Open versus closed oocyte vitrification system: a prospective randomized sibling-oocyte study

The Effect of Open and Closed Oocyte Vitrification Systems on Embryo Development: A Systematic Review and Network Meta-Analysis

Background/Objectives: Open and closed vitrification systems are commonly employed in oocyte cryopreservation; however, there is limited evidence regarding a comparison of their separate impact on oocyte competence. This study uniquely brings to the literature, data on the effect of open versus closed vitrification systems on laboratory and clinical outcomes, and the effect of cooling and warming rates. Methods: A systematic search of the literature was performed using the databases PubMed/MEDLINE and the Cochrane Central Library, limited to articles published in English up to January 2023. A network meta-analysis was conducted comparing each vitrification system versus fresh oocytes. Results: Twenty-three studies were included. When compared to fresh oocytes, both vitrification devices resulted in lower fertilization rates per MII oocyte retrieved. When comparing the two systems in terms of survival rates, no statistically significant difference was observed. However, interestingly open systems resulted in lower cleavage and blastocyst formation rates per 2 pronuclear (2PN) oocyte compared to fresh controls, while at the same time no statistically significant difference was detected when comparing closed devices with fresh oocytes. Conclusions: In conclusion, closed vitrification systems appear to exert a less detrimental impact on the oocytes' competence, which is reflected in the blastocyst formation rates. Proof of superiority of one system versus the other may lead to standardization, helping to ultimately determine optimal practice in oocyte vitrification.

The development and phase 1 evaluation of a Decision Aid for elective egg freezing

BACKGROUND

Elective egg freezing decisions are complex. We developed a Decision Aid for elective egg freezing and conducted a phase 1 study to evaluate its acceptability and utility for decision-making.

METHODS

The online Decision Aid was developed according to International Patient Decision Aid Standards and evaluated using a pre/post survey design. Twenty-six Australian women aged 18-45 years, interested in receiving elective egg freezing information, proficient in English, and with access to the internet were recruited using social media and university newsletters. Main outcomes were: acceptability of the Decision Aid; feedback on the Decision Aid design and content; concern raised by the Decision Aid, and; utility of the Decision Aid as measured by scores on the Decisional Conflict Scale and on a study-specific scale assessing knowledge about egg freezing and age-related infertility.

RESULTS

Most participants found the Decision Aid acceptable (23/25), balanced (21/26), useful for explaining their options (23/26), and for reaching a decision (18/26). Almost all reported satisfaction with the Decision Aid (25/26) and the level of guidance  it provided (25/26). No participant reported serious concerns about the Decision Aid, and most would recommend it to other women considering elective egg freezing (22/26). Median Decisional Conflict Scale score decreased from 65/100 (Interquartile range: 45-80) pre-Decision Aid to 7.5/100 (Interquartile range: 0-37.5) post-Decision Aid review (p < 0.001). Median knowledge score increased from 8.5/14 (Interquartile range: 7-11) pre-Decision Aid to 11/14 (Interquartile range: 10-12) post-Decision Aid review (p = 0.01).

CONCLUSION

This elective egg freezing Decision Aid appears acceptable and useful for decision-making. It improved knowledge, reduced decisional conflict and did not raise serious concerns. The Decision Aid will be further evaluated using a prospective randomised control trial.

STUDY REGISTRATION

ACTRN12618001685202 (retrospectively registered: 12 October 2018).

Comparison of pregnancy outcomes of 7515 same donor oocyte cycle fresh and cryopreserved-thawed oocytes in 609 donor oocyte recipient cycles: A single institution analysis

OBJECTIVE

Oocyte donation (OD) cycles have been used extensively over the last decades due to high success regarding live birth rate (LBR). We evaluated the reproductive outcomes of fresh and vitrified sibling oocytes in terms of fertilization rates, blast ratio, clinical pregnancy rates, and LBR.

MATERIALS AND METHODS

This retrospective cohort study was conducted at a tertiary in vitro fertilization (IVF) center. A total of 7515 metaphase II (MII) donor oocytes from 304 donor cycles for 609 oocyte recipients undergoing embryo transfers with either fresh or cryopreserved-thawed donor oocytes. Donor cycles that provided both 12 fresh MII oocytes to be used for one recipient and at least 12 MII oocytes which were suitable for vitrification to be used for another recipient at another time were analyzed. Fertilization rates, blastocyst ratios, clinical pregnancy rates (CPR), LBR were evaluated as main outcome measures.

RESULTS

When the fresh and cryopreserved-thawed OD cycles were compared, there was no significant differences between two groups in terms of age of the recipient (41.9 ± 5.7 and 40.3 ± 6.8, p = NS), number of MII oocytes (12.1 ± 0.3 and 12.6 ± 0.8, p = NS), number of 2 pronuclear (PN) (9.1 ± 1.6 and 9.7 ± 2.0, p = NS), blastocyst ratio (58.9 ± 21.7 and 51.3 ± 21.2, p = NS) and number of transferred embryos (1.9 ± 0.3 and 1.9 ± 0.3, p = NS). There was no significant difference between fresh and cryopreserved-thawed sibling donor oocyte cycles in terms of CPR (66.8 % and 60.7 % respectively, p = NS) or LBR (59.5 % and 55.1 %, respectively; p = NS). Miscarriage and multiple gestation rates were similar between groups (p = NS). Log-binomial regression analysis revealed that the use of fresh sibling oocytes was not associated with CPR or LBR, when compared to cryopreserved-thawed oocytes.

CONCLUSIONS

There was no significant difference in terms of reproductive outcomes between sibling fresh OD and cryopreserved-thawed OD cycles.

