Neural stem cell small extracellular vesicle-based delivery of 14-3-3t reduces apoptosis and neuroinflammation following traumatic spinal cord injury by enhancing autophagy by targeting Beclin-1

Extracellular vesicle therapy in neurological disorders

Extracellular vesicles (EVs) are vital for cell-to-cell communication, transferring proteins, lipids, and nucleic acids in various physiological and pathological processes. They play crucial roles in immune modulation and tissue regeneration but are also involved in pathogenic conditions like inflammation and degenerative disorders. EVs have heterogeneous populations and cargo, with numerous subpopulations currently under investigations. EV therapy shows promise in stimulating tissue repair and serving as a drug delivery vehicle, offering advantages over cell therapy, such as ease of engineering and minimal risk of tumorigenesis. However, challenges remain, including inconsistent nomenclature, complex characterization, and underdeveloped large-scale production protocols. This review highlights the recent advances and significance of EVs heterogeneity, emphasizing the need for a better understanding of their roles in disease pathologies to develop tailored EV therapies for clinical applications in neurological disorders.

NSPCs-ES: mechanisms and functional impact on central nervous system diseases

Patients with central neuronal damage may suffer severe consequences, but effective therapies remain unclear. Previous research has established the transplantation of neural stem cells that generate new neurons to replace damaged ones. In a new field of scientific research, the extracellular secretion of NPSCs (NSPCs-ES) has been identified as an alternative to current chemical drugs. Many preclinical studies have shown that NSPCs-ES are effective in models of various central nervous system diseases (CNS) injuries, from maintaining functional structures at the cellular level to providing anti-inflammatory functions at the molecular level, as well as improving memory and motor functions, reducing apoptosis in neurons, and mediating multiple signaling pathways. The NSPC-ES can travel to the damaged tissue and exert a broad range of therapeutic effects by supporting and nourishing damaged neurons. However, gene editing and cell engineering techniques have recently improved therapeutic efficacy by modifying NSPCs-ES. Consequently, future research and application of NSPCs-ES may provide a novel strategy for the treatment of CNS diseases in the future. In this review, we summarize the current progress on these aspects.

The role of small extracellular vesicles and microRNA as their cargo in the spinal cord injury pathophysiology and therapy

Spinal cord injury (SCI) is a devastating condition with a complex pathology that affects a significant portion of the population and causes long-term consequences. After primary injury, an inflammatory cascade of secondary injury occurs, followed by neuronal cell death and glial scar formation. Together with the limited regenerative capacity of the central nervous system, these are the main reasons for the poor prognosis after SCI. Despite recent advances, there is still no effective treatment. Promising therapeutic approaches include stem cells transplantation, which has demonstrated neuroprotective and immunomodulatory effects in SCI. This positive effect is thought to be mediated by small extracellular vesicles (sEVs); membrane-bound nanovesicles involved in intercellular communication through transport of functional proteins and RNA molecules. In this review, we summarize the current knowledge about sEVs and microRNA as their cargo as one of the most promising therapeutic approaches for the treatment of SCI. We provide a comprehensive overview of their role in SCI pathophysiology, neuroprotective potential and therapeutic effect.

Neural stem cell therapies for spinal cord injury repair: an update on recent preclinical and clinical advances

Traumatic spinal cord injury (SCI) is a leading cause of lifelong disabilities. Permanent sensory, motor and autonomic impairments after SCI are substantially attributed to degeneration of spinal cord neurons and axons, and disintegration of neural network. To date, minimal regenerative treatments are available for SCI with an unmet need for new therapies to reconstruct the damaged spinal cord neuron-glia network and restore connectivity with the supraspinal pathways. Multipotent neural precursor cells (NPCs) have a unique capacity to generate neurons, oligodendrocytes and astrocytes. Due to this capacity, NPCs have been an attractive cell source for cellular therapies for SCI. Transplantation of NPCs has been extensively tested in preclinical models of SCI in the past two decades. These studies have identified opportunities and challenges associated with NPC therapies. While NPCs have the potential to promote neuroregeneration through various mechanisms, their low long-term survival and integration within the host injured spinal cord limit the functional benefits of NPC-based therapies for SCI. To address this challenge, combinatorial strategies have been developed to optimize the outcomes of NPC therapies by enriching SCI microenvironment through biomaterials, genetic and pharmacological therapies. In this review, we will provide an in-depth discussion on recent advances in preclinical NPC-based therapies for SCI. We will discuss modes of actions and mechanism by which engrafted NPCs contribute to the repair process and functional recovery. We will also provide an update on current clinical trials and new technologies that have facilitated preparation of medical-grade human NPCs suitable for transplantation in clinical studies.

Local delivery of EGFR+NSCs-derived exosomes promotes neural regeneration post spinal cord injury via miR-34a-5p/HDAC6 pathway

Spinal cord injury (SCI) causes severe axon damage, usually leading to permanent paraparesis, which still lacks effective regenerative therapy. Recent studies have suggested that exosomes derived from neural stem cells (NSCs) may hold promise as attractive candidates for SCI treatment. Epidermal Growth Factor Receptor positive NSC (EGFR+NSC) is a subpopulation of endogenous NSCs, showing strong regenerative capability in central nervous system disease. In the current study, we isolated exosomes from the EGFR+NSCs (EGFR+NSCs-Exos) and discovered that local delivery of EGFR+NSCs-Exos can effectively promote neurite regrowth in the injury site of spinal cord-injured mice and improve their neurological function recovery. Using the miRNA-seq, we firstly characterized the microRNAs (miRNAs) cargo of EGFR+NSCs-Exos and identified miR-34a-5p which was highly enriched in EGFR+NSCs derived exosomes. We further interpreted that exosomal miR-34a-5p could be transferred to neurons and inhibit the HDAC6 expression by directly binding to its mRNA, contributing to microtubule stabilization and autophagy induction for aiding SCI repair. Overall, our research demonstrated a novel therapeutic approach to improving neurological functional recovery by using exosomes secreted from a subpopulation of endogenous NSCs and providing a precise cell-free treatment strategy for SCI repair.

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.

Transplantation of Wnt3a-modified neural stem cells promotes neural regeneration and functional recovery after spinal cord injury via Wnt-Gli2 pathway

Neural stem cell (NSCs) transplantation has great potential in the treatment of spinal cord injury (SCI). Previous studies have indicated that the Wnt pathway could regulate the expression of basic helix-loop-helix (bHLH) family factor Hes5 and Mash1 in NSCs, but not through the notch intracellular domain. This suggests that there are other signals involved in this process. The aim of this study was to investigate the role of Wnt-Gli2 pathway in the treatment of SCI by transplanting neural stem cells. NSCs were isolated from the striata of embryonic day 14 mice. Activation of the Wnt pathway was achieved using Wnt3a protein, while Gli2 was inhibited using Gli2-siRNA. Expression levels of Gli2 and bHLH factors were assessed using western blotting. NSCs proliferation was evaluated using CCK-8 assay, and neural differentiation was determined by immunofluorescence staining. Finally, the modified NSCs were transplanted into mice with SCI, and their effects were assessed using behavioral and histological tests. Our results demonstrated that Wnt3a promoted the expression of Mash1 through Gli2. Moreover, the expression of Ngn1 and Hes1 was up-regulated, while Hes5 was down-regulated. Wnt3a also promoted NSCs proliferation and neural differentiation through this signaling pathway. In vivo experiments showed that NSCs transplantation mediated by Wnt3a-Gli2 signaling increased the number of neurons and resulted in improved Basso Mouse Scale scores. In conclusion, our findings suggest that Gli2 plays a role in mediating the regulation of Wnt3a signaling on promoting NSCs proliferation and neural differentiation. This pathway is therefore important in NSCs-mediated SCI recovery.

