MicroRNA-124 is a subventricular zone neuronal fate determinant

Dual-specificity protein phosphatase 6 (DUSP6) overexpression reduces amyloid load and improves memory deficits in male 5xFAD mice

Introduction

Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal VGF gene network that regulates late-onset Alzheimer's disease (AD). Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating (CDR) in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model.

Methods

To investigate the role of DUSP6 in AD, we stereotactically injected AAV5-DUSP6 or AAV5-GFP (control) into the dorsal hippocampus (dHc) of both female and male 5xFAD or wild type mice, to induce overexpression of DUSP6 or GFP.

Results

Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß1-40 and Aß1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation, which was increased in 5xFAD mice, was significantly reduced by dHc DUSP6 overexpression in both males and females, as was the number of "microglial clusters," which correlated with reduced amyloid plaque size. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulation of inflammatory and extracellular signal-regulated kinase pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. Gene ontology analysis of DEGs (p < 0.05) identified a greater number of synaptic pathways that were regulated by DUSP6 overexpression in male compared to female 5xFAD.

Discussion

In summary, DUSP6 overexpression in dHc reduced amyloid deposition and memory deficits in male but not female 5xFAD mice, whereas reduced neuroinflammation and microglial activation were observed in both males and females, suggesting that DUSP6-induced reduction of microglial activation did not contribute to sex-dependent improvement in memory deficits. The sex-dependent regulation of synaptic pathways by DUSP6 overexpression, however, correlated with the improvement of spatial memory deficits in male but not female 5xFAD.

m5C methylated lncRncr3-MeCP2 interaction restricts miR124a-initiated neurogenesis

Coordination of neuronal differentiation with expansion of the neuroepithelial/neural progenitor cell (NEPC/NPC) pool is essential in early brain development. Our in vitro and in vivo studies identify independent and opposing roles for two neural-specific and differentially expressed non-coding RNAs derived from the same locus: the evolutionarily conserved lncRNA Rncr3 and the embedded microRNA miR124a-1. Rncr3 regulates NEPC/NPC proliferation and controls the biogenesis of miR124a, which determines neuronal differentiation. Rncr3 conserved exons 2/3 are cytosine methylated and bound by methyl-CpG binding protein MeCP2, which restricts expression of miR124a embedded in exon 4 to prevent premature neuronal differentiation, and to orchestrate proper brain growth. MeCP2 directly binds cytosine-methylated Rncr3 through previously unrecognized lysine residues and suppresses miR124a processing by recruiting PTBP1 to block access of DROSHA-DGCR8. Thus, miRNA processing is controlled by lncRNA m5C methylation along with the defined m5C epitranscriptomic RNA reader protein MeCP2 to coordinate brain development.

Fetal Brain-Derived Exosomal miRNAs from Maternal Blood: Potential Diagnostic Biomarkers for Fetal Alcohol Spectrum Disorders (FASDs)

Fetal alcohol spectrum disorders (FASDs) are leading causes of neurodevelopmental disability but cannot be diagnosed early in utero. Because several microRNAs (miRNAs) are implicated in other neurological and neurodevelopmental disorders, the effects of EtOH exposure on the expression of these miRNAs and their target genes and pathways were assessed. In women who drank alcohol (EtOH) during pregnancy and non-drinking controls, matched individually for fetal sex and gestational age, the levels of miRNAs in fetal brain-derived exosomes (FB-Es) isolated from the mothers' serum correlated well with the contents of the corresponding fetal brain tissues obtained after voluntary pregnancy termination. In six EtOH-exposed cases and six matched controls, the levels of fetal brain and maternal serum miRNAs were quantified on the array by qRT-PCR. In FB-Es from 10 EtOH-exposed cases and 10 controls, selected miRNAs were quantified by ddPCR. Protein levels were quantified by ELISA. There were significant EtOH-associated reductions in the expression of several miRNAs, including miR-9 and its downstream neuronal targets BDNF, REST, Synapsin, and Sonic hedgehog. In 20 paired cases, reductions in FB-E miR-9 levels correlated strongly with reductions in fetal eye diameter, a prominent feature of FASDs. Thus, FB-E miR-9 levels might serve as a biomarker to predict FASDs in at-risk fetuses.

A potential posttranscriptional regulator for p60-katanin: miR-124-3p

Katanin is a microtubule severing protein belonging to the ATPase family and consists of two subunits; p60-katanin synthesized by the KATNA1 gene and p80-katanin synthesized by the KATNB1 gene. Microtubule severing is one of the mechanisms that allow the reorganization of microtubules depending on cellular needs. While this reorganization of microtubules is associated with mitosis in dividing cells, it primarily takes part in the formation of structures such as axons and dendrites in nondividing mature neurons. Therefore, it is extremely important in neuronal branching. p60 and p80 katanin subunits coexist in the cell. While p60-katanin is responsible for cutting microtubules with its ATPase function, p80-katanin is responsible for the regulation of p60-katanin and its localization in the centrosome. Although katanin has vital functions in the cell, there are no known posttranscriptional regulators of it. MicroRNAs (miRNAs) are a group of small noncoding ribonucleotides that have been found to have important roles in regulating gene expression posttranscriptionally. Despite being important in gene regulation, so far no microRNA has been experimentally associated with katanin regulation. In this study, the effects of miR-124-3p, which we detected as a result of bioinformatics analysis to have the potential to bind to the p60 katanin mRNA, were investigated. For this aim, in this study, SH-SY5Y neuroblastoma cells were transfected with pre-miR-124-3p mimics and pre-mir miRNA precursor as a negative control, and the effect of this transfection on p60-katanin expression was measured at both RNA and protein levels by quantitative real-time PCR (qRT-PCR) and western blotting, respectively. The results of this study showed for the first time that miR-124-3p, which was predicted to bind p60-katanin mRNA by bioinformatic analysis, may regulate the expression of the KATNA1 gene. The data obtained within the scope of this study will make important contributions in order to better understand the regulation of the expression of p60-katanin which as well will have an incontrovertible impact on the understanding of the importance of cytoskeletal reorganization in both mitotic and postmitotic cells.

Optimized miR-124 reporters uncover differences in miR-124 expression among neuronal populations in vitro

Introduction

Although intensively studied in the last decades, how microRNAs (miRNAs) are expressed across different cell types in the brain remains largely unknown.

Materials

To address this issue, we sought to develop optimized fluorescence reporters that could be expressed in precise cellular subsets and used to accurately quantify miR contents in vivo.

Results

Focusing on miR-124, we tested different reporter designs whose efficiency was confirmed in different in vitro settings including cell lines and primary neuronal cultures from different brain structures. Unlike previous reporters, we provide experimental evidence that our optimized designs can faithfully translate miR levels in vitro.

Discussion

Tools developed here would enable assessing miRNA expression at the single cell resolution and are expected to significantly contribute to future miRNA research in vivo.

Predicting MiRNA-Disease Associations by Graph Representation Learning Based on Jumping Knowledge Networks

Growing studies have shown that miRNAs are inextricably linked with many human diseases, and a great deal of effort has been spent on identifying their potential associations. Compared with traditional experimental methods, computational approaches have achieved promising results. In this article, we propose a graph representation learning method to predict miRNA-disease associations. Specifically, we first integrate the verified miRNA-disease associations with the similarity information of miRNA and disease to construct a miRNA-disease heterogeneous graph. Then, we apply a graph attention network to aggregate the neighbor information of nodes in each layer, and then feed the representation of the hidden layer into the structure-aware jumping knowledge network to obtain the global features of nodes. The output features of miRNAs and diseases are then concatenated and fed into a fully connected layer to score the potential associations. Through five-fold cross-validation, the average AUC, accuracy and precision values of our model are 93.30%, 85.18% and 88.90%, respectively. In addition, for three case studies of the esophageal tumor, lymphoma and prostate tumor, 46, 45 and 45 of the top 50 miRNAs predicted by our model were confirmed by relevant databases. Overall, our method could provide a reliable alternative for miRNA-disease association prediction.

