Investigation of potential detrimental effects of nano- and microplastics in human endometrial stromal cells

<title>Abstract</title> Nanoplastics (NPs) and Microplastics (MPs) have become a global concern in recent years. However, the effects of NPs and MPs on the female reproductive system have not been elucidated, yet. In this study, we aimed to establish proper in vitro NPs and MPs exposure protocol and to investigate possible cytotoxic effects of NPs and MPs on human endometrial cells, using different plastic size and concentrations. It was noted that smaller plastics, specifically 100 nm NPs and 1 µm MPs, exhibited a higher propensity for cellular uptake compared to larger counterparts such as 5 µm MPs. These smaller plastic particles demonstrated the ability to induce notable morphological changes and provoke cell death at concentrations exceeding 100 µg/mL over a 24-hour period. Furthermore, we confirmed the accumulations of these particles in the nucleus and cytoplasm of endometrial cells using confocal microscopy and a real-time imaging device. A significantly higher rate of internalization was observed, manifesting a discernible correlation between the size of the plastics and the degree of penetration into both the nucleus and cytoplasm. In conclusion, this is the first study to demonstrate that exposures of 100 nm NPs and 1 µm MPs results to dynamic accumulations of these particles within endometrial stromal cells, leading to cell death at specific concentrations. Our findings imply potential adverse impacts of these particles on fertility and reproductive health, underscoring the need for further research to elucidate the exact underlying molecular mechanisms.