Blastocoele collapse by micropipetting prior to vitrification gives excellent survival and pregnancy outcomes for human day 5 and 6 expanded blastocysts

Vitrification of human blastocysts for couples undergoing assisted reproduction: an updated review

Over the past 40 years there has been a worldwide critical change in the field of assisted reproduction technology (ART), leading to the increased application of single blastocyst transfer, which is extremely important to avoid the risks of multiple pregnancy and associated complications for both mother and babies. Indeed, advancements in ART over the last few decades have been obtained thanks to several improvements, including ovarian stimulation, embryo culture conditions and, of course, progress in cryopreservation methods, especially with the application of vitrification. The ability to cryopreserve human embryos has improved significantly with vitrification compared to the initially adopted slow-freezing procedures. Since the introduction of vitrification, it has become the gold standard method to effectively cryopreserve human blastocysts. However, some new protocols are now being explored, such as the short warming procedure and even shorter exposure to the equilibration solution before vitrification, which seem to provide optimal results. Therefore, the main aim of the current narrative review, will be to illustrate the benefit of vitrification as an effective method to cryopreserve the human blastocyst and to illustrate new protocols and variations which in future may increase the performance of vitrification protocols.

Effect of different manual puncture methods on donkey embryo before vitrification

The application of embryo recovery and transfer technology in the donkey industry is far lower than that of horses and cattle. Sometimes the recovered embryos could not be transferred in time, which required embryo cryopreservation. The embryo cryopreservation technology is more conducive to the preservation and transportation of recovered embryos with excellent genetic traits. However, this technique for donkey embryos is not efficient and needs further optimization. The objective of this study was to evaluate the effect of different manual puncture methods on the viability and pregnancy rates of vitrified-thawed donkey embryos. A total of 117 donkey embryos were recovered on day 7-8 post-ovulation and were divided into four groups by random assortment. There were 28 embryos without puncture or cryopreservation (Control). 58 embryos were manually punctured using a 29G needle (VG, n = 29) or microneedle with a sharp tip of <10 μm (VM, n = 29), then vitrified in 15% EG + 15% DMSO + 0.5 M sucrose. Another 31 embryos were punctured with a microneedle and vitrified with 10% EG + 10% DMSO +0.5 M sucrose +2 mol/L proline (VMP). Both fresh embryos and vitrified-thawed embryos were incubated for 3 h (38.5 °C, 5% CO2 in air) before embryo transfer. The results showed that the embryo recovery rates on day 7.5 and 8 were higher than day 7 (P < 0.05). After incubation, dead cells were assessed and the percentages of dead cells in VM and VMP were lower than that in VG (P < 0.05), although both were higher than those in Control (P < 0.05). The pregnancy rates after 23 days post transfer were assessed and the results showed that the pregnancy rate in VG (8.0%) was lower than that in Control (41.7%), VM (24.0%) and VMP (29.6%) (P < 0.05). No pregnancies resulted from the 10 embryos with diameters ≤650 μm in VG, which lower than either VM (33.3%) or VMP (38.9%) (P < 0.05). While, there was no difference in pregnancy rates among all vitrification groups when embryos were >650 μm in diameter (P > 0.05). In conclusion, the embryo recovery rate on day 7 after ovulation was relatively low, and it was more appropriate to extend it to day 8. Microneedle puncture could reduce embryo damage and achieve a higher pregnancy rate compared with 29G needles. Proline has the potential to improve donkey embryo cryopreservation.

Optimal Stage for Cryotop Vitrification of Porcine Embryos

Different development stages of porcine embryos have different tolerance to low temperature. Therefore, we took the porcine embryos after parthenogenetic activation (PA) as the model, to explore the optimal development stage for vitrification during morula (D4), early blastocyst (D5), and expanded blastocyst (D6) after PA (D0). Embryos were observed with microscope and analyzed by different staining after cryo-recovery for 24 hours. The quality of embryos was damaged after vitrification, including embryonic nuclei, DNA, cytoskeleton, and organelles. The re-expansion rate at 24 hours of D5 embryos was significantly higher than those of D4 and D6 embryos (D5 vs. D4 vs. D6, 27.620 ± 0.041 vs. 7.809 ± 0.027 vs. 13.970 ± 0.032, p < 0.05). Therefore, D5 embryos were selected as research objects to explore the effect of vitrification on lipid in vitrified embryos. The results showed that the expression levels of perilipin PLIN3 messenger RNA (mRNA) and triacylglycerol synthesis-related genes AGPAT1 and DGAT mRNA are significantly reduced (p < 0.05). Vitrification affected lipid synthesis, which might have an irreversible impact on embryonic development. In conclusion, our data demonstrated that the optimal stage of vitrification was D5 for early blastocysts.

Standardization of Post-Vitrification Human Blastocyst Expansion as a Tool for Implantation Prediction

The increased use of vitrified blastocysts has encouraged the development of various criteria for selecting the embryo most likely to implant. Post-thaw assessment methods and timetables vary among investigators. We investigated the predictive value of well-defined measurements of human blastocyst re-expansion, following a fixed incubation period. Post-thaw measurements were taken exactly at 0 and 120 ± 15 min. Minimum and maximum cross-sectional axes were measured. Three groups were defined: Group 1: embryos that continued to shrink by 10 µm or more; group 2: embryos that ranged from −9 to +9 µm; and group 3: re-expansion of 10 µm or more. Patient and morphokinetic data were collected and integrated into the analysis. A total of 115 cases were included. The clinical pregnancy rate for group 1 was 18.9%; group 2, 27%; and group 3, 51.2% (p = 0.007). Pre-thaw morphologic grading and morphokinetic scores of the study groups did not reveal differences. p-values were 0.17 for the pre-thaw morphologic score, 0.54 for KID3, and 0.37 for KID5. The patients’ demographic and clinical data were similar. The clinical pregnancy rate correlated with the degree of thawed blastocyst re-expansion measured 2 h after incubation. This standardized measure is suggested as a tool to predict the potential of treatment success before embryo transfer.

Effects of vitrification and the superovulated environment on placental function and fetal growth in an IVF mouse model

In studies of human IVF, as compared to frozen embryo transfer (ET), fresh ET is associated with smaller infants and higher risk of small for gestational age infants. Recent observations suggest that ET using vitrified embryos is associated with higher pregnancy and live birth rates compared to fresh ET, but increased rates of large for gestational age infants. The mechanisms underlying these associations are largely unknown, and available evidence suggests that the influence of IVF, vitrification and the superovulated (SO) uterine environment on placental function and fetal growth is complex. This warrants further investigation given the prevalent practice in human IVF of both fresh ET into a SO uterine environment, and vitrification with ET into a more physiologic uterine environment. Using a mouse model that closely resembles human IVF, we investigated if vitrification of IVF embryos better preserves placental function and results in better pregnancy outcomes as compared to fresh ET because of transfer into a more physiologic endometrium. We found that the SO environment, independent of vitrification status, reduced implantation rates, inhibited placental mechanistic target of rapamycin signaling and induced placental stress signaling, resulting in fetal growth restriction (1.080 ± 0.05 g estrous fresh (n = 17 litters), 1.176 ± 0.05 g estrous vitrified (n = 12), 0.771 ± 0.06 g SO fresh (n = 15), 0.895 ± 0.08 g SO vitrified (n = 10), P < 0.0001). In addition, our study suggests that vitrification impairs the developmental potential of IVF blastocysts that resulted in a significantly smaller litter size (2.6 ± 2.3 fresh estrous vs 2.5 ± 2.4 fresh SO vs 1.6 ± 1.7 estrous vitrified vs 1.7 ± 1.8 SO vitrified, P = 0.019), with no effect on fetal growth or placental function at term. Our findings suggest that vitrification may negatively impact early embryonic viability, while the SO maternal uterine environment impairs both placental development and fetal growth in IVF.

