Polystyrene microplastics internalization by term placental chorionic villi explants

INTRODUCTION: Microplastics (MPs) are pervasive environmental contaminants increasingly found within human tissues, including the placenta. This study explores the potential of polystyrene (PS)-MPs to cross the placental barrier and their general distribution within term placental chorionic villi explants. METHODS: Term placental chorionic villi explants were exposed up to 72 h to 100 μg/mL of 5 μm-size polystyrene (PS)-MPs, and their internalization was analyzed by optical microscopy, confocal atomic force microscopy (C-AFM) and fluorescence confocal imaging. RESULTS: The PS-MPs can traverse the placental barrier. Over 72 h of exposure, these particles were not only adsorbed on the surface but also internalized within the syncytiotrophoblast and dispersed through the chorionic villi mesenchyme. Our observations indicate that PS-MPs are found up to 120 μm deep within the villi, suggesting their capability to penetrate deeply into placental tissue. Furthermore, these MPs were surrounded by a thin layer of actin, implying active internalization mechanisms possibly involving macropinocytosis or phagocytosis, although specific pathways in placental tissues remain to be fully elucidated. No evidence of barrier fissures or membrane ruptures was observed, indicating that the internalization process does not disrupt the syncytiotrophoblast barrier integrity. DISCUSSION: This study underscores the urgent need to understand the implications of such internalization and their effects on placental homeostasis. Given the potential for MPs to influence developmental processes adversely, further research is essential to delineate the mechanisms of MP internalization, possible physiological impacts, and the consequences of fetal exposure.