a scaffolding protein, played multiple roles in BBB permeability after IS, while the pros and cons of Cav-1 on BBB permeability remain controversial. Numerous studies revealed that extracellular vesicles (EVs), especially stem cells derived EVs, exerted therapeutic efficacy on IS; however, the mechanisms of BBB permeability needed to be clearly illustrated. Herein, we compared the protective efficacy on BBB integrity between bone marrow mesenchymal stem cells derived extracellular vesicles (BMSC-EVs) and EVs from brain endothelial cells (BEC-EVs) after acute IS and investigated whether the mechanism was associated with EVs antagonizing Cav-1-dependent tight junction proteins endocytosis.

METHODS

BMSC-EVs and BEC-EVs were isolated and characterized by nanoparticle tracking analysis, western blotting, and transmission electron microscope. Oxygen and glucose deprivation (OGD) treated b. End3 cells were utilized to evaluate brain endothelial cell leakage. CCK-8 and TRITC-dextran leakage assays were used to measure cell viability and transwell monolayer permeability. Permanent middle cerebral artery occlusion (pMCAo) model was established, and EVs were intravenously administered in rats. Animal neurological function tests were applied, and microvessels were isolated from the ischemic cortex. BBB leakage and tight junction proteins were analyzed by Evans Blue (EB) staining and western blotting, respectively. Co-IP assay and Cav-1 siRNA/pcDNA 3.1 vector transfection were employed to verify the endocytosis efficacy of Cav-1 on tight junction proteins.

RESULTS

Both kinds of EVs exerted similar efficacies in reducing the cerebral infarction volume and BBB leakage and enhancing the expressions of ZO-1 and Claudin-5 after 24 h pMCAo in rats. At the same time, BMSC-EVs were outstanding in ameliorating neurological function. Simultaneously, both EVs treatments suppressed the highly expressed Cav-1 in OGD-exposed b. End3 cells and ischemic cerebral microvessels, and this efficacy was more prominent after BMSC-EVs administration. Cav-1 knockdown reduced OGD-treated b. End3 cells monolayer permeability and recovered ZO-1 and Claudin-5 expressions, whereas Cav-1 overexpression aggravated permeability and enhanced the colocalization of Cav-1 with ZO-1 and Claudin-5. Furthermore, Cav-1 overexpression partly reversed the lower cell leakage by BMSC-EVs and BEC-EVs administrations in OGD-treated b. End3 cells.

CONCLUSIONS

Our results demonstrated that Cav-1 aggravated BBB permeability in acute ischemic stroke, and BMSC-EVs exerted similar antagonistic efficacy to BEC-EVs on Cav-1-dependent ZO-1 and Claudin-5 endocytosis. BMSC-EVs treatment was superior in Cav-1 suppression and neurological function amelioration.

Paracrine Effects of Mesenchymal Stem Cells in Ischemic Stroke: Opportunities and Challenges

It is well acknowledged that neuroprotective effects of transplanted mesenchymal stem cells (MSCs) in ischemic stroke are attributed to their paracrine-mediated actions or bystander effects rather than to cell replacement in infarcted areas. This therapeutic plasticity is due to MSCs' ability to secrete a broad range of bioactive molecules including growth factors, trophic factors, cytokines, chemokines, and extracellular vesicles, overall known as the secretome. The secretome derivatives, such as conditioned medium (CM) or purified extracellular vesicles (EVs), exert remarkable advantages over MSC transplantation in stroke treating. Here, in this review, we used published information to provide an overview on the secretome composition of MSCs, underlying mechanisms of therapeutic effects of MSCs, and preclinical studies on MSC-derived products application in stroke. Furthermore, we discussed current advantages and challenges for successful bench-to-bedside translation.

Mesenchymal Stem Cell-Derived Small Extracellular Vesicles: A Novel Approach for Kidney Disease Treatment

Globally, kidney disease has become a serious health challenge, with approximately 10% of adults suffering with the disease, and increasing incidence and mortality rates every year. Small extracellular vesicles (sEVs) are 30 nm-100 nm sized nanovesicles released by cells into the extracellular matrix (ECM), which serve as mediators of intercellular communication. Depending on the cell origin, sEVs have different roles which depend on internal cargoes including, nucleic acids, proteins, and lipids. Mesenchymal stem cell (MSCs) exert anti-inflammatory, anti-aging, and wound healing functions mainly via sEVs in a stable and safe manner. MSC-derived sEVs (MSC-sEVs) exert roles in several kidney diseases by transporting renoprotective cargoes to reduce oxidative stress, inhibit renal cell apoptosis, suppress inflammation, and mediate anti-fibrosis mechanisms. Additionally, because MSC-sEVs efficiently target damaged kidneys, they have the potential to become the next generation cell-free therapies for kidney disease. Herein, we review recent research data on how MSC-sEVs could be used to treat kidney disease.

