Inhibition of miR-141-3p Ameliorates the Negative Effects of Poststroke Social Isolation in Aged Mice

The impact of ischemic stroke on bone marrow microenvironment and extracellular vesicles: A study on inflammatory and molecular changes

An ischemic stroke (IS) is caused due to the lack of blood flow to cerebral tissue. Most of the studies have focused on how stroke affects the localized tissue, but it has been observed that a stroke can cause secondary complications in distant organs, such as Bone Marrow (BM). Our study focused on the effect of ischemic strokes on the bone marrow microenvironment. Bone marrow (BM) is a vital organ that maintains inflammatory homeostasis and aids in the repair of damaged tissue after injury/IS. We used the middle cerebral artery occlusion (MCAO) model of ischemic stroke on adult mice (6 months) and investigated the changes in the BM environment. BM cells were used for western blot and RT-PCR, and the BM supernatant was used for cytokine analysis and extracellular vesicle (EVs) isolation. We observed a significant increase in the total cell number within the BM and an increase in TNF-alpha and MCP-1, which are known for inducing a pro-inflammatory environment. Western blots analysis on the whole BM cell lysate demonstrated elevated levels of inflammatory factors (IL-6, TNF-alpha, and TLR-4) and senescence markers (p21 p16). EVs isolated from the BM supernatant showed no change in size or concentration; however, we found that the EVs carried increased miRNA-141-3p and miRNA-34a. Proteomic analysis on BM-derived EVs showed an alteration in the protein cargo of IS. We observed an increase in FgB, C3, Fn1, and Tra2b levels. The signaling pathway analysis showed mitochondrial function is most affected within the bone marrow. Our study demonstrated that IS induces changes in the BM environment and EVs secreted in the BM.

Inhibiting MicroRNA-141-3p Improves Musculoskeletal Health in Aged Mice

Emerging evidence shows that the microRNA-141-3p is involved in various age-related pathologies. Previously, our group and others reported elevated levels of miR-141-3p in several tissues and organs with age. Here, we inhibited the expression of miR-141-3p using antagomir (Anti-miR-141-3p) in aged mice and explored its role in healthy aging. We analyzed serum (cytokine profiling), spleen (immune profiling), and overall musculoskeletal phenotype. We found decreased levels of pro-inflammatory cytokines (such as TNF-α, IL-1β, IFN-γ) in serum with Anti-miR-141-3p treatment. The flow-cytometry analysis on splenocytes revealed decreased M1 (pro-inflammatory) and increased M2 (anti-inflammatory) populations. We also found improved bone microstructure and muscle fiber size with Anti-miR-141-3p treatment. Molecular analysis revealed that miR-141-3p regulates the expression of AU-rich RNA-binding factor 1 (AUF1) and promotes senescence (p21, p16) and pro-inflammatory (TNF-α, IL-1β, IFN-γ) environment whereas inhibiting miR-141-3p prevents these effects. Furthermore, we demonstrated that the expression of FOXO-1 transcription factor was reduced with Anti-miR-141-3p and elevated with silencing of AUF1 (siRNA-AUF1), suggesting crosstalk between miR-141-3p and FOXO-1. Overall, our proof-of-concept study demonstrates that inhibiting miR-141-3p could be a potential strategy to improve immune, bone, and muscle health with age.

CD13 facilitates immune cell migration and aggravates acute injury but promotes chronic post-stroke recovery

INTRODUCTION

Acute stroke leads to the activation of myeloid cells. These cells express adhesion molecules and transmigrate to the brain, thereby aggravating injury. Chronically after stroke, repair processes, including angiogenesis, are activated and enhance post-stroke recovery. Activated myeloid cells express CD13, which facilitates their migration into the site of injury. However, angiogenic blood vessels which play a role in recovery also express CD13. Overall, the specific contribution of CD13 to acute and chronic stroke outcomes is unknown.

METHODS

CD13 expression was estimated in both mice and humans after the ischemic stroke. Young (8-12 weeks) male wild-type and global CD13 knockout (KO) mice were used for this study. Mice underwent 60 min of middle cerebral artery occlusion (MCAO) followed by reperfusion. For acute studies, the mice were euthanized at either 24- or 72 h post-stroke. For chronic studies, the Y-maze, Barnes maze, and the open field were performed on day 7 and day 28 post-stroke. Mice were euthanized at day 30 post-stroke and the brains were collected for assessment of inflammation, white matter injury, tissue loss, and angiogenesis. Flow cytometry was performed on days 3 and 7 post-stroke to quantify infiltrated monocytes and neutrophils and CXCL12/CXCR4 signaling.

RESULTS

Brain CD13 expression and infiltrated CD13+ monocytes and neutrophils increased acutely after the stroke. The brain CD13+lectin+ blood vessels increased on day 15 after the stroke. Similarly, an increase in the percentage area CD13 was observed in human stroke patients at the subacute time after stroke. Deletion of CD13 resulted in reduced infarct volume and improved neurological recovery after acute stroke. However, CD13KO mice had significantly worse memory deficits, amplified gliosis, and white matter damage compared to wild-type animals at chronic time points. CD13-deficient mice had an increased percentage of CXCL12+cells but a reduced percentage of CXCR4+cells and decreased angiogenesis at day 30 post-stroke.

