Differential microRNA expression in blood in multiple sclerosis

A Literature Review and Meta-Analysis on the Potential Use of miR-150 as a Novel Biomarker in the Detection and Progression of Multiple Sclerosis

BACKGROUND

MicroRNA-150 (miR-150) plays a critical role in immune regulation and has been implicated in autoimmune diseases like Multiple Sclerosis (MS). This review aims to evaluate miR-150's potential as a biomarker for MS, necessitating this review to consolidate current evidence and highlight miR-150's utility in improving diagnostic accuracy and monitoring disease progression.

METHODS

A comprehensive literature search was conducted in databases like PubMed, Scopus, Google Scholar, SciSpace, MDPI and Web of Science, adhering to PRISMA guidelines. Studies focusing on miR-150 implications in MS were included. Data extraction was conducted, while quality assessment was done using the NOS and AMSTAR 2 tools. With the extracted data a statistical analyses conducted.

RESULTS

10 eligible articles were included in review. Findings show that miR-150 levels were consistently deregulated in MS patients compared to healthy controls, correlating with disease severity and clinical parameters such as (EDSS) scores and disease activity. Additionally, miR-150 is implicated in the inflammatory pathogenesis of MS, affecting immune cell regulation and inflammatory pathways.

CONCLUSIONS

MiR-150 is a promising biomarker for MS, showing significant potential for improving diagnostic accuracy and monitoring disease progression. Its consistent deregulation in MS patients and correlation with clinical parameters underscore its clinical utility. Further research should validate miR-150's salivary presence and its possible usage as a novel biomarker and therapeutic potential in the development of MS.

Analysis of potential microRNA biomarkers for multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating autoimmune neurodegenerative disorder for which no specific blood biomarker is available. MicroRNAs (miRNAs) have been investigated for their diagnostic potential in MS. However, MS-associated miRNAs are rarely replicated in different MS populations, thus impeding their use in clinical testing. Here, we evaluated the fold expression of seven reported MS miRNAs associated with MS incidence and clinical characteristics in 76 MS patients and 75 healthy control plasma samples. We found miR-23a-3p to be upregulated in relapsing-remitting MS (RRMS), while miR-326 was downregulated. MiR-150-5p and -320a-3p were significantly downregulated in secondary progressive MS (SPMS) patients compared to RRMS. High disability was associated with low miR-320a-3p, whereas low BDNF levels were associated with upregulation of miR-150-5p and downregulation of miR-326 expression in the total cohort. MiR-23a-3p and miR-326 showed significant diagnostic sensitivity, specificity, and accuracy for RRMS diagnosis. In addition, miR-150-5p and miR-320a-3p had comparable significant diagnostic test performance metrics distinguishing SPMS from RRMS. Therefore, there is potential for including miR-23a-3p and miR-326 in an RRMS diagnostic miRNA panel. Moreover, we have shown that miR-150-5p and miR-320a-3p could be novel RRMS conversion to SPMS biomarkers. The use of these miRNAs in MS diagnosis and prognosis warrants further investigation.

MicroRNA biomarkers as next-generation diagnostic tools for neurodegenerative diseases: a comprehensive review

Neurodegenerative diseases (NDs) are characterized by abnormalities within neurons of the brain or spinal cord that gradually lose function, eventually leading to cell death. Upon examination of affected tissue, pathological changes reveal a loss of synapses, misfolded proteins, and activation of immune cells-all indicative of disease progression-before severe clinical symptoms become apparent. Early detection of NDs is crucial for potentially administering targeted medications that may delay disease advancement. Given their complex pathophysiological features and diverse clinical symptoms, there is a pressing need for sensitive and effective diagnostic methods for NDs. Biomarkers such as microRNAs (miRNAs) have been identified as potential tools for detecting these diseases. We explore the pivotal role of miRNAs in the context of NDs, focusing on Alzheimer's disease, Parkinson's disease, Multiple sclerosis, Huntington's disease, and Amyotrophic Lateral Sclerosis. The review delves into the intricate relationship between aging and NDs, highlighting structural and functional alterations in the aging brain and their implications for disease development. It elucidates how miRNAs and RNA-binding proteins are implicated in the pathogenesis of NDs and underscores the importance of investigating their expression and function in aging. Significantly, miRNAs exert substantial influence on post-translational modifications (PTMs), impacting not just the nervous system but a wide array of tissues and cell types as well. Specific miRNAs have been found to target proteins involved in ubiquitination or de-ubiquitination processes, which play a significant role in regulating protein function and stability. We discuss the link between miRNA, PTM, and NDs. Additionally, the review discusses the significance of miRNAs as biomarkers for early disease detection, offering insights into diagnostic strategies.

Stem Cell-Derived Exosomal MicroRNAs as Novel Potential Approach for Multiple Sclerosis Treatment

Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by inflammation and demyelination of CNS neurons. Up to now, there are many therapeutic strategies for MS but they are only being able to reduce progression of diseases and have not got any effect on repair and remyelination. Stem cell therapy is an appropriate method for regeneration but has limitations and problems. So recently, researches were used of exosomes that facilitate intercellular communication and transfer cell-to-cell biological information. MicroRNAs (miRNAs) are a class of short non-coding RNAs that we can used to their dysregulation in order to diseases diagnosis. The miRNAs of microvesicles obtained stem cells may change the fate of transplanted cells based on received signals of injured regions. The miRNAs existing in MSCs may be displayed the cell type and their biological activities. Current studies show also that the miRNAs create communication between stem cells and tissue-injured cells. In the present review, firstly we discuss the role of miRNAs dysregulation in MS patients and miRNAs expression by stem cells. Finally, in this study was confirmed the relationship of microRNAs involved in MS and miRNAs expressed by stem cells and interaction between them in order to find appropriate treatment methods in future for limit to disability progression.

MicroRNAs dysregulated in multiple sclerosis affect the differentiation of CG-4 cells, an oligodendrocyte progenitor cell line

Introduction

Demyelination is one of the hallmarks of multiple sclerosis (MS). While remyelination occurs during the disease, it is incomplete from the start and strongly decreases with its progression, mainly due to the harm to oligodendrocyte progenitor cells (OPCs), causing irreversible neurological deficits and contributing to neurodegeneration. Therapeutic strategies promoting remyelination are still very preliminary and lacking within the current treatment panel for MS.

Methods

In a previous study, we identified 21 microRNAs dysregulated mostly in the CSF of relapsing and/or remitting MS patients. In this study we transfected the mimics/inhibitors of several of these microRNAs separately in an OPC cell line, called CG-4. We aimed (1) to phenotypically characterize their effect on OPC differentiation and (2) to identify corroborating potential mRNA targets via immunocytochemistry, RT-qPCR analysis, RNA sequencing, and Gene Ontology enrichment analysis.

Results

We observed that the majority of 13 transfected microRNA mimics decreased the differentiation of CG-4 cells. We demonstrate, by RNA sequencing and independent RT-qPCR analyses, that miR-33-3p, miR-34c-5p, and miR-124-5p arrest OPC differentiation at a late progenitor stage and miR-145-5p at a premyelinating stage as evidenced by the downregulation of premyelinating oligodendrocyte (OL) [Tcf7l2, Cnp (except for miR-145-5p)] and mature OL (Plp1, Mbp, and Mobp) markers, whereas only miR-214-3p promotes OPC differentiation. We further propose a comprehensive exploration of their change in cell fate through Gene Ontology enrichment analysis. We finally confirm by RT-qPCR analyses the downregulation of several predicted mRNA targets for each microRNA that possibly support their effect on OPC differentiation by very distinctive mechanisms, of which some are still unexplored in OPC/OL physiology.

