Glucocorticoid pathways in fetal lung development

(申请人摘要)早产儿有发展为急性和非典型肺炎的风险 慢性肺部疾病，一个重要的死亡原因，旷日持久 住院和长期发病率。产前保健的有益作用 糖皮质激素(GC)对早产儿肺的治疗是有文献记载的。尽管 近年来肺透明膜病的发病率和严重程度有所下降 产前GC和产后表面活性物质的广泛使用 治疗方法、慢性肺部疾病(CLD)的发病率(定义为氧气 妊娠36周后的依赖)没有相应的 拒绝。这表明，在患有CLD的婴儿中，无论是发育性的还是获得性的 肺缺陷不能通过即刻GC治疗而改善 产前或产后应用表面活性物质治疗。这 这一建议得到了靶向致糖皮质激素缺陷小鼠的研究结果的支持 促肾上腺皮质激素释放激素基因缺失。未经处理的小鼠 在出生后不久死亡，肺部发育有重大缺陷 (分支正常，但间充质和上皮细胞增多，异常 Clara细胞分化，肺泡化减少)，但仅轻微 表面活性物质表达不足。此外，成功的GC抢救 CRH-/-胎儿要求在胚胎13.5天前给予类固醇， 在任何先前描述的GC对胎儿肺的影响之前几天。 这表明GC对肺部发育有重要影响。 在肺器官发生的非常早期。这一时间框架可能还为时过早 影响表面活性剂合成，但很可能涉及一种或几种的调节 旁分泌生长因子系统，最近被描述为具有 在肺发育中的重要作用，包括音速刺猬的成员， 成纤维细胞生长因子、转化生长因子和血小板衍生 生长因子家族。调查人员建议找出这些因素 它们控制着对GC敏感的晚期(分支后)肺发育， 以及它们与GC相互作用的途径，使用来自 CRH-/-胎鼠及GC和/或上述生长因子的治疗 因素族。Affymetrix小鼠寡核苷酸上的候选基因、cDNA 芯片以及通过差异显示技术识别的cDNA将 被研究(特定目标1)新的候选基因的特征是 正常和正常脑组织中mRNA和蛋白质的定位及发育调控 CRH-/-胎肺，以及体内靶向基因缺失(特定目标2)。 最后，胎儿肺在刺激胎儿方面的一个重要作用 将寻求导致正常肺发育的GC分泌(特定目标 3)。

(Applicant's Abstract) Premature infants are at risk for developing acute and chronic pulmonary disease, a significant cause of mortality, prolonged hospitalization, and long-term morbidity. The beneficial effect of prenatal glucocorticoid (GC) treatment on premature lungs is well documented. Despite the decreased incidence and severity of hyaline membrane disease in recent years with the widespread use of prenatal GC and postnatal surfactant therapies, the incidence of chronic lung disease (CLD, defined as oxygen dependence after 36 weeks gestational age) has not had a corresponding decline. This suggests that in infants with CLD, developmental or acquired lung defects are not ameliorated by either GC treatment in the immediate prenatal period or surfactant treatment in the postnatal period. This suggestion is supported by findings in mice with GC deficiency due to targeted deletion of the corticotropin-releasing hormone (Crh) gene. Untreated mice die in the immediate postnatal period, with major defects in lung development (normal branching, but mesenchymal and epithelial hypercellularity, abnormal Clara cell differentiation, and decreased alveolarization), but only minor deficiencies in surfactant expression. Moreover, successful GC rescue of Crh-/- fetuses requires that the steroid be given before embryonic day 13.5, several days prior to any previously described effects of GC in fetal lung. This suggests that GC has major effects on pulmonary development that occur very early in lung organogenesis. This time frame is likely too early to affect surfactant synthesis, but may well involve modulation of one or several paracrine growth factor systems which have recently been described to have important roles in lung development, including members of the sonic hedgehog, fibroblast growth factor, transforming growth factor, and platelet derived growth factor families. The investigators propose to identify those factors which govern late (post- branching) lung development that are GC-responsive, and their pathways of interaction with GC, using organ explant cultures from Crh-/- fetal mice and treatment with GC and/or members of the above growth factor families. Candidate genes, cDNAs on Affymetrix murine oligonucleotide chips, as well as cDNAs identified via differential display techniques, will be examined (Specific Aim 1) Novel candidate genes will be characterized by mRNA and protein localization and developmental regulation in the normal and Crh-/- fetal lung, and by targeted gene deletion in vivo (Specific Aim 2). Finally, an essential role for the fetal lung in the stimulation of the fetal GC secretion leading to normal lung development will be sought (Specific Aim 3).