Exosomal MicroRNA-126 from RIPC Serum Is Involved in Hypoxia Tolerance in SH-SY5Y Cells by Downregulating DNMT3B

Exosomes: the next-generation therapeutic platform for ischemic stroke

Current therapeutic strategies for ischemic stroke fall short of the desired objective of neurological functional recovery. Therefore, there is an urgent need to develop new methods for the treatment of this condition. Exosomes are natural cell-derived vesicles that mediate signal transduction between cells under physiological and pathological conditions. They have low immunogenicity, good stability, high delivery efficiency, and the ability to cross the blood-brain barrier. These physiological properties of exosomes have the potential to lead to new breakthroughs in the treatment of ischemic stroke. The rapid development of nanotechnology has advanced the application of engineered exosomes, which can effectively improve targeting ability, enhance therapeutic efficacy, and minimize the dosages needed. Advances in technology have also driven clinical translational research on exosomes. In this review, we describe the therapeutic effects of exosomes and their positive roles in current treatment strategies for ischemic stroke, including their anti-inflammation, anti-apoptosis, autophagy-regulation, angiogenesis, neurogenesis, and glial scar formation reduction effects. However, it is worth noting that, despite their significant therapeutic potential, there remains a dearth of standardized characterization methods and efficient isolation techniques capable of producing highly purified exosomes. Future optimization strategies should prioritize the exploration of suitable isolation techniques and the establishment of unified workflows to effectively harness exosomes for diagnostic or therapeutic applications in ischemic stroke. Ultimately, our review aims to summarize our understanding of exosome-based treatment prospects in ischemic stroke and foster innovative ideas for the development of exosome-based therapies.

A systematic review of exosomes in remote ischemic conditioning

BACKGROUND

Remote ischemic conditioning (RIC) is considered a promising non-pharmacological therapeutic strategy to mitigate ischemic injury. Although the precise mechanisms of RIC's protective effects remain elusive, existing data suggest that exosomes contribute significantly to these processes through cell-to-cell communication OBJECTIVE: This review aims to elucidate the role of exosomes in RIC-mediated multi-organ protection.

METHODS

We systematically searched multiple databases through October 2023 for preclinical studies evaluating the effect of exosomes in ischemic models using RIC procedures. Key outcomes, such as improved organ function and reduced infarct size, were recorded. Articles were selected and data were extracted by independent pairs of reviewers.

FINDINGS

A total of 16 relevant studies were identified in this review, showing that circulating exosomes derived from the plasma of RIC-treated animals exhibited protective effects akin to those of the RIC procedure itself. Exosome concentrations were measured in eight studies, six of which reported significant increases in the RIC group. Additional findings indicated that RIC might primarily modulate the expression of miRNAs and bioactive molecules delivered by exosomes, rather than directly altering circulating exosome levels. Notably, the expression of 11 distinct exosomal miRNAs was altered after RIC intervention, potentially involving multiple pathways.

CONCLUSION

Exosomes appear to play a pivotal role in the protective effects induced by RIC. Clarifying their function in RIC under different pathological situations represents a grand challenge for future research.

Advancing stroke therapy: innovative approaches with stem cell-derived extracellular vesicles

Stroke is a leading cause of mortality and long-term disability globally, with acute ischemic stroke (AIS) being the most common subtype. Despite significant advances in reperfusion therapies, their limited time window and associated risks underscore the necessity for novel treatment strategies. Stem cell-derived extracellular vesicles (EVs) have emerged as a promising therapeutic approach due to their ability to modulate the post-stroke microenvironment and facilitate neuroprotection and neurorestoration. This review synthesizes current research on the therapeutic potential of stem cell-derived EVs in AIS, focusing on their origin, biogenesis, mechanisms of action, and strategies for enhancing their targeting capacity and therapeutic efficacy. Additionally, we explore innovative combination therapies and discuss both the challenges and prospects of EV-based treatments. Our findings reveal that stem cell-derived EVs exhibit diverse therapeutic effects in AIS, such as promoting neuronal survival, diminishing neuroinflammation, protecting the blood-brain barrier, and enhancing angiogenesis and neurogenesis. Various strategies, including targeting modifications and cargo modifications, have been developed to improve the efficacy of EVs. Combining EVs with other treatments, such as reperfusion therapy, stem cell transplantation, nanomedicine, and gut microbiome modulation, holds great promise for improving stroke outcomes. However, challenges such as the heterogeneity of EVs and the need for standardized protocols for EV production and quality control remain to be addressed. Stem cell-derived EVs represent a novel therapeutic avenue for AIS, offering the potential to address the limitations of current treatments. Further research is needed to optimize EV-based therapies and translate their benefits to clinical practice, with an emphasis on ensuring safety, overcoming regulatory hurdles, and enhancing the specificity and efficacy of EV delivery to target tissues.

Up-regulation of miR-126 via DNA methylation in hypoxia-preconditioned endothelial cells may contribute to hypoxic tolerance of neuronal cells

BACKGROUND

Endothelial cells (ECs) can confer neuroprotection by secreting molecules. This study aimed to investigate whether DNA methylation contributes to the neuroprotective gene expression induced by hypoxia preconditioning (HPC) in ECs and to clarify that the secretion of molecules from HPC ECs may be one of the molecular mechanisms of neuroprotection.