Neuroinflammatory Biomarkers in the Brain, Cerebrospinal Fluid, and Blood After Ischemic Stroke

The most frequent type of stroke, known as ischemic stroke (IS), is a significant global public health issue. The pathological process of IS and post-IS episodes has not yet been fully explored, but neuroinflammation has been identified as one of the key processes. Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment, and predict outcomes, and some biomarkers can also be used as therapeutic targets. After IS, various molecules are produced by different cell types, such as microglia, astrocytes, infiltrating leukocytes, endothelial cells, and damaged neurons, that participate in the neuroinflammatory response within the ischemic brain region. These molecules may either promote or inhibit neuroinflammation and may be released into extracellular spaces, including cerebrospinal fluid (CSF) and blood, due to reasons such as BBB damage. These neuroinflammatory molecules should be valued as biomarkers to monitor whether their expression levels in the blood, CSF, and brain correlate with the diagnosis and prognosis of IS patients or whether they have potential as therapeutic targets. In addition, although some molecules do not directly participate in the process of neuroinflammation, they have been reported to have potential diagnostic or therapeutic value against post-IS neuroinflammation, and these molecules will also be listed. In this review, we summarize the neuroinflammatory biomarkers in the brain, CSF, and blood after an IS episode and the potential value of these biomarkers for the diagnosis, treatment, and prognosis of IS patients.

MicroRNA‑124: an emerging therapeutic target in central nervous system disorders

The central nervous system (CNS) consists of neuron and non-neuron cells including neural stem/precursor cells (NSPCs), neuroblasts, glia cells (mainly astrocyte, oligodendroglia and microglia), which thereby form a precise and complicated network and exert diverse functions through interactions of numerous bioactive ingredients. MicroRNAs (miRNAs), with small size approximately  ~ 21nt and as well-documented post-transcriptional key regulators of gene expression, are a cluster of evolutionarily conserved endogenous non-coding RNAs. More than 2000 different miRNAs has been discovered till now. MicroRNA-124(miR-124), the most brain-rich microRNA, has been validated to possess important functions in the central nervous system, including neural stem cell proliferation and differentiation, cell fate determination, neuron migration, synapse plasticity and cognition, cell apoptosis etc. According to recent studies, herein, we provide a review of this conversant miR-124 to further understand the potential functions and therapeutic and clinical value in brain diseases.

Molecular Mechanisms Involved in the Regulation of Neurodevelopment by miR-124

miR-124 is a miRNA predominantly expressed in the nervous system and accounts for more than a quarter of the total miRNAs in the brain. It regulates neurogenesis, neuronal differentiation, neuronal maturation, and synapse formation and is the most important miRNA in the brain. Furthermore, emerging evidence has suggested miR-124 may be associated with the pathogenesis of various neurodevelopmental and neuropsychiatric disorders. Here, we provide an overview of the role of miR-124 in neurodevelopment and the underling mechanisms, and finally, we prospect the significance of miR-124 research to the field of neuroscience.

Signature of miRNAs derived from the circulating exosomes of patients with amyotrophic lateral sclerosis

Background

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disorder (NDS) with unclear pathophysiology and few therapeutic options. Mutations in SOD1 and C9orf72 are the most common in Asian and Caucasian patients with ALS, respectively. Aberrant (microRNAs) miRNAs found in patients with gene-mutated ALS may be involved in the pathogenesis of gene-specific ALS and sporadic ALS (SALS). The aim of this study was to screen for differentially expressed miRNAs from exosomes in patients with ALS and healthy controls (HCs) and to construct a miRNA-based diagnostic model to classify patients and HCs.

Methods

We compared circulating exosome-derived miRNAs of patients with ALS and HCs using the following two cohorts: a discovery cohort (three patients with SOD1-mutated ALS, three patients with C9orf72-mutated ALS, and three HCs) analyzed by microarray and a validation cohort (16 patients with gene-mutated ALS, 65 patients with SALS, and 61 HCs) confirmed by RT-qPCR. The support vector machine (SVM) model was used to help diagnose ALS using five differentially expressed miRNAs between SALS and HCs.

Results

A total of 64 differentially expressed miRNAs in patients with SOD1-mutated ALS and 128 differentially expressed miRNAs in patients with C9orf72-mutated ALS were obtained by microarray compared to HCs. Of these, 11 overlapping dysregulated miRNAs were identified in both groups. Among the 14 top-hit candidate miRNAs validated by RT-qPCR, hsa-miR-34a-3p was specifically downregulated in patients with SOD1-mutated ALS, while hsa-miR-1306-3p was downregulated in ALS patients with both SOD1 and C9orf72 mutations. In addition, hsa-miR-199a-3p and hsa-miR-30b-5p were upregulated significantly in patients with SALS, while hsa-miR-501-3p, hsa-miR-103a-2-5p, and hsa-miR-181d-5p had a trend to be upregulated. The SVM diagnostic model used five miRNAs as features to distinguish ALS from HCs in our cohort with an area under receiver operating characteristic curve (AUC) of 0.80.

Conclusion

Our study identified aberrant miRNAs from exosomes of SALS and ALS patients with SOD1/C9orf72 mutations and provided additional evidence that aberrant miRNAs were involved in the pathogenesis of ALS regardless of the presence or absence of the gene mutation. The machine learning algorithm had high accuracy in predicting the diagnosis of ALS, shedding light on the foundation for the clinical application of blood tests in the diagnosis of ALS, and revealing the pathological mechanisms of the disease.

Human cytomegalovirus infection perturbs neural progenitor cell fate via the expression of viral microRNAs

Human cytomegalovirus (HCMV) preferentially targets neural progenitor cells (NPCs) in congenitally infected fetal brains, inducing neurodevelopmental disorders. While HCMV expresses several microRNAs (miRNAs) during infection, their roles in NPC infection are unclear. Here, we characterized expression of cellular and viral miRNAs in HCMV-infected NPCs during early infection by microarray and identified seven differentially expressed cellular miRNAs and six significantly upregulated HCMV miRNAs. Deep learning approaches were used to identify potential targets of significantly upregulated HCMV miRNAs against differentially expressed cellular messenger RNA (mRNAs), and the associations with miRNA-mRNA expression changes were observed. Gene ontology enrichment analysis indicated cellular gene targets were significantly enriched in pathways involved in neurodevelopment and cell-cycle processes. Viral modulation of selected miRNAs and cellular gene targets involved in neurodevelopmental processes were further validated by real-time quantitative reverse transcription polymerase chain reaction. Finally, a predicted 3' untranslated region target site of hcmv-miR-US25-1 in Jag1, a factor important for neurogenesis, was confirmed by mutagenesis. Reduction of Jag1 RNA and protein levels in NPCs was observed in response to transient expression of hcmv-miR-US25-1. A hcmv-miR-US25-1 mutant virus (ΔmiR-US25) displayed limited ability to downregulate Jag1 mRNA levels and protein levels during the early infection stage compared with the wild type virus. Our collective experimental and computational investigation of miRNAs and cellular mRNAs expression in HCMV-infected NPCs yields new insights into the roles of viral miRNAs in regulating NPC fate and their contributions to HCMV neuropathogenesis.

Ageing at Molecular Level: Role of MicroRNAs

The progression of age triggers a vast number of diseases including cardiovascular, cancer, and neurodegenerative disorders. Regardless of our plentiful knowledge about age-related diseases, little is understood about molecular pathways that associate the ageing process with various diseases. Several cellular events like senescence, telomere dysfunction, alterations in protein processing, and regulation of gene expression are common between ageing and associated diseases. Accumulating information on the role of microRNAs (miRNAs) suggests targeting miRNAs can aid our understanding of the interplay between ageing and associated diseases. In the present chapter, we have attempted to explore the information available on the role of miRNAs in ageing of various tissues/organs and diseases and understand the molecular mechanism of ageing.

Exosomes-based therapy of stroke, an emerging approach toward recovery

Based on clinical observations, stroke is touted as one of the specific pathological conditions, affecting an individual’s life worldwide. So far, no effective treatment has been introduced to deal with stroke post-complications. Production and release of several neurotrophic factors by different cells exert positive effects on ischemic areas following stroke. As a correlate, basic and clinical studies have focused on the development and discovery of de novo modalities to introduce these factors timely and in appropriate doses into the affected areas. Exosomes (Exo) are non-sized vesicles released from many cells during pathological and physiological conditions and participate in intercellular communication. These particles transfer several arrays of signaling molecules, like several neurotrophic factors into the acceptor cells and induce specific signaling cascades in the favor of cell bioactivity. This review aimed to highlight the emerging role of exosomes as a therapeutic approach in the regeneration of ischemic areas.

