Effect of potential oocyte transport protocols on blastocyst rates after intracytoplasmic sperm injection in the horse.

The research article discusses the potential of transporting oocytes (immature/developing egg cells) using different protocols to fertility laboratories to increase the application of Intracytoplasmic Sperm Injection (ICSI). ICSI is particularly useful in breeding infertile horses and those with limited sperm count but due to its technical complexity and cost, broad implementation has been a challenge. The study evaluates different protocols of transporting oocytes while maintaining their viability.

Research Methodology

• Oocytes were extracted from dominant stimulated follicles via transvaginal ultrasound-guided follicular aspiration a day after administering deslorelin, or from immature or subordinate follicles at the same time.
• For mimicking transport conditions, oocytes from dominant stimulated follicles were incubated overnight under different conditions before the ICSI procedure. Immature oocytes were held overnight under varied circumstances before in vitro maturation and subsequently injecting sperm.
• Blastocyst development was then measured and compared across the various treatment groups.

Study Results

• Blastocysts, an essential stage in embryogenesis prior to implantation, were yielded in all groups.
• Oocytes from dominant stimulated follicles that were held in sealed tubes in a pre-equilibrated control maturation medium at 37°C produced similar blastocyst development as oocytes incubated under control conditions (70%).
• Oocytes from dominant stimulated follicles that were held in a warm passive device had poor blastocyst development (10%).
• Immature oocytes held for one to two nights in modified M199 medium or one night in commercial embryo holding solution, at room temperature, yielded a consistent 35-37% blastocyst development per injected oocyte.

Conclusions

• The study found that a commercially available medium can effectively be used for shipping immature oocytes at room temperature with a reasonable rate of blastocyst formation.
• Oocytes from dominant stimulated follicles provide better blastocyst rates, but they need to be maintained at 37°C because they are already maturing at the time of collection, and are consequently more sensitive to delays.
• Conclusively, this practical information could support the wider application of ICSI by facilitating the transportation of both immature and dominant stimulated follicle oocytes to specialized laboratories.