Mechanisms of Progression in Late Stage Emphysema

描述（由申请人提供）：肺气肿进展性的潜在机制尚不清楚。炎症本身不能完全解释肺气肿的进展，特别是在晚期。我们之前的奖项揭示了新的重要机制，导致了本提案中要测试的两个假设。第一种假设是：与肺气肿最初如何触发无关，肺气肿在晚期的进展主要是由于呼吸过程中机械力引起的肺实质破裂。我们的第二个假设是：当相对于弹性蛋白沉积在肺泡壁的新合成胶原的数量达到临界阈值时，机械力开始促进肺气肿的进展。为了验证这些假设，我们建议研究一个对照组和以下小鼠肺气肿模型：a)弹性酶治疗组，包括炎症和蛋白酶/抗蛋白酶失衡；b)皮肤紧致小鼠，基质组装异常；c)慢性胶原酶过度表达小鼠，无炎症。在肺气肿进展的三个时间点，我们将使用几种新技术来评估活体全肺、分离组织条、肺泡壁和胶原纤维的力学特性以及实质结构的异质性。我们预计这些特性在早期阶段可能不相似，但在肺气肿的晚期将趋于一致。为了测试胶原蛋白组装如何影响肺组织的失效特性，我们将使用一种独特的红色荧光蛋白-胶原蛋白，它可以与双光子二次谐波产生显微镜结合使用，在失效测试中可视化新合成的和现有的旧胶原蛋白。此外，我们将评估I型和III型胶原蛋白、弹性蛋白和几种已知影响胶原蛋白组装的小分子（如蛋白聚糖）的含量。拟议的工作将a)确定肺气肿组织破坏的主要原因必须发生的生物物理条件是呼吸引起的机械力，b)建立这些生物物理条件与宏观结构和功能测量之间的联系，以及c)确定肺气肿变得不可逆转的阈值。这些结果将激发一个更合理的方法来检测、治疗设计和治疗评估肺气肿。

DESCRIPTION (provided by applicant): The underlying mechanisms of the progressive nature of emphysema remain unclear. Inflammation alone cannot fully explain how emphysema progresses, especially in the late phase. Our previous award revealed new important mechanisms leading to the two hypotheses to be tested in this proposal. The first hypothesis is: Independent of how emphysema is initially triggered, its progression in the late phase results primarily from mechanical force-induced breakdown of the lung parenchyma during breathing. Our second hypothesis is: Mechanical forces start to contribute to the progression of emphysema when the amount of newly synthesized collagen deposited in the alveolar wall relative to elastin reaches a critical threshold. To test these hypotheses, we propose to investigate a control group and the following mouse models of emphysema: a) an elastase treated group which involves inflammation followed by protease/antiprotease imbalance, b) tight skin mouse with abnormal matrix assembly, and c) mice with chronic over-expression of collagenase without inflammation. Using several novel techniques, we will evaluate the mechanical properties of the in vivo whole lungs, isolated tissue strips, alveolar walls and collagen fibers as well as the heterogeneity of the parenchymal structure at three time points during the progression of emphysema. We anticipate that these properties may not be similar in the early stages, but will converge during the late phase of emphysema. To test how collagen assembly affects the failure properties of the lung tissue, we will use a unique Red Fluorescent Protein-collagen that can be used in conjunction with two-photon second harmonic generation microscopy to visualize both the newly synthesized and the existing old collagen during failure tests. Additionally, we will assess the contents of type I and III collagen, elastin and several small molecules such as proteoglycans that are known to influence collagen assembly. The proposed work will a) identify the biophysical conditions that must occur for the dominant cause of tissue destruction in emphysema to be breathing-induced mechanical forces, b) establish links between these biophysical conditions and macroscopic measures of structure and function, and c) identify a threshold beyond which emphysema becomes irreversible. These results will motivate a more rational approach to detection, treatment design, and treatment assessment of emphysema.