Mechanisms of Lung Development and Injury

描述（由申请人提供）：TGF β作为发育和疾病过程中的信号分子的重要性怎么强调都不过分。鉴于信号通路的复杂性，TGF β生物活性具有广泛的多功能性和选择性并不奇怪。沿着该途径，受体的选择性利用是一个潜在的机制 for generating生成versatile多功能性.肺中胚层和上皮中单个受体的体内作用一直是我们组的主要兴趣。在单独的研究中，我们使用上皮或中胚层特异性cre小鼠来抑制Alk 5或T-R2，并以高度系统的方式检查其后果。因此，我们现在对每个受体在TGF β功能中的作用有了深入的了解，尽管有限。在本项目的最后一个周期中，除了完成最初的特定目标外，我们还通过遗传和分子方法收集了Alk 5在肺中胚层中的特定作用的初步数据。这些初步的发现共同指向了一个统一的潜在主题：Alk 5介导的TGF β信号传导对各种肺室中的祖细胞/干细胞生物学至关重要。在不存在中胚层Alk 5功能的情况下观察到的简化变化是，1）气管中基底细胞群减少，2）气管中软骨形成严重异常，和3）肺实质中脂肪成纤维细胞与肌成纤维细胞之间的平衡的主要转变。表型是完全渗透的，但潜在的机制仍然未知。阐明这些机制是本应用程序的目标。假设：中胚层Alk 5介导的TGF β信号控制肺中祖细胞/干细胞的出现/维持或分化。我们将通过以下具体目标来测试该假设的有效性：具体目标1：确定肺中胚层中Alk 5失活耗尽基底细胞的机制。具体目标2：确定Alk 5在气管形态发生中的作用。具体目标3：确定Alk 5调节的脂肪成纤维细胞与肌成纤维细胞分化中的潜在表型可塑性。具体目标4：确定肺纤维化是否可以被挽救或遏制（即，限制）通过Alk 5的失活和活化的肌成纤维细胞向脂肪成纤维细胞的转分化。通过这项工作的完成，我们希望能够揭示Alk 5介导的TGF β信号在气管和肺实质中关键上皮和间充质祖细胞/干细胞群体的个体发育中所起的特定作用。本文提出的研究还提供了独特的机会，从一个新的角度研究Alk 5在小鼠模型肺纤维化发病机制中的特定作用。

DESCRIPTION (provided by applicant): The significance of TGF� as a signaling molecule during development & disease can be hardly over-stated. Given the complexity of the signaling pathway, it is not surprising that there is a wide spectrum of versatility and selectivity in TGF� biological activity. Along the pathway, selective utilization of receptors is a potential mechanism for generating versatility. The in vivo role of the individual receptors in the lung mesoderm and epithelium has been a major interest in our group. In separate studies, we have used epithelial- or mesodermal-specific cre mice to inactivate Alk5 or T�R2, and examined the consequences in a highly systematic fashion. As a consequence, we now have an insight, however limited, into the role of each receptor in TGF� function. In the last cycle of this project, in addition to completing the original specific aims, we also collected preliminary data on the specific role of Alk5 in the lung mesoderm by genetic & molecular approaches. The preliminary findings collectively point to a unified underlying theme; that Alk5-mediated TGF� signaling is critical to progenitor/stem cell biology in various lung compartments. The simplified observed changes in the absence of mesodermal Alk5 function are, 1) reduced basal cell population in the trachea, 2) profoundly abnormal cartilage formation in the trachea, and 3) a major shift in the balance between lipofibroblasts versus myofibroblasts in the lung parenchyma. The phenotypes are fully penetrant, but the underlying mechanisms remain unknown. Elucidating these mechanisms is the goal of this application. Hypothesis: Mesodermal Alk5-mediated TGF� signaling controls the emergence/maintenance or differentiation of progenitor/stem cells in the lung. We will test the validity of this hypothesis by the following specific aims: Specific Aim 1: To Determine The Mechanisms by Which Inactivation of Alk5 in The Pulmonary Mesoderm Depletes Basal Cells. Specific Aim 2: To Determine The Role of Alk5 in Tracheal Morphogenesis. Specific Aim 3: To Determine Potential Phenotype Plasticity in Alk5-Regulated Lipofibroblast versus Myofibroblast Differentiation. Specific Aim 4: To Determine Whether Pulmonary Fibrosis Can be Rescued or Contained (i.e., Limited) by Inactivation of Alk5 & Trans-Differentiation of Activated Myofibroblasts to Lipofibroblasts. By completion of this work, we hope to have unraveled the specific role played by Alk5-mediated TGF� signaling in the ontogeny of key epithelial and mesenchymal progenitor/stem cell populations in the trachea and the lung parenchyma. The studies proposed here also offer the unique opportunity of examining, from a novel perspective the specific role of Alk5 in pathogenesis of pulmonary fibrosis in a mouse model.