Intimal hyperplasia (IH) in arterialized vein bypass grafts is a significant cause of vein graft (VG) stenosis and delayed graft failure. Injury at the time of implantation or as a consequence of transplantation into the high- pressure arterial system contributes to these delayed events. In a canine model, we have identified alterations in the transcriptome following implantation/arterialization injury, and have separated genetic events in the endothelium from those in medial smooth muscle cells (SMC). Using Systems Biology, we have identified the upregulated genes that were most essential to the injury response. Through back propagation, an integrated network was built starting with genes differentially expressed at the latest time-points i.e. 30 days (D), followed by adding upstream interactive genes from each prior time-point. This identified collagen 1A1 (Col1A1) at 30D, as a central cornerstone of back propagation and dominant contributor to IH lesions, as well as Interleukin (IL)- 18, and other inflammatory genes that were differentially upregulated across different time-points, starting at 2 hours (H) post-surgery. These results establish causality relationships clarifying the pathogenesis of VG implantation injury, and identifying novel targets for its prevention. It is our hypothesis that inhibiting the early inflammatory genes such as IL-18 will prevent the downstream lesion development and will diminish processes associated with VG implantation injury and thereby IH. IL-18 is implicated in many disease process including cardiovascular diseases. Toward this goal, we would like to inhibit the action of IL-18 by treating the vein graft under operating room constrains. In the proposed study we will 1) Characterize and identify IL-18 signaling inhibitors using computational models of IL-18 and in silico techniques and 2) Using nanocarriers deliver IL-18 signaling inhibitors and test their efficacy in reducing markers of IH in in vitro cell culture models and ex vivo human saphenous vein models. In addition, standardized immunohistochemistry, cellular, biochemical and molecular techniques will be used. Our investigative team has demonstrated the multidisciplinary collaboration essential to successful conduct of this proposal. We strongly believe this work will greatly strengthen the application of small molecule inhibitors to VG in patients, forecasting its expansion to other clinical problems in vascular surgery and will undoubtedly broaden our understanding of vascular wall biology.
Scar tissue formation due to surgical injury is a major cause for failure of heart bypass grafts and bypass grafts for peripheral vascular disease. The investigators propose to prevent formation of this scar tissue from forming by inhibiting the action of one of the proteins that causes it, by developing novel compounds that can be applied to the bypass graft in the operating room.
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