Vitrification of human blastocysts with the Hemi-Straw carrier: application of assisted hatching after thawing

Oocyte and embryo cryopreservation in assisted reproductive technology: past achievements and current challenges

Cryopreservation has revolutionized the treatment of infertility and fertility preservation. This review summarizes the milestones that paved the way to the current routinary clinical implementation of this game-changing practice in assisted reproductive technology. Still, evidence to support "the best practice" in cryopreservation is controversial and several protocol adaptations exist that were described and compared here, such as cumulus-intact vs. cumulus-free oocyte cryopreservation, artificial collapse, assisted hatching, closed vs. open carriers, and others. A last matter of concern is whether cryostorage duration may impact oocyte/embryo competence, but the current body of evidence in this regard is reassuring. From social and clinical perspectives, oocyte and embryo cryopreservation has evolved from an afterthought when assisted reproduction was intended for immediate pregnancy with supernumerary embryos of secondary interest to its current purpose, which primarily is to preserve fertility long-term and more comprehensively allow for family planning. However, the initial consenting process, which still is geared to short-term fertility care, may no longer be relevant when the individuals that initially preserved the tissues have completed their reproductive journey. A more encompassing counseling model is required to address changing patient values over time.

Comparison of the effect of two commercialized vitrification carriers on pregnancy outcomes in freeze-thaw cycles

OBJECTIVE

This study aimed to compare the effects of two brands of commercial vitrification carriers on pregnancy outcomes in freeze-thaw cycles.

METHODS

We included 4871 patients who underwent a "freeze all" strategy using the commercial carriers J.Y. straw and OYASHIPS straw in the Reproductive Center of the First Hospital of Jilin University. The pregnancy outcomes of cleavage-stage embryos and blastocysts were studied separately. Detailed data and the safety of children born from mothers with the two types of carriers were also compared.

RESULTS

Patients who used J.Y. straw had similar clinical pregnancy and live birth rates with one and two cleavage-stage embryo transplantation to those who used OYASHIPS straw. In patients who had blastocyst transplantation, the clinical pregnancy rate of one blastocyst transplanted in those who used OYASHIPS straw was significantly higher than that in those who used J.Y. straw (57.85% vs 47.09%). Among children born from mothers who used J.Y. straw, the congenital disability rate was significantly higher than that in those with OYASHIPS straw.

CONCLUSION

The OYASHIPS straw carrier is cheap and can achieve clinical pregnancy and live birth outcomes comparable to those of J.Y. straw. Therefore, OYASHIPS straw is a good alternative option.

Viability assessment using fluorescent markers and ultrastructure of human biopsied embryos vitrified in open and closed systems

RESEARCH QUESTION

Are there any differences in viability and ultrastructure amongst embryos biopsied on Day 5 versus Day 3 following vitrification in open and closed systems and compared to fresh embryos?

DESIGN

One hundred human embryos (40 blastocysts biopsied on Day 5 and subsequently vitrified in open or closed systems and 60 Day 3 biopsied embryos that developed to blastocysts but were rejected for transfer following preimplantation genetic testing for monogenic/single gene defects and for aneuploidies were either treated fresh [n = 20] or vitrified [n = 40] in open or closed systems) and following warming and culture for 4 h were subjected to viability staining with carboxyfluorescein-diacetate succinimidylester/propidium iodide or processed for transmission electron microscopy.

RESULTS

No statistically significant differences were observed in the viability of human biopsied embryos following vitrification in open and closed systems. Compared to fresh embryos, vitrified ones had a higher incidence of damage (propidium iodide-stained cells) irrespective of the vitrification method (P = 0.005). These damaged cells were more prominent in Day 5 biopsied blastocysts and mainly located at the position of cutting. Characteristic lipofuscin droplets (representative of apoptosis) and a higher number of vacuoles and distension of mitochondria were also more evident in vitrified embryos, although this was not statistically assessed.

CONCLUSIONS

Vitrification in open and closed systems does not adversely affect the viability and ultrastructure of Day 5 and Day 3 biopsied embryos as revealed by the minimal yet statistically significant cell damage observed. This damage may be compensated by the embryos, which in their attempt to fully recover following vitrification, potentially enable 'rescue' processes to eliminate it.

Vitrification of Equine In Vivo-Derived Embryos After Blastocoel Aspiration

Embryo cryopreservation is normally performed with great success in species like humans and cattle. The large size of in vivo-derived equine embryos and the presence of a capsule-impermeable to cryoprotectants-have complicated the use of embryo cryopreservation in equine reproduction. A breakthrough for this technique was obtained when large equine embryos could be successfully cryopreserved after collapsing the blastocoel cavity using a micromanipulation system. High pregnancy rates have been obtained when vitrification is used in combination with embryo collapse.

