A brief history of oocyte cryopreservation: Arguments and facts

Astaxanthin Added during Post-Warm Recovery Mitigated Oxidative Stress in Bovine Vitrified Oocytes and Improved Quality of Resulting Blastocysts

Various antioxidants are tested to improve the viability and development of cryopreserved oocytes, due to their known positive health effects. The aim of this study was to find whether astaxanthin (AX), a xanthophyll carotenoid, could mitigate deteriorations that occurred during the vitrification/warming process in bovine oocytes. Astaxanthin (2.5 µM) was added to the maturation medium during the post-warm recovery period of vitrified oocytes for 3 h. Afterward, the oocytes were fertilized in vitro using frozen bull semen and presumptive zygotes were cultured in the B2 Menezo medium in a co-culture with BRL-1 cells at 38.5 °C and 5% CO2 until the blastocyst stage. AX addition significantly reduced ROS formation, lipid peroxidation, and lysosomal activity, while increasing mitochondrial activity in vitrified oocytes. Although the effect of AX on embryo development was not observed, it stimulated cell proliferation in the blastocysts derived from vitrified oocytes and improved their quality by upregulation or downregulation of some genes related to apoptosis (BCL2, CAS9), oxidative stress (GPX4, CDX2), and development (GJB5) compared to the vitrified group without AX. Therefore, the antioxidant properties of astaxanthin even during short exposure to bovine vitrified/warmed oocytes resulted in improved blastocyst quality comparable to those from fresh oocytes.

Planned oocyte cryopreservation: a systematic review and meta-regression analysis

BACKGROUND

Awareness of the age-related decline in fertility potential has increased the popularity of planned oocyte cryopreservation (POC). However, data regarding outcomes of POC, including rates of women returning to thaw oocytes, as well as pregnancy and live birth rates, are scarce and based mostly on small case series.

OBJECTIVE AND RATIONALE

POC was defined as cryopreservation exclusively for prevention of future age-related fertility loss. The primary outcome was live birth rate per patient. The secondary outcomes included the return to thaw rate and laboratory outcomes. A meta-regression analysis examining the association between live birth and age above 40 or below 35 was conducted.

SEARCH METHODS

We conducted a systematic database search from inception to August 2022. The search included PubMed (MEDLINE) and EMBASE. Our search strategies employed a combination of index terms (Mesh) and free text words to compile relevant concepts. The systematic review and meta-regression were undertaken following registration of systematic review (PROSPERO registration number CRD42022361791) and were reported following guidelines of Preferred Reporting Items for Systematic Review and Meta-Analyses 2020 (PRISMA 2020).

OUTCOMES

The database search yielded 3847 records. After the selection process, 10 studies, conducted from 1999 to 2020, were included. Overall, 8750 women underwent POC, with a mean cryopreservation age of 37.2 (±0.8). Of those, 1517 women returned to use their oocytes with a return rate of 11.1% (± 4.7%). The mean age at the time of cryopreservation for women who returned to use their oocytes was 38.1 (±0.4), with an average of 12.6 (±3.6) cryopreserved oocytes per woman. In a meta-analysis, the oocyte survival rate was 78.5% with a 95% CI of 0.74-0.83 (I2 = 93%). The live birth rate per patient was 28% with a 95% CI of 0.24-0.33 (I2 = 92%). Overall, 447 live births were reported. In a sub-group analysis, women who underwent cryopreservation at age ≥40 achieved a live birth rate per patient of 19% (95% CI 0.13-0.29, I2 = 6%), while women aged ≤35 years old or younger had a higher live birth rate per patient of 52% (95% CI 0.41-0.63, I2 = 7%).

WIDER IMPLICATIONS

POC emerges as a feasible option for women aiming to improve their chances of conceiving at a later reproductive age. Nonetheless, it must be acknowledged that the overall success rates of POC are limited and that the likelihood of successful live birth declines as the age at cryopreservation rises. With increasing interest in POC, the collation of comprehensive and high-quality data is imperative to clearly define the outcomes for various age groups.

REGISTRATION NUMBER

CRD42022361791.

A comparative analysis of the clinical pregnancy and perinatal outcomes between oocyte vitrification and embryo vitrification based on the propensity score matching method

PURPOSE

This study investigated the safety and effectiveness of oocyte vitrification by comparing the clinical pregnancy and perinatal outcomes between transfer cycles of vitrified oocytes and those of vitrified embryos.

METHODS

A retrospective cohort study was conducted to analyze the clinical data of patients who underwent cleavage-stage embryo transfer at the Department of Reproductive Medicine between January 2011 and June 2021. Seventy-seven transfer cycles of fresh cleavage-stage embryos developed from vitrified-thawed oocytes (oocyte vitrification group) and 2170 transfer cycles of vitrified-thawed cleavage-stage embryos developed from fresh oocytes (embryo vitrification group) were included. Further, 293 cases were selected from the embryo vitrification group after applying propensity score matching at 1:4. The primary outcomes were miscarriage rate, live birth rate, and neonatal birth weight.

RESULTS

No statistically significant differences were observed in the baseline data, pregnancy, perinatal outcomes, or neonatal outcomes for either singleton or twin births between the two groups after matching. Backwards stepwise regression was used to analyze the length of gestation. The age of female participants (β =  - 0.410, 95% CI =  - 1.339 ~  - 0.620, P < 0.001) had a statistically significant effect.

CONCLUSION

Oocyte vitrification results in similar clinical pregnancy and perinatal outcomes as does embryo vitrification; hence, it is a relatively safe assisted reproductive technique.

Latent class analysis of Chinese healthcare providers' attitudes towards oocyte cryopreservation: a cross-sectional study

OBJECTIVES

The present study was designed to examine the attitudes towards oocyte cryopreservation among healthcare providers working in hospitals across specialties and potential influencing factors.

DESIGN

A cross-sectional study.