CONCLUSIONS

CD13 is involved in the trans-migration of monocytes and neutrophils after stroke, and acutely, led to decreased infarct size and improved behavioral outcomes. However, loss of CD13 led to reductions in post-stroke angiogenesis by reducing CXCL12/CXCR4 signaling.

Inhibition of miR-141-3p attenuates apoptosis of neural stem cells via targeting PBX1 to regulate PROK2 transcription in MCAO mice

MicroRNA-141-3p (miR-141-3p) has been found to be altered in the brain following a stroke. Herein, we investigate the impact of miR-141-3p on the apoptosis of neural stem cells (NSCs) in mice with middle cerebral artery occlusion (MCAO) and the potential mechanisms involved. Eight-week-old mice were injected intracerebroventricularly with miR-141-3p, antagomir-141-3p, or agomir negative control 2 h before MCAO, and animal behavior tests and infraction volume measurements were performed 24 h later. MCAO-mediated brain injury and NSCs apoptosis were observed by H&E, TTC, and TUNEL staining. The expression of cleaved caspase-3 and Ki67 was detected by western blotting. The luciferase reporter assay proved that miR-141-3p in combination with its target gene PBX homeobox 1 (PBX1). Exogenous miR-141-3p (agomir-141-3p) treatment increased infraction volume and brain edema and damaged neurological functions compared to control mice. Agomir-141-3p increased miR-141-3p expression in brain tissue of mice with MCAO and suppressed PBX1 expression. The effects of the agomir-141-3p-induced apoptosis in NSCs treated with oxygen-glucose deprivation (OGD)/reoxygenation (R) were abolished by PBX1 overexpression. The results from UCSC and JASPAR database showed that prokineticin 2 (PROK2) was a transcription factor of PBX1. The expression of PROK2 was transcriptionally regulated by PBX1 using RT-PCR and western blot assays. The effects of the apoptosis-promoting caused by PBX1 inhibition in NSCs treated with OGD/R were reversed by PROK2 inhibition. In conclusion, the miR-141-3p/PBX1/PROK2 axis might be a novel therapeutic target for the apoptosis of NSCs in MCAO.

Harnessing nanobiotechnology for cerebral ischemic stroke management

Cerebral ischemic stroke remains one of the most serious neurological disorders that pose threats to human health, causing a large amount of long-term disability or even death throughout the world. Based on its physiologic and pathological features, there are limited available therapeutic options for effective ischemic stroke management. Encouragingly, a rapid advancement of nanobiotechnology is bringing new insights into exploring more alternative strategies against cerebral ischemic stroke, which can cleverly overcome the limitations related to conventional treatment methods. Therefore, this review focuses on the recent achievements of nanobiotechnology for ischemic stroke management, which emphasizes diverse targeted delivery strategies using various nanoplatforms including liposomes, micelles, polymeric nanoparticles, nanogels, inorganic nanomaterials, and cell-derived nano-vectors based on the pathophysiological features of ischemic stroke. Moreover, different therapeutic approaches against ischemic stroke such as neuroprotection, anti-inflammation, thrombolysis, increased blood-brain barrier penetration and reactive oxygen species scavenging are highlighted. Meanwhile, this review discusses how these versatile nanoplatforms were designed to assist in the treatment of ischemic stroke. Based on this, challenges, opportunities, and future perspectives using nanobiotechnology through rational design for effective ischemic stroke management are revealed.

CD11bhigh B Cells Increase after Stroke and Regulate Microglia

Recent studies have highlighted the deleterious contributions of B cells to post-stroke recovery and cognitive decline. Different B cell subsets have been proposed on the basis of expression levels of transcription factors (e.g., T-bet) as well as specific surface proteins. CD11b (α-chain of integrin) is expressed by several immune cell types and is involved in regulation of cell motility, phagocytosis, and other essential functions of host immunity. Although B cells express CD11b, the CD11b^high subset of B cells has not been well characterized, especially in immune dysregulation seen with aging and after stroke. Here, we investigate the role of CD11b^high B cells in immune responses after stroke in young and aged mice. We evaluated the ability of CD11b^high B cells to influence pro- and anti-inflammatory phenotypes of young and aged microglia (MG). We hypothesized that CD11b^high B cells accumulate in the brain and contribute to neuroinflammation in aging and after stroke. We found that CD11b^high B cells are a heterogeneous subpopulation of B cells predominantly present in naive aged mice. Their frequency increases in the brain after stroke in young and aged mice. Importantly, CD11b^high B cells regulate MG phenotype and increase MG phagocytosis in both ex vivo and in vivo settings, likely by production of regulatory cytokines (e.g., TNF-α). As both APCs and adaptive immune cells with long-term memory function, B cells are uniquely positioned to regulate acute and chronic phases of the post-stroke immune response, and their influence is subset specific.

miR-141-3p protects against blood-brain barrier disruption and brain injury after intracerebral hemorrhage by targeting ZEB2

