Regulation of Fibroblast Phenotype in Lung Fibrosis

描述（由申请方提供）：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起源尚不清楚。存在现有成纤维细胞改变、成纤维细胞前体流入和其他细胞类型转分化的证据。肺成纤维细胞的许多纤维化特征由Thy-1的表达调节，Thy-1是一种外膜小叶表面蛋白，其通过脂筏结构域中的信号改变来调节细胞粘附和迁移。Thy-1表达的缺失与致癌转化和锚定非依赖性生长相关。我们的实验室已经确定，Thy-1的缺乏与肺成纤维细胞对纤维化生长因子和改变的细胞因子信号传导的增强的增殖反应相关，而Thy-1的存在抑制肺成纤维细胞i）激活潜在转化生长因子-β（TGF-β）（一种关键的纤维化介质）和ii）表达α-平滑肌肌动蛋白的能力。Thy-1 -/-小鼠发生更严重的肺纤维化重塑，特发性肺纤维化（IPF）成纤维细胞灶中的成纤维细胞主要是Thy-1（-）。炎症信号传导引起Thy-1的脱落、潜在TGF-β的活化和成纤维细胞转化为肌成纤维细胞。这些发现支持了这样的假设，即成纤维细胞Thy-1表达的丧失与肺部功能失调、促纤维化伤口愈合反应有关。初步数据表明，除了脱落，通过启动子超甲基化的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（分化成肌成纤维细胞的骨髓来源的细胞）是Thy-1（-）。结合我们以前的工作，这些发现表明，无论是通过脱落、转录调节还是Thy-1（-）细胞的募集来调节Thy-1表达，都可能为纤维化提供新的治疗靶点。因此，拟议的研究的目的是：1。定义在演变的纤维发生的背景下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节在演变纤维发生中的作用;和3.确定Thy-1表达与纤维细胞和其他骨髓来源的细胞流入发生纤维化的肺之间的关系。将使用体外研究、相关动物模型和充分表征的人体样本，以垂直整合的方法解决这些目标中的每一个。

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.