Vitrification of mouse two-cell and blastocyst stage embryos in simplified closed system using either a hemi-straw or a hollow fiber device

Two-cell stage and blastocyst stage mouse embryos were equilibrated in a medium containing 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for 8-15 min. Vitrification was performed in a medium containing 0.5 M sucrose and either 15% EG + 15% DMSO, 17.5% EG + 17.5% DMSO, or 20% EG + 20% DMSO for 30 s. They were then placed either on a hemi-straw (HS) or a hollow fiber vitrification (HFV) device and vitrified by cooled air inside a 0.5-ml straw. In two-cell embryos, a 100% survival rate was obtained from all groups except the 20% HS group (P > .05). All vitrified two-cell groups showed similar rates of blastocyst development to that of fresh control group (P > .05), except 17.5% and 20% HFV groups, which were significantly lower than the other groups (P < .05). In the blastocyst embryos, the HFV groups were divided into two subgroups (non-collapsed; HFV-NC and collapsed; HFV-C blastocyst). Re-expansion rate in 15% HFV-NC, 17.5% HFV-NC, and 15% HFV-C groups was reduced (P < .05), whereas the rest were similar to control. In conclusion, we established a simplified, reliable, and closed system for HFV vitrification applying hemi-straw, which does not require skilled practitioners.

Birth outcomes are superior after transfer of fresh versus frozen embryos for donor oocyte recipients

STUDY QUESTION

For donor oocyte recipients, are birth outcomes superior for fresh versus frozen embryos?

SUMMARY ANSWER

Among fresh donor oocyte recipients, fresh embryos are associated with better birth outcomes when compared with frozen embryos.

WHAT IS KNOWN ALREADY

Frozen embryo transfer (ET) with vitrification has been associated with improved pregnancy rates, but also increased rates of large for gestational age infants. Donor oocyte recipients represent an attractive biological model to attempt to isolate the impact of embryo cryopreservation on IVF outcomes, yet there is a paucity of studies in this population.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort of the US national registry, the Society for Assisted Reproductive Technology Clinic Outcome Reporting System, of IVF cycles of women using fresh donor oocytes resulting in ET between 2013 and 2015. Thawed oocytes were excluded.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Good obstetric outcome (GBO), defined as a singleton, term, live birth with appropriate for gestational age birth weight, was the primary outcome measure. Secondary outcomes included live birth, clinical pregnancy, spontaneous abortion, preterm birth, multiple births and gestational age-adjusted weight. Outcomes were modeled using the generalized estimating equation approach.

MAIN RESULTS AND THE ROLE OF CHANCE

Data are from 25 387 donor oocyte cycles, in which 14 289 were fresh and 11 098 were frozen ETs. A GBO was 27% more likely in fresh ETs (26.3%) compared to frozen (20.9%) (adjusted risk ratio 1.27; 95% confidence interval (CI) 1.21-1.35; P < 0.001). Overall, fresh transfer was more likely to result in a live birth (55.7% versus 39.5%; adjusted risk ratio 1.21; 95% CI 1.18-1.26; P < 0.001). Among singleton births, there was no difference in gestational age-adjusted birth weight between groups.

LIMITATION, REASONS FOR CAUTION

Our cohort findings contrast with data from autologous oocytes. Prospective studies with this population are warranted.

WIDER IMPLICATIONS OF THE FINDINGS

Among donor oocyte recipients, fresh ETs may be associated with better birth outcomes. Reassuringly, given its prevalent use, modern embryo cryopreservation does not appear to result in phenotypically larger infants.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Equilibrium vitrification of mouse embryos at various developmental stages using low concentrations of cryoprotectants

We previously developed a new vitrification method (equilibrium vitrification) by which two-cell mouse embryos can be vitrified in liquid nitrogen in a highly dehydrated/concentrated state using low concentrations of cryoprotectants. In the present study, we examined whether this method is effective for mouse embryos at multiple developmental stages. Four-cell embryos, eight-cell embryos, morulae, and blastocysts were vitrified with EDFS10/10a, 10% (v/v) ethylene glycol and 10% (v/v) DMSO in FSa solution. The FSa solution was PB1 medium containing 30% (w/v) Ficoll PM-70 plus 0.5 M sucrose. The state of dehydration/concentration was assessed by examining the survival of vitrified embryos after storage at -80°C. When four-cell embryos and eight-cell embryos were vitrified with EDFS10/10a in liquid nitrogen and then stored at -80°C, the survival rate was high, even after 28 days, with relatively high developmental ability. On the other hand, the survival of morulae and blastocysts vitrified in liquid nitrogen and stored at -80°C for four days was low. Therefore, morulae and blastocysts cannot be vitrified in a highly dehydrated/concentrated state using the same method as with two-cell embryos. However, when blastocysts were shrunken artificially before vitrification, survival was high after storage at -80°C for four days with high developmental ability. In conclusion, the equilibrium vitrification method using low concentrations of cryoprotectants, which is effective for two-cell mouse embryos, is also useful for embryos at multiple stages. This method enables the convenient transportation of vitrified embryos using dry ice.

Prolonged interval time between blastocyst biopsy and vitrification compromised the outcomes in preimplantation genetic testing

This study aimed to evaluate to what extent the different interval times between trophectoderm (TE) biopsy and vitrification influence the clinical outcomes in preimplantation genetic testing (PGT) cycles. Patients who underwent frozen embryo transfer (FET) after PGT between 2015 and 2019 were recruited. In total, 297 cycles with single day 5 euploid blastocyst transfer were included. These cycles were divided into three groups according to the interval times: <1 h group, 1-2 h group, and ≥2 h group. Blastocyst survival, clinical pregnancy, miscarriage, and ongoing pregnancy rates were compared. The results showed that, in PGT-SR cycles, survival rate in the ≥2 h group (96.72%) was significantly lower than in the <1 h group (100%, P = 0.047). The clinical pregnancy rate in the ≥2 h group was 55.93%, significantly lower than in the <1 h group (74.26%, P = 0.017). The ongoing pregnancy rates in the 1-2 h group and the ≥2 h group were 48.28% and 47.46%, respectively, significantly lower than that in the <1 h group (67.33%, P < 0.05). The miscarriage rate in the 1-2 h group was 18.42%, significantly higher than that in the <1 h group (5.33%, P = 0.027). In PGT-A cycles, the clinical pregnancy and ongoing pregnancy rates in the <1 h group were 67.44% and 53.49%, respectively, higher than that in the 1-2 h group (52.94%, 47.06%, P > 0.05) and the ≥2 h group (52.63%, 36.84%, P > 0.05). In conclusion, vitrification of blastocysts beyond 1 h after biopsy significantly influences embryo survival and clinical outcomes and is therefore not recommended.

