Regulation of angiogenesis by nuclear receptors and cofactors

 描述（由申请人提供）：外周动脉疾病（PAD）及其严重形式的严重肢体缺血（CLI）影响近800万美国人。大多数患有慢性代谢和心血管疾病（如糖尿病）的患者也患有PAD/CLI。患有PAD/CLI的患者遭受使人衰弱的症状，例如不动、溃疡、伤口愈合受损和顽固性缺血。PAD/CLI的病理学涉及骨骼肌中的血管退化，这导致显著的肌病。治疗仅限于手术重建，这往往是昂贵和无效的，导致截肢。改善肌肉血管供应的“治疗性血管生成”是PAD/CLI的迫切研究领域。在这一领域，重点一直是促血管生成调节剂，如血管内皮生长因子-α（Vegfa）和缺氧诱导因子1（HIF 1），以及它们如何改善肌肉血管。不幸的是，单个血管生成因子甚至HIF 1迄今为止在PAD/CLI中是无效的靶点。值得注意的是，骨骼肌血管供应和新血管生成是由肌肉分泌的促血管生成因子和抗血管生成因子以旁分泌方式控制的。虽然肌肉中促血管生成因子如Vegfa的分子调节被定义，但令人惊讶的是，抗血管生成因子的分子调节定义得很差。我们已经初步发现，转录辅因子过氧化物酶体增殖物激活受体γ共激活因子1 β（PGC 1 β）通常通过激活核激素受体发挥作用，编码骨骼肌中抑制血管生成的基因程序。该程序包括诱导抗血管生成因子和抑制促血管生成因子，导致缺血时骨骼肌血管再生的净抑制。有趣的是，我们发现PGC 1 β表达沿着糖尿病肌肉中的抗血管生成因子，其特征在于PAD/CLI的病理症状，如血管退化、缺血和受损的新血管生成。因此，本研究计划的第一个目标是阐明内源性肌肉PGC 1 β在调节抑制性血管生成程序中的作用及其对缺血性肌肉血管重建和糖尿病性肌肉血管病的影响。第二个目标是建立COUP-TFI（鸡卵清蛋白上游启动子转录因子I）作为参与PGC 1 β驱动的抑制性血管生成的核受体。初步研究结果提示，PGC 1 β的抗血管生成作用可能是通过激活核受体COUP-TFI而介导的。我们的中心假设是骨骼肌中的PGC 1 β通过激活COUP-TFI激发旁分泌抗血管生成基因程序，阻断缺血性新血管生成，并导致糖尿病肌肉血管病。验证这一假设的具体目的是：（目的1）研究内源性PGC 1 β在肌肉血管生成中的作用;（目的2）研究PGC 1 β和COUPTFI是否相互作用以调节肌肉血管生成。目的1：利用小鼠肌肉特异性PGC 1 β缺失，研究肌肉PGC 1 β缺失对肌肉血管、缺血性血管重建和血管生成因子表达的影响。在目的2中，我们将首先进行体外实验以研究PGC 1 β和COUP-TFI之间的相互作用，以及它们如何调节肌肉血管生成基因。其次，我们将使用肌肉特异性复合转基因小鼠来研究肌肉特异性PGC 1 β过表达的抗血管生成作用是否在肌肉特异性COUP-TFI缺失时丧失。我们还将研究双重肌肉特异性PGC 1 β和COUP-TFI敲除对肌肉新生血管和血管重建的影响。本研究的意义在于揭示骨骼肌中抗血管生成基因程序的调控机制，以及它在骨骼肌缺血和糖尿病性肌血管病变中对血管重建的影响。我们的研究是创新的，因为我们将研究PAD/CLI治疗中抗血管生成基因编程的未开发领域。这些发现将对设计PAD/CLI肌肉缺血的新治疗方法以及广泛的其他疾病如心肌梗死，中风和肿瘤血管生成产生影响。

 DESCRIPTION (provided by applicant): Peripheral arterial disease (PAD) and its severe form critical limb ischemia (CLI) affect nearly 8 million Americans. Most patients with chronic metabolic and cardiovascular diseases such as diabetes also suffer from PAD/CLI. Patients with PAD/CLI suffer from debilitating symptoms such as immobility, ulceration, impaired wound healing, and intractable ischemia. The pathology of PAD/CLI involves vascular regression in the skeletal muscle, which leads to significant myopathy. Treatment is limited to surgical reconstruction, which is often costly and ineffective leading to limb amputations. 'Therapeutic angiogenesis' to improve muscle vascular supply is an urgent area of research in PAD/CLI. Within this field, focus has been on pro-angiogenic regulators such as vascular endothelial growth factor-alpha (Vegfa) and hypoxia inducible factor 1 (HIF1), and how they can improve muscle vasculature. Unfortunately, individual angiogenic factors and even HIF1 have so far been ineffective targets in PAD/CLI. Notably, skeletal muscle vascular supply and neo angiogenesis is controlled in a paracrine fashion by both pro-angiogenic and anti-angiogenic factors secreted by the muscle. While molecular regulation of pro-angiogenic factors such as Vegfa in the muscle is defined, surprisingly, the molecular regulation of anti-angiogenic factors is poorly defined. We have preliminarily found that a transcriptional