Conclusion

miR-33-3p, miR-34c-5p, and miR-124-5p arrest OPC differentiation at a late progenitor stage and miR-145-5p at a premyelinating stage, whereas miR-214-3p promotes the differentiation of CG-4 cells. We propose several potential mRNA targets and hypothetical mechanisms by which each microRNA exerts its effect. We hereby open new perspectives in the research on OPC differentiation and the pathophysiology of demyelination/remyelination, and possibly even in the search for new remyelinating therapeutic strategies in the scope of MS.

MicroRNAs are dysregulated in peripheral blood mononuclear cells in multiple sclerosis and correlate with T cell mediators

T cell mediators and microRNAs are involved in the pathogenesis of multiple sclerosis (MS), but their interaction largely remains undetermined. We investigated by RT-qPCR the dysregulation of microRNAs in peripheral blood mononuclear cells of MS patients versus healthy controls, according to radiological disease activity or treatment. Several microRNAs correlated positively/negatively with IL21/FOXP3 mRNA expression, but not with serum neurofilament light chain levels. Cytokine expression is conceivably balanced by several regulators, whereas microRNAs possibly target upstream transcription factors rather than directly cytokine mRNAs. Functional studies are needed to investigate their interaction, notably for the predicted targeting of FOXP3 by miR-34c-5p.

The role of microRNAs involved in the disorder of blood-brain barrier in the pathogenesis of multiple sclerosis

miRNAs are involved in various vital processes, including cell growth, development, apoptosis, cellular differentiation, and pathological cellular activities. Circulating miRNAs can be detected in various body fluids including serum, plasma, saliva, and urine. It is worth mentioning that miRNAs remain stable in the circulation in biological fluids and are released from membrane-bound vesicles called exosomes, which protect them from RNase activity. It has been shown that miRNAs regulate blood-brain barrier integrity by targeting both tight junction and adherens junction molecules and can also influence the expression of inflammatory cytokines. Some recent studies have examined the impact of certain commonly used drugs in Multiple Sclerosis on miRNA levels. In this review, we will focus on the recent findings on the role of miRNAs in multiple sclerosis, including their role in the cause of MS and molecular mechanisms of the disease, utilizing miRNAs as diagnostic and clinical biomarkers, using miRNAs as a therapeutic modality or target for Multiple Sclerosis and drug responses in patients, elucidating their importance as prognosticators of disease progression, and highlighting their potential as a future treatment for MS.

The role of miRNAs in multiple sclerosis pathogenesis, diagnosis, and therapeutic resistance

In recent years, microRNAs (miRNAs) have gained increased attention from researchers around the globe. Although it is twenty nucleotides long, it can modulate several gene targets simultaneously. Their mal expression is a signature of various pathologies, and they provide the foundation to elucidate the molecular mechanisms of each pathology. Among the debilitating central nervous system (CNS) disorders with a growing prevalence globally is the multiple sclerosis (MS). Moreover, the diagnosis of MS is challenging due to the lack of disease-specific biomarkers, and the diagnosis mainly depends on ruling out other disabilities. MS could adversely affect patients' lives through its progression, and only symptomatic treatments are available as therapeutic options, but an exact cure is yet unavailable. Consequently, this review hopes to further the study of the biological features of miRNAs in MS and explore their potential as a therapeutic target.

Data Mining of Microarray Datasets in Translational Neuroscience

Data mining involves the computational analysis of a plethora of publicly available datasets to generate new hypotheses that can be further validated by experiments for the improved understanding of the pathogenesis of neurodegenerative diseases. Although the number of sequencing datasets is on the rise, microarray analysis conducted on diverse biological samples represent a large collection of datasets with multiple web-based programs that enable efficient and convenient data analysis. In this review, we first discuss the selection of biological samples associated with neurological disorders, and the possibility of a combination of datasets, from various types of samples, to conduct an integrated analysis in order to achieve a holistic understanding of the alterations in the examined biological system. We then summarize key approaches and studies that have made use of the data mining of microarray datasets to obtain insights into translational neuroscience applications, including biomarker discovery, therapeutic development, and the elucidation of the pathogenic mechanisms of neurodegenerative diseases. We further discuss the gap to be bridged between microarray and sequencing studies to improve the utilization and combination of different types of datasets, together with experimental validation, for more comprehensive analyses. We conclude by providing future perspectives on integrating multi-omics, to advance precision phenotyping and personalized medicine for neurodegenerative diseases.

Multiplex Analysis of Cerebrospinal Fluid and Serum Exosomes MicroRNAs of Untreated Relapsing Remitting Multiple Sclerosis (RRMS) and Proposing Noninvasive Diagnostic Biomarkers

Exosomal microRNAs (miRNAs) are emerging diagnostic biomarkers for neurodegenerative diseases. In this study, we aimed to detect relapsing-remitting multiple sclerosis (RRMS)-specific miRNAs in cerebrospinal fluid (CSF) and serum exosomes with diagnostic potential. One ml of CSF and serum sample were collected from each of the 30 untreated RRMS patients and healthy controls (HCs). A panel of 18 miRNAs affecting inflammatory responses was applied, and qRT-PCR was conducted to detect differentially expressed exosomal miRNAs in CSF and serum of RRMS patients. We identified that 17 out of 18 miRNAs displayed different patterns in RRMS patients compared to HCs. Let-7 g-5p, miR-18a-5p, miR-145-5p, and miR-374a-5p with dual pro-inflammatory and anti-inflammatory actions and miR-150-5p and miR-342-3p with anti-inflammatory action were significantly upregulated in both CSF and serum-derived exosomes of RRMS patients compared to corresponding HCs. Additionally, anti-inflammatory miR-132-5p and pro-inflammatory miR-320a-5p were significantly downregulated in both CSF and serum-derived exosomes of RRMS patients compared to HCs. Ten of 18 miRNAs were differentially expressed in CSF and serum exosomes of the patients. Furthermore, miR-15a-5p, miR-19b-3p, and miR-432-5p were upregulated, and miR-17-5p was downregulated only in CSF exosomes. Interestingly, U6 housekeeping gene was differentially expressed in CSF and serum exosomes, in both RRMS and HCs. As the first report describing CSF exosomal miRNAs expression profile compared to that of serum exosomes in untreated RRMS patients, we showed that CSF and serum exosomes are not identical in terms of biological compounds and display different patterns in miRNAs and U6 expression.

The dysregulation of miRNAs in epilepsy and their regulatory role in inflammation and apoptosis

Epilepsy is a neurological disorder that impacts millions of people worldwide, and it is characterized by the occurrence of recurrent seizures. The pathogenesis of epilepsy is complex, involving dysregulation of various genes and signaling pathways. MicroRNAs (miRNAs) are a group of small non-coding RNAs that play a vital role in the regulation of gene expression. They have been found to be involved in the pathogenesis of epilepsy, acting as key regulators of neuronal excitability and synaptic plasticity. In recent years, there has been a growing interest in exploring the miRNA regulatory network in epilepsy. This review summarizes the current knowledge of the regulatory miRNAs involved in inflammation and apoptosis in epilepsy and discusses its potential as a new avenue for developing targeted therapies for the treatment of epilepsy.

Cellular and Molecular Evidence of Multiple Sclerosis Diagnosis and Treatment Challenges

Multiple sclerosis (MS) is a chronic autoimmune disease that impacts the central nervous system and can result in disability. Although the prevalence of MS has increased in India, diagnosis and treatment continue to be difficult due to several factors. The present study examines the difficulties in detecting and treating multiple sclerosis in India. A lack of MS knowledge among healthcare professionals and the general public, which delays diagnosis and treatment, is one of the significant issues. Inadequate numbers of neurologists and professionals with knowledge of MS management also exacerbate the situation. In addition, MS medications are expensive and not covered by insurance, making them inaccessible to most patients. Due to the absence of established treatment protocols and standards for MS care, India's treatment techniques vary. In addition, India's population diversity poses unique challenges regarding genetic variations, cellular and molecular abnormalities, and the potential for differing treatment responses. MS is more difficult to accurately diagnose and monitor due to a lack of specialized medical supplies and diagnostic instruments. Improved awareness and education among healthcare professionals and the general public, as well as the development of standardized treatment regimens and increased investment in MS research and infrastructure, are required to address these issues. By addressing these issues, it is anticipated that MS diagnosis and treatment in India will improve, leading to better outcomes for those affected by this chronic condition.

