CRYOPRESERVATION OF MOUSE AND HUMAN OOCYTES USING 1,2-PROPANEDIOL ANDTHE CONFIGURATION OF THE MEIOTIC SPINDLE

Human and mouse oocytes were cryopreserved by a slow freeze, rapid tha w method, using propanediol (PROH) as the cryoprotectant. A simulated cryopreservation was also included in the study to detect the level of damage attributable to the PROH alone. Comparison of the mouse and hu man oocytes cryopreserved by the same method showed opposing results, with a poor morphological survival rate of 4% observed for mouse oocyt es and a subsequent normal fertilization rate of 0%. In 171 cryopreser ved human oocytes a higher survival rate of 64% was achieved, and this showed more similarity to the mouse pronuclear oocytes survival of 53 %. A comparison of human oocytes, cryopreserved within the cumulus and denuded of cumulus and corona prior to cryopreservation, demonstrated a higher survival rate in the denuded oocytes of 69% compared to 48%. A delay prior to cryopreservation of 1 or greater-than-or-equal-to 2 days had no effect on the immediate survival of oocytes, but culture f or a further 24 h after thawing reduced survival, with the day 1 oocyt es exhibiting the most dramatic reduction in survival (28%). Using a l ectin binding method, abundant cortical granules were observed in all cryopreserved oocytes analysed. The meiotic spindle and chromosomes we re examined in cryopreserved oocytes using fluorescence microscopy and 60% of the surviving oocytes had a normal spindle and chromosome conf iguration.