Pre-hatching exposure to N2B27 medium improves post-hatching development of bovine embryos in vitro

4 Pág.Ungulate embryos undergo critical cell differentiation and proliferation events around and after blastocyst hatching. Failures in these processes lead to early pregnancy losses, which generate an important economic impact on farming. Conventional embryo culture media, such as SOF, are unable to support embryo development beyond hatching. In contrast, N2B27 medium supports early post-hatching development, evidencing a swift in embryonic nutritional requirements during this developmental window. Here, we investigate if earlier exposure to N2B27 could improve embryo development after hatching. Embryo culture in N2B27 from day (D) 5, 6 or 7 significantly enhanced complete hypoblast migration (>45 vs. ∼24%) and epiblast development into an embryonic disc (ED)-like structure at D12 (>40 vs. 23%), compared to embryos cultured in SOF up to D9. Culture in N2B27 from D5 significantly increased epiblast and hypoblast cell number in D8 blastocysts, but post-hatching embryos cultured in N2B27 from D5 or 6 frequently showed a disorganized distribution of epiblast cells. In conclusion, bovine embryo culture in N2B27 from D7 onwards improves subsequent post-hatching development. This improved fully in vitro system will be very useful to functionally explore cell differentiation mechanisms and the bases of early pregnancy failures without requiring animal experimentation.This work has been funded by the projects StG-757886-ELONGAN from the European Research Council and PID2020-117501RB-I00 and ECQ2018-005184-P from the Spanish Ministry of Science and Innovation to PBA, and by the project PID2021-122153NA-I00 from the Spanish Ministry of Science and Innovation to PRI.Peer reviewe

Trascription factor TEAD4 is not required for bovine blastocyst formation

Departamento de Reproducción animalPeer reviewe

Analysis of ZP1 gene reveals differences in zona pellucida composition in carnivores

International audienc

ZP4 confers structural properties to the zona pellucida essential for embryo development

18 Pág.Zona pellucida (ZP), the extracellular matrix sheltering mammalian oocytes and embryos, is composed by 3 to 4 proteins. The roles of the three proteins present in mice have been elucidated by KO models, but the function of the fourth component (ZP4), present in all other eutherian mammals studied so far, has remained elusive. Herein, we report that ZP4 ablation impairs fertility in female rabbits. Ovulation, fertilization and in vitro development to blastocyst were not affected by ZP4 ablation. However, in vivo development is severely impaired in embryos covered by a ZP4-devoided zona, suggesting a defective ZP protective capacity in the absence of ZP4. ZP4-null ZP was significantly thinner, more permeable, and exhibited a more disorganized and fenestrated structure. The evolutionary conservation of ZP4 in other mammals, including humans, suggests that the structural properties conferred by this protein are required to ensure proper embryo sheltering during in vivo preimplantation development.This work was supported by Grants AGL2014-58739-R, RYC-2012-10193, AGL2017-84908R, AGL2016-71890-REDT, PGC2018-094781-B-100, AGL2015-70159-P and AGL2015-65572-C2-1-R from the Spanish Ministries of Economy and Competitiveness and Science, Innovation and University, and 757886-ELONGAN from the European Research Council. ILT and NFB are supported by FPI fellowships from the Spanish Ministry of Economy and Competitiveness. AQF by Marie Curie Action FP7/2007-2013 grant 600391 from EU, and LGB by a FPU fellowship from the Spanish Ministry of Education, Culture and sportsPeer reviewe