Atrial Fibrillation Tissues Research Articles

Bioinformatic analysis of potential biomarkers and mechanisms of immune infiltration in mitral regurgitation complicated by atrial fibrillation.

Mitral regurgitation (MR) is one of the most prevalent valvular diseases. Degenerated MR-induced volume overload leads to left atrial enlargement and eventually, atrial fibrillation (AF). AF has a negative effect on patient prognosis despite recent advances in minimal invasive transcatheter devices for valve surgery. However, more effective strategies aimed at precisely treating from pathophysiology and genetic perspective are scarce. The gene expression datasets, GSE109744 and GSE79768, were obtained from the Gene Expression Omnibus database and analyzed to identify the differentially expressed genes (DEGs) in patients with mitral value prolapse (MVP) and AF. Subsequently, we predicted the extensive miRNA targets, and the protein-protein interaction (PPI) and miRNA-target gene regulatory networks were established. Functional enrichment analyses were performed for the DEGs. In addition, the co-expressed DEGs coupled with their predicted miRNAs and disease phenotypes involved in MVP and AF were assessed. Finally, the immune infiltration in both datasets was examined. A total of 491 and 180 DEGs were identified in the mitral valve and left atrial specimens, respectively. From these, 11 integrated co-expressed DEGs were identified, namely, PRG4, GPR34, RELN, CA3, IL1B, EPHA3, CHGB, TCEAL2, B3GALT2, ASB11, and CRISPLD1. The enriched Gene Ontology terms and KEGG pathways associated with the DEGs were determined, and the top 10 hub genes and top 3 gene clusters were selected from the PPI network. A prediction of target miRNAs was performed based on the co-expressed DEGs. The enrichment of the co-expressed DEGs suggested that immune and inflammatory responses might be involved in the disease development through multiple immune related pathways, including the interaction of cytokines and chemokines. Notably, this result was consistent with the immune infiltration analysis since the proportions of naïve B cells and memory B cells were significantly different in MVP and AF tissues compared to normal tissues. MR and AF are related, and 11 co-expressed DEGs were found to be significantly associated with MVP with AF, and indeed, these may represent novel biomarkers. Several immune cells were found to contribute to the process of MVP and AF via diverse mechanisms, in particular, antigen-presenting cells.

MiR-15a-5p regulates myocardial fibrosis in atrial fibrillation by targeting Smad7.

BackgroundAt present, there is no effective treatment for myocardial fibrosis in atrial fibrillation (AF). It is reported that miR-15a-5p is abnormally expressed in AF patients but its specific role remains unclear. This study aims to investigate the effect of miR-15a-5p in myocardial fibrosis.MethodsLeft atrial appendage (LAA) tissues were collected from AF and non-AF patients. In lipopolysaccharide (LPS) stimulated H9C2 cells, miR-15a-5p mimic, inhibitor, pcDNA3.1-Smad7 and small interfering RNA-Smad7 (siRNA-Smad7) were respectively transfected to up-regulate or down-regulate the intracellular expression levels of miR-15a-5p and Smad7. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot (WB) were used to determine the expression levels of miR-15a-5p, Smad7, transforming growth factor β1 (TGF-β1) and collagen I. Cell counting kit-8 (CCK-8) and ethylene deoxyuridine (EdU) were used to determine cell viability and proliferation capacity, respectively. Dual-luciferase was used to detect whether miR-15a-5p interacted with Smad7, hydroxyproline (HYP) and Hematoxylin-Eosin (HE) staining were used to detect tissue fibrosis.ResultsThe expression levels of miR-15a-5p, TGF-β1 and collagen I were up-regulated, while Smad7 was down-regulated in AF tissues and LPS-stimulated cells. MiR-15a-5p mimic can inhibit the expression of Smad7, and the dual-luciferase experiment confirmed their interaction. MiR-15a-5p inhibitor or pcDNA3.1-Smad7 can inhibit LPS-induced fibrosis and cell proliferation, while siRNA-Smad7 can reverse the changes caused by miR-15a-5p inhibitor.ConclusionWe combined clinical studies with LPS-stimulated H9C2 cell model to validate the role of miR-15a-5p in the regulation of Smad7 and fibrosis. Taken together, the miR-15a-5p/Smad7 pathway might be a potential target for AF therapy.

