The Role of Skeletal Muscle Mitochondria in Peripheral Arterial Disease

 描述（由申请人提供）：外周动脉疾病（PAD）估计影响全球超过2亿人。外周动脉疾病（PAD）表现为间歇性跛行（IC，活动性疼痛）或严重肢体缺血（CLI，持续休息，坏死组织丢失发生率高）。一个常见的误解是CLI代表了IC的自然进展。事实上，具有相同狭窄程度的患者可以表现为间歇性跛行、CLI或可以无跛行，这表明肢体灌注以外的因素调节CLI病理。目前PAD/CLI的治疗方法集中在重建缺血组织的血流，这意味着血流是决定组织是否存活的决定性因素。该项目旨在挑战这种临床模式。固有的遗传和细胞特异性特性调节细胞对缺血/缺氧的反应，从而确定组织损伤的总体程度的发现最初是令人惊讶的，因为治疗的目的仅仅是恢复血流。遗传保护（C57 BL/6）和易感（BALB/c）近交系中外周动脉疾病（PAD）的小鼠模型导致组织坏死和肌肉肌病，分别与人类IC和CLI诊断相关的病理学相似。在初步研究中，我们发现，快速和严重的线粒体呼吸功能丧失与BALB/c小鼠肌肉肌病和组织坏死的增加有关。此外，我们提供的证据支持线粒体是一个可行的PAD治疗靶点。最后，我们已经确定了一个遗传靶点，Cox 6a 2，它通过改变其表达来调节骨骼肌细胞对缺血的线粒体反应。基于这些观察，我们假设骨骼肌线粒体是对缺血反应的关键调节器，因此是肢体缺血后肌纤维再生、新血管形成和组织坏死的主要决定因素。为了研究这一假设，本提案的具体目的是：1）确定骨骼肌线粒体呼吸功能降低是否会增加对缺血性肌病和肢体组织坏死的易感性，2）确定骨骼肌线粒体呼吸功能改善是否会预防缺血性肌病和肢体组织坏死。将使用免费的体外和体内实验方法，包括生理学、药理学和遗传获得和功能丧失模型。

 DESCRIPTION (provided by applicant): Peripheral artery disease (PAD) is estimated to effect more than 200 million people worldwide. Peripheral artery disease (PAD) presents as either intermittent claudication (IC, pain with activity) or critical limb ischemia (CLI, constant rest pan with a high incidence of necrotic tissue loss). A common misconception is that CLI represents the nature progression of IC. In fact, patients with the same degree of stenosis can present with intermittent claudication, CLI, or can be symptom-free, suggesting that factors other than limb perfusion regulate CLI pathology. Current treatment approaches for PAD/CLI are focused on re-establishing blood flow to the ischemic tissue, implying that blood flow is the decisive factor tha determines whether or not the tissue survives. This project seeks to challenge this clinical paradigm. The discovery that inherent genetic and cell specific properties regulate the cellular response to ischemia/hypoxia, and thus determining the overall degree of tissue damage was initially a surprise because treatments have been aimed solely at recovering of blood flow. Mouse models of peripheral artery disease (PAD) in genetically protected (C57BL/6) and susceptible (BALB/c) inbred strains result in tissue necrosis and muscle myopathies that resemble the pathologies associated with human diagnoses of IC and CLI, respectively. In preliminary studies we discovered that rapid and severe loss of mitochondrial respiratory function is associated with increased muscle myopathy and tissue necrosis in BALB/c mice. Further, we provide evidence supporting that mitochondria are a viable therapeutic target for PAD. Finally, we have identified a genetic target, Cox6a2, which regulates the mitochondrial response to ischemia in skeletal muscle cells through alterations in its expression in response to ischemia. Based on these observations, we hypothesize that skeletal muscle mitochondria are critical regulator's of the response to ischemia, and therefore a primary determinant of myofibers regeneration, neovascularization, and tissue necrosis after limb ischemia. To investigate this hypothesis, the Specific Aims of this proposal are: 1) determine whether reduced skeletal muscle mitochondrial respiratory function increases the susceptibility to ischemic myopathy and limb tissue necrosis, 2) determine whether improved mitochondrial respiratory function in skeletal muscle protects against ischemic myopathy and limb tissue necrosis. Complimentary in vitro and in vivo experimental approaches will be used including physiological, pharmacological, and genetic gain- and loss-of-function models.