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Anisosmotic conditions lead to disruption of the MII spindle in human oocytes. Applying this fundamental knowledge to human oocyte cryopreservation should result in increased numbers of cells maintaining viability.

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Objectives-To 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.Design-An incomplete randomized block design was used for this study.Setting-A University-affiliated assisted reproductive center.Patients-Women undergoing assisted reproduction in the Center for Reproductive Medicine at Shandong University.Interventions-Oocytes were exposed to 1.0 molar ethylene glycol in a single step, and photographed during subsequent volume excursions.Main outcome measures-A 2-parameter model was employed to estimate the permeability to water and EG.Results-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. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Some of the results from this study were presented at the 62 nd annual meeting of the American Society for Reproductive Medicine, 21-25 October 2006, in New Orleans, LA USA. Conflict of Interest: None. CapsuleHuman metaphase II oocyte permeability to ethylene glycol was determined. A method for vitrification, based upon fundamental principles, was developed from these data. Conclusions-Despite the lower permeability of human MII oocytes to ethylene glycol compared to 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 which prevent excessive osmotic stress and minimize exposure to high concentrations of this compound. NIH Public Access

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