METHODS

Human microvascular endothelial cell-1 (HMEC-1) was cultured under normal conditions (C), hypoxia(H), and hypoxia preconditioning (HPC), followed by the isolation of culture medium (CM). SY5Y cell incubated with the isolated CM from HMEC-1 was exposed to oxygen-glucose deprivation (OGD). The DNA methyltransferases (DNMTs), global methylation level, miR-126 and its promotor DNA methylation level in HMEC-1 were measured. The cell viability and cell injury in SY5Y were detected.

RESULTS

HPC decreased DNMTs level and global methylation level as well as increased miR-126 expression in HMEC-1. CM from HPC treated HMEC-1 also relieved SY5Y cell damage, while CM from HMEC-1 which over-expression of miR-126 can reduce injury in SY5Y under OGD condition.

CONCLUSIONS

These findings indicate EC may secrete molecules, such as miR-126, to execute neuroprotection induced by HPC through regulating the expression of DNMTs.

Impact of remote ischemic postconditioning on acute ischemic stroke in China: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

Acute ischemic stroke (AIS) is a significant health burden in China, affecting a sizable portion of the population. Conventional pharmacological treatments frequently fall short of desirable outcomes. Therefore, exploring alternative therapies is crucial. Remote ischemic postconditioning (RIPostC) is a noninvasive and cost-effective adjunctive therapy. This study aimed to investigate the efficacy and safety of RIPostC as an adjunctive therapy for AIS to inform clinical practice.

METHODS

A comprehensive search was conducted across the PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), WanFang, Weipu (VIP), and China Biology Medicine disc (CBM) databases up to October 2023. All included studies underwent bias risk assessment using the Cochrane risk-of-bias assessment tool. The primary outcome measure was the National Institute of Health Stroke Scale (NIHSS), with secondary outcomes including the Barthel index (BI), D-dimer, C-reactive protein (CRP), fibrinogen (FIB), brain-derived neurotrophic factor (BDNF), modified Rankin scale (mRS), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) levels. The data were analyzed using fixed-effects and random-effects models in Review Manager, with mean differences (MDs) and 95% confidence intervals (CIs) calculated for each outcome. The grading of recommendations, assessment, development, and evaluations (GRADE) approach was used to evaluate the level of evidence for each outcome measure.

RESULTS

This meta-analysis included 38 studies, encompassing 4334 patients. Compared with the control group, the RIPostC group had significantly lower NIHSS scores, serum CRP, D-dimer, IL-6, TNF-α, and FIB levels, and increased BDNF levels. Moreover, it improved the patient's BI and mRS scores. According to the GRADE approach, the quality of evidence for mRS was deemed "moderate," while the NIHSS, BI, and CRP were rated as "low" quality. IL-6, TNF-α, FIB, D-dimer, and BDNF received "very low" quality ratings.

CONCLUSION

The findings suggest that RIPostC activates endogenous protective mechanisms, providing benefits to patients with AIS.

Hypoxia preconditioning increases Notch1 activity by regulating DNA methylation in vitro and in vivo

BACKGROUND

Our previous research has demonstrated that hypoxic preconditioning (HPC) can improve spatial learning and memory abilities in adult mice. Adult hippocampal neurogenesis has been associated with learning and memory. The Neurogenic locus notch homolog protein (Notch) was involved in adult hippocampal neurogenesis, as well as in learning and memory. It is currently unclear whether the Notch pathway regulates hippocampal neuroregeneration by modifying the DNA methylation status of the Notch gene following HPC.

METHOD

The HPC animal model and cell model were established through repeated hypoxia exposure using mice and the mouse hippocampal neuronal cell line HT22. Step-down test was conducted on HPC mice. Real-time PCR and Western blot analysis were used to assess the mRNA and protein expression levels of Notch1 and hairy and enhancer of split1 (HES1). The presence of BrdU-positive cells and Notch1 expression in the hippocampal dental gyrus (DG) were examined with confocal microscopy. The methylation status of the Notch1 was analyzed using methylation-specific PCR (MS-PCR). HT22 cells were employed to elucidate the impact of HPC on Notch1 in vitro.

RESULTS

HPC significantly improved the step-down test performance of mice with elevated levels of mRNA and protein expression of Notch1 and HES1 (P < 0.05). The intensities of the Notch1 signal in the control group, the H group and the HPC group were 2.62 ± 0.57 × 107, 2.87 ± 0.84 × 107, and 3.32 ± 0.14 × 107, respectively, and the number of BrdU (+) cells in the hippocampal DG were 1.83 ± 0.54, 3.71 ± 0.64, and 7.29 ± 0.68 respectively. Compared with that in C and H group, the intensity of the Notch1 signal and the number of BrdU (+) cells increased significantly in HPC group (P < 0.05). The methylation levels of the Notch1 promoter 0.82 ± 0.03, 0.65 ± 0.03, and 0.60 ± 0.02 in the C, H, and HPC groups, respectively. The methylation levels of Notch1 decreased significantly (P < 0.05). The effect of HPC on HT22 cells exhibited similarities to that observed in the hippocampus.

CONCLUSION

HPC may confer neuroprotection by activating the Notch1 signaling pathway and regulating its methylation level, resulting in the regeneration of hippocampal neurons.

