In-vitro maturation of germinal vesicle and metaphase I eggs prior to cryopreservation optimizes reproductive potential in patients undergoing fertility preservation

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.

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.

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.

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.

Cryopreservation of human embryos and oocytes for fertility preservation in cancer and non cancer patients: a mini review

The term 'cryopreservation' illustrates the process of freezing cells and storing at very low temperature in liquid nitrogen (-196 °C). Cooling is not a physiological condition for human cells especially due to the high concentration of water in the living matter, whose conversion to ice crystals may be associated with cell death. Human oocytes are particularly sensitive to the freezing process, primarily because of their large size and the presence of the meiotic spindle, which at low temperature can degenerate. In the last decade, the cryopreservation technology has become highly important as an option for fertility preservation (FP) in women with cancer. Anticancer therapy might promote premature ovarian failure and negatively affects the reproductive outcome. Over the years, scientists have proposed different cryopreservation strategies in the effort to maintain the physiological functions of oocytes and embryo. However, despite the first success obtained in the 1980s with frozen oocytes, it was not until recently that a new approach has been proposed: the 'Vitrification' which allowed a breakthrough in this procedure. FP is a major determinant for cancer survivor women in the reproductive age. This article describes the FP options currently available, focusing mainly on oocyte and embryo cryopreservation.

FERTILITY PRESERVATION IN YOUNG WOMEN WITH EARLY-STAGE BREAST CANCER

Although breast cancer (BC) occurs more often in older women, it is the most commonly diagnosed malignancy in women of childbearing age. Owing to the overall advancement of modern medicine and the growing global trend of delaying childbirth until later age, we find ever more younger women diagnosed and treated for BC who have not yet completed their family. Therefore, fertility preservation has emerged as a very important quality of life issue for young BC survivors. This paper reviews currently available options for fertility preservation in young women with early-stage BC and highlights the importance of a multidisciplinary approach to fertility preservation as a very important quality of life issue for young BC survivors. Pregnancy after BC treatment is considered not to be associated with an increased risk of BC recurrence; therefore, it should not be discouraged for those women who want to achieve pregnancy after oncologic treatment. Currently, it is recommended to delay pregnancy for at least 2 years after BC diagnosis, when the risk of recurrence is highest. However, BC patients of reproductive age should be informed about the potential negative effects of oncologic therapy on fertility, as well as on the fertility preservation options available, and if interested in fertility preservation, they should be promptly referred to a reproductive specialist. Early referral to a reproductive specialist is an important factor that increases the likelihood of successful fertility preservation. Embryo and mature oocyte cryopreservation are currently the only established fertility preservation methods but they require ovarian stimulation (OS), which delays initiation of chemotherapy for at least 2 weeks. Controlled OS does not seem to increase the risk of BC recurrence. Other fertility preservation methods (ovarian tissue cryopreservation, cryopreservation of immature oocytes and ovarian suppression with gonadotropin-releasing hormone agonists) do not require OS but are still considered to be experimental techniques for fertility preservation.

Oocyte cryopreservation for women with GATA2 deficiency

PURPOSE

To describe controlled ovarian stimulation (COS) in a population of women with GATA2 deficiency, a genetic bone marrow failure syndrome, prior to allogeneic hematopoietic stem cell transplant METHODS: This is a retrospective case series of nine women with GATA2 deficiency who underwent oocyte preservation at a research institution. Main outcomes measured include baseline fertility characteristics ((antimullerian hormone (AMH) and day 3 follicle-stimulating hormone (FSH) and estradiol (E2)) and total doses of FSH and human menopausal gonadotropins (HMG), E2 on day of trigger, and total number of metaphase II oocytes retrieved.

