Microsuction of blastocoelic fluid before vitrification increased survival and pregnancy of mouse expanded blastocysts, but pretreatment with the cytoskeletal stabilizer did not increase blastocyst survival

Blastocoel fluid aspiration improves vitrification outcomes and produces similar sexing results of in vitro-produced cattle embryos compared to microblade biopsy

The potential applications of in vitro-produced (IVP) cattle embryos are significantly enhanced when combined with genotype selection and cryopreservation techniques. While trophectoderm (TE) biopsies are frequently used for genotyping, cell-free DNA (cfDNA) found in blastocoele fluid (BF) arises as a less-invasive method. Moreover, the blastocoel collapse produced by BF aspiration could be beneficial for embryo cryotolerance. This study was conducted to test the BF as a source of cell free-DNA (cfDNA) and to compare the BF to the TE biopsy in terms of sexing efficiency/accuracy, embryo survival and gene expression after vitrification/warming. IVP day 7 expanded blastocysts were artificially collapsed by aspiration of BF (VIT-Collapsed) or biopsied (VIT-Biopsied). After sample collection, embryos were vitrified/warmed by the Cryotop method and individually cultured in vitro. Intact fresh non-vitrified and vitrified/warmed blastocysts served as Fresh Control and VIT-Control, respectively. After sex identification of BF or TE biopsies and the corresponding surviving embryos, amplification efficiency and sexing accuracy were assessed. There were no differences between the BF and TE biopsy samples in terms of sexing accuracy or efficiency. Although all vitrified groups showed lower post-warming re-expansion rates (p < 0.05), the blastocyst re-expansion rates in the VIT-Collapsed group were comparable to those in the Fresh Control group whereas biopsied blastocysts showed the lowest (p < 0.05) re-expansion rates. VIT-Collapsed blastocysts had hatching rates that were comparable to those of Fresh Control blastocysts but significantly higher than those of the other vitrification treatments. Proapoptotic gene BAX was overexpressed in VIT-Biopsied embryos, whereas BCL2 transcripts were more abundant in the VIT-Collapsed group. On the other hand, VIT-Biopsied embryos showed altered ATP1B1- and AQP3-mRNA levels. The analysis of the cfDNA present in the BF is an efficient, minimally invasive approach to sex IVP cattle embryos. Besides, the artificial collapse of blastocoel prior to vitrification resulted in higher re-expansion and hatching ability than when embryos were vitrified after being biopsied.

Liquid biopsy: state of reproductive medicine and beyond

Liquid biopsy is the process of sampling and analyzing body fluids, which enables non-invasive monitoring of complex biological systems in vivo. Liquid biopsy has myriad applications in health and disease as a wide variety of components, ranging from circulating cells to cell-free nucleic acid molecules, can be analyzed. Here, we review different components of liquid biopsy, survey state-of-the-art, non-invasive methods for detecting those components, demonstrate their clinical applications and discuss ethical considerations. Furthermore, we emphasize the importance of artificial intelligence in analyzing liquid biopsy data with the aim of developing ethically-responsible non-invasive technologies that can enhance individualized healthcare. While previous reviews have mainly focused on cancer, this review primarily highlights applications of liquid biopsy in reproductive medicine.

Low cryoprotectant concentration rapid vitrification of mouse oocytes and embryos

