Role of microRNAs in cardiovascular disease: therapeutic challenges and potentials

A 2-decade bibliometric analysis of epigenetics of cardiovascular disease: from past to present

BACKGROUND

Cardiovascular disease (CVD) remains a major health killer worldwide, and the role of epigenetic regulation in CVD has been widely studied in recent decades. Herein, we perform a bibliometric study to decipher how research topics in this field have evolved during the past 2 decades.

RESULTS

Publications on epigenetics in CVD produced during the period 2000-2022 were retrieved from the Web of Science Core Collection (WoSCC). We utilized Bibliometrix to build a science map of the publications and applied VOSviewer and CiteSpace to assess co-authorship, co-citation, co-occurrence, and bibliographic coupling. In total, 27,762 publications were included for bibliometric analysis. The yearly amount of publications experienced exponential growth. The top 3 most influential countries were China, the United States, and Germany, while the most cited institutions were Nanjing Medical University, Harbin Medical University, and Shanghai Jiao Tong University. Four major research trends were identified: (a) epigenetic mechanisms of CVD; (b) epigenetics-based therapies for CVD; (c) epigenetic profiles of specific CVDs; and (d) epigenetic biomarkers for CVD diagnosis/prediction. The latest and most important research topics, including "nlrp3 inflammasome", "myocardial injury", and "reperfusion injury", were determined by detecting citation bursts of co-occurring keywords. The most cited reference was a review of the current knowledge about how miRNAs recognize target genes and modulate their expression and function.

CONCLUSIONS

The number and impact of global publications on epigenetics in CVD have expanded rapidly over time. Our findings may provide insights into the epigenetic basis of CVD pathogenesis, diagnosis, and treatment.

Transcriptional Inhibition of MicroRNA miR-122 by Small Molecules Reduces Hepatitis C Virus Replication in Liver Cells

MicroRNAs (miRNAs) are noncoding RNA molecules of 22-24 nucleotides that are estimated to regulate thousands of genes in humans, and their dysregulation has been implicated in many diseases. MicroRNA-122 (miR-122) is the most abundant miRNA in the liver and has been linked to the development of hepatocellular carcinoma and hepatitis C virus (HCV) infection. Its role in these diseases renders miR-122 a potential target for small-molecule therapeutics. Here, we report the discovery of a new sulfonamide class of small-molecule miR-122 inhibitors from a high-throughput screen using a luciferase-based reporter assay. Structure-activity relationship (SAR) studies and secondary assays led to the development of potent and selective miR-122 inhibitors. Preliminary mechanism-of-action studies suggest a role in the promoter-specific transcriptional inhibition of miR-122 expression through direct binding to the liver-enriched transcription factor hepatocyte nuclear factor 4α. Importantly, the developed inhibitors significantly reduce HCV replication in human liver cells.

Amniotic Fluid microRNA in Severe Twin-Twin Transfusion Syndrome Cardiomyopathy-Identification of Differences and Predicting Demise

Twin-twin transfusion syndrome (TTTS) is a rare but serious cause of fetal cardiomyopathy with poorly understood pathophysiology and challenging prognostication. This study sought a nonbiased, comprehensive assessment of amniotic fluid (AF) microRNAs from TTTS pregnancies and associations of these miRNAs with clinical characteristics. For the discovery cohort, AF from ten fetuses with severe TTTS cardiomyopathy were selected and compared to ten normal singleton AF. Array panels assessing 384 microRNAs were performed on the discovery cohort and controls. Using a stringent q < 0.0025, arrays identified 32 miRNAs with differential expression. Top three microRNAs were miR-99b, miR-370 and miR-375. Forty distinct TTTS subjects were selected for a validation cohort. RT-PCR targeted six differentially-expressed microRNAs in the discovery and validation cohorts. Expression differences by array were confirmed by RT-PCR with high fidelity. The ability of these miRNAs to predict clinical differences, such as cardiac findings and later demise, was evaluated on TTTS subjects. Down-regulation of miRNA-127-3p, miRNA-375-3p and miRNA-886 were associated with demise. Our results indicate AF microRNAs have potential as a diagnostic and prognostic biomarker in TTTS. The top microRNAs have previously demonstrated roles in angiogenesis, cardiomyocyte stress response and hypertrophy. Further studies of the mechanism of actions and potential targets is warranted.

Nickel nanoparticle-induced cell transformation: involvement of DNA damage and DNA repair defect through HIF-1α/miR-210/Rad52 pathway

Background

Nickel nanoparticles (Nano-Ni) are increasingly used in industry and biomedicine with the development of nanotechnology. However, the genotoxic and carcinogenic effects of Nano-Ni and the underlying mechanisms are still unclear.

Methods

At first, dose–response (0, 10, 20, and 30 μg/mL) and time-response (0, 3, 6, 12, and 24 h) studies were performed in immortalized normal human bronchial epithelial cells BEAS-2B to observe the effects of Nano-Ni on DNA damage response (DDR)-associated proteins and the HIF-1α/miR-210/Rad52 pathway by real-time PCR or Western blot. Then, a Hsp90 inhibitor (1 µM of 17-AAG, an indirect HIF-1α inhibitor), HIF-1α knock-out (KO) cells, and a miR-210 inhibitor (20 nM) were used to determine whether Nano-Ni-induced Rad52 down-regulation was through HIF-1α nuclear accumulation and miR-210 up-regulation. In the long-term experiments, cells were treated with 0.25 and 0.5 µg/mL of Nano-Ni for 21 cycles (~ 150 days), and the level of anchorage-independent growth was determined by plating the cells in soft agar. Transduction of lentiviral particles containing human Rad52 ORF into BEAS-2B cells was used to observe the role of Rad52 in Nano-Ni-induced cell transformation. Nano-Ni-induced DNA damage and dysregulation of HIF-1α/miR-210/Rad52 pathway were also investigated in vivo by intratracheal instillation of 50 µg per mouse of Nano-Ni. gpt delta transgenic mice were used to analyze mutant frequency and mutation spectrum in mouse lungs after Nano-Ni exposure.

