Rapid Electrical Stimulation Increased Cardiac Apoptosis Through Disturbance of Calcium Homeostasis and Mitochondrial Dysfunction in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Background/Aims: Heart failure induced by tachycardia, the most common arrhythmia, is frequently observed in clinical practice. This study was designed to investigate the underlying mechanisms. Methods: Rapid electrical stimulation (RES) at a frequency of 3 Hz was applied on human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for 7 days, with 8 h/day and 24 h/day set to represent short-term and long-term tachycardia, respectively. Age-matched hiPSC-CMs without electrical stimulation or with slow electrical stimulation (1 Hz) were set as no electrical stimulation (NES) control or low-frequency electrical stimulation (LES) control. Following stimulation, JC-1 staining flow cytometry analysis was performed to examine mitochondrial conditions. Apoptosis in hiPSC-CMs was evaluated using Hoechst staining and Annexin V/propidium iodide (AV/PI) staining flow cytometry analysis. Calcium transients and L-type calcium currents were recorded to evaluate calcium homeostasis. Western blotting and qPCR were performed to evaluate the protein and mRNA expression levels of apoptosis-related genes and calcium homeostasis-regulated genes. Results: Compared to the controls, hiPSC-CMs following RES presented mitochondrial dysfunction and an increased apoptotic percentage. Amplitudes of calcium transients and L-type calcium currents were significantly decreased in hiPSC-CMs with RES. Molecular analysis demonstrated upregulated expression of Caspase3 and increased Bax/Bcl-2 ratio. Genes related to calcium re-sequence were downregulated, while phosphorylated Ca2+/calmodulin-dependent protein kinase II (CaMKII) was significantly upregulated following RES. There was no significant difference between the NES control and LES control groups in these aspects. Inhibition of CaMKII with 1 µM KN93 partly reversed these adverse effects of RES. Conclusion: RES on hiPSC-CMs disturbed calcium homeostasis, which led to mitochondrial stress, promoted cell apoptosis and caused electrophysiological remodeling in a time-dependent manner. CaMKII played a central role in the damages induced by RES, pharmacological inhibition of CaMKII activity partly reversed the adverse effects of RES on both structural and electrophysiological properties of cells

Thoracoscopic Left Atrial Appendage Excision Plus Ablation for Atrial Fibrillation to Prevent Stroke

Atrial fibrillation (AF) patients with a previous stroke are often at a high risk of recurrent stroke and bleeding. Anticoagulation therapy in such patients is a challenging dilemma. Thoracoscopic left atrial appendage excision (LAAE) plus AF ablation is an interventional approach offered to some AF patients. We hypothesized that this approach may be suitable as a secondary stroke prevention strategy for these high-risk patients. Between January 2013 and December 2016, a total of 44 patients (26 male; mean age 65.0 ± 9.1 years) with nonvalvular AF and a previous stroke or systemic thromboembolic event were enrolled. The patients underwent thoracoscopic LAAE plus AF ablation by experienced operators and were followed up for 2 years (at 1, 3, 6, 9, and 12 months postoperatively and every 6 months thereafter). Thromboembolic and major bleeding events were recorded. Cerebral computed tomography or magnetic resonance imaging and 7-day Holter monitoring were performed annually. Mean CHA2DS2-VASc and HAS-BLED scores were 4.2 ± 1.2 and 3.3 ± 0.7, respectively. All patients discontinued oral anticoagulation therapy after the surgical intervention. One patient suffered a periprocedural transient ischemic attack, and another was diagnosed with a new ischemic stroke at 491 days after surgery. The annual rate of total thromboembolism was 2.05%. No deaths or major bleeding events were observed postoperatively. The rate of successful AF ablation with no AF recurrence was 76.3%. Transthoracoscopic LAAE plus AF ablation may be a promising approach for this high-risk population. Thromboembolism event in this secondary prevention cohort was low, even without oral anticoagulation treatment

Evaluation of Stroke Risk in Patients With Atrial Fibrillation Using Morphological and Hemodynamic Characteristics

Background: It is well known that the thrombus triggering stroke in patients with atrial fibrillation (AF) mainly comes from the left atrial appendage (LAA). This study aims to characterize the morphological and hemodynamic parameters and evaluate their differences between AF patients with and without a stroke history. Methods: Cardiac CT images were obtained from AF patients with (n = 10) and without a history of stroke (n = 10). 3D models of the left atrium (LA) were reconstructed by processing the CT image, and the LA/LAA morphological parameters were measured. Computational fluid dynamics (CFD) simulations were performed to calculate the hemodynamic parameters in LA. The species-transport model and discrete phase model (DPM) were applied to analyze blood residual ratio and particle residual ratio, two qualitative parameters for thrombus formation and flow-out potential, respectively. Results: There were significant differences in LAA actual depth (p = 0.002), and direct length (p = 0.049) between the non-stroke and stroke groups. Significant differences were also found in certain hemodynamic parameters. The blood residual ratio in LAA was significantly smaller in the stroke group than in the non-stroke group (p Conclusion: There are significant differences in both morphological and hemodynamic parameters between AF patients with and without a stroke history. A high blood residual ratio in LAA confirms that thrombus is more likely to form in AF patients. A significantly smaller particle residual ratio in the stroke group may suggest the thrombus formed with LAA is more likely to flow out of LAA, leading to a higher risk of stroke. The proposed morphological and hemodynamic parameters may be additional risk factors that can be used to better risk stratify AF patients.</p

Study of the Biomechanical Properties and Microstructure of Trabecular Musculi Pectinati in the Left Atrial Appendage for patients with Atrial Fibrillation