Pathophysiology of Ischemic Stroke: Noncoding RNA Role in Oxidative Stress

Stroke is a neurological disease that causes significant disability and death worldwide. Ischemic stroke accounts for 75% of all strokes. The pathophysiological processes underlying ischemic stroke include oxidative stress, the toxicity of excitatory amino acids, ion disorder, enhanced apoptosis, and inflammation. Noncoding RNAs (ncRNAs) may have a vital role in regulating the pathophysiological processes of ischemic stroke, as confirmed by the altered expression of ncRNAs in blood samples from acute ischemic stroke patients, animal models, and oxygen-glucose-deprived (OGD) cell models. Due to specific changes in expression, ncRNAs can potentially be biomarkers for the diagnosis, treatment, and prognosis of ischemic stroke. As an important brain cell component, glial cells mediate the occurrence and progression of oxidative stress after ischemic stroke, and ncRNAs are an irreplaceable part of this mechanism. This review highlights the impact of ncRNAs in the oxidative stress process of ischemic stroke. It focuses on specific ncRNAs that underlie the pathophysiology of ischemic stroke and have potential as diagnostic biomarkers and therapeutic targets.

Reference gene identification for normalisation of RT-qPCR analysis in plasma samples of the rat middle cerebral artery occlusion model

OBJECTIVE

In quantitative reverse transcription-polymerase chain reaction (RT-qPCR) studies, the selection and validation of reference genes are crucial for the accurate analysis of MicroRNAs (miRNAs) expression. In this work, the optimal reference genes for RT-qPCR normalisation in plasma samples of rat middle cerebral artery occlusion (MCAO) models were identified.

METHODS

Six rat MCAO models were established. Blood samples were collected before modelling and approximately 16-24 h after modelling. Two commonly used reference genes (U6 and 5S) and three miRNAs (miR-24, miR-122 and miR-9a) were selected as candidate reference genes, and the expression of these genes was detected with RT-qPCR. The acquired data were analysed using geNorm, Normfinder, BestKeeper, RefFinder and comparative delta threshold cycle statistical models.

RESULTS

The analysed results consistently showed that miR-24 was the most stably expressed reference gene. The 'optimal combination' calculated by geNorm was miR-24, U6 and5S. The expression level of the target gene miR124 was similar when the most stable reference gene miR-24 or the 'optimal combination' was used as a reference gene. However, compared with miR24 or the 'optimal combination', the less stable reference genes influenced the fold change and the data accuracy with a large standard deviation.

CONCLUSION

These results confirmed the importance of selecting suitable reference genes for normalisation to obtain reliable results in RT-qPCR studies and demonstrated that the identified reference gene miR-24 or the 'optimal combination' could be used as an internal control for gene expression analysis in the rat MCAO model.

Effects of miR-124-3p Silencing on Neuronal Damage in the Hippocampus of Depression Rats by Regulating STAT3 Gene

Objective

A large amount of evidence shows that the abnormal expression of miRNA plays an important role in the development of depression. Therefore, we investigated the effect of miR-124-3p on neuronal damage in the hippocampus of depression rats.

Methods

The target genes of miR-124-3p were predicted by the database; the depression model was prepared by subcutaneous injection of corticosterone (CORT), and LV-miR-124-3p asponge lentiviral suspension was given to determine the weight of rats and open-field test, sugar preference experiment, Serum CORT, 5-HT, DA, and NE were measured, observe and record the behavior of rats, including behavior, diet, and hair. The expression of miR-124-3p, STAT3, Bcl-2, and Bax in rat hippocampus was measured. The rat hippocampal neuron cells were extracted and transfected with miR-124-3p inhibitor; the cells were cultured with CORT, and the cell survival rate was evaluated by MTT experiment, and the expressions of miR-124-3p, STAT3, Bcl-2, and Bax in the cells were detected. Luciferase reporter gene verifies the targeted regulation of miR-124-3p on STAT3.

Results

Compared with depression rats, silencing miR-124-3p increased the weight of the rats, increased the number of open-field activities, and significantly improved the general state and pathological state of the rats. The sugar water preference rate was significantly increased, the CORT content in the serum of rats decreased significantly, and the levels of 5-HT, DA, and NE increased significantly. After the treatment of silencing miR-124-3p, the expression level of miR-124-3p was decreased, while the STAT3 mRNA and protein expression levels were increased. And the protein and mRNA expression levels of Bcl-2 were increased, and the Bax protein and mRNA expression were decreased. Cell experiments verified that silencing miR-124-3p increased cell survival, the expression level of miR-124-3p decreased remarkably, while the expression levels of STAT3 mRNA and protein increased significantly. Silencing miR-124-3p reversed the effects of CORT treatment on miR-124-3p and STAT3 in neuronal cells. The luciferase reporter gene experiment confirmed that miR-124-3p targets and regulates STAT3 expression.

Conclusion

Silencing miR-124-3p may protect hippocampal neurons from damage in depression rats by upregulating STAT3 gene.

Protective Signature of IFNγ-Stimulated Microglia Relies on miR-124-3p Regulation From the Secretome Released by Mutant APP Swedish Neuronal Cells

Microglia-associated inflammation and miRNA dysregulation are key players in Alzheimer’s disease (AD) pathophysiology. Previously, we showed miR-124 upregulation in APP Swedish SH-SY5Y (SWE) and PSEN1 iPSC-derived neurons and its propagation by the secretome (soluble and exosomal fractions). After modulation with miR-124 mimic/inhibitor, we identified common responsive mechanisms between such models. We also reported miR-124 colocalization with microglia in AD patient hippocampi. Herein, we determined how miR-124 modulation in SWE cells influences microglia polarized subtypes in the context of inflammation. We used a coculture system without cell-to-cell contact formed by miR-124 modulated SWE cells and human CHME3 microglia stimulated with interferon-gamma (IFNγ-MG), in which we assessed their adopted gene/miRNA profile and proteomic signature. The increase of miR-124 in SWE cells/secretome (soluble and exosomal) was mimicked in IFNγ-MG. Treatment of SWE cells with the miR-124 inhibitor led to RAGE overexpression and loss of neuronal viability, while the mimic caused RAGE/HMGB1 downregulation and prevented mitochondria membrane potential loss. When accessing the paracrine effects on microglia, SWE miR-124 inhibitor favored their IFNγ-induced inflammatory signature (upregulated RAGE/HMGB1/iNOS/IL-1β; downregulated IL-10/ARG-1), while the mimic reduced microglia activation (downregulated TNF-α/iNOS) and deactivated extracellular MMP-2/MMP-9 levels. Microglia proteomics identified 113 responsive proteins to SWE miR-124 levels, including a subgroup of 17 proteins involved in immune function/inflammation and/or miR-124 targets. A total of 72 proteins were downregulated (e.g., MAP2K6) and 21 upregulated (e.g., PAWR) by the mimic, while the inhibitor also upregulated 21 proteins and downregulated 17 (e.g., TGFB1, PAWR, and EFEMP1). Other targets were associated with neurodevelopmental mechanisms, synaptic function, and vesicular trafficking. To examine the source of miR-124 variations in microglia, we silenced the RNase III endonuclease Dicer1 to block miRNA canonical biogenesis. Despite this suppression, the coculture with SWE cells/exosomes still raised microglial miR-124 levels, evidencing miR-124 transfer from neurons to microglia. This study is pioneer in elucidating that neuronal miR-124 reshapes microglia plasticity and in revealing the relevance of neuronal survival in mechanisms underlying inflammation in AD-associated neurodegeneration. These novel insights pave the way for the application of miRNA-based neuropharmacological strategies in AD whenever miRNA dysregulated levels are identified during patient stratification.

Expression Profile of miRs in Mesial Temporal Lobe Epilepsy: Systematic Review

Temporal lobe epilepsy (TLE) is one of the most common forms of focal epilepsy in children and adults. TLE is characterized by variable onset and seizures. Moreover, this form of epilepsy is often resistant to pharmacotherapy. The search for new mechanisms for the development of TLE may provide us with a key to the development of new diagnostic methods and a personalized approach to the treatment. In recent years, the role of non-coding ribonucleic acids (RNA) has been actively studied, among which microRNA (miR) is of the greatest interest. (1) Background: The purpose of the systematic review is to analyze the studies carried out on the role of miRs in the development of mesial TLE (mTLE) and update the existing knowledge about the biomarkers of this disease. (2) Methods: The search for publications was carried out in the databases PubMed, Springer, Web of Science, Clinicalkeys, Scopus, OxfordPress, Cochrane. The search was carried out using keywords and combinations. We analyzed publications for 2016–2021, including original studies in an animal model of TLE and with the participation of patients with TLE, thematic and systemic reviews, and Cochrane reviews. (3) Results: this thematic review showed that miR‒155, miR‒153, miR‒361‒5p, miR‒4668‒5p, miR‒8071, miR‒197‒5p, miR‒145, miR‒181, miR‒199a, miR‒1183, miR‒129‒2‒3p, miR‒143‒3p (upregulation), miR–134, miR‒0067835, and miR‒153 (downregulation) can be considered as biomarkers of mTLE. However, the roles of miR‒146a, miR‒142, miR‒106b, and miR‒223 are questionable and need further study. (4) Conclusion: In the future, it will be possible to consider previously studied miRs, which have high specificity and sensitivity in mTLE, as prognostic biomarkers (predictors) of the risk of developing this disease in patients with potentially epileptogenic structural damage to the mesial regions of the temporal lobe of the brain (congenital disorders of the neuronal migration and neurogenesis, brain injury, neuro-inflammation, tumor, impaired blood supply, neurodegeneration, etc.).

