Mechanisms Of Compensatory Lung Growth

描述(由申请人提供)：我们建议使用体内互补和 高海拔诱导机制的体外模型研究 代偿性肺生长。正常的出生后肺泡发育是由 由生长中的肋骨造成的机械肺劳损，并涉及激活 表皮生长因子(EGF)轴。有证据表明，低氧会增强 肺泡生长独立于机械肺应变，但可能会延缓肋骨 生长和延长出生后体细胞成熟的持续时间。在此基础上 想法，我们将确定慢性HA暴露对正常肺肋骨的影响 成熟过程中的相互作用，并检测EGF轴的调节作用 在HA诱导的肺生长中；这些问题从未被研究过。假设 是：1)在HA饲养的未成熟动物表现出最初的肺泡生长激增 通过减少肋骨向外回缩产生的肺泡间隔应力 CAGE，减弱正常发育信号。随后，肺净率 生长速度下降到受肋骨生长速度控制的水平，但以较高的速度增长 肺体积。2)由于延迟，HA的肺生长持续时间延长 骨痂愈合和/或骨痂后持续的牙槽骨生长 友联市。3)在海拔升高时抑制肋骨生长速度 肺大小的上限取决于动物的 年龄、海拔高度和暴露时间。4)激活EGF轴 低氧是介导HA诱导的肺泡生长的重要途径。断奶仔猪 豚鼠将在3,100米，3,800米，4,500米或低海拔(LA， 160米)，最多7个月；骨痂愈合和最大肺大小正常 在5个月前到达。在洛杉矶。单独的成年动物将暴露于HA，以 确定响应的成熟度依赖关系。静息潮气量和 将定期测量通风情况。最终，压力-体积曲线 测量肺和胸腔，然后取肺标本，并详细 腺泡结构的形态计量学分析，包括对肺的估计 弥散量、膜弥散量和肺毛细血管 音量。骨痂和肋骨的尺寸被检查。肺泡组织是 探讨EGF及其受体(EGF-R)的表达和EGF-R的活化。 低氧对EGF轴和上皮细胞生长的特异性影响 将使用人胎肺外植体和II型在体外分离成熟 有或无EGF类似物或特异性EGF-R的细胞培养 抑制剂。细胞生长是通过DNA和蛋白质合成来评估的 数量、体积和表面积；成熟度由主要表面活性物质评估 板层小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.