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

Effects of intracellular Ca2+ on developmental potential and ultrastructure of cryopreserved-warmed oocyte in mouse

Maintaining appropriate intracellular calcium of oocytes is necessary to prevent ultrastructure and organelle damage caused by freezing and cryoprotectants. The present study aimed to investigate whether cryoprotectant-induced changes in the calcium concentrations of oocytes can be regulated to reduce damage to developmental potential and ultrastructure. A total of 33 mice and 1381 oocytes were used to explore the effects of intracellular calcium on the development and ultrastructures of oocytes subjected to 2-aminoethoxydiphenyl borate (2-APB) inhibition or thapsigargin (TG) stimulation. Results suggested that high levels intracellular calcium interfered with TG compromised oocyte survival (84.4 % vs. 93.4 %, p < 0.01) and blastocyst formation in fresh and cryopreservation oocytes (78.1 % vs. 86.4 %, and 60.5 % vs. 72.5 %, p < 0.05) compared with that of 2-APB pretreated oocytes in which Ca2+ was stabilized even though no differences in fertilization and cleavage was detected (p > 0.05). Examination by transmission electron microscopy indicated that the microvilli decreased and shortened, cortical granules considerably decreased in the cortex area, mitochondrial vesicles and vacuoles increased, and the proportion of vacuole mitochondria increased after oocytes were exposed to cryoprotectants. The cryopreservation-warming process deteriorated the negative effects on organelles of survival oocytes. By contrast, a low level of intracellular calcium mediated with 2-APB was supposed to contribute to the protection of organelles. These findings suggested oocyte injuries induced by cryoprotectants and low temperatures can be alleviated. More studies are necessary to confirm the relationship among Ca2+ concentration of the cytoplasm, ultrastructural injuries, and disrupted developmental potential in oocytes subjected to cryopreservation and warming.

Optimal antimüllerian hormone levels in oocyte donors: a national database analysis

OBJECTIVE

To study the relationship between high antimüllerian hormone (AMH) levels in oocyte donors and embryo development and pregnancy outcomes among donor oocyte recipients.

DESIGN

Retrospective cohort study.

SETTING

Donor Egg Bank Database.

PATIENTS

Patients undergoing in vitro fertilization using vitrified donor oocytes from 35 in vitro fertilization centers in the United States between 2013 and 2021. For each recipient, the first oocyte lot that was received with a planned insemination and embryo transfer (ET) was included.

INTERVENTION

Oocyte donor-recipient cycles.

MAIN OUTCOME MEASURES

Ongoing pregnancy rate (OPR) per ET.

RESULTS

A total of 3,871 donor oocyte-recipient thaw cycles were analyzed. On the basis of donor AMH serum concentration, cycles were stratified into the high AMH group (AMH ≥5 ng/mL; n = 1,821) and the referent group (AMH <5 ng/mL; n = 2,050). Generalized estimating equation models were used to account for donors that contributed more than one lot of oocytes. The number of usable embryos per lot (median [interquartile range]) was significantly increased in the high AMH group (2 [2-4]) compared with the referent group (2 [1-3]) (relative risk [RR] 1.06; confidence interval [CI] 1.01-1.12). Among recipients with a planned ET, there was no difference in OPR between the high AMH group (45.4%) and the referent group (43.5%) (RR 1.04; 95% CI 0.94-1.15). Among preimplantation genetic testing for aneuploidy cycles, the embryo euploidy rate per biopsy was similar at 66.7% (50%-100%) in both groups (RR 1.04; CI 0.92-1.17). The OPR per euploid ET among patients who used preimplantation genetic testing for aneuploidy was also comparable, at 52% in the high AMH group and 54.1% in the referent group (RR 0.95; CI 0.74-1.23).

CONCLUSION

This large national database study observed that there was no association between a high level of AMH (≥5 ng/mL) in oocyte donors and an OPR in the recipient after the first ET. On the basis of these findings, recipients and physicians can be reassured that oocyte donors with a high AMH level can be expected to produce outcomes that are at least as good as donors with an AMH level (<5 ng/mL).

The live birth rate of vitrified oocyte accumulation for managing diminished ovarian reserve: a retrospective cohort study

BACKGROUND

Vitrified M-II oocyte accumulation for later simultaneous insemination has been used for managing POR. Our study aimed to determine whether vitrified oocyte accumulation strategy improves live birth rate (LBR) for managing diminished ovarian reserve (DOR).

