Table_1_Lung inflammation and interstitial fibrosis by targeted alveolar epithelial type I cell death.pdf

IntroductionThe pathogenesis of chronic lung diseases is multifaceted with a major role of recurrent micro-injuries of the epithelium. While several reports clearly indicated a prominent role for surfactant-producing alveolar epithelial type 2 (AT2) cells, the contribution of gas exchange-permissive alveolar epithelial type 1 (AT1) cells has not been addressed yet. Here, we investigated whether repeated injury of AT1 cells leads to inflammation and interstitial fibrosis.
MethodsWe chose an inducible model of AT1 cell depletion following local diphtheria toxin (DT) administration using an iDTR flox/flox (idTRfl/fl) X Aquaporin 5CRE (Aqp5CRE) transgenic mouse strain.
ResultsWe investigated repeated doses and intervals of DT to induce cell death of AT1 cells causing inflammation and interstitial fibrosis. We found that repeated DT administrations at 1ng in iDTRfl/fl X Aqp5CRE mice cause AT1 cell death leading to inflammation, increased tissue repair markers and interstitial pulmonary fibrosis.
DiscussionTogether, we demonstrate that depletion of AT1 cells using repeated injury represents a novel approach to investigate chronic lung inflammatory diseases and to identify new therapeutic targets.

引言
慢性肺部疾病的发病机制呈多因素性，上皮细胞反复微损伤在其中发挥核心作用。尽管多项研究已明确阐明分泌表面活性物质的肺泡Ⅱ型上皮（alveolar epithelial type 2, AT2）细胞的关键调控作用，但介导气体交换的肺泡Ⅰ型上皮（alveolar epithelial type 1, AT1）细胞在该病发生中的贡献尚未得到系统研究。本研究旨在探讨AT1细胞反复损伤是否会诱发炎症反应与肺间质纤维化。

方法
我们构建了可诱导的AT1细胞特异性耗竭模型：采用iDTR flox/flox（idTRfl/fl）× 水通道蛋白5-CRE（Aquaporin 5CRE, Aqp5CRE）转基因杂交小鼠品系，通过局部给予白喉毒素（diphtheria toxin, DT）诱导AT1细胞特异性死亡。

结果
我们探究了DT的重复给药剂量与给药间隔方案，以诱导AT1细胞死亡并构建炎症与肺间质纤维化模型。实验结果显示，在iDTRfl/fl × Aqp5CRE小鼠中，以1ng剂量反复给予DT可有效诱导AT1细胞死亡，进而触发炎症反应、上调组织修复相关标志物的表达，并最终导致肺间质纤维化。

讨论
综上，本研究证实，通过反复损伤实现AT1细胞耗竭是一种全新的慢性肺部炎症性疾病研究模型，可为该类疾病的新型治疗靶点筛选提供有效手段。