Smad 2,3,6,7蛋白在实验性肾间质纤维化模型中的定位和表达变化

Localization of Smad 2, 3, 6, 7 and their changes of expression in experimental interstitial fibrosis model in rats

目的 研究Smads蛋白在实验性肾纤维化模型中的定位和表达变化。方法 36只Wistar大鼠随机分为正常大鼠组,假手术组和单侧输尿管梗阻组3组,分别于术后3 d、7 d、14 d、21 d处死大鼠。采用逆转录多聚酶链反应(RT-PCR)检测TGF-β1 mRNA表达水平。用免疫组织化学和Western杂交分别检测Smad2、Smad3、Smad6及Smad7蛋白的定位和表达。纤维化程度通过测定肾组织羟脯氨酸含量来判断。结果 与对照组相比,TGF-β1 mRNA于第3天起表达即见进行性增高,并伴有肾组织羟脯氨酸含量的明显增高。Smad2、3蛋白主要在肾小管表达,肾小球偶见;Smad6、7蛋白主要在肾小球和肾小管上皮细胞内均有表达。输尿管梗阻后,Smad2、3蛋白表达逐渐增加,而Smad6、7蛋白却逐渐减少。结论 TGF-β1/Smad信号通路参与了肾间质纤维化进程。抗Smad蛋白表达下降可能是该模型TGF-β1致肾纤维化作用的主要原因。

Objective To investigate the localization of Smad protein 2, 3, 6, 7 and their changes of expression in experimental interstitial fibrosis model in rats. Methods Thirty-six rats were divided into normal control, sham operation, and unilateral ureteral obstruction(UUO) groups, and were sacrificed at postoperative day 3, 7, 14, 21. The level of TGF-β1 mRNA was examined by RT-PCR. The sites and levels of expression of Smad protein 2, 3, 6, 7 were examined by immunohistochemistry staining and Western blot . Renal fibrosis was assessed by measuring tissue hydroxyproline. Results Compared to sham operation group, TGF-β1 mRNA was significantly increased in UUO rats, and this trend was positively correlated to increased hydroxyproline content. Immunohistochemistry staining studies indicated that Smad protein 2, 3 mainly expressed in renal tubular cells, rarely in glomeruli, and Smad protein 6, 7 were presented in both the glomeruli and proximal renal tubular cells. Expression of the Smad protein 2, 3 were significantly increased from day 3 to 21 after UUO, while the Smad protein 6, 7 were significantly reduced in the obstructive kidney. Conclusions TGF-β1/Smad signaling is involved in the progression of renal tubulointerstitial fibrosis. The absence of up-regulation of these anti-Smads proteins may be the major cause of the interstitial fibrosis in this model.