Vitrification of equine expanded blastocysts following puncture with or without aspiration of the blastocoele fluid.

The research investigates the necessity of aspirating the fluid within the blastocoele cavity of equine embryos prior to vitrification. This process is perceived as essential for successful cryopreservation in larger embryos. However, results suggested that aspiration may not be as critical for smaller embryos.

Objective and Methodology

The primary objective of the study was to ascertain whether aspiration of the blastocoele fluid before vitrification plays a crucial role for post-warming survival of the equine embryos.

• A total of 50 embryos, recovered on day 7-8, were prepared and washed in a specific holding medium (HM).
• These embryos were punctured using a micromanipulator mounted biopsy needle. Out of the total, 28 embryos had over 90% of their blastocoelic fluid actively aspirated, whereas the remaining 22 were not aspirated.
• The embryos were then subjected to vitrification, a process comprising increasing concentrations of Dimethyl Sulfoxide (DMSO), ethylene glycol, and sucrose.
• After vitrification, the embryos were warmed by transferring them in HM with a specified amount of sucrose and at a certain temperature.
• The embryos were also transferred to a recipient mare for further research.

Results

The outcome of the study showed no significant difference in the diameter of the embryos between the punctured and the punctured-plus-aspirated group. However, pregnancy rates varied between the non-aspirated and aspirated embryos, with a higher rate found in the aspirated group.

The study also found a significant higher pregnancy rate in aspirated embryos larger than 550 µm. In contrast, the size of embryos appeared to make no difference in the pregnancy rates among the smaller embryos.

Conclusion

The study concluded that aspiration of blastocoele fluid from embryos of size less than or equal to 550 µm is not a pre-requisite for successful vitrification. However, for larger embryos, blasting fluid aspiration was found to be more beneficial, yielding a high pregnancy rate. Despite these results, the researchers identified limitations due to the small size of the studied groups.