microRNA Activity Research Articles

Regulatory Functions and Mechanisms of Circular RNAs in Hepatic Stellate Cell Activation and Liver Fibrosis.

Chronic liver injury induces the activation of hepatic stellate cells (HSCs) into myofibroblasts, which produce excessive amounts of extracellular matrix (ECM), resulting in tissue fibrosis. If the injury persists, these fibrous scars could be permanent and disrupt liver architecture and function. Currently, effective anti-fibrotic therapies are lacking; hence, understanding molecular mechanisms that control HSC activation could hold a key to the development of new treatments. Recently, emerging studies have revealed roles of circular RNAs (circRNAs), a class of non-coding RNAs that was initially assumed to be the result of splicing errors, as new regulators in HSC activation. These circRNAs can modulate the activity of microRNAs (miRNAs) and their interacting protein partners involved in regulating fibrogenic signaling cascades. In this review, we will summarize the current knowledge of this class of non-coding RNAs for their molecular function in HSC activation and liver fibrosis progression.

Identification of potential proteins translated from circular RNA splice variants

Circular RNAs (circRNAs) are covalently closed RNA molecules generated from precursor RNAs by the head-to-tail backsplicing of exons. Hundreds of studies demonstrated that circRNAs are ubiquitously expressed and regulate cellular events by modulating microRNA (miRNA) and RNA-binding protein (RBP) activities. A few circRNAs are also known to translate into functional polypeptides regulating cellular physiology. All these functions primarily depend on the full-length sequence of the circRNAs. CircRNA backsplice junction sequence is the key to identifying circRNAs and their full-length mature sequence. However, some multi-exonic circRNAs exist in different isoforms sharing identical backsplice junction sequences and are termed circRNA splice variants. Here, we analyzed the previously published HeLa cell RNA-seq datasets to identify circRNA splice variants using the de novo module of the CIRCexplorer2 circRNA annotation pipeline. A subset of circRNAs with splice variants was validated by the circRNA-rolling circle amplification (circRNA-RCA) method. Interestingly, several validated circRNAs were predicted to translate into proteins by the riboCIRC database. Furthermore, polyribosome fractionation followed by quantitative PCR confirmed the association of a subset of circRNAs with polyribosome supporting their protein-coding potential. Finally, bioinformatics analysis of proteins derived from splice variants of circCORO1C and circASPH suggested altered protein sequences and structures that could affect their physiological functions. Together, our study identified novel circRNA splice variants and their potential translation into protein isoforms which may regulate various physiological processes.

Mechanisms of action of cytoplasmic microRNAs. Part 6. MicroRNA-mediated translation activation

In the scientific review, the mechanisms of action of cytoplasmic miRNAs, namely miRNA-mediated activation of translation, are given. To write the article, information was searched using Scopus, Web of Science, MedLine, PubMed, Google Scholar, EMBASE, Global Health, The Cochrane Library databases. Examples of direct activation of mRNA translation by miRNA are presented. One of them is miRNA-mediated activation of translation, which is associated with the peculiarities of the state of the cell (resting cell effect). It has been shown that protein 1 of the fragile X mental retardation (FMR1) syndrome, depending on the stage of the cell cycle, can participate in both inhibition and enhancement of translation. It is known that microRNAs can influence the activity of RNP by binding to the RNA-binding sites of specific mRNAs or directly to RBP molecules, directly inhibiting their activity. Poly (rC) binding protein 2 (PCBP2) is a multifunctional adapter molecule that binds to RNA and DNA, competing with other RNA-binding factors. The PCBP2 protein limits translation initiation by preventing ribosome recruitment. The authors provided information on miR-346-mediated activation of the translation of receptor-interacting protein 140. It is emphasized that some miRNAs, preventing the degradation of the mRNA molecule, increasе the level of its stability, which is accompanied by an enhancement in their translation. MicroRNAs stabilize specific mRNA targets, preventing the association of the ARE element degradation factor, tristetraprolin, with mRNA. Data are presented on the activation of mRNA target translation by factors that sequester miRNAs or compete with miRNAs. Various intracellular factors and proteins can enter into a competitive relationship with miRNA and interfere with or remove it from the target mRNA. It is known that activation of translation can occur due to microRNA inhibition of repressor proteins. The authors indicate that increased miR-145 expression is accompanied by activation of myocardin translation, which induces the proliferation and migration of smooth muscle cells.

