ANGIOGENIC BYPASS & GENE THERAPY RESPONSE MECHANISMS

尽管血管成形术和旁路手术等挽救生命的技术得到了改进，但动脉粥样硬化仍然是西方世界的主要死亡原因，部分原因是这些疗法的应用仍然受到这种疾病的扩散性质和许多患者再狭窄的发展的限制。 新血管的生长（新血管形成）是对缺血的关键但有限的生物学反应，其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再生策略，其中施用生长因子多肽以增强天然新血管形成过程。基因治疗可能是唯一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，因为它提供了持续的生长因子输送后，只有一个剂量的适当的载体。 尽管有数据表明通过腺病毒（Ad）递送的血管内皮生长因子（VEGF）增强血管生成并保持组织灌注，但对治疗性血管生成的潜在机制仍然知之甚少。 具体而言，缺血的作用和VEGF和其他潜在的血管生成介质的表达所需的持续时间，在允许诱导和持续的新血管形成是未知的。 因此，本提案的目的是在已建立的动物模型中确定：1）缺血在诱导和允许生理相关的新血管形成的持续中是必需的，2）新血管形成可以通过血管生成“辅因子”，如血管生成素来增强，其被认为在血管发芽和稳定中起作用，和3）转基因表达可以用选择的启动子调节，包括心脏特异性和糖皮质激素反应元件，以允许相关转基因分别在特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.