Quercetin improves atrial fibrillation through inhibiting TGF-β/Smads pathway via promoting MiR-135b expression

PurposeTo investigate the role and mechanism of quercetin in isoprenaline (ISO)-induced atrial fibrillation (AF). Study designRat cardiac fibroblasts (RCFs) models and RCFs were used to explore the effect and underlying mechanism of quercetin in isoprenaline (ISO)-induced atrial fibrillation (AF) in vivo and in vitro by a series of experiments. MethodsDifferentially expressed microRNAs were screened from human AF tissues using the GEO2R and RT-qPCR. The expressions of TGF-β/Smads pathway molecules (TGFβ1, TGFBR1, Tgfbr1, Tgfbr2, Smad2, Smad3, Smad4) in AF tissues were detected by RT-qPCR and Western blot. The relationships between miR-135b and genes (Tgfbr1, Tgfbr2, Smad2) were analyzed by Pearson correlation, TargetScan and dual-luciferase activity assay. RCFs induced by ISO were treated with quercetin (20 or 50 μM), miR-135b mimic and inhibitor, siTgfbr1 and their corresponding controls, then the cell viability was determined by MTT and the expressions of cyclin D1, α-SMA, collagen-related molecules, TGF-β/Smads pathway molecules, and miR-135b were measured by RT-qPCR and Western blot. ISO-induced rats were treated with quercetin (25 mg/kg/day) via gavage, miR-135b antagomir, agomir and their corresponding controls. The treated rats were used for the detection of miR-135b expression by RT-qPCR, histopathological observation by HE and Masson staining, and the detection of Col1A1 and fibronectin contents by immunohistochemical technique. ResultsThe expression of miR-135b was downregulated, and those of TGFBR1, TGFBR2, target genes of miR-135b were upregulated in human AF tissues and negatively regulated by miR-135b in RCFs. Through inhibiting TGF-β/Smads pathway via promoting miR-135b expression, quercetin treatment inhibited proliferation, myofibroblast differentiation and collagen deposition in ISO-treated RCFs, as evidenced by reduced expressions of cyclin D1, α-SMA, collagen-related genes and proteins, and alleviated fibrosis and collagen deposition of atrial tissues in ISO-treated rats. ConclusionQuercetin may alleviate AF by inhibiting fibrosis of atrial tissues through inhibiting TGF-β/Smads pathway via promoting miR-135b expression.

Location of Parasympathetic Innervation Regions From Electrograms to Guide Atrial Fibrillation Ablation Therapy: An in silico Modeling Study.

The autonomic nervous system (ANS) plays an essential role in the generation and maintenance of cardiac arrhythmias. The cardiac ANS can be divided into its extrinsic and intrinsic components, with the latter being organized in an epicardial neural network of interconnecting axons and clusters of autonomic ganglia called ganglionated plexi (GPs). GP ablation has been associated with a decreased risk of atrial fibrillation (AF) recurrence, but the accurate location of GPs is required for ablation to be effective. Although GP stimulation triggers both sympathetic and parasympathetic ANS branches, a predominance of parasympathetic activity has been shown. This study aims was to develop a method to locate atrial parasympathetic innervation sites based on measurements from a grid of electrograms (EGMs). Electrophysiological models representative of non-AF, paroxysmal AF (PxAF), and persistent AF (PsAF) tissues were developed. Parasympathetic effects were modeled by increasing the concentration of the neurotransmitter acetylcholine (ACh) in randomly distributed circles across the tissue. Different circle sizes of ACh and fibrosis geometries were considered, accounting for both uniform diffuse and non-uniform diffuse fibrosis. Computational simulations were performed, from which unipolar EGMs were computed in a 16 × 1 6 electrode mesh. Different distances of the electrodes to the tissue (0.5, 1, and 2 mm) and noise levels with signal-to-noise ratio (SNR) values of 0, 5, 10, 15, and 20 dB were tested. The amplitude of the atrial EGM repolarization wave was found to be representative of the presence or absence of ACh release sites, with larger positive amplitudes indicating that the electrode was placed over an ACh region. Statistical analysis was performed to identify the optimal thresholds for the identification of ACh sites. In all non-AF, PxAF, and PsAF tissues, the repolarization amplitude rendered successful identification. The algorithm performed better in the absence of fibrosis or when fibrosis was uniformly diffuse, with a mean accuracy of 0.94 in contrast with a mean accuracy of 0.89 for non-uniform diffuse fibrotic cases. The algorithm was robust against noise and worked for the tested ranges of electrode-to-tissue distance. In conclusion, the results from this study support the feasibility to locate atrial parasympathetic innervation sites from the amplitude of repolarization wave.