Diurnal small RNA expression and post-transcriptional regulation in young and old Drosophila melanogaster heads

Background: MicroRNAs are a class of small (~22nt) endogenous RNAs that regulate target transcript expression post-transcriptionally. Previous studies characterized age-related changes in diurnal transcript expression but it is not understood how these changes are regulated, and whether they may be attributed in part to changes in microRNA expression or activity with age. Diurnal small RNA expression changes with age were not previously studied. Methods: To interrogate changes in small RNA expression with age, we collected young (5 day) and old (55 day) Drosophila melanogaster around-the-clock and performed deep sequencing on size-selected RNA from whole heads. Results: We found several microRNAs with changes in rhythmicity after aging, and we investigated microRNAs which are differentially expressed with age. We found that predicted targets of differentially expressed microRNAs have RNA-binding and transcription factor activity. We used a previously published method to identify mRNA transcripts which show evidence of microRNA targeting that is altered after aging, and found several that are involved in muscle development and maintenance. Finally, we identified novel microRNAs using the random-forest-based method miRWoods, which surprisingly also discovered transfer RNA-derived fragments. Conclusions: We showed a decrease in global microRNA expression and a corresponding increase in piRNA expression during aging. We also found an increase in rhythmicity of Drosophila small RNAs during aging, including microRNAs, piRNA clusters, and novel transfer RNA-derived fragments. To our knowledge this is the first study examining diurnal small RNA expression around the clock in young and old Drosophila, and as such it paves the way for future research on changes in small RNA regulatory molecules in the context of aging.

A Scoping Review of Rodent Studies Investigating the Epigenetic Mechanisms in the Brain Underlying the Effects of Diet on Depressive-like Behaviour.

A healthy diet has been highly associated with a decreased risk for mental health problems such as major depression. Evidence from human studies shows that diet can influence mood but there is a poor understanding of the molecular mechanisms behind these effects, especially the role of epigenetic alterations in the brain. Our objective was to use the Preferred Reporting Items for Systematic Reviews and Meta-Analysis extension for Scoping Reviews (PRISMA-ScR) format to gather all recent studies using animal models that investigate direct or indirect (on the offspring) effects of diet on depressive symptoms, including studies that assess epigenetic mechanisms in the brain. In this format, two authors conducted independent database searches of PubMed, Web of Science, and Academic search premier using one search block "diet epigenetics depression" to find papers published between 2000 and 2022. Relevant studies were selected using pre-defined inclusion/exclusion criteria that were performed independently by the two authors before a subset of studies were selected for qualitative analysis. A total of 11 studies met the inclusion criteria for this systematic scoping review. We found that the literature focuses primarily on the effects of individual nutrients, instead of a specific diet, on despair-like behaviour and anxiety. Studies are heterogenous with the techniques used to asses epigenetic changes in the brain and therefore making it hard to reach common mechanistic explanations. However, all studies report diet-induced changes in the epigenome mainly by the action of DNA methylation, histone acetylation and microRNAs that are parallelel with changes in behaviour. Moreover studies show that inadequate maternal diets can make the offspring more susceptible to develop anxiety and depressive-like behaviour later in life, which is paralleled with changes in the epigenome. Overall, this systematic review shows that there is some literature suggesting a role of brain epigenetics on the diet-induced protective or detrimental effects, specifically on anxiety and depressive-like behaviour. However, studies are limited, lacking the study of some types of diets, behavioural tasks or epigenetic mechanisms. Nevertherless, it shows the importance of genome-environment interactions, bringing new insights towards mechanisms that could be involved in the pathophysiology of mood disorders as well as putative therapeutic targets.

