Genetic Determinants of Limb Pathology in Peripheral Artery Disease

 描述（由申请人提供）：外周动脉疾病（PAD）是由外周动脉的动脉粥样硬化引起的，最常见于下肢，几乎与冠状动脉疾病（CAD）一样普遍，在美国有800 - 1200万人受影响。PAD表现为间歇性跛行（IC，运动时疼痛，休息时缓解）或严重肢体缺血（CLI，休息时疼痛，伴或不伴组织坏死或坏疽）。CLI的发病率和死亡率比IC低得多; CLI患者的主要截肢或死亡风险在一年内接近40%。有证据表明，遗传差异在PAD的易感性中起作用，因为近交系小鼠品系对PAD模型后肢缺血（HLI）的反应显著不同。在C57 BL/6（BL 6）小鼠中，肢体灌注恢复而无组织损失，而BALB/c小鼠显示肢体灌注恢复差和显著的组织坏死，类似于临床CLI。在基因筛选中 在小鼠HLI模型中调节肢体存活，高度显著的数量性状位点（Lsq 1)被确认了Lsq-1含有Bcl-2相关的产气基因3（Bag 3）的基因，其是骨骼肌纤维存活和再生所需的。初步研究表明，单一的BAG 3多态性导致显着的表型差异缺氧骨骼肌细胞在体外和小鼠HLI模型在体内。亲本BALB/c变体BAG 3 Met 81的表达导致体内骨骼肌纤维萎缩和肢体坏死。相比之下，BL 6变体BAG 3 Ile 81完全挽救了这些缺陷，在治疗的肌肉中肌纤维尺寸和血管密度增加。该提议的中心假设是BAG 3变体负责缺血的肌肉存活和组织损失。为了检验这一假设，该提议的具体目的是：1）确定BAG 3功能获得对体内肢体缺血后骨骼肌组织坏死和灌注的影响; 2）确定BAG 3在缺血中的血管作用的细胞起源;和3）确定BAG 3在缺血中的保护作用是否是由于对自噬的影响。虽然在阐明遗传因素对PAD的作用方面取得了进展，但确定调节患者对CLI易感性的因素对于理解疾病发病机制和开发促进CLI和目前缺乏有效治疗的其他缺血性疾病的保肢方法至关重要。

 DESCRIPTION (provided by applicant): Peripheral artery disease (PAD) is caused by atherosclerosis of the peripheral arteries, most commonly in the lower extremities, and is nearly as prevalent as coronary artery disease (CAD), with 8-12 million individuals affected in the US. PAD presents as either intermittent claudication (IC, pain with exertion that is relieved with rest or critical limb ischemia (CLI, pain at rest with or without tissue necrosis or gangrene). Less common than IC, CLI carries a substantially higher morbidity and mortality; CLI patients have a risk of major amputation or death that approaches 40% in one year. Evidence suggests that genetic differences play a role in the susceptibility to PAD, as inbred mouse strains have dramatically different responses to hind limb ischemia (HLI), a model of PAD. In C57BL/6 (BL6) mice, limb perfusion recovers without tissue loss, whereas BALB/c mice display poor recovery of limb perfusion and significant tissue necrosis, analogous to clinical CLI. In a screen for genes regulating limb survival in the mouse HLI model, a highly significant quantitative trait locus (Lsq 1) was identified. Lsq-1 contains the gene for Bcl-2-associated athanogene-3 (Bag3), which is required for skeletal myofiber survival and regeneration. Preliminary studies demonstrate that a single BAG3 polymorphism results in dramatic phenotypic differences in hypoxic skeletal muscle cells in vitro and in the mouse HLI model in vivo. Expression of the parental BALB/c variant, BAG3Met81, leads to skeletal myofiber atrophy and limb necrosis in vivo. In contrast, the BL6 variant, BAG3Ile81, completely rescues these defects with increases in myofiber size and vascular density in treated muscle. The central hypothesis of this proposal is that BAG3 variants are responsible for muscle survival and tissue loss with ischemia. To test this hypothesis, the Specific Aims of this proposal are to: 1) Determine the effects of BAG3 gain of function on skeletal muscle tissue necrosis and perfusion following limb ischemia in vivo; 2) Determine the cellular origin of BAG3's vascular effects in ischemia; and 3) Determine whether the protective role of BAG3 in ischemia is due to effects on autophagy. Although progress has been made in elucidating the contribution of genetic factors to PAD, identifying factors that modulate patients' susceptibility to CLI will be critical to understanding disease pathogenesis and in developing approaches to promote limb salvage for CLI and other ischemic diseases that currently lack effective treatments.