Exposure to phthalate mixtures impairs mouse preimplantation embryonic development in an in vitro model†

The global decline in human fertility has become an increasing public health concern, marked by notable regional disparities and a growing reliance on assisted reproductive technologies (ART). Among the environmental contributors to reproductive dysfunction, phthalates, ubiquitous endocrine-disrupting chemicals, have been implicated in adverse reproductive outcomes. This study aimed to evaluate the effects of a biologically relevant phthalate mixture on preimplantation embryo development using an in vitro mouse model. Dosing proportions were based on phthalate concentrations measured in urine samples from pregnant participants in the Illinois Kids Development Study (I-KIDS), with the following composition: 35% diethyl phthalate (DEP), 21% di(2-ethylhexyl) phthalate (DEHP), 15% dibutyl phthalate (DBP), 15% diisononyl phthalate (DiNP), 8% diisobutyl phthalate (DiBP), and 5% benzyl butyl phthalate (BBzP). Embryos were exposed to this mixture at concentrations of 0.001, 0.01, 0.1, and 1 μg/mL, alongside control groups (culture medium only and 0.075% DMSO vehicle control), from the zygote to the hatched blastocyst stage. Exposure resulted in a significant reduction in developmental progression, with increased cytoplasmic fragmentation observed during the 2- to 8-cell transition in embryos treated with 0.1 and 1 μg/mL. Concentrations of 0.01, 0.1, and 1 μg/mL caused a marked decrease in E-cadherin expression at the 8-cell stage, and a significant increase in micronucleus formation was observed at the blastocyst stage after exposure to 0.1 and 1 μg/mL. These findings suggest that phthalate exposure disrupts critical processes in early embryogenesis, including cell adhesion, and nuclear integrity, potentially compromising embryo viability.