大鼠骨髓间质干细胞向肝细胞横向分化过程中Oct4启动子区域甲基化变化的实验研究

Experimental research of OCT4 promoter region methylation changes in the process of horizontal differentiation from rat bone marrow mesenchymal stem cells into hepatic cells

目的探讨大鼠骨髓间质干细胞横向分化为肝细胞的过程中,八聚体转录因子4(Oct4)启动子甲基化的调控机制。方法体外诱导大鼠骨髓源性肝干细胞(RBMLSC)向肝细胞横向分化,于不同时间点(0 d、7 d、14 d)提取细胞的DNA及RNA。用荧光定量PCR法检测白蛋白(ALB)和Oct4的mRNA表达水平,再用焦磷酸测序法检测Oct4基因启动子中4个CpG位点的甲基化变化。结果细胞分化过程中,与0 d组相比,7 d组和14 d组的ALB mRNA分别增加5.22倍(P<0.05)和14.7倍(P<0.001),而Oct4 mRNA分别下降0.23倍(P<0.01)和0.055倍(P<0.001);同时Oct4启动子的CpG1、CpG2、CpG3甲基化频率显著上升,7 d组均明显高于对照组和0 d组(P<0.01),14 d组又均明显高于对照组、0 d组及7 d组(P<0.01),但CpG 4甲基化无明显变化。结论细胞诱导分化过程中,Oct4启动子高甲基化,导致其mRNA表达减少,从而RBMLSC多能性消失。

Objective To investigate the mechanism of OCT4 promoter methylation in rat bone marrow mesenchymal stem cells(BMSCS)differentiation into hepatocytes.Methods Rat bone marrow-derived liver stem cell(RBMLSC)were induced to differentiate into liver cells,and the DNA and RNA of the cells were extracted at different time points(0 d,7 d,14 d)during the process.mRNA expression levels of Albumin(ALB)and OCT4 were detected by fluorescence quantitative PCR,and methylation changes of 4 CpG sites in OCT4 gene promoter were detected by pyrosequencing.Results During the process of cell differentiation,compared with group 0 d,ALB mRNA in group 7 d and group 14 d increased by 5.22 times(P<0.05)and 14.7 times(P<0.001),respectively,while Oct4 mRNA decreased by 0.23 times(P<0.01)and 0.055 times(P<0.001).Meanwhile,the frequency of CpG1,CpG2 and CpG3 methylation of Oct4 promoter increased significantly,which was significantly higher in group 7 than that in control group and group 0 d(P<0.01),and significantly higher in group 14 d than that in control group,group 0 d and group 7 d(P<0.01),but CpG 4 methylation did not change significantly.Conclusion During the process of cell induction and differentiation,Oct4 promoter is hypermethylated,which leads to the decrease of mRNA expression,and thus the pluripotency of RBMLSC disappears.