In vitro viability of cryopreserved equine embryos following different freezing protocols.
Abstract: The main objective of this study was to evaluate two freezing protocols and the effect of agar embedding on survival of day 6.5 equine embryos. A total of 133 embryos were used, in one group (n = 51), embryos were first embedded in agar before the freezing protocol was started. A freezing protocol to -30 degrees C or -33 degrees C was used before plunging embryos into liquid nitrogen (LN2). The embryos were thawed in water at 37 degrees C, evaluated and placed in culture. After 24 h culture, the embryos were evaluated for their morphology and development. No differences were observed between embryos plunged at -30 degrees or at -33 degrees C in LN2. The analysis of the morphology and development after thawing showed that the diameter and developmental stage at freezing correlated with embryo survival. Morula and early blastocyst stages of development were associated with better quality after freezing and thawing and had a better potential to survive after in vitro culture (p < 0.05) compared to more advanced stages. The agar failed to protect embryos from zona pellucida damage, but a tendency to prevent rupture was observed in larger embedded embryos.
Publication Date: 1994-10-01 PubMed ID: 7889453PubMed Central: PMC1263705
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study aimed to assess the effectiveness of two protocols for cryopreserving horse embryos and the impact of embedding these embryos in agar before freezing. The researchers determined that the stage of embryo development at the time of freezing was most significant for the successful revival and continued growth of the embryos after thawing.
Research Purpose and Methodology
- This research was designed to assess the viability of equine embryos that had undergone cryopreservation using two different freezing protocols, and the potential protective effects of pre-freezing agar embedding.
- The researchers experimented with 133 embryos. In one group, embryos were embedded in agar, a jell-like substance derived from algae, before freezing to test if it increases their survival rate after thawing.
- The freezing took place at either -30 degrees C or -33 degrees C before the embryos were stored in liquid nitrogen (LN2), a standard procedure in cryogenics that ensures extremely low temperatures for long-term preservation.
- Once thawed in 37 degrees C water, the embryos were systematically evaluated and placed in a culture for continued growth.
Results and Key Findings
- There were no observable differences in the success rates between embryos frozen at -30 degrees C and those frozen at -33 degrees C in LN2, suggesting that both temperatures are equally effective for cryopreservation.
- However, the morphology and stage of embryos at freezing significantly affected their viability after thawing. Embryos that were in morula (a stage of early development) or early blastocyst (the stage of development before implantation) stages at the time of freezing yielded better results after thawing and were more likely to survive further in vitro culture.
- Agar embedding didn’t protect embryos from damage to the zona pellucida, a hard outer shell surrounding the embryo. However, in larger embryos, agar embedding showed a general trend towards preventing rupture or breakage, although it was not statistically significant.
Conclusions and Implications
- The research has potential implications for improving horse breeding and animal conservation practices as it suggests the optimal protocol for cryopreserving equine embryos, i.e., freezing during the early stages of development.
- While agar embedding did not significantly reduce damage to the embryo’s zona pellucida during freezing, it may still potentially prevent rupture in larger embryos, suggesting a need for further investigation.
Cite This Article
APA
Poitras P, Guay P, Vaillancourt D, Zidane N, Bigras-Poulin M.
(1994).
In vitro viability of cryopreserved equine embryos following different freezing protocols.
Can J Vet Res, 58(4), 235-241.
Publication
Researcher Affiliations
- Département de Médecine, Québec.
MeSH Terms
- Animals
- Cryopreservation / methods
- Cryopreservation / veterinary
- Embryo Transfer / veterinary
- Fetal Viability / physiology
- Horses / embryology
- In Vitro Techniques
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