microRNA-132 regulates dendritic growth and arborization of newborn neurons in the adult hippocampus

A novel copy number variant in the murine Cdh23 gene gives rise to profound deafness and vestibular dysfunction

Hearing loss is the most common congenital sensory deficit worldwide and exhibits high genetic heterogeneity, making molecular diagnoses elusive for most individuals. Detecting novel mutations that contribute to hearing loss is crucial to providing accurate personalized diagnoses, tailored interventions, and improving prognosis. Copy number variants (CNVs) are structural mutations that are understudied, potential contributors to hearing loss. Here, we present the Abnormal Wobbly Gait (AWG) mouse, the first documented mutant exhibiting waltzer-like locomotor dysfunction, hyperactivity, circling behaviour, and profound deafness caused by a spontaneous CNV deletion in cadherin 23 (Cdh23). We were unable to identify the causative mutation through a conventional whole-genome sequencing (WGS) and variant detection pipeline, but instead found a linked variant in hexokinase 1 (Hk1) that was insufficient to recapitulate the AWG phenotype when introduced into C57BL/6J mice using CRISPR-Cas9. Investigating nearby deafness-associated genes revealed a pronounced downregulation of Cdh23 mRNA and a complete absence of full-length CDH23 protein, which is critical for the development and maintenance of inner ear hair cells, in whole head extracts from AWG neonates. Manual inspection of WGS read depth plots of the Cdh23 locus revealed a putative 10.4 kb genomic deletion of exons 11 and 12 that was validated by PCR and Sanger sequencing. This study underscores the imperative to refine variant detection strategies to permit identification of pathogenic CNVs easily missed by conventional variant calling to enhance diagnostic precision and ultimately improve clinical outcomes for individuals with genetically heterogenous disorders such as hearing loss.

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.

miR-153 promotes neural differentiation by activating the cell adhesion/Ca2+ signaling pathway and targeting ion channel activity in HT-22 cells by bioinformatic analysis

MicroRNAs have been studied extensively in neurodegenerative diseases. In a previous study, miR-153 promoted neural differentiation and projection formation in mouse hippocampal HT-22 cells. However, the pathways and molecular mechanism underlying miR-153-induced neural differentiation remain unclear. To explore the molecular mechanism of miR-153 on neural differentiation, we performed RNA sequencing on miR-153-overexpressed HT-22 cells. Based on RNA sequencing, differentially expressed genes (DEGs) and pathways in miR-153-overexpressed cells were identified. The Database for Annotation, Visualization and Integrated Discovery and Gene Set Enrichment Analysis were used to perform functional annotation and enrichment analysis of DEGs. Targetscan predicted the targets of miR-153. The Search Tool for the Retrieval of Interacting Genes and Cytoscape, were used to construct protein-protein interaction networks and identify hub genes. Q-PCR was used to detect mRNA expression of the identified genes. The expression profiles of the identified genes were compared between embryonic days 9.5 (E9.5) and E11.5 in the embryotic mouse brain of the GDS3442 dataset. Cell Counting Kit-8 assay was used to determine cell proliferation and cellular susceptibility to amyloid β-protein (Aβ) toxicity in miR-153-overexpressed cells. The results indicated that miR-153 increased cell adhesion/Ca2+ (Cdh5, Nrcam, and P2rx4) and Bdnf/Ntrk2 neurotrophic signaling pathway, and decreased ion channel activity (Kcnc3, Kcna4, Clcn5, and Scn5a). The changes in the expression of the identified genes in miR-153-overexpressed cells were consistent with the expression profile of GDS3442 during neural differentiation. In addition, miR-153 overexpression decreased cellular susceptibility to Aβ toxicity in HT-22 cells. In conclusion, miR-153 overexpression may promote neural differentiation by inducing cell adhesion and the Bdnf/Ntrk2 pathway, and regulating electrophysiological maturity by targeting ion channels. MiR-153 may play an important role in neural differentiation; the findings provide a useful therapeutic direction for neurodegenerative diseases.

AFM Imaging Reveals MicroRNA-132 to be a Positive Regulator of Synaptic Functions

The modification of synaptic and neural connections in adults, including the formation and removal of synapses, depends on activity-dependent synaptic and structural plasticity. MicroRNAs (miRNAs) play crucial roles in regulating these changes by targeting specific genes and regulating their expression. The fact that somatic and dendritic activity in neurons often occurs asynchronously highlights the need for spatial and dynamic regulation of protein synthesis in specific milieu and cellular loci. MicroRNAs, which can show distinct patterns of enrichment, help to establish the localized distribution of plasticity-related proteins. The recent study using atomic force microscopy (AFM)-based nanoscale imaging reveals that the abundance of miRNA(miR)-134 is inversely correlated with the functional activity of dendritic spine structures. However, the miRNAs that are selectively upregulated in potentiated synapses, and which can thereby support prospective changes in synaptic efficacy, remain largely unknown. Using AFM force imaging, significant increases in miR-132 in the dendritic regions abutting functionally-active spines is discovered. This study provides evidence for miR-132 as a novel positive miRNA regulator residing in dendritic shafts, and also suggests that activity-dependent miRNAs localized in distinct sub-compartments of neurons play bi-directional roles in controlling synaptic transmission and synaptic plasticity.

Noncoding RNAs: Emerging regulators of behavioral complexity

The mammalian genome encodes thousands of non-coding RNAs (ncRNAs), ranging in size from about 20 nucleotides (microRNAs or miRNAs) to kilobases (long non-coding RNAs or lncRNAs). ncRNAs contribute to a layer of gene regulation that could explain the evolution of massive phenotypic complexity even as the number of protein-coding genes remains unaltered. We propose that low conservation, poor expression, and highly restricted spatiotemporal expression patterns-conventionally considered ncRNAs may affect behavior through direct, rapid, and often sustained regulation of gene expression at the transcriptional, post-transcriptional, or translational levels. Besides these direct roles, their effect during neurodevelopment may manifest as behavioral changes later in the organism's life, especially when exposed to environmental cues like stress and seasonal changes. The lncRNAs affect behavior through diverse mechanisms like sponging of miRNAs, recruitment of chromatin modifiers, and regulation of alternative splicing. We highlight the need for synthesis between rigorously designed behavioral paradigms in model organisms and the wide diversity of behaviors documented by ethologists through field studies on organisms exquisitely adapted to their environmental niche. Comparative genomics and the latest advancements in transcriptomics provide an unprecedented scope for merging field and lab studies on model and non-model organisms to shed light on the role of ncRNAs in driving the behavioral responses of individuals and groups. We touch upon the technical challenges and contentious issues that must be resolved to fully understand the role of ncRNAs in regulating complex behavioral traits. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.

Senktide blocks aberrant RTN3 interactome to retard memory decline and tau pathology in social isolated Alzheimer's disease mice

Sporadic or late-onset Alzheimer's disease (LOAD) accounts for more than 95% of Alzheimer's disease (AD) cases without any family history. Although genome-wide association studies have identified associated risk genes and loci for LOAD, numerous studies suggest that many adverse environmental factors, such as social isolation, are associated with an increased risk of dementia. However, the underlying mechanisms of social isolation in AD progression remain elusive. In the current study, we found that 7 days of social isolation could trigger pattern separation impairments and presynaptic abnormalities of the mossy fibre-CA3 circuit in AD mice. We also revealed that social isolation disrupted histone acetylation and resulted in the downregulation of 2 dentate gyrus (DG)-enriched miRNAs, which simultaneously target reticulon 3 (RTN3), an endoplasmic reticulum protein that aggregates in presynaptic regions to disturb the formation of functional mossy fibre boutons (MFBs) by recruiting multiple mitochondrial and vesicle-related proteins. Interestingly, the aggregation of RTN3 also recruits the PP2A B subunits to suppress PP2A activity and induce tau hyperphosphorylation, which, in turn, further elevates RTN3 and forms a vicious cycle. Finally, using an artificial intelligence-assisted molecular docking approach, we determined that senktide, a selective agonist of neurokinin3 receptors (NK3R), could reduce the binding of RTN3 with its partners. Moreover, application of senktide in vivo effectively restored DG circuit disorders in socially isolated AD mice. Taken together, our findings not only demonstrate the epigenetic regulatory mechanism underlying mossy fibre synaptic disorders orchestrated by social isolation and tau pathology but also reveal a novel potential therapeutic strategy for AD.

