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

Loss of microRNA-15a/16-1 function promotes neuropathological and functional recovery in experimental traumatic brain injury

The diffuse axonal damage in white matter and neuronal loss, along with excessive neuroinflammation, hinder long-term functional recovery after traumatic brain injury (TBI). MicroRNAs (miRs) are small noncoding RNAs that negatively regulate protein-coding target genes in a posttranscriptional manner. Recent studies have shown that loss of function of the miR-15a/16-1 cluster reduced neurovascular damage and improved functional recovery in ischemic stroke and vascular dementia. However, the role of the miR-15a/16-1 cluster in neurotrauma is poorly explored. Here, we report that genetic deletion of the miR-15a/16-1 cluster facilitated the recovery of sensorimotor and cognitive functions, alleviated white matter/gray matter lesions, reduced cerebral glial cell activation, and inhibited infiltration of peripheral blood immune cells to brain parenchyma in a murine model of TBI when compared with WT controls. Moreover, intranasal delivery of the miR-15a/16-1 antagomir provided similar brain-protective effects conferred by genetic deletion of the miR-15a/16-1 cluster after experimental TBI, as evidenced by showing improved sensorimotor and cognitive outcomes, better white/gray matter integrity, and less inflammatory responses than the control antagomir-treated mice after brain trauma. miR-15a/16-1 genetic deficiency and miR-15a/16-1 antagomir also significantly suppressed inflammatory mediators in posttrauma brains. These results suggest miR-15a/16-1 as a potential therapeutic target for TBI.

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.

Cladribine and ocrelizumab induce differential miRNA profiles in peripheral blood mononucleated cells from relapsing-remitting multiple sclerosis patients

Background and objectives

Multiple sclerosis (MS) is a chronic, progressive neurological disease characterized by early-stage neuroinflammation, neurodegeneration, and demyelination that involves a spectrum of heterogeneous clinical manifestations in terms of disease course and response to therapy. Even though several disease-modifying therapies (DMTs) are available to prevent MS-related brain damage-acting on the peripheral immune system with an indirect effect on MS lesions-individualizing therapy according to disease characteristics and prognostic factors is still an unmet need. Given that deregulated miRNAs have been proposed as diagnostic tools in neurodegenerative/neuroinflammatory diseases such as MS, we aimed to explore miRNA profiles as potential classifiers of the relapsing-remitting MS (RRMS) patients' prospects to gain a more effective DMT choice and achieve a preferential drug response.

Methods

A total of 25 adult patients with RRMS were enrolled in a cohort study, according to the latest McDonald criteria before (pre-cladribine, pre-CLA; pre-ocrelizumab, pre-OCRE, time T0) and after high-efficacy DMTs, time T1, 6 months post-CLA (n = 10, 7 F and 3 M, age 39.0 ± 7.5) or post-OCRE (n = 15, 10 F and 5 M, age 40.5 ± 10.4) treatment. A total of 15 age- and sex-matched healthy control subjects (9 F and 6 M, age 36.3 ± 3.0) were also selected. By using Agilent microarrays, we analyzed miRNA profiles from peripheral blood mononuclear cells (PBMC). miRNA-target networks were obtained by miRTargetLink, and Pearson's correlation served to estimate the association between miRNAs and outcome clinical features.

Results

First, the miRNA profiles of pre-CLA or pre-OCRE RRMS patients compared to healthy controls identified modulated miRNA patterns (40 and seven miRNAs, respectively). A direct comparison of the two pre-treatment groups at T0 and T1 revealed more pro-inflammatory patterns in the pre-CLA miRNA profiles. Moreover, both DMTs emerged as being capable of reverting some dysregulated miRNAs toward a protective phenotype. Both drug-dependent miRNA profiles and specific miRNAs, such as miR-199a-3p, miR-29b-3p, and miR-151a-3p, emerged as potentially involved in these drug-induced mechanisms. This enabled the selection of miRNAs correlated to clinical features and the related miRNA-mRNA network.

Discussion

These data support the hypothesis of specific deregulated miRNAs as putative biomarkers in RRMS patients' stratification and DMT drug response.

