The impact of endocrine disrupting chemicals diethylstilbestrol and ketoconazole on lipid storage in in vitro matured bovine cumulus-oocyte complexes

Endocrine disrupting chemicals (EDCs) impact female fertility, and their widespread presence demands deeper understanding of their effects on reproduction. In vitro maturation of bovine cumulus-oocyte complexes (COCs) serves as a relevant reproductive toxicology model aligned with the 3R principle. Given the link between lipid metabolism and COC quality, the possibility that lipid droplets (LDs) in cumulus cells (CCs) and overall COC lipid content are susceptible to EDC disruption was tested. COCs were exposed to diethylstilbestrol (DES; estrogen receptor agonist) and ketoconazole (KTZ; steroidogenesis inhibitor), during in vitro maturation. Neutral lipid dyes were used for LD visualization (count, size, area, and clustering) in CCs. Lipidomic analysis using liquid chromatography-mass spectrometry was conducted separately on oocytes and CCs. Of all tested DES concentrations (i.e., 10-9 M, 10-7 M, 10-5 M), 10-5 M DES reduced the total LD area per CC, associated with decreased LD count and increased size. KTZ at all tested concentrations (i.e., 10-8 M, 10-7 M, 10-6 M) reduced LD size and enhanced clustering. Lipidomic analysis revealed the selective depletion of cholesteryl esters in CCs exposed to 10-5 M DES or 10-6 M KTZ, with minimal changes in other neutral lipid classes. Thus EDCs can disrupt lipid storage and LD dynamics in bovine COCs. We discuss these new findings with our previous work: (i) DES-induced steroidogenesis while (ii) in contrast KTZ blocked steroidogenesis in CCs. Together, the data highlight the COC lipid metabolism as a novel EDC target, warranting further study due to potential implications for female fertility.