ANGIOGENIC BYPASS & GENE THERAPY RESPONSE MECHANISMS

动脉粥样硬化仍然是西方世界的主要死亡原因，尽管诸如血管成形术和搭桥手术等挽救生命的技术不断改进，部分原因是这些疗法的应用仍然受到这种疾病弥漫性和许多患者再狭窄发展的限制。新血管的生长（新生血管）是对缺血的一种关键但有限的生物反应，可诱导缺血组织的部分再灌注。治疗性血管生成是一种新的血管重建策略，通过使用生长因子多肽来增强原生血管再生过程。基因疗法可能特别适合于诱导治疗性血管生成，特别是在相对难以接近的部位，如心脏，因为它只在单剂量的适当载体后提供持续的生长因子递送。尽管有数据表明，通过腺病毒（Ad）传递的血管内皮生长因子（VEGF）可以促进血管生成并保持组织灌注，但治疗性血管生成的机制仍然知之甚少。具体来说，缺血的作用以及VEGF和其他潜在血管生成介质在诱导和持续新生血管中的必要表达时间尚不清楚。因此，本建议的目的是在已建立的动物模型中确定：1)缺血是诱导和维持生理相关新生血管形成的必要条件；2)新生血管形成可以通过血管生成“辅助因子”增强，如血管生成素，它被认为在血管发芽和稳定中起作用；3)转基因表达可以通过选定的启动子来调节，包括心脏特异性和糖皮质激素反应元件。允许相关转基因分别在指定的位置或时间表达（“隐形”基因治疗）。这些目标的成功实现将为治疗性血管生成的机制提供重要的见解，从而提高我们在临床上最佳应用这种生物方法治疗动脉粥样硬化的能力。

Atherosclerosis remains the leading cause of death in the Western world, despite the refinement of such life-saving techniques as angioplasty and bypass surgery, in part because the application of these therapies remains limited by the diffuse nature of this disease and the development of restenoses in many patients. The growth of new vasculature (neovascularization) is a critical but limited biologic response to ischemia that induces partial reperfusion of ischemic tissues. Therapeutic angiogenesis is a novel revascularization strategy whereby a growth factor polypeptide is administered for the purpose of augmenting the native neovascularization process. Gene therapy may be uniquely suitable for inducing therapeutic angiogenesis, especially in relatively inaccessible sites such as the heart, in that it provides sustained growth factor delivery after only a single dose of an appropriate vector. Despite data that vascular endothelial growth factor (VEGF) delivered via adenovirus (Ad) enhances angiogenesis and preserves tissue perfusion, the mechanisms underlying therapeutic angiogenesis remain poorly understood. Specifically, the role of ischemia and the necessary duration of expression of VEGF and other potential angiogenesis mediators in permitting induction and persistence of neovascularization are unknown. The aims of this proposal are therefore to determine, in established animal models, whether: 1) ischemia is requisite in inducing and allowing the persistence of physiologically relevant neovascularization, 2) neovascularization can be enhanced by angiogenesis "co-factors", such as the angiopoietins, which are thought to play a role in vascular sprouting and stabilization, and 3) transgene expression can be regulated with selected promoters, including cardiac specific and glucocorticoid response elements, to allow the expression of relevant transgenes at specified locations or times ("stealth" gene therapy), respectively. The successful accomplishment of these aims should provide significant insights into the mechanisms underlying therapeutic angiogenesis and thereby enhance our ability to optimally apply clinically this biologic approach to the treatment of atherosclerosis.