Oocyte vitrification technology has made egg-sharing donation easier in China

Automation in vitrification and thawing of mouse oocytes and embryos

Vitrification is a common technique for cryopreserving oocytes or embryos. However, manual vitrification is tedious and labor-intensive, and can be subject to variations caused by human factors. To address these challenges, we developed an automated vitrification-thawing system (AVTS) based on a cryo-handle. Our study firstly assessed the efficiency of cryoprotectant exchange through comparing the osmolalities of fresh and collected solutions during automated vitrification and thawing, and evaluated the cooling and warming rates of the cryo-handle. We also compared mouse oocyte survival, fertilization and embryo development after thawing and ICSI, and the development of re-frozen cleavage embryos between manual operation and automated system. The results showed that the osmolalities of collected samples were within normal range and comparable to fresh solutions. Furthermore, the automated system could obtain the reliable cooling and warming rates. Particularly, there were no significant differences in oocyte survival rates, fertilization rates, and subsequent embryo development and its quality between two procedures. Our findings suggest that AVTS has no impact on osmolalities of vitrification and thawing solutions, ensuring the proper exchange of cryoprotectants. The cryo-handle also shows the ability to achieve reliable cooling and warming rates, which benefits for the cryopreservation and thawing process. Moreover, the results from mouse oocytes and embryos indicate that automated system has effectively maintained the survival and fertilization of frozen oocytes and supported subsequent embryo development. Therefore, the automated vitrification and thawing system will inevitably represent a superior alternative to manual operation.

Efficiency and safety of vitrification of surplus oocytes following superovulation: a comparison of different clinical indications of oocyte cryopreservation in IVF/ICSI cycles

Objective

To evaluate the effectiveness and safety of utilizing the small number of remaining vitrified oocytes after the failure of adequate fresh sibling oocytes. The outcome of present study would provide more comprehensive information about possible benefits or disadvantage to cryopreserve supernumerary oocytes for patients who have plenty oocytes retrieved.

Methods

This retrospective cohort study included 791 IVF/ICSI cycles using 6344 oocytes that had been vitrified in the Reproductive Hospital affiliated to Shandong University between January 2013 and December 2019.They were divided into three groups: SOC group (supernumerary oocytes cryopreservation), relative-MOC group (relative male factor-oocyte cryopreservation), and absolute-MOC group (absolute male factor-oocyte cryopreservation). Laboratory and clinical outcomes were analysed, and multivariate regression analysis was used to study the effect of different indications of vitrification on CLBR.

Results

The CLBR was highest in absolute-MOC, and lowest in SOC (39.0% vs 28.9%, P=0.006); however, after adjusting for confounding factors, the difference was not statistically significant. Multivariable regression analysis showed no impact of indications of vitrified oocytes on CLBR according to controlled age, BMI, preservation duration, use of donor sperm or not, use of PESA/TESA or not, number of oocytes retrieved, number of oocytes thawed, and oocyte survival rate. The preliminary data of safety showed no significant differences in the perinatal and neonatal outcoms after ET and FET between the SOC and MOC groups.

Conclusion

Different indications of vitrification did not affect CLBR. The CLBR of vitrified oocytes for different indications was correlated with age and number of warmed oocytes. For women who have plenty oocytes retrieved, the strategy of cryopreserving a small number of oocytes is a valuable option and might benefit them in the future. Additional data from autologous oocyte vitrification research employing a large-scale and variable-controlled methodology with extending follow-up will complement and clarify the current results.

Majority of transferred mosaic embryos developed healthy live births revealed by a preclinical study using embryonic morphology assessment and noninvasive PGT-A on cell-free DNA in blastocoel fluid

PURPOSE

This preclinical study aimed to evaluate whether using transferred mosaic embryos (primarily selected by embryonic morphology assessment (EMA) and compared by the noninvasive preimplantation genetic testing for aneuploidy (niPGT-A) on cell-free DNA in blastocoel fluid (BF)) increases the rates of clinical pregnancies (CPs) and healthy live births (HLBs) and to investigate whether niPGT-A could provide valuable genetic information for the EMA-selected transferred mosaic embryos.

