The antioxidant effect of melatonin on oxidative stress and vascularization in rat whole embryo culture

Hypoxia, during early embryonic development, causes morphological and functional impairments through oxidative stress. Melatonin, a strong antioxidant, may exert potential protective effects in this process. This study investigated the effects of melatonin on yolk sac vascularization and embryonic development in rat embryos exposed to hypoxia. Rat embryos at gestational day 9.5 were cultured for 48 h using a whole embryo culture (WEC) system. Embryos were divided into six groups: Control (C), Hypoxia (H), 10 μM Melatonin (10 μM Mel), Hypoxia +10 μM Melatonin (H + 10 μM Mel), 50 μM Melatonin (50 μM Mel), and Hypoxia +50 μM Melatonin (H + 50 μM Mel). At the end of culture, morphological parameters, oxidative stress markers, and the distribution of vWF-positive cells were evaluated. Compared with the control group, the H group exhibited marked developmental delay and vascularization defects (<i>P</i> < 0.05). Melatonin administration significantly reduced these abnormalities, with the 50 μM melatonin group showing the most prominent improvements in morphological development, oxidative stress parameters, and vascularization (<i>P</i> < 0.05). Melatonin provides protective effects against hypoxia-induced early embryonic developmental impairments and holds therapeutic potential as an agent supporting development during the early intrauterine period.