Impact of cryopreservation method on dromedary camel ovary structure, viability, and development of antral follicular oocytes

The objectives of this study were, a) to compare two different vitrification techniques, the solid surface vitrification (SSV) and direct vitrification (DV) method, b) to evaluate the effect of four cryoprotectant agents and their toxicity on the morphological appearance and ultrastructural of camel ovarian cortex, c) to examine the development of oocytes recovered from the vitrified ovarian cortex. Fragments of ovarian cortex were exposed to equilibration solution consisting of TCM- 199 with 10% fetal camel serum (FCS); 0.10M sucrose and including one of the following cryoprotectants; 20% glycerol (GLY); 3.5M ethylene glycol (EG); 3.5M propanediol (PROH) or 3M dimethylsulphoxide (DMSO). After vitrification of ovarian fragments, they were warmed and evaluated by histological and transmission electron microscope. The oocytes isolated from vitrified ovarian cortex were cultured in TCM-199 at 38.5°C under 5% CO2 for 44h. Maturation was indicated through cumulus expansion and calculated by oocytes reaching first telophase and second metaphase (TI+MII). The percentage of morphologically normal and viable follicles of SSV was significantly higher P<0.05 than DV group (52.9 vs. 38.1, respectively). In conclusion, viability, histological and ultrastructural observations revealed that SSV method and ethylene glycol-based freezing solution were able to remain morphology better follicle and oocyte. Additionally, most organelles of oocytes are able to recover their normal morphology in camel ovarian cortex following cryopreservation and thawing processes, and oocytes isolated from vitrified ovarian cortex can exhibit maturation and reaches to (TI+MII).