Extracellular Vesicle-Based Therapy for COVID-19: Promises, Challenges and Future Prospects

The COVID-19 pandemic has become a serious concern and has negatively impacted public health and the economy. It primarily targets the lungs, causing acute respiratory distress syndrome (ARDS); however, it may also lead to multiple organ failure (MOF) and enhanced mortality rates. Hence, there is an urgent need to develop potential effective therapeutic strategies for COVID-19 patients. Extracellular vesicles (EVs) are released from various types of cells that participate in intercellular communication to maintain physiological and pathological processes. EVs derived from various cellular origins have revealed suppressive effects on the cytokine storm during systemic hyper-inflammatory states of severe COVID-19, leading to enhanced alveolar fluid clearance, promoted epithelial and endothelial recovery, and cell proliferation. Being the smallest subclass of EVs, exosomes offer striking characteristics such as cell targeting, being nano-carriers for drug delivery, high biocompatibility, safety, and low-immunogenicity, thus rendering them a potential cell-free therapeutic candidate against the pathogeneses of various diseases. Due to these properties, numerous studies and clinical trials have been performed to assess their safety and therapeutic efficacy against COVID-19. Hence, in this review, we have comprehensively described current updates on progress and challenges for EVs as a potential therapeutic agent for the management of COVID-19.

The Therapeutic Potential of Mesenchymal Stromal Cells for Regenerative Medicine: Current Knowledge and Future Understandings

In recent decades, research on the therapeutic potential of progenitor cells has advanced considerably. Among progenitor cells, mesenchymal stromal cells (MSCs) have attracted significant interest and have proven to be a promising tool for regenerative medicine. MSCs are isolated from various anatomical sites, including bone marrow, adipose tissue, and umbilical cord. Advances in separation, culture, and expansion techniques for MSCs have enabled their large-scale therapeutic application. This progress accompanied by the rapid improvement of transplantation practices has enhanced the utilization of MSCs in regenerative medicine. During tissue healing, MSCs may exhibit several therapeutic functions to support the repair and regeneration of injured tissue. The process underlying these effects likely involves the migration and homing of MSCs, as well as their immunotropic functions. The direct differentiation of MSCs as a cell replacement therapeutic mechanism is discussed. The fate and behavior of MSCs are further regulated by their microenvironment, which may consequently influence their repair potential. A paracrine pathway based on the release of different messengers, including regulatory factors, chemokines, cytokines, growth factors, and nucleic acids that can be secreted or packaged into extracellular vesicles, is also implicated in the therapeutic properties of MSCs. In this review, we will discuss relevant outcomes regarding the properties and roles of MSCs during tissue repair and regeneration. We will critically examine the influence of the local microenvironment, especially immunological and inflammatory signals, as well as the mechanisms underlying these therapeutic effects. Importantly, we will describe the interactions of local progenitor and immune cells with MSCs and their modulation during tissue injury. We will also highlight the crucial role of paracrine pathways, including the role of extracellular vesicles, in this healing process. Moreover, we will discuss the therapeutic potential of MSCs and MSC-derived extracellular vesicles in the treatment of COVID-19 (coronavirus disease 2019) patients. Overall, this review will provide a better understanding of MSC-based therapies as a novel immunoregenerative strategy.

Extracellular Vesicles in Regeneration and Rehabilitation Recovery after Stroke

Patients that survive after a stroke event may present disabilities that can persist for a long time or permanently after it. If stroke prevention fails, the prompt and combinatorial intervention with pharmacological and rehabilitation therapy is pivotal for the optimal recovery of patients and the reduction of disabilities. In the present review, we summarize some key features of the complex events that occur in the brain during and after the stroke event, with a special focus on extracellular vesicles (EVs) and their role as both carriers of biomarkers and potential therapeutics. EVs have already demonstrated their ability to be used for diagnostic purposes for multiple brain disorders and could represent valuable tools to track the regenerative and inflammatory processes occurring in the injured brain after stroke. Last, but not least, the use of artificial or stem cell-derived EVs were proved to be effective in stimulating brain remodeling and ameliorating recovery after stroke. Still, effective biomarkers of recovery are needed to design robust trials for the validation of innovative therapeutic strategies, such as regenerative rehabilitation approaches.

Methods to produce induced pluripotent stem cell-derived mesenchymal stem cells: Mesenchymal stem cells from induced pluripotent stem cells

Mesenchymal stem cells (MSCs) have received significant attention in recent years due to their large potential for cell therapy. Indeed, they secrete a wide variety of immunomodulatory factors of interest for the treatment of immune-related disorders and inflammatory diseases. MSCs can be extracted from multiple tissues of the human body. However, several factors may restrict their use for clinical applications: the requirement of invasive procedures for their isolation, their limited numbers, and their heterogeneity according to the tissue of origin or donor. In addition, MSCs often present early signs of replicative senescence limiting their expansion in vitro, and their therapeutic capacity in vivo. Due to the clinical potential of MSCs, a considerable number of methods to differentiate induced pluripotent stem cells (iPSCs) into MSCs have emerged. iPSCs represent a new reliable, unlimited source to generate MSCs (MSCs derived from iPSC, iMSCs) from homogeneous and well-characterized cell lines, which would relieve many of the above mentioned technical and biological limitations. Additionally, the use of iPSCs prevents some of the ethical concerns surrounding the use of human embryonic stem cells. In this review, we analyze the main current protocols used to differentiate human iPSCs into MSCs, which we classify into five different categories: MSC Switch, Embryoid Body Formation, Specific Differentiation, Pathway Inhibitor, and Platelet Lysate. We also evaluate common and method-specific culture components and provide a list of positive and negative markers for MSC characterization. Further guidance on material requirements to produce iMSCs with these methods and on the phenotypic features of the iMSCs obtained is added. The information may help researchers identify protocol options to design and/or refine standardized procedures for large-scale production of iMSCs fitting clinical demands.