Potential Role of Exosomes in Ischemic Stroke Treatment

Ischemic stroke is a life-threatening cerebral vascular disease and accounts for high disability and mortality worldwide. Currently, no efficient therapeutic strategies are available for promoting neurological recovery in clinical practice, except rehabilitation. The majority of neuroprotective drugs showed positive impact in pre-clinical studies but failed in clinical trials. Therefore, there is an urgent demand for new promising therapeutic approaches for ischemic stroke treatment. Emerging evidence suggests that exosomes mediate communication between cells in both physiological and pathological conditions. Exosomes have received extensive attention for therapy following a stroke, because of their unique characteristics, such as the ability to cross the blood brain–barrier, low immunogenicity, and low toxicity. An increasing number of studies have demonstrated positively neurorestorative effects of exosome-based therapy, which are largely mediated by the microRNA cargo. Herein, we review the current knowledge of exosomes, the relationships between exosomes and stroke, and the therapeutic effects of exosome-based treatments in neurovascular remodeling processes after stroke. Exosomes provide a viable and prospective treatment strategy for ischemic stroke patients.

Adult Neural Stem Cell Regulation by Small Non-coding RNAs: Physiological Significance and Pathological Implications

The adult neurogenic niches are complex multicellular systems, receiving regulatory input from a multitude of intracellular, juxtacrine, and paracrine signals and biological pathways. Within the niches, adult neural stem cells (aNSCs) generate astrocytic and neuronal progeny, with the latter predominating in physiological conditions. The new neurons generated from this neurogenic process are functionally linked to memory, cognition, and mood regulation, while much less is known about the functional contribution of aNSC-derived newborn astrocytes and adult-born oligodendrocytes. Accumulating evidence suggests that the deregulation of aNSCs and their progeny can impact, or can be impacted by, aging and several brain pathologies, including neurodevelopmental and mood disorders, neurodegenerative diseases, and also by insults, such as epileptic seizures, stroke, or traumatic brain injury. Hence, understanding the regulatory underpinnings of aNSC activation, differentiation, and fate commitment could help identify novel therapeutic avenues for a series of pathological conditions. Over the last two decades, small non-coding RNAs (sncRNAs) have emerged as key regulators of NSC fate determination in the adult neurogenic niches. In this review, we synthesize prior knowledge on how sncRNAs, such as microRNAs (miRNAs) and piwi-interacting RNAs (piRNAs), may impact NSC fate determination in the adult brain and we critically assess the functional significance of these events. We discuss the concepts that emerge from these examples and how they could be used to provide a framework for considering aNSC (de)regulation in the pathogenesis and treatment of neurological diseases.

The effects of altered neurogenic microRNA levels and their involvement in the aggressiveness of periventricular glioblastoma

INTRODUCTION

Glioblastoma multiforme is the most common primary brain tumour, with the least favourable prognosis. Despite numerous studies and medical advances, it continues to be lethal, with an average life expectancy of 15 months after chemo-radiotherapy.

DEVELOPMENT

Recent research has addressed several factors associated with the diagnosis and prognosis of glioblastoma; one significant factor is tumour localisation, particularly the subventricular zone, which represents one of the most active neurogenic niches of the adult human brain. Glioblastomas in this area are generally more aggressive, resulting in unfavourable prognosis and a shorter life expectancy. Currently, the research into microRNAs (miRNA) has intensified, revealing different expression patterns under physiological and pathophysiological conditions. It has been reported that the expression levels of certain miRNAs, mainly those related to neurogenic processes, are dysregulated in oncogenic events, thus favouring gliomagenesis and greater tumour aggressiveness. This review discusses some of the most important miRNAs involved in subventricular neurogenic processes and their association with glioblastoma aggressiveness.

CONCLUSIONS

MiRNA regulation and function play an important role in the development and progression of glioblastoma; understanding the alterations of certain miRNAs involved in both differentiation and neural and glial maturation could help us to better understand the malignant characteristics of glioblastoma.

Adult Neurogenesis: A Story Ranging from Controversial New Neurogenic Areas and Human Adult Neurogenesis to Molecular Regulation

The generation of new neurons in the adult brain is a currently accepted phenomenon. Over the past few decades, the subventricular zone and the hippocampal dentate gyrus have been described as the two main neurogenic niches. Neurogenic niches generate new neurons through an asymmetric division process involving several developmental steps. This process occurs throughout life in several species, including humans. These new neurons possess unique properties that contribute to the local circuitry. Despite several efforts, no other neurogenic zones have been observed in many years; the lack of observation is probably due to technical issues. However, in recent years, more brain niches have been described, once again breaking the current paradigms. Currently, a debate in the scientific community about new neurogenic areas of the brain, namely, human adult neurogenesis, is ongoing. Thus, several open questions regarding new neurogenic niches, as well as this phenomenon in adult humans, their functional relevance, and their mechanisms, remain to be answered. In this review, we discuss the literature and provide a compressive overview of the known neurogenic zones, traditional zones, and newly described zones. Additionally, we will review the regulatory roles of some molecular mechanisms, such as miRNAs, neurotrophic factors, and neurotrophins. We also join the debate on human adult neurogenesis, and we will identify similarities and differences in the literature and summarize the knowledge regarding these interesting topics.

Multifaceted Regulation of MicroRNA Biogenesis: Essential Roles and Functional Integration in Neuronal and Glial Development

MicroRNAs (miRNAs) are small, non-coding RNAs that function as endogenous gene silencers. Soon after the discovery of miRNAs, a subset of brain-enriched and brain-specific miRNAs were identified and significant advancements were made in delineating miRNA function in brain development. However, understanding the molecular mechanisms that regulate miRNA biogenesis in normal and diseased brains has become a prevailing challenge. Besides transcriptional regulation of miRNA host genes, miRNA processing intermediates are subjected to multifaceted regulation by canonical miRNA processing enzymes, RNA binding proteins (RBPs) and epitranscriptomic modifications. Further still, miRNA activity can be regulated by the sponging activity of other non-coding RNA classes, namely circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs). Differential abundance of these factors in neuronal and glial lineages partly underlies the spatiotemporal expression and function of lineage-specific miRNAs. Here, we review the continuously evolving understanding of the regulation of neuronal and glial miRNA biogenesis at the transcriptional and posttranscriptional levels and the cooperativity of miRNA species in targeting key mRNAs to drive lineage-specific development. In addition, we review dysregulation of neuronal and glial miRNAs and the detrimental impacts which contribute to developmental brain disorders.

MiR-124 and Small Molecules Synergistically Regulate the Generation of Neuronal Cells from Rat Cortical Reactive Astrocytes

Irreversible neuron loss caused by central nervous system injuries usually leads to persistent neurological dysfunction. Reactive astrocytes, because of their high proliferative capacity, proximity to neuronal lineage, and significant involvement in glial scarring, are ideal starting cells for neuronal regeneration. Having previously identified several small molecules as important regulators of astrocyte-to-neuron reprogramming, we established herein that miR-124, ruxolitinib, SB203580, and forskolin could co-regulate rat cortical reactive astrocyte-to-neuron conversion. The induced cells had reduced astroglial properties, displayed typical neuronal morphologies, and expressed neuronal markers, reflecting 25.9% of cholinergic neurons and 22.3% of glutamatergic neurons. Gene analysis revealed that induced neuron gene expression patterns were more similar to that of primary neurons than of initial reactive astrocytes. On the molecular level, miR-124-driven neuronal differentiation of reactive astrocytes was via targeting of the SOX9-NFIA-HES1 axis to inhibit HES1 expression. In conclusion, we present a novel approach to inducing endogenous rat cortical reactive astrocytes into neurons through co-regulation involving miR-124 and three small molecules. Thus, our research has potential implications for inhibiting glial scar formation and promoting neuronal regeneration after central nervous system injury or disease.