Successful vitrification of manually punctured equine embryos

BACKGROUND

Successful vitrification of equine expanded blastocysts requires collapse of the blastocoele cavity using a micromanipulator-mounted biopsy pipette on an inverted microscope. Such equipment is expensive and requires user skill.

OBJECTIVES

To develop a manual method of blastocoele collapse prior to vitrification using commercial products.

STUDY DESIGN

In vivo experiment.

METHODS

Seventy-nine Day 7 or 8 embryos were measured and graded. Twenty were vitrified following micromanipulator-assisted puncture and aspiration before being used to validate commercial human vitrification and warming kits containing, respectively, 2-step concentrations of DMSO and ethylene glycol (7.5%-15% v:v) and decreasing concentrations of sucrose. After warming, embryos were transferred to recipient mares. Once validated, the commercial kits were used to vitrify and warm a further 39 embryos which were punctured manually using a microneedle, 2 (5%) were damaged during puncture and excluded; 20 more embryos were vitrified without puncture. Embryos were grouped as follows: non-punctured ≤ 300µm (n = 10) and >300 to ≤560 µm (n = 10), punctured small (>300 to ≤560 µm; n = 17) and large (>560 µm; n = 10) and exposed to the equilibration solution (ES) in the kit for 6min. An additional group of punctured large embryos was exposed to ES for 8min (n = 10). For the initial warming step, embryos were exposed for 1min to the thawing solution at 42°C, before being moved to a dilution solution at room temperature.

RESULTS

Vitrified, manually punctured embryos ≤560 µm exposed to ES for 6min resulted in a pregnancy rate of 82% (14/17). Unpunctured embryos ≤300 µm gave an 80% (8/10) pregnancy rate. Larger unpunctured embryos, punctured embryos >560 µm and embryos exposed to ES for 8min gave significantly reduced pregnancy rates.

MAIN LIMITATIONS

Limited group sizes.

CONCLUSION

High pregnancy rates can be achieved by manually puncturing ≤560 µm equine embryos prior to their vitrification and subsequent warming in commercial media.

Blastocoel fluid removal and melatonin supplementation in the culture medium improve the viability of vitrified bovine embryos

In this study, we investigated the effects of melatonin supplementation in the culture medium and blastocoel fluid removal (BFR) before vitrification on the quality and viability of in vitro-derived bovine embryos. After fertilization, presumptive zygotes were assigned to one of the following treatments: control, in vitro standard culture (IVC) medium; IVC + M10^-9, IVC medium supplemented 10^-9 M melatonin; or IVC + M10^-9 BFR, IVC medium supplemented with 10^-9 M melatonin plus BFR on day 7 (D7) of culture. D7 blastocysts were vitrified by the Cryotop method and, after 5 mo of storage, were warmed and incubated for an additional 72 h. The re-expansion rate was evaluated after 2 and 24 h, and the hatching rate was evaluated after 24, 48, and 72 h. At 72 h, the total number of cells (TNC); number of apoptotic cells (NAC); and expression of genes related to oxidative stress (HSPA5), cell metabolism (SLC2A3), cell repair (MSH6), placentation (KRT8 and PLAC8), and implantation (FOSL1) were assessed in the blastocysts. Less than 30% of the control blastocysts re-expanded until 2 h, whereas more than 85% of the IVC + M10^-9 and IVC + M10^-9 BFR blastocysts re-expanded (P < 0.05). The hatching rate of IVC + M10^-9 BFR blastocysts increased at all time points (P < 0.05), reaching 66.8% at 72 h of incubation. The TNC was similar among treatments (P > 0.05), regardless of vitrification/warming and re-cultivation. The NAC:TNC was smaller for melatonin-treated blastocysts (P < 0.05). BFR increased HSPA5 (P = 0.0118) expression and did not affect SLC2A3, MSH6, KRT8, and FOSL1 expression (P > 0.05). In conclusion, melatonin (10^-9 M) supplementation in the culture medium and BFR on D7 of culture increased the hatching rate 24, 48, and 72 h after warming of the vitrified embryos, indicating an improvement in cryotolerance.

Vitrification of the human embryo: a more efficient and safer in vitro fertilization treatment

Cryopreservation has become a central pillar in assisted reproduction, reflected in the exponential increase of "freeze all" cycles in the past few years. Vitrification makes it possible to cool and warm human eggs and embryos with far less cryo-damage than 'slow-freeze' and allows nearly intact survival of embryos with very high survival rates for eggs as well. This has resulted in a complete transformation how we manage treatment for in vitro fertilization patients. Fresh transfers can be avoided without compromising outcomes, and in fact, cumulative pregnancy/delivery rates may be improved by performing sequential elective "frozen" single embryo transfers. Some recent evidence suggests that previously vitrified embryos give better perinatal outcomes than fresh embryo transfers. Frozen embryo transfer, especially when coupled with preimplantation genetic testing allows for highly efficient single embryo transfers that translate to more singleton and therefore safer pregnancies, as well as healthier babies. Additionally, vitrification has also opened new options for patients, most notably fertility preservation (through oocyte cryopreservation), and donor egg banking.

Selection of high-quality and viable blastocysts based on timing of morula compaction and blastocyst formation

PURPOSE

The time-lapse system is a device that allows continuous monitoring without removing embryos from the incubator. Using a time-lapse system, we retrospectively investigated cleavage speed time points as potential indicators for selecting high-quality viable blastocysts.

METHODS

This study included 963 zygotes of two pronuclei retrieved from 196 patients between January 2015 and December 2016. All embryos in culture were monitored by time-lapse after intracytoplasmic sperm injection. Of 492 blastocysts developed in vitro, 128 vitrified-warmed single blastocyst transfers were classified into pregnancy and non-pregnancy groups, and the parameters were compared.

RESULTS

In the pregnancy group, timing of both morula compaction and regular blastocyst formation was significantly faster than in the non-pregnancy group. Furthermore, the optimal cutoff values for compacted morula (94.9 hours) and regular blastocyst (113.9 hours) were determined using the receiver operator characteristic curve analysis. Embryos that formed compacted morulae within 94.9 hours and developed into regular blastocysts within 113.9 hours were associated with a significantly higher pregnancy rate than those that did not (44.4% vs 16.0%).

CONCLUSION

The timing of morula compaction and regular blastocyst formation is important as an indicator of high-quality blastocysts to increase odds for pregnancy after embryo transfer.

