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Published on: July 6, 2022
Partial Recovery of Mitochondrial Function of Vitrified Porcine MII Stage Oocytes During Post-Thaw Incubation
J J Dai1, J H Yang1, S S Zhang1
1Institute of Animal Science and Veterinary Medicine, Shanghai Academy of Agricultural Sciences; Division of Animal Genetic Engineering, Shanghai Municipal Key Laboratory of Agri-Genetics and Breeding, Shanghai, China.
Abstract:
The survival of porcine oocytes is still very low after cryopreservation.
Objective:
To investigate whether and when the mitochondrial function of vitrified porcine oocytes could be recovered post-thaw.
Materials And Methods:
Mitochondrial potential, ROS level, ATP content, apoptotic rate, caspase activity, and parthenogenetics developmental ability of thawed porcine oocytes were measured after culture in vitro for 0, 1, 2 or 4 h.
Results:
Mitochondrial potential after 2 h and 4 h post-thaw culture were 1.19 and 1.26, significantly lower than that of fresh oocytes but much higher than the groups cultured for 0 h and 1 h (P<0.05). Cryopreservation increased the ROS level in oocytes considerably, which decreased only after 2 to 4 h incubation following thaw. ATP content increased gradually over time and recovered to the level comparable to that of fresh oocytes after 4 h. Pan caspase levels increased after cryopreservation and reached the highest level at 1 h incubation. Thereafter it decreased to a low value, but still higher than fresh oocytes. Oocytes showing an early apoptotic event decreased upon 2 to 4 h incubation. The parthenogenetic cleavage and blastocyst rates were the highest (19.8% and 5.6%) after 2 h incubation.
Conclusion:
The recovery of mitochondrial function could complete after 2 to 4 h post-thaw incubation. Post-thaw incubation for 2 to 4 h reduced apoptotic events and improved parthenogenetic developmental ability of vitrified porcine MII stage oocytes.
Insights
Post-thaw incubation for 2-4 hours aids mitochondrial function recovery in cryopreserved porcine oocytes. This incubation period reduces apoptosis and enhances parthenogenetic developmental potential, improving oocyte survival rates.
Area of Science:
- Reproductive Biology
- Cryobiology
- Oocyte Biology
Background:
- Porcine oocyte cryopreservation survival rates remain suboptimal.
- Mitochondrial dysfunction is a key factor limiting post-thaw oocyte viability.
Purpose of the Study:
- To determine if and when mitochondrial function recovers in vitrified porcine oocytes after thawing.
- To assess the impact of post-thaw incubation time on oocyte viability and developmental capacity.
Main Methods:
- Vitrified porcine oocytes were thawed and cultured in vitro for 0, 1, 2, or 4 hours.
- Key parameters measured included mitochondrial potential, reactive oxygen species (ROS) levels, ATP content, apoptotic rate, caspase activity, and parthenogenetic developmental ability.
Main Results:
- Mitochondrial potential and ATP content significantly improved with 2-4 hours of incubation.
- Reactive oxygen species (ROS) levels decreased, and apoptotic events reduced after 2-4 hours post-thaw.
- Parthenogenetic cleavage (19.8%) and blastocyst rates (5.6%) were highest after 2 hours of incubation.
Conclusions:
- Mitochondrial function recovery in vitrified porcine oocytes is achieved within 2-4 hours of post-thaw incubation.
- This incubation period is crucial for mitigating cryopreservation-induced damage, reducing apoptosis, and enhancing developmental competence.
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