Whole blood miRNAs in relapsing MS patients treated with dimethyl fumarate in the phase 4 TREMEND trial

We investigated the impact of dimethyl fumarate (DMF), an oral therapy for relapsing multiple sclerosis (MS), on blood microRNA (miRNA) signatures and neurofilament light (NFL) levels. DMF normalized miR-660-5p and modulated various miRNAs associated with the NF-kB pathway. These alterations reached a peak 4-7 months after treatment. Notably, particular miRNAs correlated with high or low NFL levels, implying their potential role as markers of treatment efficacy. Our findings broaden the understanding of DMF's immunomodulatory effects and may aid in predicting treatment responses.

In silico prioritisation of microRNA-associated common variants in multiple sclerosis

BACKGROUND

Genome-wide association studies (GWAS) have highlighted over 200 autosomal variants associated with multiple sclerosis (MS). However, variants in non-coding regions such as those encoding microRNAs have not been explored thoroughly, despite strong evidence of microRNA dysregulation in MS patients and model organisms. This study explores the effect of microRNA-associated variants in MS, through the largest publicly available GWAS, which involved 47,429 MS cases and 68,374 controls.

METHODS

We identified SNPs within the coordinates of microRNAs, ± 5-kb microRNA flanking regions and predicted 3'UTR target-binding sites using miRBase v22, TargetScan 7.0 RNA22 v2.0 and dbSNP v151. We established the subset of microRNA-associated SNPs which were tested in the summary statistics of the largest MS GWAS by intersecting these datasets. Next, we prioritised those microRNA-associated SNPs which are among known MS susceptibility SNPs, are in strong linkage disequilibrium with the former or meet a microRNA-specific Bonferroni-corrected threshold. Finally, we predicted the effects of those prioritised SNPs on their microRNAs and 3'UTR target-binding sites using TargetScan v7.0, miRVaS and ADmiRE.

RESULTS

We have identified 30 candidate microRNA-associated variants which meet at least one of our prioritisation criteria. Among these, we highlighted one microRNA variant rs1414273 (MIR548AC) and four 3'UTR microRNA-binding site variants within SLC2A4RG (rs6742), CD27 (rs1059501), MMEL1 (rs881640) and BCL2L13 (rs2587100). We determined changes to the predicted microRNA stability and binding site recognition of these microRNA and target sites.

CONCLUSIONS

We have systematically examined the functional, structural and regulatory effects of candidate MS variants among microRNAs and 3'UTR targets. This analysis allowed us to identify candidate microRNA-associated MS SNPs and highlights the value of prioritising non-coding RNA variation in GWAS. These candidate SNPs could influence microRNA regulation in MS patients. Our study is the first thorough investigation of both microRNA and 3'UTR target-binding site variation in multiple sclerosis using GWAS summary statistics.

Impact of the Voltage-Gated Calcium Channel Antagonist Nimodipine on the Development of Oligodendrocyte Precursor Cells

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). While most of the current treatment strategies focus on immune cell regulation, except for the drug siponimod, there is no therapeutic intervention that primarily aims at neuroprotection and remyelination. Recently, nimodipine showed a beneficial and remyelinating effect in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Nimodipine also positively affected astrocytes, neurons, and mature oligodendrocytes. Here we investigated the effects of nimodipine, an L-type voltage-gated calcium channel antagonist, on the expression profile of myelin genes and proteins in the oligodendrocyte precursor cell (OPC) line Oli-Neu and in primary OPCs. Our data indicate that nimodipine does not have any effect on myelin-related gene and protein expression. Furthermore, nimodipine treatment did not result in any morphological changes in these cells. However, RNA sequencing and bioinformatic analyses identified potential micro (mi)RNA that could support myelination after nimodipine treatment compared to a dimethyl sulfoxide (DMSO) control. Additionally, we treated zebrafish with nimodipine and observed a significant increase in the number of mature oligodendrocytes (* p≤ 0.05). Taken together, nimodipine seems to have different positive effects on OPCs and mature oligodendrocytes.

miRNA Signature in CSF From Patients With Primary Progressive Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Primary progressive multiple sclerosis (PPMS) displays a highly variable disease progression with a characteristic accumulation of disability, what makes difficult its diagnosis and efficient treatment. The identification of microRNAs (miRNAs)-based signature for the early detection in biological fluids could reveal promising biomarkers to provide new insights into defining MS clinical subtypes and potential therapeutic strategies. The objective of this cross-sectional study was to describe PPMS miRNA profiles in CSF and serum samples compared with other neurologic disease individuals (OND) and relapsing-remitting MS (RRMS).

