Embryonic Stem Cell Derived Small Extracellular Vesicles Modulate Regulatory T Cells to Protect against Ischemic Stroke

Mechanism of inflammatory response and therapeutic effects of stem cells in ischemic stroke: current evidence and future perspectives

Ischemic stroke is a leading cause of death and disability worldwide, with an increasing trend and tendency for onset at a younger age. China, in particular, bears a high burden of stroke cases. In recent years, the inflammatory response after stroke has become a research hotspot: understanding the role of inflammatory response in tissue damage and repair following ischemic stroke is an important direction for its treatment. This review summarizes several major cells involved in the inflammatory response following ischemic stroke, including microglia, neutrophils, monocytes, lymphocytes, and astrocytes. Additionally, we have also highlighted the recent progress in various treatments for ischemic stroke, particularly in the field of stem cell therapy. Overall, understanding the complex interactions between inflammation and ischemic stroke can provide valuable insights for developing treatment strategies and improving patient outcomes. Stem cell therapy may potentially become an important component of ischemic stroke treatment.

Cartilage progenitor cells derived extracellular vesicles-based cell-free strategy for osteoarthritis treatment by efficient inflammation inhibition and extracellular matrix homeostasis restoration

Osteoarthritis (OA) is a common degenerative joint disease which currently lacks of effective agents. It is therefore urgent and necessary to seek an effective approach that can inhibit inflammation and promote cartilage matrix homeostasis. Cartilage progenitor cells (CPCs) are identified as a cell population of superficial zone in articular cartilage which possess strong migration ability, proliferative capacity, and chondrogenic potential. Recently, the application of CPCs may represent a novel cell therapy strategy for OA treatment. There is growing evidence that extracellular vesicles (EVs) are primary mediators of the benefits of stem cell-based therapy. In this study, we explored the protective effects of CPCs-derived EVs (CPCs-EVs) on IL-1β-induced chondrocytes. We found CPCs-EVs exhibited chondro-protective effects in vitro. Furthermore, our study demonstrated that CPCs-EVs promoted matrix anabolism and inhibited inflammatory response at least partially via blocking STAT3 activation. In addition, liquid chromatography-tandem mass spectrometry analysis identified 991 proteins encapsulated in CPCs-EVs. By bioinformatics analysis, we showed that STAT3 regulatory proteins were enriched in CPCs-EVs and could be transported to chondrocytes. To promoting the protective function of CPCs-EVs in vivo, CPCs-EVs were modified with cationic peptide ε-polylysine-polyethylene-distearyl phosphatidylethanolamine (PPD) for surface charge reverse. In posttraumatic OA mice, our results showed PPD modified CPCs-EVs (PPD-EVs) effectively inhibited extracellular matrix catabolism and attenuated cartilage degeneration. Moreover, PPD-EVs down-regulated inflammatory factors expressions and reduced OA-related pain in OA mice. In ex-vivo cultured OA cartilage explants, PPD-EVs successfully promoted matrix anabolism and inhibited inflammation. Collectively, CPCs-EVs-based cell-free therapy is a promising strategy for OA treatment.

Role of Regulatory T Cells in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease that can lead to severe neurological dysfunction in surviving patients, resulting in a heavy burden on patients and their families. When ICH occurs, the blood‒brain barrier is disrupted, thereby promoting immune cell migration into damaged brain tissue. As important immunosuppressive T cells, regulatory T (Treg) cells are involved in the maintenance of immune homeostasis and the suppression of immune responses after ICH. Treg cells mitigate brain tissue damage after ICH in a variety of ways, such as inhibiting the neuroinflammatory response, protecting against blood‒brain barrier damage, reducing oxidative stress damage and promoting nerve repair. In this review, we discuss the changes in Treg cells in ICH clinical patients and experimental animals, the mechanisms by which Treg cells regulate ICH and treatments targeting Treg cells in ICH, aiming to support new therapeutic strategies for clinical treatment.

Extracellular vesicles as nanotheranostic platforms for targeted neurological disorder interventions

Central Nervous System (CNS) disorders represent a profound public health challenge that affects millions of people around the world. Diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and traumatic brain injury (TBI) exemplify the complexities and diversities that complicate their early detection and the development of effective treatments. Amid these challenges, the emergence of nanotechnology and extracellular vesicles (EVs) signals a new dawn for treating and diagnosing CNS ailments. EVs are cellularly derived lipid bilayer nanosized particles that are pivotal in intercellular communication within the CNS and have the potential to revolutionize targeted therapeutic delivery and the identification of novel biomarkers. Integrating EVs with nanotechnology amplifies their diagnostic and therapeutic capabilities, opening new avenues for managing CNS diseases. This review focuses on examining the fascinating interplay between EVs and nanotechnology in CNS theranostics. Through highlighting the remarkable advancements and unique methodologies, we aim to offer valuable perspectives on how these approaches can bring about a revolutionary change in disease management. The objective is to harness the distinctive attributes of EVs and nanotechnology to forge personalized, efficient interventions for CNS disorders, thereby providing a beacon of hope for affected individuals. In short, the confluence of EVs and nanotechnology heralds a promising frontier for targeted and impactful treatments against CNS diseases, which continue to pose significant public health challenges. By focusing on personalized and powerful diagnostic and therapeutic methods, we might improve the quality of patients.

A Panorama of Extracellular Vesicle Applications: From Biomarker Detection to Therapeutics

Extracellular vesicles (EVs) secreted by all cell types are involved in the cell-to-cell transfer of regulatory factors that influence cell and tissue phenotypes in normal and diseased tissues. EVs are thus a rich source of biomarker targets for assays that analyze blood and urinary EVs for disease diagnosis. Sensitive biomarker detection in EVs derived from specific cell populations is a key major hurdle when analyzing complex biological samples, but innovative approaches surveyed in this Perspective can streamline EV isolation and enhance the sensitivity of EV detection procedures required for clinical application of EV-based diagnostics and therapeutics, including nanotechnology and microfluidics, to achieve EV characterizations. Finally, this Perspective also outlines opportunities and challenges remaining for clinical translation of EV-based assays.

Identification of specific markers for human pluripotent stem cell-derived small extracellular vesicles

Pluripotent stem cell-derived small extracellular vesicles (PSC-sEVs) have demonstrated great clinical translational potential in multiple aging-related degenerative diseases. Characterizing the PSC-sEVs is crucial for their clinical applications. However, the specific marker pattern of PSC-sEVs remains unknown. Here, the sEVs derived from two typical types of PSCs including induced pluripotent stem cells (iPSC-sEVs) and embryonic stem cells (ESC-sEVs) were analysed using proteomic analysis by liquid chromatography with tandem mass spectrometry (LC-MS/MS), and surface marker phenotyping analysis by nanoparticle flow cytometry (NanoFCM). A group of pluripotency-related proteins were found to be enriched in PSC-sEVs by LC-MS/MS and then validated by Western Blot analysis. To investigate whether these proteins were specifically expressed in PSC-sEVs, sEVs derived from seven types of non-PSCs (non-PSC-sEVs) were adopted for analysis. The results showed that PODXL, OCT4, Dnmt3a, and LIN28A were specifically enriched in PSC-sEVs but not in non-PSC-sEVs. Then, commonly used surface antigens for PSC identification (SSEA4, Tra-1-60 and Tra-1-81) and PODXL were gauged at single-particle resolution by NanoFCM for surface marker identification. The results showed that the positive rates of PODXL (>50%) and SSEA4 (>70%) in PSC-sEVs were much higher than those in non-PSC-sEVs (<10%). These results were further verified with samples purified by density gradient ultracentrifugation. Taken together, this study for the first time identified a cohort of specific markers for PSC-sEVs, among which PODXL, OCT4, Dnmt3a and LIN28A can be detected with Western Blot analysis, and PODXL and SSEA4 can be detected with NanoFCM analysis. The application of these specific markers for PSC-sEVs identification may advance the clinical translation of PSCs-sEVs.

