Exosome-shuttled miR-92b-3p from ischemic preconditioned astrocytes protects neurons against oxygen and glucose deprivation

Research progress on astrocyte-derived extracellular vesicles in the pathogenesis and treatment of neurodegenerative diseases

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), pose significant global health risks and represent a substantial public health concern in the contemporary era. A primary factor in the pathophysiology of these disorders is aberrant accumulation and aggregation of pathogenic proteins within the brain and spinal cord. Recent investigations have identified extracellular vesicles (EVs) in the central nervous system (CNS) as potential carriers for intercellular transport of misfolded proteins associated with neurodegenerative diseases. EVs are involved in pathological processes that contribute to various brain disorders including neurodegenerative disorders. Proteins linked to neurodegenerative disorders are secreted and distributed from cell to cell via EVs, serving as a mechanism for direct intercellular communication through the transfer of biomolecules. Astrocytes, as active participants in CNS intercellular communication, release astrocyte-derived extracellular vesicles (ADEVs) that are capable of interacting with diverse target cells. This review primarily focuses on the involvement of ADEVs in the development of neurological disorders and explores their potential dual roles - both advantageous and disadvantageous in the context of neurological disorders. Furthermore, this review examines the current studies investigating ADEVs as potential biomarkers for the diagnosis and treatment of neurodegenerative diseases. The prospects and challenges associated with the application of ADEVs in clinical settings were also comprehensively reviewed.

miR-92b-3p Protects against Myocardial Ischemia-Reperfusion Injury by Inhibiting MAP3K2 in a Mouse Model

OBJECTIVE

 MicroRNAs are well-known RNA regulators modulating biological functions in complex signaling networks. This work aims to explore the impact of microRNA-92b-3p (miR-92b-3p) on myocardial ischemia-reperfusion (I/R) injury.

MATERIALS AND METHODS

 The I/R model was established by left anterior descending coronary artery ligation in mice. The hemodynamic parameters were detected through a multichannel physiological recorder. Myocardial injury markers: serum cardiac troponin I, myocardial kinase isoenzyme (creatine kinase-MB), and serum inflammatory factors (tumor necrosis factor-α, interleukin [IL]-1β, and IL-6) were evaluated by enzyme-linked immunosorbent assay. Cardiac tissue oxidative stress-related factors (malondialdehyde, glutathione peroxidase, total antioxidation capability, and superoxide dismutase) were assessed by colorimetry, myocardial pathology was observed by hematoxylin-eosin staining, and cardiomyocyte apoptosis was measured by triphosphate nick end-labeling staining, as well as the expression of miR-92b-3p and mitogen-activated protein kinase kinase kinase 2 (MAP3K2) in cardiac tissues were determined by reverse transcription quantitative polymerase chain reaction or western blot assay. The targeting relationship between miR-92b-3p and MAP3K2 was verified by bioinformatics, RNA immunoprecipitation, and luciferase reporter assays.

RESULTS

 miR-92b-3p was lowly expressed and MAP3K2 was highly expressed in myocardial I/R injury mice. Upregulation of miR-92b-3p improved hemodynamic indices, decreased serum levels of myocardial injury biomarkers, inhibited serum inflammatory response, alleviated cardiac tissue oxidative stress, relieved myocardial pathology, and reduced cardiomyocyte apoptosis during the myocardial I/R injury in mice. MAP3K2 was a direct target gene of miR-92b-3p.

CONCLUSION

 This research suggests that miR-92b-3p protects against myocardial I/R injury by inhibiting MAP3K2, which may provide novel candidates for treatment of myocardial I/R injury.

Extracellular vesicles: Mediators of microenvironment in hypoxia-associated neurological diseases

Hypoxia is a prevalent characteristic of numerous neurological disorders including stroke, Alzheimer's disease, and Parkinson's disease. Extracellular vesicles (EVs) are minute particles released by cells that contain diverse biological materials, including proteins, lipids, and nucleic acids. They have been implicated in a range of physiological and pathological processes including intercellular communication, immune responses, and disease progression. EVs are believed to play a pivotal role in modulating the microenvironment of hypoxia-associated neurological diseases. These EVs are capable of transporting hypoxia-inducible factors such as proteins and microRNAs to neighboring or remote cells, thereby influencing their behavior. Furthermore, EVs can traverse the blood-brain barrier, shielding the brain from detrimental substances in the bloodstream. This enables them to deliver their payload directly to the brain cells, potentially intensifying the effects of hypoxia. Nonetheless, the capacity of EVs to breach the blood-brain barrier presents new opportunities for drug delivery. The objective of this study was to elucidate the role of EVs as mediators of information exchange during tissue hypoxia, a pathophysiological process in ischemic stroke and malignant gliomas. We also investigated their involvement in the progression and regression of major diseases of the central nervous system, which are pertinent to the development of therapeutic interventions for neurological disorders.

Understanding exosomes: Part 2-Emerging leaders in regenerative medicine

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with the ability to communicate with other tissues and cell types over long distances. Their use in regenerative medicine has gained tremendous momentum recently due to their ability to be utilized as therapeutic options for a wide array of diseases/conditions. Over 5000 publications are currently being published yearly on this topic, and this number is only expected to dramatically increase as novel therapeutic strategies continue to be developed. Today exosomes have been applied in numerous contexts including neurodegenerative disorders (Alzheimer's disease, central nervous system, depression, multiple sclerosis, Parkinson's disease, post-traumatic stress disorders, traumatic brain injury, peripheral nerve injury), damaged organs (heart, kidney, liver, stroke, myocardial infarctions, myocardial infarctions, ovaries), degenerative processes (atherosclerosis, diabetes, hematology disorders, musculoskeletal degeneration, osteoradionecrosis, respiratory disease), infectious diseases (COVID-19, hepatitis), regenerative procedures (antiaging, bone regeneration, cartilage/joint regeneration, osteoarthritis, cutaneous wounds, dental regeneration, dermatology/skin regeneration, erectile dysfunction, hair regrowth, intervertebral disc repair, spinal cord injury, vascular regeneration), and cancer therapy (breast, colorectal, gastric cancer and osteosarcomas), immune function (allergy, autoimmune disorders, immune regulation, inflammatory diseases, lupus, rheumatoid arthritis). This scoping review is a first of its kind aimed at summarizing the extensive regenerative potential of exosomes over a broad range of diseases and disorders.

Astrocyte-Derived Exosomal miR-148a-3p Suppresses Neuroinflammation and Restores Neurological Function in Traumatic Brain Injury by Regulating the Microglial Phenotype

Interactions between astrocytes and microglia play an important role in the regeneration and repair of traumatic brain injury (TBI), and exosomes are involved in cell-cell interactions. A TBI model was constructed in rats. Brain extract (Ext) was isolated 1 d after TBI. Astrocyte-derived exosomes were obtained by coculturing Ext with primary astrocytes, and the morphology of exosomes was observed by electron microscopy. The isolated exosomes were cocultured with microglia to observe phenotypic changes in M1 and M2 markers. Aberrant RNA expression was detected in necrotic brain tissue and edematous brain tissue. The role of miR-148a-3p in regulating microglial phenotype was explored by knocking down or overexpressing miR-148a-3p. Finally, the effect of miR-148a-3p on TBI was studied in a rat TBI model. Astrocyte-derived exosomes stimulated by Ext promoted the transition of microglia from the M1 phenotype to the M2 phenotype. MiR-148a-3p was highly expressed in TBI. Transfecting miR-148a-3p promoted the transition of microglia from the M1 phenotype to the M2 phenotype and inhibited the lipopolysaccharide-induced inflammatory response in pre-microglia. In a rat TBI model, miR-148a-3p significantly improved the modified neurological severity score and attenuated brain injury, which promoted the transition of microglia from the M1 phenotype to the M2 phenotype. MiR-148a-3p alleviated TBI by inhibiting the nuclear factor κB pathway. Astrocyte-derived exosomal miR-148a-3p regulates the microglial phenotype, inhibits neuroinflammation, and restores neurological function in TBI. These results provide new potential targets for the treatment of TBI.