METHODS

This study collected 215 blastocyst culture samples and 182 BF samples. Cell-free DNA from the BF was amplified and examined by next-generation sequencing-based niPGT-A. All 182 patients underwent EMA. However, only 147 underwent in vitro fertilization and embryo transfer, and only 113 clinical outcomes were followed up. Comprehensive chromosome screening for the chorionic villus sampling of spontaneous miscarriages and noninvasive prenatal testing for ongoing pregnancies were also performed.

RESULTS

The implantation rate was 77.55% in 147 transferred high-quality embryos selected by EMA. Among 113 CPs, 16 led to spontaneous miscarriage (14.16%), and 97 resulted in HLBs (85.84%). According to the niPGT-A results for 113 patients with clinical outcomes, 80.4% had CP (euploid, 20.54%; single aneuploid, 1.79%; mosaic chromosome aneuploid and/or segmental aneuploid, 58.04%). Of all the mosaic aneuploids, 90.76% were false positive, transforming to euploid.

CONCLUSIONS

Transferred EMA-selected embryos showed higher implantation rates. The niPGT-A of BF provided valuable genetic status ("-ploid") information, which helped reduce aneuploid-induced implantation failure and miscarriage, thereby increasing the CP and HLB rates. Additionally, majority of the transferred embryos with complex/chaotic mosaic aneuploid would likely develop HLBs.

An Eight Year Experience of Autologous Oocyte Vitrification for Infertile Patients Owing to Unavailability of Sperm on Oocyte Retrieval Day

Objective: The objective of this study was to provide a descriptive analysis of the clinical outcomes achieved in oocyte vitrification in cases where sperm was unavailable on oocyte retrieval day, and to identify predictors of oocyte survival. Methods: This retrospective cohort study used data from a university-affiliated reproductive medical center. There were 321 cycles in which some of, or all oocytes were vitrified owing to the unavailability of sperm between March 2009 and October 2017. A descriptive analysis of the clinical outcomes including both fresh embryo transfers and cryopreserved embryo transfers was provided. The ability of an individual parameter to forecast oocyte survival per thawing cycle was assessed by binary logistic regression analysis. The cumulative probability of live birth (CPLB) was estimated by using the Kaplan-Meier method according to the total number of oocytes thawed in consecutive procedures. Results: The average survival rate was 83.13%. High-quality embryo rate and blastocyst rate decreased significantly decreased significantly in vitrification oocyte group compared to fresh control oocytes. The comparison of sibling oocytes in part-oocyte-vitrified cycles shows fewer high-quality embryos developed in the vitrified group. The live birth rate per warmed-oocyte was 4.3%. Reasons for lack of sperm availability on oocyte retrieval day and serum cholesterol levels were found to be associated with oocyte survival rate in the present study. Kaplan-Meier analysis showed no significant difference in CPLB between patients ≤35 vs. >35 years. Conclusions: Oocyte vitrification is an indispensable and effective alternative when sperm are not available on oocyte retrieval day. The present study provided evidence that oocytes from infertile couples were more likely to suffer oocyte/embryo vitrification injury. Clinicians need to take this into account when advising patients in similar situations. Further studies will be necessary to clarify the correlation between serum metabolism parameters and human oocyte survival after vitrification.

Current perspectives on social oocyte freezing

Demand for oocyte freezing in absence of a medical indication is growing as women delay childbirth and seek to extend the window of opportunity for parenthood. The optimum age for oocyte freezing is below 35 years, whereas currently the mean age of women undergoing oocyte freezing in the UK is 38 years. Nearly half of women undergoing oocyte freezing are not in a relationship. The treatment is not publicly funded and the average price for a complete oocyte freezing and thawing cycle, including annual storage fees, could reach over £7000. The live birth rate per oocyte thaw cycle is 18% and is influenced by age at the time of oocyte freezing. Women considering social oocyte freezing should be thoroughly counselled about the efficacy, limitations, cost implications and alternatives to oocyte freezing and provided with the appropriate support to enable a truly informed reproductive choice.