The Landscape of Biomimetic Nanovesicles in Brain Diseases

Brain diseases, such as brain tumors, neurodegenerative diseases, cerebrovascular diseases, and brain injuries, are caused by various pathophysiological changes, which pose a serious health threat. Brain disorders are often difficult to treat due to the presence of the blood-brain barrier (BBB). Biomimetic nanovesicles (BNVs), including endogenous extracellular vesicles (EVs) derived from various cells and artificial nanovesicles, possess the ability to penetrate the BBB and thus can be utilized for drug delivery to the brain. BNVs, especially endogenous EVs, are widely distributed in body fluids and usually carry various disease-related signal molecules such as proteins, RNA, and DNA, and may also be analyzed to understand the etiology and pathogenesis of brain diseases. This review covers the exhaustive classification and characterization of BNVs and pathophysiological roles involved in various brain diseases, and emphatically focuses on nanotechnology-integrated BNVs for brain disease theranostics, including various diagnosis strategies and precise therapeutic regulations (e.g., immunity regulation, disordered protein clearance, anti-neuroinflammation, neuroregeneration, angiogenesis, and the gut-brain axis regulation). The remaining challenges and future perspectives regarding the nanotechnology-integrated BNVs for the diagnosis and treatment of brain diseases are also discussed and outlined.

Hippocampal-derived extracellular vesicle synergistically deliver active adenosine hippocampus targeting to promote cognitive recovery after stroke

Ischemic stroke is a neurological disease that leads to brain damage and severe cognitive impairment. In this study, extracellular vesicles(Ev) derived from mouse hippocampal cells (HT22) were used as carriers, and adenosine (Ad) was encapsulated to construct Ev-Ad to target the damaged hippocampus. The results showed that, Ev-Ad had significant antioxidant effect and inhibited apoptosis. In vivo, Ev-Ad reduced cell death and reversed inflammation in hippocampus of ischemic mice, and improved long-term memory and learning impairment by regulating the expression of the A1 receptor and the A2A receptor in the CA1 region. Thus, the developmental approach based on natural carriers that encapsulating Ad not only successfully restored nerves after ischemic stroke, but also improved cognitive impairment in the later stage of ischemic stroke convalescence. The development and design of therapeutic drugs provides a new concept and method for the treatment of cognitive impairment in the convalescent phase after ischemic stroke.

Extracellular vesicles set the stage for brain plasticity and recovery by multimodal signalling

Extracellular vesicles (EVs) are extremely versatile naturally occurring membrane particles that convey complex signals between cells. EVs of different cellular sources are capable of inducing striking therapeutic responses in neurological disease models. Differently from pharmacological compounds that act by modulating defined signalling pathways, EV-based therapeutics possess multiple abilities via a variety of effectors, thus allowing the modulation of complex disease processes that may have very potent effects on brain tissue recovery. When applied in vivo in experimental models of neurological diseases, EV-based therapeutics have revealed remarkable effects on immune responses, cell metabolism and neuronal plasticity. This multimodal modulation of neuroimmune networks by EVs profoundly influences disease processes in a highly synergistic and context-dependent way. Ultimately, the EV-mediated restoration of cellular functions helps to set the stage for neurological recovery. With this review we first outline the current understanding of the mechanisms of action of EVs, describing how EVs released from various cellular sources identify their cellular targets and convey signals to recipient cells. Then, mechanisms of action applicable to key neurological conditions such as stroke, multiple sclerosis and neurodegenerative diseases are presented. Pathways that deserve attention in specific disease contexts are discussed. We subsequently showcase considerations about EV biodistribution and delineate genetic engineering strategies aiming at enhancing brain uptake and signalling. By sketching a broad view of EV-orchestrated brain plasticity and recovery, we finally define possible future clinical EV applications and propose necessary information to be provided ahead of clinical trials. Our goal is to provide a steppingstone that can be used to critically discuss EVs as next generation therapeutics for brain diseases.

Stem cell-based ischemic stroke therapy: Novel modifications and clinical challenges

Ischemic stroke (IS) causes severe disability and high mortality worldwide. Stem cell (SC) therapy exhibits unique therapeutic potential for IS that differs from current treatments. SC's cell homing, differentiation and paracrine abilities give hope for neuroprotection. Recent studies on SC modification have enhanced therapeutic effects for IS, including gene transfection, nanoparticle modification, biomaterial modification and pretreatment. These methods improve survival rate, homing, neural differentiation, and paracrine abilities in ischemic areas. However, many problems must be resolved before SC therapy can be clinically applied. These issues include production quality and quantity, stability during transportation and storage, as well as usage regulations. Herein, we reviewed the brief pathogenesis of IS, the "multi-mechanism" advantages of SCs for treating IS, various SC modification methods, and SC therapy challenges. We aim to uncover the potential and overcome the challenges of using SCs for treating IS and convey innovative ideas for modifying SCs.

Bioactive Ceria Nanoenzymes Target Mitochondria in Reperfusion Injury to Treat Ischemic Stroke

Overproduction of reactive oxygen species by damaged mitochondria after ischemia is a key factor in the subsequent cascade of damage. Delivery of therapeutic agents to the mitochondria of damaged neurons in the brain is a potentially promising targeted therapeutic strategy for the treatment of ischemic stroke. In this study, we developed a ceria nanoenzymes synergistic drug-carrying nanosystem targeting mitochondria to address multiple factors of ischemic stroke. Each component of this nanosystem works individually as well as synergistically, resulting in a comprehensive therapy. Alleviation of oxidative stress and modulation of the mitochondrial microenvironment into a favorable state for ischemic tolerance are combined to restore the ischemic microenvironment by bridging mitochondrial and multiple injuries. This work also revealed the detailed mechanisms by which the proposed nanodelivery system protects the brain, which represents a paradigm shift in ischemic stroke treatment.

Extracellular vesicle biogenesis of three-dimensional human pluripotent stem cells in a novel Vertical-Wheel bioreactor

Extracellular vesicles (EVs) secreted by human-induced pluripotent stem cells (hiPSCs) have great potential as cell-free therapies in various diseases, including prevention of blood-brain barrier senescence and stroke. However, there are still challenges in pre-clinical and clinical use of hiPSC-EVs due to the need for large-scale production of a large quantity. Vertical-Wheel bioreactors (VWBRs) have design features that allow the biomanufacturing of hiPSC-EVs using a scalable aggregate or microcarrier-based culture system under low shear stress. EV secretion by undifferentiated hiPSCs expanded as 3-D aggregates and on Synthemax II microcarriers in VWBRs were investigated. Additionally, two types of EV collection media, mTeSR and HBM, were compared. The hiPSCs were characterized by metabolite and transcriptome analysis as well as EV biogenesis markers. Protein and microRNA cargo were analysed by proteomics and microRNA-seq, respectively. The in vitro functional assays of microglia stimulation and proliferation were conducted. HiPSCs expanded as 3-D aggregates and on microcarriers had comparable cell number, while microcarrier culture had higher glucose consumption, higher glycolysis and lower autophagy gene expression based on mRNA-seq. The microcarrier cultures had at least 17-23 fold higher EV secretion, and EV collection in mTeSR had 2.7-3.7 fold higher yield than HBM medium. Microcarrier culture with mTeSR EV collection had a smaller EV size than other groups, and the cargo was enriched with proteins (proteomics) and miRNAs (microRNA-seq) reducing apoptosis and promoting cell proliferation (e.g. Wnt-related pathways). hiPSC-EVs demonstrated the ability of stimulating proliferation and M2 polarization of microglia in vitro. HiPSC expansion on microcarriers produces much higher yields of EVs than hiPSC aggregates in VWBRs. EV collection in mTeSR increases yield compared to HBM. The biomanufactured EVs from microcarrier culture in mTeSR have exosomal characteristics and are functional in microglia stimulation, which paves the ways for future in vivo anti-aging study.