SETTING

The questionnaire was distributed among Chinese healthcare providers via the Credamo platform.

PARTICIPANTS

There were 877 respondents recruited from 8 April to 8 May 2022, among whom 160 were identified as unqualified because of inconsistency between the IP and work addresses.

OUTCOME MEASURES

Individual attitudes towards oocyte cryopreservation under four different settings, familiarity with oocyte cryopreservation and perceived risks about oocyte cryopreservation of healthcare providers were measured using a self-designed questionnaire.

RESULTS

There were 877 respondents recruited, and 717 were identified as qualified respondents. Two latent classes of healthcare providers characterised by different attitudes towards oocyte cryopreservation under four different settings were identified, the supportive and reluctant. Familiarity with oocyte cryopreservation had a significant direct effect on perceived risks, with better familiarity predicting lower perceived risks (β=-0.102, p<0.05). Perceived risks showed a significant direct effect on participants' attitudes towards oocyte cryopreservation, with higher perceived risks predicting a more reluctant attitude (β=0.165, p<0.001).

CONCLUSIONS

The majority of healthcare providers held a reluctant attitude towards oocyte cryopreservation of unmarried women for non-medical reasons, which might relate to their worries about the risks to offspring's health and lack of knowledge about a reproductive technique.

Vitrification of Mammalian Oocytes: Recent Studies on Mitochondrial Dysfunction

Vitrification of reproductive cells is definitely essential and integral in animal breeding, as well as in assisted reproduction. However, issues accompanied with this technology such as decreased oocyte competency and relatively low embryo survival rates appear to be a tough conundrum that has long perplexed us. As significant organelles in cell metabolism, mitochondria play pivotal roles in numerous pathways. Nonetheless, extensive evidence has demonstrated that vitrification can seriously impair mitochondrial function in mammalian oocytes. Thus, in this article, we summarize the current progress in oocyte vitrification and particularly outline the common mitochondrial abnormalities alongside subsequent injury cascades seen in mammalian oocytes following vitrification. Based on existing literature, we tentatively come up with the potential mechanisms related to mitochondrial dysfunction and generalize efficacious ways which have been recommended to restore mitochondrial function.

BRCA Mutations and Fertility Preservation

Hereditary cancers mostly affect the adolescent and young adult population (AYA) at reproductive age. Mutations in BReast CAncer (BRCA) genes are responsible for the majority of cases of hereditary breast and ovarian cancer. BRCA1 and BRCA2 act as tumor suppressor genes as they are key regulators of DNA repair through homologous recombination. Evidence of the accumulation of DNA double-strand break has been reported in aging oocytes, while BRCA expression decreases, leading to the hypothesis that BRCA mutation may impact fertility. Moreover, patients exposed to anticancer treatments are at higher risk of fertility-related issues, and BRCA mutations could exacerbate the treatment-induced depletion of the ovarian reserve. In this review, we summarized the functions of both genes and reported the current knowledge on the impact of BRCA mutations on ovarian ageing, premature ovarian insufficiency, female fertility preservation strategies and insights about male infertility. Altogether, this review provides relevant up-to-date information on the impact of BRCA1/2 mutations on fertility. Notably, BRCA-mutated patients should be adequately counselled for fertility preservation strategies, considering their higher sensitivity to chemotherapy gonadotoxic effects.

Examining reasons that patients discard cryopreserved oocytes

PURPOSE

Assess the rate, rationale, and characteristics of patients who cryopreserved and subsequently discarded their oocytes, and compare their characteristics to patients with continued cryopreservation of oocytes.

METHODS

All patients who disposed of cryopreserved oocytes between 2009 and 2022 reported their reason for discarding their oocytes. This was a retrospective cohort study.

RESULTS

Of 5,010 patients who underwent oocyte cryopreservation (OC) cycles, 201 (4%) patients elected to discard their oocytes and 751 (15%) thawed oocytes for clinical use. The average ages of OC and disposal were 35 and 39 years old, respectively. Of the 201 patients who discarded their oocytes, 71 patients (35%) requested disposal after having a child. Twenty-six (13%) discarded oocytes because of worsening cancer and three (1.4%) discarded because of death. 16 (8%) discarded oocytes due to cost of cryopreservation and eight (4%) due to low oocyte yield. Ten (5%) patients underwent new IVF cycles and discarded previously stored oocytes. Sixty-seven patients (33%) discarded oocytes for unspecified reasons. When comparing patients who discarded oocytes with those who did not, the former had lower AMH (2.7 vs 3.5 ng/ml, p < 0.001) but otherwise comparable age and number of cryopreserved oocytes. The mean age for those with continued cryopreservation was 35.4 years at time of OC and 40 years at time of data collection in June 2023.

CONCLUSION

Childbirth was the most common reason to dispose of oocytes followed by unspecified reasons. Larger studies of oocyte disposal may better define clinical characteristics of patients most likely to use, maintain or discard their oocytes.

Oocyte and embryo cryopreservation in assisted reproductive technology: past achievements and current challenges

Cryopreservation has revolutionized the treatment of infertility and fertility preservation. This review summarizes the milestones that paved the way to the current routinary clinical implementation of this game-changing practice in assisted reproductive technology. Still, evidence to support "the best practice" in cryopreservation is controversial and several protocol adaptations exist that were described and compared here, such as cumulus-intact vs. cumulus-free oocyte cryopreservation, artificial collapse, assisted hatching, closed vs. open carriers, and others. A last matter of concern is whether cryostorage duration may impact oocyte/embryo competence, but the current body of evidence in this regard is reassuring. From social and clinical perspectives, oocyte and embryo cryopreservation has evolved from an afterthought when assisted reproduction was intended for immediate pregnancy with supernumerary embryos of secondary interest to its current purpose, which primarily is to preserve fertility long-term and more comprehensively allow for family planning. However, the initial consenting process, which still is geared to short-term fertility care, may no longer be relevant when the individuals that initially preserved the tissues have completed their reproductive journey. A more encompassing counseling model is required to address changing patient values over time.