Mechanisms of microRNA-132 in central neurodegenerative diseases: A comprehensive review

MicroRNA-132 (miR-132) is a highly conserved molecule that plays a crucial regulatory role in central nervous system (CNS) disorders. The expression levels of miR-132 exhibit variability in various neurological disorders and have been closely linked to disease onset and progression. The expression level of miR-132 in the CNS is regulated by a diverse range of stimuli and signaling pathways, including neuronal migration and integration, dendritic outgrowth, and complexity, synaptogenesis, synaptic plasticity, as well as inflammation and apoptosis activation. The aberrant expression of miR-132 in various central neurodegenerative diseases has garnered widespread attention. Clinical studies have revealed altered miR-132 expression levels in both chronic and acute CNS diseases, positioning miR-132 as a potential biomarker or therapeutic target. An in-depth exploration of miR-132 holds the promise of enhancing our understanding of the mechanisms underlying CNS diseases, thereby offering novel insights and strategies for disease diagnosis and treatment. It is anticipated that this review will assist researchers in recognizing the potential value of miR-132 and in generating innovative ideas for clinical trials related to CNS degenerative diseases.

Small RNA Profiles of Brain Tissue-Derived Extracellular Vesicles in Alzheimer's Disease

Background

Extracellular vesicles (EVs) and non-coding RNAs (ncRNAs) are emerging contributors to Alzheimer's disease (AD) pathophysiology. Differential abundance of ncRNAs carried by EVs may provide valuable insights into underlying disease mechanisms. Brain tissue-derived EVs (bdEVs) are particularly relevant, as they may offer valuable insights about the tissue of origin. However, there is limited research on diverse ncRNA species in bdEVs in AD.

Objective

This study explored whether the non-coding RNA composition of EVs isolated from post-mortem brain tissue is related to AD pathogenesis.

Methods

bdEVs from age-matched late-stage AD patients (n = 23) and controls (n = 10) that had been separated and characterized in our previous study were used for RNA extraction, small RNA sequencing, and qPCR verification.

Results

Significant differences of non-coding RNAs between AD and controls were found, especially for miRNAs and tRNAs. AD pathology-related miRNA and tRNA differences of bdEVs partially matched expression differences in source brain tissues. AD pathology had a more prominent association than biological sex with bdEV miRNA and tRNA components in late-stage AD brains.

Conclusions

Our study provides further evidence that EV non-coding RNAs from human brain tissue, including but not limited to miRNAs, may be altered and contribute to AD pathogenesis.

Salvianolic acid A improves nerve regeneration and repairs nerve defects in rats with brain injury by downregulating miR-212-3p-mediated SOX7

This study was to probe the protective effects and mechanisms of salvianolic acid A (SAA) on cerebral ischemia-reperfusion injury (CIRI). The middle cerebral artery occlusion model (MCAO) was established in rats. Rats' behavior, neurological deficits, brain injury, inflammation, and apoptosis in the brain tissue were evaluated. The inflammatory response and apoptosis of PC12 cells induced by oxygen glucose deprivation/reperfusion (OGD/R) were detected. SAA-mediated changes in miR-212-3p, SOX7, and Wnt/β-catenin pathway were determined, and the targeting relationship between miR-212-3p and SOX7 was clarified. SAA alleviated the neurological deficits and brain injury of MCAO rats and inhibited the inflammatory response and apoptosis of OGD/R-conditioned PC-12 cells. SAA upregulated miR-212-3p, Wnt3a, and β-catenin, whereas inhibited SOX7 levels. Silencing miR-212-3p counteracted the protective effect of SAA in the context of CIRI. SOX7 was a target protein of miR-212-3p. Silencing SOX7 based on SAA and miR-212-3p knockdown suppressed OGD/R-induced inflammation and apoptosis and increased Wnt3a and β-catenin levels in PC12 cells. SAA can improve the brain and nervous system injury caused by cerebral ischemia-reperfusion by upregulating miR-212-3p, thereby inhibiting SOX7 and activating the Wnt/βcatenin signaling pathway.

Small molecule regulators of microRNAs identified by high-throughput screen coupled with high-throughput sequencing

MicroRNAs (miRNAs) regulate fundamental biological processes by silencing mRNA targets and are dysregulated in many diseases. Therefore, miRNA replacement or inhibition can be harnessed as potential therapeutics. However, existing strategies for miRNA modulation using oligonucleotides and gene therapies are challenging, especially for neurological diseases, and none have yet gained clinical approval. We explore a different approach by screening a biodiverse library of small molecule compounds for their ability to modulate hundreds of miRNAs in human induced pluripotent stem cell-derived neurons. We demonstrate the utility of the screen by identifying cardiac glycosides as potent inducers of miR-132, a key neuroprotective miRNA downregulated in Alzheimer's disease and other tauopathies. Coordinately, cardiac glycosides downregulate known miR-132 targets, including Tau, and protect rodent and human neurons against various toxic insults. More generally, our dataset of 1370 drug-like compounds and their effects on the miRNome provides a valuable resource for further miRNA-based drug discovery.

Role of Long Non-coding RNA in Nerve Regeneration

Nerve injury can be caused by a variety of factors. It often takes a long time to repair a nerve injury and severe nerve injury is even difficult to heal. Therefore, increasing attention has focused on nerve injury and repair. Long non-coding RNA (lncRNA) is a newly discovered non-coding RNA with a wide range of biological activities. Numerous studies have shown that a variety of lncRNAs undergo changes in expression after nerve injury, indicating that lncRNAs may be involved in various biological processes of nerve repair and regeneration. Herein, we summarize the biological roles of lncRNAs in neurons, glial cells and other cells during nerve injury and regeneration, which will help lncRNAs to be better applied in nerve injury and regeneration in the future.

circ_0000018 downregulation peripherally ameliorates neuroprotection against acute ischemic stroke through the miR‑871/BCL2L11 axis

Acute ischemic stroke (AIS) is a common acute cerebrovascular disease. Circular RNAs (circRNAs) have been demonstrated to have critical functions in a wide range of physiological processes and disorders in humans. However, their precise function in ischemic stroke (IS) remains largely unknown. The present study explored the function and potential mechanisms of circ_0000018 in AIS in vivo and in vitro. The cerebral ischemia/reperfusion injury model was established in vivo and in vitro using the oxygen‑glucose deprivation (OGD/R) and transient middle cerebral artery occlusion (tMCAO) methods. Subsequently, the impact of circ_0000018 on cerebral ischemia/reperfusion injury was assessed using various techniques, including TTC staining, quantitative PCR, western blotting, cell counting kit‑8 assay, Annexin V‑FITC Apoptosis Detection Kit, luciferase reporter gene assays, and others. The levels of circ_0000018 were markedly increased in the OGD/R‑treated neuronal cells and in a mouse model of tMCAO. The blocking of microRNA (miR)‑871 by circ_0000018 promoted Bcl‑2‑like protein 11 (BCL2L11) expression to increase neuronal cell damage. Furthermore, circ_0000018 knockdown significantly improved neuronal cell viability and attenuated OGD/R‑treated neuronal cell death. Meanwhile, circ_0000018 knockdown improved brain infarct volume and neuronal apoptosis in tMCAO mice. The present study found that circ_0000018 knockdown relieved cerebral ischemia‑reperfusion injury progression in vitro and in vivo. Mechanistically, circ_0000018 regulated the levels of BCL2L11 by sponging miR‑871.