Comparison of Human Oocyte Activation Between Round-Headed Sperm Injection Followed by Calcium Ionophore Treatment and Normal Sperm Injection in a Patient With Globozoospermia

Fertilization failure is common in patients with round-headed sperm, a form of globozoospermia. Artificial oocyte activation is able to assist oocyte fertilization after sperm injection in these patients. Comparisons between oocyte fertilization with or without calcium ionophore have been reported in patients with round-headed sperm. However, no comparison has been reported between round-headed sperm injection followed by calcium ionophone activation and normal sperm injection. In this case report, half of oocytes from a patient were injected with her partner's round-headed sperm followed by calcium ionophore activation, and the other half of oocytes were injected with a donor sperm without calcium ionophore activation. The injected oocytes were cultured to examine fertilization, embryo development, and embryonic aneuploidies in the resulting blastocysts. The fertilization rate was lower in round-headed sperm injected oocytes (3/6) than that in donor sperm injected oocytes (5/6), but rates of blastocyst and aneuploidies were similar in the resulting embryos between the two groups. A euploid blastocyst resulted from round-headed sperm injection was transferred, and a healthy baby was delivered. These results indicate that calcium ionophore treatment can assist oocyte activation in patients with round-headed sperm, but its efficiency to activate oocytes is lower than that induced by a normal sperm injection. However, embryo development and chromosome integrity may not be affected by calcium ionophore treatment.

Obstetric, Neonatal, and Clinical Outcomes of Day 6 vs. Day 5 Vitrified-Warmed Blastocyst Transfers: Retrospective Cohort Study With Propensity Score Matching

Despite the large number of studies on blastocyst transfers, it is unclear whether day 6 blastocysts have similar pregnancy rates and safety with day 5 blastocysts. Thus, this study aimed to compare the obstetric, neonatal, and clinical outcomes of day 5 and day 6 vitrified blastocyst transfers (VBT). In this retrospective cohort study with propensity score matching, we evaluated 1,313 cycles of VBT performed between January 2014 and December 2015 at the Fertility Center of CHA Gangnam Medical Center. All cycles underwent natural endometrial preparation. We used propensity score matching to compare day 5 and day 6 VBTs in a matched comparison. After propensity score matching, there were 465 cycles of day 5 VBT and 155 cycles of day 6 VBT. Implantation rate (IR), clinical pregnancy rate (CPR), and live birth rate (LBR) were significantly lower in day 6 VBTs (44.2 vs. 53.1%, p = 0.023; 48.4 vs. 60.4%, p = 0.009; 33.5 vs. 51.8%, p < 0.001). Miscarriage rate was significantly higher in day 6 VBTs (29.3 vs. 10.7%, p < 0.001). Rate of multiple gestations was similar between the two groups (29.3 vs. 30.2%, p = 0.816). Assessing 241 and 52 babies from day 5 and day 6 VBTs, no differences were found in neonatal outcomes including rates of low birth weight, preterm birth, and congenital malformations. In propensity score-matched analysis, obstetric, and neonatal outcomes between day 5 and day 6 VBTs were similar so that day 6 VBTs are as safe as day 5 VBTs. IR, CPR, and LBR were are all significantly lower in day 6 VBTs. Therefore, if there are no differences in the morphological grade between day 5 and day 6 blastocysts, transfer of day 5 vitrified blastocysts should be considered first.

Effect on clinical and neonatal outcomes of blastocelic microsuction prior to vitrification

PURPOSE

Microsuction (MS) is a technique for mechanically emptying fluid from blastocele using a microneedle. In this study, we evaluated the improvement in clinical and neonatal outcomes of vitrified blastocyst transfer programs when MS of blastocelic fluid was used before vitrification.

METHODS

This was a retrospective study based on data collected between March 2014 and August 2016. A total of 317 blastocysts obtained from 211 patients were analyzed. The blastocelic fluid of expanded blastocysts was aspirated completely, and blastocysts were collapsed prior to vitrification. Clinical and neonatal outcomes of warmed blastocysts were compared.

RESULTS

The survival rate of the MS blastocyst was significantly higher compared with the nontreatment control (98.7% vs 89.3%, OR: 9.34, 95% CI: 2.35-36.8, P < 0.01). The rates of implantation and live birth were higher in the MS group than in the control group, but the differences were not significant. There were no differences in gestational age, birthweight, proportion of male babies, rates of cesarean section, and congenital abnormalities.

CONCLUSION

The MS procedure improved blastocyst survival and had little effect on further embryo development after warming.

Different Origin, Different Response: Gene Expression Pattern in Collapsed Vitrified Blastocyst

There is a large body of animal experimental data about assisted reproductive techniques that could be applied to improve clinical outcomes. The great part of this information was obtained from research on in vivo-derived embryos. But whether these results are always similar with those we expect from embryos having in vitro origin in the clinical cases is a critical question. The present study was designed to compare the effects of vitrification (VIT) and artificial collapse (AC) as two commonly used techniques on in vivo- and in vitro-derived mouse embryos. In this regard, both origins of blastocysts were produced and randomly divided into three experimental groups, including control (non-vitrified), VIT, and AC-VIT. The survival and hatching rates and the expression of development-related genes were assessed in all groups and compared with their control counterpart. According to our results, although in vivo and in vitro origins followed the same pattern in the hatching rate, the real-time PCR data showed two distinct patterns of gene expression. Compared to the control, vitrification increased the expression of pluripotency genes in in vivo group. While in vitro vitrified blastocysts showed a significant reduction in the transcripts of these genes. More interestingly, although AC resulted in a sharp decrease of Gata6 and Grb2 in post warmed in vivo blastocysts, it could not affect the vitrified IVP ones. In conclusion, it seems that vitrification and artificial collapse techniques have different effects on embryo fate depending on in vivo or in vitro origins of the embryos.

The Domestic Dog Embryo: In Vitro Fertilization, Culture, and Transfer

Advances in embryo technologies in the domestic dog have made significant strides in the past decade. This progress has been spurred by interests in taking advantage of the dog as a biomedical research model for human and companion animal medicine, developing assisted reproductive technologies to manage genetic diversity in endangered canids maintained ex situ, and improving breeding in rare or working breeds of dogs. Here, we focus on recent advancements and techniques for collection of in vivo-matured oocytes, in vitro fertilization (IVF), in vitro culture of early (≤8-cell) and advanced stage (≥16-cell) embryos, and embryo transfer.

Update on the vitrification of bovine oocytes and invitro-produced embryos

The combined use of reproductive technologies, such as transvaginal ovum-pick up and invitro embryo production followed by direct transfer of cryopreserved embryos, has great potential for enhancing genetic selection and optimising cross-breeding schemes in beef and dairy cattle production systems. This, along with an effective cryopreservation procedure for cow oocytes, will enable the long-term conservation of female genetic traits and the advance of embryo biotechnology in this species. However, the low fertilisation rates and developmental competence of cryopreserved oocytes still need to be improved. Over the past two decades, many research efforts tried to overcome individual features of the bovine oocyte that make it notoriously difficult to cryopreserve. In addition, pregnancy rates associated with invitro-produced (IVP) embryos remain lower than those obtained using invivo counterparts. This, together with a lack of a standard methodology for IVP embryo cryopreservation that provides easier and more practical logistics for the transfer of IVP embryos on farms, has hindered international genetic trade and the management of embryo banks. This review updates developments in oocyte and IVP embryo vitrification strategies targeting high production efficiency and better outcomes.

