An effective method for trophectoderm biopsy using mechanical blunt dissection: a step-by-step demonstration

OBJECTIVE

To present an effective approach to trophectoderm biopsy for blastocysts of different stages and characteristics by mechanical blunt dissection (MBD).

DESIGN

Stepwise demonstration with still pictures and operational video clips to explain tips and tricks for trophectoderm biopsy. (This demonstration was approved by the Reproductive Study Ethics Committee at Shengjing Hospital of China Medical University.) SETTING: In vitro fertilization laboratory.

PATIENT(S)

Patients who underwent preimplantation genetic testing.

INTERVENTION(S)

The illustrated techniques of blastocyst trophectoderm biopsy using micromanipulation methods include artificial shrinkage, zona pellucida drilling, injecting media from the drilling, aspiration of trophectoderm cells into the biopsy pipette (outer diameter 27 μm for fully expanded blastocysts and peanut-shaped hatching blastocysts; outer diameter 20 μm for 8-shaped hatching and hatched blastocysts), detachment of the trophectoderm cells by laser pulse combined with MBD (performed using the rims of the biopsy and holding pipettes), and release of the biopsy fragment.

MAIN OUTCOME MEASURE(S)

Successful biopsy rate and survival after warming.

RESULT(S)

Our biopsy strategy does not involve assisted hatching on day-3 or day-4 embryos, which can leave the embryo undisturbed in culture up to the expanded blastocyst stage. Notably, this approach demonstrates several noteworthy advantages for sampling blastocysts of different stages and characteristics, and it maintains a desirable successful biopsy rate (95.4%, n = 1,872) and survival rate after warming (100%, n = 440). The MBD method may reduce thermal damage because fewer laser pulses are used, compared with the traditional laser-only biopsy techniques. For noncollapsed blastocysts after artificial shrinkage, the strategy of injecting medium from the zona pellucida drilling helps to separate the trophectoderm cells from the zona pellucida, thus facilitating the biopsy procedure. For peanut-shaped hatching blastocysts, this approach could provide better control over the aspiration of trophectoderm cells into the biopsy pipette. Especially if the inner cell mass is herniating from the zona pellucida, the trophectoderm biopsy can be performed away from the inner cell mass to avoid damaging it. In addition, the MBD approach combined with the biopsy pipette (outer diameter 20 μm) can effectively control the target number of trophectoderm cells, thus simplifying the process of obtaining a biopsy from a hatched blastocyst.

CONCLUSION(S)

Our biopsy approach demonstrates several noteworthy advantages. Considering its benefits and the simplicity of its execution, this systematic biopsy method for blastocysts of different stages and characteristic can be widely applied.

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.

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.

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.

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.

[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.