MicroRNAs (miRNAs) participate in the diagnosis and treatment of intracerebral hemorrhage (ICH). miR-141-3p has been widely reported to regulate neurological disorders and cerebropathy. However, the specific role of miR-141-3p in ICH has not yet been revealed. The aim of this study was exploration of the biological functions and mechanism of miR-141-3p in ICH by establishing a collagenase-induced ICH mouse model. After ICH induction, miR-141-3p mimics or miR-NC were administered into the right striatum of the model mice followed by the performance of neurological tests. After euthanasia of the mice, the injury volume, brain water content, and injury to the blood-brain barrier (BBB) were evaluated. Evans blue (EB) was used to stain the brain slices, and EB extravasation was detected to evaluate the injury to BBB. miR-141-3p expression in perihematomal edema and hematoma areas after ICH was assessed by RT-qPCR. The levels of tight junction proteins in brain tissues and human brain microvascular endothelial cells (BMECs) were evaluated by western blotting. The FITC-dextran 20 method was used to assess BMEC permeability. The binding between miR-141-3p and zinc finger E-box-binding homeobox 2 (ZEB2) was verified with a luciferase reporter assay. In this study, miR-141-3p overexpression alleviated ICH-induced brain injury and protected BBB integrity in vivo. ZEB2 was a target gene of miR-141-3p. ZEB2 overexpression promoted BBB disruption, and miR-141-3p overexpression attenuated the promoting effect exerted by ZEB2. Overall, miR-141-3p protects against BBB disruption and attenuates brain injuries induced by ICH by targeting ZEB2.

Stroke Genomics: Current Knowledge, Clinical Applications and Future Possibilities

The pathophysiology of stoke involves many complex pathways and risk factors. Though there are several ongoing studies on stroke, treatment options are limited, and the prevalence of stroke is continuing to increase. Understanding the genomic variants and biological pathways associated with stroke could offer novel therapeutic alternatives in terms of drug targets and receptor modulations for newer treatment methods. It is challenging to identify individual causative mutations in a single gene because many alleles are responsible for minor effects. Therefore, multiple factorial analyses using single nucleotide polymorphisms (SNPs) could be used to gain new insight by identifying potential genetic risk factors. There are many studies, such as Genome-Wide Association Studies (GWAS) and Phenome-Wide Association Studies (PheWAS) which have identified numerous independent loci associated with stroke, which could be instrumental in developing newer drug targets and novel therapies. Additionally, using analytical techniques, such as meta-analysis and Mendelian randomization could help in evaluating stroke risk factors and determining treatment priorities. Combining SNPs into polygenic risk scores and lifestyle risk factors could detect stroke risk at a very young age and help in administering preventive interventions.

The Enticing Path of miR Therapeutics: Difficult but Not without Prospects

MicroRNAs (miRs) are short non-coding RNAs that regulate the translation and stability of mRNAs to fine-tune gene expression [...].

LncRNA SNHG15 Promotes Oxidative Stress Damage to Regulate the Occurrence and Development of Cerebral Ischemia/Reperfusion Injury by Targeting the miR-141/SIRT1 Axis

Ischemic stroke is a kind of disease with high mortality and high disability, which brings a huge burden to the public health system (Hu et al. (2017)), and it poses a serious threat to the quality of life of patients. Cerebral ischemia/reperfusion injury is an important pathophysiological mechanism. This study aims to assess the mechanism of SNHG15 in the occurrence and development of cerebral ischemia/reperfusion injury of nerve cells and to investigate its potential value for diagnosis and treatment. SNHG15 targeted miRNA molecules and target genes were predicted with bioinformatics tools such as StarBase and TargetScan. The process of ischemic reperfusion in cerebral apoplexy in normal cultured and oxygen-glucose-deprived and reoxygenated neurons was simulated with RT-PCR and western blot technique. The expressions of SNHG15 and miR-141 were detected with qPCR, and the expressions of SIRT1 and p65, TNF-α, ROS, iNOS, and IL-6 were detected with western blot. Meanwhile, SNHG15 siRNAs and miR-141 mimics were transfected for SH-SY5Y, with western blot testing. And the expressions of miR-141, SIRT1, and p65, TNF-α, ROS, iNOS, and IL-6 were tested. According to the prediction with bioinformatics tools of StarBase and TargetScan, miR-141 is the target of lncSNHG15. In the luciferase reporter plasmid double-luciferase assay, miR-141 and SIRT1 were defined as the target relationship. In the oxygen-glucose-deprived reoxygenation model group, SNHG15 expression increased, miR-141 expression decreased, SIRT1 expression increased, and the expressions of p65, TNF-α, ROS, iNOS, and IL-6 decreased. In the SNHG15-siRNA-transfected oxygen-glucose-deprived reoxygenation cell model group, miR-141 expression increased, SIRT1 expression decreased, and the expressions of p65, TNF-α, and IL-6 increased compared with the si-NC group. In the miR-141-mimic-transfected oxygen-glucose-deprived reoxygenation cell model, SNHG15 expression decreased, SIRT1 expression decreased, and the expressions of p65, TNF-α, IL-1β, and IL-6 increased. In conclusion, SNHG15 expression increased during the process of oxygen-glucose-deprived reoxygenation, and the oxidative stress process was reduced by miR-141/SIRT1.

