Comparison of clinical artificial oocyte activation protocols on mouse egg activation and embryo development

Artificial oocyte activation (AOA) with Ca2+ ionophores is an experimental procedure that benefits patients who fail to obtain fertilized eggs. However, the impact of non-physiological Ca2+ increases on cellular events involved in egg-embryo transition and early development remains poorly understood. Using the mouse model, this study compares common Ca2+ ionophore protocols applied in clinical practice - one or two exposures to A23187 or a single exposure to ionomycin - focusing on embryonic development and cellular events associated with egg activation. All groups of ionophore-activated eggs exhibit lower levels of first mitotic division compared to those activated by spermatozoa or SrCl2, attributable to the variations in Ca2+ dynamics during activation. At the cellular level, these eggs presented defects in spindle morphology and chromosome segregation during meiosis progression, associated with lower levels of cytoplasmic ATP, without changes in reactive oxygen species (ROS). These findings highlight the importance of optimizing Ca2+ management in AOA protocols.