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.