Ambient temperature transport of human oocytes: an unexpected research resource

This study aimed to determine the viability and meiotic competence of human oocytes deemed not suitable for clinical use following controlled ovarian stimulation of young egg donors receiving treatment at an egg bank.

A total of 432 oocytes were shipped at ambient temperature overnight, in a medium containing caffeine and dibutyryl cyclic-AMP to limit meiotic cell cycle progression, and estrogen and progesterone to mimic the intrafollicular environment. In some experiments, transport medium was also supplemented with 1 µg/ml ZnSO₄. Oocytes were either fixed immediately upon arrival or cultured for 20-24 or up to 143 h followed by fixation. Time-lapse imaging and fluorescence imaging were used to establish viability, meiotic status, and spontaneous activation.

Greater than 95% of transported oocytes retained viability, whether transported with or without added ZnSO₄, exhibiting meiotic progression and/or spontaneous activation following overnight culture. Time-lapse imaging and fluorescence imaging revealed a higher incidence of spontaneous activation and subsequent cleavage activity for up to 5 days in culture in samples transported in ZnSO₄.

Under the experimental conditions described here, immature human oocytes retain viability and meiotic competence following ambient temperature transport, providing a novel and experimentally tractable resource for future research in human oocyte biology and the development of human parthenote stem cells.