Effect of embryo cryopreservation duration on pregnancy-related complications and birthweight after frozen-thawed embryo transfer: a retrospective cohort study

Frozen embryo transfer (FET) has been adopted by growing number of reproductive medicine centers due to the improved outcome compared with fresh embryo transfer. However, few studies have focused on the impact of embryo cryopreservation duration on pregnancy-related complications and neonatal birthweight. Thus, a retrospective cohort study including all FET cycles with livebirth deliveries in a university affiliated hospital from May 2010 to September 2017 was conducted. These deliveries were grouped by the cryopreservation duration of the transferred embryo (≤3 months, 4-6 months, 7-12 months, and >12 months). The associations between embryo cryopreservation duration and pregnancy-related complications were evaluated among the groups using multinomial logistic regression. Neonatal birthweight was compared according to the stratification of singletons and multiples using multinomial and multilevel logistic regression, respectively. Among all 12,158 FET cycles, a total of 3864 livebirth deliveries comprising 2995 singletons and 1739 multiples were included. Compared with those within 3 months, women undergoing FET after a cryopreservation time longer than 3 months did not show any increased risk of gestational diabetes mellitus, gestational hypertension, preeclampsia, meconium staining of the amniotic fluid, or preterm birth. Furthermore, the risk of lower birthweight, macrosomia, small-for-gestational-age, or large-for-gestational-age for either singletons or multiples was not affected by long-term cryopreservation. In summary, embryo cryopreservation duration does not have negative effects on pregnancy-related complications or birthweight after FET.

Changing Fertility Landscapes: Exploring the Reproductive Routes and Choices of Fertility Patients from China for Assisted Reproduction in Russia

Global reproductive landscapes and with them cross-border routes are rapidly changing. This paper examines the reproductive routes and choices of fertility travellers from China to Russia as reported by medical professionals and fertility service providers. Providing new empirical data, it raises new ethical questions on the facilitation of cross-border reproductive travel and the commercialisation of reproductive treatment. The relaxation of the one-child policy in 2014 in China, the increasing demand for ART exceeding the capacity of national fertility clinics and the difficulty of accessing treatment with donor eggs concomitant with a growing economic power of the upper–middle class are shaping the ART industry in Asia in new ways. A new development is Chinese citizens increasingly seeking ART treatment in Russia, which has a long-standing practice of ART governed by a liberal legislation. Furthermore, as China prohibits the export of gametes, Chinese fertility travellers rely on acquiring donor gametes once starting treatment abroad. Clinicians in Russia report three strategies amongst their Chinese patients: One group is using donor eggs of women of Asian appearance living in Russia or is hiring women of resembling appearance from third-party countries to donate their eggs in Russia to create resemblance in their offspring. Another group is buying white donor gametes to create Eurasian mixed children and thus ‘enhance’ their offspring. Providing novel empirical data, this article informs ethical deliberation and raises imminent questions for further research in this understudied geographic region and on cross-border reproductive treatment.

Is It Possible to Expand Oocyte Donors by Decreasing Number of Oocytes for Own Use? Insights From a Large Single-Center Study

BACKGROUND

Currently, in China, only women undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles can donate oocytes to others, but at least 15 oocytes must be kept for their own treatment. Thus, the aim of this study was to determine whether oocyte donation compromises the cumulative live birth rate (CLBR) of donors and whether it is possible to expand oocyte donors' crowd.

