Maintenance of the alveolar niche in emphysema

项目概要/摘要 肺具有沿着近端-远端轴的多个干/祖细胞隔室， 上皮干细胞/祖细胞位于非常接近下面的基质的位置。尽管他们 由于外观的均匀性，越来越明显的是，肺间质包含不同的子集， 每一个都独特地适合于维持最近的干/祖群体。因此，目前的差距 知识不是基质区室是否多样，而是如何分离基质 身份维持在不同的生态位，以及不同基质身份的破坏如何导致 疾病利用单细胞RNA测序和我们建立的独特的小鼠遗传工具的组合， 为了分离间质，我们的初步数据表明，hedgehog（Hh）激活促进近端 间质基因，同时抑制与远端肺泡间质相关的基因。此外，远端 肺泡间质中Hh激活的扩展减弱了间质有丝分裂原对肺泡上皮细胞的反馈， 干/祖细胞，导致肺泡损失相当于肺气肿。与人类疾病有关， 全基因组关联研究（GWASes）已经确定了许多肺气肿的易感基因座 Hedgehog相互作用蛋白（HHIP）基因附近，HHIP是Hh激活的负调节因子，但 缺乏确定致病关联的机制研究。我们的核心假设是 HHIP是SHH结合的负调节因子，它将Hh激活限制在近端基质， 基质特性的近端-远端分离，其丧失导致肺泡破裂 干/祖细胞龛和肺泡丧失与肺气肿相当。利用新型鼠标 我们开发的遗传工具，我们的单细胞分析，以及我们对临床标本的获取， 该提案旨在解决基质亚群如何在正常稳态期间保持其独特的特性， Hh如何改变基质对肺泡干细胞/祖细胞的反馈，以及如何破坏肺泡 小生境可导致肺气肿等慢性肺部疾病。

Project Summary/Abstract The lung possesses multiple stem/progenitor compartments along the proximal-distal axis where the epithelial stem/progenitors are situated in close proximity to the underlying stroma. Despite their homogeneity in appearance, it is increasingly apparent that the lung stroma contains diverse subsets, each uniquely suited to maintain the nearest stem/progenitor population. Thus, the current gap in knowledge is not whether stromal compartments are diverse, but rather how segregated stromal identities are maintained in different niches, and how disruption of distinct stromal identity can lead to disease. Utilizing a combination of single cell RNA-sequencing and a unique mouse genetic tool we built to isolate the stroma, our preliminary data demonstrate that hedgehog (Hh) activation promotes proximal stromal genes while suppressing genes associated with the distal alveolar stroma. Furthermore, distal expansion of Hh activation in the alveolar stroma attenuates stromal mitogen feedback to the alveolar stem/progenitors, leading to alveolar loss comparable to emphysema. Relevant to human disease, genome-wide association studies (GWASes) have identified numerous susceptibility loci for emphysema near the gene for Hedgehog-interacting protein (HHIP), a negative regulator of Hh activation, but mechanistic studies to define the pathogenic association have been lacking. Our central hypothesis is that HHIP, a negative regulator of SHH binding, restricts Hh activation to the proximal stroma to maintain proximal-distal segregation of stromal identity, the loss of which leads to disruption of the alveolar stem/progenitor niche and loss of alveoli comparable to emphysema. Leveraging the novel mouse genetic tools we have developed, our single cell analysis, and our access to clinical specimen, this proposal aims to address how stromal subsets maintain their distinct identity during normal homeostasis, how Hh alters the stromal feedback to the alveolar stem/progenitors, and how disruption of the alveolar niche can lead to chronic lung diseases such as emphysema.