Oxygen glucose deprivation-pretreated astrocyte-derived exosomes attenuates intracerebral hemorrhage (ICH)-induced BBB disruption through miR-27a-3p /ARHGAP25/Wnt/β-catenin axis

BACKGROUND

Blood brain barrier (BBB) breakdown is one of the key mechanisms of secondary brain injury following intracerebral hemorrhage (ICH). Astrocytes interact with endothelial and regulate BBB integrity via paracrine signaling factors. More and more studies reveal astrocyte-derived extracellular vesicles (ADEVs) as an important way of intercellular communication. However, the role of ADEV in BBB integrity after ICH remains unclear.

METHODS

ADEVs were obtained from astrocytes with or without oxygen and glucose deprivation (OGD) pre-stimulation and the role of ADEVs in ICH was investigated using ICH mice model and ICH cell model. The potential regulatory effect of ADEVs on endothelial barrier integrity was identified by TEER, western blot and immunofluorescence in vitro. In vivo, functional evaluation, Evans-blue leakage and tight junction proteins (TJPs) expression were analyzed. MiRNA sequencing revealed that microRNA-27a-3p (miR-27a-3p) was differentially expressed miRNA in the EVs from OGD-pretreated astrocytes compared with normal control. The regulatory mechanism of miR-27a-3p was assessed using Luciferase assay, RT-PCR, western blot and immunofluorescence.

RESULTS

OGD-activated astrocytes reduced hemin-induced endothelial hyper-permeability through secreting EVs. OGD-activated ADEVs alleviated BBB dysfunction after ICH in vivo and in vitro. MicroRNA microarray analysis indicated that miR-27a-3p is a major component that was highly expressed miRNA in OGD pretreated-ADEVs. OGD-ADEVs mitigated BBB injury through transferring miR-27a-3p into bEnd.3 cells and regulating ARHGAP25/Wnt/β-catenin pathway.

CONCLUSION

Taken together, these findings firstly revealed that miR-27a-3p, as one of the main components of OGD-pretreated ADEVs, attenuated BBB destruction and improved neurological deficits following ICH by regulating endothelial ARHGAP25/Wnt/β-catenin axis. OGD-ADEVs might be a novel strategy for the treatment of ICH. this study implicates that EVs from OGD pre-stimulated astrocytes.

A New Paradigm in Spinal Cord Injury Therapy: from Cell-free Treatment to Engineering Modifications

Spinal cord injury (SCI) is an intractable and poorly prognostic neurological disease, and current treatments are still unable to cure it completely and avoid sequelae. Extracellular vesicles (EVs), as important carriers of intercellular communication and pharmacological effects, are considered to be the most promising candidates for SCI therapy because of their low toxicity and immunogenicity, their ability to encapsulate endogenous bioactive molecules (e.g., proteins, lipids, and nucleic acids), and their ability to cross the blood-brain/cerebrospinal barriers. However, poor targeting, low retention rate, and limited therapeutic efficacy of natural EVs have bottlenecked EVs-based SCI therapy. A new paradigm for SCI treatment will be provided by engineering modified EVs. Furthermore, our limited understanding of the role of EVs in SCI pathology hinders the rational design of novel EVbased therapeutic approaches. In this study, we review the pathophysiology after SCI, especially the multicellular EVs-mediated crosstalk; briefly describe the shift from cellular to cell-free therapies for SCI treatment; discuss and analyze the issues related to the route and dose of EVs administration; summarize and present the common strategies for EVs drug loading in the treatment of SCI and point out the shortcomings of these drug loading methods; finally, we analyze and highlight the feasibility and advantages of bio-scaffold-encapsulated EVs for SCI treatment, providing scalable insights into cell-free therapy for SCI.

Neuroprotective astroglial response to neural damage and its relevance to affective disorders

Astrocytes not only support neuronal function with essential roles in synaptic neurotransmission, action potential propagation, metabolic support, or neuroplastic and developmental adaptations. They also respond to damage or dysfunction in surrounding neurons and oligodendrocytes by releasing neurotrophic factors and other molecules that increase the survival of the supported cells or contribute to mechanisms of structural and molecular restoration. The neuroprotective responsiveness of astrocytes is based on their ability to sense signals of degeneration, metabolic jeopardy and structural damage, and on their aptitude to locally deliver specific molecules to remedy threats to the molecular and structural features of their cellular partners. To the extent that neuronal and other glial cell disturbances are known to occur in affective disorders, astrocyte responsiveness to those disturbances may help to better understand the roles astrocytes play in affective disorders. The astrocytic sensing apparatus supporting those responses involves receptors for neurotransmitters, purines, cell adhesion molecules and growth factors. Astrocytes also share with the immune system the capacity of responding to cytokines released upon neuronal damage. In addition, in responses to specific signals astrocytes release unique factors such as clusterin or humanin that have been shown to exert potent neuroprotective effects. Astrocytes integrate the signals above to further deliver structural lipids, removing toxic metabolites, stabilizing the osmotic environment, normalizing neurotransmitters, providing anti-oxidant protection, facilitating synaptogenesis and acting as barriers to contain varied deleterious signals, some of which have been described in brain regions relevant to affective disorders and related animal models. Since various of the injurious signals that activate astrocytes have been implicated in different aspects of the etiopathology of affective disorders, particularly in relation to the diagnosis of depression, potentiating the corresponding astrocyte neuroprotective responses may provide additional opportunities to improve or complement available pharmacological and behavioral therapies for affective disorders.

Role of hypoxic exosomes and the mechanisms of exosome release in the CNS under hypoxic conditions

Hypoxia is characterized by low oxygen levels in the body or environment, resulting in various physiological and pathological changes. The brain, which has the highest oxygen consumption of any organ, is particularly susceptible to hypoxic injury. Exposure to low-pressure hypoxic environments can cause irreversible brain damage. Hypoxia can occur in healthy individuals at high altitudes or in pathological conditions such as trauma, stroke, inflammation, and autoimmune and neurodegenerative diseases, leading to severe brain damage and impairments in cognitive, learning, and memory functions. Exosomes may play a role in the mechanisms of hypoxic injury and adaptation and are a current focus of research. Investigating changes in exosomes in the central nervous system under hypoxic conditions may aid in preventing secondary damage caused by hypoxia. This paper provides a brief overview of central nervous system injury resulting from hypoxia, and aimed to conduct a comprehensive literature review to assess the pathophysio-logical impact of exosomes on the central nervous system under hypoxic conditions.

Extracellular Vesicles in Neurodegenerative Diseases: An Update

Neurodegenerative diseases affect millions of people worldwide. The likelihood of developing a neurodegenerative disease rises dramatically as life expectancy increases. Although it has drawn significant attention, there is still a lack of proper effective treatments for neurodegenerative disease because the mechanisms of its development and progression are largely unknown. Extracellular vesicles (EVs) are small bi-lipid layer-enclosed nanosized particles in tissues and biological fluids. EVs are emerging as novel intercellular messengers and regulate a series of biological responses. Increasing evidence suggests that EVs are involved in the pathogenesis of neurodegenerative disorders. In this review, we summarize the recent findings of EVs in neurodegenerative diseases and bring up the limitations in the field.