METHODS

This was a retrospective cohort study from August 2015 to July 2017 including a total of 2,144 patients, in which 830 IVF-embryo transfer (IVF-ET) patients were eligible for oocyte donation and 1,314 patients met all other oocyte donation criteria but had fewer oocytes retrieved (10-17 oocytes). All 830 patients were advised to donate approximately three to five oocytes to others and were eventually divided into two groups: the oocyte donation group (those who donated) and the control group (those who declined). The basic patient parameters and CLBR, as well as the number of supernumerary embryos after achieving live birth, were compared. These two factors were also compared in all patients (2,144) with oocyte ≥10.

RESULTS

In 830 IVF-ET patients who were eligible for oocyte donation, only the oocyte number was significantly different between two groups, and the donation group had more than the control group (25.49 ± 5.76 vs. 22.88 ± 5.11, respectively; p = 0.09). No significant differences were found between the two groups in other factors. The results indicate that the live birth rate in the donation group was higher than that in the control group (81.31% vs. 82.95%, p = 0.371), without significance. In addition, CLBR can still reach as high as 73% when the oocyte number for own use was 10. Supernumerary embryos also increased as the oocyte number increased in all patients (oocyte ≥10).

CONCLUSIONS

Currently, oocyte donation did not compromise CLBR, and oocyte donation can decrease the waste of embryos. In addition, in patients with 10 oocytes retrieved, the CLBR was still good (73%). Thus, it is possible to expand oocyte donors if the number of oocyte kept for own use was decreased from 15 to 10 after enough communication with patients.

What impact does oocyte vitrification have on epigenetics and gene expression?

Children conceived by assisted reproductive technologies (ART) have a moderate risk for a number of adverse events and conditions. The question whether this additional risk is associated with specific procedures used in ART or whether it is related to the intrinsic biological factors associated with infertility remains unresolved. One of the main hypotheses is that laboratory procedures could have an effect on the epigenome of gametes and embryos. This suspicion is linked to the fact that ART procedures occur precisely during the period when there are major changes in the organization of the epigenome. Oocyte freezing protocols are generally considered safe; however, some evidence suggests that vitrification may be associated with modifications of the epigenetic marks. In this manuscript, after describing the main changes that occur during epigenetic reprogramming, we will provide current information regarding the impact of oocyte vitrification on epigenetic regulation and the consequences on gene expression, both in animals and humans. Overall, the literature suggests that epigenetic and transcriptomic profiles are sensitive to the stress induced by oocyte vitrification, and it also underlines the need to improve our knowledge in this field.

Postponing Pregnancy Through Oocyte Cryopreservation for Social Reasons: Considerations Regarding Clinical Practice and the Socio-Psychological and Bioethical Issues Involved

Oocyte freezing for 'social reasons' refers to women of reproductive age who are aiming to prolong, protect and secure their fertility. The term emerged to describe application of the highly promising technique, namely vitrification on oocytes retrieved through controlled ovarian stimulation (COS) from women intending to preserve their fertility for social reasons. These women opt to cryopreserve their oocytes at a point in their life when they need to postpone childbearing on the grounds of so called 'social' reasons. These reasons may include a highly driven career, absence of an adequate partner, financial instability, or personal reasons that make them feel unprepared for motherhood. This is a sensitive and multifaceted issue that entails medical, bioethical and socio-psychological components. The latest trend and the apparent increase noted on oocyte freezing for 'social reasons' has prompted our team of fertility specialists, embryologists, obstetricians, gynecologists and psychologists to proceed with a thorough, critical and all-inclusive comprehensive analysis. The wide range of findings of this analysis involve concerns of embryology and epigenetics that shape decisions made in the IVF laboratory, issues regarding obstetric and perinatal concerns on the pregnancy concluding from these oocytes and the respective delivery management and neonatal data, to the social and bioethical impact of this trend's application. This literature review refers to matters rising from the moment the 'idea' of this option is 'birthed' in a woman's thoughts, to proceeding and executing it clinically, up until the point of the pediatric follow up of the children born. We aim to shed light to the controversial issue of oocyte freezing, while objectively exhibit all aspects regarding this complex matter, as well as to respectfully approach how could the prospect of our future expectations be shaped from the impact of its application.