Dysregulation of extracellular vesicle protein cargo in female myalgic encephalomyelitis/chronic fatigue syndrome cases and sedentary controls in response to maximal exercise

In healthy individuals, physical exercise improves cardiovascular health and muscle strength, alleviates fatigue and reduces the risk of chronic diseases. Although exercise is suggested as a lifestyle intervention to manage various chronic illnesses, it negatively affects people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), who suffer from exercise intolerance. We hypothesized that altered extracellular vesicle (EV) signalling in ME/CFS patients after an exercise challenge may contribute to their prolonged and exacerbated negative response to exertion (post-exertional malaise). EVs were isolated by size exclusion chromatography from the plasma of 18 female ME/CFS patients and 17 age- and BMI-matched female sedentary controls at three time points: before, 15 min, and 24 h after a maximal cardiopulmonary exercise test. EVs were characterized using nanoparticle tracking analysis and their protein cargo was quantified using Tandem Mass Tag-based (TMT) proteomics. The results show that exercise affects the EV proteome in ME/CFS patients differently than in healthy individuals and that changes in EV proteins after exercise are strongly correlated with symptom severity in ME/CFS. Differentially abundant proteins in ME/CFS patients versus controls were involved in many pathways and systems, including coagulation processes, muscle contraction (both smooth and skeletal muscle), cytoskeletal proteins, the immune system and brain signalling.

Hydrogel-encapsulated extracellular vesicles for the regeneration of spinal cord injury

Spinal cord injury (SCI) is a critical neurological condition that may impair motor, sensory, and autonomous functions. At the cellular level, inflammation, impairment of axonal regeneration, and neuronal death are responsible for SCI-related complications. Regarding the high mortality and morbidity rates associated with SCI, there is a need for effective treatment. Despite advances in SCI repair, an optimal treatment for complete recovery after SCI has not been found so far. Therefore, an effective strategy is needed to promote neuronal regeneration and repair after SCI. In recent years, regenerative treatments have become a potential option for achieving improved functional recovery after SCI by promoting the growth of new neurons, protecting surviving neurons, and preventing additional damage to the spinal cord. Transplantation of cells and cells-derived extracellular vesicles (EVs) can be effective for SCI recovery. However, there are some limitations and challenges related to cell-based strategies. Ethical concerns and limited efficacy due to the low survival rate, immune rejection, and tumor formation are limitations of cell-based therapies. Using EVs is a helpful strategy to overcome these limitations. It should be considered that short half-life, poor accumulation, rapid clearance, and difficulty in targeting specific tissues are limitations of EVs-based therapies. Hydrogel-encapsulated exosomes have overcome these limitations by enhancing the efficacy of exosomes through maintaining their bioactivity, protecting EVs from rapid clearance, and facilitating the sustained release of EVs at the target site. These hydrogel-encapsulated EVs can promote neuroregeneration through improving functional recovery, reducing inflammation, and enhancing neuronal regeneration after SCI. This review aims to provide an overview of the current research status, challenges, and future clinical opportunities of hydrogel-encapsulated EVs in the treatment of SCI.

Neural stem cell-derived extracellular vesicles: The light of central nervous system diseases

Central nervous system (CNS) diseases are the leading cause of death worldwide. By performing compensatory functions and improving the inflammatory microenvironment, the transplantation of neural stem cells (NSCs) can promote functional recovery from brain injury, aging, brain tumours, and other diseases. However, the ability of NSCs to differentiate into neurons is limited, and they are associated with a risk of tumourigenicity. NSC-derived extracellular vesicles (NSC-EVs) can modulate the local microenvironment of the nervous system as well as distant neuronal functions. Thus, cell-free therapy may be a novel remedy for CNS disorders. This article reviews the characteristics, contents, and mechanisms of action of NSC-EVs as well as their roles and application prospects in various CNS diseases.

A swift expanding trend of extracellular vesicles in spinal cord injury research: a bibliometric analysis

Extracellular vesicles (EVs) in the field of spinal cord injury (SCI) have garnered significant attention for their potential applications in diagnosis and therapy. However, no bibliometric assessment has been conducted to evaluate the scientific progress in this area. A search of articles in Web of Science (WoS) from January 1, 1991, to May 1, 2023, yielded 359 papers that were analyzed using various online analysis tools. These articles have been cited 10,842 times with 30.2 times per paper. The number of publications experienced explosive growth starting in 2015. China and the United States led this research initiative. Keywords were divided into 3 clusters, including "Pathophysiology of SCI", "Bioactive components of EVs", and "Therapeutic effects of EVs in SCI". By integrating the average appearing year (AAY) of keywords in VoSviewer with the time zone map of the Citation Explosion in CiteSpace, the focal point of research has undergone a transformative shift. The emphasis has moved away from pathophysiological factors such as "axon", "vesicle", and "glial cell" to more mechanistic and applied domains such as "activation", "pathways", "hydrogels" and "therapy". In conclusions, institutions are expected to allocate more resources towards EVs-loaded hydrogel therapy and the utilization of innovative materials for injury mitigation.

Differentiation state and culture conditions impact neural stem/progenitor cell-derived extracellular vesicle bioactivity

Extracellular vesicles (EVs) derived from neural progenitor/stem cells (NPSCs) have shown promising efficacy in a variety of preclinical models. However, NPSCs lack critical neuroregenerative functionality such as myelinating capacity. Further, culture conditions used in NPSC EV production lack standardization, limiting reproducibility challenging and potentially potency of the overall approach via lack of optimization. Here, we assessed whether oligodendrocyte precursor cells (OPCs) and immature oligodendrocytes (iOLs), which are further differentiated than NPSCs and which both give rise to mature myelinating oligodendrocytes, could yield EVs with neurotherapeutic properties comparable or superior to those from NPSCs. We additionally examined the effects of extracellular matrix (ECM) coating materials and the presence or absence of growth factors in cell culture on the ultimate properties of EVs. The data show that OPC EVs and iOL EVs performed similarly to NPSC EVs in cell proliferation and anti-inflammatory assays, but NPSC EVs performed better in a neurite outgrowth assay. Additionally, the presence of nerve growth factor (NGF) in culture was found to maximize NPSC EV bioactivity among the conditions tested. NPSC EVs produced under rationally-selected culture conditions (fibronectin + NGF) enhanced axonal regeneration and muscle reinnervation in a rat nerve crush injury model. These results highlight the need for standardization of culture conditions for neurotherapeutic NPSC EV production.

Neural stem cell-derived extracellular vesicles: mini players with key roles in neurogenesis, immunomodulation, neuroprotection and aging

Neural stem/progenitor cells (NSPCs) are self-renewing and multipotent cells of the central nervous system where they give rise to neurons, astrocytes and oligodendrocytes both during embryogenesis and throughout adulthood, although only in a few discrete niches. NSPC can integrate and send a plethora of signals not only within the local microenvironment but also at distance, including the systemic macroenvironment. Extracellular vesicles (EVs) are currently envisioned as main players in cell-cell communication in basic and translational neuroscience where they are emerging as an acellular alternative in regenerative medicine. At present NSPC-derived EVs represent a largely unexplored area compared to EVs from other neural sources and EVs from other stem cells, i.e., mesenchymal stem cells. On the other hand, available data suggest that NSPC-derived EVs can play key roles on neurodevelopmental and adult neurogenesis, and they are endowed with neuroprotective and immunomodulatory properties, and even endocrine functions. In this review we specifically highlight major neurogenic and "non-neurogenic" properties of NSPC-EVs, the current knowledge on their peculiar cargos and their potential translational value.