Klotho Upregulation via PPARγ Contributes to the Induction of Brain Ischemic Tolerance by Cerebral Ischemic Preconditioning in Rats

Cerebral ischemic preconditioning (CIP)-induced brain ischemic tolerance protects neurons from subsequent lethal ischemic insult. However, the specific mechanisms underlying CIP remain unclear. In the present study, we explored the hypothesis that peroxisome proliferator-activated receptor gamma (PPARγ) participates in the upregulation of Klotho during the induction of brain ischemic tolerance by CIP. First we investigated the expression of Klotho during the brain ischemic tolerance induced by CIP. Lethal ischemia significantly decreased Klotho expression from 6 h to 7 days, while CIP significantly increased Klotho expression from 12 h to 7 days in the hippocampal CA1 region. Inhibition of Klotho expression by its shRNA blocked the neuroprotection induced by CIP. These results indicate that Klotho participates in brain ischemic tolerance by CIP. Furthermore, we tested the role of PPARγ in regulating Klotho expression after CIP. CIP caused PPARγ protein translocation to the nucleus in neurons in the CA1 region of the hippocampus. Pretreatment with GW9962, a PPARγ inhibitor, significantly attenuated the upregulation of Klotho protein and blocked the brain ischemic tolerance induced by CIP. Taken together, it can be concluded that Klotho upregulation via PPARγ contributes to the induction of brain ischemic tolerance by CIP.

Immune response following traumatic spinal cord injury: Pathophysiology and therapies

Traumatic spinal cord injury (SCI) is a devastating condition that is often associated with significant loss of function and/or permanent disability. The pathophysiology of SCI is complex and occurs in two phases. First, the mechanical damage from the trauma causes immediate acute cell dysfunction and cell death. Then, secondary mechanisms of injury further propagate the cell dysfunction and cell death over the course of days, weeks, or even months. Among the secondary injury mechanisms, inflammation has been shown to be a key determinant of the secondary injury severity and significantly worsens cell death and functional outcomes. Thus, in addition to surgical management of SCI, selectively targeting the immune response following SCI could substantially decrease the progression of secondary injury and improve patient outcomes. In order to develop such therapies, a detailed molecular understanding of the timing of the immune response following SCI is necessary. Recently, several studies have mapped the cytokine/chemokine and cell proliferation patterns following SCI. In this review, we examine the immune response underlying the pathophysiology of SCI and assess both current and future therapies including pharmaceutical therapies, stem cell therapy, and the exciting potential of extracellular vesicle therapy.

Enhanced BPGM/2,3-DPG pathway activity suppresses glycolysis in hypoxic astrocytes via FIH-1 and TET2

OBJECTIVE

Bisphosphoglycerate mutase (BPGM) is expressed in human erythrocytes and responsible for the production of 2,3-bisphosphoglycerate (2,3-DPG). However, the expression and role of BPGM in other cells have not been reported. In this work, we found that BPGM was significantly upregulated in astrocytes upon acute hypoxia, and the role of this phenomenon will be clarified in the following report.

METHODS

The mRNA and protein expression levels of BPGM and the content of 2,3-DPG with hypoxia treatment were determined in vitro and in vivo. Furthermore, glycolysis was evaluated upon in hypoxic astrocytes with BPGM knockdown and in normoxic astrocytes with BPGM overexpression or 2,3-DPG treatment. To investigate the mechanism by which BPGM/2,3-DPG regulated glycolysis in hypoxic astrocytes, we detected the expression of HIF-1α, FIH-1 and TET2 with silencing or overexpression of BPGM and 2,3-DPG treatment.

RESULTS

The expression of glycolytic genes and the capacity of lactate markedly increased with 6 h, 12 h, 24 h, 36 h and 48 h 1 % O₂ hypoxic treatment in astrocytes. The expression of BPGM was upregulated, and the production of 2,3-DPG was accelerated upon hypoxia. Moreover, when BPGM expression was knocked down, glycolysis was promoted in HEB cells. However, overexpression of BPGM and addition of 2,3-DPG to the cellular medium in normoxic cells could downregulate glycolytic genes. Furthermore, HIF-1α and TET2 exhibited higher expression levels and FIH-1 showed a lower expression level upon BPGM silencing, while these changes were reversed under BPGM overexpression and 2,3-DPG treatment.

CONCLUSIONS

Our study revealed that the BPGM/2,3-DPG pathway presented a suppressive effect on glycolysis in hypoxic astrocytes by negatively regulating HIF-1α and TET2.

Bidirectional Communication Between Microglia and Astrocytes in Neuroinflammation

Neuroinflammation is a common feature of diverse nervous system pathologies. In many instances, it begins at an early stage of the disease, paving the way for further exacerbations. The main drivers of neuroinflammation are brain-resident glial cells, such as microglia and astrocytes. Microglia are the primary responders to any insult to the brain parenchyma, translating the signals into diverse molecules. These molecules derived from microglia can regulate the stimuli-dependent reactivity of astrocytes. Once activated, astrocytes in turn, can control microglia phenotypes. Recent evidence indicates that the crosstalk between these glial cells plays an important role in delaying or accelerating neuroinflammation and overall disease progression. To date, various molecules have been recognized as key mediators of the bidirectional communication between microglia and astrocytes. The current review aims to discuss the novel molecules identified recently, which play a critical role in interglial crosstalk, highlighting their therapeutic potential.

Analysis of the Research Hotspot of Exosomes in Cardiovascular Disease: A Bibliometric-based Literature Review

OBJECTIVE

To investigate the current status and development trend of research on exosomes in cardiovascular disease (CVD) using bibliometric analysis and to elucidate trending research topics.

METHODS

Research articles on exosomes in CVD published up to April 2022 were retrieved from the Web of Science database. Data were organized using Microsoft Office Excel 2019. CiteSpace 6.1 and VOSviewer 1.6.18 were used for bibliometric analysis and result visualization.

RESULTS

Overall, 256 original research publications containing 190 fundamental research publications and 66 clinical research publications were included. "Extracellular vesicle" was the most frequent research keyword, followed by "microrna," "apoptosis," and "angiogenesis." Most publications were from China (187, 73.05%), followed by the United States (57, 22.27%), the United Kingdom (7, 2.73%), and Japan (7, 2.73%). A systematic review of the publications revealed that myocardial infarction and stroke were the most popular topics and that exosomes and their contents, such as microRNAs (miRNAs), play positive roles in neuroprotection, inhibition of autophagy and apoptosis, promotion of angiogenesis, and protection of cardiomyocytes.

CONCLUSION

Research on exosomes in CVD has attracted considerable attention, with China having the most published studies. Fundamental research has focused on CVD pathogenesis; exosomes regulate the progression of CVD through biological processes, such as the inflammatory response, autophagy, and apoptosis. Clinical research has focused on biomarkers for CVD; studies on using miRNAs in exosomes as disease markers for diagnosis could become a future trend.

Effects and Mechanisms of Exosomes from Different Sources in Cerebral Ischemia

Cerebral ischemia refers to the symptom of insufficient blood supply to the brain. Cells of many different origins participate in the process of repairing damage after cerebral ischemia occurs, in which exosomes secreted by the cells play important roles. For their characteristics, such as small molecular weight, low immunogenicity, and the easy penetration of the blood-brain barrier (BBB), exosomes can mediate cell-to-cell communication under pathophysiological conditions. In cerebral ischemia, exosomes can reduce neuronal damage and improve the brain microenvironment by regulating inflammation, mediating pyroptosis, promoting axonal growth, and stimulating vascular remodeling. Therefore, exosomes have an excellent application prospect for the treatment of cerebral ischemia. This article reviews the roles and mechanisms of exosomes from different sources in cerebral ischemia and provides new ideas for the prevention and treatment of cerebral ischemia.

Mesenchymal stem cell therapy for ischemic stroke: Novel insight into the crosstalk with immune cells

Stroke, a cerebrovascular accident, is prevalent and the second highest cause of death globally across patient populations; it is as a significant cause of morbidity and mortality. Mesenchymal stem cell (MSC) transplantation is emerging as a promising treatment for alleviating neurological deficits, as indicated by a great number of animal and clinical studies. The potential of regulating the immune system is currently being explored as a therapeutic target after ischemic stroke. This study will discuss recent evidence that MSCs can harness the immune system by interacting with immune cells to boost neurologic recovery effectively. Moreover, a notion will be given to MSCs participating in multiple pathological processes, such as increasing cell survival angiogenesis and suppressing cell apoptosis and autophagy in several phases of ischemic stroke, consequently promoting neurological function recovery. We will conclude the review by highlighting the clinical opportunities for MSCs by reviewing the safety, feasibility, and efficacy of MSCs therapy.

