转录中介因子1γ (TIF1γ)对肾小管间质纤维化的调控作用与机制研究

Transcriptional intermediary factor 1 γ (TIF1γ) plays a crucial role in maintaining homeostasis of cells. Previous studies found that in various types of cells such as hematopoietic stem cells, breast epithelial cells, and cancer cells, TIF1γ exerted its role in homeostasis through inhibition of TGF-β signaling, whereas the precise role of TIF1γ in renal tubular epithelial cells (RTECs) were not investigated before. Our previous work found that both in the unilateral ureteral obstruction (UUO) models of mice and rats, the expression of TIF1γ in RTECs was reduced during the development of tubulointerstitial fibrosis. From these results and our previous investigations we suppose that in RTECs, TIF1γ restrains the activity of TGF-β signaling, whereas the downregulation of TIF1γ in RTECs causes the uncontrolled TGF-β signaling and induces the development of tubulointerstitial fibrosis. To confirm this hypothesis, we plan to carry out in vitro and in vivo experiments to investigate the regulatory role of TIF1γ in TGF-β signaling and its downstream effects in RTECs, and the mechanism of downregulation of TIF1γ in the fibrotic kidney were also to be investigated. Besides TGF-β signaling, fibrotic signaling cascades regulated by TIF1γ in RTECs will also be screened by antibody array and be verified by in vitro and in vivo functional experiments. The results of purposed experiments will elucidate the regulatory role of TIF1γ in RTECs and in tubulointerstitial fibrosis, and could help us finding a novel strategy for the prevention and treatment of tubulointerstitial fibrosis.

转录中介因子1γ(TIF1γ)在细胞内环境稳态的维持中发挥重要作用，包括我们前期研究在内的多项研究均证明其在多种类型细胞中通过抑制TGF-β通路发挥效应。在正常肾小管上皮细胞有TIF1γ的表达，然而我们在大/小鼠UUO模型中均发现纤维化肾脏中TIF1γ表达下调。TIF1γ在肾小管间质纤维化中的作用尚无研究报道。我们在前期基础上提出：在正常肾小管上皮细胞，TIF1γ抑制TGF-β通路的活性。TIF1γ的表达下调引起TGF-β通路的过度激活和肾小管间质纤维化的进展。我们拟在UUO模型和肾小管上皮细胞系中研究TIF1-γ对TGF-β通路及其下游效应的调控，同时探索TIF1γ是否调控除TGF-β通路外的纤维化相关通路。此外，我们也将研究肾纤维化进展中引起TIF1γ下调的机制。我们将通过体内外研究方案明确TIF1γ在肾小管间质纤维化中的作用及调控机制，为肾小管间质纤维化的防治提供新的靶点和思路。

肾小管间质纤维化是许多慢性肾脏疾病终末期的特征性表现。目前对于肾小管间质纤维化及其引起的慢性肾衰竭缺乏有效的根治手段，原因之一在于肾小管间质纤维化的发病机制与疾病进程尚待深入研究.本项目在前期研究的基础上提出假说：TIF1γ在肾小管间质纤维化进展中的表达下调进而导致经典的促纤维化TGF-β信号的过度活化，并设计体内外实验证实。目前本项目已如期完成，主要的研究内容及成果概述如下：.我们在慢性肾纤维化的肾脏组织中TIF1γ表达较正常肾脏组织降低，且在鼠单侧输尿管结扎（UUO）这一经典肾小管间质纤维化模型中，随着肾脏病变进展TGF-β1与α-SMA的表达逐渐上升，TIF1γ的表达逐渐下降，但TIF1γ的mRNA水平无明显变化。这一结果提示TIF1γ在肾小管间质纤维化进展中的表达下降可能为转录后调控导致。我们进而设计相关实验证实，UUO模型中随着肾脏组织中病变进展的TIF1γ表达下降是由降解增加引起，TIF1γ的泛素化降解参与该过程。我们进而发现，在肾小管上皮细胞中敲减TIF1γ的表达后，细胞发生上皮-间质转化，并可增强TGF-β信号的促上皮-间质转化效应。在肾小管上皮细胞过表达TIF1γ则使细胞对TGF-β信号的促上皮-间质转化效应不敏感。上述结果提示TGF-β信号通路在肾小管上皮细胞中的活性受TIF1γ调控。综上，我们的结果证明肾小管间质纤维化进展中TIF1γ的表达降低可由TIF1γ的泛素化降解增强引起，且在肾小管上皮细胞中TIF1γ可抑制TGF-β信号的促上皮-间质转化效应。研究结果为肾小管间质纤维化的防治提供了新的思路和理论依据。.