Results

Nano-Ni exposure caused DNA damage at both in vitro and in vivo settings, which was reflected by increased phosphorylation of DDR-associated proteins such as ATM at Ser1981, p53 at Ser15, and H2AX. Nano-Ni exposure also induced HIF-1α nuclear accumulation, miR-210 up-regulation, and down-regulation of homologous recombination repair (HRR) gene Rad52. Inhibition of or knocking-out HIF-1α or miR-210 ameliorated Nano-Ni-induced Rad52 down-regulation. Long-term low-dose Nano-Ni exposure led to cell malignant transformation, and augmentation of Rad52 expression significantly reduced Nano-Ni-induced cell transformation. In addition, increased immunostaining of cell proliferation markers, Ki-67 and PCNA, was observed in bronchiolar epithelial cells and hyperplastic pneumocytes in mouse lungs at day 7 and day 42 after Nano-Ni exposure. Finally, using gpt delta transgenic mice revealed that Nano-Ni exposure did not cause increased gpt mutant frequency and certain DNA mutations, such as base substitution and small base insertions/deletions, are not the main types of Nano-Ni-induced DNA damage.

Conclusions

This study unraveled the mechanisms underlying Nano-Ni-induced cell malignant transformation; the combined effects of Nano-Ni-induced DNA damage and DNA repair defects through HIF-1α/miR-210/Rad52 pathway likely contribute to Nano-Ni-induced genomic instability and ultimately cell transformation. Our findings will provide information to further elucidate the molecular mechanisms of Nano-Ni-induced genotoxicity and carcinogenicity.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01117-7.

AAV3-miRNA vectors for growth suppression of human hepatocellular carcinoma cells in vitro and human liver tumors in a murine xenograft model in vivo

We have previously reported that recombinant adeno-associated virus serotype 3 (AAV3) vectors transduce human liver tumors more efficiently in a mouse xenograft model following systemic administration. Others have utilized AAV8 vectors expressing miR-26a and miR-122 to achieve near total inhibition of growth of mouse liver tumors. Since AAV3 vectors transduce human hepatic cells more efficiently than AAV8 vectors, in the present studies, we wished to evaluate the efficacy of AAV3-miR-26a/122 vectors in suppressing the growth of human hepatocellular carcinoma (HCC) cells in vitro, and human liver tumors in a mouse model in vivo. To this end, a human HCC cell line, Huh7, was transduced with various multiplicities of infection (MOIs) of AAV3-miR-26a or scAAV3-miR-122 vectors, or both, which also co-expressed a Gaussia luciferase (GLuc) reporter gene. Only a modest level of dose-dependent growth inhibition of Huh7 cells (~12-13%) was observed at the highest MOI (1 × 105 vgs/cell) with each vector. When Huh7 cells were co-transduced with both vectors, the extent of growth inhibition was additive (~26%). However, AAV3-miR-26a and scAAV3-miR-122 vectors led to ~70% inhibition of growth of Huh-derived human liver tumors in a mouse xenograft model in vivo. Thus, the combined use of miR-26a and scAAV3-miR-122 delivered by AAV3 vectors offers a potentially useful approach to target human liver tumors.

Regulatory microRNAs and vascular cognitive impairment and dementia

Vascular cognitive impairment and dementia (VCID) is defined as a progressive dementia disease related to cerebrovascular injury and often occurs in aged populations. Despite decades of research, effective treatment for VCID is still absent. The pathological processes of VCID are mediated by the molecular mechanisms that are partly modulated at the post-transcriptional level. As small endogenous non-coding RNAs, microRNAs (miRs) can regulate target gene expression through post-transcriptional gene silencing. miRs have been reported to play an important role in the pathology of VCID and have recently been suggested as potential novel pharmacological targets for the development of new diagnosis and treatment strategies in VCID. In this review, we summarize the current understanding of VCID, the possible role of miRs in the regulation of VCID and attempt to envision future therapeutic strategies. Since manipulation of miR levels by either pharmacological or genetic approaches has shown therapeutic effects in experimental VCID models, we also emphasize the potential therapeutic value of miRs in clinical settings.

miR-21 mediates nickel nanoparticle-induced pulmonary injury and fibrosis

We and other groups have demonstrated that exposure to nickel nanoparticles (Nano-Ni) results in severe and persistent lung inflammation and fibrosis, but the underlying mechanisms remain unclear. Here, we propose that miR-21 may play an important role in Nano-Ni-induced lung inflammation, injury, and fibrosis. Our dose- and time-response studies demonstrated that exposure of C57BL/6J (WT) mice to Nano-Ni resulted in upregulation of miR-21, proinflammatory cytokines, and profibrotic mediators. Histologically, exposure to Nano-Ni caused severe pulmonary inflammation and fibrosis. Based on the dose- and time-response studies, we chose a dose of 50 µg of Nano-Ni per mouse to compare the effects of Nano-Ni on WT with those on miR-21 KO mouse lungs. At day 3 post-exposure, Nano-Ni caused severe acute lung inflammation and injury that were reflected by increased neutrophil count, CXCL1/KC level, LDH activity, total protein concentration, MMP-2/9 protein levels and activities, and proinflammatory cytokines in the BALF or lung tissues from WT mice, which were confirmed histologically. Although Nano-Ni had similar effects on miR-21 KO mice, the above-mentioned levels were significantly lower than those in WT mice. Histologically, lungs from WT mice exposed to Nano-Ni had infiltration of a large number of polymorphonuclear (PMN) cells and macrophages in the alveolar space and interstitial tissues. However, exposure of miR-21 KO mice to Nano-Ni only caused mild acute lung inflammation and injury. At day 42 post-exposure, Nano-Ni caused extensive pulmonary fibrosis and chronic inflammation in the WT mouse lungs. However, exposure of miR-21 KO mice to Nano-Ni only caused mild lung fibrosis and chronic lung inflammation. Our results also showed that exposure to Nano-Ni caused upregulation of TGF-β1, phospho-Smad2, COL1A1, and COL3A1 in both WT and miR-21 KO mouse lungs. However, levels were significantly lower in miR-21 KO mice than in WT mice, except TGF-β1, which was similar in both kinds of mice. Decreased expression of Smad7 was observed in WT mouse lungs, but not in miR-21 KO mice. Our results demonstrated that knocking out miR-21 ameliorated Nano-Ni-induced pulmonary inflammation, injury, and fibrosis, suggesting the important role of miR-21 in Nano-Ni-induced pulmonary toxicity.