Modulation of Small RNA Signatures by Astrocytes on Early Neurodegeneration Stages; Implications for Biomarker Discovery

Diagnosis of neurodegenerative disease (NDD) is complex, therefore simpler, less invasive, more accurate biomarkers are needed. small non-coding RNA (sncRNA) dysregulates in NDDs and sncRNA signatures have been explored for the diagnosis of NDDs, however, the performance of previous biomarkers is still better. Astrocyte dysfunction promotes neurodegeneration and thus derived scnRNA signatures could provide a more precise way to identify of changes related to NDD course and pathogenesis, and it could be useful for the dissection of mechanistic insights operating in NDD. Often sncRNA are transported outside the cell by the action of secreted particles such as extracellular vesicles (EV), which protect sncRNA from degradation. Furthermore, EV associated sncRNA can cross the BBB to be found in easier to obtain peripheral samples, EVs also inherit cell-specific surface markers that can be used for the identification of Astrocyte Derived Extracellular Vesicles (ADEVs) in a peripheral sample. By the study of the sncRNA transported in ADEVs it is possible to identify astrocyte specific sncRNA signatures that could show astrocyte dysfunction in a more simpler manner than previous methods. However, sncRNA signatures in ADEV are not a copy of intracellular transcriptome and methodological aspects such as the yield of sncRNA produced in ADEV or the variable amount of ADEV captured after separation protocols must be considered. Here we review the role as signaling molecules of ADEV derived sncRNA dysregulated in conditions associated with risk of neurodegeneration, providing an explanation of why to choose ADEV for the identification of astrocyte-specific transcriptome. Finally, we discuss possible limitations of this approach and the need to improve the detection limits of sncRNA for the use of ADEV derived sncRNA signatures.

MicroRNA: A Linking between Astrocyte Dysfunction, Mild Cognitive Impairment, and Neurodegenerative Diseases

Simple Summary

Neurodegenerative diseases are complex neurological disorders with a high incidence worldwide in older people, increasing hospital visits and requiring expensive treatments. As a precursor phase of neurodegenerative diseases, cognitive impairment needs to be studied to understand the factors that influence its development and improve patients’ quality of life. The present review compiles possible factors and biomarkers for diagnosing mild cognitive impairment based on the most recent studies involving miRNAs. These molecules can direct the gene expression in multiple cells, affecting their behavior under certain conditions, such as stressing factors. This review encourages further research into biomarkers that identify cognitive impairment in cellular models such as astrocytes, which are brain cells capable of maintaining the optimal conditions for the central nervous system functioning.

Abstract

The importance of miRNAs in cellular processes and their dysregulation has taken significant importance in understanding different pathologies. Due to the constant increase in the prevalence of neurodegenerative diseases (ND) worldwide and their economic impact, mild cognitive impairment (MCI), considered a prodromal phase, is a logical starting point to study this public health problem. Multiple studies have established the importance of miRNAs in MCI, including astrocyte regulation during stressful conditions. Additionally, the protection mechanisms exerted by astrocytes against some damage in the central nervous system (CNS) lead to astrocytic reactivation, in which a differential expression of miRNAs has been shown. Nevertheless, excessive reactivation can cause neurodegeneration, and a clear pattern defining the equilibrium point between a neuroprotective or detrimental astrocytic phenotype is unknown. Therefore, the miRNA expression has gained significant attention to understand the maintenance of brain balance and improve the diagnosis and treatment at earlier stages in the ND. Here, we provide a comprehensive review of the emerging role of miRNAs in cellular processes that contribute to the loss of cognitive function, including lipotoxicity, which can induce chronic inflammation, also considering the fundamental role of astrocytes in brain homeostasis.

Exosomes in Alpha-Synucleinopathies: Propagators of Pathology or Potential Candidates for Nanotherapeutics?

The pathological accumulation of alpha-synuclein governs the pathogenesis of neurodegenerative disorders, such as Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy, collectively termed alpha-synucleinopathies. Alpha-synuclein can be released in the extracellular space, partly via exosomes, and this extracellular protein pool may contribute to disease progression by facilitating the spread of pathological alpha-synuclein or activating immune cells. The content of exosomes depends on their origin and includes specific proteins, lipids, functional mRNAs and various non-coding RNAs. Given their ability to mediate intercellular communication via the transport of multilevel information, exosomes are considered to be transporters of toxic agents. Beyond neurons, glial cells also release exosomes, which may contain inflammatory molecules and this glia-to-neuron or neuron-to-glia transmission of exosomal alpha-synuclein may contribute to the propagation of pathology and neuroinflammation throughout the brain. In addition, as their content varies as per their originating and recipient cells, these vesicles can be utilized as a diagnostic biomarker for early disease detection, whereas targeted exosomes may be used as scaffolds to deliver therapeutic agents into the brain. This review summarizes the current knowledge regarding the role of exosomes in the progression of alpha-synuclein-related pathology and their potential use as biomarkers and nanotherapeutics in alpha-synucleinopathies.

Role of exosomes in the pathogenesis, diagnosis, and treatment of central nervous system diseases

Central nervous system (CNS) diseases, such as multiple sclerosis, Alzheimer's disease (AD), and Parkinson’s disease (PD), affect millions of people around the world. Great efforts were put in disease related research, but few breakthroughs have been made in the diagnostic and therapeutic approaches. Exosomes are cell-derived extracellular vesicles containing diverse biologically active molecules secreted by their cell of origin. These contents, including nucleic acids, proteins, lipids, amino acids, and metabolites, can be transferred between different cells, tissues, or organs, regulating various intercellular cross-organ communications and normal and pathogenic processes. Considering that cellular environment and cell state strongly impact the content and uptake efficiency of exosomes, their detection in biological fluids and content composition analysis potentially offer a multicomponent diagnostic readout of several human diseases. Recently, studies have found that aberrant secretion and content of exosomes are closely related to the pathogenesis of CNS diseases. Besides, loading natural cargoes, exosomes can deliver drugs cross the blood brain barrier, making them emerging candidates of biomarkers and therapeutics for CNS diseases. In this review, we summarize and discuss the advanced research progress of exosomes in the pathological processes of several CNS diseases in regarding with neuroinflammation, CNS repair, and pathological protein aggregation. Moreover, we propose the therapeutic strategies of applying exosomes to the diagnosis, early detection, and treatment of CNS diseases.

Neuroprotective and Neurotoxic Effects of Glial-Derived Exosomes

Exosomes derived from glial cells such as astrocytes, microglia, and oligodendrocytes can modulate cell communication in the brain and exert protective or neurotoxic effects on neurons, depending on the environmental context upon their release. Their isolation, characterization, and analysis under different conditions in vitro, in animal models and samples derived from patients has allowed to define the participation of other molecular mechanisms behind neuroinflammation and neurodegeneration spreading, and to propose their use as a potential diagnostic tool. Moreover, the discovery of specific molecular cargos, such as cytokines, membrane-bound and soluble proteins (neurotrophic factors, growth factors, misfolded proteins), miRNA and long-non-coding RNA, that are enriched in glial-derived exosomes with neuroprotective or damaging effects, or their inhibitors can now be tested as therapeutic tools. In this review we summarize the state of the art on how exosomes secretion by glia can affect neurons and other glia from the central nervous system in the context of neurodegeneration and neuroinflammation, but also, on how specific stress stimuli and pathological conditions can change the levels of exosome secretion and their properties.