METHODS

A retrospective study included 440 women with DOR fulfilling Poseidon classification groups 3 and 4, defined as the presence of serum anti-Müllerian hormone (AMH) hormone level < 1.2 ng/ml or antral follicle count (AFC) < 5, from January 1, 2014, to December 31, 2019, in a single department. Patients underwent accumulation of vitrified oocytes (DOR-Accu) and embryo transfer (ET) or controlled ovarian stimulation (COS) using fresh oocytes (DOR-fresh) and ET. Primary outcomes were LBR per ET and cumulative LBR (CLBR) per intention to treat (ITT). Secondary outcomes were clinical pregnancy rate (CPR) and miscarriage rate (MR).

RESULTS

Two hundred eleven patients underwent simultaneous insemination of vitrified oocyte accumulation and ET in the DOR-Accu group (maternal age: 39.29 ± 4.23 y, AMH: 0.54 ± 0.35 ng/ml), and 229 patients underwent COS and ET in the DOR-fresh group (maternal age: 38.07 ± 3.77 y, AMH: 0.72 ± 0.32 ng/ml). CPR in the DOR-Accu group was similar in the DOR-fresh group (27.5% vs. 31.0%, p = 0.418). However, MR was statistically higher (41.4% vs. 14.1%, p = 0.001), while LBR per ET was statistically lower (15.2% vs. 26.2%, p < 0.001) in the DOR-Accu group. There is no difference in CLBR per ITT between groups (20.4% vs. 27.5%, p = 0.081). The secondary analysis categorized clinical outcomes into four groups regarding patients' age. CPR, LBR per ET, and CLBR did not improve in the DOR-Accu group. In the group of 31 patients, accumulated vitrified metaphase II (M-II) oocytes reached a total number of ≥ 15, and CPR improved among the DOR-Accu group (48.4% vs. 31.0%, p = 0.054); however, higher MR (40.0% vs. 14.1%, p = 0.03) resulted in similar LBR per ET (29.0% vs. 26.2%, p = 0.738).

CONCLUSIONS

Vitrified oocyte accumulation for managing DOR did not improve LBR. Higher MR resulted in lower LBR in the DOR-Accu group. Therefore, the vitrified oocyte accumulation strategy for managing DOR is not clinically practical.

TRIAL REGISTRATION

The study protocol was retrospectively registered and was approved by Institutional Review Board of Mackay Memorial Hospital (21MMHIS219e) on August 26, 2021.

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.

Factors affecting live birth rates in donor oocytes from commercial egg banks vs. program egg donors: an analysis of 40,485 cycles from the Society for Assisted Reproductive Technology registry in 2016-2018

OBJECTIVE

To examine the differences in live birth rates (LBRs), with single embryo transfer (SET), using oocytes from program generated egg donors vs. commercial egg bank donors and other factors affecting LBRs using donor oocytes.

DESIGN

Retrospective cohort study.

SETTING

Not applicable.

PATIENT(S)

A total of 40,485 in vitro fertilization cycles using donor oocytes reported to the Society for Assisted Reproductive Technology registry in 2016-2018.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth rate and cumulative LBR for SET using donor oocytes.

RESULT(S)

Multivariate results from the first SET from 19,128 cycles, including 15,429 from program generated egg donors and 3,699 from commercial egg banks, showed, when controlling for all other variables, the following: the LBR in the first SET cycle using commercial egg banks was 53.3% compared with 55.4% using program recruited egg donors (odds ratio [OR], 0.92); a reduction in the LBR with increasing recipient age, ages 40-44 years (OR, 0.80), 45-49 years (OR, 0.77), and >49 years (OR, 0.65); a steady decline in the LBR with increases in recipient body mass index above normal; and a steady increase in the LBR in association with >16 oocytes retrieved. Double embryo transfer increased the LBR (SET, 52%, vs. double embryo transfer, 58%) but also significantly increased the multiple pregnancy LBR, with 43% twins and 0.9% triplets. Blastocyst transfer had a higher LBR than cleavage stage embryos (52.5% vs. 39.5%). Intracytoplasmic sperm injection vs. conventional insemination when using fresh oocytes from program donors had similar LBRs.

CONCLUSION(S)

When performing in vitro fertilization using donor oocytes with SET, the LBR is affected by oocyte source, recipient age, recipient body mass index, stage of embryo at transfer, and number of oocytes retrieved.

Evidence-based outcomes after oocyte cryopreservation for donor oocyte in vitro fertilization and planned oocyte cryopreservation: a guideline

OBJECTIVE

To provide evidence-based recommendations to practicing physicians and others regarding the efficacy of oocyte cryopreservation (OC) for donor oocyte in vitro fertilization and planned OC.

