Vitrification of equine expanded blastocysts following puncture with or without aspiration of the blastocoele fluid.
Authors: Wilsher S, Rigali F, Couto G, Camargo S, Allen W R
Journal: Equine veterinary journal
Summary
# Editorial Summary: Blastocoele Aspiration in Equine Embryo Vitrification Cryopreservation of equine embryos larger than 300 µm has historically yielded disappointing pregnancy rates unless the blastocoele fluid was actively removed before vitrification; Wilsher and colleagues investigated whether this aspiration step is truly essential for post-thaw survival. Fifty day 7–8 embryos underwent controlled puncture of the blastocoele cavity, with 28 subsequently having >90% of their fluid aspirated and 22 left unaspirated, before both groups were vitrified using a two-step cryoprotectant protocol and warmed using a standardised sucrose gradient. Overall pregnancy rates favoured the aspirated group (75% vs. 45%), but the critical finding emerged when embryos were stratified by diameter: larger embryos (>550 µm) showed a dramatic difference between aspirated and non-aspirated cohorts (72% vs. 10% pregnancy rates, P=0.006), whilst smaller embryos (≤550 µm) performed equally well regardless of aspiration (80% vs. 75%). For equine reproduction practitioners, this suggests that aspiration of blastocoele fluid remains important for larger expanded blastocysts to maximise post-warming viability, but can be omitted for smaller embryos—a distinction that may streamline preparation protocols and reduce procedural time without compromising success rates in the latter group.
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Practical Takeaways
- •Blastocoele fluid aspiration is critical for larger expanded blastocysts (>550 μm) but can be omitted for smaller embryos, simplifying the vitrification protocol
- •Size-based stratification of embryos allows practitioners to optimize cryopreservation procedures and reduce unnecessary manipulation of viable smaller embryos
- •Overall pregnancy rates of 45-75% support vitrification as a practical method for equine embryo preservation when proper technique is applied
Key Findings
- •Non-aspirated embryos achieved 45% pregnancy rate (10/22) versus 75% (21/28) for aspirated embryos overall (P=0.061)
- •For larger embryos >550 μm, aspiration significantly improved pregnancy rates: 72% (13/18) with aspiration vs 10% (1/10) without (P=0.006)
- •For smaller embryos ≤550 μm, aspiration was not necessary: 80% (8/10) without aspiration vs 75% (8/10) with aspiration (P=0.8)
- •Embryo diameter did not differ significantly between punctured only and punctured plus aspirated groups (646.4 vs 754.8 μm, P=0.215)