Crosstalk of Astrocytes and Other Cells during Ischemic Stroke

Stroke is a leading cause of death and long-term disability worldwide. Astrocytes structurally compose tripartite synapses, blood–brain barrier, and the neurovascular unit and perform multiple functions through cell-to-cell signaling of neurons, glial cells, and vasculature. The crosstalk of astrocytes and other cells is complicated and incompletely understood. Here we review the role of astrocytes in response to ischemic stroke, both beneficial and detrimental, from a cell–cell interaction perspective. Reactive astrocytes provide neuroprotection through antioxidation and antiexcitatory effects and metabolic support; they also contribute to neurorestoration involving neurogenesis, synaptogenesis, angiogenesis, and oligodendrogenesis by crosstalk with stem cells and cell lineage. In the meantime, reactive astrocytes also play a vital role in neuroinflammation and brain edema. Glial scar formation in the chronic phase hinders functional recovery. We further discuss astrocyte enriched microRNAs and exosomes in the regulation of ischemic stroke. In addition, the latest notion of reactive astrocyte subsets and astrocytic activity revealed by optogenetics is mentioned. This review discusses the current understanding of the intimate molecular conversation between astrocytes and other cells and outlines its potential implications after ischemic stroke. “Neurocentric” strategies may not be sufficient for neurological protection and recovery; future therapeutic strategies could target reactive astrocytes.

The Emerging Role of Extracellular Vesicle Derived From Neurons/Neurogliocytes in Central Nervous System Diseases: Novel Insights Into Ischemic Stroke

Neurons and neurogliocytes (oligodendrocytes, astrocytes, and microglia) are essential for maintaining homeostasis of the microenvironment in the central nervous system (CNS). These cells have been shown to support cell-cell communication via multiple mechanisms, most recently by the release of extracellular vesicles (EVs). Since EVs carry a variety of cargoes of nucleic acids, lipids, and proteins and mediate intercellular communication, they have been the hotspot of diagnosis and treatment. The mechanisms underlying CNS disorders include angiogenesis, autophagy, apoptosis, cell death, and inflammation, and cell-EVs have been revealed to be involved in these pathological processes. Ischemic stroke is one of the most common causes of death and disability worldwide. It results in serious neurological and physical dysfunction and even leads to heavy economic and social burdens. Although a large number of researchers have reported that EVs derived from these cells play a vital role in regulating multiple pathological mechanisms in ischemic stroke, the specific interactional relationships and mechanisms between specific cell-EVs and stroke treatment have not been clearly described. This review aims to summarize the therapeutic effects and mechanisms of action of specific cell-EVs on ischemia. Additionally, this study emphasizes that these EVs are involved in stroke treatment by inhibiting and activating various signaling pathways such as ncRNAs, TGF-β1, and NF-κB.

Exosomes Derived From Mesenchymal Stem Cells: Novel Effects in the Treatment of Ischemic Stroke

Ischemic stroke is defined as an infarction in the brain, caused by impaired cerebral blood supply, leading to local brain tissue ischemia, hypoxic necrosis, and corresponding neurological deficits. At present, revascularization strategies in patients with acute ischemic stroke include intravenous thrombolysis and mechanical endovascular treatment. However, due to the short treatment time window (<4.5 h) and method restrictions, clinical research is focused on new methods to treat ischemic stroke. Exosomes are nano-sized biovesicles produced in the endosomal compartment of most eukaryotic cells, containing DNA, complex RNA, and protein (30-150 nm). They are released into surrounding extracellular fluid upon fusion between multivesicular bodies and the plasma membrane. Exosomes have the characteristics of low immunogenicity, good innate stability, high transmission efficiency, and the ability to cross the blood-brain barrier, making them potential therapeutic modalities for the treatment of ischemic stroke. The seed sequence of miRNA secreted by exosomes is base-paired with complementary mRNA to improve the microenvironment of ischemic tissue, thereby regulating downstream signal transduction activities. With exosome research still in the theoretical and experimental stages, this review aims to shed light on the potential of exosomes derived from mesenchymal stem cells in the treatment of ischemic stroke.

Hypoxia Induced Changes of Exosome Cargo and Subsequent Biological Effects

Exosomes are small extracellular vesicles that are secreted by almost all types of cells and exist in almost all extracellular spaces. As an important mediator of intercellular communication, exosomes encapsulate the miRNA, lncRNA, cirRNA, mRNA, cytokine, enzyme, lipid, and other components from the cytoplasm into its closed single membrane structure and transfer them to recipient units in an autocrine, paracrine, or endocrine manner. Hypoxia is a state of low oxygen tension and is involved in many pathological processes. Hypoxia influences the size, quantity, and expression of exosome cargos. Exosomes derived from hypoxic tumor cells transfer genetics, proteins, and lipids to the recipient units to exert pleiotropic effects. Different donor cells produce different cargo contents, target different recipient units and lead to different biological effects. Hypoxic exosomes derived from tumor cells uptaken by normoxic tumor cells lead to promoted proliferation, migration, and invasion; uptaken by extracellular space or liver lead to promoted metastasis; uptaken by endothelial cells lead to promoted angiogenesis; uptaken by immune cells lead to promoted macrophage polarization and changed tumor immune microenvironment. In addition to various types of tumors, hypoxic exosomes also participate in the development of diseases in the cardiovascular system, neuron system, respiratory system, hematology system, endocrine system, urinary system, reproduction system, and skeletomuscular system. Understanding the special characteristics of hypoxic exosomes provide new insight into elaborating the pathogenesis of hypoxia related disease. This review summarizes hypoxia induced cargo changes and the biological effects of hypoxic exosomes in tumors and non-malignant diseases in different systems.

Role of Extracellular Vesicles in Glia-Neuron Intercellular Communication

Cross talk between glia and neurons is crucial for a variety of biological functions, ranging from nervous system development, axonal conduction, synaptic transmission, neural circuit maturation, to homeostasis maintenance. Extracellular vesicles (EVs), which were initially described as cellular debris and were devoid of biological function, are now recognized as key components in cell-cell communication and play a critical role in glia-neuron communication. EVs transport the proteins, lipids, and nucleic acid cargo in intercellular communication, which alters target cells structurally and functionally. A better understanding of the roles of EVs in glia-neuron communication, both in physiological and pathological conditions, can aid in the discovery of novel therapeutic targets and the development of new biomarkers. This review aims to demonstrate that different types of glia and neuronal cells secrete various types of EVs, resulting in specific functions in intercellular communications.

Ischemic Preconditioning Modulates the Peripheral Innate Immune System to Promote Anti-Inflammatory and Protective Responses in Mice Subjected to Focal Cerebral Ischemia

The development of tolerance triggered by a sublethal ischemic episode (preconditioning, PC) involves a complex crosstalk between neurons, astrocytes and microglia, although the role of the peripheral immune system in this context is largely unexplored. Here, we report that severe cerebral ischemia caused by transient middle cerebral artery occlusion (MCAo) in adult male mice elevates blood counts of inflammatory neutrophils and monocytes, and plasma levels of miRNA-329-5p. These inflammatory responses are prevented by ischemic PC induced by 15 min MCAo, 72h before the severe insult (1h MCAo). As compared with sham-operated animals, mice subjected to either ischemic PC, MCAo or a combination of both (PC+MCAo) display spleen contraction. However, protein levels of Ym1 (a marker of polarization of myeloid cells towards M2/N2 protective phenotypes) are elevated only in spleen from the experimental groups PC and PC+MCAo, but not MCAo. Conversely, Ym1 protein levels only increase in circulating leukocytes from mice subjected to 1h MCAo, but not in preconditioned animals, which is coincident with a dramatic elevation of Ym1 expression in the ipsilateral cortex. By immunofluorescence analysis, we observe that expression of Ym1 occurs in amoeboid-shaped myeloid cells, mainly representing inflammatory monocytes/macrophages and neutrophils. As a result of its immune-regulatory functions, ischemic PC prevents elevation of mRNA levels of the pro-inflammatory cytokine interleukin (IL)-1β in the ipsilateral cortex, while not affecting IL-10 mRNA increase induced by MCAo. Overall, the elevated anti-inflammatory/pro-inflammatory ratio observed in the brain of mice pre-exposed to PC is associated with reduced brain infarct volume and ischemic edema, and with amelioration of functional outcome. These findings reaffirm the crucial and dualistic role of the innate immune system in ischemic stroke pathobiology, extending these concepts to the context of ischemic tolerance and underscoring their relevance for the identification of novel therapeutic targets for effective stroke treatment.