Cholecalciferol Supplementation Induced Up-Regulation of SARAF Gene and Down-Regulated miR-155-5p Expression in Slovenian Patients with Multiple Sclerosis

Multiple sclerosis is a common immune-mediated inflammatory and demyelinating disease. Lower cholecalciferol levels are an established environmental risk factor in multiple sclerosis. Although cholecalciferol supplementation in multiple sclerosis is widely accepted, optimal serum levels are still debated. Moreover, how cholecalciferol affects pathogenic disease mechanisms is still unclear. In the present study, we enrolled 65 relapsing-remitting multiple sclerosis patients who were double-blindly divided into two groups with low and high cholecalciferol supplementation, respectively. In addition to clinical and environmental parameters, we obtained peripheral blood mononuclear cells to analyze DNA, RNA, and miRNA molecules. Importantly, we investigated miRNA-155-5p, a previously published pro-inflammatory miRNA in multiple sclerosis known to be correlated to cholecalciferol levels. Our results show a decrease in miR-155-5p expression after cholecalciferol supplementation in both dosage groups, consistent with previous observations. Subsequent genotyping, gene expression, and eQTL analyses reveal correlations between miR-155-5p and the SARAF gene, which plays a role in the regulation of calcium release-activated channels. As such, the present study is the first to explore and suggest that the SARAF miR-155-5p axis hypothesis might be another mechanism by which cholecalciferol supplementation might decrease miR-155 expression. This association highlights the importance of cholecalciferol supplementation in multiple sclerosis and encourages further investigation and functional cell studies.

Nanomedicine based strategies for oligonucleotide traversion across the blood-brain barrier

Neurological disorders are considered the most prominent cause of disability worldwide. The major hurdle in the management of neurological disorders is the existence of the blood-brain barrier (BBB), which hinders the entry of several therapeutic moieties. In recent years, oligonucleotides have gained tremendous attention for their target specificity, diminished dose and adverse effects, thereby halting disease progression. However, enzymatic degradation, rapid clearance, limited circulation and availability at the bio-active site, etc., limit its clinical translation. Nanomedicine has opened up a breadth of opportunities in the delivery of oligonucleotides across the BBB. This review addresses the pitfalls associated with oligonucleotide delivery in traversing the BBB via nanotherapeutics for the management of brain disorders. Regulatory perspectives pertaining to hastening the clinical translation of oligonucleotide-loaded nanocarriers for brain delivery have been highlighted.

MicroRNAs expression in peripheral blood mononuclear cells of patients with multiple sclerosis propose

BACKGROUND

MicroRNAs (miRs) are involved in the autoimmune and neurological diseases, including multiple sclerosis (MS), through modulating post-transcriptional gene regulation. Accumulating evidence indicates that miR-10, miR-24a, miR-124, and miR-21 play an imperative role in MS pathogenesis. Therefore, the current research aimed to analyze the expression of the selected miRNAs for MS in Iranian population.

METHODS AND RESULTS

Blood sample of 75 relapsing-remitting MS (RRMS) patients and 75 healthy individuals suffering no neurodegenerative illness was collected. Subsequently, the isolation of peripheral blood mononuclear cells (PBMCs) was performed by employing Ficoll-Hypaque density gradient method. Afterward, total RNA was extracted and subjected to qRT-PCR analysis. The obtained results evidenced that the relative expression of miR-10 (P = 0.0002), miR-21 (P = 0.0014), and miR-124 (P = 0.0091) significantly decreased in RRMS patients compared to healthy participants. On the contrary, no notable change was observed between the studies groups regarding miR-24a expression levels (P = 0.107). ROC curve analysis estimated an area under the curve (AUC) value equal to 0.75 with P = 0.0006 for miR-10, while it was decreased for miR-21 (AUC = 0.67 and P = 0.0054) and miR-124 (AUC = 0.66 and P = 0.012).

CONCLUSION

The change in miR-10, miR-124, and miR-21 expression patterns was implied to participate in MS development. Further large scale observational studies are recommended.

Association between miRNA-145 and miRNA-155 expression in peripheral blood mononuclear cells of patients with multiple sclerosis: a case-control study

Introduction

MicroRNAs (miR or miRNA) are short regulatory RNAs, which modulate post-transcriptional gene expression. Dysregulation of these molecules contributes to pathogenicity of autoimmune disorders, such as multiple sclerosis (MS).

Aims

This study was conducted to investigate changed expression pattern of miRNA-145 and miRNA-155 in MS.

Methods

We collected blood samples of 75 patients with relapsing-remitting MS patients and 75 healthy controls. Ficoll-Hypaque density gradient method was used to isolate peripheral blood mononuclear cells. Also, total RNA was extracted and subjected to RT-PCR analysis. We used the Mann–Whitney U test to evaluate the differences in expression levels of target miRNAs between the groups.

Results

We found that expression of miRNA-145 (P = 0.012) and miRNA-155 (P = 0.005) were partly reduced in patients with relapse-remitting MS in comparison with healthy controls. The miRNA-145 had an area under curve (AUC) of 0.621 (P = 0.01) and miRNA-155 levels had an AUC of 0.625 (P = 0.008).

Conclusion

Decreased expression of miRNA-145 and miRNA-155 contributes to development of relapse-remitting MS, while further large scale observational studies and meta-analyses are required.

Adipose-derived exosomes block muscular stem cell proliferation in aged mouse by delivering miRNA Let-7d-3p that targets transcription factor HMGA2

Sarcopenia is an aging-associated attenuation of muscular volume and strength and is the major cause of frailty and falls in elderly individuals. The number of individuals with sarcopenia is rapidly increasing worldwide; however, little is known about the underlying mechanisms of the disease. Sarcopenia often copresents with obesity, and some patients with sarcopenia exhibit accumulation of peri-organ or intra-organ adipose tissue as ectopic fat deposition, including atrophied skeletal muscle. In this study, we showed that transplantation of the perimuscular adipose tissue (PMAT) to the hindlimb thigh muscles of young mice decreased the number of integrin α7/CD29-double positive muscular stem/progenitor cells and that the reaction was mediated by PMAT-derived exosomes. We also found that the inhibition of cell proliferation was induced by Let-7d-3p miRNA that targets HMGA2, which is an important transcription factor for stem cell self-renewal, in muscular stem/progenitor cells and the composite molecular reaction in aged adipocytes. Reduction of Let-7 miRNA repressor Lin28 A/B and activation of nuclear factor-kappa B signaling can lead to the accumulation of Let-7d-3p in the exosomes of aged PMAT. These findings suggest a novel crosstalk between adipose tissue and skeletal muscle in the development of aging-associated muscular atrophy and indicate that adipose tissue–derived miRNAs may play a key role in sarcopenia.

Sensitive and convenient detection of miRNA-145 using a gold nanoparticle-HCR coupled system: computational and in vitro validations

Multiple sclerosis (MS) remains a challenging disease that requires timely diagnosis. Therefore, an ultrasensitive optical biosensor based on hybridization chain reaction (HCR) was developed to detect microRNA-145 (miRNA-145) as an MS biomarker. To construct such a sensor, HCR occurred between specific hairpin probes, as MB1 contains a poly-cytosine nucleotide loop and MB2 has a poly-guanine nucleotide sticky end. By introducing miR-145 as a target sequence, long-range dsDNA polymers are formed. Then, positively charged gold nanoparticles (AuNPs) were incubated with the HCR product, which adsorbed onto the dsDNA polymers due to electrostatic adsorption. This resulted in the precipitation of the AuNPs. By incubating different concentrations of miR-145 with AuNPs, the changes in the UV-vis spectrum of the supernatant were analyzed. The proposed biosensor showed a great ability to detect miR-145 in a wide linear range from 1 pM-1 nM with an excellent detection limit (LOD) of 0.519 nM. Furthermore, the developed biosensor indicated considerable selectivity in discriminating between miR-145 and mismatched sequences. It shows high selectivity in differentiating targets. Interestingly, the proposed method was also able to detect miRNA-145 in the diluted serum samples. In conclusion, this sensing platform exhibits high selectivity and specificity for the detection of circulating microRNAs, which holds great promise for translation to routine clinical applications.