Investigating microRNAs as biomarkers in disorders of consciousness: a longitudinal multicenter study

MicroRNAs (miRNAs) are involved in gene regulation and may affect secondary brain injury and recovery in patients with disorders of consciousness (DoC). This study investigated the role of five miRNAs (150-5p, 132-3p, 23b-3p, 451a, and 16-5p) in prolonged DoC. miRNA levels were assessed in serum samples from 30 patients with unresponsive wakefulness syndrome or minimally conscious state due to traumatic or hypoxic-ischemic brain injury (TBI, HIBI) at baseline (1-3 months) and 6 months post-injury. Patients' diagnoses were determined using the Coma Recovery Scale revised, and functional outcomes were evaluated 6 months after injury with the Glasgow Outcome Scale Extended (GOSE) and the Functional Independence Measure (FIM). Compared to healthy controls, patients with TBI had lower levels of miRNAs 150-5p, 132-3p, and 23b-3p at baseline, while patients with HIBI had lower levels of miRNA 150-5p at baseline and 6 months post-injury and a reduction of miRNA 451a at baseline. Higher levels of miRNAs 132-3p and 23b-3p were associated with better outcomes in TBI patients as indicated by GOSE and FIM scores. This study highlights distinct miRNA dysregulated patterns in patients with prolonged DoC, dependent on etiology and post-injury time, and suggests that miRNAs 132-3p and 23b-3p may serve as prognostic biomarkers.

The role of microRNAs in neurobiology and pathophysiology of the hippocampus

MicroRNAs (miRNAs) are short non-coding and well-conserved RNAs that are linked to many aspects of development and disorders. MicroRNAs control the expression of genes related to different biological processes and play a prominent role in the harmonious expression of many genes. During neural development of the central nervous system, miRNAs are regulated in time and space. In the mature brain, the dynamic expression of miRNAs continues, highlighting their functional importance in neurons. The hippocampus, as one of the crucial brain structures, is a key component of major functional connections in brain. Gene expression abnormalities in the hippocampus lead to disturbance in neurogenesis, neural maturation and synaptic formation. These disturbances are at the root of several neurological disorders and behavioral deficits, including Alzheimer's disease, epilepsy and schizophrenia. There is strong evidence that abnormalities in miRNAs are contributed in neurodegenerative mechanisms in the hippocampus through imbalanced activity of ion channels, neuronal excitability, synaptic plasticity and neuronal apoptosis. Some miRNAs affect oxidative stress, inflammation, neural differentiation, migration and neurogenesis in the hippocampus. Furthermore, major signaling cascades in neurodegeneration, such as NF-Kβ signaling, PI3/Akt signaling and Notch pathway, are closely modulated by miRNAs. These observations, suggest that microRNAs are significant regulators in the complicated network of gene regulation in the hippocampus. In the current review, we focus on the miRNA functional role in the progression of normal development and neurogenesis of the hippocampus. We also consider how miRNAs in the hippocampus are crucial for gene expression mechanisms in pathophysiological pathways.

Stabilizing the neural barrier - A novel approach in pain therapy

Chronic and neuropathic pain are a widespread burden. Incomplete understanding of underlying pathomechanisms is one crucial factor for insufficient treatment. Recently, impairment of the blood nerve barrier (BNB) has emerged as one key aspect of pain initiation and maintenance. In this narrative review, we discuss several mechanisms and putative targets for novel treatment strategies. Cells such as pericytes, local mediators like netrin-1 and specialized proresolving mediators (SPMs), will be covered as well as circulating factors including the hormones cortisol and oestrogen and microRNAs. They are crucial in either the BNB or similar barriers and associated with pain. While clinical studies are still scarce, these findings might provide valuable insight into mechanisms and nurture development of therapeutic approaches.

Endocrine-Disrupting Chemicals and Hippocampal Development: The Role of Estrogen and Androgen Signaling

Hormones are important regulators of key processes during fetal brain development. Thus, the developing brain is vulnerable to the action of chemicals that can interfere with endocrine signals. Epidemiological studies have pointed toward sexually dimorphic associations between neurodevelopmental outcomes, such as cognitive abilities, in children and prenatal exposure to endocrine-disrupting chemicals (EDCs). This points toward disruption of sex steroid signaling in the development of neural structures underlying cognitive functions, such as the hippocampus, an essential mediator of learning and memory processes. Indeed, during development, the hippocampus is subjected to the organizational effects of estrogens and androgens, which influence hippocampal cell proliferation, differentiation, dendritic growth, and synaptogenesis in the hippocampal fields of Cornu Ammonis and the dentate gyrus. These early organizational effects correlate with a sexual dimorphism in spatial cognition and are subject to exogenous chemical perturbations. This review summarizes the current knowledge about the organizational effects of estrogens and androgens on the developing hippocampus and the evidence for hippocampal-dependent learning and memory perturbations induced by developmental exposure to EDCs. We conclude that, while it is clear that sex hormone signaling plays a significant role during hippocampal development, a complete picture at the molecular and cellular levels would be needed to establish causative links between the endocrine modes of action exerted by EDCs and the adverse outcomes these chemicals can induce at the organism level.

microRNA-132 regulates gene expression programs involved in microglial homeostasis

microRNA-132 (miR-132), a known neuronal regulator, is one of the most robustly downregulated microRNAs (miRNAs) in the brain of Alzheimer's disease (AD) patients. Increasing miR-132 in AD mouse brain ameliorates amyloid and Tau pathologies, and also restores adult hippocampal neurogenesis and memory deficits. However, the functional pleiotropy of miRNAs requires in-depth analysis of the effects of miR-132 supplementation before it can be moved forward for AD therapy. We employ here miR-132 loss- and gain-of-function approaches using single-cell transcriptomics, proteomics, and in silico AGO-CLIP datasets to identify molecular pathways targeted by miR-132 in mouse hippocampus. We find that miR-132 modulation significantly affects the transition of microglia from a disease-associated to a homeostatic cell state. We confirm the regulatory role of miR-132 in shifting microglial cell states using human microglial cultures derived from induced pluripotent stem cells.

miRNA-132/212 Deficiency Disrupts Selective Corticosterone Modulation of Dorsal vs. Ventral Hippocampal Metaplasticity

Cortisol is a potent human steroid hormone that plays key roles in the central nervous system, influencing processes such as brain neuronal synaptic plasticity and regulating the expression of emotional and behavioral responses. The relevance of cortisol stands out in the disease, as its dysregulation is associated with debilitating conditions such as Alzheimer's Disease, chronic stress, anxiety and depression. Among other brain regions, cortisol importantly influences the function of the hippocampus, a structure central for memory and emotional information processing. The mechanisms fine-tuning the different synaptic responses of the hippocampus to steroid hormone signaling remain, however, poorly understood. Using ex vivo electrophysiology and wild type (WT) and miR-132/miR-212 microRNAs knockout (miRNA-132/212-/-) mice, we examined the effects of corticosterone (the rodent's equivalent to cortisol in humans) on the synaptic properties of the dorsal and ventral hippocampus. In WT mice, corticosterone predominantly inhibited metaplasticity in the dorsal WT hippocampi, whereas it significantly dysregulated both synaptic transmission and metaplasticity at dorsal and ventral regions of miR-132/212-/- hippocampi. Western blotting further revealed significantly augmented levels of endogenous CREB and a significant CREB reduction in response to corticosterone only in miR-132/212-/- hippocampi. Sirt1 levels were also endogenously enhanced in the miR-132/212-/- hippocampi but unaltered by corticosterone, whereas the levels of phospo-MSK1 were only reduced by corticosterone in WT, not in miR-132/212-/- hippocampi. In behavioral studies using the elevated plus maze, miRNA-132/212-/- mice further showed reduced anxiety-like behavior. These observations propose miRNA-132/212 as potential region-selective regulators of the effects of steroid hormones on hippocampal functions, thus likely fine-tuning hippocampus-dependent memory and emotional processing.

