The effect of co-culture on the development of in vitro matured equine oocytes after intracytoplastic sperm injection.
Authors: Rosati I, Berlinguer F, Bogliolo L, Leoni G, Ledda S, Naitana S
Journal: Equine veterinary journal
Summary
# Editorial Summary Equine in vitro embryo production remains technically challenging, with no universally optimal culture protocol established; this 2002 study compared three post-fertilisation culture systems to determine which best supported embryonic development following intracytoplasmic sperm injection (ICSI). After collecting 261 oocytes from 55 ovaries and maturing them in TCM 199 medium supplemented with foetal calf serum and gonadotrophins, 149 metaphase II oocytes were fertilised via ICSI using frozen semen (achieving a 32% fertilisation rate) and then cultured in three different environments: simple TCM 199 alone, TCM 199 on a granulosa cell monolayer (co-culture), or SOF medium with reduced oxygen conditions. Co-culture with granulosa cells produced superior results, with a 73.5% cleavage rate and the highest proportion of advanced-stage embryos (five reaching >32 cells), compared to 74.4% cleavage but poorer development in simple medium and only 39.1% cleavage with significant oocyte degeneration in the reduced-oxygen SOF system. These findings suggest that factors secreted by somatic cells substantially enhance equine embryo viability in vitro, indicating that future optimisation of assisted reproduction protocols should prioritise identifying and replicating the supportive mechanisms provided by granulosa cell co-culture rather than relying on defined chemical media alone.
Read the full abstract on PubMed
Practical Takeaways
- •For equine breeding programmes using assisted reproductive technologies, co-culture with granulosa cells significantly improves post-ICSI embryo development compared to standard culture media
- •The identification of specific beneficial factors produced by somatic cells in co-culture systems could lead to optimised defined media formulations for equine embryo culture
- •Simple culture media alone are insufficient for supporting equine embryo development beyond early cleavage stages; co-culture approaches should be considered as standard practice in equine IVF programmes
Key Findings
- •Co-culture on granulosa cell monolayer (Group B) achieved 73.5% cleavage rate with superior embryonic development compared to TCM 199 alone (74.4% cleavage but less advanced development)
- •SOF + MEM amino acids + BSA culture system (Group C) showed significantly lower cleavage rates (39.1%) with maximum development limited to 2-6 cell stage
- •32% fertilisation rate achieved using ICSI with frozen equine semen on in vitro matured oocytes
- •Co-culture systems supported more advanced embryonic stages (up to >32 cell stage in Group B) compared to simple culture media alone