Recent Advances in Chemically Engineered Nanostructures Impact on Ischemic Stroke Treatment

Stroke is a serious public health problem that raises expenses for society and causes long-term impairment and death. However, due to restricted blood-brain barrier (BBB) penetration, there are few treatment alternatives for treating stroke. Recanalization techniques, neuroprotective medications, and recovery techniques are all forms of treatment. The ischemic stroke treatment window is too narrow for logical and efficient therapy, and detection is possible only in advanced stages. BBB integrity disruption, neurotoxicity, and the brief half-life of therapeutic thrombolytics are the key molecular pathogenic causes of ischemic stroke. Existing neuroprotective drugs' inability to promote the recovery of ischemic brain tissue after a stroke is another factor that contributes to the disease's progression, chronic nature, and severity. A possible approach to getting around these medication restrictions and boosting the effectiveness of therapies is nanotechnology. In order to get around these drug-related restrictions and boost the effectiveness of therapies for neurological conditions such as stroke, nanotechnology has emerged as a viable option. These problems might be avoided by using nanoparticle-based methods to create a thrombolytic medication that is safe to use after the tissue plasminogen activator (tPA) treatment window has passed. The idea of using biomimetic nanoparticles in the future for the treatment of ischemic stroke through immunotherapy and stem cell therapy is highlighted, along with recent advancements in the study of nanomaterials for ischemic stroke diagnostics and treatment.

Nano-Plumber Reshapes Glymphatic-Lymphatic System to Sustain Microenvironment Homeostasis and Improve Long-Term Prognosis after Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Long-term changes in the microenvironment of the brain contribute to the degeneration of neurological function following TBI. However, current research focuses primarily on short-term modulation during the early phases of TBI, not on the critical significance of long-term homeostasis in the brain microenvironment. Notably, dysfunction of the glymphatic-lymphatic system results in the accumulation of danger/damage-associated molecular patterns (DAMPs) in the brain, which is regarded as the leading cause of long-term microenvironmental disturbances following TBI. Here, a nanostructure, Nano-plumber, that co-encapsulates the microenvironment regulator pro-DHA and the lymphatic-specific growth factor VEGF-C is developed, allowing for a sustainable and orderly regulation of the microenvironment to promote long-term neurological recovery. Nano-plumber reverses the injury microenvironment by suppressing microglia and astrocytes activation and maintaining reduced activation via enhanced glymphatic-lymphatic drainage, and significantly improves the neurological function of rodents with TBI. This study demonstrates that glymphatic-lymphatic system reconstruction is essential for enhancing long-term prognosis following TBI, and that the Nano-plumber developed here may serve as a clinically translatable treatment option for TBI.

Ginkgo biloba extract promotes Treg differentiation to ameliorate ischemic stroke via inhibition of HIF-1α/HK2 pathway

The ischemic brain can dialogue with peripheral tissues through the immune system. Ginkgo biloba extract (EGb) was used to regulate various neurological disorders; however, the impact of EGb on ischemic stroke is still unclear. Here, we aimed to investigate whether immunomodulation has participated in the beneficial effects of EGb on ischemia/reperfusion (I/R) brain injury. Mice were orally administered with EGb once daily for 7 days before the induction of I/R. Neurobehavioral scores, infarct volume, and brain inflammation were determined. The proportion of CD4+ T cells was detected by flow cytometry. EGb significantly lowered neurobehavioral scores, infarct volume, and the level of inflammatory cytokines in I/R mice. Interestingly, EGb altered the proportion of CD4+ T cells, particularly increasing the proportion of Treg cells. Depletion of Treg cells weakened the neuroprotective effects of EGb on ischemic stroke; furthermore, EGb decreased the expression of HIF-1α and HK2 and promoted the differentiation of Treg cells in vitro. EGb suppressed the HIF-1α/HK2 signaling pathway to promote the differentiation of Treg cells and ameliorate ischemic stroke in mice. The expansion effect of EGb on Treg cells could be exploited as part of future stroke therapy.

Regulatory T cells: A suppressor arm in post-stroke immune homeostasis

The activation of the immune system and the onset of pro- and anti-inflammatory responses play crucial roles in the pathophysiological processes of ischaemic stroke (IS). CD4+ regulatory T (Treg) cells is the main immunosuppressive cell population that is studied in the context of peripheral tolerance, autoimmunity, and the development of chronic inflammatory diseases. In recent years, more studies have focused on immune modulation after IS, and Treg cells have been demonstrated to be essential in the remission of inflammation, nerve regeneration, and behavioural recovery. However, the exact effects of Treg cells in the context of IS remain controversial, with some studies suggesting a negative correlation with stroke outcomes. In this review, we aim to provide a comprehensive overview of the current understanding of Treg cell involvement in post-stroke homeostasis. We summarized the literature focusing on the temporal changes in Treg cell populations after IS, the mechanisms of Treg cell-mediated immunomodulation in the brain, and the potential of Treg cell-based therapies for treatment. The purposes of the current article are to address the importance of Treg cells and inspire more studies to help physicians, as well as scientists, understand the whole map of immune responses during IS.

Insight into extracellular vesicles in vascular diseases: intercellular communication role and clinical application potential

BACKGROUND

Cells have been increasingly known to release extracellular vesicles (EVs) to the extracellular environment under physiological and pathological conditions. A plethora of studies have revealed that EVs contain cell-derived biomolecules and are found in circulation, thereby implicating them in molecular trafficking between cells. Furthermore, EVs have an effect on physiological function and disease development and serve as disease biomarkers.

MAIN BODY

Given the close association  between EV circulation and vascular disease, this review aims to provide a brief introduction to EVs, with a specific focus on the EV cargoes participating in pathological mechanisms, diagnosis, engineering, and clinical potential, to highlight the emerging evidence suggesting promising targets in vascular diseases. Despite the expansion of research in this field, some noticeable limitations remain for clinical translational research.

CONCLUSION

This review makes a novel contribution to a summary of recent advances and a perspective on the future of EVs in vascular diseases. Video Abstract.

Surface-tethered ROS-responsive micelle backpacks for boosting mesenchymal stem cell vitality and modulating inflammation in ischemic stroke treatment

Mesenchymal stem cells (MSCs) exhibited remarkable therapeutic potential in ischemic stroke due to their exceptional immunomodulatory ability and paracrine effect; they have also been regarded as excellent neuroprotectant delivery vehicles with inflammatory tropism. However, the presence of high levels of reactive oxygen species (ROS) and an oxidative stress environment at the lesion site inhibits cell survival and further therapeutic effects. Using bioorthogonal click chemistry, ROS-responsive luteolin-loaded micelles were tethered to the surface of MSCs. As MSCs migrated to the ischemic brain, the micelles would achieve ROS-responsive release of luteolin to protect MSCs from excessive oxidative damage while inhibiting neuroinflammation and scavenging ROS to ameliorate ischemic stroke. This study provided an effective and prospective therapeutic strategy for ischemic stroke and a framework for a stem cell-based therapeutic system to treat inflammatory cerebral diseases.

Amniotic membrane mesenchymal stromal cell-derived secretome in the treatment of acute ischemic stroke: A case report

BACKGROUND

Stroke is the second and third leading cause of death and disability, respectively. To date, no definitive treatment can repair lost brain function. Recently, various preclinical studies have been reported on mesenchymal stromal cells (MSCs) and their derivatives and their potential as alternative therapies for stroke.

CASE SUMMARY

A 45-year-old female suffered an acute stroke, which led to paralysis in the left upper and lower limbs. The amniotic membrane MSC-derived secretome (MSC-secretome) was intravenously transplanted once a week for 4 wk. MSC-secretome-regulated regulatory T cells were investigated for the beneficial effects. The clinical improvement of this patient was accompanied by an increased frequency of regulatory T cells after transplantation.

CONCLUSION

Intravenous administration of MSC-secretome can potentially treat patients who suffer from acute ischemic stroke.

Lycium barbarum polysaccharide inhibits ischemia-induced autophagy by promoting the biogenesis of neural stem cells-derived extracellular vesicles to enhance the delivery of miR-133a-3p

BACKGROUND

Neural stem cell-derived extracellular vesicles (NSC-EVs) mediated endogenous neurogenesis determines a crucial impact on spontaneous recovery after stroke. Here, we checked the influence of Lycium barbarum polysaccharide (LBP) on the biogenesis of NSC-EVs and then focused on studying mechanisms of LBP in ameliorating ischemic stroke outcome.

METHODS

LBP was prepared to precondition NSCs and isolate EVs. MCAO models and primary NSCs were administrated to evaluate the therapeutic effect. RT-PCR, western blot, flow cytometry, and immunofluorescence techniques were performed to explore the mechanism.