Obesity as a Risk Factor for Breast Cancer—The Role of miRNA

Breast cancer (BC) is the most common cancer diagnosed among women in the world, with an ever-increasing incidence rate. Due to the dynamic increase in the occurrence of risk factors, including obesity and related metabolic disorders, the search for new regulatory mechanisms is necessary. This will help a complete understanding of the pathogenesis of breast cancer. The review presents the mechanisms of obesity as a factor that increases the risk of developing breast cancer and that even initiates the cancer process in the female population. The mechanisms presented in the paper relate to the inflammatory process resulting from current or progressive obesity leading to cell metabolism disorders and disturbed hormonal metabolism. All these processes are widely regulated by the action of microRNAs (miRNAs), which may constitute potential biomarkers influencing the pathogenesis of breast cancer and may be a promising target of anti-cancer therapies.

CfDNA Methylation Profiles and T-Cell Differentiation in Women with Endometrial Polyps.

DNA methylation is a part of the regulatory mechanisms of gene expression, including chromatin remodeling and the activity of microRNAs, which are involved in the regulation of T-cell differentiation and function. However, the role of cfDNA methylation in T-cell differentiation is entirely unknown. In patients with endometrial polyps (EPs), we have found an imbalance of T-cell differentiation and an aberrant cfDNA methylation profile, respectively. In this study, we investigated the relationship between cfDNA methylation profiles and T-cell differentiation in 14 people with EPs and 27 healthy controls. We found that several differentially methylated genes (DMGs) were associated with T-cell differentiation in people with EPs (ITGA2-Naïve CD4, r = -0.560, p = 0.037; CST9-EMRA CD4, r = -0.626, p = 0.017; and ZIM2-CM CD8, r = 0.576, p = 0.031), but not in healthy controls (all p > 0.05). When we combined the patients' characteristics, we found a significant association between ITGA2 methylation and polyp diameter (r = 0.562, p = 0.036), but this effect was lost when adjusting the level of Naïve CD4 T-cells (r = 0.038, p = 0.903). Moreover, the circulating sex hormone levels were associated with T-cell differentiation (estradiol-Naïve CD4, r = -0.589, p = 0.027), and the cfDNA methylation profile (testosterone-ZIM2, r = -0.656, p = 0.011). In conclusion, this study has established a link between cfDNA methylation profiles and T-cell differentiation among people with EPs, which may contribute to the etiology of EPs. Further functional studies are warranted.

Revisiting the Anti-Cancer Toxicity of Clinically Approved Platinating Derivatives.

Cisplatin (CDDP), carboplatin (CP), and oxaliplatin (OXP) are three platinating agents clinically approved worldwide for use against a variety of cancers. They are canonically known as DNA damage inducers; however, that is only one of their mechanisms of cytotoxicity. CDDP mediates its effects through DNA damage-induced transcription inhibition and apoptotic signalling. In addition, CDDP targets the endoplasmic reticulum (ER) to induce ER stress, the mitochondria via mitochondrial DNA damage leading to ROS production, and the plasma membrane and cytoskeletal components. CP acts in a similar fashion to CDDP by inducing DNA damage, mitochondrial damage, and ER stress. Additionally, CP is also able to upregulate micro-RNA activity, enhancing intrinsic apoptosis. OXP, on the other hand, at first induces damage to all the same targets as CDDP and CP, yet it is also capable of inducing immunogenic cell death via ER stress and can decrease ribosome biogenesis through its nucleolar effects. In this comprehensive review, we provide detailed mechanisms of action for the three platinating agents, going beyond their nuclear effects to include their cytoplasmic impact within cancer cells. In addition, we cover their current clinical use and limitations, including side effects and mechanisms of resistance.