MicroRNA miR-21 Decreases Post-stroke Brain Damage in Rodents

Due to their role in controlling translation, microRNAs emerged as novel therapeutic targets to modulate post-stroke outcomes. We previously reported that miR-21 is the most abundantly induced microRNA in the brain of rodents subjected to preconditioning-induced cerebral ischemic tolerance. We currently show that intracerebral administration of miR-21 mimic decreased the infarct volume and promoted better motor function recovery in adult male and female C57BL/6 mice subjected to transient middle cerebral artery occlusion. The miR-21 mimic treatment is also efficacious in aged mice of both sexes subjected to focal ischemia. Mechanistically, miR-21 mimic treatment decreased the post-ischemic levels of several pro-apoptotic and pro-inflammatory RNAs, which might be responsible for the observed neuroprotection. We further observed post-ischemic neuroprotection in adult mice administered with miR-21 mimic intravenously. Overall, the results of this study implicate miR-21 as a promising candidate for therapeutic translation after stroke.

miR-146b Protects the Perinatal Brain against Microglia-Induced Hypomyelination

Objectives

In the premature newborn, perinatal inflammation mediated by microglia contributes significantly to neurodevelopmental injuries including white matter injury (WMI). Brain inflammation alters development through neuroinflammatory processes mediated by activation of homeostatic microglia toward a pro‐inflammatory and neurotoxic phenotype. Investigating immune regulators of microglial activation is crucial to find effective strategies to prevent and treat WMI.

Methods

Ex vivo microglial cultures and a mouse model of WMI induced by perinatal inflammation (interleukin‐1‐beta [IL‐1β] and postnatal days 1–5) were used to uncover and elucidate the role of microRNA‐146b‐5p in microglial activation and WMI.

Results

A specific reduction in vivo in microglia of Dicer, a protein required for microRNAs maturation, reduces pro‐inflammatory activation of microglia and prevents hypomyelination in our model of WMI. Microglial miRNome analysis in the WMI model identified miRNA‐146b‐5p as a candidate modulator of microglial activation. Ex vivo microglial cell culture treated with the pro‐inflammatory stimulus lipopolysaccharide (LPS) led to overexpression of immunomodulatory miRNA‐146b‐5p but its drastic reduction in the microglial extracellular vesicles (EVs). To increase miRNA‐146b‐5p expression, we used a 3DNA nanocarrier to deliver synthetic miRNA‐146b‐5p specifically to microglia. Enhancing microglial miRNA‐146b‐5p overexpression significantly decreased LPS‐induced activation, downregulated IRAK1, and restored miRNA‐146b‐5p levels in EVs. In our WMI model, 3DNA miRNA‐146b‐5p treatment significantly prevented microglial activation, hypomyelination, and cognitive defect induced by perinatal inflammation.

Interpretations

These findings support that miRNA‐146b‐5p is a major regulator of microglia phenotype and could be targeted to reduce the incidence and the severity of perinatal brain injuries and their long‐term consequences. ANN NEUROL 2022;91:48–65

Noncoding RNA crosstalk in brain health and diseases

The mammalian brain expresses several classes of noncoding RNAs (ncRNAs), including long ncRNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs). These ncRNAs play vital roles in regulating cellular processes by RNA/protein scaffolding, sponging and epigenetic modifications during the pathophysiological conditions, thereby controlling transcription and translation. Some of these functions are the result of crosstalk between ncRNAs to form a competitive endogenous RNA network. These intricately organized networks comprise lncRNA/miRNA, circRNA/miRNA, or lncRNA/miRNA/circRNA, leading to crosstalk between coding and ncRNAs through miRNAs. The miRNA response elements predominantly mediate the ncRNA crosstalk to buffer the miRNAs and thereby fine-tune and counterbalance the genomic changes and regulate neuronal plasticity, synaptogenesis and neuronal differentiation. The perturbed levels and interactions of the ncRNAs could lead to pathologic events like apoptosis and inflammation. Although the regulatory landscape of the ncRNA crosstalk is still evolving, some well-known examples such as lncRNA Malat1 sponging miR-145, circRNA CDR1as sponging miR-7, and lncRNA Cyrano and the circRNA CDR1as regulating miR-7, has been shown to affect brain function. The ability to manipulate these networks is crucial in determining the functional outcome of central nervous system (CNS) pathologies. The focus of this review is to highlights the interactions and crosstalk of these networks in regulating pathophysiologic CNS function.

Metformin protects against neuroinflammation through integrated mechanisms of miR-141 and the NF-ĸB-mediated inflammasome pathway in a diabetic mouse model