Effect of TFAM on ATP content in tachypacing primary cultured cardiomyocytes and atrial fibrillation patients.

Atrial fibrillation (AF) is one of the most common types of arrhythmia worldwide; although a number of theories have been proposed to explain the mechanisms of AF, the treatment of AF is far from satisfactory. Energy metabolism is associated with the development of AF. Mitochondrial transcription factor A (TFAM) serves a role in the maintenance and transcription of mitochondrial DNA. The present study aimed to investigate the association between TFAM and AF and the effect of TFAM on ATP content in cardiomyocytes. Left atrial appendage tissues were collected from 20 patients with normal sinus rhythm (SR) and 20 patients with AF, and the expression levels of TFAM in SR and AF tissues were evaluated. In addition, a tachypacing model of primary cultured cardiomyocytes was constructed to assess ATP content, cell viability and expression levels of TFAM, mitochondrially encoded (MT)-NADH dehydrogenase 1 (ND1), MT-cytochrome c oxidase 1 (CO1), NADH ubiquinone oxidoreductase core subunit 1 (NDUFS1) and cytochrome c oxidase subunit 6C (COX6C). Finally, the effects of overexpression and inhibition of TFAM on ATP content, cell viability and the expression levels of MT-ND1 and MT-CO1 were investigated. The expression levels of TFAM were decreased in AF tissues compared with SR tissues (P<0.05). The ATP content, cell viability and expression levels of TFAM, MT-ND1 and MT-CO1 were decreased in tachypacing cardiomyocytes compared with non-pacing cardiomyocytes (P<0.05), whereas the expression levels of NDUFS1 and COX6C were not changed (P>0.05). Overexpression of TFAM increased ATP content, cell viability and expression levels of MT-ND1 and MT-CO1 (P<0.05). The inhibition of TFAM decreased ATP content, cell viability and expression levels of MT-ND1 and MT-CO1 (P<0.05). In summary, the results of the present study demonstrated that the expression levels of TFAM were decreased in AF tissues and tachypacing cardiomyocytes and that the restoration of TFAM increased the ATP content by upregulating the expression levels of MT-ND1 and MT-CO1 in tachypacing cardiomyocytes. Thus, TFAM may be a novel beneficial target for treatment of patients with AF.

Long non-coding RNA PCAT-1 promotes cardiac fibroblast proliferation via upregulating TGF-β1.

Recently, the vital functions of long non-coding RNAs (lncRNAs) in many diseases have been explored. This study aims to identify the function of lncRNA PCAT-1 in the development of atrial fibrillation (AF). Real Time-quantitative Polymerase Chain Reaction (RT-qPCR) was performed to detect PCAT-1 expression in right atrial appendage (RAA) tissues of 51 AF patients and 35 patients with sinus rhythm (SR). Besides, cell proliferation assay was conducted in AC16 cells with PCAT-1 knockdown. Molecular mechanism of PCAT-1 in influencing the progression of AF was finally investigated. PCAT-1 expression was higher in RAA tissues of AF patients than those of SR patients. Moreover, knockdown of PCAT-1 inhibited proliferation in AC16 cells. Transforming growth factor-β1 (TGF-β1) was a target of PCAT-1 and its expression in AF tissues positively correlated to PCAT-1 expression. PCAT-1 could promote cell proliferation of AF via promoting TGF-β1, which may provide a new theory for AF development.

