• Clinical and Experimental Reproductive Medicine
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• v.27 no.1
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• pp.67-74
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• 2000

Objective: This study was conducted to investigate the effect of vitrification on the implantation and the pregnancy of human blastocysts. Method: The transfer of the frozen-thawed blastocysts by the slow freezing or vitrification was performed between January 1998 and July 1999. The zygotes derives from IVF were cocultured with cumulus cells in YS medium containing 20% hFF for 5days. Two or three of the best balstocysts produced on day 5 were transferred into the uterus, and then supernumerary blastocysts were randomly divided into two groups. One was frozen by slow freezing and the other was frozen by vitrification method. The slow freezing procedure was performed in two steps (5% glycerol and 9% glycerol + 0.2 M sucrose for 10 min, respectively) using programmed freezer ($-2^{\circ}C$/min to $-7^{\circ}C$, manual seeding at $-7^{\circ}C$, $-0.3^{\circ}C$/min to $-38^{\circ}C$ and plunged into $LN_{2}$). The blastocysts frozen by slow freezing were thawed at $36^{\circ}C$ then removed glycerol in 7 steps. The vitrification procedure was performed in three steps (10% glycerol for 5 min, 10% glycerol + 20% ethylene glycol for 5 min, 25% glycerol + 25% ethylene glycol and directly $LN_{2}$ within 1 min). The blastocysts frozen by vitrification were thawed at $20^{\circ}C$ water then removed cryoprotectant in 3 steps. In each group, thawed blastocysts were cocultured with cumulus cells in YS medium containing 20% hFF for 18h and transferred into the uterus. The implantation rate was evaluated per transferred blastocysts and the pregnancy rate was evaluated per transfers. Results: The survival rate of vitrified group (74.5%) was higher than slow freezing group (68.0%), but not significant. When 98 thawed blastocysts of vitrification were transferred in 40 cycles, 19 pregnancies (clinical pregnancy rate; 47.5%) were established. One miscarriage occurred in the eighth week of pregnancy (ongoing pregnancy rate; 45.0%). 7 pregnancies were ongoing, 11 pregnancies went to term, and 16 healthy infants were born. The Implantation rate was 31.6%. These results were higher than those obtained by the slow freezing (clinical pregnancy rate; 40.3%, ongoing pregnancy rate; 32.5% and implantation rate; 25.3%), but not significant. Conclusion: Vitrification is a simple, quick and economical method when compared to slow freezing. It will be chosen as a good method of human embryo freezing in IVF-ET programs.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2002.11a
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• pp.78-78
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• 2002

The role of heat shock proteins in shielding organism from environmental stress is illustrated by the large-scale synthesis of these protein by the organism studied to date. However, recent evidence also suggests an important role for heat shock protein in fertilization and early development of mammalian embryos. Effects of elevated in vitro temperature on in vitro produced bovine embryos were analysed in order to determine its impact on the expression of heat shock protein 70 (HSP70) by control and frozen-thawed after in vitro fertilization (IVF) or nuclear transfer (NT). The objective of this study was to assess the developmental potential in vitro produced embryos with using of the various containers and examined expression and localization of heat shock protein 70 after it's frozen -thawed. For the vitrification, in vitro produced embryos at 2 cell, 8 cell and blastocysts stage after IVF and NT were exposed the ethylene glycol 5.5 M freezing solution (EG 5.5) for 30 sec, loaded on each containers such EM grid, straw and cryo-loop and then immediately plunged into liquid nitrogen. Thawed embryos were serially diluted in sucrose solution, each for 1 min, and cultured in CRI-aa medium. Survival rates of the vitrification production were assessed by re-expanded, hatched blastocysts. There were no differences in the survival rates of IVF using EM grid, cryo-loop. However, survival rates by straw were relatively lower than other containers. Only, nuclear transferred embryos survived by using cryo-loop. After IVF or NT, in vitro matured bovine embryos 2 cell, 8 cell and blastocysts subjected to control and thawed conditions were analysed by semiquantitive reverse transcription polymerase chain reaction methods for hsp 70 mRNA expression. Results revealed the expression of hsp 70 mRNA were higher thawed embryos than control embryos. Immunocytochemistry used to localization the hsp70 protein in embryos. Two, 8-cell embryos derived under control condition was evenly distributed in the cytoplasm but appeared as aggregates in some embryos exposed frozen-thawed. However, under control condition, blastocysts displayed aggregate signal while Hsp70 in frozen-thawed blastocysts appeared to be more uniform in distribution.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.108-108
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• 2003

