Mechanical Ventilation of Newborn Mice:Impact on Alveolarization and Lung Elastin

描述(申请人提供)：富含氧气的机械通气(MV)为早产儿呼吸衰竭提供了挽救生命的治疗方法，但通常会导致慢性肺部疾病(CLD)，其特征是肺泡化受损和肺弹性蛋白过多、紊乱。这项研究的目的是提高对导致这些异常的机制的理解，并制定有效的治疗策略。在最近对新生小鼠的研究中，我们发现肺间隔和基质组织主要发生在足月出生后，我们发现40%O2的MV作用24小时会导致肺泡形成和弹性蛋白组装的失调，产生与CLD相似的肺结构缺陷。这一建议适用于突变的新生小鼠，一种新的实验方法，以帮助确定发育中的肺的长期周期性伸展，无论是否有适度的高氧，都可以损害肺泡化和弹性蛋白组装的机制，并测试抑制这些结构缺陷的新策略。具体目标1将确定(A)在40%O2的MV后24小时，过度表达特定弹性酶抑制剂elafin的新生突变小鼠是否显示出比非转基因小鼠更多的肺泡和肺毛细血管形成，以及更少的无序弹性蛋白沉积；以及(B)出生后早期直接给予Elafin的治疗是否可以保护正常的肺泡和肺毛细血管形成，并防止或减少新生小鼠在延长MV期间过度的肺弹性蛋白形成。如果Elafin治疗保留了MV中的肺结构，我们将测试其在特定目标2和3中描述的突变小鼠的MV中的益处。特定目标2将确定患有弹性蛋白单倍体功能不全(ELN)的新生小鼠是否比非突变新生小鼠更容易在MV后用空气或40%O2进行MV 24小时后出现肺发育异常的肺泡形成和肺弹性蛋白组装缺陷。具体目标3将确定缺乏纤毛蛋白-5(Fbln5，Fbln5-/-)的新生小鼠，与非突变新生儿相比，在空气或40%O2的长时间MV后，是否表现出夸大的肺表型，表现为肺泡和弹性纤维形成缺陷。将使用分子、生化和组织学方法阐明MV如何在肺生长过程中扰乱肺泡间隔和弹性蛋白组装，并提供关于如何在因呼吸衰竭而需要延长MV的婴儿中预防这些不利影响的见解。项目简介：这项研究建议使用正常和转基因新生小鼠，旨在提高我们对机械通气如何应用于呼吸衰竭的早产儿，经常抑制肺生长并导致肺内弹性纤维的无序组装，导致一种称为支气管肺发育不良(BPD)的慢性新生儿肺部疾病的理解。该项目的一个重要目标是测试在机械通风过程中直接将一种名为elafin的药物输送到肺部的潜在好处，这种药物可以防止弹性纤维的分解，我们希望这种药物将保持肺生长，并为易患BPD的新生儿提供有效的治疗。由于BPD类似于肺气肿，这项研究也可能有助于更好地理解和治疗成年人的慢性阻塞性肺疾病(COPD)。

DESCRIPTION (provided by applicant): Mechanical ventilation (MV) with O2-rich gas offers life-saving treatment for premature infants with respiratory failure, but often leads to chronic lung disease (CLD), characterized by impaired alveolarization and excess, disordered lung elastin. The goal of this research is to improve understanding of mechanisms that cause these abnormalities, and to formulate effective treatment strategies. In recent studies of newborn mice, in which lung septation and matrix organization occur mainly after term birth, we found that MV with 40% O2 for 24h led to dysregulated alveolar formation and elastin assembly, yielding lung structural defects similar to those seen in CLD. This proposal applies to mutant neonatal mice a novel experimental approach to help define mechanisms by which prolonged cyclic stretch of the developing lung, with or without modest hyperoxia, can impair alveolarization and elastin assembly, and to test a novel strategy for inhibiting these structural defects. Specific Aim 1 will determine (a) if neonatal mutant mice that over-express the specific elastase inhibitor elafin show greater alveolar and lung capillary formation and less deposition of disordered elastin than non-transgenic pups show after 24h of MV with 40% O2; and (b) if early postnatal treatment with elafin given directly into the lungs will preserve normal alveolar and lung capillary formation, and prevent or reduce excess lung elastin during prolonged MV of newborn mice. If elafin treatment preserves lung structure in MV, we will test its benefit during MV of mutant mice described in Specific Aims 2 and 3. Specific Aim 2 will determine if neonatal mice with elastin haploinsufficiency (Eln), which show abnormal lung growth after pneumonectomy or smoke inhalation, are more susceptible than non-mutant newborns to defective alveolar formation and lung elastin assembly after MV with either air or 40% O2 for 24h. Specific Aim 3 will determine if neonatal mice deficient in fibulin-5 (Fbln5, Fbln5-/-), a matrix protein that plays a critical role in elastin assembly, exhibit an exaggerated lung phenotype, compared to non-mutant newborns, in terms of defective alveolar and elastic fiber formation after lengthy MV with either air or 40% O2. Molecular, biochemical and histological methods will be used to clarify how MV can disrupt alveolar septation and elastin assembly during lung growth, and also provide insight on how these adverse effects might be prevented in infants who require prolonged MV for respiratory failure. PROJECT NARRATIVE: This research proposal, which uses normal and genetically modified newborn mice, is designed to improve our understanding of how mechanical ventilation, as applied to premature infants with respiratory failure, often inhibits lung growth and causes disorganized assembly of elastic fibers in the lung, leading to a chronic form of neonatal lung disease called bronchopulmonary dysplasia (BPD). An important aim of the project is to test the potential benefit of delivering, directly into the lungs during mechanical ventilation, a drug called elafin that prevents the breakdown of elastic fibers, which we hope will preserve lung growth and provide effective treatment for newborn infants who are susceptible to BPD. Because BPD is similar to emphysema, this research also may lead to better understanding and treatment of chronic obstructive pulmonary disease (COPD) in adults.