Animal board invited review: Germplasm technologies for use with poultry

Over the last century, several reproductive biotechnologies beyond the artificial incubation of eggs were developed to improve poultry breeding stocks and conserve their genetic diversity. These include artificial insemination (AI), semen storage, diploid primordial germ cell (PGC) methodologies, and gonad tissue storage and transplantation. Currently, AI is widely used for selection purposes in the poultry industry, in the breeding of turkeys and guinea fowl, and to solve fertility problems in duck interspecies crosses for the production of mule ducklings. The decline in some wild game species has also raised interest in reproductive technologies as a means of increasing the production of fertile eggs, and ultimately the number of birds that can be raised. AI requires viable sperm to be preserved in vitro for either short (fresh) or longer periods (chilling or freezing). Since spermatozoa are the most easily accessed sex cells, they are the cell type most commonly preserved by genetic resource banks. However, the cryopreservation of sperm only preserves half of the genome, and it cannot preserve the W chromosome. For avian species, the problem of preserving oocytes and zygotes may be solved via the cryopreservation and transplantation of PGCs and gonad tissue. The present review describes all these procedures and discusses how combining these different technologies allows poultry populations to be conserved and even rapidly reconstituted.

High-security closed devices are efficient and safe to protect human oocytes from potential risk of viral contamination during vitrification and storage especially in the COVID-19 pandemic

PURPOSE

The main purpose and research question of the study are to compare the efficacy of high-security closed versus open devices for human oocytes' vitrification.

METHODS

A prospective randomized study was conducted. A total of 737 patients attending the Infertility and IVF Unit at S.Orsola University Hospital (Italy) between October 2015 and April 2020 were randomly assigned to two groups. A total of 368 patients were assigned to group 1 (High-Security Vitrification™ - HSV) and 369 to group 2 (Cryotop® open system). Oocyte survival, fertilization, cleavage, pregnancy, implantation, and miscarriage rate were compared between the two groups.

RESULTS

No statistically significant differences were observed on survival rate (70.3% vs. 73.3%), fertilization rate (70.8% vs. 74.9%), cleavage rate (90.6% vs. 90.3%), pregnancy/transfer ratio (32.0% vs. 31.8%), implantation rate (19.7% vs. 19.9%), nor miscarriage rates (22.1% vs. 21.5%) between the two groups. Women's mean age in group 1 (36.18 ± 3.92) and group 2 (35.88 ± 3.88) was not significantly different (P = .297). A total of 4029 oocytes were vitrified (1980 and 2049 in groups 1 and 2 respectively). A total of 2564 were warmed (1469 and 1095 in groups 1 and 2 respectively). A total of 1386 morphologically eligible oocytes were inseminated by intracytoplasmic sperm injection (792 and 594 respectively, P = .304).

CONCLUSIONS

The present study shows that the replacement of the open vitrification system by a closed one has no impact on in vitro and in vivo survival, development, pregnancy and implantation rate. Furthermore, to ensure safety, especially during the current COVID-19 pandemic, the use of the closed device eliminates the potential samples' contamination during vitrification and storage.

Oocyte cryopreservation - current scenario and future perspectives: A narrative review

Oocyte cryopreservation is a boon for women undergoing assisted reproductive technology. With the evolution in the technique of cryopreservation over the last three decades, there has been an exponential rise in the number of oocyte cryopreservation cycles for diverse indications. Apart from cancer patients, it has also been promoted as a mode of fertility insurance to overcome the age-related decline in fertility as well as post-surgical decline following endometriosis surgery. The objective of the review is to evaluate its clinical applications, ideal age at freezing, optimal oocyte number, freezing method of choice, efficacy, safety and recent advances. In the last decade, vitrification has surpassed slow freezing for oocyte cryopreservation. Although closed system of vitrification provides the aseptic environment, open vitrification is commonly followed in practice. Early to mid-thirties is a reasonable age group for planned oocyte cryopreservation, although it might be recommended at a younger age, in patients with diminished ovarian reserve. The patients should be motivated to preserve around 14–20 mature oocytes for successful live birth. Various studies have shown comparable fertilisation and pregnancy rates between Intracytoplasmic sperm injection with fresh and frozen-thawed oocytes. The available evidence has shown no increase in the incidence of congenital abnormalities in babies born through vitrified oocytes. In the future, image analysis using artificial intelligence, and spindle visualisation using poloscope may further enhance the outcome of oocyte cryopreservation.

Cryopreservation and IVF in the time of Covid-19: what is the best good tissue practice (GTP)?

Examine good tissue practices as relates to in vitro fertilization, biopsying, and vitrificationto compare current knowledge of ova, sperm, and embryos as vectors for disease transmission as it relates to our current knowledge regarding the SARS-CoV-2 virus.Unknown risks relating to the SARS-CoV-2 virus and sperm, ova, and embryos necessitate a reexamining of how human IVF is performed. Over the last decade, improvements in cryosurvival and live birth outcomes have been associated with zona pellucida breaching procedures (e.g., blastocyst collapsing and biopsying). In turn, today embryos are generally no longer protected by an intact zona pellucida when vitrified and in cryostorage. Additionally, high security storage containers have proven to be resilient to potential cross-contamination and reliable for routine human sperm freezing and embryo vitrification.Several options to current IVF practices are presented that can effectively mitigate the risks of cross-contamination and infection due to the current Covid-19 pandemic or other viral exposures. The question remains; is heightened security and change warranted where the risks of disease transmission likely remain negligible?

Closed vitrification system and egg donation: Predictive factors of oocyte survival and pregnancy

Although many studies have demonstrated the superiority of ultra-fast freezing compared with slow freezing, the debate is still ongoing concerning the best type of vitrification method: direct exposure to liquid nitrogen (i.e., open systems), or sterile system without contact with liquid nitrogen (i.e., closed systems). The aims of this study were to share our experience on closed vitrification systems in the framework of our egg donation programme with fully asynchronous cycles, and to identify predictive factors of successful outcome in this context. Logistic regression analysis indicated that the number of vitrified oocytes was the only factor predictive of the oocyte survival rate and of clinical pregnancy. The addition of one vitrified oocyte increased by 15 % the odds of oocyte survival. When the oocyte survival rate was considered as a continuous variable, the following results were obtained: 7 % of clinical pregnancy probability for 50 % survival rate, 15 % for 75 % survival rate, and 32 % for 100 % survival rate. The rates of oocyte survival and fertilization, embryo implantation, and clinical pregnancy were in agreement with the recommended values established by ALPHA Scientists in Reproductive Medicine in 2012. On the basis of these results, and according to the European directives on safety, we validate the routine use of closed oocyte vitrification systems for egg donation programmes. These results must be confirmed in larger samples before extrapolation to all patient types.

