Membrane permeability of human oocytes in the presence of the cryoprotectant propane-1,2-diol

Objective: To determine the permeability of unfertilized human oocytes to water and the cryoprotectant propane-1,2-diol over a range of temperatures and to use these data to predict osmotic responses under given conditions. Design: Laboratory-based study. Setting: Teaching hospital. Patient(s): Infertility patients donating unfertilized oocytes in excess of those required for treatment. Intervention(s): None. Main Outcome Measure(s): Water and cryoprotectant permeability were determined from measurements of oocyte volume excursions on exposure to 1.5 M propane-1,2-diol at 30°C, 24°C, and 10°C. Result(s): Permeability of human oocytes to water and cryoprotectant increased as temperature increased. The predicted response of oocytes, based on these data, closely matched the measured response of an oocyte on exposure to a widely used method for addition of cryoprotectant before freezing. Conclusion(s): Commonly used cryopreservation protocols involving slow cooling in the presence of propane-1,2-diol cause potentially damaging excursions in cell volume on exposure to cryoprotectant. Modifications that can be expected to reduce cell volume excursions, based on oocyte permeability data, are suggested