GROWTH FACTOR MEDIATION OF HEALING OF VASCULAR GRAFTS

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DESCRIPTION (Adapted from applicant's abstract): All current therapeutic interventional modalities in atherosclerosis have had disappointing results due largely to the blood:arterial wall and the blood:material interface. The main problems have been high rates of both early thrombosis and late myointimal hyperplasia. Both failure modes would likely be reduced by recruitment of a normal functioning endothelial cell (ECM) monolayer. The investigator and his colleagues have developed and characterized a novel method for controlled local delivery of biologically active growth factors and/or cells impregnated into a vascular graft or a vessel wall. Using FGF-1, the investigators have shown the system's capability of inducing angiogenesis via transmural capillarization and confluent endothelialization. These studies have been conducted in grafts as long as 30 cm in dogs and these studies have shown significant inhibition of myointimal hyperplasia following balloon de-endothelialization of canine carotid arteries. Limitations of this system have been identified and solutions proposed. The hypothesis of the present proposal is that the previously described performance of the FGF-1 supplemented fibrin glue in promoting endothelialization in models of vascular therapeutic interventions can be maintained without simultaneously promoting myointimal hyperplasia by the use of site directed EC specific mutants of FGF-1 and/or by inclusion of additional factors that increase the EC specificity of the mitogenic signal. The present proposal was organized about three specific aims. Specific Aim #1 is designed to characterize existing FGF-1 mutants and chimeric proteins and to generate and characterize logically derived second generation mutations based on existing in vitro assays. Specific Aim #2 is designed to evaluate the potential improved performance of the optimized FGF-1 mutant chimera supplemented fibrin glue through the addition of factors likely to increase the specificity of the mitogenic potential for the EC using EC and SMC cultures and co-cultures. In Specific Aim #3, the investigators propose to quantitate the biomechanical integrity of the graft tissue and evaluate cell specific responses to the in vitro based optimized formulation of supplemented FG in vivo in well characterized animal models of bypass grafting and of endarterectomy. The applicants will systematically evaluate the kinetics of EC and SMC ingrowth and functional characteristics of ingrowing ECs and SMCs using biochemical, histologic, immunohistochemical, and molecular biologic analysis of cellular proliferation and protein and mRNA production as a function of time following surgery. The ultimate goals of this work are to apply the technology to improve the clinical efficacy of small diameter vascular grafts, to optimize healing with diminished restenosis of endarterectomy procedures, and in future studies to modify the technology for catheter delivery of these growth factor containing suspensions to arteries following transluminal procedures including angioplasty and atherectomy. Furthermore, it is hoped that this technology will provide an optimal system for the application of transfected genetically modified ECs for purposes of gene product delivery.