cofactor peroxisome proliferator-activated receptor gamma co-activator 1 beta (PGC1β), which typically functions by activating nuclear hormone receptors, encodes an inhibitory angiogenesis gene program in the skeletal muscles. This program constitutes induction of anti-angiogenic factors and repression of proangiogenic factors, resulting in a net inhibition of skeletal muscle revascularization in ischemia. Interestingly, we found that PGC1β expression is induced along with the anti-angiogenic factors in diabetic muscles, which are characterized by the pathological symptoms of PAD/CLI such as vascular regression, ischemia and impaired neo-angiogenesis. Therefore, the first objective of this research proposal is to decipher the role of endogenous muscle PGC1β in regulating inhibitory angiogenic program and its effect on ischemic muscle revascularization and diabetic muscle angiopathy. The second objective is to establish COUP-TFI (chicken ovalbumin upstream promoter transcription factor I) as the nuclear receptor involved in PGC1β-driven inhibitory angiogenesis. Our preliminary data indicates that the anti-angiogenic effects of PGC1β may be mediated by activating nuclear receptor COUP-TFI. Our central hypothesis is that PGC1β in the skeletal muscle instigates a paracrine anti-angiogenic gene program by activating COUP-TFI, blocks ischemic neo angiogenesis, and contributes to diabetic muscle angiopathy. The specific aims to test this hypothesis are to: (Aim 1) Investigate the role of endogenous PGC1β in muscle angiogenesis and (Aim 2) Investigate whether PGC1β and COUPTFI interact to regulate muscle angiogenesis. In Aim 1, we will use muscle-specific deletion of PGC1β in mice to investigate how the loss of muscle PGC1β affects muscle vasculature, ischemic revascularization and the expression of angiogenic factors. In Aim 2, we will first perform in vitro experiments to study the interaction between PGC1β and COUP-TFI, and how they regulate muscle angiogenic genes. Second, we will use muscle-specific compound transgenic mice to investigate whether the anti-angiogenic effects of musclespecific PGC1β over-expression is lost on muscle-specific COUP-TFI deletion. We will also investigate the impact of double muscle-specific PGC1β and COUP-TFI knockout on muscle neo-angiogenesis and revascularization. The significance of our work is that it aims to discover how anti-angiogenic gene program is regulated in the skeletal muscle, and how it affects revascularization in muscle ischemia and diabetic muscle angiopathy. Our research is innovative as we will study the unexplored area of anti-angiogenic gene programming in the treatment of PAD/CLI. The findings will have implications for devising new treatment for muscle ischemia in PAD/CLI, and broadly in other diseases such as cardiac infarction, stroke and tumor angiogenesis.