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尚不清楚。仅靠炎症不能完全解释肺气肿是如何发展的，特别是在晚期。我们之前的奖项揭示了导致这两个假设在本提案中得到检验的新的重要机制。第一个假设是：与肺气肿最初是如何触发的无关，肺气肿在晚期的进展主要是由于机械力在呼吸过程中导致肺实质的破坏。我们的第二个假设是：当肺泡壁中新合成的胶原蛋白与弹性蛋白的比例达到临界值时，机械力开始促进肺气肿的进展。为了验证这些假设，我们建议研究对照组和下列肺气肿小鼠模型：a)弹性蛋白酶治疗组，涉及炎症，随后是蛋白酶/抗蛋白酶失衡；b)皮肤紧绷，基质组装异常；c)胶原酶慢性过度表达，无炎症。利用几种新技术，我们将评估活体全肺、分离的组织条、肺泡壁和胶原纤维的力学性质，以及肺气肿进展过程中三个时间点的实质结构的异质性。我们预计，这些特性在早期可能不会相似，但在肺气肿的晚期将会聚在一起。为了测试胶原蛋白组装如何影响肺组织的失败特性，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显微镜结合使用，在失败测试中显示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、弹性蛋白和几个已知影响胶原组装的小分子如蛋白多糖的含量。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诱导的机械力，b)建立这些生物物理条件与结构和功能的宏观测量之间的联系，c)确定超过该阈值肺气肿不可逆转。这些结果将促使对肺气肿的检测、治疗设计和治疗评估采取更合理的方法。

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.