Enriched Environment Induces Sex-Specific Changes in the Adult Neurogenesis, Cytokine and miRNA Expression in Rat Hippocampus

An enriched environment stimulates adult hippocampal plasticity, but the exact cellular and molecular mechanisms are complex, and thus a matter of debate. We studied the behavior and hippocampal neurogenesis in adult male and female Wistar rats that were housed in an enriched environment (EE) for two months. Both EE males and females performed better than control animals in a Barnes maze, meaning that EE enhances spatial memory. However, the expression levels of neurogenesis markers KI67, DCX, Nestin, and Syn1 increased only in EE females, while in EE males only KI67 and BDNF were higher than in the corresponding control. The number of DCX+ neurons on brain slices increased in the dentate gyrus of EE females only, i.e., the level of adult hippocampal neurogenesis was increased in female but not in male rats. The level of anti-inflammatory IL-10 and signaling pathway components was upregulated in EE females. Of 84 miRNAs tested, in the hippocampi of EE female rats we detected upregulation in the expression levels of 12 miRNAs related to neuronal differentiation and morphogenesis, while in EE males four miRNAs were upregulated and involved in the regulation of cell proliferation/differentiation, and one was downregulated and associated with the stimulation of proliferation. Taken altogether, our results point to sex-specific differences in adult hippocampal plasticity, IL-10 expression, and miRNA profiles induced by an enriched environment.

The gut-brain connection: Exploring the influence of the gut microbiota on neuroplasticity and neurodevelopmental disorders

Neuroplasticity refers to the ability of brain circuits to reorganize and change the properties of the network, resulting in alterations in brain function and behavior. It is traditionally believed that neuroplasticity is influenced by external stimuli, learning, and experience. Intriguingly, there is new evidence suggesting that endogenous signals from the body's periphery may play a role. The gut microbiota, a diverse community of microorganisms living in harmony with their host, may be able to influence plasticity through its modulation of the gut-brain axis. Interestingly, the maturation of the gut microbiota coincides with critical periods of neurodevelopment, during which neural circuits are highly plastic and potentially vulnerable. As such, dysbiosis (an imbalance in the gut microbiota composition) during early life may contribute to the disruption of normal developmental trajectories, leading to neurodevelopmental disorders. This review aims to examine the ways in which the gut microbiota can affect neuroplasticity. It will also discuss recent research linking gastrointestinal issues and bacterial dysbiosis to various neurodevelopmental disorders and their potential impact on neurological outcomes.

MicroRNA Profiling of Self-Renewing Human Neural Stem Cells Reveals Novel Sets of Differentially Expressed microRNAs During Neural Differentiation In Vitro

The involvement of microRNAs (miRNAs) in orchestrating self-renewal and differentiation of stem cells has been revealed in a number of recent studies. And while in human pluripotent stem cells, miRNAs have been directly linked to the core pluripotency network, including the cell cycle regulation and the maintenance of the self-renewing capacity, their role in the onset of differentiation in other contexts, such as determination of neural cell fate, remains poorly described. To bridge this gap, we used three model cell types to study miRNA expression patterns: human embryonic stem cells (hESCs), hESCs-derived self-renewing neural stem cells (NSCs), and differentiating NSCs. The comprehensive miRNA profiling presented here reveals novel sets of miRNAs differentially expressed during human neural cell fate determination in vitro. Furthermore, we report a miRNA expression profile of self-renewing human NSCs, which has been lacking to this date. Our data also indicates that miRNA clusters enriched in NSCs share the target-determining seed sequence with cell cycle regulatory miRNAs expressed in pluripotent hESCs. Lastly, our mechanistic experiments confirmed that cluster miR-17-92, one of the NSCs-enriched clusters, is directly transcriptionally regulated by transcription factor c-MYC.

Small Molecule Regulators of microRNAs Identified by High-Throughput Screen Coupled with High-Throughput Sequencing

MicroRNAs (miRNAs) regulate fundamental biological processes by silencing mRNA targets and are dysregulated in many diseases. Therefore, miRNA replacement or inhibition can be harnessed as potential therapeutics. However, existing strategies for miRNA modulation using oligonucleotides and gene therapies are challenging, especially for neurological diseases, and none have yet gained clinical approval. We explore a different approach by screening a biodiverse library of small molecule compounds for their ability to modulate hundreds of miRNAs in human induced pluripotent stem cell-derived neurons. We demonstrate the utility of the screen by identifying cardiac glycosides as potent inducers of miR-132, a key miRNA downregulated in Alzheimer's disease and other tauopathies. Coordinately, cardiac glycosides downregulate known miR-132 targets, including Tau, and protect rodent and human neurons against various toxic insults. More generally, our dataset of 1370 drug-like compounds and their effects on the miRNome provide a valuable resource for further miRNA-based drug discovery.

Electroconvulsive Stimulation in Rats Induces Alterations in the Hippocampal miRNome: Translational Implications for Depression

MicroRNAs (miRNAs) may contribute to the development of depression and its treatment. Here, we used the hypothesis-neutral approach of next-generation sequencing (NGS) to gain comprehensive understanding of the effects of a course of electroconvulsive stimulation (ECS), the animal model equivalent of electroconvulsive therapy (ECT), on rat hippocampal miRNAs. Significant differential expression (p < 0.001) of six hippocampal miRNAs was noted following NGS, after correcting for multiple comparisons. Three of these miRNAs were upregulated (miR-132, miR-212, miR-331) and three downregulated (miR-204, miR-483, miR-301a). qRT-PCR confirmed significant changes in four of the six miRNAs (miR-132, miR-212, miR-204, miR-483). miR-483 was also significantly reduced in frontal cortex, though no other significant alterations were noted in frontal cortex, cerebellum, or whole blood. Assessing the translatability of the results, miR-132 and miR-483 were significantly reduced in whole blood samples from medicated patients with depression (n = 50) compared to healthy controls (n = 45), though ECT had no impact on miRNA levels. Notably, pre-ECT miR-204 levels moderately positively correlated with depression severity at baseline and moderately negatively correlated with mood score reduction post-ECT. miRNAs were also examined in cerebrospinal fluid and serum from a separate cohort of patients (n = 8) treated with ECT; no significant changes were noted post-treatment. However, there was a large positive correlation between changes in miR-212 and mood score post-ECT in serum. Though replication studies using larger sample sizes are required, alterations in miRNA expression may be informative about the mechanism of action of ECS/ECT and in turn might give insight into the neurobiology of depression.