A new vitrification device that absorbs excess vitrification solution adaptable to a closed system for the cryopreservation of mouse embryos

Several closed vitrification devices that avoid contact with liquid nitrogen have been reported. Recently, based on the Kitasato Vitrification System (KVS), we developed the Closed-KVS, which is a closed vitrification device. The KVS is an open vitrification device that can absorb excess vitrification solution. In this study, we performed two experiments to evaluate the efficacy of the Closed-KVS as a vitrification device for the cryopreservation of mouse embryos at the blastocyst and two-cell stage. In the first experiment, the blastocysts were vitrified using either the Closed-KVS or the KVS (control device). The survival, re-expansion, and hatching rates were not significantly different between embryos vitrified using the Closed-KVS and those vitrified using the KVS. In the second experiment, we evaluated the embryonic development of the two-cell stage embryos vitrified using the Closed-KVS. There were no significant differences in the survival, blastocyst formation, or hatching rates between vitrified or non-vitrified embryos. Additionally, we evaluated the cooling and warming rates of these devices using a numerical simulation method. The cooling rates of the Closed-KVS were similar regardless of whether the outer cap was pre-cooled and were lower than those of the KVS. However, the warming rates of the Closed-KVS (irrespective of cap pre-cooling) were the same as those of the KVS (612,000 °C/min). In summary, the Closed-KVS is a novel closed vitrification device for the cryopreservation of mouse embryos at the blastocyst and two-cell stage.

Open versus closed vitrification system of human oocytes and embryos: a systematic review and meta-analysis of embryologic and clinical outcomes

BACKGROUND

The objective of this study was to carry out a systematic review and meta-analysis of embryologic and clinical outcomes following open versus closed vitrification of human oocytes and embryos.

METHODS

An electronic literature search was conducted in main electronic databases up to June 30, 2018 using the following key terms: 'oocyte', 'embryo', 'blastocyst', 'vitrification', 'cryopreservation', 'device', 'survival rate', 'pregnancy rate', etc. A meta-analysis was performed using a random effect model to estimate the value of risk ratios (RRs) and 95% confidence interval (CI). Subgroup analyses and sensitivity analyses were carried out to further confirm the results.

RESULTS

Twelve (Eight prospective and four retrospective) studies comparing open versus closed vitrification of human oocytes or embryos were included. For prospective studies on oocytes, no evidence for a significant difference in cryosurvival rate (RR = 0.91, 95% CI: 0.80-1.03, P = 0.14; n = 2048) or clinical pregnancy rate (RR = 1.29, 95% CI: 0.80-2.06, P = 0.30; n = 150) was observed. Additionally, there were no significant differences between the two methods concerning secondary endpoints included positive βHCG rate, implantation rate, miscarriage rate, ongoing pregnancy rate, live birth rate, cancellation rate, babies born per transferred blastocysts, or multiple birth rate (P > 0.05). The results of the retrospective studies were similar as the prospective studies.

CONCLUSIONS

It is still impossible to conclude that closed vitrification system could be a substitution for open system in human oocyte and embryo cryopreservation based on current evidence. Therefore, more well-designed prospective studies addressing these issues are still warranted.

Recent advances in oncofertility care worldwide and in Japan

BACKGROUND

Oncofertility is a crucial facet of cancer supportive care. The publication of guidelines for the cryopreservation of oocytes and ovarian tissue is becoming increasingly prevalent in Japan and an updated overview is necessary.

METHODS

In order to provide an updated overview of oncofertility care, original research and review articles were searched from the PubMed database and compared in order to present clinical care in Japan.

RESULTS

In Western countries, various methods for ovarian stimulation, such as the combined use of aromatase inhibitors and random-start protocols, have been reported. Although ovarian tissue cryopreservation, mainly performed via the slow-freezing method, also has yielded >100 live births, the optimal indications and procedures for the auto-transplantation of cryopreserved tissue have been under investigation. In Japan, however, vitrification is prevalent for ovarian tissue cryopreservation, although its efficacy has not yet been established. The quality of network systems for providing oncofertility care in Japan varies greatly, based on the region.

CONCLUSION

There remain many issues in the optimization of oncofertility care in Japan. Along with the regional oncofertility networks, the creation of "oncofertility navigators" from healthcare providers who are familiar with oncofertility, such as nurses, psychologists, and embryologists, could be useful for supplementing oncofertility care coordination, overcoming the issues in individual regions.

Oocyte freezing: reproductive panacea or false hope of family?

Advanced technology now allows young women to freeze and store oocytes with a realistic chance of future pregnancy. Vitrification has revolutionized oocyte preservation, with comparable pregnancy rates to fresh oocyte use. Traditionally used for women who were about to undergo sterilizing oncology treatment, now the opportunity has been extended for 'social freezing'. A steady rise in all women accessing freezing continues. Despite this, there is a lack of understanding of natural fertility and the impact of age on pregnancy outcomes. The optimum time for freezing is before a woman reaches her late 30s, which unfortunately is not reflected in those accessing egg freezing. The underlying message prevails that planning for fertility is best done early, whether that be by physical completion of family size or storing oocytes before the passage of time and age prevents it.

