Embryonic disc formation following post-hatching bovine embryo development in vitro

Area of Science:

• Reproductive Biology
• Developmental Biology
• Embryology

Background:

• Conceptus elongation failures cause significant economic losses in ungulate farming.
• Current in vitro methods (post-hatching development system) fail to support embryonic disc formation and show poor embryo viability.
• Understanding early ungulate development is hindered by the inability to replicate it in vitro.

Purpose of the Study:

• To develop an improved in vitro culture system that supports embryonic disc formation in ungulate embryos.
• To overcome limitations of existing post-hatching development systems, specifically regarding embryonic disc development and cell survival.

Main Methods:

• Comparison of embryo development in agarose tunnels versus free-floating cultures using standard post-hatching development medium.
• Evaluation of a chemically defined N2B27 medium for supporting post-blastocyst development without agarose coating.
• Assessment of hypoblast migration, epiblast survival, and expression of the pluripotency marker SOX2.

Main Results:

• Agarose tunnels restricted embryo growth without improving hypoblast/epiblast lineage development.
• The N2B27 medium supported complete hypoblast migration and epiblast survival in vitro.
• Embryonic disc-like structures composed of SOX2+ cells formed in approximately 25% of embryos cultured in N2B27 medium.

Conclusions:

• A novel chemically defined medium (N2B27) supports key developmental events, including hypoblast migration and epiblast survival, post-blastocyst.
• This culture system facilitates the formation of embryonic disc-like structures in vitro, a critical step previously unattainable.
• The developed system offers a promising avenue for studying ungulate embryonic development and improving reproductive efficiency in livestock.