Role of brain extracellular vesicles in air pollution-related cognitive impairment and neurodegeneration

A relationship between environmental exposure to air pollution and cognitive impairment and neurological disorders has been described. Previous literature has focused on the direct effects of the air pollution components on neuronal and glial cells, as well as on involvement of oxidative stress and neuroinflammation on microglia and astrocyte reactivity. However, other mechanisms involved in the air pollution effects on central nervous system (CNS) toxicity can be playing critical roles. Increasingly, extracellular vesicle's (EVs) mediated intercellular communication is being recognized as impacting the development of cognitive impairment and neurological disorders like Alzheimer's disease and others. Here we describe the available evidence about toxic air pollutants and its components on brain, an involvement of brain cells specific and EVs types (based in the origin or in the size of EVs) in the initiation, exacerbation, and propagation of the neurotoxic effects (inflammation, neurodegeneration, and accumulation of neurotoxic proteins) induced by air pollution in the CNS. Additionally, we discuss the identification and isolation of neural-derived EVs from human plasma, the most common markers for neural-derived EVs, and their potential for use as diagnostic or therapeutic molecules for air pollution-related cognitive impairment and neurodegeneration.

Intercellular Communication in the Brain through Tunneling Nanotubes

Simple Summary

Tunneling nanotubes (TNTs) are a means of cell communication which have been recently discovered. They allow the intercellular trafficking of many types of cellular compounds ranging from ions, such as Ca²⁺, to whole organelles such as mitochondria. TNTs are found in many tissues, both in physiological and pathological conditions. They are also found in the brain where they contribute to brain development and function and also to degenerative diseases and glioma.

Abstract

Intercellular communication is essential for tissue homeostasis and function. Understanding how cells interact with each other is paramount, as crosstalk between cells is often dysregulated in diseases and can contribute to their progression. Cells communicate with each other through several modalities, including paracrine secretion and specialized structures ensuring physical contact between them. Among these intercellular specialized structures, tunneling nanotubes (TNTs) are now recognized as a means of cell-to-cell communication through the exchange of cellular cargo, controlled by a variety of biological triggers, as described here. Intercellular communication is fundamental to brain function. It allows the dialogue between the many cells, including neurons, astrocytes, oligodendrocytes, glial cells, microglia, necessary for the proper development and function of the brain. We highlight here the role of TNTs in connecting these cells, for the physiological functioning of the brain and in pathologies such as stroke, neurodegenerative diseases, and gliomas. Understanding these processes could pave the way for future therapies.

Astrocytic MicroRNA in Ageing, Inflammation, and Neurodegenerative Disease

Astrocytes actively regulate numerous cell types both within and outside of the central nervous system in health and disease. Indeed, astrocyte morphology, gene expression and function, alongside the content of astrocyte-derived extracellular vesicles (ADEVs), is significantly altered by ageing, inflammatory processes and in neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Here, we review the relevant emerging literature focussed on perturbation in expression of microRNA (miRNA), small non-coding RNAs that potently regulate gene expression. Synthesis of this literature shows that ageing-related processes, neurodegenerative disease-associated mutations or peptides and cytokines induce dysregulated expression of miRNA in astrocytes and in some cases can lead to selective incorporation of miRNA into ADEVs. Analysis of the miRNA targets shows that the resulting downstream consequences of alterations to levels of miRNA include release of cytokines, chronic activation of the immune response, increased apoptosis, and compromised cellular functioning of both astrocytes and ADEV-ingesting cells. We conclude that perturbation of these functions likely exacerbates mechanisms leading to neuropathology and ultimately contributes to the cognitive or motor symptoms of neurodegenerative diseases. This field requires comprehensive miRNA expression profiling of both astrocytes and ADEVs to fully understand the effect of perturbed astrocytic miRNA expression in ageing and neurodegenerative disease.

MicroRNA Sequencing Analysis in Obstructive Sleep Apnea and Depression: Anti-Oxidant and MAOA-Inhibiting Effects of miR-15b-5p and miR-92b-3p through Targeting PTGS1-NF-κB-SP1 Signaling

The aim of this study was to identify novel microRNAs related to obstructive sleep apnea (OSA) characterized by intermittent hypoxia with re-oxygenation (IHR) injury. Illumina MiSeq was used to identify OSA-associated microRNAs, which were validated in an independent cohort. The interaction between candidate microRNA and target genes was detected in the human THP-1, HUVEC, and SH-SY5Y cell lines. Next-generation sequencing analysis identified 22 differentially expressed miRs (12 up-regulated and 10 down-regulated) in OSA patients. Enriched predicted target pathways included senescence, adherens junction, and AGE-RAGE/TNF-α/HIF-1α signaling. In the validation cohort, miR-92b-3p and miR-15b-5p gene expressions were decreased in OSA patients, and negatively correlated with an apnea hypopnea index. PTGS1 (COX1) gene expression was increased in OSA patients, especially in those with depression. Transfection with miR-15b-5p/miR-92b-3p mimic in vitro reversed IHR-induced early apoptosis, reactive oxygen species production, MAOA hyperactivity, and up-regulations of their predicted target genes, including PTGS1, ADRB1, GABRB2, GARG1, LEP, TNFSF13B, VEGFA, and CXCL5. The luciferase assay revealed the suppressed PTGS1 expression by miR-92b-3p. Down-regulated miR-15b-5p/miR-92b-3p in OSA patients could contribute to IHR-induced oxidative stress and MAOA hyperactivity through the eicosanoid inflammatory pathway via directly targeting PTGS1-NF-κB-SP1 signaling. Over-expression of the miR-15b-5p/miR-92b-3p may be a new therapeutic strategy for OSA-related depression.

Role of Glia-Derived Extracellular Vesicles in Neurodegenerative Diseases

Extracellular vesicles (EVs), as nano-sized vesicles secreted by almost all cells, have been recognized as the essential transmitter for cell-to-cell communication and participating in multiple biological processes. Neurodegenerative diseases (ND), such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis, share common mechanisms of the aggregation and propagation of distinct pathologic proteins among cells in the nervous systems and neuroinflammatory reactions mediated by glia during the pathogenic process. This feature indicates the vital role of crosstalk between neurons and glia in the pathogenesis of ND. In recent years, glia-derived EVs have been investigated as potential mediators of signals between neurons and glia, which provides a new direction and strategy for understanding ND. By a comprehensive summary, it can be concluded that glia-derived EVs have both a beneficial and/or a detrimental effect in the process of ND. Therefore, this review article conveys the role of glia-derived EVs in the pathogenesis of ND and raises current limitations of their potential application in the diagnosis and treatment of ND.

The role and therapeutic potential of exosomes in ischemic stroke

Ischemic stroke is a disease caused by insufficient blood and oxygen supply to the brain, which is mainly due to intracranial arterial stenosis and middle cerebral artery occlusion. Exosomes play an important role in cerebral ischemia. Nucleic acid substances such as miRNA, circRNA, lncRNA in exosomes can play communication roles and improve cerebral ischemia by regulating the development and regeneration of the nervous system, remodeling of blood vessels and inhibiting neuroinflammation. Furthermore, exosomes modulate stroke through various mechanisms, including improving neural communication, promoting the development of neuronal cells and myelin synapses, neurovascular unit remodeling and maintaining homeostasis of the nervous system. At the same time, exosomes are also a good carrier of bioactive substances, which can be modified and targeted to the lesion site. Here, we review the roles of exosomes in cerebral ischemia, and discuss the possible mechanisms and potentials of modification of exosomes for targeting stroke, providing a new idea for the prevention and treatment of cerebral ischemia.

