Vascular reconstructions (whether bypass or endarterectomy) frequently fail because of proliferation of vessel wall cells at times long after operation. Experimental studies suggest that after injury to the vessel wall, cells not covered by endothelial cells (EC) proliferate more rapidly than adjacent regions covered by EC. One major surgical form of vessel wall injury, carotid endarterectomy, may also cause chronic proliferation, since clinical studies suggest a surprisingly high incidence (6-20%) of major narrowing (50%) following carotid endarterectomy. This proposal will study cell proliferation after endarterectomy and use one currently proposed method of improving prosthetic graft patency-endothelial cell seeding-to improve vessel healing after endarterectomy. After characterizing the effect endothelial cells have on healing after endarterectomy, we will genetically alter endothelial cells to improve specific functions to further improve patency in small caliber arteries subjected to endarterectomy.
SPECIFIC AIM 1 : We will study vascular healing of small caliber low flow arteries subjected to endarterectomy in a canine model. To study the endothelialization process we will introduce marker genes to these cells while in culture, then reimplant these cells, and document the pattern and time course of reendothelialization. We will determine the minimal inoculum necessary to successfully reendothelialize endarterectomized arteries.
SPECIFIC AIM 2 : We will compare patency using this form of small caliber reconstruction (endarterectomy and EC seeding) with one currently proposed alternative to autogenous small caliber bypass, EC seeding of prosthetic bypass grafts.
SPECIFIC AIM 3 : We will genetically modify endothelial cells to improve patency in low flow reconstructions. We will investigate two strategies to improve patency, improving EC proliferation immediately after endarterectomy, and inducing secretion of a potent vasodilator after endarterectomy. Our preliminary data demonstrates that we can efficiently express a gene not normally found in cultured human EC, a receptor gene for platelet-derived growth factor (PDGF receptor). Expression of this gene confers a significant proliferative advantage to human EC cells in vitro. Since PDGF is present at sites of platelet activation (such as endarterectomized vessels) this may also impart a replicative advantage to the seeded cells and improve endothelial repopulation after endarterectomy. Alternatively, the secretion of the vasodilator atrial natriuretic peptide (ANP) from EC's relining endarterectomized vessels may improve patency either by directly decreasing vessel spasm after injury, or by dilating distal small caliber resistance vessels and increasing blood flow across an endarterectomized segment.
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