Mechanisms of Progression in Late Stage Emphysema

描述（由申请人提供）：肺气肿进行性的潜在机制仍不清楚。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，导致本提案中要测试的两个假设。第一个假设是：与肺气肿最初如何触发无关，其在晚期阶段的进展主要是由于呼吸期间机械力诱导的肺实质破裂。我们的第二个假设是：当新合成的胶原蛋白相对于弹性蛋白沉积在肺泡壁中的量达到临界阈值时，机械力开始促成肺气肿的进展。为了检验这些假设，我们建议研究对照组和以下肺气肿小鼠模型：a）弹性蛋白酶治疗组，其涉及炎症，随后是蛋白酶/抗蛋白酶失衡，B）具有异常基质组装的紧皮肤小鼠，和c）具有胶原酶慢性过度表达而无炎症的小鼠。使用几种新的技术，我们将评估在体内的整个肺，孤立的组织条，肺泡壁和胶原纤维的机械性能，以及在肺气肿的进展过程中的三个时间点的实质结构的异质性。我们预计这些性质在早期可能不相似，但在肺气肿的晚期会收敛。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，该蛋白可与双光子二次谐波发生显微镜结合使用，以在失效测试期间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，弹性蛋白和几个小分子，如蛋白聚糖，已知影响胶原蛋白组装的内容。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和结构和功能的宏观测量之间的联系，和c）确定一个阈值，超过该阈值肺气肿变得不可逆。这些结果将促使一个更合理的方法来检测，治疗设计，肺气肿的治疗评估。

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.