Regulation of Fibroblast Phenotype in Lung Fibrosis

描述（由申请人提供）：成纤维细胞介导纤维化的异常组织修复特征，但其在纤维化肺中的来源尚不清楚。有证据表明，现有的成纤维细胞发生改变，成纤维细胞前体内流，以及其他细胞类型的转分化。肺成纤维细胞的许多成纤维特性受Thy-1的表达调控，Thy-1是一种外膜小叶表面蛋白，通过脂质筏结构域的信号改变调节细胞粘附和迁移。他们-1表达的缺失与致癌转化和非锚定生长有关。我们的实验室已经证实，Thy-1的缺失与肺成纤维细胞对纤维化生长因子的增殖反应增强和细胞因子信号传导的改变有关，而Thy-1的存在抑制肺成纤维细胞激活潜在转化生长因子- β (TGF-)的能力，TGF-是一种关键的纤维化介质；ii)表达-平滑肌肌动蛋白。Thy-1 -/-小鼠的肺纤维化重塑更为严重，特发性肺纤维化（IPF）的成纤维细胞主要是Thy-1（-）。炎症信号导致Thy-1的脱落，潜在TGF-(的激活，成纤维细胞转化为肌成纤维细胞。这些发现支持了一种假设，即成纤维细胞Thy-1表达的缺失与肺中功能失调的促纤维化伤口愈合反应有关。初步数据表明，除了脱落外，通过启动子超甲基化进行表观遗传调控是抑制Thy-1表达的重要机制。此外，大多数肺纤维细胞（骨髓来源的细胞，可分化为肌成纤维细胞）是Thy-1（-）。结合我们之前的工作，这些发现表明，无论是通过脱落、转录调节还是y-1（-）细胞的募集，y-1表达的调节可能是纤维化的一个新的治疗靶点。因此，拟议研究的目的是：1。在纤维发生进化的背景下，明确Thy-1脱落的机制和后果；2. 确定Thy-1表达的转录和表观遗传调控在纤维形成过程中的作用；和3。确定Thy-1表达与纤维细胞和其他骨髓源性细胞流入肺纤维化之间的关系。每个目标都将通过使用体外研究、相关动物模型和具有良好特征的人类样本的垂直整合方法来解决。

DESCRIPTION (provided by applicant): Fibroblasts mediate the abnormal tissue repair characteristic of fibrosis, but their origin in fibrotic lung remains unclear. Evidence exists for alteration of existing fibroblasts, influx of fibroblast precursors, and transdifferentiation of other cell types. Many of the fibrogenic characteristics of lung fibroblasts are regulated by expression of Thy-1, an outer membrane leaflet surface protein which modulates cell adhesion and migration via signaling alterations in lipid raft domains. Loss of Thy-1 expression is associated with oncogenic transformation and anchorage-independent growth. Our laboratory has established that absence of Thy-1 correlates with enhanced proliferative responses of lung fibroblasts to fibrogenic growth factors and altered cytokine signaling, whereas presence of Thy-1 inhibits the ability of lung fibroblasts to i) activate latent transforming growth factor-beta (TGF-(), a key fibrogenic mediator; and to ii) express alpha-smooth muscle actin. Thy-1 -/- mice develop more severe fibrotic remodeling of the lung, and fibroblasts in fibroblastic foci of idiopathic pulmonary fibrosis (IPF) are predominantly Thy-1 (-). Inflammatory signaling causes shedding of Thy-1, activation of latent TGF-(, and transformation of fibroblasts into myofibroblasts. These findings support the hypothesis that loss of fibroblast Thy-1 expression is associated with a dysfunctional, profibrotic wound healing response in the lung. Preliminary data indicate that in addition to shedding, epigenetic regulation through promoter hypermethylation is an important mechanism for inhibition of Thy-1 expression. Furthermore, the majority of lung fibrocytes (bone-marrow derived cells which differentiate into myofibroblasts) are Thy-1 (-). Taken together with our previous work, these findings suggest that the regulation of Thy-1 expression, whether by shedding, transcriptional regulation, or recruitment of Thy-1 (-) cells, may present a novel therapeutic target for fibrosis. Thus the aims of the proposed studies are to: 1. define mechanisms for and consequences of Thy-1 shedding in the context of evolving fibrogenesis; 2. determine the roles of transcriptional and epigenetic regulation of Thy-1 expression in evolving fibrogenesis; and 3. define the relationship between Thy-1 expression and influx of fibrocytes and other bone marrow-derived cells into lungs undergoing fibrogenesis. Each of these aims will be addressed in a vertically-integrated approach using in vitro studies, relevant animal models and well-characterized human samples.