Engineered exosomes: desirable target-tracking characteristics for cerebrovascular and neurodegenerative disease therapies

As extracellular vesicles secreted by cells, exosomes are intercellular signalosomes for cell communication and pharmacological effectors. Because of their special properties, including low toxicity and immunogenicity, biodegradability, ability to encapsulate endogenous biologically active molecules and cross the blood-brain barrier (BBB), exosomes have great therapeutic potential in cerebrovascular and neurodegenerative diseases. However, the poor targeting ability of natural exosomes greatly reduces the therapeutic effect. Using engineering technology, exosomes can obtain active targeting ability to accumulate in specific cell types and tissues by attaching targeting units to the membrane surface or loading them into cavities. In this review, we outline the improved targeting functions of bioengineered exosomes, tracing and imaging techniques, administration methods, internalization in the BBB, and therapeutic effects of exosomes in cerebrovascular and neurodegenerative diseases and further evaluate the clinical opportunities and challenges in this research field.

Role of White Matter Hyperintensities and Related Risk Factors in Vascular Cognitive Impairment: A Review

White matter hyperintensities (WMHs) of presumed vascular origin are one of the imaging markers of cerebral small-vessel disease, which is prevalent in older individuals and closely associated with the occurrence and development of cognitive impairment. The heterogeneous nature of the imaging manifestations of WMHs creates difficulties for early detection and diagnosis of vascular cognitive impairment (VCI) associated with WMHs. Because the underlying pathological processes and biomarkers of WMHs and their development in cognitive impairment remain uncertain, progress in prevention and treatment is lagging. For this reason, this paper reviews the status of research on the features of WMHs related to VCI, as well as mediators associated with both WMHs and VCI, and summarizes potential treatment strategies for the prevention and intervention in WMHs associated with VCI.

Extracellular Vesicles Derived from Human Umbilical Cord Perivascular Cells Improve Functional Recovery in Brain Ischemic Rat via the Inhibition of Apoptosis

Background:

Ischemic stroke, as a health problem caused by the reduced blood supply to the brain, can lead to the neuronal death. The number of reliable therapies for stroke is limited. MSCs exhibit therapeutic achievement. A major limitation of MSC application in cell therapy is the short survival span. MSCs affect target tissues through the secretion of many paracrine agents including EVs. This study aimed to investigate the effect of HUCPVCs-derived EVs on apoptosis, functional recovery, and neuroprotection.

Methods:

Ischemia was induced by MCAO in male Wistar rats. Animals were classified into sham, MCAO, MCAO + HUCPVC, and MCAO + EV groups. Treatments began at two hours after ischemia. Expressions of apoptotic-related proteins (BAX/BCl-2 and caspase-3 and -9), the amount of TUNEL-positive cells, neuronal density (MAP2), and dead neurons (Nissl staining) were assessed on day seven post MCAO.

Results:

Administration of EVs improved the sensorimotor function (p < 0.001) and reduced the apoptotic rate of Bax/Bcl-2 ratio (p < 0.001), as well as caspases and TUNEL-positive cells (p < 0.001) in comparison to the MCAO group. EV treatment also reduced the number of dead neurons and increased the number of MAP2⁺ cells in the IBZ (p < 0.001), as compared to the MCAO group.

Conclusion:

Our findings showed that HUCPVCs-derived EVs are more effective than their mother’s cells in improving neural function, possibly via the regulation of apoptosis in the ischemic rats. The strategy of cell-free extracts is, thus, helpful in removing the predicaments surrounding cell therapy in targeting brain diseases.

Exosomes with high level of miR-181c from bone marrow-derived mesenchymal stem cells inhibit inflammation and apoptosis to alleviate spinal cord injury

Stem cell transplantation is a promising method in the treatment of spinal cord injury (SCI). Researches have shown that stem cell-derived exosomes as well as its contents such as microRNAs contribute to the protective effects of stem cell against SCI. However, the effects of exosomes derived from bone marrow stem cells on SCI and the underlying mechanisms remain unknown. In this study, we collected bone marrow stem cells derived exosomes (BMSCs-exo) to deal with SCI rats and LPS induced microglia to explore the possible mechanisms. We found that BMSCs-exo showed significant effects on decreasing pro-inflammatory cytokines as well as increasing Basso-Beattie-Bresnahan score after acute SCI. MicroRNA-181c levels in tissue were elevated with the use of BMSCs-exo. Then we verified the effect in vitro and found that in LPS induced microglia, the administration of BMSCs-exo could inhibit the expression of pro-inflammatory cytokines, and the phosphorylation of NF-κB signal was also suppressed. During which, the expression of microRNA-181c in microglia was elevated. When LPS induced microglia were treated with BMSCs-exo over-expressing microRNA-181c, the levels of pro-inflammatory cytokines decreased. Then bioinformatics techniques were used to detect the possible target gene of microRNA-181c and then PTEN was found as a candidate. Further experiments showed that the protection effects of BMSCs-exo over-expressing microRNA-181c could be antagonized by the elevation of PTEN expression both in vitro and in vivo. In conclusion, we verified that BMSCs-exo could protect against SCI through its content microRNA-181c which suppressed the inflammation in microglia and spinal cord. It was related to the inhibition of PTEN and the suppression of NF-κB signal, and finally decreasing inflammation and apoptosis in spinal cord and improved SCI.