RESULTS

LBP pretreatment increased the production of NSC-EVs and improved the neuroprotective and recovery effects of NSC-EV in ischemic stroke mice. LBP-pretreated NSC-EV in a dose-dependent manner substantially reduced neuronal death compared with NSC-EV. Screening of the signaling cascade involved in the interaction between NSC-EV and neurons revealed that AMPK/mTOR signaling pathway inhibited autophagic activity in neurons receiving either treatment paradigm. NSC-EVs but not EVs collected from NSCs pretreated with the anti-miR-133a-3p oligonucleotide reduced cell death, whereas the anti-oligonucleotide promoted autophagy activity and cell death by modulating AMPK/mTOR signaling in OGD-induced primary neurons.

CONCLUSION

LBP activated AMPK/mTOR signaling pathway by increasing the enrichment and transfer of miR-133a-3p in NSC-EVs to inhibit stroke-induced autophagy activity.

Observing Extracellular Vesicles Originating from Endothelial Cells in Vivo Demonstrates Improved Astrocyte Function Following Ischemic Stroke via Aggregation-Induced Emission Luminogens

Extracellular vesicles (EVs) obtained from endothelial cells (ECs) have significant therapeutic potential in the clinical management of individuals with ischemic stroke (IS) because they effectively treat ischemic stroke in animal models. However, because molecular probes with both high labeling efficiency and tracer stability are lacking, monitoring the actions of EC-EVs in the brain remains difficult. The specific intracellular targets in the brain that EC-EVs act on to produce their protective effects are still unknown, greatly impeding their use in clinical settings. For this research, we created a probe that possessed aggregation-induced emission (AIE) traits (namely, TTCP), enabling the effective labeling of EC-EVs while preserving their physiological properties. In vitro, TTCP simultaneously had a higher EC-EV labeling efficiency and better tracer stability than the commercial EV tags PKH-67 and DiI. In vivo, TTCP precisely tracked the actions of EC-EVs in a mouse IS model without influencing their protective effects. Furthermore, through the utilization of TTCP, it was determined that astrocytes were the specific cells affected by EC-EVs and that EC-EVs exhibited a safeguarding impact on astrocytes following cerebral ischemia-reperfusion (I/R) injury. These protective effects encompassed the reduction of the inflammatory reaction and apoptosis as well as the enhancement of cell proliferation. Further analysis showed that miRNA-155-5p carried by EC-EVs is responsible for these protective effects via regulation of the c-Fos/AP-1 pathway; this information provided a strategy for IS therapy. In conclusion, TTCP has a high EC-EV labeling efficiency and favorable in vivo tracer stability during IS therapy. Moreover, EC-EVs are absorbed by astrocytes during cerebral I/R injury and promote the restoration of neurological function through the regulation of the c-Fos/AP-1 signaling pathway.

Delivery of mitochondria-containing extracellular vesicles to the BBB for ischemic stroke therapy

INTRODUCTION

Ischemic stroke-induced mitochondrial dysfunction in brain endothelial cells (BECs) leads to breakdown of the blood-brain barrier (BBB) causing long-term neurological dysfunction. Restoration of mitochondrial function in injured BECs is a promising therapeutic strategy to alleviate stroke-induced damage. Mounting evidence demonstrate that selected subsets of cell-derived extracellular vehicles (EVs), such as exosomes (EXOs) and microvesicles (MVs), contain functional mitochondrial components. Therefore, development of BEC-derived mitochondria-containing EVs for delivery to the BBB will (1) alleviate mitochondrial dysfunction and limit long-term neurological dysfunction in ischemic stroke and (2) provide an alternative therapeutic option for treating numerous other diseases associated with mitochondrial dysfunction.

AREA COVERED

This review will discuss (1) how EV subsets package different types of mitochondrial components during their biogenesis, (2) mechanisms of EV internalization and functional mitochondrial responses in the recipient cells, and (3) EV biodistribution and pharmacokinetics - key factors involved in the development of mitochondria-containing EVs as a novel BBB-targeted stroke therapy.

EXPERT OPINION

Mitochondria-containing MVs have demonstrated therapeutic benefits in ischemic stroke and other pathologies associated with mitochondrial dysfunction. Delivery of MV mitochondria to the BBB is expected to protect the BBB integrity and neurovascular unit post-stroke. MV mitochondria quality control, characterization, mechanistic understanding of its effects in vivo, safety and efficacy in different preclinical models, large-scale production, and establishment of regulatory guidelines are foreseeable milestones to harness the clinical potential of MV mitochondria delivery.

Murine Coronavirus Disease 2019 Lethality Is Characterized by Lymphoid Depletion Associated with Suppressed Antigen-Presenting Cell Functionality

The disease severity of coronavirus disease 2019 (COVID-19) varies considerably from asymptomatic to serious, with fatal complications associated with dysregulation of innate and adaptive immunity. Lymphoid depletion in lymphoid tissues and lymphocytopenia have both been associated with poor disease outcomes in patients with COVID-19, but the mechanisms involved remain elusive. In this study, human angiotensin-converting enzyme 2 (hACE2) transgenic mouse models susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were used to investigate the characteristics and determinants of lethality associated with the lymphoid depletion observed in SARS-CoV-2 infection. The lethality of Wuhan SARS-CoV-2 infection in K18-hACE2 mice was characterized by severe lymphoid depletion and apoptosis in lymphoid tissues related to fatal neuroinvasion. The lymphoid depletion was associated with a decreased number of antigen-presenting cells (APCs) and their suppressed functionality below basal levels. Lymphoid depletion with reduced APC function was a specific feature observed in SARS-CoV-2 infection but not in influenza A infection and had the greatest prognostic value for disease severity in murine COVID-19. Comparison of transgenic mouse models resistant and susceptible to SARS-CoV-2 infection revealed that suppressed APC function could be determined by the hACE2 expression pattern and interferon-related signaling. Thus, we demonstrated that lymphoid depletion associated with suppressed APC function characterizes the lethality of COVID-19 mouse models. Our data also suggest a potential therapeutic approach to prevent the severe progression of COVID-19 by enhancing APC functionality.

Intranasally administered extracellular vesicles from human induced pluripotent stem cell-derived neural stem cells quickly incorporate into neurons and microglia in 5xFAD mice

Introduction

Extracellular vesicles (EVs) released by human-induced pluripotent stem cell (hiPSC)-derived neural stem cells (NSCs) have robust antiinflammatory and neurogenic properties due to therapeutic miRNAs and proteins in their cargo. Hence, hiPSC-NSC-EVs are potentially an excellent biologic for treating neurodegenerative disorders, including Alzheimer's disease (AD).

Methods

This study investigated whether intranasally (IN) administered hiPSC-NSC-EVs would quickly target various neural cell types in the forebrain, midbrain, and hindbrain regions of 3-month-old 5xFAD mice, a model of β-amyloidosis and familial AD. We administered a single dose of 25 × 10⁹ hiPSC-NSC-EVs labeled with PKH26, and different cohorts of naïve and 5xFAD mice receiving EVs were euthanized at 45 min or 6 h post-administration.

Results

At 45 min post-administration, EVs were found in virtually all subregions of the forebrain, midbrain, and hindbrain of naïve and 5xFAD mice, with predominant targeting and internalization into neurons, interneurons, and microglia, including plaque-associated microglia in 5xFAD mice. EVs also came in contact with the plasma membranes of astrocytic processes and the soma of oligodendrocytes in white matter regions. Evaluation of CD63/CD81 expression with the neuronal marker confirmed that PKH26 + particles found within neurons were IN administered hiPSC-NSC-EVs. At 6 h post-administration, EVs persisted in all cell types in both groups, with the distribution mostly matching what was observed at 45 min post-administration. Area fraction (AF) analysis revealed that, in both naïve and 5xFAD mice, higher fractions of EVs incorporate into forebrain regions at both time points. However, at 45 min post-IN administration, AFs of EVs within cell layers in forebrain regions and within microglia in midbrain and hindbrain regions were lower in 5xFAD mice than naïve mice, implying that amyloidosis reduces EV penetrance.

Discussion

Collectively, the results provide novel evidence that IN administration of therapeutic hiPSC-NSC-EVs is an efficient avenue for directing such EVs into neurons and glia in all brain regions in the early stage of amyloidosis. As pathological changes in AD are observed in multiple brain areas, the ability to deliver therapeutic EVs into various neural cells in virtually every brain region in the early stage of amyloidosis is attractive for promoting neuroprotective and antiinflammatory effects.