Preimplantation genetic testing for complex chromosomal rearrangement carriers by next-generation sequencing

RESEARCH QUESTION

Can preimplantation genetic testing (PGT) with next-generation sequencing (NGS) increase the chance of achieving a balanced euploid pregnancy in complex chromosome rearrangement (CCR) carriers?

DESIGN

Six couples underwent PGT at the Clinical Centre of Reproductive Medicine, First Affiliated Hospital, Nanjing Medical University. The CCR carriers in the six couples were: Case A: 46,XY,t(1;4;11)(p31;p16;q22); Case B: 46,XY,t(3;13;5)(p14;q21;p14); Case C: 46,XX,t(6;11;21)(q21;q21;q13); Case D: 46,XX,inv(9)(p12; q13),t(13;15)(q14;q24); Case E: 46,XX,inv(9)(p12;q13),t(7;9)(q22;p22); and Case F: 46,XX,t(2;7)(q21;q36),t(2;4)(p10;q10),t(2;4)(q15;q10). After ovarian stimulation followed by oocyte retrieval and embryo culture, PGT was performed on day 5 or 6 blastocyst biopsies using NGS to identify normal/balanced euploid embryos. Vitrified-warmed single embryo transfers were performed using normal/balanced euploid embryos.

RESULTS

After seven cycles, 84 oocytes were retrieved. Whole genome sequencing by NGS was performed on 25 trophectoderm biosies. Six (24%) embryos were identified as normal/balanced euploid, four were transferred resulting in four live births. Case A, C, D and E each gave birth to a healthy baby after their first cycle. There was no transferable embryo after two cycles for Case B and one cycle for Case F. The implantation rate per transfer was 4/4 and the live birth rate was 4/4.

CONCLUSION

These results strongly support the use of NGS for CCR carriers.

Chapter 3 Current Challenges in Immature Oocyte Cryopreservation

Current freezing technology, especially the vitrification method, has markedly improved oocyte survival rate after warming, and the pregnancy rate is comparable to that achieved with fresh oocytes. However, most groups report using oocytes matured in vivo for vitrification. Although immature oocytes can be vitrified successfully, clinical outcomes do not reach that of vitrification of matured oocytes. The current literature suggests that oocytes should be vitrified at mature metaphase II (M-II) stage following IVM rather than at the immature germinal vesicle (GV) stage, because the potential for oocyte maturation is reduced when vitrification is performed on immature oocytes at the GV stage.

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.

The Experience of Chinese Couples Undergoing In Vitro Fertilization Treatment: Perception of the Treatment Process and Partner Support

Background

Couples undergoing In Vitro Fertilization (IVF) Treatment suffer as dyads from the stressful experience of the painful treatment and the fear that the IVF cycle will fail. They are likely to report that their marital relationship has become unstable due to the prolonged period of treatment.

Methods

This is a qualitative study that was conducted to explore the experiences that Chinese couples have had with IVF treatment, especially their perceptions of the process and the support between couples.

Results

The interviews revealed that couples suffered from the process, experiencing physical and emotional pain, struggling with the urgency and inflexibility of bearing a child, and experiencing disturbances in their daily routines and work. The participants described how they endured the hardships as a couple and how it affected their relationship. The couples felt that sharing feelings and supporting each other contribute to psychological well-being and improves the marital relationship. They also identified some unfavorable aspects in their partner relationship. They were ambivalent about receiving social support from friends and family members.

Conclusions

With the couples indicating that the support that they received from each other affected their experience during the treatment process, it is suggested that a supportive intervention that focuses on enhancing the partnership of the couples and dealing with their inflexibility on the issue of bearing a child might result in improvements in the psychological status and marital relationship of infertile couples undergoing IVF treatment.

