Mechanisms Of Compensatory Lung Growth

描述（由申请人提供）：我们提出在体内使用互补的， 体外模型，以探索高海拔（HA）诱导的 代偿性肺生长正常的出生后肺泡生长是由 由不断增长的胸腔造成的机械性肺张力，并涉及激活 表皮生长因子（EGF）轴。有证据表明缺氧会增强 肺泡生长不依赖于机械性肺应变，但可能阻碍胸腔 生长和延长出生后躯体成熟的持续时间。基于此 我们将定义慢性HA暴露对正常肺-肋骨架的影响 成熟过程中的相互作用，并检查EGF轴的调节作用 HA诱导的肺生长;这些问题从未被研究过。假设 是：1）在HA中饲养的未成熟动物显示初始肺泡生长突增 通过减少肋骨向外回缩产生的肺泡间隔应力 笼，减弱正常发育信号。随后，肺的净比率 生长下降到由肋骨笼的生长速率所控制的水平，但在较高的生长速率下， 肺容量2)在HA，肺生长的持续时间延长， 骨骺愈合和/或骨骺后持续的牙槽生长 联盟3)在海拔升高的情况下，抑制胸腔的生长速度， 以取决于动物的方式可实现的肺尺寸上限 年龄、海拔高度和暴露时间。4)EGF轴的激活 缺氧是介导HA诱导的肺泡生长的重要途径。断奶 豚鼠将在3，100 m、3，800 m、4，500 m或低海拔（LA， 160米），最多7个月;骨骺愈合和最大肺大小正常 到达5个月。在洛杉矶单独的成年动物将暴露于HA， 确定响应的成熟度依赖性。静息潮气量和 并会定期量度空气流通量。最后，压力-容积曲线 测量肺和胸腔，然后进行肺取样并详细描述 腺泡结构的形态测量分析，包括肺的估计 弥散量、膜弥散量与肺毛细血管血 音量.检查骨骺和肋骨尺寸。肺泡组织是 探讨EGF及其受体（EGF-R）的表达和EGF-R的活化。 缺氧对EGF轴和上皮细胞生长的特异性影响， 成熟将使用人胎肺外植体和II型 在EGF类似物或特异性EGF-R存在或不存在下的细胞培养物 抑制剂的细胞生长从DNA和蛋白质合成、细胞生长和细胞增殖来评估。 数量、体积和表面积;从主要表面活性剂评估成熟度 板层体的蛋白质含量和体积。

DESCRIPTION (provided by applicant): We propose using complementary in vivo and in vitro models to explore the mechanisms underlying high altitude (HA)-induced compensatory lung growth. Normal postnatal alveolar growth is driven by mechanical lung strain imposed by the growing rib cage and involves activation of epidermal growth factor (EGF) axis. There is evidence that hypoxia enhances alveolar growth independent of mechanical lung strain, but may retard rib cage growth and prolong the duration of postnatal somatic maturation. Based on this idea, we will define the effect of chronic HA exposure on normal lung-rib cage interaction during maturation, and examine the regulatory role of the EGF axis in HA-induced lung growth; these issues have never been examined. Hypotheses are: 1) Immature animals raised at HA show an initial alveolar growth spurt that, by reducing alveolar septal stress from the outward recoil of the rib cage, attenuates normal developmental signals. Subsequently, net rate of lung growth declines to that governed by growth rate of the rib cage but at a higher lung volume. 2) Duration of lung growth is prolonged at HA, due to delayed skeletal epiphyseal union and/or continued alveolar growth after epiphyseal union. 3) Inhibition of rib cage growth rate at increasing altitudes sets the upper limit of lung dimensions achievable in a manner dependent on the animal's age, the altitude and the duration of exposure. 4) Activation of EGF axis by hypoxia is an important pathway mediating HA-induced alveolar growth. Weanling guinea pigs will be raised at 3,l00 m, 3,800 m, 4,500 m or at low altitude (LA, 160 m) for up to 7 mo.; epiphyseal union and maximum lung size are normally reached by 5 mo. at LA. Separate adult animals will be exposed to HA to determine the maturity-dependence of response. Resting tidal volume and ventilation will be measured regularly. Terminally, pressure-volume curves of lung and thorax are measured followed by lung sampling and detailed morphometric analysis of acinar structures, including estimates of lung diffusing capacity, membrane diffusing capacity and pulmonary capillary blood volume. Bony epiphyses and rib dimensions are examined. Alveolar tissues are probed for expressions of EGF, its receptor (EGF-R) and EGF-R activation. Specific effects of hypoxia on the EGF axis and epithelial cell growth and maturation will be isolated in vitro using human fetal lung explant and type II cell cultures in the presence or absence of EGF analogs or specific EGF-R inhibitors. Cell growth is assessed from DNA and protein synthesis, cell number, volume and surface area; maturation is assessed from major surfactant protein content and volume of lamellar bodies.