Development and ultrastructure of bovine matured oocytes vitrified using electron microscopy grids

The aim of this study was to establish a methodology of cryopreservation of cattle oocytes and the quality assessment of oocytes and subsequent embryos produced in vitro under our laboratory conditions. Previously in vitro matured (IVM) oocytes were vitrified in minimum volume by ultra-rapid cooling technique. The oocytes were put into the equilibration solution (3% ethylene glycol in M199-HEPES + 10% foetal bovine serum) for 12 min, transferred to vitrification solution (30% ethylene glycol + 1 M sucrose in M199-HEPES + 10% foetal bovine serum) at room temperature for 25 s, then placed onto nickel electron microscopy grids and plunged into liquid nitrogen. After warming 75% of the oocytes were assessed as viable. Part of viable oocytes was taken for electron microscopy, the remaining oocytes were fertilized in vitro, and the presumptive zygotes were cultured until the blastocyst stage. Embryo cleavage and blastocyst rates in vitrified group after warming were 64.98% and 17.3%, resp. versus 70.72% and 25.54% in the control group (P < 0.05). No significant differences were found in the blastocyst total cell number, TUNEL and dead cell indexes between both groups. Ultrastructure of vitrified oocytes showed damages in smooth endoplasmic reticulum (SER) vesicles and lipid droplets as well as irregular arrangement of solitary cortical granules. Several mitochondria were damaged and the microtubules around the chromosomes were less occurred compared to the control group. However, the extent of injuries was lower than reported by other authors studying the ultrastructure of vitrified bovine oocytes, what is also supported by the better development of our oocytes after IVF. In conclusion, the designed oocyte vitrification technique ensures obtaining the blastocysts of the quality comparable to the fresh oocytes.

Assisted hatching of vitrified-warmed blastocysts prior to embryo transfer does not improve pregnancy outcomes

Objective

This study aims to determine the impact of assisted hatching (AH) on pregnancy outcomes in vitrified-warmed blastocyst transfers, and evaluate if embryo expansion or morphology influences outcomes.

Methods

A retrospective cohort study was performed including vitrified-warmed blastocyst transfers at our clinic between 2013 and 2017. Of the 2165 embryo transfers, 1986 underwent laser AH and 179 were non-assisted hatched (NAH). The primary outcome was live birth. Secondary outcomes included conception, implantation, clinical pregnancy, clinical pregnancy loss, and monozygotic twinning (MZT).

Results

AH and NAH groups had similar rates of conception (38.7% vs 42.1%), implantation (26.2% vs 27.3%), clinical pregnancy (29.1% vs 30.3%), clinical pregnancy loss (24.0% vs 17.8%), live birth (19.9% vs 20.5%), and MZT (2.08% vs 2.86%). Five pairs of dichorionic/diamniotic twins resulted from single embryo transfers. AH of embryos with expansion grades ≤3 was associated with lower rates of conception (32.5% vs 44.3%%, p < 0.05) and clinical pregnancy (24.0% vs 32.8%, p < 0.05).

Conclusion

AH prior to transfer of vitrified-warmed blastocysts was not associated with improved pregnancy outcomes. The identification of dichorionic/diamniotic twins from single blastocyst transfers challenges the previously held notion that dichorionic/diamniotic MZTs can only occur from division prior to the blastocyst stage. Prospective studies are needed to validate the novel finding of lower rates of conception and clinical pregnancy after AH in embryos with lower expansion grade.

Human oocytes and zygotes are ready for ultra-fast vitrification after 2 minutes of exposure to standard CPA solutions

Vitrification of human oocytes and embryos in different stages of development is a key element of daily clinical practice of in vitro fertilization treatments. Despite the cooling and warming of the cells is ultra-fast, the procedure as a whole is time consuming. Most of the duration is employed in a long (8–15 minutes), gradual or direct exposure to a non-vitrifying cryoprotectant solution, which is followed by a short exposure to a more concentrated vitrifying solution. A reduction in the duration of the protocols is desirable to improve the workflow in the IVF setting and reduce the time of exposure to suboptimal temperature and osmolarity, as well as potentially toxic cryoprotectants. In this work it is shown that this reduction is feasible. In silico (MatLab program using two-parameter permeability model) and in vitro observations of the oocytes’ osmotic behaviour indicate that the dehydration upon exposure to standard cryoprotectant solutions occurs very fast: the point of minimum volume of the shrink-swell curve is reached within 60 seconds. At that point, intracellular water ejection is complete, which coupled with the permeation of low molecular weight cryoprotectants results in similar intracellular and extracellular solute concentrations. This shows that prolonging the exposure to the cryoprotectant solutions does not improve the cytosolic glass forming tendency and could be avoided. To test this finding, human oocytes and zygotes that were donated for research were subjected to a shortened, dehydration-based protocol, consisting of two consecutive exposures of one-minute to two standard cryoprotectant solutions, containing ethylene glycol, dimethyl sulfoxide and sucrose. At the end of this two-minute dehydration protocol, the critical intracellular solute concentration necessary for successful vitrification was attained, confirmed by the post-warming survival and ability to resume cytokinesis of the cells. Further studies of the developmental competency of oocytes and embryos would be necessary to determine the suitability of this specific dehydration protocol for clinical practice, but based on our results, short times of exposure to increasingly hypertonic solutions could be a more time-efficient strategy to prepare human oocytes and embryos for vitrification.

