Vitrification of in vivo fertilised mouse embryos at different embryonic stages using modified carrier

Vitrification has dominated the cryopreservation field and has seen extensive progress predominantly contributing to research in human, domestic animals and laboratory animals. However, there is still lack of information on the ovulation and fertilisation rates, consensus towards the optimal embryonic stages for vitrification and the high cost of commercially available microcarriers often poses a concern to researchers. Thus, this study aims (1) to compare the ovulation and fertilisation rates of oocytes following superovulation (2) to compare the survival and in vitro development (IVD) between vitrified-warmed embryos at two embryonic stages and (3) to determine the efficacy of using a modified PCR tube as an open carrier for vitrification. Imprinting Control Region (ICR) mice of 6-10 weeks old were superovulated, followed by 1:1 mating with mice of similar strain. The mice were sacrificed via cervical dislocation, dissected and embryos at 2-cell stage were selected for in vitro culture (IVC) until desired stages. The compact morula (CM) and early blastocyst (EB) embryos obtained were randomly assigned to treatment groups, (A) control group (B) toxicity test group (C) PCR tube as modified carrier (MC) (D) commercial cryoleaf (CL) carrier. The embryos from treatment groups (B), (C) and (D) were vitrified-warmed using the two-step vitrification. The embryos from all treatment groups were then further cultured in IVC medium to assess on its survivability and IVD. This study found that there were no significant differences (p  0.05) in the ovulation and fertilisation rates between the right and left ovaries, the survival and IVD between the vitrified-warmed embryos at CM or EB and the efficacy of the proposed modified carrier were similar to cryoleaf. Thus, this study suggests that the MC holds a promising alternative as an open carrier for vitrification and further improvements could be conducted to increase its efficacy.