Human oocyte cryopreservation with slow freezing versus vitrification. Results from the National Italian Registry data, 2007–2011

A comprehensive review and update on human fertility cryopreservation methods and tools

The broad conceptualization of fertility preservation and restoration has become already a major concern in the modern western world since a large number of individuals often face it in the everyday life. Driven by different health conditions and/or social reasons, a variety of patients currently rely on routinely and non-routinely applied assisted reproductive technologies, and mostly on the possibility to cryopreserve gametes and/or gonadal tissues for expanding their reproductive lifespan. This review embraces the data present in human-focused literature regarding the up-to-date methodologies and tools contemporarily applied in IVF laboratories' clinical setting of the oocyte, sperm, and embryo cryopreservation and explores the latest news and issues related to the optimization of methods used in ovarian and testicular tissue cryopreservation.

The effect of high-throughput vitrification of human ovarian cortex tissue on follicular viability: a promising alternative to conventional slow freezing?

BACKGROUND

The standard procedure most frequently used for ovarian tissue cryopreservation (OTC) is slow freezing, while vitrification has been proposed as promising alternative and has built an impressive catalog of success in fertility laboratories regarding cryopreservation of oocytes and embryos.

METHODS

We developed and evaluated a high-throughput protocol for vitrification of human ovarian tissue suitable for clinical processing. Follicular viability was assessed via calcein staining prior and after cryopreservation analyzing ovarian tissue of a cohort of 30 patients.

RESULTS

We found no significant differences regarding follicular viability between slow frozen and vitrified cortex tissue samples 24 h after thawing and rapid warming. Follicular viability of thawed and rapid warmed samples was not significantly different in comparison to fresh samples, indicating high proportions of follicular survival rates with both methods.

CONCLUSIONS

High-throughput vitrification is a promising option in a clinical setting. More research is required to determine the status of other tissue-specific quality indicators potentially influencing on autotransplantation.

Endometrial Cancer in Reproductive Age: Fertility-Sparing Approach and Reproductive Outcomes

Endometrial cancer is the most common gynecologic malignancy in developed countries and approximately 7% of the women with endometrial cancer are below the age of 45. Management of endometrial cancer in young women who desire to maintain fertility presents a unique set of challenges since the standard surgical treatment based on hysterectomy and salpingo-oophorectomy is often not compatible with the patient's goals. A fertility-preserving approach can be considered in selected patients with early stage and low-grade endometrial cancer. An increasing amount of data suggest that oncologic outcomes are not compromised if a conservative approach is utilized with close monitoring until childbearing is completed. If a fertility-preserving approach is not possible, assisted reproductive technologies can assist patients in achieving their fertility goals.

Antioxidant procyanidin B2 protects oocytes against cryoinjuries via mitochondria regulated cortical tension

BACKGROUND

Irreversible cryodamage caused by oocyte vitrification limited its wild application in female fertility preservation. Antioxidants were always used to antagonist the oxidative stress caused by vitrification. However, the comprehensive mechanism underlying the protective role of antioxidants has not been studied. Procyanidin B2 (PCB2) is a potent natural antioxidant and its functions in response to vitrification are still unknown. In this study, the effects of PCB2 on vitrified-thawed oocytes and subsequent embryo development were explored, and the mechanisms underlying the protective role of PCB2 were systematically elucidated.

RESULTS

Vitrification induced a marked decline in oocyte quality, while PCB2 could improve oocyte viability and further development after parthenogenetic activation. A subsequent study indicated that PCB2 effectively attenuated vitrification-induced oxidative stress, rescued mitochondrial dysfunction, and improved cell viability. Moreover, PCB2 also acts as a cortical tension regulator apart from strong antioxidant properties. Increased cortical tension caused by PCB2 would maintain normal spindle morphology and promote migration, ensure correct meiosis progression and finally reduce the aneuploidy rate in vitrified oocytes. Further study reveals that ATP biosynthesis plays a crucial role in cortical tension regulation, and PCB2 effectively increased the cortical tension through the electron transfer chain pathway. Additionally, PCB2 would elevate the cortical tension in embryo cells at morula and blastocyst stages and further improve blastocyst quality. What's more, targeted metabolomics shows that PCB2 has a beneficial effect on blastocyst formation by mediating saccharides and amino acids metabolism.

CONCLUSIONS

Antioxidant PCB2 exhibits multi-protective roles in response to vitrification stimuli through mitochondria-mediated cortical tension regulation.

Successful Pregnancies, Births, and Child Development Following Oocyte Cryostorage in Female Cancer Patients During 25 Years of Fertility Preservation

Simple Summary

The study goal is to demonstrate that oocyte cryopreservation is a feasible and efficient option for fertility preservation in cancer patients through the comparison of in vitro fertilization treatments in nononcological patients.

Abstract

The preservation of fertility in cancer patients is a crucial aspect of modern reproductive medicine. Amenorrhea and infertility often occur after cancer therapy, worsening the quality of life. Cryopreservation of oocytes in young cancer patients is a therapeutic option for preserving fertility. A prospective study was conducted on 508 cancer patients who underwent oocyte cryopreservation to preserve fertility between 1996 and 2021 including the COVID-19 pandemic period. Patients underwent ovarian stimulation, followed by egg retrieval, and oocytes were cryopreserved by slow freezing or vitrification. Sixty-four thawing/warming cycles were performed. Survival, fertilization, pregnancy, and birth rate over the thawing/warming cycles were obtained. The data were compared with those from a group of 1042 nononcological patients who cryopreserved supernumerary oocytes. An average of 8.8 ± 6.9 oocytes were retrieved per cycle, and 6.1 ± 4.2 oocytes were cryopreserved. With their own stored oocytes, 44 patients returned to attempt pregnancy. From a total of 194 thawed/warmed oocytes, 157 survived (80%). In total, 100 embryos were transferred in 57 transfer/cycles, and 18 pregnancies were achieved. The pregnancy rate per transfer and pregnancy rate per patient were 31% and 41%, respectively. No statistically significant differences were observed between oncological patients and nononcological patients. A total of 15 babies were born from oncological patients. Children born showed normal growth and development. One minor malformation was detected.

