Structural Plasticity in Compensatory Lung Growth and Remodeling

项目摘要 在成年犬右肺切除术(PNX)中失去约58%的肺单位后，阈值以上组织 和微血管机械应力附加刺激代偿性肺生长和重塑(CLGR) 剩余的肺单位，导致肺泡组织毛细血管再生，并恢复约50%的丢失 功能。这种强大的再生模型模拟了破坏性肺部疾病的后果，允许 探索其余功能肺单位的适应机制，无论其是否有反应 造成破坏的特定病理。CLGR是塑料；补充生长促进剂，例如， 维甲酸或促红细胞生成素(EPO)进一步促进剩余肺叶的肺泡组织毛细血管形成，但 没有进一步增强肺功能，表明对外源性激素的反应存在结构-功能差异 刺激。这可能是因为机械诱导的肺生长也会增加氧化应激，而氧化应激在 转弯限制了生长和重塑；此外，新增加的组织毛细血管可能会扭曲腺泡的结构， 气体交换的基本单位，有损于功能的增强。 抗氧化可能是解决结构-功能差异的关键因素。氧化应激，旁分泌 促红细胞生成素信号通过其受体(EpoR)和循环中的抗氧化因子αKlotho都是持久的 在PNX术后CLGR期间升高。αKlotho作用于EpoR的上游，在体外增强EpoR的细胞保护， 提示αKlotho也可能通过EPO-EpoR轴增强血管生成刺激作用。我们建议 最佳的CLGR需要机械信号和细胞保护之间的平衡，以及并发αKlotho 抗氧化作用可能增强EPOR刺激的CLGR血管生成。 目标1将验证αKlotho和EpoR相互增强以缓解氧化应激的假设 在肺组织中，使用具有肺特异性条件性EPOR缺失±遗传性Klotho功能不全的小鼠，暴露于 氧化剂挑战赛。目标2将验证αKlotho增强EpoR介导的血管生成的假设 CLGR中的刺激和腺泡重塑，以促进将结构增长转化为功能获得。我们 将同时向PNX术后的年轻人和成年人运送含有EpoR和/或αKlotho基因的纳米颗粒 犬肺，以评估肺泡-毛细血管再生(活体CT和电子显微镜)，血管生成因子和 祖细胞分布、分层腺泡结构(MicroCT)和功能代偿。最后，我们会 犬单侧弹性蛋白酶联合(α、Klotho+EpoR)基因治疗PNX模型的建立及比较 以机械应激降低和炎性氧化应激升高为特征的肺气肿模型。 这些问题包括腺泡分层重塑、生长刺激与细胞保护的平衡以及克服 CLGR中的结构-功能差异尚未被检查；它们直接影响任何旨在进行的干预 在促进破坏性肺疾病中天然功能肺单位的修复和再生方面，例如， 肺气肿或纤维化，以及移植肺或生物工程肺。

Project Summary Following loss of ~58% of lung units by right pneumonectomy (PNX) in adult canines, supra-threshold tissue and microvascular mechanical stress additively stimulate compensatory lung growth and remodeling (CLGR) of remaining lung units, leading to regeneration of alveolar tissue-capillaries and restoring ~50% of the lost function. This robust model of regeneration mimics the consequences of destructive lung disease, allowing exploration of adaptive mechanisms in the remaining functioning lung units capable of responding, irrespective of the specific pathology causing destruction. CLGR is plastic; supplementation of growth promoters, e.g., retinoic acid or erythropoietin (Epo), further enhances alveolar tissue-capillary formation in remaining lobes but has not further augmented lung function, indicating a structure-function discrepancy in response to exogenous stimulation. This may be because mechanically induced lung growth also increases oxidative stress, which in turn limits growth and remodeling; also newly added tissue-capillaries may distort architecture of the acinus, the fundamental unit of gas exchange, and detract from functional enhancement. Anti-oxidation may be a key factor in resolving the structure-function discrepancy. Oxidative stress, paracrine Epo signaling via its receptor (EpoR), and the circulating anti-oxidative factor αKlotho, are all persistently elevated during post-PNX CLGR. αKlotho acts upstream of EpoR to enhance EpoR cytoprotection in vitro, suggesting that αKlotho may also enhance angiogenic stimulation via the Epo-EpoR axis. We propose that optimal CLGR requires a balance between mechanical signals and cytoprotection, and concurrent αKlotho anti-oxidation may enhance EpoR-stimulated angiogenesis in CLGR. Aim 1 will test the hypothesis that αKlotho and EpoR mutually enhance each other to relieve oxidative stress in the lung, using mice with lung-specific conditional EpoR deletion ± genetic Klotho insufficiency, exposed to oxidant challenge. Aim 2 will test the hypothesis that αKlotho augments EpoR-mediated angiogenic stimulation and acinar remodeling in CLGR to facilitate translation of structural growth into functional gain. We will concurrently deliver nanoparticles containing EpoR and/or αKlotho cDNA to post-PNX young and adult canine lungs, to assess alveolar-capillary regrowth (in vivo CT and electron microscopy), angiogenic factor and progenitor cell distribution, stratified acinar architecture (microCT) and functional compensation. Finally, we will develop and compare (αKlotho+EpoR) cDNA treatment in PNX model with a canine unilateral elastase emphysema model characterized by reduced mechanical stress and elevated inflammatory oxidative stress. These issues of stratified acinar remodeling, growth-stimulation vs. cytoprotection balance, and overcoming structure-function discrepancy in CLGR, have not been examined; they directly impact any intervention aimed at promoting repair and regeneration of the native functioning lung units in destructive lung disease, e.g., emphysema or fibrosis as well as in transplanted or bioengineered lungs.