MiRNAs as potential therapeutic targets and biomarkers for non-traumatic intracerebral hemorrhage

Non-traumatic intracerebral hemorrhage (ICH) is the most common type of hemorrhagic stroke, most often occurring between the ages of 45 and 60. Hypertension is most often the cause of ICH. Less often, atherosclerosis, blood diseases, inflammatory changes in cerebral vessels, intoxication, vitamin deficiencies, and other reasons cause hemorrhages. Cerebral hemorrhage can occur by diapedesis or as a result of a ruptured vessel. This very dangerous disease is difficult to treat, requires surgery and can lead to disability or death. MicroRNAs (miRNAs) are a class of non-coding RNAs (about 18-22 nucleotides) that are involved in a variety of biological processes including cell differentiation, proliferation, apoptosis, etc., through gene repression. A growing number of studies have demonstrated miRNAs deregulation in various cardiovascular diseases, including ICH. In addition, given that computed tomography (CT) and/or magnetic resonance imaging (MRI) are either not available or do not show clear signs of possible vessel rupture, accurate and reliable analysis of circulating miRNAs in biological fluids can help in early diagnosis for prevention of ICH and prognosis patient outcome after hemorrhage. In this review, we highlight the up-to-date findings on the deregulated miRNAs in ICH, and the potential use of miRNAs in clinical settings, such as therapeutic targets and non-invasive diagnostic/prognostic biomarker tools.

Remote ischemic conditioning alleviates chronic cerebral hypoperfusion-induced cognitive decline and synaptic dysfunction via the miR-218a-5p/SHANK2 pathway

Vascular cognitive impairment (VCI) due to chronic cerebral hypoperfusion (CCH), is the second leading cause of dementia. Although synaptic impairment plays a critical role in VCI, its exact mechanism remains unknown. Our previous research revealed that remote ischemic conditioning (RIC) could alleviate cognitive decline resulting from CCH, however, its effects on synaptic impairment remain unclear. In this study, we confirmed that RIC alleviated both cognitive decline and its associated synaptic dysfunction caused by CCH. RNA sequencing revealed that CCH increased in miR-218a-5p expression, which was decreased by RIC. Elevated miR-218a-5p levels limited the benefits of RIC, however, inhibiting miR-218a-5p in hippocampal CA1 neurons rescued synaptic dysfunction. Additionally, we found that SHANK2 is a downstream target of miR-218a-5p, and inhibiting SHANK2 expression reduced the alleviation caused by hypoxic conditioning in synaptic impairment in vitro. In conclusion, our results suggested that RIC alleviated synaptic impairment via the miR-218a-5p/SHANK2 pathway, which could be a potential biomarker or therapeutic target for cognitive impairment caused by CCH.

Plasma Small Extracellular Vesicle Cardiac miRNA Expression in Patients with Ischemic Heart Failure, Randomized to Percutaneous Intramyocardial Treatment of Adipose Derived Stem Cells or Placebo: Subanalysis of the SCIENCE Study

Small extracellular vesicles (EVs) and their cargo are an important component of cell-to-cell communication in cardiac disease. Allogeneic adipose derived stem cells (ADSCs) are thought to be a potential approach for cardiac regenerative therapy in ischemic heart disease. The SCIENCE study investigated the effect of ADSCs administered via intramyocardial injection on cardiac function in patients with ischemic heart disease. The aim of this substudy, based on samples from 15 patients, was to explore small EV miRNA dynamics after treatment with ADSCs compared to a placebo. Small EVs were isolated at several timepoints after the percutaneous intramyocardial application of ADSCs. No significant effect of ADSC treatment on small EV concentration was detected. After 12 months, the expression of miR-126 decreased significantly in ADSC patients, but not in the placebo-treated group. However, all cardiac miRNAs correlated with plasma cardiac biomarkers. In line with the overall negative results of the SCIENCE study, with the exception of one miR, we did not detect any significant regulation of small EV miRNAs in this patient collective.

Hypoxic Preconditioning Modulates BDNF and Its Signaling through DNA Methylation to Promote Learning and Memory in Mice

Hypoxic preconditioning (HPC) as an endogenous mechanism can resist hypoxia/ischemia injury and exhibit protective effects on neurological function including learning and memory. Although underlying molecular mechanisms remain unclear, HPC probably regulates the expression of protective molecules by modulating DNA methylation. Brain-derived neurotrophic factor (BDNF) activates its signaling upon binding to the tropomyosin-related kinase B (TrkB) receptor, which is involved in neuronal growth, differentiation, and synaptic plasticity. Therefore, this study focused on the mechanism by which HPC regulates BDNF and BDNF/TrkB signaling through DNA methylation to influence learning and memory. Initially, the HPC model was established by hypoxia stimulations on ICR mice. We found that HPC downregulated the expression of DNA methyltransferase (DNMT) 3A and DNMT3B. Then, the upregulation of BDNF expression in HPC mice was generated from a decrease in DNA methylation of the BDNF gene promoter detected by pyrophosphate sequencing. Subsequently, upregulation of BDNF activated BDNF/TrkB signaling and ultimately improved learning and spatial memory in HPC mice. Moreover, after mice were intracerebroventricularly injected with the DNMT inhibitor, the restraint of DNA methylation accompanied by an increase of BDNF and BDNF/TrkB signaling was also discovered. Finally, we observed that the inhibitor of BDNF/TrkB signaling prevented HPC from ameliorating learning and memory in mice. However, the DNMT inhibitor promoted spatial cognition in mice. Thus, we suggest that HPC may upregulate BDNF by inhibiting DNMTs and decreasing DNA methylation of the BDNF gene and then activate BDNF/TrkB signaling to improve learning and memory in mice. This may provide theoretical guidance for the clinical treatment of cognitive dysfunction caused by ischemia/hypoxia disease.

