Validation of microRNAs in Cerebrospinal Fluid as Biomarkers for Different Forms of Dementia in a Multicenter Study

miR-6076 targets BCL6 in SH-SY5Y cells to regulate amyloid-β-induced neuronal damage

Amyloid-β1-42 (Aβ1-42 ) is strongly associated with Alzheimer's disease (AD). The aim of this study is to elucidate whether and how miR-6076 participates in the modulation of amyloid-β (Aβ)-induced neuronal damage. To construct the neuronal damage model, SH-SY5Y cells were treated with Aβ1-42 . By qRT-PCR, we found that miR-6076 is significantly upregulated in Aβ1-42 -treated SH-SY5Y cells. After miR-6076 inhibition, p-Tau and apoptosis levels were downregulated, and cell viability was increased. Through online bioinformatics analysis, we found that B-cell lymphoma 6 (BCL6) was a directly target of miR-6076 via dual-luciferase reporter assay. BCL6 overexpression mediated the decrease in elevated p-Tau levels and increased viability in SH-SY5Y cells following Aβ1-42 treatment. Our results suggest that down-regulation of miR-6076 could attenuate Aβ1-42 -induced neuronal damage by targeting BCL6, which provided a possible target to pursue for prevention and treatment of Aβ-induced neuronal damage in AD.

Discerning the Prospects of miRNAs as a Multi-Target Therapeutic and Diagnostic for Alzheimer's Disease

Although over the last few decades, numerous attempts have been made to halt Alzheimer's disease (AD) progression and mitigate its symptoms, only a few have been proven beneficial. Most medications available, still only cater to the symptoms of the disease rather than fixing the cause at the root level. A novel approach involving the use of miRNAs, which work on the principle of gene silencing, is being explored by scientists. Naturally present miRNAs in the biological system help to regulate various genes than may be implicated in AD-like BACE-1 and APP. One miRNA thus, holds the power to keep a check on several genes, conferring it the ability to be used as a multi-target therapeutic. With aging and the onset of diseased pathology, dysregulation of these miRNAs is observed. This flawed miRNA expression is responsible for the unusual buildup of amyloid proteins, fibrillation of tau proteins in the brain, neuronal death and other hallmarks leading to AD. The use of miRNA mimics and miRNA inhibitors provides an attractive perspective for fixing the upregulation and downregulation of miRNAs that led to abnormal cellular activities. Furthermore, the detection of miRNAs in the CSF and serum of diseased patients might be considered an earlier biomarker for the disease. While most of the therapies designed around AD have not succeeded completely, the targeting of dysregulated miRNAs in AD patients might give a new direction to scholars to develop an effective treatment for Alzheimer's disease.

Biomarkers of diagnosis, prognosis, pathogenesis, response to therapy: Convergence or divergence? Lessons from Alzheimer's disease and synucleinopathies

Alzheimer's disease (AD) is the most common disorder associated with cognitive impairment. Recent observations emphasize the pathogenic role of multiple factors inside and outside the central nervous system, supporting the notion that AD is a syndrome of many etiologies rather than a "heterogeneous" but ultimately unifying disease entity. Moreover, the defining pathology of amyloid and tau coexists with many others, such as α-synuclein, TDP-43, and others, as a rule, not an exception. Thus, an effort to shift our AD paradigm as an amyloidopathy must be reconsidered. Along with amyloid accumulation in its insoluble state, β-amyloid is becoming depleted in its soluble, normal states, as a result of biological, toxic, and infectious triggers, requiring a shift from convergence to divergence in our approach to neurodegeneration. These aspects are reflected-in vivo-by biomarkers, which have become increasingly strategic in dementia. Similarly, synucleinopathies are primarily characterized by abnormal deposition of misfolded α-synuclein in neurons and glial cells and, in the process, depleting the levels of the normal, soluble α-synuclein that the brain needs for many physiological functions. The soluble to insoluble conversion also affects other normal brain proteins, such as TDP-43 and tau, accumulating in their insoluble states in both AD and dementia with Lewy bodies (DLB). The two diseases have been distinguished by the differential burden and distribution of insoluble proteins, with neocortical phosphorylated tau deposition more typical of AD and neocortical α-synuclein deposition peculiar to DLB. We propose a reappraisal of the diagnostic approach to cognitive impairment from convergence (based on clinicopathologic criteria) to divergence (based on what differs across individuals affected) as a necessary step for the launch of precision medicine.

Diminazene Ameliorates Neuroinflammation by Suppression of Astrocytic miRNA-224-5p/NLRP3 Axis in Alzheimer's Disease Model

Purpose

ACE2/Ang(1-7)/Mas Receptor, the momentous component of the renin-angiotensin system, has been shown to be involved in Alzheimer's disease (AD). We had previously found that enhancing brain ACE2 activity ameliorated cognitive impairment and attenuated brain neuroinflammation in SAMP8 mice, an animal model of AD. However, the exact mechanism of action of Diminazene (DIZE) has not been revealed.

Methods

APP/PS1 mice were injected intraperitoneally with DIZE. Cognitive functions, neuronal and synaptic integrity, and inflammation-related markers were assessed by Morris water maze, Nissl staining, Western blotting and ELISA, respectively. Since astrocytes played a crucial role in AD-related neuroinflammation whilst miRNAs were reported to participate in modulating inflammatory responses, astrocytes of APP/PS1 mice were then isolated for high-throughput miRNAs sequencing to identify the most differentially expressed miRNA following DIZE treatment. Afterward, the downstream pathway of this miRNA in the anti-inflammatory action of DIZE was investigated using primary astrocytes.

Results

The results showed that DIZE alleviated cognitive impairment and neuronal and synaptic damage in APP/PS1 mice. Simultaneously, DIZE suppressed the secretion of pro-inflammatory cytokines and the expression of NLRP3 inflammasome. Importantly, miR-224-5p was significantly up-regulated in the astrocytes of APP/PS1 mice treated by DIZE, and NLRP3 is one of the targets of miR-224-5p. Upregulation of miR-224-5p inhibited the expression of NLRP3 in Aβ1-42-stimulated cells, whereas miR-224-5p downregulation reversed this effect. Furthermore, the inhibition of miR-224-5p could reverse the inhibitory effect of DIZE on astrocytic NLRP3 inflammasome.

Conclusion

These findings firstly suggested that DIZE could inhibit astrocyte-regulated neuroinflammation via miRNA-224-5p/NLRP3 pathway. Furthermore, our study reveals the underlying mechanism by which DIZE suppresses neuroinflammatory responses in AD mice and uncovers the potential of DIZE in AD treatment.

Changes of tRNA-Derived Fragments by Alzheimer's Disease in Cerebrospinal Fluid and Blood Serum

BACKGROUND

Alzheimer's disease (AD) is the most common type of dementia, affecting individuals over 65. AD is also a multifactorial disease, with disease mechanisms incompletely characterized, and disease-modifying therapies are marginally effective. Biomarker signatures may shed light on the diagnosis, disease mechanisms, and the development of therapeutic targets. tRNA-derived RNA fragments (tRFs), a family of recently discovered small non-coding RNAs, have been found to be significantly enhanced in human AD hippocampus tissues. However, whether tRFs change in body fluids is unknown.

