Regulation of distal lung epithelial regeneration by microRNA-Hippo pathway

 描述(由申请人提供)：呼吸道上皮对损伤的再生能力对于肺从环境损害中恢复和防止呼吸道疾病的发展至关重要。因此，重要的是要了解上皮再生是如何调节的，以潜在地促进恢复和减少肺损伤。MicroRNAs和Hippo途径已经成为器官发育和成人组织修复和再生的关键调节器。我们最近证明，microRNA簇miR302-367在发育中的肺和心脏促进高水平的细胞增殖，但分化较低的表型。MiR302-367在成人心脏过表达可促进心肌细胞增殖和心脏再生。MiR302-367的部分功能是通过靶向河马信号通路的几个组件来发挥作用，河马信号通路负向调节YAP和Taz的活性。YAP和Taz是关键的转录共激活因子，可以驱动其下游靶标的表达，从而促进细胞增殖和抑制细胞死亡。我们探讨了细菌性肺炎致成人肺损伤后肺泡上皮修复和再生的调控机制。细菌性肺炎仍然是儿童和老年人死亡的主要原因。虽然广泛的研究集中在细菌毒力和宿主免疫反应上，但对细菌性肺炎引起的肺损伤类型及其随后的再生和修复知之甚少。我们发现感染肺炎链球菌(Sp)的小鼠肺实质有明显的损伤，随后可见修复和再生。在Sp诱导的损伤反应中，肺泡中预先存在的表达SPC的II型上皮细胞作为上皮祖细胞发挥作用。它们在受影响的肺泡区增殖和分化I型细胞。值得注意的是，miR302-367和YAP/Taz靶标富含半胱氨酸的蛋白61在远端肺上皮细胞中的表达增加。在表达SPC的细胞中过表达miRNA302-367可促进肺泡上皮的修复和再生。小分子miR302-模拟物在细菌性肺炎小鼠中的应用促进了远端呼吸道上皮的再生，提高了小鼠的恢复和存活。在这些初步研究的基础上，我们假设miR302-367和Hippo途径调控肺上皮细胞基因转录，促进上皮修复和再生。靶向microRNA-Hippo通路可能是促进细菌性肺炎损伤恢复的一种新的治疗方法。本项目旨在通过(1)在小鼠肺泡上皮祖细胞中调节miR302-367和YAP/Taz的表达，以及(2)通过确定miR302-367和Hippo信号在控制肺泡上皮修复和再生的基因网络中的相互作用，以及(3)通过研究miR-模拟物和抑制河马信号通路在细菌诱导的损伤恢复中的治疗潜力，来确定miR302-367和Hippo信号在远端呼吸道上皮修复和再生中的机制作用。

 DESCRIPTION (provided by applicant): The regenerative capacity of airway epithelium in response to injury is critical for lung recovery from environmental insults and preventing the progression of respiratory diseases. So it is important to understand how epithelial regeneration is regulated to potentially enhance recovery and reduce lung injury. MicroRNAs and Hippo pathway have emerged as key modulators of both organ development and adult tissue repair and regeneration. We recently demonstrated that the microRNA cluster, miR302-367, promotes a high level of cell proliferation but less differentiated phenotype in the developing lung and heart. Overexpression of miR302-367 in adult heart promotes cardiomyocyte proliferation and cardiac regeneration. MiR302-367 functions, in part, by targeting several components of the Hippo signaling pathway, which negatively regulates the activity of Yap and Taz. Yap and Taz are key transcriptional co-activators that drive the expression of their downstream targets to promote cell proliferation and inhibit cell death. We have explored the mechanisms that regulate alveolar epithelial repair and regeneration in adult lung following injury induced by bacterial pneumonia. Bacterial pneumonia remains a leading cause of mortality in children and the elderly. While extensive studies have focused on bacterial virulence and host immune responses, little is known about the type lung injury induced by bacterial pneumonia and their subsequent regeneration and repair. We show that mice with infection of Streptococcus pneumoniae (Sp) have markedly injuries in the lung parenchyma followed by visible repair and regeneration. In response to Sp-induced injury, pre-existing SPC-expressing epithelial type II cells in the alveolus function as epithelial progenitor cells. They proliferate and differentiate ito type I cell at the sites of affected alveolar region. Notably, the expression of miR302-367 and Yap/Taz target, Cysteine rich protein 61, is increased in distal lung epithelium. Overexpression of miRNA302-367 in SPC- expressing cells enhanced alveolar epithelial repair and regeneration. Administration of small molecule miR302-mimics in mice with bacterial pneumonia promoted distal airway epithelial regeneration, enhanced mouse recovery and survival. Based on these preliminary studies, we hypothesize that miR302-367 and Hippo pathway regulate lung epithelial gene transcription to promote epithelial repair and regeneration. Targeting microRNA-Hippo pathway may represent a novel therapeutic approach to promote recovery from injury induced by bacterial pneumonia. This project aims to define the mechanistic role of miR302-367 and Hippo signaling in distal airway epithelial repair and regeneration by (1) modulating miR302-367 and Yap/Taz expression in alveolar epithelial progenitor cells in murine model system, and (2) by defining the interactions of miR302-367 and Hippo signaling in governing gene network that control alveolar epithelial repair and regeneration, and (3) by examining the therapeutic potentials of miR-mimics and inhibiting Hippo pathway in recovery from bacteria-induced injury.