Effect of Embryo Density onIn vitroDevelopmental Characteristics of Bovine Preimplantative Embryos with Respect to Micro and Macroenvironments

Abstract

To overcome developmental problems as a consequence of single embryo culture, the Well of the Well (WOW) culture system has been developed. In this study, we aimed to examine the effect of embryo densities with respect to both microenvironment and macroenvironment on developmental rates and embryo quality to get a deeper insight into developmentally important mechanisms. WOW diameter and depth significantly affected developmental rates (p < 0.05). WOWs with diameter of 500 μm reached significantly higher blastocyst rates (32.5 vs 21.1% vs 20.3%) compared to embryos cultured in WOWs of 300 μm diameter or plain cultured controls. Embryos cultured in WOWs with 700 μm depth reached significant higher developmental rates compared with embryos cultured in WOWs of 300 μm depth and control embryos (30.6 vs 22.6% vs 20.3%). Correlation of the embryo per WOW volume with developmental rates was higher (r(2) = 0.92, p = 0.0004) than correlation of WOW diameter or WOW depth with developmental rates. However, the embryo per WOW volume did not affect differential cell counts. An embryo per culture dish volume of 1 : 30 μl was identified to be optimal when the embryo per WOW volume was 1 : 0.27 μl increasing developmental rates up to the level of mass embryo production. Giving the opportunity to track each embryo over the complete culture period while keeping high developmental rates with normal mitotic dynamics, the results of this work will provide benefit for the single culture of embryos in human assisted reproduction, mammalian embryos with high economic interest as well as for scientific purpose.

Effect of culture medium volume and embryo density on early mouse embryonic development: Tracking the development of the individual embryo

“…It has been postulated to dilute metabolized toxic products while accumulating autocrine and/or paracrine factors released by the embryos, resulting in improved embryonic development [8,16,18,19]. Although the WOW system was developed initially for shortterm co-culture of zona-free mouse embryos to produce chimerae [34], the system has been shown to be useful in tracking individual zona-intact embryo cultured in groups [8,16,18,19], which presents an alternative to single embryo culture. Our future research will be aimed at developing a culture system for tracking individual embryo development following in vitro oocyte maturation (IVM) without imparirment of embryo development to the blastocyst stage.…”

“…For this purpose, the well-of-the-well (WOW) system has been adapted in order to track the development of individual embryo [8,[16][17][18][19]. An embryo to culture dish volume ratio of 1:30 μl has been identified to be optimal when each embryo was cultured in a 0.27 μl micro-well, producing developmental rates up to the level of mass embryo production in cattle [18]. However, the optimal volume of medium droplets or density of embryos to be used with the WOW system remains to be determined.…”

Improved blastocyst formation with reduced culture volume: comparison of three different culture conditions on 1128 sibling human zygotes

“…In animal models, small culture volume as well embryo grouping have been proposed as two different strategies to improve embryo developmental potential [2,4,5,7,8,10,18,19,30] since autocrine and paracrine factors of embryonic origin are likely to mimick in vivo conditions [1,4,5,7,9,13]. In a recent review, Reed and coauthors [7] describe the impact of group versus individual cultures on embryo development.…”

“…Studies concerning embryo physiology and metabolism have highlighted the importance of autocrine and paracrine growth factors affecting embryo development in vivo [1][2][3][4][5][6][7][8][9][10]. However, recent data have shown that preimplantation embryos promote their own development in vitro also in absence of paracrine factors secreted by the female reproductive tract [4,6,7,11,12].…”

“…However, recent data have shown that preimplantation embryos promote their own development in vitro also in absence of paracrine factors secreted by the female reproductive tract [4,6,7,11,12]. It seems that embryos generate an autocrine loop of growth stimulation, producing their own growth factors and receptors [1,4,6,7,13].…”