Discovery and Validation of Circulating microRNAs as Biomarkers for Epileptogenesis after Experimental Traumatic Brain Injury-The EPITARGET Cohort

Traumatic brain injury (TBI) causes 10-20% of structural epilepsies and 5% of all epilepsies. The lack of prognostic biomarkers for post-traumatic epilepsy (PTE) is a major obstacle to the development of anti-epileptogenic treatments. Previous studies revealed TBI-induced alterations in blood microRNA (miRNA) levels, and patients with epilepsy exhibit dysregulation of blood miRNAs. We hypothesized that acutely altered plasma miRNAs could serve as prognostic biomarkers for brain damage severity and the development of PTE. To investigate this, epileptogenesis was induced in adult male Sprague Dawley rats by lateral fluid-percussion-induced TBI. Epilepsy was defined as the occurrence of at least one unprovoked seizure during continuous 1-month video-electroencephalography monitoring in the sixth post-TBI month. Cortical pathology was analyzed by magnetic resonance imaging on day 2 (D2), D7, and D21, and by histology 6 months post-TBI. Small RNA sequencing was performed from tail-vein plasma samples on D2 and D9 after TBI (n = 16, 7 with and 9 without epilepsy) or sham operation (n = 4). The most promising miRNA biomarker candidates were validated by droplet digital polymerase chain reaction in a validation cohort of 115 rats (8 naïve, 17 sham, and 90 TBI rats [21 with epilepsy]). These included 7 brain-enriched plasma miRNAs (miR-434-3p, miR-9a-3p, miR-136-3p, miR-323-3p, miR-124-3p, miR-212-3p, and miR-132-3p) that were upregulated on D2 post-TBI (p < 0.001 for all compared with naïve rats). The acute post-TBI plasma miRNA profile did not predict the subsequent development of PTE or PTE severity. Plasma miRNA levels, however, predicted the cortical pathology severity on D2 (Spearman ρ = 0.345-0.582, p < 0.001), D9 (ρ = 0.287-0.522, p < 0.001-0.01), D21 (ρ = 0.269-0.581, p < 0.001-0.05) and at 6 months post-TBI (ρ = 0.230-0.433, p < 0.001-0.05). We found that the levels of 6 of 7 miRNAs also reflected mild brain injury caused by the craniotomy during sham operation (ROC AUC 0.76-0.96, p < 0.001-0.05). In conclusion, our findings revealed that increased levels of neuronally enriched miRNAs in the blood circulation after TBI reflect the extent of cortical injury in the brain but do not predict PTE development.

Regulation by noncoding RNAs of local translation, injury responses, and pain in the peripheral nervous system

Neuropathic pain is a chronic condition arising from damage to somatosensory pathways that results in pathological hypersensitivity. Persistent pain can be viewed as a consequence of maladaptive plasticity which, like most enduring forms of cellular plasticity, requires altered expression of specific gene programs. Control of gene expression at the level of protein synthesis is broadly utilized to directly modulate changes in activity and responsiveness in nociceptive pathways and provides an effective mechanism for compartmentalized regulation of the proteome in peripheral nerves through local translation. Levels of noncoding RNAs (ncRNAs) are commonly impacted by peripheral nerve injury leading to persistent pain. NcRNAs exert spatiotemporal regulation of local proteomes and affect signaling cascades supporting altered sensory responses that contribute to hyperalgesia. This review discusses ncRNAs found in the peripheral nervous system (PNS) that are dysregulated following nerve injury and the current understanding of their roles in pathophysiological pain-related responses including neuroimmune interactions, neuronal survival and axon regeneration, Schwann cell dedifferentiation and proliferation, intercellular communication, and the generation of ectopic action potentials in primary afferents. We review progress in the field beyond cataloging, with a focus on the relevant target transcripts and mechanisms underlying pain modulation by ncRNAs.

microRNA Biology on Brain Development and Neuroimaging Approach

Proper brain development requires the precise coordination and orchestration of various molecular and cellular processes and dysregulation of these processes can lead to neurological diseases. In the past decades, post-transcriptional regulation of gene expression has been shown to contribute to various aspects of brain development and function in the central nervous system. MicroRNAs (miRNAs), short non-coding RNAs, are emerging as crucial players in post-transcriptional gene regulation in a variety of tissues, such as the nervous system. In recent years, miRNAs have been implicated in multiple aspects of brain development, including neurogenesis, migration, axon and dendrite formation, and synaptogenesis. Moreover, altered expression and dysregulation of miRNAs have been linked to neurodevelopmental and psychiatric disorders. Magnetic resonance imaging (MRI) is a powerful imaging technology to obtain high-quality, detailed structural and functional information from the brains of human and animal models in a non-invasive manner. Because the spatial expression patterns of miRNAs in the brain, unlike those of DNA and RNA, remain largely unknown, a whole-brain imaging approach using MRI may be useful in revealing biological and pathological information about the brain affected by miRNAs. In this review, we highlight recent advancements in the research of miRNA-mediated modulation of neuronal processes that are important for brain development and their involvement in disease pathogenesis. Also, we overview each MRI technique, and its technological considerations, and discuss the applications of MRI techniques in miRNA research. This review aims to link miRNA biological study with MRI analytical technology and deepen our understanding of how miRNAs impact brain development and pathology of neurological diseases.

Silencing of miR-132-3p protects against neuronal injury following status epilepticus by inhibiting IL-1β-induced reactive astrocyte (A1) polarization

Mesial temporal lobe epilepsy (MTLE) is one of the most common refractory epilepsies and is usually accompanied by a range of brain pathological changes, such as neuronal injury and astrocytosis. Naïve astrocytes are readily converted to cytotoxic reactive astrocytes (A1) in response to inflammatory stimulation, suppressing the polarization of A1 protects against neuronal death in early central nervous system injury. Our previous study found that pro-inflammatory cytokines and miR-132-3p (hereinafter referred to as "miR-132") expression were upregulated, but how miR-132 affected reactive astrocyte polarization and neuronal damage during epilepsy is not fully understood. Here, we aimed to explore the effect and mechanism of miR-132 on A1 polarization. Our results confirmed that A1 markers were significantly elevated in the hippocampus of MTLE rats and IL-1β-treated primary astrocytes. In vivo, knockdown of miR-132 by lateral ventricular injection reduced A1 astrocytes, neuronal loss, mossy fiber sprouting, and remitted the severity of status epilepticus and the recurrence of spontaneous recurrent seizures. In vitro, the neuronal cell viability and axon length were reduced by additional treatment with A1 astrocyte conditioned media (ACM), and downregulation of astrocyte miR-132 rescued the inhibition of cell activity by A1 ACM, while the length of axons was further inhibited. The regulation of miR-132 on A1 astrocytes may be related to its target gene expression. Our results show that interfering with astrocyte polarization may be a breakthrough in the treatment of refractory epilepsy, which may extend to the research of other astrocyte polarization-mediated brain injuries.

Inhibition of Glycogen Synthase Kinase and the Neuroprotective Function of Conjugated ZnO-Osthol Nanoparticles in Alzheimer’s Disease

A critical factor in the cause and progression of Alzheimer’s disease (AD) is the growth of β-amyloid peptide (Aβ) in the brain. The mechanism of this effect is still unknown, although the effect of osthol on Aβ-induced inflammation is neuroprotective in AD and supplementation with zinc might prevent or delay the onset of dementia. In the current study, by inducing APP vector in human BE (2)-M17 cells, we established a cellular model of AD and investigated the protective effect of osthol (7-methoxy-8-3-methyl-2-butenyl-2H-1-benzopyran-2-one)-zinc oxide nanoparticles. The osthol-conjugated zinc oxide nanoparticles could significantly increase cell viability by inhibiting cell apoptosis. Osthol treatment has also prevented synaptic proteins such as postsynaptic density-95 (PSD-95), synaptophysin (SYP), and synapsin-1 from decreasing in APP-induced BE (2)-M17 cells. In addition, the expression of miR-132 was significantly upregulated by osthol by triggering the Wnt/β-catenin signaling pathway. We conclude from our observations that osthol is a potential drug for the treatment of a neurodegenerative disease, Alzheimer’s. The key reason was that by upregulating miR-132, osthol could inhibit APP expression to prevent AD from occurring.