Engineered extracellular vesicles for delivery of siRNA promoting targeted repair of traumatic spinal cord injury

Spinal cord injury (SCI) is a severe disease of the nervous system that causes irreparable damage and loss of function, for which no effective treatments are available to date. Engineered extracellular vesicles (EVs) carrying therapeutic molecules hold promise as an alternative SCI therapy depending on the specific functionalized EVs and the appropriate engineering strategy. In this study, we demonstrated the design of a drug delivery system of peptide CAQK-modified, siRNA-loaded EVs (C-EVs-siRNA) for SCI-targeted therapy. The peptide CAQK was anchored through a chemical modification to the membranes of EVs isolated from induced neural stem cells (iNSCs). CCL2-siRNA was then loaded into the EVs through electroporation. The modified EVs still maintained the basic properties of EVs and showed favorable targeting and therapeutic effects in vitro and in vivo. C-EVs-siRNA specifically delivered siRNA to the SCI region and was taken up by target cells. C-EVs-siRNA used the inherent anti-inflammatory and neuroreparative functions of iNSCs-derived EVs in synergy with the loaded siRNA, thus enhancing the therapeutic effect against SCI. The combination of targeted modified EVs and siRNA effectively regulated the microenvironmental disturbance after SCI, promoted the transformation of microglia/macrophages from M1 to M2 and limited the negative effects of the inflammatory response and neuronal injury on functional recovery in mice after SCI. Thus, engineered EVs are a potentially feasible and efficacious treatment for SCI, and may also be used to develop targeted treatments for other diseases.

Proteomic analysis of extracellular vesicles from tick hemolymph and uptake of extracellular vesicles by salivary glands and ovary cells

BACKGROUND

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that are important mediators of intercellular communication. Arthropods transport nutrients, signaling molecules, waste and immune factors to all areas of the body via the hemolymph. Little is known about tick hemolymph EVs.

METHODS

Hemolymph was collected from partially fed Rhipicephalus haemaphysaloides and Hyalomma asiaticum ticks by making an incision with a sterile scalpel in the middle (between the femur and metatarsus) of the first pair of legs, which is known as leg amputation. EVs were isolated from hemolymph by differential centrifugation and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Proteins extracted from the hemolymph EVs were analyzed by 4D label-free proteomics. The EVs were also examined by western blot and immuno-electron microscopy analysis. Intracellular incorporation of PHK26-labeled EVs was tested by adding labeled EVs to tick salivary glands and ovaries, followed by fluorescence microscopy.

RESULTS

In this study, 149 and 273 proteins were identified by 4D label-free proteomics in R. haemaphysaloides and H. asiaticum hemolymph EVs, respectively. TEM and NTA revealed that the sizes of the hemolymph EVs from R. haemaphysaloides and H. asiaticum were 133 and 138 nm, respectively. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses of identified proteins revealed pathways related to binding, catalytic and transporter activity, translation, transport and catabolism, signal transduction and cellular community. The key EV marker proteins RhCD9, RhTSG101, Rh14-3-3 and RhGAPDH were identified using proteomics and western blot. The presence of RhFerritin-2 in tick hemolymph EVs was confirmed by western blot and immuno-electron microscopy. We demonstrated that PKH26-labeled hemolymph EVs are internalized by tick salivary glands and ovary cells in vitro.

CONCLUSIONS

The results suggest that tick EVs are secreted into, and circulated by, the hemolymph. EVs may play roles in the regulation of tick development, metabolism and reproduction.

Modulating neuroinflammation through molecular, cellular and biomaterial-based approaches to treat spinal cord injury

The neuroinflammatory response that is elicited after spinal cord injury contributes to both tissue damage and reparative processes. The complex and dynamic cellular and molecular changes within the spinal cord microenvironment result in a functional imbalance of immune cells and their modulatory factors. To facilitate wound healing and repair, it is necessary to manipulate the immunological pathways during neuroinflammation to achieve successful therapeutic interventions. In this review, recent advancements and fresh perspectives on the consequences of neuroinflammation after SCI and modulation of the inflammatory responses through the use of molecular-, cellular-, and biomaterial-based therapies to promote tissue regeneration and functional recovery will be discussed.

Advances in molecular therapies for targeting pathophysiology in spinal cord injury

INTRODUCTION

Spinal cord injury (SCI) affects 25,000-50,000 people around the world each year and there is no cure for SCI patients currently. The primary injury damages spinal cord tissues and secondary injury mechanisms, including ischemia, apoptosis, inflammation, and astrogliosis, further exacerbate the lesions to the spinal cord. Recently, researchers have designed various therapeutic approaches for SCI by targeting its major cellular or molecular pathophysiology.

AREAS COVERED

Some strategies have shown promise in repairing injured spinal cord for functional recoveries, such as administering neuroprotective reagents, targeting specific genes to promote robust axon regeneration of disconnected spinal fiber tracts, targeting epigenetic factors to enhance cell survival and neural repair, and facilitating neuronal relay pathways and neuroplasticity for restoration of function after SCI. This review focuses on the major advances in preclinical molecular therapies for SCI reported in recent years.

EXPERT OPINION

Recent progress in developing novel and effective repairing strategies for SCI is encouraging, but many challenges remain for future design of effective treatments, including developing highly effective neuroprotectants for early interventions, stimulating robust neuronal regeneration with functional synaptic reconnections among disconnected neurons, maximizing the recovery of lost neural functions with combination strategies, and translating the most promising therapies into human use.

Enhancement of nerve regeneration with nimodipine treatment after sciatic nerve injury

Peripheral nerve injuries (PNI/s) are common orthopedic conditions, characterized by motor and sensory deficits in the damaged region. There is growing evidence that the L-type calcium channel antagonist nimodipine has neuroprotective and neuroregenerative effects in animal models of neurological disorders. The efficacy of nimodipine on improving motor function and sensation following a sciatic nerve crush model was investigated in male Wistar rats as a model of PNI. At different time periods following damage, we evaluated motor function, sensory recovery, electrophysiology, histomorphometry, and gene expression. Moreover, we used histological and mass ratio analysis of the gastrocnemius muscle to assess atrophy. Our findings suggest that the nimodipine improves motor and sensory function more quickly in the damaged region 2, 4, and 6 weeks after 1 week of treatment. Nimodipine treatment also increased the number of myelinated fibers while decreasing their thickness, as shown by histomorphometry. Additionally, nimodipine treatment increases the mRNA levels of neurotrophic factors (BDNF and NGF), which are known to contribute to the regeneration of injured neurons. The impact of nimodipine in PNI recovery may be due to its stimulation of the CREB signaling pathway and suppression of pro-inflammatory factor production.

Neural stem/progenitor cell-derived extracellular vesicles: A novel therapy for neurological diseases and beyond

As bilayer lipid membrane vesicles secreted by neural stem/progenitor cells (NSCs), NSC-derived extracellular vesicles (NSC-EVs) have attracted growing attention for their promising potential to serve as novel therapeutic agents in treatment of neurological diseases due to their unique physicochemical characteristics and biological functions. NSC-EVs exhibit advantages such as stable physical and chemical properties, low immunogenicity, and high penetration capacity to cross blood-brain barrier to avoid predicaments of the clinical applications of NSCs that include autoimmune responses, ethical/religious concerns, and the problematic logistics of acquiring fetal tissues. More importantly, NSC-EVs inherit excellent neuroprotective and neuroregenerative potential and immunomodulatory capabilities from parent cells, and display outstanding therapeutic effects on mitigating behavioral alterations and pathological phenotypes of patients or animals with neurological diseases. In this review, we first comprehensively summarize the progress in functional research and application of NSC-EVs in different neurological diseases, including neurodegenerative diseases, acute neurological diseases, dementia/cognitive dysfunction, and peripheral diseases. Next, we provide our thoughts on current limitations/concerns as well as tremendous potential of NSC-EVs in clinical applications. Last, we discuss future directions of further investigations on NSC-EVs and their probable applications in both basic and clinical research.

