In-vitro maturation of human oocytes: before or after vitrification?

Preservation of fertility in female patients with hematologic diseases

Recent developments of assisted reproduction techniques turned possible to avoid the infertility consequences of oncologic treatments, but fertility preservation (FP) has been somewhat neglected in women with hematologic diseases undergoing gonadotoxic treatments. For these specific cases, the current options for FP include the cryopreservation of embryos, mature oocytes and ovarian tissue, and oocyte in-vitro maturation. We intend to make patients and clinicians aware of this important and relevant issue, and provide hematologists, assisted reproduction physicians and patients, with updated tools to guide decisions for FP. The physicians of the units responsible for female FP should always be available to decide on the best-individualized FP option in strict collaboration with hematologists. With a wide range of options for FP tailored to each case, a greater level of training and information is needed among clinicians, so that patients proposed to gonadotoxic treatments can be previously advised for FP techniques in hematological conditions. ABBREVIATED ABSTRACT: Recent developments of assisted reproduction techniques turned possible to preserve the fertility of women with hematologic diseases undergoing gonadotoxic treatments. Current options for fertility preservation in women with hematologic diseases are presented. It is imperative to offer fertility preservation to all women before starting any gonadotoxic treatment and in some cases after treatment. Fertility preservation methods enable to later achieve the desired pregnancy.

Cumulus cell co-culture in media drops does not improve rescue in vitro maturation of vitrified-warmed immature oocytes

OBJECTIVE

To assess whether co-culture with vitrified-warmed cumulus cells (CCs) in media drops improves rescue in vitro maturation (IVM) of previously vitrified immature oocytes. Previous studies have shown improved rescue IVM of fresh immature oocytes when cocultured with CCs in a three-dimensional matrix. However, the scheduling and workload of embryologists would benefit from a simpler IVM approach, particularly in the setting of time-sensitive oncofertility oocyte cryopreservation (OC) cases. Although the yield of developmentally competent mature metaphase II (MII) oocytes is increased when rescue IVM is performed before cryopreservation, it is unknown whether maturation of previously vitrified immature oocytes is improved after coculture with CCs in a simple system not involving a three-dimensional matrix.

DESIGN

Randomized controlled trial.

SETTING

Academic hospital.

PATIENTS

A total of 320 (160 germinal vesicles [GVs] and 160 metaphase I [MI]) immature oocytes and autologous CC clumps were vitrified from patients who were undergoing planned OC or intracytoplasmic sperm injection from July 2020 until September 2021.

INTERVENTIONS

On warming, the oocytes were randomized to culture in IVM media with CCs (+CC) or without CCs (-CC). Germinal vesicles and MI oocytes were cultured in 25 μL (SAGE IVM medium) for 32 hours and 20-22 hours, respectively.

MAIN OUTCOME MEASURES

Oocytes with a polar body (MII) were randomized to confocal microscopy for analysis of spindle integrity and chromosomal alignment to assess nuclear maturity or to parthenogenetic activation to assess cytoplasmic maturity. Wilcoxon rank sum tests for continuous variables and the chi square or Fisher's exact test for categorical variables assessed statistical significance. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Patient demographic characteristics were similar for both the GV and MI groups after randomization to +CC vs. -CC. No statistically significant differences were observed between +CC vs. -CC groups regarding the percentage of MII from either GV (42.5% [34/80] vs. 52.5% [42/80]; RR 0.81; 95% CI: 0.57-1.15]) or MI (76.3% [61/80]; vs. 72.5% [58/80]; RR 1.05; 95% CI: 0.88-1.26]) oocytes. An increased percentage of GV-matured MIIs underwent parthenogenetic activation in the +CC group (92.3% [12/13] vs. 70.8% [17/24]), but the difference was not statistically significant (RR 1.30; 95% CI: 0.97-1.75), whereas the activation rate was identical for MI-matured oocytes (74.3% [26/35] vs. 75.0% [18/24], CC+ vs. CC-; RR 0.99; 95% CI: 0.74-1.32). No significant differences were observed between +CC vs. -CC groups for cleavage of parthenotes from GV-matured oocytes (91.7% [11/12] vs. 82.4% [14/17]) or blastulation (0 for both) or for MI-matured oocytes (cleavage: 80.8% [21/26] vs. 94.4% [17/18]; blastulation: 0 [0/26] vs. 16.7% [3/18]). Further, no significant differences were observed between +CC vs. -CC for GV-matured oocytes regarding incidence of bipolar spindles (38.9% [7/18] vs. 33.3% [5/15]) or aligned chromosomes (22.2% [4/18] vs. 0.0 [0/15]); or for MI-matured oocytes (bipolar spindle: 38.9% [7/18] vs. 42.9% [2/28]); aligned chromosomes (35.3% [6/17] vs. 24.1% [7/29]).

CONCLUSIONS

Cumulus cell co-culture in this simple two-dimensional system does not improve rescue IVM of vitrified, warmed immature oocytes, at least by the markers assessed here. Further work is required to assess the efficacy of this system given its potential to provide flexibility in a busy, in vitro fertilization clinic.

Effects of meiotic stage-specific oocyte vitrification on mouse oocyte quality and developmental competence

Introduction

Acquisition of germinal vesicle (GV) stage oocytes for fertility preservation (FP) offers several benefits over in vivo matured oocyte cryopreservation following ovarian stimulation, particularly for cancer patients necessitating immediate treatment. Two FP approaches for GV oocytes are available: vitrification before in vitro maturation (IVM) at the GV stage (GV-VI) or post-IVM at the metaphase II (MII) stage (MII-VI). The optimal method remains to be determined.

Methods

In this study, mouse oocytes were collected without hormonal stimulation and vitrified either at the GV stage or the MII stage following IVM; non-vitrified in vitro matured MII oocytes served as the control (CON). The oocyte quality and developmental competence were assessed to obtain a better method for immediate FP.

Results

No significant differences in IVM and survival rates were observed among the three groups. Nevertheless, GV-VI oocytes exhibited inferior quality, including abnormal spindle arrangement, mitochondrial dysfunction, and early apoptosis, compared to MII-VI and CON oocytes. Oocyte vitrification at the GV stage impacted maternal mRNA degradation during IVM. In addition, the GV-VI group demonstrated significantly lower embryonic developmental competence relative to the MII-VI group. RNA sequencing of 2-cell stage embryos revealed abnormal minor zygotic genome activation in the GV-VI group.

Conclusion

Vitrification at the GV stage compromised oocyte quality and reduced developmental competence. Consequently, compared to the GV stage, oocyte vitrification at the MII stage after IVM is more suitable for patients who require immediate FP.

Oocyte Cryopreservation for Medical and Planned Indications: A Practical Guide and Overview

Oocyte cryopreservation (OC) is the process in which ovarian follicles are stimulated, the follicular fluid is retrieved, and mature oocytes are isolated and vitrified. Since the first successful pregnancy utilizing previously cryopreserved oocytes in 1986, OC has become increasingly utilized as an option for future biologic children in patients facing gonadotoxic therapies, such as for the treatment of cancer. Planned OC, also termed elective OC, is growing in popularity as a means to circumvent age-related fertility decline. In this narrative review, we describe both medically indicated and planned OC, focusing on the physiology of ovarian follicular loss, OC technique and risks, timing of when OC should be performed, associated financial considerations, and outcomes.

