The Role of Skeletal Muscle Mitochondria in Peripheral Arterial Disease

 描述(申请人提供)：外周动脉疾病(PAD)估计影响全球2亿多人。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，持续静息状态，坏死性组织丢失发生率高)。一种常见的误解是，CLI代表了IC的自然进程。事实上，狭窄程度相同的患者可以出现间歇性跛行，CLI，也可以没有症状，这表明除了肢体灌注外，其他因素调节CLI的病理。目前治疗PAD/CLI的方法主要集中在重建流向缺血组织的血流量，这意味着血流量是决定组织存活与否的决定性因素。这个项目试图挑战这一临床范例。发现固有的遗传和细胞特异性调节细胞对缺血/缺氧的反应，从而确定组织损伤的总体程度，这一发现最初是令人惊讶的，因为治疗的目的一直只是恢复血液流动。在遗传保护(C57BL/6)和易感(BALB/c)近交系中，外周动脉疾病(PAD)的小鼠模型会导致组织坏死和肌肉肌肉病变，分别类似于人类诊断IC和CLI的病理学。在初步研究中，我们发现BALB/c小鼠线粒体呼吸功能的快速和严重丧失与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PAD的一个可行的治疗靶点。最后，我们确定了一个基因靶点Cox6a2，它通过改变骨骼肌细胞对缺血的表达来调节线粒体对缺血的反应。基于这些观察，我们假设骨骼肌线粒体是缺血反应的关键调节因子，因此是肢体缺血后肌纤维再生、新生血管和组织坏死的主要决定因素。为了研究这一假说，这一建议的具体目的是：1)确定骨骼肌线粒体呼吸功能降低是否增加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对缺血性肌病和肢体组织坏死具有保护作用。将使用免费的体外和体内实验方法，包括生理学、药理学和遗传功能获得和丧失模型。

 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.