Liquid Biomarkers for Pediatric Brain Tumors: Biological Features, Advantages and Perspectives

Tumors of the central nervous system are the most frequent solid tumor type and the major cause for cancer-related mortality in children and adolescents. These tumors are biologically highly heterogeneous and comprise various different entities. Molecular diagnostics are already well-established for pediatric brain tumors and have facilitated a more accurate patient stratification. The availability of targeted, biomarker-driven therapies has increased the necessity of longitudinal monitoring of molecular alterations within tumors for precision medicine-guided therapy. Nevertheless, diagnosis is still primarily based on analyses of the primary tumor and follow-up is usually performed by imaging techniques which lack important information on tumor biology possibly changing the course of the disease. To overcome this shortage of longitudinal information, liquid biopsy has emerged as a promising diagnostic tool representing a less-invasive source of biomarkers for tumor monitoring and therapeutic decision making. Novel ultrasensitive methods for detection of allele variants, genetic alterations with low abundance, have been developed and are promising tools for establishing and integrating liquid biopsy techniques into clinical routine. Pediatric brain tumors harbor multiple molecular alterations with the potential to be used as liquid biomarkers. Consequently, studies have already investigated different types of biomarker in diverse entities of pediatric brain tumors. However, there are still certain pitfalls until liquid biomarkers can be unleashed and implemented into routine clinical care. Within this review, we summarize current knowledge on liquid biopsy markers and technologies in pediatric brain tumors, their advantages and drawbacks, as well as future potential biomarkers and perspectives with respect to clinical implementation in patient care.

In vivo Monitoring and Assessment of Exogenous Mesenchymal Stem Cell-Derived Exosomes in Mice with Ischemic Stroke by Molecular Imaging

Purpose

Mesenchymal stem cell-derived exosomes (MSC-exos) are considered an important restorative treatment for ischemic stroke. However, the migration ability and survival of exogenous MSC-exos remain unclear. Here, we investigated whether MSC-exos migrate into the ischemic brain and play a protective role against ischemic stroke.

Methods

MSC-exos labeled with DiR were injected intravenously into mice with ischemic stroke. Near-infrared fluorescence (NIRF) images were obtained on days 0, 1, 3, 5, 7, 10, and 14, and magnetic resonance (MR) images were obtained on days 1, 7 and 14. On day 14, the functional outcomes, angiogenesis, neurogenesis, and white matter remodeling were assessed, and Western blot assays were performed.

Results

Fluorescence signals from the MSC-exos appeared in the injured brain from day 1 and peaked on day 3. The immunofluorescence staining of the brain samples revealed that the MSC-exos were localized in neurons. The behavioral scores and T2-weighted imaging indicated that the MSC-exos improved neurological functional recovery after stroke. In addition, the in vivo MR-diffusion tensor imaging (DTI) indicated that the exogenous MSC-exos increased the fractional anisotropy (FA) value, fiber length, and fiber number ratio. Furthermore, in the mice with ischemic stroke treated with MSC-exos, angiogenesis and neurogenesis were significantly improved, and the expression of IL-1β was reduced.

Conclusion

MSC-exos can migrate into the brains of mice with ischemic stroke and exert therapeutic effects against ischemic stroke; therefore, MSC-exos may have broad clinical applications in the future.

Pleiotropic Effects of Exosomes as a Therapy for Stroke Recovery

Stroke is the leading cause of disability, and stroke survivors suffer from long-term sequelae even after receiving recombinant tissue plasminogen activator therapy and endovascular intracranial thrombectomy. Increasing evidence suggests that exosomes, nano-sized extracellular membrane vesicles, enhance neurogenesis, angiogenesis, and axonal outgrowth, all the while suppressing inflammatory reactions, thereby enhancing functional recovery after stroke. A systematic literature review to study the association of stroke recovery with exosome therapy was carried out, analyzing species, stroke model, source of exosomes, behavioral analyses, and outcome data, as well as molecular mechanisms. Thirteen studies were included in the present systematic review. In the majority of studies, exosomes derived from mesenchymal stromal cells or stem cells were administered intravenously within 24 h after transient middle cerebral artery occlusion, showing a significant improvement of neurological severity and motor functions. Specific microRNAs and molecules were identified by mechanistic investigations, and their amplification was shown to further enhance therapeutic effects, including neurogenesis, angiogenesis, axonal outgrowth, and synaptogenesis. Overall, this review addresses the current advances in exosome therapy for stroke recovery in preclinical studies, which can hopefully be preparatory steps for the future development of clinical trials involving stroke survivors to improve functional outcomes.

Intranasal administration of Cytoglobin modifies human umbilical cord‑derived mesenchymal stem cells and improves hypoxic‑ischemia brain damage in neonatal rats by modulating p38 MAPK signaling‑mediated apoptosis