Advances in Therapeutic Applications of Extracellular Vesicles

Extracellular vesicles (EVs) are nanoscale bilayer phospholipid membrane vesicles released by cells. Contained large molecules such as nucleic acid, protein, and lipid, EVs are an integral part of cell communication. The contents of EVs vary based on the cell source and play an important role in both pathological and physiological conditions. EVs can be used as drugs or targets in disease treatment, and changes in the contents of EVs can indicate the progression of diseases. In recent years, with the continuous exploration of the structure, characteristics, and functions of EVs, the potential of engineered EVs for drug delivery and therapy being constantly explored. This review provides a brief overview of the structure, characteristics and functions of EVs, summarizes the advanced application of EVs and outlook on the prospect of it. It is our hope that this review will increase understanding of the current development of medical applications of EVs and help us overcome future challenges.

SENP3-mediated deSUMOylation of c-Jun facilitates microglia-induced neuroinflammation after cerebral ischemia and reperfusion injury

Recent evidences have implicated that SENP3 is a deSUMOylase which possesses neuronal damage effects in cerebral ischemia. However, its role in microglia remains poorly understood. Here, we found that SENP3 was upregulated in the peri-infarct areas of mice following ischemic stroke. Furthermore, knockdown of SENP3 significantly inhibits the expression of proinflammatory cytokines and chemokines in microglial cells. Mechanistically, SENP3 can bind and then mediated the deSUMOylation of c-Jun, which activated its transcriptional activity, ultimately followed by the activation of MAPK/AP-1 signaling pathway. In addition, microglia-specific SENP3 knockdown alleviated ischemia-induced neuronal damage, and markedly diminished infract volume, ameliorated sensorimotor and cognitive function in animals subjected to ischemic stroke. These results indicated SENP3 functions as a novel regulator of microglia-induced neuroinflammation by activating the MAPK/AP-1 signaling pathway via mediating the deSUMOylation of c-Jun. Interventions of SENP3 expression or its interaction with c-Jun would be a new and promising therapeutic strategy for ischemic stroke.

Human pluripotent stem cell-derived extracellular vesicles: From now to the future

Extracellular vesicles (EVs) are nanometric particles that enclose cell-derived bioactive molecules in a lipid bilayer and serve as intercellular communication tools. Accordingly, in various biological contexts, EVs are reported to engage in immune modulation, senescence, and cell proliferation and differentiation. Therefore, EVs could be key elements for potential off-the-shelf cell-free therapy. Little has been studied regarding EVs derived from human pluripotent stem cells (hPSC-EVs), even though hPSCs offer good opportunities for induction of tissue regeneration and unlimited proliferative ability. In this review article, we provide an overview of studies using hPSC-EVs, focusing on identifying the conditions in which the cells are cultivated for the isolation of EVs, how they are characterized, and applications already demonstrated. The topics reported in this article highlight the incipient status of the studies in the field and the significance of hPSC-EVs’ prospective applications as PSC-derived cell-free therapy products.

Tailored Apoptotic Vesicle Delivery Platform for Inflammatory Regulation and Tissue Repair to Ameliorate Ischemic Stroke

Apoptotic vesicles (ApoVs) hold great promise for inflammatory regulation and tissue repair. However, little effort has been dedicated to developing ApoV-based drug delivery platforms, while the insufficient targeting capability of ApoVs also limits their clinical applications. This work presents a platform architecture that integrates apoptosis induction, drug loading, and functionalized proteome regulation, followed by targeting modification, enabling the creation of an apoptotic vesicle delivery system to treat ischemic stroke. Briefly, α-mangostin (α-M) was utilized to induce mesenchymal stem cell (MSC) apoptosis while being loaded onto MSC-derived ApoVs as an anti-oxidant and anti-inflammatory agent for cerebral ischemia/reperfusion injury. Matrix metalloproteinase activatable cell-penetrating peptide (MAP), a microenvironment-responsive targeting peptide, was modified on the surface of ApoVs to obtain the MAP-functionalized α-M-loaded ApoVs. Such engineered ApoVs targeted the injured ischemic brain after systemic injection and achieved an enhanced neuroprotective activity due to the synergistic effect of ApoVs and α-M. The internal protein payloads of ApoVs, upon α-M activation, were found engaged in regulating immunological response, angiogenesis, and cell proliferation, all of which contributed to the therapeutic effects of ApoVs. The findings provide a universal framework for creating ApoV-based therapeutic drug delivery systems for the amelioration of inflammatory diseases and demonstrate the potential of MSC-derived ApoVs to treat neural injury.

The central role of peripheral inflammation in ischemic stroke

Stroke pathology and its treatments conventionally focus on the brain. Probing inflammation, a critical secondary cell death mechanism in stroke, has been largely relegated to the brain. To this end, peripheral inflammation has emerged as an equally potent contributor to the onset and progression of stroke secondary cell death. Here, we review novel concepts on peripheral organs displaying robust inflammatory response to stroke. These inflammation-plagued organs include the spleen, cervical lymph nodes, thymus, bone marrow, gastrointestinal system, and adrenal glands, likely converging their inflammatory effects through B and T-cells. Recognizing the significant impact of this systemic inflammation, we also discuss innovative stroke therapeutics directed at sequestration of peripheral inflammation. This review paper challenges the paradigm of a brain-centered disease pathology and treatment and offers a peripheral approach to our stroke understanding.

Therapeutic potential of stem cell extracellular vesicles for ischemic stroke in preclinical rodent models: a meta-analysis

BACKGROUND

Extracellular vesicles derived from stem cells (SC-EVs) have been proposed as a novel therapy for ischemic stroke. However, their effects remain incompletely understood. Therefore, we conducted this meta-analysis to systematically review the efficacy of SC-EVs on ischemic stroke in preclinical rodent models.

METHODS

Using PubMed, EMBASE, and the Web of Science, we searched through studies published up to August 2021 that investigated the treatment effects of SC-EVs in a rodent ischemic stroke model. Infarct volume was the primary outcome. Neurological severity scores (mNSS) were the secondary outcome. The standard mean difference (SMD) and the confidence interval (CI) were calculated using a random-effects model. R and Stata 15.1 were used to conduct the meta-analysis.

RESULTS

Twenty-one studies published from 2015 to 2021 met the inclusion criteria. We also found that SCs-EVs reduced infarct volume by an SMD of - 2.05 (95% CI - 2.70, - 1.40; P < 0.001). Meanwhile, our results revealed an overall positive effect of SCs-derived EVs on the mNSS with an SMD of - 1.42 (95% CI - 1.75, - 1.08; P < 0.001). Significant heterogeneity among studies was observed. Further stratified and sensitivity analyses did not identify the source of heterogeneity.

CONCLUSION

The present meta-analysis confirmed that SC-EV therapy could improve neuron function and reduce infarct volume in a preclinical rodent ischemic stroke model, providing helpful clues for human clinical trials on SC-EVs.

iPSC-sEVs alleviate microglia senescence to protect against ischemic stroke in aged mice

The polarization of microglia plays an important role in the outcome of ischemic stroke (IS). In the aged population, senescent microglia show a predominant pro-inflammatory phenotype, which leads to worse outcomes in aged ischemic stroke compared to young ischemic stroke. Recent research demonstrated that inducible pluripotent stem cell-derived small extracellular vesicles (iPSC-sEVs) possess the significant anti-ageing ability. We hypothesized that iPSC-sEVs could alleviate microglia senescence to regulate microglia polarization in aged ischemic stroke. In this study, we showed that treatment with iPSC-sEVs significantly alleviated microglia senescence as indicated by the decreased senescence-associated proteins including P16, P21, P53, and γ-H2AX as well as the activity of SA-β-gal, and inhibited pro-inflammatory activation of microglia both in vivo and in vitro. Furthermore, iPSC-sEVs shifted microglia from pro-inflammatory phenotype to anti-inflammatory phenotype, which reduced the apoptosis of neurons, and improved the outcome of aged stroke mice. Mechanism studies showed that iPSC-sEVs reversed the loss of Rictor and downstream p-AKT (s473) in senescent microglia, which was involved in the senescence and pro-inflammatory phenotype regulation of microglia. Inhibition of Rictor abolished the iPSC-sEVs-afforded phosphorylation of AKT and alleviation of inflammation of senescent microglia. Proteomics results indicated that iPSC-sEVs carried transforming growth factor-β1 (TGF-β1) to upregulate Rictor and p-AKT in senescent microglia, which could be hindered by blocking TGF-β1. Taken together, our work demonstrates iPSC-sEVs reverse the senescent characteristic of microglia in aged brains and therefore improve the outcome after stroke, at least, via delivering TGF-β1 to upregulate Rictor and p-AKT. Our data suggest that iPSC-sEVs might be a novelty therapeutic method for aged ischemic stroke and other diseases involving senescent microglia.