The brain responds to diabetic stress by inducing the inflammatory response. Under normal circumstances this process is tightly regulated. However, uncontrolled inflammatory responses lead to compromised function and eventual neurodegeneration. The microRNA (miR)-200 family, specifically miR-141, is differentially expressed in diseased states including cognitive decline, thereby triggering changes in downstream genes. We hypothesised that Metformin (MF) regulates the miR-141/protein phosphatase 2A (PP2A) axis, and associated NF-ĸB-mediated inflammasome expression in diabetic mice brain. Diabetes was induced by intraperitoneal injection of Streptozotocin (STZ), thereafter mice were treated with MF (20 mg/kg BW). Whole brain tissue was harvested for further analysis. In silico analysis showed that Sirt1 and PP2A are prediction targets of miR-141. Selected protein and gene expressions were established through western blotting and qPCR, respectively. Diabetic mice brain tissue demonstrated overexpression of miR-141 and related pro-inflammatory factors as well as decreased PP2A gene expression. MF was able to counteract this by regulating expression of miR-141, PP2A, and p-tau at Ser396 protein expressions. Further experimentation revealed MF's inhibitory action on the inflammasome system by regulating the expression of the upstream controller NLRP3, related cytokines and NF-κB signalling pathway. Collectively, we demonstrate that MF promotes neuroprotection in diabetic mice by dampening inflammatory responses through its inhibitory effects on various signalling pathways. CATEGORIES: Inflammation and Immunopharmacology, Metabolic Disorders and Endocrinology, Neuropharmacology.

Non-Coding RNAs Based Molecular Links in Type 2 Diabetes, Ischemic Stroke, and Vascular Dementia

This article reviews recent advances in the study of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and their functions in type 2 diabetes mellitus (T2DM), ischemic stroke (IS), and vascular dementia (VaD). miRNAs and lncRNAs are gene regulation markers that both regulate translational aspects of a wide range of proteins and biological processes in healthy and disease states. Recent studies from our laboratory and others have revealed that miRNAs and lncRNAs expressed differently are potential therapeutic targets for neurological diseases, especially T2DM, IS, VaD, and Alzheimer's disease (AD). Currently, the effect of aging in T2DM, IS, and VaD and the cellular and molecular pathways are largely unknown. In this article, we highlight results from the works on the molecular connections between T2DM and IS, and IS and VaD. In each disease, we also summarize the pathophysiology and the differential expressions of miRNAs and lncRNAs. Based on current research findings, we hypothesize that 1) T2DM bi-directionally and age-dependently induces IS and VaD, and 2) these changes are precursors to the onset of dementia in elderly people. Research into these hypotheses is required to examine further whether research efforts on reducing T2DM, IS, and VaD may affect dementia and/or delay the AD disease process in the aged population.

Nanoparticle Delivered Anti-miR-141-3p for Stroke Therapy

Ischemic stroke and factors modifying ischemic stroke responses, such as social isolation, contribute to long-term disability worldwide. Several studies demonstrated that the aberrant levels of microRNAs contribute to ischemic stroke injury. In prior studies, we established that miR-141-3p increases after ischemic stroke and post-stroke isolation. Herein, we explored two different anti-miR oligonucleotides; peptide nucleic acid (PNAs) and phosphorothioates (PS) for ischemic stroke therapy. We used US FDA approved biocompatible poly (lactic-co-glycolic acid) (PLGA)-based nanoparticle formulations for delivery. The PNA and PS anti-miRs were encapsulated in PLGA nanoparticles by double emulsion solvent evaporation technique. All the formulated nanoparticles showed uniform morphology, size, distribution, and surface charge density. Nanoparticles also exhibited a controlled nucleic acid release profile for 48 h. Further, we performed in vivo studies in the mouse model of ischemic stroke. Ischemic stroke was induced by transient (60 min) occlusion of middle cerebral artery occlusion followed by a reperfusion for 48 or 72 h. We assessed the blood-brain barrier permeability of PLGA NPs containing fluorophore (TAMRA) anti-miR probe after systemic delivery. Confocal imaging shows uptake of fluorophore tagged anti-miR in the brain parenchyma. Next, we evaluated the therapeutic efficacy after systemic delivery of nanoparticles containing PNA and PS anti-miR-141-3p in mice after stroke. Post-treatment differentially reduced both miR-141-3p levels in brain tissue and infarct injury. We noted PNA-based anti-miR showed superior efficacy compared to PS-based anti-miR. Herein, we successfully established that nanoparticles encapsulating PNA or PS-based anti-miRs-141-3p probes could be used as a potential treatment for ischemic stroke.

Post-Stroke Social Isolation Reduces Cell Proliferation in the Dentate Gyrus and Alters miRNA Profiles in the Aged Female Mice Brain

Social isolation and loneliness are risk factors for stroke. Elderly women are more likely to be isolated. Census data shows that in homeowners over the age of 65, women are much more likely to live alone. However, the underlying mechanisms of the detrimental effects of isolation have not been well studied in older females. In this study, we hypothesized that isolation impairs post-stroke recovery in aged female mice, leading to dysregulated microRNAs (miRNAs) in the brain, including those previously shown to be involved in response to social isolation (SI). Aged C57BL/6 female mice were subjected to a 60-min middle cerebral artery occlusion and were randomly assigned to either single housing (SI) or continued pair housing (PH) immediately after stroke for 15 days. SI immediately after stroke led to significantly more brain tissue loss after stroke and higher mortality. Furthermore, SI significantly delayed motor and sensory recovery and worsened cognitive function, compared to PH. A decrease in cell proliferation was seen in the dentate gyrus of SI mice assessed by bromodeoxyuridine (BrdU) labeling. miRNAome data analysis revealed changes in several miRNAs in the brain, such as miR-297a-3p and miR-200c-3p, which are known to regulate pathways involved in cell proliferation. In conclusion, our data suggest that SI can lead to a poor post-stroke recovery in aged females and dysregulation of miRNAs and reduced hippocampal cell proliferation.