Electroacupuncture Enhances Cognitive Deficits in a Rat Model of Rapid Eye Movement Sleep Deprivation via Targeting MiR-132

Deprivation of rapid eye movement sleep (REMSD) reduces the potential for learning and memory. The neuronal foundation of cognitive performance is synapse plasticity. MicroRNA-132 (MiR-132) is an important microRNA related to cognitive and synapse plasticity. Acupuncture is effective at improving cognitive impairment caused by sleep deprivation. Furthermore, its underlying principle is still unclear. Herein, whether electroacupuncture (EA) helps alleviate cognitive impairment in REMSD by targeting miR-132 was assessed. A rat model of REMSD was constructed using the developing multiplatform water environment technique, as well as EA therapy in Baihui (GV20) and Dazhui (GV14) was performed for 15 minutes, once daily for 7 days. Agomir or antagomir of MiR-132 was injected into the hippocampal CA1 areas to assess the EA mechanism in rats with REMSD. Then, the learning and memory abilities were detected by behavioral tests; synapse structure was assessed by transmission electron microscope (TCM); and dendrites branches and length were examined by Golgi staining. MiR-132-3p was assessed by real-time quantitative polymerase chain reaction (qRT-PCR). P250GAP, ras-related C3 botulinum toxin substrate 1 (Rac1), and cell division cycle 42 (Cdc42) expression levels in hippocampal tissues were evaluated by immunohistochemistry and Western blot. According to the research, EA therapy enhanced cognitive in REMSD rats, as evidenced by reduced escape latency; upregulated the performance of platform crossings and prolonged duration in the goal region; and improved spontaneous alternation. EA administration restored synaptic and dendritic structural damage in hippocampal neurons, enhanced miR-132 expression, and reduced p250GAP mRNA and protein levels. Additionally, EA boosted the protein level of Rac1 and Cdc42 associated with synaptic plasticity. MiR-132 agomir enhanced this effect, whereas miR-13 antagomir reversed this action. The current data demonstrate that EA at GV20 and GV14 attenuates cognitive impairment and modulates synaptic plasticity in hippocampal neurons via miR-132 in a sleep-deprived rat model.

Disrupting interaction between miR-132 and Mmp9 3'UTR improves synaptic plasticity and memory in mice

As microRNAs have emerged to be important regulators of molecular events occurring at the synapses, the new questions about their regulatory effect on the behavior have araised. In the present study, we show for the first time that the dysregulated specific targeting of miR132 to Mmp9 mRNA in the mouse brain results in the increased level of Mmp9 protein, which affects synaptic plasticity and has an effect on memory formation. Our data points at the importance of complex and precise regulation of the Mmp9 level by miR132 in the brain.

miRNAs as potential diagnostic biomarkers and pharmacogenomic indicators in psychiatric disorders

The heterogeneity of psychiatric disorders and the lack of reliable biomarkers for prediction and treatments follow-up pose difficulties towards recognition and understanding of the molecular basis of psychiatric diseases. However, several studies based on NGS approaches have shown that miRNAs could regulate gene expression during onset and disease progression and could serve as potential diagnostic and pharmacogenomics biomarkers during treatment. We provide herein a detailed overview of circulating miRNAs and their expression profiles as biomarkers in schizophrenia, bipolar disorder and major depressive disorder and their role in response to specific treatments. Bioinformatics analysis of miR-34a, miR-106, miR-134 and miR-132, which are common among SZ, BD and MDD patients, showed brain enrichment and involvement in the modulation of critical signaling pathways, which are often deregulated in psychiatric disorders. We propose that specific miRNAs support accurate diagnosis and effective precision treatment of psychiatric disorders.

Short-Term, Voluntary Exercise Affects Morpho-Functional Maturation of Adult-Generated Neurons in Rat Hippocampus

Physical exercise is a well-proven neurogenic stimulus, promoting neuronal progenitor proliferation and affecting newborn cell survival. Besides, it has beneficial effects on brain health and cognition. Previously, we found that three days of physical activity in a very precocious period of adult-generated granule cell life is able to antedate the appearance of the first GABAergic synaptic contacts and increase T-type Ca²⁺ channel expression. Considering the role of GABA and Ca²⁺ in fostering neuronal maturation, in this study, we used short-term, voluntary exercise on a running wheel to investigate if it is able to induce long-term morphological and synaptic changes in newborn neurons. Using adult male rats, we found that: (i) three days of voluntary physical exercise can definitively influence the morpho-functional maturation process of newborn granule neurons when applied very early during their development; (ii) a significant percentage of new neurons show more mature morphological characteristics far from the end of exercise protocol; (iii) the long-term morphological effects result in enhanced synaptic plasticity. Present findings demonstrate that the morpho-functional changes induced by exercise on very immature adult-generated neurons are permanent, affecting the neuron maturation and integration in hippocampal circuitry. Our data contribute to underpinning the beneficial potential of physical activity on brain health, also performed for short times.

MicroRNA‐132 is overexpressed in fetuses with late‐onset fetal growth restriction

Background and Aims

To evaluate the expression of microRNA 132 (miR‐132) in fetuses with normal growth and in fetuses with late‐onset growth restriction (FGR).

Methods

In a prospective cohort study, 48 fetuses (24 with late‐onset FGR and 24 with normal growth) were scanned with Doppler ultrasound after 34 weeks to measure the umbilical artery and middle cerebral artery pulsatility indices and followed until birth. Subsequently, blood samples from the umbilical cord were collected to evaluate the expression of miR‐132 by means of Real‐time quantitative polymerase chain reaction, determining the existence of normality cut‐offs and associations with birth weight (BW) centile, cerebroplacental ratio multiples of the median (CPR MoM), and intrapartum fetal compromise (IFC).

Results

In comparison with normal fetuses, late‐onset FGR fetuses showed upregulation of miR‐132 (33.94 ± 45.04 vs. 2.88 ± 9.32 2−ddC_t, p < 0.001). Using 5 as a cut‐off we obtained a sensitivity of 50% and a specificity of 96% for the diagnosis of FGR, while for IFC these values were respectively 27% and 73%. Expression of miR‐132 was associated with BW centile but not with CPR MoM. Finally, the best detection of IFC was achieved combining miR‐132 expression and CPR MoM (AUC = 0.69, p < 0.05).

Conclusion

Fetuses with late‐onset FGR show upregulation of miR‐132. Further studies are needed to investigate the role of miR‐132 in the management of late‐onset FGR.

The role of miRNA in retinal ganglion cell health and disease

miRNA are short non-coding RNA responsible for the knockdown of proteins through their targeting and silencing of complimentary mRNA sequences. The miRNA landscape of a cell thus affects the levels of its proteins and has significant consequences to its health. Deviations in this miRNA landscape have been implicated in a variety of neurodegenerative diseases and have also garnered interest as targets for treatment. Retinal ganglion cells are the sole projection neuron of the retina with their axons making up the optic nerve. They are a focus of study not only for their importance in vision and the myriad of blinding diseases characterized by their dysfunction and loss, but also as a model of other central nervous system diseases such as spinal cord injury and traumatic brain injury. This review summarizes current knowledge on the role of miRNA in retinal ganglion cell function, highlighting how perturbations can result in disease, and how modulating their abundance may provide a novel avenue of therapeutic research.

Niclosamide induces miR-148a to inhibit PXR and sensitize colon cancer stem cells to chemotherapy

Tumor recurrence is often attributed to cancer stem cells (CSCs). We previously demonstrated that down-regulation of Pregnane X Receptor (PXR) decreases the chemoresistance of CSCs and prevents colorectal cancer recurrence. Currently, no PXR inhibitor is usable in clinic. Here, we identify miR-148a as a targetable element upstream of PXR signaling in CSCs, which when over-expressed decreases PXR expression and impairs tumor relapse after chemotherapy in mouse tumor xenografts. We then develop a fluorescent reporter screen for miR-148a activators and identify the anti-helminthic drug niclosamide as an inducer of miR-148a expression. Consequently, niclosamide decreased PXR expression and CSC numbers in colorectal cancer patient-derived cell lines and synergized with chemotherapeutic agents to prevent CSC chemoresistance and tumor recurrence in vivo. Our study suggests that endogenous miRNA inducers is a viable strategy to down-regulate PXR and illuminates niclosamide as a neoadjuvant repurposing strategy to prevent tumor relapse in colon cancer.