Ca2+ Regulates Autophagy Through CaMKKβ/AMPK/mTOR Signaling Pathway in Mechanical Spinal cord Injury: An in vitro Study

Spinal cord injury (SCI), resulting in damage of the normal structure and function of the spinal cord, would do great harm to patients, physically and psychologically. The mechanism of SCI is very complex. At present, lots of studies have reported that autophagy was involved in the secondary injury process of SCI, and several researchers also found that calcium ions (Ca²⁺) played an important role in SCI by regulating necrosis, autophagy, or apoptosis. However, to our best of knowledge, no studies have linked the spinal cord mechanical injury, intracellular Ca²⁺, and autophagy in series. In this study, we have established an in vitro model of SCI using neural cells from fetal rats to explore the relationship among them, and found that mechanical injury could promote the intracellular Ca²⁺ concentration, and the increased Ca²⁺ level activated autophagy through the CaMKKβ/AMPK/mTOR pathway. Additionally, we found that apoptosis was also involved in this pathway. Thus, our study provides new insights into the specific mechanisms of SCI and may open up new avenues for the treatment of SCI.

Immunomodulatory and Anti-inflammatory effect of Neural Stem/Progenitor Cells in the Central Nervous System

Neuroinflammation is a critical event that responds to disturbed homeostasis and governs various neurological diseases in the central nervous system (CNS). The excessive inflammatory microenvironment in the CNS can adversely affect endogenous neural stem cells, thereby impeding neural self-repair. Therapies with neural stem/progenitor cells (NSPCs) have shown significant inhibitory effects on inflammation, which is mainly achieved through intercellular contact and paracrine signalings. The intercellular contact between NSPCs and immune cells, the activated CNS- resident microglia, and astrocyte plays a critical role in the therapeutic NSPCs homing and immunomodulatory effects. Moreover, the paracrine effect mainly regulates infiltrating innate and adaptive immune cells, activated microglia, and astrocyte through the secretion of bioactive molecules and extracellular vesicles. However, the molecular mechanism involved in the immunomodulatory effect of NSPCs is not well discussed. This article provides a systematic analysis of the immunomodulatory mechanism of NSPCs, discusses efficient ways to enhance its immunomodulatory ability, and gives suggestions on clinical therapy.

Crosstalk between exosomes and autophagy in spinal cord injury: fresh positive target for therapeutic application

Spinal cord injury (SCI) is a very serious clinical traumatic illness with a very high disability rate. It not only causes serious functional disorders below the injured segment, but also causes unimaginable economic burden to social development. Exosomes are nano-sized cellular communication carriers that exist stably in almost all organisms and cell types. Because of their capacity to transport proteins, lipids, and nucleic acids, they affect various physiological and pathological functions of recipient cells and parental cells. Autophagy is a process that relies on the lysosomal pathway to degrade cytoplasmic proteins and organelles and involves a variety of pathophysiological processes. Exosomes and autophagy play critical roles in cellular homeostasis following spinal cord injury. Presently, the coordination mechanism of exosomes and autophagy has attracted much attention in the early efficacy of spinal cord injury. In this review, we discussed the interaction of autophagy and exosomes from the perspective of molecular mechanisms, which might provide novel insights for the early therapeutic application of spinal cord injury.

Macrophage Extracellular Traps Exacerbate Secondary Spinal Cord Injury by Modulating Macrophage/Microglia Polarization via LL37/P2X7R/NF-κB Signaling Pathway

Persistent inflammation in the secondary spinal cord injury (SCI) is an important reason for the failure of nerve repair, which is partly due to the continuous activation of local M1-like macrophage/microglia. It is reported that extracellular trap (ET) has been a new way of cell death, which can be released by macrophages and named macrophage extracellular trap (Met). Furthermore, it exists widely in the pathophysiological process of many diseases, but it has been rarely studied in the field of SCI. In this study, we constructed a spinal cord contusion model and assessed the function outcome of SCI rats. We used immunofluorescence, flow cytometry, and transmission electron microscope (TEM) to demonstrate the existence of Mets. Besides, some related experiments had also been employed to explore the relationship between Mets and M1 polarization of macrophage/microglia. We also performed Co-IP and Western blotting to reveal a new extracellular proinflammatory signal pathway. Finally, we made a linear regression analysis between the concentrations of specific markers of Mets in human serum and ASIA scores. Briefly, our results suggested that macrophages infiltrated in SCI area could induce macrophage/microglia to differentiate into M1-like cells by releasing Mets, which may be achieved partly through LL37-P2X37-NF-κB signal pathway. However, limiting Mets could effectively inhibit M1 polarization and promote function recovery. In addition, the concentrations of Met related proteins in human serum showed high correlation with ASIA scores and could be applied to reflect the severity of SCI. In conclusion, Mets may be a new target for SCI therapy and a promising index for SCI assessment.

Next generation of neurological therapeutics: Native and bioengineered extracellular vesicles derived from stem cells

Extracellular vesicles (EVs)-based cell-free therapy, particularly stem cell-derived extracellular vesicles (SC-EVs), offers new insights into treating a series of neurological disorders and becomes a promising candidate for alternative stem cell regenerative therapy. Currently, SC-EVs are considered direct therapeutic agents by themselves and/or dynamic delivery systems as they have a similar regenerative capacity of stem cells to promote neurogenesis and can easily load many functional small molecules to recipient cells in the central nervous system. Meanwhile, as non-living entities, SC-EVs avoid the uncontrollability and manufacturability limitations of live stem cell products in vivo (e.g., low survival rate, immune response, and tumorigenicity) and in vitro (e.g., restricted sources, complex preparation processes, poor quality control, low storage, shipping instability, and ethical controversy) by strict quality control system. Moreover, SC-EVs can be engineered or designed to enhance further overall yield, increase bioactivity, improve targeting, and extend their half-life. Here, this review provides an overview on the biological properties of SC-EVs, and the current progress in the strategies of native or bioengineered SC-EVs for nerve injury repairing is presented. Then we further summarize the challenges of recent research and perspectives for successful clinical application to advance SC-EVs from bench to bedside in neurological diseases.

MicroRNA-451 Attenuates the Inflammatory Response of Activated Microglia by Downregulating Nucleotide Binding Oligomerization Domain-Like Receptor Protein 3

BACKGROUND

Spinal cord injury is the most common problem encountered during spinal surgery. After the initial trauma, the disruption of the blood-brain barrier and subsequent microglia activation result in extensive inflammatory responses. Inflammasomes are large protein complexes that are essential during inflammation. One of the most studied inflammasome components, nucleotide binding oligomerization domain-like receptor protein 3 (NLRP; nucleotide binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing 3), is widely expressed in the central nervous system. Previous research has shown that microRNA-451 (miR-451) might play a role in regulating inflammatory conditions.

METHODS

Using bioinformatics analysis, we found that NLRP3 is a direct target of miR-451. This in silico prediction was confirmed using dual-luciferase reporter gene assays. To further demonstrate that miR-451 influenced microglial NLRP3 production, we activated microglial cells with lipopolysaccharides.

RESULTS

Activating microglial cells with lipopolysaccharides resulted in the production of NLRP3 inflammasomes and the secretion of the proinflammatory cytokines interleukin-1β and interleukin-18. We were able to demonstrate that overexpression of miR-451 suppressed this NLRP3-induced proinflammatory cascade of events.

CONCLUSIONS

Our findings have highlighted the potential anti-inflammatory role of miR-451 in reducing the secondary neuronal damage after spinal cord injury.

The roles and applications of neural stem cells in spinal cord injury repair

Spinal cord injury (SCI), which has no current cure, places a severe burden on patients. Stem cell-based therapies are considered promising in attempts to repair injured spinal cords; such options include neural stem cells (NSCs). NSCs are multipotent stem cells that differentiate into neuronal and neuroglial lineages. This feature makes NSCs suitable candidates for regenerating injured spinal cords. Many studies have revealed the therapeutic potential of NSCs. In this review, we discuss from an integrated view how NSCs can help SCI repair. We will discuss the sources and therapeutic potential of NSCs, as well as representative pre-clinical studies and clinical trials of NSC-based therapies for SCI repair.