Pre-clinical validation of a closed surface system (Cryotop SC) for the vitrification of oocytes and embryos in the mouse model

Vitrification is currently a well-established technique for the cryopreservation of oocytes and embryos. It can be achieved either by direct (open systems) or indirect (closed systems) contact with liquid nitrogen. While there is not a direct evidence of disease transmission by transferred cryopreserved embryos, it was experimentally demonstrated that cross-contamination between liquid nitrogen and embryos may occur, and thus, the use of closed devices has been recommended to avoid the risk of contamination. Unfortunately, closed systems may result in lower cooling rates compared to open systems, due to the thermal insulation of the samples, which may cause ice crystal formation resulting in impaired results. In our study, we aimed to validate a newly developed vitrification device (Cryotop SC) that has been specifically designed for being used as a closed system. The cooling and warming rates calculated for the closed system were 5.254 °C/min and 43.522 °C/min, respectively. Results obtained with the closed system were equivalent to those with the classic Cryotop (open system), with survival rates in oocytes close to 100%. Similarly, the potential of the survived oocytes to develop up to good quality blastocysts after parthenogenetic activation between both groups was statistically equivalent. Assessment of the meiotic spindle and chromosome distribution by fluorescence microscopy in vitrified oocytes showed alike morphologies between the open and closed system. No differences were found either between the both systems in terms of survival rates of one-cell stage embryos or blastocysts, as well as, in the potential of the vitrified/warmed blastocysts to develop to full-term after transferred to surrogate females.

Why all women should freeze their eggs

PURPOSE OF REVIEW

The use of oocyte cryopreservation via vitrification has increased lately, becoming a common strategy in many IVF centers. This review summarizes the current state of oocyte vitrification, by analyzing the most recent reports on its use in IVF as part of infertile treatment and its contribution to elective fertility preservation (EFP).

RECENT FINDINGS

Oocyte vitrification has become helpful for managing different clinical situations currently providing similar results to fresh oocytes. Owing to satisfactory results, oocyte vitrification is being offered to healthy women to extend their reproductive options (EFP). Although little is known about outcomes in this specific population, new evidence is starting to emerge. Currently, most women are motivated by age and lack of partner. Age is strongly related to the probability of having a child with better chances when they do EFP younger than 35. In contrast to the biological efficiency, the majority of studies show that EFP is more cost-effective at 37-38 years.

SUMMARY

Oocyte vitrification is an efficient tool which can be helpful in managing the IVF cycle. Fertility preservation providers should inform women about their specific probabilities according to their age at vitrification, making emphasis in the fact that egg freezing does not guarantee success, but increases the possibilities of having a biological child in the future.

Survival Rates in Closed and Open Vitrification for Human Mature Oocyte Cryopreservation: A Meta-Analysis

BACKGROUND/AIMS

Survival of warmed oocytes is the first part and is one of the most important aspects of in vitro fertilization following oocyte cryopreservation. There is no definite conclusion about the difference in survival rates between closed and open vitrification for oocyte cryopreservation. This study aimed to investigate whether there is a difference in survival rates between closed and open vitrification for cryopreservation of human mature oocytes.

METHODS

A literature search was performed using the MEDLINE, Cochrane Central Register of Controlled Trials, and Embase databases. A total of 4 studies were included in the meta-analysis.

RESULTS

In the frequentist meta-analysis, the random effects model showed no statistically significant difference in survival rates between closed and open vitrification (risk ratio [RR] 0.8873, 95% confidence interval [CI] 0.7658-1.0280). However, an effect size deviation of the RR from 1.0 and a borderline trend of the 95% CI were noted. In the Bayesian meta-analysis, the posterior probability that closed vitrification would decrease the survival rate when compared to that with open vitrification was 83.04% for the random effects model.

CONCLUSION

It is not yet possible to conclude that closed vitrification is an aseptic alternative to open vitrification in human mature oocyte cryopreservation.

Vitrification of human immature oocytes before and after in vitro maturation: a review

The use of immature oocytes subjected to in vitro maturation (IVM) opens interesting perspectives for fertility preservation where ovarian reserves are damaged by pathologies or therapies, as in PCO/PCOS and cancer patients. Human oocyte cryopreservation may offer some advantages compared to embryo freezing, such as fertility preservation in women at risk of losing fertility due to oncological treatment or chronic disease, egg donation and postponing childbirth. It also eliminates religious and/or other ethical, legal, and moral concerns of embryo freezing. In addition, a successful oocyte cryopreservation program could eliminate the need for donor and recipient menstrual cycle synchronization. Recent advances in vitrification technology have markedly improved the oocyte survival rate after warming, with fertilization and implantation rates comparable with those of fresh oocytes. Healthy live births can be achieved from the combination of IVM and vitrification, even if vitrification of in vivo matured oocytes is still more effective. Recently, attention is given to highlight whether vitrification procedures are more successful when performed before or after IVM, on immature GV-stage oocytes, or on in vitro matured MII-stage oocytes. In this review, we emphasize that, even if there are no differences in survival rates between oocytes vitrified prior to or post-IVM, reduced maturation rates of immature oocytes vitrified prior to IVM can be, at least in part, explained by underlying ultrastructural and biomolecular alterations.

Safety and efficiency of oocyte vitrification

As the oocyte is the starting point for a new life, artificial reproductive technology (ART) techniques should not affect the (ultra) structural and functional integrity, or the developmental competence. Oocyte vitrification -one of the most significant achievements in human ART during the past decade- should therefore be a safe and efficient technique. This review discusses the principles and developments of the existing and future techniques, applications possibilities and safety concerns. The broad range of vitrification media and devices that are currently available, show differences in their effects on the oocyte ultrastructure and preimplantation development. It is not yet fully decided whether this has an influence on the obstetric and neonatal outcome, since only limited information is available with different media and devices. For autologous oocytes, the obstetric and neonatal outcomes appear promising and comparable to pregnancies obtained with fresh oocytes. This however, is not the case for heterologous fresh or vitrified oocytes, where the immunological foreign foetus induces adverse obstetric and neonatal outcomes. Besides the oocyte vitrification process itself, the effect of multiple stimulations (for oocyte banking or for oocyte donors), seems to influence the possibility to develop gynaecological cancers further in life. Automated vitrification/warming should offer a consistent, cross-contamination free process that offers the highest safety level for the users. They should also produce more consistent results in survival, development and clinical pregnancies between different IVF clinics.

