TGF-beta inhibition to promote lung growth in mechanically ventilated newborn mice: a novel strategy to prevent ventilator-induced lung injury

早产儿长时间机械通气富氧气体（MV-O2）导致肺泡和肺微血管形成失败，导致肺生长停滞。这种形式的新生儿肺损伤是一种最初被描述为支气管肺发育不良的疾病的变体，现在更恰当地称为新生儿慢性肺病（CLD），是早产儿长期住院和复发性呼吸系统疾病的主要原因。此外，一个新出现的问题是，成年人患肺气肿的风险可能会增加。最近对早产后用MV-O2治疗的婴儿发展CLD的研究，以及CLD的动物模型，提供了令人信服的证据，即两种重要生长因子-TGF-β和VEGF -的失调信号传导可以破坏肺上皮细胞和内皮细胞的存活，从而破坏暴露于长时间MV-O2的发育中的肺中的肺泡分隔和血管生成。将TGF-β和VEGF信号传导失调与CLD中肺生长失败联系起来的分子机制仍然不清楚。 这项研究计划的总体目标是测试以下假设：发育中的肺的MV-O2激活TGF-β，从而下调VEGF信号传导，导致细胞凋亡增加和肺生长停滞。我们将使用一种独特的动物模型来检验这一假设，该模型以新生小鼠长达48小时的MV-O2（MV和40% O2）为特征。该研究计划有3个具体目标：首先（目标1），我将确定抑制TGF-β信号传导是否能保护肺泡和微血管的正常生长，以及恢复VEGF信号传导和减少暴露于MV-O2的新生小鼠肺中的细胞凋亡。5日龄小鼠将用TGF-β中和抗体（TGF-β-Nab）或血管紧张素-2受体拮抗剂（Losartan）治疗，其已显示出抑制TGF-β信号传导，之后它们将接受MV-O2 24小时或48小时。呼吸40%O2的未通气幼崽将作为对照，治疗小鼠将与给予安慰剂（TGF-β-Nab或氯沙坦载体）的小鼠进行比较。接下来（目标2），我将分析抑制TGF-β信号传导对肺基质蛋白代谢的影响，特别是弹性蛋白。最后（目的3），我将确定TGF-β抑制对新生小鼠肺功能的影响，MV-O2。通过在这种独特的MV-O2模型中抑制TGF-β信号传导，我追求的总体目标是恢复VEGF信号传导，从而保护肺泡和血管的形成。这个临床转化项目的长期益处包括评估CLD的有前途的创新疗法，以及改善出生时肺部不成熟的儿童的生活质量。

Prolonged mechanical ventilation with O2-rich gas (MV-O2) of premature infants leads to failed formation of alveoli and pulmonary micro-vessels, resulting in lung growth arrest. This form of neonatal lung injury is a variant of a condition initially described as bronchopulmonary dysplasia, now more aptly called neonatal chronic lung disease (CLD) and is the leading cause of long-term hospitalization and recurrent respiratory disorders among prematurely born infants. Moreover, there is an emerging concern that the risk of pulmonary emphysema could be increased in adults. Recent studies of infants evolving CLD treated with MV-O2 after premature birth, and animal models of CLD, provide compelling evidence that dysregulated signaling of two important growth factors - TGF-beta and VEGF - can undermine survival of lung epithelial and endothelial cells and thereby disrupt alveolar septation and angiogenesis in the developing lung exposed to lengthy MV-O2.However, the molecular mechanisms that link dysregulated TGF-beta and VEGF signaling to failed lung growth in CLD still remain unclear. The overall goal of this research proposal is to test the hypothesis that MV-O2 of the developing lung activates TGF-beta, which in turn down-regulates VEGF signaling, resulting in increased apoptosis and in lung growth arrest. We will test this hypothesis using a unique animal model featuring MV-O2 (MV with 40% O2) of newborn mice for up to 48 hours. The research plan has 3 specific aims: First (Aim 1), I will determine whether inhibiting TGF-beta signaling preserves normal growth of alveoli and micro-vessels as well as restores VEGF signaling and decrease apoptosis in lungs of neonatal mice exposed to MV-O2. 5d-old mice will be treated with either a TGF-beta neutralizing antibody (TGF-beta-Nab) or an angiotensin-2 receptor antagonist (Losartan), which has been shown to inhibit TGF-beta signaling, after which they will receive MV-O2 for 24h or 48h. Unventilated pups breathing 40% O2 will serve as controls, and treated mice will be compared to those given placebo (TGF-beta-Nab or Losartan vehicle). Next (Aim 2), I will analyze the effects of inhibiting TGF-beta signaling on lung matrix protein metabolism, specifically elastin. Finally (Aim 3), I will determine the effects of TGF-beta inhibition on lung function in newborn mice subjected to MV-O2. By inhibiting TGF-beta signaling in this unique model of MV-O2, I pursue the overall goal to restore VEGF signaling and thereby to preserve formation of alveoli and vessels. The long-term benefits of this clinically translational project include the evaluation of a promising innovative therapy for CLD and improvement of quality of life for children who were born with immature lungs.