Exosomes Derived from Baicalin-Pretreated Mesenchymal Stem Cells Alleviate Hepatocyte Ferroptosis after Acute Liver Injury via the Keap1-NRF2 Pathway

Acute liver injury (ALI) is characterized as a severe metabolic dysfunction caused by extensive damage to liver cells. Ferroptosis is a type of cell death dependent on iron and oxidative stress, which differs from classical cell death, such as apoptosis and necrosis. Ferroptosis has unique morphological features, which mainly include mitochondrial dissolution and mitochondrial outline reduction. Furthermore, the intracellular accumulation of lipid peroxides directly affects the occurrence of ferroptosis. Baicalin, the main compound isolated from Scutellaria baicalensis, has anti-inflammatory and antioxidative effects. Recently, exosomes derived from preconditioned mesenchymal stem cells (MSCs) have shown great potential in the treatment of various diseases including ALI. This study investigates the ability of exosomes derived from baicalin-pretreated MSCs (Ba-Exo) to promote liver function recovery in mice with ALI compared with those without pretreatment. Through in vivo and in vitro experiments, this study demonstrates for the first time that Ba-Exo greatly attenuates D-galactosamine and lipopolysaccharide (D-GaIN/LPS)-induced liver damage and inhibits reactive oxygen species (ROS) production and lipid peroxide-induced ferroptosis. Moreover, P62 was significantly upregulated in Ba-Exo, whereas its downregulation in Ba-Exo counteracted the beneficial effect of Ba-Exo. P62 regulates hepatocyte ferroptosis by activating the Keap1-NRF2 pathway. The beneficial effect of Ba-Exo in inhibiting ferroptosis was also attenuated after the NRF2 pathway was inhibited. Therefore, baicalin pretreatment is an effective and promising approach to optimize the therapeutic efficacy of MSC-derived exosomes in ALI.

TSG-6 released from adipose stem cells-derived small extracellular vesicle protects against spinal cord ischemia reperfusion injury by inhibiting endoplasmic reticulum stress

Background

Spinal cord ischemia reperfusion injury (SCIRI) is a complication of aortic aneurysm repair or spinal cord surgery that is associated with permanent neurological deficits. Mesenchymal stem cell (MSC)-derived small extracellular vesicles (sEVs) have been shown to be potential therapeutic options for improving motor functions after SCIRI. Due to their easy access and multi-directional differentiation potential, adipose‐derived stem cells (ADSCs) are preferable for this application. However, the effects of ADSC-derived sEVs (ADSC-sEVs) on SCIRI have not been reported.

Results

We found that ADSC-sEVs inhibited SCIRI-induced neuronal apoptosis, degradation of tight junction proteins and suppressed endoplasmic reticulum (ER) stress. However, in the presence of the ER stress inducer, tunicamycin, its anti-apoptotic and blood–spinal cord barrier (BSCB) protective effects were significantly reversed. We found that ADSC-sEVs contain tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6) whose overexpression inhibited ER stress in vivo by modulating the PI3K/AKT pathway.

Conclusions

ADSC-sEVs inhibit neuronal apoptosis and BSCB disruption in SCIRI by transmitting TSG-6, which suppresses ER stress by modulating the PI3K/AKT pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02963-4.

Autologous exosome facilitates load and target delivery of bioactive peptides to repair spinal cord injury

Spinal cord injury (SCI) causes motor, sensory and automatic impairment due to rarely axon regeneration. Developing effective treatment for SCI in the clinic is extremely challenging because of the restrictive axonal regenerative ability and disconnection of neural elements after injury, as well as the limited systemic drug delivery efficiency caused by blood spinal cord barrier. To develop an effective non-invasive treatment strategy for SCI in clinic, we generated an autologous plasma exosome (AP-EXO) based biological scaffold where AP-EXO was loaded with neuron targeting peptide (RVG) and growth-facilitating peptides (ILP and ISP). This scaffold can be targeted delivered to neurons in the injured area and elicit robust axon regrowth across the lesion core to the levels over 30-fold greater than naïve treatment, thus reestablish the intraspinal circuits and promote motor functional recovery after spinal cord injury in mice. More importantly, in ex vivo, human plasma exosomes (HP-EXO) loaded with combinatory peptides of RVG, ILP and ISP showed safety and no liver and kidney toxicity in the application to nude SCI mice. Combining the efficacy and safety, the AP-EXO-based personalized treatment confers functional recovery after SCI and showed immense promising in biomedical applications in treating SCI. It is helpful to expand the application of combinatory peptides and human plasma derived autologous exosomes in promoting regeneration and recovery upon SCI treatment.

Oligodendroglia-derived extracellular vesicles activate autophagy via LC3B/BAG3 to protect against oxidative stress with an enhanced effect for HSPB8 enriched vesicles

Background

The contribution of native or modified oligodendroglia-derived extracellular vesicles (OL-EVs) in controlling chronic inflammation is poorly understood. In activated microglia, OL-EVs contribute to the removal of cytotoxic proteins following a proteotoxic stress. Intracellular small heat shock protein B8 (HSPB8) sustain this function by facilitating autophagy and protecting cells against oxidative stress mediated cell death. Therefore, secretion of HSPB8 in OL-EVs could be beneficial for neurons during chronic inflammation. However, how secreted HSPB8 contribute to cellular proteostasis remains to be elucidated.

Methods

We produced oligodendroglia-derived EVs, either native (OL-EVs) or HSPB8 modified (OL-HSPB8-EVs), to investigate their effects in controlling chronic inflammation and cellular homeostasis. We analyzed the impact of both EV subsets on either a resting or activated microglial cell line and on primary mixed neural cell culture cells. Cells were activated by stimulating with either tumor necrosis factor-alpha and interleukin 1-beta or with phorbol-12-myristate-13-acetate.

Results

We show that OL-EVs and modified OL-HSPB8-EVs are internalized by C20 microglia and by primary mixed neural cells. The cellular uptake of OL-HSPB8-EVs increases the endogenous HSPB8 mRNA expression. Consistently, our results revealed that both EV subsets maintained cellular homeostasis during chronic inflammation with an increase in the formation of autophagic vesicles. Both EV subsets conveyed LC3B-II and BAG3 autophagy markers with an enhanced effect observed for OL-HSPB8-EVs. Moreover, stimulation with either native or modified OL-HSPB8-EVs showed a significant reduction in ubiquitinated protein, reactive oxygen species and mitochondrial depolarization, with OL-HSPB8-EVs exhibiting a more protective effect. Both EV subsets did not induce cell death in the C20 microglia cell line or the primary mixed neural cultures.

Conclusion

We demonstrate that the functions of oligodendroglia secreted EVs enriched with HSPB8 have a supportive role, comparable to the native OL-EVs. Further development of engineered oligodendroglia derived EVs could be a novel therapeutic strategy in countering chronic inflammation.

Extracellular Vesicles in the Pathogenesis, Treatment, and Diagnosis of Spinal Cord Injury: A Mini-Review

BACKGROUND

Benefiting from in-depth research into stem cells, extracellular vesicles (EVs), which are byproducts of cells and membrane-wrapped microvesicles (30-120 nm) containing lipids, proteins, and nucleic acids, may cast light on the research and development of therapeutics capable of improving the neurological recovery of spinal cord injury (SCI) animals. However, the mechanistic modes of action for EVs in alleviating the lesion size of SCI remain to be solved, thus presenting a tremendous gap existing in translation from the laboratory to the clinic.

OBJECTIVE

The purpose of this minireview was to cover a wide range of basic views on EVs involved in SCI treatment, including the effects of EVs on the pathogenesis, treatment, and diagnosis of spinal cord injury.

