Polystyrene/polylactic acid microplastics impair transzonal projections and oocyte maturation via gut microbiota-mediated lipoprotein lipase inhibition

This study focuses on the impacts of polystyrene/polylactic acid microplastics (PS/PLA-MPs) on ovarian reserve and oocyte maturation in female mice, along with the underlying mechanisms. 1 μm PS-MPs and PLA-MPs were prepared, with PLA-MPs having a rougher surface and broader size distribution. In vitro, PLA-MPs showed higher cytotoxicity to granulosa cells compared to PS-MPs. In vivo, MPs exposure disrupted the estrous cycle, and damaged ovarian reserve. Granulosa cell apoptosis and cytokine activation led to transzonal projection retraction, oocyte oxidative stress, meiotic abnormalities, and reduced oocyte retrieval and polar body extrusion rate, thus reducing litter size. PS-MPs induced more severe intestinal and ovarian impairment. Analysis of feces 16S rRNA, serum metabolomics, and ovarian RNA sequencing revealed that lipoprotein lipase (LPL) was suppressed by both MPs, linking gut microbiota, lipid metabolism, and ovarian injury. Fecal microbiota transplantation as a rescue strategy in MPs exposed mice upregulated LPL, alleviating ovarian reserve decline. In PLA-MPs exposed mice, ovarian reserve related indicators partially recovered after a two-week exposure cessation. These results clarify the similarities and differences in how PS-MPs and PLA-MPs impair ovarian function via gut-ovary axis and lipid metabolism dysregulation.