MicroRNA Alteration, Application as Biomarkers, and Therapeutic Approaches in Neurodegenerative Diseases

MicroRNAs (miRNAs) are essential post-transcriptional gene regulators involved in various neuronal and non-neuronal cell functions and play a key role in pathological conditions. Numerous studies have demonstrated that miRNAs are dysregulated in major neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, amyotrophic lateral sclerosis, or Huntington’s disease. Hence, in the present work, we constructed a comprehensive overview of individual microRNA alterations in various models of the above neurodegenerative diseases. We also provided evidence of miRNAs as promising biomarkers for prognostic and diagnostic approaches. In addition, we summarized data from the literature about miRNA-based therapeutic applications via inhibiting or promoting miRNA expression. We finally identified the overlapping miRNA signature across the diseases, including miR-128, miR-140-5p, miR-206, miR-326, and miR-155, associated with multiple etiological cellular mechanisms. However, it remains to be established whether and to what extent miRNA-based therapies could be safely exploited in the future as effective symptomatic or disease-modifying approaches in the different human neurodegenerative disorders.

Emerging Biomarkers of Multiple Sclerosis in the Blood and the CSF: A Focus on Neurofilaments and Therapeutic Considerations

INTRODUCTION

Multiple Sclerosis (MS) is the most common immune-mediated chronic neurodegenerative disease of the central nervous system (CNS) affecting young people. This is due to the permanent disability, cognitive impairment, and the enormous detrimental impact MS can exert on a patient's health-related quality of life. It is of great importance to recognise it in time and commence adequate treatment at an early stage. The currently used disease-modifying therapies (DMT) aim to reduce disease activity and thus halt disability development, which in current clinical practice are monitored by clinical and imaging parameters but not by biomarkers found in blood and/or the cerebrospinal fluid (CSF). Both clinical and radiological measures routinely used to monitor disease activity lack information on the fundamental pathophysiological features and mechanisms of MS. Furthermore, they lag behind the disease process itself. By the time a clinical relapse becomes evident or a new lesion appears on the MRI scan, potentially irreversible damage has already occurred in the CNS. In recent years, several biomarkers that previously have been linked to other neurological and immunological diseases have received increased attention in MS. Additionally, other novel, potential biomarkers with prognostic and diagnostic properties have been detected in the CSF and blood of MS patients.

AREAS COVERED

In this review, we summarise the most up-to-date knowledge and research conducted on the already known and most promising new biomarker candidates found in the CSF and blood of MS patients.

DISCUSSION

the current diagnostic criteria of MS relies on three pillars: MRI imaging, clinical events, and the presence of oligoclonal bands in the CSF (which was reinstated into the diagnostic criteria by the most recent revision). Even though the most recent McDonald criteria made the diagnosis of MS faster than the prior iteration, it is still not an infallible diagnostic toolset, especially at the very early stage of the clinically isolated syndrome. Together with the gold standard MRI and clinical measures, ancillary blood and CSF biomarkers may not just improve diagnostic accuracy and speed but very well may become agents to monitor therapeutic efficacy and make even more personalised treatment in MS a reality in the near future. The major disadvantage of these biomarkers in the past has been the need to obtain CSF to measure them. However, the recent advances in extremely sensitive immunoassays made their measurement possible from peripheral blood even when present only in minuscule concentrations. This should mark the beginning of a new biomarker research and utilisation era in MS.

The role of glial cells in multiple sclerosis disease progression

Despite the development of highly effective treatments for relapsing-remitting multiple sclerosis (MS), limited progress has been made in addressing primary progressive or secondary progressive MS, both of which lead to loss of oligodendrocytes and neurons and axons, and to irreversible accumulation of disability. Neuroinflammation is central to all forms of MS. The current effective therapies for relapsing-remitting MS target the peripheral immune system; these treatments, however, have repeatedly failed in progressive MS. Greater understanding of inflammation driven by CNS-resident cells - including astrocytes and microglia - is, therefore, required to identify novel potential therapeutic opportunities. Advances in imaging, biomarker analysis and genomics suggest that microglia and astrocytes have central roles in the progressive disease process. In this Review, we provide an overview of the involvement of astrocytes and microglia at major sites of pathology in progressive MS. We discuss current and future therapeutic approaches to directly target glial cells, either to inhibit pathogenic functions or to restore homeostatic functions lost during the course of the disease. We also discuss how bidirectional communication between astrocytes and microglia needs to be considered, as therapeutic targeting of one is likely to alter the functions of the other.

Circulating miRNAs as Potential Biomarkers Distinguishing Relapsing-Remitting from Secondary Progressive Multiple Sclerosis. A Review

Multiple sclerosis (MS) is a debilitating neurodegenerative, highly heterogeneous disease with a variable course. The most common MS subtype is relapsing–remitting (RR), having interchanging periods of worsening and relative stabilization. After a decade, in most RR patients, it alters into the secondary progressive (SP) phase, the most debilitating one with no clear remissions, leading to progressive disability deterioration. Among the greatest challenges for clinicians is understanding disease progression molecular mechanisms, since RR is mainly characterized by inflammatory processes, while in SP, the neurodegeneration prevails. This is especially important because distinguishing RR from the SP subtype early will enable faster implementation of appropriate treatment. Currently, the MS course is not well-correlated with the biomarkers routinely used in clinical practice. Despite many studies, there are still no reliable indicators correlating with the disease stage and its activity degree. Circulating microRNAs (miRNAs) may be considered valuable molecules for the MS diagnosis and, presumably, helpful in predicting disease subtype. MiRNA expression dysregulation is commonly observed in the MS course. Moreover, knowledge of diverse miRNA panel expression between RRMS and SPMS may allow for deterring disability progression through successful treatment. Therefore, in this review, we address the current state of research on differences in miRNA panel expression between the phases.

Prediction of Single-Nucleotide Polymorphisms within microRNAs Binding Sites of Neuronal Genes Related to Multiple Sclerosis: A Preliminary Study

Background:

Different genetic variants, including the single-nucleotide polymorphisms (SNPs) present in microRNA recognition elements (MREs) within 3'UTR of genes, can affect miRNA-mediated gene regulation and susceptibility to a variety of human diseases such as multiple sclerosis (MS), a disease of the central nervous system. Since the expression of many genes associated with MS is controlled by microRNAs (miRNAs), the aim of this study was to analyze SNPs within miRNA binding sites of some neuronal genes associated with MS.

Materials and Methods:

Fifty-seven neuronal genes related to MS were achieved using dbGaP, DAVID, DisGeNET, and Oviddatabases. 3'UTR of candidate genes were assessed for SNPs, and miRNAs' target prediction databases were used for predicting miRNA binding sites.

Results:

Three hundred and eight SNPs (minor allele frequency >0.05) were identified in miRNA binding sites of 3'UTR of 44 genes. Among them, 42 SNPs in 22 genes had miRNA binding sites and miRNA prediction tools suggested 71 putative miRNAs binding sites on these genes. Moreover, in silico analysis predicted 22 MRE-modulating SNPs and 22 MRE-creating SNPs in the 3'UTR of these candidate genes.

