II型肺泡上皮细胞（AT2）在重症流感肺泡损伤修复过程中的参与作用及调控机制

The intermittent outbreak of pandemic influenza and emerge of novel avian influenza A virus in human has caused great threat to people’s health worldwide. The main target organ was considered to be the lung during influenza virus infection. Our preliminary data revealed that the alveolar function following influenza pneumonia was still not fully recovered even three months after discharge. The expression of TLR4 in the lungs of influenza mice was significantly increased. Based on the recent researches and our preliminary data, we hypothesize that type II alveolar epithelial cells (AT2) are involved in the process of alveolar regeneration in adult influenza mice. AT2 cells are able to quickly undergo self-renewal and to subsequently differentiate into AT1 cells. The cellular mechanisms involved in the repair of alveolar epithelial cells after different types of influenza virus infection are not exactly the same. This process is mainly mediated via TLR4-TRIF-p38 / JNK-YAP pathway. In this study, we will use adult Sftpc-CreERT2, Rosa26-mTmG mice for lineage tracing of AT2 cells and to demonstrate their role as progenitor cells in the repair of the alveolar epithelium. Further, with YAP-/-、TLR4-/- mice, we planned to characterize the genetic program and pathway that regulate the AT2 cell proliferation by utilizing RNA-seq, immunostaining , and immunoblot. This finding will provide clue for the exploration of novel drugs to ameliorate the lung injury during severe influenza infection.

季节性流感的间断暴发流行以及新型人感染禽流感的不断增加，对人类健康造成严重威胁。人感染流感病毒的主要靶器官为肺，课题组前期研究证实流感肺炎患者出院三个月后损伤肺泡依然未完全恢复，流感小鼠肺组织中TLR4表达明显上调。基于最新研究及本课题组对肺泡再生修复的研究结果。我们提出核心假说：II型肺泡上皮细胞（AT2）参与成年流感小鼠肺泡再生修复过程，不同类别流感病毒感染后，参与肺泡上皮细胞修复的细胞机制不完全一致；AT2参与成年流感小鼠肺泡再生修复具体活化机制为，流感病毒感染后AT2表面TLR4上调，进而通过TLR4-TRIF-p38/JNK-YAP途径调控肺泡的再生修复。本课题拟利用Sftpc-CreERT2, Rosa26-mTmG等系列小鼠模型研究流感肺损伤修复过程中参与上皮修复的主要细胞类型；明确YAP对肺泡再生的调控及其上游的主要信号分子，为未来重症流感肺损伤的救治提供新思路。

呼吸道病毒感染对人类健康造成重大威胁，目前造成全球大流行的传染性疾病多数由呼吸道病毒感染引起。呼吸道病毒感染通过直接病毒攻击或者免疫损伤等引起急性肺泡上皮大量死亡，造成通气功能障碍，免疫屏障受损，继发感染风险增加。深入研究病毒感染后损伤修复调控机制，探索可能干预靶点，加速病毒感染过程中损伤上皮的修复，为重症呼吸道病毒感染肺损伤的救治提供新思路。该研究围绕重症流感病毒肺损伤后修复调控机制，取得如下成果：成功构建重症流感病毒感染肺损伤修复模型。明确在肺损伤修复期，上皮前体细胞会迁移到损伤部位形成Krt5+细胞群参与屏障修复，但不能再分化为有气体交换功能的AT1细胞。揭示Krt5+细胞并非Sox2+细胞分化而来，Sox2+细胞不能参与肺泡上皮细胞的修复。证实AT2是参与重症流感病毒感染肺损伤后肺泡修复的主要干细胞。病毒感染肺损伤后的肺泡上皮细胞修复过程受到炎症微环境的精细调控。上述研究结果为进一步明确病毒感染肺损伤肺泡上皮细胞修复过程中AT2细胞的调控机制、开发干预靶点提供思路。在本项目资助期间以第一作者身份（含共同）发表SCI论文4篇,以第9完成人身份荣获华夏医学科技奖一等奖一项。