Artificial blastocyst collapse prior to vitrification significantly improves Na+/K+-ATPase-dependent post-warming blastocoel re-expansion kinetics without inducing endoplasmic reticulum stress gene expression in the mouse

Blastocoel expansion during embryo development is known to be reliant on the Na+/K+-ATPase pump, but little is known about the relative contribution of active (Na+/K+-ATPase pump) and facilitated diffusion (aquaporins) water transport during blastocoel re-expansion after vitrification. The aims of this study were to examine potential effects of artificial blastocoel collapse (ABC) on markers of embryo stress and the contribution of active and facilitated diffusion water transport mechanisms to blastocoel re-expansion. Day 5 mouse embryos were vitrified using either a standard protocol, laser pulse ABC, a hyperosmotic sucrose ABC protocol or both laser pulse and sucrose. Using real-time polymerase chain reaction, no differences were found in the gene expression of the endoplasmic reticulum (ER) stress markers activating transcription factor 4 (Atf4) or heat shock protein 90-alpha (Hsp90α) 2h after warming. Similarly, expression of the Na+/K+-ATPase pump gene, ATPase, Na+/K+ transporting, beta 1 polypeptide (Atp1b1) and protein did not differ between groups. Aquaporin 8 (Aqp8) gene expression was significantly lower in the laser+sucrose ABC group than in fresh controls, and aquaporin 3 (Aqp3) expression significantly higher in standard vitrified embryos compared with all other groups. Ouabain, a potent and specific Na+/K+-ATPase pump inhibitor, inhibited blastocoel re-expansion in both standard protocol- and laser ABC-vitrified embryos, reducing both groups to the same rate of re-expansion 3h after warming. These results demonstrate that ABC before vitrification does not alter mRNA or protein expression of Na+/K+-ATPase, or mRNA levels of ER stress genes Atf4 and Hsp90α. Activity of the pump may be increased in ABC embryos, with potential compensation by AQP3 when it is compromised.

Artificial blastocoel collapse of human blastocysts before vitrification and its effect on re-expansion after warming - a prospective observational study using time-lapse microscopy

Vitrified human blastocysts show varied re-expansion capacity after warming. This prospective observational study compared behaviour of artificially collapsed blastocysts (study group patients, n = 69) to that of blastocysts that were vitrified without artificial collapse (control group patients, n = 72). Warmed blastocysts were monitored by time-lapse microscopy and blastocoel re-expansion speed and growth patterns compared between study and control groups. These parameters were also retrospectively compared between blastocysts that resulted in live birth and those that failed. Artificially collapsed blastocysts re-expanded on average 15.01 µm²/min faster than control blastocysts (P = 0.0013). Warmed blastocysts expressed four different patterns of blastocoel growth. The pattern showing contractions at the end of culture was observed to have a lower prevalence in control blastocysts, which coincided with the lower incidence of hatching in this group. Re-expansion speed and prevalence of growth patterns were comparable between blastocysts that did and did not result in a live birth. This was seen in the study and control groups. Despite faster re-expansion and different growth patterns of artificially collapsed blastocysts, live birth rate did not differ between groups. However, this result should be interpreted with caution due to the small sample size and high risk of bias.

Chapter 11 Human Embryo Vitrification

Cryopreservation is one of the keystones in clinical infertility treatment. In particular vitrification has become a well-established and widely used routine procedure that has allowed important expansion of therapeutic strategies when IVF is used to treat infertility. Vitrification of human blastocysts allows us to maximize the potential for conception from any single in vitro fertilization cycle and prevents wastage of embryos. The technology may even be used to eliminate fresh embryo transfers for reasons of convenience, uterine receptivity, fertility preservation, preimplantation genetic diagnosis, or emergency management. In this chapter, the application of vitrification technology for cryopreserving human blastocysts will be revealed through step-by-step protocols. The results that are presented using the described protocols underscore the robustness of the vitrification technology for embryo cryopreservation.

Pregnancy rates for single embryo transfer (SET) of day 5 and day 6 blastocysts after cryopreservation by vitrification and slow freeze

PURPOSE

The purpose of this study was to compare clinical and ongoing pregnancy rates in cycles with single embryo transfer (SET) of blastocysts cryopreserved on day 5 or day 6. Our aim was to determine whether day 6 blastocysts perform adequately to recommend SET.

METHODS

Retrospective cohort study including 468 transfer cycles for 392 women younger than age 38 undergoing SET at a university-affiliated IVF clinic in the USA. A total of 261 day 5 blastocysts and 207 day 6 blastocysts for frozen-thawed SET between 2010 and 2016 were analyzed. Data included cryopreservation by both a slow freeze method and vitrification.

RESULTS

In total, 59.0% of day 5 SET cycles resulted in a clinical pregnancy compared to 54.1% of day 6 blastocysts (p = 0.54). Ongoing pregnancy rates from day 5 frozen-thawed blastocysts (51.7%) were comparable to day 6 (44.9%, p = 0.14). When looking at vitrified blastocysts only, there were no significant differences between day 5 and day 6 blastocysts, with a clinical pregnancy rate of 69.2% for day 5 and 72.5% for day 6 (p = 0.68).

CONCLUSIONS

SETs of day 6 cryopreserved blastocysts resulted in similar clinical and ongoing pregnancy rates compared to day 5, particularly after vitrification.

Effect of different artificial shrinkage methods, when applied before blastocyst vitrification, on perinatal outcomes

BACKGROUND

In recent years, single blastocyst transfer combined with vitrification has been applied widely, which can maximize the cumulative pregnancy rate in per oocyte retrieval cycles and minimize the multiple pregnancy rate. Thus, the guarantee for these is the effectiveness of vitrified blastocyst. Studies has shown that AS of the blastocoel cavity prior to vitrification can reduce injuries, increase the thawed blastocyst survival rate and implantation rate. Several AS methods have been established. However, only a few studies have compared the effectiveness and safety of these AS methods. In this study, we aimed to compare the clinical outcomes and neonatal outcomes in FET cycles with single blastocyst that were artificially shrunk before vitrification by either LAS or MNAS method.

METHODS

A retrospective comparative study of FET cycles in infertile patients which were at our clinic between January 2013 and December 2014. These FET cycles were divided into two groups by the shrinking methods used before vitrification and the clinical and neonatal outcomes were assessed.

RESULTS

There were no statistically differences in blastocyst survival rates (95.40% vs 94.05%, P > 0.05) between the LAS and MNAS groups. However, compared with MNAS, LAS improved the warmed blastocyst implantation/clinical pregnancy rate (60.82% vs 54.37%, P < 0.05), live birth rate (50.43% vs 45.22%, P < 0.05) and also increased the monozygotic twin rate (4.07% vs 1.73%, P < 0.05). There were no differences in the average gestational weeks (38.83 ± 1.57 vs 38.74 ± 1.75), premature birth rate (0.30% vs 0.49%), average birth weight (3217.89 ± 489.98 g vs 3150.88 ± 524.03 g), low birth weight rate (5.60% vs 8.63%) and malformation rate (0.59% vs 0.48%) (P > 0.05).

CONCLUSIONS

No significant differences in neonatal outcomes were observed, while in clinical outcomes, LAS improved the warmed blastocyst implantation/clinical pregnancy rate and live birth rate markedly, there was also an increased risk of monozygotic twin pregnancies.