Vitrification of mammalian oocytes and embryos is typically a two-step procedure involving two solutions of increasing concentrations of cryoprotectants. In the present study, we report a simple vitrification protocol that uses low cryoprotectant concentration and a single medium (LCSM). This medium, along with the traditional high concentration two media (HCTM) protocol, was used to vitrify mouse oocytes, zygotes, and blastocysts using silica capillary, cryotop, cryolock, and 0.25 ml straws. Survival rates, two-cell rates, and blastocyst formation rates were compared for oocytes and zygotes vitrified using both protocols. Results show that the LCSM protocol was as good as or better than the traditional HCTM protocol for vitrifying mouse MII oocytes and zygotes using silica capillary, cryotop, and cryolock. On the other hand, for blastocysts, only silica capillary using LCSM had comparable results with the traditional HCTM protocol while cryolock and cryotop had significantly lower percentages of re-expanded and hatched blastocysts. Collapsing blastocysts prior to vitrification or longer duration for better cryoprotectant distribution in multicellular embryos may improve the outcome. In conclusion, the LCSM protocol, with one medium of much lower cryoprotectant concentrations and shorter equilibration time, reduces exposure to cryoprotectant toxicity while improves efficiency, consistency and reliability for mammalian oocyte and embryo preservation.

Preimplantation Genetic Testing: Where We Are Today

Background: Preimplantation genetic testing (PGT) is widely used today in in-vitro fertilization (IVF) centers over the world for selecting euploid embryos for transfer and to improve clinical outcomes in terms of embryo implantation, clinical pregnancy, and live birth rates. Methods: We report the current knowledge concerning these procedures and the results from different clinical indications in which PGT is commonly applied. Results: This paper illustrates different molecular techniques used for this purpose and the clinical significance of the different oocyte and embryo stage (polar bodies, cleavage embryo, and blastocyst) at which it is possible to perform sampling biopsies for PGT. Finally, genetic origin and clinical significance of embryo mosaicism are illustrated. Conclusions: The preimplantation genetic testing is a valid technique to evaluated embryo euploidy and mosaicism before transfer.

Effects of laser zona thinning and artificial blastocoel collapse on the cryosurviving and hatching of buffalo (Bubalus bulalis) blastocysts of different ages

The objectives of this study were to investigate whether blastocoel collapse before vitrification induced by laser improves the cryo-survivability of buffalo in-vitro-fertilized (IVF) blastocysts and whether laser assisted hatching (LAH) promotes hatchability of fresh and frozen-thawed IVF blastocysts. The expanded blastocysts were harvested on Days 6-9 and randomly allocated into five groups as follows: (1) blastocysts were vitrified and thawed without any treatment; (2) blastocysts were vitrified after 15-20 μm zona pellucida (ZP) thinning opposite to the inner cell mass, and blastocoels were also blotted in order to outflow the blastocoelic fluid before vitrification; (3) ZP thinning was made immediately after thawing; (4) fresh blastocysts underwent LAH; and (5) as a control, fresh blastocysts without treatment. Results of the present study showed that the cryosurvival rates of vitrified Day 8 and Day 9 blastocysts in Group 2 were significantly (P < 0.01) higher in Group 2 than Group 1. The hatching rates of Day 8 and Day 9 blastocysts in Group 2 and Group 3 were also significantly (P < 0.01) higher compared with Group 1. Moreover, the hatching rate of Day 9 blastocysts in Group 4 was notably (P < 0.05) higher than Group 5. In conclusion, LAH promotes the hatching rates of Day 9 fresh and Days 8-9 vitrified blastocysts, and artificial blastocoel collapse before vitrification improves the cryosurvival rate of Days 8-9 IVF buffalo blastocysts.

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.

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.

Characterization and quantification of proteins secreted by single human embryos prior to implantation

The use of in vitro fertilization (IVF) has revolutionized the treatment of infertility and is now responsible for 1–5% of all births in industrialized countries. During IVF, it is typical for patients to generate multiple embryos. However, only a small proportion of them possess the genetic and metabolic requirements needed in order to produce a healthy pregnancy. The identification of the embryo with the greatest developmental capacity represents a major challenge for fertility clinics. Current methods for the assessment of embryo competence are proven inefficient, and the inadvertent transfer of non-viable embryos is the principal reason why most IVF treatments (approximately two-thirds) end in failure. In this study, we investigate how the application of proteomic measurements could improve success rates in clinical embryology. We describe a procedure that allows the identification and quantification of proteins of embryonic origin, present in attomole concentrations in the blastocoel, the enclosed fluid-filled cavity that forms within 5-day-old human embryos. By using targeted proteomics, we demonstrate the feasibility of quantifying multiple proteins in samples derived from single blastocoels and that such measurements correlate with aspects of embryo viability, such as chromosomal (ploidy) status. This study illustrates the potential of high-sensitivity proteomics to measure clinically relevant biomarkers in minute samples and, more specifically, suggests that key aspects of embryo competence could be measured using a proteomic-based strategy, with negligible risk of harm to the living embryo. Our work paves the way for the development of “next-generation” embryo competence assessment strategies, based on functional proteomics.