Human Follicular Fluid and Mesenchymal Stem Cell Conditioned Medium Improves in Vitro Development of Vitrified-Warmed Mouse Oocytes

BACKGROUND: In vitro maturation (IVM) and oocyte cryopreservation are therapeutic options in assisted reproductive technology which is used to preserve fertility in patients with different causes of infertility. OBJECTIVE: To analyze in vitro development of vitrified-warmed oocytes in the presence of human follicular fluid (FF) and bone marrow mesenchymal stem cell-conditioned medium (BMSC- CM) as a rescue strategy in fertility preservation. MATERIALS AND METHODS: BMSC-CM and FF media were used as two natural media. Not only osteogenic and adipogenic differentiation but also flow cytometry was carried out to confirm the nature of mesenchymal stem cells. A total of 327 vitrified-warmed oocytes were randomly assigned to three groups with different maturation media. After 24 h the maturation rate was evaluated. In vitro fertilization and also embryo development were also assessed. RESULTS: Oocytes matured in the BMSC-CM and FF groups showed a significant increase compared to the control group (76.6±2.9, 53.2±1.0 , and 40.8±6.1, respectively) (P < 0.05). Embryo cleavage rates in the BMSC-CM were dramatically higher than FF and control groups (85.6±2.2, 70.5±2.2, and 60.7±1.5, respectively). Blastocyst formation rates in the BMSC-CM group were statically different compared to FF and control groups (73.6±1.0, 58.5±1.0, and 45.8±4.2, respectively). CONCLUSION: BMSC-CM and FF media not only improve the maturation rate of vitrified warmed oocytes but also significantly increase embryo cleavage and blastocyst rates.

IVM of human immature oocytes for infertility treatment and fertility preservation

Background

Thousands of healthy babies are born from in vitro maturation (IVM) procedures, but the rate of efficiency differs with the source of immature oocytes obtained. Recently, there are different IVM protocols proposed for infertility treatment and fertility preservation.

Methods

Based on the literature, the clinical application for IVM of immature oocytes was summarized.

Main findings Results

Immature oocytes may be retrieved from women after priming with or without the use of follicular stimulation hormone (FSH), human chorionic gonadotrophin (hCG) or a combination of both FSH and hCG. Successful pregnancy rates with IVM technology seem to be correlated with the number of immature oocytes obtained. With the source and culture course of immature oocytes, there are various IVM protocols. IVM of immature oocytes is profoundly affected by the culture conditions, but no breakthrough has been made by improving the IVM medium itself. Thus, the clinical application of IVM technology continues to evolve.

Conclusion

IVM technology is a useful technique for infertile women and fertility preservation. Mild stimulation IVF combined with IVM of immature oocytes is a viable alternative to the conventional stimulation IVF cycle treatment as it may prove to be an optimal first-line treatment approach.

Potential Development of Vitrified Immature Human Oocytes: Influence of the Culture Medium and the Timing of Vitrification

How does the in vitro maturation (IVM) medium and the vitrification procedure affect the survival of germinal vesicle (GV) oocytes obtained from stimulated cycles and their development to the blastocyst stage? In total, 1085 GV human oocytes were obtained after women underwent a cycle of controlled ovarian stimulation, and these oocytes were subjected to IVM before or after their vitrification. IVM was carried out in two commercial culture media not specifically designed for maturation. MII oocytes were then activated and embryo development until day 6 was evaluated. According to the results, a higher percentage of oocytes reach the MII stage if they are vitrified before they undergo IVM. Nevertheless, the medium used and the sample size determine whether these differences become significant or not. Similar survival rates and development to blastocysts were observed in all the conditions studied.

High pressure frozen oocytes have improved ultrastructure but reduced cleavage rates compared to conventionally fixed or vitrified oocytes

Context Live birth rates are lower for cryopreserved oocytes than for fresh IVF cycles, indicating a need for improved methodologies. Aims The aim of this study was to determine if high pressure freezing (HPF) could improve both ultrastructural preservation and cryopreserved oocyte quality when compared to conventional fixation and vitrification methods. Methods Sheep oocytes and embryos were prepared by HPF or vitrification, with or without cryoprotectants. Frozen oocytes were prepared for transmission electron microscopy or warmed, in vitro fertilised and the recovery and cleavage rates recorded. Key results Blastocyst rates were similar between fresh, HPF and vitrified embryos. HPF oocytes had improved ultrastructure compared to conventional fixation or vitrification, but had poorer survival and cleavage rates compared to vitrified oocytes. Freeze-substitution of cryopreserved oocytes and transmission electron microscopy demonstrated disruption of the oocyte ultrastructure in the presence of cryoprotectants. Conclusions Superior preservation of ultrastructure was observed in HPF oocytes compared to vitrification or conventional fixation methods. In the presence of CP, both embryos and oocytes could survive HPF and warming but oocytes had reduced development. Implications The HPF method has potential to be developed and lead to improved oocyte and embryo cryopreservation and outcomes for assisted reproduction.

Potential use of immature oocyte to improve fertility preservation outcome: A narrative review

Fertility preservation through gamete vitrification has become one of the critical strategies to secure a childbearing potential in patients who are diagnosed with cancer or risks of infertility. Preserving the gametes would prevent the deleterious effects of cancer drugs or radiotherapy exposure on the quality of the gametes. Furthermore, in vitro fertilisation of vitrified mature human oocytes has lately demonstrated promising results that are reflected in the increased survival rate of thawed oocytes and the resultant clinical pregnancy rate. However, limitations in the cryopreservation of mature oocytes of cancer patients persist. Ovarian stimulation protocols which comprise administering gonadotrophin-releasing hormones could aggravate cancer or delay essential cancer therapy. Considering such circumstances, vitrification of immature oocytes would become a rational option. While the vitrification procedure of mature oocytes has been established, the vitrification of immature oocytes remains controversial due to a low post-thaw in vitro maturation and fertilisation rate. Apparent cryoinjuries to the immature oocytes post thawing or warming have been observed in both human and animal model oocytes. An alternative strategy was therefore proposed to improve the effectiveness of utilising immature oocytes for fertility preservation by conducting the in vitro oocyte maturation process first before vitrification. This method has prevailed, especially in oncofertility patients. Although the success rate of the clinical outcomes remains low, this approach, in conjugation with proper counselling, might provide oncofertility patients with an opportunity to preserve their reproductive potential.

Effects of melatonin and human follicular fluid supplementation of in vitro maturation medium on mouse vitrified germinal vesicle oocytes: A laboratory study

Background

Vitrification as the most efficient method of cryopreservation, enables successful storage of oocytes for couples who undergo specific procedures including surgery and chemotherapy. However, the efficacy of in vitro maturation (IVM) methods with vitrified germinal vesicle (GV) oocytes could be improved.

Objective

As melatonin and follicular fluid (FF) might enhance IVM conditions, we used these supplements to assess the maturation rate of vitrified GV oocytes and their artificial fertilization rate.

Materials and Methods

Four hundred mouse GV oocytes were harvested, vitrified, and assigned into control (C-Vit-GV) and treatment groups of melatonin (M-Vit-GV), human follicular fluid (HFF-Vit-GV), and a combination (M + HFF-Vit-GV). A non-vitrified group of GV oocytes (non-Vit-GV) and a group of in vivo matured metaphase II (Vivo-MII) oocytes served as control groups to evaluate the vitrification and IVM conditions, respectively. Maturation of GV oocytes to MII and further development to two-cell-stage embryos were determined in the different groups.