OBJECTIVE

To investigate whether tRFs in body fluids are impacted by AD.

METHODS

We first used T4 polynucleotide kinase-RNA-seq, a modified next-generation sequencing technique, to identify detectable tRFs in human cerebrospinal fluid and serum samples. The detectable tRFs were then compared in these fluids from control, AD, and mild cognitive impairment patients using tRF qRT-PCR. The stability of tRFs in serum was also investigated by checking the change in tRFs in response to protein digestion or exosome lysis.

RESULTS

Among various tRFs, tRF5-ProAGG seemed to be impacted by AD in both cerebrospinal fluid and serum. AD-impacted serum tRF5-ProAGG showed a correlation with the AD stage. Putative targets of tRF5-ProAGG in the hippocampus were also predicted by a computational algorithm, with some targets being validated experimentally and one of them being in a negative correlation with tRF5-ProAGG even using a small size of samples.

CONCLUSIONS

tRF5-ProAGG showed the potential as an AD biomarker and may play a role in disease progression.

Circulating Non-Coding RNA Levels Are Altered in Autosomal Dominant Frontotemporal Dementia

Frontotemporal Dementia (FTD) represents a highly heritable neurodegenerative disorder. Most of the heritability is caused by autosomal dominant mutations in the Microtubule-Associated Protein Tau (MAPT), Progranulin (GRN), and the pathologic exanucleotide expansion of C9ORF72 genes. At the pathological level, either the tau or the TAR DNA-binding protein (TDP-43) account for almost all cases of FTD. Pathogenic mechanisms are just arising, and the emerging role of non-coding RNAs (ncRNAs), such as microRNAs (miRNA) and long non-coding RNAs (lncRNAs), have become increasingly evident. Using specific arrays, an exploratory analysis testing the expression levels of 84 miRNAs and 84 lncRNAs has been performed in a population consisting of 24 genetic FTD patients (eight GRN, eight C9ORF72, and eight MAPT mutation carriers), eight sporadic FTD patients, and eight healthy controls. The results showed a generalized ncRNA downregulation in patients carrying GRN and C9ORF72 when compared with the controls, with statistically significant results for the following miRNAs: miR-155-5p (Fold Change FC: 0.45, p = 0.037 FDR = 0.52), miR-15a-5p (FC: 0.13, p = 0.027, FDR = 1), miR-222-3p (FC: 0.13, p = 0.027, FDR = 0.778), miR-140-3p (FC: 0.096, p = 0.034, FRD = 0.593), miR-106b-5p (FC: 0.13, p = 0.02, FDR = 0.584) and an upregulation solely for miR-124-3p (FC: 2.1, p = 0.01, FDR = 0.893). Conversely, MAPT mutation carriers showed a generalized robust upregulation in several ncRNAs, specifically for miR-222-3p (FC: 22.3, p = 7 × 10-6, FDR = 0.117), miR-15a-5p (FC: 30.2, p = 0.008, FDR = 0.145), miR-27a-3p (FC: 27.8, p = 6 × 10-6, FDR = 0.0005), miR-223-3p (FC: 18.9, p = 0.005, FDR = 0.117), and miR-16-5p (FC: 10.9, p = 5.26 × 10-5, FDR = 0.001). These results suggest a clear, distinctive pattern of dysregulation among ncRNAs and specific enrichment gene pathways between mutations associated with the TDP-43 and tau pathologies. Nevertheless, these preliminary results need to be confirmed in a larger independent cohort.

Small and long RNA transcriptome of whole human cerebrospinal fluid and serum as compared to their extracellular vesicle fractions reveal profound differences in expression patterns and impacts on biological processes

BACKGROUND

Next generation sequencing (NGS) of human specimen is expected to improve prognosis and diagnosis of human diseases, but its sensitivity urges for well-defined sampling and standardized protocols in order to avoid error-prone conclusions.

METHODS

In this study, large volumes of pooled human cerebrospinal fluid (CSF) were used to prepare RNA from human CSF-derived extracellular vesicles (EV) and from whole CSF, as well as from whole human serum and serum-derived EV. In all four fractions small and long coding and non-coding RNA expression was analyzed with NGS and transcriptome analyses.

RESULTS

We show, that the source of sampling has a large impact on the acquired NGS pattern, and differences between small RNA fractions are more distinct than differences between long RNA fractions. The highest percentual discrepancy between small RNA fractions and the second highest difference between long RNA fractions is seen in the comparison of CSF-derived EV and whole CSF. Differences between miR (microRNA) and mRNA fractions of EV and the respective whole body fluid have the potential to affect different cellular and biological processes. I.e. a comparison of miR in both CSF fractions reveals that miR from EV target four transcripts sets involved in neurobiological processes, whereas eight others, also involved in neurobiological processes are targeted by miR found in whole CSF only. Likewise, three mRNAs sets derived from CSF-derived EV are associated with neurobiological and six sets with mitochondrial metabolism, whereas no such mRNA transcript sets are found in the whole CSF fraction. We show that trace amounts of blood-derived contaminations of CSF can bias RNA-based CSF diagnostics.

CONCLUSIONS

This study shows that the composition of small and long RNA differ significantly between whole body fluid and its respective EV fraction and thus can affect different cellular and molecular functions. Trace amounts of blood-derived contaminations of CSF can bias CSF analysis. This has to be considered for a meaningful RNA-based diagnostics. Our data imply a transport of EV from serum to CSF across the blood-brain barrier.

MicroRNA biomarkers in frontotemporal dementia and to distinguish from Alzheimer's disease and amyotrophic lateral sclerosis

Frontotemporal lobar degeneration describes a group of progressive brain disorders that primarily are associated with atrophy of the prefrontal and anterior temporal lobes. Frontotemporal lobar degeneration is considered to be equivalent to frontotemporal dementia. Frontotemporal dementia is characterized by progressive impairments in behavior, executive function, and language. There are two main clinical subtypes: behavioral-variant frontotemporal dementia and primary progressive aphasia. The early diagnosis of frontotemporal dementia is critical for developing management strategies and interventions for these patients. Without validated biomarkers, the clinical diagnosis depends on recognizing all the core or necessary neuropsychiatric features, but misdiagnosis often occurs due to overlap with a range of neurologic and psychiatric disorders. In the studies reviewed a very large number of microRNAs were found to be dysregulated but with limited overlap between individual studies. Measurement of specific miRNAs singly or in combination, or as miRNA pairs (as a ratio) in blood plasma, serum, or cerebrospinal fluid enabled frontotemporal dementia to be discriminated from healthy controls, Alzheimer's disease, and amyotrophic lateral sclerosis. Furthermore, upregulation of miR-223-3p and downregulation of miR-15a-5p, which occurred both in blood serum and cerebrospinal fluid, distinguished behavioral-variant frontotemporal dementia from healthy controls. Downregulation of miR-132-3p in frontal and temporal cortical tissue distinguished frontotemporal lobar degeneration and frontotemporal dementia, respectively, from healthy controls. Possible strong miRNA biofluid biomarker contenders for behavioral-variant frontotemporal dementia are miR-223-3p, miR-15a-5p, miR-22-3p in blood serum and cerebrospinal fluid, and miR-124 in cerebrospinal fluid. No miRNAs were identified able to distinguish between behavioral-variant frontotemporal dementia and primary progressive aphasia subtypes. Further studies are warranted on investigating miRNA expression in biofluids and frontal/temporal cortical tissue to validate and extend these findings.