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.

A review of best practices of rapid-cooling vitrification for oocytes and embryos: a committee opinion

The focus of this paper is to review best practices for rapid-cooling cryopreservation of oocytes and embryos. The discussion of best practices includes the types of cryoprotectants and cryo devices typically used. Key performance indicators of rapid-cooling vitrification success are defined.

Glutathione Ethyl Ester Protects In Vitro-Maturing Bovine Oocytes against Oxidative Stress Induced by Subsequent Vitrification/Warming

This study aimed to examine whether the addition of glutathione ethyl ester (GSH-OEt) to the in vitro maturation (IVM) medium would improve the resilience of bovine oocytes to withstand vitrification. The effects of GSH-OEt on spindle morphology, levels of reactive oxygen species (ROS), mitochondrial activity and distribution, and embryo developmental potential were assessed together with the expression of genes with a role in apoptosis (BAX, BCL2), oxidative-stress pathways (GPX1, SOD1), water channels (AQP3), implantation (IFN-τ) and gap junctions (CX43) in oocytes and their derived blastocysts. Vitrification gave rise to abnormal spindle microtubule configurations and elevated ROS levels. Supplementation of IVM medium with GSH-OEt before vitrification preserved mitochondrial distribution pattern and diminished both cytoplasmic and mitochondrial ROS contents and percentages of embryos developing beyond the 8-cell stage were similar to those recorded in fresh non-vitrified oocytes. Although not significantly different from control vitrified oocytes, vitrified oocytes after GSH-OEt treatment gave rise to similar day 8-blastocyst and hatching rates to fresh non-vitrified oocytes. No effects of GSH-OEt supplementation were noted on the targeted gene expression of oocytes and derived blastocysts, with the exception of GPX1, AQP3 and CX43 in derived blastocysts. The addition of GSH-OEt to the IVM medium before vitrification may be beneficial for embryo development presumably as the consequence of additional anti-oxidant protection during IVM.

Germinal ovarian tumors in reproductive age women: Fertility-sparing and outcome

MOGCTs (malignant ovarian germ cell tumors) are rare tumors that mainly affect patients of reproductive age. The aim of this study was to evaluate the fertility and survival outcomes in young women with MOCGTs treated with fertility-sparing surgery (FSS).From 2000 to 2018, data from 28 patients of reproductive age with a diagnosis of MOGCT at the University of Bari were collected. Most received FSS, and in patients treated conservatively, the reproductive outcome and survival were investigated. Data of patient demographics, clinical presentation, oncology marker dosage, staging, type of surgery, histological examination, survival, and reproductive outcome were collected from hospital and office charts. All informed consent was obtained from all patients. The median age was 24 (range: 9-45 years). The majority of the patients had stage IIIC. Twenty-four woman received FSS consisting of unilateral ovariectomy and omentectomy, whereas only 4 women, based on their stage (IIIC), received a radical surgery (hysterectomy with bilateral adnexectomy, lymphadenectomy, and omentectomy). Our study shows that FSS in MOGCTs can produce good results both on reproductive outcomes and on survival. Indeed, in our group, there was only 1 case of exitus as result of recurrence. Furthermore, patients after FSS maintained normal ovarian function and 5 of 5 women who tried to get pregnant succeeded spontaneously. The median follow-up was 90 months (range 3-159).Conservative surgery for MOGCTs should be considered for women of reproductive age who wish to preserve fertility.

Effects of vitrification and cryostorage duration on single-cell RNA-Seq profiling of vitrified-thawed human metaphase II oocytes

Oocyte cryopreservation is widely used for clinical and social reasons. Previous studies have demonstrated that conventional slow-freezing cryopreservation procedures, but not storage time, can alter the gene expression profiles of frozen oocytes. Whether vitrification procedures and the related frozen storage durations have any effects on the transcriptomes of human metaphase II oocytes remain unknown. Four women (30-32 years old) who had undergone IVF treatment were recruited for this study. RNA-Seq profiles of 3 fresh oocytes and 13 surviving vitrified-thawed oocytes (3, 3, 4, and 3 oocytes were cryostored for 1,2, 3, and 12 months) were analyzed at a single-cell resolution. A total of 1987 genes were differentially expressed in the 13 vitrified-thawed oocytes. However, no differentially expressed genes were found between any two groups among the 1-, 2-, 3-, and 12-month storage groups. Further analysis revealed that the aberrant genes in the vitrified oocytes were closely related to oogenesis and development. Our findings indicated that the effects of vitrification on the transcriptomes of mature human oocytes are induced by the procedure itself, suggesting that long-term cryostorage of human oocytes is safe.

Effects of oocyte vitrification on the behaviors and physiological indexes of aged first filial generation mice

To evaluate the long-term effects of oocyte cryopreservation on the health of the first filial generation (F1), we used B6D2F1 mice for oocyte collection, in vitro fertilization, and breeding. The female F1 mice born from the offspring of fresh mature oocytes (control group) and from the offspring of vitrified oocytes with traditional vitrification medium (VM group) and new improved vitrification medium (2P10E7D group) were maintained until 14-15 months of age for behavioral tests and 16-17 months of age for physiological analyses. Behavioral indexes, including anxiety-like status, discrimination ability, learning and memory ability, were investigated. Physiological indexes including body weight, body fat, heart rate, blood pressure, and blood lipids were also analyzed. In our results, the behavioral indexes, body weight, body fat, heart rate, blood pressure, total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL) did not show significant differences among the three groups. However, the triglyceride (TG) level of the VM group was higher than that of the 2P10E7D group. Moreover, compared with the control group, both the VM group and the 2P10E7D group showed greatly increased diastolic blood pressure. This study is the first to report that oocyte vitrification might affect metabolic physiological indexes via transgenerational inheritance rather than behaviors related to anxiety-like status and cognitive ability. Furthermore, different vitrification media might have differential transgenerational effects.

