Preimplantation embryo metabolism and culture systems: experience from domestic animals and clinical implications

Abstract

Despite advantages of in vitro embryo production in many species, widespread use of this technology is limited by generally lower developmental competence of in vitro derived embryos compared to in vivo counterparts. Regardless, in vivo or in vitro gametes and embryos face and must adjust to multiple microenvironments especially at preimplantation stages. Moreover, the embryo has to be able to further adapt to environmental cues in utero to result in the birth of live and healthy offspring. Enormous strides have been made in understanding and meeting stage-specific requirements of preimplantation embryos, but interpretation of the data is made difficult due to the complexity of the wide array of culture systems and the remarkable plasticity of developing embryos that seem able to develop under a variety of conditions. Nevertheless, a primary objective remains meeting, as closely as possible, the preimplantation embryo requirements as provided in vivo. In general, oocytes and embryos develop more satisfactorily when cultured in groups. However, optimization of individual culture of oocytes and embryos is an important goal and area of intensive current research for both animal and human clinical application. Successful culture of individual embryos is of primary importance in order to avoid ovarian superstimulation and the associated physiological and psychological disadvantages for patients. This review emphasizes stage specific shifts in embryo metabolism and requirements and research to optimize in vitro embryo culture conditions and supplementation, with a view to optimizing embryo culture in general, and culture of single embryos in particular.

Oviduct: roles in fertilization and early embryo development

“…During this time, the fertilized embryos transition from oxidative metabolism to glycolic metabolism (Folmes & Terzic 2014). This transition is accompanied by (1) different nutrient compositions as the embryo travels through the oviduct, (2) maturation of the mitochondria to enable the embryo to establish its own metabolism and (3) a change in oxygen tension parallel to this shift in metabolism (Gardner et al 1996, Absalon-Medina et al 2014.…”

Exogenous glutathione supplementation in culture medium improves the bovine embryo development after in vitro fertilization

“…28 In normal cellular metabolism, ROS, which are generated in our body by various 29 endogenous systems, play an important role in signal transduction and modulating cellular 30 functions [3]. Excess ROS have been known to exert harmful effects on cells, such as DNA 31 damage, oxidation of polyunsaturated fatty acids in lipids, oxidation of amino acids in 32 proteins and inactivation of specific enzymes by oxidation of cofactors [4]. In particular, 33 hydrogen peroxide (H 2 O 2 ) produced from mitochondria induces oxidative damage.…”

The strategy of group embryo culture based on pronuclear pattern on blastocyst development: a two center analysis

“…Explanations for these findings is not easy to unravel. Indeed, despite greater understanding of the biology of the embryo, the dynamic and complex nature of in vivo conditions makes it difficult to completely elucidate factors involved in determining developmental competence [5].…”

“…Thus, in litter-bearing species, the grouped embryo culture is a standard procedure. Conversely, this group effect or spacing effect in non-litter-bearing species such as the human has to be fully defined [5]. Many ART laboratories culture groups of embryos in small volumes to obtain this perceived benefit of concentrating growth-promoting autocrine/paracrine biomolecules.…”