Computational prediction and analysis of histone H3k27me1-associated miRNAs

The mono-methylation of histone H3 on lysine 27 (H3K27me1) plays key roles in the cellular processes. The H3K27me1 interacts with the DNA sequence of the miRNAs and regulates the transcription of miRNAs. Therefore, biological roles of the H3K27me1 are closely related to the downstream miRNAs. We proposed a machine learning-based computational method to predict H3K27me1-associated miRNAs and obtained AUCs of 0.6866 and 0.6849 on the leave-one-out and five-fold cross validation, respectively. We also performed enrichment analysis of the transcript factors, GO terms and pathways of H3K27me1-associated miRNAs. Among the top 10 significantly enriched transcription factors, five were unfavorable prognostic marker in renal cancer. The enrichment analysis of molecular function showed that the H3K27me1-associated miRNAs were linked to RNA binding and protein binding which were involved in the transcription and translation regulation. The enrichment of pathway showed that H3K27me1-associated miRNAs were mainly involved in pathways related to cancers, signaling and virus.

MicroRNA-26a targets the mdm2/p53 loop directly in response to liver regeneration

Liver regeneration (LR) is the result of a dynamic balance between the increased proliferation and decreased apoptosis of hepatocytes. However, the role of microRNA (miR)‑26a in regulating complex signalling networks involving E3 ubiquitin‑protein ligase Mdm2 (mdm2), p53, p21 and p27 in the process of LR is currently unclear. In the present study, it was hypothesized that miR‑26a may negatively regulate the mdm2/p53 signalling loop in response to LR. In vitro experiments were performed, whereby mouse liver cells were transfected with an miR‑26a vector or an anti/miR‑26a vector. Cell proliferation was analysed using an MTS assay and cell apoptosis, and cell cycle progression were analysed by flow cytometry. In addition, the expression of mdm2, p53, p21 and p27 were assessed using western blotting and reverse transcription‑quantitative polymerase chain reaction analyses. Dual‑luciferase reporter assays were also used to examine the association between mdm2 and miR‑26a. A 70% partial hepatectomy in C57BL/6J mice was then performed, which was followed by injection with an mdm2‑cDNA vector or an mdm2‑small interfering RNA vector. The liver‑to‑body weight ratio and liver function of mice were measured at 72 h following vector administration. The results demonstrated an increase in hepatocyte proliferation accompanied by decreased hepatocyte apoptosis levels. In addition, inhibition of miR‑26a expression was associated with a marked increase in mdm2 expression, while the expression of p53, p21 and p27 was decreased when compared with negative controls. The opposite effects were observed when miR‑26a was overexpressed. Notably, miR‑26a was demonstrated to target the 3'‑untranslated region of mdm2 directly. The results of the present study are the first to demonstrate as far as the authors are aware that the mdm2/p53 negative feedback loop may be targeted by miR‑26a directly in response to LR, and that mdm2 negatively regulates p53, p21 and p27 but not miR‑26a. miR‑26a may therefore function as an important factor that regulates the interaction between mdm2 and p53.

MicroRNA-based therapeutics in central nervous system injuries

Central nervous system (CNS) injuries, such as stroke, traumatic brain injury (TBI) and spinal cord injury (SCI), are important causes of death and long-term disability worldwide. MicroRNA (miRNA), small non-coding RNA molecules that negatively regulate gene expression, can serve as diagnostic biomarkers and are emerging as novel therapeutic targets for CNS injuries. MiRNA-based therapeutics include miRNA mimics and inhibitors (antagomiRs) to respectively decrease and increase the expression of target genes. In this review, we summarize current miRNA-based therapeutic applications in stroke, TBI and SCI. Administration methods, time windows and dosage for effective delivery of miRNA-based drugs into CNS are discussed. The underlying mechanisms of miRNA-based therapeutics are reviewed including oxidative stress, inflammation, apoptosis, blood-brain barrier protection, angiogenesis and neurogenesis. Pharmacological agents that protect against CNS injuries by targeting specific miRNAs are presented along with the challenges and therapeutic potential of miRNA-based therapies.

Myocardial microRNAs associated with reverse remodeling in human heart failure

BACKGROUND

In dilated cardiomyopathies (DCMs) changes in expression of protein-coding genes are associated with reverse remodeling, and these changes can be regulated by microRNAs (miRs). We tested the general hypothesis that dynamic changes in myocardial miR expression are predictive of β-blocker-associated reverse remodeling.

METHODS

Forty-three idiopathic DCM patients (mean left ventricular ejection fraction 0.24 ± 0.09) were treated with β-blockers. Serial ventriculography and endomyocardial biopsies were performed at baseline, and after 3 and 12 months of treatment. Changes in RT-PCR (candidate miRs) or array-measured miRs were compared based on the presence (R) or absence (NR) of a reverse-remodeling response, and a miR-mRNA-function pathway analysis (PA) was performed.

RESULTS

At 3 months, 2 candidate miRs were selectively changed in Rs, decreases in miR-208a-3p and miR-591. PA revealed changes in miR-mRNA interactions predictive of decreased apoptosis and myocardial cell death. At 12 months, 5 miRs exhibited selective changes in Rs (decreases in miR-208a-3p, -208b-3p, 21-5p, and 199a-5p; increase in miR-1-3p). PA predicted decreases in apoptosis, cardiac myocyte cell death, hypertrophy, and heart failure, with increases in contractile and overall cardiac functions.

CONCLUSIONS

In DCMs, myocardial miRs predict the time-dependent reverse-remodeling response to β-blocker treatment, and likely regulate the expression of remodeling-associated miRs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01798992.

FUNDING

NIH 2R01 HL48013, 1R01 HL71118 (Bristow, PI); sponsored research agreements from Glaxo-SmithKline and AstraZeneca (Bristow, PI); NIH P20 HL101435 (Lowes, Port multi-PD/PI); sponsored research agreement from Miragen Therapeutics (Port, PI).

Inflammation and vascular smooth muscle cell dedifferentiation following carotid artery ligation

Following vascular injury medial smooth muscle cells dedifferentiate and migrate through the internal elastic lamina where they form a neointima. The goal of the current study was to identify changes in gene expression that occur before the development of neointima and are associated with the early response to injury. Vascular injury was induced in C57BL/6 mice and in Myh11-creER(T2) mTmG reporter mice by complete ligation of the left carotid artery. Reporter mice were used to visualize cellular changes in the injured vessels. Total RNA was isolated from control carotid arteries or from carotid arteries 3 days following ligation of C57BL/6 mice and analyzed by Affymetrix microarray and quantitative RT-PCR. This analysis revealed decreased expression of mRNAs encoding smooth muscle-specific contractile proteins that was accompanied by a marked increase in a host of mRNAs encoding inflammatory cytokines following injury. There was also marked decrease in molecules associated with BMP, Wnt, and Hedgehog signaling and an increase in those associated with B cell, T cell, and macrophage signaling. Expression of a number of noncoding RNAs were also altered following injury with microRNAs 143/145 being dramatically downregulated and microRNAs 1949 and 142 upregulated. Several long noncoding RNAs showed altered expression that mirrored the expression of their nearest coding genes. These data demonstrate that following carotid artery ligation an inflammatory cascade is initiated that is associated with the downregulation of coding and noncoding RNAs that are normally required to maintain smooth muscle cells in a differentiated state.

