Oocyte maturation in a contaminated environment : effects of perfluoroalkyl substances on bovine early embryo development in vitro

Sammanfattning: The content of this thesis is dedicated to female fertility, and more specifically the maturing oocyte. The aim was to investigate chemicals present in the direct environment of the oocyte and more specifically to investigate the sensitivity of the oocyte to perfluoroalkyl substances (PFASs) using a bovine in vitro embryo production model. Human ovarian follicular fluid and serum were subjected to non-target screening. Substances were prioritized according to ubiquitous exposure, calculated hazard, accumulation in follicular fluid, and association to embryo quality. The results showed that the follicular fluid contained a complex mixture of endogenous and exogenous compounds. Standards were used to confirm the identity of selected compounds, of which some were associated with embryo quality. The effects of oocyte exposure to perfluorononanoic acid (PFNA), perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) were analysed by combining confocal imaging of nuclei and lipids with microarray-based transcriptomic and epigenomic studies of blastocysts. The results showed how oocyte exposure to high concentrations of PFASs caused embryo lethality. At lower concentrations, the developmental rate and lipid distribution in the blastocyst were affected. The molecular data showed potential pathways related to these findings. To conclude, the results presented in this thesis highlight the complexity of the environment in which the oocyte develops and furthermore how exposure to PFASs interfere with bovine early pre-implantation embryonic development in vitro.