VEIN GRAFT PRESERVATION: THROMBOSIS & NEOINTIMAL DISEASE

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(Adapted from applicant?s abstract) The development of vein graft atherosclerosis is a major concern for patients undergoing coronary artery bypass grafting. My career plans are to develop as a clinician-scientist through a program of mentored training in vascular biology and hands-on experience using a transgenic murine model of vein graft disease. Recent data shows that the process of saphenous vein harvest from humans results in marked upregulation of P-selectin on the endothelial surface. In murine cardiac grafts, restoration of deficient cAMP or NO/cGMP second messenger pathways at the time of preservation improves endothelial homeostatic properties and suppresses neointimal proliferation. Recruitment of mononuclear phagocytes to postischemic vessels is a key trigger for thrombosis, due to 1) de novo expression of tissue factor (TF), driven by ischemic induction of the transcription factor early growth response gene-1 (Egr-1), as well as 2) by inhibition of fibrinolysis via induction of plasminogen activator inhibitor-1 (PAI-1) and suppression of endogenous PA genes. Mice null for the Egr-1 gene exhibit diminished hypoxic induction of TF expression and reduced intravascular thrombosis; mice null for PAI-1 similarly exhibit reduced accrual of fibrin. These data lead me to hypothesize that; 1) Egr-1 driven induction of TF expression within saphenous veins may be an important mechanism driving early vein graft thrombosis; II) intravascular fibrin accrual is likely to be amplified by suppression of the fibrinolytic axis, which may contribute to neoinitmal proliferation; III) alteration of the preservation milieu,, by restoring deficient second messenger cyclic nucleotides, can result in reduction in vein graft neointimal proliferation. These hypotheses will be tested in a murine model of vein graft disease, using specific gene-deleted mice, basic molecular tools to detect/quantify thrombosis, and histomorphometric image analysis to assess neointimal formation. The current proposal is driven by the applicant?s desire to use a model of vein graft disease as a tool to learn how to undertake basic studies to elucidate mechanisms of early and late vein graft failure.