Spindle and chromosome configuration analysis of human biopsied versus non-biopsied embryos by confocal laser scanning microscopy following vitrification

SummaryThe aim of this study was to investigate the effects of zona drilling and biopsy on day 3 followed by vitrification on day 5 on the cytoskeleton and development of human embryos, by analysing survival rates and spindle and chromosome configurations by fluorescence and confocal laser scanning microscopy in human biopsied and non-biopsied embryos. In total, 98 human blastocysts (50 non-biopsied and 48 following biopsy on day 3) were vitrified on day 5 using either a commercial dimethyl sulphoxide (DMSO)-free vitrification kit or increasing concentrations of DMSO/EG (5%/5-10%/10-20%/20%). Following warming, the blastocysts were allowed to recover in culture for 24 h and were immunostained with α-tubulin, acetylated tubulin, and/or γ-tubulin antibodies in combination with 4',6-diamidino-2-phenylindole (DAPI). Labelled embryos were examined by both fluorescence and confocal laser scanning microscopy. The survival rates following warming (92% non-biopsied vs 83.3% biopsied) and the incidence of normal spindle chromosome configurations was not statistically different between the two groups (65.2% non-biopsied vs 59.2% biopsied, P&gt;0.05). The incidence of spindle abnormalities including multipolarity, chromosome lagging, congression failure and chromosome bridging were also similar between the two groups (P&gt;0.05). This study is the first to compare the incidence of cytoskeletal abnormalities in biopsied and non-biopsied human embryos following vitrification. We conclude that there was no significant difference in the survival rates and the incidence of spindle abnormalities between the two groups.

Rapid freezing versus Cryotop vitrification of mouse two-cell embryos

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±10.44, 88.29±14.79, and 86.42±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.

Effect of different penetrating and non-penetrating cryoprotectants and media temperature on the cryosurvival of vitrified in vitro produced porcine blastocysts

The aim of this study was to determine the most efficient vitrification protocol for the cryopreservation of day 7 in vitro produced (IVP) porcine blastocysts. The post-warm survival rate of blastocysts vitrified in control (17% dimethyl sulfoxide + 17% ethylene glycol [EG] + 0.4 mol/L sucrose) and commercial media did not differ, nor did the post-warm survival rate of blastocysts vitrified in medium containing 1,2-propandiol in place of EG. However, vitrifying embryos in EG alone decreased the cryosurvival rate (55.6% and 33.6%, respectively, p < .05). Furthermore, the post-warm survival rates of blastocysts vitrified with either trehalose or sucrose as the non-penetrating cryoprotectant did not differ. There was also no significant difference in post-warm survival of blastocysts vitrified in control (38°C) media and room temperature (22°C) media with extended equilibration times, although when blastocysts were vitrified using control media at room temperature, the post-warm survival rate increased (56.8%, 57.3%, 72.5%, respectively, p < .05). The findings show that most cryoprotectant combinations examined proved equally effective at supporting the post-warm survival of IVP porcine blastocysts. The improved post-warm survival rate of blastocysts vitrified using media held at room temperature suggests that the cryoprotectant toxicity exerted in 22°C media was reduced.

Revisiting embryo assisted hatching approaches: a systematic review of the current protocols

Zona pellucida (ZP) manipulation, termed "assisted hatching" (AH), has been introduced in order to favor embryo hatching and ultimately improve assisted reproductive technology success but with poor proofs of safety and biological plausibility. We herein provide a systematic review of clinical outcomes following the application of different methods of ZP manipulation on fresh or frozen/thawed embryos at different developmental stages in different groups of patients. Out of the 69 papers that compared the clinical outcomes deriving from hatched versus non-hatched embryos, only 11 considered blastocysts while the rest referred to cleavage stage embryos. The ZP thinning of fresh embryos either by chemical or laser approach was shown to provide very limited benefit in terms of clinical outcomes. Better results were observed with procedures implying a higher degree of zona manipulation, including zona removal. Studies comparing the mechanical or chemical procedures to those laser-mediated consistently reported a superiority of the latter ones over the former. Literature is consistent for a benefit of ZP breaching in thawed blastocysts. This review provides the current knowledge on the AH procedure in order to improve its efficacy in the appropriate context. Embryologists might benefit from the approaches presented herein in order to improve Assisted Reproduction Technologies (ART) outcomes.

