Abstract
Pre-eclampsia is associated with inadequate placental blood flow and placental ischaemia. Placental vascular tone is essential for maintaining adequate placental blood flow. Oxytocin is increased in placental system at late pregnancy and onset of labour, and presented strongly concentration-dependent contractions in placental vascular, suggesting that oxytocin could be involved in regulating placental vascular tone and circulation. However, information about the reactivity of oxytocin in pre-eclamptic placental vasculature is limited. This study used a large number of human placentas to reveal the pathophysiological changes and its underlying mechanisms of oxytocin-induced vasoconstrictions in placental vessels under pre-eclamptic condition. Present study found that oxytocin-induced contractions were significantly decreased in human pre-eclamptic placental vasculature, associated with a deactivated transcription of oxytocin receptor gene. The deactivated oxytocin receptor gene transcription was ascribed to a relatively higher DNA methylation status of CpG islands in oxytocin receptor gene promoter. This study was first to reveal that a hyper-methylation of CpG islands in oxytocin receptor gene promoter, leading to a relatively low pattern of oxytocin receptor expression, was responsible for the decreased sensitivity of oxytocin in pre-eclamptic placental vessels.