METHODS

We searched databases (i.e., PubMed, Web of Science, Scopus, Medline, and EMBASE) and acquired all accessible articles published in the English language within five years. Studies reporting laboratory applications of EVs in the treatment of SCI were included and screened to include studies presenting relevant molecular mechanisms.

RESULTS

This review first summarized the basic role of EVs in cell communication, cell death, inflammatory cascades, scar formation, neuronal regrowth, and angiogenesis after SCI, thereby providing insights into neuroprotection and consolidated theories for future clinical application of EVs.

CONCLUSION

EVs participate in an extremely wide range of cell activities, play a critical role in cell communication centring neurons, and are considered potential therapies and biomarkers for SCI. miRNAs are the most abundant nucleic acids shipped by EVs and effluent cytokines, and they may represent important messengers of EVs and important factors in SCI treatment.

Advanced approaches to regenerate spinal cord injury: The development of cell and tissue engineering therapy and combinational treatments

Spinal cord injury (SCI) is a central nervous system (CNS) devastate event that is commonly caused by traumatic or non-traumatic events. The reinnervation of spinal cord axons is hampered through a myriad of devices counting on the damaged myelin, inflammation, glial scar, and defective inhibitory molecules. Unfortunately, an effective treatment to completely repair SCI and improve functional recovery has not been found. In this regard, strategies such as using cells, biomaterials, biomolecules, and drugs have been reported to be effective for SCI recovery. Furthermore, recent advances in combinatorial treatments, which address various aspects of SCI pathophysiology, provide optimistic outcomes for spinal cord regeneration. According to the global importance of SCI, the goal of this article review is to provide an overview of the pathophysiology of SCI, with an emphasis on the latest modes of intervention and current advanced approaches for the treatment of SCI, in conjunction with an assessment of combinatorial approaches in preclinical and clinical trials. So, this article can give scientists and clinicians' clues to help them better understand how to construct preclinical and clinical studies that could lead to a breakthrough in spinal cord regeneration.

Extracellular vesicle-associated small heat shock proteins as therapeutic agents in neurodegenerative diseases and beyond

Increasing evidence points towards using extracellular vesicles (EVs) as a therapeutic strategy in neurodegenerative diseases such as multiple sclerosis, Parkinson's, and Alzheimer's disease. EVs are nanosized carriers that play an essential role in intercellular communication and cellular homeostasis by transporting an active molecular cargo, including a large variety of proteins. Recent publications demonstrate that small heat shock proteins (HSPBs) exhibit a beneficial role in neurodegenerative diseases. Moreover, it is defined that HSPBs target the autophagy and the apoptosis pathway, playing a prominent role in chaperone activity and cell survival. This review elaborates on the therapeutic potential of EVs and HSPBs, in particular HSPB1 and HSPB8, in neurodegenerative diseases. We conclude that EVs and HSPBs positively influence neuroinflammation, central nervous system (CNS) repair, and protein aggregation in CNS disorders. Moreover, we propose the use of HSPB-loaded EVs as advanced nanocarriers for the future development of neurodegenerative disease therapies.

USP11 regulates autophagy-dependent ferroptosis after spinal cord ischemia-reperfusion injury by deubiquitinating Beclin 1

Spinal cord ischemia-reperfusion injury (SCIRI) is a serious trauma that can lead to loss of sensory and motor function. Ferroptosis is a new form of regulatory cell death characterized by iron-dependent accumulation of lipid peroxides. Ferroptosis has been studied in various diseases; however, the exact function and molecular mechanism of ferroptosis in SCIRI remain unknown. In this study, we demonstrated that ferroptosis is involved in the pathological mechanism of SCIRI. Inhibition of ferroptosis could promote the recovery of motor function in mice after SCIRI. In addition, we found that ubiquitin-specific protease 11 (USP11) was significantly upregulated in neuronal cells after hypoxia-reoxygenation and in the spinal cord in mice with I/R injury. Knockdown of USP11 in vitro and KO of USP11 in vivo (USP11^-/Y) significantly decreased neuronal cell ferroptosis. In mice, this promotes functional recovery after SCIRI. In contrast, in vitro, USP11 overexpression leads to classic ferroptosis events. Overexpression of USP11 in mice resulted in increased ferroptosis and poor functional recovery after SCIRI. Interestingly, upregulating the expression of USP11 also appeared to increase the production of autophagosomes and to cause substantial autophagic flux, a potential mechanism through which USP11 may enhance ferroptosis. The decreased autophagy markedly weakened the ferroptosis mediated by USP11 and autophagy induction had a synergistic effect with USP11. Importantly, USP11 promotes autophagy activation by stabilizing Beclin 1, thereby leading to ferroptosis. In conclusion, this study shows that ferroptosis is closely associated with SCIRI, and that USP11 plays a key role in regulating ferroptosis and additionally identifies USP11-mediated autophagy-dependent ferroptosis as a promising target for the treatment of SCIRI.

Small extracellular vesicles encapsulating CCL2 from activated astrocytes induce microglial activation and neuronal apoptosis after traumatic spinal cord injury

Background

Spinal cord injury (SCI) is a severe traumatic disease which causes high disability and mortality rates. The molecular pathological features after spinal cord injury mainly involve the inflammatory response, microglial and neuronal apoptosis, abnormal proliferation of astrocytes, and the formation of glial scars. However, the microenvironmental changes after spinal cord injury are complex, and the interactions between glial cells and nerve cells remain unclear. Small extracellular vesicles (sEVs) may play a key role in cell communication by transporting RNA, proteins, and bioactive lipids between cells. Few studies have examined the intercellular communication of astrocytes through sEVs after SCI. The inflammatory signal released from astrocytes is known to initiate microglial activation, but its effects on neurons after SCI remain to be further clarified.

Methods

Electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting were applied to characterize sEVs. We examined microglial activation and neuronal apoptosis mediated by astrocyte activation in an experimental model of acute spinal cord injury and in cell culture in vitro.

Results

Our results indicated that astrocytes activated after spinal cord injury release CCL2, act on microglia and neuronal cells through the sEV pathway, and promote neuronal apoptosis and microglial activation after binding the CCR2. Subsequently, the activated microglia release IL-1β, which acts on neuronal cells, thereby further aggravating their apoptosis.

Conclusion

This study elucidates that astrocytes interact with microglia and neurons through the sEV pathway after SCI, enriching the mechanism of CCL2 in neuroinflammation and spinal neurodegeneration, and providing a new theoretical basis of CCL2 as a therapeutic target for SCI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02268-y.

Spinal Cord Repair: From Cells and Tissue Engineering to Extracellular Vesicles

Spinal cord injury (SCI) is a debilitating condition, often leading to severe motor, sensory, or autonomic nervous dysfunction. As the holy grail of regenerative medicine, promoting spinal cord tissue regeneration and functional recovery are the fundamental goals. Yet, effective regeneration of injured spinal cord tissues and promotion of functional recovery remain unmet clinical challenges, largely due to the complex pathophysiology of the condition. The transplantation of various cells, either alone or in combination with three-dimensional matrices, has been intensively investigated in preclinical SCI models and clinical trials, holding translational promise. More recently, a new paradigm shift has emerged from cell therapy towards extracellular vesicles as an exciting "cell-free" therapeutic modality. The current review recapitulates recent advances, challenges, and future perspectives of cell-based spinal cord tissue engineering and regeneration strategies.

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.

Stem cell-derived exosomes as a cell free therapy against spinal cord injury

Recent evidence suggests that stem cell therapy has beneficial effects on spinal cord injury. It was subsequently established that these beneficial effects may be mediated through release of paracrine factors, a kind of extracellular vesicle known as exosomes. Stem cell-secreted nano-sized exosomes have shown great potential to reduce apoptosis and inflammation, enhance angiogenesis, and improve functional behavioral recovery following spinal cord injury. This review summarizes current knowledge about the influence of exosomes derived from stem cells on spinal cord protection and regeneration with their molecular mechanisms after injury.

