Profiling of Serum Exosome MiRNA Reveals the Potential of a MiRNA Panel as Diagnostic Biomarker for Alzheimer's Disease

Exosomes for neurodegenerative diseases: diagnosis and targeted therapy

PURPOSE OF REVIEW

Neurodegenerative diseases are still challenging clinical issues, with no curative interventions available and early, accurate diagnosis remaining difficult. Finding solutions to them is of great importance. In this review, we discuss possible exosomal diagnostic biomarkers and explore current explorations in exosome-targeted therapy for some common neurodegenerative diseases, offering insights into the clinical transformation of exosomes in this field.

RECENT FINDINGS

The burgeoning research on exosomes has shed light on their potential applications in disease diagnosis and treatment. As a type of extracellular vesicles, exosomes are capable of crossing the blood - brain barrier and exist in various body fluids, whose components can reflect pathophysiological changes in the brain. In addition, they can deliver specific drugs to brain tissue, and even possess certain therapeutic effects themselves. And the recent advancements in engineering modification technology have further enabled exosomes to selectively target specific sites, facilitating the possibility of targeted therapy for neurodegenerative diseases. The unique properties of exosomes give them great potential in the diagnosis and treatment of neurodegenerative diseases, and provide novel ideas for dealing with such diseases.

Extracellular vesicles as nanotheranostic platforms for targeted neurological disorder interventions

Central Nervous System (CNS) disorders represent a profound public health challenge that affects millions of people around the world. Diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and traumatic brain injury (TBI) exemplify the complexities and diversities that complicate their early detection and the development of effective treatments. Amid these challenges, the emergence of nanotechnology and extracellular vesicles (EVs) signals a new dawn for treating and diagnosing CNS ailments. EVs are cellularly derived lipid bilayer nanosized particles that are pivotal in intercellular communication within the CNS and have the potential to revolutionize targeted therapeutic delivery and the identification of novel biomarkers. Integrating EVs with nanotechnology amplifies their diagnostic and therapeutic capabilities, opening new avenues for managing CNS diseases. This review focuses on examining the fascinating interplay between EVs and nanotechnology in CNS theranostics. Through highlighting the remarkable advancements and unique methodologies, we aim to offer valuable perspectives on how these approaches can bring about a revolutionary change in disease management. The objective is to harness the distinctive attributes of EVs and nanotechnology to forge personalized, efficient interventions for CNS disorders, thereby providing a beacon of hope for affected individuals. In short, the confluence of EVs and nanotechnology heralds a promising frontier for targeted and impactful treatments against CNS diseases, which continue to pose significant public health challenges. By focusing on personalized and powerful diagnostic and therapeutic methods, we might improve the quality of patients.

A comprehensive guide to extract information from extracellular vesicles: a tutorial review towards novel analytical developments

In the medical field, extracellular vesicles (EVs) are gaining importance as they act as cells mediators. These are phospholipid bilayer vesicles and contain crucial biochemical information about their mother cells being carrier of different biomolecules such as small molecules, proteins, lipids, and nucleic acids. After release into the extracellular matrix, they enter the systemic circulation and can be found in all human biofluids. Since EVs reflect the state of the cell of origin, there is exponential attention as potential source of new circulating biomarkers for liquid biopsy. The use of EVs in clinical practice faces several challenges that need to be addressed: these include the standardization of lysis protocols, the availability of low-cost reagents and the development of analytical tools capable of detecting biomarkers. The process of lysis is a crucial step that can impact all subsequent analyses, towards the development of novel analytical strategies. To aid researchers to support the evolution of measurement science technology, this tutorial review evaluates and discuss the most commonly protocols used to characterize the contents of EVs, including their advantages and disadvantages in terms of experimental procedures, time and equipment. The purpose of this tutorial review is to offer practical guide to researchers which are intended to develop novel analytical approaches. Some of the most significant applications are considered, highlighting their main characteristics divided per mechanism of action. Finally, comprehensive tables which provide an overview at a glance are provided to readers.

A combined circulating microRNA panel predicts the risk of vascular calcification in community-dwelling older adults with age strata differences

BACKGROUND

Older adults have a higher risk of developing vascular calcification (VC). Circulating miRNAs can be potential risk indicators. However, prior studies used single miRNA mostly, whereas miRNA panels were rarely evaluated. We aimed to examine whether a miRNA panel outperformed each miRNA alone, and analyzed whether advanced age affected VC risk predictive performance offered by the miRNA panel.

METHODS

We prospectively enrolled older adults (age ≥65 years) during their annual health checkup in 2017, and examined their VC severity followed by analyzing sera for VC regulatory miRNAs (miR-125b-5p, miR-125b-3p, and miR-378a-3p). We used multiple regression analyses to determine associations between each miRNA or a 3-combind panel and VC risk, followed by area under the receiver-operating-characteristics curve (AUROC) analysis. Participants were further divided to those of 65-75 and ≥75 years for comparison.

RESULTS

From 199 older adults screened, 169 (median age, 73.3 years) with available calcification assessment were analyzed, among whom 74.6 % having VC. Those with VC had significantly lower circulating miR-125b-5p, miR-125b-3p, and miR-378a-3p levels than those without. Regression analyses showed that the 3-combined miRNA panel exhibited significant associations with VC risk, with significantly higher AUROC than those of models based on individual miRNA. Importantly, in those ≥75 years, the miRNA-predicted risk of VC was more prominent than that in the 65-75 years group.

CONCLUSION

A miRNA panel for VC risk prediction might outperform individual miRNA alone in older adults, and advanced age modified the association between circulating miRNAs and the risk of VC.

Regulation of Zbp1 by miR-99b-5p in microglia controls the development of schizophrenia-like symptoms in mice

Current approaches to the treatment of schizophrenia have mainly focused on the protein-coding part of the genome; in this context, the roles of microRNAs have received less attention. In the present study, we analyze the microRNAome in the blood and postmortem brains of schizophrenia patients, showing that the expression of miR-99b-5p is downregulated in both the prefrontal cortex and blood of patients. Lowering the amount of miR-99b-5p in mice leads to both schizophrenia-like phenotypes and inflammatory processes that are linked to synaptic pruning in microglia. The microglial miR-99b-5p-supressed inflammatory response requires Z-DNA binding protein 1 (Zbp1), which we identify as a novel miR-99b-5p target. Antisense oligonucleotides against Zbp1 ameliorate the pathological effects of miR-99b-5p inhibition. Our findings indicate that a novel miR-99b-5p-Zbp1 pathway in microglia might contribute to the pathogenesis of schizophrenia.