The Need for New Biomarkers to Assist with Stroke Prevention and Prediction of Post-Stroke Therapy Based on Plasma-Derived Extracellular Vesicles

The risk of having a stroke event doubles each decade after the age of 55. Therefore, it is of great interest to develop neurorestorative therapies of stroke which occurs mostly in elderly people. However, to date, patients at risk for these sequels of stroke are not duly diagnosed and treated due to the lack of reliable biomarkers. Extracellular vesicles (EVs) are lipid bilayer-delimited particles that are shed by the brain cells and are able to cross the blood–brain barrier and enter the blood stream; thus, they may be used to interrogate molecular and cellular events in the brain damaged area. In this review, we summarize the major molecular and cellular responses of astroglia and neurons to cerebral ischemia and assess their impact on post-stroke recovery and rehabilitation. In particular, we ask if EVs secreted by brain cells are responses to cerebral ischemia, and they may shed new light on the interplay between exosomes-mediated interactions between brain cells and the question of how to exploit it in order to predict the individual course of the disease and to introduce specific preventive or therapeutic strategies. Given these findings, we are left with two options: either to (i) transplant neuronal precursors into the damaged cortical area or (ii) to covert abundantly present proliferating astrocytes in the perilesional area into neurons by using recently developed genetic technologies. However, given the complexity of molecular and cellular responses to cerebral ischemia and our limited capabilities to restore brain structure and function, we are left with only one realistic aim: to invest more in prevention.

Dental pulp stem cell-derived exosomes alleviate cerebral ischaemia-reperfusion injury through suppressing inflammatory response

Objectives

The study aimed to determine whether dental pulp stem cell‐derived exosomes (DPSC‐Exos) exert protective effects against cerebral ischaemia‐reperfusion (I/R) injury and explore its underlying mechanism.

Materials and Methods

Exosomes were isolated from the culture medium of human DPSC. Adult male C57BL/6 mice were subjected to 2 hours transient middle cerebral artery occlusion (tMCAO) injury followed by 2 hours reperfusion, after which singular injection of DPSC‐Exos via tail vein was administrated. Brain oedema, cerebral infarction and neurological impairment were measured on day 7 after exosomes injection. Then, oxygen‐glucose deprivation–reperfusion (OGD/R) induced BV2 cells were studied to analyse the therapeutic effects of DPSC‐Exos on I/R injury in vitro. Protein levels of TLR4, MyD88, NF‐κB p65, HMGB1, IL‐6, IL‐1β and TNF‐α were determined by western blot or enzyme‐linked immunosorbent assay. The cytoplasmic translocation of HMGB1 was detected by immunofluorescence staining.

Results

DPSC‐Exos alleviated brain oedema, cerebral infarction and neurological impairment in I/R mice. DPSC‐Exos inhibited the I/R‐mediated expression of TLR4, MyD88 and NF‐κB significantly. DPSC‐Exos also reduced the protein expression of IL‐6, IL‐1β and TNF‐α compared with those of the control both in vitro and in vivo. Meanwhile, DPSC‐Exos markedly decreased the HMGB1 cytoplasmic translocation induced by I/R damage.

Conclusions

DPSC‐Exos can ameliorate I/R‐induced cerebral injury in mice. Its anti‐inflammatory mechanism might be related with the inhibition of the HMGB1/TLR4/MyD88/NF‐κB pathway.

MSCs‑derived exosomes attenuate ischemia-reperfusion brain injury and inhibit microglia apoptosis might via exosomal miR-26a-5p mediated suppression of CDK6

Background

This study aimed to explore the role of mesenchymal stromal cells (MSCs)-derived exosomes (MSCs-Exo) in the cerebral ischemia–reperfusion (I/R) injury.

Methods

Exosomes were isolated from MSCs of adult C57BL/6J mice by the gradient centrifugation method. The expression of miR-26a-5p and CDK6 in MSCs-Exo and mice brain tissues were evaluated by qRT-PCR and western blot. miR-26a-5p mimics and miR-NC were transfected into MSCs, and exosomes were isolated from the MSCs stably expressing miR-26a-5p. Then MSCs-Exo-miR-26a-5p mimics or MSCs-Exo-miR-NC was injected into mice through the tail vein, or added into medium to stimulate BV-2 cells. Cell viability was evaluated by CCK-8 assay. Cell apoptosis was detected by flow cytometry. The apoptosis in brain tissues was evaluated by TUNEL staining assay. Bioinformatics analysis and luciferase reporter assay were performed to determine the binding relationship between miR-26a-5p and CDK6.

Results

miR-26a-5p was downregulated and CDK6 was upregulated in MSCs-Exo of MCAO-mice and OGD-induced MSCs. MSCs-Exo-miR-26a-5p mimics significantly reduced cell apoptosis of OGD-injured BV-2 cells. MSCs-Exo-miR-26a-5p mimics significantly reduced the infarct volume of MCAO-induced mice. Luciferase reporter assay revealed that CDK-6 was a target of miR-26a-5p. In addition, MSCs-Exo-miR-26a-5p mimics significantly decreased the expression of CDK6 in both OGD-induced BV-2 cells and the brain tissues of MCAO-treated mice.

Conclusion

Our results indicated that MSCs‑Exo attenuated I/R injury in mice by inhibiting microglia apoptosis might via exosomal miR-26a-5p mediated suppression of CDK6. Our study shed light on the application of MSC-Exo as a potential therapeutic tool for cerebral I/R injury.

Glial Cells as Therapeutic Approaches in Brain Ischemia-Reperfusion Injury

Ischemic stroke is the second cause of mortality and the first cause of long-term disability constituting a serious socioeconomic burden worldwide. Approved treatments include thrombectomy and rtPA intravenous administration, which, despite their efficacy in some cases, are not suitable for a great proportion of patients. Glial cell-related therapies are progressively overcoming inefficient neuron-centered approaches in the preclinical phase. Exploiting the ability of microglia to naturally switch between detrimental and protective phenotypes represents a promising therapeutic treatment, in a similar way to what happens with astrocytes. However, the duality present in many of the roles of these cells upon ischemia poses a notorious difficulty in disentangling the precise pathways to target. Still, promoting M2/A2 microglia/astrocyte protective phenotypes and inhibiting M1/A1 neurotoxic profiles is globally rendering promising results in different in vivo models of stroke. On the other hand, described oligodendrogenesis after brain ischemia seems to be strictly beneficial, although these cells are the less studied players in the stroke paradigm and negative effects could be described for oligodendrocytes in the next years. Here, we review recent advances in understanding the precise role of mentioned glial cell types in the main pathological events of ischemic stroke, including inflammation, blood brain barrier integrity, excitotoxicity, reactive oxygen species management, metabolic support, and neurogenesis, among others, with a special attention to tested therapeutic approaches.

Extracellular Vesicles as an Emerging Frontier in Spinal Cord Injury Pathobiology and Therapy

Extracellular vesicles (EVs) are membrane-delimited particles that are secreted by nearly all cell types. EVs mediate crucial physiological functions and pathophysiological processes in the CNS. As carriers of diverse bioactive cargoes (e.g., proteins, lipids, and nucleic acids) that can be modified in response to external stimuli, EVs have emerged as pathological mediators following neurotrauma such as spinal cord injury (SCI). We discuss the roles of endogenous EVs in the CNS as well as crosstalk with peripheral EVs in relation to neurotrauma, with a particular focus on SCI. We then summarize the status of EV-based therapeutic advances in preclinical animal models for these conditions. Finally, we discuss new bioengineering strategies that are poised to enhance CNS-specific therapeutic capabilities of EVs.

