缺氧经DNA甲基化途径致滋养细胞合体化异常的分子机制及在子痫前期发生中的作用

Human placental multinucleate syncytiotrophoblast (STB) is responsible for transport functions between maternal and fetal blood supplies and is a major site of protein synthesis and steroid production. Aberrant syncytialization causes the release of adverse factors and maternal vascular damage, and it is closely associated with progression of preeclampsia (PE). We hypothesize that hypoxia exposure inducing abnormal epigenetical changes in STB fusion might one of the underlying mechanisms of preeclampsia. Cell model and cross sectional study are used to clarify the following issues. STB syncytialization is under coordinated regulation of DNA methyltransferases (DNMTs) - induced demethylation and forskolin-activated cAMP/PKA/CREB signal pathway. Increased DNMTs expression induced by hypoxia through HIF-1α, coordinating with cAMP/PKA/CREB signal pathway， may increase promoter hypermethylation of syncytialization relative genes such as ERVWE1. Insufficient fusion may release placenta-derived reverse factors such as sFlt、sEng and causes vascular endothelial injury. The correlation between aberrant DNA methylation during STB syncytialization and preeclampsia development and occurrence. Our study will provide novel views on pathogenetic mechanism of preeclampsia, potential early diagnosis indicators and new intervention targets.

人胎盘细胞滋养细胞（CTB）合体化形成的合体滋养细胞（STB）负责母胎间物质转运且具有重要的激素分泌功能。滋养细胞合体化异常可释放不良因子至母体并造成后者血管损伤，这与子痫前期的发生关系密切。基于前期结果，本研究提出PE发生的潜在新机理—“缺氧诱导滋养细胞合体化异常的表观遗传学机制”。研究利用细胞、胎盘/绒毛移植物等模型和横断面样本拟阐明：滋养细胞合体化过程受到DNA甲基转移酶（DNMTs）下调的被动去甲基化过程和 cAMP/PKA /CREB 信号通路激活的协同调控。缺氧环境可通过 HIF-1α 和/或 cAMP/PKA /CREB 信号通路干扰合体化过程中的 DNMTs 平衡,引起 ERVWE1(syn-1)等合体化相关基因启动子超甲基化/表达抑制,导致滋养细胞合体化障碍,并释放胎盘源性不良因子致血管内皮损伤和PE的发生。研究可能为PE的早期诊断和潜在的治疗方案提出新见解。

DNA甲基化等表观遗传学调控在胎盘发育，尤其是合体滋养细胞分化异常中的作用和机制，以及在子痫前期中的作用，目前尚不清楚。本研究探索了DNMTs在滋养细胞合体化过程的表达及其调控下游因子；cAMP/PKA/CREB 信号通路如何参与调控DNA甲基化及滋养细胞融合；缺氧通过何种途径影响DNMT表达和下游基因启动子甲基化和表达异常；DNA甲基化失衡导致的滋养细胞融合异常与PE发生的相关性。重要结果如下：1）甲基化转移酶（DNMTs）和整体基因组甲基化水平在早孕绒毛合体滋养细胞及原代滋养细胞自发融合形成的合体滋养细胞中的表达降低，在人工诱导BeWo细胞合体化后DNMTs表达降低，但是在PE中合体化过程异常且DNMT表达异常；2）过表达DNMTs可干扰福斯克林诱导的滋养细胞合体化；3）去甲基化抑制剂可诱导BeWo细胞发生合体化，并促进pCREB激活、水平升高。4）结合甲基化芯片测序，CREB结合位点公共数据，共发现合体化过程上调表达且去甲基化修饰的59个潜在靶点（28个共有因子）；5）初步证实了THBS1通过CD36影响滋养细胞合体化。我们的研究成果重点阐明了DNA甲基化在调控滋养细胞合体化及其异常在PE发生中的作用和意义，为PE发生的机制研究、可能的早期诊断指标或干预的新靶点提供思路。