Results

Development to two-cell embryos was comparable between the Vivo-MII and non-Vit-GV groups. IVM and in vitro fertilization (IVF) results in the non-Vit-GV group were also comparable with the C-Vit-GV oocytes. In addition, the IVM and IVF outcomes were similar across the different treatment groups including the M-Vit-GV, HFF-Vit-GV, M + HFF-Vit-GV, and C-Vit-GV oocytes.

Conclusion

Employing an appropriate technique of vitrification followed by suitable IVM conditions can lead to reasonable IVF outcomes which may not benefit from extra supplementations. However, whether utilizing other supplementation formulas could improve the outcome requires further investigation.

Case report: two cases of mature oocytes found in prepubertal girls during ovarian tissue cryopreservation

Objective

To report two cases of mature oocytes found in prepubertal girls undergoing ovarian tissue cryopreservation (OTC).

Design

Case report.

Setting

Large tertiary care children’s hospital and a private fertility clinic.

Patient(s)

An 8-year-old prepubertal girl with β-thalassemia and a 2-year-old girl with sickle cell disease who both underwent OTC before bone marrow transplantations.

Intervention(s)

Laparoscopic right oophorectomy was performed in each patient. The ovarian cortical tissue was processed for slow freezing and long-term storage, and all oocytes were subsequently vitrified.

Main Outcome Measure(s)

Oocytes found at the time of OTC processing for fertility preservation.

Result(s)

After a complete right oophorectomy, one mature metaphase II oocyte was discovered on tissue processing for OTC in each patient. Neither patient has yet returned for use of tissue or oocytes.

Conclusion(s)

To our knowledge, this is the first report of mature oocytes found during prepubertal OTC processing. These findings may indicate the need for increased research regarding prepubertal oocyte development and suggest that the technique of examining the media for both mature and immature oocytes at the time of OTC should become more widespread and perhaps recommended in prepubertal patients to optimize fertility preservation methods.

Impact of Maturation and Vitrification Time of Human GV Oocytes on the Metaphase Plate Configuration

The combination of in vitro maturation (IVM) techniques and oocyte vitrification (OV) could increase the number of useful oocytes in different types of patients. IVM and subsequent OV is the most widely used clinical strategy. Would the results improve if we reverse the order of the techniques? Here, we evaluated survival, in vitro maturation, time to extrude the first polar body (PB), and the metaphase plate configuration of human prophase I (GV) oocytes before or after their vitrification. Specific, 195 GV oocytes from 104 patients subjected to controlled ovarian stimulation cycles were included. We stablished three experimental groups: GV oocytes vitrified and IVM (Group GV-Vit), GV oocytes IVM and vitrified at MII stage (Group MII-Vit), and GV oocytes IVM (Group not-Vit). All of them were in vitro matured for a maximum of 48 h and fixed to study the metaphase plate by confocal microscopy. According to our results, the vitrification of immature oocytes and their subsequent maturation presented similar survival, maturation, and metaphase plate conformation rates, but a significantly higher percentage of normal spindle than the standard strategy. Additionally, the extension of IVM time to 48 h did not seem to negatively affect the oocyte metaphase plate configuration.

Maturation and fertilization of African lion (Panthera leo) oocytes after vitrification

The African lion is an excellent model species for the highly endangered Asiatic lion. African lions reproduce well in zoos, leading to the fact that occasionally ovaries and testis are available for in-vitro experiments. We previously performed in-vitro maturation (IVM) and fertilization of lion oocytes and were able to produce advanced embryos after intracytoplasmic sperm injection (ICSI) with cryopreserved sperm. Here we examined whether our in-vitro method is also applicable after vitrification of immature oocytes. Oocytes of four lionesses (5-7 years old) were obtained after euthanasia and immediately processed on site. Half of the oocytes (n = 60) were subjected to IVM for a total of 32-34 h at 39 °C, 5% CO₂ and humidified air atmosphere. The second group (59 oocytes) was vitrified instantly using the Cryotop method. Following 6 days of storage in liquid nitrogen, oocytes were warmed and subjected to IVM as well. Mature oocytes of both groups were fertilized with frozen-thawed African lion sperm using ICSI. Maturation rate was 55% and 49.2% for the control and vitrified group, respectively. In the control group, three oocytes cleaved and another three were arrested at the pronuclei stage. Due to the low fertilization result, a sperm sample of another male was used for the vitrified group. Of the vitrified oocytes 7 cleaved and 9 more oocytes stopped at pronuclei stage. All embryos of the vitrified group did not develop beyond 4 cell stage. This is the first time that African lion in-vitro-derived embryos have been produced following oocyte vitrification.

Follicular extracellular vesicles enhance meiotic resumption of domestic cat vitrified oocytes

Extracellular vesicles (EVs) contain multiple factors that regulate cell and tissue function. However, understanding of their influence on gametes, including communication with the oocyte, remains limited. In the present study, we characterized the proteome of domestic cat (Felis catus) follicular fluid EVs (ffEV). To determine the influence of follicular fluid EVs on gamete cryosurvival and the ability to undergo in vitro maturation, cat oocytes were vitrified using the Cryotop method in the presence or absence of ffEV. Vitrified oocytes were thawed with or without ffEVs, assessed for survival, in vitro cultured for 26 hours and then evaluated for viability and meiotic status. Cat ffEVs had an average size of 129.3 ± 61.7 nm (mean ± SD) and characteristic doughnut shaped circular vesicles in transmission electron microscopy. Proteomic analyses of the ffEVs identified a total of 674 protein groups out of 1,974 proteins, which were classified as being involved in regulation of oxidative phosphorylation, extracellular matrix formation, oocyte meiosis, cholesterol metabolism, glycolysis/gluconeogenesis, and MAPK, PI3K-AKT, HIPPO and calcium signaling pathways. Furthermore, several chaperone proteins associated with the responses to osmotic and thermal stresses were also identified. There were no differences in the oocyte survival among fresh and vitrified oocyte; however, the addition of ffEVs to vitrification and/or thawing media enhanced the ability of frozen-thawed oocytes to resume meiosis. In summary, this study is the first to characterize protein content of cat ffEVs and their potential roles in sustaining meiotic competence of cryopreserved oocytes.

Germinal stage vitrification is superior to MII stage vitrification in prepubertal mouse oocytes

This study investigated if in vitro maturation (IVM) before or after vitrification would be more successful for prepubertal oocytes. To mimic prepubertal conditions in an experimental setup, oocytes were collected from healthy 14, 21 and 28day old Swiss albino mice. The germinal vesicle (GV) stage oocytes and in vitro matured MII oocytes were subjected to vitrification-warming. Both structural (meiotic spindle morphology, mitochondrial integrity, cortical granules) and functional (sperm zona binding, fertilization) characteristics were assessed in oocytes after warming. This study demonstrated that IVM was more detrimental to prepubertal oocytes than to young adults. Further, vitrification of the IVM oocytes resulted in an increase in the number of abnormal meiotic spindles, a change in the cortical distribution pattern, a reduction in sperm zona binding and the fertilization rate. Importantly, oocyte integrity was better when prepubertal oocytes were vitrified before, rather than after, IVM. The above observations support GV stage vitrification for prepubertal oocytes requiring fertility preservation. Understanding the mechanisms behind the differing outcomes for oocytes from immature females will help in refining current protocol, thereby retaining the oocytes' maximum structural and functional integrity Further investigation is necessary to determine whether human prepubertal oocytes also behave in a similar way. It is to be noted here, with great emphasis, that a major limitation of this study is that the oocytes' abilities were tested only until fertilisation, as a consequence of which the study cannot reveal the developmental potentials of the embryos beyond fertilisation.

