DLL4 in the Developing Lung and Bronchopulmonary Dysplasia (BPD)

支气管肺发育不良是早产儿的一种使人衰弱的肺部疾病， 血管化和肺泡化。内皮细胞（EC）分子参与调节正常和 异常（BPD）肺泡化仍不清楚。我们在DLl4 +/-小鼠中的数据表明，δ样蛋白4（DLL4）， EC缺口配体是肺血管化和肺泡化所必需的。DLL4似乎 调节Car4 + EC的发育，Car4 + EC是与肺泡上皮I型细胞相互作用的肺特异性EC亚群 （AT1）。有趣的是，我们还发现AT 1群体在Dll 4 +/-小鼠以及EC-1小鼠中被耗尽。 特异性Dll4缺失[Dll4EC +/-]与受损EC肝细胞生长因子-AT1 MET [HGF受体]相关 信号研究DLL4在BPD中的作用，我们注意到在实验性BPD和人类BPD中， DLL4表达降低和异常肺血管化。测试BPD的新疗法，我们注意到， 环索奈德（CIC）是一种具有脑保护作用的合成糖皮质激素前体药物， 在小鼠肺和人肺微血管内皮细胞（HPMEC）中诱导DLL4抑制。 这些数据为我们的假设提供了依据，即EC-DLL4在远端肺发育过程中调节CAR4 + EC和AT 1的发育。 形态发生和EC-DLL4信号传导的破坏， 波士顿警局我们将通过以下方式研究这一假设：1）测试CAR4 + EC的EC-DLL4调节是否对CAR4 + EC的表达至关重要。 肺血管化，2）确定EC-DLL4调节AT1发育的分子途径， 肺个体发育，以及3）确定EC DLL4信号传导的抑制是否在实验和人类中进行 波士顿警局在目的1中，我们将研究在连续的肺阶段中EC-Dll 4缺失如何重新编程肺EC命运， Car 4 + EC群体。CAR4+命运和血管生成的细胞自主调节 DLL4将在我们创建的原代和Dll4缺陷HPMEC系中探测。在目标2中，我们将研究 AT 1发育/功能和肺泡化（EC DLL4）。我们将使用单细胞RNA测序来鉴定 EC D114缺失可导致EC配体-AT 1受体相互作用和AT 1分子通路的破坏。我们将 还研究了Dll 4缺失是否通过肝细胞生长因子破坏EC血管分泌信号。在目标3中，我们 将人BPD样品的分子表型分析与Dll 4 EC-/-对比+/-对比+/+小鼠中的研究结合联合收割机，以确定EC- Dll4在破坏HOX中EC命运、AT1个体发育和肺形态发生中的作用。治疗机制 环索奈德通过何种途径挽救DLL4信号传导和HOX中的肺损伤也将被测试。 我们的提议通过发现DLL4在肺EC命运特化和AT1个体发生中的作用而影响了该领域 运用创新战略。其意义在于解决支撑血管起源的关键障碍 BPD和翻译潜能的结合。在SA 1和SA 2中，我们研究了DLL4对Car4 EC和AT 1个体发育的调节， 作为DLL4调节肺发育的关键机制。在SA3中，我们研究了DLL4在BPD中的作用， 并在临床前模型中测试环索奈德拯救DLL4信号传导和减轻BPD的功效。

Bronchopulmonary dysplasia is a debilitating lung disease in premature infants characterized by disrupted lung vascularization and alveolarization. The endothelial cell (EC) molecular players that regulate normal and abnormal (BPD) alveolarization remain unclear. Our data in Dll4+/- mice indicate that Delta-like protein 4 (DLL4), an EC notch ligand, is required for lung vascularization and alveolarization. Specifically, DLL4 appears to regulate the development of Car4+EC, a lung-specific EC subset that interacts with alveolar epithelial type I cells (AT1). Interestingly, we also found that the AT1 population is depleted in Dll4+/- mice, as well as mice with EC- specific Dll4 deletion [Dll4EC+/-] in relation with impaired EC hepatocyte growth factor - AT1 MET [HGF receptor] signaling. Examining DLL4’s role in BPD, we noted that both in experimental BPD and in human BPD, there was decreased DLL4 expression and deviant lung vascularization. Testing a new therapy for BPD, we noted that ciclesonide (CIC), a synthetic glucocorticoid pro-drug with brain-sparing effects, rescued hyperoxia (HOX)- induced DLL4 repression in the mouse lung and in human pulmonary microvascular endothelial cells (HPMEC). These data inform our hypothesis that EC-DLL4 regulates CAR4+ EC and AT1 development during distal lung morphogenesis, and disruption of EC-DLL4 signaling in hyperoxia programs vascular and alveolar defects in BPD. We will investigate this hypothesis by: 1) Testing whether EC-DLL4 regulation of CAR4+ EC is critical for lung vascularization, 2) Defining the molecular pathways by which EC-DLL4 regulates AT1 development during lung ontogeny, and 3) Determining whether repression of EC DLL4 signaling programs experimental and human BPD. In Aim 1, we will study how EC-Dll4 deletion in sequential lung stages reprograms lung EC fate, heterogeneity and the Car4+ EC population. Cell autonomous regulation of CAR4+ fate and angiogenesis by DLL4 will be probed in primary and Dll4-deficient HPMEC lines we created. In Aim 2, we will study regulation of AT1 development/function and alveolarization by EC DLL4. We will use single cell RNA sequencing to identify the EC ligand - AT1 receptor interactions and AT1 molecular pathways disrupted with EC Dll4 deletion. We will also study whether Dll4 loss disrupts EC angiocrine signaling through hepatocyte growth factor. In Aim 3, we will combine molecular phenotyping of human BPD samples with studies in Dll4EC -/- vs. +/- vs. +/+ mice to determine EC- Dll4’s role in disrupting EC fate, AT1 ontogeny and lung morphogenesis in HOX. The therapeutic mechanisms by which ciclesonide rescues DLL4 signaling and lung injury in HOX will also be tested. Our proposal impacts the field by discovering DLL4’s role in lung EC fate specification and AT1 ontogeny using innovative strategies. The significance lies in addressing critical barriers underpinning the vascular origins of BPD and translational potential. In SA1 and SA2, we examine DLL4-regulation of Car4 EC and AT1 ontogeny as critical mechanisms underpinning DLL4-regulation of lung development. In SA3, we study DLL4’s role in BPD, and test the efficacy of ciclesonide to rescue DLL4 signaling and mitigate BPD in a pre-clinical model.