Involvement of transposable elements in Alzheimer's disease pathogenesis

Alzheimer's disease affects an average of 5 % of the population with a significant increase in prevalence with age, suggesting that the same mechanisms that underlie aging may influence this pathology. Investigation of these mechanisms is promising for effective methods of treatment and prevention of the disease. Possible participants in these mechanisms are transposons, which serve as drivers of epigenetic regulation, since they form species-specific distributions of non-coding RNA genes in genomes in evolution. Study of miRNA involvement in Alzheimer's disease pathogenesis is relevant, since the associations of protein-coding genes (APOE4, ABCA7, BIN1, CLU, CR1, PICALM, TREM2) with the disease revealed as a result of GWAS make it difficult to explain its complex pathogenesis. Specific expression changes of many genes were found in different brain parts of Alzheimer's patients, which may be due to global regulatory changes under the influence of transposons. Experimental and clinical studies have shown pathological activation of retroelements in Alzheimer's disease. Our analysis of scientific literature in accordance with MDTE DB revealed 28 miRNAs derived from transposons (17 from LINE, 5 from SINE, 4 from HERV, 2 from DNA transposons), the expression of which specifically changes in this disease (decreases in 17 and increases in 11 microRNA). Expression of 13 out of 28 miRNAs (miR-151a, -192, -211, -28, -31, -320c, -335, -340, -378a, -511, -576, -708, -885) also changes with aging and cancer development, which indicates the presence of possible common pathogenetic mechanisms. Most of these miRNAs originated from LINE retroelements, the pathological activation of which is associated with aging, carcinogenesis, and Alzheimer's disease, which supports the hypothesis that these three processes are based on the primary dysregulation of transposons that serve as drivers of epigenetic regulation of gene expression in ontogeny.

Isolation and usage of exosomes in central nervous system diseases

BACKGROUND

Exosomes are vesicles secreted by all types of mammalian cells. They are characterized by a double-layered lipid membrane structure. They serve as carriers for a plethora of signal molecules, including DNA, RNA, proteins, and lipids. Their unique capability of effortlessly crossing the blood-brain barrier underscores their critical role in the progression of various neurological disorders. This includes, but is not limited to, diseases such as Alzheimer's, Parkinson's, and ischemic stroke. Establishing stable and mature methods for isolating exosomes is a prerequisite for the study of exosomes and their biomedical significance. The extraction technologies of exosomes include differential centrifugation, density gradient centrifugation, size exclusion chromatography, ultrafiltration, polymer coprecipitation, immunoaffinity capture, microfluidic, and so forth. Each extraction technology has its own advantages and disadvantages, and the extraction standards of exosomes have not been unified internationally.

AIMS

This review aimed to showcase the recent advancements in exosome isolation techniques and thoroughly compare the advantages and disadvantages of different methods. Furthermore, the significant research progress made in using exosomes for diagnosing and treating central nervous system (CNS) diseases has been emphasized.

CONCLUSION

The varying isolation methods result in differences in the concentration, purity, and size of exosomes. The efficient separation of exosomes facilitates their widespread application, particularly in the diagnosis and treatment of CNS diseases.

Exosomes: A Cellular Communication Medium That Has Multiple Effects On Brain Diseases

Exosomes, as membranous vesicles generated by multiple cell types and secreted to extracellular space, play a crucial role in a range of brain injury-related brain disorders by transporting diverse proteins, RNA, DNA fragments, and other functional substances. The nervous system's pathogenic mechanisms are complicated, involving pathological processes like as inflammation, apoptosis, oxidative stress, and autophagy, all of which result in blood-brain barrier damage, cognitive impairment, and even loss of normal motor function. Exosomes have been linked to the incidence and progression of brain disorders in recent research. As a result, a thorough knowledge of the interaction between exosomes and brain diseases may lead to the development of more effective therapeutic techniques that may be implemented in the clinic. The potential role of exosomes in brain diseases and the crosstalk between exosomes and other pathogenic processes were discussed in this paper. Simultaneously, we noted the delicate events in which exosomes as a media allow the brain to communicate with other tissues and organs in physiology and disease, and compiled a list of natural compounds that modulate exosomes, in order to further improve our understanding of exosomes and propose new ideas for treating brain disorders.

Mesenchymal Stem Cells from Familial Alzheimer's Patients Express MicroRNA Differently

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the predominant form of dementia globally. No reliable diagnostic, predictive techniques, or curative interventions are available. MicroRNAs (miRNAs) are vital to controlling gene expression, making them valuable biomarkers for diagnosis and prognosis. This study examines the transcriptome of olfactory ecto-mesenchymal stem cells (MSCs) derived from individuals with the PSEN1(A431E) mutation (Jalisco mutation). The aim is to determine whether this mutation affects the transcriptome and expression profile of miRNAs and their target genes at different stages of asymptomatic, presymptomatic, and symptomatic conditions. Expression microarrays compare the MSCs from mutation carriers with those from healthy donors. The results indicate a distinct variation in the expression of miRNAs and mRNAs among different symptomatologic groups and between individuals with the mutation. Using bioinformatics tools allows us to identify target genes for miRNAs, which in turn affect various biological processes and pathways. These include the cell cycle, senescence, transcription, and pathways involved in regulating the pluripotency of stem cells. These processes are closely linked to inter- and intracellular communication, vital for cellular functioning. These findings can enhance our comprehension and monitoring of the disease's physiological processes, identify new disorder indicators, and develop innovative treatments and diagnostic tools for preventing or treating AD.

