早发重度子痫前期、HELLP综合征及抗磷脂综合征对胎盘滋养细胞LCHAD基因甲基化的影响及其与基因mRNA表达相关性的研究

摘要

目的：探讨早发重度子痫前期、HELLP综合征及抗磷脂综合征（APS）对胎盘滋养细胞线粒体长链3-羟基酰基辅酶A脱氢酶（LCHAD）基因甲基化程度的影响及其与基因mRNA表达的相关性。方法采集2013年1月至2015年3月在北京大学第三医院产前检查及住院治疗的病理妊娠孕妇的血清，其中早发重度子痫前期14例（子痫前期组）、HELLP综合征12例（HELLP组）及APS 14例（APS组）为病理妊娠组，以正常妊娠的14例孕妇的血清为对照（对照组）；原代绒毛滋养细胞来自于2014年3月至8月在北京大学第三医院自愿要求人工流产、胚胎正常、无妊娠合并症和并发症妇女40例的绒毛组织。在体外培养原代绒毛滋养细胞和永久性滋养细胞系HTR-8/Svneo细胞，分别加入相同浓度（10%）的4组孕妇的血清，孵育24 h后收集各组滋养细胞。（1）采用在线生物信息学预测软件（MethPrimer软件）预测滋养细胞中LCHAD基因启动子区二核苷酸胞嘧啶（CpG）岛甲基化位点的数量及位置；（2）通过MassARRAY甲基化DNA定量分析平台检测4组滋养细胞中LCHAD基因启动子区各位点的甲基化程度；（3）采用实时荧光定量逆转录（RT）-PCR技术检测4组滋养细胞中LCHAD mRNA的表达水平；（4）采用Pearson相关系数对4组滋养细胞中LCHAD基因启动子区各位点的甲基化程度与LCHAD mRNA的表达水平进行相关性分析。结果因原代滋养细胞和HTR-8/Svneo细胞两种细胞的实验结果完全一致，故将两种细胞合并用“滋养细胞”表述。（1）滋养细胞中LCHAD基因启动子区目标CpG岛（长度558 bp）中，含有17个胞嘧啶鸟嘌呤（CG）位点，获得其中11个（11/17）位点的甲基化程度，其位置分别为：-984、-960、-899、-853、-811、-796、-774、-727、-615、-595、-579位点，其中-899、-796及-774位点为复合位点（含有2个及以上CG序列），另外8个为单独位点（含有1个CG序列）。（2）病理妊娠组滋养细胞中甲基化程度较高的位点为-899、-853、-615及-595位点，子痫前期组、HELLP组-899、-853及-615位点的甲基化程度均明显高于对照组（P<0.01），子痫前期组-853位点的甲基化程度明显高于HELLP组（P<0.05）；HELLP组、APS组及对照组-595位点均呈无甲基化状态，分别与子痫前期组比较，差异均有统计学意义（P<0.01）。（3）子痫前期组滋养细胞中LCHAD mRNA的表达水平为0.048±0.005，HELLP组为0.045±0.006，APS组为0.044±0.004，均显著低于对照组的0.076±0.009（P<0.01）。（4）子痫前期组滋养细胞中LCHAD基因启动子区-899、-853、-727、-615及-579位点的甲基化程度与基因mRNA的表达水平均呈明显负相关（P<0.05）；HELLP组滋养细胞中LCHAD基因启动子区-899、-853、-615位点的甲基化程度与基因mRNA的表达水平均呈明显负相关（P<0.05）；而APS和对照组滋养细胞中两者均无显著相关性（P>0.05）。结论早发重度子痫前期、HELLP综合征、APS对滋养细胞中LCHAD基因启动子区的甲基化修饰存在差异，早发重度子痫前期、HELLP综合征滋养细胞中LCHAD基因启动子区甲基化修饰程度明显升高，并与LCHAD mRNA表达水平呈明显负相关性，进一步揭示了长链脂肪酸氧化改变在不同病理妊娠中的分子学基础。%Objective By detecting the DNA methylation and gene expression of long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) in trophoblast cells, analyze the correlation of DNA methylation and gene expression in early-onset preeclampsia (EPE), hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome and antiphospholipid syndrome (APS), to investigate the molecular basis of long-chain fatty acid oxidation changes in different preeclampsia and pathological pregnancy. Methods Primary human cytotrophoblast cells and HTR8/Svneo cells were treated with serum from patients with EPE (14 cases), HELLP (12 cases), APS (14 cases), and normal pregnant women (NP, 14 cases). The methylation level of LCHAD gene promoter region through the MassARRAY platform and mRNA expression level by real-time fluorescent quantitative PCR technique were conducted. Results (1) Cytosine-phosphate-guanine (CpG)sites in human LCHAD DNA promoter region:CpG sites were detected in the range of 558 bp before LCHAD gene transcription start site, the detected CpG sites were 11 sites including 8 single sites and 3 complex sites. The position of these sites were at-984,-960,-899,-853,-811,-796,-774,-727,-615,-595,-579 respectively. (2) The sites of-899,-853,-615 and-595 showed increased methylation level in EPE and HELLP groups. The methylation level at-899,-853 and-615 sites in EPE and HELLP groups were significantly higher than those in NP group(P<0.01). The methylation level at-853 site was higher in EPE group than that in HELLP group(P<0.05). The-595 site showed the unmethylated in EPE, HELLP and APS groups. There were significantly difference between the 3 groups and EPE group(P<0.01). (3) The gene expression of LCHAD mRNA in EPE(0.048±0.005), HELLP(0.045±0.006)and APS(0.044±0.004) groups were significantly lower than NP group(0.076 ± 0.009;P<0.01). (4) The correlation of methylation level and gene expression in all groups: the methylation level at-899,-853,-727,-615 and-579 sites were negatively correlated with gene mRNA expression in EPE group (P<0.05). The methylation level at-899,-853 and-615 sites were negatively correlated with gene mRNA expression in HELLP group(P<0.05). Conclusions The variation of LCHAD DNA methylation of trophoblast cells are found among EPE, HELLP syndrome and APS. The different correlation of LCHAD DNA methylation and gene expression are different in pathological groups. LCHAD DNA methylation of EPE and HELLP syndrome were significantly increased and negatively correlated with LCHAD gene mRNA expression. These results further revealed the molecular basis of long-chain fatty acid oxidation in different preeclampsia and pathological pregnancy.