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.

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.

[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.

Retrospective clinical analysis of two artificial shrinkage methods applied prior to blastocyst vitrification on the outcome of frozen embryo transfer

PURPOSE

Vitrification significantly improves the rates of blastocyst survival and clinical pregnancy following frozen embryo transfer (FET). However, ice crystal formation during the freezing process reduces the blastocyst survival rate. Artificial shrinkage (AS) prior to blastocyst vitrification decreases the formation of ice crystals, increasing the blastocyst survival rate. The aim of this study was to identify an efficient AS method to improve blastocyst survival rates following vitrification.

METHOD

Use of the 29-gauge needle AS and Laser pulse AS methods prior to vitrification was compared in terms of the impacts on the rates of blastocyst survival in FET cycles, blastocyst hatching, clinical pregnancy after transfer, embryo implantation, abortion, gestational duration and birth weight.

RESULT

In total, 438 blastocysts in 219 cycles were thawed, resulting in survival of 407 (92.9 %). Of these, 213 cycles were transferred, resulting in 129 clinical pregnancies (60.6 %) and 140 successful births. There were no differences between the two methods in the rates of blastocyst survival, clinical pregnancy, embryo implantation and abortion. However, the 29-gauge needle AS group was associated with a significantly lower blastocyst hatching rate (83.6 % vs. 91.2 %), shorter average gestational duration (37.36 ± 2.34 vs. 38.06 ± 1.76), and higher premature birth rate (40.00 % vs. 21.15 %) compared with Laser pulse AS group.

CONCLUSION

No significant differences in the effectiveness of the two methods applied prior to blastocyst vitrification were observed before birth, while after birth, a significantly improved clinical outcome was obtained with laser pulse AS indicating that this is a more effective pre-processing method for blastocyst vitrification.

Genomic DNA in human blastocoele fluid

IVF often requires embryo cryopreservation through vitrification. During the vitrification process, the embryos can be collapsed by withdrawing the blastocoele fluid. The metabolomic profile of blastocoele fluid has been recently investigated by high-performance liquid chromatography-electrospray ionization-mass spectrometry to provide metabolite information that can help estimations of implantation efficiency. However, the presence of embryo DNA in blastocoele fluid has not been reported to date. This study shows using real-time PCR that genomic DNA was present in about 90% of blastocoele fluid samples harvested during the vitrification procedure. Moreover, the potential for determining embryo sex directly from blastocoele fluid is demonstrated by amplifying the multicopy genes TSPY1 (on the Y chromosome) and TBC1D3 (on chromosome 17). This opens up the possibility of screening embryos from couples carrying an X-linked disorder to identify male embryos at high risk of disease. The application of whole-genome amplification technologies to fluid samples is also shown to be feasible, potentially allowing more comprehensive genetic tests. As proof of principle, microarray comparative genomic hybridization was attempted to confirm the sex of embryos as well as detect several aneuploidies. However, further studies are needed to validate this approach and confirm that the accuracy is sufficient for diagnostic purposes.

Effect of artificial shrinkage on clinical outcome in fresh blastocyst transfer cycles

OBJECTIVE

This study aimed to determine the safety and clinical effect of artificial shrinkage (AS) in terms of assisted hatching of fresh blastocysts. Also, we evaluated the correlation between patient age and the effect of AS on clinical outcome.

