The Role of Complement in Airway Microvascular Disease

描述（由申请人提供）： 6.微血管损失可能是所有实体器官移植慢性排斥反应的一个不受重视的根本原因。作为唯一一种在手术时不经历原发性全身动脉血运重建的实体器官移植，肺移植依赖于微循环的建立，并且特别容易受到微血管损失的影响。微血管病及其伴随的局部缺血可导致组织梗死和气道纤维化。在肺移植物中维持健康的脉管系统对于预防终末气道纤维化（也称为闭塞性细支气管炎综合征）可能至关重要。这种情况是肺移植成功的主要障碍，影响高达60%的存活五年的患者。补体在排斥反应中引起急性微血管损失和缺血的作用以前在移植中没有研究过。小鼠原位气管移植是研究气道血管在排斥反应中作用的理想模型。在排斥性同种异体移植物中发生气道纤维化之前，C3沉积在血管内皮上，就像首次检测到组织缺氧一样。随着血管的最终破坏，流向移植物的微血管血液完全停止了几天。初步结果表明，补体缺乏和补体抑制导致显著改善组织氧合，减少气道重塑和加速血管修复。这些结果共同表明，补体活性是有害的，部分原因是补体介导的血管损伤导致移植物缺血。该项目研究了补体级联反应中的两个关键步骤，C3和膜攻击复合物（MAC），以及这些步骤中的每一个如何具体地促进气道血管损伤和修复。互补调节蛋白，包括CD 55和CD 59，通常调节补体活性。在排斥反应中，这些调节蛋白在血管内皮上的下调可能是补体激活在排斥反应期间损害血管系统的关键。在本项目中要检验的总体假设是，在C3和MAC激活水平控制补体激活将限制气道缺血并促进血管修复。具体目标1将是确定C3活化如何影响移植物缺氧、血管灌注和移植受者的气道重塑，并测试C3转化酶活化对排斥气道的功能性微循环的有害影响通常被CD 55活性抑制的假设。Subaims将研究C3转化酶激活和调节的全面和有针对性的减少如何影响血管流向移植物。具体目标2将确定MAC激活如何影响移植物缺氧、血管灌注和移植排斥中的气道重塑，并测试MAC组装对排斥气道的功能性微循环的有害影响通常由CD 59活性控制的假设。Subaims将研究干扰MAC组装和调节对气道血管流量的影响。最后，具体目标3将确定补体抑制如何在治疗上加速排斥反应后移植物微血管的修复。该目的检验补体抑制通过促进血管内皮细胞的流入促进移植物微血管修复的假设。该目的利用具有Cre重组酶（Tie-2 Cre）的内皮特异性表达的小鼠与报告小鼠Rosa 26 R（loxP Stop loxP yfp）杂交以产生具有永久标记的内皮细胞的移植受体。通过获得有关补体活性和排斥反应调节的知识来预防气道缺血可能会促进肺移植受者的有用和潜在的挽救生命的治疗。

DESCRIPTION (provided by applicant): 6. Project Summary/Abstract Microvascular loss may be an unappreciated root cause of chronic rejection for all solid organ transplants. As the only solid organ transplant that does not undergo primary systemic arterial revascularization at the time of surgery, lung transplants rely on the establishment of a microcirculation and are especially vulnerable to the effects of microvascular loss. Microangiopathy, with its attendant ischemia, can lead to tissue infarction and airway fibrosis. Maintaining healthy vasculature in lung allografts may be critical for preventing terminal airway fibrosis, also known as the bronchiolitis obliterans syndrome. This condition is the major obstacle to lung transplant success and affects up to 60% of patients surviving five years. The role of complement in causing acute microvascular loss and ischemia during rejection has not been studied previously in transplantation. Mouse orthotopic tracheal transplantation is an ideal model for parsing the role of airway vasculature in rejection. Prior to the development of airway fibrosis in rejecting allografts, C3 deposits on the vascular endothelium just as tissue hypoxia is first detected. With the eventual destruction of vessels, microvascular blood flow to the graft stops altogether for several days. Preliminary results suggest that complement deficiency and complement inhibition lead to markedly improved tissue oxygenation, diminished airway remodeling and accelerated vascular repair. These results collectively suggest that complement activity is harmful, in part, because complement-mediated vascular injury results in graft ischemia. This project examines two pivotal steps in the complement cascade, C3 and the membrane attack complex (MAC), and how each of these steps specifically contributes to airway vascular injury and repair. Complementary regulatory proteins, including CD55 and CD59, ordinarily regulate complement activity. The down-regulation of these regulatory proteins on vascular endothelium in rejection may be key to why complement activation damages the vasculature during rejection. The global hypothesis to be tested in this project is that controlling complement activation at the level of C3 and MAC activation will limit airway ischemia and promote vascular repair. Specific Aim 1 will be to determine how C3 activation impacts graft hypoxia, vascular perfusion and airway remodeling in transplant recipients and tests the hypothesis that the deleterious impact of C3 convertase activation on the functional microcirculation of rejecting airways is normally inhibited by CD55 activity. Subaims will investigate how both global and targeted reduction of C3 convertase activation and regulation affects vascular flow to the transplant. Specific Aim 2 will be to determine how MAC activation impacts graft hypoxia, vascular perfusion and airway remodeling in transplant rejection and tests the hypothesis that the deleterious impact of MAC assembly on the functional microcirculation of rejecting airways is ordinarily controlled by CD59 activity. Subaims will study the impact of interfering with MAC assembly and regulation on vascular flow to the airways. Finally, Specific Aim 3 will be to determine how complement inhibition therapeutically hastens the repair of graft microvasculature following rejection. This Aim tests the hypothesis that complement inhibition facilitates the repair of the graft microvasculature by promoting the influx of recipient-derived endothelial cells. This aim utilizes mice with endothelial-specific expression of Cre-recombinase (Tie-2 Cre) intercrossed with reporter mice Rosa26R (loxP Stop loxp yfp) to create graft recipients which have permanently labeled endothelial cells. Preventing airway ischemia through knowledge gained about complement activity and regulation in rejection may promote useful and potentially life-saving therapies for lung transplant recipients.