RESULTS

The mean age was 24 years [16-32], mean AMH was 5.2 ng/mL [0.7-10], and day 3 mean FSH was 5.1 U/L [0.7-8.1], and E2 was 31.5 pg/mL [< 5-45]. The mean dose of FSH was 1774 IU [675-4035], and HMG was 1412 IU [375-2925] with a mean E2 of 2267 pg/mL [60.7-4030] on day of trigger. The mean total of metaphase II oocytes was 7.7 [0-15]. One patient was diagnosed with a deep vein thrombosis (DVT) with pulmonary embolism (PE) during COS.

CONCLUSION

This study is the first to analyze the outcomes of COS in women with GATA2 deficiency. The response to ovarian stimulation suggests that oocyte cryopreservation should be considered prior to gonadotoxic therapy. However, due to the risk of potentially life-threatening complications, it is prudent that patients are properly counseled of the risks and are evaluated by a multi-disciplinary medical team prior to COS.

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.

Production of Live Offspring from Vitrified-Warmed Oocytes Collected at Metaphase I Stage

Vitrification of matured oocytes is widely adopted in human clinics and animal research laboratories. Cryopreservation of immature oocytes, particularly those at metaphase I (MI), remains a challenge. In the present work, mouse MI oocytes denuded of cumulus cells were vitrified and warmed (V/W) either prior to (V/W-BEFORE-IVM, n = 562) or after (V/W-AFTER-IVM, n = 664) in vitro maturation (IVM). Derivative metaphase II (MII) oocytes were then used for intracytoplasmic sperm injection (ICSI). In the control groups, in vivo matured MII oocytes were used freshly (FRESH-MII, n = 517) or after V/W (MII-V/W, n = 617). In vitro and in vivo developmental competencies were compared among groups. Satisfactory blastocyst rates were achieved in V/W-BEFORE-IVM (27.5%) and V/W-AFTER-IVM (32.4%) groups, albeit as expected still lower than those from fresh-MII (56.1%) or MII-V/W (45.6%) oocytes. Similarly, the term development rates from V/W-BEFORE-IVM and V/W-AFTER-IVM were 12.4% and 16.7% respectively, acceptable but lower than those of the fresh-MII (41.2%) and MII-V/W (23.3%) groups. These data demonstrate that oocytes collected at MI stage are amenable to V/W, which can be performed before or after IVM with acceptable development rates including production of healthy pups. These findings provide useful knowledge to researchers and clinical practitioners for preservation and use of the otherwise discarded MI oocytes.

What threshold values of antral follicle count and serum AMH levels should be considered for oocyte cryopreservation after in vitro maturation?

STUDY QUESTION

What threshold values of ultrasonographic antral follicle count (AFC) and serum anti-Müllerian hormone (AMH) levels should be considered for ensuring the cryopreservation of sufficient number of in vitro matured (IVM) oocytes, in cancer patients seeking fertility preservation (FP)?

SUMMARY ANSWER

AFC and serum AMH values >20 follicles and 3.7 ng/ml, respectively, are required for obtaining at least 10 IVM oocytes for cryopreservation.

WHAT IS KNOWN ALREADY

IVM of cumulus oocyte complexes (COCs) followed by oocyte cryopreservation has emerged recently as an option for urgent FP. Recent data have reported that, in healthy patients, 8-20 cryopreserved oocytes after ovarian stimulation would maximize the chance of obtaining a live birth. Although both AFC and AMH have been reported as predictive factors of IVM success in infertile patients with polycystic ovary syndrome (PCOS), there is a dramatic lack of data regarding the values of these parameters in oncological patients as candidates for FP.

STUDY DESIGN, SIZE, DURATION

From January 2009 to April 2015, we prospectively studied 340 cancer patients, aged 18-41 years, as candidates for oocyte cryopreservation following IVM.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All patients had AFC and AMH measurements, 48-72 h before oocyte retrieval, regardless of the phase of the cycle. COCs were recovered under ultrasound guidance 36 h after hCG priming. Logistic regression allowed the determination of threshold values of AFC and AMH, for obtaining at least 8, 10 or 15 matures oocytes frozen after the IVM procedure. Similar analyses were performed for a final number of mature oocytes ≤2.

