Primary Effect of SERCA2a Gene Transfer on Conduction Reserve in Chronic Myocardial Infarction

Abstract

Background SERCA2a gene transfer (GT) improves mechano‐electrical function in animal models of nonischemic heart failure Whether SERCA2a GT reverses pre‐established remodeling at an advanced stage of ischemic heart failure is unclear. We sought to uncover the electrophysiological effects of adeno‐associated virus serotype 1.SERCA2a GT following myocardial infarction (MI).Methods and ResultsPigs developed mechanical dysfunction 1 month after anterior MI, at which point they received intracoronary adeno‐associated virus serotype 1.SERCA2a (MI+SERCA2a) or saline (MI) and were maintained for 2 months. Age‐matched naive pigs served as controls (Control). In vivo ECG‐and‐hemodynamic properties were assessed before and after dobutamine stress. The electrophysiological substrate was measured using optical action potential (AP) mapping in controls, MI, and MI+SERCA2a preparations. In vivo ECG measurements revealed comparable QT durations between groups. In contrast, prolonged QRS duration and increased frequency of R′ waves were present in MI but not MI+SERCA2a pigs relative to controls. SERCA2a GT reduced in in vivo arrhythmias in response to dobutamine. Ex vivo preparations from MI but not MI+SERCA2a or control pigs were prone to pacing‐induced ventricular tachycardia and fibrillation. Underlying these arrhythmias was pronounced conduction velocity slowing in MI versus MI+SERCA2a at elevated rates leading to ventricular tachycardia and fibrillation. Reduced susceptibility to ventricular tachycardia and fibrillation in MI+SERCA2a pigs was not related to hemodynamic function, contractile reserve, fibrosis, or the expression of Cx43 and Nav1.5. Rather, SERCA2a GT decreased phosphoactive CAMKII‐delta levels by >50%, leading to improved excitability at fast rates.Conclusions SERCA2a GT increases conduction velocity reserve, likely by preventing CAMKII overactivation. Our findings suggest a primary effect of SERCA2a GT on myocardial excitability, independent of altered mechanical function.

Localized Co-delivery of Serca2a and Cx43 Genes Combined With Bone Marrow Mesenchymal Stem Cells Restores Rat Ischemic Cardiac Mechano-electrical Function

“…Based on these ndings, we surmised that there were no interactions between SERCA2a and Cx43 [8], and overexpression of neither of them solely could meet our goal. Guided by these ndings above, we applied two genes together after BMSCs transplantation.…”

“…Also, data from qPCR (Fig. 1h) showed that gene-loading ratio reaches the maximum ((91.59±1.04% for S-Ad, 90.72±1.69% for C-Ad when adding 10 μl Ad (1×10p pfu/ml) to BMBs (100 μl, 1×10 9 /ml)), revealing that 1×10 8 BMBs could bind approximately 1×10 7 pfu of Ad. To determine both S-Ad and C-Ad loading capacity of BMBs (S/C-BMBs), both S-Ad and C-Ad were incubated with BMBs (100 μl, 1×10 9 bubbles/ml) at the ratio of 1:1 (10 μl : 10 μl), 1:2 (5 μl : 10 μl) or 2:1 (10 μl : 5 μl), respectively.…”

“…It has been well established that myocardial ischemic stress strongly modi es the pro le of gene expression in heart [7] including sarcoplasmic reticulum Ca 2+ -ATPase 2a (SERCA2a) and Connexin 43 (Cx43), two key proteins that regulate mechano-electrical function [8,9]. SERCA2a governs the intracellular Ca 2+ handling process [10], by which cardiac contraction and relaxation is maintained through mediating Ca 2+ reuptake into sarcoplasmic reticulum (SR) [11].…”

Conditional Up-Regulation of SERCA2a Exacerbates RyR2-Dependent Ventricular and Atrial Arrhythmias

“…The interpretation of these results is complicated by adaptive or maladaptive changes caused by constitutive genetic upregulation of SERCA obscuring primary consequences of combining RyR2 hyperactivity with enhanced SERCA2 function. Defining both direct and secondary consequences of SERCA2a stimulation against the backdrop of enhanced RyR2 activity is not only required for understanding the pathophysiology of Ca-dependent cardiac disease states but also has implications for the development and implementation of new therapies such as upregulation of SERCA2a in HF [19][20][21][22]. Therefore, to examine the primary effects of SERCA2 upregulation in the present study, we developed a mouse model that combines ablation of CASQ2 with doxycycline-inducible cardiac-specific overexpression of SERCA2a.…”

Tracking nitroxyl-derived posttranslational modifications of phospholamban in cardiac myocytes

“…A hallmark of HF in both human and animal models is impaired Ca 2+ sequestration into the SR, which contributes to the decreased contractile performance in this disease (Gwathmey et al, 1987; Meyer et al, 1995; del Monte et al, 2002). Not surprisingly, this defective mechanism has been targeted with novel therapeutic strategies that are now undergoing experimental and clinical testing in animals and patients (Pfeffer et al, 2015; Hulot et al, 2016, 2017; Motloch et al, 2018). In this issue of JGP , provide novel insights into the molecular mechanism from which nitroxyl (HNO), nitric oxide (NO)’s one-electron-reduced and protonated sibling, recently emerged as a promising candidate for HF treatment.…”