METHODS

First, a screening stage analyzing multiple miRNAs in few samples using OpenArray plates was performed. Second, individual quantitative polymerase chain reactions (qPCRs) were used to validate specific miRNAs in a greater number of samples.

RESULTS

A specific profile of dysregulated circulating miRNAs (let-7b-5p and miR-143-3p) was found downregulated in PPMS CSF samples compared with OND. In addition, in serum samples, miR-20a-5p and miR-320b were dysregulated in PPMS against RRMS and OND, miR-26a-5p and miR-485-3p were downregulated in PPMS vs RRMS, and miR-142-5p was upregulated in RRMS compared with OND.

DISCUSSION

We described a 2-miRNA signature in CSF of PPMS individuals and several dysregulated miRNAs in serum from patients with MS, which could be considered valuable candidates to be further studied to unravel their actual role in MS.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that specific miRNA profiles accurately distinguish PPMS from RRMS and other neurologic disorders.

Significant Association of rs77493513 Polymorphism in 3'-UTR of the NRG1 Gene with the Risk of Multiple Sclerosis Disease

Multiple sclerosis (MS) is a chronic inflammatory and autoimmune disease characterized by demyelination of the central nervous system (CNS). Neuregulin 1 (NRG1) is a signaling protein that plays an important role in a variety of biological processes, including potentiate oligodendrocyte differentiation and myelination in the CNS, immune response regulation, and inflammation. Single nucleotide polymorphism (SNP) rs77493513 is located in the untranslated region of the 3' mRNA (3'-UTR) of the NRG1 gene, which is predicted to be the binding site of several microRNAs and may play an important role in post-transcriptional regulation. Study aimed to investigate the association of SNP rs77493513 in the NRG1 gene with the risk of MS disease. In this study, genomic DNA was extracted from whole blood samples of 182 patients with relapsing-remitting multiple sclerosis (RRMS) and 198 controls. Different genotypes of rs77493513 polymorphism were determined using RFLP-PCR technique. Statistical analysis was performed using SPSS 21.0 software and by t, χ2 and logistic regression tests. Our data showed that genotypes AC (OR=3.63, CI= 1.93-6.81, p<0.001) and CC (OR=7.90, CI= 4.13-15.11, p<0.001) significantly increased the risk of MS disease and C allele is risk allele. Also, AC (OR=0.16, CI= 0.04-0.63, p= 0.009) and CC (OR=0.14, CI= 0.03-0.53, p=0.04) genotypes significantly decrease the age of onset of the disease. The results show that allele C of rs77493513 polymorphism in the NRG1 gene can be a risk factor for MS.

Newly Identified Deficiencies in the Multiple Sclerosis Central Nervous System and Their Impact on the Remyelination Failure

The pathogenesis of multiple sclerosis (MS) remains enigmatic and controversial. Myelin sheaths in the central nervous system (CNS) insulate axons and allow saltatory nerve conduction. MS brings about the destruction of myelin sheaths and the myelin-producing oligodendrocytes (ODCs). The conundrum of remyelination failure is, therefore, crucial in MS. In this review, the roles of epidermal growth factor (EGF), normal prions, and cobalamin in CNS myelinogenesis are briefly summarized. Thereafter, some findings of other authors and ourselves on MS and MS-like models are recapitulated, because they have shown that: (a) EGF is significantly decreased in the CNS of living or deceased MS patients; (b) its repeated administration to mice in various MS-models prevents demyelination and inflammatory reaction; (c) as was the case for EGF, normal prion levels are decreased in the MS CNS, with a strong correspondence between liquid and tissue levels; and (d) MS cobalamin levels are increased in the cerebrospinal fluid, but decreased in the spinal cord. In fact, no remyelination can occur in MS if these molecules (essential for any form of CNS myelination) are lacking. Lastly, other non-immunological MS abnormalities are reviewed. Together, these results have led to a critical reassessment of MS pathogenesis, partly because EGF has little or no role in immunology.