miR-153 regulates apoptosis and autophagy of cardiomyocytes by targeting Mcl-1

MicroRNAs (miRs) are a class of important regulators, which are involved in the regulation of apoptosis. Oxidative stress‑induced apoptosis is the predominant factor accounting for cardiac ischemia‑reperfusion injury. miR‑153 has been previously shown to have an antitumor effect in cancer. However, whether miR‑153 is involved in oxidative stress‑induced apoptosis in the heart remains to be elucidated. To this end, the present study used reverse transcription‑quantitative polymerase chain reaction to detect miR-153 levels upon oxidative stress, and evaluated apoptosis, autophagy and expression of critical genes by western blotting. A luciferase assay was also used to confirm the potential target gene. In the present study, it was found that the expression of miR‑153 was significantly increased upon H2O2 stimulation, and the inhibition of endogenous miR‑153 decreased apoptosis. To further identify the mechanism underlying the pro‑apoptotic effect of miR‑153, the present study analyzed the 3'untranslated region of myeloid cell leukemia‑1 (Mcl‑1), and found that Mcl‑1 was potentially targeted by miR‑153. The forced expression of miR‑153 inhibited the expression of Mcl‑1 and luciferase activity, which was reversed by its antisense inhibitor. Furthermore, it was shown that the inhibition of miR‑153 induced autophagy during oxidative stress, and that its effects of autophagy induction and apoptosis inhibition were efficiently abrogated by Mcl‑1 small interfering RNA. In conclusion, the results of the present study elucidated a novel mechanism by which miR‑153 regulates the survival of cardimyocytes during oxidative stress through the modulation of apoptosis and autophagy. These effects may be mediated directly by targeting Mcl‑1. These finding revealed the potential clinical value of miR‑153 in the treatment of cardiovascular disease.

miR-26a regulates mouse hepatocyte proliferation via directly targeting the 3' untranslated region of CCND2 and CCNE2

BACKGROUND

The deficiency of liver regeneration needs to be addressed in the fields of liver surgery, split liver transplantation and living donor liver transplantation. Researches of microRNAs would broaden our understandings on the mechanisms of various diseases. Our previous research confirmed that miR-26a regulated liver regeneration in mice; however, the relationship between miR-26a and its target, directly or indirectly, remains unclear. Therefore, the present study further investigated the mechanism of miR-26a in regulating mouse hepatocyte proliferation.

METHODS

An established mouse liver cell line, Nctc-1469, was transfected with Ad5-miR-26a-EGFP, Ad5-anti-miR-26a-EGFP or Ad5-EGFP vector. Cell proliferation was assessed by MTS, cell apoptosis and cell cycle by flow cytometry, and gene expression by Western blotting and quantitative real-time PCR. Dual-luciferase reporter assays were used to test targets of miR-26a.

RESULTS

Compared with the Ad5-EGFP group, Ad5-anti-miR-26a-EGFP down-regulated miR-26a and increased proliferation of hepatocytes, with more cells entering the G1 phase of cell cycle (82.70%+/-1.45% vs 75.80%+/-3.92%), and decreased apoptosis (5.50%+/-0.35% vs 6.73%+/-0.42%). CCND2 and CCNE2 were the direct targeted genes of miR-26a. miR-26a down-regulation up-regulated CCND2 and CCNE2 expressions and down-regulated p53 expression in Nctc-1469 cells. On the contrary, miR-26a over-expression showed the opposite results.

CONCLUSIONS

miR-26a regulated mouse hepatocyte proliferation by directly targeting the 3' untranslated regions of cyclin D2/cyclin E2; miR-26a also regulated p53-mediated apoptosis. Our data suggested that miR-26a may be a promising regulator in liver regeneration.

MicroRNA-181b stimulates inflammation via the nuclear factor-κB signaling pathway in vitro

Acute lung injury (ALI) is characterized by severe lung edema and an increase in the inflammatory reaction. Considerable evidence has indicated that microRNAs (miRNAs or miRs) are involved in various human diseases; however, the expression profile and function of miRNAs in ALI have been rarely reported. The present study used miRNA microarray and reverse transcription-quantitative polymerase chain reaction to demonstrate that miR-181b is the one of the most significantly upregulated miRNA after lipopolysaccharide (LPS) stimulation in human bronchial epithelial cells, BEAS-2B. To elaborate the role of miR-181b in ALI, an assay was performed to investigate the overexpression of miR-181b in BEAS-2B cells, and the expression of inflammatory factors was then analyzed. The overexpression of miR-181b resulted in the induction of an increment in interleukin (IL)-6 levels. p65 was identified to be a primary component of NF-κB, since it was upregulated in the miR-181b overexpression in the BEAS-2B cells, while pyrrolidine dithiocarbamate, a specific inhibitor of NF-κB, was found to be able to abrogate the upregulation of the expression of p65. In conclusion, the findings of the present study suggested that miR-181b may be involved in the process of LPS-induced inflammation in BEAS-2B cells by activating the NF-κB signaling pathway, which implies that it may serve as a potential therapeutic target for ALI.

The Emerging Role of miR-223 in Platelet Reactivity: Implications in Antiplatelet Therapy

Platelets are anuclear cells and are devoid of genomic DNA, but they are capable of de novo protein synthesis from mRNA derived from their progenitor cells, megakaryocytes. There is mounting evidence that microRNA (miRNA) plays an important role in regulating gene expression in platelets. miR-223 is the most abundant miRNAs in megakaryocytes and platelets. One of the miR-223-regulated genes is ADP P2Y12, a key target for current antiplatelet drug therapy. Recent studies showed that a blunted response to P2Y12 antagonist, that is, high on-treatment platelet reactivity (HTPR), is a strong predictor of major cardiovascular events (MACEs) in coronary heart disease (CHD) patients receiving antiplatelet treatment. Recent clinical cohort study showed that the level of circulating miR-223 is inversely associated with MACE in CHD patients. In addition, our recent data demonstrated that the level of both intraplatelet and circulating miR-223 is an independent predictor for HTPR, thus providing a link between miR-223 and MACE. These lines of evidence indicate that miR-223 may serve as a potential regulatory target for HTPR, as well as a diagnostic tool for identification of HTPR in clinical settings.