Ovarian Diffuse Large B-cell Lymphoma Initially Suspected Dysgerminoma Managed by Laparoscopic Staging Surgery

Ovarian diffuse large B-cell lymphoma (DLBCL) is rare. DLBCL is a complex type of lymphoma. The ovarian DLBCL usually harbor a favorable prognosis. We report a case of ovarian DLBCL that presented as an ovarian mass with lower abdominal pain and was managed using laparoscopic staging surgery. A 29-year-old female (gravida 2, para 0, abortion 2) with a history of polycystic ovarian syndrome with irregular medication control visited our clinic due to lower abdominal pain. Transvaginal ultrasound revealed a heterogeneous, septated mass over the left adnexa with a diameter of approximately 6 cm × 8 cm. The tumor marker CA 19-9 was elevated (65.77 IU/mL); CA125 and carcinoembryonic antigen were not elevated. Laparoscopic surgery with left salpingo-oophorectomy was first performed. Frozen section indicated dysgerminoma. Then, we continued staging surgery through bilateral pelvic lymph node dissection, para-aortic lymph node dissection, omentectomy, right ovary and peritoneum biopsy, and washing cytology. Ovarian tumor and para-aortic lymph nodes were positive for lymphoma. The tumor cells were positive staining for CD20, CD5, ki67, BCL-6, and MUM-1, which was associated with DLBCL. The patient was then consulted for oocyte preservation and referred to hematology for further chemotherapy. In conclusion, an ovarian lymphoma is a rare event. The presence of an enlarged ovarian tumor should raise the suspicion of ovarian lymphoma. To differentiate ovarian lymphoma from dysgerminoma, immunohistochemistry is useful. Fertility preservation should be considered before chemotherapy. Ovarian tissue or oocyte preservation or gonadotropin-releasing hormone agonist injection before chemotherapy can be performed for fertility preservation.

Contribution of cryopreservation to the cumulative live birth rate: a large multicentric cycle-based data analysis from the Italian National Registry

PURPOSE

To estimate the contribution of cryopreservation to the cumulative live birth rate (CLBR) after law modification in Italy in the era of vitrification and freeze-all.

METHODS

The Italian National Registry performed a cycle-based data collection. Nine Italian IVF clinics were involved incorporating a total of 10,260 fresh cycles performed between January 2015 and April 2016 resulting in 9273 oocyte retrievals and 3266 subsequent warming cycles from the same oocyte retrievals performed up to December 2016. Mean female age was 37 ± 4.3 years. Primary outcome measure was CLBR per oocyte retrieval. Confounding factors were tested in multivariate regression analysis, and the relative impact of cryopreservation to the CLBR in different patient categories was calculated.

RESULTS

CLBR per oocyte retrieval was 32.6%, 26.5%, 18.7%, 13.0%, and 5.5% for women younger than 36, aged 36-39, 40-41, and older than 41 years, respectively. The total relative contribution of oocyte/embryo cryopreservation was 40.6% (95% CI 38.41-42.75). An association between maternal age, number of oocytes retrieved, fertilization rate, cryopreservation, and cumulative live birth was shown. When adjusted for confounders, a 2.3-fold increase was observed in the chance of live birth when cryopreservation was performed (OR 2.3; 95% CI 1.99-2.56). In high responder patients (> 15 oocytes retrieved) where freeze-all was applied in 67.6% of cycles to avoid the risk of hyper stimulation syndrome, the relative contribution of vitrification to the CLBR was 80.6%.

CONCLUSIONS

Cryopreservation is essential in IVF and should always be available to patients to optimize success rates. Multicentric, cycle-based data analyses are crucial to provide infertile couples, clinicians, and regulatory bodies with accurate information on IVF effectiveness including fresh and cryopreserved cycles.

Abandoned frozen embryos in Argentina: a committee opinion

Argentina, like many other countries in the region, faces the dilemma of what to do with the increasing accumulation of frozen embryos, which are often abandoned. This report aims to address the issue of abandoned frozen embryos, following the main concerns: 1) when is an embryo considered abandoned, according to regulatory documents; 2) how can the number of cryopreserved abandoned embryos be decreased; and 3) what are the current available options for discarding these abandoned embryos. Issues concerning the fate of abandoned embryos call for a revision of the technical aspects, as well as the symbolic aspects associated with the embryos and their options for discarding. Embryo disposal is a complex and intimate decision, which depends not only, on the quality of the cryopreserved embryo, but also on the social, cultural, economic, labor and health insurance aspects. In the absence of a formal regulatory framework for such decisions in Argentina, current practices and standard procedures face significant developmental hurdles. Among future actions to be developed in the short, medium and long term by this committee are building interdisciplinary teams, fostering patient-awareness, devising guidelines, and enforcing policies regarding embryo abandonment.

Tolerance of lamb and mouse oocytes to cryoprotectants during vitrification

SummaryMouse and lamb oocytes were vitrified with, or exposed to, different cryoprotectants and evaluated for their effects on their survival and developmental competence after in vitro fertilization (IVF) and activation treatments. Control oocytes remained untreated, whilst the remainder were exposed to three different combinations of vitrification solutions [dimethyl sulfoxide (DMSO) + ethylene glycol (EG), EG only, or propanediol (PROH) + EG] and either vitrified or left unfrozen (exposed groups). Oocytes in the control and vitrified groups underwent IVF and developmental competence was assessed to the blastocyst stage. In lambs, survival rate in vitrified oocytes was significantly lower than for oocytes in the exposed groups (P <0.05). Blastocyst development was low in vitrified oocytes compared with controls (<6% vs 38.9%, P <0.01). Parthenogenetic activation was more prevalent in vitrified lamb oocytes compared with controls (P <0.05). No evidence of zona pellucida hardening or cortical granule exocytosis could account for reduced fertilization rates in vitrified lamb oocytes. Mouse oocytes demonstrated a completely different response to lamb oocytes, with survival and parthenogenetic activation rates unaffected by the vitrification process. Treatment of mouse oocytes with DMSO + EG yielded significantly higher survival and cleavage rates than treatment with PROH + EG (87.8% and 51.7% vs 32.7% and 16.7% respectively, P <0.01), however cleavage rate for vitrified oocytes remained lower than for the controls (51.7% vs 91.7%, P <0.01) as did mean blastocyst cell number (33 ± 3.1 vs 42 ± 1.5, P <0.05). From this study, it is clear that lamb and mouse show different tolerances to cryoprotectants commonly used in vitrification procedures, and careful selection and testing of species-compatible cryoprotectants is required when vitrifying oocytes to optimize survival and embryo development.