Non-Coding RNAs in Human Cancer and Other Diseases: Overview of the Diagnostic Potential

Non-coding RNAs (ncRNAs) are abundant single-stranded RNA molecules in human cells, involved in various cellular processes ranging from DNA replication and mRNA translation regulation to genome stability defense. MicroRNAs are multifunctional ncRNA molecules of 18-24 nt in length, involved in gene silencing through base-pair complementary binding to target mRNA transcripts. piwi-interacting RNAs are an animal-specific class of small ncRNAs sized 26-31 nt, responsible for the defense of genome stability via the epigenetic and post-transcriptional silencing of transposable elements. Long non-coding RNAs are ncRNA molecules defined as transcripts of more than 200 nucleotides, their function depending on localization, and varying from the regulation of cell differentiation and development to the regulation of telomere-specific heterochromatin modifications. The current review provides recent data on the several forms of small and long non-coding RNA's potential to act as diagnostic, prognostic or therapeutic target for various human diseases.

Circulating exosomal has-miR-24-3p and has-miR-128-3p reflect early efficacy of sublingual immunotherapy in allergic rhinitis

OBJECTIVE

Sublingual immunotherapy (SLIT) can improve the symptoms of allergic rhinitis (AR) and modify its natural course, but its effectiveness varies among individuals. This study aims to analyze miRNAs from serum exosomes and evaluate their predictive values for the early response of SLIT in AR.

METHODS

RNA sequencing was performed to investigate the differential expressions of serum exosomal miRNAs between ineffective and effective AR patients who treated with SLIT. The identified candidate miRNAs were validated in two independent cohorts, and the predictive capabilities of these miRNAs and alterations of their expression levels between pre- and 1 year post-SLIT were evaluated.

RESULTS

The serum exosome-derived miRNA profiles were significantly different between the effective and ineffective groups. The five most up-regulated and down-regulated miRNAs were verified in the first validation cohort, and the results demonstrated that serum exosomal has-miR-24-3p and has-miR-206 were reduced, while has-miR-128-3p was increased in the effective group compared to the ineffective group (P < 0.05). Additionally, the receiver operating characteristic (ROC) curves revealed that serum levels of has-miR-24-3p and has-miR-128-3p displayed potential values for predicting the early efficacy of SLIT (P < 0.05). In the second validation cohort, it was observed that the baseline levels of serum exosomal has-miR-24-3p were significantly lower, while has-miR-128-3p levels were significantly higher in the effective group compared to the ineffective group (P < 0.05). After 1 year of SLIT, there was a significant decrease in serum exosomal levels of has-miR-24-3p compared to baseline. On the other hand, effective patients showed a notable increase in serum exosomal levels of has-miR-128-3p (P < 0.05).

CONCLUSION

Serum exosome-derived miRNAs have the potential to impact the efficacy of SLIT in AR patients. Among them, serum exosomal has-miR-24-3p and has-miR-128-3p show promise as biomarkers for predicting the early effectiveness of SLIT and monitoring therapeutic outcomes.

Impaired myelin ultrastructure is reversed by citalopram treatment in a mouse model for major depressive disorder

Major depressive disorder (MDD) is the most common and widespread mental disorder. Selective serotonin reuptake inhibitors (SSRIs) are the first-line treatment for MDD. The relation between the inhibition of serotonin reuptake in the central nervous system and remission from MDD remains controversial, as reuptake inhibition occurs rapidly, but remission from MDD takes weeks to months. Myelination-related deficits and white matter abnormalities were shown to be involved in psychiatric disorders such as MDD. This may explain the delay in remission following SSRI administration. The raphe nuclei (RN), located in the brain stem, consist of clusters of serotonergic (5-HT) neurons that project to almost all regions of the brain. Thus, the RN are an intriguing area for research of the potential effect of SSRI on myelination, and their involvement in MDD. MicroRNAs (miRNAs) regulate many biological features that might be altered by antidepressants. Two cohorts of chronic unpredictable stress (CUS) mouse model for depression underwent behavioral tests for evaluating stress, anxiety, and depression levels. Following application of the CUS protocol and treatment with the SSRI, citalopram, 48 mice of the second cohort were tested via magnetic resonance imaging and diffusion tensor imaging for differences in brain white matter tracts. RN and superior colliculus were excised from both cohorts and measured for changes in miRNAs, mRNA, and protein levels of candidate genes. Using MRI-DTI scans we found lower fractional anisotropy and axial diffusivity in brains of stressed mice. Moreover, both miR-30b-5p and miR-101a-3p were found to be downregulated in the RN following CUS, and upregulated following CUS and citalopram treatment. The direct binding of these miRNAs to Qki, and the subsequent effects on mRNA and protein levels of myelin basic protein (Mbp), indicated involvement of these miRNAs in myelination ultrastructure processes in the RN, in response to CUS followed by SSRI treatment. We suggest that SSRIs are implicated in repairing myelin deficits resulting from chronic stress that leads to depression.

A meta-analysis of neurogenic exosomes in the diagnosis of Alzheimer's disease

Background

Alzheimer's disease (AD) is an irreversible and difficult-to-treat neurodegenerative disease. It is necessary to search for reliable biomarkers for the early diagnosis of AD in a timely and effective manner in high-risk or preclinical AD populations. Studies have shown that neurogenic exosomes in the blood can be effectively used as biomarkers for AD.

Objective

In this meta-analysis, we aimed to find reliable biomarkers (Aβ42, T-tau, and P-tau181 in peripheral blood neurogenic exosomes) for the early diagnosis of AD to provide theoretical support for the early diagnosis of high-risk or preclinical AD populations.

Methods

By searching the literature database, relevant studies on AD diagnostic markers were collected. The study period was from April 1, 2012, to April 1, 2022. The average concentrations of Aβ42, T-tau, and P-tau181 in the exosomes of the AD group and healthy control group were compared using RevMan 5.3 software.

Results

A total of 13 studies were screened, including 842 subjects. Meta-analysis showed that the combined SMD value of neurogenic exosome Aβ42 was 1.70 (95% CI = [1.20,2.20], Z = 6.69, P < 0.05). The combined SMD value of T-tau was 1.02 (95% CI = [0.27,1.77], Z = 2.67, P < 0.05). The combined SMD value of P-tau181 was 1.75 (95% CI = [1.16, 2.35], Z = 5.75, P < 0.05). The levels of neurogenic exosomes Aβ42, T-tau, and P-tau181 in AD patients were significantly higher than those in healthy controls.

Conclusion

Aβ42, T-tau, and P-tau181 in blood neurogenic exosomes can be effectively used as biomarkers for AD and can be applied in the diagnosis, screening, prognosis prediction and disease monitoring of AD.

