RETINOIC ACID EFFECT ON POSTPNEUMONECTOMY LUNG GROWTH

我们以前的研究通过生理学和形态计量学的方法表明，在成年犬肺切除(PNX)后的剩余肺中出现了新的肺泡和腺泡状气道生长。左侧PNX(切除45%)后未出现再生性肺生长；生理补偿是通过补充现有的毛细血管储备进行的；右侧PNX(切除55%)后功能显著增长，但不完全，运动能力、气体交换和机械功能的异常持续存在。当右侧PNX术后通过充气假体阻止纵隔移位时，再生性肺生长仍然发生，证明肺伸展不是唯一的生长信号。在诱发肺气肿的大鼠中，维甲酸也可以在没有施加拉伸的情况下促进肺生长；然而，在大鼠的一生中，躯体生长仍然存在。对维甲酸的结构反应与功能无关，也没有在成年后停止生长的大型成熟动物中进行测量。我们将使用我们的成年犬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，当肺生长不再发生时，维甲酸将诱导肺泡和腺泡的气道生长。2)再生生长不完全的肺切除55%后，维甲酸可显著促进再生生长。3)生长诱导型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在PNX后诱导表皮生长因子(EGF)和/或其受体(EGFR)和/或其受体(EGFR)，促进肺生长。在左侧PNX、右侧PNX或假手术后(6个实验组)，给予全反式维甲酸或其稀释液，每周5天，连续3个月。每隔一段时间。测量肺力学、肺弥散能力、膜弥散能力、毛细血管容量和肺组织体积，并进行高分辨率CT扫描，测量活体肺组织体积和气道内径。在3个月或6个月时取肺，对肺泡间隔、腺泡通道的大小和数量、肺泡和毛细血管表面积以及形态计量扩散能力的结构变化进行形态定量测定。EGF和EGFR的解剖分布和体内表达将通过免疫组织化学、免疫金标记法、免疫印迹和RNA印迹来确定。这些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作用，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.