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.

Fertility Preservation for Patients with Malignant Disease. Guideline of the DGGG, DGU and DGRM (S2k-Level, AWMF Registry No. 015/082, November 2017) - Recommendations and Statements for Girls and Women

Aim

The aim of this official guideline published by the German Society of Gynecology and Obstetrics (DGGG) and coordinated with the German Society of Urology (DGU) and the German Society of Reproductive Medicine (DGRM) is to provide consensus-based recommendations, obtained by evaluating the relevant literature, on counseling and fertility preservation for prepubertal girls and boys as well as patients of reproductive age. Statements and recommendations for girls and women are presented below. Statements or recommendations for boys and men are not the focus of this guideline.

Methods

This S2k guideline was developed at the suggestion of the guideline commission of the DGGG, DGU and DGRM and represents the structured consensus of representative members from various professional associations (n = 40).

Recommendations

The guideline provides recommendations on counseling and fertility preservation for women and girls which take account of the patientʼs personal circumstances, the planned oncologic therapy and the individual risk profile as well as the preferred approach for selected tumor entities.

New national outcome data on fresh versus cryopreserved donor oocytes

BACKGROUND

Improvements in oocyte cryopreservation techniques and establishment of cryopreserved donor oocyte banks have led to improved access to and lower cost of donor oocytes, upending the traditional practice of fresh oocyte donation. The objective of this study was to examine national trends in utilization and live birth rates with fresh versus cryopreserved donor oocytes.

METHODS

A retrospective analysis of 2013 through 2015 aggregate U.S. national data reported by the Society for Assisted Reproductive Technology which included 30,160 IVF cycles with either fresh or cryopreserved donor oocytes was performed.

RESULTS

During the study period utilization of fresh oocyte donations rapidly declined by 32.9%, while cryopreserved oocyte donation increased by 44.4%. Fresh donor oocytes produced significantly higher live birth rates per recipient cycle start than cryopreserved donor oocytes (51.1% vs. 39.7%). Over the three-year study period fresh donor oocytes produced stable live birth rates per recipient cycle start while those with cryopreserved oocytes significantly declined year-by-year.

CONCLUSION

Despite rising popularity of cryopreserved donor oocytes, prospective patients should be counselled that fresh donor oocytes still represent standard of care due to higher live birth rates.

Recent advances in fertility preservation and counseling for female cancer patients

INTRODUCTION

Ensuring quality of life for increasing numbers of women surviving cancer has become a key challenge. Patients need to be counseled on potential fertility loss resulting from gonadotoxic treatments, and referred to fertility specialists to discuss existing options and available results. Areas covered: Fertility preservation options have existed for over twenty years. The proposed fertility preservation approach depends on patient age, the urgency of required chemotherapy, and psychosocial factors such as financial concerns, especially in countries where techniques are not covered by social security. Efficacy in terms of pregnancy rates has been demonstrated with frozen-thawed embryos, oocytes and re-implanted ovarian tissue. Appropriate counseling by oncologists is on the increase, despite persistently low rates of referral to fertility specialists. Expert commentary: Access to oncofertility services is steadily improving, facilitated by the growing involvement of public healthcare systems and sustained efforts all over the world to establish specific oncofertility programs. Early referral to reproductive specialists before initiation of chemo/radiotherapy is crucial to success in the field of female fertility preservation. In the near future, efforts should focus on increasing patient referrals and establishing international registries on short- and long-term outcomes of fertility preservation strategies.

Calcium ion regulation by BAPTA-AM and ruthenium red improved the fertilisation capacity and developmental ability of vitrified bovine oocytes

Vitrification reduces the fertilisation capacity and developmental ability of mammalian oocytes; this effect is closely associated with an abnormal increase of cytoplasmic free calcium ions ([Ca²⁺]i). However, little information about the mechanism by which vitrification increases [Ca²⁺]i levels or a procedure to regulate [Ca²⁺]i levels in these oocytes is available. Vitrified bovine oocytes were used to analyse the effect of vitrification on [Ca²⁺]i, endoplasmic reticulum Ca²⁺ (ER Ca²⁺), and mitochondrial Ca²⁺ (mCa²⁺) levels. Our results showed that vitrification, especially with dimethyl sulfoxide (DMSO), can induce ER Ca²⁺ release into the cytoplasm, consequently increasing the [Ca²⁺]i and mCa²⁺ levels. Supplementing the cells with 10 μM 1,2-bis (o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA-AM or BAPTA) significantly decreased the [Ca²⁺]i level and maintained the normal distribution of cortical granules in the vitrified bovine oocytes, increasing their fertilisation ability and cleavage rate after in vitro fertilisation (IVF). Treating vitrified bovine oocytes with 1 μM ruthenium red (RR) significantly inhibited the Ca²⁺ flux from the cytoplasm into mitochondria; maintained normal mCa²⁺ levels, mitochondrial membrane potential, and ATP content; and inhibited apoptosis. Treating vitrified oocytes with a combination of BAPTA and RR significantly improved embryo development and quality after IVF.

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.