METHODS

Two AS methods, using a 29-gauge needle and laser pulse, were compared. Seventy-three blastocysts were shrunk using a 29-gauge needle and the same number of other blastocysts were shrunk by a laser pulse. We evaluated the shrunken blastocysts hourly and considered them viable if they re-expanded >70%. Blastocyst transfer cycles (n=134) were divided into two groups: a control group consisted of the cycles whose intact embryos were transferred (n=100), while the AS group consisted of the cycles whose embryos were replaced following AS (n=34). The implantation and pregnancy rates of the control group and AS group were compared (p<0.05).

RESULTS

The re-expansion rates of the 29-gauge needle and laser pulse AS groups were similar (56 [76.7%] vs. 62 [84.9%], respectively). All of the remaining shrunken blastocysts were re-expanded within 2 hours. There was no degeneration of shrunken blastocysts. The total and clinical pregnancy rate of the AS group (23 [67.6%]; 20 [58.8%], respectively) was significantly higher than that of the control group (47 [47.0%]; 39 [39.0%], respectively). In the older patient group, there was no difference in the clinical outcomes between the AS and control groups.

CONCLUSION

These results suggest that AS of blastocoele cavity, followed by the transfer, would be a useful approach to improve the clinical outcome in cycles in which fresh blastocyst stage embryos are transferred.

Vitrification in open and closed carriers at different cell stages: assessment of embryo survival, development, DNA integrity and stability during vapor phase storage for transport

Background

High cooling rates with vitrification can be achieved through the use of carriers that allow cryopreservation in fluid volumes < one μl. Open carriers allow direct contact of embryos with liquid nitrogen (LN2) whereas closed carrier systems sequester the embryo within a sealed system during immersion in LN2. The use of closed systems may be preferable to reduce the possibility of cross-contamination. In the present study, we compare open and closed carriers for vitrification of embryos. We also examine their ability to retain embryo viability during vapor phase transport.

Methods

Frozen one-cell mouse embryos were thawed and randomly allocated to treatment groups. Embryos were cultured and vitrified at the 8-cell (CL) or at the blastocyst (BL) stage. The cryoloop, an open carrier was tested against two closed systems, the Cryotip and the HSV straw. Carriers were tested for their ability to maintain embryo viability when held in the vapor phase of a dry shipper for a period of 96 hours. Outcome parameters monitored were embryo survival, recovery, subsequent development and signs of DNA damage.

Results

A total of 561 embryos were vitrified. The only parameter significantly affected by the type of carrier was the percentage of embryos recovered after warming. Vitrification of both CL and BL stage embryos in the Cryotip resulted in significantly lower recovery rates (P < 0.001). The subsequent developmental parameters were unaffected by either the carrier or the cell stage. Vapor phase storage for 96 hours under "transport conditions" did not appear to adversely affect the viability after warming. Quantitative analysis for DNA damage showed that <5% of cells were TUNEL positive. Interestingly, the overall percent of cells exhibiting DNA damage was lower after CL stage vitrification (P < 0.001).

Conclusion

This study is one of the first to examine DNA integrity after vitrification on different carriers and at different cell stages. It also provides insight on relative safety of short term vapor storage of vitrified embryos during transport. Within the limits of this study we could not detect an adverse effect of vapor storage on blastomere DNA or other measured outcome parameters.

Current progress in oocyte and embryo cryopreservation by slow freezing and vitrification

Preservation of female genetics is currently done primarily by means of oocyte and embryo cryopreservation. The field has seen much progress during its four-decade history, progress driven predominantly by research in humans, cows, and mice. Two basic cryopreservation techniques rule the field – controlled-rate freezing, the first to be developed, and vitrification, which, in recent years, has gained a foothold. While much progress has been achieved in human medicine, the cattle industry, and in laboratory animals, this is far from being the case for most other mammals and even less so for other vertebrates. The major strides and obstacles in human and other vertebrate oocyte and embryo cryopreservation will be reviewed here.

