Several polypeptides with the potential to cause blood vessel growth (angiogenesis) via endothelial cell proliferation and migration have been sequenced and synthesized during the last few years. Our ultimate goal is to utilize these angiogenic agent(s) to facilitate myocardial revascularization in patients with coronary heart disease. The specific purpose of this investigation is to utilize two of these peptides, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), to effect angiogenesis and ameliorate myocardial ischemia in a canine model. These polypeptides, available to us in large quantities, are potent stimulators of angiogenesis in vitro. In our experimental model, the left circumflex coronary artery (LCX) of dogs is occluded gradually over a 2 to 3 week period by an ameroid constrictor applied to the proximal vessel. As a result of LCX occlusion, its perfusion territory becomes dependent on collateral vessels. Myocardial infarction generally does not occur as long as the occlusion is gradual. Five weeks after placement of the ameroid, regional myocardial blood flow will be quantitated with radiolabeled microspheres under basal conditions, and during pharmacologically induced coronary vasodilatation. Dogs will then be randomized to receive bFGF, VEGF, or placebo directly into the coronary circulation. After 4 weeks, resting and maximal myocardial blood flow will again be quantitated. Thus, collateral function can be compared before and after treatment in the three groups. Vessels will be examined morphometrically to determine the capillary density in the areas exposed to bFGF and VEGF. In addition, proliferating cells will be labeled by incorporation of an analog of thymidine, bromodeoxyuridine, into the DNA of s-phase cells. The bromodeoxyuridine is then detectable using an immunostaining technique employing a monoclonal antibody. Dogs will be monitored for any potential adverse effects of bFGF and VEGF by periodically assessing (through blood tests) various hematologic and biochemical parameters in the three groups.
