环状RNA BRAF_2在子痫前期胎盘滋养细胞增殖和凋亡中的作用及其机制

Role and mechanism of circRNA BRAF_2 in proliferation and apoptosis of placental trophoblast cells in preeclampsia

目的 探讨环状RNABRAF_2(circRNABRAF_2)在子痫前期(PE)胎盘滋养细胞增殖和凋亡中的作用及其机制。方法 收集2018年1月-2019年2月宁夏医科大学总医院正常妊娠与PE孕妇的胎盘组织(n=21),采用qRTPCR检测两组胎盘组织中circRNABRAF_2的表达水平,并分析circRNABRAF_2表达水平与血压的相关性。体外培养人源胎盘滋养细胞株(HTR8-S/Vneo):(1)将细胞分为对照组与缺氧组,采用qRT-PCR检测circRNA BRAF_2的表达;(2)在HTR8-S/Vneo中转染circRNABRAF_2慢病毒空载体和过表达慢病毒,分为对照组、circRNABRAF_2阴性对照组及circRNA BRAF_2过表达组,使用qRT-PCR对circRNA BRAF_2进行过表达验证;(3)在circRNA BRAF_2过表达慢病毒转染成功的基础上,将细胞分为对照组、circRNA BRAF_2阴性对照组、circRNA BRAF_2过表达组、缺氧组、缺氧+circRNABRAF_2阴性对照组与缺氧+circRNABRAF_2过表达组,采用EdU和CCK-8法检测细胞增殖情况,流式细胞术检测细胞凋亡水平,Western blotting检测凋亡相关蛋白caspase-3、caspase-9、Bcl-2及Bax的表达。采用qRT-PCR检测circRNABRAF_2在HTR8-S/Vneo细胞质和细胞核中的表达水平,通过生物信息学分析筛选与circRNABRAF_2可能结合的miRNA并检测其在组织和细胞中的表达水平。结果 与正常妊娠组比较,PE组孕妇胎盘组织中circRNA BRAF_2表达水平明显降低(P<0.001),且circRNA BRAF_2表达水平与收缩压、舒张压呈负相关(r=±0.4531,P<0.01;r=±0.4381,P<0.01)。qRT-PCR检测结果显示,与对照组比较,缺氧组circRNABR AF_2表达水平明显降低(P<0.01)。circRNA BRAF_2阴性对照组circRNA BRAF_2表达水平与对照组比较差异无统计学意义(P>0.05);与circRNA BRAF_2阴性对照组比较,circRNA BRAF_2过表达组circRNA BRAF_2表达水平明显升高(P<0.001)。EdU及CCK-8法检测结果显示,与对照组比较,缺氧组EdU阳性细胞百分比明显下降(P<0.001),滋养细胞增殖能力降低(P<0.001);与缺氧+circRNA BRAF_2阴性对照组比较,缺氧+circRNA BRAF_2过表达组滋养细胞EdU阳性细胞百分比明显升高(P<0.001),滋养细胞增殖能力明显增强(P<0.001)。流式细胞术检测结果显示,与对照组比较,缺氧组细胞凋亡率明显增高(P<0.001);与缺氧+circRNABRAF_2阴性对照组比较,缺氧+circRNABRAF_2过表达组细胞凋亡率明显降低(P<0.001)。Westernblotting检测结果显示,与对照组比较,缺氧组caspase-3、caspase-9及Bax蛋白表达水平升高(P<0.01或P<0.001),Bcl-2蛋白表达水平降低(P<0.01);与缺氧+circRNA BRAF_2阴性对照组比较,缺氧+circRNA BRAF_2过表达组caspase-3、caspase-9及Bax蛋白表达水平降低(P<0.001或P<0.01),Bcl-2蛋白表达水平升高(P<0.05)。qRT-PCR检测结果显示,circRNA BRAF_2主要在细胞质中表达,生物信息学分析结果显示,circRNA BRAF_2与miR-7855-5p存在结合位点。qRT-PCR检测结果显示,与正常妊娠组比较,miR-7855-5p在PE胎盘组织中高表达(P<0.05);与对照组细胞比较,缺氧组miR-7855-5p明显高表达(P<0.001)。结论 circRNA BRAF_2可促进PE胎盘滋养细胞增殖并抑制其凋亡,作用机制可能与miR-7855-5p有关。

