Polystyrene nanoplastics disrupt ovarian development via cytoskeletal remodeling and epigenetic reprogramming particularly in granulosa cells.

Emerging environmental health issues posed by micro- and nanoplastics (M/NPs) have raised significant concerns. Accumulating evidence suggested that M/NPs can bioaccumulate in gonads and impair fertility in animals, yet the underlying cellular mechanisms and tissue-specific responses remain poorly understood. In this study, we employed in vivo and in vitro models to systematically investigate the impact of polystyrene micro- and nanoplastics (PS-M/NPs, 100 nm and 5 µm) on ovarian development and function in pubertal female mice. Following 35-day exposure, we observed size-dependent reproductive toxicity, with 100 nm PS-NPs causing reduced body weight gain and ovarian size, disrupted folliculogenesis, and altered hormone levels. Leveraging single-cell RNA-sequencing (scRNA-seq), we uncovered profound alterations in intracellular communication networks across seven ovarian cell types. Granulosa cells (GCs) were identified as the primary target of PS-NPs, exhibiting marked transcriptional changes, including dysregulation of FSCN1, a critical actin cytoskeleton regulator. In vitro experiments confirmed that only 100 nm PS-NPs were internalized by GCs, leading to cell cycle arrest, necroptosis, and hormonal dysfunction. Mechanistically, PS-NPs triggered F-actin cytoskeleton remodeling, increasing cell stiffness and histone modifications (H3K4me3, H3K27ac) associated with chromatin accessibility. Integrated ATAC-seq and RNA-seq analyses implicated STAT1 as a key transcriptional regulator driving PS-NP-induced epigenetic and transcriptional changes. Overall, our findings establish the first single-cell resolution atlas of PS-NP-mediated ovarian toxicity, revealing that NPs disrupt reproduction through cytoskeletal damage and epigenetic reprogramming. This work provides unprecedented insights into the molecular and epigenetic consequences of M/NPs in mammalian reproduction, emphasizing the potential health risks of environmental M/NP exposure.