Preconception paternal PFAS exposure in mice reprograms the placental epigenome

The placenta plays a vital role in supporting fetal growth and development by facilitating nutrient exchange, hormone signalling and immune regulation. Environmental toxicants such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) can disrupt placental homeostasis, leading to increased risk of disease later in life. Paternal environmental exposures may influence offspring health by inducing epigenetic changes in sperm, which may affect sex-dependent placental programming. Here, male mice were exposed to a PFAS mixture (PFOS, PFOA, PFNA, PFHxS, GenX; 20 μg/L each) for 10 weeks and mated with unexposed females. We identified 6,656 and 3,242 differentially methylated regions (DMRs) in E12.5 placentas of female and male offspring, respectively. Female placentas showed predominantly hypermethylation (78.5%), whereas male placentas were mostly hypomethylated (62%). Gene ontology analyses linked female placental DMRs to cell and embryonic morphogenesis, and male DMRs to anatomical size regulation and hemostasis. Bulk RNA sequencing revealed 168 and 148 differentially expressed genes (DEGs) in female and male placentas, respectively. Female DEGs were related to immune regulation, while male DEGs were involved in muscle and mesenchyme development. Sex-by-PFAS interaction models identified distinct methylation and transcription biological pathways. Overlap analysis between F0 sperm and F1 placentas identified 265 shared genes, including 289 female-specific and 124 male-specific genes. Paternal exposure to the PFAS mixture increased glycogen concentrations in male, but not female, placentas. No effects were observed at imprinted loci. These findings demonstrate that paternal preconception exposure to a PFAS mixture alter placental epigenomic and transcriptomic landscapes, which may contribute to sex-dependent trajectories of fetal health and development and offspring phenotypes.