Ovarian tissue cryopreservation and transplantation: a review on reactive oxygen species generation and antioxidant therapy

Cancer is the leading cause of death worldwide. Fortunately, the survival rate of cancer continues to rise, owing to advances in cancer treatments. However, these treatments are gonadotoxic and cause infertility. Ovarian tissue cryopreservation and transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with significant follicle loss and an accompanying short lifespan of the grafts. There has been a decade of research in cryopreservation-induced oxidative stress in single cells with significant successes in mitigating this major source of loss of viability. However, despite its success elsewhere and beyond a few promising experiments, little attention has been paid to this key aspect of OTCT-induced damage. As more and more clinical practices adopt OTCT for fertility preservation, it is a critical time to review oxidative stress as a cause of damage and to outline potential ameliorative interventions. Here we give an overview of the application of OTCT for female fertility preservation and existing challenges; clarify the potential contribution of oxidative stress in ovarian follicle loss; and highlight potential ability of antioxidant treatments to mitigate the OTCT-induced injuries that might be of interest to cryobiologists and reproductive clinicians.

Live birth rate after female fertility preservation for cancer or haematopoietic stem cell transplantation: a systematic review and meta-analysis of the three main techniques; embryo, oocyte and ovarian tissue cryopreservation

STUDY QUESTION

What are the chances of achieving a live birth after embryo, oocyte and ovarian tissue cryopreservation (OTC) in female cancer survivors?

SUMMARY ANSWER

The live birth rates (LBRs) following embryo and oocyte cryopreservation are 41% and 32%, respectively, while for IVF and spontaneous LBR after tissue cryopreservation and transplantation, these rates are 21% and 33%, respectively.

WHAT IS KNOWN ALREADY

Currently, fertility preservation (FP) has become a major public health issue as diagnostic and therapeutic progress has made it possible to achieve an 80% survival rate in children, adolescents and young adults with cancer. In the latest ESHRE guidelines, only oocyte and embryo cryopreservation are considered as established options for FP. OTC is still considered to be an innovative method, while it is an acceptable FP technique in the American Society for Reproductive Medicine guidelines. However, given the lack of studies on long-term outcomes after FP, it is still unclear which technique offers the best chance to achieve a live birth.

STUDY DESIGN, SIZE, DURATION

We performed a systematic review and meta-analysis of published controlled studies. Searches were conducted from January 2004 to May 2021 in Medline, Embase and the Cochrane Library using the following search terms: cancer, stem cell transplantation, FP, embryo cryopreservation, oocyte vitrification, OTC and reproductive outcome.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 126 full-text articles were preselected from 1436 references based on the title and abstract and assessed via the Newcastle-Ottawa Quality Assessment Scale. The studies were selected, and their data were extracted by two independent reviewers according to the Cochrane methods. A fixed-effect meta-analysis was performed for outcomes with high heterogeneity.

MAIN RESULTS AND THE ROLE OF CHANCE

Data from 34 studies were used for this meta-analysis. Regarding cryopreserved embryos, the LBR after IVF was 41% (95% CI: 34-48, I2: 0%, fixed effect). Concerning vitrified oocytes, the LBR was 32% (95% CI: 26-39, I2: 0%, fixed effect). Finally, the LBR after IVF and the spontaneous LBR after ovarian tissue transplantation were 21% (95% CI: 15-26, I2: 0%, fixed-effect) and 33% (95% CI: 25-42, I2: 46.1%, random-effect), respectively. For all outcomes, in the sensitivity analyses, the maximum variation in the estimated percentage was 1%.

LIMITATIONS, REASONS FOR CAUTION

The heterogeneity of the literature prevents us from comparing these three techniques. This meta-analysis provides limited data which may help clinicians when counselling patients.

WIDER IMPLICATIONS OF THE FINDINGS

This study highlights the need for long-term follow-up registries to assess return rates, as well as spontaneous pregnancy rates and birth rates after FP.

STUDY FUNDING/COMPETING INTEREST(S)

This work was sponsored by an unrestricted grant from GEDEON RICHTER France. The authors have no competing interests to declare.

REGISTRATION NUMBER

CRD42021264042.

Reconsideration of the safety and effectiveness of human oocyte cryopreservation

Mature oocyte cryopreservation (OC) has become increasingly common since the American Society for Reproductive Medicine declared OC to no longer be experimental. Utilization of the open vitrification protocol has led to a marked improvement in the efficacy of oocyte cryopreservation. However, the safety and effectiveness of this cryopreservation method remain controversial. A previous report stated that among all initiated recipient cycles, the live-birth rate among recipients of all ages was significantly higher when using fresh donor oocytes (FDOs) rather than cryopreserved donor oocytes (CDOs). Confounding patient characteristics were noted as possible causes. OC stands as an acceptable elective medical intervention for preserving fertility in women. To further understand the effects of OC on the live birth rate resulting from fresh versus cryopreserved donor oocytes, reported data from the Society for Assisted Reproductive Technology from 2013 to 2020 were analyzed. The mean of the mean live-birth rate in all ages resulting from FDOs was 49.0% (44.6-53.3%) versus 41.0% (39.1-43.2%) for CDOs (difference, 8.0% [95% confidence interval, 5.35-10.57%], p value < 0.001). The lower live-birth rate observed for CDOs versus FDOs has been consistent throughout past decades. While there has been no reported increase in the aneuploidy rate for CDOs compared to FDOs, differences in the nondisjunction separation rate among different chromosomes were described in a recent report. Open vitrification culture medium usually contains high concentrations of cryoprotectants, such as 15% dimethyl sulfoxide (DMSO) and 15% ethylene glycol (EG). Recent studies showed that tissue culture with 0.1% DMSO or 10% EG resulted in deregulation of gene expression, disruption of epigenetic imprints, and accumulation of reactive oxygen species. The addition of melatonin, which can remove reactive oxygen species from vitrification medium, was shown to improve CDOs qualities and functions to conditions similar to those of FDOs; however, there were insufficient data to conclude that melatonin could improve the lower live-birth rate. These factors that affect live birth rates, birth defects, birth weights and developmental health cannot be ignored and perhaps need to be studied again and followed when evaluating the true effectiveness of human oocyte cryopreservation.