Conclusions:

These candidate MRE-SNPs can alter miRNAs binding sites and mRNA gene regulation. Therefore, these genetic variants and miRNAs might be involved in MS susceptibility and pathogenesis and hence would be valuable for further functional verification investigation.

Multiple sclerosis is linked to MAPKERK overactivity in microglia

Reassessment of published observations in patients with multiple sclerosis (MS) suggests a microglial malfunction due to inappropriate (over)activity of the mitogen-activated protein kinase pathway ERK (MAPK^ERK). These observations regard biochemistry as well as epigenetics, and all indicate involvement of this pathway. Recent preclinical research on neurodegeneration already pointed towards a role of MAPK pathways, in particular MAPK^ERK. This is important as microglia with overactive MAPK have been identified to disturb local oligodendrocytes which can lead to locoregional demyelination, hallmark of MS. This constitutes a new concept on pathophysiology of MS, besides the prevailing view, i.e., autoimmunity. Acknowledged risk factors for MS, such as EBV infection, hypovitaminosis D, and smoking, all downregulate MAPK^ERK negative feedback phosphatases that normally regulate MAPK^ERK activity. Consequently, these factors may contribute to inappropriate MAPK^ERK overactivity, and thereby to neurodegeneration. Also, MAPK^ERK overactivity in microglia, as a factor in the pathophysiology of MS, could explain ongoing neurodegeneration in MS patients despite optimized immunosuppressive or immunomodulatory treatment. Currently, for these patients with progressive disease, no effective treatment exists. In such refractory MS, targeting the cause of overactive MAPK^ERK in microglia merits further investigation as this phenomenon may imply a novel treatment approach.

Serum Based miRNA as a Diagnostic Biomarker for Multiple Sclerosis: a Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to identify deferentially expressed serum miRNAs in multiple sclerosis patients and to evaluate their diagnostic value in multiple sclerosis diagnosis. Studies were identified on PubMed, Google scholar and Saudi digital library up to 30 September 2019. Articles that examined miRNA expression level in MS patients compared to healthy control group were included in the review and the data were extracted by three independent author. The comprehensive Meta-Analysis version 3 software was used for meta-analysis and heterogeneity of studies was identified according to I2 value. Our literatures search identified 9 eligible articles concerning the serum miRNA as a diagnostic biomarker for multiple sclerosis in comparison to healthy control group. 19 serum miRNAs differentially expressed in MS patients were identified (8 downregulated, 11 upregulated and 1 with discordant result). In publications that provided information on specific miRNA diagnostic value, the pooled AUC was 72% (95% CI 0.65-0.78, p-value 0.00) for the overall multiple sclerosis patients and primary progressive MS (PPMS) (95% CI 0.66-0.78 p-value 0.00). A miRNA panel of four miRNAs showed high sensitivity (73%) and specificity (68%) in distinguishing multiple sclerosis from control groups. When using single miRNA (miR-145), the sensitivity increased to 79% and the specificity to 87%. The available data from the literature and this meta-analysis suggests the potential use of serum miRNA as biomarkers for early diagnosis of MS with high sensitivity and specificity in distinguishing multiple sclerosis subtypes from healthy controls.Abbreviation: MS: Multiple sclerosis; IDD: inflammatory demyelinating diseases; RRMS: relapsing-remitting Multiple sclerosis; PPMS: primary progressive Multiple sclerosis; SPMS: secondary progressive Multiple sclerosis; NMO: Neuromyelitis optica; miRNA: microRNA; ECmiRNA: extracellular microRNA; AUC: Area Under the Curve; ROC: Receiver Operator Characteristic.

MicroRNA in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system (CNS). Despite a complex pathogenesis, it appears that an imbalanced immune system plays an important role in the disease process. MicroRNAs (miRNAs) are comprised of short non-coding single-stranded molecules mainly involved in regulating gene expression through the inhibition of transcription and translation. miRNAs are key regulatory molecules in the nucleus and participate in the proliferation, differentiation, and apoptosis of various cells throughout the body. Recent studies, however, have found that miRNAs are also involved in MS pathogenesis, mainly affecting glial cells and peripheral immune cells. Fortunately, miRNAs are highly stable and have high specificity in peripheral body fluids. Accordingly, these molecules have become new diagnostic and therapeutic targets. The present review discusses the role of miRNAs in the pathogenesis of MS. We highlight the potential of miRNAs as new biomarkers of MS and potential therapeutic agents.

miRNAs in Microglia: Important Players in Multiple Sclerosis Pathology

Microglia are the resident immune cells of the central nervous system and important regulators of brain homeostasis. Central to this role is a dynamic phenotypic plasticity that enables microglia to respond to environmental and pathological stimuli. Importantly, different microglial phenotypes can be both beneficial and detrimental to central nervous system health. Chronically activated inflammatory microglia are a hallmark of neurodegeneration, including the autoimmune disease multiple sclerosis (MS). By contrast, microglial phagocytosis of myelin debris is essential for resolving inflammation and promoting remyelination. As such, microglia are being explored as a potential therapeutic target for MS. MicroRNAs (miRNAs) are short non-coding ribonucleic acids that regulate gene expression and act as master regulators of cellular phenotype and function. Dysregulation of certain miRNAs can aberrantly activate and promote specific polarisation states in microglia to modulate their activity in inflammation and neurodegeneration. In addition, miRNA dysregulation is implicated in MS pathogenesis, with circulating biomarkers and lesion specific miRNAs identified as regulators of inflammation and myelination. However, the role of miRNAs in microglia that specifically contribute to MS progression are still largely unknown. miRNAs are being explored as therapeutic agents, providing an opportunity to modulate microglial function in neurodegenerative diseases such as MS. This review will focus firstly on elucidating the complex role of microglia in MS pathogenesis. Secondly, we explore the essential roles of miRNAs in microglial function. Finally, we focus on miRNAs that are implicated in microglial processes that contribute directly to MS pathology, prioritising targets that could inform novel therapeutic approaches to MS.

A hypothesis-generating scoping review of miRs identified in both multiple sclerosis and dementia, their protein targets, and miR signaling pathways

Cognitive impairment (CI) is a frequent complication affecting people with multiple sclerosis (MS). The causes of CI in MS are not fully understood. Besides MRI measures, few other biomarkers exist to help us predict the development of CI and understand its biology. MicroRNAs (miRs) are relatively stable, non-coding RNA molecules about 22 nucleotides in length that can serve as biomarkers and possible therapeutic targets in several autoimmune and neurodegenerative diseases, including the dementias. In this review, we identify dysregulated miRs in MS that overlap with dysregulated miRs in cognitive disorders and dementia and explore how these overlapping miRs play a role in CI in MS. MiR-15, miR-21, miR-128, miR-132, miR-138, miR-142, miR-146a, miR-155, miR-181, miR-572, and let-7 are known to contribute to various forms of dementia and show abnormal expression in MS. These overlapping miRs are involved in pathways related to apoptosis, neuroinflammation, glutamate toxicity, astrocyte activation, microglial burst activity, synaptic dysfunction, and remyelination. The mechanisms of action suggest that these miRs may be related to CI in MS. From our review, we also delineated miRs that could be neuroprotective in MS, namely miR-23a, miR-219, miR-214, and miR-22. Further studies can help clarify if these miRs are responsible for CI in MS, leading to potential therapeutic targets.

The role of microRNAs in multiple sclerosis

Despite numerous studies on multiple sclerosis (MS) and understanding many aspects of this disease, researchers still struggle to find proper biomarkers that facilitate diagnosis; prognosis and monitoring of treatment efficacy in MS. MicroRNAs (miRNAs) are considered as endogenous, comparatively stable and small non-coding RNAs involved in various biological and pathological signaling pathways. Interestingly, miRNAs have been emerged as a potential biomarker for monitoring novel therapies in MS patients. In this review, we described the miRNAs alteration in the MS patients as well as their altered expression in patients under common MS therapies.

