The spatial zonation of the placental vasculature is specified by epigenetic mechanisms

The labyrinthian fetoplacental capillary network is of vital importance for proper nourishment of the developing embryo. An inadequate function of the maternal-fetal circulation has emerged as one of the primary causes of placental insufficiency. Here, we show that the spatial zonation of the placental labyrinth vasculature is controlled by flow-regulated epigenetic mechanisms. The spatial and temporal analysis of gene transcription revealed a gradual change in the expression of epigenetic enzymes with the de novo DNA methyltransferase 3a (DNMT3A) as primary enzyme introducing DNA methylation in cells of the vascular system. Loss of Dnmt3a resulted in DNA hypomethylation and disturbance of the spatial-zonated placental gene expression. The resulting global DNA hypomethylation impaired the angiogenic capacity of endothelial cells. Global as well as endothelium-predominant deletion of Dnmt3a resulted in impaired placental vascularization and fetal growth retardation. A meta-analysis of human placental endothelial cell gene expression identified an association between preeclampsia and reduction of DNMT3A. Collectively, our study identified DMNT3A as critical methylome-regulator of placental endothelial cell gene expression and function with clinical implications for the pathogenesis of placental dysfunction, as it occurs during preeclampsia or fetal growth retardation. We performed single-cell RNA-seq on labyrinth endothelial cells (EC) dissected from four litter-matched E16.5 wildtype placentas.胎儿胎盘迷宫状毛细血管网络对发育中胚胎的正常营养供给至关重要。母胎循环功能不全已被证实是胎盘功能不全的主要诱因之一。本研究证实，胎盘迷宫血管的空间分区调控依赖于血流调控的表观遗传机制。对基因转录的时空分析显示，表观遗传酶的表达呈渐进式变化，其中从头DNA甲基转移酶3A（de novo DNA methyltransferase 3a, DNMT3A）是在血管系统细胞中引入DNA甲基化的核心酶。Dnmt3a缺失会导致DNA低甲基化，并破坏胎盘基因表达的空间分区模式。由此产生的全基因组DNA低甲基化会损伤内皮细胞的血管生成能力。全身性以及内皮细胞特异性敲除Dnmt3a，均会导致胎盘血管生成受损以及胎儿生长受限。对人类胎盘内皮细胞基因表达的荟萃分析显示，子痫前期与DNMT3A表达下调存在关联。综上，本研究证实DNMT3A是调控胎盘内皮细胞基因表达与功能的关键甲基化组调控因子，其与子痫前期或胎儿生长受限等情况下发生的胎盘功能障碍的发病机制密切相关，具有重要临床意义。我们从4只同窝匹配的胚胎发育第16.5天（E16.5）的野生型胎盘中分离得到迷宫层内皮细胞（EC），并对其进行了单细胞RNA测序。