The purpose of this is to investigate the effects of vitrification in open pulled straws (OPS) on in vitro survival of porcine embryos. Blastocysts were produced by in vitro fertilization of slaughterhouse-derived, in vitro matured oocytes with frozen-thawed boar semen, and subsequent culture on granulosa cell monolayer. After frozen-thawing, embryos were culture in NCSU-23 medium with 5 mM hypotaurine, 4 mg/$m\ell$ BSA and 10 ng/$m\ell$ for 48 hrs to survival tests. When blastocysts were frozen-thawed by OPS methods, the embryos with normal morphology were 32.1, 34.5 and 38.9 % in early blastocyst, blastocyst and expanded blastocyat stages. The rates of partial damaged embryos were significantly (P<0.05) higher in early biastocysts than expanded blastocysts. In another experiment, the embryos frozen by OPS methods were cultured for 48 hrs for survival and developmental rates in vitro. The proportions of embryos hatched were 11.8, 20.2 and 33.3% in embryos frozen-thawed at stages of early blastocyst, blastocyst and expanded embryos. On the other hand, The proportions of embryo with normal morphology after culture were 23.5, 25.0 and 33.3% in embryos frozen-thawed at stages of early blastocyst, blastocyst and expanded embryos. These finding indicate the possible broader application for OPS methods that this procedure described is relatively harmless, that it can be used for blastocysts of different developmental stages.

• Clinical and Experimental Reproductive Medicine
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• v.29 no.3
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• pp.201-207
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• 2002

Objective: To observe the capability of fertilization and embryo development including blastocyst formation of the oocytes in simple media after thawing of the cryopreserved cumulus-free mouse oocytes by vitrification method. Methods: Oocytes were collected from 5 to 6 weeks old ICR female mice, and were denuded from the cumulus cells by 0.1% hyaluronidase. Recovered mature oocytes in study group were cryopreserved by vitrification method using EM grid for $5{\sim}7$ days. In brief, oocytes were exposed in dPBS containing 1.5 M EG and 5.5 M EG+1 M sucrose for 2.5 minutes and 20 seconds each, and then executed vitrification by plunging in LN2 after loading on EM grid. Thawing treated by exposure of 1, 0.5, 0.25 and 0.125 M sucrose solution for 2.5 minutes each in order and used for experiments. Spermatozoa aspirated form the epididymis of 12 weeks old ICR male mice were used for insemination after capacitation. T6 media containing 0.4% BSA were used for fertilization and development. Results: Survival and fertilization rates after thawing were 76.9% and 79.6% respectively. Fertilization rate was lower (p<0.005) than that of control group (92.9%). There was no difference in embryo developmental rates from 2-cell to morula, however, the blastocyst formation rate and mean cell numbers of blastocysts in study group (63.3%, $58.9{\pm}9.2$) were lower compared with those of control group (76.1%, $63.5{\pm}8.9$). Conclusion: Vitrification is an effective method for mouse mature oocyte cryopreservation with high survival and fertilization rate after thawing. And in simple media, fertilization rates and embryo development of frozen-thawed mouse oocytes are satisfactory.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.3
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• pp.343-349
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• 2009