The Role of MicroRNAs in Repair Processes in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disorder characterised by demyelination of central nervous system neurons with subsequent damage, cell death and disability. While mechanisms exist in the CNS to repair this damage, they are disrupted in MS and currently there are no treatments to address this deficit. In recent years, increasing attention has been paid to the influence of the small, non-coding RNA molecules, microRNAs (miRNAs), in autoimmune disorders, including MS. In this review, we examine the role of miRNAs in remyelination in the different cell types that contribute to MS. We focus on key miRNAs that have a central role in mediating the repair process, along with several more that play either secondary or inhibitory roles in one or more aspects. Finally, we consider the current state of miRNAs as therapeutic targets in MS, acknowledging current challenges and potential strategies to overcome them in developing effective novel therapeutics to enhance repair mechanisms in MS.

Epigenetics in Multiple Sclerosis

Multiple sclerosis (MS) is an aggravating autoimmune disease that cripples young patients slowly with physical, sensory and cognitive deficits. The break of self-tolerance to neuronal antigens is the key to the pathogenesis of MS, with autoreactive T cells causing demyelination that subsequently leads to inflammation-mediated neurodegenerative events in the central nervous system. The exact etiology of MS remains elusive; however, the interplay of genetic and environmental factors contributes to disease development and progression. Given that genetic variation only accounts for a fraction of risk for MS, extrinsic risk factors including smoking, infection and lack of vitamin D or sunshine, which cause changes in gene expression, contribute to disease development through epigenetic regulation. To date, there is a growing body of scientific evidence to support the important roles of epigenetic processes in MS. In this chapter, the three main layers of epigenetic regulatory mechanisms, namely DNA methylation, histone modification and microRNA-mediated gene regulation, will be discussed, with a particular focus on the role of epigenetics on dysregulated immune responses and neurodegenerative events in MS. Also, the potential for epigenetic modifiers as biomarkers and therapeutics for MS will be reviewed.

microRNAs: key modulators of disease-modifying therapies in multiple sclerosis

There is a high level of heterogeneity in symptom manifestations and response to disease-modifying therapies (DMTs) in multiple sclerosis (MS), an immune-based neurodegenerative disease with ever-increasing prevalence in recent decades. Because of unknown aspects of the etiopathology of MS and mechanism of action of DMTs, the reason for this variability is undetermined, and much remains to be understood. Traditionally, physicians consider switching to other DMTs based on the exacerbation of symptoms and/or change in the results of magnetic resonance imaging and biochemical factors. Therefore, identifying biological treatment response markers that help us recognizing non-responders rapidly and subsequently choosing another DMTs is necessary. microRNAs (miRNAs) are micromanagers of gene expression which have been profiled in different samples of MS patients, highlighting their role in pathogenetic of MS. Recent studies have investigated expression profiling of miRNAs after treatment with DMTs to clarify possible DMTs-mediated mechanism and obtaining response to therapy biomarkers. In this review, we will discuss the modulation of miRNAs by DMTs in cells and pathways involved in MS.

Early diagnosis of secondary progressive multiple sclerosis: focus on fluid and neurophysiological biomarkers

BACKGROUND AND AIMS

Most patients with multiple sclerosis presenting with a relapsing-remitting disease course at diagnosis transition to secondary progressive multiple sclerosis (SPMS) 1-2 decades after onset. SPMS is characterized by predominant neurodegeneration and atrophy. These pathogenic hallmarks result in unsatisfactory treatment response in SPMS patients. Therefore, early diagnosis of SPMS is necessary for prompt treatment decisions. The aim of this review was to assess neurophysiological and fluid biomarkers that have the potential to monitor disease progression and support early SPMS diagnosis.

METHODS

We performed a systematic review of studies that analyzed the role of neurophysiological techniques and fluid biomarkers in supporting SPMS diagnosis using the preferred reporting items for systematic reviews and meta-analyses statement.

RESULTS

From our initial search, we selected 24 relevant articles on neurophysiological biomarkers and 55 articles on fluid biomarkers.

CONCLUSION

To date, no neurophysiological or fluid biomarker is sufficiently validated to support the early diagnosis of SPMS. Neurophysiological measurements, including short interval intracortical inhibition and somatosensory temporal discrimination threshold, and the neurofilament light chain fluid biomarker seem to be the most promising. Cross-sectional studies on an adequate number of patients followed by longitudinal studies are needed to confirm the diagnostic and prognostic value of these biomarkers. A combination of neurophysiological and fluid biomarkers may be more sensitive in detecting SPMS conversion.

A Meta-Analytic Review of the Value of miRNA for Multiple Sclerosis Diagnosis

Backgrounds and Purpose: Multiple sclerosis (MS) is an immune-mediated chronic inflammatory demyelinating disease of the central nervous system. The etiology of MS is unclear, disease diagnosis mainly based on symptoms, and lacks effective laboratory test index. Circulating microRNAs (miRNAs) as sensitive biomarkers have been widely studied, the expression levels of certain miRNAs are dynamically changed in MS patients. This meta-analysis aims to assess the overall diagnostic accuracy of circulating miRNAs for MS.

Methods: We searched PubMed, EMBASE, Cochrane Library, CNKI databases as of July 20, 2019. QUADAS was used to assess the quality of included studies. All studies were processed by Stata 15.0 software. Eleven articles with 600 patients with MS and 389 controls were included.

Results: The sensitivity and specificity, PLR, NLR, and DOR of the overall studies were 0.81 (95% CI 0.77–0.84), 0.75 (95% CI 0.68–0.81), 3.3 (95% CI 2.5–4.3), 0.25 (95% CI 0.20–0.32), 13 (95% CI: 8–20), and 0.85 (95% CI 0.82–0.88). Subgroup analysis indicated that miRNA assay had higher diagnostic accuracy for relapsing-remitting MS (RRMS) when compared with other MS subtypes.

Conclusion: Our study performed a meta-analysis to generate an estimate of the relevance of miRNA change and the occurrence of MS, and revealed circulating miRNAs has the potential to be used for MS diagnosis, especially for RRMS. Future studies should clarify to which specific miRNAs can accurately diagnose disease subtypes. The miRNA-related pathogenesis may provide theoretical basis for drug development for early intervention.

MicroRNAs in gray and white matter multiple sclerosis lesions: impact on pathophysiology

Multiple sclerosis (MS) is a chronic disease of the CNS, hallmarked by inflammation and demyelination. Early stages of the disease frequently show active lesions containing numerous foamy macrophages and inflammatory cells. Disease progression is highlighted by increasing numbers of mixed active/inactive or inactive lesions showing sparse inflammation and pronounced astrogliosis. Furthermore, gray matter lesions increase in number and extent during disease progression. MicroRNAs (miRNAs) comprise a group of several thousand (in humans more than 2000), small non-coding RNA molecules with a fundamental influence on about one-third of all protein-coding genes. Furthermore, miRNAs have been detected in body fluids, including spinal fluid, and they are assumed to participate in intercellular communications. Several studies have determined miRNA profiles from dissected white and gray matter lesions of autoptic MS patients. In this review, we summarize in detail the current knowledge of individual miRNAs in gray and white matter lesions of MS patients and present the concepts of MS tissue lesion development based on the altered miRNA profiles. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

MicroRNAs in blood and cerebrospinal fluid as diagnostic biomarkers of multiple sclerosis and to monitor disease progression

Multiple sclerosis is a chronic autoimmune disease of the central nervous system. It is the main cause of non-traumatic neurological disability in young adults. Multiple sclerosis mostly affects people aged 20-50 years; however, it can occur in young children and much older adults. Factors identified in the distribution of MS include age, gender, genetics, environment, and ethnic background. Multiple sclerosis is usually associated with progressive degrees of disability. The disease involves demyelination of axons of the central nervous system and causes brain and spinal cord neuronal loss and atrophy. Diagnosing multiple sclerosis is based on a patient's medical history including symptoms, physical examination, and various tests such as magnetic resonance imaging, cerebrospinal fluid and blood tests, and electrophysiology. The disease course of multiple sclerosis is not well correlated with the biomarkers presently used in clinical practice. Blood-derived biomarkers that can detect and distinguish the different phenotypes in multiple sclerosis may be advantageous in personalized treatment with disease-modifying drugs and to predict response to treatment. The studies reviewed have shown that the expression levels of a large number of miRNAs in peripheral blood, serum, exosomes isolated from serum, and cerebrospinal fluid are altered in multiple sclerosis and can distinguish the disease phenotypes from each other. Further studies are warranted to independently validate these findings so that individual or pairs of miRNAs in serum or cerebrospinal fluid can be used as potential diagnostic markers for adult and pediatric multiple sclerosis and for monitoring disease progression and response to therapy.