Vitrification of Human Germinal Vesicle Oocytes: before or after In Vitro Maturation?

BACKGROUND

The use of immature oocytes derived from stimulated cycles could be of great importance, particularly for urgent fertility preservation cases. The current study aimed to determine whether in vitro maturation (IVM) was more successful before or after vitrification of these oocytes.

MATERIALS AND METHODS

This prospective study was performed in a private in vitro fertilization (IVF) center. We collected 318 germinal vesicle (GV) oocytes from 104 stimulated oocyte donation cycles. Oocytes were divided into two groups according to whether vitrification was applied at the GV stage (group 1) or in vitro matured to the metaphase II (MII) stage and then vitrified (group 2). In the control group (group 3), oocytes were in vitro matured without vitrification. In all three groups, we assessed survival rate after warming, maturation rate, and MII-spindle/chromosome configurations. The chi-square test was used to compare rates between the three groups. Statistical significance was defined at P<0.05 and we used Bonferroni criterion to assess statistical significance regarding the various pairs of groups. The Statistical Package for the Social Sciences version 17.0 was used to perform statistical analysis.

RESULTS

There was no significant difference in the survival rate after vitrification and warming of GV (93.5%) and MII oocytes (90.8%). A significantly higher maturation rate occurred when IVM was performed before vitrification (82.9%) compared to after vitrification (51%). There was no significant difference in the incidence of normal spindle/ chromosome configurations among warmed oocytes matured in vitro before (50.0%) or after (41.2%) vitrification. However, a higher incidence of normal spindle/chromosome configurations existed in the in vitro matured oocytes which were not subjected to vitrification (fresh oocytes, 77.9%).

CONCLUSION

In stimulated cycles, vitrification of in vitro matured MII oocytes rather than GV oocytes seems to be more efficient. This approach needs to be verified in nonstimulated fertility preservation cases.

Modified MicroSecure Vitrification: A Safe, Simple and Highly Effective Cryopreservation Procedure for Human Blastocysts

Clinical embryo vitrification evolved with the development of unique vitrification devices in the 21^st century and with the misconception that ultra-rapid cooling in an "open" system (i.e., direct LN₂ contact) was a necessity to optimize vitrification success. The dogma surrounding the importance of cooling rates led to unsafe practices subject to technical variation and to the creation of vitrification devices that disregarded important quality-control factors (e.g., ease of use, repeatability, reliability, labeling security, and storage safety). Understanding the quality-control flaws of other devices allowed for the development of a safe, secure, repeatable, and reliable µS-VTF method aimed to minimize intra- and inter-technician variation. Equally important, it combined the availability of two existing FDA-compliant devices: 1) a 0.3-mL ionomeric resin embryo straw with internalized, dual-colored, tamper-proof labeling with repeatable weld seal potential; and 2) shortened, commonly-used, 300-µm ID sterile flexipettes to directly load the embryo(s) in order to create a highly-effective global vitrification device. Like other aseptic, closed vitrification systems (e.g., High Security Vitrification (HSV), Rapid-i, and VitriSafe) effectively used in reproductive medicine, microSecure Vitrification (µS-VTF) has proven that it can achieve high post-warming survival and pregnancy outcomes with its attention to simplicity, and reduced technical variation. Although the 0.3-mL embryo straw containing an internal hydrophobic plug was commercially replaced with a standard semen straw possessing cotton-polyvinyl pyrrolidone (PVP) plugs, it maintained its ionomeric resin composition to ensure weld sealing. However, the cotton plugs can wick out the fluid-embryo contents of the flexipettes upon contact. A modified µS-VTF method was adapted to include an additional internal weld seal before the plug on the device loading side. The added technical step to the µS-VTF procedure has not affected its successful application, as high survival rates (> 95%) and pregnancy rates continue today.

Fresh versus cryopreserved oocyte donation

PURPOSE OF REVIEW

Utilization of cryopreserved instead of fresh donor oocytes has rapidly increased in recent years. Whether treatment outcomes are comparable has, however, remained controversial.

RECENT FINDINGS

More than 24% of initiated oocyte donation cycles in the USA during 2013-2014 involved previously cryopreserved oocytes. The use of cryopreserved-donated oocytes may simplify logistics and lower costs per treatment cycle. Whether cryopreserved donor oocytes also lower costs per live birth is still undetermined as they result in lower live birth rates in comparison to fresh donor oocyte cycles. National data regarding the safety of donated oocytes, including miscarriage rates and neonatal health outcomes, are lacking.

SUMMARY

Currently available data on cryopreserved-donated oocytes are incomplete and, therefore, still insufficient to claim equivalency between fresh and cryopreserved donor oocytes. Until sufficient data are available, patients should be advised about advantages and disadvantages of both methods of oocyte donation, and the use of cryopreserved oocytes should be considered only with caution and appropriate informed consent. Because banking of donated human oocytes facilities their commercial trade, it challenges basic ethical considerations, which have been the basis of oocyte donation since its inception.

Thermal and clinical performance of a closed device designed for human oocyte vitrification based on the optimization of the warming rate

Although it was qualitatively pointed out by Fahy et al. (1984), the key role of the warming rates in non-equillibrium vitrification has only recently been quantitatively established for murine oocytes by Mazur and Seki (2011). In this work we study the performance of a closed vitrification device designed under the new paradigm, for the vitrification of human oocytes. The vitrification carrier consists of a main straw in which a specifically designed capillary is mounted and where the oocytes are loaded by aspiration. It can be hermetically sealed before immersion in liquid nitrogen for vitrification, and it is warmed in a sterile water bath at 37 °C. Measured warming rates achieved with this design were of 600.000 ºC/min for a standard DMEM solution and 200.000 ºC/min with the vitrification solution for human oocytes. A cohort of 143 donor MII sibling human oocytes was split into two groups: control (fresh) and vitrified with SafeSpeed device. Similar results were found in both groups: survival (97.1%), fertilization after ICSI (74.7% in control vs. 77.3% in vitrified) and good quality embryos at day three (54.3% in control vs. 58.1% in vitrified) were settled as performance indicators. The pregnancy rate was 3/6 (50%) for the control, 2/3 (66%) for vitrified and 4/5 (80%) for mixed transfers.

