228 EVALUATION OF EMBRYO VIABILITY AFTER PROLONGED TRANSPORT IN DIFFERENT MEDIA AND AT DIFFERENT TEMPERATURES

Abstract

In vitro-produced embryos (IVP) are known to have poor quality and be susceptible to heat and oxidative stress. In addition, they constantly undergo long-distance transport, which causes low conception rates. The aim of this study was to search for alternatives to long-distances transport of embryos produced in vitro by evaluating the use of different media and different temperatures. Bos indicus cumulus–oocyte complexes (COC; 823, quality I and II) were matured in TCM-199 bicarbonate–10% FBS (38.5°C, 5% CO₂, in air) for 24 h. The fertilization was performed in TALP-IVF medium for 18 h of incubation. Presumptive zygotes were transferred to SOF medium and in vitro culture in a controlled atmosphere (5% O₂, 5% CO₂, 90% N₂) for 7 days at 38.5°C. At Day 7, 366 embryos (quality I and II, IETS), were randomly allocated to the designated experimental groups. For Experiment 1, blastocysts were filled into straws and kept for 12 h at 36°C, using the medium as an independent variable according to the following groups: GSup, embryo support medium without FCS and amino acids (n = 115); and GHSOF, embryo culture medium SOF (HSOF) with FCS and amino acids (n = 105). Both media were buffered with HEPES. For Experiment 2, blastocysts were filled into straws with HSOF medium and sustained in transportation for 12 h, using temperature as the independent variable according to the following groups: G36, 36°C (n = 65); and G38, 38°C (n = 81). After 12 h of transport in both experiments, embryos were evaluated and classified as viable or nonviable blastocysts and were recultured in the same conditions mentioned. On Day 10, hatching rates and degeneration were evaluated. Logistic regression was used to compare the groups in each experiment. In Experiment 1, blastocyst viability after 12 h of transport was higher in the culture medium (GHSOF: 91.4%) than the support medium (GSup: 75.6%; P < 0.001). The hatching capacity in the culture medium (GHSOF: 72.4%) was higher than that in the support medium (GSup: 34.5%; P < 0.001). In Experiment 2, blastocyst viability post-transport was the same in both temperatures (G36: 92.3%, G38: 82.7%; P > 0.09). Blastocyst hatching capacity at 36°C (G36: 75.4%) was superior to that at 38°C (G38: 49%; P < 0.001). The hatching capacity immediately after 12 h of transport was minimal, so it was not possible to apply the logistic regression method in any experiment. In conclusion, the culture medium was more efficient for long-distance transport than the support medium; moreover, a temperature of 36°C for the culture medium increased embryo development compared with a temperature of 38°C during transport.