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

Area of Science:

• Reproductive Biology
• Developmental Biology
• Animal Science

Background:

• Ungulate embryo development involves critical cell differentiation and proliferation around blastocyst hatching.
• Failures in these stages cause early pregnancy losses, impacting livestock farming economically.
• Conventional embryo culture media (e.g., SOF) do not support development beyond hatching, unlike N2B27 medium.

Purpose of the Study:

• To investigate if earlier exposure to N2B27 medium can enhance ungulate embryo development after hatching.
• To determine the optimal timing for initiating N2B27 culture to improve post-hatching development and cell differentiation.

Main Methods:

• Embryos were cultured in N2B27 medium from different time points (Day 5, 6, or 7) and compared to SOF medium.
• Evaluated hypoblast migration and epiblast development into embryonic disc (ED)-like structures at Day 12.
• Assessed epiblast and hypoblast cell numbers in Day 8 blastocysts.

Main Results:

• Culture in N2B27 from Day 5, 6, or 7 significantly enhanced hypoblast migration and ED-like structure formation compared to SOF.
• N2B27 from Day 5 increased Day 8 blastocyst cell numbers but sometimes led to disorganized epiblast cells.
• Culture in N2B27 from Day 7 onwards improved subsequent post-hatching development.

Conclusions:

• Bovine embryo culture in N2B27 from Day 7 onwards significantly improves post-hatching development.
• This optimized in vitro system facilitates research into cell differentiation and early pregnancy failure mechanisms.
• The findings offer a valuable tool for studying developmental biology without animal experimentation.