Closed vitrification of human oocytes and blastocysts: outcomes from a series of clinical cases

PURPOSE

High survival rates and clinical outcomes similar to those from fresh oocytes and blastocysts have been observed with open oocyte vitrification systems. It has been suggested that the extremely fast cooling rates that are only achieved with open systems are necessary for human oocyte and blastocyst vitrification. However, there is a potential risk of introducing contamination with open systems. The aim of this study was to assess whether similar survival and subsequent implantation rates could be achieved using a closed vitrification system for human oocytes and blastocysts.

METHODS

Initially, donated immature oocytes that were matured in vitro were vitrified using the cryoprotectants ethylene glycol (EG) + dimethyl sulphoxide (DMSO) + sucrose and either a closed system (Rapid-i®) or an open system (Cryolock). The closed system was subsequently introduced clinically for mature oocyte cryopreservation cases and blastocyst vitrification.

RESULTS

Using in vitro matured oocytes, a similar survival was achieved with the open system of 92.4 % (73/79) and with the closed system of 89.7 % (35/39). For clinical oocyte closed vitrification, high survival rate of 90.5 % (374/413) and an implantation rate of 32.7 % (18/55) from the transfer of day 2 embryos was achieved, which is similar to fresh day 2 embryo transfers. Blastocysts have also been successfully cryopreserved using the Rapid-i closed vitrification system with 94 % of blastocysts having an estimated ≥75 % of cells intact and a similar implantation rate (31.5 %) to fresh single blastocyst transfers.

CONCLUSION

Closed vitrification can achieve high survival and similar implantation rates to fresh for both oocytes and blastocysts.

Fertility Preservation: A Key Survivorship Issue for Young Women with Cancer

Fertility preservation in the young cancer survivor is recognized as a key survivorship issue by the American Society of Clinical Oncology and the American Society of Reproductive Medicine. Thus, health-care providers should inform women about the effects of cancer therapy on fertility and should discuss the different fertility preservation options available. It is also recommended to refer women expeditiously to a fertility specialist in order to improve counseling. Women’s age, diagnosis, presence of male partner, time available, and preferences regarding use of donor sperm influence the selection of the appropriate fertility preservation option. Embryo and oocyte cryopreservation are the standard techniques used while ovarian tissue cryopreservation is new, yet promising. Despite the importance of fertility preservation for cancer survivors’ quality of life, there are still communication and financial barriers faced by women who wish to pursue fertility preservation.

New methods for cooling and storing oocytes and embryos in a clean environment of -196°C

It is well documented that oocyte vitrification using open systems provides better results than closed systems. However, its use is limited owing to risks of contamination posed by direct exposure to liquid nitrogen and cross-contamination when stored in liquid nitrogen tanks. A device that produces clean liquid air (CLAir) having similar a temperature as liquid nitrogen and a sterile storage canister device (Esther) that keeps samples sealed in their own compartment while in regular liquid nitrogen tanks were developed. The following experiments were performed: temperature measurements, bioburden tests, vitrification and storage experiments with mice embryos and human oocytes. Results showed similar cooling rates for liquid nitrogen and liquid air. Bioburden tests of CLAir and Esther showed no contamination, while massive contamination was found in "commercial" liquid nitrogen and storage canisters. Mice blastocysts had a survival rate of over 90%, with 80% hatching rate after vitirification in CLAir and 1 week storage in Esther, similar to the fresh (control) results. Human oocytes vitrified in CLAir and in liquid nitrogen for three consecutive vitrification/warming cycles showed 100% survival, seen as re-expansion in both groups. These new systems represent a breakthrough for safe vitrification using open systems and a safe storage process generally.

[A prospective study to compare the efficiency of oocyte vitrification using closed or open devices]

OBJECTIVES

Oocyte vitrification using an open device is thought to be a source of microbiological and chemical contaminations that can be avoided using a closed device. The principal purpose of this study was to compare the two vitrification protocols: closed and open system. The secondary aim was to study the effects of the storage in the vapor phase of nitrogen (VPN) on oocytes vitrified using an open system and to compare it to those of a storage in liquid nitrogen (LN).

METHODS

Forty-four patients have been included in our study between November 2014 and May 2015. Two hundred and fourteen oocytes have been vitrified at germinal vesicle (GV), metaphase I (0PB) and metaphase II (1PB) stages. We vitrified 96 oocytes (59 GV/37 0PB) using a closed vitrification device and 118 oocytes (57 GV/31 0PB/30 1PB) using an open device. The vitrified oocytes were then stored either in LN or in VPN. The main outcome measures were the survival rate after warming (SR), meiosis resumption rate (MRR) and maturation rate (MR).

RESULTS

The global post-thaw SR was significantly higher for oocytes vitrified using an open system (93.2%) compared to those vitrified using a closed one (64.5%; P<0.001). On the contrary, there was no significant difference in terms of global MRR and MR (82.1% vs. 87.5% and 60.7% vs. 61.2% using closed and open system respectively). The SR, MRR and the MR were not significantly different when vitrified oocytes were stored in VPN or LN (91.6, 83.8, 64.5% vs. 93.9, 89.8, 59.1% respectively).

CONCLUSION

Taking into account the limits of our protocol, the open vitrification system remains the more efficient system. The use of sterile liquid nitrogen for oocyte vitrification and the subsequent storage in vapor phase of nitrogen could minimize the hypothetical risks of biological and chemical contaminations.