Hatching status before embryo transfer is not correlated with implantation rate in chromosomally screened blastocysts

STUDY QUESTION

Do the reproductive outcomes from the transfer of fully hatched (FH) blastocysts differ from those of not fully hatched (NFH) blastocysts?

SUMMARY ANSWER

Biochemical pregnancy rate (BPR), implantation rate (IR), live birth rate (LBR) and early pregnancy loss (EPL) rate are similar in FH and NFH single euploid blastocyst embryo transfers.

WHAT IS KNOWN ALREADY

The use of extended culture and PGS often leads to transfer of an embryo that is well developed and frequently FH from the zona pellucida. Without the protection of the zona, an FH embryo could be vulnerable to trauma during the transfer procedure. To date, no other study has evaluated the reproductive competence of an FH blastocyst transfer.

STUDY DESIGN, SIZE, DURATION

The retrospective study included 808 patients who underwent 808 cycles performed between September 2013 and July 2015 at a private academic IVF center. Of these, 436 cycles entailed transfer of a NFH blastocyst (n = 123 fresh transfer, n = 313 frozen/thawed embryo transfer (FET)) and 372 cycles entailed transfer of an FH blastocyst (n = 132 fresh, 240 FET). Fresh and FET cycles and associated clinical outcomes were considered separately. LBR was defined as the delivery of a live infant after 24 weeks of gestation.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Trophectoderm biopsies were performed on Day 5 (d5) or 6 (d6) for embryos meeting morphology eligibility criteria (set at ≥3BC). Morphologic grading was determined using a modified Gardner-Schoolcraft scale prior to transfer. A single euploid embryo was selected for transfer per cycle on either the morning of d6, for fresh transfers or 5 days after progesterone supplementation for patients with transfer in an FET cycle. Embryos were classified as NFH (expansion Grade 3, 4 or 5) or FH (expansion Grade 6) cohorts. The main outcome measure was IR.

MAIN RESULTS AND THE ROLE OF CHANCE

In the fresh transfer group, IR was similar between NFH and FH cycles (53.7% versus 55.3%, P = 0.99, odds ratio (OR) 0.9; 95% confidence interval (CI) 0.6-1.5). Secondary outcomes were also statistically similar between groups: BPR (65.9% versus 66.7%, OR 1.0; 95% CI: 0.6-1.6), LBR (43.1% versus 47.7%, P = 0.45, OR 1.2; 95% CI: 0.7-1.9) and EPL rate (22.8% versus 18.2%, OR 1.3; 95% CI: 0.7-2.4). After adjusting for age, BMI, endometrial thickness at the LH surge and oocytes retrieved in a logistic regression (LR) model, the hatching status remained not associated with IR (P > 0.05). In the FET cycles, IR was similar between NFH and FH cycles (62.6% versus 61.7%, OR 1.0; 95% CI: 0.7-1.5). Secondary outcomes were similar between groups: BPR (74.1% versus 72.9%, respectively, OR 1.1; 95% CI: 0.7-1.6), LBR (55.0% versus 50.0%, OR 0.8; 95% CI: 0.6-1.1) and EPL rate (18.9% versus 22.9%, respectively, OR 0.8; 95% CI: 0.5-1.2). After adjusting for age, BMI, endometrial thickness at the LH surge and oocytes retrieved in an LR model, the hatching status was not shown to be associated with implantation (P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

Limitations include the retrospective design and data from a single institution. Additionally, the study was limited to patients that developed high-quality blastocysts suitable for biopsy.

WIDER IMPLICATIONS OF THE FINDINGS

The results suggest that FH embryos are not more fragile or less likely to implant when compared to NFH counterparts. We found no evidence of altered IR or other clinical outcomes in the transfer of FH euploid embryos.

STUDY FUNDING/COMPETING INTERESTS

JG is funded by MSTP grant T32 GM007280 (NIH). No additional funding was received. There are no conflicts of interest to declare..

Failure mode and effects analysis of witnessing protocols for ensuring traceability during PGD/PGS cycles

Preimplantation genetic diagnosis and aneuploidy testing (PGD/PGS) use is constantly growing in IVF, and embryo/biopsy traceability during the additional laboratory procedures needed is pivotal. An electronic witnessing system (EWS), which showed a significant value in decreasing mismatch occurrence and increasing detection possibilities during standard care IVF, still does not guarantee the same level of efficiency during PGD/PGS cycles. Specifically, EWS cannot follow single embryos throughout the procedure. This is however critical when an unambiguous diagnosis corresponds to each embryo. Failure Mode and Effects Analysis (FMEA) is a proactive method generally adopted to define tools ensuring safety along a procedure. Due to the implementation of a large quantitative PCR (qPCR)-based blastocyst stage PGD/PGS programme in our centre, and to evaluate the potential procedural risks, a FMEA was performed in September 2014. Forty-four failure modes were identified, among which six were given a moderate risk priority number (>15) (RPN; product of estimated occurrence, severity and detection). Specific corrective measures were then introduced and implemented, and a second evaluation performed six months later. The meticulous and careful application of such measures allowed the risks to be decreased along the whole protocol, by reducing their estimated occurrence and/or increasing detection possibilities.

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.

Micromanipulation of equine blastocysts to allow vitrification

Embryo cryopreservation presents an essential method for banking of valuable genetics. However, in equine species the cryopreservation of embryos is complicated by three interacting factors: (1) the late entry of the embryo into the uterus (~6 days after ovulation); (2) the rapid expansion of the blastocyst; and (3) the formation of the equine embryonic capsule, a glycoprotein membrane that forms between the embryo and zona. Efforts to freeze or vitrify equine expanded blastocysts were initially met with little success. In addition, it was thought that breaching the capsule led to loss of embryo viability. We found that micromanipulation with the Piezo drill to puncture the capsule and collapse the blastocyst before vitrification provided a means for successful cryopreservation of equine expanded blastocysts, and that this can be done successfully using a standard sperm injection pipette. Modification of cryoprotectants and methods for vitrification and warming resulted in a technique that allowed successful vitrification of expanded equine blastocysts up to 650 µm diameter, with pregnancy rates approaching those for fresh embryos. After blastocyst collapse, vitrification is performed with ethylene glycol and galactose as cryoprotectants, and the embryo is cooled in a low-volume micropipette tip. Vitrification of expanded equine blastocysts provides a valuable tool for use in exotic equids to preserve genetics.

Artificial shrinkage of blastocoel using a laser pulse prior to vitrification improves clinical outcome

PURPOSE

Blastocysts contain a large amount of fluid in the blastocoel, which may pose a risk for ice crystal formation during vitrification. This study aimed to evaluate the effectiveness of laser-induced artificial shrinkage of blastocoel before vitrification on clinical outcome.

METHODS

Patients were divided into two groups: a control group with untreated, expanded blastocysts (n = 115) and a study group with blastocoel artificially eliminated by a laser pulse prior to vitrification (n = 309). Blastocyst survival, clinical pregnancy, and implantation rates were compared.

RESULT(S)

The survival rate was significantly higher in the study group compared with the control group (97.3 and 74.9 %, respectively; p > 0.01). The clinical pregnancy and implantation rates of the study group were significantly higher (p < 0.01) than that of the control group (clinical pregnancy, 67.2 vs. 41.1 %; implantation, 39.1 vs. 24.5 %.

