骨髓源内皮祖细胞介导感染性肺损伤后内皮屏障功能重建的作用及分子机制

Current research into inflammatory acute lung injury (ALI) focuses primarily on inflammatory mechanisms. Anti-inflammation is considered the major therapeutic option. However, research along this direction has failed to lead to the development of therapies for inflammatory ALI. Recently there has been a great interest in the role of endothelial and vascular repair in ALI. We have demonstrated a novel concept that endothelial cells control the development and progression of ALI. This grant application takes a new strategy and proposes that enhancing endothelial barrier repair and thereby organ repair mechanisms would be better therapeutic strategy for inflammatory ALI. Towards achieving this goal, this grant proposal will explore the role of bone marrow derived endothelial progenitor cells (BMDEPCs) in endothelial barrier repair and restoration, and investigate the mechanisms regulating BMDEPC-mediated endothelial barrier repair. We hypothesize that BMDEPCs recruitment and proliferation are necessary and indispensible mechanisms of endothelial barrier repair and restoration following inflammatory ALI, and that inflammatory ALI stimulates BMDEPC-mediated endothelial repair barrier mechanism by activating the NF-kB pathway. We will create several novel chimeric mouse models. Using LPS-induced ALI model and those chimeric mouse models, we will track BMDEPCs recruitment and proliferation in the lungs following ALI. We will determine the causal roles of BMDEPCs recruitment and proliferation in endothelial barrier repair and restoration following inflammatory ALI. Using a combined in vitro and in vivo studies as well as in vivo "loss-of-function" studies, we will examine the effects of blocking NF-kB pathway on BMDEPCs mobilization, recruitment and proliferation, on BMDEPC's angiogenic activity and on endothelial barrier recovery following LPS-induced ALI. These studies will define the mechanistic role of the NF-kB signal pathway in BMDEPC-mediated endothelial barrier repair and restoration. Completion of the proposed studies will reveal novel cellular and molecular mechanism regulating endothelial barrier repair and restoration. Results from the proposed studies will add new knowledge an open new direction of studies of inflammatory lung injury.

目前感染性急性肺损伤（ALI）的研究大多集中在炎症机制方面，但以抗炎为主的治疗方针并未能显著改善ALI病人的预后。我们先前的研究结果显示，微血管内皮细胞损伤与激活是感染性脏器损伤发生发展及预后的主要瓶颈控制点之一，提示通过增强内皮屏障功能修复进而促进肺功能恢复可能是开发ALI治疗方法的新策略。本课题利用基因细胞标记、细胞追踪、组织成像分析技术，内源性骨髓源内皮祖细胞（BMDEPCs）耗竭及血管内皮屏障功能测量等手段，证明BMDEPCs募集与增殖是感染性ALI后血管内皮屏障功能重建中不可替代的细胞机制；通过观察NF-κB信号通路失活对BMDEPCs介导的内皮屏障功能修复过程的各环节的影响，阐明NF-κB信号通路在BMDEPCSs介导的内皮屏障功能修复与重建中的调节作用。本课题的完成将阐明调节肺血管内皮屏障功能修复的新机制，为"增强BMDEPCs介导的内皮屏障功能修复"的治疗策略提供实验依据。

目前感染性急性肺损伤（ALI）的研究大多集中在炎症及组织损伤机制方面，但以抗炎为主的治疗方针并未能为改善ALI病人的预后带来实质性进展。我们的新研究结果显示，微血管内皮细胞损伤与激活是感染性脏器损伤发生，发展及预后的主要瓶颈控制点之一, 提示通过增强内皮屏障功能修复进而促进肺功能恢复可能是开发ALI治疗方法的新策略。本课题利用基因细胞标记、细胞追踪、组织成像分析技术, BMDEPC增殖功能失活 （loss-of-cell-function）及血管内皮屏障功能测量等研究手段，研究BMDEPCs募集/增殖在感染性ALI后血管内皮屏障功能修复中的作用及阐明 NF-kB信号通路在BMDEPCs介导的血管 内皮功能修复中的调节作用。我们发现，损伤后肺微血管内皮屏障功能修复与肺内BMDEPCs募集与增殖增多有关。从组织学和细胞学证据证实了募集肺内的BMDEPCs融入损伤的肺微血管内皮单层中，转化为新生成熟的肺内皮细胞，并参与受损内皮细胞层的修复。在肺修复的活跃期，选择性抑制BMDEPCs增殖可阻碍受损内皮细胞层的修复，证明了BMDEPCs增殖与肺血管内皮屏障功能恢复与重建之间的因果关系。. 全身性或细胞定向性NF-kB信号通路失活对BMDEPCs介导的内皮屏障功能修复过程的各环节的影响。发现NF-kB信号通路失活可使肺内BMDEPCs募集减少81%、显著抑制肺内BMDEPCs增殖。进一步实验证实，肺实质细胞固有的NF-kB信号通路和BMDEPCs固有的NF-kB信号通路在调控BMDEPCs增殖方面的作用是相反的。本研究证明了BMDEPCs肺内募集/增殖是感染性感染性肺损伤后血管内皮屏障功能修复重建中不可替代的细胞机制， NF-kB信号通路在调控BMDEPCs介导的肺血管内皮屏障功能修复与重建中起核心作用。本课题的完成解析出了调节肺血管 内皮屏障功能修复和重建的新机制及信号通路，为以"促进BMDEPCs介导的内皮屏障功能修复和重建”作为治疗感染性肺损伤的治疗策略提供了实验依据，为感染性肺损伤治疗策略的研究打开了新思路、开拓了新的研究方向，具有重要的理论意义和应用价值。