The Effects of Cryopreservation on the Cell Ultrastructure in Aquatic Organisms

This review provides an update on the current state of cryopreservation studies coupled with ultrastructural observation. Research in these fields has evolved and advanced since its inception in the 1950s. Different techniques have different advantages, but the researcher's technical proficiency is also necessary to derive a sound conclusion. Sperm samples are the most widely studied specimen because they are less sensitive to freezing and have high fluidity in the membrane and low water content. Some studies have also investigated oocytes, embryos, larvae, and algae from aquatic species. Cryopreservation studies have formulated a method applicable to every species of interest to preserve their biodiversity and prevent extinction. However, the avoidance of cryoinjury because of intracellular ice formation is a species-specific challenge. More comprehensive studies on ultrastructural observation can assist in understanding the underlying mechanisms of failed cellular responses to cryopreservation. Thus, optimizing protocols and increasing the survival rates of thawed samples can improve current cryopreservation techniques. Nevertheless, investigations into the effects of freezing on organisms' ultrastructure remain limited, especially regarding aquatic organisms.

Effect of bovine oocyte vitrification with EGTA and post-warming recovery with resveratrol on meiotic spindle, mitochondrial function, reactive oxygen species, and developmental competence

The present study aimed to determine the effects of the addition of EGTA to vitrification solutions and a post-warming recovery period supplemented with 1 μM resveratrol on meiotic spindle integrity, mitochondrial activity, ATP content, reactive oxygen species (ROS) levels, and developmental potential of partially denuded, vitrified-warmed bovine oocytes. Results of microtubule distribution and chromosomal arrangement indicated that resveratrol supplementation, irrespective to EGTA addition, reduced the incidence of abnormal meiotic spindles to similar levels of the control group. Mitochondrial membrane potential was similar in all groups, but ATP content was negatively affected by the vitrification-warming procedure and failed to recover after 4 h of post-warming culture. Resveratrol caused the reduction of ROS to lower levels of the control group, and showed the lowest ROS levels when combined with EGTA treatment. Oocytes in all vitrification groups presented lower developmental potential when compared to fresh oocytes. However, oocytes that underwent vitrification supplemented with EGTA and post-warming culture along with resveratrol showed higher developmental competence compared with vitrified-warmed oocytes not supplemented with resveratrol. The results of our study indicate that submitting vitrified-warmed, partially denuded bovine oocytes to a post-warming recovery period supplemented with 1 μM resveratrol improves vitrification outcomes. However, the benefits of EGTA on vitrification and warming of bovine oocytes need to be further investigated.

Unraveling female reproductive senescence to enhance healthy longevity

In a society where women often want successful careers and equal opportunities to men, the early nature of ovarian aging often forces women to make difficult life choices between career and family development. Fertility in women begins to decline after the age of 37 years and it is rare for pregnancies to occur after 45. This reproductive decline in women is inevitable and culminates in menopause, which is a major driver of age-related diseases. In a world where biomedical advances are leading to modifiable biological outcomes, it is time to focus on mitigating female reproductive senescence to maintain fertility and preserve age-related hormonal functions, with the goal of providing increased life choices and enhancing healthspan. To date, reproductive longevity research remains an understudied field. More needs to be done to unravel the biology of the ovarian follicles, which are the functional units of reproductive lifespan and are comprised of cell types including the oocyte (female gamete) and a group of specialized supporting somatic cells. Biological attempts to maintain the quality and quantity of follicles in animal models through manipulating pathways involved in aging can potentially prolong female reproductive lifespan and healthspan. Here, we summarize the molecular events driving ovarian aging and menopause and the interventional strategies to offset these events. Developing solutions to female reproductive senescence will open doors to discover ways to enhance true healthy longevity for both men and women.

Effects of human placenta cryopreservation on molecular characteristics of placental mesenchymal stromal cells

Cryopreservation of placenta tissue for long-term storage provides the opportunity in the future to isolate mesenchymal stromal cells that could be used for cell therapy and regenerative medicine. Despite being widely used, the established cryopreservation protocols for freezing and thawing still raise concerns about their impact on molecular characteristics, such as epigenetic regulation. In our study, we compared the characteristics of human placental mesenchymal stromal cells (hPMSCs) isolated from fresh (native) and cryopreserved (cryo) placenta tissue. We assessed and compared the characteristics of native and cryo hPMSCs such as morphology, metabolic and differentiation potential, expression of cell surface markers, and transcriptome. No significant changes in immunophenotype and differentiation capacity between native and cryo cells were observed. Furthermore, we investigated the epigenetic changes and demonstrated that both native and cryo hPMSCs express only slight variations in the epigenetic profile, including miRNA levels, DNA methylation, and histone modifications. Nevertheless, transcriptome analysis defined the upregulation of early-senescence state-associated genes in hPMSCs after cryopreservation. We also evaluated the ability of hPMSCs to improve pregnancy outcomes in mouse models. Improved pregnancy outcomes in a mouse model confirmed that isolated placental cells both from native and cryo tissue have a positive effect on the restoration of the reproductive system. Still, the native hPMSCs possess better capacity (up to 66%) in comparison with cryo hPMSCs (up to 33%) to restore fertility in mice with premature ovarian failure. Our study demonstrates that placental tissue can be cryopreserved for long-term storage with the possibility to isolate mesenchymal stromal cells that retain characteristics suitable for therapeutic use.