A new perspective on Alzheimer's disease: microRNAs and circular RNAs

microRNAs (miRNAs) play a multifaceted role in the pathogenesis of Alzheimer's disease (AD). miRNAs regulate several aspects of the disease, such as Aβ metabolism, tau phosphorylation, neuroinflammation, and synaptic function. The dynamic interaction between miRNAs and their target genes depends upon various factors, including the subcellular localization of miRNAs, the relative abundance of miRNAs and target mRNAs, and the affinity of miRNA-mRNA interactions. The miRNAs are released into extracellular fluids and subsequently conveyed to specific target cells through various modes of transportation, such as exosomes. In comparison, circular RNAs (circRNAs) are non-coding RNA (ncRNA) characterized by their covalently closed continuous loops. In contrast to linear RNA, RNA molecules are circularized by forming covalent bonds between the 3'and 5'ends. CircRNA regulates gene expression through interaction with miRNAs at either the transcriptional or post-transcriptional level, even though their precise functions and mechanisms of gene regulation remain to be elucidated. The current stage of research on miRNA expression profiles for diagnostic purposes in complex disorders such as Alzheimer's disease is still in its early phase, primarily due to the intricate nature of the underlying pathological causes, which encompass a diverse range of pathways and targets. Hence, this review comprehensively addressed the alteration of miRNA expression across diverse sources such as peripheral blood, exosome, cerebrospinal fluid, and brain in AD patients. This review also addresses the nascent involvement of circRNAs in the pathogenesis of AD and their prospective utility as biomarkers and therapeutic targets for these conditions in future research.

Research progress on the role of extracellular vesicles in neurodegenerative diseases

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease, affect millions of people worldwide. Tremendous efforts have been put into disease-related research, but few breakthroughs have been made in diagnostic and therapeutic approaches. Extracellular vesicles (EVs) are heterogeneous cell-derived membrane structures that arise from the endosomal system or are directly separated from the plasma membrane. EVs contain many biomolecules, including proteins, nucleic acids, and lipids, which can be transferred between different cells, tissues, or organs, thereby regulating cross-organ communication between cells during normal and pathological processes. Recently, EVs have been shown to participate in various aspects of neurodegenerative diseases. Abnormal secretion and levels of EVs are closely related to the pathogenesis of neurodegenerative diseases and contribute to disease progression. Numerous studies have proposed EVs as therapeutic targets or biomarkers for neurodegenerative diseases. In this review, we summarize and discuss the advanced research progress on EVs in the pathological processes of several neurodegenerative diseases. Moreover, we outline the latest research on the roles of EVs in neurodegenerative diseases and their therapeutic potential for the diseases.

Common microRNA regulated pathways in Alzheimer's and Parkinson's disease

MicroRNAs (miRNAs) are small non-coding RNAs involved in gene regulation. Recently, miRNA dysregulation has been found in neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). The diagnosis of Alzheimer's and Parkinson's is currently challenging, mainly occurring when pathology is already present, and although treatments are available for both diseases, the role of treatment is primarily to prevent or delay the progress of the diseases instead of fully overcoming the diseases. Therefore, the challenge in the near future will be to determine effective drugs to tackle the dysregulated biological pathways in neurodegenerative diseases. In the present study, we describe the dysregulation of miRNAs in blood of Alzheimer's and Parkinson's patients with the aim to identify common mechanisms between the 2 pathologies and potentially to identify common therapeutic targets which can stop or delay the progression of two most frequent neuropathologies. Two independent systematic reviews, bioinformatic analysis, and experiment validation were performed to identify whether AD and PD share common pathways. A total of 15 common miRNAs were found in the literature and 13 common KEGG pathways. Among the common miRNAs, two were selected for validation in a small cohort of AD and PD patients. Let-7f-5p and miR-29b-3p showed to be good predictors in blood of PD patients.

Long non-coding RNA and circular RNA and coding RNA profiling of plasma exosomes of osteosarcoma by RNA seq

Osteosarcoma (OS) is a primary bone tumor with high malignancy and the mechanism of hematogenous metastasis in OS is still not clear. The plasma exosomes derived from osteosarcoma play a key role in the process of tumor metastasis. Here, we established RNA-seq dataset for lncRNAs, circRNAs and mRNAs in plasma exosomes from 10 OS patients and 5 healthy donors. A total of 329.52 Gb of clean data was obtained. Besides, 1754 lincRNAs, 7096 known and 1935 new circRNA was identified. Finally, gene expression profiles and differentially expressed genes (DEGs) were analyzed among these 15 samples. There were 331 DEGs of mRNA, 132 of lincRNA and 489 of circRNA was obtained, respectively. This data set provides a significant resource for relevant researchers to excavate potential dysregulated lncRNAs, circRNAs and mRNAs of plasma exosomes in OS versus normal conditions.

Recent advances in isolation and detection of exosomal microRNAs related to Alzheimer's disease

Alzheimer's disease, a progressive neurological condition, is associated with various internal and external risk factors in the disease's early stages. Early diagnosis of Alzheimer's disease is essential for treatment management. Circulating exosomal microRNAs could be a new class of valuable biomarkers for early Alzheimer's disease diagnosis. Different kinds of biosensors have been introduced in recent years for the detection of these valuable biomarkers. Isolation of the exosomes is a crucial step in the detection process which is traditionally carried out by multi-step ultrafiltration. Microfluidics has improved the efficiency and costs of exosome isolation by implementing various effects and forces on the nano and microparticles in the microchannels. This paper reviews recent advancements in detecting Alzheimer's disease related exosomal microRNAs based on methods such as electrochemical, fluorescent, and SPR. The presented devices' pros and cons and their efficiencies compared with the gold standard methods are reported. Moreover, the application of microfluidic devices to detect Alzheimer's disease related biomarkers is summarized and presented. Finally, some challenges with the performance of novel technologies for isolating and detecting exosomal microRNAs are addressed.

Decoding the genetic relationship between Alzheimer's disease and type 2 diabetes: potential risk variants and future direction for North Africa

Introduction

Alzheimer's disease (AD) and Type 2 diabetes (T2D) are both age-associated diseases. Identification of shared genes could help develop early diagnosis and preventive strategies. Although genetic background plays a crucial role in these diseases, we noticed an underrepresentation tendency of North African populations in omics studies.

