ANGIOGENIC BYPASS & GENE THERAPY RESPONSE MECHANISMS

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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.