MicroRNA profiles of MS gray matter lesions identify modulators of the synaptic protein synaptotagmin-7

We established microRNA (miRNA) profiles in gray and white matter multiple sclerosis (MS) lesions and identified seven miRNAs which were significantly more upregulated in the gray matter lesions. Five of those seven miRNAs, miR‐330‐3p, miR‐4286, miR‐4488, let‐7e‐5p, miR‐432‐5p shared the common target synaptotagmin7 (Syt7). Immunohistochemistry and transcript analyses using nanostring technology revealed a maldistribution of Syt7, with Syt7 accumulation in neuronal soma and decreased expression in axonal structures. This maldistribution could be at least partially explained by an axonal Syt7 transport disturbance. Since Syt7 is a synapse‐associated molecule, this maldistribution could result in impairment of neuronal functions in MS patients. Thus, our results lead to the hypothesis that the overexpression of these five miRNAs in gray matter lesions is a cellular mechanism to reduce further endogenous neuronal Syt7 production. Therefore, miRNAs seem to play an important role as modulators of neuronal structures in MS.

Extracellular RNA in Central Nervous System Pathologies

The discovery of extracellular RNA (exRNA) has shifted our understanding of the role of RNA in complex cellular functions such as cell-to-cell communication and a variety of pathologies. ExRNAs constitute a heterogenous group of RNAs ranging from small (such as microRNAs) and long non-coding to coding RNAs or ribosomal RNAs. ExRNAs can be liberated from cells in a free form or bound to proteins as well as in association with microvesicles (MVs), exosomes, or apoptotic bodies. Their composition and quantity depend heavily on the cellular or non-cellular component, the origin, and the RNA species being investigated; ribosomal RNA provides the majority of exRNA and miRNAs are predominantly associated with exosomes or MVs. Several studies showed that ribosomal exRNA (rexRNA) constitutes a proinflammatory and prothrombotic alarmin. It is released by various cell types upon inflammatory stimulation and by damaged cells undergoing necrosis or apoptosis and contributes to innate immunity responses. This exRNA has the potential to directly promote the release of cytokines such as tumor necrosis factor factor-α (TNF-α) or interleukin-6 from immune cells, thereby leading to a proinflammatory environment and promoting cardiovascular pathologies. The potential role of exRNA in different pathologies of the central nervous system (CNS) has become of increasing interest in recent years. Although various exRNA species including both ribosomal exRNA as well as miRNAs have been associated with CNS pathologies, their precise roles remain to be further elucidated. In this review, the different entities of exRNA and their postulated roles in CNS pathologies including tumors, vascular pathologies and neuroinflammatory diseases will be discussed. Furthermore, the potential role of exRNAs as diagnostic markers for specific CNS diseases will be outlined, as well as possible treatment strategies addressing exRNA inhibition or interference.

Decoding the Role of Platelets and Related MicroRNAs in Aging and Neurodegenerative Disorders

Platelets are anucleate cells that circulate in blood and are essential components of the hemostatic system. During aging, platelet numbers decrease and their aggregation capacity is reduced. Platelet dysfunctions associated with aging can be linked to molecular alterations affecting several cellular systems that include cytoskeleton rearrangements, signal transduction, vesicular trafficking, and protein degradation. Age platelets may adopt a phenotype characterized by robust secretion of extracellular vesicles that could in turn account for about 70-90% of blood circulating vesicles. Interestingly these extracellular vesicles are loaded with messenger RNAs and microRNAs that may have a profound impact on protein physiology at the systems level. Age platelet dysfunction is also associated with accumulation of reactive oxygen species. Thereby understanding the mechanisms of aging in platelets as well as their age-dependent dysfunctions may be of interest when evaluating the contribution of aging to the onset of age-dependent pathologies, such as those affecting the nervous system. In this review we summarize the findings that link platelet dysfunctions to neurodegenerative diseases including Alzheimer's Disease, Parkinson's Disease, Multiple Sclerosis, Huntington's Disease, and Amyotrophic Lateral Sclerosis. We discuss the role of platelets as drivers of protein dysfunctions observed in these pathologies, their association with aging and the potential clinical significance of platelets, and related miRNAs, as peripheral biomarkers for diagnosis and prognosis of neurodegenerative diseases.

Circular RNAs as a novel layer of regulatory mechanism in multiple sclerosis

Multiple sclerosis (MS) is believed to be an autoimmune disease of the central nervous system (CNS) in which autoreactive immune cells recognizing myelin antigens lead to demyelination and axonal injury. Mechanisms inducing and controlling the pathogenesis of MS have not been fully elucidated. Recent studies suggest an important role of epigenetic processes during the development of MS. One of the most significant discoveries in the field of epigenetic contribution to immune response has been the recognition of a group of microRNAs (miRNAs). These single-stranded non-coding RNA molecules regulate the expression of genes encoding proteins and have already been shown to be involved in pathogenesis of MS. Some miRNAs enhance generation of pro-inflammatory immune cells by promoting Th1 and Th17 pathways and others contribute to regulatory and tissue repair processes. The miRNA-dependent controlling process of autoimmune reactions is highly complex because of miRNA redundancy and multitarget nature of most of these molecules. Recently it was discovered that circular RNAs (circRNA) representing a new class of RNA possess a unique ability to control miRNAs by blocking their activity. CircRNAs are called natural miRNA "sponges" as the single circRNA molecule is able to neutralize several miRNAs and thus might determine the availability of miRNAs for their posttranscription regulation. Thus, circRNAs emerged as critical factors in epigenetic regulation of many human diseases including MS. In addition, in contrary to other RNA species they are very stable in the blood and other biological fluids and thus might be considered as a candidate for a biomarker of MS.

Downregulation of miR-145-5p contributes to hyperproliferation of keratinocytes and skin inflammation in psoriasis

BACKGROUND

The extensive involvement of microRNAs (miRNAs) in the pathogenesis of psoriasis is well documented. However, little is known about the contribution of specific miRNAs to the prevalence of this disease.

OBJECTIVES

To explore the role of miR-145-5p in psoriasis.

METHODS

miRNA microarray analysis was performed in four patients with psoriasis and four controls. Quantitative reverse-transcriptase polymerase chain reaction and fluorescence in situ hybridization were used to identify the dysregulated miRNAs. Luciferase assays were performed to determine whether miR-145-5p targets mixed-lineage kinase (MLK)3. CCK-8 assay and Magnetic Luminex Assay were performed to measure cell proliferation and chemokine secretion. Western blot analysis was used to investigate the protein levels of MLK3 and its downstream effectors. Mouse models of psoriasis were established for in vivo experiments.

