Polystyrene nanoparticles incorporate into the endoplasmic reticulum and disturb translation during meiotic...

Polystyrene (PS) is one of the most common polymers that cause plastic pollution after release into the environment. Although a growing body of evidence has shown the adverse effects of PS on living organisms including humans, their effects on mammalian oocytes have not been extensively studied. In this study, we investigated the effect of exposure to PS-nanoparticle (PS-NPs) on meiotic maturation in mouse oocytes. We found that exogenous PS-NPs internalized into oocytes after penetrating the zona pellucida and accumulated in the cytoplasm of oocytes during meiotic maturation. Exposure to PS-NPs did not affect meiotic resumption but inhibited meiotic maturation by impairing spindle assembly and chromosome alignment. Moreover, exposure to PS-NPs increased oxidative stress and mitochondrial aggregation during meiotic maturation. Notably, internalized PS-NPs localized around the endoplasmic reticulum (ER) and disturbed translation in oocytes. Therefore, it is suggested that PS-NPs impair meiotic maturation not only by increasing oxidative stress and mitochondrial dysfunction, but also by decreasing translation efficiency after incorporating into the ER during meiotic maturation in mouse oocytes.