Assessment of aneuploidy formation in human blastocysts resulting from cryopreserved donor eggs

Background

Increased embryo implantation rates were reported after transfer of euploid embryos selected by preimplantation genetic screening (PGS). Egg cryopreservation by vitrification has become one of the most important assisted human reproduction technologies. Although reports indicate that development and implantation of human embryos derived from frozen donor eggs are comparative to fresh eggs, it is still unknown whether egg vitrification increases chromosomal abnormalities in eggs, which in turn causes formation of embryonic aneuploidy. Therefore, in this study, we evaluated the aneuploidy formation in the blastocysts derived from frozen donor eggs and also evaluated the efficiency of egg vitrification as an advanced technology for egg cryopreservation.

Results

In this study, donated human eggs from young women were cryopreserved by vitrification and PGS was performed in the resulted blastocysts by DNA microarray. A total of 764 frozen eggs from 75 egg thawing cycles were warmed and 38 blastocysts were biopsied for PGS before embryo transfer. A 97.1% of egg survival rate was obtained and 59.1% of embryos developed to blastocyst stage. After biopsy and PGS, it was found that 84.2% of blastocysts were euploid and 15.8% were aneuploid. Aneuploidy rates varied among donors. Transfers of blastocysts without PGS resulted in higher clinical pregnancy and implantation rates as compared with transfer of blastocysts with PGS.

Conclusions

Although the overall aneuploidy rate was low in the blastocysts derived from frozen donor eggs, high aneuploidy rates were observed in the embryos resulting from some donated eggs. Clinical pregnancy rate was not improved by PGS of embryos resulting from donor eggs, indicating that PGS may not be necessary for embryos derived from donor eggs in most cases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-015-0117-8) contains supplementary material, which is available to authorized users.

Oocyte vitrification: advances, progress and future goals

BACKGROUND

Recent advances in vitrification technology have markedly improved the efficacy of oocyte cryopreservation in terms of oocyte survival and pregnancy, as well as live birth rates. However, there still remains room for improvement in terms of vitrification techniques.

OBJECTIVE

The remaining challenges include the development of a less cytotoxic vitrification solution and of a safe vitrification device in order to have vitrification techniques considered as a standard clinical laboratory procedure.

METHODS

A systematic electronic literature search strategy has been conducted using PubMed (Medline) databases with the use of the following key words: oocyte, vitrification, cryoprotectant, preservation, pregnancy, and live birth. A list of published papers focused on the improvement of vitrification techniques to have the vitrification protocol standardized have been evaluated in full text for this review. Only key references were cited.

CONCLUSIONS

Vitrification technology has made significant advancements and holds great promise, but many issues remains to be addressed before it becomes a standardized procedure in clinical laboratories such as the fact that oocyte vitrification may not require a high concentration of cryoprotectant in the vitrification solution when it has a suitable cooling and warming rate. There is also no consistent evidence that indicates the absence of risk to the vitrified oocytes when they are stored for a prolonged period of time in direct-contact with liquid nitrogen. The long-term development of infants born as a result of this technology equally remains to be evaluated.

The effect of minimal concentration of ethylene glycol (EG) combined with polyvinylpyrrolidone (PVP) on mouse oocyte survival and subsequent embryonic development following vitrification

PURPOSE

Vitrification techniques employ a relatively high concentration of cryoprotectant in vitrification solutions. Exposure of oocytes to high concentrations of cryoprotectant is known to damage the oocytes via both cytotoxic and osmotic effects. Therefore, the key to successful vitrification of oocytes is to strike a balance between the usage of minimal concentration of cryoprotectant without compromising their cryoprotective actions.