Neonatal hypoxic‑ischemic brain damage (HIBD) is a common clinical syndrome in newborns. Hypothermia is the only approved therapy for the clinical treatment; however, the therapeutic window of hypothermia is confined to 6 h after birth and even then, >40% of the infants either die or survive with various impairments, including cerebral palsy, seizure disorder and intellectual disability following hypothermic treatment. The aim of the present study was to determine whether nasal transplantation of Cytoglobin (CYGB) genetically modified human umbilical cord‑derived mesenchymal stem cells (CYGB‑HuMSCs) exhibited protective effects in neonatal rats with HIBD compared with those treated without genetically modified CYGB. A total of 120 neonatal Sprague‑Dawley rats (postnatal day 7) were assigned to either a Sham, HIBD, HuMSCs or CYGB‑HuMSCs group (n = 30 rats/group). For HIBD modeling, rats underwent left carotid artery ligation and were exposed to 8% oxygen for 2.5 h. A total of 30 min after HI, HuMSCs (or CYGB‑HuMSCs) labeled with enhanced‑green fluorescent protein (eGFP) were intranasally administered. After modeling for 3, 14 and 29 days, five randomly selected rats were sacrificed in each group, and the expression levels of CYGB, ERK, JNK and p38 in brain tissues were determined. Nissl staining of the cortex and hippocampal Cornu Ammonis 1 area of rats in each group were compared after 3 days of modeling. TUNEL assay and immunofluorescence were performed 3 days after modeling. Long term memory in rats was assessed using a Morris‑water maze 29 days after modeling. The HIBD group demonstrated significant deficiencies compared with the Sham group based on Nissl staining, TUNEL assay and the Morris‑water maze test. HuMSC treated rats exhibited improvement on in all the tests, and CYGB‑HuMSCs treatment resulted in further improvements. PCR and western blotting results indicated that the CYGB mRNA and protein levels were increased from day 3 to day 29 after transplantation of CYGB‑HuMSCs. Furthermore, it was identified that CYGB‑HuMSC transplantation suppressed p38 signaling at all experimental time points. Immunofluorescence indicated the scattered presence of HuMSCs or CYGB‑HuMSCs in damaged brain tissue. No eGFP and glial fibrillary acidic protein or eGFP and neuron‑specific enolase double‑stained positive cells were found in the brain tissues. Therefore, CYGB‑HuMSCs may serve as a gene transporter, as well as exert a neuroprotective and antiapoptotic effect in HIBD, potentially via the p38 mitogen‑activated protein kinase signaling pathway.

Immunosuppressive properties of cytochalasin B-induced membrane vesicles of mesenchymal stem cells: comparing with extracellular vesicles derived from mesenchymal stem cells

Extracellular vesicles derived from mesenchymal stem cells (MSCs) represent a novel approach for regenerative and immunosuppressive therapy. Recently, cytochalasin B-induced microvesicles (CIMVs) were shown to be effective drug delivery mediators. However, little is known about their immunological properties. We propose that the immunophenotype and molecular composition of these vesicles could contribute to the therapeutic efficacy of CIMVs. To address this issue, CIMVs were generated from murine MSC (CIMVs-MSCs) and their cytokine content and surface marker expression determined. For the first time, we show that CIMVs-MSCs retain parental MSCs phenotype (Sca-1⁺, CD49e⁺, CD44⁺, CD45⁻). Also, CIMVs-MSCs contained a cytokine repertoire reflective of the parental MSCs, including IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12(p40), IL-13, IL-17, CCL2, CCL3, CCL4, CCL5, CCL11, G-CSF, GM-CSF and TNF-α. Next, we evaluated the immune-modulating properties of CIMVs-MSCs in vivo using standard preclinical tests. MSCs and CIMVs-MSCs reduced serum levels of anti-sheep red blood cell antibody and have limited effects on neutrophil and peritoneal macrophage activity. We compared the immunomodulatory effect of MSCs, CIMVs and EVs. We observed no immunosuppression in mice pretreated with natural EVs, whereas MSCs and CIMVs-MSCs suppressed antibody production in vivo. Additionally, we have investigated the biodistribution of CIMVs-MSCs in vivo and demonstrated that CIMVs-MSCs localized in liver, lung, brain, heart, spleen and kidneys 48 h after intravenous injection and can be detected 14 days after subcutaneous and intramuscular injection. Collectively our data demonstrates immunomodulatory efficacy of CIMVs and supports their further preclinical testing as an effective therapeutic delivery modality.

Mechanisms underlying the protective effects of mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. The therapeutic potential of MSCs is attributed to complex cellular and molecular mechanisms of action including differentiation into multiple cell lineages and regulation of immune responses via immunomodulation. The plasticity of MSCs in immunomodulation allow these cells to exert different immune effects depending on different diseases. Understanding the biology of MSCs and their role in treatment is critical to determine their potential for various therapeutic applications and for the development of MSC-based regenerative medicine. This review summarizes the recent progress of particular mechanisms underlying the tissue regenerative properties and immunomodulatory effects of MSCs. We focused on discussing the functional roles of paracrine activities, direct cell-cell contact, mitochondrial transfer, and extracellular vesicles related to MSC-mediated effects on immune cell responses, cell survival, and regeneration. This will provide an overview of the current research on the rapid development of MSC-based therapies.

The Therapeutic Potential of Extracellular Vesicles Versus Mesenchymal Stem Cells in Liver Damage

BACKGROUND

The extracellular vesicles (EVs) secreted by bone marrow-derived mesenchymal stem cells (MSCs) hold significant potential as a novel alternative to whole-cell therapy. We herein compare the therapeutic potential of BM-MSCs versus their EVs (MSC-EVs) in an experimental Carbon tetrachloride (CCl₄)-induced liver damage rat model.

METHODS

Rats with liver damage received a single IV injection of MSC-EVs, 1 million MSCs, or 3 million MSCs. The therapeutic efficacy of each treatment was assessed using liver histopathology, liver function tests and immunohistochemistry for liver fibrosis and hepatocellular injury.

RESULTS

Animals that received an injection of either MSCs-EVs or 3 million MSCs depicted significant regression of collagen deposition in the liver tissue and marked attenuation of hepatocellular damage, both structurally and functionally.