The Impact of Vitrification in Artificial Reproductive Technology Programmes

Cryopreservation is an integral part of the current methods of assisted reproductive technology (ART). In the past two decades, slow freezing has been replaced worldwide by vitrification due to its association with improved survival rates and clinical outcomes comparable to fresh embryo transfers. Successful embryo vitrification programmes have led to a significant reduction in the incidences of two major complications of ART: ovarian hyperstimulation syndrome and multiple gestations. Multiple embryo transfer cycles from the single ovum aspiration cycle have had a cumulative effect on the numbers of live births. Oocyte vitrification has also helped women to delay their pregnancies for medical or social reasons. This has made oocyte banking a viable option for better synchronisation of oocyte donation programmes. The emerging field of ovarian tissue vitrification has made fertility preservation possible for women undergoing gonadotoxic therapy. In this review, we have discussed the basic principles and methodology of slow freezing and vitrification along with its need and impact on ART.

Optimal timing of blastocyst vitrification after trophectoderm biopsy for preimplantation genetic screening

Is the timing of vitrification after trophectoderm (TE) biopsy associated with successful implantation and pregnancy after the embryo transfer of blastocysts subjected to preimplantation genetic screening (PGS)? In this retrospective cohort study, 1329 blastocysts from 223 patients were subjected to TE biopsy for performing array comparative genomic hybridization (CGH) tests. The PGS and frozen blastocyst transfer (FET) cycles were performed from December 2012 to May 2015. Only the good quality and expanded blastocysts on day 5 or 6 were selected for biopsy. After TE biopsy, the re-expansion grades relative to the original blastocoel were (1) collapsed blastocysts (CB), (2) 3/4 re-expansion but not full expansion (RE), and (3) full re-expansion or hatching (FE). All biopsied blastocysts were subjected to vitrification within 0.5-6 h after biopsy; the time intervals between TE biopsy and vitrification and the expansion grades at the time of vitrification were recorded. By combining two factors, namely the expansion grades and culture intervals between biopsy and vitrification, the patients were further divided into four groups, namely CB with a < 3 h culture interval (n = 34 cycles, Group I), RE and FE blastocysts with a < 3 h culture interval (n = 10 cycles, Group II); CB blastocysts with a ≥ 3 h culture interval (n = 6 cycles, Group III); and RE or FE blastocysts with a ≥ 3 h culture interval (n = 173 cycles, Group IV). The implantation (63.7%, 179/281) and clinical pregnancy (74.0%, 128/173) rates in Group IV were significantly higher than those in Group I (45.3%, 24/53; 50.0%, 17/34; P = 0.012 and 0.005, respectively). According to our findings, optimal vitrification timing > 3 hours to enable blastocysts to reach RE or FE provides improved implantation and pregnancy rates after FET.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03065114.

Cryopreservation of cynomolgus macaque (Macaca fascicularis) sperm with glycerol and ethylene glycol, and its effect on sperm-specific ion channels - CatSper and Hv1

The cryoprotective agent (CPA) is one of the most important factors that affects the cryosurvival of sperm. The aim of the present study was to compare two different CPAs, glycerol (Gly) and ethylene glycol (EG), on the cryopreservation of cynomolgus macaques sperm and evaluate the effects of cryopreservation on sperm motility, acrosomal integrity, DNA integrity, mitochondrial function and the sperm membrane ion channels CatSper and Hv1. Compared to fresh sperm, cryopreservation with either 0.7 M Gly or EG decreased the sperm motility (79.8 ± 1.5% Vs. 47.3 ± 1.8% and 47.6 ± 1.4%), acrosomal integrity (89.6 ± 1.2% Vs. 80.1 ± 1.8% and 79.6 ± 1.7%), DNA integrity (91.9 ± 0.7% Vs. 82.9 ± 1.0% and 82.3 ± 1.0%) and mitochondrial membrane potential (87.9 ± 1.8% Vs. 70.6 ± 2.7% and 67.9 ± 2.5%) and the quantity of the CatSper and Hv1 channels determined by Western Blot (p < 0.05), and EG showed equal cryoprotection to cynomolgus sperm in all of the sperm parameters. Our results indicated, for the first time, that cryopreservation decreases the quantity of sperm membrane ion channels (CatSper and Hv1), which might be one of the reasons that frozen sperm have a low fertilizing ability. The study will be beneficial to understand the biological process involved in sperm cryopreservation of nonhuman primates and contribute to improving cryopreservation protocols than can maintain sperm function and fertilizing ability.

