Fibroblast control of TGF-beta activation by Thy-1 and lung fibrosis

描述（由申请人提供）：特发性肺纤维化是一种罕见的进行性致命疾病，目前尚无有效的治疗方法。由成纤维性肺成纤维细胞亚群引起的伤口愈合失调导致特发性肺纤维化。TGF-（）是伤口愈合反应的关键调节因子，其作用对纤维化进展至关重要。TGF-(必须从潜伏状态激活才能影响这些反应。我们的数据表明，成纤维细胞亚群的差异特征之一是在损伤反应中激活潜在TGF-（）的能力。肺成纤维细胞上gpi锚定蛋白Thy-1的存在限制了TGF-（）的激活能力。这些数据表明，Thy-1是一种限制TGF-(激活的生物反应调节剂。在博来霉素刺激下，Thy-1（-）成纤维细胞比Thy-1（+）细胞表达更高水平的潜伏TGF-结合蛋白4 (LTBP-4)，这与LTBP-4亚型小鼠肺中TGF-(活性增加一致。Thy-1 (-) LTBP-4亚型肺成纤维细胞在对博莱霉素的应答中未能激活潜伏的TGF-(，提示LTBP-4是Thy-1（-）细胞应答能力所必需的。由于TGF-活性对肺纤维化的成纤维性进展至关重要，因此间质成纤维细胞激活潜伏TGF-的能力可能是肺损伤良性消退或纤维化并发症发生的关键决定因素。我们假设肺成纤维细胞在刺激下激活潜在TGF-的能力对肺损伤后的纤维化进展至关重要。因此，TGF-激活减弱的成纤维细胞有利于有限的伤口愈合反应，而对损伤表现出强烈TGF-激活的成纤维细胞有利于成纤维反应。本提案的总体目标是确定肺成纤维细胞调节TGF-(激活如何影响肺纤维化的进展。我们将采用一种新的策略，利用一种改良的腺病毒和成纤维细胞特异性启动子在体内驱动Thy-1和LTBP-4的成纤维细胞特异性转基因表达，在博莱霉素诱导的肺纤维化小鼠模型中测试这些蛋白的成纤维细胞特异性表达对成纤维细胞纤维化进展的影响。我们提出以下目的：具体目的1：验证成纤维细胞特异性过表达Thy-1通过限制TGF-（）激活来保护博莱霉素诱导的肺纤维化的假设，并确定组成活性TGF-（）的表达是否消除了Thy-1过表达的潜在保护作用；特异性目的2：在体外验证成纤维细胞表达LTBP-4是激活潜伏TGF-(的必要条件，在体内验证LTBP-4是否能消除Thy-1的保护作用。这些研究将为肺成纤维细胞亚群如何决定纤维化进展提供新的见解，并有可能确定治疗特发性肺纤维化的新治疗方法。

DESCRIPTION (provided by applicant): Idiopathic pulmonary fibrosis is a rare and progressive, fatal disease for which there is no effective treatment. Dysregulated wound healing by subsets of fibrogenic lung fibroblasts leads to fibrosis in idiopathic pulmonary fibrosis. TGF-( is a key regulator of wound healing responses and its action is critical for fibrogenic progression. TGF-( must be activated from its latent state to affect these responses. Our data show that one of the differential characteristics of fibroblast subsets is the capacity to activate latent TGF-( in response to injury. The presence of the GPI-anchored protein, Thy-1, on lung fibroblasts limits the ability to activate TGF-(. These data suggest that Thy-1 is a biological response modifier which limits TGF-( activation. Thy-1 (-) fibroblasts express higher levels of the latent TGF-( binding protein 4 (LTBP-4) when stimulated with bleomycin than do Thy-1 (+) cells, consistent with the increased TGF-( activity in the lungs of LTBP-4 hypomorphic mice. Thy-1 (-) LTBP-4 hypomorphic lung fibroblasts fail to activate latent TGF-( in response to bleomycin, suggesting that LTBP-4 is necessary for the ability of Thy-1 (-) cells to respond. Since TGF-( activity is critical to the fibrogenic progression of pulmonary fibrosis, the capacity of interstitial fibroblasts to activate latent TGF-( could be a key determinant of either benign resolution of lung injury or the development of fibrotic complications. We hypothesize that the ability of pulmonary fibroblasts to activate latent TGF-( in response to stimulation is critical to fibrogenic progression following lung injury. Thus fibroblasts with attenuated TGF-( activation would favor limited wound healing responses, whereas, fibroblasts that exhibit robust TGF-( activation in response to injury would favor fibrogenic responses. The overall goal of this proposal is to determine how modulating TGF-( activation by lung fibroblasts affects progression of pulmonary fibrosis. We will use a novel strategy that employs a modified adenovirus and a fibroblast-specific promoter to drive fibroblast specific transgene expression of Thy-1 and LTBP-4 in vivo to test the effects of fibroblast-specific expression of these proteins on fibrogenic progression in a mouse model of bleomycin-induced pulmonary fibrosis. We propose the following aims: Specific Aim 1: To test the hypothesis that fibroblast-specific over-expression of Thy-1 protects from bleomycin-induced pulmonary fibrosis by limiting TGF-( activation and to determine if expression of constitutively active TGF-( abrogates the potential protective effects of Thy-1 overexpression; Specific Aim 2: To test the hypothesis that fibroblast expression of LTBP-4 is necessary for activation of latent TGF-( in vitro and whether LTBP-4 abrogates Thy-1 protection in vivo. These studies will provide new insights into how lung fibroblast subpopulations determine fibrogenic progression and potentially identify new therapeutic approaches to treat idiopathic pulmonary fibrosis.