Vitrification of human early cavitating and deflated expanded blastocysts: clinical outcome of 474 cycles

PURPOSE

The present study was undertaken to evaluate and compare the post thaw survival, implantation and pregnancy rates of vitrified human early cavitating blastocysts with deflated expanded blastocysts.

MATERIAL AND METHODS

Supernumerary blastocysts were vitrified in 30% ethylene glycol-dimethyl sulphoxide based solution using cryoloop. Fully expanded blastocysts were deflated by gentle aspiration of the blastocoelic fluid using a micromanipulator until the cavity collapses prior to vitrification.

RESULTS

Of the 576 vitrified blastocysts, 545 (94.61%) survived thawing in the early cavitating blastocyst group which was significantly higher than deflated expanded blastocyst group, in which only 370 survived thawing out of 459 (80.62%). However, no significant difference was observed in implantation and pregnancy rates between early cavitating and deflated expanded blastocyst groups.

CONCLUSIONS

Early cavitating blastocyst would be the ideal stage for cryopreservation of human blastocysts as it has higher survival rate and avoids additional invasive procedures like deflation of the blastocoele.

Several aspects of animal embryo cryopreservation: anti-freeze protein (AFP) as a potential cryoprotectant

With the development of embryo technologies, such as in vitro fertilization, cloning and transgenesis, cryopreservation of mammalian gametes and embryos has acquired a particular interest. Despite a certain success, various cryopreservation techniques often cause significant morphological and biochemical alterations, which lead to the disruption of cell organelles, cytoskeleton damages, cell death and loss of embryo viability. Ultrastructural studies confirm high sensitivity of the cell membrane and organelle membrane to freezing and thawing. It was found that many substances with low molecular weights have a protective action against cold-induced damage. In this concern, an anti-freeze protein (AFP) and anti-freeze glycoproteins (AFGPs), which occur at extremely high concentrations in fish that live in Arctic waters and protect them against freezing, may be of potential interest for cryostorage of animal embryos at ultra-low temperatures. This mini-review briefly describes several models of AFP/AFGP action to preserve cells against chilling-induced damages and indicates several ways to improve post-thaw developmental potential of the embryo.

Factors affecting the outcome of human blastocyst vitrification

With single blastocyst transfer practice becoming more common in ART, there is a greater demand for a convenient and reliable cryostorage of surplus blastocysts. Vitrification has emerged in the last decade as an alternative promising substitute for slow freezing. Blastocysts represent a unique challenge in cryostorage due to their size, multicellular structure and presence of blastocoele. The continuous acquisition of experience and introduction of many different technological developments has led to the improvement of vitrification as a technology and improved the results of its application in blastocyst cryostorage. The current information concerning safety and efficacy of the vitrification of blastocysts will be reviewed along with the variables that can impact the outcome of the procedure.

Effect of culture system on survival rate of vitrified bovine embryos produced in vitro

This study was designed to evaluate the effect of in vitro culture system on bovine blastocyst yield and quality after vitrification. In Experiment 1, IVM/IVF zygotes were allocated to three culture conditions: (I) Oviductal cells-SOF (OCM-SOF); (II) Oviductal cells-TCM (OCM-TCM); and (III) SOF for 8 days. There was no significant difference between blastocyst rates among groups. In Experiment 2, the IVP-blastocysts in three above culture conditions were vitrified within groups segregated according to age (Day 7 and 8) and blastocoelic cavity size (early and expanded blastocysts). A trend of higher survival rate was obtained in vitrified/warmed early blastocysts compared with expanded ones, so that the difference in OCM-TCM group was significant (P<0.001). Higher survival and hatching rates (P<0.001) were obtained in OCM-SOF and OCM-TCM groups (co-culture) compared with SOF group and the age of blastocyst had no effect on post-thaw survival and hatching rates. In Experiment 3, after staining of blastocysts, in fresh blastocysts the highest number of trophectoderm cells was observed in OCM-TCM group and the number of inner cell mass (ICM) was higher in co-culture groups than SOF group (P<0.001). In vitrified/warmed blastocysts the number of ICM and trophectoderm cells in co-culture groups was higher than SOF group (P<0.001) except for the ICM of expanded blastocysts. In conclusion, in our culture conditions, the blastocyst yield is not influenced by culture system, while the cryotolerance of IVP-blastocysts is positively influenced by the presence of somatic cells. Moreover, the expanded blastocysts are more susceptible to cryoinjury than early blastocysts.