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.

Non-coding RNAs and their bioengineering applications for neurological diseases

Engineering of cellular biomolecules is an emerging landscape presenting creative therapeutic opportunities. Recently, several strategies such as biomimetic materials, drug-releasing scaffolds, stem cells, and dynamic culture systems have been developed to improve specific biological functions, however, have been confounded with fundamental and technical roadblocks. Rapidly emerging investigations on the bioengineering prospects of mammalian ribonucleic acid (RNA) is expected to result in significant biomedical advances. More specifically, the current trend focuses on devising non-coding (nc) RNAs as therapeutic candidates for complex neurological diseases. Given the pleiotropic and regulatory role, ncRNAs such as microRNAs and long non-coding RNAs are deemed as attractive therapeutic candidates. Currently, the list of non-coding RNAs in mammals is evolving, which presents the plethora of hidden possibilities including their scope in biomedicine. Herein, we critically review on the emerging repertoire of ncRNAs in neurological diseases such as Alzheimer’s disease, Parkinson’s disease, neuroinflammation and drug abuse disorders. Importantly, we present the advances in engineering of ncRNAs to improve their biocompatibility and therapeutic feasibility as well as provide key insights into the applications of bioengineered non-coding RNAs that are investigated for neurological diseases.

MicroRNAs, Multiple Sclerosis, and Depression

Multiple sclerosis (MS) is a chronic disease of the central nervous system that affects the brain and spinal cord. There are several disease courses in MS including relapsing–remitting MS (RRMS), primary progressive MS (PPMS), and secondary progressive MS (SPMS). Up to 50% of MS patients experience depressive disorders. Major depression (MD) is a serious comorbidity of MS. Many dysfunctions including neuroinflammation, peripheral inflammation, gut dysbiosis, chronic oxidative and nitrosative stress, and neuroendocrine and mitochondrial abnormalities may contribute to the comorbidity between MS and MD. In addition to these actions, medical treatment and microRNA (miRNA) regulation may also be involved in the mechanisms of the comorbidity between MS and MD. In the study, I review many common miRNA biomarkers for both diseases. These common miRNA biomarkers may help further explore the association between MS and MD.

The microRNA let-7b-5p Is Negatively Associated with Inflammation and Disease Severity in Multiple Sclerosis

The identification of microRNAs in biological fluids for diagnosis and prognosis is receiving great attention in the field of multiple sclerosis (MS) research but it is still in its infancy. In the present study, we observed in a large sample of MS patients that let-7b-5p levels in the cerebrospinal fluid (CSF) were highly correlated with a number of microRNAs implicated in MS, as well as with a variety of inflammation-related protein factors, showing specific expression patterns coherent with let-7b-5p-mediated regulation. Additionally, we found that the CSF let-7b-5p levels were significantly reduced in patients with the progressive MS compared to patients with relapsing-remitting MS and were negatively correlated with characteristic hallmark processes of the two phases of the disease. Indeed, in the non-progressive phase, let-7b-5p inversely associated with both central and peripheral inflammation; whereas, in progressive MS, the CSF levels of let-7b-5p negatively correlated with clinical disability at disease onset and after a follow-up period. Overall, our results uncovered, by the means of a multidisciplinary approach and multiple statistical analyses, a new possible pleiotropic action of let-7b-5p in MS, with potential utility as a biomarker of MS course.

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.

Recent Advances in Pathology: the 2020 Annual Review Issue of The Journal of Pathology

This year's Annual Review Issue of The Journal of Pathology contains 18 invited reviews on current research areas in pathology. The subject areas reflect the broad range of topics covered by the journal and this year encompass the development and application of software in digital histopathology, implementation of biomarkers in pathology practice; genetics and epigenetics, and stromal influences in disease. The reviews are authored by experts in their field and provide comprehensive updates in the chosen areas, in which there has been considerable recent progress in our understanding of disease. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.