Roles of intracellular ice formation, vitrification of cell water, and recrystallisation of intracellular ice on the survival of mouse embryos and oocytes

Mazur and collaborators began examining the validity of initial views regarding mouse oocyte and embryo vitrification and found that most are partially or fully wrong. First, the relative effects of warming and cooling rates on the survival of mouse oocytes subjected to a vitrification procedure were determined. The high sensitivity to warming rate strongly suggests that the lethality of slow warming is a consequence of either the crystallisation of intracellular glassy water during warming or the recrystallisation during slow warming of small intracellular crystals that had formed during cooling. Warming rates of 107°C min-1 were achieved in 0.1-µL drops of ethylene glycol-acetamide-Ficoll-sucrose (EAFS) solution plus a small amount of India ink on Cryotops warmed using an infrared laser pulse. Under these conditions, survival rates of 90% were obtained even when mouse oocytes were suspended in 0.3× EAFS, a concentration that falls in the range that many cells can tolerate. A second important finding was that the survival of oocytes is more dependent on the osmotic withdrawal of much of the intracellular water before vitrification than it is on the penetration of cryoprotective solutes into the cells. Herein we review the roles of internal ice formation, vitrification and recrystallisation. It remains to be seen how widely these findings will be applicable to other types of cells and tissues from other species.

Open versus closed oocyte vitrification in an oocyte donation programme: a prospective randomized sibling oocyte study

STUDY QUESTION

Is the survival of donor oocytes with the CryotopSC device superior to the survival with the closed CBSvit device?

SUMMARY ANSWER

The CryotopSC device and the CBSvit device showed similar survival rates.

WHAT IS KNOWN ALREADY

Health authorities are cautious about possible cross contamination during liquid nitrogen storage or handling when working with open vitrification devices. At present, the use of open devices is still allowed since little information is available on the efficiency of closed devices.

STUDY DESIGN, SIZE, DURATION

A prospective randomized sibling oocyte study was performed in the Centre for Reproductive Medicine (UZBrussel) between January 2014 and July 2015. The survival after warming and the embryological outcome of donor oocytes vitrified using two devices was compared: the CBSvit device (closed vitrification and closed storage) and the CryotopSC device (open vitrification and closed storage). A difference of 10% was defined to prove the superiority of the CryotopSC device. In total, 250 warmed oocytes were needed in each arm.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocytes from 48 donors were included in the study: 253 vitrified with the CBSvit device and 257 with the CryotopSC device. Equal numbers of oocytes from both devices and originated from the same donor cycle were allocated to each of 78 recipients, in order to exclude donor and recipient (male factor) effects.

MAIN RESULTS AND THE ROLE OF CHANCE

There were no differences found between the CBSvit and the CryotopSC in terms of survival after warming (93.7 versus 89.9%) or fertilization per injected oocyte (74.3 versus 81.4%). The degeneration rate after ICSI was significantly higher for the CBSvit device: 11.4 versus 6.1% (P = 0.041). A significantly higher number of zygotes in the CryotopSC group finished their first mitosis 25-27 h post-injection (34.1 versus 52.1%, P = 0.001). On Day 3, the overall embryo quality distribution did not vary between groups, but a significantly higher cell number was obtained in the CryotopSC device: 6.8 ± 2.8 versus 7.6 ± 2.8 (P = 0.01). The utilization rate per mature oocyte, per surviving oocyte or per fertilized oocyte did not differ. The embryos with the highest quality were selected for transfer on Day 3. The clinical pregnancy rate per transfer cycle was 36.5%.

LIMITATIONS, REASONS FOR CAUTION

The results of this study should not be extrapolated to other female groups, since oocytes from young fertile donors were used in this study.

WIDER IMPLICATIONS OF THE FINDINGS

In many countries, the use of open devices is still allowed due to the limited reports on the efficiency of closed devices. Knowing the caution of health authorities about the use of open devices, there is an urgent need for efficiency studies with closed devices. The results obtained in the current study shows the efficiency of a safe closed vitrification device, leaving behind any concern about possible cross contamination during handling or storage.

STUDY FUNDING/COMPETING INTERESTS

No funding was obtained. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

NCT01952184.

TRIAL REGISTRATION DATE

24 September 2013.

DATE OF FIRST PATIENT'S ENROLMENT

23 January 2014.

Comparison of the Developmental Potential and Clinical Results of In Vivo Matured Oocytes Cryopreserved with Different Vitrification Media

Background:

Oocyte vitrification is widely used throughout the world, but its clinical efficacy is inconsistent and depends on the vitrification media. This study compared the developmental potential and clinical results of in vivo matured oocytes cryopreserved with different vitrification media.

Methods:

This retrospective study involved vitrified-warmed oocytes at one in vitro fertilization laboratory. Vitrification media kits comprised the MC kit (ethylene glycol [EG] plus 1,2-propanediol [PROH]), the KT kit (EG plus dimethyl sulphoxide [DMSO]), and the Modified kit (EG plus DMSO and PROH kit). Rates of oocyte survival and subsequent developmental potential were recorded and analyzed. The t-test and the Chi-square test were used to evaluate each method's efficacy.

Results:

Oocyte survival rate was significantly higher for the Modified kit (92.0%) than for the MC kit (88.2%) (P < 0.05) and the KT kit (77.3%) (P < 0.001). The rate of high-quality embryo development in the Modified kit group (35.8%) was significantly higher than in the MC kit group (29.0%) and the KT kit group (28.3%) (P < 0.001). No significant differences were observed in the clinical pregnancy and implantation rates among the MC, KT, and Modified kit groups (37.2% vs. 30.2% vs. 39.6%; 21.9% vs. 18.8% vs. 27.4%, respectively) (P > 0.05). The high-quality embryo rate per warmed oocyte was significantly higher (23.4%) in the Modified kit group than in the other groups (P < 0.001). The embryo utilization and live birth rates per warmed oocyte were the highest in the Modified kit group, but not significantly (P > 0.05).

Conclusions:

Modified vitrification media are efficient for oocyte vitrification and, with further verification, may be able to replace commercially available media in future clinical applications.