Transplantation of Exercise-Induced Extracellular Vesicles as a Promising Therapeutic Approach in Ischemic Stroke

Clinical evidence affirms physical exercise is effective in preventive and rehabilitation approaches for ischemic stroke. This sustainable efficacy is independent of cardiovascular risk factors and associates substantial reprogramming in circulating extracellular vesicles (EVs). The intricate journey of pluripotent exercise-induced EVs from parental cells to the whole-body and infiltration to cerebrovascular entity offers several mechanisms to reduce stroke incidence and injury or accelerate the subsequent recovery. This review delineates the potential roles of EVs as prospective effectors of exercise. The candidate miRNA and peptide cargo of exercise-induced EVs with both atheroprotective and neuroprotective characteristics are discussed, along with their presumed targets and pathway interactions. The existing literature provides solid ground to hypothesize that the rich vesicles link exercise to stroke prevention and rehabilitation. However, there are several open questions about the exercise stressors which may optimally regulate EVs kinetic and boost brain mitochondrial adaptations. This review represents a novel perspective on achieving brain fitness against stroke through transplantation of multi-potential EVs generated by multi-parental cells, which is exceptionally reachable in an exercising body.

Exosomal HSP90 induced by remote ischemic preconditioning alleviates myocardial ischemia/reperfusion injury by inhibiting complement activation and inflammation

BACKGROUND/AIMS

The activation of the complement system and subsequent inflammatory responses are important features of myocardial ischemia/reperfusion (I/R) injury. Exosomes are nanoscale extracellular vesicles that play a significant role in remote ischemic preconditioning (RIPC) cardioprotection. The present study aimed to test whether RIPC-induced plasma exosomes (RIPC-Exo) exert protective effects on myocardial I/R injury by inhibiting complement activation and inflammation and whether exosomal heat shock protein 90 (HSP90) mediates these effects.

METHODS

Rat hearts underwent 30 min of coronary ligation followed by 2 h of reperfusion. Plasma exosomes were isolated from RIPC rats and injected into the infarcted myocardium immediately after ligation. Sixty rats were randomly divided into Sham, I/R, I/R + RIPC-Exo (50 µg/µl), and RIPC-Exo + GA (geldanamycin, 1 mg/kg, administration 30 min before ligation) groups. Cardiomyocyte apoptosis, the release of myocardial markers (LDH, cTnI and CK-MB), infarct size, the expression of HSP90, complement component (C)3, C5a, c-Jun N-terminal kinase (JNK), interleukin (IL)-1β, tumor necrosis factor (TNF)-alpha and intercellular adhesion molecule -1 (ICAM-1) were assessed.

RESULTS

RIPC-Exo treatment significantly reduced I/R-induced cardiomyocyte apoptosis, the release of myocardial markers (LDH, cTnI and CK-MB) and infarct size. These beneficial effects were accompanied by decreased C3 and C5a expression, decreased inflammatory factor levels (IL-1β, TNF-α, and ICAM-1), decreased JNK and Bax, and increased Bcl-2 expression. Meanwhile, the expression of HSP90 in the exosomes from rat plasma increased significantly after RIPC. However, treatment with HSP90 inhibitor GA significantly reversed the cardioprotection of RIPC-Exo, as well as activated complement component, JNK signalling and inflammation, indicating that HSP90 in exosomes isolated from the RIPC was important in mediating the cardioprotective effects during I/R.

CONCLUSION

Exosomal HSP90 induced by RIPC played a significant role in cardioprotection against I/R injury, and its function was in part linked to the inhibition of the complement system, JNK signalling and local and systemic inflammation, ultimately alleviating I/R-induced myocardial injury and apoptosis by the upregulation of Bcl-2 expression and the downregulation of proapoptotic Bax.

Protective effect of Xingnaojing injection on ferroptosis after cerebral ischemia injury in MCAO rats and SH-SY5Y cells

ETHNOPHARMACOLOGICAL RELEVANCE

Xingnaojing（XNJ）injection is a traditional Chinese medicine injection with neuroprotective effect, which has been widely used in the treatment of stroke for many years.

AIM OF THE STUDY

This study aimed to explore the potential mechanism of XNJ in cerebral ischemia mediated by ferroptosis using proteomics and in vivo and in vitro experiments.

MATERIALS AND METHODS

After the rat model of middle cerebral artery occlusion (MCAO) was successfully established, they were randomly divided into model, XNJ, and deferoxamine (DFO) group. Triphenyl tetrazolium chloride (TTC) staining, Hematoxylin and eosin (H&E), and Nissl staining were used to observe the infarct area, pathological changes and the degree of neuronal apoptosis of rat brain. Proteins extracted from rat brain tissues were analyzed by quantitative proteomics using tandem mass tags (TMT). Western blotting and immunohistochemical assessment were used to measure the expression of ferroptosis-related proteins. In vitro, the SH-SY5Y cells were subjected to hypoxia (37°C/5% CO2/1% O2) for 24 h to observe the survival rate, and detect the reactive oxygen species (ROS) content and ferroptosis-related proteins.