Effects of cyclic adenosine monophosphate modulators on maturation and quality of vitrified-warmed germinal vesicle stage mouse oocytes

BACKGROUND

It is still one of the unresolved issues if germinal vesicle stage (GV) oocytes can be successfully cryopreserved for fertility preservation and matured in vitro without damage after warming. Several studies have reported that the addition of cyclic adenosine monophosphate (cAMP) modulators to in vitro maturation (IVM) media improved the developmental potency of mature oocytes though vitrification itself provokes cAMP depletion. We evaluated whether the addition of cAMP modulators after GV oocytes retrieval before vitrification enhances maturation and developmental capability after warming of GV oocytes.

METHODS

Retrieved GV oocytes of mice were divided into cumulus-oocyte complexes (COCs) and denuded oocytes (DOs). Then, GV oocytes were cultured with or without dibutyryl-cAMP (dbcAMP, cAMP analog) and 3-isobutyl-l-methylxanthine (phosphodiesterase inhibitor) during the pre-vitrification period for 30 min.

RESULTS

One hour after warming, the ratio of oocytes that stayed in the intact GV stage was significantly higher in groups treated with cAMP modulators. After 18 h of IVM, the percentage of maturation was significantly higher in the COC group treated with dbcAMP. The expression of F-actin, which is involved in meiotic spindle migration and chromosomal translocation, is likewise increased in this group. However, there was no difference in chromosome and spindle organization integrity or developmental competence between the MII oocytes of all groups.

CONCLUSIONS

Increasing the intracellular cAMP level before vitrification of the GV oocytes maintained the cell cycle arrest, and this process may facilitate oocyte maturation after IVM by preventing cryodamage and synchronizing maturation between nuclear and cytoplasmic components. The role of cumulus cells seems to be essential for this mechanism.

[Causes of oocyte vitrification and its value in assisted reproductive technology]

OBJECTIVE

To explore the causes of oocyte vitrification and its application in assisted reproduction.

METHODS

We retrospectively analyzed the data of 26 patients with 27 cycles of oocyte vitrification cryopreservation undergoing intracytoplasmic sperm injection (ICSI) and embryo transfer between January, 2008 and October, 2018. The causes of oocyte vitrification and the outcomes of ICSI and clinical pregnancy were analyzed.

RESULTS

The causes of oocytes vitrification included mainly azoospermia or severe spermatogenesis disorder of the husband, failure to obtain sperms from the husband, failure of the husband to be present on the day of oocyte retrieval and acute diseases of the husband to not allow sperm collection. A total of 274 oocytes were frozen in 27 oocyte retrieval cycles, and 217 eggs were thawed in 19 cycles with a survival rate of 81.11% (176/217). The normal fertilization rate, cleavage rate and high-quality embryo rate was 74.81% (98/131), 89.80% (88/98) and 36.73% (36/98), respectively. Fifteen patients underwent embryo transfer, and the clinical pregnancy rate and live birth rate was 53.33% (8/15) and 33.33% (5/15), respectively. Compared with patients below 35 years of age, the patients aged above 35 years had significantly lower oocyte survival rate after thawing (82.76% vs 74.42%, P=0.211), clinical pregnancy rate (77.78% vs 16.67%, P=0.041) and live birth rate (55.56% vs 0, P=0.044).

CONCLUSIONS

Oocytes vitrification can be used as a remedy for infertile couples who fail to provide sperms due to male factors on the day of oocyte retrieval. Vitrification of the oocytes does not significantly affect the fertilization rate or the clinical pregnancy rate. The survival rate of the thawed oocytes is related to the age of the wife, and an age younger than 35 years can be optimal for achieving favorable clinical pregnancy outcomes after oocyte vitrification.

Vitrification has detrimental effects on maturation, viability, and subcellular quality of oocytes post IVM in cancerous women: An experimental study

Background

In vitro maturation (IVM) of immature oocytes retrieved from ovarian tissue has been considered as a valuable approach for fertility preservation in cancerous patients.

Objective

To evaluate the efficacy of vitrification on oocyte maturation, survival rates, as well as the subcellular oocyte quality post IVM.

Materials and Methods

The ovarian cortexes from 19 women with cervix and uterine malignancy aged 21-39 yr were collected. Cumulus-oocyte complexes were aspirated from all visible antral follicles. 102 immature oocytes were collected, and 43 oocytes were detected appropriately for IVM (control group). Also, 59 immature oocytes were vitrified, then matured in vitro (IVM) in two groups: with Growth/differentiation factor 9 (GDF9) (group 1) and without GDF9 (group 2) supplementation. Rates of oocytes viability, maturation, and survival along with meiotic spindle visualization and zona pellucida birefringence were assessed with Polyscope.

Results

The rate of maturation was significantly higher in controls (55.8%) compared to the other groups. Maturation rate was 23.3% in oocytes cultured in IVM medium enriched with GDF9, and 27.6% in those cultured in IVM medium lacking GDF9 (p = 0.86). Also, the meiotic spindle was present in 74.4% of control oocytes which was significantly higher than the other groups. The proportion of high zona pellucida birefringence was higher in the controls when compared with group 1 (51.2% vs. 23.3%, respectively, p = 0.04).

Conclusion

Vitrification had a detrimental effect on oocyte maturation, viability as well as the subcellular quality of the oocytes after IVM in cancerous women.

Immature Oocyte for Fertility Preservation

In vitro maturation (IVM) of human immature oocytes has been offered to women who are at risk of developing ovarian hyperstimulation syndrome (OHSS) caused by gonadotropin stimulation, such as PCO(S) patients or who have poor ovarian reserve. Cryopreservation of oocytes matured in vivo obtained in IVF cycles has improved after implementing the vitrification method and many successful results have been reported. Now, this procedure can be successfully offered to fertility preservation programs for patients who are in danger of losing their ovarian function due to medical or social reasons, and to oocyte donation programs. This vitrification technique has also been applied to cryopreserve oocytes obtained from IVM program. Some advantages of oocytes vitrification related with IVM are: (1) eliminating costly drugs and frequent monitoring; (2) completing treatment within 2 to 10 days (3) avoiding the use of hormones in cancer patients with hormone-sensitive tumors; and (4) retrieving oocytes at any point in menstrual cycle, even in the luteal phase. In addition, immature oocytes can also be collected from extracorporeal ovarian biopsy specimens or ovaries during caesarian section. Theoretically, there are two possible approaches for preserving immature oocytes: oocyte cryopreservation at the mature stage (after IVM) and oocyte cryopreservation at the Germinal Vesicle (GV)-stage (before IVM). Both vitrification of immature oocyte before/after IVM is not currently satisfactory. Nevertheless, many IVF centers worldwide are doing IVM oocyte cryopreservation as one of the options to preserve fertility for female cancer. Therefore, more studies are urgently required to improve IVM- and vitrification method to successfully preserve oocytes collected from cancer patients. In this review, present oocyte maturation mechanisms and recent progress of human IVM cycles will be discussed first, followed by some studies of the vitrification of human IVM oocyte.

