Integrated Molecular and Cellular Drivers of Alveologenesis

项目摘要 在肺发育的囊状期（妊娠23-32周）出生的新生儿， 支气管肺发育不良（BPD），一种主要的早产并发症。这背后的机制 脆弱性定义不清，我们认为这一知识差距是缺乏治愈性BPD的基础 治疗为了了解BPD中肺泡形成受阻的不可逆性，我们需要一个精炼的， 对正常囊泡到肺泡过渡的机械理解。我们的初步数据来自4- 三维活体成像和单细胞转录组学支持一种新的肺泡发生模型， 肌成纤维细胞环结构支持AT 2（肺泡2型细胞）的挤出，然后它们的细胞被释放。 分化为AT 1（肺泡1型细胞）。根据我们的模型，成熟的AT 1产生ECM蛋白， 以及其他招募特化内皮细胞成为肺泡毛细血管床的因素。连续的， 包括Wnt和BMP在内的时空受限的信号传导途径，协调细胞运动， 扩散和架构。我们已经建立了一个新生儿损伤模型， 肺泡发生与人BPD相关，通过将新生小鼠暴露于高氧和炎症， 囊状阶段我们从该模型获得的初步数据将Wnt 5A/Wnt 11的过表达与 肺泡形成受损损伤后的缺陷包括肺泡上皮细胞中BMP的产生和活性降低， 上皮细胞和受损的AT 2到AT 1细胞分化和细胞外基质表达减少 (ECM)AT 1细胞。根据初步和已发表的数据，我们假设， 肺泡发生涉及表达Wnt 5a和Wnt 11以驱动AT 2的成肌纤维细胞环的形成 增殖并促进通过环的挤出。随后的上皮BMP产生下调 Wnt，促进AT 2向AT 1分化和产生用于毛细血管组装的细胞外支架。 损伤使Wnt和Bmp信号传导失调，扰乱了这一关键过程中的精确时空模式。 时间范围内，并导致肺泡生成停滞和长期功能缺陷。我们将测试这个 1）确定肌成纤维细胞Wnt表达在调节肌成纤维细胞增殖中的作用。 AT 2增殖和肺泡发育; 2）表征BMP信号传导的机制， 调节AT 2-到-AT 1细胞分化; 3）确定新生AT 1细胞 为发育中的肺泡提供支架。成功完成这一提案预计将 改变我们对肺泡发生的理解，确定新的分子靶点， 牙槽修复和部署这种新定向疗法的最佳时间窗。

PROJECT SUMMARY Neonates born during the saccular stage of lung development (23-32 wks gestation) are at highest risk for bronchopulmonary dysplasia (BPD), a leading preterm birth complication. The mechanisms underlying this vulnerability are poorly defined, a knowledge gap we consider foundational to the lack of curative BPD therapies. To understand the irreversibility of arrested alveologenesis in BPD, we require a refined, mechanistic understanding of the normal saccular to alveolar transition. Our preliminary data from 4- dimensional live imaging and single-cell transcriptomics support a new model of alveologenesis in which myofibroblast ring structures support the extrusion of AT2s (alveolar type 2 cells) followed by their differentiation into AT1s (alveolar type 1 cells). According to our model, mature AT1s produce ECM proteins and other factors that recruit specialized endothelial cells to become the alveolar capillary bed. Sequential, spatiotemporally restricted signaling pathways, including Wnt and BMP, coordinate cell movement, proliferation, and architecture. We have developed a neonatal injury model with a phenotype of impaired alveologenesis that is relevant to human BPD by exposing neonatal mice to hyperoxia and inflammation during the saccular stage. Our preliminary data from this model associate overexpression of Wnt5A/Wnt11 with impaired alveologenesis. Post-injury deficits include decreased BMP production and activity in alveolar epithelial cells and impaired AT2 to AT1 cell differentiation and decreased expression of extracellular matrix (ECM) components by AT1 cells. Based on preliminary and published data, we hypothesize that alveologenesis involves formation of a ring of myofibroblasts that express Wnt5a and Wnt 11 to drive AT2 proliferation and promote extrusion through the ring. Subsequent epithelial BMP production down-regulates Wnt, promoting AT2 to AT1 differentiation and generation of an extracellular scaffold for capillary assembly. Injury dysregulates Wnt and Bmp signaling, perturbing the precise spatiotemporal patterning during this critical timeframe and resulting in arrested alveologenesis and long-term functional deficits. We will test this hypothesis in the following specific aims: 1) Define the role of myofibroblast Wnt expression in regulating AT2 proliferation and alveolar development; 2) Characterize mechanisms by which BMP signaling regulates AT2-to-AT1 cell differentiation; 3) Determine the mechanisms whereby nascent AT1 cells generate a scaffold for the developing alveolus. Successful completion of this proposal is anticipated to transform our understanding of alveologenesis, identifying new molecular targets to promote post-injury alveolar restoration and the optimal time windows for deployment of such newly directed therapies.