Morphokinetics of vitrified and warmed blastocysts predicts implantation potential

PURPOSE

It was studied whether morphokinetics of blastocoele re-expansion and hatching in vitrified-warmed blastocysts is predictive of implantation, clinical pregnancy, and live birth.

METHODS

In 144 patients aiming for single warmed blastocyst transfer, blastocysts were cultured in a new time-lapse system (Miri® TL) immediately after warming. Video sequences with an image interval of 5 min were annotated and the corresponding morphokinetic variables were correlated with pregnancy outcome. In detail, tRE (start of re-expansion), tCRE (completion of re-expansion), tAH (hatching from the manipulated zona pellucida), and presence of collapses were recorded.

RESULTS

In the pregnant group, tRE and tCRE were significantly lower (0.69 ± 0.45 h and 2.16 ± 0.94 h) as compared to the non-pregnant group (1.23 ± 1.08 h and 2.70 ± 1.20 h). Both variables and the duration of re-expansion (tCRE-tRE) allowed for distinction between "non-pregnant," "loss of pregnancy," and live birth/ongoing pregnancy. Presence and number of collapses showed no correlation with outcome.

CONCLUSIONS

Time-lapse imaging of vitrified-warmed blastocysts offers additional selection criteria allowing for prediction of implantation potential. As a consequence, cumulative pregnancy rate could be increased and time-to-pregnancy reduced.

Effects of vitrification on blastomere viability and cytoskeletal integrity in mouse embryos

Vitrification is widely used to cryopreserve supernumerary embryos following in vitro fertilization (IVF). The mouse model was used to investigate the effects of vitrification on blastomere viability, using viability markers, and on the cytoskeleton, by analysing spindle/chromosome configurations, using confocal scanning microscopy. Ninety cleavage and morula stage dimethyl sulphoxide (DMSO)/EG vitrified mouse embryos were either processed immediately following warming for viability assessment by labelling with the fluorescent markers carboxyfluorescein-diacetate succinimidylester (CFSE) and propidium iodide (PI) or were cultured to the blastocyst stage and immunostained with α-tubulin antibody to visualize microtubules and DAPI or PI to visualize DNA. Sixty-five fresh embryos were also used as the control. Vitrified embryos showed high survival rates following warming, but they had a higher incidence of damaged blastomeres compared with fresh embryos. Most mitotic spindles examined in all groups were normal, but multivariable analysis revealed that the proportion of abnormal spindles was significantly higher in vitrified/warmed embryos (P < 0.05). This study is the first to examine the immediate effects of vitrification on blastomere viability, using fluorescent markers and shows that although vitrification results in a higher incidence of damaged blastomeres, vitrified embryos may compensate for this limited number of damaged/abnormal cells, as development to the blastocyst stage was not compromised.

Comparison of vitrified outcomes between human early blastocysts and expanded blastocysts

We compared the vitrified outcomes between early and expanded blastocysts with or without laser drilling. The grade III embryos from the patients undergoing in vitro fertilization-embryo transfer (IVF-ET) in our reproductive center from September 2009 to February 2015 were incubated into early blastocysts and expanded blastocysts. The early blastocysts and expanded blastocysts were, respectively, divided into laser group (vitrification after laser drilling), non-laser group (direct vitrification), and control group (fresh non-vitrified blastocysts). After thawing, the blastular anabiosis rate, expansion rate, hatching rate, and apoptosis were observed in each group and then were compared amongst groups. This study indicated that the blastular expansion rate (all P < 0.01) and hatching rate (all P < 0.01) were significantly lower, but the blastular apoptosis (all P < 0.05) was significantly higher in both laser and non-laser groups than in the control group in the early blastocysts. In the expanded blastocysts, the blastular anabiosis rate was significantly higher in the laser group than in the non-laser group (P < 0.01), and the blastular expansion rate was significantly higher, but the blastular apoptosis was significantly lower in both laser group and control group than in the non-laser group (all P < 0.05). The blastular expansion rate (all P < 0.01) and hatching rate (all P < 0.01) were significantly higher, but the blastular apoptosis (all P < 0.05) was significantly lower in the expanded laser group than in both early laser and early non-laser groups. We conclude that vitrification for laser-drilling expanded blastocysts can achieve the best outcomes.

