Epithelial Stem Cells in Lung Transplantation

描述(由申请人提供)：研究人员的长期目标是成为一名多产和独立的临床科学家，拥有一个资金雄厚的专注于肺移植研究的实验室。调查员的直接目标是获得成为一名独立调查员所需的技能。这项建议侧重于了解闭塞性毛细支气管炎(OB)的发病机制，该疾病在肺移植后5年内发生在50%的受者身上。我们已经开发了一种原位左肺移植模型，它再现了人类肺移植组织病理学的方方面面，包括OB的发展。使用这一新的模型，我们建议研究肺移植后呼吸道上皮干细胞是否异常反应，并确定这种异常反应是否有助于OB的发展。具体地说，这项提案将侧重于失神经对控制呼吸道干细胞增殖的异常降钙素基因相关肽(CGRP)神经肽反应的贡献。这位研究人员的导师约翰·恩格尔哈特博士在研究肺内的干细胞/祖细胞方面有着悠久的历史，并在雪貂身上研究了十多年的呼吸道生物学。肺移植是终末期肺部疾病的主要治疗选择。OB被认为是移植肺中的一种慢性排斥反应，它影响了几乎每两个人中的一个，从而阻止了长期存活。 受助者提前五年。一旦OB在同种异体移植物中发生，它就会逐渐致命，并且没有有效的治疗方法。引起OB的机制尚不清楚，有人认为上皮干细胞耗尽可能是一个促成因素。然而，目前还没有正在进行的研究来检验这一假设。我们最近开发了一种在雪貂身上进行原位肺移植的模型，该模型发展为经典的OB。我们还表明，CGRP是远端呼吸道干/祖细胞壁龛的已知标记物，它促进慢周期呼吸道干细胞的增殖和分化为瞬时放大细胞，但增殖能力有限。在这个方案中，我们将解决以下假设：1)在移植肺中，上皮损伤导致慢周期干细胞在供体肺/同种异体移植的不同位置异常募集和增殖。2)在移植肺中，由于缺乏神经支配，CGRP对损伤的反应是失调的。3)在移植肺中，CGRP水平的失调导致远端呼吸道慢循环干细胞的耗竭，最终导致异常的损伤反应。我们期望了解移植肺中的上皮干细胞损伤反应将有助于阐明OB的发病机制 从而为预防或延缓同种异体移植物中OB的发展提供了机会。此外，我们的建议将解决几个基本的生物学问题，即神经如何通过神经肽信号控制肺内的干细胞损伤反应。这些信息对肺部生物学领域也可能是普遍有用的。

DESCRIPTION (provided by applicant): The long-term goal of the investigator is to become a productive and independent clinician scientist with a well- funded laboratory focused on lung transplantation research. The immediate goal of the investigator is to acquire the skill set necessary to become an independent investigator. This proposal focuses on understanding the pathogenesis of obliterative bronchiolitis (OB) that develops in 50% of the recipients following lung transplantation within 5 years. We have developed a model of orthotopic left lung transplant that reproduces all aspect of human lung transplant histopathology, including development of OB. Using this novel model we propose to investigate whether airway epithelial stem cells respond abnormally following lung transplantation and to determine if this abnormal response contributes to the development of OB. Specifically, this proposal will focus on the contribution of denervation to aberrant calcitonin gene related peptide (CGRP) neuropeptide responses that control stem cell proliferation in the airways. The investigator's mentor, Dr. John Engelhardt, has a long-standing history in studying stem/progenitor cells in the lung and has studied airway biology in the ferret for more than a decade. Lung transplantation is a major treatment option for end-stage lung diseases. OB, which is considered to be a form of chronic rejection in the transplanted lung, prevents long-term survival as it affects almost one out of two recipients by five years. Once OB sets in the allograft, it is progressively fatal and there is no effective treatment available. The mechanisms that cause OB are unclear and it has been proposed that epithelial stem cell depletion may be a contributing factor. However, there is currently no research being done to test this hypothesis. We recently developed an orthotopic lung transplant model in the ferret that develops classic OB. We have also shown that CGRP, a known marker for the stem/progenitor celI niches in the distal airways, promotes proliferation and differentiation of slow-cycling airway stem cells into transient-amplifying cells with limited proliferative capacity. In this proposal we will address the following hypotheses: 1) In a transplanted lung, epithelial injury results in the aberrant recruitment and proliferation of slow- cycling stem cells at different sites within the donor lung/allograft. 2) In a transplanted lung, he CGRP response to injury is dysregulated due to the lack of innervation. 3) In a transplanted lung, dysregulation of CGRP levels leads to exhaustion of slow-cycling stem cells in the distal airways and, ultimately, an aberrant injury response. We expect that understanding the epithelial stem cells injury responses in the transplanted lung will clarify the pathogenesis of OB and thereby provide an opportunity to prevent or delay the development of OB in the allografts. Furthermore, our proposal will address several basic biologic questions about how innervations controls stem cell injury responses in the lung through neuropeptide signals. Such information may also be generally useful to the field of lung biology.