Cellular damage suffered by equine embryos after exposure to cryoprotectants or cryopreservation by slow-freezing or vitrification.
Authors: Hendriks W K, Roelen B A J, Colenbrander B, Stout T A E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Cellular Damage in Cryopreserved Equine Embryos Hendriks and colleagues examined whether slow-freezing or vitrification causes less cellular injury to equine embryos, since current practice shows small embryos (<300 µm) tolerate cryopreservation reasonably well whilst larger ones do not. Using multiphoton microscopy and fluorescent staining to assess cellular integrity markers, the team evaluated 63 Day 6.5–7 embryos across five treatments: control, exposure to slow-freezing or vitrification cryoprotectants alone, and cryopreservation by each technique. Large embryos exposed to vitrification cryoprotectants suffered substantially more cell death (6.8%) than those in slow-freezing media (0.3%), whilst both cryopreservation methods induced cell death and cytoskeletal disruption; however, vitrification of small embryos resulted in a higher proportion of apoptotic cells (6.7% vs 5.0%) yet a lower rate of complete embryo disintegration than slow-freezing. Although vitrification offers practical advantages, the significantly elevated cell death in large embryos makes it unsuitable for this size group, and modifications to the vitrification protocol are needed before it can become the standard method for equine embryo preservation, particularly given the variable and occasionally severe cellular damage observed even in smaller embryos.
Read the full abstract on PubMed
Practical Takeaways
- •Do not use vitrification for cryopreserving large equine embryos (>300 μm) due to significantly higher cell death rates; slow-freezing is the safer choice
- •For small embryos, slow-freezing may be preferable despite occasional high cell damage with vitrification, as it reduces the risk of complete embryo disintegration
- •Current vitrification protocols require further optimization before becoming standard practice in equine embryo cryopreservation programs
Key Findings
- •Large embryos exposed to vitrification cryoprotectants showed significantly more dead cells (6.8%) compared to slow-freezing media (0.3%; P=0.001)
- •Vitrification of small embryos resulted in higher proportions of apoptotic nuclei (6.7% vs 5.0%; P=0.002) than slow-freezing
- •Slow-freezing caused higher incidence of embryo disintegration than vitrification (P=0.01)
- •Vitrification altered mitochondrial distribution from crystalline to granulated pattern but did not differentially affect mitochondrial activity compared to slow-freezing (P=0.05)