SURFACTANT PROTEIN REGULATION IN DEVELOPING LUNG

几种肺部病理，特别是呼吸窘迫综合征(RDS) 早产儿，与胎肺发育不成熟有关。RDS是 无可争议地与肺表面活性物质缺乏有关，这是 一种磷脂和四种肺特异性载脂蛋白的复杂混合物 已被指定为SP-A、SP-B、SP-C和SP-D。肺表面活性物质， 由肺泡II型细胞合成和分泌，其功能通过 降低气液界面的表面张力，从而防止 低肺容量时肺泡塌陷。疏水蛋白SP-B和 SP-C在表面活性剂的表面活性中起重要作用， 而SP-A似乎更多地参与了表面活性物质的调节 肺泡的新陈代谢。对SP-D的作用还没有完全了解， 尽管它似乎参与了肺部的非免疫宿主防御。 鉴于它们对正常表面活性物质功能和新陈代谢的重要性，许多 人们在研究SP-A、SP-B和SP-B的调节方面做了大量的工作。 C.最近的一个重要观察是SP-A、SP-B的表达 与以前相比，肺发育中SP-C开始的时间要早得多 想着。上皮-间充质相互作用，到目前为止 被证明是肺内正常的分支形态发生所必需的， 似乎也参与了指定分化的远端 早期肺上皮细胞的表型，如 早期胎肺间充质对胎儿期气管重构能力的研究 上皮细胞表达肺泡II型细胞表型。我们有 开发了几个系统，我们将使用它们来调查 上皮-间充质相互作用。为了确定的范围 上皮细胞在组织重组中的命运，我们将使用 远端肺和气管上皮细胞分化的特征 胎肺和胎气管上皮细胞对三氯甲烷影响的反应 肺和气管间充质均可见。我们已经证明了归纳式 肺间充质对气管上皮细胞的影响 可扩散分子(S)。我们将扩大这些研究以确定规模 在这些因素中，它们的见效速度有多快，它们是否必须 持续存在以维持远端肺上皮的发育。我们 发展了一个复杂的文化系统，在这个系统中，我们能够 诱导肺远端特异性标志物SP-C的表达 上皮，在胎儿气管上皮细胞中。我们会彻底 描述一下这个系统的特点。然后我们将确定关键组件 在这种介质中，测试额外的生长因子和激素，并开发出 一种用于这种诱导的明确的细胞外基质。这个 黄曲霉毒素诱导气管上皮一种新的细胞表型的表达 肺间充质细胞伴随着新基因的表达。使用 差异显示反转录聚合酶链法技术 反应，我们将鉴定和分离其中的一些基因。这将提供 研究上皮细胞机制的新思路和新试剂 胎肺的测定和分化。在完成时 我们预计这笔赠款将极大地增加我们对 调节远端肺上皮细胞分化的因子和 发育中的胎儿中的增殖。这些知识将被证明是有用的 肺不成熟病肺不成熟所致疾病的防治

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.