• Journal of Embryo Transfer
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• v.29 no.1
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• pp.13-19
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• 2014

This study was carried out to study the survival rate of thawed Hanwoo embryos frozen by the slow-rate freezing or the cryotop vitrification method. Hanwoo cumulus-oocyte complexes were recovered from ovaries at a slaughter house, matured for 20~22 hours, fertilized with Hanwoo semen for 5~6 hours, and cultured for 7~9 days in $38.5^{\circ}C$, 5% $CO_2$ incubator. For freezing, Day 7~9 blastocysts were collected. Embryos for the slow-rate freezing were equilibrated in 1.8 M ethylene glycol (EG) with Dulbecco's phosphate-buffered saline (D-PBS). Programmable cell freezer was precooled down to $-7^{\circ}C$, and the straw was seeded during 8 minutes-holding time, and was cooled to $-35^{\circ}C$ at the cooling rate of $0.3^{\circ}C/min$, and then was plunged and stored in liquid nitrogen. Embryos for the cryotop vitrification were treated in TCM199 with 0.5 M sucrose, 16% EG, 16% dimethylsulfoxide (DMSO). Embryos were then loaded individually onto cryotop and plunged directly into liquid nitrogen. The survival rates of embryos frozen by these two freezing methods were evaluated at 12 to 24h post-thawing. The survival rates of frozen/thawed Hanwoo embryos by the cryotop vitrification method ($56.86{\pm}26.53%$) were slightly higher than those by the slow-rate freezing method ($55.07{\pm}26.43%$) with no significant difference. Using the cryotop vitrification and the slow-rate freezing of Hanwoo blastocysts on Day 7 following in-vitro fertilization (IVF) treatment, the survival rates of frozen/thawed Hanwoo embryos were $72.65{\pm}18.3%$ and $79.06{\pm}17.8%$, respectively. The survival rates by the cryotop vitrification were higher than those by the slow-rate freezing on both Day 8 and 9 with significantly higher survival rate on Day 9 (p<0.05). Using the cryotop vitrification and the slow-rate freezing of Hanwoo embryos to compare between three different blastocyst stages, the survival rates of the blastocyst stage embryos were $66.22{\pm}18.8%$ and $45.76{\pm}12.8%$, respectively with higher survival rate by the vitrification method (p<0.05). And the survival rate of expanded blastocysts was higher than those of early blastocysts and blastocysts in two freezing methods with significantly higher survival rate by the slow-rate freezing method (p<0.05).

• Clinical and Experimental Reproductive Medicine
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• v.45 no.3
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• pp.110-115
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• 2018

Objective: To compare our in-house method of embryo freezing with Cryotop vitrification in terms of immediate survival, subsequent cleavage and blastocyst formation, and cell numbers in blastocysts. Methods: Two-cell mouse embryos were randomly allocated into three groups: a non-frozen control group (group 1, n = 300), a group that underwent Cryotop vitrification (group 2, n = 300), and a group that underwent our in-house freezing method (group 3, n = 300). Results: There were no significant differences between groups 2 and 3 in the immediate survival rate (96.3% vs. 98.6%, respectively; p= 0.085), the further cleavage rate (91.7% vs. 95.0%, respectively; p= 0.099), or the blastocyst formation rate (80.7% vs. 78.6%, respectively; p= 0.437). The cell numbers in the blastocysts from groups 1, 2, and 3 were comparable ($88.99{\pm}10.44$, $88.29{\pm}14.79$, and $86.42{\pm}15.23$, respectively; p= 0.228). However, the percentage of good-quality blastocysts in the Cryotop vitrification group was significantly higher than in the group in which our in-house method was performed, but was lower than in the control group (58.0%, 37.0%, and 82.7%, respectively; p< 0.001). Conclusion: At present, our method is inferior to the commercial Cryotop vitrification system. However, with further improvements, it has the potential to be useful in routine practice, as it is easier to perform than the current vitrification system.

• Journal of Embryo Transfer
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• v.27 no.4
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• pp.259-264
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• 2012

Solution of glycerol, ethylene glycol, sucrose, dextrose (GESD) and cryotop methods were carried out to investigate the survivability on vitrification of embryos. Embryos cultured in vitro were vitrified by GESD of 10 or 8 step and cryotop methods of 6 step, from cryopreservation step to frozen-thawed and culture step. Survival rate and ICM, TE cells of embryos were investigated after frozen-thawed 24 h. As a results, cryotop method was significantly (p<0.05) higher ($85.76{\pm}5.3$ vs. $66.71{\pm}2.4$, $44.80{\pm}2.1%$) than GESD 10 or 8 step methods on survivability. Also, In ICM cell number, cryotop method was significantly (p<0.05) higher to $45.67{\pm}4.7$ cells than GESD 8 step method. TE cell number was significantly (p<0.05) highest to $111.00{\pm}11.0$ cells in cryotop method. On the other hand, survival rate, TE and total cell number were all the significantly (p<0.05) high, except ICM in GESD 10 step method between GESD 10 step method and GESD 8 step method. In conclusion cryotop method was to be most effective, but it is considered necessary to study vitrification method for step-by-step freezing and thawing process.