Angiogenesis-regulating microRNAs and Ischemic Stroke

Stroke is a leading cause of death and disability worldwide. Ischemic stroke is the dominant subtype of stroke and results from focal cerebral ischemia due to occlusion of major cerebral arteries. Thus, the restoration or improvement of reduced regional cerebral blood supply in a timely manner is very critical for improving stroke outcomes and poststroke functional recovery. The recovery from ischemic stroke largely relies on appropriate restoration of blood flow via angiogenesis. Newly formed vessels would allow increased cerebral blood flow, thus increasing the amount of oxygen and nutrients delivered to affected brain tissue. Angiogenesis is strictly controlled by many key angiogenic factors in the central nervous system, and these molecules have been well-documented to play an important role in the development of angiogenesis in response to various pathological conditions. Promoting angiogenesis via various approaches that target angiogenic factors appears to be a useful treatment for experimental ischemic stroke. Most recently, microRNAs (miRs) have been identified as negative regulators of gene expression in a post-transcriptional manner. Accumulating studies have demonstrated that miRs are essential determinants of vascular endothelial cell biology/angiogenesis as well as contributors to stroke pathogenesis. In this review, we summarize the knowledge of stroke-associated angiogenic modulators, as well as the role and molecular mechanisms of stroke-associated miRs with a focus on angiogenesis-regulating miRs. Moreover, we further discuss their potential impact on miR-based therapeutics in stroke through targeting and enhancing post-ischemic angiogenesis.

Control of oncogenic miRNA function by light-activated miRNA antagomirs

MicroRNAs (miRNAs) are single stranded noncoding RNAs of approximately 22 nucleotides that act as posttranscriptional gene regulators by binding partially complementary sequences in the 3' untranslated region (3'-UTR) of target messenger RNAs (mRNAs). MicroRNAs regulate many biological processes including embryonal development, differentiation, apoptosis, and proliferation and the targets of miRNAs range from signalling proteins and transcription factors to RNA binding proteins. Recently, variations in the expression of certain miRNAs have been linked to a variety of human diseases including cancer and viral infections, validating miRNAs as potential targets for drug discovery. Several tools have been developed to control the function of individual miRNAs and have been applied to study their biological role and therapeutic potential; however, common methods lack a precise level of control that allows for the study of miRNA function with high spatial and temporal resolution. Toward this goal, a light-activated miRNA antagomir for mature miR-21 was developed through the site-specific installation of caging groups on the bases of selected nucleotides. Installation of caged nucleotides led to complete inhibition of the antagomir-miRNA hybridization and inactivation of antagomir function. The miRNA-inhibitory activity of the caged antagomirs was fully restored upon decaging through a brief UV irradiation. The synthesized antagomir was applied to the photochemical regulation of miR-21 function in mammalian cells. Moreover, spatial and temporal control over antagomir activity and thus miR-21 function was obtained in mammalian cells. The presented approach enables the precise regulation of miRNA function with unprecedented spatial and temporal resolution using UV irradiation and can be readily extended to any miRNA of interest.

Cellular microRNA sensors based on luciferase reporters

Recently, microRNAs (miRNAs) have been linked to a variety of human diseases including cancer and viral infections. Small molecule modifiers of miRNAs could represent new therapeutic agents and be used as tools for elucidating the biological roles of miRNAs. In order to identify small molecule modifiers of miRNAs, functional assays for specific miRNAs must be developed and optimized. Here, we report the construction of a luciferase reporter assay for miRNA miR-122 function and the development of a stable Huh7 cell line that can be used for high-throughput screening of small molecule miR-122 inhibitors. The steps described here can be applied not only to Huh7 cells and miR-122 but also to virtually any cell line and miRNA combination.

Identification of inhibitors of microRNA function from small molecule screens

Aberrant expression of microRNAs (miRNAs) has been linked to many human diseases including cancer, immune disorders, heart disease, and viral infections. Thus, small molecule inhibitors of miRNAs have potential as new therapeutic agents, as probes for the elucidation of detailed mechanisms of miRNA function, and as tools for the discovery of new targets for the treatment of human diseases. In order to identify small molecule inhibitors of specific miRNAs, functional assays have been developed and applied to the screening of small molecule libraries. Here, we report the application of a luciferase-based reporter assay of miRNA miR-122 function to the discovery of small molecule miR-122 inhibitors.

Regulation of vascular function on posttranscriptional level

Posttranscriptional control of gene expression is crucial for regulating plurality of proteins and functional plasticity of the proteome under (patho)physiologic conditions. Alternative splicing as well as micro (mi)RNA-mediated mechanisms play an important role for the regulation of protein expression on posttranscriptional level. Both alternative splicing and miRNAs were shown to influence cardiovascular functions, such as endothelial thrombogenicity and the vascular tone, by regulating the expression of several vascular proteins and their isoforms, such as Tissue Factor (TF) or the endothelial nitric oxide synthase (eNOS). This review will summarize and discuss the latest findings on the (patho)physiologic role of alternative splicing processes as well as of miRNAs on modulation of vascular functions, such as coagulation, thrombosis, and regulation of the vascular tone.

Flank sequences of miR-145/143 and their aberrant expression in vascular disease: mechanism and therapeutic application

BACKGROUND

Many microRNAs (miRNAs) are downregulated in proliferative vascular disease. Thus, upregulation of these miRNAs has become a major focus of research activity. However, there is a critical barrier in gene therapy to upregulate some miRNAs such as miR-145 and miR-143 because of their significant downregulation by the unclear endogenous mechanisms under disease conditions. The purpose of this study was to determine the molecular mechanisms responsible for their downregulation and to overcome the therapeutic barrier.

METHODS AND RESULTS

In cultured proliferative rat vascular smooth muscle cells (VSMCs) in vitro and in diseased rat and mouse arteries in vivo, we have identified that the impairment of pri-miR-145 into pre-miR-145 is the critical step related to the downregulation of miR-145, in which the PI3-kinase/Akt/p53 pathway is involved. We further identified that the flank sequences of pri-miR-145 are the critical structural components responsible for the aberrant miR-145 expression. Switching of the flank sequence of downregulated miR-145 and miR-143 to the flank sequence of miR-31 confers resistance to their downregulation. The genetically engineered miR-145 (smart miR-145) restored the downregulated miR-145 in proliferative rat VSMCs and in rat carotid arteries with balloon injury and mouse atherosclerotic aortas and demonstrated much better therapeutic effects on the abnormal growth of VSMCs, expression of its target gene, KLF5 expression, VSMC marker gene expression, and vascular neointimal growth.

