Novel Molecular Mechanisms Regulating Postnatal Pulmonary Angiogenesis

描述（由申请人提供）：肺毛细血管的血管生成对肺泡形成至关重要，而肺血管生成的破坏有助于支气管肺发育不良（BPD）的发病机制，这是早产最常见的并发症。然而，在发育和疾病过程中协调肺血管生成的分子途径尚不完全清楚。这种知识上的差距继续困扰着开发靶向治疗方法来治疗由血管生成受损引起的肺部疾病的努力，包括BPD。核因子κ-B （NFκB）是炎症的关键调节因子，越来越多的证据表明NFκB在癌症伤口愈合过程中调节血管生成。相比之下，我们对NFκB在肺发育中的作用知之甚少。我们最近证明NFκB对肺泡形成至关重要。

DESCRIPTION (provided by applicant): Growth of the pulmonary capillaries by angiogenesis is essential for alveolarization, and disruption of pulmonary angiogenesis contributes to the pathogenesis of bronchopulmonary dysplasia (BPD), the most common complication of premature birth. However, the molecular pathways that orchestrate pulmonary angiogenesis during development and disease are not fully understood. This gap in knowledge continues to confound efforts to develop targeted therapies to treat lung diseases caused by impaired angiogenesis, including BPD. Nuclear factor κ-B (NFκB) is a key regulator of inflammation, and growing evidence suggests that NFκB regulates angiogenesis in wound healing in cancer. In contrast, little is known about the role of NFκB in the developing lung. We recently demonstrated that NFκB is essential for alveolarization. NFκB is constitutively active in the neonatal, but quiescent in the adult lung, and inhibiting NFκB disrupts pulmonary angiogenesis and alveolarization in neonatal mice, but has no effect in adults. Blocking NFκB in neonatal primary pulmonary endothelial cells (PEC) impairs survival, proliferation, and in vitro angiogenesis. Activation of NFκB in the PEC corresponds to the period of angiogenesis in the developing lung, peaking at the onset of alveolarization, and decreasing to low levels by mid-alveolarization. However, the capacity for NFκB to be activated in the PEC is not intrinsic to the cell's maturation, as conditioned media obtained from early alveolar lung organ culture (EA-LCM), robustly activates NFκB and enhances migration in adult PEC. Global proteomic analysis to compare the early alveolar and adult lung secretomes identified factors secreted only by the early alveolar lung (EAL). Studies to examine the effect of neutralizing each of these proteins on the ability of the EA-LCM to promote NFκB activation and migration, allowed the identification of two putative activators of NFκB in the early alveolar lung: transforming growth factor-ß induced protein (TGFBI) and alpha-fetoprotein (AFP). Both factors are expressed in the EAL in vivo but minimally expressed in the adult lung, and both are suppressed by injuries that disrupt alveolarization. Therefore, our data suggest the overall working hypothesis that factors uniquely secreted by the EAL promote lung angiogenesis and alveolarization by activating NFκB in the pulmonary endothelium by addressing two inter-related specific aims. In Aim 1, we will examine if TGFBI and AFP secretion by the EAL induces a pro-angiogenic phenotype in the PEC via an NFκB-dependent pathway, and explore if TGFBI and AFP activate common or complementary patterns of gene expression. Aim 2 will utilize in vivo gain and loss of function strategies to determine if disrupting TGFBI- or AFP-mediated activation of NFκB impairs alveolar growth during development and injury. The successful completion of these studies will establish a novel, physiologic role for NFκB in the developing lung, and identify new angiogenic factors that can be directly translated into therapeutic strategies to promote lung growth and regeneration in diseases marked by impaired pulmonary angiogenesis.