Department of Medicine, University of Giessen Lung Center, University of Giessen, Giessen, Germany.
Thorax. 2009 Dec;64(12):1053-61. doi: 10.1136/thx.2009.121798. Epub 2009 Oct 22.
Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease characterised by accumulation of activated (myo)fibroblasts and excessive extracellular matrix deposition. The enhanced accumulation of (myo)fibroblasts may be attributed, in part, to the process of transforming growth factor beta1 (TGFbeta1)-induced epithelial-mesenchymal transition (EMT), the phenotypic switching of epithelial to fibroblast-like cells. Although alveolar epithelial type II (ATII) cells have been shown to undergo EMT, the precise mediators and mechanisms remain to be resolved. The objective of this study is to investigate the role of SNAI transcription factors in the process of EMT and in IPF.
Using quantitative reverse transcription-PCR (RT-PCR), immunofluorescence, immunohistochemistry, western blotting, as well as gain- and loss-of-function studies and functional assays, the role of SNAI1 and SNAI2 in TGFbeta1-induced EMT in ATII cells in vitro was assessed; and the expression of SNAI transcription factors was analysed in experimental and human IPF in vivo.
TGFbeta1 treatment increased the expression and nuclear accumulation of SNAI1 and SNAI2, in concert with induction of EMT in ATII cells. SNAI overexpression was sufficient to induce EMT, and small interfering RNA (siRNA)-mediated SNAI depletion attenuated TGFbeta1-induced ATII cell migration and EMT. SNAI expression was elevated in experimental and human IPF and localised to hyperplastic ATII cells in vivo.
The results demonstrate that TGFbeta1-induced EMT in ATII cells is essentially controlled by the expression and nuclear translocation of SNAI transcription factors. Increased SNAI1 and SNAI2 expression in experimental and human IPF in vivo suggests that SNAI-mediated EMT may contribute to the fibroblast pool in idiopathic pulmonary fibrosis.
特发性肺纤维化（IPF）是一种致命的间质性肺疾病，其特征是激活的（肌）成纤维细胞积累和细胞外基质过度沉积。（肌）成纤维细胞的积累增加可能部分归因于转化生长因子β1（TGFβ1）诱导的上皮-间充质转化（EMT）过程，即上皮细胞向成纤维细胞样细胞的表型转换。尽管已经表明肺泡上皮细胞 II 型（ATII）细胞经历 EMT，但确切的介质和机制仍有待解决。本研究旨在探讨 SNAI 转录因子在 EMT 过程和 IPF 中的作用。
使用定量逆转录-PCR（RT-PCR）、免疫荧光、免疫组织化学、Western blot 以及功能获得和功能丧失研究和功能测定，评估 SNAI1 和 SNAI2 在体外 TGFβ1 诱导的 ATII 细胞 EMT 中的作用；并分析实验性和人类 IPF 中 SNAI 转录因子的表达。
TGFβ1 处理增加了 SNAI1 和 SNAI2 的表达和核积累，与 ATII 细胞 EMT 的诱导一致。SNAI 过表达足以诱导 EMT，而小干扰 RNA（siRNA）介导的 SNAI 耗竭减弱了 TGFβ1 诱导的 ATII 细胞迁移和 EMT。SNAI 在实验性和人类 IPF 中表达上调，并在体内定位于增生的 ATII 细胞。
结果表明，TGFβ1 诱导的 ATII 细胞 EMT 主要由 SNAI 转录因子的表达和核易位控制。体内实验性和人类 IPF 中 SNAI1 和 SNAI2 表达增加表明 SNAI 介导的 EMT 可能有助于特发性肺纤维化中的成纤维细胞池。
