Cryopreservation of in vitro-produced embryos: challenges for commercial implementation
Sanches, Bruno ValenteZangirolamo, Amanda FonsecaSilva, Nathalia Covre daMorotti, FabioSeneda, Marcelo Marcondes
In the last several years, the high demand for embryo production has resulted in the need to study new methods to make the cryopreservation of bovine embryos produced in vitro more efficient. Despite the advantages offered by in vitro embryo production (IVEP), the major challenge to its greater dissemination is to improve embryonic survival after cryopreservation. Embryos that are produced in vitro are less resistant to cryopreservation compared to those produced in vivo, which is due to the higher accumulation of lipids in their cells, among other factors. In this context, changes in the culture conditions such as the addition of lipolytic chemical substances and the adjustment of fetal calf serum in the medium have been proposed to decrease the lipid amount within the embryos. Several years ago, vitrification allowed good results for in vitro produced (IVP) embryos because of its simplicity, speed and low cost. More recently, another technique applied to simplify the embryo post-thawing rehydration step in vivo, direct transfer (DT), is a strategy that has proven to be of interest in helping to overcome limitations to the cryopreservation of in vitro produced embryos. DT has been performed by commercial laboratories, ensuring good embryo viability after thawing. However, commercial and operational limitations prevent the large-scale use of these techniques. Thus, this review aims to discuss the use of strategies to improve the post-cryopreservation survival capacity and the aspects to be overcome so that the cryopreservation of IVP embryos becomes a well-established and commercially applicable technique in addition to presenting new guidelines for embryo transfer (ET) programs from a better selection of recipients.(AU)
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