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miR-148a expression is decreased in colon cancer stem cells

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Forced expression of miR-148a inhibits colon cancer stem cell chemoresistance

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High-content screening identified niclosamide as a potent miR-148a inducer

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Niclosamide induces miR-148a expression, inhibits PXR expression in CSCs and prevents tumor

Age-Dependent and Pathway-Specific Bimodal Action of Nicotine on Synaptic Plasticity in the Hippocampus of Mice Lacking the miR-132/212 Genes

Nicotine addiction develops predominantly during human adolescence through smoking. Self-administration experiments in rodents verify this biological preponderance to adolescence, suggesting evolutionary-conserved and age-defined mechanisms which influence the susceptibility to nicotine addiction. The hippocampus, a brain region linked to drug-related memory storage, undergoes major morpho-functional restructuring during adolescence and is strongly affected by nicotine stimulation. However, the signaling mechanisms shaping the effects of nicotine in young vs. adult brains remain unclear. MicroRNAs (miRNAs) emerged recently as modulators of brain neuroplasticity, learning and memory, and addiction. Nevertheless, the age-dependent interplay between miRNAs regulation and hippocampal nicotinergic signaling remains poorly explored. We here combined biophysical and pharmacological methods to examine the impact of miRNA-132/212 gene-deletion (miRNA-132/212-/-) and nicotine stimulation on synaptic functions in adolescent and mature adult mice at two hippocampal synaptic circuits: the medial perforant pathway (MPP) to dentate yrus (DG) synapses (MPP-DG) and CA3 Schaffer collaterals to CA1 synapses (CA3-CA1). Basal synaptic transmission and short-term (paired-pulse-induced) synaptic plasticity was unaltered in adolescent and adult miRNA-132/212-/- mice hippocampi, compared with wild-type controls. However, nicotine stimulation promoted CA3-CA1 synaptic potentiation in mature adult (not adolescent) wild-type and suppressed MPP-DG synaptic potentiation in miRNA-132/212-/- mice. Altered levels of CREB, Phospho-CREB, and acetylcholinesterase (AChE) expression were further detected in adult miRNA-132/212-/- mice hippocampi. These observations propose miRNAs as age-sensitive bimodal regulators of hippocampal nicotinergic signaling and, given the relevance of the hippocampus for drug-related memory storage, encourage further research on the influence of miRNAs 132 and 212 in nicotine addiction in the young and the adult brain.

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.

MicroRNA-132 is involved in morphine dependence via modifying the structural plasticity of the dentate gyrus neurons in rats

Repeated morphine exposure has been shown to induce neuronal plasticity in reward-related areas of the brain. miR-132, a CREB-induced and activation-dependent microRNA, has been suggested to be involved in the neuronal plasticity by increasing neuronal dendritic branches and spinogenesis. However, it is still unclear whether miR-132 is related to morphine dependence. Here, we investigate whether miR-132 is involved in morphine dependence and whether it is related to the structural plasticity of the dentate gyrus (DG) neurons. Sprague-Dawley rats are treated with increasing doses of morphine injection for six consecutive days to develop morphine dependence. Our results show that dendritic branching and spinogenesis of the DG neurons of morphine dependent rats are increased. Morphine treatment (24 h) promotes the differentiation of N2a cells stably expressing μ-opioid receptor by up-regulating miR-132 expression. Moreover, inhibiting miR-132 3p (but not 5p) of the DG neurons can reverse the structural plasticity and disrupt the formation of morphine dependence in rats. These findings indicate that miR-132 in the DG neurons is involved in morphine dependence via modifying the neuronal plasticity.

Assessment of cerebral spinal fluid biomarkers and microRNA-mediated disease mechanisms in spinal muscular atrophy patient samples

Cerebral spinal fluid (CSF) is a promising biospecimen for the detection of central nervous system biomarkers to monitor therapeutic efficacy at the cellular level in neurological diseases. Spinal muscular atrophy (SMA) patients receiving intrathecal antisense oligonucleotide (nusinersen) therapy tend to show improved motor function, but the treatment effect on cellular health remains unknown. The objective of this study was to assess the potential of extracellular RNAs and microRNAs in SMA patient CSF as indicators of neuron and glial health following nusinersen treatment. Extracellular RNA analysis of CSF samples revealed ongoing cellular stress related to inflammation and glial differentiation, even after treatment administration. Downregulated microRNA expression associated with SMA-specific or general motor neuron dysfunction in animal and cellular models, tended to increase in nusinersen treated patient CSF samples and correlated with SMA Type 1 and 2 motor functioning improvements. However, miR-146a, known to be upregulated in SMA induced pluripotent stem cell (iPSC)-derived astrocytes, showed increased expression in nusinersen treated CSF samples. We then used mRNA sequencing and multi-electrode arrays to assess the transcriptional and functional effects of miR-146a on healthy and SMA iPSC-derived motor neurons. miR-146a treatment on iPSC-derived motor neurons led to a downregulation of extracellular matrix genes associated with synaptic perineuronal net and alterations in spontaneous electrophysiological activity. Together, this study suggests that extracellular RNAs and microRNAs may serve as useful biomarkers to monitor cellular health during nusinersen treatment. Moreover, these data highlight the importance of addressing astrocyte health and response to nusinersen in SMA pathogenesis and treatment strategies.

The promise of microRNA-based therapies in Alzheimer's disease: challenges and perspectives

Multi-pathway approaches for the treatment of complex polygenic disorders are emerging as alternatives to classical monotarget therapies and microRNAs are of particular interest in that regard. MicroRNA research has come a long way from their initial discovery to the cumulative appreciation of their regulatory potential in healthy and diseased brain. However, systematic interrogation of putative therapeutic or toxic effects of microRNAs in (models of) Alzheimer's disease is currently missing and fundamental research findings are yet to be translated into clinical applications. Here, we review the literature to summarize the knowledge on microRNA regulation in Alzheimer's pathophysiology and to critically discuss whether and to what extent these increasing insights can be exploited for the development of microRNA-based therapeutics in the clinic.

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.

Neurotransmitter-stimulated neuron-derived sEVs have opposite effects on amyloid β-induced neuronal damage

The ratio of excitatory to inhibitory neurotransmitters is essential for maintaining the firing patterns of neural networks, and is strictly regulated within individual neurons and brain regions. Excitatory to inhibitory (E/I) imbalance has been shown to participate in the progression of neurodegenerative diseases, including Alzheimer's disease (AD). Glutamate excitotoxicity and GABAergic neuron dysfunction appear to be key components of the neuronal cell death that takes place in AD. Since extracellular vesicles (EVs) are now explored as an important vehicle in transmitting signals between cells, we hypothesized that the function of neuron-derived small EVs (sEVs) might be regulated by the status of neurotransmitter balance and that sEVs might affect amyloid β (Aβ) toxicity on neurons. This study aimed to reveal the effects of sEVs from unbalanced neurotransmitter-stimulated neurons on Aβ-induced toxicity. We demonstrated the opposite effects of the two groups of sEVs isolated from neurons stimulated by glutamate or GABA on Aβ toxicity in vivo and in vitro. The sEVs released from GABA-treated neurons alleviated Aβ-induced damage, while those released from glutamate-treated neurons aggravated Aβ toxicity. Furthermore, we compared the microRNA (miRNA) composition of sEVs isolated from glutamate/GABA/PBS-treated neurons. Our results showed that glutamate and GABA oppositely regulated miR-132 levels in sEVs, resulting in the opposite destiny of recipient cells challenged with Aβ. Our results indicated that manipulating the function of sEVs by different neurotransmitters may reveal the mechanisms underlying the pathogenesis of AD and provide a promising strategy for AD treatment.

