All current therapeutic interventional modalities in atherosclerosis have had disappointing results due largely to blood/arterial wall and blood/material interfacial phenomena resulting in high rates of both early thrombosis and late myointimal hyperplasia. Both failure modes would likely be reduced by successful recruitment of a normal functioning endothelial cell (EC) monolayer. Our laboratory has developed a system by which EC chemoattractant and mitogenic agents can be impregnated in a slowly released bioactive fashion into expanded polytetrafluoroethylene (ePTFE) grafts. We have shown that this system induces in vivo a significant increase in transinterstitial capillary ingrowth and EC proliferation yielding a rapidly developed confluent EC layer at the interface with no later persistent subendothelial cell proliferation or intimal hyperplasia. Our objectives in this proposal are to expand upon this data to optimize the growth factor (GF) delivery system as applied to synthetic vascular grafts and to extend its application to arteries following mechanical deendothelialization. We will combine these techniques with EC transplantation using a novel system in which the cells are seeded at high density within suspensions containing GFs. EC and smooth muscle cell (SMC) growth and functional characteristics will by systematically determined at the message and protein levels and extracellular matrix components quantitated. Transplanted ECs will be both wild-type and genetically modified and the efficacy of gene product delivery determined.
The Specific Aims of this proposal are: l) to optimize the delivery system by which cell growth modulating substances are made available in a bioactive form to maximize endothelialization of vascular grafts and de- endothelialized arteries; 2) to determine the effect of the optimized growth factor delivery system on endothelialization in vivo of ePTFE grafts and de-endothelialized arteries in dogs and to systematically investigate the functional characteristics of ingrowing ECs and SMCs; and 3) to investigate the application of this technology for gene therapy using ECs transfected first with reporter genes and then with the gene encoding FGF- l with a conjugated secretory signal sequence.
This specific aim may result in still more rapid endothelialization and will document the applicability of this approach for use in gene therapy. The ultimate goals of this proposal are to improve the clinical efficacy of small diameter vascular grafts, to optimize healing with diminished restenosis of endarterectomy and angioplasty procedures, and to provide an optimal system for the application of genetically modified ECs for purposes of gene product delivery.
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