Abstract A030: Deciphering the micro-RNA landscape of AKT isoforms and its clinical impact in patients with lung adenocarcinoma

Abstract Over the last 25 years, AKT kinase has been thoroughly investigated and characterized as a crucial regulator of cellular homeostasis, affecting a plethora of essential molecular functions. The three identified isoforms of this kinase, namely AKT1, AKT2 and AKT3, often display opposing and antagonizing cellular functions. One of these important cellular functions is the expression and activation of micro-RNAs (miRNAs), an important RNA process that epigenetically regulates the human transcriptome. In the context of human cancer and based on several reports, AKT kinase has been associated with aberrant expression of oncogenic miRNAs, that in turn hijack oncogenic pathways, leading to tumor progression, metastasis and resistance to therapy, especially in lung adenocarcinoma (LUAD). Nevertheless, a comprehensive analysis of the impact of each AKT isoform on the regulation and enrichment of a specific miRNA signature in lung adenocarcinoma has yet to be performed. Here, we were willing to elucidate the miRNA epigenetic landscape and downstream targets, driven by each AKT isoform, and its clinical importance in patients with lung adenocarcinoma. To this extent, we utilized RNA-Seq and Small RNA-Seq data from The Cancer Genome Atlas (TCGA-LUAD) to identify the miRNA signatures related with the expression of each AKT isoform in LUAD. Gene Set Enrichment Analysis from RNA-Seq and miRNA levels analysis from Small RNA-Seq, identified a unique miRNA signature for each AKT isoform, demonstrating their largely opposing effect in miRNA profiling. In parallel analysis, in silico target analysis of the top 50 regulated miRNAs, demonstrated another set of unique targets for each isoform-dependent miRNA signature, which is involved in metabolism, DNA damage, RNA processing, cell survival, immune response and metastasis. More importantly, clinical and survival analysis revealed that the top 50 Differentially regulated miRNAs, ranked by q-value, for each isoform correlated with poor progression free survival in patients with LUAD. Collectively, our atlas of AKT isoform-driven miRNA landscapes implicates AKT as a global effector of miRNA landscape in lung adenocarcinoma. Due to the lack of reliable isoform-specific AKT inhibitors, the identification of the oncogenic miRNA networks regulated by each isoform, acts as an important transnational resource for the design and testing of inhibitors that bypass AKT inhibition toxicity, sparing its impactful physiological functions. Citation Format: George Laliotis, Pauline Lin. Deciphering the micro-RNA landscape of AKT isoforms and its clinical impact in patients with lung adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr A030.

Mechanisms of action of cytoplasmic microRNAs. Part 5. MicroRNA-mediated silencing caused during translation initiation and post-initiation

The scientific review considers the mechanisms of action of cytoplasmic microRNAs, namely miRNA-mediated silencing, which is caused during the initiation and post-initiation period of translation. To write the article, information was searched using Scopus, Web of Science, MedLine, PubMed, Google Scholar, EMBASE, Global Health, The Cochrane Library, CyberLeninka databases. It is known that miRNA-mediated silencing caused during translation initiation occurs due to Argonaute proteins, which compete with cap-binding proteins and the eukaryotic translation initiation factor eIF4E during interaction with the 5’cap structure of mRNA. In cap-dependent translation, the eukaryotic initiation factor eIF4E recognizes the 5’cap and promotes the recruitment of other initiation factors, in particular eIF4G, to assemble the translation initiation complex. Also, the eIF4G factor interacts with some PABP proteins, which leads to the formation of a closed loop of mRNA, determining the recruitment of the ribosome. It is stated that in the post-initiation period of translation, microRNAs can: 1) terminate translation, preventing the attachment or promoting the dissociation of ribosome subunits; 2) induce mRNA degradation during the elongation period or 3) activate protein degradation and sequestration. The authors state that microRNAs can directly or indirectly inhibit the functioning of ribosomes, disrupting the formation of a competent 80S ribosome, or preventing the attachment of ribosome subunits to mRNA, or its promotion along the mRNA, or promoting the dissociation of ribosome subunits. AGO2 protein plays a leading role in the development of silencing caused by disruption of the association of ribosomal subunits. The authors showed that the miRNA-mRNA-target complex migrates to lighter polysomes than mRNA that is not associated with miRNA. The miRISC complex with mRNA and ribosomes can recruit proteolytic enzymes that degrade the nascent polypeptide chain. Thus, miRNA-mediated silencing can be induced during the initiation and post-initiation periods of translation.