Multiple Disruptions of Glial-Neuronal Networks in Epileptogenesis That Follows Prolonged Febrile Seizures

Background and Rationale: Bi-directional neuronal-glial communication is a critical mediator of normal brain function and is disrupted in the epileptic brain. The potential role of aberrant microglia and astrocyte function during epileptogenesis is important because the mediators involved provide tangible targets for intervention and prevention of epilepsy. Glial activation is intrinsically involved in the generation of childhood febrile seizures (FS), and prolonged FS (febrile status epilepticus, FSE) antecede a proportion of adult temporal lobe epilepsy (TLE). Because TLE is often refractory to treatment and accompanied by significant memory and emotional difficulties, we probed the role of disruptions of glial-neuronal networks in the epileptogenesis that follows experimental FSE (eFSE).

Methods: We performed a multi-pronged examination of neuronal-glia communication and the resulting activation of molecular signaling cascades in these cell types following eFSE in immature mice and rats. Specifically, we examined pathways involving cytokines, microRNAs, high mobility group B-1 (HMGB1) and the prostaglandin E2 signaling. We aimed to block epileptogenesis using network-specific interventions as well as via a global anti-inflammatory approach using dexamethasone.

Results: (A) eFSE elicited a strong inflammatory response with rapid and sustained upregulation of pro-inflammatory cytokines. (B) Within minutes of the end of the eFSE, HMGB1 translocated from neuronal nuclei to dendrites, en route to the extracellular space and glial Toll-like receptors. Administration of an HMGB1 blocker to eFSE rat pups did not decrease expression of downstream inflammatory cascades and led to unacceptable side effects. (C) Prolonged seizure-like activity caused overall microRNA-124 (miR-124) levels to plunge in hippocampus and release of this microRNA from neurons via extra-cellular vesicles. (D) Within hours of eFSE, structural astrocyte and microglia activation was associated not only with cytokine production, but also with activation of the PGE₂ cascade. However, administration of TG6-10-1, a blocker of the PGE₂ receptor EP2 had little effect on spike-series provoked by eFSE. (E) In contrast to the failure of selective interventions, a 3-day treatment of eFSE–experiencing rat pups with the broad anti-inflammatory drug dexamethasone attenuated eFSE-provoked pro-epileptogenic EEG changes.

Conclusions: eFSE, a provoker of TLE-like epilepsy in rodents leads to multiple and rapid disruptions of interconnected glial-neuronal networks, with a likely important role in epileptogenesis. The intricate, cell-specific and homeostatic interplays among these networks constitute a serious challenge to effective selective interventions that aim to prevent epilepsy. In contrast, a broad suppression of glial-neuronal dysfunction holds promise for mitigating FSE-induced hyperexcitability and epileptogenesis in experimental models and in humans.

MiRNA Regulatory Functions in Photoreceptors

MicroRNAs (miRNAs) are important regulators of gene expression. These small, non-coding RNAs post-transcriptionally silence messenger RNAs (mRNAs) in a sequence-specific manner. In this way, miRNAs control important regulatory functions, also in the retina. If dysregulated, these molecules are involved in several retinal pathologies. For example, several miRNAs have been linked to essential photoreceptor functions, including light sensitivity, synaptic transmission, and modulation of inflammatory responses. Mechanistic miRNA knockout and knockdown studies further linked their functions to degenerative retinal diseases. Of note, the type and timing of genetic manipulation before, during, or after retinal development, is important when studying specific miRNA knockout effects. Within this review, we focus on miR-124 and the miR-183/96/182 cluster, which have assigned functions in photoreceptors in health and disease. As a single miRNA can regulate hundreds of mRNAs, we will also discuss the experimental validation and manipulation approaches to study complex miRNA/mRNA regulatory networks. Revealing these networks is essential to understand retinal pathologies and to harness miRNAs as precise therapeutic and diagnostic tools to stabilize the photoreceptors’ transcriptomes and, thereby, function.

Potential role of exosome in post-stroke reorganization and/or neurodegeneration

Currently, stroke is a common and devastating condition, which is sometimes associated with permanent cerebral damages. Although in early time after stroke, the related treatments are mainly focused on the restoration of cerebral blood flow (CBF), at the same time, some changes are commencing that continue for a long time and need to be specially noticed. Previous studies have proposed several molecular mechanisms in these post-stroke events. Exosomes are a type of vesicle, which are formed and secreted by most cells as a mean to transfer cellular constituents such as proteins, DNA and/or RNA to distant cells. Therefore, they are considered as a novel mechanism of cellular communication. Herein, we reviewed the current knowledge on cascades, which are activated after stroke and consequently lead to the reorganization and/or continuance of tissue damage and development of other disorders such as Neurodegenerative diseases (ND). Thereafter, we summarized the latest proofs about the possible participation of exosomes in transferring some components such as proteins and micro-RNAs (miRs), from the affected areas to other parts of the brain and eventually cause the above-mentioned post-stroke events.

Extracellular Vesicles, Influential Players of Intercellular Communication within Adult Neurogenic Niches

Adult neurogenesis, involving the generation of functional neurons from adult neural stem cells (NSCs), occurs constitutively in discrete brain regions such as hippocampus, sub-ventricular zone (SVZ) and hypothalamus. The intrinsic structural plasticity of the neurogenic process allows the adult brain to face the continuously changing external and internal environment and requires coordinated interplay between all cell types within the specialized microenvironment of the neurogenic niche. NSC-, neuronal- and glia-derived factors, originating locally, regulate the balance between quiescence and self-renewal of NSC, their differentiation programs and the survival and integration of newborn cells. Extracellular Vesicles (EVs) are emerging as important mediators of cell-to-cell communication, representing an efficient way to transfer the biologically active cargos (nucleic acids, proteins, lipids) by which they modulate the function of the recipient cells. Current knowledge of the physiological role of EVs within adult neurogenic niches is rather limited. In this review, we will summarize and discuss EV-based cross-talk within adult neurogenic niches and postulate how EVs might play a critical role in the regulation of the neurogenic process.

Epigenetic principles underlying epileptogenesis and epilepsy syndromes

Epilepsy is a network disorder driven by fundamental changes in the function of the cells which compose these networks. Driving this aberrant cellular function are large scale changes in gene expression and gene expression regulation. Recent studies have revealed rapid and persistent changes in epigenetic control of gene expression as a critical regulator of the epileptic transcriptome. Epigenetic-mediated gene output regulates many aspects of cellular physiology including neuronal structure, neurotransmitter assembly and abundance, protein abundance of ion channels and other critical neuronal processes. Thus, understanding the contribution of epigenetic-mediated gene regulation could illuminate novel regulatory mechanisms which may form the basis of novel therapeutic approaches to treat epilepsy. In this review we discuss the effects of epileptogenic brain insults on epigenetic regulation of gene expression, recent efforts to target epigenetic processes to block epileptogenesis and the prospects of an epigenetic-based therapy for epilepsy, and finally we discuss technological advancements which have facilitated the interrogation of the epigenome.

Regulatory Role of MicroRNAs in Brain Development and Function

MicroRNAs (miRNAs) are small non-coding RNA molecules of about 20-22 nucleotides. After their posttranscriptional maturation, miRNAs are loaded into the ribonucleoprotein complex RISC and modulate gene expression by binding to the 3' untranslated region of their target mRNAs through base-pairing, which in turn triggers mRNA degradation or translational inhibition. There is mounting evidence that miRNAs regulate various biological processes, including cell proliferation, differentiation, and apoptosis. Several studies have shown that miRNAs play an important role in neurogenesis and brain development.This review discusses recent progress on understanding the implication of precisely regulated miRNA expression in normal brain development and function. In addition, it reports known cases of dysregulation of miRNA expression and function implicated in the pathogenesis of neurodevelopmental disorders, craniofacial dysmorphic syndromes, neurodegenerative diseases, and psychiatric disorders. Current knowledge regarding the role of miRNAs in the brain in conjunction with the complex interplay between genetic and epigenetic factors are discussed.

