Impact of polystyrene microplastics (PS-MPs) on the entire female mouse reproductive cycle: Assessing reproductive toxicity of microplastics through in vitro follicle culture

This study aims to investigate the effects of polystyrene microplastics (PS-MPs) on the entire female reproductive cycle and to elucidate the molecular mechanisms underlying their adverse impact on female ovaries. Additionally, it develops an in vitro follicle culture system as a novel methodological approach to evaluate reproductive toxicity, mimicking in vivo reproductive outcomes. First, PS-MPs were characterized using FTIR spectroscopy, TEM, and fluorescence microscopy. To assess reproductive toxicity, female mice were exposed to polystyrene microplastics (PS-MPs) at a dose of 30 mg/kg with an average particle size of 1 μm for 35 days. As a result, PS-MPs accumulated in the ovaries, leading to increased follicular atresia and apoptosis of granulosa cells. TEM revealed abnormal mitochondrial morphology in granulosa cells. Post-superovulation treatment, significant differences were noted in the number of ovulated metaphase II (MII) oocytes, spindle chromosome integrity, mitochondrial patterns, and ROS levels compared to controls. Mating with PS-MPs-exposed females led to fewer offspring. The in vitro follicle culture system proved promising for assessing PS-MPs reproductive toxicity. Immunohistochemistry showed increased Cleaved Caspase 3 and decreased Bcl2 levels in PS-MPs-treated groups, indicating apoptosis in granulosa cells. PS-MPs activate JNK and ERK pathways to mediate cell death, while impairing AKT signaling, reducing granulosa cell survival and ovarian function. This study highlights PS-MPs adverse reproductive effects and aids in developing strategies to protect female reproductive health.