Improvement of Fertilization Capacity and Developmental Ability of Vitrified Bovine Oocytes by JUNO mRNA Microinjection and Cholesterol-Loaded Methyl-β-Cyclodextrin Treatment

Vitrification of oocytes is crucial for embryo biotechnologies, germplasm cryopreservation of endangered and excellent female animals, and the fertility of humans. However, vitrification significantly impairs the fertilization ability of oocytes, which significantly limits its widely used application. JUNO protein, a receptor for Izumo1, is involved in sperm-oocyte fusion and is an indispensable protein for mammalian fertilization, and its abundance is susceptible to vitrification. However, it is still unclear how vitrification reduces the fertilization capacity of bovine oocytes by affecting JUNO protein. This study was designed to investigate the effect of vitrification on the abundance and post-translational modifications of JUNO protein in bovine oocytes. Our results showed that vitrification did not alter the amino acid sequence of JUNO protein in bovine oocytes. Furthermore, the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis results showed that vitrification significantly reduced the number and changed the location of disulfide bonds, and increased the number of both phosphorylation and glycosylation sites of JUNO protein in bovine oocytes. Finally, the fertilization capacity and development ability of vitrified oocytes treated with 200 pg JUNO mRNA microinjection and cholesterol-loaded methyl-β-cyclodextrin (CLC/MβCD) were similar to those of fresh oocytes. In conclusion, our results showed that vitrification of bovine oocytes did not alter the protein sequence of JUNO, but induced post-translational modifications and changed protein abundance. Moreover, the fertilization and development ability of vitrified bovine oocytes were improved by the combination treatment of JUNO mRNA microinjection and CLC/MβCD.

The Beneficial Effects of Static Magnetic Field and Iron Oxide Nanoparticles on the Vitrification of Mature Mice Oocytes

This study was conducted to evaluate the effects of static magnetic field (SMF) and nanoparticles (NPs) on the vitrification of cumulus-oocyte-complex (COC). To this end, the non-vitrified (nVit) and vitrified groups (Vit) that contain NPs, with or without SMF were labeled nVit_NPs, nVit_NPs_SMF, Vit_NPs, and Vit_NPs_SMF, respectively. The non-toxic dosages of NPs were first determined to be 0.008% w/v. The survival, apoptosis, and necrosis, mitochondrial activity, fertilization rate, subsequent-derived embryo development, and gene expressions were examined. The viability rates obtained by trypan blue and Anx-PI staining were meaningfully smaller in the Vit groups, compared to the nVit groups. The JC1 red/green signal ratios were reduced considerably in the Vit group, compared to the nVit. Transmission electron microscopy (TEM) was performed to assess the entry of the NPs into the oocytes. TEM images showed that NPs were present in nVit_NPs, and Vit_NPs. Thereafter, the effects of NPs and SMF on in vitro fertilization (IVF) were examined. The difference in blastocyst rates between nVit and Vit_NPs_SMF groups was significant. Finally, Nanog, Cdx2, Oct4, and Sox2 genes were evaluated. There were substantial differences in Cdx2 gene expressions between the Vit_NPs and nVit groups. The expression of Nanog in Vit was significantly higher than those of the Vit_NPs, Vit_NPs_SMF, and nVit groups. The data presented here provide deeper insight into the application of iron oxide nanoparticles in COC vitrification. It appears that using SMF and supplemented CPA by NPs inhibits cryoinjury and promote the embryo development capacity of vitrified-warmed COCs.

Clinical outcome of planned oocyte cryopreservation at advanced age

PURPOSE

To report outcome of planned oocyte cryopreservation (POC) in the first 8 years of this treatment in our center.

METHODS

A retrospective study in a university-affiliated medical center.

RESULTS

A total of 446 women underwent POC during 2011-2018. Fifty-seven (13%) women presented to use these oocytes during the study period (until June 2021). POC was performed at a mean age of 37.9 ± 2.0 (range 33-41). Age at thawing was 43.3 ± 2.1 (range 38-49). A total of 34 (60%) women transferred their oocytes for thawing at other units. Oocyte survival after thawing was significantly higher at our center than following shipping to ancillary sites (78 vs. 63%, p = 0.047). Forty-nine women completed their treatment, either depleting their cryopreserved oocytes without conceiving (36) or attaining a live birth (13)-27% live birth rate per woman. Only one of eleven women who cryopreserved oocytes aged 40 and older had a live birth using thawed oocytes.

CONCLUSION

Women should be advised to complete planned oocyte cryopreservation before age 40, given low success rates in women who underwent cryopreservation at advanced reproductive age. In this study, oocyte shipping was associated with lower survival rate. These findings may be relevant for women considering POC and utilization of cryopreserved oocytes.

Germline stem cells in human

The germline cells are essential for the propagation of human beings, thus essential for the survival of mankind. The germline stem cells, as a unique cell type, generate various states of germ stem cells and then differentiate into specialized cells, spermatozoa and ova, for producing offspring, while self-renew to generate more stem cells. Abnormal development of germline stem cells often causes severe diseases in humans, including infertility and cancer. Primordial germ cells (PGCs) first emerge during early embryonic development, migrate into the gentile ridge, and then join in the formation of gonads. In males, they differentiate into spermatogonial stem cells, which give rise to spermatozoa via meiosis from the onset of puberty, while in females, the female germline stem cells (FGSCs) retain stemness in the ovary and initiate meiosis to generate oocytes. Primordial germ cell-like cells (PGCLCs) can be induced in vitro from embryonic stem cells or induced pluripotent stem cells. In this review, we focus on current advances in these embryonic and adult germline stem cells, and the induced PGCLCs in humans, provide an overview of molecular mechanisms underlying the development and differentiation of the germline stem cells and outline their physiological functions, pathological implications, and clinical applications.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Comparing the effects of a commercial and a prototype vitrification medium on meiotic spindle morphology and survival rate of mouse oocytes

OBJECTIVE

To compare oocyte survival and meiotic spindle normality between vitrified-warmed oocytes in a mouse embryo assay using Tvitri-4 or Ingámed vitrification media.