Materials and methods

First, we conducted a comprehensive review of genes and pathways shared between T2D and AD through PubMed. Then, the function of the identified genes and variants was investigated using annotation tools including PolyPhen2, RegulomeDB, and miRdSNP. Pathways enrichment analyses were performed with g:Profiler and EnrichmentMap. Next, we analyzed variant distributions in 16 worldwide populations using PLINK2, R, and STRUCTURE software. Finally, we performed an inter-ethnic comparison based on the minor allele frequency of T2D-AD common variants.

Results

A total of 59 eligible papers were included in our study. We found 231 variants and 363 genes shared between T2D and AD. Variant annotation revealed six single nucleotide polymorphisms (SNP) with a high pathogenic score, three SNPs with regulatory effects on the brain, and six SNPs with potential effects on miRNA-binding sites. The miRNAs affected were implicated in T2D, insulin signaling pathways, and AD. Moreover, replicated genes were significantly enriched in pathways related to plasma protein binding, positive regulation of amyloid fibril deposition, microglia activation, and cholesterol metabolism. Multidimensional screening performed based on the 363 shared genes showed that main North African populations are clustered together and are divergent from other worldwide populations. Interestingly, our results showed that 49 SNP associated with T2D and AD were present in North African populations. Among them, 11 variants located in DNM3, CFH, PPARG, ROHA, AGER, CLU, BDNF1, CST9, and PLCG1 genes display significant differences in risk allele frequencies between North African and other populations.

Conclusion

Our study highlighted the complexity and the unique molecular architecture of North African populations regarding T2D-AD shared genes. In conclusion, we emphasize the importance of T2D-AD shared genes and ethnicity-specific investigation studies for a better understanding of the link behind these diseases and to develop accurate diagnoses using personalized genetic biomarkers.

MicroRNAs in Extracellular Vesicles of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease with dysfunction of memory, language and thinking. More than 55 million people were diagnosed with AD or other dementia around the world in 2020. The pathology of AD is still unclear and there are no applicable therapies for AD. MicroRNAs (miRNAs) play key roles in AD pathology and have great potential for the diagnosis and treatment of AD. Extracellular vesicles (EVs) widely exist in body fluids such as blood and cerebrospinal fluid (CSF) and contain miRNAs that are involved in cell-to-cell communication. We summarized the dysregulated miRNAs in EVs derived from the different body fluids of AD patients, as well as their potential function and application in AD. We also compared these dysregulated miRNAs in EVs to those in the brain tissues of AD patients aiming to provide a comprehensive view of miRNAs in AD. After careful comparisons, we found that miR-125b-5p and miR-132-3p were upregulated and downregulated in several different brain tissues of AD and EVs of AD, respectively, suggesting their value in AD diagnosis based on EV miRNAs. Furthermore, miR-9-5p was dysregulated in EVs and different brain tissues of AD patients and had also been tested as a potential therapy for AD in mice and human cell models, suggesting that miR-9-5p could be used to design new therapies for AD.

Progress in blood biomarkers of subjective cognitive decline in preclinical Alzheimer's disease

ABSTRACT

Alzheimer's disease (AD) is a neurodegenerative disease that gradually impairs cognitive functions. Recently, there has been a conceptual shift toward AD to view the disease as a continuum. Since AD is currently incurable, effective intervention to delay or prevent pathological cognitive decline may best target the early stages of symptomatic disease, such as subjective cognitive decline (SCD), in which cognitive function remains relatively intact. Diagnostic methods for identifying AD, such as cerebrospinal fluid biomarkers and positron emission tomography, are invasive and expensive. Therefore, it is imperative to develop blood biomarkers that are sensitive, less invasive, easier to access, and more cost effective for AD diagnosis. This review aimed to summarize the current data on whether individuals with SCD differ reliably and effectively in subjective and objective performances compared to cognitively normal elderly individuals, and to find one or more convenient and accessible blood biomarkers so that researchers can identify SCD patients with preclinical AD in the population as soon as possible. Owing to the heterogeneity and complicated pathogenesis of AD, it is difficult to make reliable diagnoses using only a single blood marker. This review provides an overview of the progress achieved to date with the use of SCD blood biomarkers in patients with preclinical AD, highlighting the key areas of application and current challenges.

Exosomes for the diagnosis and treatment of dementia

PURPOSE OF REVIEW

Dementia is a syndrome with several possible pathologies. To date, definitive methods for diagnosis and treatment of sub-types of dementia have not been established. Emerging evidence suggests that exosomes can provide important information for the diagnosis and treatment of several subtypes of dementia. This article reviews recent studies on the application of exosomes in dementia.

RECENT FINDINGS

Exosomes are involved in the pathogenesis of Alzheimer's disease (AD) and Parkinson's disease (PD) through transporting toxic proteins such as amyloid beta (Aβ), tau, and α-synuclein. Exosomal microRNAs (miR) and proteins reflect the disease state, and therefore, exosomes can be used as diagnostic markers for diseases such as AD, PD, Huntington's disease (HD), vascular dementia (VaD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD). Mesenchymal stem cell (MSC)-derived exosomes have been shown to ameliorate disease pathology, and improve cognitive function in AD, PD, and VAD.

SUMMARY

Recent studies have shown that exosomes could be novel diagnostic agents for dementia because they contain molecules that could be potential biomarker candidates indicative of the type and stage of dementia. Therapeutic application of exosomes in dementia has revealed that exosomes only, or exosomes loaded with an active pharmaceutical ingredient (API), ameliorate disease phenotype of dementia. Further work is needed to exploit this potential.

Extracellular vesicles and Alzheimer's disease in the novel era of Precision Medicine: implications for disease progression, diagnosis and treatment

Extracellular vesicles (EVs), secreted membranous nano-sized particles, are critical intercellular messengers participating in nervous system homeostasis, while recent evidence implicates EVs in Alzheimer's disease (AD) pathogenesis. Specifically, small EVs have been shown to spread toxic proteins, induce neuronal loss, and contribute to neuroinflammation and AD progression. On the other hand, EVs can reduce amyloid-beta deposition and transfer neuroprotective substances between cells, mitigating disease mechanisms. In addition to their roles in AD pathogenesis, EVs also exhibit great potential for the diagnosis and treatment of other brain disorders, representing an advantageous tool for Precision Medicine. Herein, we summarize the contribution of small EVs to AD-related mechanisms and disease progression, as well as their potential as diagnostic and therapeutic agents for AD.

