Foxf1 Transcription Factor in Development of Pulmonary Capillaries

描述（由申请人提供）：支气管肺发育不良（BPD）是早产儿在机械通气和高水平补充氧后发生的一种慢性肺部疾病。虽然由于围产期护理的改善，早产新生儿的存活率有所增加，但BPD仍然是一种严重而常见的早产并发症，每年在美国约有15,000名婴儿受到影响。患有BPD的婴儿在幼儿期呼吸系统疾病和死亡的风险较高。BPD有长期的呼吸系统和神经发育并发症，这些并发症会超过儿童时期，并增加医疗保健费用。鉴于在BPD的预防和治疗方面缺乏重大进展，迫切需要创新的分子方法来补充现有的BPD治疗方法。有希望的BPD治疗方法包括增加出生后血管生成和保护肺泡内皮细胞免受机械通气和高氧水平损伤后的凋亡。基于我们的初步结果，我们认为叉头盒F1 （Foxf1）转录因子（也称为hhh -8和Freac-1）在这两个过程中都起着关键作用，因此，针对Foxf1可能有益于BPD儿童的化学预防和治疗。我的实验室发表的研究表明，Foxf1在胚胎和新生儿肺内皮细胞（EC）中表达。Foxf1零等位基因杂合的小鼠在新生儿早期表现为肺发育不全，肺泡毛细血管数量减少，EC细胞凋亡增加，死亡率增加。最近在30%的人类肺泡毛细血管发育不良（ACD）患者中发现了FoxF1基因位点的基因组突变，ACD是一种先天性致死肺病。暴露于高氧环境的新生小鼠（BPD小鼠模型）肺Foxf1 mRNA和蛋白水平降低。在高氧处理的新生小鼠和BPD患者中，Foxf1水平的降低与肺血管的丧失有关。鉴于Foxf1在小鼠和人类肺血管发育中的关键作用，确定Foxf1在BPD发病机制中的作用非常重要。我们将使用新生小鼠高氧介导的肺损伤作为BPD模型来验证Foxf1通过刺激血管生成和增加内皮细胞存活来维持高氧损伤后正常肺形态发生的假设。在Aim I中，我们将使用Foxf1缺乏的两种转基因小鼠系Foxf1小鼠和Tie2-Cre- fl/fl ER Foxf1小鼠来确定BPD模型中Foxf1是否需要形成新的肺毛细血管。在Aim II中，我们将确定Foxf1是否直接调节抗凋亡基因的表达，是否为BPD模型中内皮细胞存活所必需。由于我们研究的长期目标是寻找预防人类BPD的新型治疗药物，在Aim III中，我们将确定增加新生儿肺部Foxf1水平是否会加速血管形成，提高EC存活率并预防BPD。在高氧处理的新生小鼠中，Foxf1水平可以通过药理学方法（TAT-Foxf1融合蛋白）或遗传学方法（多西环素诱导的内皮细胞中Foxf1的过表达）来增加。这些研究的完成将确定增加Foxf1水平是否是一种有希望的治疗方法，以防止BPD患者内皮细胞凋亡和诱导血管生成。

DESCRIPTION (provided by applicant): Bronchopulmonary dysplasia (BPD) is a chronic lung disease that occurs in preterm infants following mechanical ventilation and high levels of supplemental oxygen. While survival of premature newborns has increased due to recent improvements in perinatal care, BPD remains a serious and common complication of prematurity, affecting approximately 15,000 infants annually in USA. Infants with BPD are at higher risk of respiratory morbidity and mortality in early childhood. BPD has long-term respiratory and neurodevelopmental complications that reach beyond childhood and increase health care costs. Given the lack of major improvements in prevention and treatment of BPD, there is a major need for innovative molecular approaches to complement existing BPD therapies. Promising therapeutic approaches for BPD treatment include increasing postnatal angiogenesis and protection of alveolar endothelial cells from apoptosis after the injury caused by mechanical ventilation and high levels of oxygen. Based on our preliminary results, we believe that Forkhead Box F1 (Foxf1) transcription factor (also known as HFH-8 and Freac-1) plays a key role in both these processes and therefore, targeting the Foxf1 can be beneficial for both chemoprevention and treatment of children with BPD. Published studies from my laboratory have demonstrated that Foxf1 is expressed in pulmonary endothelial cells (EC) of embryonic and neonatal lungs. Mice heterozygous for the Foxf1 null allele exhibited lung hypoplasia, decreased number of alveolar capillaries, increased apoptosis of EC, and increased mortality in the early neonatal period. Genomic mutations in FoxF1 gene locus were recently found in 30% of human patients with Alveolar Capillary Dysplasia (ACD), a congenital lethal lung disease. Pulmonary Foxf1 mRNA and protein levels are reduced in newborn mice exposed to hyperoxia, a mouse model of BPD. Diminished Foxf1 levels are associated with loss of pulmonary vasculature in hyperoxia-treated newborn mice and human patients with BPD. Given the critical role of Foxf1 for pulmonary vascular development in mice and humans, it is important to determine the role of Foxf1 in the pathogenesis of BPD. We will use hyperoxia- mediated lung injury in newborn mice as a model of BPD to test the hypothesis that Foxf1 is required to maintain normal lung morphogenesis after hyperoxia injury by stimulating angiogenesis and increasing survival of endothelial cells. In Aim I, we will determine whether Foxf1 is required for formation of new pulmonary capillaries in a BPD model using two transgenic mouse lines with Foxf1 deficiency: Foxf1 mice and Tie2-Cre- fl/fl ER Foxf1 mice. In Aim II, we will determine whether Foxf1 directly regulates expression of anti-apoptotic genes and is required for survival of endothelial cells in a BPD model. Since the long-term goal of our studies is to find novel therapeutic agents preventing BPD in human patients, in Aim III we will determine whether increasing Foxf1 levels in neonatal lungs will accelerate vessel formation, increase EC survival and prevent BPD. Foxf1 levels in hyperoxia-treated newborn mice will be increased by either pharmacological approach (TAT-Foxf1 fusion protein) or genetic approach (Doxycycline-inducible over-expression of Foxf1 in endothelial cells). Completion of these studies will determine whether increasing Foxf1 levels is a promising therapeutic approach to prevent endothelial apoptosis and induce angiogenesis in BPD patients. PUBLIC HEALTH RELEVANCE: Foxf1 transcription factor is an important and clinically-relevant transcriptional regulator of pulmonary vascular development in mice and humans, but its role in Bronchopulmonary dysplasia (BPD) remains unknown. Using two novel mouse models with Foxf1 deficiency, we propose to determine whether Foxf1 is required to maintain postnatal lung morphogenesis by stimulating angiogenesis and increasing survival of endothelial cells (EC) after hyperoxia-mediated injury, a mouse model of BPD. We also propose to use cell-penetrating TAT-Foxf1 fusion protein, a novel therapeutic agent, to determine whether increasing Foxf1 in newborn mice will promote vascular repair after hyperoxia lung injury, decrease EC apoptosis and prevent BPD.