METHODS

C57BL/6 female mice aged 8-12 weeks were submitted to superovulation with pregnant mare's serum gonadotropin and human chorionic gonadotropin (hCG) for obtaining of in vivo matured oocytes. The oocytes were randomly distributed into one of the following three groups: CTR - control (fresh oocytes); ING - oocytes vitrified-warmed in a standard commercial kit supplied by Ingámed, and T4 - oocytes vitrified-warmed in the novel prototype Tvitri-4 medium. After warming and recovery culture, oocytes were assessed with respect to survival rate (SR) and both meiotic spindle morphology and chromosome alignment of each oocyte fixed in the sagittal position after immunostaining and analysis by confocal microscopy.

RESULTS

A total of 354 mature oocytes were vitrified in ING (n=178) and T4 (n=176), out of which 299 (85%) survived after warming. Oocyte survival rates were not statistically different (p=0.08) between ING (145/178=81.5%) and T4 (154/176=87.5%). Regarding meiotic normality, there were no significant changes in the proportion of oocytes with normal meiotic spindle morphology and chromosome structure between ING (52,2%) and T4 (63.4%) after warming (RR: 0.95, 95% CI: 0.92-1.607). When the meiotic normality was assessed using the CTR group as a reference in the analysis of relative risk, no significant differences were observed between T4 (63.4%) and CTR (70.5%) (RR: 0.95, 95% CI: 0.72-1.12). On the other hand, the percentage of oocytes retaining normal meiotic spindle morphology and chromosome configuration in ING (52.2%) was lower than in the CTR group (RR: 0.95, 95% CI: 0.57-0.97).

CONCLUSIONS

The novel prototype Tvitri-4 medium was efficient in preserve survival rate and meiotic spindle normality of oocytes and, with further verification, may be able to replace commercially available media in future clinical applications.

Mitochondria Transfer from Adipose Stem Cells Improves the Developmental Potential of Cryopreserved Oocytes

Although it is not a well-established technology, oocyte cryopreservation is becoming prevalent in assisted reproductive technologies in response to the growing demands of patients’ sociological and pathological conditions. Oocyte cryopreservation can adversely affect the developmental potential of oocytes by causing an increase in intracellular oxidative stresses and damage to the mitochondrial structure. In this study, we studied whether autologous adipose stem cell (ASC) mitochondria supplementation with vitrified and warmed oocytes could restore post-fertilization development that decreased due to mitochondrial damage following cryopreservation. ASC mitochondria showed similar morphology to oocytes’ mitochondria and had a higher ATP production capacity. The vitrified-warmed oocytes from juvenile mice were supplemented with ASC mitochondria at the same time as intracellular sperm injection (ICSI), after which we compared their developmental capacity and the mitochondria quality of 2-cell embryos. We found that, compared to their counterpart, mitochondria supplementation significantly improved development from 2-cell embryos to blastocysts (56.8% vs. 38.2%) and ATP production in 2-cell embryos (905.6 & 561.1 pmol), while reactive oxygen species levels were comparable. With these results, we propose that ASC mitochondria supplementation could restore the quality of cryopreserved oocytes and enhance the embryo developmental capacity, signifying another possible approach for mitochondrial transplantation therapy.

Optimizing embryological aspects of oocyte retrieval, oocyte denudation, and embryo loading for transfer: a state of the art review

Oocyte retrieval, oocyte denudation, and embryo transfer are crucial processes during assisted reproduction (ART). Air quality in the ART laboratory, temperature, pH of the media used and the time interval between oocyte retrieval and insemination are all critical factors. Anesthesia is required for oocyte retrieval, however evidence regarding the potential impact of different methods (general anesthesia, conscious sedation, and local anesthesia) on the clinical outcomes is unclear. The optimal timing of oocyte denudation following retrieval has not been established. Regarding the mechanical denudation process, there is a lack of evidence to demonstrate the safest minimum inner diameter of denuding pipettes used to complete the removal of granulosa cells surrounding the oocytes. During embryo transfer, many clinics worldwide flush the catheter before embryo loading, in an attempt to potentially rinse off any toxic agents; however, there is insufficient evidence to show that flushing the embryo transfer catheter before loading increases the success of ART outcome. Considering the serious gaps in knowledge in ART practice, the aim of this review is to provide an updated overview of the current knowledge regarding the various steps and techniques involved in oocyte retrieval, oocyte denudation, and embryo loading for transfer.

Acentriolar spindle assembly in mammalian female meiosis and the consequences of its perturbations on human reproduction

The purpose of meiosis is to generate developmentally competent, haploid gametes with the correct number of chromosomes. For reasons not completely understood, female meiosis is more prone to chromosome segregation errors than meiosis in males, leading to an abnormal number of chromosomes, or aneuploidy, in gametes. Meiotic spindles are the cellular machinery essential for the proper segregation of chromosomes. One unique feature of spindle structures in female meiosis is spindles poles that lack centrioles. The process of building a meiotic spindle without centrioles is complex and requires precise coordination of different structural components, assembly factors, motor proteins, and signaling molecules at specific times and locations to regulate each step. In this review, we discuss the basics of spindle formation during oocyte meiotic maturation focusing on mouse and human studies. Finally, we review different factors that could alter the process of spindle formation and its stability. We conclude with a discussion of how different assisted reproductive technologies (ART) could affect spindles and the consequences these perturbations may have for subsequent embryo development.

Embryology outcomes after oocyte vitrification with super-cooled slush nitrogen are similar to outcomes with conventional liquid nitrogen: a randomized controlled trial

OBJECTIVE

To determine whether the use of slush nitrogen (SN), a super-cooled form of nitrogen with a temperature from -207 to -210 °C, can improve oocyte survival after vitrification and warming compared with conventional liquid nitrogen (LN).