Systematic Search for Novel Circulating Biomarkers Associated with Extracellular Vesicles in Alzheimer's Disease: Combining Literature Screening and Database Mining Approaches

miRNAs play an important role in neurodegenerative diseases. Many miRNA-target gene interactions (MTI) have been experimentally confirmed and associated with Alzheimer’s disease (AD). miRNAs may also be contained within extracellular vesicles (EVs), mediators of cellular communication and a potential source of circulating biomarkers in body fluids. Therefore, EV-associated miRNAs (EV-miRNAs) in peripheral blood could support earlier and less invasive AD diagnostics. We aimed to prioritize EV-related miRNA with AD-related genes and to identify the most promising candidates for novel AD biomarkers. A list of unique EV-miRNAs from the literature was combined with a known set of AD risk genes and enriched for MTI. Additionally, miRNAs associated with the AD phenotype were combined with all known target genes in MTI enrichment. Expression in different sample types was analyzed to identify AD-associated miRNAs with the greatest potential as AD circulating biomarkers. Four common MTI were observed between EV-miRNAs and AD-associated miRNAs: hsa-miR-375–APH1B, hsa-miR-107–CDC42SE2, hsa-miR-375–CELF2, and hsa-miR-107–IL6. An additional 61 out of 169 unique miRNAs (36.1%) and seven out of 84 unique MTI (8.3%), observed in the body fluids of AD patients, were proposed as very strong AD-circulating biomarker candidates. Our analysis summarized several potential novel AD biomarkers, but further studies are needed to evaluate their potential in clinical practice.

Next-Generation RNA-Sequencing of Serum Small Extracellular Vesicles Discovers Potential Diagnostic Biomarkers for Dementia With Lewy Bodies

OBJECTIVE

There is an urgent clinical need for identifying blood-based diagnostic biomarkers for Dementia with Lewy Bodies (DLB). Transcriptomic studies have reported unique RNA changes in postmortem DLB brains. Small extracellular vesicles (SEV) that transport RNA between brain and peripheral circulation enable identifying molecular changes in living human brain. Hence, we aimed to identify differentially expressed RNA in serum SEVs from people with DLB.

METHODS

We investigated serum SEV total RNA profiles in people with DLB (n = 10) and age and gender matched comparisons (n = 10) using next-generation RNA-sequencing. SEVs were separated by ultracentrifugation with density gradient and were characterized by nanoparticle analysis and western blotting. We verified the differential expression levels of identified differentially expressed genes (DEG) using high-throughput qPCR. Functional implications of identified DEG were evaluated using Ingenuity pathway analyses.

RESULTS

We identified 846 nominally significant DEG including 30 miRNAs in DLB serum SEVs. We identified significant downregulation of proinflammatory genes, IL1B, CXCL8, and IKBKB. Previously reported postmortem DLB brain DEGs were significantly enriched (χ²=4.99; df=1; p = 0.03) among the identified DEGs, and the differential expression of 40 postmortem DLB brain DEGs could be detected in serum SEVs of people living with DLB. Functional pathway and network analyses highlighted the importance of immunosenescence, ubiquitin proteasome system (UPS) dysfunction, DNA repair, and RNA post-transcriptional modification deficits in DLB pathology.

CONCLUSION

Identified DEGs, especially reduced expression levels of inflammation, and UPS-associated RNA, may aid diagnosing DLB, and their biomarker potential warrants further investigation in larger clinical cohorts. Our findings corroborate the absence of chronic neuroinflammation in DLB.

Molecular Changes in Circulating microRNAs' Expression and Oxidative Stress in Adults with Mild Cognitive Impairment: A Biochemical and Molecular Study

BACKGROUND

The release of miRNAs in tissue fluids significantly recommends its use as non-invasive diagnostic biomarkers for the progression and pathogenesis of mild cognitive impairment (MCI) in aged patients.

OBJECTIVE

The potential role of circulated miRNAs in the pathogenesis of MCI and its association with cellular oxidative stress, apoptosis, and circulated BDNF, Sirtuin 1 (SIRT1), and dipeptidyl peptidase-4 (DPP4) were evaluated in older adults with MCI.

METHODS

A total of 150 subjects aged 65.4±3.7 years were recruited in this study. The participants were classified into two groups: healthy normal (n=80) and MCI (n=70). Real-time PCR analysis was performed to estimate the relative expression of miRNAs; miR-124a, miR-483-5p, miR-142-3p, and miR-125b, and apoptotic-related genes Bax, Bcl-2, and caspase-3 in the sera of MCI and control subjects. In addition, oxidative stress parameters; MDA, NO, SOD, and CAT; as well as plasma DPP4 activity, BDNF, SIRT1 levels were colorimetrically estimated.

RESULTS

The levels of miR-124a and miR-483-5p significantly increased and miR-142-3p and miR-125b significantly reduced in the serum of MCI patients compared to controls. The expressed miRNAs significantly correlated with severe cognitive decline, measured by MMSE, MoCA, ADL, and memory scores. The expression of Bax, and caspase-3 apoptotic inducing genes significantly increased and Bcl-2 antiapoptotic gene significantly reduced in MCI subjects compared to controls. In addition, the plasma levels of MDA, NO, and DPP4 activity significantly increased, and the levels of SOD, CAT, BDNF, and SIRT1 significantly reduced in MCI subjects compared to controls. The expressed miRNAs correlated positively with NO, MDA, DPP4 activity, BDNF, and SIRT-1, and negatively with the levels of CAT, SOD, Bcl-2, Bax, and caspase-3 genes.

CONCLUSION

Circulating miR-124a, miR-483-5p, miR-142-3p, and miR-125b significantly associated with severe cognitive decline, cellular oxidative stress, and apoptosis in patients with MCI. Thus, it could be potential non-invasive biomarkers for the diagnosis of MCI with high diagnostic performance.

Systematic review of gene expression studies in people with Lewy body dementia

OBJECTIVES

Lewy body dementia (LBD) is the second most prevalent neurodegenerative dementia and it causes more morbidity and mortality than Alzheimer's disease. Several genetic associations of LBD have been reported and their functional implications remain uncertain. Hence, we aimed to do a systematic review of all gene expression studies that investigated people with LBD for improving our understanding of LBD molecular pathology and for facilitating discovery of novel biomarkers and therapeutic targets for LBD.

METHODS

We systematically reviewed five online databases (PROSPERO protocol: CRD42017080647) and assessed the functional implications of all reported differentially expressed genes (DEGs) using Ingenuity Pathway Analyses.