Potential caveats of putative microglia-specific markers for assessment of age-related cerebrovascular neuroinflammation

BACKGROUND

The ability to distinguish resident microglia from infiltrating myeloid cells by flow cytometry-based surface phenotyping is an important technique for examining age-related neuroinflammation. The most commonly used surface markers for the identification of microglia include CD45 (low-intermediate expression), CD11b, Tmem119, and P2RY12.

METHODS

In this study, we examined changes in expression levels of these putative microglia markers in in vivo animal models of stroke, cerebral amyloid angiopathy (CAA), and aging as well as in an ex vivo LPS-induced inflammation model.

RESULTS

We demonstrate that Tmem119 and P2RY12 expression is evident within both CD45^int and CD45^high myeloid populations in models of stroke, CAA, and aging. Interestingly, LPS stimulation of FACS-sorted adult microglia suggested that these brain-resident myeloid cells can upregulate CD45 and downregulate Tmem119 and P2RY12, making them indistinguishable from peripherally derived myeloid populations. Importantly, our findings show that these changes in the molecular signatures of microglia can occur without a contribution from the other brain-resident or peripherally sourced immune cells.

CONCLUSION

We recommend future studies approach microglia identification by flow cytometry with caution, particularly in the absence of the use of a combination of markers validated for the specific neuroinflammation model of interest. The subpopulation of resident microglia residing within the "infiltrating myeloid" population, albeit small, may be functionally important in maintaining immune vigilance in the brain thus should not be overlooked in neuroimmunological studies.

Identifying Genetic and Biological Determinants of Race-Ethnic Disparities in Stroke in the United States

In the United States, causes of racial differences in stroke and its risk factors remain only partly understood, and there is a long-standing disparity in stroke incidence and mortality impacting Black Americans. Only half of the excess risk of stroke in the United States Black population is explained by traditional risk factors, suggesting potential effects of other factors including genetic and biological characteristics. Here, we nonsystematically reviewed candidate laboratory biomarkers for stroke and their relationships to racial disparities in stroke. Current evidence indicates that IL-6 (interleukin-6), a proinflammatory cytokine, mediates racial disparities in stroke through its association with traditional risk factors. Only one reviewed biomarker, Lp(a) (lipoprotein[a]), is a race-specific risk factor for stroke. Lp(a) is highly genetically determined and levels are substantially higher in Black than White people; clinical and pharmaceutical ramifications for stroke prevention remain uncertain. Other studied stroke risk biomarkers did not explain racial differences in stroke. More research on Lp(a) and other biological and genetic risk factors is needed to understand and mitigate racial disparities in stroke.

Approaches to Studying Determinants of Racial-Ethnic Disparities in Stroke and Its Sequelae

Disparities are differences in health outcomes among groups that originate from sources including historically experienced social injustice and broadly defined environmental exposures. Large health disparities exist, defined by many factors including race/ethnicity, sex, age, geography, and socioeconomic status. Studying disparities relies on measures of disease burden. Traditional measures, such as mortality, may be less applicable to neurological disorders, which often lead to substantial morbidity and lower quality of life, without necessarily causing death. Measures such as disability-adjusted life-years or healthy life expectancy may be more appropriate for assessing neurological disease and permit comparisons across diseases and communities. There are many approaches that can be used to study disparities. Analyses of population-based observational studies, patient registries, and administrative data all contribute to the understanding of disparities in humans. Animal and other experimental designs, including clinical trials, may be used to identify mechanisms and strategies to reduce disparities. All of these approaches have strengths and weaknesses. Ultimately, understanding and mitigating disparities will require use of all of these methods. Crucially, a focus on not only improving outcomes among all individuals in society but minimizing or eliminating differences between those with better outcomes and those who have historically been disadvantaged should drive the ongoing investigations into disparities. This review is focused on epidemiological approaches to examining the depth and determinants of racial-ethnic disparities in the United States related to stroke, stroke care, and stroke outcomes.

Long-Term Impact of Social Isolation and Molecular Underpinnings

Prolonged periods of social isolation can have detrimental effects on the physiology and behavior of exposed individuals in humans and animal models. This involves complex molecular mechanisms across tissues in the body which remain partly identified. This review discusses the biology of social isolation and describes the acute and lasting effects of prolonged periods of social isolation with a focus on the molecular events leading to behavioral alterations. We highlight the role of epigenetic mechanisms and non-coding RNA in the control of gene expression as a response to social isolation, and the consequences for behavior. Considering the use of strict quarantine during epidemics, like currently with COVID-19, we provide a cautionary tale on the indiscriminate implementation of such form of social isolation and its potential damaging and lasting effects in mental health.

