Embryo competence and cryosurvival: Molecular and cellular features

Abstract

Global cattle genetic market is experiencing a change of strategy, large genetic companies, traditionally recognized in the artificial insemination field, have also begun to operate in the embryo market. Consequently, the demand for in vitro produced (IVP) embryos has grown. However, the overall efficiency of the biotechnology process remains low. Additionally, the lack of homogeneity of post-cryopreservation survival results of IVP embryos still impairing a massive dissemination of this biotechnology in the field. A great challenge for in vitro production labs is to increase the amount of embryos produced with exceptional quality after each round of in vitro fertilization. Herein, we discuss the molecular and cellular features associated with the competence and cryosurvival of IVP embryos. First, morphofunctional, cellular and molecular competence of the embryos were addressed and a relationship between embryo developmental ability and quality were established with cryosurvival and pregnancy success. Additionally, determinant factors of embryo competence and cryosurvival were discussed including the following effects: genotype, oocyte quality and follicular microenvironment, in vitro production conditions, and lipids and other determining molecules. Finally, embryo cryopreservation aspects were addressed and an embryofocused approach to improve cryosurvival was presented.

Developmental Plasticity in Response to Embryo Cryopreservation: The Importance of the Vitrification Device in Rabbits

“…A plausible explanation for this difference is that preimplantation embryos can develop a stress-dependent response when faced with different cooling-warming rates during vitrification. On the other hand, some studies suggested that embryo cryopreservation may acts as selection pressure, filtering-out ART-sensitive embryos that not sustain the stresses associated with vitrification and warming processes [52][53][54]. In this sense, and in concordance with the higher mortality exhibited by the VTs embryos, it is well stablished that straw devices provoke slower cooling-warming rates, and thus more troublesome conditions for embryo survival than Cryotop devices [18,19,[27][28][29].…”

A shorter equilibration period in the VitTrans in-straw bovine embryo vitrification method improves post-warming outcomes

“…The timing of blastocyst formation is a good marker of embryo quality determining that early-cavitating embryos are of better quality than later cavitating embryos in terms of total cell numbers, inner cell mass and trophectoderm cell distributions, and cryosurvival [30,34]. While we still lack reliable blastocyst stage morphological predictors of competence after embryo transfer, it is accepted by many research groups and commercial companies that best pregnancy rates are achieved after the transfer of day 7 expanded bovine blastocysts whether fresh or cryopreserved (reviewed by [41,42]).…”

Transcriptional profiling of embryo cryotolerance

“…Cryopreservation challenges the embryonic cells thermally, osmotically, toxically, and mechanically (for review, see Marsico et al, 2019). Typically, deleterious effects within the plasma membrane, cytoplasmic organelles, and cytoskeleton of embryonic cells can occur (Dobrinsky et al, 2000; Zeron et al, 2002).…”

“…However, the overall efficiency of the in vitro production process remains low (Lonergan & Fair, 2016; Luciano et al, 2018; Marsico et al, 2019). Additionally, the lack of homogeneity of postcryopreservation survival results of IVP embryos continues to hinder the massive dissemination of this technology.…”