RESULTS

In TTC and H&E experiments, we found that XNJ drug treatment reduced the infarct volume and brain tissue damage in MCAO rats. Nissl staining also showed that compared with MCAO group rats, the Nissl bodies of brain tissue after XNJ drug intervention were clear with a 3.54-fold increased times, suggesting that XNJ improved cerebral infraction, and neurological deficits in MCAO rats. Proteomics identified 101 intersected differentially expressed proteins (DEPs). According to the bioinformatics analysis, these DEPs were closely related to ferroptosis. Further research indicated that MCAO-induced cerebral ischemia was alleviated by upregulating recombinant glutathione peroxidase 4 (GPX4), ferroportin (FPN) expression, Heme oxygenase-1 (HO-1) expression, and downregulating cyclooxygenase-2 (COX-2), transferring receptor (TFR) and divalent metal transporter-1 (DMT1) expression after XNJ treatment. In addition, in vitro experiment indicated that XNJ improved the survival rate of hypoxia-damaged SH-SY5Y cells. XNJ increased the level of GPX4 and inhibited the protein expression of COX-2 and TFR after cell hypoxia. Moreover, different concentrations of XNJ (0.25%, 0.5%, 1%) reduced the ROS content of hypoxic cells, suggesting that XNJ could inhibit hypoxia-induced cell damage by regulating the expression of ferroptosis-related proteins and decreasing the production of ROS.

CONCLUSIONS

XNJ could promote the recovery of neurological function in MCAO rats and hypoxia SH-SY5Y cells by regulating ferroptosis.

Downregulation of ELAVL1 attenuates ferroptosis-induced neuronal impairment in rats with cerebral ischemia/reperfusion via reducing DNMT3B-dependent PINK1 methylation

BACKGROUND

Ferroptosis is a non-apoptotic form of programmed cell death and has been found in ischemic stroke. Increasing evidence revealed that ELAVL1 is associated with ferroptosis, but it remains largely unclear whether ELAVL1 is involved in ischemic stroke. Here, we aimed to investigate the biological role and mechanism of ELAVL1 in cerebral ischemia/reperfusion (I/R) injury.

METHODS

ELAVL1 shRNA were intravenously injected into rat brain, and then ischemic/reperfusion (I/R) model was constructed in rats to detect infarct volume, neurobehavioral deficit, and several ferroptosis factors (GSH, GPX4, SLC7A11, MDA, ROS, iron ion) in vivo. Oxygen-glucose deprivation/reperfusion (OGD/R) treated pheochromocytoma-12 (PC12) cells were used as in vitro models of I/R. RIP, biotin pull-down and ChIP assays was used to explore the relationship among ELAVL1, DNMT3B, and PINK1.

RESULTS

ELAVL1 was highly expressed in rat brain tissue after I/R injury. Compared with those in the I/R group, the injection of RSL3 (30 mg/kg) or ferrostatin-1 (10 mg/kg) aggravated or alleviated infarct volume, neurobehavioral impairments, and increased or decreased ferroptosis factor levels, respectively. ELAVL1 silencing ameliorated brain damage in I/R-treated rats by inhibiting ferroptosis. Moreover, ELAVL1 silencing observably facilitated cell viability, GSH content, GPX4 and SLC7A11 expression, and reduced iron ion concentration, ROS and MDA levels in OGD/R-treated PC12 cells. ELAVL1 bound with DNMT3B mRNA 3'UTR and promoted DNMT3B expression. ELAVL1 inhibited PINK1 expression through stabilizing DNMT3B mRNA and blocking DNMT3B-mediated DNA methylation of PINK1 promoter. PINK1 knockdown reversed the effects of ELAVL1 inhibition on cell viability, GSH, GPX4, SLC7A11, iron ion concentration, ROS and MDA levels in OGD/R-treated PC12 cells.

CONCLUSION

ELAVL1 plays a critical role in protecting against ferroptosis-induced cerebral I/R and subsequent brain damage via DNMT3B/PINK1 axis, thus providing a new potential target for ischemic stroke treatment.

Effects and Mechanisms of Exosomes from Different Sources in Cerebral Ischemia

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

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

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

Effects of 5-Aza on neurogenesis contribute to learning and memory in the mouse hippocampus

BACKGROUND

5-Aza-2'-deoxycytidine (5-Aza-CdR) is a demethylating agent that has various biological effects related to DNA methylation. DNA methylation plays important roles in learning and memory. We have reported that 5-Aza-CdR improved the performance of mice in the water maze and step-down tests. Some behaviours have been well recognized to be mediated by neurogenesis in the hippocampus. The Notch signalling pathway plays a key role in adult hippocampal neurogenesis. In this study, we examined whether 5-Aza-CdR (DNA methyltransferase inhibitor) affects neurogenesis and Notch1 expression.

METHODS

The learning and memory behaviour of mice was evaluated by a conditioned avoidance learning 24 h after 5-Aza-CdR treatment. The mRNA and protein expression levels of Notch1 and HES1 were measured by real-time PCR and Western blotting. The 5-bromo-2'-deoxyuridine (BrdU)-positive cells and the expression of Notch1 in the hippocampal DG were observed through laser confocal microscopy. To further clarify whether 5-Aza-CdR affects behaviour through neurogenesis, the expression level of Notch1, cell viability and cell cycle were analysed using the HT22 cell line.

RESULTS

The behaviour in conditioned avoidance learning was improved, while neurogenesis and the Notch1 pathway were increased in the hippocampus of mice that were injected with 5-Aza-CdR. In vitro experiments showed that 5-Aza-CdR increased the expression of the Notch1 pathway and upregulated S-phase in the cell cycle and cell viability.

