SURFACTANT PROTEIN REGULATION IN DEVELOPING LUNG

几种肺部病变，特别是呼吸窘迫综合征（RDS）， 早产儿与胎儿肺不成熟有关。RDS是 毫无疑问与肺表面活性物质缺乏有关， 磷脂和四种肺特异性脱辅基蛋白的复杂混合物， 被指定为特别程序A、特别程序B、特别程序C和特别程序D。肺表面活性剂， 其由肺泡II型细胞合成和分泌， 降低空气-液体界面处的表面张力，从而防止 低肺容量时肺泡萎陷。疏水蛋白SP-B和 SP-C在表面活性剂的表面活性中起着重要作用， 而SP-A似乎更多地参与调节表面活性剂 肺泡中的新陈代谢。SP-D的功能尚未完全了解， 尽管它似乎参与肺中的非免疫宿主防御。 鉴于它们对正常表面活性剂功能和代谢的重要性， 研究了SP-A、SP-B和SP-B的调节作用， C.最近的一项重要观察结果是，SP-A、SP-B的表达 SP-C在肺发育中比以前早得多 想的上皮-间质相互作用，迄今为止， 被证明是肺中正常分支形态发生所必需的， 似乎也参与指定分化的远端 上皮细胞表型在早期肺，所证明的 早期胎儿肺间质对早期胎儿气管的重编程能力 上皮表达肺泡II型细胞表型。我们有 开发了几个系统，我们将用于调查的基础上， 上皮-间质相互作用。为了确定 组织重组中上皮细胞的命运，我们将使用 远端肺和气管上皮分化，以表征 胎肺和胎气管上皮细胞对不同浓度的地塞米松影响的反应 肺和气管间质。我们已经证明， 肺间质对气管上皮细胞的影响是由 可扩散分子。我们将扩大这些研究以确定 这些因素，他们是如何迅速有效，以及他们是否必须 持续存在以维持远端肺上皮发育。我们 已经发展出一个复杂的文化体系， 诱导肺远端特异性标志物SP-C表达 上皮，在胎儿气管上皮细胞中。深入 描述这个系统。然后我们将确定关键组件 测试额外的生长因子和激素， 一个确定的细胞外基质的这种诱导。的 诱导气管上皮细胞表达新细胞表型 肺间质伴随着新基因的表达。使用 差异显示反转录聚合酶链技术 反应，我们将鉴定和分离这些基因。这将提供 上皮细胞凋亡机制研究的新视角和新试剂 在胎儿肺中的确定和分化。完成时 我们希望这笔赠款能大大增加我们对 调节远端肺上皮细胞分化的因子， 在发育中的胎儿中增殖。这些知识将被证明是有用的， 预防和治疗肺不成熟引起的疾病。

Several lung pathologies, notably respiratory distress syndrome (RDS) in the premature infant, are related to fetal lung immaturity. RDS is incontrovertibly linked to a deficiency in pulmonary surfactant, which is a complex mixture of phospholipids and four lung-specific apoproteins that have been designated SP-A, SP-B, SP-C and SP-D. Pulmonary surfactant, which is synthesized and secreted by alveolar type II cells, functions by lowering surface tension at the air-liquid interface, thereby preventing alveolar collapse at low lung volumes. The hydrophobic proteins SP-B and SP-C are importantly involved in the surface activities of surfactant, while SP-A appears to be more involved in regulation of surfactant metabolism in the alveolus. The function of SP-D is not fully understood, although it appears to be involved in non-immune host defense in the lung. Given their importance to normal surfactant function and metabolism, much effort has been expended on studying the regulation of SP-A, SP-B and SP- C. An important recent observation is that the expression of SP-A, SP-B and SP-C begins much earlier in lung development than was previously thought. Epithelial-mesenchymal interactions, which have heretofore been documented to be essential for normal branching morphogenesis in the lung, also appear to be involved in specifying the differentiated distal epithelial cell phenotype in the early lung, as demonstrated by the ability of early fetal lung mesenchyme to reprogram early fetal tracheal epithelium to express the alveolar type II cell phenotype. We have developed several systems that we will use for investigating the basis of epithelial-mesenchymal interactions. In order to ascertain the range of epithelial cell fates in tissue recombinations, we will use markers of distal lung and tracheal epithelial differentiation to characterize the response of fetal lung and fetal tracheal epithelia to the influences of both lung and tracheal mesenchyme. We have demonstrated that the inductive influence of lung mesenchyme on tracheal epithelium is mediated by diffusible molecule(s). We will expand these studies to determine the size of these factors, how quickly they are effective, and whether they must be continuously present to sustain distal lung epithelial development. We have developed a complex culture system in which we have been able to induce expression of SP-C, a specific marker of the distal lung epithelium, in fetal tracheal epithelial cells. We will thoroughly characterize this system. We will then determine the critical components of this medium, test additional growth factors and hormones, and develop a defined extracellular matrix substratum for this induction. The induction of expression of a new cell phenotype in tracheal epithelium by lung mesenchyme is accompanied by the expression of new genes. Using the technique of differential display reverse transcription polymerase chain reaction, we will identify and isolate some these genes. This will provide new insight and reagents for the study of mechanisms of epithelial cell determination and differentiation in the fetal lung. At the completion of this grant we expect to have substantially increased our knowledge of the factors that regulate distal lung epithelial cell differentiation and proliferation in the developing fetus. This knowledge will prove useful in the prevention and treatment of disease resulting from lung immaturity.