DESIGN

Randomized controlled trial.

SETTING

Academic-affiliated private practice.

PATIENT(S)

A total of 556 metaphase II oocytes from 32 oocyte donor cycles were included.

INTERVENTION(S)

Donor oocytes were block randomized to undergo vitrification with either SN or LN. Vitrification was followed by warming, fertilization with donor sperm, embryo culture to the blastocyst stage, and preimplantation genetic testing for aneuploidy via trophectoderm biopsy with targeted next-generation sequencing.

MAIN OUTCOME MEASURE(S)

The primary outcome was oocyte survival after vitrification and warming. Secondary outcomes included rates of fertilization, usable blastocyst formation, and whole chromosome aneuploidy.

RESULT(S)

Half of the metaphase II oocytes (n = 278) were randomized to undergo vitrification with SN, whereas the other half (n = 278) were randomized to undergo vitrification with LN. There were no statistically significant differences noted in oocyte survival rate (85.3% vs. 86.3%), fertilization rate (84.0% vs. 80.0%), rate of usable blastocyst formation (54.3% vs. 55.7%), or rate of whole chromosome aneuploidy (9.4% vs. 11.7%) between the SN and LN arms, respectively.

CONCLUSION(S)

The implementation of an SN oocyte vitrification protocol resulted in similar embryology outcomes compared with LN. The use of SN did not lead to any demonstrable improvement in oocyte survival after vitrification and warming.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04342364.

Enhanced Cellular Cryopreservation by Biopolymer-Associated Suppression of RhoA/ROCK Signaling Pathway

With increasing demands on long-term storage of cells, cryopreservation of cells is gaining more importance in cell-based research and applications. Dimethyl sulfoxide (DMSO) is a commonly used&nbsp;chemical cryoprotectant, providing increased cell survival during the freezing process. However, its use is limited in clinical applications due to its low biocompatibility above cryogenic temperatures. Herein, we present a new approach for reducing the use of DMSO in cryopreservation by using biodegradable hyaluronic acids (HAs). By adding HAs into cryoprotectant media containing a low concentration of DMSO, higher cell viability and cell proliferation rate were observed upon thawing after cryopreservation. The HA-supplemented cryopreservation media did not reduce the size of the ice crystal, which significantly influenced cell viability during cell freezing, but decreased the Ras homolog family member A (RhoA)/Rho-associated protein kinase (ROCK) signaling pathway related to apoptosis. The cell-interactive cryoprotectants containing HA can be applied to the development of a new cryoprotectant that reduces the adverse effect of DMSO.

Cryopreservation of Gametes and Embryos and Their Molecular Changes

The process of freezing cells or tissues and depositing them in liquid nitrogen at -196 °C is called cryopreservation. Sub-zero temperature is not a physiological condition for cells and water ice crystals represent the main problem since they induce cell death, principally in large cells like oocytes, which have a meiotic spindle that degenerates during this process. Significantly, cryopreservation represents an option for fertility preservation in patients who develop gonadal failure for any condition and those who want to freeze their germ cells for later use. The possibility of freezing sperm, oocytes, and embryos has been available for a long time, and in 1983 the first birth with thawed oocytes was achieved. From the mid-2000s forward, the use of egg vitrification through intracytoplasmic sperm injection has improved pregnancy rates. Births using assisted reproductive technologies (ART) have some adverse conditions and events. These risks could be associated with ART procedures or related to infertility. Cryopreservation generates changes in the epigenome of gametes and embryos, given that ART occurs when the epigenome is most vulnerable. Furthermore, cryoprotective agents induce alterations in the integrity of germ cells and embryos. Notably, cryopreservation extensively affects cell viability, generates proteomic profile changes, compromises crucial cellular functions, and alters sperm motility. This technique has been widely employed since the 1980s and there is a lack of knowledge about molecular changes. The emerging view is that molecular changes are associated with cryopreservation, affecting metabolism, cytoarchitecture, calcium homeostasis, epigenetic state, and cell survival, which compromise the fertilization in ART.

Antifreeze proteins for low-temperature preservation in reproductive medicine: A systematic review over the last three decades

Antifreeze proteins (AFPs) are synthesized by diverse non-mammalian species, allowing them to survive in severely cold environments. Since the 1990s, the scientific literature reports their use for low-temperature preservation of germplasm. The aim of this systematic review was to compile available scientific evidence regarding the use of AFP for low-temperature preservation of several reproductive specimens. Internet databases were consulted using the terms: "antifreeze protein" OR "AFP" OR "antifreeze glycoprotein" OR "AFGP" OR "ice-binding protein" OR "IBP" OR "thermal hysteresis protein" AND "cryopreservation". From 56 articles, 87 experiments testing AFPs in low-temperature preservation of gametes, embryos or reproductive tissues/cells were fully analyzed and outcomes were annotated. A positive outcome was considered as a statistically significant improvement on any parameter evaluated after low-temperature preservation with AFP, whereas a negative outcome included worsening of any evaluated parameter, in comparison to untreated groups or groups treated with a lower concentration of AFP. The findings indicated that research on the use of AFP as a cryoprotectant for reproductive specimens has increased markedly over the past decade. Some experiments reported both positive and negative results, which depended, on AFP concentration in the preservation media. Variation in the outcomes associated with species was also observed. Among the 66 experiments conducted in mammals, 77.3% resulted in positive, and 28.8% in negative outcomes after the use of AFP. In fishes, positive and negative outcomes were observed in 71.4% and 33.3% of 21 experiments, respectively. Most positive outcomes included preserving cell post-warming survival. The beneficial effect of AFP supports its use in cryobiological approaches used in human and veterinary medicines and animal protein industry. Moreover, combination of different AFP types, or AFP with antioxidants, or even the use of AFP-biosimilar, comprise some promising approaches to be further explored in cryopreservation.