• Clinical and Experimental Reproductive Medicine
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• v.39 no.4
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• pp.153-160
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• 2012

Objective: The aim of this study was to compare vitrification optimization of mouse embryos using electron microscopy (EM) grid, cryotop, and thin plastic strip (TPS) containers by evaluating developmental competence and apoptosis rates. Methods: Mouse embryos were obtained from superovulated mice. Mouse cleavage-stage, expanded, hatching-stage, and hatched-stage embryos were cryopreserved in EM grid, cryotop, and TPS containers by vitrification in 15% ethylene glycol, 15% dimethylsulfoxide, 10 ${\mu}g/mL$ Ficoll, and 0.65 M sucrose, and 20% serum substitute supplement (SSS) with basal medium, respectively. For the three groups in which the embryos were thawed in the EM grid, cryotop, and TPS containers, the thawing solution consisted of 0.25 M sucrose, 0.125 M sucrose, and 20% SSS with basal medium, respectively. Rates of survival, re-expansion, reaching the hatched stage, and apoptosis after thawing were compared among the three groups. Results: Developmental competence after thawing of vitrified expanded and hatching-stage blastocysts using cryotop and TPS methods were significantly higher than survival using the EM grid (p<0.05). Also, apoptosis positive nuclei rates after thawing of vitrified expanded blastocysts using cryotop and TPS were significantly lower than when using the EM grid (p<0.05). Conclusion: The TPS vitrification method has the advantages of achieving a high developmental ability and effective preservation.

• Clinical and Experimental Reproductive Medicine
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• v.40 no.4
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• pp.148-154
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• 2013

Objective: To compare the mouse oocyte vitrification outcomes of the CryoLogic vitrification method (CVM) and the conventional open method using a Cryotop. Two CVM methods (original CVM and modified CVM) were tested. Methods: Mature oocytes obtained from female BDF-1 mice were vitrified by two-step exposure to equilibrium and vitrification solutions. Three vitrification protocols were tested on three groups: the CVM-kit, modified CVM, and Cryotop groups. After exposure to the two solutions, the oocytes were vitrified. After warming, the oocytes were fertilized in vitro, and the embryo development was assessed. Blastomeres positive for caspase were counted using an in situ assay kit. The spindle morphology and chromosome configurations of warmed vitrified oocytes were also assessed. Results: The modified CVM and Cryotop groups showed similar developmental capacities, and similar proportions of cells with intact spindles and chromosome configurations. The modified CVM protocol was superior to the original CVM protocol for developmental competence and intact spindle preservation. However, the CVM group showed a relatively higher number of apoptotic cells in blastocysts. Conclusion: Closed vitrification using the modified CVM protocol may be used as an alternative to the conventional open method, but strategies to decrease apoptosis in the blastomere need to be investigated.

• Journal of Animal Reproduction and Biotechnology
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• v.35 no.2
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• pp.207-213
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• 2020

Cryopreservation is used for blastocyst preservation of most mammalian embryos and is an important technique for breeding. We aimed to compare the efficiency of the cryopreservation method using the standard Cryotop device and the ReproCarrier device, a domestic product manufactured in Korea. The efficacy of the two devices was analyzed based on the survival rate, intracellular levels of reactive oxygen species (ROS), and apoptosis of the vitrified bovine blastocysts. The survival rates of the vitrified-warmed blastocysts were similar between the ReproCarrier group (58.4 ± 17.7%) and Cryotop group (59.9 ± 14.1%). Intracellular ROS levels and apoptotic index were determined by DCFDA staining and TUNEL assay. Changes in intracellular ROS levels, number of total nuclei, and cellular apoptosis of vitrified blastocysts after cryopreservation were not significantly different between the two groups. These results indicate that the ReproCarrier device method is as effective as the standard Cryotop method for vitrification of bovine blastocysts in vitro.

• Journal of Embryo Transfer
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• v.32 no.4
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• pp.311-317
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• 2017

Cryopreservation of oocytes by vitrification technique may contribute a lot in the field of reproductive biotechnology. The objectives of the present study were to evaluate the effectiveness of two cryo-devices for vitrification of immature oocytes of indigenous zebu cows. Slaughter house derived immature cumulus-oocyte-complexes (COCs) of cows were vitrified using 15% dimethyl sulphoxide (DMSO) as cryoprotective agent (CPA) with 0.5 mol sucrose in TCM 199 supplemented with 20% FBS. Vitrification of COCs was completed after immediate plunging of COCs loaded cryotop or French mini straw into the liquid nitrogen ($LN_2$). Then the COCs containing cryotop or French mini straws were warmed in 0.25 mol sucrose and 20% FBS supplemented TCM 199 followed by in vitro culture in $50{\mu}l$ droplets of bicarbonate buffered TCM 199 supplemented with 10% FBS, pyruvate, FSH and oestradiol for 24 hrs at $39^{\circ}C$ with 5% CO2 in humidified air. After maturation culture, oocytes were denuded and examined under inverted microscope for presence of polar body as the indication of maturation. Denuded oocytes were also stained by whole mount technique using 1% orcein to examine the maturation by presence of MII chromosomes. The in vitro maturation rate was significantly (p<0.05) higher in oocytes vitrified and warmed using crytop ($47.1{\pm}6.9%$) than that of French mini straw ($15.9{\pm}12.5%$). Moreover, in vitro maturation rate was significantly (p<0.05) highe r in control oocytes (not vitrified) ($84.5{\pm}14.2%$) than that of vitrified oocytes. In conclusion, cryotop is better than French mini straw as cryo-device for vitrification of bovine immature oocytes.