RESULTS

We screened 3,809 articles and identified 31 eligible studies. In that, 1,242 statistically significant (p < 0.05) DEGs including 70 microRNAs have been reported in people with LBD. Expression levels of alternatively spliced transcripts of SNCA, SNCB, PRKN, APP, RELA, and ATXN2 significantly differ in LBD. Several mitochondrial genes and genes involved in ubiquitin proteasome system and autophagy-lysosomal pathway were significantly downregulated in LBD. Evidence supporting chronic neuroinflammation in LBD was inconsistent. Our functional analyses highlighted the importance of ribonucleic acid (RNA)-mediated gene silencing, neuregulin signalling, and neurotrophic factors in the molecular pathology of LBD.

CONCLUSIONS

α-synuclein aggregation, mitochondrial dysfunction, defects in molecular networks clearing misfolded proteins, and RNA-mediated gene silencing contribute to neurodegeneration in LBD. Larger longitudinal transcriptomic studies investigating biological fluids of people living with LBD are needed for molecular subtyping and staging of LBD. Diagnostic biomarker potential and therapeutic promise of identified DEGs warrant further research.

Circulating Exosome microRNAs as Diagnostic Biomarkers of Dementia

Dementia is a syndrome of acquired cognitive impairment that leads to a significant decline in a patient’s daily life, ability to learn, and the ability to communicate with others. Dementia occurs in many diseases, including Alzheimer’s disease (AD), dementia with Lewy bodies, frontotemporal dementia, and Parkinson’s disease dementia (PDD). Although the analysis of biomarkers in the cerebrospinal fluid (CSF) and peripheral blood physicochemical analysis can indicate neurological impairment, there are currently no sensitive biomarkers for early clinical diagnosis of dementia or for identifying the cause of dementia. Previous studies have suggested that circulating micro (mi)RNAs may be used as biomarkers for diagnosing neurological disorders. However, miRNAs are susceptible to interference by other components in the peripheral circulation, bringing into question the diagnostic value of circulating miRNAs. Exosomes secreted by most cell types contain proteins, mRNAs, and miRNAs that are closely associated with changes in cellular functions. Exosome miRNAs (ex-miRNAs) are highly stable and resistant to degradation. Therefore, these may serve as useful biomarkers for the early clinical diagnosis of dementia. Here, we review studies of ex-miRNAs that commonly cause clinical dementia and explore whether ex-miRNAs may be used as early diagnostic biomarkers of dementia.

MicroRNA Expression Signature in Mild Cognitive Impairment Due to Alzheimer's Disease

Mild cognitive impairment (MCI) defines an intermediate state between normal ageing and dementia, including Alzheimer’s disease (AD). Identification of MCI subjects who will progress to AD (MCI-AD) is today of crucial importance, especially in light of the possible development of new pathogenic therapies. Several evidences suggest that miRNAs could play relevant roles in the biogenesis of AD, and the links between selected miRNAs and specific pathogenic aspects have been partly explored. In this study, we analysed the composition of microRNA transcriptome in blood, serum and cerebrospinal fluid samples from MCI-AD subjects, from an enriched small RNA library. Real-time qPCR from MCI-AD and AD patients and normal controls was performed to profile miRNA expression. In particular, four microRNAs, hsa-mir-5588-5p, hsa-mir-3658, hsa-mir-567 and hsa-mir-3908, among all selected microRNAs, are dysregulated. Hsa-mir-567 was found to be differentially expressed in cerebrospinal fluid samples, blood and serum from MCI-AD patients, showing the highest fold change and statistical significance. Target prediction analysis have been performed to evaluate mRNAs whose expression was controlled by miRNAs found to be dysregulated here, showing that hsa-mir-567 target genes are functionally active in neuronal cells. We propose that miRNA profiles found in samples from MCI-AD patients might be relevant for a better understanding of AD-related cognitive decline and could lead to set up suitable and potential biomarkers for MCI-AD progression to AD.

MicroRNA-146a Is a Wide-Reaching Neuroinflammatory Regulator and Potential Treatment Target in Neurological Diseases

Progressive functional deterioration and loss of neurons underlies neurological diseases and constitutes an important cause of disability and death worldwide. The causes of various types of neurological diseases often share several critical nerve-related cellular mechanisms and pathological features, particularly the neuroinflammatory response in the nervous system. A rapidly growing body of evidence indicates that various microRNAs play pivotal roles in these processes in neurological diseases and might be viable therapeutic targets. Among these microRNAs, microRNA-146a (miR-146a) stands out due to the rapid increase in recent literature on its mechanistic involvement in neurological diseases. In this review, we summarize and highlight the critical role of miR-146a in neurological diseases. MiR-146a polymorphisms are associated with the risk of neurological disease. Alterations in miR-146a expression levels are crucial events in the pathogenesis of numerous neurological diseases that are spatially and temporally diverse. Additionally, the target genes of miR-146a are involved in the regulation of pathophysiological processes in neurological diseases, particularly the neuroinflammatory response. In summary, miR-146a mainly plays a critical role in neuroinflammation during the progression of neurological diseases and might be a prospective biomarker and therapeutic target. Understanding the mechanisms by which miR-146a affects the neuroinflammatory response in different neurological injuries, different cell types, and even different stages of certain neurological diseases will pave the way for its use as a therapeutic target in neurodegenerative diseases.

Validation of MicroRNA Biomarkers for Alzheimer's Disease in Human Cerebrospinal Fluid

We previously discovered microRNAs (miRNAs) in cerebrospinal fluid (CSF) that differentiate Alzheimer's disease (AD) patients from Controls. Here we examined the performance of 37 candidate AD miRNA biomarkers in a new and independent cohort of CSF from 47 AD patients and 71 Controls on custom TaqMan arrays. We employed a consensus ranking approach to provide an overall priority score for each miRNA, then used multimarker models to assess the relative contributions of the top-ranking miRNAs to differentiate AD from Controls. We assessed classification performance of the top-ranking miRNAs when combined with apolipoprotein E4 (APOE4) genotype status or CSF amyloid-β42 (Aβ42):total tau (T-tau) measures. We also assessed whether miRNAs that ranked higher as AD markers correlate with Mini-Mental State Examination (MMSE) scores. We show that of 37 miRNAs brought forth from the discovery study, 26 miRNAs remained viable as candidate biomarkers for AD in the validation study. We found that combinations of 6-7 miRNAs work better to identify AD than subsets of fewer miRNAs. Of 26 miRNAs that contribute most to the multimarker models, 14 have higher potential than the others to predict AD. Addition of these 14 miRNAs to APOE4 status or CSF Aβ42:T-tau measures significantly improved classification performance for AD. We further show that individual miRNAs that ranked higher as AD markers correlate more strongly with changes in MMSE scores. Our studies validate that a set of CSF miRNAs serve as biomarkers for AD, and support their advancement toward development as biomarkers in the clinical setting.

The European medical information framework: A novel ecosystem for sharing healthcare data across Europe

INTRODUCTION

The European medical information framework (EMIF) was an Innovative Medicines Initiative project jointly supported by the European Union and the European Federation of Pharmaceutical Industries and Associations, that generated a common technology and governance framework to identify, assess and (re)use healthcare data, to facilitate real-world data research. The objectives of EMIF included providing a unified platform to support a wide range of studies within two verification programmes-Alzheimer's disease (EMIF-AD), and metabolic consequences of obesity (EMIF-MET).

