A comparison of the efficacy of three commercial human embryo vitrification kits for cryopreservation of in vivo produced equine embryos.
Authors: Wilsher Sandra, Ismer Ann, Grippo Agustina, Hoogewijs Maarten, Bussade Pedro, Kovacsy Sofia
Journal: Equine veterinary journal
Summary
# Editorial Summary: Equine Embryo Vitrification Kit Comparison Embryo freezing success in equine reproduction depends critically on the cryoprotective agents used during the vitrification process, yet limited research has directly compared commercially available systems adapted from human embryology. Wilsher and colleagues evaluated 108 in vivo-produced equine embryos (≤500 µm) vitrified using three commercial kits that shared the same penetrating cryoprotectants (DMSO and ethylene glycol) but differed in their non-penetrating agents: Kitazato (trehalose and hydroxypropyl cellulose), Vit Kit Freeze (sucrose and dextran serum supplement), and Vit Kit Freeze NX (trehalose and dextran serum supplement). For smaller embryos ≤400 µm, pregnancy rates were comparable across all three kits (72.7–90.9%), but for the largest embryos (>400–500 µm), the Kitazato kit achieved significantly superior pregnancy rates of 71.4% compared to just 21.4% and 14.3% for the other two kits. The combination of trehalose with hydroxypropyl cellulose appears particularly effective at protecting larger embryos through the vitrification and warming process, likely by optimising osmotic balance and reducing intracellular ice crystal formation in larger cells. For practitioners performing embryo transfer programmes, these findings suggest that embryo size should guide kit selection, with Kitazato offering meaningful advantages for larger embryos that might otherwise be discarded or have substantially lower viability using alternative systems.
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Practical Takeaways
- •When vitrifying equine embryos larger than 400 μm, use the Kitazato kit formulation (trehalose + hydroxypropyl cellulose) to maximize pregnancy rates post-transfer
- •For smaller embryos (≤400 μm), choice of commercial vitrification kit appears less critical as all three show comparable success rates
- •The specific combination of non-penetrating cryoprotectants, not just penetrating agents, significantly affects cryopreservation success in larger equine embryos
Key Findings
- •Pregnancy rates were equivalent across all three vitrification kits for smaller embryos (G1 ≤300 μm: 85.7% vs 72.7% vs 87.5%, p=0.63; G2 >300-400 μm: 83.3% vs 90.9% vs 81.8%, p=0.81)
- •For larger embryos (G3 >400-500 μm), Kitazato kit achieved significantly higher pregnancy rates (71.4%) compared to Vit Kit Freeze (21.4%) and Vit Kit Freeze NX (14.3%, p=0.003)
- •The combination of trehalose and hydroxypropyl cellulose as non-penetrating cryoprotectants in the Kitazato kit was superior for vitrifying larger embryos