骨形成蛋白-7基因转染对人肾小管上皮细胞外基质分泌的影响

目的构建骨形成蛋白-7(BMP-7)全长基因表达质粒,观察BMP-7过表达对转化生长因子(TGF)-β诱导的人肾小管上皮细胞细胞外基质分泌(ECM)的作用。方法将BMP-7全长cDNA连接进入真核细胞表达质粒pcDNA3·1中,以脂质体Superfect介导的方法将重组表达质粒pcDNA3·1-BMP-7转染入人肾小管上皮细胞,挑选阳性克隆,以获得稳定转染的人肾小管上皮细胞株。采用Western印迹方法检测BMP-7在肾小管上皮细胞培养上清液中的表达。给予TGF-β(5ng/ml)进行处理,应用RT-PCR和ELISA的方法,观察BMP-7过表达对纤维粘连蛋白(FN)、胶原Ⅰ、Ⅲ(ColⅠ、Ⅲ)等细胞外基质mRNA和蛋白质表达的作用。结果EcoR I限制性酶切鉴定以及DNA双向测序结果均说明所构建的重组质粒为BMP-7全长基因表达质粒。Western印迹方法检测稳定转染人肾小管上皮细胞蛋白表达量明显高于空载体转染组(P<0·05)。TGF-β处理24、48、72h后,5ng/ml TGF-β处理组、空白质粒转染(pcDNA3·1)+5ng/ml TGF-β组ColⅠ、Ⅲ、FN mRNA的表达量明显高于正常对照组,空白质粒转染组(pcDNA3·1)ColⅠ(A值):0·897±0·100、1·054±0·090vs0·286±0·010、0·319±0·080;ColⅢ(A值):1·114±0·040、0·961±0·090vs0·354±0·020、0·403±0·040;FN(A值):1·257±0·090、1·188±0·060vs0·413±0·020、0·454±0·060,均P<0·05];Col I、FN mRNA表达量pcDNA3·1-BMP-7转染组+5ng/ml TGF-β组明显低于TGF-β处理组(0·591±0·007、0·687±0·020,P<0·05),ColⅢmRNA表达有降低趋势(0·809±0·090),但差异无统计学意义。细胞培养上清液FN含量5ng/ml TGF-β处理组、空白质粒转染(pcDNA3·1)+5ng/mlTGF-β组明显高于正常对照组(P<0·05),而pcDNA3·1-BMP-7转染组+5ng/ml TGF-β组表达明显低于TGF-β处理组(P<0·05)。结论BMP-7过表达可以显著减少TGF-β所致的人肾小管上皮细胞FN、ColⅠ、ⅢmRNA和细胞培养上清液中的FN的表达。表明BMP-7减少小管间质炎症反应和纤维化的发生,改善肾功能的作用,部分是通过抑制肾小管上皮细胞分泌细胞外基质实现的。

Transfection of recombinant bone morphogenetic protein-7 expressing plasmid into cultured human renal tubular epithelial cells attenuates the extracellular matrix accumulation induced by transforming growth factor-beta

OBJECTIVE: To investigate the effects of bone morphogenetic protein (BMP)-7 on the extracellular matrix (ECM) accumulation induced by transforming growth factor (TGF)-beta. METHODS: Mouse full length BMP-7 cDNA was ligated into a eukaryotic expression vector pcDNA3.1. Restriction enzymatic analyses and DNA sequencing were used to confirm the accuracy of the BMP-7 expressing plasmid thus constructed. The recombinant expression plasmid pcDNA3.1-BMP-7 was transfected into cultured human renal tubular epithelial cells of the line HK-2 mediated by liposome. Positive clones were selected so as to obtain the human renal epithelial cells with stable transfection. These HK-2 cells were cultured and divided into 5 groups to be treated with 5 ng/ml TGF-beta, blank plasmid pcDNA3.1, blank plasmid pcDNA3.1 + 5 ng/ml TGF-beta, pcDNA3.1-BMP-7, pcDNA3.1-BMP-7 + 5 ng/ml TGF-beta, and an additional grin the cells and the supernatant of the cell culture fluid were collected. The expression level of BMP-7 protein was determined by Western blotting. RT-PCR and ELISA were used to determine the mRNA and protein expression of collagen (Col) I and III, and fibronectin (FN) in the human renal tubular epithelial cells and supernatant of different groups. RESULTS: The recombinant plasmid pcDNA3.1-BMP-7 was successfully constructed. The cell mRNA expression levels of Col I and III and FN of the 5 ng/ml TGF-beta group and blank plasmid pcDNA3.1 + 5 ng/ml TGF-beta group were all significantly higher than those of the blank plasmid pcDNA3.1 group, pcDNA3.1-BMP-7 group, and control group (all P < 0.05). The cell mRNA expression levels of Col I and FN of the pcDNA3.1-BMP-7 + 5 ng/ml TGF-beta were all significantly lower than those of the TGF-beta group (all P < 0.05). The cell mRNA expression level of Col III of the pcDNA3.1-BMP-7 + 5 ng/ml TGF-beta was lower, however, not significantly, than that of the TGF-beta group. The supernatant FN levels of the 5 ng/ml TGF-beta group and pcDNA3.1 + 5 ng/ml TGF-beta group were both significantly higher than that of the control group (both P < 0.05), and the supernatant FN level of the pcDNA3.1-BMP-7 + 5 ng/ml TGF-beta group was significantly lower that that of the 5 ng/ml TGF-beta group (P < 0.05). CONCLUSION: Over-expression of BMP-7 significantly inhibits the increased syntheses of collagen I and III, and fibronectin induced by TGF-beta. BMP-7 exerts its antifibrotic effect partially through blocking the TGF-beta-induced accumulation of extracellular matrix in human renal tubular epithelial cells.