The Role of Plexin C1 in Scleroderma Related Interstitial Lung Disease

描述（由申请人提供）：系统性硬化症（SSc）或硬皮病是一种以皮肤和内脏纤维化影响皮肤和内脏为特征的破坏性疾病。与系统性硬化症相关的间质性肺病（SSc- ILD）是该人群死亡的主要原因，并与转化生长因子β 1 （TGF-¿1）的高反应性以及受影响个体血液和肺实质中纤维细胞的积累有关。尽管正在进行研究，但SSc-ILD中促进纤维细胞积累和疾病进展的机制仍不清楚。信号蛋白7a （Sema 7a）是一个高度保守的膜结合和分泌蛋白家族的一部分，在调节神经元和免疫系统功能中起重要作用。我们发现造血表达Sema 7a足以在TGF-¿1转基因过表达引起的小鼠肺纤维化模型中诱导纤维化和纤维细胞积累。Sema 7A通过两个已知的受体，刺激受体-1整合素亚基和抑制性受体丛蛋白C1发出信号。我们实验室最近对动物模型和原代人细胞的研究表明，¿-1整合素促进Sema 7a诱导的肺纤维化和纤维细胞积累。Plexin C1的作用尚不清楚，因此是本研究计划的重点。丛蛋白C1是一种大型跨膜糖蛋白，在免疫调节和肿瘤侵袭中起重要作用。我们之前的研究表明，丛状蛋白C1 mRNA在SSc-ILD患者的循环中升高，并且丛状蛋白C1在原代人细胞培养中抑制人纤维细胞的发育。我们的初步数据显示，在博莱霉素暴露的小鼠肺和TGF-¿1转基因肺特异性小鼠模型中，Plexin C1的表达均升高。然而，其对体内纤维细胞积累和纤维化的影响及其与ILD中纤维细胞发育的关系尚不清楚。在本研究中，我们提出在两种实验性肺纤维化小鼠模型中验证以下假设：1)SSc-ILD患者血液中纤维细胞前体丛蛋白C1增加，其功能是阻碍纤维细胞分化；2)丛蛋白C1缺失促进纤维细胞积聚和肺纤维化。荧光抗体细胞分选，原代人细胞培养和动物模型将用于测试我们的假设。如果成功，这些研究可能会对肺纤维化的免疫发病机制产生新的见解，有一天可能会使基于Plexin c1的治疗成为可能。

DESCRIPTION (provided by applicant): Systemic sclerosis (SSc) or scleroderma is a devastating disease characterized by cutaneous and visceral fibrosis affecting the skin and internal organs. Interstitial lung disease associated with systemic sclerosis (SSc- ILD) is a leading cause of death in this population and is associated with hyper-responsiveness to transforming growth factor beta 1 (TGF-¿1) and accumulation of fibrocytes in the blood and lung parenchyma of affected individuals. Despite ongoing efforts, the mechanisms promoting fibrocyte accumulation and disease progression in SSc-ILD remain unclear. Semaphorin 7a (Sema 7a) is part of a family of highly conserved membrane bound and secreted proteins that appear to be important in regulating neuronal and immune system functions. We have shown that hematopoietic expression of Sema 7a is sufficient to induce fibrosis and fibrocyte accumulation in a murine model of pulmonary fibrosis caused by transgenic overexpression of TGF-¿1. Sema 7A signals through two known receptors, the stimulatory receptor ¿-1 integrin subunit and the inhibitory receptor Plexin C1. Recent work by our lab in animal models and primary human cells has shown that ¿-1 integrin promotes Sema 7a induced pulmonary fibrosis and fibrocyte accumulation. The role of Plexin C1 is less well understood and thus is the focus of this research proposal. Plexin C1 is a large transmembrane glycoprotein important in immunomodulation and tumor invasion. We have previously shown that Plexin C1 mRNA is elevated in the circulation of patients with SSc-ILD, and that Plexin C1 suppresses human fibrocyte development in primary human cell cultures. Our preliminary data shows that Plexin C1 expression is increased in both the bleomycin exposed murine lung and the TGF-¿1 transgenic lung specific murine model. However, its effect on fibrocyte accumulation and fibrosis in vivo and its relationship to fibrocyte development in ILD remain undefined. In this study, we propose to test the hypotheses that 1) Plexin C1 is increased on fibrocyte precursors in the blood of SSc-ILD patients where it functions to impede fibrocyte differentiation and 2) Plexin C1 deletion promotes fibrocyte accumulation and lung fibrosis in two murine models of experimentally induced lung fibrosis. Fluorescent antibody cell sorting, primary human cell culture and animal modeling will be used to test our hypotheses. If successful, these studies could lead to novel insights into the immunopathogenesis of pulmonary fibrosis that might one day allow Plexin C1-based therapeutics.