Maintenance of the alveolar niche in emphysema

项目摘要/摘要 肺具有沿近-远轴线的多个干/祖细胞隔室，其中 上皮干/祖细胞位于靠近基质的位置。尽管他们 外观上的同质性，越来越明显的是肺间质包含不同的亚群， 每一株都独一无二地适合维持最近的茎/祖种群。因此，目前的差距是 知识不在于基质是否多样，而在于基质的分离程度。 身份在不同的利基中保持，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)的激活促进了近端 基质基因，同时抑制与远端牙槽间质相关的基因。此外，远端 牙槽间质中HH活性的扩大减弱了间质有丝分裂原对牙槽骨的反馈 干/祖细胞，导致肺泡丢失，可与肺气肿相媲美。与人类疾病有关， 全基因组关联研究(GWASes)发现了许多肺气肿的易感基因 接近Hedgehog相互作用蛋白(HHIP)的基因，HHIP是HH激活的负面调节因子，但 定义致病关联的机制研究一直缺乏。我们的中心假设是 HHIP是SHH结合的负调控因子，它将HH的激活限制在近端间质以维持 基质特性的近端-远端分离，其丢失会导致牙槽骨的破坏 可与肺气肿相提并论的干/祖细胞巢和肺泡丢失。利用新奇的鼠标 我们开发的基因工具，我们的单细胞分析，以及我们获得临床标本的途径，这 该提案旨在解决基质亚群如何在正常内稳态期间保持其独特的身份， HH如何改变对牙槽干/祖细胞的基质反馈，以及如何破坏牙槽 生态位可能导致慢性肺部疾病，如肺气肿。

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.