Regulation of alveolar epithelial regeneration by T cells

总结 肺实质中的肺泡上皮在保护肺免受吸入颗粒/化学物质的影响方面起着关键作用 和呼吸道感染。因此，肺泡上皮细胞的再生能力对于恢复至关重要 以重建上皮屏障并恢复肺功能。肺泡上皮 由肺泡上皮I型细胞（AECI）和肺泡上皮II型细胞（AECII）组成。的更新 AECI被认为是依赖于AECII，肺泡上皮前体细胞，其分化为AECI。 因此，AECII在肺泡上皮细胞对损伤的快速再生中是必不可少的。 已知宿主免疫应答在细菌性肺炎期间引起肺损伤，并且还可能在以下方面发挥作用： 调节修复和再生。我们发现了一种以前未被认识到的T细胞在调节 细菌性肺炎诱导的肺损伤和修复过程中AECII分化能力使用组合 遗传谱系追踪，流式细胞术和免疫染色，我们的初步研究表明，小鼠感染 肺炎链球菌T4株（SpT 4），社区获得性肺炎最常见的病原体， 肺炎，仅在肺实质中有损伤，AECI和AECII丧失， 免疫细胞的浸润。随后通过分化的前肺上皮细胞进行肺泡上皮再生， 将现有的表面活性剂蛋白C（SPC）表达AECII转化为AECI。AECII与AECI差异化的增加 与AECII中雅普和Taz核蛋白水平的上调以及T细胞的快速消退相关 肺泡细胞。在AECII中特异性缺乏雅普/Taz的小鼠表现出AECII对AECI的减少 分化，表明雅普/Taz在AECII分化中的重要作用。此外，我们发现， 当AECII与CD 4或CD 8 T细胞共培养时，AECII向AECI的分化基本上被抑制 在体外小鼠和人模型系统中。SpT 4诱导的小鼠肺损伤后，持续性T细胞 肺泡中的AECII-应答引起AECII-向AECI分化的显著抑制，并且降低了肺泡 上皮再生我们发现，CD 4/CD 8 T细胞的功能部分是通过抑制雅普/Taz核转录因子的表达来实现的。 在AECII的活动。基于这些初步研究，中心假设是持续的CD 4/CD 8 T细胞 反应通过下调AECII中的雅普/Taz核活性抑制AECII分化能力。 旨在加速肺中CD 4/CD 8 T细胞消退的免疫调节策略将促进 AECII至AECI分化和肺泡上皮再生。 该提案旨在通过以下方式来定义CD 4/CD 8 T细胞在调节AECII功能中的机制作用： 研究CD 4/CD 8 T细胞调节AECII向AECI分化的潜在机制， 实验性细菌性肺炎小鼠模型及AECII与T细胞亚群的体外共培养体系 人类和老鼠的基因我们还将研究T细胞疗法在促进AECII到AECI方面的潜力。 分化和肺泡上皮再生。

SUMMARY Alveolar epithelium in lung parenchyma plays a pivotal role in protecting lung from inhaled particles/chemicals and respiratory infections. Therefore, the regenerative capacity of the alveolar epithelium is critical for recovery from these insults in order to rebuild the epithelial barrier and restore pulmonary functions. Alveolar epithelium is composed of alveolar epithelial type I cells (AECI) and alveolar epithelial type II cells (AECII). The renewal of AECI is considered to be depend on AECII, the alveolar epithelial progenitor cells, which differentiate into AECI. Thus AECII are essential in the rapid regeneration of the alveolar epithelium in response to injury. Host immune responses are known to cause lung injury during bacterial pneumonia and may also play a role in regulating repair and regeneration. we have uncovered a previously unrecognized role of T cells on regulating AECII differentiation capacity during bacterial pneumonia-induced lung injury and repair. Using a combination of genetic lineage tracing, flow cytometry, and immunostaining, our preliminary studies show that mice infected with Streptococcus pneumonia Strain T4 (SpT4), the most common pathogen of community-acquired pneumonia, had injuries exclusively in the lung parenchyma, with loss of AECI and AECII and increased infiltration of immune cells. This was followed by alveolar epithelial regeneration via differentiation of pre- existing Surfactant Protein C (SPC)- expressing AECII into AECI. This increase in AECII-to-AECI differentiation was correlated with up-regulation of nuclear protein levels of Yap and Taz in AECII and rapid resolution of T cells in lung alveoli. Mice that lacked Yap/Taz specifically in AECII exhibited diminished AECII-to-AECI differentiation, indicating the essential role of Yap/Taz in AECII differentiation. Furthermore, we found that AECII-to-AECI differentiation was substantially inhibited when AECII were co-cultured with CD4 or CD8 T cells in both murine and human model systems in vitro. After SpT4-induced lung injury in mice, persistent T-cell response in lung alveoli caused dramatic inhibition on AECII-to-AECI differentiation and decreased alveolar epithelial regeneration. We identified that CD4/CD8 T cells functioned, in part, by suppressing Yap/Taz nuclear activity in AECII. Based on these preliminary studies, the central hypothesis is that persistent CD4/CD8 T-cell response inhibits AECII differentiation capacity through down-regulation of Yap/Taz nuclear activity in AECII. Immunomodulatory strategies aimed at accelerating resolution of CD4/CD8 T cells in the lung will promote AECII-to-AECI differentiation and alveolar epithelial regeneration. This proposal aims to define the mechanistic role of CD4/CD8 T cells in regulating AECII function by investigating the mechanisms underlying CD4/CD8 T-cell regulation on AECII-to-AECI differentiation in an experimental bacterial pneumonia mouse model, and an in vitro co-culture system of AECII with T-cell subset from both human and mouse. We will also examine the potential of T-cell therapy in promoting AECII-to-AECI differentiation and alveolar epithelial regeneration in an animal model.