Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Animal Production

Embryo cryopreservation becomes a pivotal side in shaping assisted reproductive technologies. It plays an essential role in several cases such as, embryo storage during transportation, embryo preservation for future uses and establishment of cryobanks for endangered species and rare breeds. The present experiment was conducted to evaluate the cryotolerance of in vitro produced buffalo embryos at blastocyst stage to vitrification process using cryotop. Embryos were produced using conventional in vitro fertilization technique and had been divided into two categories: non-vitrified group, which was cultured in vitro till hatched blastocyst stage and used as a control group. On the other hand, vitrified group, which was collected at day 7 following IVF for cryopreservation. A stepwise vitrification and thawing procedures were performed using Cryotop. Survival rate of embryos was observed within 24 hours of thawing, then the ability for expansion and hatching was recorded. The expansion rate was significantly (P<0.05) higher in control group compared to vitrified group (89.72 vs. 79.07%, respectively). In both groups, all expanded blastocysts reached the hatching stage normally. Moreover, gene expression pattern for HSPA1A, SLC2A1 and POU5F1 was upregulated in vitrified group compared with control group. On the contrary, KRT18 was downregulated in cryopreserved group compared with control group. Therefore, the current results suggested that Cryotop is an effective tool for cryopreservation of in vitro produced Egyptian buffalo blastocyst. Furthermore, the freezing technique modification of gene regulation for the purpose of maintaining embryo viability

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