CONCLUSION

Similar to high doses of MSC-based therapy (3 million MSCs), MSC-EVs mitigated the fibrogenesis and hepatocellular injury in a rat model of CCl₄-induced liver fibrosis. The anti-fibrinogenic effect was induced by attenuating hepatic stellate cell activation. Therefore, the administration of MSC-EVs could be considered as a candidate cell-free therapeutic strategy for liver fibrosis and hepatocellular damage.

Extracellular Vesicle Isolation and Characterization from Periprosthetic Joint Synovial Fluid in Revision Total Joint Arthroplasty

Extracellular vesicles (EVs) comprise an as yet insufficiently investigated intercellular communication pathway in the field of revision total joint arthroplasty (RTJA). This study examined whether periprosthetic joint synovial fluid contains EVs, developed a protocol for their isolation and characterized them with respect to quantity, size, surface markers as well as documented their differences between aseptic implant failure (AIF) and periprosthetic joint infection (PJI). EV isolation was accomplished using ultracentrifugation, electron microscopy (EM) and nanoparticle tracking analysis evaluated EV presence as well as particle size and quantity. EV surface markers were studied by a bead-based multiplex analysis. Using our protocol, EM confirmed the presence of EVs in periprosthetic joint synovial fluid. Higher EV particle concentrations and decreased particle sizes were apparent for PJI. Multiplex analysis confirmed EV-typical surface epitopes and revealed upregulated CD44 and HLA-DR/DP/DQ for AIF, as well as increased CD40 and CD105. Our protocol achieved isolation of EVs from periprosthetic joint synovial fluid, confirmed by EM and multiplex analysis. Characterization was documented with respect to size, concentration and epitope surface signature. Our results indicate various differences between PJI and AIF EVs. This pilot study enables new research approaches and rising diagnostic opportunities in the field of RTJA.

A comprehensive proteomics profiling identifies NRP1 as a novel identity marker of human bone marrow mesenchymal stromal cell-derived small extracellular vesicles

BACKGROUND

Clinical applications have shown extracellular vesicles (EVs) to be a major paracrine effector in therapeutic responses produced by human mesenchymal stromal/stem cells (hMSCs). As the regenerative capacity of EVs is mainly ascribed to the transfer of proteins and RNA composing its cargo, and to the activity attributed by the protein surface markers, we sought to profile the protein composition of small EVs released from hMSCs to identify hMSC-EV biomarkers with potential clinical relevance.

METHODS

Small EVs were produced and qualified from five human bone marrow MSC donors at low passage following a 48-h culture in exosome-depleted medium further processed by steps of centrifugation, filtration, and precipitation. Quantitative proteomic analysis comparing the protein profile of the EVs released from hMSCs and their parental cell was conducted using tandem mass tag labeling combined to mass spectrometry (LC-MS/MS) to identify enriched EV protein markers.

RESULTS

Nanoparticle tracking analysis showed no differences in the EV concentration and size among the five hMSC donors (1.83 × 1010 ± 3.23 × 109/mL), with the mode particle size measuring at 109.3 ± 5.7 nm. Transmission electron microscopy confirmed the presence of nanovesicles with bilayer membranes. Flow cytometric analysis identified commonly found exosomal (CD63/CD81) and hMSC (CD105/CD44/CD146) markers from released EVs in addition to surface mediators of migration (CD29 and MCSP). Quantitative proteomic identified 270 proteins significantly enriched by at least twofold in EVs released from hMSCs as compared to parental hMSCs, where neuropilin 1 (NRP1) was identified among 21 membrane-bound proteins regulating the migration and invasion of cells, as well as chemotaxis and vasculogenesis. Validation by western blot of multiple batches of EVs confirmed consistent enrichment of NRP1 in the nanovesicles released from all five hMSC donors.

CONCLUSION

The identification and verification of NRP1 as a novel enriched surface marker from multiple batches of EVs derived from multiple hMSC donors may serve as a biomarker for the assessment and measurement of EVs for therapeutic uses.

Metabolomics Analysis of Mesenchymal Stem Cells

Various mesenchymal stem cells as easily accessible and multipotent cells can share different essential signaling pathways related to their stemness ability. Understanding the mechanism of stemness ability can be useful for controlling the stem cells for regenerative medicine targets. In this context, OMICs studies can analyze the mechanism of different stem cell properties or stemness ability via a broad range of current high-throughput techniques. This field is fundamentally directed toward the analysis of whole genome (genomics), mRNAs (transcriptomics), proteins (proteomics) and metabolites (metabolomics) in biological samples. According to several studies, metabolomics is more effective than other OMICs ّfor various system biology concerns. Metabolomics can elucidate the biological mechanisms of various mesenchymal stem cell function by measuring their metabolites such as their secretome components. Analyzing the metabolic alteration of mesenchymal stem cells can be useful to promote their regenerative medicine application.

Synechococcus elongatus PCC7942 secretes extracellular vesicles to accelerate cutaneous wound healing by promoting angiogenesis

Poor wound healing affects millions of people worldwide each year and needs better therapeutic strategies. Synechococcus elongatus PCC 7942 is a naturally occurring photoautotrophic cyanobacterium that can be easily obtained and large-scale expanded. Here, we investigated the therapeutic efficacy of this cyanobacterium in a mouse model of acute burn injury and whether the secretion of extracellular vesicles (EVs), important mediators of cell paracrine activity, is a key mechanism of the cyanobacterium-induced regulation of wound healing.