A comparison of live birth rates and perinatal outcomes between cryopreserved oocytes and cryopreserved embryos

PURPOSE

Prior studies suggest that pregnancy outcomes after autologous oocyte cryopreservation are similar to fresh in vitro fertilization (IVF) cycles. It is unknown whether there are differences in pregnancy and perinatal outcomes between cryopreserved oocytes and cryopreserved embryos.

METHODS

This is a retrospective cohort study comparing pregnancy and perinatal outcomes between oocyte and embryo cryopreservation at a university-based fertility center. We included 42 patients and 68 embryo transfers in patients who underwent embryo transfer after elective oocyte preservation (frozen oocyte-derived embryo transfer (FOET)) from 2005 to 2015. We compared this group to 286 patients and 446 cycles in women undergoing cryopreserved embryo transfer (frozen embryo transfer (FET)) from 2012 to 2015.

RESULTS

Five hundred fourteen transfer cycles were included in our analysis. The mean age was lower in the FOET vs FET group (34.3 vs 36.0 years), but there were no differences in ovarian reserve markers. Thawed oocytes had lower survival than embryos (79.1 vs 90.1%); however, fertilization rates were similar (76.2 vs 72.8%). In the FOET vs FET groups, clinical pregnancies were 26.5 and 30%, and live birth rates were 25 and 25.1%. Miscarriages were higher in the FET group, 8.1 vs 1.5%. There were no differences in perinatal outcomes between the two groups. The mean gestational age at delivery was 39.1 vs 38.6 weeks, mean birth weight 3284.2 vs 3161.1 gms, preterm gestation rate 5.9 vs 13.4%, and multiple gestation rate 5.9 vs 11.6%.

CONCLUSIONS

In our study, live birth rates and perinatal outcomes were not significantly different in patients after oocyte and embryo cryopreservation.

State of the art on oocyte cryopreservation in female cancer patients: A critical review of the literature

During the last decades, important advances in therapeutic options have led to increased survival rates in cancer patients; however, cancer treatments are associated with several potential adverse effects including infertility in those diagnosed during their reproductive years. A proper discussion about fertility preservation options before the use of therapies with potential gonadotoxicity (i.e. oncofertility counseling) is standard of care and should be offered to all patients of childbearing age. Temporary ovarian suppression with LH-RH analogs, oocyte and embryo cryopreservation are standard strategies for fertility preservation in female cancer patients. Oocyte cryopreservation should be preferred to embryo cryopreservation when this latter is prohibited by law, avoided for ethical or religious issues and in single women refusing sperm donation. Despite the increasing use of this strategy, data are still lacking about the efficacy and safety of the procedure in female cancer patients, with most of the evidence on this regard deriving from infertile non-oncologic women. This article aims at critically review the available evidence about the success of oocyte cryopreservation in female cancer patients with the final goal to further improve the oncofertility counseling of these women.

Effect of vitrification on the mRNA transcriptome of bovine oocytes

Vitrification has been shown to decrease the developmental capacity of mammalian oocytes, and this is closely associated with the abnormal mRNA expressions of vitrified oocytes. However, the effect of vitrification on transcriptional machinery of oocytes examined by RNA sequencing (RNA-seq) has yet to be defined. In the present study, the mRNA transcriptomes of fresh and vitrified bovine oocytes were analysed by Smart-seq2 with the differently expressed genes determined by DEseq2 (an adjusted p-value of .05 and a minimum fold change of 2). The differentially expressed mRNAs were then searched against the Gene Ontology (GO) and Genomes (KEGG) database. Finally, the mRNA expressions of 10 candidate genes were validated using quantitative real-time PCR (qRT-PCR). Approximately 12,000 genes were detected in each sample of fresh or vitrified oocytes. Of these, the expression levels of 102 genes differed significantly in vitrified groups: 12 genes mainly involved in cell cycle, fertilization and glucose metabolism were upregulated, and 90 genes mainly involved in mitochondria, ribosomal protein, cytoskeleton, transmembrane protein, cell cycle and calcium ions were downregulated. GO analysis showed that these genes were mainly enriched in terms of membrane-bounded organelles, macromolecular complex, and intracellular part. The mRNA expression levels of 10 candidate genes selected randomly were in agreement with the results of the RNA-seq. In conclusion, our results showed that vitrification affected the mRNA transcriptome of bovine oocytes by downregulating genes, which contributed to the decreased developmental capacity of vitrified oocytes. Our findings will be useful in determining approaches to improve the efficiency of vitrified oocytes.

A modified vitrification method reduces spindle and chromosome abnormalities

Development of an effective system for oocyte-cryopreservation is of clinical relevance in reproductive medicine. However, oocyte-preservation is not as effective as embryo preservation. In this study, we used a 37°C pre-equilibrium temperature as part of a modified vitrification method for human oocyte cryopreservation. The effect of the new method on spindle configuration, chromosomal arrangement, and mitochondrial distribution was investigated in in vitro-matured human oocytes. A total of 101 in vitro-matured oocytes were randomly assigned for vitrification at pre-equilibrium temperature of 37°C (37°C Group, n=50) or at room temperature (RT Group, 22-24°C, n=51). The time needed for vitrification in the 37°C group was significantly shorter than that in the RT group. Defective spindles were found in 45.5% and 69.0% oocytes in the 37°C group and RT group, respectively (p < 0.05). Abnormal chromosomes were found in 47.7% and 71.4% oocytes, respectively (p < 0.05). There were no significant differences with respect to oocyte survival rate and mitochondrial distribution pattern between the two groups. These results indicate that vitrification at a pre-equilibrium temperature of 37°C may reduce the incidence of defective spindle configuration and chromosomal abnormalities in in-vitro-matured human oocytes.

ABBREVIATIONS

ICSI: intracytoplasmic sperm injection; FSH: follicle-stimulating hormone; MII: metaphase II; EG: ethylene glycol; PROH: 1,2-propanediol.

Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance

BACKGROUND

Successful cryopreservation of oocytes and embryos is essential not only to maximize the safety and efficacy of ovarian stimulation cycles in an IVF treatment, but also to enable fertility preservation. Two cryopreservation methods are routinely used: slow-freezing or vitrification. Slow-freezing allows for freezing to occur at a sufficiently slow rate to permit adequate cellular dehydration while minimizing intracellular ice formation. Vitrification allows the solidification of the cell(s) and of the extracellular milieu into a glass-like state without the formation of ice.

OBJECTIVE AND RATIONALE

The objective of our study was to provide a systematic review and meta-analysis of clinical outcomes following slow-freezing/thawing versus vitrification/warming of oocytes and embryos and to inform the development of World Health Organization guidance on the most effective cryopreservation method.

SEARCH METHODS

A Medline search was performed from 1966 to 1 August 2016 using the following search terms: (Oocyte(s) [tiab] OR (Pronuclear[tiab] OR Embryo[tiab] OR Blastocyst[tiab]) AND (vitrification[tiab] OR freezing[tiab] OR freeze[tiab]) AND (pregnancy[tiab] OR birth[tiab] OR clinical[tiab]). Queries were limited to those involving humans. RCTs and cohort studies that were published in full-length were considered eligible. Each reference was reviewed for relevance and only primary evidence and relevant articles from the bibliographies of included articles were considered. References were included if they reported cryosurvival rate, clinical pregnancy rate (CPR), live-birth rate (LBR) or delivery rate for slow-frozen or vitrified human oocytes or embryos. A meta-analysis was performed using a random effects model to calculate relative risk ratios (RR) and 95% CI.

OUTCOMES

One RCT study comparing slow-freezing versus vitrification of oocytes was included. Vitrification was associated with increased ongoing CPR per cycle (RR = 2.81, 95% CI: 1.05-7.51; P = 0.039; 48 and 30 cycles, respectively, per transfer (RR = 1.81, 95% CI 0.71-4.67; P = 0.214; 47 and 19 transfers) and per warmed/thawed oocyte (RR = 1.14, 95% CI: 1.02-1.28; P = 0.018; 260 and 238 oocytes). One RCT comparing vitrification versus fresh oocytes was analysed. In vitrification and fresh cycles, respectively, no evidence for a difference in ongoing CPR per randomized woman (RR = 1.03, 95% CI: 0.87-1.21; P = 0.744, 300 women in each group), per cycle (RR = 1.01, 95% CI: 0.86-1.18; P = 0.934; 267 versus 259 cycles) and per oocyte utilized (RR = 1.02, 95% CI: 0.82-1.26; P = 0.873; 3286 versus 3185 oocytes) was reported. Findings were consistent with relevant cohort studies. Of the seven RCTs on embryo cryopreservation identified, three met the inclusion criteria (638 warming/thawing cycles at cleavage and blastocyst stage), none of which involved pronuclear-stage embryos. A higher CPR per cycle was noted with embryo vitrification compared with slow-freezing, though this was of borderline statistical significance (RR = 1.89, 95% CI: 1.00-3.59; P = 0.051; three RCTs; I2 = 71.9%). LBR per cycle was reported by one RCT performed with cleavage-stage embryos and was higher for vitrification (RR = 2.28; 95% CI: 1.17-4.44; P =  0.016; 216 cycles; one RCT). A secondary analysis was performed focusing on embryo cryosurvival rate. Pooled data from seven RCTs (3615 embryos) revealed a significant improvement in embryo cryosurvival following vitrification as compared with slow-freezing (RR = 1.59, 95% CI: 1.30-1.93; P < 0.001; I2 = 93%).

WIDER IMPLICATIONS

Data from available RCTs suggest that vitrification/warming is superior to slow-freezing/thawing with regard to clinical outcomes (low quality of the evidence) and cryosurvival rates (moderate quality of the evidence) for oocytes, cleavage-stage embryos and blastocysts. The results were confirmed by cohort studies. The improvements obtained with the introduction of vitrification have several important clinical implications in ART. Based on this evidence, in particular regarding cryosurvival rates, laboratories that continue to use slow-freezing should consider transitioning to the use of vitrification for cryopreservation.

The Human Oocyte Preservation Experience (HOPE) Registry: evaluation of cryopreservation techniques and oocyte source on outcomes

BACKGROUND

This prospective, Phase IV, multicenter, observational registry of assisted reproductive technology clinics in the USA studied outcomes of first cycles using thawed/warmed cryopreserved (by slow-freezing/vitrification) oocytes (autologous or donor).

METHODS

Patients were followed up through implantation, clinical pregnancy, and birth outcomes. The main outcome measure was live birth rate (LBR), defined as the ratio of live births to oocytes thawed/warmed minus the number of embryos cryopreserved for each cycle, averaged over all thawing cycles. Clinical pregnancy rate (CPR) was also evaluated, and was defined as the presence of a fetal sac with heart activity, as detected by ultrasound scan performed on Day 35-42 after embryo transfer.

RESULTS

A total of 16 centers enrolled 204 patients; data from 193 patients were available for analyses. For donor oocytes, in the slow-freezing (n = 40) versus vitrification (n = 94) groups, respectively, CPR and LBR were significantly different: 32.4% versus 62.6%, and 25.0% versus 52.1%; outcomes from Day 3 transfers did not differ significantly. For vitrified oocytes, in the autologous (n = 46) versus donor (n = 94) group, respectively, CPR and LBR were significantly different: 30.0% versus 62.6% and 17.4% versus 52.1%. This was largely due to a significant difference in CPR with Day 5/6 transfers.

CONCLUSIONS

In two subgroup data analyses, in women who received cryopreserved oocytes from donors, CPR and LBR were significantly higher in cycles using oocytes cryopreserved via vitrification versus slow-freezing, reflecting differences in methodologies and more Day 5/6 transfers; in women who received vitrified oocytes, CPR and LBR were significantly higher in cycles using donor versus autologous oocytes with Day 5/6 transfers.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00699400 . Registered June 13, 2008.