METHODS

The EMIF platform was built around two main data-types: electronic health record data and research cohort data, and the platform architecture composed of a set of tools designed to enable data discovery and characterisation. This included the EMIF catalogue, which allowed users to find relevant data sources, including the data-types collected. Data harmonisation via a common data model were central to the project especially for population data sources. EMIF also developed an ethical code of practice to ensure data protection, patient confidentiality and compliance with the European Data Protection Directive, and GDPR.

RESULTS

Currently 18 population-based disease agnostic and 60 cohort-based Alzheimer's data partners from across 14 countries are contained within the catalogue, and this will continue to expand. The work conducted in EMIF-AD and EMIF-MET includes standardizing cohorts, summarising baseline characteristics of patients, developing diagnostic algorithms, epidemiological studies, identifying and validating novel biomarkers and selecting potential patient samples for pharmacological intervention.

CONCLUSIONS

EMIF was designed to provide a sustainable model as demonstrated by the sustainability plans for EMIF-AD. Although network-wide studies using EMIF were not conducted during this project to evaluate its sustainability, learning from EMIF will be used in the follow-on IMI-2 project, European Health Data and Evidence Network (EHDEN). Furthermore, EMIF has facilitated collaborations between partners and continues to promote a wider adoption of principles, technology and architecture through some of its continued work.

Study on the mechanism of curcumin to reduce the inflammatory response of temporal lobe in Alzheimer's disease by regulating miR-146a

BACKGROUND

To explore the potential mechanism of curcumin in the treatment of Alzheimer's disease and clarify the role of miR-146a in the neuroinflammatory response to Alzheimer's disease.

METHODS

Clinical case study: 20 AD patients and 20 age-gender matched non-inflammatory and non-dementia patients in the department of neurology of our hospital were included, peripheral venous blood and cerebrospinal fluid were collected, and mir-146a levels in peripheral blood and cerebrospinal fluid were detected by real-time fluorescence quantitative PCR. Animal experimental study group: There were 3 groups, including APP/PS1 mice control group, APP/PS1 mice low-dose curcumin treatment group, and C57BL/6J mice wild-type (WT) control group, with 10 mice in each group. mir-146a levels in mice brain tissue were detected by quantitative real-time PCR. Aβ, APP, complement factor H (CFH) and M1 microglia labeled IL-1 β and iNOS in temporal lobe tissues of mice were detected by using Westernblot method.

RESULTS

The plasma miRNA-146a level in AD group was 39.10 ±12.97 fmol/L, and that in control group was 60.54 ±13.16 fmol/L. The plasma miRNA-146a level in AD group was significantly lower than that in control group. The level of miRNA-146a in cerebrospinal fluid of AD group (25.16 ± 5.16 fmol/L) was significantly higher than that of control group (11.35 ±3.58 fmol/L). After treatment with low dose curcumin, the level of miRNA-146a in APP/PS1 mice decreased significantly, and the expression of A β and APP/PS1 in temporal lobe of mice detected by Western blot decreased significantly, the levels of IL-1 β and iNOS protein decreased significantly, and the protein of CFH increased signifanctly.

CONCLUSIONS

miRNA-146a can be used as one of the potential biomarkers of AD. Low dose curcumin can significantly reduce the level of neuropro-inflammatory miR-146A, up-regulate the expression of CFH protein, inhibit the phenotype of M1 microglia, and play a role in the treatment of AD by promoting the phagocytosis and clearance mechanism of A β.

miR-146a Plasma Levels Are Not Altered in Alzheimer's Disease but Correlate With Age and Illness Severity

miR-146a is a microRNA (miRNA) involved in neuroinflammation and aging; alterations in its expression were described in Alzheimer’s disease (AD). However, most of the studies conducted so far on this miRNA included a limited number of participants and produced contradictory results. We compared miR-146a levels in plasma from 33 AD patients vs. 28 age-matched non-affected controls (CTRL) through quantitative real-time polymerase chain reaction (qRT-PCR). No difference between the case and the control group was evidenced, but a correlation was detected between miR-146a levels and subjects’ age (p < 0.001) as well as between miR-146a levels and patients’ Mini-Mental State Examination (MMSE) scores (p = 0.011), in an enlarged group of 51 AD patients and 45 CTRL supporting a role for this miRNA in aging processes and disease progression.

Cerebral Amyloid Angiopathy, Alzheimer's Disease and MicroRNA: miRNA as Diagnostic Biomarkers and Potential Therapeutic Targets

The protein molecules must fold into unique conformations to acquire functional activity. Misfolding, aggregation, and deposition of proteins in diverse organs, the so-called "protein misfolding disorders (PMDs)", represent the conformational diseases with highly ordered assemblies, including oligomers and fibrils that are linked to neurodegeneration in brain illnesses such as cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD). Recent studies have revealed several aspects of brain pathology in CAA and AD, but both the classification and underlying mechanisms need to be further refined. MicroRNAs (miRNAs) are critical regulators of gene expression at the post-transcriptional level. Increasing evidence with the advent of RNA sequencing technology suggests possible links between miRNAs and these neurodegenerative disorders. To provide insights on the small RNA-mediated regulatory circuitry and the translational significance of miRNAs in PMDs, this review will discuss the characteristics and mechanisms of the diseases and summarize circulating or tissue-resident miRNAs associated with AD and CAA.

Potential Fluid Biomarkers for the Diagnosis of Mild Cognitive Impairment

Mild cognitive impairment (MCI) is characterized by a level of cognitive impairment that is lower than normal for a person’s age, but a higher function than that that observed in a demented person. MCI represents a transitional state between normal aging and dementia disorders, especially Alzheimer’s disease (AD). Much effort has been made towards determining the prognosis of a person with MCI who will convert to AD. It is now clear that cerebrospinal fluid (CSF) levels of Aβ40, Aβ42, total tau and phosphorylated tau are useful for predicting the risk of progression from MCI to AD. This review highlights the advantages of the current blood-based biomarkers in MCI, and discusses some of these challenges, with an emphasis on recent studies to provide an overview of the current state of MCI.