Methods: The effects of Synechococcus elongatus PCC 7942 on burn wound healing in mice under light or dark conditions were evaluated by measuring wound closure rates, histological and immunofluorescence analyses. A series of assays in vivo and in vitro were conducted to assess the impact of the cyanobacterium on angiogenesis. GW4869 was used to interfere with the secretion of EVs by the cyanobacterium and the abilities of the GW4869-pretreated and untreated Synechococcus elongatus PCC 7942 to regulate endothelial angiogenesis were compared. The direct effects of the cyanobacterium-derived EVs (S. elongatus-EVs) on angiogenesis, wound healing and expressions of a class of pro-inflammatory factors that have regulatory roles in wound healing were also examined.

Results: Synechococcus elongatus PCC 7942 treatment under light and dark conditions both significantly promoted angiogenesis and burn wound repair in mice. In vitro, the cyanobacterium enhanced angiogenic activities of endothelial cells, but the effects were markedly blocked by GW4869 pretreatment. S. elongatus-EVs were capable of augmenting endothelial angiogenesis in vitro, and stimulating new blood vessel formation and burn wound healing in mice. The expression of interleukin 6 (IL-6), which has an essential role in angiogenesis during skin wound repair, was induced in wound tissues and wound healing-related cells by S. elongatus-EVs and Synechococcus elongatus PCC 7942.

Conclusion: Synechococcus elongatus PCC 7942 has the potential as a promising strategy for therapeutic angiogenesis and wound healing primarily by the delivery of functional EVs, not by its photosynthetic activity. The promotion of IL-6 expression may be a mechanism of the cyanobacterium and its EVs-induced pro-angiogenic and -wound healing effects.

Perspective in Nuclear Theranostics Using Exosome for the Brain

Owing to its highly biocompatible property as naturally produced nanoscale particle and drug carrying ability, exosome has attracted much interest in the biomedical area. Versatile functions of exosome in biological system play an important role in elucidating mysterious and unknown biological processes and pathological disease progression. For usage of exosome as brain disease therapeutics, even though the ability of exosomes crossing blood brain barrier (BBB) is not well clearly proven, the small size and their own characteristics possessing cell-derived molecular contents may provide great and beneficial tools for brain delivery and brain-associated disease therapy. A variety of trials related to bioapplications using stem cell-derived exosome in regenerative therapy or autologous exosome shuttling inhibitor targeting brain disease-associated protein marker enhance possibility of exosome toward clinical application. The radionuclide PET or SPECT imaging of radiolabeled exosome will be clearly able to provide accurate clues for analyzing their whole body distribution, targeting efficacy, and the degree of non-specific tissue uptake. In this perspective, the practical information on thranostics of exosome for brain delivery and therapy is offered and radionuclide-based exosome applicability will be dealt with.

Potential of Exosomes for the Treatment of Stroke

Stroke is the result of blockage or rupture of blood vessels in the brain and is the leading cause of death and disability in the world. Currently only a very limited number of therapeutic approaches are available for treatment of stroke patients, and the vast majority of neuroprotective agents that tested positively in pre-clinical studies failed in clinical trials. In recent years, the clinical value of the use of exosomes for stroke treatment has received widespread attention due their unique characteristics such as low immunogenicity, low toxicity and biodegradability, ability to cross the blood–brain barrier (BBB), and their important role in communication between cells. More and more evidence suggests that the secretion of exosomes is the mechanism underlying the protection induced by mesenchymal stromal cells (MSCs) after stroke. Exosomes are thought to support brain restoration and induce repairing effects, including neurovascular remodeling, and anti-apoptosis and anti-inflammatory effects. Recent reports have focused on the clinical application of exosomes as a potential drug delivery approach. This review focuses on the ability of exosomes to interrupt the stroke-induced pathologic processes of stroke, and on publications describing how to achieve more effective treatment of stroke with exosomes.

Hypoxia-elicited mesenchymal stem cell-derived exosomes facilitates cardiac repair through miR-125b-mediated prevention of cell death in myocardial infarction

Exosomes (Exo) secreted from hypoxia-conditioned bone marrow mesenchymal stem cells (BM-MSCs) were found to be protective for ischemic disease. However, the role of exosomal miRNA in the protective effect of hypoxia-conditioned BM-MSCs-derived Exo (Hypo-Exo) remains largely uncharacterized and the poor specificity of tissue targeting of Exo limits their clinical applications. Therefore, the objective of this study was to examine the effect of miRNA in Hypo-Exo on the repair of ischemic myocardium and its underlying mechanisms. We further developed modified Hypo-Exo with high specificity to the myocardium and evaluate its therapeutic effects.

Methods: Murine BM-MSCs were subjected to hypoxia or normoxia culture and Exo were subsequently collected. Hypo-Exo or normoxia-conditioned BM-MSC-derived Exo (Nor-Exo) were administered to mice with permanent condition of myocardial infarction (MI). After 28 days, to evaluate the therapeutic effects of Hypo-Exo, infarction area and cardio output in Hypo-Exo and Nor-Exo treated MI mice were compared through Masson's trichrome staining and echocardiography respectively. We utilized the miRNA array to identify the significantly differentially expressed miRNAs between Nor-Exo and Hypo-Exo. One of the most enriched miRNA in Hypo-Exo was knockdown by applying antimiR in Hypoxia-conditioned BM-MSCs. Then we performed intramyocardial injection of candidate miRNA-knockdown-Hypo-Exo in a murine MI model, changes in the candidate miRNA's targets expression of cardiomyocytes and the cardiac function were characterized. We conjugated Hypo-Exo with an ischemic myocardium-targeted (IMT) peptide by bio-orthogonal chemistry, and tested its targeting specificity and therapeutic efficiency via systemic administration in the MI mice.