Microarray Profiling Reveals Distinct Circulating miRNAs in Aged Male and Female Mice Subjected to Post-stroke Social Isolation

Social isolation (SI) increases ischemic injury and significantly delays recovery after experimental stroke. Changes in circulating microRNAs (miRNAs) have been implicated in several neurological disorders, including stroke. However, potential biomarkers to elucidate the mechanisms that underlie the detrimental effects of post-stroke isolation are unknown. Aged C57BL/6 male and female mice (18-20 months) were subjected to a 60-min middle cerebral artery occlusion followed by reperfusion and were assigned to either isolation (SI) or continued pair housing (PH) immediately after stroke. On day 15, mice were sacrificed, and plasma samples were collected for miRNAome analysis. Top candidate miRNAs and their biological functions were identified using integrated bioinformatics. The miRNAome analysis revealed a total of 21 differentially expressed miRNAs across both sexes with fold change of 3 or higher. Within the female cohort, miR-206-3p, -376a-3p, -34b-5p, -133a-5p, -466f, and -671-3p were highly altered relative to the PH housing condition. Similarly in males, miR-376c-3p, -181d-5p, -712-5p, -186-5p, -21a-3p, -30d-3p, -495-3p, -669c-5p, -335-5p, -429-3p, -31-3p, and -217-5p were identified. Following Kyoto Encyclopedia of Genes and Genomes analysis, the identified miRNAs effected distinct subset of pathways within sexes. Interactional network analysis revealed miR-495-3p (male) and miR-34b-5p (female) as pivotal nodes that targeted the largest subset of genes. We identified several sex-specific miRNAs as candidate biomarkers for post-stroke SI in aged male and female mice. Additionally, these results suggest that there is potential to use plasma-based circulating miRNAs as a source of novel biomarkers to identify biological pathways involved in post-stroke SI.

Potential Associations Among Alteration of Salivary miRNAs, Saliva Microbiome Structure, and Cognitive Impairments in Autistic Children

Recent evidence has demonstrated that salivary molecules, as well as bacterial populations, can be perturbed by several pathological conditions, including neuro-psychiatric diseases. This relationship between brain functionality and saliva composition could be exploited to unveil new pathological mechanisms of elusive diseases, such as Autistic Spectrum Disorder (ASD). We performed a combined approach of miRNA expression profiling by NanoString technology, followed by validation experiments in qPCR, and 16S rRNA microbiome analysis on saliva from 53 ASD and 27 neurologically unaffected control (NUC) children. MiR-29a-3p and miR-141-3p were upregulated, while miR-16-5p, let-7b-5p, and miR-451a were downregulated in ASD compared to NUCs. Microbiome analysis on the same subjects revealed that Rothia, Filifactor, Actinobacillus, Weeksellaceae, Ralstonia, Pasteurellaceae, and Aggregatibacter increased their abundance in ASD patients, while Tannerella, Moryella and TM7-3 decreased. Variations of both miRNAs and microbes were statistically associated to different neuropsychological scores related to anomalies in social interaction and communication. Among miRNA/bacteria associations, the most relevant was the negative correlation between salivary miR-141-3p expression and Tannerella abundance. MiRNA and microbiome dysregulations found in the saliva of ASD children are potentially associated with cognitive impairments of the subjects. Furthermore, a potential cross-talking between circulating miRNAs and resident bacteria could occur in saliva of ASD.

Lack of TLR4 modifies the miRNAs profile and attenuates inflammatory signaling pathways

TLR4 is a member of the toll-like receptors (TLR) immune family, which are activated by lipopolysaccharide, ethanol or damaged tissue, among others, by triggering proinflammatory cytokines release and inflammation. Lack of TLR4 protects against inflammatory processes and neuroinflammation linked with several neuropathologies. By considering that miRNAs are key post-transcriptional regulators of the proteins involved in distinct cellular processes, including inflammation, this study aimed to assess the impact of the miRNAs profile in mice cortices lacking the TLR4 response. Using mice cerebral cortices and next-generation sequencing (NGS), the findings showed that lack of TLR4 significantly reduced the quantity and diversity of the miRNAs expressed in WT mice cortices. The results also revealed a significant down-regulation of the miR-200 family, while cluster miR-99b/let-7e/miR-125a was up-regulated in TLR4-KO vs. WT. The bioinformatics and functional analyses demonstrated that TLR4-KO presented the systematic depletion of many pathways closely related to the immune system response, such as cytokine and interleukin signaling, MAPK and ion Channels routes, MyD88 pathways, NF-κβ and TLR7/8 pathways. Our results provide new insights into the molecular and biological processes associated with the protective effects of TLR-KO against inflammatory damage and neuroinflammation, and reveal the relevance of the TLR4 receptors response in many neuropathologies.

Bone Marrow-Derived NCS-01 Cells Advance a Novel Cell-Based Therapy for Stroke

Human mesenchymal stem cells have been explored for their application in cell-based therapies targeting stroke. Identifying cell lines that stand as safe, accessible, and effective for transplantation, while optimizing dosage, timing, and method of delivery remain critical translational steps towards clinical trials. Preclinical studies using bone marrow-derived NCS-01 cells show the cells' ability to confer functional recovery in ischemic stroke. Coculturing primary rat cortical cells or human neural progenitor cells with NCS-01 cells protects against oxygen-glucose deprivation. In the rodent middle cerebral artery occlusion model, intracarotid artery administration of NCS-01 cells demonstrate greater efficacy than other mesenchymal stem cells (MSCs) at improving motor and neurological function, as well as reducing infarct volume and peri-infarct cell loss. NCS-01 cells secrete therapeutic factors, including basic fibroblast growth factor and interleukin-6, while also demonstrating a potentially novel mechanism of extending filopodia towards the site of injury. In this review, we discuss recent preclinical advancements using in vitro and in vivo ischemia models that support the transplantation of NCS-01 in human stroke trials. These results, coupled with the recommendations put forth by the consortium of Stem cell Therapeutics as an Emerging Paradigm for Stroke (STEPS), highlight a framework for conducting preclinical research with the ultimate goal of initiating clinical trials.