Driving Neuronal Differentiation through Reversal of an ERK1/2-miR-124-SOX9 Axis Abrogates Glioblastoma Aggressiveness

Identifying cellular programs that drive cancers to be stem-like and treatment resistant is critical to improving outcomes in patients. Here, we demonstrate that constitutive extracellular signal-regulated kinase 1/2 (ERK1/2) activation sustains a stem-like state in glioblastoma (GBM), the most common primary malignant brain tumor. Pharmacological inhibition of ERK1/2 activation restores neurogenesis during murine astrocytoma formation, inducing neuronal differentiation in tumorspheres. Constitutive ERK1/2 activation globally regulates miRNA expression in murine and human GBMs, while neuronal differentiation of GBM tumorspheres following the inhibition of ERK1/2 activation requires the functional expression of miR-124 and the depletion of its target gene SOX9. Overexpression of miR124 depletes SOX9 in vivo and promotes a stem-like-to-neuronal transition, with reduced tumorigenicity and increased radiation sensitivity. Providing a rationale for reports demonstrating miR-124-induced abrogation of GBM aggressiveness, we conclude that reversal of an ERK1/2-miR-124-SOX9 axis induces a neuronal phenotype and that enforcing neuronal differentiation represents a therapeutic strategy to improve outcomes in GBM.

Circular RNA CircHIPK3 Elevates CCND2 Expression and Promotes Cell Proliferation and Invasion Through miR-124 in Glioma

As a malignant tumor of the central nervous system, glioma exhibits high incidence and poor prognosis. Circular RNA HIPK3 (circHIPK3) is a circular RNA (circRNA) related to cancer progression. However, the role of circHIPK3 in gliomas remains unclear. The purpose of this study was to investigate the role of circHIPK3 in gliomas and its mechanism. The qRT-PCR method was used to determine the expression pattern of circHIPK3 in glioma cell lines. CCK-8 assay was used to detect cell proliferation. Cell migration and invasion were evaluated using the Transwell assay. Our results showed that circHIPK3 expression was significantly up-regulated in glioma tissues and cell lines. In vitro, the down-regulation of circHIPK3 significantly inhibited the proliferation, migration and invasion of glioma cells. Besides, we demonstrated that circHIPK3 acted as a sponge to absorb miR-124 and promoted CCND2 expression. In summary, our results indicated that circHIPK3 had carcinogenic effects by regulating the expression of CCND2 in glioma by sponging miR-124. These findings provided favorable evidence to reveal the role of circHIPK3 in the development of gliomas.

MiR224-5p Inhibitor Restrains Neuronal Apoptosis by Targeting NR4A1 in the Oxygen-Glucose Deprivation (OGD) Model

This study was designed to investigate the molecular mechanism of stroke and to explore the effect of miR-224-5p in hypoxic cortical neurons. Firstly, we established a middle cerebral artery occlusion (MCAO) model with Sprague–Dawley rats. Triphenyltetrazolium chloride (TTC) staining showed the brain infarction of an MCAO rat. Longa scores of rats were significantly increased in 12th, 24th, and 48th hours after MCAO. Then, we found that miR-224-5p was increased after MCAO in rats by qRT-PCR. In order to investigate the effect of miR-224-5p in hypoxic neurons, we established an oxygen-glucose deprivation (OGD) model with cortical neurons. MiR-224-5p was also upregulated in neurons after OGD by qRT-PCR. After transfection of the miR-224-5p inhibitor, the number of neurons in the anti-miR-224-5p group significantly increased (P < 0.01) in comparison to the anti-NC group. Furthermore, Tuj1⁺ (neuronal marker) staining and TUNEL assay (to detect apoptotic cells) were performed in neurons. The survival of neurons in the anti-miR-224-5p group was significantly improved (P < 0.01), while the apoptosis of neurons in the anti-miR-224-5p group was significantly decreased (P < 0.01), when compared with that of the anti-NC group. In addition, we predicted that potential target genes of miR-224-5p were nuclear receptor subfamily 4 group A member 1 (NR4A1), interleukin 1 receptor antagonist (IL1RN), and ring finger protein 38 (RNF38) with bioinformatics databases, such as TargetScan, miRDB, miRmap, and miRanda. The result of qRT-PCR confirmed that NR4A1 was significantly decreased after hypoxic injury (P < 0.01). Meanwhile, luciferase reporter’s assay indicated that NR4A1 was the direct target of miR-224-5p. Compared with the anti-miR-224-5p + siNC group, the number of cortical neurons and the length of the neuron axon in the anti-miR-224-5p + si-NR4A1 group were significantly decreased (P < 0.01), and the number of neuronal apoptosis in the anti-miR-224-5p + si-NR4A1 group was increased (P < 0.01). In conclusion, miR-224-5p played a crucial role in hypoxic neuron injury through NR4A1, which might be an important regulatory mechanism in OGD injury of neurons.

MicroRNA-183-5p is stress-inducible and protects neurons against cell death in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the death of motor neurons. A fundamental pathogenesis of ALS is the prolonged cell stress in neurons, which is caused by either accumulation of protein aggregates or reactive oxygen species. However, the mechanistic link between stress sensing and cell death is unsettled. Here, we identify that miR-183-5p, a neuron-enriched miRNA, couples stress sensing and cell death programming in ALS. miR-183-5p is immediately induced by hydrogen peroxide, tunicamycin or TNF-α in neurons. The overexpression of miR-183-5p increases neuron survival under stress conditions, whereas its knockdown causes neuron death. miR-183-5p coordinates apoptosis and necroptosis pathways by directly targeting PDCD4 and RIPK3, and thus protects neurons against cell death under stress conditions. The consistent reduction of miR-183-5p in ALS patients and mouse models enhances the notion that miR-183-5p is a central regulator of motor neuron survival under stress conditions. Our study supplements current understanding of the mechanistic link between cell stress and death/survival, and provides novel targets for clinical interventions of ALS.

Olfactory Dysfunction in Diabetic Rats is Associated with miR-146a Overexpression and Inflammation

Type 2 diabetes (T2D) is associated with cognitive decline and dementia. Both neurodegenerative conditions are characterized by olfactory dysfunction (OD) which is also observed in diabetic patients. Diabetes and neurodegeneration display altered miRNAs expression; therefore, the study of miRNAs in the diabetic olfactory system is important in order to know the mechanisms involved in neurodegeneration induced by T2D. In this work we evaluated the expression of miRs206, 451, 146a and 34a in the olfactory bulb (OB) of T2D rats and its association with OD. T2D induction was performed by administering streptozotocin to neonatal rats. The olfactory function was evaluated after reaching the adulthood by employing the buried pellet and social recognition tests. After 18 weeks, animals were sacrificed to determinate miRNAs and protein expression in the OB. T2D animals showed a significant increase in the latency to find the odor stimulus in the buried pellet test and a significant reduction in the interest to investigate the novel juvenile subjects in the social recognition test, indicating OD. In miRNAs analysis we observed a significant increase of miR-146a expression in the OB of T2D rats when compared to controls. This increase in miR-146a correlated with the overexpression of IL-1β in the OB of T2D rats. The present results showed that OD in T2D rats is associated with IL-1β mediated-inflammation and miR-146a overexpression, suggesting that high levels of IL-1β could trigger miR-146a upregulation as a negative feedback of the inflammatory response in the OB of T2D rats.

Chronic Regulation of miR-124-3p in the Perilesional Cortex after Experimental and Human TBI

Traumatic brain injury (TBI) dysregulates microRNAs, which are the master regulators of gene expression. Here we investigated the changes in a brain-enriched miR-124-3p, which is known to associate with major post-injury pathologies, such as neuroinflammation. RT-qPCR of the rat tissue sampled at 7 d and 3 months in the perilesional cortex adjacent to the necrotic lesion core (aPeCx) revealed downregulation of miR-124-3p at 7 d (fold-change (FC) 0.13, p < 0.05 compared with control) and 3 months (FC 0.40, p < 0.05) post-TBI. In situ hybridization confirmed the downregulation of miR-124-3p at 7 d and 3 months post-TBI in the aPeCx (both p < 0.01). RT-qPCR confirmed the upregulation of the miR-124-3p target Stat3 in the aPeCx at 7 d post-TBI (7-fold, p < 0.05). mRNA-Seq revealed 312 downregulated and 311 upregulated miR-124 targets (p < 0.05). To investigate whether experimental findings translated to humans, we performed in situ hybridization of miR-124-3p in temporal lobe autopsy samples of TBI patients. Our data revealed downregulation of miR-124-3p in individual neurons of cortical layer III. These findings indicate a persistent downregulation of miR-124-3p in the perilesional cortex that might contribute to post-injury neurodegeneration and inflammation.

