Feline cumulus cells and oocytes show massive accumulation of lipid droplets and upregulation of PLIN2 expression after in vitro maturation

This study investigates lipid content and expression of genes involved in lipid metabolism in feline cumulus cells and oocytes before and after in vitro maturation (IVM). Domestic cats represent valuable models in reproductive research, yet the efficiency of in vitro embryo production remains suboptimal, with contributing factors still under investigation. We characterized lipid droplets (LDs) in oocytes collected from adult queens, both before and after IVM, using confocal microscopy with Bodipy 493/503 staining. We also quantified the expression of four genes involved in regulation of lipid metabolism. Our findings revealed a substantial accumulation of LDs and a significant upregulation of PLIN2 expression in both cumulus cells and oocytes following IVM. The number and total area of LDs and fluorescence intensity increased markedly in oocytes at the MII stage, while the average LD diameter decreased. Similarly, cumulus cells showed an increase in number and total area of LDs post-IVM, suggesting their involvement in oocyte maturation by modulating lipid homeostasis. This study presents the first detailed characterization of lipid droplet dynamics in feline oocytes and cumulus cells, providing insights into metabolic processes during IVM, which are critical for optimizing assisted reproductive technologies in felids.