This study was designed to simplify a cryopreservation program for embryonic stem cells (ESCs) by selection of cooling method and cryoprotectant. Commercially available mouse E14 embryonic stem cells (ESCs) were cryopreserved with various protocols, and morphology and viability of the frozen-thawed ESCs and their reactive oxygen species (ROS) production were subsequently monitored. Post-thaw colony-formation of ESCs was detected only after a slow freezing using dimethyl sulfoxide (DMSO) by stepwise placement of a freezing container into a $-80^{\circ}C$ deep freezer and subsequently into -$196^{\circ}C$ liquid nitrogen, while no proliferation was detected after vitrification. When the simplified protocol was employed, the replacement of DMSO with a mixture of DMSO and ethylene glycol (EG) further improved the post-thaw survival. ROS generation in ESCs frozen-thawed with the optimized protocol was not increased compared with non-frozen ESCs. The use of fresh mouse embryonic fibroblasts as feeder cells for post-thaw subculture did not further increase post-thaw cell viability. In conclusion, a simplified slow-freezing program without employing programmable freezer but using DMSO and EG was developed which maintains cell viability and colony-forming activity of ESCs during post-thaw subculture.

• Journal of Embryo Transfer
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• v.28 no.2
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• pp.141-147
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• 2013

The purpose of this study was attempted to new methods in mammalian embryos vitrification. This method was affected to increase of the embryo vitrification efficiency and it would be applied to the field of embryo transfer to recipient by modified loading method of embryo into 0.25 ml plastic straw. The frozen mouse embryos were carried out warmed from two different cell stages (8-cell and blastocyst, respectively) by attachment of an embryo in the vitrification straw (aV) method. All groups were cultured in M-16 medium to determine the development and survivability for 24 h, respectively. Results shown that, the survivability of two different groups were significantly different (94.8% vs. 70.9%). Total cell number was not significantly different the non-frozen blastocyst ($99.7{\pm}12.4$) compared to the post-thaw blastocyst ($94.8{\pm}15.1$). From the 8-cell embryo, total cell number of frozen blastocysts were significantly lower than others groups ($74.7{\pm}14.6$, p<0.05). In the case of cell death analysis, the blastocysts from non-frozen and frozen-thawed 8-cell group were not different ($0.0{\pm}0.0$ vs. $1.9{\pm}3.1$, p>0.05). However, the apoptotic nuclei of blastocyst were significantly observed the frozen-thawed group ($5.4{\pm}4.4$) compared to non-frozen group (p<0.05). Therefore, this new method of embryos using in-straw dilution and direct transfer into other species would be more simple procedure of embryo transfer rather than step-wise dilution method and cryopreservation vessels, so we can be applied in animal as well as human embryo cryopreservation in further.

• Clinical and Experimental Reproductive Medicine
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• v.37 no.1
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• pp.57-64
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• 2010

Objectives: Likewise fresh cycle, it is also important to select right blastocysts for transfer in purpose of improving the pregnancy and implantation rates in frozen-thawed embryo transfer (ET) cycles. To investigate the relationship between the developmental velocity at the time of cryopreservation and pregnancy rates, we compared pregnancy rates between the day 5 cryopreservation group and the day 6 cryopreservation group. Methods: Transfers of frozen-thawed blastocysts which had been cryopreserved by vitrification on day 5 or day 6 were performed between January 2006 and June 2007. Ethylene glycol, DMSO, and pull and cut straws were used for vitrification and artificial shrinkage was done in expanded blastocysts. Thawing was performed on the day before transfer and thawed blastocysts were cultured in for 15~18 hrs in Quinn's blastocyct media. Blastocyst survival was assessed before transfer and post-thaw survival was defined as >50% of cells remaining intact and blastocoele re-expansion by the time of transfer. Results: Transfers of thawed blastocyst had been cryopreserved on day 5 were 52 cycles and 41 transfer cycles were cryopreserved on day 6. Patient characteristics, the number of transferred embryos and the survival rate of thawed blastocysts were not different in each cryopreservation day. But the biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and implantation rate were significantly high in transfer of frozen-thawed blastocyst which were cryopreserved on day 5. Conclusions: The clinical pregnancy and implantation rate of day-5 blastocyst showed significantly higher than those of day-6 blastocyst in frozen-ET cycles. This result indicated that developmental rate of blastocyst at cryopreservation time in frozen-thawed cycle is discriminative marker of pregnancy outcome as like in fresh cycle.