CONCLUSION(S)

This study demonstrated that the removal of blastocoel fluid before vitrification by laser pulse of in vitro-produced human blastocysts significantly improves blastocyst survival, clinical pregnancy, and implantation rates.

Optimizing the culture environment and embryo manipulation to help maintain embryo developmental potential

With increased use of comprehensive chromosome screening (CCS), the question remains as to why some practices do not experience the same high levels of clinical success after implementation of the approach. Indeed, the debate surrounding the efficacy and usefulness of blastocyst biopsy and CCS continues. Importantly, several variables impact the success of an assisted reproductive technology cycle. Transfer of a euploid embryo is but one factor in an intricate system that requires numerous steps to occur successfully. Certainly, the culture environment and the manipulations of the embryo during its time in the laboratory can impact its reproductive potential. Environmental stressors ranging from culture media to culture conditions and even culture platform can impact biochemical, metabolic, and epigenetic patterns that can affect the developing cell independent of chromosome number. Furthermore, accompanying procedures, such as biopsy and vitrification, are complex and, when performed improperly, can negatively impact embryo quality. These are areas that likely still carry room for improvement within the IVF laboratory.

Artificial shrinkage of blastocysts prior to vitrification improves pregnancy outcome: analysis of 1028 consecutive warming cycles

PURPOSE

This study aims to compare implantation, pregnancy, and delivery rates in frozen transfer cycles with blastocysts that were vitrified either with artificial shrinking (AS group) or without (NAS group).

METHODS

Retrospective comparative study of artificial shrinking of blastocysts prior to vitrification and frozen embryo transfer cycles in infertile patients undergoing frozen embryo transfer (FET) was done at the Humanitas Fertility Center between October 2009 and December 2013. Main outcome measure(s) were implantation (IR), pregnancy (PR), and delivery rates (DR) between the two groups.

RESULTS

A total of 1028 consecutive warming blastocyst transfer cycles were considered. In 580 cycles (total of 822 blastocysts), artificial shrinking was performed prior to vitrification (AS group), while in the remaining 448 cycles (total of 625 blastocysts), the artificial shrinking was not performed (NAS group). There were no differences in patient age (36.4 ± 3.7 vs. 36.3 ± 3.9) and number of embryos transferred (1.41 ± 0.49 vs. 1.38 ± 0.50) between groups. The IR, PR, and DR in the AS group were significantly higher (p < 0.05) than in the NAS group (29.9 vs. 23.0 %, 36.3 vs. 27.9 %, and 26.5 vs. 18.1 %, respectively).

CONCLUSIONS

Performing AS of blastocysts prior to vitrification appears to improve implantation, pregnancy, and delivery rates probably related to a decreased risk of ultrastructural cryodamages, plausible when cryopreserving expanded blastocysts.

Cryotolerance of porcine in vitro-produced blastocysts relies on blastocyst stage and length of in vitro culture prior to vitrification

The aim of our study was to assess whether the cryotolerance of in vitro-produced embryos could be influenced by the length of in vitro culture and size of blastocoel cavity before vitrification, using the pig as a model. For this purpose we analysed the cryoresistance and apoptosis rate of blastocysts at different stages of development as derived on Day 5 and 6 of in vitro culture. Blastocysts were subsequently vitrified, warmed and cultured for 24 h. Re-expansion rates were recorded at 3 and 24 h and total cell number and apoptotic cells were determined at 24 h. Day-6 blastocysts showed the highest rates of survival after warming, which indicates higher quality compared with Day-5 blastocysts. Higher re-expansion rates were observed for expanded blastocysts and those in the process of hatching when compared with early blastocysts. Total cell number and apoptotic cells were affected by blastocyst stage, vitrification–warming procedures and length of in vitro culture, as expanding and hatching–hatched blastocysts from Day 6 presented higher percentages of apoptotic cells than fresh blastocysts and blastocysts vitrified at Day 5. Our findings suggest that the cryotop vitrification method is useful for the cryopreservation of porcine blastocysts presenting a high degree of expansion, particularly when vitrification is performed after 6 days of in vitro culture. Furthermore, these results show that faster embryo development underlies higher blastocyst cryotolerance and provide evidence that blastocoel cavity expansion before vitrification is a reliable index of in vitro-produced embryo quality and developmental potential.

Cryopreservation of Day 8 equine embryos after blastocyst micromanipulation and vitrification

Pregnancy rates after cryopreservation of large equine blastocyst stage embryos have remained lower than other domesticated livestock species. It is generally accepted that the embryonic capsule is the primary barrier to cryoprotectant entry into the embryo proper and techniques need to be developed to circumvent this obstacle. Therefore, the objective of this study was to develop an efficient Day 8 equine embryo cryopreservation protocol through blastocyst micromanipulation and vitrification. Grade 1 and 2 embryos recovered from mares (n = 15) 8 days after ovulation were used in these experiments. In experiment 1, the effect of either one- or two-puncture treatments before aspiration of blastocoel fluid and exposure to vitrification solutions was evaluated. No difference was detected in mean embryo volume across treatment groups after exposure to vitrification solutions or after 1, 24, 48, and 72 hours of culture. Percent of embryos re-expanding at 24 hours and percent of embryos showing diameter increase at 48 and 72 hours during in vitro culture were 100%, 83%, and 75% compared with 93%, 67%, and 50% for one- and two-puncture treatment groups, respectively. Capsule loss was 25% for one-puncture and 50% for two-puncture treatment groups. In experiment 2, no difference was detected in mean embryo volume for indirect introduction (aspiration of blastocoel fluid + equilibration) and direct introduction (injection of cryoprotectant into blastocoel cavity) treatment groups, after exposure to dilution solution or to culture medium. There was no difference in mean embryo volume for the indirect and direct introduction treatment groups after 1, 24, 48, and 72 hours of culture. Percent of embryos re-expanding at 24 hours and percent of embryos showing diameter increases at 48 and 72 hours during in vitro culture were 100%, 76.9%, and 69.2%, respectively, for both treatment groups. Those embryos subjected to the direct introduction treatment had a higher (P = 0.05) percent capsule loss (70%) compared with the indirect introduction treatment group (31%). The pregnancy rate after transfer of vitrified expanded Grade 1 blastocysts using the indirect introduction method was 83% (5/6). Three pregnancies were allowed to continue to term and resulted in the birth of three healthy foals. The vitrification protocol used in this study has the potential to become a key tool for the successful cryopreservation of equine expanded blastocysts.

