Short-Term Exposure to Culture Media Used in Human ART Shapes Early Calcium Oscillations in ICSI-Fertilized Mouse Oocytes and Impacts Adult Phenotype.

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 Ca2+ 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 Ca2+ 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 Ca2+ 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 Ca2+ dynamics and adult phenotypes. Optimizing embryo culture protocols in assisted reproductive technologies may improve IVF outcomes by modulating metabolic pathways linked to development.