The ovarian-related effects of polystyrene nanoplastics on human ovarian granulosa cells and female mice

Nanoplastics (NPs) have recently emerged in the context of global plastic pollution. They may be more toxic than macroplastics litter and microplastic fragments due to its abundances, tiny sizes, and cellular accessibility. The female reproductive toxicity of NPs has been widely documented for aquatic animals, but their effects and underlying mechanisms remain poorly understood in mammals. This study aimed to explore the effects of NPs on female reproduction using human ovarian granulosa cells (GCs) and female mice. The accumulation of polystyrene NPs (PS-NPs) in human granulosa-like tumor cells (KGN cells) and the ovaries of female Balb/c mice were evaluated by exposure to fluorescent PS-NPs. Proliferation and apoptosis, reactive oxygen species (ROS), and Hippo signaling pathway-related factors were analyzed in KGN cells. In addition, fertility rate, litter size, ovarian weight and microstructure, follicle development, serum level of anti-Mullerian hormone, and apoptosis in ovaries were examined in female mice. Here, the PS-NPs can penetrate the KGN cells and accumulate in the ovaries. In vitro, 100 μg/ml PS-NPs inhibited proliferation, induced apoptosis, accumulated ROS, activated three key regulators of the Hippo signaling pathway (MST1, LATS1, and YAP1), and downregulated the mRNA levels of CTGF and Cyr61 in KGN cells. Furthermore, salidroside, an antioxidative compound extracted from Rhodiola rosea, alleviated the damage of PS-NPs to KGN and inhibited the activation of the Hippo signal pathway. In vivo, exposure to 1 mg/day PS-NPs resulted in decreased fertility, abnormal ovarian function, and increased ovarian apoptosis in female mice. Overall, our data suggest that PS-NPs cause granulosa cell apoptosis and affect ovarian functions, leading to reduced fertility in female mice, by inducing oxidative stress and dysregulating the Hippo pathway.