CONCLUSIONS

The flank sequences of miR-145 and miR-143 play a critical role in their aberrant expression in VSMCs and vascular walls. The genetically engineered "smart" miRNAs based on their flank sequences may have broadly therapeutic applications for many vascular diseases.

Spatiotemporal control of microRNA function using light-activated antagomirs

MicroRNAs (miRNAs) are small non-coding RNAs that act as post-transcriptional gene regulators and have been shown to regulate many biological processes including embryonal development, cell differentiation, apoptosis, and proliferation. Variations in the expression of certain miRNAs have been linked to a wide range of human diseases - especially cancer - and the diversity of miRNA targets suggests that they are involved in various cellular networks. Several tools have been developed to control the function of individual miRNAs and have been applied to study their biogenesis, biological role, and therapeutic potential; however, common methods lack a precise level of control that allows for the study of miRNA function with high spatial and temporal resolution. Light-activated miRNA antagomirs for mature miR-122 and miR-21 were developed through the site-specific installation of caging groups on the bases of selected nucleotides. Installation of caged nucleotides led to complete inhibition of the antagomir-miRNA hybridization and thus inactivation of antagomir function. The miRNA-inhibitory activity of the caged antagomirs was fully restored upon decaging through a brief UV irradiation. The synthesized antagomirs were applied to the photochemical regulation of miRNA function in mammalian cells. Moreover, spatial control over antagomir activity was obtained in mammalian cells through localized UV exposure. The presented approach enables the precise regulation of miRNA function and miRNA networks with unprecedented spatial and temporal resolution using UV irradiation and can be extended to any miRNA of interest.

Bone marrow mesenchymal stem cells for post-myocardial infarction cardiac repair: microRNAs as novel regulators

Transplantation of bone marrow-derived mesenchymal stem cells (MSCs) is safe and may improve cardiac function and structural remodelling in patients following myocardial infarction (MI). Cardiovascular cell differentiation and paracrine effects to promote endogenous cardiac regeneration, neovascularization, anti-inflammation, anti-apoptosis, anti-remodelling and cardiac contractility, may contribute to MSC-based cardiac repair following MI. However, current evidence indicates that the efficacy of MSC transplantation was unsatisfactory, due to the poor viability and massive death of the engrafted MSCs in the infarcted myocardium. MicroRNAs are short endogenous, conserved, non-coding RNAs and important regulators involved in numerous facets of cardiac pathophysiologic processes. There is an obvious involvement of microRNAs in almost every facet of putative repair mechanisms of MSC-based therapy in MI, such as stem cell differentiation, neovascularization, apoptosis, cardiac remodelling, cardiac contractility and arrhythmias, and others. It is proposed that therapeutic modulation of individual cardiovascular microRNA of MSCs, either mimicking or antagonizing microRNA actions, will hopefully enhance MSC therapeutic efficacy. In addition, MSCs may be manipulated to enhance functional microRNA expression or to inhibit aberrant microRNA levels in a paracrine manner. We hypothesize that microRNAs may be used as novel regulators in MSC-based therapy in MI and MSC transplantation by microRNA regulation may represent promising therapeutic strategy for MI patients in the future.

miRSystem: an integrated system for characterizing enriched functions and pathways of microRNA targets

Background

Many prediction tools for microRNA (miRNA) targets have been developed, but inconsistent predictions were observed across multiple algorithms, which can make further analysis difficult. Moreover, the nomenclature of human miRNAs changes rapidly. To address these issues, we developed a web-based system, miRSystem, for converting queried miRNAs to the latest annotation and predicting the function of miRNA by integrating miRNA target gene prediction and function/pathway analyses.

Results

First, queried miRNA IDs were converted to the latest annotated version to prevent potential conflicts resulting from multiple aliases. Next, by combining seven algorithms and two validated databases, potential gene targets of miRNAs and their functions were predicted based on the consistency across independent algorithms and observed/expected ratios. Lastly, five pathway databases were included to characterize the enriched pathways of target genes through bootstrap approaches. Based on the enriched pathways of target genes, the functions of queried miRNAs could be predicted.

Conclusions

MiRSystem is a user-friendly tool for predicting the target genes and their associated pathways for many miRNAs simultaneously. The web server and the documentation are freely available at http://mirsystem.cgm.ntu.edu.tw/.

Micro-RNA-195 and -451 regulate the LKB1/AMPK signaling axis by targeting MO25

Background

Recently, MicroRNAs (miR) and AMP-kinase (AMPK) have emerged as prominent players in the development of cardiac hypertrophy and heart failure. We hypothesized that components of the adenosine monophosphate-activated kinase (AMPK) pathway are targeted by miRs and alter AMPK signaling during pathological cardiac stress.

Methodology/Principal Findings

Using a mouse model of hypertrophic cardiomyopathy (HCM), we demonstrated early elevation of miR-195 and miR-451 in HCM hearts, which targets MO25, a central component of the MO25/STRAD/LKB1 complex that acts as an upstream kinase for AMPK. We show functional targeting of MO25 by miR-195 and -451. Further in vitro interrogation of MO25 as a functional target validated this hypothesis where over-expression of miR-195 in C2C12 cells knocked down MO25 expression levels and downstream AMPK signaling (phosphorylation of Acetyl CoA carboxylase [ACC] and AMPK activity assay), similar to MO25 knockdown in C2C12 cells by siRNA. Parallel changes were measured in 60 day R403Q HCM male hearts that were rescued by short-term administration of AICAR, an AMPK agonist.

Conclusions/Significance

Elevated miR-195 targets the LKB1/AMPK signaling axis in HCM progression and implicates a functional role in HCM disease progression. MiR-195 may serve as potential therapeutics or therapeutic targets for heart disease.

