Polychlorinated biphenyls (PCBs) are one of the most common endocrine-disrupting chemicals and have obvious toxicity on human reproductive development. The aim of our study was to investigate the toxicity of chronic 2,3',4,4',5-pentachlorobiphenyl (PCB 118) exposure on embryo implantation and endometrial receptivity, with the possible mechanism of DNA methylation involved. Virgin CD-1 female mice (3 weeks old) were housed and orally treated with PCB 118 (0, 1, 10, 100 μg/kg) for a month. After mating with fertile males, the pregnant mice were killed on gestation day 4.5. Compared with the control group, implantation failures were observed in 1 μg/kg PCB 118- and 100 μg/kg PCB 118-treated groups. Abnormal endometrial morphology with open uterine lumens and densely compact stromal cells and poorly developed pinopodes were substantially in response to PCB 118 doses above, as well as the significant downregulation of implantation-associated genes (estrogen receptor 1, homeobox A10 [HOXA10], integrin subunit beta 3) and hypermethylation in the promoter region of HOXA10 further. It was confirmed that chronic exposure to PCB 118 produced an increased number of implantation failures in association with a defective uterine morphology during the implantation period. Alterations in methylation of HOXA10 could explain, at least in part, the mechanism of effects of PCB 118 exposure on the implantation process.
Keywords: HOXA10; PCB 118; endometrial receptivity; methylation.