MAIN RESULTS AND THE ROLE OF CHANCE

Among the 340 cancer patients included, 300 were diagnosed with breast cancers, 14 had hematological malignancies and 26 underwent the procedure for others indications. Overall, the mean age of the population was 31.8 ± 4.5 years. Mean AFC and serum AMH levels were 21.7 ± 13.3 follicles and 4.4 ± 3.8 ng/ml, respectively. IVM was performed in equal proportions during the follicular or luteal phase of the cycle (49 and 51%, respectively). Statistical analysis showed that AFC and AMH values above 28 follicles and 3.9 ng/ml, 20 follicles and 3.7 ng/ml and 19 follicles and 3.5 ng/ml are required, respectively, for obtaining at least 15, 10 or 8 frozen IVM oocytes with a sensitivity ranging from 0.82 to 0.90. On the contrary, ≤2 IVM oocytes were cryopreserved when AFC and AMH were <19 follicles and 3.0 ng/ml, respectively.

LIMITATIONS, REASONS FOR CAUTION

Although the potential of cryopreserved IVM oocytes from cancer patients remains unknown, data obtained from infertile PCOS women have shown a dramatically reduced competence of these oocytes when compared with that of oocytes recovered after ovarian stimulation. As a consequence, the optimal number of IVM oocytes frozen in candidates for FP is currently unpredictable.

WIDER IMPLICATIONS OF THE FINDINGS

Cryopreservation of oocytes after IVM should be considered in the FP strategy when ovarian stimulation is unfeasible, in particular when markers of the follicular ovarian status are at a relatively high range. Further investigation is needed to objectively assess the real potential of these IVM oocytes after cryopreservation. Therefore, even when a good COCs yield is expected, we should systematically encourage IVM in combination with ovarian tissue cryopreservation.

STUDY FUNDING/COMPETING INTERESTS

No external funding was obtained for the present study. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

The impact of vitrification on murine germinal vesicle oocyte In vitro maturation and aurora kinase A protein expression

PURPOSE

Investigate the effect of vitrification on in vitro maturation (IVM) and expression of Aurora kinases A, B, and C in germinal vesicle (GV)-stage oocytes.

METHODS

GV-stage oocytes from B6D2F1 female mice 7-11 weeks of age were vitrified after collection, thawed, and matured in vitro for 0, 4, 8, and 12 h (hrs). The rate of germinal vesicle breakdown (GVBD), spindle apparatus assembly, and Aurora kinase mRNA and protein expression during IVM was measured.

RESULTS

Oocyte vitrification was associated with significant delays in both GVBD and normal spindle apparatus assembly at 4 and 8 h of IVM (p < 0.05). There was no difference in mRNA levels between control and vitrified oocytes for any of the Aurora kinases. Aurora A protein levels were reduced in vitrified compared to control oocytes at 0 h (p = 0.008), and there was no difference at 4 and 8 h (p = 0.08 and 0.69, respectively) of IVM.

CONCLUSIONS

Vitrified oocytes have delayed GVBD and normal spindle assembly during in vitro maturation. Reduced levels of Aurora A protein immediately post-thaw may be associated with the impaired oocyte maturation manifested by the delayed progression through meiosis I and II, and the atypical timing of the formation of meiotic spindles in vitrified GV-stage oocytes.

[In vitro oocyte maturation for female fertility preservation]

Recovering immature oocytes from unstimulated ovaries, followed by in vitro maturation (IVM) was initially proposed to avoid the risks and side effects of exogenous gonadotropin administration. Therefore, during the past decades, IVM was mainly offered to patients with polycystic ovary syndrome at high risk of ovarian hyperstimulation syndrome. However, the development of fertility preservation has recently opened new perspectives in the field of IVM. The present review reports the possible indications of IVM, in the strategy of female fertility preservation.