Down-regulation of MiR-127 facilitates hepatocyte proliferation during rat liver regeneration

Liver regeneration (LR) after partial hepatectomy (PH) involves the proliferation and apoptosis of hepatocytes, and microRNAs have been shown to post-transcriptionally regulate genes involved in the regulation of these processes. To explore the role of miR-127 during LR, the expression patterns of miR-127 and its related proteins were investigated. MiR-127 was introduced into a rat liver cell line to examine its effects on the potential target genes Bcl6 and Setd8, and functional studies were undertaken. We discovered that miR-127 was down-regulated and inversely correlated with the expression of Bcl6 and Setd8 at 24 hours after PH, a time at which hypermethylation of the promoter region of the miR-127 gene was detected. Furthermore, in BRL-3A rat liver cells, we observed that overexpression of miR-127 significantly suppressed cell growth and directly inhibited the expression of Bcl6 and Setd8. The results suggest that down-regulation of miR-127 may be due to the rapid methylation of its promoter during the first 24 h after PH, and this event facilitates hepatocyte proliferation by releasing Bcl6 and Setd8. These findings support a miRNA-mediated negative regulation pattern in LR and implicate an anti-proliferative role for miR-127 in liver cells.

Down-regulation of microRNA-26a promotes mouse hepatocyte proliferation during liver regeneration

Background

Inadequate liver regeneration (LR) is still an unsolved problem in major liver resection and small-for-size syndrome post-living donor liver transplantation. A number of microRNAs have been shown to play important roles in cell proliferation. Herein, we investigated the role of miR-26a as a pivotal regulator of hepatocyte proliferation in LR.

Methodology/Principal Findings

Adult male C57BL/6J mice, undergoing 70% partial hepatectomy (PH), were treated with Ad5-anti-miR-26a-LUC or Ad5-miR-26a-LUC or Ad5-LUC vector via portal vein. The animals were subjected to in vivo bioluminescence imaging. Serum and liver samples were collected to test liver function, calculate liver-to-body weight ratio (LBWR), document hepatocyte proliferation (Ki-67 staining), and investigate potential targeted gene expression of miR-26a by quantitative real-time PCR and Western blot. The miR-26a level declined during LR after 70% PH. Down-regulation of miR-26a by anti-miR-26a expression led to enhanced proliferation of hepatocytes, and both LBWR and hepatocyte proliferation (Ki-67⁺ cells %) showed an increased tendency, while liver damage, indicated by aspartate aminotransferase (AST), alanine aminotransferase (ALT) and total bilirubin (T-Bil), was reduced. Furthermore, CCND2 and CCNE2, as possible targeted genes of miR-26a, were up-regulated. In addition, miR-26a over-expression showed converse results.

Conclusions/Significance

MiR-26a plays crucial role in regulating the proliferative phase of LR, probably by repressing expressions of cell cycle proteins CCND2 and CCNE2. The current study reveals a novel miRNA-mediated regulation pattern during the proliferative phase of LR.

Myocardial therapeutic angiogenesis: a review of the state of development and future obstacles

A significant percentage of patients have coronary artery disease that is too advanced or diffuse for percutaneous or surgical intervention. Therapeutic angiogenesis is a treatment modality to induce vessel formation that is being developed for patients with advanced coronary disease not amenable to currently available interventions. A number of approaches to induce coronary collateralization are being developed. These include gene, protein, cellular and miRNA modalities, each of which have advantages and disadvantages. At this time, no modality has emerged as the single clear choice, and combination therapies may provide synergistic benefits. However, there have been a number of recent studies advancing our knowledge as to how we can refine procollateralizing treatments. In this article, we will examine some recent successes and future obstacles in the effort to bring therapeutic angiogenesis to patients.

MicroRNAs are dynamically regulated and play an important role in LPS-induced lung injury

Acute lung injury is characterized by an increase of inflammatory reaction and severe lung edema. Even if there have been great advances in the identification of genes and signaling pathways involved in acute lung injury, the fundamental mechanisms of initiation and propagation of acute lung injury have not been understood completely. A growing amount of evidence indicates that microRNAs (miRNAs) are involved in various human diseases. However, the expression profile and function of miRNAs in acute lung injury have not been investigated. Here, using real-time polymerase chain reaction analysis, we show that a collection of miRNAs is dynamically regulated in lipopolysaccharide (LPS)-induced mouse acute lung injury. Among them, miR-199a and miR-16 are the most significantly down-regulated miRNAs. To study the role of miR-199a and miR-16 in acute lung injury, an over-expression of miR-199a or miR-16 assay was performed in LPS-treated A549 cells, and then the expression of inflammatory factors was analyzed. Over-expression of miR-199a could not alter the expression level of interleukin (IL)-6 and tumor necrosis factor-alpha (TNFα), while up-regulation of miR-16 could significantly down-regulate IL-6 and TNFα expression level. Using bioinformatic analysis, we show that a 3' untranslational region (UTR) of IL-6 and TNFα contains the binding sites of miR-16. Accordingly, over-expression of miR-16 could significantly suppress the luciferase activity of reporter fusion with the binding sites of TNFα in its 3'UTR region, suggesting that miR-16 played its role in LPS-induced lung inflammation by a direct manner. In this study, we show for the first time that miRNAs are dynamically regulated and play an important function in LPS-induced lung injury.

Cardiac hypertrophy is positively regulated by MicroRNA miR-23a

MicroRNAs (miRNAs) are a class of small noncoding RNAs that mediate post-transcriptional gene silencing. Myocardial hypertrophy is frequently associated with the development of heart failure. A variety of miRNAs are involved in the regulation of cardiac hypertrophy, however, the molecular targets of miRNAs in the cardiac hypertrophic cascades remain to be fully identified. We produced miR-23a transgenic mice, and these mice exhibit exaggerated cardiac hypertrophy in response to the stimulation with phenylephrine or pressure overload by transverse aortic banding. The endogenous miR-23a is up-regulated upon treatment with phenylephrine, endothelin-1, or transverse aortic banding. Knockdown of miR-23a attenuates hypertrophic responses. To identify the downstream targets of miR-23a, we found that transcription factor Foxo3a is suppressed by miR-23a. Luciferase assay indicates that miR-23a directly inhibits the translation activity of Foxo3a 3' UTR. Introduction or knockdown of miR-23a leads to the alterations of Foxo3a protein levels. Enforced expression of the constitutively active form of Foxo3a counteracts the provocative effect of miR-23a on hypertrophy. Furthermore, we observed that miR-23a is able to alter the expression levels of manganese superoxide dismutase and the consequent reactive oxygen species, and this effect is mediated by Foxo3a. In addition, our results show that miR-23a and Foxo3a bi-transgenic mice exhibit a reduced hypertrophic response compared with the miR-23a transgenic mice alone. Our present study reveals that miR-23a can mediate the hypertrophic signal through regulating Foxo3a. They form an axis in hypertrophic machinery and can be targets for the development of hypertrophic treatment.