Chapter 1 Historical Background on Gamete and Embryo Cryopreservation

This chapter describes the development of the science of cryopreservation of gametes and embryos of various species including human. It attempts to record in brief the main contributions of workers in their attempts to cryopreserve gametes and embryos. The initial difficulties faced and subsequent developments and triumphs leading to present-day state of the art are given in a concise manner. The main players and their contributions are mentioned and the authors' aim is to do justice to them. This work also attempts to ensure that credit is correctly attributed for significant advances in gamete and embryo cryopreservation. In general this chapter has tried to describe the historical development of the science of cryopreservation of gametes and embryos as accurately as possible without bias or partiality.

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.

Evolution of human oocyte cryopreservation: slow freezing versus vitrification

PURPOSE OF REVIEW

The purpose is to determine the efficiency and efficacy of oocyte cryopreservation by slow freezing versus vitrification, recent data collected from the Italian National Assisted Reproductive Technology Register during the period 2009-2014 will be presented and reviewed. The data on oocyte cryopreservation were also compared with the results obtained with embryo cryopreservation and relative IVF with fresh oocytes.

RECENT FINDINGS

During the period 2009-2014 preservation of oocytes by vitrification had a significantly higher survival rate, implantation, and pregnancy rate than slow freezing; however, there are still large variations in success rates among centers in relation to the number of procedures performed.

SUMMARY

Vitrification has now become the method of choice for oocyte cryopreservation because of better results than slow freezing, but still requires a more standardized utilization. The transfer of fresh or cryopreserved embryo still shows a statistically significant better performance than transfers with embryos obtained with cryopreserved oocytes. Only in a few centers with much experience in cryopreservation are the results between transfers of frozen embryos or embryos obtained from oocyte cryopreservation comparable.

Freeze/thaw stress induces organelle remodeling and membrane recycling in cryopreserved human mature oocytes

PURPOSE

Our aim was to evaluate the ultrastructure of human metaphase II oocytes subjected to slow freezing and fixed after thawing at different intervals during post-thaw rehydration.

METHODS

Samples were studied by light and transmission electron microscopy.

RESULTS

We found that vacuolization was present in all cryopreserved oocytes, reaching a maximum in the intermediate stage of rehydration. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates decreased following thawing, particularly in the first and intermediate stages of rehydration, whereas mitochondria-vesicle (MV) complexes augmented in the same stages. At the end of rehydration, vacuoles and MV complexes both diminished and M-SER aggregates increased again. Cortical granules (CGs) were scarce in all cryopreserved oocytes, gradually diminishing as rehydration progressed.

CONCLUSIONS

This study also shows that such a membrane remodeling is mainly represented by a dynamic process of transition between M-SER aggregates and MV complexes, both able of transforming into each other. Vacuoles and CG membranes may take part in the membrane recycling mechanism.

[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.

Melatonin inhibits apoptosis and improves the developmental potential of vitrified bovine oocytes

Vitrification of oocytes has been shown to be closely associated with increased levels of reactive oxygen species (ROS) and apoptotic events. However, little information is available the effect of melatonin on the ROS levels and apoptotic events in vitrified oocytes. Therefore, we studied the effect of melatonin on ROS and apoptotic events in vitrified bovine oocytes by supplementing vitrification solution or in vitro maturation (IVM) and vitrification solution with 10(-9) m melatonin. We analyzed the ROS, mitochondrial Ca(2+) (mCa(2+) ) and membrane potential (ΔΨm), externalization of phosphatidylserine (PS), caspase-3 activation, DNA fragmentation, mRNA expression levels of Bax and Bcl2 l1, and developmental potential of vitrified bovine oocytes. Vitrified bovine oocytes exhibited increased levels of ROS, mCa(2+) , Bax mRNA, and caspase-3 protein and higher rates of PS externalization and DNA fragmentation, and decreased ΔΨm and Bcl2 l1 mRNA expression level. However, melatonin supplementation in vitrification solution or IVM and vitrification solution significantly decreased the levels of ROS, mCa(2+) , Bax mRNA expression, and caspase-3 protein, and PS externalization and DNA fragmentation rates, and increased the ΔΨm and Bcl2 l1 mRNA expression level in vitrified oocytes, resulting in an increased developmental ability of vitrified bovine oocytes after parthenogenetic activation. The developmental ability of vitrified oocytes with melatonin supplementation in IVM and vitrification solution was similar to that of fresh ones. This study showed that supplementing the IVM and vitrification medium or vitrification medium with 10(-9) m melatonin significantly decreased the ROS level and inhibited apoptotic events of vitrified bovine oocytes, consequently increasing their developmental potential.

Cancer and fertility preservation: international recommendations from an expert meeting

In the last years, thanks to the improvement in the prognosis of cancer patients, a growing attention has been given to the fertility issues. International guidelines on fertility preservation in cancer patients recommend that physicians discuss, as early as possible, with all patients of reproductive age their risk of infertility from the disease and/or treatment and their interest in having children after cancer, and help with informed fertility preservation decisions. As recommended by the American Society of Clinical Oncology and the European Society for Medical Oncology, sperm cryopreservation and embryo/oocyte cryopreservation are standard strategies for fertility preservations in male and female patients, respectively; other strategies (e.g. pharmacological protection of the gonads and gonadal tissue cryopreservation) are considered experimental techniques. However, since then, new data have become available, and several issues in this field are still controversial and should be addressed by both patients and their treating physicians.In April 2015, physicians with expertise in the field of fertility preservation in cancer patients from several European countries were invited in Genova (Italy) to participate in a workshop on the topic of "cancer and fertility preservation". A total of ten controversial issues were discussed at the conference. Experts were asked to present an up-to-date review of the literature published on these topics and the presentation of own unpublished data was encouraged. On the basis of the data presented, as well as the expertise of the invited speakers, a total of ten recommendations were discussed and prepared with the aim to help physicians in counseling their young patients interested in fertility preservation.Although there is a great interest in this field, due to the lack of large prospective cohort studies and randomized trials on these topics, the level of evidence is not higher than 3 for most of the recommendations highlighting the need of further research efforts in many areas of this field. The participation to the ongoing registries and prospective studies is crucial to acquire more robust information in order to provide evidence-based recommendations.