Hypoxic pretreatment of small extracellular vesicles mediates cartilage repair in osteoarthritis by delivering miR-216a-5p

Osteoarthritis (OA) is a regressive joint disease that mainly affects the cartilage and surrounding tissues. Mounting studies have confirmed that the paracrine effect is related to the potential mechanism of mesenchymal stem cell (MSC) transplantation and that small extracellular vesicles (sEVs) play an imperative role in this paracrine signaling. In fact, hypoxia can significantly improve the effectiveness of MSC transplantation in various disease models. However, it remains unknown whether MSCs in the state of a hypoxic environment can enhance OA cartilage repair and whether this enhancement is mediated by sEV signaling. The primary aim of the present study was to determine whether sEVs from MSCs in the state of hypoxia (Hypo-sEVs) have a superior effect on OA cartilage repair relative to sEVs from MSCs in the normoxia (Nor-sEVs) state. By using an OA model and performing in vitro studies, we verified that Hypo-sEV treatment facilitated the proliferation, migration, and apoptosis suppression of chondrocytes to a greater extent than Nor-sEV treatment. Furthermore, we verified the functional role of sEV miR-216a-5p in the OA cartilage repair process. We also identified JAK2 as the target gene of sEV miR-216a-5p through a series of experiments. Our findings indicated that HIF-1α induces hypoxic BMSCs to release sEVs, which promote the proliferation, migration, and apoptosis inhibition of chondrocytes through the miR-216a-5p/JAK2/STAT3 signaling pathway. Therefore, hypoxic pretreatment is a prospective and effective method to maximize the therapeutic effect of MSC-derived sEVs on OA.

A bioactive injectable self-healing anti-inflammatory hydrogel with ultralong extracellular vesicles release synergistically enhances motor functional recovery of spinal cord injury

The repair and motor functional recovery after spinal cord injury (SCI) remains a worldwide challenge. The inflammatory microenvironment is one of main obstacles on inhibiting the recovery of SCI. Using mesenchymal stem cells (MSCs) derived extracellular vesicles to replace MSCs transplantation and mimic cell paracrine secretions provides a potential strategy for microenvironment regulation. However, the effective preservation and controlled release of extracellular vesicles in the injured spinal cord tissue are still not satisfied. Herein, we fabricated an injectable adhesive anti-inflammatory F127-polycitrate-polyethyleneimine hydrogel (FE) with sustainable and long term extracellular vesicle release (FE@EVs) for improving motor functional recovery after SCI. The orthotopic injection of FE@EVs hydrogel could encapsulate extracellular vesicles on the injured spinal cord, thereby synergistically induce efficient integrated regulation through suppressing fibrotic scar formation, reducing inflammatory reaction, promoting remyelination and axonal regeneration. This study showed that combining extracellular vesicles into bioactive multifunctional hydrogel should have great potential in achieving satisfactory locomotor recovery of central nervous system diseases.

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The novel FE hydrogel was designed for encapsulating the extracellular vesicles (FE@EVs).

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FE hydrogel exert the capabilities of temperature-responsive, injectable, adhesive and biocompatible.

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FE hydrogel with sustainable and long-term extracellular vesicle release for improving motor functional recovery after SCI.

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FE@EVs plays a vital role in pathological process of spinal cord injury in rats.

Lithium alleviated spinal cord injury (SCI)-induced apoptosis and inflammation in rats via BDNF-AS/miR-9-5p axis

Spinal cord injury (SCI) is a major cause of paralysis, disability and even death in severe cases. Lithium has neuroprotective effects on SCI, while the underlying mechanisms remain obscure. In the present study, we established a SCI rat model, which subsequently received lithium treatment. Results displayed that lithium treatment improved the locomotor function recovery and reduced apoptosis by increasing anti-apoptotic molecule expression and decreasing pro-apoptotic factor expression in SCI rats. Furthermore, lithium treatment alleviated the inflammatory response by inactivating the nuclear factor-kappa B (NF-κB) pathway and inhibited the expression of lncRNA brain-derived neurotrophic factor antisense (BDNF-AS) in SCI rats. Subsequent researches indicated that miR-9-5p was targeted and regulated by BDNF-AS. Lithium treatment rescued the upregulation of BDNF-AS expression and downregulation of miR-9-5p expression induced by H₂O₂ in SH-SY5Y cells. BDNF-AS overexpression or miR-9-5p interference attenuated the anti-apoptotic and anti-inflammatory effects of lithium chloride in SH-SY5Y cells that was damaged by H₂O₂ induction, revealing that lithium might act through the BDNF-AS/miR-9-5p axis. In vivo studies showed that the injection of BDNF-AS adenovirus vector or miR-9-5p inhibitor reversed the effects of lithium on the histologic morphology of spinal cord, motor function, inflammatory reaction and apoptosis in SCI rats, which was consistent with the results of in vitro studies. In conclusion, our data demonstrated that lithium reduced SCI-induced apoptosis and inflammation in rats via the BDNF-AS/miR-9-5p axis.

ESC-sEVs Rejuvenate Aging Hippocampal NSCs by Transferring SMADs to Regulate the MYT1-Egln3-Sirt1 Axis

Tissue stem cell senescence leads to stem cell exhaustion, which results in tissue homeostasis imbalance and a decline in regeneration capacity. However, whether neural stem cell (NSC) senescence occurs and causes neurogenesis reduction during aging is unknown. In this study, mice at different ages were used to detect age-related hippocampal NSC (H-NSC) senescence, as well as the function and mechanism of embryonic stem cell-derived small extracellular vesicles (ESC-sEVs) in rejuvenating H-NSC senescence. We found a progressive cognitive impairment, as well as age-related H-NSC senescence, in mice. ESC-sEV treatment significantly alleviated H-NSC senescence, recovered compromised self-renewal and neurogenesis capacities, and reversed cognitive impairment. Transcriptome analysis revealed that myelin transcription factor 1 (MYT1) is downregulated in senescent H-NSCs but upregulated by ESC-sEV treatment. In addition, knockdown of MYT1 in young H-NSCs accelerated age-related phenotypes and impaired proliferation and differentiation capacities. Mechanistically, ESC-sEVs rejuvenated senescent H-NSCs partly by transferring SMAD family members 4 (SMAD4) and 5 (SMAD5) to activate MYT1, which downregulated egl-9 family hypoxia inducible factor 3 (Egln3), followed by activation of hypoxia inducible factor 2 subunit α (HIF-2α), nicotinamide phosphoribosyl transferase (NAMPT), and sirtuin 1 (Sirt1) successively. Taken together, our results indicated that H-NSC senescence caused cellular exhaustion, neurogenesis reduction, and cognitive impairment during aging, which can be reversed by ESC-sEVs. Thus, ESC-sEVs may be promising therapeutic candidates for age-related diseases.

Niche Cells Crosstalk In Neuroinflammation After Traumatic Brain Injury

Traumatic brain injury (TBI) is recognized as the disease with high morbidity and disability around world in spite of the work ongoing in neural protection. Due to heterogeneity among the patients, it's still hard to acquire satisfying achievements in clinic. Neuroinflammation, which exists since primary injury occurs, with elusive duality, appear to be of significance from recovery of injury to neurogenesis. In recent years, studied have revealed that communication in neurogenic niche is more than “cell to cell” communication, and study on NSCs represent it as central role in the progress of neural regeneration. Hence, the neuroinflammation-affecting crosstalk after TBI, and clarifying definitive role of NSCs in the course of regeneration is a promising subject for researchers, for its great potential in overcoming the frustrating status quo in clinic, promoting welfare of TBI patient.

