Human oocyte vitrification: the permeability of metaphase II oocytes to water and ethylene glycol and the appliance toward vitrification

ObjectiveTo determine the permeability of human metaphase II oocytes to ethylene glycol and water in the presence of ethylene glycol, and to use this information to develop a method to vitrify human oocytes.DesignAn incomplete randomized block design.SettingA university-affiliated assisted reproductive center.Patient(s)Women undergoing assisted reproduction in the Center for Reproductive Medicine at Shandong University.Intervention(s)Oocytes were exposed to 1.0 molar ethylene glycol in a single step and photographed during subsequent volume excursions.Main Outcome Measure(s)A two-parameter model was employed to estimate the permeability to water and ethylene glycol.Result(s)Water permeability ranged from 0.15 to 1.17 μm/(min·atm), and ethylene glycol permeability ranged from 1.5 to 30 μm/min between 7°C at 36°C. The activation energies for water and ethylene glycol permeability were 14.42 Kcal/mol and 21.20 Kcal/mol, respectively.Conclusion(s)Despite the lower permeability of human metaphase II oocytes to ethylene glycol compared with previously published values for propylene glycol and dimethylsulfoxide, methods to add and remove human oocytes with a vitrifiable concentration of ethylene glycol can be designed that prevent excessive osmotic stress and minimize exposure to high concentrations of this compound.