Aims: (1) Quantitatively characterize the Pseudo Fibrosis Burden (PFB) of Left Atrial Appendage (LAA) Trabecular Musculi Pectinati (TMP) in patients with atrial fibrillation based on histological analysis; (2) Explore the passive dynamic properties of LAA TMP based on uniaxial tensile experiments and determine the hyperelastic constitutive parameters; (3) Explore samples Effects of different storage conditions on the mechanical properties of left atrial appendage TMP. Methods: Fifty TMP were isolated from the resected LAAs of 21 patients with atrial fibrillation and stored (23 strips in the -78 C cryopreservation group and 27 strips in the 4 C normal temperature storage group). The TMP stress-strain curve was obtained through uniaxial tension. According to this curve, the elastic modulus of the low strain zone (EMLS) and the high strain zone (EMHS) were respectively defined. The correlation between the TMPa's diameter and its mechanical properties and the impact of storage temperature on TMP mechanics were analyzed. Four strain energy functions were used to fit the TMP stress-strain curve to obtain the hyperelastic model constitutive parameters. Histological analysis of the axial and transverse microstructure of TMP was performed using Verhoeff-Van Gieson double staining method of Elastic fibers and collagen fibers (EVG) and Masson staining respectively, and the Pseudo Fiber Burden (PFB) was calculated. Analyze the correlation between mechanical properties and PFB. Results: Cryopreservation reduced the elastic modulus in the hyperelastic stage of TMP mechanical properties. EMLS (r=-0.7228, P<0.0001)/EMHS (r=-0.6772, P<0.0001) showed a significantly negative correlation with TMP diameter, while PFB only showed a significantly higher positive correlation with EMHS (r=0.6646, P=0.0057). Conclusion: This study quantitatively characterized the morphological and mechanical features of TMP. The research revealed that different storage temperatures to some extent affected the mechanical properties of TMP. Moreover, there was a significant correlation between the mechanical properties of TMP and TMP diameter. This held potential significance for a deeper understanding of the mechanical aspects of TMP under atrial fibrillation conditions and for constructing atrial fibrillation simulation models of the LAA.</p

Příloha - nedílná součást účetní závěrky podnikatelských subjektů

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Ekonomická fakulta. Katedra (116) marketingu a obchod

A Study on the Causes of Apomixis in <i>Malus shizongensis</i>

Apomixis is a unique reproductive process that produces fertile offspring without the combination of sperm and egg cells. This process perfectly reproduces maternal DNA, making it possible to fix heterosis during reproduction. Malus shizongensis is a newly discovered species that is closely related to Malus hupehensis Rehd. After de-male bagging, it was found that the fruit set rate reached 78.7%. Preliminary analysis indicated that M. shizongensis have apomictic reproductive characteristics. In this work, we employed paraffin sectioning and electron scanning microscopy to explore apomixis in M. shizongensis during the development of male–female gametes and embryo sacs. Stigma fluorescence assays showed that pollen germination was normal, but less pollen entered the ovaries. Additionally, analysis of anthers indicated the presence of dysplasia and paraffin sectioning revealed that the pollen mother cells were aborted due to abnormal disintegration of the tapetum layer. Taken together, our results indicate that the primary causes of apomixis in M. shizongensis are anther dysplasia and male gamete development failure, resulting in reduced pollen tube entry into ovaries and reduced reproduction of female gametes. In conclusion, this study provide a theoretical basis and technical supports for apple stock breeding and apple industry development

Patient-specific pulmonary venous flow characterization and its impact on left atrial appendage thrombosis in atrial fibrillation patients

Background: Cardioembolic strokes are commonly occurred in non-valvular atrial fibrillation (AF) patients, with over 90% of cases originating from clot in left atrial appendage (LAA), which is believed to be greatly related with hemodynamic characters. Numerical simulation is widely accepted in the hemodynamic analysis, and patient-specific boundaries are required for realistic numerical simulations. Method: This paper firstly proposed a method that maps personalized pulmonary venous flow (PVF) by utilizing the volume changes of the left atrium (LA) over the cardiac cycle. Then we used data from patients with AF to investigate the correlation between PVF patterns and hemodynamics within the LAA. Meanwhile, we conducted a fluid-structure interaction analysis to assess the impact of velocity- and time-related PVF parameters on LAA hemodynamic characters. Results: The analysis reveal that the ratio of systolic to diastolic peak velocity (VS/VD), and systolic velocity-time integral (VTI) showed a significant influence on LAA velocity in patients with atrial fibrillation, and the increases of velocity- and time-related parameters were found to be positively correlated with the blood update in the LAA. Conclusions: This study established a method for mapping patient-specific PVF based on LA volume change, and evaluated the relationship between PVF parameters and thrombosis risk. The present work provides an insight from PVF characters to evaluate the risk of thrombus formation within LAA in patients with AF.</p

Stroke risk evaluation for patients with atrial fibrillation : Insights from left atrial appendage

Left atrial appendage (LAA) is believed to be a common site of thrombus formation in patients with atrial fibrillation (AF). However, the commonly-applied stroke risk stratification model (such as. CHA2DS2-VASc score) does not include any structural or hemodynamic features of LAA. Recent studies have suggested that it is important to incorporate LAA geometrical and hemodynamic features to evaluate the risk of thrombus formation in LAA, which may better delineate the AF patients for anticoagulant administration and prevent strokes. This review focuses on the LAA-related factors that may be associated with thrombus formation and cardioembolic events.</p