Circulating Small Extracellular Vesicle-Derived miR-342-5p Ameliorates Beta-Amyloid Formation via Targeting Beta-site APP Cleaving Enzyme 1 in Alzheimer's Disease

Alzheimer's disease (AD) is a common neurodegenerative disorder with progressive cognitive impairment in the elderly. Beta-amyloid (Aβ) formation and its accumulation in the brain constitute one of the pathological hallmarks of AD. Until now, how to modulate Aβ formation in hippocampal neurons remains a big challenge. Herein, we investigated whether the exosomal transfer of microRNA (miR) relates to amyloid pathology in the recipient neuron cells. We isolated circulating small extracellular vesicles (sEVs) from AD patients and healthy controls, determined the miR-342-5p level in the sEVs by RT-PCR, and evaluated its diagnostic performance in AD. Then, we took advantage of biomolecular assays to estimate the role of miR-342-5p in modulating the amyloid pathway, including amyloid precursor protein (APP), beta-site APP cleaving enzyme 1 (BACE1), and Aβ42. Furthermore, we subjected HT22 cells to the sEVs from the hippocampal tissues of transgenic APP mice (Exo-APP) or C57BL/6 littermates (Exo-CTL), and the Exo-APP enriched with miR-342-5p mimics or the control to assess the effect of the sEVs' delivery of miR-342-5p on Aβ formation. We observed a lower level of miR-342-5p in the circulating sEVs from AD patients compared with healthy controls. MiR-342-5p participated in Aβ formation by modulating BACE1 expression, specifically binding its 3'-untranslated region (UTR) sequence. Exo-APP distinctly promoted Aβ42 formation in the recipient cells compared to Exo-CTL. Intriguingly, miR-342-5p enrichment in Exo-APP ameliorated amyloid pathology in the recipient cells. Our study indicated that miR-342-5p was dysregulated in human circulating sEVs from AD patients; sEV transfer of miR-342-5p ameliorates Aβ formation by modulating BACE1 expression. These findings highlight the promising potential of exosomal miRNAs in AD clinical therapy.

Circulating extracellular vesicle-containing microRNAs reveal potential pathogenesis of Alzheimer’s disease

The pathogenesis of Alzheimer’s disease (AD) remains unknown till today, hindering the research and development of AD therapeutics and diagnostics. Circulating extracellular vesicles (EVs) can be utilized as a new window to spy upon AD pathogenesis. Altered microRNA profiles were noted in both the cerebrospinal fluid (CSF)- and blood-isolated EVs of AD patients, implying the outstanding potential of circulating EV-containing miRNAs (CEmiRs) to serve as important regulators in AD pathogenesis. Although several CEmiRs were found to play a part in AD, the association of globally altered miRNA profiles in patients’ serum-derived EVs with AD pathogenesis remains unclear. In this study, we first investigated the miRNA profile in serum-derived EVs from AD, mild cognitive impairment (MCI) patients, and healthy individuals. We observed differential expression patterns of CEmiRs and classified them into 10 clusters. We identified the predicted targets of these differentially expressed CEmiRs (DECEmiRs) and analyzed their biological functions and interactions. Our study revealed the temporal regulation of complex and precise signaling networks on AD pathogenesis, shedding light on the development of novel therapeutic strategies, including multi-target drug combination for AD treatment.

Epigenetic Changes in Prion and Prion-like Neurodegenerative Diseases: Recent Advances, Potential as Biomarkers, and Future Perspectives

Prion diseases are transmissible spongiform encephalopathies (TSEs) caused by a conformational conversion of the native cellular prion protein (PrP^C) to an abnormal, infectious isoform called PrP^Sc. Amyotrophic lateral sclerosis, Alzheimer’s, Parkinson’s, and Huntington’s diseases are also known as prion-like diseases because they share common features with prion diseases, including protein misfolding and aggregation, as well as the spread of these misfolded proteins into different brain regions. Increasing evidence proposes the involvement of epigenetic mechanisms, namely DNA methylation, post-translational modifications of histones, and microRNA-mediated post-transcriptional gene regulation in the pathogenesis of prion-like diseases. Little is known about the role of epigenetic modifications in prion diseases, but recent findings also point to a potential regulatory role of epigenetic mechanisms in the pathology of these diseases. This review highlights recent findings on epigenetic modifications in TSEs and prion-like diseases and discusses the potential role of such mechanisms in disease pathology and their use as potential biomarkers.

MicroRNAs in extracellular vesicles: Sorting mechanisms, diagnostic value, isolation, and detection technology

MicroRNAs (miRNAs) are a class of short, single-stranded, noncoding RNAs, with a length of about 18–22 nucleotides. Extracellular vesicles (EVs) are derived from cells and play a vital role in the development of diseases and can be used as biomarkers for liquid biopsy, as they are the carriers of miRNA. Existing studies have found that most of the functions of miRNA are mainly realized through intercellular transmission of EVs, which can protect and sort miRNAs. Meanwhile, detection sensitivity and specificity of EV-derived miRNA are higher than those of conventional serum biomarkers. In recent years, EVs have been expected to become a new marker for liquid biopsy. This review summarizes recent progress in several aspects of EVs, including sorting mechanisms, diagnostic value, and technology for isolation of EVs and detection of EV-derived miRNAs. In addition, the study reviews challenges and future research avenues in the field of EVs, providing a basis for the application of EV-derived miRNAs as a disease marker to be used in clinical diagnosis and even for the development of point-of-care testing (POCT) platforms.

Exosomal MicroRNA-Based Predictive Model for Preclinical Alzheimer's Disease: A Multicenter Study

BACKGROUND

Exosomal microRNAs (miRNAs) have been demonstrated to be biomarkers of Alzheimer's disease (AD). However, whether exosomal miRNAs can predict AD at the asymptomatic stage remains unclear.