CONCLUSIONS

Our results suggest that the effect of 5-Aza-CdR on behaviour may be related to an increase in neurogenesis with upregulation of the Notch1 pathway in the hippocampus.

Human platelet lysate-derived extracellular vesicles enhance angiogenesis through miR-126

OBJECTIVES

Extracellular vesicles (EVs) are key biological mediators of several physiological functions within the cell microenvironment. Platelets are the most abundant source of EVs in the blood. Similarly, platelet lysate (PL), the best platelet derivative and angiogenic performer for regenerative purposes, is enriched of EVs, but their role is still too poorly discovered to be suitably exploited. Here, we explored the contribution of the EVs in PL, by investigating the angiogenic features extrapolated from that possessed by PL.

METHODS

We tested angiogenic ability and molecular cargo in 3D bioprinted models and by RNA sequencing analysis of PL-derived EVs.

RESULTS

A subset of small vesicles is highly represented in PL. The EVs do not retain aggregation ability, preserving a low redox state in human umbilical vein endothelial cells (HUVECs) and increasing the angiogenic tubularly-like structures in 3D endothelial bioprinted constructs. EVs resembled the miRNome profile of PL, mainly enriched with small RNAs and a high amount of miR-126, the most abundant angiogenic miRNA in platelets. The transfer of miR-126 by EVs in HUVEC after the in vitro inhibition of the endogenous form, restored angiogenesis, without involving VEGF as a downstream target in this system.

CONCLUSION

PL is a biological source of available EVs with angiogenic effects involving a miRNAs-based cargo. These properties can be exploited for targeted molecular/biological manipulation of PL, by potentially developing a product exclusively manufactured of EVs.

Infarct-preconditioning exosomes of umbilical cord mesenchymal stem cells promoted vascular remodeling and neurological recovery after stroke in rats

Background

Stroke is the leading cause of disability worldwide, resulting in severe damage to the central nervous system and disrupting neurological functions. There is no effective therapy for promoting neurological recovery. Growing evidence suggests that the composition of exosomes from different microenvironments may benefit stroke. Therefore, it is reasonable to assume that exosomes secreted in response to infarction microenvironment could have further therapeutic effects.

Methods

In our study, cerebral infarct tissue extracts were used to pretreat umbilical cord mesenchymal stem cells (UCMSC). Infarct-preconditioned exosomes were injected into rats via tail vein after middle cerebral artery occlusion (MCAO). The effect of infarct-preconditioned exosomes on the neurological recovery of rats was examined using Tunel assay, 2,3,5-triphenyltetrazolium chloride (TTC) assay, magnetic resonance imaging (MRI) analyses, modified Neurological Severity Score (mNSS), Morris water maze (MWM), and vascular remodeling analysis. Mi-RNA sequencing and functional enrichment analysis were used to validate the signal pathway involved in the effect of infarct-preconditioned exosomes. Human umbilical vein endothelial cells (HUVECs) were co-cultured with the isolated exosomes. Cell Counting Kit-8 (CCK-8) assay, scratch healing, and Western blot analysis were used to detect the biological behavior of HUVECs.

Results

The results showed that compared with normal exosomes, infarct-preconditioned exosomes further promoted vascular remodeling and recovery of neurological function after stroke. The function of upregulated miRNAs and their target genes which is beneficial to vascular smooth muscle cells verified the importance of vascular remodeling in improving stroke. Better resistance to oxygen–glucose deprivation/reoxygenation (OGD/R), reduced apoptosis, and enhanced migration were observed in infarct-preconditioned exosomes-treated umbilical vein endothelial cells.

Conclusions

Our results demonstrated that infarct-preconditioned exosomes promoted neurological recovery after stroke by enhancing vascular endothelial remodeling, suggested that infarct-preconditioned exosomes could be a novel way to alleviate brain damage following a stroke.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03083-9.

Regulating DNA methylation could reduce neuronal ischemia response and apoptosis after ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is an important pathophysiological condition that can cause cell injury and large-scale tissue injury in the nervous system. Previous studies have shown that epigenetic regulation may play a role in the pathogenesis of IRI.

METHODS

In this study, we isolated mouse cortical neurons and constructed an oxygen-glucose deprivation/reoxygenation (OGD) model to explore the change in DNA methylation and its effect on the expression of corresponding genes.

RESULTS

We found that DNA methylation in neurons increased with hypoxia duration and that hypermethylation of numerous promoters and 3'-untranslated regions increased. We performed Gene Ontology enrichment analysis to study gene function and Kyoto Encyclopedia of Genes and Genomes pathway analysis to identify the pathways associated with gene regulation. The results showed that hypermethylation-related genes expressed after OGD were related to physiological pathways such as neuronal projection, ion transport, growth and development, while hypomethylation-related genes were related to pathological pathways such as the external apoptosis signaling pathway, neuronal death regulation, and regulation of oxidative stress. However, the changes in DNA methylation were specific for certain genes and may have been related to OGD-induced neuronal damage. Importantly, we integrated transcription and DNA methylation data to identify several candidate target genes, including hypomethylated Apoe, Pax6, Bmp4, and Ptch1 and hypermethylated Adora2a, Crhr1, Stxbp1, and Tac1. This study further indicated the effect of DNA methylation on gene function in brain IRI from the perspective of epigenetics, and the identified genes may become new targets for achieving neuroprotection in the brain after IRI.