MYCN mRNA degradation and cancer suppression by a selective small-molecule inhibitor in MYCN-amplified neuroblastoma.

Amplification of the MYCN gene leads to its overexpression at both the mRNA and protein levels. Overexpression of MYCN mRNA may also have an important role in promoting neuroblastoma (NB) beyond the translation of MYCN protein. In the present study, we report a small molecule compound (MX25-1) that was able to bind to the 3'UTR of MYCN mRNA and induce MYCN mRNA degradation; this resulted in potent cell-growth inhibition and cell death specifically in MYCN-amplified or MYCN 3'UTR overexpressing NB cells. To evaluate the role of MYCN 3'UTR-mediated signals in contributing to the anticancer activity of MX25-1, we examined the status and activation of the tumor suppressor microRNA (miRNA) let-7, which is a target of MYCN 3'UTR in MYCN-amplified NB. We first observed that overexpression of MYCN mRNA was associated with high-level expression of the let-7 oncogenic targets DICER1, ARID3B and HMGA2. Following MYCN mRNA degradation, the expression of DICER1, ARID3B and HMGA2 was downregulated in MX25-1-treated cells. Inhibition of let-7 reversed the downregulation of these oncogenic mRNAs and significantly increased resistance of NB cells to MX25-1. Our results from this study supported the notion that overexpression of MYCN mRNA due to gene amplification has an independent function in NB cell growth and disease progression and suggest that targeting MYCN mRNA may represent an attractive strategy for therapy of MYCN amplified NB, both by inhibiting MYCN's cell-survival effects and activating the tumor-suppressor effect of let-7.

TBX1 targets the miR-200–ZEB2 axis to induce epithelial differentiation and inhibit stem cell properties

TBX1, which encodes a T-box transcription factor, is considered a candidate gene for DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly face syndrome. Transduction of TBX1 decreases cell proliferation in epithelial cancer cells and Tbx1 ablation induces epithelial proliferation during palatal development. Here, we report that TBX1 regulates stem cell properties and epithelial differentiation through the transcriptional activation of microRNAs. Stable expression of TBX1 induces microRNA-200 (miR-200), whose members repress the epithelial-to-mesenchymal transition and induce epithelial differentiation. TBX1 rescues ZEB2-dependent transcriptional inhibition of the miR-200b/200a/429 cluster, whose promoter region contains conserved overlapping cis-regulatory motifs of the ZEB-binding E-box and TBX-binding element. Consequently, TBX1 activates the expression of both miR-200 and stemness-inhibitor miR-203 to inhibit their common targets, BMI1 and ZEB2. Moreover, Tbx1 ablation affects the differentiation of the palatal epithelium and perturbs the expression of miR-200, miR-203, and their target genes. We propose that TBX1 links stem cell properties and epithelial differentiation by inducing miR-200 and miR-203. Thus, targeting of the ZEB2–miR-200 axis by TBX1 may have potential therapeutic implications in miR-200-associated tumors and cleft palate.

Role of Adipose Tissue microRNAs in the Onset of Metabolic Diseases and Implications in the Context of the DOHaD

The worldwide epidemic of obesity is associated with numerous comorbid conditions, including metabolic diseases such as insulin resistance and diabetes, in particular. The situation is likely to worsen, as the increase in obesity rates among children will probably lead to an earlier onset and more severe course for metabolic diseases. The origin of this earlier development of obesity may lie in both behavior (changes in nutrition, physical activity, etc.) and in children's history, as it appears to be at least partly programmed by the fetal/neonatal environment. The concept of the developmental origin of health and diseases (DOHaD), involving both organogenesis and epigenetic mechanisms, encompasses such programming. Epigenetic mechanisms include the action of microRNAs, which seem to play an important role in adipocyte functions. Interestingly, microRNAs seem to play a particular role in propagating local insulin resistance to other key organs, thereby inducing global insulin resistance and type 2 diabetes. This propagation involves the active secretion of exosomes containing microRNAs by adipocytes and adipose tissue-resident macrophages, as well as long-distance communication targeting the muscles and liver, for example. Circulating microRNAs may also be useful as biomarkers for the identification of populations at risk of subsequently developing obesity and metabolic diseases.