Results: The miRNA array revealed significant enrichment of miR-125b-5p in Hypo-Exo compared with Nor-Exo. Administration of miR-125b knockdown Hypo-Exo significantly increased the infarction area and suppressed cardiomyocyte survival post-MI. Mechanistically, miR-125b knockdown Hypo-Exo lost the capability to suppress the expression of the proapoptotic genes p53 and BAK1 in cardiomyocytes. Intravenous administration of IMT-conjugated Hypo-Exo (IMT-Exo) showed specific targeting to the ischemic lesions in the injured heart and exerted a marked cardioprotective function post-MI.

Conclusion: Our results illustrate a new mechanism by which Hypo-Exo-derived miR125b-5p facilitates ischemic cardiac repair by ameliorating cardiomyocyte apoptosis. Furthermore, our IMT- Exo may serve as a novel drug carrier that enhances the specificity of drug delivery for ischemic disease.

Multicellular Crosstalk Between Exosomes and the Neurovascular Unit After Cerebral Ischemia. Therapeutic Implications

Restorative strategies after stroke are focused on the remodeling of cerebral endothelial cells and brain parenchymal cells. The latter, i.e., neurons, neural precursor cells and glial cells, synergistically interact with endothelial cells in the ischemic brain, providing a neurovascular unit (NVU) remodeling that can be used as target for stroke therapies. Intercellular communication and signaling within the NVU, the multicellular brain-vessel-blood interface, including its highly selective blood-brain barrier, are fundamental to the central nervous system homeostasis and function. Emerging research designates cell-derived extracellular vesicles and especially the nano-sized exosomes, as a complex mean of cell-to-cell communication, with potential use for clinical applications. Through their richness in active molecules and biological information (e.g., proteins, lipids, genetic material), exosomes contribute to intercellular signaling, a condition particularly required in the central nervous system. Cerebral endothelial cells, perivascular astrocytes, pericytes, microglia and neurons, all part of the NVU, have been shown to release and uptake exosomes. Also, exosomes cross the blood-brain and blood-cerebrospinal fluid barriers, allowing communication between periphery and brain, in normal and disease conditions. As such exosomes might be a powerful diagnostic tool and a promising therapeutic shuttle of natural nanoparticles, but also a means of disease spreading (e.g., immune system modulation, pro-inflammatory action, propagation of neurodegenerative factors). This review highlights the importance of exosomes in mediating the intercellular crosstalk within the NVU and reveals the restorative therapeutic potential of exosomes harvested from multipotent mesenchymal stem cells in ischemic stroke, a frequent neurologic condition lacking an efficient therapy.

Application of Mesenchymal Stem Cell-Derived Extracellular Vesicles for Stroke: Biodistribution and MicroRNA Study

Mesenchymal stem cells (MSCs) exert their therapeutic capability through a variety of bioactive substances, including trophic factors, microRNAs, and extracellular vesicles (EVs) in infarcted tissues. We therefore hypothesized that MSC-derived EVs (MSC-EVs) possess therapeutic molecules similar to MSCs. Moreover, given their nature as nanosized and lipid-shielded particles, the intravenous infusion of MSC-EVs would be advantageous over MSCs as a safer therapeutic approach. In this study, we investigated the biodistribution, therapeutic efficacy, and mode of action of MSC-EVs in a rat stroke model. MSC-EVs successfully stimulated neurogenesis and angiogenesis in vivo. When compared to the MSC-treated group, rats treated with MSC-EVs exhibited greater behavioral improvements than the control group (p < 0.05). Our biodistribution study using fluorescence-labeled MSC-EVs and MSCs demonstrated that the amounts of MSC-EVs in the infarcted hemisphere increased in a dose-dependent manner, and were rarely found in the lung and liver. In addition, MSC-EVs were highly inclusive of various proteins and microRNAs (miRNAs) associated with neurogenesis and/or angiogenesis compared to fibro-EVs. We further analyzed those miRNAs and found that miRNA-184 and miRNA-210 were essential for promoting neurogenesis and angiogenesis of MSC-EVs, respectively. MSC-EVs represent an ideal alternative to MSCs for stroke treatment, with similar medicinal capacity but an improved safety profile that overcomes cell-associated limitations in stem cell therapy.

Potential of Extracellular Vesicles in Neurodegenerative Diseases: Diagnostic and Therapeutic Indications

Extracellular vesicles (EVs) are membrane-bound vesicles, including exosomes and microvesicles. EVs are nanometer sized, found in physiological fluids such as urine, blood, cerebro-spinal fluid (CSF), with a capacity of transferring various biological materials such as microRNAs, proteins, and lipids among cells without direct cell-to-cell contact. Many cells in the nervous system have been shown to release EVs. These vesicles are involved in intercellular communication and a variety of biological processes such as modulation of immune response, signal transduction, and transport of genetic materials with low immunogenicity; therefore, they have also been recently investigated for the delivery of therapeutic molecules such as siRNAs and drugs in the treatment of diseases. In addition, since EV components reflect the physiological status of the cells and tissues producing them, they can be utilized as biomarkers for early detection of various diseases. In this review, we summarize EV application, in diagnosis as biomarker sources and as a carrier tool for drug delivery in EV-based therapies in neurodegenerative diseases.