Selective ischemic-hemisphere targeting Ginkgolide B liposomes with improved solubility and therapeutic efficacy for cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CI/RI) remains the main cause of disability and death in stroke patients due to lack of effective therapeutic strategies. One of the main issues related to CI/RI treatment is the presence of the blood-brain barrier (BBB), which affects the intracerebral delivery of drugs. Ginkgolide B (GB), a major bioactive component in commercially available products of Ginkgo biloba, has been shown significance in CI/RI treatment by regulating inflammatory pathways, oxidative damage, and metabolic disturbance, and seems to be a candidate for stroke recovery. However, limited by its poor hydrophilicity and lipophilicity, the development of GB preparations with good solubility, stability, and the ability to cross the BBB remains a challenge. Herein, we propose a combinatorial strategy by conjugating GB with highly lipophilic docosahexaenoic acid (DHA) to obtain a covalent complex GB-DHA, which can not only enhance the pharmacological effect of GB, but can also be encapsulated in liposomes stably. The amount of finally constructed Lipo@GB-DHA targeting to ischemic hemisphere was validated 2.2 times that of free solution in middle cerebral artery occlusion (MCAO) rats. Compared to the marketed ginkgolide injection, Lipo@GB-DHA significantly reduced infarct volume with better neurobehavioral recovery in MCAO rats after being intravenously administered both at 2 h and 6 h post-reperfusion. Low levels of reactive oxygen species (ROS) and high neuron survival in vitro was maintained via Lipo@GB-DHA treatment, while microglia in the ischemic brain were polarized from the pro-inflammatory M1 phenotype to the tissue-repairing M2 phenotype, which modulate neuroinflammatory and angiogenesis. In addition, Lipo@GB-DHA inhibited neuronal apoptosis via regulating the apoptotic pathway and maintained homeostasis by activating the autophagy pathway. Thus, transforming GB into a lipophilic complex and loading it into liposomes provides a promising nanomedicine strategy with excellent CI/RI therapeutic efficacy and industrialization prospects.

LILRB2-containing small extracellular vesicles from glioblastoma promote tumor progression by promoting the formation and expansion of myeloid-derived suppressor cells

BACKGROUND

Leukocyte immunoglobulin-like receptor subfamily B2 (LILRB2) was reported to be an inhibitory molecule with suppressive functions. sEVs mediate communication between cancer cells and other cells. However, the existence of LILRB2 on sEVs in circulation and the function of sEVs-LILRB2 are still unknown. This study aims to investigate the role of LILRB2 in GBM and determine how LILRB2 in sEVs regulates tumor immunity.

METHODS

LILRB2 expression in normal brain and GBM tissues was detected by immunohistochemistry, and the effect of LILRB2 on prognosis was evaluated in an orthotopic brain tumor model. Next, a subcutaneous tumor model was constructed to evaluate the function of pirb in vivo. The immune cells in the tumor sites and spleen were detected by immunofluorescence staining and flow cytometry. Then, the presence of pirb in sEVs was confirmed by WB. The percentage of immune cells after incubation with sEVs from GL261 (GL261-sEVs) or sEVs from GL261-pirb⁺ (GL261-sEVs-pirb) was detected by flow cytometry. Then, the effect of pirb on sEVs was evaluated by a tumor-killing assay and proliferation assay. Finally, subcutaneous tumor models were constructed to evaluate the function of pirb on sEVs.

RESULTS

LILRB2 was overexpressed in human GBM tissue and was closely related to an immunosuppressive TME in GBM. Then, a protumor ability of LILRB2 was observed in subcutaneous tumor models, which was related to lower CD8 + T cells and higher MDSCs (myeloid-derived suppressor cells) in the tumor and spleen compared to those of the control group. Next, we found that pirb on sEVs (sEVs-pirb) inhibits the function of CD8 + T cells by promoting the formation and expansion of MDSCs. Furthermore, the protumor function of sEVs-pirb was demonstrated in subcutaneous tumor models.

CONCLUSION

We discovered that LILRB2/pirb can be transmitted between GBM cells via sEVs and that pirb on sEVs induces the formation and expansion of MDSCs. The induced MDSCs facilitate the formation of an immunosuppressive TME.

Gut-brain axis: Mechanisms and potential therapeutic strategies for ischemic stroke through immune functions

After an ischemic stroke (IS) occurs, immune cells begin traveling to the brain and immune system from the gut and gastrointestinal tract, where most of them typically reside. Because the majority of the body's macrophages and more than 70% of the total immune cell pool are typically found within the gut and gastrointestinal tract, inflammation and immune responses in the brain and immune organs require the mobilization of a large number of immune cells. The bidirectional communication pathway between the brain and gut is often referred to as the gut-brain axis. IS usually leads to intestinal motility disorders, dysbiosis of intestinal microbiota, and a leaky gut, which are often associated with poor prognosis in patients with IS. In recent years, several studies have suggested that intestinal inflammation and immune responses play key roles in the development of IS, and thus may become potential therapeutic targets that can drive new therapeutic strategies. However, research on gut inflammation and immune responses after stroke remains in its infancy. A better understanding of gut inflammation and immune responses after stroke may be important for developing effective therapies. This review discusses the immune-related mechanisms of the gut-brain axis after IS and compiles potential therapeutic targets to provide new ideas and strategies for the future effective treatment of IS.

Inducible Pluripotent Stem Cell-Derived Small Extracellular Vesicles Rejuvenate Senescent Blood-Brain Barrier to Protect against Ischemic Stroke in Aged Mice

Blood-brain barrier (BBB) breakdown after ischemic stroke exacerbates brain injury and BBB senescence can cause severe neurological deficits in aged ischemic stroke population. Recent evidence reveals that inducible pluripotent stem cell-derived small extracellular vesicles (iPSC-sEVs) possess phenomenal antisenescence capability. However, whether iPSC-sEVs can rejuvenate BBB senescence to improve stroke outcomes in aged mice remains unknown. Here, we showed that long-term treatment with iPSC-sEVs alleviated aging-induced BBB senescence in aged mice. In aged stroke mice, iPSC-sEVs significantly mitigated BBB integrity damage, reduced the following infiltration of peripheral leukocytes, and decreased the release of pro-inflammatory factors from the leukocytes, which ultimately inhibited neuronal death and improved neurofunctional recovery. Mechanism studies showed that iPSC-sEVs could activate the endothelial nitric oxide synthase (eNOS) and up-regulate sirtuin 1 (Sirt1) in senescent endothelial cells. Blocking the activation of eNOS abolished iPSC-sEV-mediated rejuvenation of BBB senescence and the protection of BBB integrity. Proteomics results demonstrated that iPSC-sEVs were enriched with bioactive factors including AKT serine/threonine kinase 1 (AKT1) and calmodulin (CALM) to activate the eNOS-Sirt1 axis. Further investigation showed that AKT1 and CALM inhibitors blocked iPSC-sEV-afforded activation of the eNOS-Sirt1 axis in senescent endothelial cells. Taken together, iPSC-sEVs can protect against ischemic stroke in aged mice by rejuvenating BBB senescence, partially, through delivering AKT1 and CALM to activate eNOS-Sirt1 axis, which indicates that iPSC-sEVs treatment is an effective alternative to treat ischemic stroke in the aged population.