Oocyte in vitro maturation: A sytematic review

In vitro maturation (IVM) is one of the most controversial aspects of assisted reproductive technology. Although it has been studied extensively, it is still not a conventional treatment option and is accepted as an alternative treatment. However, studies have shown that IVM can be used in almost all areas where in vitro fertilization (IVF) is used and it has a strong place in fertility protection and Ovarian Hyperstimulation syndrome management. The aim of this systematic review was to address all aspects of the current knowledge of IVM treatment together with the evolution of IVM and IVF.

Decreased pregnancy and live birth rates after vitrification of in vitro matured oocytes

PURPOSE

To assess effects on fertilization rate, embryo quality, pregnancy, and live birth rates of vitrification and warming of oocytes that matured in vitro (vIVM) compared to fresh in vitro maturation (fIVM) cycles.

METHODS

A retrospective cohort study conducted at a university hospital-affiliated IVF unit. Fifty-six cycles of vIVM cycles and 263 fIVM in women diagnosed with polycystic ovarian syndrome (PCOS) ovaries were included in the analysis. The study group included PCOS patients who failed ovulation induction with intrauterine insemination and were offered IVM cycle followed by oocyte vitrification and warming. The embryological aspects and clinical outcomes were compared to those of controls undergoing fresh IVM cycles during the same period. The main outcome measure was live birth rate.

RESULTS

One thousand seventy oocytes were collected from 56 patients and underwent vitrification and warming. In the control group, 4781 oocytes were collected from 219 patients who had undergone a fresh IVM cycle. Oocyte maturation rates were similar between the groups (mean ± SD: 0.7 ± 0.2 vs. 0.6 ± 0.2, for vIVM and fIVM, respectively). Survival rate after warming was 59.8%. Fertilization and embryo cleavage rates per oocyte were significantly lower in the vIVM group. Clinical pregnancy (10.7 vs. 36.1%) and live birth rates (8.9 vs. 25.9%) per cycle were significantly lower in the vIVM group than those in the fIVM group (P = 0.005 and P < 0.001, respectively). Five healthy babies were born in the vIVM group.

CONCLUSIONS

The reproductive potential of vitrified IVM oocytes is impaired. This injury likely occurs through vitrification and warming.

Impact of vitrification on human oocytes before and after in vitro maturation: A systematic review and meta-analysis

OBJECTIVE

There are controversies regarding in vitro maturation (IVM) procedure, the time of storing frozen oocytes and maturation stage of vitrified oocytes and its impact on oocytes fertilization capability. The aim of this systematic review and meta-analysis was to evaluate the impact of vitrification on human oocytes during IVM procedure.

STUDY DESIGN

A systematic review with meta-analysis was undertaken. Main search terms were those related key words. We searched Medline, Embase, Scopus and ISI web of science to detect English-language studies. The final search was performed on 27 January 2018. The original articles which studied laboratory outcomes after vitrification of MII or GV oocytes before or after IVM were included. Exclusion criteria were animal trials and the studies that performed cryopreservation using slow-freeze method. Oocyte maturation, survival, fertilization and cleavage rates were assessed. Bias and quality assessments were applied.

RESULTS

2476 articles were screened and after duplicates removing together with application of inclusion and exclusion criteria, 14 studies assessed for eligibility. Finally 5 studies included for analysis. All studies compared laboratory outcomes between oocytes that vitrified at the GV stage and those which firstly matured in vitro, and then vitrified. Meta-analysis showed that vitrification of oocytes at GV stage had a negative impact on maturation rate (RR = 1.28, 95% CI: 0.96-1.70); but not on cleavage rate (RR = 1.07, 95% CI: 0.70-1.64); fertilization rate (RR = 0.99, 95% CI: 0.85-1.14) and survival rate(RR = 1.01, 95% CI: 0.96-1.06).

CONCLUSION

In general, Based on our results, oocyte vitrification decreases the maturation rate. In addition, survival, fertilization as well as cleavage rates did not significantly differ between the oocytes vitrified before IVM versus oocytes vitrified after IVM.

Autophagy inhibition of immature oocytes during vitrification-warming and in vitro mature activates apoptosis via caspase-9 and -12 pathway

OBJECTIVE

The aim of this study is to determine the role of autophagy in the immature oocytes during vitrification-warming and in vitro maturation (IVM); the correlations among autophagy, apoptosis, and the activities of caspase in the immature oocytes during vitrification-warming and IVM were also explored.

STUDY DESIGN

Immature oocytes from mice were vitrified-warmed and IVM. An autophagy inhibitor (3-methyladenine) was supplemented in cryopreservation solutions and warming solutions. The expression of beclin-1 (an autophagy marker), caspase-3, -8, -9, and -12 were measured. Moreover, the viability of vitrified-warmed immature oocytes and their subsequent developmental competence were measured.

RESULTS

The levels of beclin-1 expression in both mRNA and protein in oocytes experienced vitrification-warming and IVM were significantly higher than that in fresh immature oocytes experienced IVM. The levels of caspase-3, -9, -12 expression in both mRNA and protein in oocytes vitrified with 3-methyladenine were significantly higher than that vitrified without 3-methyladenine. However, the differences in the caspase-8 expression in both mRNA and protein between the oocytes vitrified with 3-methyladenine and that vitrified without 3-methyladenine were not significant.

CONCLUSION

Immature oocyte cryopreservation exhibits autophagic activation. Autophagy inhibition of the immature oocytes during vitrification-warming and IVM activates apoptosis via caspase-9 and -12 pathway.

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

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

In vitro maturation of human immature oocytes for fertility preservation and research material

Aim

In recent years, the importance of fertility preservation (FP) has increased. In vitro maturation (IVM), an important technique in FP, has started to be used in the clinic, but controversies persist regarding this technique. Here, a survey of IVM for FP is provided.

Methods

Based on a literature review, the applications of FP, methods of FP, IVM of oocytes that had been collected in vivo and ex vivo, maturation of oocytes after IVM for FP, cryopreservation of oocytes for FP, explanation of the procedures to patients, and recent research on FP using IVM were investigated.

Results

Although IVM for FP remains controversial, the application of FP is expected to expand. Depending on the age and disease status of the patient, various methods of oocyte collection and ovarian stimulation, as well as various needle types and aspiration pressures, have been reported. The maturation rate of IVM in FP ranges widely and requires optimization in the future. In regard to cryopreservation for matured oocytes, the vitrification method is currently recommended.

Conclusion

Regarding FP for patients with cancer, the treatment of cancer is prioritized; thus, the time and use of medicines are often constrained. As several key points regarding IVM remain unclear, well‐designed and specific counseling for patients is necessary.

Ultrastructural characteristics of human oocytes vitrified before and after in vitro maturation

The development of an effective program that combines in vitro maturation (IVM) and cryopreservation for immature oocytes would represent a novel advance for in vitro fertilization (IVF), especially as a means to preserve the fertility of women in unique situations. The aim of this study was to analyze the ultrastructural characteristics of human oocytes, obtained after controlled ovarian stimulation, to determine whether IVM is best performed before or after vitrification. To this end, we analyzed the following features in a total of 22 MII oocytes: size, zona pellucida and perivitelline space, mitochondria number, M-SER (mitochondria-smooth endoplasmic reticulum) aggregates and M-V (mitochondria-vesicle) complexes, the number of cortical granules and microvilli, and the presence of vacuolization using transmission electron microscopy (TEM). Each oocyte presented a rounded shape, with an intact oolemma, and was surrounded by a continuous zona pellucida and perivitelline space. Statistical analysis comparing oocytes vitrified before or after IVM indicated that there were no significant differences between examined characteristics.