METHODS

This study is a multicenter study with four independent datasets to verify the capacity of exosomal miRNAs to identify preclinical AD. Subjects were recruited from a Beijing center in the pilot study (dataset 1: subjects with AD, n = 20; control subjects, n = 20), from other centers across China (dataset 2: subjects with AD, n = 95; control subjects, n = 93), a longitudinal cohort (dataset 3: subjects with preclinical AD, n = 101; control subjects, n = 102), and a confirmation study on familial AD (dataset 4: mutation carriers, n = 56; nonmutation carriers, n = 57).

RESULTS

A panel of miRNAs was changed in subjects with AD and can detect preclinical AD 5 to 7 years before the onset of cognitive impairment (areas under the curve = 0.85-0.88).

CONCLUSIONS

Exosomal miRNAs can be effective biomarkers for predicting AD 5 to 7 years prior to cognitive impairment onset.

Exosome: The “Off-the-Shelf” Cellular Nanocomponent as a Potential Pathogenic Agent, a Disease Biomarker, and Neurotherapeutics

Exosomes are nanosized “off-the-shelf” lipid vesicles released by almost all cell types and play a significant role in cell–cell communication. Exosomes have already been proven to carry cell-specific cargos of proteins, lipids, miRNA, and noncoding RNA (ribonucleic acid). These vesicles can be selectively taken up by the neighboring cell and can regulate cellular functions. Herein, we have discussed three different roles of exosomes in neuroscience. First, we have discussed how exosomes play the role of a pathogenic agent as a part of cell–cell communication and transmit pathogens such as amyloid-beta (Aβ), further helping in the propagation of neurodegenerative and other neurological diseases. In the next section, the review talks about the role of exosomes in biomarker discovery in neurological disorders. Toward the end, we have reviewed how exosomes can be harnessed and engineered for therapeutic purposes in different brain diseases. This review is based on the current knowledge generated in this field and our comprehension of this domain.

A Diagnostic Model for Alzheimer’s Disease Based on Blood Levels of Autophagy-Related Genes

Alzheimer’s disease (AD) is a common neurodegenerative disease. The major problems that exist in the diagnosis of AD include the costly examinations and the high-invasive sampling tissue. Therefore, it would be advantageous to develop blood biomarkers. Because AD’s pathological process is considered tightly related to autophagy; thus, a diagnostic model for AD based on ATGs may have more predictive accuracy than other models. We obtained GSE63060 dataset from the GEO database, ATGs from the HADb and screened 64 differentially expressed autophagy-related genes (DE-ATGs). We then applied them to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses as well as DisGeNET and PaGenBase enrichment analyses. By using the univariate analysis, least absolute shrinkage and selection operator (LASSO) regression method and the multivariable logistic regression, nine DE-ATGs were identified as biomarkers, which are ATG16L2, BAK1, CAPN10, CASP1, RAB24, RGS19, RPS6KB1, ULK2, and WDFY3. We combined them with sex and age to establish a nomogram model. To evaluate the model’s distinguishability, consistency, and clinical applicability, we applied the receiver operating characteristic (ROC) curve, C-index, calibration curve, and on the validation datasets GSE63061, GSE54536, GSE22255, and GSE151371 from GEO database. The results show that our model demonstrates good prediction performance. This AD diagnosis model may benefit both clinical work and mechanistic research.

Alteration of miRNAs in Small Neuron-Derived Extracellular Vesicles of Alzheimer's Disease Patients and the Effect of Extracellular Vesicles on Microglial Immune Responses

Alzheimer's disease (AD) is one of the most severe neurodegenerative diseases observed in the elderly population. Although the hallmarks of AD have been identified, the methods for its definitive diagnosis and treatment are still lacking. Extracellular vesicles (EVs) have become a promising source for biomarkers since the identification of their content. EVs are released from multiple cell types and, when released from neurons, they pass from the brain to the blood with their cargo molecules. Hence, neuron-specific EV-resident microRNAs (miRNAs) are promising biomarkers for diagnosis of AD. This study aimed to identify altered miRNA content in small neuron-derived extracellular vesicles (sNDEVs) isolated from AD patients and healthy individuals. Furthermore, we examined the role of sNDEV-resident miRNAs in neuron-glia cellular interaction to understand their role in AD propagation. We identified 10 differentially expressed miRNAs in the sNDEVs of patients via next-generation sequencing and validated the most dysregulated miRNA, let-7e, with qRT-PCR. Let-7e was significantly increased in the sNDEVs of AD patients compared with those of healthy controls in a larger cohort. First, we evaluated the diagnostic utility of let-7e via ROC curve analysis, which revealed an AUC value of 0.9214. We found that IL-6 gene expression was increased in human microglia after treatment with sNDEVs of AD patients with a high amount of let-7e. Our study suggests that sNDEV-resident let-7e is a potential biomarker for AD diagnosis, and that AD patient-derived sNDEVs induce a neuroinflammatory response in microglia.

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.

Engineered Exosomes-Mediated Transfer of hsa-miR-320a Overcomes Chemoresistance in Cervical Cancer Cells via Targeting MCL1

In cervical cancer (CC), cisplatin resistance greatly restricts the application in clinical. Here, we report that engineered exosomes-mediated transfer of hsa-miR-320a overcomes chemoresistance in cervical cancer cells via targeting Myeloid Cell Leukemia Sequence 1 (MCL1). In DDP resistant CC tissues, as well as cell lines, it was found that miR-320a expression is lower, engineered miR-320a exosomes were used to attenuate DDP resistance in Hela/DDP and Caski/DDP cells. Mechanistically, we find that MCL1, which is a target of miR-320a, overcomes DDP resistance in Hela/DDP cells and in mice. In conclusion, we report that the engineered miR-320a exosomes is proved to be effective and safe.