The effect of artificial shrinkage and assisted hatching on the development of mouse blastocysts and cell number after vitrification

Objective

The goal of this study was to ascertain optimal assisted hatching (AH) method in frozen embryo transfer. We compared the effect of depending on whether mechanical or laser-AH was performed before or after the vitrification of embryo development rate and blastocyst cell numbers.

Methods

In order to induce superovulation, pregnant mare's serum gonadotropin followed by human chorionic gonadotropin were injected into 4- to 5-week-old female mice. 2-cell embryos were then collected by flushing out the oviducts. The Expanded blastocysts were recovered after the collected embryos were incubated for 48 hours, and were then subjected to artificial shrinkage (AS) and cross-mechanical AH (cMAH) or quarter-laser zona thinning-AH (qLZT-AH) were carried out using the expanded blastocysts before or after vitrification. After 48 hours of incubation, followed by vitrification and thawing (V-T), and blastocysts were fluorescence stained and observed.

Results

The rate of formation of hatched blastocysts after 24 and 72 hours of incubation was significantly higher in the AS/qLZT-AH/V-T group than in the other groups (p<0.05). The cell number of the inner cell mass was higher in AS/V-T/non-AH and AS/V-T/cMAH groups than those of others (p<0.05). In the control group, the number of trophectoderm and the total cell number were higher than in the AS-AH group (p<0.05).

Conclusion

The above results suggest that AS and AH in vitrification of expanded blastocysts lead to the more efficient formation of hatched blastocysts in mice.

Efficiency of an automatic dehydrated carrier for the vitrification of human embryos derived from three pronuclei fertilized zygotes

The efficiency of a new vitrification technique using embryos obtained after abnormal fertilization was assesed. A total of 100 embryos were vitrified, 48 with the automatic dehydrated carrier (ADC) technique and 52 with cryotop. The survival rates in ADC and cryotop groups were similar (85.4% versus 92.3%). The loss rates of 10.4% for the ADC group and 1.9% for the cryotop group were not significantly different. The intact rate was significantly lower in the ADC group (26.8% versus 64.6%; P = 0.001). After 48 h of culture, blastocyst formation rates in the ADC and cryotop groups were 14.6% and 25.0%, respectively, which were not significantly different. In conclusion, the practicability of ADC vitrification was demonstrated. The study has some limitations, which necessitates further work.

Vitrification solution without sucrose for cryopreservation in mouse blastocysts

Objective

This study was designed to investigate the survival rate of vitrified mouse blastocysts depending on the presence or absence of sucrose in vitrification solution.

Methods

Mouse two-cell embryos were collected and cultured to blastocysts. Two vitrification solutions were prepared. The control solution was composed of 25% glycerol, 25% ethylene glycol, and 0.5 M sucrose (G25E250.5S) containing 2.5 mL glycerol, 2.5 mL ethylene glycol, 2 mL SSS, and 0.855 g sucrose in 5 mL PB1. The experimental solution was composed of 25% glycerol and 25% ethylene glycol (G25E25) and contained 2.5 mL glycerol and 2.5 mL ethylene glycol in 5 mL PB1. Artificial shrinkage was conducted by aspirating the blastocoelic fluid using an ICSI pipette. To examine the effect of sucrose in the vitrification solution on the survival rate of mouse blastocysts, the shrunken-equilibrated blastocysts were rehydrated or vitrified after being exposed to one of the two vitrification solutions. After exposure and the vitrification-thawing process, the re-expansion rate and hatching rate were evaluated after 6 hours of in vitro culture.

Results

The re-expansion rate of mouse blastocysts exposed to vitrification solution with and without sucrose were not different in the experimental solution (without sucrose) (98%) and the control solution (with sucrose) (92%) (p>0.05). The hatching rate was higher in the experimental solution (95%) than in the control solution (88%), but did not differ across two treatments (p>0.05). The re-expansion rate of mouse blastocysts vitrified in the control solution was 92% and 94%, respectively (p>0.05), and the hatching rate was higher in the experimental solution (90%) than in the control solution (74%) (p<0.05).

Conclusion

Sucrose need not be added in vitrification solution for freezing of artificially shrunken mouse blastocysts.

[Update on preimplantation genetic diagnosis and screening]

Recent advancement in both human embryology and genomics has created a completely new situation for practical and widespread application of preimplantation genetic diagnosis and screening with a dramatic effect on assisted reproduction. The mapping of the first human genome and the advancement in sequencing technology and bioinformatics has led to the discovery of the exact genetic background of exponentially increasing number of diseases. In parallel, methods for culturing human embryos have also radically improved, enabling the late transfer, and the procedure of vitrification the safe cryopreservation. In consequence, refined genetic analyses have become available from blastocyst biopsy followed by the application of novel genomic methods. Furthermore, some studies suggest that by the selection of aneuploid embryos the pregnancy- and birth-rates can be increased. The amount and the depth of information obtainable from the embryos raise several technical and ethical questions that can be answered by further prospective randomized trials.

