RETINOIC ACID EFFECT ON POSTPNEUMONECTOMY LUNG GROWTH

我们之前的研究通过生理学和形态计量学方法表明，成年犬全肺切除术（PNX）后，在剩余的肺中会出现新的肺泡和腺泡气道生长。左侧PNX（45%切除）后未出现再生肺生长；生理代偿是通过招募现有的毛细血管储备。右侧PNX（切除55%）后出现了显著的生长，但不完全，因此运动能力、气体交换和机械功能的异常持续存在。在右侧PNX术后，当纵隔移位被充气假体阻止时，再生肺生长仍然发生，证明肺伸展不是唯一的生长信号。在大鼠肺气肿诱导后，维甲酸也能在不施加拉伸的情况下促进肺生长；然而，在大鼠的一生中，躯体生长持续存在。对维甲酸的结构反应与功能没有关联，也没有在成年后停止生长的大型成熟动物中进行测量。我们将通过我们的成年狗模型来探索维甲酸对pnx后肺生长的体内影响和作用机制。假设：1)肺切除45%后肺生长失败，维甲酸会诱导肺泡和腺泡气道生长。2)切除55%再生生长不完全的肺后，维甲酸能显著促进肺的生长。3)促生长维甲酸能改善气体交换和机械功能。4)维甲酸的作用机制之一是诱导PNX后的表皮生长因子（EGF）和/或其受体（EGFR）和/或其受体（EGFR），促进肺生长。在左PNX、右PNX或SHAM手术后给予全反式维甲酸或其稀释剂，每周5天，连续3个月（6个实验组）。在间隔,。测量肺力学、肺弥漫性、膜弥漫性、毛细血管血容量和肺组织体积，并获得高分辨率CT扫描，评估体内肺组织体积和气道尺寸。在3个月或6个月时取肺，以形态学量化肺泡间隔的结构变化、腺泡气道的尺寸和数量、肺泡和毛细血管表面积以及形态量化弥散能力。通过免疫组织化学、免疫金标、免疫印迹和RNA印迹检测EGF和EGFR的解剖分布和体内表达。研究结果将确定维甲酸对大型成年哺乳动物成熟肺再生生长的结构和生理影响，并确定维甲酸对EGF和EGFR的体内影响。

Our previous studies have shown by physiologic and morphometric methods that new alveolar and acinar airway growth occurs in the remaining lung after pneumonectomy (PNX) in adult dogs. Regenerative lung growth did not occur after left PNX (45% resection); physiologic compensation was by recruitment of existing capillary reserves functionally significant growth occurred after right PNX (55% resection) but was incomplete, so that abnormalities in exercise capacity, gas exchange and mechanical function persisted. Regenerative lung growth still occurred when mediastinal shift was prevented by an inflatable prosthesis after right PNX, proving that lung stretch was not the only growth signal. In rats after induction of emphysema, retinoic acid can also augment lung growth in the absence of applied stretch; however, somatic growth persists in rats throughout life. The structural response to retinoic acid has not been correlated with function, nor measured in large mature animals that stop growing as adults. We will explore in vivo effects and mechanisms of action of retinoic acid on post-PNX lung growth using our adult dog model. Hypotheses are: 1) After 45% lung resection where lung growth failed to occur, retinoic acid will induce alveolar and acinar airway growth. 2) After 55% lung resection where incomplete regenerative growth occurred, retinoic acid will significantly augment growth. 3) Growth induced retinoic acid will improve gas exchange and mechanical function. 4) One mechanism of action by retinoic acid will be induction of epidermal growth factor (EGF) and/or its receptor (EGFR) and/or its receptor (EGFR) after PNX, enhancing lung growth. All-trans retinoic acid or its diluent will be administered 5 days/week for 3 months after left PNX, right PNX or SHAM surgery (6 experimental groups). At intervals,. Lung mechanics, lung diffusing capacity, membrane diffusing capacity, capillary blood volume and lung tissue volume will be measured and high resolution CT scan obtained to asess in vivo lung tissue volume and airway dimensions. Lungs are harvested at 3 or 6 months for morphometric quantification of structural changes in alveolar septa, dimensions and number of acinar airways, alveolar and capillary surface areas, and morphometric diffusing capacity. Anatomic distribution and in vivo expression of EGF and EGFR will be determined by immunohistochemistry, immunogold labeling, immunoblots and RNA blots. Results will define both structural and physiological effects of retinoic acid on regenerative growth in the mature lung of a large fully grown mammal, and determine the in vivo effect of retinoic acid on EGF and EGFR.