Evaluation of development after cryopreservation of in vitro bovine produced embryos

Author(s)

Alessandra Corallo Nicacio

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2008-03-07

Examining board members

José Antonio Visintin; Mayra Elena Ortiz D\'Avila Assumpção; Paula Ripamonte Figueiredo; Fabíola Freitas de Paula Lopes; Marco Roberto Bourg de Mello

• Advisor: José Antonio Visintin

Abstract

The inefficiency of embryo cryopreservation protocols limits the broad use of in vitro production (IVP) of bovine embryos. The aim of this work was to identify the damage caused by cryopreservation and embryo culture of in vitro produced bovine embryos after thawing by morphological analysis, gene expression and in vitro development before and after cryopreservation. Cummulus-oocyte complexes were in vitro matured, fertilized and cultured. Expanded blastocysts (n= 600) harvested on days 7-9 were submitted controlled freezing [controlled group: 10% ethylene glycol (EG) for 10 minutes and 1.2oC per minute cryopreservation], quick-freezing [quick group: 10% EG for 10 minutes, 20% EG + 20% Glycerol (Gly) for 30 seconds] or vitrification [vitrification group: 10% EG for 10 minutes, 25% EG + 25% Gly for 30 seconds] protocols. The embryos of the control group were not exposed to cryoprotectant or crypreservation method and the hatching rate was evaluated on day12 post-insemination. The straws (quick and vitrification groups) were first placed on nitrogen vapor (0.8 cm over the liquid nitrogen) for 2 minutes and than immersed in liquid nitrogen. Embryos were thawed in air for 10 seconds followed by 25oC water bath for 20 seconds. Embryos were rehydrated in PBS + 0.2% BSA + 0.3M sucrose for 3 minutes and PBS + 0.2% BSA for the same time. In order to evaluate development of frozen-thawed embryos they were cocultured on granulosa cells in TCM 199 or SOFaa for 4 days. Hatching rate of control group was 46.09%. Data was analyzed by PROC MIXED model of SAS Sistems for Windows®. Controlled group hatching rate was 44.65% ± 5.94 and 11.65% ± 3.37 for TCM 199 and in SOFaa, respectively. Embryos submitted to quick group did not hatch regardless of culture condition. Vitrification group showed hatching rates of 9.43% ± 6.77 and 8.67% ± 4.47, respectively, in TCM 199 and SOFaa., and values were significant at p<0.05. The controlled group showed difference between the other groups of cryopreservation in both medium (TCM 199 and SOFaa). However, TCM 199 showed high rates of re-expansion and hatching. To gene expression analysis, 2 pools of 10 expanded blastocysts of fresh and cryopreserved embryos (controlled freezing) was used to RNA extraction, Reverse Transcription PCR (RT-PCR) was done and submitted to a Real Time PCR. The results of the Real Time PCR showed that the amount of material was not enough to the amplification of products in all reactions. In conclusion, the culture medium influences the embryo development after the cryopreservation being TCM199 more appropriate than SOFaa. And more number of expanded blastocysts is necessary to analysis the gene expression in a Real Time PCR reaction. (AU)