Long noncoding RNA GAS5 attenuates cardiac fibroblast proliferation in atrial fibrillation via repressing ALK5.

Recently, long noncoding RNAs (lncRNAs) have caught more attention for their role in the progression of many diseases. Among them, lncRNA GAS5 (Growth Inhibition Specificity 5) was studied in this research to identify how it affects the progression of atrial fibrillation (AF). In 40 patients with AF and 30 patients with sinus rhythm (SR), the GAS5 expression of the right atrial appendage (RAA) tissues was detected by the quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Moreover, the cell proliferation assay was conducted in AC16 cells transfected with GAS5 inhibitor and mimics, respectively. Furthermore, the qRT-PCR was performed to uncover the mechanism. In the research, the expression of GAS5 in RAA tissues was decreased significantly in AF patients than that in SR ones. Moreover, overexpression of GAS5 inhibited cell growth in AC16 cells, while knockdown of GAS5 promoted cell growth in AC16 cells. In addition, further experiments revealed that ALK5 was a target of GAS5 and its expression in AF tissues negatively correlated to GAS5 expression. These results indicate that GAS5 could inhibit cell proliferation of AF via suppressing ALK5, which may offer a new vision for interpreting the mechanism of AF development.

MiR-138-5p is downregulated in patients with atrial fibrillation and reverses cardiac fibrotic remodeling via repressing CYP11B2.

To investigate the connection between atrial fibrillation (AF) and miR-138-5p and to further explore the possible mechanism. MiR-138-5p expression of right atrial appendage (RAA) tissues in 28 patients with AF and 22 patients with sinus rhythm (SR) was detected by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Moreover, cell proliferation assay was conducted in AC16 cells which were transfected by miR-138-5p inhibitors or mimics. Furthermore, Western blot assay, luciferase assay, and RNA immunoprecipitation assay were performed to uncover the mechanism. In the present research, miR-138-5p expression in RAA samples decreased significantly in AF patients than that in SR ones. Moreover, in AC16 cells, higher miR-138-5p expression level suppressed cell growth, while cell growth was promoted after miR-138-5p was knockdown. In addition, further experiments showed that CYP11B2 acted as the main target of miR-138-5p and its expression in AF tissues negatively correlated to miR-138-5p expression. All the results above elucidated that cell proliferation of AF could be inhibited by miR-138-5p via suppressing CYP11B2, which may offer a new vision for interpreting the mechanism of AF development.

Identification of microRNA-mRNA interactions in atrial fibrillation using microarray expression profiles and bioinformatics analysis

The present study integrated microRNA (miRNA) and mRNA expression data obtained from atrial fibrillation (AF) tissues and healthy tissues, in order to identify miRNAs and target genes that may be important in the development of AF. The GSE28954 miRNA expression profile and GSE2240 mRNA gene expression profile were downloaded from the Gene Expression Omnibus. Differentially expressed miRNAs and genes (DEGs) in AF tissues, compared with in control samples, were identified and hierarchically clustered. Subsequently, differentially expressed miRNAs and DEGs were searched for in the miRecords database and TarBase, and were used to construct a regulatory network using Cytoscape. Finally, functional analysis of the miRNA-targeted genes was conducted. After data processing, 71 differentially expressed miRNAs and 390 DEGs were identified between AF and normal tissues. A total of 3,506 miRNA-mRNA pairs were selected, of which 372 were simultaneously predicted by both miRecords and TarBase, and were therefore used to construct the miRNA-mRNA regulatory network. Furthermore, 10 miRNAs and 12 targeted mRNAs were detected, which formed 14 interactive pairs. The miRNA-targeted genes were significantly enriched into 14 Gene Ontology (GO) categories, of which the most significant was gene expression regulation (GO 10468), which was associated with 7 miRNAs and 8 target genes. These results suggest that the screened miRNAs and target genes may be target molecules in AF development, and may be beneficial for the early diagnosis and future treatment of AF.