Elevated Acute Plasma miR-124-3p Level Relates to Evolution of Larger Cortical Lesion Area after Traumatic Brain Injury

Mechanisms initiated by traumatic brain injury (TBI), leading to the development of progressive secondary injury are poorly understood. MicroRNAs (miRNAs) have a proposed role in orchestrating the post-injury aftermath as a single miRNA can control the expression of several genes. We hypothesized that the post-injury level of circulating brain-enriched miR-124-3p explains the extent of post-TBI cortical lesion. Three separate cohorts of adult male Sprague-Dawley rats (total n = 57) were injured with lateral fluid-percussion-induced TBI. The miR-124-3p levels were measured in whole blood and/or plasma in cohorts 1 and 2 before TBI as well as at 2 d, 7 d, 2 months or 3 months post-TBI. The third cohort (22/57) was imaged with T2-weighted magnetic resonance imaging (MRI) at 2 months post-TBI to quantify cortical lesion area and perilesional T2-enhancement volume. Our data shows that miR-124-3p levels were elevated at 2 d post-TBI in both blood (FC 4.63, p < 0.01) and plasma (FC 1.39, p < 0.05) as compared to controls. Receiver operating curve (ROC) analysis indicated that plasma miR-124-3p level of 34 copies/µl or higher differentiated TBI animals from controls [area under curve (AUC) 0.815, p < 0.05]. The data was validated in the third cohort (FC 1.68, p < 0.05). T2-weighted MRI revealed inter-animal differences in cortical lesion area. Linear regression analysis revealed that higher the plasma miR-124-3p level at 2 d post-TBI, larger the lesion area at chronic time point (R² = 0.327, p < 0.01). Our findings indicate that the extent of lateral fluid-percussion injury-induced chronic cortical pathology associated with the acutely elevated plasma miR-124-3p level.

The effects of altered neurogenic microRNA levels and their involvement in the aggressiveness of periventricular glioblastoma

INTRODUCTION

Glioblastoma multiforme is the most common primary brain tumour, with the least favourable prognosis. Despite numerous studies and medical advances, it continues to be lethal, with an average life expectancy of 15 months after chemo-radiotherapy.

DEVELOPMENT

Recent research has addressed several factors associated with the diagnosis and prognosis of glioblastoma; one significant factor is tumour localisation, particularly the subventricular zone, which represents one of the most active neurogenic niches of the adult human brain. Glioblastomas in this area are generally more aggressive, resulting in unfavourable prognosis and a shorter life expectancy. Currently, the research into microRNAs (miRNA) has intensified, revealing different expression patterns under physiological and pathophysiological conditions. It has been reported that the expression levels of certain miRNAs, mainly those related to neurogenic processes, are dysregulated in oncogenic events, thus favouring gliomagenesis and greater tumour aggressiveness. This review discusses some of the most important miRNAs involved in subventricular neurogenic processes and their association with glioblastoma aggressiveness.

CONCLUSIONS

MiRNA regulation and function play an important role in the development and progression of glioblastoma; understanding the alterations of certain miRNAs involved in both differentiation and neural and glial maturation could help us to better understand the malignant characteristics of glioblastoma.

Overexpression of miR-124 Protects Against Neurological Dysfunction Induced by Neonatal Hypoxic-Ischemic Brain Injury

Neonatal hypoxic-ischemic encephalopathy (HIE) is a major cause of lifelong disabilities worldwide, without effective therapies and clear regulatory mechanisms. MicroRNAs (miRNAs) act as a significant regulator in neuroregeneration and neuronal apoptosis, thus holding great potential as therapeutic targets in HIE. In this study, we established the hypoxia-ischemia (HI) model in vivo and oxygen-glucose deprivation (OGD) model in vitro. Zea-longa score and magnetic resonance imaging were applied to verify HI-induced neuronal dysfunction and brain infarction. Subsequently, a miRNA microarray analysis was employed to profile miRNA transcriptomes. Down-regulated miR-124 was found 24 h after HIE, which corresponded to the change in PC12, SHSY5Y, and neurons after OGD. To determine the function of miR-124, mimics and lentivirus-mediated overexpression were used to regulate miR-124 in vivo and in vitro, respectively. Our results showed that miR-124 overexpression obviously promoted cell survival and suppressed neuronal apoptosis. Further, the memory and neurological function of rats was also obviously improved at 1 and 2 months after HI, indicated by the neurological severity score, Y-maze test, open field test, and rotating rod test. Our findings showed that overexpression of miR-124 can be a promising new strategy for HIE therapy in future clinical practice.

The Potential Role of MicroRNA-124 in Cerebral Ischemia Injury

Cerebral ischemia injury, the leading cause of morbidity and mortality worldwide, initiates sequential molecular and cellular pathologies that underlie ischemic encephalopathy (IE), such as ischemic stroke, Alzheimer disease (AD), Parkinson's disease (PD), epilepsy, etc. Targeted therapeutic treatments are urgently needed to tackle the pathological processes implicated in these neurological diseases. Recently, accumulating studies demonstrate that microRNA-124 (miR-124), the most abundant miRNA in brain tissue, is aberrant in peripheral blood and brain vascular endothelial cells following cerebral ischemia. Importantly, miR-124 regulates a variety of pathophysiological processes that are involved in the pathogenesis of age-related IE. However, the role of miR-124 has not been systematically illustrated. Paradoxically, miR-124 exerts beneficial effects in the age-related IE via regulating autophagy, neuroinflammation, oxidative stress, neuronal excitability, neurodifferentiation, Aβ deposition, and hyperphosphorylation of tau protein, while it may play a dual role via regulating apoptosis and exerts detrimental effects on synaptic plasticity and axonal growth. In the present review, we thus focus on the paradoxical roles of miR-124 in age-related IE, as well as the underlying mechanisms. A great understanding of the effects of miR-124 on the hypoxic-ischemic brain will open new avenues for therapeutic approaches to protect against cerebral ischemia injury.

MicroRNA-Based Separation of Cortico-Fugal Projection Neuron-Like Cells Derived From Embryonic Stem Cells

The purification of pluripotent stem cell-derived cortico-fugal projection neurons (PSC-CFuPNs) is useful for disease modeling and cell therapies related to the dysfunction of cortical motor neurons, such as amyotrophic lateral sclerosis (ALS) or stroke. However, no CFuPN-specific surface markers for the purification are known. Recently, microRNAs (miRNAs) have been reported as alternatives to surface markers. Here, we investigated this possibility by applying the miRNA switch, an mRNA technology, to enrich PSC-CFuPNs. An array study of miRNAs in mouse fetal brain tissue revealed that CFuPNs highly express miRNA-124-3p at E14.5 and E16.5. In response, we designed a miRNA switched that responds to miRNA-124-3p and applied it to mouse embryonic stem cell (ESC)-derived cortical neurons. Flow cytometry and quantitative polymerase chain reaction (qPCR) analyses showed the miRNA-124-3p switch enriched CFuPN-like cells from this population. Immunocytechemical analysis confirmed vGlut1/Emx1/Bcl11b triple positive CFuPN-like cells were increased from 6.5 to 42%. Thus, our miRNA-124-3p switch can uniquely enrich live CFuPN-like cells from mouse ESC-derived cortical neurons.

Challenges in microRNAs' targetome prediction and validation

MicroRNAs (miRNAs) are small RNA molecules with important roles in post-transcriptional regulation of gene expression. In recent years, the predicted number of miRNAs has skyrocketed, largely as a consequence of high-throughput sequencing technologies becoming ubiquitous. This dramatic increase in miRNA candidates poses multiple challenges in terms of data deposition, curation, and validation. Although multiple databases containing miRNA annotations and targets have been developed, ensuring data quality by validating miRNA-target interactions requires the efforts of the research community. In order to generate databases containing biologically active miRNAs, it is imperative to overcome a multitude of hurdles, including restricted miRNA expression patterns, distinct miRNA biogenesis machineries, and divergent miRNA-mRNA interaction dynamics. In the present review, we discuss recent advances and limitations in miRNA prediction, identification, and validation. Lastly, we focus on the most enriched neuronal miRNA, miR-124, and its gene regulatory network in human neurons, which has been revealed using a combined computational and experimental approach.

miR-124 regulates cerebromicrovascular function in APP/PS1 transgenic mice via C1ql3

Many neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease, are associated with microvascular dysfunction, but the cellular and molecular mechanisms are poorly understood. Recently, microRNAs (miRNAs) have been suggested to be involved in the microvascular dysfunction and subsequent memory impairment. MicroRNA-124 (miR-124) is one of the most abundant miRNAs in the brain that is dysregulated in the hippocampus of AD animals. To explore the role of miR-124 in AD pathology, we employed the APP/PS1 transgenic mice and found downregulation of miR-124 and upregulation of complement C1q-like protein 3 (C1ql3) in the hippocampus and cerebral cortex. Downregulation of miR-124 expression resulted in Aβ deposition and a variety of cerebromicrovascular impairments, including the decline in microvascular density, reduced angiogenesis, accompanied by C1ql3 alteration. Treatment with lentivirus-mediated overexpression of miR-124 or the C1q inhibitor C1INH rescued breakdown of blood-brain barrier, promoted angiogenesis and reduced Aβ deposition, and finally alleviated learning and memory deficit in APP/PS1 mice. Moreover, we found that C1ql3, a component of the classical complement, might be a potential target of miR-124. These results suggested that miR-124 was involved in the angiogenesis and vascular integrity in the hippocampus and the cerebral cortex of the AD mice by regulating the classical complement C1ql3.

