Dystrophin Function in Aging Heart

描述(申请人提供)：这项工作的长期目标是实施基于基因的疗法来对抗老化心脏的进行性收缩功能障碍。心力衰竭是老年人住院、发病率和死亡率的主要原因。心脏营养不良蛋白是老年人进行性心功能障碍的关键和潜在的统一成分。肌营养不良蛋白是连接收缩肌节和细胞膜的重要纽带。营养不良蛋白缺乏与心肌缺血和心力衰竭有关，并导致Duchenne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在这里被用作心脏功能障碍的模型，随着年龄的增长逐渐恶化。新数据显示，在老化的啮齿动物心脏中，营养不良蛋白减少。这一建议的主要假设是，dystrophin缺乏是心肌对疾病损伤易感性的原因，也是老化心肌对损伤易感性增加的中心成分。第二个假设：在活体老年动物体内，增加心肌肌营养不良蛋白水平高于基线水平将对老年动物的心肌具有长期保护作用。目的：1.研究血管内rAAV介导的微肌营养不良蛋白基因治疗对幼年、老年野生型和抗肌营养不良蛋白缺陷小鼠心功能的影响。假设：全身性微肌营养不良蛋白基因转移将防止衰老依赖的心室重构，并在体内心脏应激测试中提供长期(一年)的保护；微肌营养不良蛋白将逆转年龄依赖的心室重构，但不能纠正最大压力不足；微肌营养不良蛋白将防止野生型小鼠舒张期表现的年龄依赖性下降。目的2.优化微型肌营养不良蛋白和铰链修饰的微肌营养不良蛋白基因盒，以纠正野生型和肌营养不良蛋白缺陷型动物体内衰老介导的心脏血流动力学缺陷。假设：在体内，与第一代微肌营养不良蛋白相比，截短型抗肌营养不良蛋白具有优化的铰链和像幽灵蛋白一样的重复结构域，可以提高心功能。目的3.在野生型小鼠心脏中实现年龄依赖性的全长dystrophin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：暂时性肌营养不良蛋白基因缺失将导致心脏损伤和心脏功能缺陷，与年轻动物相比，老年动物的影响更大。 公共卫生相关性：心力衰竭是一种临床综合征，定义为总体心泵性能下降，是老年人住院的主要原因。由于当前的医疗保健和美国人口结构的变化，老年人进行性心脏功能障碍是一个越来越不可避免的公共卫生现实。因此，该提案关注老化衰竭心脏的健康相关性对国家老龄研究所和美国国立卫生研究院的使命是实质性的和非常重要的。

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.