Neuron-derived exosomes-transmitted miR-124-3p protect traumatically injured spinal cord by suppressing the activation of neurotoxic microglia and astrocytes

Background

Spinal cord injury (SCI) is a catastrophic injury that can cause irreversible motor dysfunction with high disability. Exosomes participate in the transport of miRNAs and play an essential role in intercellular communication via transfer of genetic material. However, the miRNAs in exosomes which derived from neurons, and the underlying mechanisms by which they contribute to SCI remain unknown.

Methods

A contusive in vivo SCI model and a series of in vitro experiments were carried out to explore the therapeutic effects of exosomes. Then, a miRNA microarray analysis and rescue experiments were performed to confirm the role of neuron-derived exosomal miRNA in SCI. Western blot, luciferase activity assay, and RNA-ChIP were used to investigate the underlying mechanisms.

Results

The results indicated that neuron-derived exosomes promoted functional behavioral recovery by suppressing the activation of M1 microglia and A1 astrocytes in vivo and in vitro. A miRNA array showed miR-124-3p to be the most enriched in neuron-derived exosomes. MYH9 was identified as the target downstream gene of miR-124-3p. A series of experiments were used to confirm the miR-124-3p/MYH9 axis. Finally, it was found that PI3K/AKT/NF-κB signaling cascades may be involved in the modulation of microglia by exosomal miR-124-3p.

Conclusion

A combination of miRNAs and neuron-derived exosomes may be a promising, minimally invasive approach for the treatment of SCI.

Resveratrol-primed exosomes strongly promote the recovery of motor function in SCI rats by activating autophagy and inhibiting apoptosis via the PI3K signaling pathway

Spinal cord injury (SCI) is a traumatic condition of the central nervous system (CNS) that can cause paralysis of the limbs. The molecular mechanisms of neural repair following SCI remain unclear and no effective treatment for SCI currently exists, since drugs have difficulty crossing the blood-brain barrier (BBB). The present study aimed to investigate whether exosomes could be used as specific carriers of resveratrol for induction of neuronal autophagy both in vitro and in vivo for the treatment of SCI. The results indicate that exosomes are able to enhance the solubility of resveratrol and enhance penetration of the drug through the BBB, thereby increasing its concentration in the CNS. Exosomes derived from resveratrol-treated primary microglia (Exo + Res) assisted the rehabilitation of paralyzed limbs in rats. Restoration of neural function following SCI was mediated through increased induction of autophagy and inhibition of apoptosis of neurons both in vitro and in vivo via activation of the PI3K signaling pathway. The mechanism of action of Exo + Res may be associated with the PI3K inhibitor 3-methyladenine (3-MA) in primary spinal neurons. The results suggest that Exo + Res are highly effective at crossing the BBB with good stability, suggesting they have potential for enhancing targeted drug delivery and the recovery of neuronal function in SCI therapy, likely associated with the induction of autophagy and inhibition of apoptosis via the PI3K signaling pathway.

MicroRNA-421-3p-abundant small extracellular vesicles derived from M2 bone marrow-derived macrophages attenuate apoptosis and promote motor function recovery via inhibition of mTOR in spinal cord injury

Background

Spinal cord injury (SCI) has a very disabling central nervous system impact but currently lacks effective treatment. Bone marrow-derived macrophages (BMDMs) are recruited to the injured area after SCI and participate in the regulation of functional recovery with microglia. Previous studies have shown that M2 microglia-derived small extracellular vesicles (SEVs) have neuroprotective effects, but the effects of M2 BMDM-derived sEVs (M2 BMDM-sEVs) have not been reported in SCI treatment.

Results

In this study, we investigated the role of M2 BMDM-sEVs in vivo and in vitro for SCI treatment and its mechanism. Our results indicated that M2 BMDM-sEVs promoted functional recovery after SCI and reduced neuronal apoptosis in mice. In addition, M2 BMDM-sEVs targeted mammalian target of rapamycin (mTOR) to enhance the autophagy level of neurons and reduce apoptosis. MicroRNA-421-3P (miR-421-3p) can bind to the 3′ untranslated region (3′UTR) of mTOR. MiR-421-3p mimics significantly reduced the activity of luciferase-mTOR 3′UTR constructs and increased autophagy. At the same time, tail vein injection of inhibitors of SEVs (Inh-sEVs), which were prepared by treatment with an miR-421-3p inhibitor, showed diminished protective autophagy of neuronal cells in vivo.

Conclusions

In conclusion, M2 BMDM-sEVs inhibited the mTOR autophagy pathway by transmitting miR-421-3p, which reduced neuronal apoptosis and promoted functional recovery after SCI, suggesting that M2 BMDM-sEVs may be a potential therapy for SCI.

Bone Marrow Mesenchymal Stem Cell-Derived Exosomes Improves Spinal Cord Function After Injury in Rats by Activating Autophagy

Background

Spinal cord injury (SCI) is a global medical problem. The smallest membrane-bound nanovesicles, known as exosomes, have a role in complex intercellular communication systems and can be used directly as therapeutic agents by acting as important paracrine factors. Nevertheless, the use of exosomes derived from BMSCs (BMSC-Exos) to treat SCI has been less, and the specific mechanism has not yet been reported.

Methods

BMSC-Exos were characterized by TEM, NTA and Western blot. The effects of BMSC-Exos treatment were compared by SCI in vivo model and a series of in vitro experiments.

Results

BMSC-Exos were found to enhance the expression of autophagy-related proteins LC3IIB and Beclin-1 and enabled autophagosomes formation. After BMSC-Exos treatment, there was marked decline in the level of expression of proapoptotic protein cleaved caspase-3, while that of the antiapoptotic protein Bcl-2 was upregulated.

Conclusion

BMSC-Exos can attenuate neuronal apoptosis by promoting autophagy and promote the potential efficacy of functional behavior recovery in SCI rats. In summary, these findings expand the theoretical knowledge and forms a realistic route for the future treatment of SCI by BMSC-Exos.

An appropriate level of autophagy reduces emulsified isoflurane-induced apoptosis in fetal neural stem cells

Autophagy plays essential roles in cell survival. However, the functions and regulation of the autophagy-related proteins Atg5, LC3B, and Beclin 1 during anesthetic-induced developmental neurotoxicity remain unclear. This study aimed to understand the autophagy pathways and mechanisms that affect neurotoxicity, induced by the anesthetic emulsified isoflurane, in rat fetal neural stem cells. Fetal neural stem cells were cultured, in vitro, and neurotoxicity was induced by emulsified isoflurane treatment. The effects of pretreatment with the autophagy inhibitors 3-methyladenine and bafilomycin and the effects of transfection with small interfering RNA against ATG5 (siRNA-Atg5) were observed. Cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and apoptosis was assessed using flow cytometry. Ultrastructural changes were analyzed through transmission electron microscopy. The levels of the autophagy-related proteins LC3B, Beclin 1, Atg5, and P62 and the pro-apoptosis-related protein caspase-3 were analyzed using western blot assay. The inhibition of cell proliferation and that of apoptosis rate increased after treatment with emulsified isoflurane. Autophagolysosomes, monolayer membrane formation due to lysosomal degradation, were observed. The autophagy-related proteins LC3B, Beclin 1, Atg5, and P62 and caspase-3 were upregulated. These results confirm that emulsified isoflurane can induce toxicity and autophagy in fetal neural stem cells. Pre-treatment with 3-methyladenine and bafilomycin increased the apoptosis rate in emulsified isoflurane-treated fetal neural stem cells, which indicated that the complete inhibition of autophagy does not alleviate emulsified isoflurane-induced fetal neural stem cell toxicity. Atg5 expression was decreased significantly by siRNA-Atg5 transfection, and cell proliferation was inhibited. These results verify that the Atg5 autophagy pathway can be regulated to maintain appropriate levels of autophagy, which can inhibit the neurotoxicity induced by emulsified isoflurane anesthetic in fetal neural stem cells.