Cryopreservation of embryos and oocytes in human assisted reproduction

Both sperm and embryo cryopreservation have become routine procedures in human assisted reproduction and oocyte cryopreservation is being introduced into clinical practice and is getting more and more widely used. Embryo cryopreservation has decreased the number of fresh embryo transfers and maximized the effectiveness of the IVF cycle. The data shows that women who had transfers of fresh and frozen embryos obtained 8% additional births by using their cryopreserved embryos. Oocyte cryopreservation offers more advantages compared to embryo freezing, such as fertility preservation in women at risk of losing fertility due to oncological treatment or chronic disease, egg donation, and postponing childbirth, and eliminates religious and/or other ethical, legal, and moral concerns of embryo freezing. In this review, the basic principles, methodology, and practical experiences as well as safety and other aspects concerning slow cooling and ultrarapid cooling (vitrification) of human embryos and oocytes are summarized.

Cryopreservation in ART and concerns with contamination during cryobanking

The cryopreservation of gametes and embryos is vital to numerous fields of reproductive biology, including assisted human reproduction. With improved culture conditions, there are an increasing number of embryos to cryopreserve for potential use in subsequent cycles. Many of the gametes and embryos in human IVF are cryopreserved in open systems. Because liquid nitrogen is not sterile, concerns have been raised with regard to contamination from the liquid nitrogen and also cross-contamination between patients' germplasm. Human gamete and embryo cryopreservation are discussed, with recommendations on how to minimize and eliminate contamination, emphasizing the benefits of closed vitrification devices.

Clinical outcomes of vitrified-thawed embryo transfer using a pull and cut straw method

Objective

To compare the clinical outcomes of patients with vitrified-thawed embryos transferred using either the 0.25 mL straw method and the pull and cut straw (PNC) method. To evaluate the clinical outcomes of patients with transferred embryos that underwent assisted hatching at the cleaved embryo (day 3) or the blastocyst (day 5) stage.

Methods

The study population consisted of women who underwent vitrified-warmed embryo transfer between May 2000 and December 2011 and assisted hatching was performed after warming of embryos. Cycles of thawing between assisted hatching treated and non treated groups were compared for survival and pregnancy rates.

Results

The PNC vitrification method improved survival and pregnancy rates in partial lysed embryos. While assisted hatching did not affect the developmental and clinical pregnancy rates of the vitrified-warmed blastocyst group, it did increase the pregnancy rate of poor quality vitrified-warmed cleaved embryos.

Conclusion

These results suggest that PNC may increase the number of clinical pregnancies via the vitrification of both cleaved embryos and blastocysts. In addition, selective assisted hatching treatment of embryos that show a poor prognosis after warming may increase the rate of clinical pregnancy.

A randomized controlled trial comparing two vitrification methods versus slow-freezing for cryopreservation of human cleavage stage embryos

Purpose

To compare two different vitrification methods to slow freezing method for cryopreservation of human cleavage stage embryos. Design: Prospective randomised trial. Setting: University assisted reproduction centre. Patient(s): 568 patients (mean age 33.4 ± 5.2) from April 2009 to April 2011.

Methods

1798 supernumerary good-quality cleavage stage embryos in 645 IVF cycles intended to be cryopreserved were randomly allocated to three groups: slow freezing, vitrification with the Irvine® method, vitrification with the Vitrolife® method. Main Outcome Measure(s): Embryo survival and cleavage rates, implantation rate.

Results

A total of 1055 embryos were warmed, 836 (79.2 %) survived and 676 were finally transferred (64.1 %). Post-warming embryos survival rate was significantly higher after vitrification (Irvine: 89.4 %; Vitrolife: 87.6 %) than after slow freezing (63.8 %) (p < 0.001). No differences in survival rates were observed between the two vitrification methods, but a significant higher cleavage rate was observed using Irvine compared to Vitrolife method (p < 0.05). Implantation rate (IR) per embryo replaced and per embryo warmed were respectively 15.8 % (41/259) and 12.4 % (41/330) for Irvine, 17.0 % (40/235) and 12.1 % (40/330) for Vitrolife, 21.4 % (39/182) and 9.9 % (39/395) for slow-freezing (NS).

Conclusions

Both vitrification methods (Irvine and Vitrolife) are more efficient than slow freezing for cryopreservation of human cleavage stage embryos in terms of post-warming survival rate. No significant difference in the implantation rate was observed between the three cryopreservation methods.

