NOVEL IN VIVO MODEL OF CHRONIC ALLOGRAFT REJECTION

描述（由申请人提供）：目前最先进的免疫抑制策略在抑制急性排斥反应方面最为成功，并显著提高了移植体的短期存活率。然而，这些相同的策略未能阻断慢性同种异体移植排斥反应的发展，更重要的是，未能阻断慢性同种异体移植排斥反应的进展。由于慢性同种异体排斥反应是目前实体器官移植后移植物衰竭的主要原因，因此非常需要开发新的范例和模型，以便开发新的治疗方法来针对这一过程。普遍的观点是，对供体抗原的免疫反应的性质或程度决定了排斥过程。此外，人们认为免疫反应的表型（和局部炎症细胞因子环境）决定了同种异体移植物的激活状态。然而，从最近的研究中可以明显看出，移植物本身，而不是免疫反应，可以主导形成排斥过程（即使面对免疫耐受）。一致地，一些研究已经确定了移植物内皮细胞（EC）的激活状态是急性和慢性排斥反应的决定因素。此外，最近的研究表明，mTOR抑制剂靶向移植物EC，表明这些药物减轻慢性排斥反应（和慢性血管疾病）进展的作用可能与它们靶向EC激活反应的能力有关。然而，迄今为止，移植物EC在排斥反应发展中的选择性作用一直难以研究。在EC中，mTOR信号增强了Akt激酶的活性，进而调节了许多EC激活反应。在这个探索性的研究方案中，我们计划利用独特的VE-Cadherin:tTA+/TET-Akt+双转基因小鼠，在内皮中有可能选择性调节Akt。我们将使用这只小鼠的心脏作为心脏移植的供体，这样我们就可以：目的1，建立一个移植模型来研究akt诱导和EC激活反应在慢性排斥过程中的选择作用；目的2，评估移植物EC在慢性排斥发生中的主导地位；目的3，研究akt诱导的供体EC激活在免疫调节和耐受中的作用。这种独特的慢性排斥模型的发展将为我们提供一个令人兴奋的机会，第一次直接评估移植物EC在慢性同种异体移植排斥发展和/或维持同种异体免疫耐受中的作用和功能作用。

DESCRIPTION (provided by applicant): Current state-of-the-art immunosuppressive strategies have been most successful at inhibiting acute rejection and have significantly improved short-term graft survival rates. However, these same strategies have failed to interrupt the development of, and more importantly, the progression of chronic allograft rejection. Since chronic allograft rejection is currently the leading cause of graft failure following solid organ transplantation, it has become most apparent that there is a great need to develop new paradigms and models in order that novel therapeutics can be developed to target this process. The prevailing view is that the nature or magnitude of the immune response to donor antigen determines the rejection process. In addition, it is thought that the phenotype of the immune response (and the local inflammatory cytokine milieu) determines the activation state of the allograft. However, it is evident from recent studies that the graft itself, and not the immune response, can be dominant to shape the rejection process (even in the face of immune tolerance). Consistently, several studies have identified the activation state of the graft endothelial cell (EC) as a determinant of acute and chronic rejection. Furthermore, recent studies indicating that mTOR inhibitors target graft EC indicate that the effect of these agents to attenuate the progression of chronic rejection (and chronic vascular disease(s)), may be associated with their ability to target the EC activation response. Nevertheless, to date, the select role of the graft EC in the development of rejection has been difficult to study. In EC, mTOR signals enhance the activity of the kinase Akt, which in turn regulate many EC activation responses. In this exploratory research proposal, we plan to utilize the unique VE-Cadherin:tTA+/TET-Akt+ double transgenic mouse, in which it is possible to regulate Akt selectively within the endothelium. We will use hearts from this mouse as donors of cardiac transplants such that we can: Aim 1, develop a transplantation model to study the select role of Akt-inducible and EC activation responses in the chronic rejection process; Aim 2, evaluate the dominance of the graft EC in the development of chronic rejection, and Aim 3, study the effect of Akt-induced activation of donor EC in immune regulation and tolerance. The development of this unique model of chronic rejection will provide us with an exciting opportunity for the first time to directly assess the role and functional effect of the graft EC in the development of chronic allograft rejection and/or in the maintenance of alloimmune tolerance. PUBLIC HEALTH RELEVANCE: Organ transplantation is a life saving therapy for individuals with end stage organ failure. However, despite the development of novel immunosuppressive strategies, all transplants eventually fail due to a reaction called chronic allograft rejection. While currently dogma dictates that the immune response is the major determinant of acute rejection, additional events within the graft also dictate the development and progression of chronic rejection. In this research proposal we will develop a novel and unique transgenic mouse model in which we will establish whether the graft itself, and specifically the vasculature within the graft is a major functional determinant of this process. Our goal is to develop new paradigms to understand and treat chronic rejection.