Angiographic quantification of angiogenesis

Therapeutic angiogenesis is the attempt to increase vascular density by means of an exogenously administered proangiogenic agent and offers a potential treatment for diseases associated with tissue ischemia. Vascular endothelial growth factor (VEGF) expressed by gene therapy has been shown to be a potent stimulator of angiogenesis and to improve the function of ischemic tissues in patients [Isner, 1998]. Unregulated gene therapy is disconcerting since there is no assurance that the treatment will target the ischemic territory. A new regulated adeno-associated viral vector expressing VEGF₁₆₃ that is conditionally silenced has been developed by one of the authors (KAW). The transgene expression is regulated by silencing the genes in the absence of the disease and at the same time having strong and local activation in the presence of the disease. The purpose of this work is to establish protocols and techniques to quantify the efficacy of therapeutic angiogenesis. The initial phase of this research involves assessment of angiogenesis using an unregulated, adenoviral vector that is encoded to express VEGF₁₆₅. Using the rabbit hind limb ischemia model, angiography was performed on animals that were given the proangiogenic treatment and on a sham group, in which phosphate buffered saline (PBS) was injected. Angiographic contrast intensity curves were obtained, modeled, and the optimized model parameters provided insight into flow characteristics within the targeted vascular bed. In the second phase of the project the conditionally silent vector will be employed using the developed protocols and methods of the first phase to afford comparisons with the previous groups.