Dysfunction of the Neurovascular Unit in Ischemic Stroke: Highlights on microRNAs and Exosomes as Potential Biomarkers and Therapy

Ischemic stroke is a damaging cerebral vascular disease associated with high disability and mortality rates worldwide. In spite of the continuous development of new diagnostic and prognostic methods, early detection and outcome prediction are often very difficult. The neurovascular unit (NVU) is a complex multicellular entity linking the interactions between neurons, glial cells, and brain vessels. Novel research has revealed that exosome-mediated transfer of microRNAs plays an important role in cell-to-cell communication and, thus, is integral in the multicellular crosstalk within the NVU. After a stroke, NVU homeostasis is altered, which induces the release of several potential biomarkers into the blood vessels. The addition of biological data representing all constituents of the NVU to clinical and neuroradiological findings can significantly advance stroke evaluation and prognosis. In this review, we present the current literature regarding the possible beneficial roles of exosomes derived from the components of the NVU and multipotent mesenchymal stem cells in preclinical studies of ischemic stroke. We also discuss the most relevant clinical trials on the diagnostic and prognostic roles of exosomes in stroke patients.

Astrocyte Activation in Neurovascular Damage and Repair Following Ischaemic Stroke

Transient or permanent loss of tissue perfusion due to ischaemic stroke can lead to damage to the neurovasculature, and disrupt brain homeostasis, causing long-term motor and cognitive deficits. Despite promising pre-clinical studies, clinically approved neuroprotective therapies are lacking. Most studies have focused on neurons while ignoring the important roles of other cells of the neurovascular unit, such as astrocytes and pericytes. Astrocytes are important for the development and maintenance of the blood-brain barrier, brain homeostasis, structural support, control of cerebral blood flow and secretion of neuroprotective factors. Emerging data suggest that astrocyte activation exerts both beneficial and detrimental effects following ischaemic stroke. Activated astrocytes provide neuroprotection and contribute to neurorestoration, but also secrete inflammatory modulators, leading to aggravation of the ischaemic lesion. Astrocytes are more resistant than other cell types to stroke pathology, and exert a regulative effect in response to ischaemia. These roles of astrocytes following ischaemic stroke remain incompletely understood, though they represent an appealing target for neurovascular protection following stroke. In this review, we summarise the astrocytic contributions to neurovascular damage and repair following ischaemic stroke, and explore mechanisms of neuroprotection that promote revascularisation and neurorestoration, which may be targeted for developing novel therapies for ischaemic stroke.

Roles of glia-derived extracellular vesicles in central nervous system diseases: an update

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous vesicles secreted by various cells in the extracellular space. Accumulating evidence shows that EVs regulate cell-to-cell communication and signaling in the pathological processes of various diseases by carrying proteins, lipids, and nucleic acids to recipient cells. Glia-derived EVs act as a double-edged sword in the pathogenesis of central nervous system (CNS) diseases. They may be vectors for the spread of diseases or act as effective clearance systems to protect tissues. In this review, we summarize recent studies on glia-derived EVs with a focus on their relationships with CNS diseases.

Astrocyte-derived exosomes carry microRNA-17-5p to protect neonatal rats from hypoxic-ischemic brain damage via inhibiting BNIP-2 expression

Exosomes play critical roles in neurogenesis. This study aims to explore the mechanism of astrocyte-derived exosomes in neonatal rats with hypoxic-ischemic brain damage (HIBD). Astrocytes were collected and astrocyte-derived exosomes were isolated and identified. Neonatal rats were pre-treated with exosomes and then subjected to HIBD induction. Then the neurobehaviors, neuronal apoptosis, inflammation and oxidative stress in rat brain were measured. Differentially expressed microRNAs (miRNAs) in rat brain before and after HI procedure were analyzed. H19-7 cells were subjected to oxygen and glucose deprivation (OGD) for in vitro studies. Target relation between miR-17-5p and BNIP2 was identified. Gain- and loss-of functions of miR-17-5p and BNIP2 were conducted to identify their roles in viability, apoptosis, oxidative stress and inflammation of OGD-treated cells. Collectively, astrocyte-derived exosomes improved neurobehaviors, and reduced cerebral infarction, neuronal apoptosis, oxidative and inflammation in vivo and in vitro. The exosomes carried miR-17-5p bound to BNIP2 and negatively regulated BNIP2 expression in OGD-treated cells. Over-expression of miR-17-5p increased viability, and decreased OGD-induced apoptosis, oxidative stress and inflammation of H19-7 cells, which were reversed by over-expression of BNIP2. Taken together, the study suggested that astrocyte-derived exosomes could carry miR-17-5p to protect neonatal rats from HIBD via inhibiting BNIP-2 expression.

Astrocyte-derived extracellular vesicles: A double-edged sword in central nervous system disorders

Recent studies suggest that astrocytes released a great quantity of extracellular vesicles (AEVs) to communicate with other brain cells. Under pathological conditions, AEVs are widely associated with the pathogenesis of neurobiological diseases by horizontally transferring pathogenic factors to neighboring cells or peripheral immune cells. Their beneficial role is also evident by the fact that they are involved in neuroprotection and neuroregeneration through alleviating apoptosis, maintaining neuronal function, and repairing neural injuries. The strong association of AEVswith neurological disorders makes AEVs a promising target for disease diagnosis, treatment, and prevention. The identification of disease-specific cargos in AEVs isolated from the patients' biofluids suggests AEVs as an attractive platform for biomarker development. Furthermore, the inhibition of inflammatory/toxic AEV release and the preservation of neuroprotective AEV release have been considered as potential therapeutic strategies in CNS disorder treatment and prevention, respectively. Here, we summarize the biological roles of AEVs as pathological contributors, protective/regenerative factors, and potential diagnostic biomarkers and therapeutic targets for neurological disorders, with a focus on recent progresses and emerging concepts.

Glia-Derived Extracellular Vesicles: Role in Central Nervous System Communication in Health and Disease

Glial cells are crucial for the maintenance of correct neuronal functionality in a physiological state and intervene to restore the equilibrium when environmental or pathological conditions challenge central nervous system homeostasis. The communication between glial cells and neurons is essential and extracellular vesicles (EVs) take part in this function by transporting a plethora of molecules with the capacity to influence the function of the recipient cells. EVs, including exosomes and microvesicles, are a heterogeneous group of biogenetically distinct double membrane-enclosed vesicles. Once released from the cell, these two types of vesicles are difficult to discern, thus we will call them with the general term of EVs. This review is focused on the EVs secreted by astrocytes, oligodendrocytes and microglia, aiming to shed light on their influence on neurons and on the overall homeostasis of the central nervous system functions. We collect evidence on neuroprotective and homeostatic effects of glial EVs, including neuronal plasticity. On the other hand, current knowledge of the detrimental effects of the EVs in pathological conditions is addressed. Finally, we propose directions for future studies and we evaluate the potential of EVs as a therapeutic treatment for neurological disorders.

Therapeutic application of exosomes in ischaemic stroke

Ischaemic stroke is a leading cause of long-term disability in the world, with limited effective treatments. Increasing evidence demonstrates that exosomes are involved in ischaemic pathology and exhibit restorative therapeutic effects by mediating cell–cell communication. The potential of exosome therapy for ischaemic stroke has been actively investigated in the past decade. In this review, we mainly discuss the current knowledge of therapeutic applications of exosomes from different cell types, different exosomal administration routes, and current advances of exosome tracking and targeting in ischaemic stroke. We also briefly summarised the pathology of ischaemic stroke, exosome biogenesis, exosome profile changes after stroke as well as registered clinical trials of exosome-based therapy.