Research hotspots and frotiers of stem cells in stroke: A bibliometric analysis from 2004 to 2022

Background: Stroke is one of the leading causes of mortality and permanent disability worldwide. However, the current stroke treatment has a limited effect. Therefore, a new treatment is urgently needed. Stem cell therapy is a cutting-edge treatment for stroke patients. This study aimed to gain better understanding of global stem cell trends in stroke via a bibliometric analysis. Methods: We used the Web of Science Core Collection to search pertinent articles about stem cells in stroke published between 2004 and 2022. Analysis was conducted using CiteSpace, VOSviewer, and the R package "bibliometrix" to identify publication outputs, countries/regions, institutions, authors/co-cited authors, journals/co-cited journals, co-cited references, and keywords. Results: A total of 6,703 publications were included in the bibliometric analysis. The total number of citations significantly and rapidly increased between 2004 and 2022, with the most pronounced growth pattern observed in the period of 2008-2009. In terms of authoritarian countries, the USA had the most publications among the countries. As for institutions and authors, the most prolific institution was the University of South Florida, followed by Oakland University and then Shanghai Jiao Tong University, and Chopp, M. and Borlongan, Cesario V, had the most output among the authors. Regarding the journals, Cell Transplantation had the highest publication, followed by Brain Research. As for references, "Mesenchymal stem cells as trophic mediators" was the most frequently cited (2,082), and the article entitled Neuronal replacement from endogenous precursors in the adult brain after stroke had the strongest burstiness (strength = 81.35). Emerging hot words in the past decade included "adhesion molecule," "mesenchymal stromal cell," "extracellular vesicle," "pluripotent stem cells," "signaling pathway," "plasticity," and "exosomes." Conclusion: Between 2004 and 2022, the terms "neurogenesis," "angiogenesis," "mesenchymal stem cells," "extracellular vesicle," "exosomes," "inflammation," and "oxidative stress" have emerged as the hot research areas for research on stem cells in stroke. Although stem cells exert a number of positive effects, the main mechanisms for mitigating the damage caused by stroke are still unknown. Clinical challenges may include complicating factors that can affect the efficacy of stem cell therapy, which are worth a deep exploration.

Molecular Mechanisms and Clinical Application of Multipotent Stem Cells for Spinal Cord Injury

Spinal Cord Injury (SCI) is a common neurological disorder with devastating psychical and psychosocial sequelae. The majority of patients after SCI suffer from permanent disability caused by motor dysfunction, impaired sensation, neuropathic pain, spasticity as well as urinary complications, and a small number of patients experience a complete recovery. Current standard treatment modalities of the SCI aim to prevent secondary injury and provide limited recovery of lost neurological functions. Stem Cell Therapy (SCT) represents an emerging treatment approach using the differentiation, paracrine, and self-renewal capabilities of stem cells to regenerate the injured spinal cord. To date, multipotent stem cells including mesenchymal stem cells (MSCs), neural stem cells (NSCs), and hematopoietic stem cells (HSCs) represent the most investigated types of stem cells for the treatment of SCI in preclinical and clinical studies. The microenvironment of SCI has a significant impact on the survival, proliferation, and differentiation of transplanted stem cells. Therefore, a deep understanding of the pathophysiology of SCI and molecular mechanisms through which stem cells act may help improve the treatment efficacy of SCT and find new therapeutic approaches such as stem-cell-derived exosomes, gene-modified stem cells, scaffolds, and nanomaterials. In this literature review, the pathogenesis of SCI and molecular mechanisms of action of multipotent stem cells including MSCs, NSCs, and HSCs are comprehensively described. Moreover, the clinical efficacy of multipotent stem cells in SCI treatment, an optimal protocol of stem cell administration, and recent therapeutic approaches based on or combined with SCT are also discussed.

miR-126-3p-loaded small extracellular vesicles secreted by urine-derived stem cells released from a phototriggered imine crosslink hydrogel could enhance vaginal epithelization after vaginoplasty

Background

Due to the large area and deep width of the artificial neovagina after vaginoplasty, it takes a considerable amount of time to achieve complete epithelization of the neovagina. Currently, the clinical therapies for vaginal epithelization after vaginoplasty are still dissatisfactory. Recent studies showed that small extracellular vesicles (sEVs) derived from stem cells could accelerate wound epithelization. The sustained release of sEVs from optimized hydrogels may be a promising strategy to accelerate vaginal epithelization after vaginoplasty.

Methods

The efficacy of phototriggered imine crosslink hydrogels (piGEL) containing sEVs derived from human urine-derived stem cells (hUSC-sEVs, piGEL-sEVs) on vaginal mucosa defects in rabbits was assessed by wound closure rates, histological analysis and immunofluorescence staining analysis. Cell counting kit-8, 5-ethynyl-2′-deoxyuridine and scratch wound assays were performed to assess the effects of hUSC-sEVs on the proliferation and migration ability of vaginal epithelial cells (VK2/E6E7). Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to test the expression of epithelial differentiation markers in VK2 cells. Moreover, a microRNA (miRNA) microarray was used to find hUSC-sEVs-specific miRNAs that potentially affected the proliferation, migration and differentiation ability of VK2 cells.

Results

The in vitro release profile revealed that the piGEL could ensure sustained release of hUSC-sEVs. The in vivo results showed that piGEL-sEVs effectively promoted epithelization and angiogenesis of vaginal mucosa defects in rabbits. According to miRNA microarray and qRT-PCR results, miR-126-3p might be the crucial molecule among the various miRNAs contained in hUSC-sEVs. The data showed that hUSC-sEVs promoted the migration and differentiation of VK2 cells by delivering miR-126-3p to suppress the expression of Spred1 and PIK3R2, thereby activating the ERK1/2 and ATK signaling pathways.

Conclusion

The results indicated that piGEL-sEVs could be a novel promising approach for enhancing the epithelization of the neovagina after vaginoplasty and provided useful data for understanding the underlying mechanism of the effect of hUSC-sEVs on epithelization.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03003-x.

Extracellular Vesicle-Based Therapeutics in Neurological Disorders

Neurological diseases remain some of the major causes of death and disability in the world. Few types of drugs and insufficient delivery across the blood-brain barrier limit the treatment of neurological disorders. The past two decades have seen the rapid development of extracellular vesicle-based therapeutics in many fields. As the physiological and pathophysiological roles of extracellular vesicles are recognized in neurological diseases, they have become promising therapeutics and targets for therapeutic interventions. Moreover, advanced nanomedicine technologies have explored the potential of extracellular vesicles as drug delivery systems in neurological diseases. In this review, we discussed the preclinical strategies for extracellular vesicle-based therapeutics in neurological disorders and the struggles involved in their clinical application.

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.

An ischemia-homing bioengineered nano-scavenger for specifically alleviating multiple pathogeneses in ischemic stroke

Background

Ischemic stroke is one of the most serious global public health problems. However, the performance of current therapeutic regimens is limited due to their poor target specificity, narrow therapeutic time window, and compromised therapeutic effect. To overcome these barriers, we designed an ischemia-homing bioengineered nano-scavenger by camouflaging a catalase (CAT)-loaded self-assembled tannic acid (TA) nanoparticle with a M2-type microglia membrane (TPC@M2 NPs) for ischemic stroke treatment.

Results

The TPC@M2 NPs can on-demand release TA molecules to chelate excessive Fe²⁺, while acid-responsively liberating CAT to synergistically scavenge multiple ROS (·OH, ·O₂⁻, and H₂O₂). Besides, the M2 microglia membrane not only can be served as bioinspired therapeutic agents to repolarize M1 microglia into M2 phenotype but also endows the nano-scavenger with ischemia-homing and BBB-crossing capabilities.

Conclusions

The nano-scavenger for specific clearance of multiple pathogenic elements to alleviate inflammation and protect neurons holds great promise for combating ischemic stroke and other inflammation-related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01602-7.

Future of Digital Assays to Resolve Clinical Heterogeneity of Single Extracellular Vesicles

Extracellular vesicles (EVs) are complex lipid membrane vehicles with variable expressions of molecular cargo, composed of diverse subpopulations that participate in the intercellular signaling of biological responses in disease. EV-based liquid biopsies demonstrate invaluable clinical potential for overhauling current practices of disease management. Yet, EV heterogeneity is a major needle-in-a-haystack challenge to translate their use into clinical practice. In this review, existing digital assays will be discussed to analyze EVs at a single vesicle resolution, and future opportunities to optimize the throughput, multiplexing, and sensitivity of current digital EV assays will be highlighted. Furthermore, this review will outline the challenges and opportunities that impact the clinical translation of single EV technologies for disease diagnostics and treatment monitoring.