Exosomal microRNAs as Potential Biomarkers and Therapeutic Agents for Acute Ischemic Stroke: New Expectations

The morbidity and mortality rates of ischemic stroke (IS) are very high, and IS constitutes one of the main causes of disability and death worldwide. The pathogenesis of ischemic stroke includes excitotoxicity, calcium overload, oxygen radical injury, inflammatory reactions, necrosis/apoptosis, destruction of the blood-brain barrier (BBB), and other pathologic processes. Recent studies have shown that exosomes are critical to the pathogenesis, diagnosis, and treatment of cerebral infarctions resulting from ischemic stroke; and there is growing interest in the role of exosomes and exosomal miRNAs in the diagnosis and treatment of IS. Exosomes from central nervous system cells can be found in cerebrospinal fluid and peripheral bodily fluids, and exosomal contents have been reported to change with disease occurrence. Exosomes are small membranous extracellular vesicles (EVs), 30–150 nm in diameter, that are released from the cell membrane into the depressions that arise from the membranes of multivesicular bodies. Exosomes carry lipids, proteins, mRNAs, and microRNAs (miRNAs) and transport information to target cells. This exosomal transfer of functional mRNAs/miRNAs and proteins ultimately affects transcription and translation within recipient cells. Exosomes are EVs with a double-membrane structure that protects them from ribonucleases in the blood, allowing exosomal miRNAs to be more stable and to avoid degradation. New evidence shows that exosomes derived from neural cells, endothelial cells, and various stem cells create a fertile environment that supports the proliferation and growth of neural cells and endothelial cells, inhibits apoptosis and inflammatory responses, and promotes angiogenesis. In the present review, we discuss how circulating exosomes—and exosomal miRNAs in particular—may provide novel strategies for the early diagnosis and treatment of ischemic stroke via their potential as non-invasive biomarkers and drug carriers.

Remote but not Distant: a Review on Experimental Models and Clinical Trials in Remote Ischemic Conditioning as Potential Therapy in Ischemic Stroke

Stroke is one of the main causes of neurological disability worldwide and the second cause of death in people over 65 years old, resulting in great economic and social burden. Ischemic stroke accounts for 85% of total cases, and the approved therapies are based on re-establishment of blood flow, and do not directly target brain parenchyma. Thus, novel therapies are urgently needed. In this review, limb remote ischemic conditioning (RIC) is revised and discussed as a potential therapy against ischemic stroke. The review targets both (i) fundamental research based on experimental models and (ii) clinical research based on clinical trials and human interventional studies with healthy volunteers. Moreover, it also presents two approaches concerning RIC mechanisms in stroke: (i) description of the underlying cerebral cellular and molecular mechanisms triggered by limb RIC that promote neuroprotection against stroke induced damage and (ii) the identification of signaling factors involved in inter-organ communication following RIC procedure. Limb to brain remote signaling can occur via circulating biochemical factors, immune cells, and/or stimulation of autonomic nervous system. In this review, these three hypotheses are explored in both humans and experimental models. Finally, the challenges involved in translating experimentally generated scientific knowledge to a clinical setting are also discussed.

The role and therapeutic potential of exosomes in ischemic stroke

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

Serum Exosomal microRNA-27-3p Aggravates Cerebral Injury and Inflammation in Patients with Acute Cerebral Infarction by Targeting PPARγ

Acute cerebral infarction (ACI) possesses high mortality. Exosomes present in serum have potential application value in ACI diagnosis. This study investigated the mechanism of serum exosomes in ACI. Serum exosomes isolated from ACI patients and normal people were identified and then injected into the established middle cerebral artery occlusion (MCAO) rat model to evaluate cerebral injury and inflammation. Exosomal microRNA (miR)-27-3p expression was detected and interfered to analyze rat cerebral inflammation. The binding relationship between miR-27-3p and PPARγ was predicted and verified. The lipopolysaccharide (LPS)-treated microglia model was established and intervened with miR-27-3p to detect PPARγ, Iba-1, and inflammation-related factor expressions. After overexpressing PPARγ, rat cerebral inflammation was evaluated. The clinical significance of serum exosomal miR-27-3p in ACI was evaluated. Serum exosomes from ACI patients caused exacerbated MCAO rat cerebral injury and poor behavior recovery, as well as promoted cerebral inflammation. Serum exosomal miR-27-3p deepened rat brain inflammation. miR-27-3p targeted PPARγ to promote microglia activation and inflammation-related factor expressions in MCAO rats, and overexpressing PPARγ attenuated MCAO rat cerebral inflammation. Serum exosomal miR-27-3p promised to be a biomarker for ACI. We proved that serum exosomes from ACI patients aggravated ACI patient cerebral inflammation via the miR-27-3p/PPARγ axis.

New epigenetic players in stroke pathogenesis: From non-coding RNAs to exosomal non-coding RNAs

Non-coding RNAs (ncRNAs) have critical role in the pathophysiology as well as recovery after ischemic stroke. ncRNAs, particularly microRNAs, and the long non-coding RNAs (lncRNAs) are critical for angiogenesis and neuroprotection, and they have been suggested to be therapeutic, diagnostic and prognostic tools in cerebrovascular diseases, including stroke. Moreover, exosomes have been considered as nanocarriers capable of transferring various cargos, such as lncRNAs and miRNAs to recipient cells, with prominent inter-cellular roles in the mediation of neuro-restorative events following strokes and neural injuries. In this review, we summarize the pathogenic role of ncRNAs and exosomal ncRNAs in the stroke.