Bibliometric and visual analysis of mesenchymal stem cells in the treatment of osteoporosis based on CiteSpace software.

The focus of research in the treatment of osteoporosis (OP) has evolved from promoting bone formation and inhibiting bone resorption to current stem cell therapy. Due to their multipotent differentiation properties, mesenchymal stem cells (MSCs) can repair degenerated bones through transplantation, and have become a new method for the treatment of OP. Relevant literatures included in the Web of Science database core collection database from 2012 to 2021 were retrieved. CiteSpace software was used to analyze the cooperative relationship among authors, journals, institutions, and countries, and to analyze the co-citation situation of the literature. And performed co-occurrence analysis, cluster analysis and burst analysis of keywords, draw visual maps and analyzed the results. A total of 2100 papers were included, and the number of papers published from 2012 to 2021 was on the rise. A total of 484 authors were included, and 176 authors published more than 3 papers. The high-yield authors were mainly represented by YAN JIN and BO GAO. A total of 99 journals were included, and the journal with the most publications was J BONE MINER RES. A total of 787 institutions were included, and the institution with the largest number of publications was Shanghai Jiao Tong University. A total of 65 countries were included. The country with the largest number of publications was China, and the United States had the highest centrality. The co-citation analysis of the literature found 2 articles with high citation frequency and high centrality. The main research direction was the mechanism of MSCs in the treatment of osteoporosis. A total of 133 keywords were included, and the hot keywords were osteogenic differentiation, expression, proliferation, bone marrow, etc. The research hotspots in this field mainly focused on the mechanism of bone regeneration, proliferation and osteogenic differentiation of bone marrow MSCs, and the expression of osteogenic-related genes. The future research trends in this field are predicted to be the mechanism of action of microRNA and long non-coding RNA on MSCs and their relationship with OP, the mechanism of MSCs adipogenic and osteogenic differentiation, and tissue engineering scaffolds applications.

Identification of Key Genes in Atherosclerosis by Combined DNA Methylation and miRNA Expression Analyses.

Atherosclerosis is a significant cause of coronary heart disease, cerebral infarction, and peripheral vascular disease. The objective of this study was to identify the key genes aberrantly expressed in atherosclerosis, which were regulated by microRNAs and DNA methylation. We acquired data on DNA methylation and microRNA and messenger RNA expression from Gene Expression Omnibus data sets (GSE46394, GSE53675, and GSE12288, respectively) and identified differentially methylated genes, differentially expressed genes, and differentially expressed microRNAs between atherosclerosis and control samples. The miRDB, miRTarBase, and TargetScan databases were used to predict differentially expressed microRNAs-targeted genes, which were then intersected with differentially methylated genes and differentially expressed genes to identify genes associated with aberrant DNA methylation and microRNA activity. The DAVID database was used to perform functional enrichment analysis of differentially methylated genes and the key genes involved in atherosclerosis. Potential therapeutic agents for atherosclerosis were predicted by Connectivity Map analysis. In total, we identified 47 upregulated hypomethylated and 90 downregulated hypermethylated genes in atherosclerosis. Among them, 24 differentially expressed genes were found to be modulated both through aberrant DNA methylation and microRNA expression, and 10 such differentially expressed genes were defined as the key genes in atherosclerosis. Fifteen chemicals were selected for their potential effect in . We identified 10 key genes significantly associated with aberrant DNA methylation and microRNA expression in atherosclerosis and suggested 15 chemicals with potential effects on these genes, which could be further investigated as candidate drugs for atherosclerosis.

