In vitro bovine embryo production in a synthetic medium:Embryo development, cryosurvival, and establishment ofpregnancy

The aim of this study was to develop an in vitro embryo culture medium without either fetal calf serum (FCS) or bovine serum albumin (BSA), using various growth factors and cytokines (GF-CYK) (IGF-I, IGF-II, bFGF, LIF, GM-CSF, TGF-β1 and PDGF-BB), and other molecules with surfactant and embryotrophic properties, such as recombinant albumin (RA) and hyaluronan (HA). The first part of the study was dedicated to defining the best combination of GF-CYK + RA + HA for optimal embryonic development. Next, we compared development rates and embryo quality (inner cell mass (ICM) to total cell number (TCN) ratio), and post-thaw survival and hatching rates using this synthetic medium (T1) and a control medium: SOF + BSA + ITS (Insulin, transferrin, selenium). The blastocyst rates were significantly higher with TI than with the control at 7 and 8 days post fertilization. There was no significant difference in TCN or the ICM/TCN ratio between the two treatments. Survival and hatching rates 48 hours after thawing were similar for both treatments. Finally, nine embryo transfers were conducted using fresh and previously frozen day-7 blastocysts to evaluate the in vivo viability of embryos produced in this synthetic medium; four gestations were obtained from 6 fresh embryos and one gestation from 3 frozen embryos. In conclusion, the FCS and BSA free medium, supplemented with GF-CYK + RA + HA, improved embryo development and gave comparable ICM/TCN ratios and post-thaw survival rates to the control with BSA. Fresh and frozen embryos produced in this medium are viable for embryo transfer. This fully synthetic method of embryo culture is a useful means of reducing the risk of disease transmission via embryo transfer.