113 EVALUATION OF DIFFERENT CRYOPROTECTANT AND FORSKOLIN IN THE CULTURE MEDIUM FOR IMPROVING THE EFFICACY OF VITRIFICATION OF BOS INDICUS IN VITRO-DERIVED EMBRYOS

Abstract

Embryo cryopreservation is an essential method for the biotechnology of reproduction. This is the safest option for interchange of genetic material for research and commercial purposes. For cattle, Brazil has become the leading country in the world for the number of in vitro-produced embryos, using mostly Bos indicus animals. However, considering the in vitro method of embryo production, field results have shown a lower resistance to cryopreservation for B. indicus when compared with Bos taurus embryos. A possible explanation for this is a great concentration of lipid droplets in the cytoplasm of cells fromB. indicus embryos. The objective of this study was to compare 2 cryoprotectants (Propanediol and DMSO) to vitrification and evaluate the effect of adding 10 μM forskolin to the SOF medium for embryo culture before cryopreservation. For all the experiments, ovaries from slaughtered Nelore Bos indicus donors were recovered and maintained at 30 to 35°C in NaCl solution until recovery of the COC. Embryos submmited to vitrification were expanded blastocysts at Day 7 of in vitro culture. In the first experiment embryos were first incubated in 10% ethylene glycol (EG) plus 10% DMSO dissolved in holding medium (TCM-HEPES with 20% calf serum) for 1 min and then transferred to droplet of 20% EG plus 20% DMSO in holding medium and 0.5 M sucrose for 20 s before immersing in liquid nitrogen (n = 107; group EG + DMSO). For the group EG + Propanediol (EG + PRO; n = 96), blastocysts were placed in 10% EG plus 10% PRO in holding medium for 1 min and then transferred to a droplet of 20% EG plus 20% PRO in holding medium and 0.5 M sucrose for 20 s before immersing in liquid nitrogen. Both treatments were performed using the Cryotop system. Results were compared with embryos (n = 118) not submitted to cryopreservation. The evaluation was done by the hatching rate of blastocysts at Day 9, being higher (86.4%) for embryos not cryopreserved, when comparing with 77.1% for group EG + PRO and 72.9% for group EG + DMSO (P < 0.05). In the second experiment, Day 5 embryos obtained in vitro from Nelore donors were cultured using SOF medium with 10 μM forskolin (n = 112) or not (control; n = 101), being all submitted to cryopreservation using Cryotop and the same vitrification method for group EG + DMSO. Results were compared with embryos cultured with SOF medium and not submitted to cryopreservation (n = 96). The evaluation was performed by considering hatching rate at Day 9, being higher (85.4%) for not cryopreserved, when compared with 63.3% for control and 70.5% for forskolin group (P < 0.05). Considering embryos submitted to cryopreservation, the hatching rate was higher (P < 0.05) for the forskolin group.