Use of bovine embryo as a biosensor to evaluate embryo toxicity of environmental phthalates and its impact on molecular signatures of fertility

Abstract

Endocrine disruptors (EDs) are synthetic or natural chemicals that can modulate the normal function of endogenous hormones, inducing an antagonistic effect on reproduction. In the last decade, special attention has been directed to studies involving EDs, however, focusing only on the isolated effects or minute associations of compounds, without a real prospect of environmental exposure to animals and humans. Studies about EDs behave in the environment reproduction is scarce in the literature, including an assessment of complex mixtures of illuminated phthalates in actual environmental exposure. Aiming to increase knowledge about the impacts of environmental EDs on the oocyte microenvironment and subsequent embryonic development, we propose investigated the effect of a mixture of six phthalates based on environmental exposure, on the microenvironment of in vitro maturation (IVM) of oocytes and its subsequent impact on early embryo development, evaluating the global profile of gene expression and microRNAs in bovine blastocysts. This is because isolated in bovine species, some phthalates administered during an IVM have been shown a negative impact the meiotic progression of oocytes, and subsequently, in decreasing cleavage rates, impairing embryonic development. Furthermore, this toxicological approach was able to increase the apoptosis rate, modify the gene expression pattern in oocytes, and modulate the transcriptional profile in bovine blastocysts. The phthalates also modulated the profile of microRNAs (miRNAs) involved in follicular development in mice and extracellular vesicles (EV-miRNAs) in follicular fluid in women under assisted reproduction programs. For this, bovine cumulus-oocytes-complex (COCs) the ovaries from a slaughterhouse, will be matured with a mixture of six different phthalates, in different concentrations base on environmental exposition to determine an initial screening. After IVM, the COCs will proceed to fertilization and subsequent in vitro embryo culture to characterize the concentration capable of generated embryotoxicity. Then, the embryos will be submitted to the evaluation of transcriptome and microRNA molecular signatures by RNA sequencing and the biological networks of the interaction of these signatures in bovine blastocysts will be created. Such analyzes will allow the construction of molecular studies on the impact of phthalates on early embryonic development. These results will provide a holistic view of the mixture of phthalates based on human and animal environmental exposure influence on in vitro microenvironment. And it will also provide subsidies for the construction of global networks of alterations found in embryonic quality, and the cellular pathways involved with such phenotype. (AU)