Effect of Lipids on Vascular Graft Healing

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DESCRIPTION (provided by applicant): Prosthetic grafts are used widely in vascular reconstructive surgery, but their long-term patency is limited, in part due to altered cell function that could be caused by oxidized low density lipoprotein (oxLDL). We have shown that: 1) graft material stimulates monocytic cells to oxidize LDL in vitro, 2) this oxLDL inhibits endothelial cell (EC) migration in vitro, 3) explanted grafts contain lipid oxidation products, and 4) hypercholesterolemia leads to reduced EC migration onto grafts in rabbits. We also have preliminary data that lysophosphatidylcholine (lysoPC), a lipid oxidation product that accounts for most of oxLDL's inhibitory activity causes an oxidative stress that activates protein kinase C-delta (PKCdelta), and PKCdelta inhibits EC migration. Based on these data, we propose as a hypothesis that specific lipid oxidation products formed within synthetic vascular grafts inhibit EC migration, thereby limiting endothelialization of prosthetic grafts in vivo. The goals of this project are to determine the oxidation pathways active in prosthetic grafts, the mechanism by which oxidized lipids inhibit EC migration, particularly the role of reactive oxygen species (ROS) and activation of PKCdelta, and methods to improve migration. To test our hypothesis, we will identify the mechanism by which lipids in the prosthetic graft are oxidized by assessing molecular markers of specific oxidation pathways. In addition, we will identify the types of lysoPC that are present in synthetic grafts. We will investigate one mechanism by which oxLDL and ROS inhibit EC migration by studying their activation of PKCdelta and the subsequent effects on cytoskeletal proteins. Finally, we will investigate the ability of antioxidants and lipid lowering agents to improve EC migration onto prosthetic grafts implanted in normal and hypercholesterolemic rabbits. The proposed studies will investigate the role of lipids and lipoproteins, and their oxidatively-modified derivatives, in the limited endothelialization of synthetic vascular grafts. Studies will also address the efficacy of antioxidants to control lipid oxidation and promote EC healing. This will lead to a better understanding of the role of lipids in the pathophysiology of graft failure, and ultimately, to methods promoting endothelialization of prosthetic grafts and prolonging patency of small-diameter vascular grafts. I