Negative effects of brain regulatory T cells depletion on epilepsy

The infiltration of immune cells is observed in the epileptogenic zone; however, the relationship between epilepsy and regulatory T cells (Tregs) remains only partially understood. We aimed to investigate brain-infiltrating Tregs to reveal their underlying role in epilepsy. We analyzed the infiltration of Tregs in the epileptogenic zones from patients with epilepsy and a pilocarpine-induced temporal lobe epilepsy (TLE) model. Next, we evaluated the effects of brain Treg depletion on neuroinflammation, neuronal loss, oxidative stress, seizure activity and behavioral changes in the pilocarpine model. We also explored the impact of Treg expansion in the brain on seizure activity. There were a large number of Tregs in the epileptogenic zones of human and experimental epilepsy. The number of brain Tregs was negatively correlated with the frequency of seizures in patients with epilepsy. Our further findings demonstrated that brain Treg depletion promoted astrocytosis, microgliosis, inflammatory cytokine production, oxidative stress, and neuronal loss in the hippocampus after status epilepticus (SE). Moreover, brain Treg depletion increased seizure activity and contributed to behavioral impairments in experimental chronic TLE. Interestingly, intracerebroventricular injection of CCL20 amplified Tregs in brain tissue, thereby inhibiting seizure activity. Taken together, our study highlights the therapeutic potential of regulating Tregs in epileptic brain tissue.

Engineered Nanoerythrocytes Alleviate Central Nervous System Inflammation by Regulating the Polarization of Inflammatory Microglia

Microglial polarization is one of the most promising therapeutic strategies for multiple central nervous system (CNS) disorders. However, safe, effective, and controllable microglial regulation still faces formidable challenges. Although some anti-inflammatory factors promote microglia polarization, their short half-life, high cost, unpredictable in vivo behavior, and complex delivery operations, hamper their clinical application. Here, inspired by the natural microhemorrhage cleaning mechanism, an MG1 peptide and RVG29 peptide engineered nanoerythrocyte (NEMR) that can reprogram microglia are developed from classical M1 toward alternative M2 by inducing heme oxygenase-1 (HO-1), stimulating Notch1/Hes1/Stat3 signaling, and further inhibiting NF-κB p65 translocation. Moreover, anti-inflammatory carbon monoxide (CO) and bilirubin produced by endogenous metabolism of heme further reinforces the anti-inflammatory effect. In middle cerebral artery occlusion and experimental autoimmune encephalomyelitis models, a satisfactory prognosis is achieved, with precise regulation of inflammatory microglia in lesion sites, increased expression of anti-inflammatory factors, reduced blood-brain barrier permeability, as well as promotion of neurogenesis and functional recovery. Furthermore, NEMR can be integrated with clinical therapeutic agents, which facilitates precise drug delivery to enhance therapeutic effects. Hence, the natural nanoerythrocytes, as a feasible, efficient, safe, and practical tool, provides a new strategy for rebalancing of the immune environment in the CNS disorders.

Extracellular vesicles as bioactive nanotherapeutics: An emerging paradigm for regenerative medicine

In recent decades, extracellular vesicles (EVs), as bioactive cell-secreted nanoparticles which are involved in various physiological and pathological processes including cell proliferation, immune regulation, angiogenesis and tissue repair, have emerged as one of the most attractive nanotherapeutics for regenerative medicine. Herein we provide a systematic review of the latest progress of EVs for regenerative applications. Firstly, we will briefly introduce the biogenesis, function and isolation technology of EVs. Then, the underlying therapeutic mechanisms of the native unmodified EVs and engineering strategies of the modified EVs as regenerative entities will be discussed. Subsequently, the main focus will be placed on the tissue repair and regeneration applications of EVs on various organs including brain, heart, bone and cartilage, liver and kidney, as well as skin. More importantly, current clinical trials of EVs for regenerative medicine will also be briefly highlighted. Finally, the future challenges and insightful perspectives of the currently developed EV-based nanotherapeutics in biomedicine will be discussed. In short, the bioactive EV-based nanotherapeutics have opened new horizons for biologists, chemists, nanoscientists, pharmacists, as well as clinicians, making possible powerful tools and therapies for regenerative medicine.

The in vivo fate and targeting engineering of crossover vesicle-based gene delivery system

Exosomes and biomimetic vesicles are widely used for gene delivery because of their excellent gene loading capacity and stability and their natural targeting delivery potential. These vesicles take advantages of both cell-based bioactive delivery system and synthetical lipid-derived nanovectors to form crossover characteristics. To further optimize the specific targeting properties of crossover vesicles, studies of their in vivo fate and various engineering approaches including nanobiotechnology are required. This review describes the preparation process of exosomes and biomimetic vesicles, and summarizes the mechanism of loading and delivery of nucleic acids or gene editing systems. We provide a comprehensive overview of the techniques employed for preparing the targeting crossover vesicles based on their cellular uptake and targeting mechanism. To delineate the future prospects of crossover vesicle gene delivery systems, various challenges and clinical applications of vesicles have also been discussed.

Proficiency of Extracellular Vesicles From hiPSC-Derived Neural Stem Cells in Modulating Proinflammatory Human Microglia: Role of Pentraxin-3 and miRNA-21-5p

Extracellular vesicles (EVs) shed by human-induced pluripotent stem cell (hiPSC)-derived neural stem cells (hNSC-EVs) have shown potent antiinflammatory properties in a mouse macrophage assay and a mouse model of acute neuroinflammation. They can also quickly permeate the entire brain after intranasal administration, making them attractive as an autologous or allogeneic off-the-shelf product for treating neurodegenerative diseases. However, their ability to modulate activated human microglia and specific proteins and miRNAs mediating antiinflammatory effects of hNSC-EVs are unknown. We investigated the proficiency of hNSC-EVs to modulate activated human microglia and probed the role of the protein pentraxin 3 (PTX3) and the miRNA miR-21-5p within hNSC-EVs in mediating the antiinflammatory effects. Mature microglia generated from hiPSCs (iMicroglia) expressed multiple microglia-specific markers. They responded to lipopolysaccharide (LPS) or interferon-gamma challenge by upregulating tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) mRNA expression and protein release. iMicroglia also exhibited proficiency to phagocytose amyloid-beta (Aβ). The addition of hNSC-EVs decreased TNF-α and IL-1β mRNA expression and the release of TNF-α and IL-1β by LPS-stimulated iMicroglia (proinflammatory human Microglia). However, the antiinflammatory activity of hNSC-EVs on LPS-stimulated microglia was considerably diminished when the PTX3 or miR-21-5p concentration was reduced in EVs. The results demonstrate that hNSC-EVs are proficient for modulating the proinflammatory human microglia into non-inflammatory phenotypes, implying their utility to treat neuroinflammation in neurodegenerative diseases. Furthermore, the role of PTX3 and miR-21-5p in the antiinflammatory activity of hNSC-EVs provides a new avenue for improving the antiinflammatory effects of hNSC-EVs through PTX3 and/or miR-21-5p overexpression.

Neuronal Death Mechanisms and Therapeutic Strategy in Ischemic Stroke

Ischemic stroke caused by intracranial vascular occlusion has become increasingly prevalent with considerable mortality and disability, which gravely burdens the global economy. Current relatively effective clinical treatments are limited to intravenous alteplase and thrombectomy. Even so, patients still benefit little due to the short therapeutic window and the risk of ischemia/reperfusion injury. It is therefore urgent to figure out the neuronal death mechanisms following ischemic stroke in order to develop new neuroprotective strategies. Regarding the pathogenesis, multiple pathological events trigger the activation of cell death pathways. Particular attention should be devoted to excitotoxicity, oxidative stress, and inflammatory responses. Thus, in this article, we first review the principal mechanisms underlying neuronal death mediated by these significant events, such as intrinsic and extrinsic apoptosis, ferroptosis, parthanatos, pyroptosis, necroptosis, and autophagic cell death. Then, we further discuss the possibility of interventions targeting these pathological events and summarize the present pharmacological achievements.