Temporal analysis of mRNA and miRNA expression in transgenic mice overexpressing Arg- and Gly389 polymorphic variants of the β1-adrenergic receptor

Several studies in humans or transgenic animals have reported that the 389 Arg or Gly polymorphic variation of the β1-adrenergic receptor (AR) is associated with differential responses to beta-blocker therapy and/or myocardial disease progression. Analysis of changes in gene expression is an important means of defining molecular differences associated with structural or functional phenotypic variations. To determine if structural and functional myocardial phenotypic differences between β1389 Arg vs. Gly transgenic overexpressors are associated with qualitative and/or quantitative differences in gene expression, a comprehensive analysis of mRNAs and miRNAs expressed in the hearts of 3 and 6-8 mo old β1-Arg389 and β1-Gly389 overexpressor transgenic mice was performed. Changes in mRNA and miRNA expression were analyzed by arrays and partially confirmed by RT-qPCR. Bioinformatic analysis demonstrated that several genes, including those involved in PKA and CaMK signaling pathways, are regulated in a temporal- or phenotype-specific manner. Furthermore, expression signature analyses indicated that miRNAs have the potential to target expression of a number of genes involved in multiple cardiomyopathy-related pathways, and changes in miRNA expression can precede the onset of disease. Differences in gene expression between β1-Arg389 and β1-Gly389 transgenic mice are largely quantitative rather than qualitative and are associated with the development of cardiomyopathy in a time-dependent manner. Chronic β1-AR overdrive results in increased expression of components of the CaMK pathway, with correspondingly decreased levels of components of the PKA pathway. Based on the temporal and genotype-specific pattern of miRNA expression, miRNAs are likely to be important predictors of disease states, especially when miRNA expression is paired with mRNA expression, and that miRNA/mRNA expression signatures have the potential to be useful in determining the underlying risk associated with cardiac disease progression.

Temporal expression of miRNAs and mRNAs in a mouse model of myocardial infarction

Analysis of changes in gene expression is an important means to define molecular differences associated with the phenotypic changes observed in response to myocardial infarction (MI). Several studies in humans or animal models have reported differential miRNA expression in response to MI acutely (animal) or chronically (human). To determine the relative contribution of microRNA (miRNA) and mRNAs to acute and chronic temporal changes in response to MI, mRNA and miRNA expression profiles were performed in three time points post-MI. Changes in mRNA and miRNA expression was analyzed by arrays and confirmed by RT-PCR. Bioinformatic analysis demonstrated that several genes and miRNAs in various pathways are regulated in a temporal or phenotype-specific manner. Furthermore miRNA analyses indicated that miRNAs can target expression of several genes involved in multiple cardiomyopathy-related pathways. Our results suggest that: 1) Differentially regulated miRNAs are predicted to target expression of several genes in multiple biological processes involved in the response to MI; 2) antithetical and compensatory changes in miRNA expression are observed at later disease stages, including antithetical regulation of miR-29, which correlates with the expression of collagen genes, and upregulation of apoptosis-related miRNAs at early stages and antiapoptotic/growth promoting miRNAs at later stages; 3) temporally dependent changes in miRNA and mRNA expression post-MI are generally characterized by dramatic changes acutely postinjury and are normalized as disease progresses; 4) A combinatorial analysis of mRNA and miRNA expression may aid in determining factors involved in compensatory and decompensated responses to cardiac injury.

Practical Aspects of microRNA Target Prediction

microRNAs (miRNAs) are endogenous non-coding RNAs that control gene expression at the posttranscriptional level. These small regulatory molecules play a key role in the majority of biological processes and their expression is also tightly regulated. Both the deregulation of genes controlled by miRNAs and the altered miRNA expression have been linked to many disorders, including cancer, cardiovascular, metabolic and neurodegenerative diseases. Therefore, it is of particular interest to reliably predict potential miRNA targets which might be involved in these diseases. However, interactions between miRNAs and their targets are complex and very often there are numerous putative miRNA recognition sites in mRNAs. Many miRNA targets have been computationally predicted but only a limited number of these were experimentally validated. Although a variety of miRNA target prediction algorithms are available, results of their application are often inconsistent. Hence, finding a functional miRNA target is still a challenging task. In this review, currently available and frequently used computational tools for miRNA target prediction, i.e., PicTar, TargetScan, DIANA-microT, miRanda, rna22 and PITA are outlined and various practical aspects of miRNA target analysis are extensively discussed. Moreover, the performance of three algorithms (PicTar, TargetScan and DIANA-microT) is both demonstrated and evaluated by performing an in-depth analysis of miRNA interactions with mRNAs derived from genes triggering hereditary neurological disorders known as trinucleotide repeat expansion diseases (TREDs), such as Huntington’s disease (HD), a number of spinocerebellar ataxias (SCAs), and myotonic dystrophy type 1 (DM1).

MicroRNAs as biomarkers of disease onset

MicroRNAs (miRNAs) are small, noncoding RNA molecules with the ability to posttranscriptionally regulate gene expression via targeting the 3' untranslated region of messenger RNAs. miRNAs are critical for normal cellular functions such as the regulation of the cell cycle, differentiation, and apoptosis, and they target genes during embryonal and postnatal development, whereas their expression is unbalanced in various pathological states. Importantly, miRNAs are abundantly present in body fluids (e.g., blood), which are routinely examined in patients. These molecules circulate in free and exosome encapsulated forms, and can be efficiently detected and amplified by means of molecular biology tools such as real-time PCR. Together with relative stability, specificity, and reproducibility, they are seen as good candidates for early recognition of the onset of disease. Thus, miRNAs might be considered as biomarkers for many pathological states.

Down-regulation of miR-23b may contribute to activation of the TGF-β1/Smad3 signalling pathway during the termination stage of liver regeneration

MicroRNAs (miRNAs) are known to play important roles in liver regeneration, although the role of miRNAs associated with the termination of liver regeneration is not as well studied. Here we reported the down-regulation of miR-23b in the termination stage of liver regeneration in rats. In addition, Smad3 was identified as a target of miR-23b during liver regeneration. Up-regulation of miR-23b promoted BRL-3A cell proliferation and partially inhibited transforming growth factor (TGF)-β1-induced apoptosis. Furthermore, TGF-β1 transcriptionally inhibited miR-23b expression. We conclude that down-regulation of miR-23b may contribute to activation of the TGF-β1/Smad3 signalling pathway during the termination stage of liver regeneration.