Dystrophin Function in Aging Heart

描述（由申请人提供）：这项工作的长期目标是实施基于基因的治疗方法来对抗衰老心脏中的进行性收缩功能障碍。心衰是老年人住院、发病和死亡的主要原因。心肌营养不良蛋白是衰老过程中进行性心功能障碍的关键和潜在的统一组成部分。肌营养不良蛋白是连接收缩性肌节和细胞膜的重要纽带。肌营养不良蛋白缺乏与心肌缺血和心力衰竭有关，并导致杜氏肌营养不良症（DMD），这是一种进行性横纹肌退化的致命疾病。DMD在这里被用作心功能障碍的模型，随着年龄的增长逐渐恶化。新的数据显示，衰老的啮齿动物心脏中的肌营养不良蛋白减少。该建议的总体假设是，肌营养不良蛋白缺乏是导致心肌对疾病损伤易感性的原因，并且是衰老心肌对损伤易感性增加的核心组成部分。第二种假设：将心肌肌营养不良蛋白增加到高于基线水平，将在体内对老年动物的心肌提供长期保护。具体目标是：目标1。研究raav介导的血管内微肌营养不良蛋白基因传递对幼龄和老年野生型和肌营养不良蛋白缺陷小鼠心脏功能的衰老依赖性影响。假设：全身微肌营养不良蛋白基因转移可防止衰老依赖性心室重构，并在体内心脏应激试验中提供长期（一年）保护；微肌营养不良蛋白可以逆转年龄依赖性心室重构，但不能纠正最大压力缺陷；微肌营养不良蛋白可以防止野生型小鼠舒张性能的年龄依赖性下降。目标2。优化微型肌营养不良蛋白和铰链修饰的微型肌营养不良蛋白基因盒，用于校正野生型和肌营养不良蛋白缺乏动物体内衰老介导的心脏血流动力学缺陷。假设：在肌营养不良蛋白缺陷小鼠体内，与第一代微肌营养不良蛋白相比，具有优化铰链和谱蛋白样重复结构域的截断肌营养不良蛋白会增加心脏功能。目标3。在野生型小鼠心脏中完成年龄依赖性的全长肌营养不良蛋白基因切除/沉默，并直接评估由此产生的体内病理和血流动力学结果。假设：颞叶肌营养不良蛋白基因缺失会导致心脏损伤和心脏功能缺陷，老年动物的影响比年轻动物更大。

DESCRIPTION (provided by applicant): The long-term goal of this work is to implement gene-based therapeutics to combat progressive contractile dysfunction in the aging heart. Heart failure is the primary cause of hospitalization, morbidity and mortality in the elderly. Cardiac dystrophin is a key and potentially unifying component of progressive heart dysfunction in aging. Dystrophin is a vital link between the contractile sarcomere and the cell membrane. Dystrophin deficiency is associated with myocardial ischemia and heart failure and causes Duchenne Muscular Dystrophy (DMD), a fatal disease of progressive striated muscle deterioration. DMD is used here as a model of cardiac dysfunction that progressively worsens in aging. New data shows dystrophin protein is decreased in the aging rodent heart. The overarching hypothesis of this proposal is that dystrophin deficiency is causal for cardiac muscle susceptibility to damage in disease and is a central component to increased susceptibility to damage in the aging myocardium. Second hypothesis: increasing cardiac dystrophin protein above baseline levels will confer long-term protection to the myocardium in aged animals in vivo. The Specific Aims are: Aim 1. To determine the aging-dependent effects of intravascular rAAV-mediated micro-dystrophin gene delivery on cardiac performance in young and old wild-type and dystrophin-deficient mice in vivo. Hypotheses: systemic micro-dystrophin gene transfer will prevent aging-dependent ventricular remodeling and confer long-term (year) protection during in vivo cardiac stress testing in vivo; micro- dystrophin will reverse age-dependent ventricular remodeling but not redress maximum pressure deficits; micro-dystrophin will prevent age-dependent decline in diastolic performance in wild-type mice. Aim 2. To optimize mini-dystrophin and hinge modified micro-dystrophin gene cassettes for correction of aging-mediate cardiac hemodynamic deficits in wild-type and dystrophin deficient animals in vivo. Hypothesis: truncated dystrophin with optimized hinge and spectrin-like repeat domains will confer increased cardiac performance relative to first generation micro-dystrophin in dystrophin-deficient mice in vivo. Aim 3. To accomplish age-dependent, full-length dystrophin gene excision/silencing in the hearts of wild- type mice and to directly assess the resulting pathological and hemodynamic outcomes in vivo. Hypothesis: temporal dystrophin gene deletion will cause cardiac injury and heart performance deficits with effects greater in old compared to young animals. PUBLIC HEALTH RELEVANCE: Heart failure, a clinical syndrome defined as reduction in overall heart pump performance, is the leading cause of hospitalization of the elderly. Progressive heart dysfunction in the elderly is an increasingly inescapable public health reality owing to current medical care and shifting US demographics. Therefore the health relevance of the proposal's focus on the aging failing heart is substantial and highly significant to the mission of the National Institute of Aging and NIH.