Artificial plasticenta: how polystyrene nanoplastics affect in-vitro cultured human trophoblast cells

Antonio Ragusa ¹ Loredana Cristiano ^2* Pierluigi Di Vinci ³ Giuseppe Familiari ² Stefania Annarita Nottola ² Guido Macchiarelli ⁴ Alessandro Svelato ⁵ Caterina De Luca ⁵ Denise Rinaldo ⁶ Isabella Neri ³ Fabio Facchinetti ³

• ¹ Department of Obstetrics and Gynecology, Maggiore Hospital Carlo Alberto Pizzardi, Bologna, Italy
• ² Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Sapienza University, Rome, Rome, Italy
• ³ Department of Medical and Surgical, Maternal-Infantile and Adult Sciences, University of Modena and Reggio Emilia, Modena, Lombardy, Italy
• ⁴ Department of Life, Health and Environmental Sciences, University of L'Aquila, L’Aquila, Abruzzo, Italy
• ⁵ Department of Obstetrics and Gynecology, Magna Grecia University of Catanzaro, Catanzaro, Italy
• ⁶ Department of Obstetrics and Gynecology, ASST Bergamo Est, Bolognini Hospital, Bergamo, Lombardy, Italy

In the human placenta, we have detected the MPs by Raman microspectroscopy analysis and with transmission electron microscopy. MPs fragments have been localized in different compartments of placental tissue, free in the cytoplasm and within organelles like lysosomes. Their presence has been correlated with ultrastructural alterations of some organelles, typical of metabolic stress, such rough endoplasmic reticulum and mitochondria. We have speculated that microplastics in the placenta could be responsible for pathological traits activation such as oxidative stress, apoptosis, and inflammation causing long-term effects on the health of the mother and child. In this paper we also demonstrate the in vitro cytotoxicity of PS-NPs on a trophoblast human cell line. Our study shows that starting from 24h exposure, PS-NPs treatment, at 50µg/ml dose, has a cytotoxic effect on placental cells, causing the death of 40% of cells and affecting the morphology of the surviving cells. In the surviving cells, we found that NPs enter the cells, affecting the ultrastructure of endoplasmic reticulum and mitochondria and accumulating as aggregates within lysosome-like organelles. Interestingly, the NPs aggregates become larger as the concentration of NPs increases. We speculated that the accumulation of NPs inside lysosome-like organelles could result from a prolonged and impossible attempt by the cell to remove and destroy PS. This would lead to ER and mitochondrial stress, impairing mitochondria/ER functions and oxidative stress, and activating the apoptotic pathway. So, we suggest that PS-NPs could act as a cell stressor, leading to the death of cells. In support of our hypothesis, we also found NPs associated with morphological signs of cellular regression and degeneration. An abnormal amount of NPs in the cells might determine a persistent cellular alarm CDR (cell danger response), the evolutionarily conserved metabolic response that protects the cells and hosts from harm triggered by chemical (as in the case of NPs/MPs), physical, or biological agents that exceed the cellular capacity for homeostasis. This in vitro study could further help to demonstrate that the inevitable exposure of MPs/NPs in the environment, which characterizes the modern world, might be partially responsible for the epidemic of non-transmissible disease.