Abstract
PURPOSE: The influence of culture media used during in vitro fertilization (IVF) on offspring phenotype remains controversial. However, specific effects of short exposure time after fertilization remain underexplored. By evaluating Ca(2+) oscillations as a readout of the first response of eggs to their microenvironment, we aim to investigate if early differences correlate with later adult phenotypes. METHODS: Oocytes fertilized by ICSI were cultured for 4 h in three different media (Cook and Vitrolife, used in human IVF, and KSOM, used for mouse embryos). They were either measured for Ca(2+) oscillations or transferred into pseudo-pregnant females. After birth, growth curves of pups were measured up to adulthood and various organs were weighed. RESULTS: 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 variability compared to KSOM. These early differences correlated with long-term developmental outcomes: females from Cook and Vitrolife cultures were heavier throughout growth and had larger adult organ sizes compared to those from KSOM. CONCLUSIONS: Brief exposure to media immediately after ICSI shapes Ca(2+) dynamics and adult phenotypes. Optimizing embryo culture protocols in assisted reproductive technologies may improve IVF outcomes by modulating metabolic pathways linked to development.