Exosomal MicroRNAs Released by Activated Astrocytes as Potential Neuroinflammatory Biomarkers

Neuroinflammation is a hallmark of several neurodegenerative diseases and disorders, including traumatic brain injury (TBI). Neuroinflammation results in the activation of glial cells which exacerbates the neuroinflammatory process by secretion of pro-inflammatory cytokines and results in disruption of glial transmission networks. The glial cells, including astrocytes, play a critical role in the maintenance of homeostasis in the brain. Activated astrocytes release several factors as part of the inflammatory process including cytokines, proteins, and microRNAs (miRNAs). MiRNAs are noncoding RNA molecules involved in normal physiological processes and disease pathogenesis. MiRNAs have been implicated as important cell signaling molecules, and they are potential diagnostic biomarkers and therapeutic targets for various diseases, including neurological disorders. Exosomal miRNAs released by astrocytic response to neuroinflammation is not yet studied. In this study, primary human astrocytes were activated by IL-1β stimulation and we examined astrocytic exosomal miRNA cargo released in a neuroinflammatory stress model. Results indicate that acute neuroinflammation and oxidative stress induced by IL-1β generates the release of a specific subset of miRNAs via exosomes, which may have a potential role in regulating the inflammatory response. Additionally, these miRNAs may serve as potential biomarkers of neuroinflammation associated with neurological disorders and injuries.

Micro RNA 181c-5p: A promising target for post-stroke recovery in socially isolated mice

Dysregulation of microRNAs (miRNAs) has been tied to several neurological disorders, including ischemic stroke. It has also been established that social environments can modulate miRNA profiles. We have previously shown that post-stroke social isolation (SI) is linked to poor stroke outcomes and that miR-181c-5p emerged as one of few lead miRNAs that was downregulated in both stroke and SI. Therefore, in this study we examined the potential role of miR-181c-5p mimic in reversing the detrimental effects of post-stroke SI. Two to three-month-old C57BL/6 male mice were pair-housed (PH) for at least two weeks. After two weeks, mice underwent stroke survival surgery using middle cerebral artery occlusion (MCAO) and were randomly assigned to one of two housing conditions: stroke isolation (ST-ISO) or stroke pair-housing with a healthy partner (ST-PH). ST-ISO mice were randomized to receive either miR-181c-5p mimic or a scrambled RNA (7 mg/kg i.v./day×drug) control at 24 h and 48 h after stroke. The effects of miR-181c-5p mimic treatment were evaluated at 1, 3, and 7 days after stroke at histological, behavioral, and biochemical levels. Target genes of miR-181c-5p were then analyzed by qPCR using an RT2 Profiler qPCR Array of pre-coated miR-181c gene targets. Temporal profile expression data suggested that miR-181c-5p was significantly downregulated (p < 0.05 vs ST-PH) up to 7 days after post-stroke SI. MiR-181c-5p mimic treatment significantly increased miR-181c-5p expression in brain tissue and showed partial swift recovery in sensorimotor deficit. Target gene analysis identified downregulation of several calcium signaling-related genes, e.g., Cpne2 and Gria 1 & 2 after miR-181c-5p mimic treatment. In summary, present data suggests that miR-181c-5p is a potential target for post-stroke SI. Data also suggests that genes related to calcium and glutamate signaling might be involved in the beneficial effect of the miR-181c-5p mimic.

MiRNA-27b Regulates Angiogenesis by Targeting AMPK in Mouse Ischemic Stroke Model

Stroke is a leading cause of mortality and serious disability worldwide with limited treatment options. Angiogenesis has been reported to be involved in post-stroke recovery. Although the molecular mechanisms that regulate angiogenesis remain ambiguous, microRNAs have emerged as effective regulators of angiogenesis, involved in neurological function outcome. The present study aims to investigate the regulatory effects of miRNA-27b on post-stroke angiogenesis. In primary cultured brain microvascular endothelial cells (BMECs), the inhibition of miRNA-27b induced the activation of adenosine monophosphate-activated protein kinase (AMPK), which increased tube formation and migration. This action was attenuated when AMPKα2 was knocked down. Mice were subjected to middle cerebral artery occlusion (MCAo) surgery and administrated with Lentivirus miR-27b inhibitor. Enhanced angiogenesis in ischemic boundary zone (IBZ) was observed, and the neurological outcome during the entire study period was improved. The number of phosphate-AMPKα2⁺ cells that co-expressed endothelial cell marker CD31 was significantly increased. Taken together, the present study demonstrated that downregulated miRNA-27b promoted recovery after ischemic stroke via AMPK stimulus.