Functional Role and Mechanism of microRNA-28b in Atrial Myocyte in a Persistent Atrial Fibrillation Rat Model

Effects of Atrial Fibrillation-Derived Exosome Delivery of miR-107 to Human Umbilical Vein Endothelial Cells

The aim of this study was to explore the effects of atrial fibrillation (AF)-derived exosome delivery of miR-107 to human umbilical vein endothelial cells (HUVECs) and its related mechanisms. Exosomes were isolated from the plasma of patients with AF and healthy controls, followed by characterization. The expression levels of miR-320d, miR-103a-3p, and miR-107 were measured using real-time quantitative PCR (RT-qPCR). The dual-luciferase reporter gene was used to verify the downstream target of miR-107. Afterward, HUVECs were treated with AF-derived exosomes or transfected with miR-107 mimics. After cell culture, Cell Counting Kit-8, Transwell, and flow cytometry were used to determine cell viability, migration, and apoptosis and cell cycle phase. Finally, RT-qPCR was performed to examine the expression of related genes. NanoSight, transmission electron microscopy, and western blotting showed that exosomes were successfully isolated, and that AF-derived exosomes could be taken up by HUVECs. The expression of miR-107 was significantly higher in AF-derived exosomes than in normal exosomes (p < 0.05). USP14 was shown to be the direct target of miR-107. In addition, miR-107 mimics and AF-derived exosomes significantly suppressed cell viability and migration (p < 0.05) and enhanced cell apoptosis; they also increased G0/G1-phase cells and reduced S-phase cells. RT-qPCR showed that exosomal miR-107 overexpression significantly downregulated the expression of USP14 and Bcl2 (p < 0.05), whereas it markedly upregulated the expression of ERK2, FAK, and Bax (p < 0.05). AF-derived exosomes can deliver miR-107 to HUVECs, and exosomal miR-107 may regulate cell viability, migration, and apoptosis and cell cycle progression by mediating the miR-107/USP14 pathway.

Arrhythmia susceptibility in a rat model of acute atrial dilation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, associated with an increased risk of stroke and heart failure. Acute AF occurs in response to sudden increases of atrial hemodynamic load, leading to atrial stretch. The mechanisms of stretch-induced AF were investigated in large mammals with controversial results. We optimized an approach to monitor rat atrial electrical activity using a red-shifted voltage sensitive dye (VSD). The methodology includes cauterization of the main ventricular coronary arteries, allowing improved atrial staining by the VSD and appropriate atrial perfusion for long experiments. Next, we developed a rat model of acute biatrial dilation (ABD) through the insertion of latex balloons into both atria, which could be inflated with controlled volumes. A chronic model of atrial dilation (spontaneous hypertensive rats; SHR) was used for comparison. ABD was performed on atria from healthy Wistar-Kyoto (WKY) rats (WKY-ABD). The atria were characterized in terms of arrhythmias susceptibility, action potential duration and conduction velocity. The occurrence of arrhythmias in WKY-ABD was significantly higher compared to non-dilated WKY atria. In WKY-ABD we found a reduction of conduction velocity, similar to that observed in SHR atria, while action potential duration was unchanged. Low-dose caffeine was used to introduce a drop of CV in WKY atria (WKY-caff), quantitatively similar to the one observed after ABD, but no increased arrhythmia susceptibility was observed with caffeine only. In conclusion, CV decrease is not sufficient to promote arrhythmias; enlargement of atrial surface is essential to create a substrate for acute reentry-based arrhythmias.

MicroRNAs: Emerging biomarkers for atrial fibrillation

Atrial fibrillation (AF) causes severe cardiac dysrhythmia among patients with cardiovascular diseases. AF increases the risk of stroke and heart failure and is a growing public health concern. AF is also associated with various disease conditions such as hypertension, coronary artery disease, aging, and diabetes mellitus. The mechanism underlying AF is not completely understood due to its complexity. However, experimental and clinical data have revealed that the prevalence of this disease is associated with atrial arrhythmogenic remodeling. Currently, there are no biomarkers that are available for the early diagnosis of AF. Several studies have proposed microRNAs (miRNAs) as useful biomarkers for the diagnosis of AF due to their stability and easy availability both in atrial tissue and circulating blood. miRNAs play an important role in the development of the heart. The dysregulation of miRNA expression is associated with cardiac remodeling. Genetic factors strongly contribute to the pathogenesis of AF. Recently, single nucleotide polymorphisms (SNPs) in various genes and miRNAs have been reported to be associated with AF. The aim of this review was to discuss the correlation between SNPs in miRNAs and AF, including those miRNAs that are commonly reported as potential biomarkers for AF.

Rs12976445 Polymorphism Is Associated with Post-Ablation Recurrence of Atrial Fibrillation by Modulating the Expression of MicroRNA-125a and Interleukin-6R

BACKGROUND This study aimed to identify the relationship between miR-125a polymorphism rs12976445 and the post-ablation recurrence of atrial fibrillation (AF), as well as to explore the underlying mechanism of miR-125a in AF recurrence. MATERIAL AND METHODS Microarray analysis was performed to search for miRNAs potentially involved in the regulation of AF recurrence, while real-time PCR (polymerase chain reaction) and Western blot analyses were carried out to study the expression of miR-125a (microRNA-125a), IL-6R (interleukin-6 receptor), and IL-16 (interleukin-16) in different experimental groups, so as to understand the regulatory relationships among miR-125a, IL-6R, and IL-16. Subsequently, a logistic regression analysis was utilized to investigate the survival status of recurrent AF in subjects harboring different genotypes of rs12976445. RESULTS The subjects in the GG and GC/CC groups of miR-125a polymorphism rs12976445 showed no obvious difference regarding all demographic characteristics that were collected in this study. In addition, 19 miRNAs were identified as potentially involved in the regulation of AF recurrence. Among these miRNAs, 6 were upregulated and 13 were downregulated in the group with early recurrence. According to real-time PCR results, the expression of miR-125a was dramatically upregulated in LRAF (late recurrence of atrial fibrillation) as well as in subjects harboring the GG genotype. On the contrary, the level of IL-6R mRNA was dramatically downregulated in LRAF and subjects harboring the GG genotype. Furthermore, IL-6R was confirmed as a candidate target of miR-125a by a luciferase reporter assay. CONCLUSIONS MicroRNA-125a polymorphism rs12976445 plays a role in AF recurrence via the regulation of IL-6R.