Autologous human saphenous vein (HSV) continues to be the most widely used conduit for approximately 1,000,000 coronary artery bypass grafting (CABG) and peripheral vascular (PV) revascularization procedures performed each year. Vein grafts fail in over 40% of patients at 12-18 months after revascularization procedures. Vein graft failure leads to myocardia infarction and death in CABG patients, while in lower extremities, PV bypass failure leads to recurrent claudication and limb loss that negatively impacts quality of life. The primary cause of graft failure is intimal hyperplasia which represents a response to injury that leads to intimal thickening and in some instances, graft occlusion. Therefore, there is a general consensus that inhibition of intimal hyperplasia would reduce vein graft failure. The tenet of this proposal is that injury to the endothelial and smooth muscle cells during procurement and graft preparation accelerates the development of intimal hyperplasia. Preserving conduit viability and function can minimize the development of intimal hyperplasia, and in so doing, reduce the incidence of vein graft failure. The preliminary data for this proposal identified injurious vein graft preparation techniques and offered evidence supporting the detrimental contribution of these current graft preparation methodologies on HSV endothelial and smooth muscle function. These injurious techniques include mechanical manipulation (longitudinal stretch and distention), vein storage in heparinized saline (pH 6.2), and the off-label use of surgical skin markers to orient the HSV. Despite the advent of organ preservation for other transplantation procedures, little attention has been given to modify current preparation practices of the HSV as an autologous transplant organ. Hence, vein graft preparation denotes a window of opportunity to improve the quality of the bypass conduit. We propose a new paradigm for vein graft injury, namely the activation of the P2X7 receptor (P2X7R) by mechanical stretching during surgical harvest of the graft, and hypothesize that antagonism to the P2X7R results in the amelioration of stretch injury to the bypass conduit.
The aims of this proposal are to 1) Determine the mechanism(s) by which P2X7R antagonism restores viability and functional responses after stretch injury in porcine saphenous veins and 2) Determine if stretch injury accelerates intimal hyperplasia and whether P2X7R blockade will reduce intimal hyperplasia in a porcine vein graft model. Data generated by this study will advance our understanding of the molecular mechanisms of vein graft failure and provide in vivo data regarding the effect of mechanical injury on the subsequent development of intimal hyperplasia. Consequently, a safe and potent therapeutic modality targeting the P2X7R can be explored as an approach to reduce injury-triggered biological response. These data will also be used to influence surgical harvest and vein graft preparation practices. The research outlined in this proposal will impact the outcomes of the most commonly performed surgical procedure in the United States, namely CABG.
The leading cause of graft failure for coronary artery bypass grafting, the most common operation performed in the United States, is intimal hyperplasia which represents a response to injury. This proposal will identify the specific injuries that occur to the vein graft during harvest and preparation prior to implantation as an autologous transplanted organ and identify modalities to reduce injury to the conduit. By understanding how these injuries can be minimized, morbidity, mortality and costs associated with vein graft failure can be reduced.
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