The emerging role of miRNA-132/212 cluster in neurologic and cardiovascular diseases: Neuroprotective role in cells with prolonged longevity

miRNA-132/212 are small regulators of gene expression with a function that fulfills a vital function in diverse biological processes including neuroprotection of cells with prolonged longevity in neurons and the cardiovascular system. In neurons, miRNA-132 appears to be essential for controlling differentiation, development, and neural functioning. Indeed, it also universally promotes axon evolution, nervous migration, plasticity as well, it is suggested to be neuroprotective against neurodegenerative diseases. Moreover, miRNA-132/212 disorder leads to neural developmental perturbation, and the development of degenerative disorders covering Alzheimer's, Parkinson's, and epilepsy's along with psychiatric perturbations including schizophrenia. Furthermore, the cellular mechanisms of the miRNA-132/212 have additionally been explored in cardiovascular diseases models. Also, the miRNA-132/212 family modulates cardiac hypertrophy and autophagy in cardiomyocytes. The protective and effective clinical promise of miRNA-132/212 in these systems is discussed in this review. To sum up, the current progress in innovative miRNA-based therapies for human pathologies seems of extreme concern and reveals promising novel therapeutic strategies.

The importance of non-coding RNAs in environmental stress-related developmental brain disorders: A systematic review of evidence associated with exposure to alcohol, anesthetic drugs, nicotine, and viral infections

Brain development is a dynamic and lengthy process that includes cell proliferation, migration, neurogenesis, gliogenesis, synaptogenesis, and pruning. Disruption of any of these developmental events can result in long-term outcomes ranging from brain structural changes, to cognitive and behavioral abnormality, with the mechanisms largely unknown. Emerging evidence suggests non-coding RNAs (ncRNAs) as pivotal molecules that participate in normal brain development and neurodevelopmental disorders. NcRNAs such as long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are transcribed from the genome but not translated into proteins. Many ncRNAs have been implicated as tuners of cell fate. In this review, we started with an introduction of the current knowledge of lncRNAs and miRNAs, and their potential roles in brain development in health and disorders. We then reviewed and discussed the evidence of ncRNA involvement in abnormal brain development resulted from alcohol, anesthetic drugs, nicotine, and viral infections. The complex connections among these ncRNAs were also discussed, along with potential overlapping ncRNA mechanisms, possible pharmacological targets for therapeutic/neuroprotective interventions, and potential biomarkers for brain developmental disorders.

A review study on the modulation of SIRT1 expression by miRNAs in aging and age-associated diseases

Sirtuin-1 (SIRT1) as a NAD + -dependent Class III protein deacetylase, involves in longevity and various cellular physiological processes. SIRT1 via deacetylating transcription factors regulates cell growth, inflammation, metabolism, hypoxic responses, cell survival, senescence, and aging. MicroRNAs (miRNAs) are short non-coding RNAs that modulate the expression of target genes in a post-transcriptional manner. Recent investigations have exhibited that miRNAs have an important role in regulating cell growth, development, stress responses, tumor formation and suppression, cell death, and aging. In the present review, we summarize recent findings about the roles of miRNAs in regulating SIRT1 and SIRT1-associated signaling cascade and downstream effects, like apoptosis and aging. Here we introduce and discuss how activity and expression of SIRT1 are modulated by miRNAs and further review the therapeutic potential of targeting miRNAs for age-associated diseases that involve SIRT1 dysfunction. Although at its infancy, research on the roles of miRNAs in aging and their function through modulating SIRT1 may provide new insights in deciphering the key molecular pathways related to aging and age-associated disorders.

MiR-132 down-regulates high glucose-induced β-dystroglycan degradation through Matrix Metalloproteinases-9 up-regulation in primary neurons

Cognitive dysfunction is one of the complications of diabetes. Unfortunately, there is no effective methods to block its progression currently. One of the pathophysiological mechanisms is synaptic protein damage and neuronal signal disruption because of glucose metabolism disorder. Dystroglycan protein, located in the post‐synaptic membrane of neurons, links the intracellular cytoskeleton with extracellular matrix. Abnormal expression of dystroglycan protein affects neuronal biological functions and leads to cognitive impairment. However, there are no relevant studies to observe the changes of β‐dystroglycan protein in diabetes rat brain and in primary neurons under high glucose exposure. Our data demonstrated the alterations of cognitive abilities in the diabetic rats; β‐dystroglycan protein degradation occurred in hippocampal and cortical tissues in diabetic rat brain. We further explored the mechanisms underlying of this phenomenon. When neurons are exposed to high glucose environment in long‐term period, microRNA‐132 (miR‐132) would be down‐regulated in neurons. Matrix Metalloproteinases‐9 (MMP‐9) mRNA, as a target of miR‐132, could be up‐regulated; higher expression and overlay activity of MMP‐9 protein could increase β‐DG protein degradation. In this way, β‐DG degradation may affect structure and functions among the synapses, which related to cognition decline. It may provide some theoretical basis for elucidating the molecular mechanism of diabetes‐induced cognitive dysfunction.

miR-132 and miR-942 Expression Levels in Children with Attention Deficit and Hyperactivity Disorder: A Controlled Study

OBJECTIVE

Although attention deficit hyperactivity disorder (ADHD) is a disease with high genetic transition, our knowledge about the mechanism of the disease is limited. In this study, it was aimed to evaluate the levels of miR-132-3p and miR-942-5p that are associated with the dopamine carrier protein gene (DAT1) and dopamine receptor 5 (DRD5) genes, which have been shown to play a role in the development of ADHD.

METHODS

According to the Diagnostic and Statistical Manual of Mental Disorders 5th edition, 50 children diagnosed with ADHD and 48 healthy controls were included in the study. Affective Disorders and Schizophrenia Interview Schedule-Now and Lifetime Version-Turkish Adaptation was used to evaluate ADHD and the diagnoses accompanying ADHD. Quantitative Real-Time Polymerase Chain Reaction was used to evaluate miR-132-3p and miR-942-5p expression levels.

RESULTS

It was observed that miR-132-3p level (p = 0.001) was significantly higher with children with ADHD compared to the control group, and the level of miR-942-5p (p = 0.181) was higher in ADHD but did not reach statistically significant level.

CONCLUSION

In our study, we found that the increase in the miR-132-3p levels of children with ADHD may be a therapeutic target of the disease.

Alzheimer's Disease and microRNA-132: A Widespread Pathological Factor and Potential Therapeutic Target

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly and is the most common type of dementia. AD is mostly gradual onset, and involves slow, progressive mental decline, accompanied by personality changes; the incidence of AD gradually increases with age. The etiology of AD is unknown, although it is currently believed to be related to abnormal deposition of amyloid β-protein (Aβ) in the brain, hyperphosphorylation of microtubule-associated protein tau, and the release of various cytokines, complements, activators and chemokines by cells. MicroRNAs (miRNAs) are a class of highly conserved non-coding RNAs that regulate gene expression at the post-transcriptional level, and manipulate the functions of intracellular proteins and physiological processes. Emerging studies have shown that miRNA plays an important role in regulating AD-related genes. MiR-132 is known as "NeurimmiR" due to its involvement in numerous neurophysiological and pathological processes. Accumulating pre-clinical results suggest that miR-132 may be involved in the progression of Aβ and tau pathology. Moreover, clinical studies have indicated that decreased circulating miR-132 levels could be used a potential diagnostic biomarker in AD. Here, we review the pathogenic role of miR-132 activity in AD, and the potential of targeting miR-132 for developing future therapeutic strategies.