Outcomes of immature oocytes collected from ovarian tissue for cryopreservation in adult and prepubertal patients

The efficiency of oocyte in-vitro maturation (IVM) and vitrification procedures after ex-vivo collection from ovarian tissue were assessed according to patient age, number of retrieved oocytes and tissue transport conditions. The combined procedure was performed in 136 patients: 130 adults (mean 27.6 ± 5.6 years) and six prepubertal girls (mean 8.7 ± 2.3 years). A higher mean number of oocytes were collected in girls compared with adults (11.5 ± 8.0 versus 3.8 ± 4.2, respectively, P < 0.001) but the percentage of degenerated oocytes was significantly higher in girls (35.5% versus 17.1%, respectively, P < 0.001). IVM rates were significantly lower in prepubertal than postpubertal population (10.3% versus 28.1%, P = 0.002). In adults, a negative correlation was observed between number of retrieved oocytes and age (P = 0.002; r = -0.271); the correlation was positive between anti-Müllerian hormone (AMH) and number of collected oocytes (P = 0.002; r = 0.264). IVM rates were not correlated with AMH levels (r = 0.06) or age (r = -0.033). At present, nine oocytes and one embryo have been warmed in four patients and one biochemical pregnancy obtained. This suggests the combined procedure could be an additional option for fertility preservation.

Should metaphase 1 and 2 stages oocytes be vitrified in the same time for fertility preservation?

Aims: Could metaphase 1 (M1) and 2 (M2) stages oocytes from in vitro maturation (IVM) cycles and controlled-ovarian hyperstimulation (COH) cycles be frozen at the same time without any adverse effect of vitrification on further survival (SR) and maturation rates (MR)? Materials & methods: M1 from cancer patients were prospectively included in IVM/COH groups, and in study or control subgroups if they were vitrified or not. In each study subgroup, SR were compared with that of M2 oocytes vitrified/warmed from egg donors. MR were compared with those of fresh-M1 oocytes from control IVM/COH subgroups. Results: SR were not different between groups. MR compared respectively between survived- and fresh-M1 oocytes were similar when resulting from COH (85.2 vs 81.1%) but significantly lower after IVM (39.1 vs 73.3%). Conclusion: Simultaneous freezing of M1/M2 oocytes could be applied to COH but not to IVM during the course of fertility preservation.

Cryopreservation of in vitro matured oocytes after ex vivo oocyte retrieval from gynecologic cancer patients undergoing radical surgery

Objective

The aim of this study was to report a case series of in vitro matured (IVM) oocyte freezing in gynecologic cancer patients undergoing radical surgery under time constraints as an option for fertility preservation (FP).

Methods

Case series report. University-based in vitro fertilization center. Six gynecologic cancer patients who were scheduled to undergo radical surgery the next day were referred for FP. The patients had endometrial (n=2), ovarian (n=3), and double primary endometrial and ovarian (n=1) cancer. Ex vivo retrieval of immature oocytes from macroscopically normal ovarian tissue was followed by mature oocyte freezing after IVM or embryo freezing with intracytoplasmic sperm injection.

Results

A total of 53 oocytes were retrieved from five patients, with a mean of 10.6 oocytes per patient. After IVM, a total of 36 mature oocytes were obtained, demonstrating a 67.9% maturation rate. With regard to the ovarian cancer patients, seven IVM oocytes were frozen from patient 3, who had stage IC cancer, whereas one IVM oocyte was frozen from patient 4, who had stage IV cancer despite being of a similar age. With regard to the endometrial cancer patients, 15 IVM oocytes from patient 1 were frozen. Five embryos were frozen after the fertilization of IVM oocytes from patient 6.

Conclusion

Immature oocytes can be successfully retrieved ex vivo from macroscopically normal ovarian tissue before radical surgery. IVM oocyte freezing provides a possible FP option in patients with advanced-stage endometrial or ovarian cancer without the risk of cancer cell spillage or time delays.

Osmotic-shock produced by vitrification solutions improves immature human oocytes in vitro maturation

BACKGROUND

During cytoplasmic oocyte maturation, Ca(2+) currents are vital for regulating a broad range of physiological processes. Recent studies have demonstrated that DMSO and EG cause large transient increases in intracellular Ca(2+) in mouse oocytes. The CP used in vitrifying protocols also increases the intracellular calcium transient. The aim of this study is to evaluate the effects of vitrifying time (before and after IVM) and exposure to the vitrification solutions and ionomycin on oocyte quality and embryonic development.

METHODS

221 GV-oocytes unsuitable for IVF-ICSI cycles were randomly distributed into one of the following three groups. G1 (control group): 41 GV-oocytes IVM until MII; G2: 43 oocytes vitrified at GV stage and IVM until MII stage; and G3: 53 GV-oocytes IVM until MII and then vitrified. In order to clarify the effect of vitrification solutions (VS) on human oocyte IVM through the intracellular Ca(2+) oscillation, the following two groups were also included. G4: 43 GV-oocytes exposed to VS and IVM until MII; and G5: 41 GV-oocytes exposed to ionomycin and IVM until MII. All GV-oocytes that reached MII-stage were parthenogenetically activated to assess oocyte viability. IVM was performed in IVF-medium (24-48 h). Chemical treatment (ionomycin) and osmotic treatment (vitrification solutions) were performed without liquid-N2 immersion. The following rates were evaluated: survival (SR), in-vitro maturation (IVMR), activation (AR), development to 2-cell (DRC), development to morula (DRCM) and development to blastocyst (DRB). Ratios between the different treatment groups were compared using contingency tables analysis (chi-square test).

RESULTS

A high survival rate was obtained in G2 (95.5 %) and G4 (96.6 %). In-vitro maturation rate was significantly higher for G4 (86 %) and G2 (83.7 %) compared to G1 (63.4 %), G3 (56.6 %) and G5 (48.8 %). DRCM was significantly higher for G1 and G2 compared to G3 (G1: 15.8 %, G2: 20.7 % and G3: 0 %). DRB was only obtained for the oocytes vitrified before IVM (G2: 3.4 %). AR was also significantly higher for G2 and G4 compared to G5 (G2: 80.5 %, G4: 86.5 % and G5: 55 %). DRCM and DRB were only obtained in G2 and G4. DRCM was significantly higher for oocytes vitrified at GV stage (G2) and for oocytes exposed to the VS in G4 compared to the oocytes exposed to the ionomycin in G5 (G2: 20.7 %; G4: 37.5 % and G5: 0 %).

CONCLUSIONS

Vitrifying GV-oocytes improves their IVM. Further investigation could look to increase the oocyte pool and improve fertility preservation options.

Updates in preserving reproductive potential of prepubertal girls with cancer: Systematic review

INTRODUCTION

With increasing numbers of adult female survivors of childhood cancers due to advances in early diagnosis and treatment, the issue of preserving the reproductive potential of prepubertal girls undergoing gonadotoxic treatments has gained greater attention.

METHODS

According to PRISMA guidelines, a systematic review of the literature was performed for all relevant full-text articles published in PubMed in English throughout the past 15 years to explore the significant updates in preserving the reproductive potential of prepubertal girls with cancer.

