Molecular regulation of vein graft adapation

描述（由申请人提供）：静脉移植物成功适应动脉环境而不过度增厚的机制尚不完全清楚。Ephrin- eph通路的几个成员最近被描述为发育特定的血管身份的关键决定因素，其中Ephrin- B2配体是动脉的胚胎决定因素，epf - b4受体是静脉的胚胎决定因素。我们最近在人类和大鼠中发现，在静脉移植物适应过程中，epf - b4表达的减少和静脉特性的丧失与内膜增厚有关，而VEGF-A是内膜增厚的上游抑制剂。此外，我们发现在人类和大鼠静脉移植适应过程中，血管保护蛋白Nogo-B的含量都有所增加。然而，目前尚不清楚成人血管规范基因是否存在可塑性，Ephrin-Eph通路是否在静脉移植物适应动脉环境过程中发挥机制作用，以及Nogo-B是否与Eph-B4信号通路相关。我们提出了令人兴奋的新数据：1)在静脉移植适应小鼠模型中，Eph-B4基因表达和免疫反应蛋白的减少与内膜增厚有关；2)通过调控epf - b4信号通路，直接检测epf - b4在小鼠静脉移植物适应中的作用；3) Nogo-B抑制静脉移植物适应过程中的内膜增厚；4)在靶向VEGF-A的siRNA处理的静脉移植物中，Nogo-B蛋白增加，将Nogo-B通路与VEGF-A- eff - b4通路连接起来。我们假设，静脉规范基因的表达减少而动脉规范基因的表达不同时导致内膜过度增厚，最终导致静脉移植失败。我们将以以下具体目的来验证我们的假设：目的1 .确定Eph-B4信号是否在静脉移植物适应过程中介导内膜增厚。目的二世。目的：探讨VEGF-A对内膜增厚的抑制是否通过调节血管特性和Eph-B4表达介导。第三目标。探讨Nogo-B在静脉移植物适应过程中的血管保护作用是否通过调节Eph-B4功能介导。这些研究的创新之处在于，以前没有在小鼠身上进行过静脉移植物身份的分析，并且以前也没有在成人身上证明Eph-B4通路的可塑性。在这些研究完成后，我们期望确定Eph-B4在静脉移植物适应中的作用，并确定通过改变血管特性来限制静脉移植物适应过程中内膜增厚的策略是否将成为一种用于人体临床试验的新方法。公共卫生相关性：大量手术放置的冠状动脉和周围静脉移植物由于内膜过度增厚而继续失败，从而导致患者发病率和死亡率。改善长期心肌血运重建和肢体保留的结果仍然严重依赖于理解在静脉移植物适应动脉环境过程中过度内膜增厚的机制。该建议采用一种新颖的方法，即操纵血管身份来控制内膜增厚。

DESCRIPTION (provided by applicant): The mechanisms of successful long-term vein graft adaptation to the arterial environment without excessive intimal thickening are still not completely understood. Several members of the Ephrin-Eph pathway have recently been described as developmentally specified critical determinants of vessel identity, with Ephrin- B2 ligand an embryonic determinant of arteries and Eph-B4 receptor an embryonic determinant of veins. We have recently shown in both humans and rats that diminished Eph-B4 expression and loss of venous identity is associated with intimal thickening during vein graft adaptation, and that VEGF-A is an upstream inhibitor of intimal thickening. In addition, we showed increased amounts of the vasculoprotective protein Nogo-B during both human and rat vein graft adaptation. However, it is currently not established whether plasticity exists in vessel specification genes in adults, whether the Ephrin-Eph pathway plays a mechanistic role during vein graft adaptation to the arterial environment, or whether Nogo-B is linked to Eph-B4 signaling pathways. We present our exciting new data that: 1) diminished Eph-B4 gene expression and immunoreactive protein is associated with intimal thickening in the mouse model of vein graft adaptation; 2) we can manipulate Eph-B4 signaling in vivo to directly test the role of Eph-B4 in vein graft adaptation in mice; 3) Nogo-B inhibits intimal thickening during vein graft adaptation; and 4) Nogo-B protein is increased in vein grafts treated with siRNA directed against VEGF-A, linking the Nogo-B pathway with the VEGF-A-Eph-B4 pathway. We hypothesize that decreased expression of venous specification genes without concomitant expression of arterial specification genes leads to excessive intimal thickening, and ultimately vein graft failure. We will test our hypothesis with the following specific aims: Aim I. To determine whether Eph-B4 signaling mediates intimal thickening during vein graft adaptation. Aim II. To determine whether VEGF-A inhibition of intimal thickening is mediated by regulation of vessel identity and Eph-B4 expression. Aim III. To determine whether the vasculoprotective effects of Nogo-B during vein graft adaptation are mediated by regulation of Eph-B4 function. The studies are innovative in that analyses of vein graft identity have not been previously performed in mice, and plasticity of the Eph-B4 pathway has not been previously demonstrated in adults. At the completion of these studies, we expect to identify a role for Eph-B4 in vein graft adaptation and to determine whether strategies to limit intimal thickening during vein graft adaptation by altering vessel identity will be a novel approach for a human clinical trial. PUBLIC HEALTH RELEVANCE: Significant numbers of surgically placed coronary and peripheral vein grafts continue to fail due to excessive intimal thickening with resultant patient morbidity and mortality. Improving results of long-term myocardial revascularization and limb salvage remain critically dependent on understanding the mechanisms of excessive intimal thickening during vein graft adaptation to the arterial environment. This proposal takes a novel approach, manipulation of vessel identity, to control intimal thickening.