The new Rapid-i carrier is an effective system for human embryo vitrification at both the blastocyst and cleavage stage

BACKGROUND

The Rapid-i is a new FDA cleared closed carrier for embryo vitrification. The cooling rate of - 1220°C/min is far lower than that reported with open vitrification systems such as the cryoloop (-15,000°C/min). Little published data is currently available on this device. This study presents our initial clinical data, as well as live birth outcomes, with the Rapid-i. The efficacy of this device for the cryopreservation of cleavage, as well as blastocyst stage human embryos is also analyzed. We further compare outcomes to those achieved with the cryoloop, an "open" vitrification system routinely used in our laboratory.

METHODS

Human embryos were vitrified at either the 8-10 cell stage or else the blastocyst stage. The vitrification protocol was: 7.5% DMSO/7.5% ethylene glycol (EG) (2-3 min) followed by incubation in 15% DMSO /15% EG (45 sec) before loading on the vitrification carrier. Cryoprotectant was removed during warming by sequential washes in 0.25 M and 0.125 M sucrose in culture medium. Clinical outcome data for frozen cycles between January 2011 and August 2012 were stratified according to carrier and cell stage. The student t-test and chi square test were used to compare results. P value of < 0.05 was considered significant.

RESULTS

A total of 486 vitrified-warmed embryos were assessed and 92% of them were transferred. The clinical pregnancy rate (CPR) and implantation rate (IR) with Rapid-i vitrified blastocysts were 59% and 49%, versus 47% and 37%, respectively for cleavage stage embryos. This was not statistically different from results with the cryoloop vitrified blastocysts (CPR 46%, IR 38%) nor the cleavage stage vitrified embryos (CPR 49%, IR 35%). To date, there have been 31 deliveries of 34 healthy infants from Rapid-i vitrified embryos, with another 12 pregnancies still on-going.

CONCLUSIONS

The Rapid-i offers an excellent alternative to existing open vitrification devices for embryo cryopreservation at the 8-10 cell stage as well as the blastocyst stage. Use of this type of "closed" sealed system that prevents direct contact between the embryos and liquid nitrogen reduces the potential risk of sample cross-contamination or infection. These preliminary data and live birth outcomes have paved the way toward transitioning to a closed vitrification system in our own IVF program.

Effects of partial or complete laser-assisted hatching on the hatching of mouse blastocysts and their cell numbers

BACKGROUND

It is still debatable whether a full-thickness assisted hatching (AH) is better than the partial zona thinning. In this research, we used a mouse model to study the effect of partial and complete laser-AH on the rate of completely hatched blastocyst and their cell numbers.

METHODS

In experiment 1, mouse morulae had 0, 1, 2 or 3 full-thickness openings of 10 microns created in the zona pellucida with an infrared laser beam. In the second experiment, 0, 1 and 2 openings of 20 microns were studied. In the third experiment, a full-thickness opening of 20 microns or quarter-thinning of the zonal circumference to a depth of 90% was compared with non-AH controls.

RESULTS

No difference in blastocyst formation was found in laser-treated groups and in the controls. In experiment 1, the rate of completely hatched blastocysts was significantly lower than the controls. In experiment 2 when the size of the opening was increased, blastocysts completely hatched at a significantly higher rate than that in the controls. In experiment 3, the rate of completely hatched blastocysts was the highest in the full-thickness group. Cell numbers in completely hatched blastocysts from both AH groups were significantly fewer than those in the controls.

CONCLUSIONS

Full-thickness opening resulted in a higher rate of completely hatched blastocysts than quarter zonal-thinning and controls, but the cell numbers were significantly decreased.

Vitrification of mouse embryos using the thin plastic strip method

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 µg/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.

Vitrified blastocysts from Preimplantation Genetic Diagnosis (PGD) as a source for human Embryonic Stem Cell (hESC) derivation

Embryos diagnosed as abnormal in Preimplantation Genetic Diagnosis (PGD) cycles are useful for the establishment of human Embryonic Stem Cells (hESC) lines with genetic disorders. These lines can be helpful for drug screening and for the development of new treatments. Vitrification has proved to be an efficient method to preserve human blastocysts. One hundred and three abnormal or undiagnosed vitrified blastocysts from the PGD programme at Institut Universitari Dexeus were donated for human embryonic stem cell derivation. The overall survival rate after warming was 70.6 %. Our results showed better survival rates when blastocysts have not started the hatching process (initial/expanded 87.8 %, hatching 68.3 % and hatched 27.3 %). Thirty-five blastocysts and 12 partially surviving embryos were seeded. One hESC line with the multiple exostoses type 2 paternal mutation was obtained.