RESULTS

The two established fertility preservation options, embryo freezing and egg freezing, cannot be offered routinely to prepubertal girls as these options necessitate prior ovarian stimulation and subsequent mature oocytes retrieval that are contraindicated or infeasible before puberty. Therefore, the most suitable fertility preservation options to prepubertal girls are (1) ovarian tissue freezing and autotransplantation, (2) in vitro maturation, and (3) ovarian protection techniques. In this review, we discuss in detail those options as well as their success rates, advantages, disadvantages and future directions. We also suggest a new integrated strategy to preserve the reproductive potential of prepubertal girls with cancer.

CONCLUSION

Although experimental, ovarian tissue slow freezing and orthotopic autotransplantation may be the most feasible option to preserve the reproductive potential of prepubertal girls with cancer. However, this technique has two major and serious disadvantages: (1) the risk of reintroducing malignant cells, and (2) the relatively short lifespan of ovarian tissue transplants. Several medical and ethical considerations should be taken into account before applying this technique to prepubertal girls with cancer.

[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.

Similar in vitro maturation rates of oocytes retrieved during the follicular or luteal phase offer flexible options for urgent fertility preservation in breast cancer patients

STUDY QUESTION

Are in vitro maturation (IVM) rates of cumulus-oocyte complexes (COCs), retrieved from breast cancer patients seeking urgent fertility preservation (FP) before neoadjuvant chemotherapy, different between those recovered in the follicular or in the luteal phase of the cycle?

SUMMARY ANSWER

The present investigation reveals no major difference in the number of COCs recovered or their IVM rates whatever the phase of the cycle at which egg retrieval is performed, suggesting that IVM is a promising tool for breast cancer patients seeking urgent oocyte cryopreservation.

WHAT IS KNOWN ALREADY

FP now represents a standard of care for young cancer patients having to undergo gonadotoxic treatment. Mature oocyte cryopreservation after IVM of COCs has been proposed for urgent FP, especially in women, who have no time to undergo ovarian stimulation, or when it is contraindicated.

STUDY DESIGN, SIZE, DURATION

From January 2011 to December 2014, we prospectively studied 248 breast cancer patients awaiting neoadjuvant chemotherapy, aged 18-40 years, candidates for oocyte vitrification following IVM, either at the follicular or the luteal phase of the cycle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Serum anti-Müllerian hormone and progesterone levels and antral follicle count (AFC) were measured prior to oocyte retrieval. Patients were sorted into two groups according to the phase of the cycle during which eggs were harvested (Follicular phase group, n = 127 and Luteal phase group, n = 121). Number of COCs recovered, maturation rates after 48 h of culture and total number of oocytes cryopreserved were assessed. Moreover, the oocyte retrieval rate (ORR) was calculated by the number of COCs recovered ×100/AFC.

MAIN RESULTS AND THE ROLE OF CHANCE

In the Follicular and the Luteal phase groups, women were comparable in terms of age, BMI and markers of follicular ovarian status. There was no significant difference in the number of COCs recovered (mean ± SEM), 9.3 ± 0.7 versus 11.1 ± 0.8, and ORR (median (range)) 43.1 (1-100) versus 47.8 (7.7-100)%. Moreover, maturation rates after 48 h of culture (median (range)) were comparable in the follicular and luteal phase groups, 66.7 (20-100) versus 64.5 (0-100)%. Finally, the total number of oocytes cryopreserved (mean ± SEM) was similar in both groups (6.2 ± 0.4 versus 6.8 ± 0.5).

LIMITATIONS, REASONS FOR CAUTION

Despite the intact meiotic competence of immature oocytes recovered during the follicular or the luteal phase, there is a dramatic lack of data regarding the outcome of IVM oocytes cryopreserved in cancer patients.

WIDER IMPLICATIONS OF THE FINDINGS

IVM of oocytes may be an interesting method of FP in urgent situations. Improving the culture conditions will be needed to increase the maturation rates and the overall potential of in vitro matured oocytes.

STUDY FUNDING/COMPETING INTERESTS

None.

TRIAL REGISTRATION NUMBER

N/A.

Caspase activity and oxidative stress of granulosa cells are associated with the viability and developmental potential of vitrified immature oocytes

OBJECTIVE

The aim of this study is to determine whether caspase activity and oxidative stress of granulosa cells are associated with the viability and developmental potential of vitrified immature oocytes.

STUDY DESIGN

Oocytes from mice were exposed to genistein or/and Z-VAD-FMK with or without vitrification. Ultrastructural alterations of granulosa cells in vitrified immature oocytes were observed. Moreover, the level of superoxide dismutase (SOD) in granulosa cells, incidence of apoptotic follicles, the viability of vitrified-warmed oocytes and their subsequent developmental competence were measured.

RESULTS

Ultrastructural alterations of granulosa cells vitrified in the presence of genistein or Z-VAD-FMK were slighter than that of granulosa cells vitrified in the absence of genistein or Z-VAD-FMK. The incidence of apoptotic follicles vitrified in the presence of genistein or Z-VAD-FMK was significantly lower than that of immature oocytes vitrified in the absence of genistein or Z-VAD-FMK, whereas, the level of SOD in granulosa cells, the viability and developmental competence of immature oocytes vitrified in the presence of genistein or Z-VAD-FMK were significantly higher than that of immature oocytes vitrified in the absence of genistein or Z-VAD-FMK.

CONCLUSION

Both antioxidant (genistein) and caspase inhibition (Z-VAD-FMK) improve the viability and developmental competence of vitrified immature oocytes. Genistein is superior to Z-VAD-FMK in improving the efficacy of immature oocyte vitrification.

Female fertility: is it safe to "freeze?"

Objective:

To evaluate the safety and risk of cryopreservation in female fertility preservation.

Data sources:

The data analyzed in this review were the English articles from 1980 to 2013 from journal databases, primarily PubMed and Google scholar. The criteria used in the literature search show as following: (1) human; embryo; cryopreservation/freezing/vitrification, (2) human; oocyte/immature oocyte; cryopreservation/ freezing/vitrification, (3) human; ovarian tissue transplantation; cryopreservation/freezing/vitrification, (4) human; aneuploidy/DNA damage/epigenetic; cryopreservation/freezing/vitrification, and (5) human; fertility preservation; maternal age.

Study selection:

The risk ratios based on survival rate, maturation rate, fertilization rate, cleavage rate, implantation rate, pregnancy rate, and clinical risk rate were acquired from relevant meta-analysis studies. These studies included randomized controlled trials or studies with one of the primary outcome measures covering cryopreservation of human mature oocytes, embryos, and ovarian tissues within the last 7 years (from 2006 to 2013, since the pregnancy rates of oocyte vitrification were significantly increased due to the improved techniques). The data involving immature oocyte cryopreservation obtained from individual studies was also reviewed by the authors.

Results:

Vitrifications of mature oocytes and embryos obtained better clinical outcomes and did not increase the risks of DNA damage, spindle configuration, embryonic aneuploidy, and genomic imprinting as compared with fresh and slow-freezing procedures, respectively.

Conclusions:

Both embryo and oocyte vitrifications are safe applications in female fertility preservation.

In vitro maturation (IVM) of oocytes recovered from ovariectomy specimens in the laboratory: a promising "ex vivo" method of oocyte cryopreservation resulting in the first report of an ongoing pregnancy in Europe

PURPOSE

We present our center's experience with 34 consecutive cases who underwent in vitro maturation (IVM) of oocytes obtained from ovariectomy specimens and compare our data with updated literature data.