Six years' experience in ovum donation using vitrified oocytes: report of cumulative outcomes, impact of storage time, and development of a predictive model for oocyte survival rate

OBJECTIVE

To describe the clinical outcomes achieved after 6 years' experience in ovum donation conducted with vitrified oocytes; to attempt to find predictors of survival; and to provide information about the probability of having a baby according to the number of oocytes consumed.

DESIGN

Retrospective, observational study.

SETTING

Private university-affiliated in vitro fertilization center.

PATIENT(S)

Recipients of vitrified oocytes (January 2007-March 2013), including all the warming procedures (n = 3,610) and all the donations made during the same period (n = 3,467).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Survival rate per warming procedure, cumulative delivery rates (CDR) per single donation cycle, oocyte-to-baby rate, and cumulative live birth rate (CLBR) per oocyte consumed.

RESULT(S)

Oocyte survival rate was 90.4%. It was not possible to develop a predictive model for survival owing to the lack of prognostic value of the studied variables. Implantation, clinical, and ongoing pregnancy rates per donation cycle were 39.0% (95% confidence interval [CI], 37.8-40.5), 48.4% (95% CI, 46.7-50.1), and 39.9% (95% CI, 38.3-41.5), respectively. Statistical differences were found when comparing blastocysts versus day 3 ETs (42.5%; 95% CI, 40.4-45.2 vs. 37.5%; 95% CI, 35.3-39.7 ongoing pregnancy rate). The CDR/donation cycle, including cryotransfers, was 78.8% (95% CI, 73.5-84.1). The oocyte-to-baby rate was 6.5%. CLBR increased progressively according to the number of oocytes consumed.

CONCLUSION(S)

We provide detailed information about the high efficiency of using vitrified/warmed oocytes. There is currently no way of estimating donors' oocytes survival when considering baseline characteristics, storage time, or controlled ovarian stimulation parameters. The probability of achieving a baby using vitrified oocytes increases progressively with the number of oocytes consumed.

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.

[Vitrification: Principles and results]

Sperm and embryos cryopreservation is a commonly applied technique for several years. Recently authorized in France, vitrification tends to replace gradually the conventional technique of slow freezing, so upsetting the practices in the management of patients. It allows from now on the cryopreservation of oocytes and opens new perspectives in egg donation either still in fertility preservation. This review thus attempted to examine the contribution of vitrification in the freezing of oocytes and human embryos at various stages of development. If obviously vitrification appears as the current method of choice for the cryopreservation of oocytes as well as blastocysts, the results are less cut as regards embryos to early stages. No increase in adverse obstetric and perinatal outcomes in children conceived from vitrified oocytes or embryos is noted in the literature.

Neonatal outcomes after the implantation of human embryos vitrified using a closed-system device

PURPOSE

Closed vitrification poses a risk of adversely affecting embryo development, while it may minimize the risk of contamination. We assessed the effects of closed-system human embryo vitrification on fetal development after implantation, neonatal outcome, and clinical safety.

METHODS

This was a retrospective cohort study conducted at a private fertility clinic. A total of 875 vitrified-warmed blastocysts that were single-transferred under hormone-replacement cycles between November 2011 and December 2013 were randomly divided into two groups (closed vitrification, n 313; open vitrification, n 562) after receiving the patients' consent forms. Developmental competence after implantation, including gestational age, birth weight, sex, Apgar score, and anomalies of newborns, after the transfer of blastocysts vitrified by closing vitrification was compared with that obtained in the case of open vitrification.

RESULTS

There were no significant differences between the use of closed and open vitrification systems in embryo development after implantation, gestational age, birth weight, sex ratio, Apgar score, and congenital anomalies of newborns.

CONCLUSION

Human embryos can be vitrified using a closed vitrification system without impairment of neonatal development.

Fine morphological assessment of quality of human mature oocytes after slow freezing or vitrification with a closed device: a comparative analysis

BACKGROUND

Human mature oocytes are very susceptible to cryodamage. Several reports demonstrated that vitrification might preserve oocyte better than slow freezing. However, this is still controversial. Thus, larger clinical, biological and experimental trials to confirm this concept are necessary. The aim of the study was to evaluate and compare fine morphological features in human mature oocytes cryopreserved with either slow freezing or vitrification.

METHODS

We used 47 supernumerary human mature (metaphase II) oocytes donated by consenting patients, aged 27-32 years, enrolled in an IVF program. Thirtyfive oocytes were cryopreserved using slow freezing with 1.5 M propanediol +0.2 M sucrose concentration (20 oocytes) or a closed vitrification system (CryoTip Irvine Scientific CA) (15 oocytes). Twelve fresh oocytes were used as controls. All samples were prepared for light and transmission electron microscopy evaluation.

RESULTS

Control, slow frozen/thawed and vitrified/warmed oocytes (CO, SFO and VO, respectively) were rounded, 90-100 μm in diameter, with normal ooplasm showing uniform distribution of organelles. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates and small mitochondria-vesicle (MV) complexes were the most numerous structures found in all CO, SFO and VO cultured for 3-4 hours. M-SER aggregates decreased, and large MV complexes increased in those SFO and VO maintained in culture for a prolonged period of time (8-9 hours). A slight to moderate vacuolization was present in the cytoplasm of SFO. Only a slight vacuolization was present in VO, whereas vacuoles were almost completely absent in CO. Amount and density of cortical granules (CG) appeared abnormally reduced in SFO and VO, irrespective of the protocol applied.

CONCLUSIONS

Even though, both slow freezing and vitrification ensured a good overall preservation of the oocyte, we found that: 1) prolonged culture activates an intracellular membrane "recycling" that causes the abnormal transformation of the membranes of the small MV complexes and of SER into larger rounded vesicles; 2) vacuolization appears as a recurrent form of cell damage during slow freezing and, at a lesser extent, during vitrification using a closed device; 3) premature CG exocytosis was present in both SFO and VO and may cause zona pellucida hardening.