Development of Alzheimer’s Disease Biomarkers: From CSF- to Blood-Based Biomarkers

In the 115 years since the discovery of Alzheimer’s disease (AD), our knowledge, diagnosis, and therapeutics have significantly improved. Biomarkers are the primary tools for clinical research, diagnostics, and therapeutic monitoring in clinical trials. They provide much insightful information, and while they are not clinically used routinely, they help us to understand the mechanisms of this disease. This review charts the journey of AD biomarker discovery and development from cerebrospinal fluid (CSF) amyloid-beta 1-42 (Aβ42), total tau (T-tau), and phosphorylated tau (p-tau) biomarkers and imaging technologies to the next generation of biomarkers. We also discuss advanced high-sensitivity assay platforms for CSF Aβ42, T-tau, p-tau, and blood analysis. The recently proposed Aβ deposition/tau biomarker/neurodegeneration or neuronal injury (ATN) scheme might facilitate the definition of the biological status underpinning AD and offer a common language among researchers across biochemical biomarkers and imaging. Moreover, we highlight blood-based biomarkers for AD that offer a scalable alternative to CSF biomarkers through cost-saving and reduced invasiveness, and may provide an understanding of disease initiation and development. We discuss different groups of blood-based biomarker candidates, their advantages and limitations, and paths forward, from identification and analysis to clinical validation. The development of valid blood-based biomarkers may facilitate the implementation of future AD therapeutics and diagnostics.

Exosomes in Age-Related Cognitive Decline: Mechanistic Insights and Improving Outcomes

Aging is the most prominent risk factor for cognitive decline, yet behavioral symptomology and underlying neurobiology can vary between individuals. Certain individuals exhibit significant age-related cognitive impairments, while others maintain intact cognitive functioning with only minimal decline. Recent developments in genomic, proteomic, and functional imaging approaches have provided insights into the molecular and cellular substrates of cognitive decline in age-related neuropathologies. Despite the emergence of novel tools, accurately and reliably predicting longitudinal cognitive trajectories and improving functional outcomes for the elderly remains a major challenge. One promising approach has been the use of exosomes, a subgroup of extracellular vesicles that regulate intercellular communication and are easily accessible compared to other approaches. In the current review, we highlight recent findings which illustrate how the analysis of exosomes can improve our understanding of the underlying neurobiological mechanisms that contribute to cognitive variation in aging. Specifically, we focus on exosome-mediated regulation of miRNAs, neuroinflammation, and aggregate-prone proteins. In addition, we discuss how exosomes might be used to enhance individual patient outcomes by serving as reliable biomarkers of cognitive decline and as nanocarriers to deliver therapeutic agents to the brain in neurodegenerative conditions.

The role of Exosomal miRNAs in cancer

Exosomal miRNAs have attracted much attention due to their critical role in regulating genes and the altered expression of miRNAs in virtually all cancers affecting humans (Sun et al. in Mol Cancer 17(1):14, 2018). Exosomal miRNAs modulate processes that interfere with cancer immunity and microenvironment, and are significantly involved in tumor growth, invasion, metastasis, angiogenesis and drug resistance. Fully investigating the detailed mechanism of miRNAs in the occurrence and development of various cancers could help not only in the treatment of cancers but also in the prevention of malignant diseases. The current review highlighted recently published advances regarding cancer-derived exosomes, e.g., sorting and delivery mechanisms for RNAs. Exosomal miRNAs that modulate cancer cell-to-cell communication, impacting tumor growth, angiogenesis, metastasis and multiple biological features, were discussed. Finally, the potential role of exosomal miRNAs as diagnostic and prognostic molecular markers was summarized, as well as their usefulness in detecting cancer resistance to therapeutic agents.

Effects of exosomal miRNAs in the diagnosis and treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Exosomes are extracellular vesicles secreted by a variety of cells, and they participate in intercellular communication by transferring microRNA (miRNA) and other substances. Among the various internal and external factors involved in the occurrence and development of AD, exosome-derived miRNAs have become essential in the pathogenesis and treatment of AD. As nanocarriers of miRNA, exosomes are expected to become an important tool in the pathogenesis, diagnosis, and treatment of AD. This article reviews the roles of exosomal miRNAs in the pathophysiological process, diagnostic biomarkers and treatment of AD.

Isolation of sensory hair cell specific exosomes in human perilymph

Evaluation of hearing loss patients using clinical audiometry has been unable to give a definitive cellular or molecular diagnosis, hampering the development of treatments of sensorineural hearing loss. However, biopsy of inner ear tissue without losing residual hearing function for pathologic diagnosis is extremely challenging. In a clinical setting, perilymph can be accessed, potentially allowing the development of fluid based diagnostic tests. Recent approaches to improving inner ear diagnostics have been focusing on the evaluation of the proteomic or miRNA profiles of perilymph. Inspired by recent characterization and classification of many neurodegenerative diseases using exosomes which not only are produced in locally in diseased tissue but are transported beyond the blood brain barrier, we demonstrate the isolation of human inner ear specific exosomes using a novel ultrasensitive immunomagnetic nano pom-poms capture-release approach. Using perilymph samples harvested from surgical procedures, we were able to isolate exosomes from sensorineural hearing loss patients in only 2–5 μL of perilymph. By isolating sensory hair cell derived exosomes through their expression level of myosin VIIa, we for the first-time sample material from hair cells in the living human inner ear. This work sets up the first demonstration of immunomagnetic capture-release nano pom-pom isolated exosomes for liquid biopsy diagnosis of sensorineural hearing loss. With the ability to isolate exosomes derived from different cell types for molecular characterization, this method also can be developed for analyzing exosomal biomarkers from more accessible patient tissue fluids such as plasma.

MiRNA Detection Using a Rolling Circle Amplification and RNA-Cutting Allosteric Deoxyribozyme Dual Signal Amplification Strategy

A microRNA (miRNA) detection platform composed of a rolling circle amplification (RCA) system and an allosteric deoxyribozyme system is proposed, which can detect miRNA-21 rapidly and efficiently. Padlock probe hybridization with the target miRNA is achieved through complementary base pairing and the padlock probe forms a closed circular template under the action of ligase; this circular template results in RCA. In the presence of DNA polymerase, RCA proceeds and a long chain with numerous repeating units is formed. In the presence of single-stranded DNA (H1 and H2), multi-component nucleic acid enzymes (MNAzymes) are formed that have the ability to cleave substrates. Finally, substrates containing fluorescent and quenching groups and magnesium ions are added to the system to activate the MNAzyme and the substrate cleavage reaction, thus achieving fluorescence intensity amplification. The RCA-MNAzyme system has dual signal amplification and presents a sensing platform that demonstrates broad prospects in the analysis and detection of nucleic acids.