Association Between Fecal MicroRNAs and B-Glucuronidase Activity in Kidney Transplant Recipients

Association Between Fecal MicroRNAs and B-Glucuronidase Activity in Kidney Transplant Recipients

Validation of Inferred MicroRNA Activity From Kidney scRNAseq

Validation of Inferred MicroRNA Activity From Kidney scRNAseq

Major approaches to melatonin and nutrients regulation in the bone regeneration process with exosomes and microRNAs: a systematic review

Introduction: Bone diseases comprise a large group of common diseases, including fractures, osteoporosis, and osteoarthritis that affect a large number of individuals. Without intervention, the prevalence of osteopenia is projected to increase to 64.3 million Americans and that of osteoporosis to 11.9 million by the year 2030. Melatonin exerts numerous physiological effects, including the induction of anti-inflammatory and antioxidants, resetting circadian rhythms, and promoting wound healing and tissue regeneration, participating in the maintenance and regenerative processes of bones and cartilage. Objective: A systematic review was carried out to present the state of the art of melatonin regulation, mesenchymal stem cells, exosomes, microRNAs, and nutrients in the bone regeneration process. Methods: The systematic review rules (PRISMA) were followed. The search was carried out from July to September 2022 in the Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases, using scientific articles from 2019 to 2022. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 126 articles were found. A total of 59 articles were fully evaluated and 46 were included in this systematic review. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 9 studies at high risk of bias and 24 studies that did not meet the GRADE. Most studies showed homogeneity in their results, with I2 =97.8%>50%. The symmetrical funnel plot does not suggest a risk of bias between small sample-size studies. Based on the results, melatonin has important functions in regulating the regenerative activities of mesenchymal stem cells that modulate, together with nutrients, the activities of exosomes and microRNAs in the bone regeneration process.

An miRISC-initiated DNA nanomachine for monitoring MicroRNA activity in living cells

MicroRNAs (miRNAs) play an important role in post-transcriptional regulation of gene expression. However, methods to accurately detect miRNA activity in living cells are still limited. Here we developed a DNA nanomachine initiated by a miRNA-induced silencing complex (miRISC) for imaging miRNA activity in living cells. miRISC-mediated RNA cleavage reaction activated the DNA nanomachine by the specific cleavage of an RNA strand on the machine, resulting in autonomous movement of the walking leg around the AuNP surface with the release of a large number of fluorescently labeled DNA strands. The DNA nanomachine was successfully applied to detect miR-21 activity in three cell lines with different miR-21 expression profiles. We also demonstrated that terminal uridylyltransferase Tut4 knockdown by siRNA significantly increased the activity of let-7b miRNA, which further verifies the versatility of our DNA nanomachine. This new nanomachine has distinct advantages compared with reported methods for detecting miRNA activity, including simple operating procedures, short analysis time and sensitive signal output. Collectively, this work not only expands the application of the DNA nanomachine in the detection of miRNA activity, but also provides a promising tool for basic research in cell biology and development of clinical biomedicine.

Genetically Encoded Light-Up RNA Amplifier Dissecting MicroRNA Activity in Live Cells.

Live cell dissection of microRNA activities is crucial for basic and translational medicine, but current hybridization-based strategies may fail to dissect surrounding-dependent activities. Here, we develop a genetically encoded miRNA-induced light-up RNA amplifier (iLAMP) that enables fast-activated, signal-amplified, fluorogenic imaging of miRNA activities in live cells. iLAMP responds to miRNA targets in the mode of "activation upon cleavage", in which the light-up RNA aptamer restores its fluorescence rapidly upon cleavage by the RNA-induced silencing complex. We demonstrate that iLAMP affords substantial signal amplification of ∼100-fold and high specificity in single nucleotide discrimination because of the miRNA-mediated cyclic cleavage. Combined with a Mango RNA aptamer reference module and a pseudoknot terminal stabilizer, iLAMP is shown for quantitative ratiometric imaging and dynamic monitoring of miRNA activities under exogenous stimulations. iLAMP is featured by a modular "plug and play" design and can be readily adapted to the detection of other miRNAs, highlighting its potential in tracking cell differentiation and screening miRNA therapeutics.