METHODS

The minimal concentration of ethylene glycol (EG) on mouse oocyte survival and subsequent embryonic development was evaluated following vitrification-warming and parthenogenetic activation. Polyvinylpyrrolidone (PVP) combined with EG on mouse oocyte survival and subsequent embryonic development as well as morphology of the spindle and chromosome alignment were also evaluated. Vitrification system was adapted with JY Straw and the cooling rate was approximately 442-500 °C/min. In contrast, the warming rate was approximately 2,210-2,652 °C/min.

RESULTS

Survival rate of oocytes increased significantly when 15 % EG was combined with 2 % PVP in vitrification solution (VS). The effect of combination of EG and PVP was not significant when the concentration of EG was 20 % and higher. Although there were no significant differences in embryonic development, the percentage of abnormal spindle and chromosome alignment was significantly higher in the oocytes without 2 % PVP in VS.

CONCLUSIONS

Our data provide a proof of principle for oocyte vitrification that may not require a high concentration of cryoprotectant. There are synergic effects of EG combined with PVP for oocyte vitrification, which may provide important information to the field in developing less cytotoxic VS.

The root of reduced fertility in aged women and possible therapentic options: current status and future perspects

It is well known that maternal ageing not only causes increased spontaneous abortion and reduced fertility, but it is also a high genetic disease risk. Although assisted reproductive technologies (ARTs) have been widely used to treat infertility, the overall success is still low. The main reasons for age-related changes include reduced follicle number, compromised oocyte quality especially aneuploidy, altered reproductive endocrinology, and increased reproductive tract defect. Various approaches for improving or treating infertility in aged women including controlled ovarian hyperstimulation with intrauterine insemination (IUI), IVF/ICSI-ET, ovarian reserve testing, preimplantation genetic diagnosis and screening (PGD/PGS), oocyte selection and donation, oocyte and ovary tissue cryopreservation before ageing, miscarriage prevention, and caloric restriction are summarized in this review. Future potential reproductive techniques for infertile older women including oocyte and zygote micromanipulations, derivation of oocytes from germ stem cells, ES cells, and iPS cells, as well as through bone marrow transplantation are discussed.

Optimized protocol for cryopreservation of human eggs improves developmental competence and implantation of resulting embryos

Background

Successful egg cryopreservation has many potential benefits to a variety of patients. However, a superior standard protocol describing all aspects of oocyte cryopreservation has not yet been identified. Oocyte cryopreservation is still a technical challenge for many infertility clinics. To maintain satisfactory clinical outcomes, there is a need to develop an easy to use, yet efficient laboratory protocol. The present study was designed to examine if human embryos resulting from eggs frozen with an optimized vitrification protocol have similar developmental competence as those from fresh eggs.

Methods

Twenty recipients received donated eggs vitrified with a protocol in which short exposure time to the vitrification solution was used and 23 recipients received donated eggs and 6 patients had their own eggs vitrified with a modified protocol in which long exposure time to the vitrification solution was used. After warming, egg survival, fertilization, cleavage, blastocyst formation, clinical pregnancy and implantation rates were compared. The developmental competence of eggs vitrified with the optimized protocol was further compared with fresh eggs donated from the same donors.

Results

There was no difference in the oocyte survival, fertilization, cleavage, clinical pregnancy or implantation rates between the short and long protocol groups. However, blastocyst formation rate was significantly (P < 0.001) higher in the long protocol group (50.8%) than that in short protocol group (26.5%), resulting in more blastocysts being transferred and frozen. When frozen eggs vitrified with long protocol and fresh eggs from the same donors (12) were compared in 39 recipients, no differences were observed in terms of fertilization (86.4 vs 80.1%), blastocyst formation (50.0 vs 59.2%), clinical pregnancy (63.2 vs 60.0%) and implantation (41.7 vs 44.7%) rates. Four out of 6 patients had ongoing pregnancy after transfer of embryos from their own frozen eggs with a 46.2% implantation rate.

Conclusions

These results indicate that blastocyst development is an appropriate measure for egg survival after cryopreservation and frozen eggs have similar developmental potential as fresh eggs if they are frozen with an optimized method.