Short-term exposure to Cook, Vitrolife, and KSOM media shapes early calcium oscillations in ICSI-fertilized mouse oocytes and impacts adult phenotype

The influence of culture media used during in vitro fertilization (IVF) on the offspring phenotype remains controversial and not subject to consensus. However, the specific effects of short exposure time and duration immediately after fertilization remain underexplored. In this study, we investigated Ca ²⁺ oscillatory responses in mouse oocytes fertilized by intracytoplasmic sperm injection (ICSI) as an indicator of early metabolic activity. We evaluated the long-term effects of a short but critical 4-hour exposure to three different culture media: Cook and Vitrolife - commonly used in human IVF - and KSOM, a standard mouse embryo culture medium. Our results indicate that culture media significantly modulate Ca ²⁺ oscillations during oocyte activation. ICSI-fertilized oocytes cultured in Cook and Vitrolife exhibited fewer oscillations, lower frequency, and reduced inter-individual variability compared to KSOM, which produced a more diverse oscillation pattern. Notably, these early differences correlated with long-term developmental outcomes: females derived from Cook and Vitrolife embryo cultures exhibited were heavier throughout their growth period and had larger adult organ sizes compared to those derived from KSOM. These findings highlight the critical influence of this short post-fertilization window in shaping Ca ²⁺ dynamics, which serve as biomarkers of metabolic variation and ultimately influence adult phenotype. Further research is needed to explore additional IVF media and refine culture conditions to better understand the metabolic pathways linking fertilization environment to offspring development. Optimization of embryo culture protocols in assisted reproductive technologies may improve developmental outcomes in IVF.