DSCR1-mediated TET1 splicing regulates miR-124 expression to control adult hippocampal neurogenesis

Whether epigenetic factors such as DNA methylation and microRNAs interact to control adult hippocampal neurogenesis is not fully understood. Here, we show that Down syndrome critical region 1 (DSCR1) protein plays a key role in adult hippocampal neurogenesis by modulating two epigenetic factors: TET1 and miR-124. We find that DSCR1 mutant mice have impaired adult hippocampal neurogenesis. DSCR1 binds to TET1 introns to regulate splicing of TET1, thereby modulating TET1 level. Furthermore, TET1 controls the demethylation of the miRNA-124 promoter to modulate miR-124 expression. Correcting the level of TET1 in DSCR1 knockout mice is sufficient to prevent defective adult neurogenesis. Importantly, restoring DSCR1 level in a Down syndrome mouse model effectively rescued adult neurogenesis and learning and memory deficits. Our study reveals that DSCR1 plays a critical upstream role in epigenetic regulation of adult neurogenesis and provides insights into potential therapeutic strategy for treating cognitive defects in Down syndrome.

Exosomal microRNA and stroke: A review

Blood vessels rupture or occlusion in brain results in stroke. Stroke is the major reason for mortality and dysfunction worldwide. Despite several attempts, there are no any approved therapeutic approaches for stroke subjects. The most neuroprotective agents showed the positive effects in preclinical reports, while there are no significant therapeutic impacts in the clinical trials. MicroRNAs (miRNAs) are small noncoding RNAs which involved in the modulation of a variety of cellular and molecular pathways. Given that deregulation of these molecules is related to initiation and progression of stroke. Exosomes are nano-carriers which are able to transfer different cargos such as miRNAs to recipient cells. Increasing evidence revealed that exosomal miRNAs are one of very important factors which are involved in the pathogenesis of stroke. Hence, more understanding about the role of exosomal miRNAs in stroke pathogenesis could contribute in discovering and developing new therapeutic approaches. Moreover, it has been proved the exosomal miRNAs could be used as noninvasive biomarkers in diagnosis and monitoring response to therapy in subjects with stroke. Herein for first time, we summarized different exosomal miRNAs involved in pathogenesis of stroke.

Rabies virus glycoprotein (RVG29)-linked microRNA-124-loaded polymeric nanoparticles inhibit neuroinflammation in a Parkinson's disease model

In the present study, we have prepared microRNA(miR)-124-loaded Rabies virus glycoprotein (RVG)29 surface-conjugated polymeric nanoparticles (NPs) to improve neuroinflammation in Parkinson's disease (PD). We hypothesize that an increase in the intracellular concentration of miR-124 will result in a better prognosis for Parkinson's disease. Minimal toxicity for the RVG29 NPs was observed at concentrations <100 µg/mL, while the cell viability of cells treated with blank NPs at concentrations of 200 µg/mL markedly decreased, indicating the safety of the carrier system. Results showed that mRNA levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-α), and interleukin (IL)-6, significantly increased upon lipopolysaccharide (LPS) administration. However, the mRNA levels of these cytokines reflected those of the miR-NPs-treated control group, indicating the influence of miR-124 exposure. After transfection with miR-NPs, levels of pro-inflammatory cytokines and neuroprotective molecules were reduced and increased, respectively. Administration of LPS significantly increased the levels of mitogen activated protein kinase kinase kinase (MEKK)3 and P-P65 levels, while transfection with miR-NPs significantly reduced the expression of both MEKK3 and P-P65, reflecting that of the control. This research has revealed that miR-124 could target both the MEKK3 and nuclear factor kappa light chain enhancer of activated B cell (NF-Kb) pathways, while also reducing inflammatory cytokine levels. In addition, a 3-fold decrease in apoptosis was observed in miR-NP transfected cells. The exogenous delivery of miR-NPs significantly downregulated MEKK3 expression in animal studies, as outlined by immunohistochemical staining (IHC). Overall, miR-NPs have the potential to inhibit pro-inflammatory signaling and enhance neuroprotection in PD.

Comparative analysis of microRNA expression profiles of adult Schistosoma japonicum isolated from water buffalo and yellow cattle

BACKGROUND

Yellow cattle and water buffalo are important natural reservoir hosts and the main transmission sources of Schistosoma japonicum in endemic areas of China. The worms from the two hosts have marked differences in general worm morphology and ultrastructure, gene transcription and protein expression profiles.

RESULTS

To investigate microRNAs (miRNAs) involved in the regulation of schistosome development and survival, we compared miRNA expression profiles of adult schistosomes derived from yellow cattle and water buffalo by using high-throughput sequencing with Illumina Hiseq Xten. Schistosoma japonicum from water buffalo and yellow cattle yielded 63.78 million and 63.21 million reads, respectively, of which nearly 50% and 49% could be mapped to selected miRNAs in miRbase. A total of 206 miRNAs were identified, namely 79 previously annotated miRNAs of S. japonicum and 127 miRNAs that matched with the S. japonicum genome and were highly similar to the annotated miRNAs from other organisms. Among the 79 miRNAs, five (sja-miR-124-3p, sja-miR-219-5p, sja-miR-2e-3p, sja-miR-7-3p and sja-miR-3490) were significantly upregulated in the schistosomes from water buffalo compared with those from yellow cattle. A total of 268 potential target genes were predicted for these five differentially expressed miRNAs. Eleven differentially expressed targets were confirmed by qRT-PCR among 15 tested targets, one of which was further validated through dual-luciferase reporter assay. Among the 127 'possible' S. japonicum miRNAs, ten were significantly differentially expressed in the schistosomes from these two hosts.

CONCLUSIONS

These results highlight the important roles of miRNAs in regulating the development and survival of schistosomes in water buffalo and yellow cattle and facilitate understanding of the miRNA regulatory mechanisms in schistosomes derived from different susceptible hosts.

Emerging Roles of miRNAs in Brain Development and Perinatal Brain Injury

In human beings the immature brain is highly plastic and depending on the stage of gestation is particularly vulnerable to a range of insults that if sufficiently severe, can result in long-term motor, cognitive and behavioral impairment. With improved neonatal care, the incidence of major motor deficits such as cerebral palsy has declined with prematurity. Unfortunately, however, milder forms of injury characterized by diffuse non-cystic white matter lesions within the periventricular region and surrounding white matter, involving loss of oligodendrocyte progenitors and subsequent axonal hypomyelination as the brain matures have not. Existing therapeutic options for treatment of preterm infants have proved inadequate, partly owing to an incomplete understanding of underlying post-injury cellular and molecular changes that lead to poor neurodevelopmental outcomes. This has reinforced the need to improve our understanding of brain plasticity, explore novel solutions for the development of protective strategies, and identify biomarkers. Compelling evidence exists supporting the involvement of microRNAs (miRNAs), a class of small non-coding RNAs, as important post-transcriptional regulators of gene expression with functions including cell fate specification and plasticity of synaptic connections. Importantly, miRNAs are differentially expressed following brain injury, and can be packaged within exosomes/extracellular vesicles, which play a pivotal role in assuring their intercellular communication and passage across the blood-brain barrier. Indeed, an increasing number of investigations have examined the roles of specific miRNAs following injury and regeneration and it is apparent that this field of research could potentially identify protective therapeutic strategies to ameliorate perinatal brain injury. In this review, we discuss the most recent findings of some important miRNAs in relation to the development of the brain, their dysregulation, functions and regulatory roles following brain injury, and discuss how these can be targeted either as biomarkers of injury or neuroprotective agents.