Human Electrophysiological and Pharmacological Properties of XEN-D0101

The human electrophysiological and pharmacological properties of XEN-D0101 were evaluated to assess its usefulness for treating atrial fibrillation (AF). XEN-D0101 inhibited Kv1.5 with an IC50 of 241 nM and is selective over non-target cardiac ion channels (IC50 Kv4.3, 4.2 μM; hERG, 13 μM; activated Nav1.5, >100 μM; inactivated Nav1.5, 34 μM; Kir3.1/3.4, 17 μM; Kir2.1, >>100 μM). In atrial myocytes from patients in sinus rhythm (SR) and chronic AF, XEN-D0101 inhibited non-inactivating outward currents (Ilate) with IC50 of 410 and 280 nM, respectively, and peak outward currents (Ipeak) with IC50 of 806 and 240 nM, respectively. Whereas Ilate is mainly composed of IKur, Ipeak consists of IKur and Ito. Therefore, the effects on Ito alone were estimated from a double-pulse protocol where IKur was inactivated (3.5 µM IC50 in SR and 1 µM in AF). Thus, inhibition of Ipeak is because of IKur reduction and not Ito. XEN-D0101 significantly prolonged the atrial action potential duration at 20%, 50%, and 90% of repolarization (AF tissue only) and significantly elevated the atrial action potential plateau phase and increased contractility (SR and AF tissues) while having no effect on human ventricular action potentials. In healthy volunteers, XEN-D0101 did not significantly increase baseline- and placebo-adjusted QTc up to a maximum oral dose of 300 mg. XEN-D0101 is a Kv1.5/IKur inhibitor with an attractive atrial-selective profile.

Second-harmonic generation imaging of collagen fibers in myocardium for atrial fibrillation diagnosis

Atrial fibrillation (AF) is the most common irregular heart rhythm and the mortality rate for patients with AF is approximately twice the mortality rate for patients with normal sinus rhythm (NSR). Some research has indicated that myocardial fibrosis plays an important role in predisposing patients to AF. Therefore, realizing the relationship between myocardial collagen fibrosis and AF is significant. Second-harmonic generation (SHG) is an optically nonlinear coherent process to image the collagen network. We perform SHG microscopic imaging of the collagen fibers in the human atrial myocardium. Utilizing the SHG images, we can identify the differences in morphology and the arrangement of collagen fibers between NSR and AF tissues. We also quantify the arrangement of the collagen fibers using Fourier transform images and calculating the values of angle entropy. We indicate that SHG imaging, a nondestructive and reproducible method to analyze the arrangement of collagen fibers, can provide explicit information about the relationship between myocardial fibrosis and AF.

Upregulation of matrix metalloproteinase-9 and tissue inhibitors of metalloproteinases in rapid atrial pacing-induced atrial fibrillation

Remodeling of atrial extracellular matrix (ECM) in atrial fibrillation (AF) involves changes in the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). The contributions of MMPs and TIMPs to the pathogenesis of AF development have not been clearly defined. This study evaluated the in situ activity and expression of gelatinases (MMP-2 and MMP-9) and their relationship with TIMP-1 or TIMP-3 in atria undergoing rapid atrial pacing for the induction of AF (4 weeks' pacing followed by 2 weeks of maintained AF) in pigs. In AF atria, in situ gelatinase activity was mainly localized in the interstitium of atrial myocardium, and was significantly larger than that of sinus rhythm control (i.e., sham control). The significant increase of MMP-9 in its pro-form and mRNA level, but not MMP-2, was shown to be responsible for the increased gelatinase activity in atria with AF. The inhibitory activities of glycosylated TIMP-1 and TIMP-3, but not TIMP-2, in AF tissues were markedly elevated and also localized in the atrial interstitium. TIMP-1 was found to be mostly colocalized with gelatinase activity over the AF tissues, implying the coexistence of gelatinase activity and TIMP-1, but TIMP-3 appeared only partially colocalized and discontinued the gelatinase activity surrounding the cardiomyocytes. TIMP-1 and TIMP-3 may play differential roles in the inhibition of gelatinase activity in vivo. Together with the survey of several MMPs transcripts and the level of transforming growth factor-β1 (TGF-β1), we proposed that the increased activity of gelatinase (i.e., MMP-9), TIMP-1 and TIMP-3 and their interaction may contribute to atrial ECM remodeling of AF.