A Systematic Review of MicroRNA Expression as Biomarker of Late-Onset Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a high-occurrence neurological disorder but the difficulty in identifying precise and early biomarkers has complicated the understanding of the disease and the development of new treatments. In this sense, important knowledge is emerging regarding novel molecular and biological candidates with diagnostic potential, including microRNAs (miRNAs), which have a key role in gene repression. The aim of this systematic review was to define the role of miRNAs' expression as biomarkers for LOAD both in brain tissues, which could help understand the biology of the disease, and circulating tissues, which could serve as non-invasive markers of the pathology. A systematic search was performed in Web of Science and PubMed using the keywords ((Alzheimer or Alzheimer's) and (microRNA or microRNAs or miRNA or miRNAs or miR)) until August 2018 to retrieve all articles that presented independent original data evaluating the impact of miRNA expression on the development of LOAD in human population. A total of 90 studies investigating the role of miRNAs' expression in the development of LOAD were identified. While other widely studied miRNAs such as hsa-miR-146a presented contradictory results among studies, deregulation in brain tissue of seven miRNAs, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-107, hsa-miR-125-5p, hsa-miR-132-3p, hsa-miR-181-3p, and hsa-miR-212-3p, was consistently identified in LOAD patients. Their role in the disease could be mediated through the regulation of key pathways, such as axon guidance, longevity, insulin, and MAPK signaling pathway. However, regarding their role as non-invasive biomarkers of LOAD in fluids, although the limited results available are promising, further studies are required.

miR-146a and miR-181a are involved in the progression of mild cognitive impairment to Alzheimer's disease

The identification of mechanisms associated with Alzheimer's disease (AD) development in mild cognitive impairment (MCI) would be of great usefulness to clarify AD pathogenesis and to develop preventive and therapeutic strategies. In this study, blood levels of the candidate microRNAs (small noncoding RNAs that play a pivotal role in gene expression) miR-146a, miR-181a, miR-181b, miR-24-3p, miR-186a, miR-101, miR-339, miR-590, and miR-22 have been investigated for association to AD conversion within 2 years in a group of 45 patients with MCI. Baseline miR-146a (p = 0.036) and miR-181a (p = 0.026) showed a significant upregulation in patients with MCI who later converted to AD. These alterations were related to AD hallmarks: a significant negative correlation was found with amyloid beta cerebrospinal fluid concentration for miR-146a (p = 0.006) and miR-181a (p = 0.001). Moreover, higher levels of miR-146a were associated to apolipoprotein E ε4 allele presence, smaller volume of the hippocampus (p = 0.045) and of the CA1 (p = 0.013) and the subiculum (p = 0.027) subfields. Increased levels of miR-146a (p = 0.031) and miR-181a (p = 0.002) were also linked with diffusivity alterations in the cingulum. These data support a role for miR-146a and miR-181a in the mechanisms of AD progression.

Extracellular Vesicle as a Source of Alzheimer's Biomarkers: Opportunities and Challenges

Alzheimer’s disease (AD) is a chronic progressive neurodegenerative disease characterized by memory decline and cognitive dysfunction. Although the primary causes of AD are not clear, it is widely accepted that the accumulation of amyloid beta (Aβ) and consecutive hyper-phosphorylation of tau, synaptic loss, oxidative stress and neuronal death might play a vital role in AD pathogenesis. Recently, it has been widely suggested that extracellular vesicles (EVs), which are released from virtually all cell types, are a mediator in regulating AD pathogenesis. Clinical evidence for the diagnostic performance of EV-associated biomarkers, particularly exosome biomarkers in the blood, is also emerging. In this review, we briefly introduce the biological function of EVs in the central nervous system and discuss the roles of EVs in AD pathogenesis. In particular, the roles of EVs associated with autophagy and lysosomal degradation systems in AD proteinopathy and in disease propagation are discussed. Next, we summarize candidates for biochemical AD biomarkers in EVs, including proteins and miRNAs. The accumulating data brings hope that the application of EVs will be helpful for early diagnostics and the identification of new therapeutic targets for AD. However, at the same time, there are several challenges in developing valid EV biomarkers. We highlight considerations for the development of AD biomarkers from circulating EVs, which includes the standardization of pre-analytical sources of variability, yield and purity of isolated EVs and quantification of EV biomarkers. The development of valid EV AD biomarkers may be facilitated by collaboration between investigators and the industry.

MicroRNAs and mild cognitive impairment: A systematic review

BACKGROUND

Mild cognitive impairment (MCI) is usually described as an intermediate phase between normal cognition and dementia. Identifying the subjects at a higher risk of progressing from MCI to AD is essential to manage this condition. The diagnosis of MCI is mainly clinical. Several biomarkers have been proposed, but mostly for research purposes, as they are based on an invasive procedure to obtain the sample, such as cerebrospinal fluid (CSF). As a consequence, rapid and non-invasive biomarkers are needed to improve diagnosis. The objective of this systematic review is to summarize available evidence on the use of miRNAs as biomarkers in subjects with MCI.

METHODS

Relevant literature published up to June 2018 was retrieved searching the databases PubMed, ISI Web of Knowledge and the Cochrane Database. Only studies considering microRNAs (miRNAs) and a diagnosis of MCI were included. Data were extracted using a specifically-designed standardized form, and their methodological quality was assessed using QUADAS-2 and QUIPS.

RESULTS

Twenty-one studies of 153 retrieved articles met the predefined inclusion/exclusion criteria. Studies included participants ranging from 6 to 330. More than 40 miRNAs resulted as dysregulated, and miR-206 was the only miRNA that was found as differentially expressed in patients with MCI by more than two studies. However, these results have either not yet been confirmed in other independent cohorts, or data are still inconsistent. Inconsistencies among included studies could be due to several issues including the selection of participants, pre-analytical and analytical procedures, and statistical analyses.

Systematic Review of miRNA as Biomarkers in Alzheimer's Disease

Currently there are 850,000 people with Alzheimer's disease in the UK, with an estimated rise to 1.1 million by 2025. Alzheimer's disease is characterised by the accumulation of amyloid-beta plaques and hyperphosphorylated tau in the brain causing a progressive decline in cognitive impairment. Small non-coding microRNA (miRNA) sequences have been found to be deregulated in the peripheral blood of Alzheimer patients. A systematic review was conducted to extract all miRNA found to be significantly deregulated in the peripheral blood. These deregulated miRNAs were cross-referenced against the miRNAs deregulated in the brain at Braak Stage III. This resulted in a panel of 10 miRNAs (hsa-mir-107, hsa-mir-26b, hsa-mir-30e, hsa-mir-34a, hsa-mir-485, hsa-mir200c, hsa-mir-210, hsa-mir-146a, hsa-mir-34c, and hsa-mir-125b) hypothesised to be deregulated early in Alzheimer's disease, nearly 20 years before the onset of clinical symptoms. After network analysis of the 10 miRNAs, they were found to be associated with the immune system, cell cycle, gene expression, cellular response to stress, neuron growth factor signalling, wnt signalling, cellular senescence, and Rho GTPases.