METHODS

The American Society for Reproductive Medicine conducted a literature search, which included systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 1986 to 2018. The American Society for Reproductive Medicine Practice Committee and a task force of experts used available evidence and through consensus developed evidence-based guideline recommendations.

MAIN OUTCOME MEASURE(S)

Outcomes of interest included live birth rate, clinical pregnancy rate, obstetrical and neonatal outcomes, and factors predicting reproductive outcomes.

RESULT(S)

The literature search identified 30 relevant studies to inform the evidence base for this guideline.

RECOMMENDATION(S)

Evidence-based recommendations were developed for predicting the likelihood of live births after planned OC, autologous OC in infertile women, and donor OC, as well as factors that may impact live birth rates. Recommendations were developed regarding neonatal outcomes after using fresh vs. cryopreserved oocytes in cases of autologous or donor oocytes.

CONCLUSION(S)

There is insufficient evidence to predict live birth rates after planned OC. On the basis of limited data, ongoing and live birth rates appear to be improved for women who undergo planned OC at a younger vs. older age. Although there are no significant differences in per transfer pregnancy rates with cryopreserved vs. fresh donor oocytes, there is insufficient evidence that the live birth rate is the same with vitrified vs. fresh donor oocytes. Neonatal outcomes appear similar with cryopreserved oocytes compared with fresh oocytes. Future studies that compare cumulative live birth rates are needed.

Comparing four laboratory three-parent techniques to construct human aged non-surrounded nucleolus germinal vesicle oocytes: A case-control study

Background

The three-parent assisted reproductive technique may increase oocyte competence.

Objective

In this case-control study, the suitability of germinal vesicle transfer (GVT), synchronous ooplasmic transfer (sOT), asynchronous ooplasmic transfer using cryopreserved MII oocyte (caOT), and asynchronous ooplasmic transfer using waste MII oocyte (waOT) for maturation of the human-aged non-surrounded nucleolus germinal vesicle-stage (NSN-GV) oocyte were investigated.

Materials and Methods

NSN-GV oocytes were subjected to four methods: group A (GVT), B (sOT), C (caOT) D (waOT), and E (Control). The fusion rates, MI, MII, ICSI observations and cleavage at 2-cell, 4-cell, and 8-cell stages were compared in the groups.

Results

In GVT, none of the oocytes fused. In sOT, all oocytes fused, 20 achieved the MI, 14 progressed to MII, 8 fertilized, 6 cleaved and 5, 4, and 3 achieved the 2-cells, 4-cells and 8-cells, respectively. In caOT, all oocytes fused and achieved the MI, 8 progressed to MII and fertilized, 6 cleaved and 6, 5, and 5 achieved the 2-cells, 4-cells, and 8-cells respectively. In waOT, all oocytes fused, 5 and 3 progressed to MI and MII, respectively, but only one fertilized, cleaved and reached a 4-cells stage. In group E, 6 and 2 oocytes progressed to MI and MII, respectively, and only one fertilized but arrested at the zygote stage. caOT had the highest survival rate when compared to sOT (p = 0.04), waOT (p = 0.002), and control (p = 0.001).

Conclusion

The caOT method was beneficial over sOT, waOT, and GVT in supplementing the developmental capacity of human-aged NSN-GV oocytes.

Chemotherapy Associated Ovarian Failure

As the incidence of malignancies in young adults is increasing, fertility preservation in cancer survivors arises as a major concern. Especially among female cancer patients, pregnancy rates are estimated to be 40% lower compared to women of the same age. Nowadays oncologists are to be preoccupied not only with their patients' successful treatment, but also with the maintenance of the potential of the latter to conceive and obtain children. Chemotherapy associated ovarian failure (COF), refers to disruption of ovarian function both as an endocrine gland and as a reproductive organ, due to previous exposure to chemotherapy agents. Although the underlying mechanism is not fully understood, it is supposed that chemotherapy agents may induce either DNA damage of premature ovarian follicle or early activation and apoptosis of them, resulting into early exhaustion of available follicle deposit. Various chemotherapy agents have been associated with COF with the highest incidence being reported for patients undergoing combination regimens. Although a variety of alternatives in order to maintain ovarian function and fertility in female cancer survivors are available, adequately established practices to do so are lacking. Thus, it is of major importance to investigate further and collect sufficient evidence, aiming to guide patients and physicians in everyday clinical practice.

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.

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

Background

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

Results

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

Conclusions

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

Electronic supplementary material

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