METHODS

Feasibility and efficiency of oocyte collection during ovarian tissue processing was assessed by the recovery rate, maturation rate, and embryological development after IVM.

RESULTS

On average, 14 immature oocytes were retrieved per patient during ovarian tissue processing in 33/34 patients. The overall maturation rate after IVM was 36%. The maturation rate correlated with the age of the patient and the duration of IVM. Predominately, oocyte vitrification was performed. Eight couples preferred embryo cryopreservation. Here, a 65% fertilization rate was obtained and at least one good-quality day 3 embryo was cryopreserved in 7/8 couples. The retrieval of oocytes ex vivo resulted in mature oocytes or embryos available for vitrification in 79% of patients. One patient with ovarian insufficiency following therapeutic embolization of the left uterine and the right ovarian artery because of an arteriovenous malformation had an embryo transfer of one good-quality warmed embryo generated after IVM ex vivo, which resulted in an ongoing clinical pregnancy.

CONCLUSIONS

IVM of oocytes obtained ex vivo during the processing of ovarian cortex prior to cryopreservation is a procedure with emerging promise for patients at risk for fertility loss, as illustrated by the reported pregnancy. However, more data are needed in order to estimate the overall success rate and safety of this novel approach.

Developmental Competence of Vitrified-Warmed Bovine Oocytes at the Germinal-Vesicle Stage is Improved by Cyclic Adenosine Monophosphate Modulators during In Vitro Maturation

Cryopreservation of mature oocytes and embryos has provided numerous benefits in reproductive medicine. Although successful cryopreservation of germinal-vesicle stage (GV) oocytes holds promise for further advances in reproductive biology and clinical embryology fields, reports regarding cryopreservation of immature oocytes are limited. Oocyte survival and maturation rates have improved since vitrification is being performed at the GV stage, but the subsequent developmental competence of GV oocytes is still low. The purpose of this study was to evaluate the effects of supplementation of the maturation medium with cyclic adenosine monophosphate (cAMP) modulators on the developmental competence of vitrified-warmed GV bovine oocytes. GV oocytes were vitrified-warmed and cultured to allow for oocyte maturation, and then parthenogenetically activated or fertilized in vitro. Our results indicate that addition of a cAMP modulator forskolin (FSK) or 3-isobutyl-1-methylxanthine (IBMX) to the maturation medium significantly improved the developmental competence of vitrified-warmed GV oocytes. We also demonstrated that vitrification of GV oocytes led to a decline in cAMP levels and maturation-promoting factor (MPF) activity in the oocytes during the initial and final phases of maturation, respectively. Nevertheless, the addition of FSK or IBMX to the maturation medium significantly elevated cAMP levels and MPF activity during IVM. Taken together, our results suggest that the cryopreservation-associated meiotic and developmental abnormalities observed in GV oocytes may be ameliorated by an artificial increase in cAMP levels during maturation culture after warming.

Endoplasmic reticulum stress inhibition is a valid therapeutic strategy in vitrifying oocytes

The aim of this study is to determine the link between oocyte cryopreservation and endoplasmic reticulum (ER) stress; whether ER stress inhibition improves the efficiency of oocyte vitrification is also explored. Oocytes from mice were exposure to tauroursodeoxycholic acid (TUDCA, an ER stress inhibitor) or TM (tunicamycin, an ER stress inducer) with or without vitrification. The expressions of X-box binding protein-1 (XBP-1) protein and caspase-12 protein, viability of vitrified-warmed oocytes, and their subsequent embryo competence were measured. The levels of XBP-1 protein and caspase-12 protein expression in vitrified-warmed oocytes were significantly higher than those of fresh control oocytes. TUDCA improved the viability of vitrified-warmed oocytes and their subsequent embryo competence. Mouse oocyte cryopreservation is associated with ER stress, and ER stress inhibition improves the efficiency of oocyte vitrification.

Ultrastructure of immature and mature human oocytes after cryotop vitrification

In vitro maturation of vitrified immature germinal vesicle (GV) oocytes is a promising fertility preservation option. We analyzed the ultrastructure of human GV oocytes after Cryotop vitrification (GVv) and compared it with fresh GV (GVc), fresh mature metaphase II (MIIc) and Cryotop-vitrified mature (MIIv) oocytes. By phase contrast microscopy and light microscopy, the oolemmal and cytoplasmic organization of fresh and vitrified oocytes did not show significant changes. GVv oocytes showed significant ultrastructural alterations of the microvilli in 40% of the samples; small vacuoles and occasional large/isolated vacuoles were abnormally present in the ooplasm periphery of 50% of samples. The ultrastructure of nuclei and mitochondria-vesicle (MV) complexes, as well as the distribution and characteristics of cortical granules (CGs), were comparable with those of GVc oocytes. MIIv oocytes showed an abnormal ultrastructure of microvilli in 30% of the samples and isolated large vacuoles in 70% of the samples. MV complexes were normal, but mitochondria-smooth endoplasmic reticulum aggregates appeared to be of reduced size. CGs were normally located under the oolemma but presented abnormalities in distribution and matrix electron density. In conclusion, Cryotop vitrification preserved main oocyte characteristics in the GV and MII stages, even if peculiar ultrastructural alterations appeared in both stages. This study also showed that the GV stage appears more suitable for vitrification than the MII stage, as indicated by the good ultrastructural preservation of important structures that are present only in immature oocytes, like the nucleus and migrating CGs.

Live birth after frozen-thawed oocytes matured in vitro in a PCOS patient: a model for improving implantation rates in IVM cycles and objectively assessing the real potential of development of frozen oocytes matured in vitro

Over the past 20 years, in vitro maturation (IVM) of oocytes has emerged in the strategy of infertility treatment, with the main indication being in patients suffering from polycystic ovarian syndrome (PCOS). More recently, IVM has been proposed as an option for fertility preservation in women having to undergo gonadotoxic treatments. However, despite the increasing application of IVM, the potential of development of in vitro matured oocytes after thawing remains ill-established and few pregnancies have been reported so far. We report herein a case of live birth after frozen-thawed oocytes matured in vitro and embryo transfer during an artificial cycle in a 29-year-old patient with primary infertility due to PCOS. The present case demonstrates that the transfer of frozen-thawed IVM oocytes during an artificial cycle in PCOS patients is feasible and leads to pregnancy and live birth. This strategy may also be an interesting option to objectively assess the developmental potential of these oocytes after freezing and thawing, which is a major concern for physicians who include the IVM approach in their fertility preservation program.

In vitro growth and maturation of vitrified-warmed bovine oocytes collected from early antral follicles

Cryopreservation of growing oocytes enriches the choice of timing and location of artificial embryo production. However, completion of oocyte growth after warming is crucial when using such cryopreserved oocytes. Our research objective was to develop a sequential system that incorporates cryopreservation of growing bovine oocytes and their subsequent in vitro growth. Oocyte-granulosa cell complexes with a mean oocyte diameter of approximately 100 µm were vitrified-warmed and then cultured for 14 days. The percentage of surviving oocytes following cryopreservation and 14-day culture was approximately 80%. More than half of the surviving oocytes were capable of maturing to metaphase II after in vitro maturation; the rate was comparable to that of control oocytes grown in vitro without cryopreservation. Taken together, the combined protocols for vitrification-warming of growing oocytes and subsequent in vitro growth can produce oocytes capable of undergoing meiotic maturation.