Departments of Cardiovascular Medicine, Pediatric and Adolescent Medicine, and Molecular Pharmacology & Experimental Therapeutics, Divisions of Heart Rhythm Services and Pediatric Cardiology, Windland Smith Rice Genetic Heart Rhythm Clinic and The Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Guggenheim 501, Rochester, MN 55905, USA.
Translational Cardiology, Department of Cardiology and Department of Physiology, University Hospital Bern, University of Bern, Bühlplatz 5, 3012 Bern, Switzerland.
Eur Heart J. 2024 Sep 29;45(36):3751-3763. doi: 10.1093/eurheartj/ehae476.
Type 1 long QT syndrome (LQT1) is caused by pathogenic variants in the KCNQ1-encoded Kv7.1 potassium channels, which pathologically prolong ventricular action potential duration (APD). Herein, the pathologic phenotype in transgenic LQT1 rabbits is rescued using a novel KCNQ1 suppression-replacement (SupRep) gene therapy.
KCNQ1-SupRep gene therapy was developed by combining into a single construct a KCNQ1 shRNA (suppression) and an shRNA-immune KCNQ1 cDNA (replacement), packaged into adeno-associated virus serotype 9, and delivered in vivo via an intra-aortic root injection (1E10 vg/kg). To ascertain the efficacy of SupRep, 12-lead electrocardiograms were assessed in adult LQT1 and wild-type (WT) rabbits and patch-clamp experiments were performed on isolated ventricular cardiomyocytes.
KCNQ1-SupRep treatment of LQT1 rabbits resulted in significant shortening of the pathologically prolonged QT index (QTi) towards WT levels. Ventricular cardiomyocytes isolated from treated LQT1 rabbits demonstrated pronounced shortening of APD compared to LQT1 controls, leading to levels similar to WT (LQT1-UT vs. LQT1-SupRep, P < .0001, LQT1-SupRep vs. WT, P = ns). Under β-adrenergic stimulation with isoproterenol, SupRep-treated rabbits demonstrated a WT-like physiological QTi and APD90 behaviour.
This study provides the first animal-model, proof-of-concept gene therapy for correction of LQT1. In LQT1 rabbits, treatment with KCNQ1-SupRep gene therapy normalized the clinical QTi and cellular APD90 to near WT levels both at baseline and after isoproterenol. If similar QT/APD correction can be achieved with intravenous administration of KCNQ1-SupRep gene therapy in LQT1 rabbits, these encouraging data should compel continued development of this gene therapy for patients with LQT1.
1 型长 QT 综合征（LQT1）是由 KCNQ1 编码的 Kv7.1 钾通道的致病变异引起的，该变异病理性地延长心室动作电位持续时间（APD）。在此，通过一种新型的 KCNQ1 抑制-替代（SupRep）基因治疗来挽救转基因 LQT1 兔的病理表型。
KCNQ1-SupRep 基因治疗是通过将 KCNQ1 shRNA（抑制）和 shRNA 免疫 KCNQ1 cDNA（替代）结合到单个构建体中，包装成腺相关病毒血清型 9，并通过主动脉根内注射（1E10 vg/kg）在体内传递来开发的。为了确定 SupRep 的疗效，在成年 LQT1 和野生型（WT）兔中评估了 12 导联心电图，并在分离的心室心肌细胞上进行了膜片钳实验。
KCNQ1-SupRep 治疗 LQT1 兔可显著缩短病理性延长的 QT 指数（QTi）至 WT 水平。与 LQT1 对照相比，来自治疗的 LQT1 兔的心室心肌细胞表现出明显的 APD 缩短，导致与 WT 相似的水平（LQT1-UT 与 LQT1-SupRep，P <.0001，LQT1-SupRep 与 WT，P = ns）。在用异丙肾上腺素进行β-肾上腺素刺激下，SupRep 治疗的兔表现出 WT 样的生理性 QTi 和 APD90 行为。
本研究提供了首例用于校正 LQT1 的动物模型、概念验证基因治疗。在 LQT1 兔中，用 KCNQ1-SupRep 基因治疗治疗可使基线和异丙肾上腺素后临床 QTi 和细胞 APD90 正常化至接近 WT 水平。如果在 LQT1 兔中通过静脉内给予 KCNQ1-SupRep 基因治疗可获得类似的 QT/APD 校正，则这些令人鼓舞的数据应该促使继续开发这种基因治疗用于 LQT1 患者。