The study of developmental capacity of vitrified mouse blastocysts in different straws after transfer to mouse pseudo pregnant

Vitrification is the commonly used method for long-term storage of pre-implantation mammalian embryos. It is an essential part of assisted reproductive technologies. The re-expansion rate, pregnancy and birth rate of vitrified blastocysts using CPS were compared with OPS and Conventional Straw. Female NMRI mice were injected with Gonadotrophins in order induce them for super ovulation. At that time the mice were sacrified by cervical dislocation and dissected of mouse abdomen. The uterine horns were existed blastocysts were collected in PBS and randomly allocated to four groups: vitrification in CPS, conventional straw, OPS and untreated controls. The vitrification solution was EFS40%. After storage for 1 month in liquid nitrogen, the blastocysts were thawed in 0.5 M sucrose for in vitro culture in M16 medium. After 6 h of culture, the numbers of expanded blastocysts was recorded and ready for transfer to uterus of pseudo pregnant mouse. The re-expansion rate of the CPS group (72.1%) was significantly higher (p < 0.05) than OPS (52.55) and C.S. (38.6%) groups. The pregnancy (70%) and birth rate (45%) of blastocysts in CPS were similar to those of fresh blastocysts (80% and 45.5%) and the pregnancy (10%) and birth rate (5.1%) in Conventional Straws lower than OPS (20 and 7.5%), but were not significantly different. Mouse blastocysts vitrified using CPS had a better result compared with OPS and Conventional Straw. The value of CPS for vitrification of blastocysts may also merit investigation.

Higher harmonic generation microscopy of in vitro cultured mammal oocytes and embryos

Oocyte and embryo selection governs the success of assisted reproductive technologies. The imaging tools applied for selecting embryos may need to contain several key properties: noninvasiveness, high 3D resolution, and the contrast capability to provide as much information about the embryos as possible, such as spindle fibers, zona pellucida, and organelles. Currently adopted imaging techniques can only provide one or two of these desired properties and are with limited contrast of the embryos. Some image techniques can even damage the embryos. Previous studies have shown that harmonic generation microscopy (HGM), a virtual-transition based technology, can provide noninvasive imaging in zebrafish embryos with a sub-cellular 3D resolution and a millimeter penetration depth, and thus could be a suitable tool for future oocyte and embryo selection of assisted reproductive technologies. However to evaluate HGM in clinical use, the intrinsic contrast origin of the second harmonic generation (SHG) and third harmonic generation (THG) inside the mammal embryos has to be studied. In this work we performed HGM studies on the in vitro cultured mouse oocytes and embryos by combining the SHG and THG modalities, with a focus on the contrast origin evaluation. Through the noninvasive HGM imaging, we can clearly identify various structures in the whole oocytes and embryos, including spindle fibers, zona pellucida, polar bodies, cell membranes, and the laminated organelles in the cells. The origin of the THG contrast was further confirmed through the standard staining studies. Through SHG signals, we could not only observe the spindle fibers when the oocytes were arrested at metaphase II or during the cleavage of the embryos, but can also distinguish and analyze the thickness of the three layers of the zona pellucida. Combining two different higher-harmonic generation modalities, SHG and THG, HGM successfully revealed the sub-cellular structures of the whole mouse embryos with a high 3D spatial resolution.