Relation between ligament of Marshall and adrenergic atrial tachyarrhythmia.

The mechanism of the adrenergic atrial tachyarrhythmia is unclear. We hypothesize that the ligament of Marshall (LOM) is sensitive to adrenergic stimulation and may serve as a source of the adrenergic atrial tachyarrhythmia. We performed computerized mapping studies in isolated-perfused canine left atrial tissues from normal dogs (n=9) and from dogs with chronic atrial fibrillation (AF) induced by 10 to 41 weeks of rapid pacing (n=3). Before isoproterenol, spontaneous activity occurred in only one normal tissue (cycle length, CL >1300 ms). During isoproterenol infusion, automatic rhythm was induced in both normal tissues (CL=578+/-172 ms) and AF tissues (CL=255+/-29 ms, P<0.05). The origin of spontaneous activity was mapped to the LOM. In the AF tissues, but not the normal tissues, we observed the transition from rapid automatic activity to multiple wavelet AF. Ablation of the LOM terminated the spontaneous activity and prevented AF. Immunocytochemical studies of the LOM revealed muscle tracts surrounded by tyrosine hydroxylase-positive (sympathetic) nerves. We conclude that the LOM is richly innervated by sympathetic nerves and serves as a source of isoproterenol-sensitive focal automatic activity in normal canine atrium. The sensitivity to isoproterenol is upregulated after long-term rapid pacing and may contribute to the development of AF in this model.

Expression and activity of metalloprotease-2 in tumoral and non-tumoral areas of livers with metastasis: [formula omitted] Unité de Recherches Hépatologiques, INSERM U-49, ∗Laboratoire d'Anatomie Pathologique B, +Clinique Chirurgicale B, Faculté de Médecine, CHRU Pontchaillou, 35033 RENNES, France

Remodeling of atrial extracellular matrix (ECM) in atrial fibrillation (AF) involves changes in the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). The contributions of MMPs and TIMPs to the pathogenesis of AF development have not been clearly defined. This study evaluated the in situ activity and expression of gelatinases (MMP-2 and MMP-9) and their relationship with TIMP-1 or TIMP-3 in atria undergoing rapid atrial pacing for the induction of AF (4 weeks' pacing followed by 2 weeks of maintained AF) in pigs. In AF atria, in situ gelatinase activity was mainly localized in the interstitium of atrial myocardium, and was significantly larger than that of sinus rhythm control (i.e., sham control). The significant increase of MMP-9 in its pro-form and mRNA level, but not MMP-2, was shown to be responsible for the increased gelatinase activity in atria with AF. The inhibitory activities of glycosylated TIMP-1 and TIMP-3, but not TIMP-2, in AF tissues were markedly elevated and also localized in the atrial interstitium. TIMP-1 was found to be mostly colocalized with gelatinase activity over the AF tissues, implying the coexistence of gelatinase activity and TIMP-1, but TIMP-3 appeared only partially colocalized and discontinued the gelatinase activity surrounding the cardiomyocytes. TIMP-1 and TIMP-3 may play differential roles in the inhibition of gelatinase activity in vivo. Together with the survey of several MMPs transcripts and the level of transforming growth factor-β1 (TGF-β1), we proposed that the increased activity of gelatinase (i.e., MMP-9), TIMP-1 and TIMP-3 and their interaction may contribute to atrial ECM remodeling of AF.