Validation of microSecure vitrification (μS-VTF) for the effective cryopreservation of human embryos and oocytes

A novel, aseptic closed system vitrification (VTF) technique for the cryopreservation of embryos and oocytes has been developed and clinically validated in this study. It combines the practicality of embryo-containing sterile flexipettes stored safely and securely with 0.3 ml CBS™ embryo straws possessing weld seals. The cooling and warming rates of this double container system were determined using a data logger. Upon direct plunging into LN(2), the flexipettes cool at an average rate of 1391°C/min, while warming occurs at an average rate of 6233°C/min in a 37°C 0.5 M sucrose bath. Direct deposition of the flexipette into a warming bath insured a rapid transition between -100 and -60°C to minimize potentially harmful recrystalization associated with devitrification. In conclusion, the μS-VTF system has exhibited higher (p<0.05) intact survival, implantation and live birth rates than conventional slow freezing methods. The effective embryo transfer of vitrified blastocysts proved similar to or better than fresh embryo transfer outcomes. The sustained clinical use of μS-VTF has justified a change in our infertility practice. Capsule: The microSecure vitrification (μS-VTF) procedure is a low-cost, non-commercial, aseptic, closed system that offers technical simplicity and repeatability, while effectively attaining an estimated 4:1 warming-to-cooling rate ratio, which supports excellent embryo survival and sustained viability.

A comparison of different vitrification devices and the effect of blastocoele collapse on the cryosurvival of in vitro produced porcine embryos

The aim of this study was to determine the optimum conditions for vitrifying in vitro produced day 7 porcine embryos using different vitrification devices and blastocoele collapse methods. Firstly embryos were collapsed by micro-pipetting, needle puncture and sucrose with and without conducting vitrification. In the next experiment, non-collapsed embryos were vitrified in an open device using either superfine open-pulled straws (SOPS) or the CryoLoop^TM system, or vitrified in a closed device using either the CryoTip^TM or Cryo Bio^TM’s high security vitrification system (HSV). The post-thaw survival of embryos vitrified in the open devices did not differ significantly (SOPS: 37.3%; CryoLoop^TM: 37.3%) nor did the post-thaw survival of embryos vitrified in the closed devices (CryoTip™: 38.5%; HSV: 42.5%). The re-expansion rate of embryos that were collapsed via micro-pipetting (76.0%) did not differ from those that were punctured (75.0%) or collapsed via sucrose (79.6%) when vitrification was not performed. However, embryos collapsed via sucrose solutions (24.5%) and needle puncture (16.0%) prior to vitrification were significantly less likely to survive vitrification than the control (non-collapsed) embryos (53.6%, P < 0.05). The findings show that both open and closed vitrification devices were equally effective for the vitrification of porcine blastocysts. Collapsing blastocysts prior to vitrification did not improve survival, which is inconsistent with the findings of studies in other species. This may be due to the extremely sensitive nature of porcine embryos, and/or the invasiveness of the collapsing procedures.

Blastocoel fluid from differentiated blastocysts harbors embryonic genomic material capable of a whole-genome deoxyribonucleic acid amplification and comprehensive chromosome microarray analysis

OBJECTIVE

To obtain embryonic molecular karyotypes from genomic DNA (deoxyribonucleic acid) isolated from blastocoel fluid (BF) and to compare these karyotypes with the karyotypes from the remaining inner cell mass (ICM) and trophectoderm (TE) of the blastocyst.

DESIGN

Prospective cohort study.

SETTING

Academic center and preimplantation genetics laboratory.

PATIENT(S)

Ninety-six donated cryopreserved embryos.

INTERVENTION(S)

Embryo biopsy, BF aspiration, DNA analysis using a comparative genomic hybridization microarray (aCGH).

MAIN OUTCOME MEASURE(S)

The aCGH of a single blastomere, BF-DNA, and ICM-TE.

RESULT(S)

The BF-DNA samples resulted in a successful aCGH in 63% of cases. Discordance in karyotypes was found between the BF-DNA and the ICM-TE in 52% of cases. A total of 70% of aneusomic (mosaicism), cleavage-stage embryos differentiated into euploid blastocysts. Probabilities for diagnostic accuracy were calculated and demonstrated the following: sensitivity of 0.88 (95% confidence interval [CI]: 0.62-0.98); specificity of 0.55 (95% CI: 0.39-0.70); positive predictive value of 0.41 (95% CI: 0.25-0.60); negative predictive value of 0.92 (95% CI: 0.75-0.99).

CONCLUSION(S)

Genomic DNA from the BF can be amplified and characterized by comprehensive chromosome microarrays. The results demonstrated that aneusomic cleavage-stage embryos differentiated into euploid blastocysts, possibly using a mechanism that marginalizes aneuploid nuclei into the blastocoel cavity. In addition, owing to the high discordance between the karyotypes obtained from the BF-DNA and the ICM-TE, using BF-DNA for preimplantation genetic testing is not yet advised.

Perinatal outcomes for transfer of blastocysts vitrified and warmed in defined solutions with recombinant human albumin: 374 babies born after 898 embryo transfers

PURPOSE

To assess the efficacy of a novel, defined vitrification procedure using recombinant human albumin (rHA) for cryopreservation of human blastocysts.

DESIGN

Retrospective study.

SETTING

Private IVF clinic.

PATIENTS

1,496 patients received vitrified/warmed embryo transfer (ET).

METHODS

Surplus blastocysts, and blastocysts from patients undergoing elective embryo cryopreservation, were vitrified/warmed using Cryotop carriers in homemade solutions containing either human serum albumin (HSA) or rHA.

MAIN OUTCOME MEASURES

Clinical and neonatal outcomes regarding the vitrified/warmed ET procedures.

RESULTS

The HSA and rHA groups had a total of 1,163 and 898 vitrified/warmed cycles, respectively. Embryo survival rates (98.7% vs. 98.9%, respectively) and the number of embryos transferred (1.08 ± 0.01 vs. 1.06 ± 0.01, respectively) were similar in the HSA and rHA groups. Clinical pregnancy rates/ET were higher (P < 0.05) in the rHA group (56.0%) than in the HSA group (51.5%). The HSA and rHA groups had similar live delivery rates/pregnancy (72.2% vs. 72.3%, respectively) and perinatal outcomes, including birth weight (2,988 ± 28 vs. 3,046 ± 26 g, respectively). Birth defects occurred in 0.9% and 1.6% of neonates in the HSA and rHA groups, respectively.

CONCLUSIONS

rHA effectively replaced HSA for human embryo vitrification procedures, and yielded high rates of pregnancy and live births after vitrified/warmed ET. This new approach will support the development of defined ART systems, which will eliminate the variation and risks associated with the use of blood-derived products.

[Effects of artificial shrinkage prior to vitrification in a closed system: a randomized controlled trial]

OBJECTIVE

To evaluate the effect of induced blastocoele shrinkage before vitrification in a closed carrier device.

PATIENTS AND METHODS

Prior to vitrification, blastocyst cavity was artificially shrinked by laser pulse or not treated according to a 2:1 randomized procedure. A total of 185 warming cycles from April 2011 to March 2013 have been analyzed. Clinical pregnancy rate and survival rate were compared between the two groups. The mean (±SD) women age was 33.5±5.7 years for both groups.

RESULTS

The pregnancy rate in the group with artificial reduction of the cavity was higher ([32/67] 47.7%) than in the control group but not significantly ([43/113] 38%). The survival rate in the artificial shrinkage group was significantly higher compared with the control group : 99% (102/103) and 91.8% (168/183) respectively (P=0.01).

DISCUSSION AND CONCLUSION

This study reveals that artificial shrinkage of blastocoelic cavity by laser pulse before vitrification in a closed carrier device improves survival rate after warming.

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.