• 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.

• Journal of Embryo Transfer
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• v.23 no.1
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• pp.1-4
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• 2008

This study was performed to investigate the effect of laser-assisted hole in the zona pellucida (ZP) of frozen-thawed ICR mouse embryos on the process of hatching that is critical for expanded blastocysts to implant into endometrium, Vitrification medium, composed of ethylene glycol and sucrose supplemented with 7.5% (w/v) PVP, was used to freeze $2{\sim}4$ cell stage embryos recovered from oviducts of superovulated and mated female mice before storing them in $LN_2$. Right after thawing them, a laser beam was shot to make a hole in ZP followed by culturing in KSOM for $96{\sim}120\;hr$ and examining development to blastocyst and hatching every 12 hr. Laser-treated embryos showed significantly higher hatching rate compared to control (92.9% vs. 22.1%, p<0.05). From around Day 4, blastocysts developed from laser-treated embryos started hatching while the blastocysts of control group failed to hatch showing a lot of shrinkage. This study shows that a laser-assisted hole in ZP improves the hatching rate of blastocysts developed from frozen-thawed, in vitro cultured ICR mouse embryos.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.1
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• pp.23-28
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• 2003

The present study was undertaken to investigate the effects of PVP concentration and exposure temperature to vitrification solution on the post-thaw survival, in vitro maturation and development of immature bovine oocytes (germinal vesicle stage). The vitrification solution (VS) consisted of 40% ethylene glycol (EG)+0.5 M sucrose (S)+10% FBS. PVP was added to VS: 0%, 5% or 10%. The cumulus-oocyte complexes (COCs) were diluted in VS as one step, after 2 min the COCs were loaded in straw and vitrified by direct immersion into liquid nitrogen. For thawing, the straws were plunged into $30^{\circ}C$ water bath for 10s. After thawing, the oocytes were diluted in 0.5 M (in DPBS with 10% FBS) sucrose solution for 5 min. The survival rate (FDA-test and trypan blue) of immature bovine oocytes was measured. The survival rate was higher in 5% PVP (91.5%) than in 0% (64.2%) or in 10% PVP (79.7%). The proportion of metaphase II formation was 69.35% in control (no vitrified COCs), 9.3% in 40% EG+0.5 M S+0% PVP and 21.05% in 40% EG+0.5 M S+5% PVP (p<0.05). The effect of room temperature ($25^{\circ}C$ for 10 min) and cold temperature ($4^{\circ}C$ for 10 min) on COCs were determined in this study. After IVF, the cleavage and blastocysts rate of oocytes exposed to room temperature and cold temperature in VS+5% PVP was significantly different (2 cell: 63.20% vs 37.97%, blastocysts: 18.40% vs 2.53%). The cleavage rates of frozen-thawed oocytes were 20.53% with PVP and 22.13% without PVP (p>0.05). Two out of 151 oocytes (1.32%) developed to blastocyst stage after frozen-thawed with 5% PVP (p>0.05). Development of oocytes after frozen-thawing to the 2 cell were not significantly affected with or without PVP following IVF. However, the vitrification of immature bovine oocytes with PVP maintained the ability to develop to the blastocyst stage after IVM-IVF and IVC, while no blastocysts were obtained from oocytes vitrified without PVP. These results suggested that PVP has a protective role for vitrification of immature bovine oocytes as far as survival is concerned, however, the protection was not sufficient enough to support blastocyst formation.