Neuroinflammatory In Vitro Cell Culture Models and the Potential Applications for Neurological Disorders

Cell cultures are used in pharmaceutical, medical and biological sciences. Due to the ethical and cost limitations of in vivo models, the replaceable cell model that is more closely related to the characteristics of organisms, which has broad prospects and can be used for high-throughput drug screening is urgent. Neuronal and glial cell models have been widely used in the researches of neurological disorders. And the current researches on neuroinflammation contributes to blood-brain barrier (BBB) damage. In this review, we describe the features of healthy and inflamed BBB and summarize the main immortalized cell lines of the central nervous system (PC12, SH-SY5Y, BV2, HA, and HBMEC et al.) and their use in the anti-inflammatory potential of neurological disorders. Especially, different co-culture models of neuroinflammatory, in association with immune cells in both 2D and 3D models are discussed in this review. In summary, 2D co-culture is easily practicable and economical but cannot fully reproduce the microenvironment in vivo. While 3D models called organs-on-chips or biochips are the most recent and very promising approach, which made possible by bioengineering and biotechnological improvements and more accurately mimic the BBB microenvironment.

Does remote ischaemic conditioning reduce inflammation? A focus on innate immunity and cytokine response

The benefits of remote ischaemic conditioning (RIC) have been difficult to translate to humans, when considering traditional outcome measures, such as mortality and heart failure. This paper reviews the recent literature of the anti-inflammatory effects of RIC, with a particular focus on the innate immune response and cytokine inhibition. Given the current COVID-19 pandemic, the inflammatory hypothesis of cardiac protection is an attractive target on which to re-purpose such novel therapies. A PubMed/MEDLINE™ search was performed on July 13th 2020, for the key terms RIC, cytokines, the innate immune system and inflammation. Data suggest that RIC attenuates inflammation in animals by immune conditioning, cytokine inhibition, cell survival and the release of anti-inflammatory exosomes. It is proposed that RIC inhibits cytokine release via a reduction in nuclear factor kappa beta (NF-κB)-mediated NLRP3 inflammasome production. In vivo, RIC attenuates pro-inflammatory cytokine release in myocardial/cerebral infarction and LPS models of endotoxaemia. In the latter group, cytokine inhibition is associated with a profound survival benefit. Further clinical trials should establish whether the benefits of RIC in inflammation can be observed in humans. Moreover, we must consider whether uncomplicated MI and elective surgery are the most suitable clinical conditions in which to test this hypothesis.

Overexpression of miR-146b-5p Ameliorates Neonatal Hypoxic Ischemic Encephalopathy by Inhibiting IRAK1/TRAF6/TAK1/NF-αB Signaling

PURPOSE

Neonatal hypoxic ischemic encephalopathy (HIE) is an essential factor underlying neonatal death and disability. This study sought to explore the role of miR-146b-5p in regulating neonatal HIE.

MATERIALS AND METHODS

In vitro and in vivo HIE models were established in PC12 cells and 10-day neonatal Sprague Dawley rats, respectively. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to assess miR-146b-5p expression and inflammatory factors [interleukin (IL)-6 and tumor necrosis factor (TNF)-α] in brain lesions and PC12 cells, while enzyme-linked immunosorbent assay was employed to detect the expression of oxidative stress factors (SOD and GSH-Px). Gain- and loss-assays of miR-146b-5p were conducted to verify its role in modulating the viability and apoptosis of PC12 cells under oxygen-glucose deprivation (OGD) treatment. Expression of TLR4, IRAK1, TRAF6, TAK1, and NF-κB were examined by qRT-PCR and/or Western blot. Dual luciferase activity assay was conducted to identify relationships between miR-146b-5p and IRAK1.

RESULTS

In the HIE models, significant oxidative stress and inflammatory responses emerged upon upregulation of TLR4/IRAK1/TRAF6/TAK1/NF-κB signaling. Overexpression of miR-146b-5p greatly inhibited OGD-induced PC12 cell injury, inflammatory responses, and oxidative stress. Inhibiting miR-146b-5p, however, had the opposite effects. IRAK1 was found to be a target of miR-146b-5p, and miR-146b-5p overexpression suppressed the activation of IRAK1/TRAF6/TAK1/NF-κB signaling.

CONCLUSION

This study demonstrated that miR-146b-5p overexpression alleviates HIE-induced neuron injury by inhibiting the IRAK1/TRAF6/TAK1/NF-κB pathway.

Distinct Cargos of Small Extracellular Vesicles Derived from Hypoxic Cells and Their Effect on Cancer Cells

Hypoxia is a common hallmark of solid tumors and is associated with aggressiveness, metastasis and poor outcome. Cancer cells under hypoxia undergo changes in metabolism and there is an intense crosstalk between cancer cells and cells from the tumor microenvironment. This crosstalk is facilitated by small extracellular vesicles (sEVs; diameter between 30 and 200 nm), including exosomes and microvesicles, which carry a cargo of proteins, mRNA, ncRNA and other biological molecules. Hypoxia is known to increase secretion of sEVs and has an impact on the composition of the cargo. This sEV-mediated crosstalk ultimately leads to various biological effects in the proximal tumor microenvironment but also at distant, future metastatic sites. In this review, we discuss the changes induced by hypoxia on sEV secretion and their cargo as well as their effects on the behavior and metabolism of cancer cells, the tumor microenvironment and metastatic events.