Polystyrene microplastics disrupt ovarian development via cytoskeletal remodeling and epigenetic reprogramming particularly in granulosa cells [ATAC-seq]

The emerging environmental health issue posed by micro (nano) plastics (MNPs) has raised significant concerns. Accumulating evidence suggested that MNPs 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 microplastics (PS-MPs; 100 nm and 5 µm) on ovarian development and function in pubertal female mice. Following 35 days of exposure, we observed size-dependent reproductive toxicity, with 100 nm PS-MPs causing reduced body weight gain and ovarian size, and compromised ovarian structures and functions, including altered follicle and corpora lutea counts, alongside disrupted hormone levels. Leveraging single-cell RNA-sequencing (scRNA-seq), we uncovered profound alterations in intracellular communication networks and signaling flow patterns across seven identified ovarian cell types. Granulosa cells (GCs) were identified as the primary target PS-MPs, exhibiting marked transcriptional changes, including dysregulation of FSCN1, a critical actin cytoskeleton regulator. In vitro experiments confirmed that only 100 nm PS-MPs were internalized by GCs, leading to cell cycle arrest, necroptosis and hormonal dysfunction. Mechanistically, PS-MPs triggered F-actin cytoskeleton remodeling, increasing cell stiffness and reducing histone marks (H3K4me3, H3K27ac) associated with chromatin accessibility. Integrated ATAC-seq and RNA-seq analyses implicated STAT1 as a key transcriptional regulator driving PS-MP-induced epigenetic and transcriptional changes. Overall, this study first revealed PS-MP-mediated reproductive toxicity from a single-cell perspective, identifying granulosa cells as particularly vulnerable targets. It uncovered novel mechanisms involving cytoskeletal disruption and epigenetic reprogramming, while demonstrating size-dependent internalization patterns that directly correlate with reproductive impairment. These findings provide unprecedented insights into the molecular and epigenetic consequences of MNPs in mammalian reproduction, emphasizing the potential health risks of environmental MNPs exposure.