Wide Profiling of Circulating MicroRNAs in Spinocerebellar Ataxia Type 7

Spinocerebellar ataxia type 7 (SCA7), a neurodegenerative disease characterized by cerebellar ataxia and retinal degeneration, is caused by a CAG repeat expansion in the ATXN7 gene coding region. Disease onset and progression are highly variable between patients, thus identification of specific/sensitive biomarkers that can improve the monitoring of disease progression is an immediate need. Because altered expression of circulating microRNAs (miRNAs) has been shown in various neurological diseases, they could be useful biomarkers for SCA7. In this study, we showed, to our knowledge for the first time, the expression profile of circulating miRNAs in SCA7. Using the TaqMan profiling low density array (TLDA), we found 71 differentially expressed miRNAs in the plasma of SCA7 patients, compared with healthy controls. The reliability of TLDA data was validated independently by quantitative real-time polymerase chain reaction in an independent cohort of patients and controls. We identified four validated miRNAs that possesses the diagnostic value to discriminate between healthy controls and patients (hsa-let-7a-5p, hsa-let7e-5p, hsa-miR-18a-5p, and hsa-miR-30b-5p). The target genes of these four miRNAs were significantly enriched in cellular processes that are relevant to central nervous system function, including Fas-mediated cell-death, heparansulfate biosynthesis, and soluble-N-ethylmaleimide-sensitive factor activating protein receptor pathways. Finally, we identify a signature of four miRNAs associated with disease severity that discriminate between early onset and adult onset, highlighting their potential utility to surveillance disease progression. In summary, circulating miRNAs might provide accessible biomarkers for disease stage and progression and help to identify novel cellular processes involved in SCA7.

MicroRNAs as diagnostic and therapeutic tools for Alzheimer's disease: advances and limitations

Alzheimer’s disease (AD) is the most common age-related, progressive neurodegenerative disease. It is characterized by memory loss and cognitive decline and responsible for most cases of dementia in the elderly. Late-onset or sporadic AD accounts for > 95% of cases, with age at onset > 65 years. Currently there are no drugs or other therapeutic agents available to prevent or delay the progression of AD. The cellular and molecular changes occurring in the brains of individuals with AD include accumulation of β-amyloid peptide and hyperphosphorylated tau protein, decrease of acetylcholine neurotransmitter, inflammation, and oxidative stress. Aggregation of β-amyloid peptide in extracellular plaques and the hyperphosphorylated tau protein in intracellular neurofibrillary tangles are characteristic of AD. A major challenge is identifying molecular biomarkers of the early-stage AD in patients as most studies have been performed with blood or brain tissue samples (postmortem) at late-stage AD. Subjects with mild cognitive impairment almost always have the neuropathologic features of AD with about 50% of mild cognitive impairment patients progressing to AD. They could provide important information about AD pathomechanism and potentially also highlight minimally or noninvasive, easy-to-access biomarkers. MicroRNAs are dysregulated in AD, and may facilitate the early detection of the disease and potentially the continual monitoring of disease progression and allow therapeutic interventions to be evaluated. Four recent reviews have been published of microRNAs in AD, each of which identified areas of weakness or limitations in the reported studies. Importantly, studies in the last three years have shown considerable progress in overcoming some of these limitations and identifying specific microRNAs as biomarkers for AD and mild cognitive impairment. Further large-scale human studies are warranted with less disparity in the study populations, and using an appropriate method to validate the findings.

microRNA diagnostic panel for Alzheimer's disease and epigenetic trade-off between neurodegeneration and cancer

microRNAs (miRNAs) have been extensively studied as potential biomarkers for Alzheimer's disease (AD). Their profiles have been analyzed in blood, cerebrospinal fluid (CSF) and brain tissue. However, due to the high variability between the reported data, stemming from the lack of methodological standardization and the heterogeneity of AD, the most promising miRNA biomarker candidates have not been selected. Our literature review shows that out of 137 miRNAs found to be altered in AD blood, 36 have been replicated in at least one independent study, and out of 166 miRNAs reported as differential in AD CSF, 13 have been repeatedly found. Only 3 miRNAs have been consistently reported as altered in three analyzed specimens: blood, CSF and the brain (hsa-miR-146a, hsa-miR-125b, hsa-miR-135a). Nonetheless, all 36 repeatedly differential miRNAs in AD blood are promising as components of the diagnostic panel. Given their predicted functions, such miRNA panel may report multiple pathways contributing to AD pathology, enabling the design of personalized therapies. In addition, the analysis revealed that the miRNAs dysregulated in AD overlap highly with miRNAs implicated in cancer. However, the directions of the miRNA changes are usually opposite in cancer and AD, indicative of an epigenetic trade-off between the two diseases.

Circulating miRNAs as Diagnostic Biomarkers for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide. Its main neuropathological hallmarks are the degeneration of dopaminergic neurons in the substantia nigra and alpha-synuclein containing protein inclusions, called Lewy Bodies. The diagnosis of idiopathic PD is still based on the assessment of clinical criteria, leading to an insufficient diagnostic accuracy. Additionally, there is no biomarker available allowing the prediction of the disease course or monitoring the response to therapeutic approaches. So far, protein biomarker candidates such as alpha-synuclein have failed to improve diagnosis of PD. Circulating microRNAs (miRNAs) in body fluids are promising biomarker candidates for PD, as they are easily accessible by non- or minimally-invasive procedures and changes in their expression are associated with pathophysiological processes relevant for PD. Advances in miRNA analysis methods resulted in numerous recent publications on miRNAs as putative biomarkers. Here, we discuss the applicability of different body fluids as sources for miRNA biomarkers, highlight technical aspects of miRNA analysis and give an overview on published studies investigating circulating miRNAs as biomarker candidates for diagnosis of PD and other Parkinsonian syndromes.

MicroRNA Profile in Patients with Alzheimer's Disease: Analysis of miR-9-5p and miR-598 in Raw and Exosome Enriched Cerebrospinal Fluid Samples

BACKGROUND

MicroRNAs have been postulated as potential biomarkers for Alzheimer's disease (AD). Exosomes are nanovesicles which transport microRNAs, proteins, and other cargos. It has been hypothesized that the exosome traffic might be increased in neurodegenerative disorders.

OBJECTIVE

i) To assess the cerebrospinal fluid (CSF) microRNA profile in a group of AD patients and control subjects and to validate a group of microRNAs previously reported by other authors. ii) To compare microRNA levels in whole CSF and in the exosome-enriched fraction in AD patients.

METHODS

A panel of 760 microRNAs was analyzed in the CSF of 10 AD patients and 10 healthy subjects. Among microRNAs differently expressed, we selected those that had been previously reported by other authors. Candidates were validated in a larger group by individual qPCR assays. MicroRNA expression was also evaluated in exosome-enriched CSF samples of patients with AD and controls.

RESULTS

Fifteen microRNAs were differently expressed in AD. MiR-9-5p, miR-134, and miR-598 were selected as candidates for further analysis. MiR-9-5p and miR-598 were detected in 50 and 75% of control CSF samples, respectively, while they were not detected in any AD CSF samples. We observed an opposite pattern when we evaluated the microRNA expression in the exosome-enriched CSF AD samples. No pattern variations were noted among healthy subjects.

CONCLUSION

These data propose miR-9-5p and miR-598 as potential biomarkers for AD. Further studies in plasma and other body fluids will confirm their potential role as easily accessible biomarkers. In addition, our data suggest that exosome trafficking is different between AD and control subjects raising the need to take this phenomenon into consideration in future studies of AD biomarkers.

MicroRNAs in Human Cerebrospinal Fluid as Biomarkers for Alzheimer's Disease

BACKGROUND

Currently available biomarkers of Alzheimer's disease (AD) include cerebrospinal fluid (CSF) protein analysis and amyloid PET imaging, each of which has limitations. The discovery of extracellular microRNAs (miRNAs) in CSF raises the possibility that miRNA may serve as novel biomarkers of AD.