Objective To investigate the role and mechanism of circRNA BRAF_2 in proliferation and apoptosis of placental trophoblast cells in preeclampsia(PE).Methods Placental tissues of pregnant women with normal pregnancy and PE were collected(n=21)in the General Hospital of Ningxia Medical University from January 2018 to February 2019.The expression level of circRNA BRAF_2 in placental tissues of the two groups was detected by qRT-PCR,and the correlation between circRNA BRAF_2 expression level and blood pressure was analyzed.Human placental trophoblast cell lines(HTR8-S/Vneo)were cultured in vitro,(1)Cells were divided into control group and hypoxia group,and the expression of circRNA BRAF_2 were detected by qRTPCR.(2)HTR8-S/Vneo was transfected with circRNA BRAF_2 lentivirus empty vector and circRNA BRAF_2 overexpression lentivirus,and then divided into control group,circRNA BRAF_2 negative control group and circRNA BRAF_2 overexpression group.The overexpression of circRNA BRAF 2 was verified with qRT-PCR.(3)Based on the successful transfection of circRNA BRAF_2 overexpressing lentivirus,the cells were divided into control group,circRNA BRAF_2 negative control group,circRNA BRAF_2 overexpression group,hypoxia group,hypoxia+circRNA BRAF_2 negative control group,and hypoxia+circRNA BRAF_2 overexpression group.EdU and CCK-8 methods were used to detect the proliferation.Flow cytometry was used to detect the changes of apoptosis level.Western blotting was used to detect the expression levels of apoptosis-related proteins caspase-3,caspase-9,Bcl-2 and Bax.qRT-PCR was used to detect the expression levels of circRNA BRAF_2 in HTR8-S/Vneo cytoplasm and nucleus.Bioinformatics analysis was performed to screen out the miRNA that might bind circRNA BRAF_2 and detect their expression levels in tissues and cells.Results Compared with normal pregnancy group,the expression level of circRNA BRAF_2 was significantly decreased in placenta of PE group(P<0.001),and of circRNA BRAF_2 was negatively correlated with systolic pressure and diastolic pressure(r=–0.4531,P<0.01;r=–0.4381,P<0.01).qRT-PCR showed that compared with control group,the expression level of circRNA BRAF_2 in hypoxia group was significantly decreased(P<0.01),and the relative expression level of circRNA BRAF_2 in negative control group showed no significant difference when ompared with control group(P>0.05).Compared with that in circRNA BRAF_2 negative control group,the circRNA BRAF_2 expression level increased significantly in circRNA BRAF_2 overexpression group(P<0.001).The detection results of EdU and CCK-8 showed that,compared with control group,the percentage of positive EdU cells decreased significantly(P<0.001)in hypoxia group,trophoblast proliferation ability decreased(P<0.001);Compared with the hypoxia+circRNA BRAF_2 negative control group,the percentage of EdU positive trophoblast cells increased significantly in hypoxia+circRNA BRAF_2 overexpression group(P<0.001),and the proliferation ability of trophoblast cells was significantly enhanced(P<0.001).The detection results of flow cytometry showed that,compared with control group,the apoptosis rate of hypoxia group increased obviously(P<0.001);Compared with the hypoxia+circRNA BRAF_2 negative control group,the apoptosis rate of the hypoxia+circRNA BRAF_2 overexpression group decreased significantly(P<0.001).Western blotting showed that compared with control group,the relative expressions of caspase-3,caspase-9 and Bax proteins increased(P<0.01 or P<0.001),and of Bcl-2 protein decreased(P<0.01)in hypoxia group;Compared with the hypoxia+circRNA BRAF_2 negative control group,the relative expressions of caspase-3,caspase-9 and Bax proteins decreased(P<0.001 or P<0.01),and of Bcl-2 protein increased(P<0.05)in hypoxia+circRNA BRAF_2 overexpression group.The results of qRT-PCR showed that circRNA BRAF_2 was expressed mainly in cytoplasm,and bioinformatics analysis showed that binding sites existed between circRNA BRAF_2 and miR-7855-5p.and miR-7855-5p was highly expressed in PE placental tissue than that in normal pregnancy group(P<0.05);Compared with control group,miR-7855-5p was obviously highly expressed in hypoxia group(P<0.001).Conclusion circRNA BRAF_2 can promote proliferation and inhibit apoptosis of PE placental trophoblast cells,and the mechanism may be related to miR-7855-5p.