ART results with frozen oocytes: data from the Italian ART registry (2005-2013)

PURPOSE

This study is a retrospective collection of aggregated data from all the Italian ART centers reporting to the Italian National Register from cycles started between January 2005 and December 2013.

METHODS

Data from both slow freezing (SF) and vitrification (V) were assessed for the period 2007-2013, while during the years 2005-2006 cryopreservation was exclusively performed by SF.

RESULTS

In the study period, a total of 2,526,024 oocytes were retrieved (from 378,543 retrievals), of which 1,346,061 (53.3 %) were inseminated in fresh cycles and 214,481 (8.5 %) were cryopreserved. Cryopreserved oocytes were used in 24,173 cycles yielding 19,453 transfer cycles (80.5 % of the thawing/warming cycles) and 3043 clinical pregnancies (15.6 % per transfer). A significant difference in implantation (8.7 vs 12.9 % OR 1.30 CI 1.20-1.40) and pregnancy rates per transfer (12.2 vs 14.9 % OR 1.34 CI 1.23-1.46) was found between SF and V. Complete outcome data was available for 2708 pregnancies (89.8 %), leading to 1882 deliveries and 2152 live births. Neonatal major congenital anomalies were 0.9 % (20/2152).

CONCLUSIONS

A wide variation in pregnancy rates were found among different centers and lower rates were reported in donor cycles and in centers with more experience.

Storage time does not modify the gene expression profile of cryopreserved human metaphase II oocytes

STUDY QUESTION

Does storage time have any impact on the transcriptome of slowly frozen cryopreserved human metaphase II (MII) oocytes?

SUMMARY ANSWER

The length of cryostorage has no effect on the gene expression profile of human MII oocytes.

WHAT IS KNOWN ALREADY

Oocyte cryopreservation is a widely used technique in IVF for storage of surplus oocytes, as well as for fertility preservation (i.e. women undergoing gonadotoxic therapies) and oocyte donation programs. Although cryopreservation has negative impacts on oocyte physiology and it is associated with decrease of transcripts, no experimental data about the effect of storage time on the oocyte molecular profile are available to date.

STUDY DESIGN, SIZE, DURATION

This study included 27 women, ≤38 years aged, without any ovarian pathology, undergoing IVF treatment. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pools of ≈10 oocytes for each group were prepared. Total RNA was extracted from each pool, amplified, labeled and hybridized on oligonucleotide microarrays. Analyses were performed by R software using the limma package.

MAIN RESULTS AND THE ROLE OF CHANCE

Comparison of gene expression profiles between surviving thawed oocytes after 3 and 6 years of storage in liquid nitrogen found no differently expressed genes. The expression profiles of cryopreserved MII oocytes significantly differed from those of non-cryopreserved oocytes in 107 probe sets corresponding to 73 down-regulated and 29 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics resource disclosed that cryopreservation deregulates genes involved in oocyte function and early embryo development, such as chromosome organization, RNA splicing and processing, cell cycle, cellular response to DNA damage and to stress, DNA repair, calcium ion binding, malate dehydrogenase activity and mitochondrial activity. Among the probes significantly up-regulated in cryopreserved oocytes, two corresponded to ovary-specific expressed large intergenic noncoding (linc)RNAs.

LIMITATIONS, REASONS FOR CAUTION

Data validation in a larger cohort of samples would be beneficial, although we applied stringent criteria for gene selection (fold-change >3 or <1/3 and FDR < 0.1). Further research should be undertaken to verify experimentally that the length of cryostorage has no effect on gene expression profile of vitrified/warmed MII oocytes, as well as to include in analyses 'older' frozen oocytes.

WIDER IMPLICATIONS OF THE FINDINGS

Confirmation that the length of storage does not alter the gene expression profile of frozen oocytes is noteworthy for the safety issue of long-term oocyte banking, i.e. fertility preservation, gamete donation.

STUDY FUNDING/COMPETING INTEREST

This study was supported by a grant of the Italian Ministry of Health (CCM 2012) and by Ferring Pharmaceutical company. The authors have no conflicts of interest to declare.

Fertility preservation for non-medical reasons: controversial, but increasingly common

BACKGROUND

Fertility-preserving measures for women are increasingly being performed for non-medical reasons in Germany. This is now a controversial matter.

METHODS

The authors searched the PubMed database for pertinent publications on the basis of their clinical and scientific experience and evaluated relevant data from the registry of the German FertiPROTEKT network (www.fertiprotekt. com). The various fertility-preserving measures that are available are described and critically discussed.

RESULTS

In most cases, the creation of a fertility reserve currently involves the cryopreservation of unfertilized oocytes, rather than of ovarian tissue. Most of the women who decide to undergo this procedure are over 35 years old. According to data from the FertiPROTEKT registry, most such procedures carried out in the years 2012 and 2013 involved a single stimulation cycle. The theoretical probability of childbirth per stimulation is 40% in women under age 35 and 30% in women aged 35 to 39. If the oocytes are kept for use at a later date, rather than at once, the maternal risk is higher, because the mother is older during pregnancy. The risk to the child may be higher as well because of the need for in vitro fertilization (IVF). Pregnancy over age 40 often leads to complications such as gestational diabetes and pre-eclampsia. IVF may be associated with a higher risk of epigenetic abnormalities. Ethicists have upheld women's reproductive freedom while pointing out that so-called social freezing merely postpones social problems, rather than solving them.

CONCLUSION

Fertility preservation for non-medical reasons should be critically discussed, and decisions should be made on a case-by-case basis.

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.