OBJECTIVE

Investigate miRNAs in CSF obtained from living donors as biomarkers for AD.

METHODS

We profiled miRNAs in CSF from 50 AD patients and 49 controls using TaqMan® arrays. Replicate studies performed on a subset of 32 of the original CSF samples verified 20 high confidence miRNAs. Stringent data analysis using a four-step statistical selection process including log-rank and receiver operating characteristic (ROC) tests, followed by random forest tests, identified 16 additional miRNAs that discriminate AD from controls. Multimarker modeling evaluated linear combinations of these miRNAs via best-subsets logistic regression, and computed area under the ROC (AUC) curve ascertained classification performance. The influence of ApoE genotype on miRNA biomarker performance was also evaluated.

RESULTS

We discovered 36 miRNAs that discriminate AD from control CSF. 20 of these retested in replicate studies verified differential expression between AD and controls. Stringent statistical analysis also identified these 20 miRNAs, and 16 additional miRNA candidates. Top-performing linear combinations of 3 and 4 miRNAs have AUC of 0.80-0.82. Addition of ApoE genotype to the model improved performance, i.e., AUC of 3 miRNA plus ApoE4 improves to 0.84.

CONCLUSIONS

CSF miRNAs can discriminate AD from controls. Combining miRNAs improves sensitivity and specificity of biomarker performance, and adding ApoE genotype improves classification.

Intra- and Inter-individual Variability of microRNA Levels in Human Cerebrospinal Fluid: Critical Implications for Biomarker Discovery

MicroRNAs are emerging as promising biomarkers for diagnosis of various diseases. Notably, cerebrospinal fluid (CSF) contains microRNAs that may serve as biomarkers for neurological diseases. However, there has been a lack of consistent findings among CSF microRNAs studies. Although such inconsistent results have been attributed to various technical issues, inherent biological variability has not been adequately considered as a confounding factor. To address this critical gap in our understanding of microRNA variability, we evaluated intra-individual variability of microRNAs by measuring their levels in the CSF from healthy individuals at two time points, 0 and 48 hours. Surprisingly, the levels of most microRNAs were stable between the two time points. This suggests that microRNAs in CSF may be a good resource for the identification of biomarkers. However, the levels of 12 microRNAs (miR-19a-3p, miR-19b-3p, miR-23a-3p, miR-25a-3p, miR-99a-5p, miR-101-3p, miR-125b-5p, miR-130a-3p, miR-194-5p, miR-195-5p, miR-223-3p, and miR-451a) were significantly altered during the 48 hours interval. Importantly, miRNAs with variable expression have been identified as biomarkers in previous studies. Our data strongly suggest that these microRNAs may not be reliable biomarkers given their intrinsic variability even within the same individual. Taken together, our results provide a critical baseline resource for future microRNA biomarker studies.

Linking deregulation of non-coding RNA to the core pathophysiology of Alzheimer's disease: An integrative review

The human genome encodes a vast repertoire of protein non-coding RNAs (ncRNA), some specific to the brain. MicroRNAs, which interfere with the translation of target mRNAs, are of particular interest since their deregulation has been implicated in neurodegenerative disorders like Alzheimer's disease (AD). However, it remains challenging to link the complex body of observations on miRNAs and AD into a coherent framework. Using extensive graphical support, this article discusses how a diverse panoply of miRNAs convergently and divergently impact (and are impacted by) core pathophysiological processes underlying AD: neuroinflammation and oxidative stress; aberrant generation of β-amyloid-42 (Aβ42); anomalies in the production, cleavage and post-translational marking of Tau; impaired clearance of Aβ42 and Tau; perturbation of axonal organisation; disruption of synaptic plasticity; endoplasmic reticulum stress and the unfolded protein response; mitochondrial dysfunction; aberrant induction of cell cycle re-entry; and apoptotic loss of neurons. Intriguingly, some classes of miRNA provoke these cellular anomalies, whereas others act in a counter-regulatory, protective mode. Moreover, changes in levels of certain species of miRNA are a consequence of the above-mentioned anomalies. In addition to miRNAs, circular RNAs, piRNAs, long non-coding RNAs and other types of ncRNA are being increasingly implicated in AD. Overall, a complex mesh of deregulated and multi-tasking ncRNAs reciprocally interacts with core pathophysiological mechanisms underlying AD. Alterations in ncRNAs can be detected in CSF and the circulation as well as the brain and are showing promise as biomarkers, with the ultimate goal clinical exploitation as targets for novel modes of symptomatic and course-altering therapy.

MicroRNAs in Cerebrospinal Fluid as Potential Biomarkers for Parkinson's Disease and Multiple System Atrophy

Parkinson’s disease (PD) and multiple system atrophy (MSA) are both part of the spectrum of neurodegenerative movement disorders and α-synucleinopathies with overlap of symptoms especially at early stages of the disease but with distinct disease progression and responses to dopaminergic treatment. Therefore, having biomarkers that specifically classify patients, which could discriminate PD from MSA, would be very useful. MicroRNAs (miRNAs) regulate protein translation and are observed in biological fluids, including cerebrospinal fluid (CSF), and may therefore have potential as biomarkers of disease. The aim of our study was to determine if miRNAs in CSF could be used as biomarkers for either PD or MSA. Using quantitative PCR (qPCR), we evaluated expression levels of 10 miRNAs in CSF patient samples from PD (n = 28), MSA (n = 17), and non-neurological controls (n = 28). We identified two miRNAs (miR-24 and miR-205) that distinguished PD from controls and four miRNAs that differentiated MSA from controls (miR-19a, miR-19b, miR-24, and miR-34c). Combinations of miRNAs accurately discriminated either PD (area under the curve (AUC) = 0.96) or MSA (AUC = 0.86) from controls. In MSA, we also observed that miR-24 and miR-148b correlated with cerebellar ataxia symptoms, suggesting that these miRNAs are involved in cerebellar degeneration in MSA. Our findings support the potential of miRNA panels as biomarkers for movement disorders and may provide more insights into the pathological mechanisms related to these disorders.

CSF microRNA Profiling in Alzheimer's Disease: a Screening and Validation Study

MicroRNAs (miRNAs) are short non-coding RNA molecules that regulate gene expression through post-transcriptional repression of target genes. They have been shown to be implicated in the pathophysiology of Alzheimer's disease (AD) and proposed as disease biomarkers. In the present work, we have studied the expression levels of 754 miRNAs in cerebrospinal fluid (CSF) from AD patients and control subjects. We have explored a first screening cohort (N = 20) and selected 12 miRNAs to be further tested in a second independent validation cohort (N = 69). We have found a significant upregulation of miR-222 and miR-125b in AD CSF. Of these, the association of miR-222 with AD is novel and reported here for the first time whereas upregulation of miR-125b has been previously reported in AD brain. Yet we do not find association with other miRNAs which were previously linked to AD. Our results shed light on potential underlying pathophysiological processes of AD and also point out the need for consensus procedures in CSF miRNA detection and data analysis.