RESULTS

miR-145-5p was downregulated in psoriatic lesional skin. Luciferase assays showed that MLK3 is a direct target of miR-145-5p. Overexpression of miR-145-5p in normal human epidermal keratinocytes (NHEKs) suppressed cell proliferation and secretion of chemokines. In contrast, silencing miR-145-5p promoted NHEK proliferation and increased chemokine secretion. Silencing MLK3 abrogated miR-145-5p inhibitor-induced promotion of cell proliferation and chemokine expression. miR-145-5p regulates nuclear factor-κB and signal transducer and activator of transcription 3 by targeting MLK3. Delivery of agomiR-145-5p into the skin decreased epidermal hyperplasia and ameliorated psoriasis-like dermatitis. Delivery of antagomiR-145-5p led to the opposite effects.

CONCLUSIONS

Our findings indicate that miR-145-5p negatively regulates proliferation and chemokine secretion of NHEKs by targeting MLK3, and downregulation of miR-145-5p contributes to skin inflammation in psoriasis lesions.

Increased expression of mir-301a in PBMCs of patients with relapsing-remitting multiple sclerosis is associated with reduced NKRF and PIAS3 expression levels and disease activity

Most of the multiple sclerosis (MS) patients are initially diagnosed with relapsing remitting multiple sclerosis (RRMS). Th17 cells and macrophages have been shown to play critical roles in pathogenesis of MS and initiation of CNS tissue damage. MiR-301a have recently been exposed as an activator of STAT3 in Th17 cells as well as an activator of NF-κB in macrophages by targeting PIAS3 and NKRF correspondingly. However, the possible role of miR-301a in RRMS has not yet been elucidated. Herewith, for the first time, we have studied the expression of miR-301a, NKRF and PIAS3 by quantitative real-time PCR and western blotting method in peripheral blood mononuclear cells (PBMCs) of 71 RRMS patients, including two groups of patients in relapse phase (n = 44) and a group of remitting phase patients (n = 28) in comparison to healthy volunteers (n = 28). In this work, we demonstrate a significant upregulation of miR-301a in relapse phase of MS patients compared to healthy controls and remitting phase patients (P < .05). Our findings also showed a striking decrease of NKRF and PIAS3 expression in relapse phase patients, in contrast to miR-301a and, NF-κB and STAT3 downstream genes (SKA2 and RORc) (P < .05). Subsequently, using luciferase reporter system we confirmed that miR-301a directly targets the mRNA encoding PIAS3 and NKRF proteins. We also showed that miR-301a increasing expression is correlated with down-regulation of PIAS3 and NKRF expression in RRMS patients. Our findings suggest that miR-301a, PIAS3 and NKRF play crucial roles in RRMS and could be considered as promising therapeutic targets.

MiR-409-3p and MiR-1896 co-operatively participate in IL-17-induced inflammatory cytokine production in astrocytes and pathogenesis of EAE mice via targeting SOCS3/STAT3 signaling

Th17 cells and interleukin-17 (IL-17) have been found to play an important role in the pathology of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Response to IL-17, reactive astrocytes accompany with immune cells infiltration and axonal damage in MS/EAE. However, the role and the regulatory mechanism of IL-17-activated astrocytes in inflammation and in the EAE process still remain largely unknown. Here, we elucidated that miR-409-3p and miR-1896, as co-upregulated microRNAs in activated astrocytes and in EAE mice, targeted suppressor of cytokine signaling proteins 3 (SOCS3). Overexpression of miR-409-3p or miR-1896 significantly reduced SOCS3 expression and increased phosphorylation of STAT3 as well as induced the inflammatory cytokines production (IL-1β, IL-6, IP-10, MCP-1, and KC), CD4⁺ T cells migration and demyelination, in turn aggravating EAE development. Importantly, the effects of co-overexpression of miR-409-3p and miR-1896 in vitro or in vivo are strongly co-operative. In contrast, simultaneously silenced miR-409-3p and miR-1896 co-operatively ameliorates inflammation and demyelination in the central nervous system of EAE mice. Collectively, our findings highlight that miR-409-3p and miR-1896 co-ordinately promote the production of inflammatory cytokines in reactive astrocytes through the SOCS3/STAT3 pathway and enhance reactive astrocyte-directed chemotaxis of CD4⁺ T cells, leading to aggravate pathogenesis in EAE mice. Co-inhibition of miR-409-3p and miR-1896 may be a therapeutic target for treating MS and neuroinflammation.

Identification of MS-specific serum miRNAs in an international multicenter study

Objective

To identify circulating microRNAs (miRNAs) linked to disease, disease stage, and disability in MS across cohorts.

Methods

Samples were obtained from the Comprehensive Longitudinal Investigation of Multiple Sclerosis (CLIMB, Boston, MA), EPIC (San Francisco, CA), AMIR (Beirut, Lebanon) as part of the SUMMIT consortium, and Stockholm Prospective Assessment of Multiple Sclerosis (Stockholm, Sweden) cohorts. Serum miRNA expression was measured using locked nucleic acid–based quantitative PCR. Four groups were compared: (1) MS vs healthy control (HC), (2) relapsing-remitting (RR) vs HC, (3) secondary progressive (SP) vs HC, and (4) RR vs SP. A Wilcoxon rank-sum test was used for the comparisons. The association between each miRNA and the Expanded Disability Status Scale (EDSS) score was assessed using the Spearman correlation coefficient. For each comparison, the p values were corrected for multiple comparisons using the approach of Benjamini and Hochberg to control the false discovery rate.

Results

In the CLIMB cohort, 5 miRNAs (hsa-miR-484, hsa-miR-140-5p, hsa-miR-320a, hsa-miR-486-5p, and hsa-miR-320c) showed a significant difference between patients with MS and healthy individuals; among these, miR-484 remained significant after accounting for multiple comparisons (p = 0.01). When comparing RRMS with HCs, hsa-miR-484 showed a significant difference (p = 0.004) between the groups after accounting for multiple group comparisons. When SP and HC were compared, 6 miRNAs (hsa-miR-484, hsa-miR-140-5p, hsa-miR-142-5p, hsa-miR-320a, hsa-miR-320b, and hsa-miR-320c) remained significantly different after accounting for multiple comparisons. Disability correlation analysis with miRNA provided 4 miRNAs (hsa-miR-320a, hsa-miR-337-3p, hsa-miR-199a-5p, and hsa-miR-142-5p) that correlated with the EDSS during the internal reproducibility phase. Among these, hsa-miR-337-3p was the most statistically significant miRNA that negatively correlated with the EDSS in three of the MS cohorts tested.

Conclusions

These findings further confirm the use of circulating serum miRNAs as biomarkers to diagnose and monitor disease status in MS.

Classification of evidence

This study provides Class III evidence that levels of circulating miRNAs identify patients with MS.

Evaluation of serum miR-191-5p, miR-24-3p, miR-128-3p, and miR-376c-3 in multiple sclerosis patients

BACKGROUND

Biomarkers that could be used in early diagnosis of multiple sclerosis (MS), segregation of disease subtypes, and discrimination of the aggressive disease course from the benign one are urgently needed.

OBJECTIVE

The aim of this study was to investigate the specificity of circulating microRNAs: miR-191-5p, miR-128-3p, miR-24-3p, and miR-376c-3p in MS and evaluate their association with disease activity and disability progression.

METHODS

The expressions of circulating miRNAs were studied in serum of 100 subjects (53 relapsing-remitting (RRMS), 20 primary progressive (PPMS), and 27 controls), using miScript serum miRNA RT-PCR assay techniques.

RESULTS

In comparison with controls, miR-191-5p and miR-24-3p were overexpressed in RRMS and PPMS, with no differences between the subtypes. miR-24-3p correlated positively with the disability progression index in the combined group of all patients with MS. miR-128-3p showed tendency toward the predominant expression in PPMS and correlated positively with the annual relapse rate in RRMS. miR-376c-3p expression levels did not differ between the groups, and no associations were found to clinical parameters.

CONCLUSION

This study highlighted the connection of circulating miRNAs to MS. miR-24-3p and miR-128-3p showed a tendency of association with disability accumulation and disease activity, respectively. Further studies should evaluate their suitability for clinical use.