Improved developmental potential of mouse vitrified-warmed oocytes achieved by culturing in recovery medium with glutathione ethyl ester (GSH-OEt)

PURPOSE

The aim of the present study was to investigate the effect of glutathione ethyl ester (GSH-OEt) in the recovery medium on the developmental competence of mouse vitrified-warmed MII oocytes.

METHODS

Vitrified-warmed oocytes were incubated for 1 h in recovery medium in the presence or absence of 0.5 mM GSH-OEt. The authors examined the effects of GSH-OEt, first on the levels of glutathione (GSH) and reactive oxygen species (ROS) in vitrified-warmed oocytes, and second, on in vitro blastocyst development, division speed to blastocysts, and total cell numbers of blastocysts from vitrified-warmed oocytes fertilized by Intracytoplasmic sperm injection (ICSI).

RESULTS

Adding GSH-OEt to the recovery medium significantly (p < 0.05) increased GSH content and decreased ROS levels in vitrified-warmed oocytes. The blastocyst rate did not differ significantly between the two groups, but the speed of development to blastocysts in the GSH-OEt (+) group was significantly more rapid. In addition, the total blastocyst cell number was significantly higher in the GSH-OEt (+) group than in the GSH-OEt (-) group (92.8 ± 5.1 vs. 71.4 ± 3.5, p < 0.01).

CONCLUSION

Adding GSH-OEt to the recovery medium of vitrified-warmed mouse oocytes enhances the development potential of oocytes and improves the quality of blastocysts.

Nomogram to predict pregnancy outcomes of emergency oocyte freeze-thaw cycles

Background:

Existing clinical prediction models for in vitro fertilization are based on the fresh oocyte cycle, and there is no prediction model to evaluate the probability of successful thawing of cryopreserved mature oocytes. This research aims to identify and study the characteristics of pre-oocyte-retrieval patients that can affect the pregnancy outcomes of emergency oocyte freeze-thaw cycles.

Methods:

Data were collected from the Reproductive Center, Peking University Third Hospital of China. Multivariable logistic regression model was used to derive the nomogram. Nomogram model performance was assessed by examining the discrimination and calibration in the development and validation cohorts. Discriminatory ability was assessed using the area under the receiver operating characteristic curve (AUC), and calibration was assessed using the Hosmer–Lemeshow goodness-of-fit test and calibration plots.

Results:

The predictors in the model of “no transferable embryo cycles” are female age (odds ratio [OR] = 1.099, 95% confidence interval [CI] = 1.003–1.205, P = 0.0440), duration of infertility (OR = 1.140, 95% CI = 1.018–1.276, P = 0.0240), basal follicle-stimulating hormone (FSH) level (OR = 1.205, 95% CI = 1.051–1.382, P = 0.0084), basal estradiol (E2) level (OR = 1.006, 95% CI = 1.001–1.010, P = 0.0120), and sperm from microdissection testicular sperm extraction (MESA) (OR = 7.741, 95% CI = 2.905–20.632, P < 0.0010). Upon assessing predictive ability, the AUC for the “no transferable embryo cycles” model was 0.799 (95% CI: 0.722–0.875, P < 0.0010). The Hosmer–Lemeshow test (P = 0.7210) and calibration curve showed good calibration for the prediction of no transferable embryo cycles. The predictors in the cumulative live birth were the number of follicles on the day of human chorionic gonadotropin (hCG) administration (OR = 1.088, 95% CI = 1.030–1.149, P = 0.0020) and endometriosis (OR = 0.172, 95% CI = 0.035–0.853, P = 0.0310). The AUC for the “cumulative live birth” model was 0.724 (95% CI: 0.647–0.801, P < 0.0010). The Hosmer–Lemeshow test (P = 0.5620) and calibration curve showed good calibration for the prediction of cumulative live birth.

Conclusions:

The predictors in the final multivariate logistic regression models found to be significantly associated with poor pregnancy outcomes were increasing female age, duration of infertility, high basal FSH and E2 level, endometriosis, sperm from MESA, and low number of follicles with a diameter >10 mm on the day of hCG administration.

'Why have women not returned to use their frozen oocytes?': a 5-year follow-up of women after planned oocyte cryopreservation

RESEARCH QUESTION

What are the reproductive choices and retrospective reflections of women at least 4 years after planned oocyte cryopreservation (POC)?

DESIGN

This was an internet survey, using the REDCap application, of women who underwent POC, at a single-centre university-affiliated IVF unit, 4-8 years before the survey. The questionnaire addressed reproductive choices and outcomes following POC.

RESULTS

Seventy-nine women who underwent POC during 2011-2014 were invited to participate, and 70 (89%) responded. Mean age at cryopreservation was 37.1 ± 2.4 (range 30-41) years, mean age at study participation 42.6 ± 2.6 (range 35-48) years, and mean time from first cryopreservation cycle to study participation 5.5 ± 1.3 (range 4-8) years. The main retrospectively reported reason for POC was not wanting to become pregnant without a partner (59, 84%). During the follow-up period, 44 women (63%) attempted to conceive either naturally or by assisted reproductive technology using fresh or cryopreserved oocytes. Of those, 28 women achieved a live birth (64% of those who tried to conceive). Fourteen respondents (20% of all respondents) reported using their cryopreserved oocytes, and three (21%) achieved a birth using those oocytes. Fifteen women (34%) of those who tried to conceive used donor spermatozoa.

CONCLUSIONS

The most common reasons for not using frozen oocytes were achieving pregnancy without frozen oocytes or preferring not to have a child without a partner. A considerable proportion of women who had POC and were not interested in being a single parent by choice eventually try to conceive using donor spermatozoa several years later.

Advanced Maternal Age Deteriorates the Developmental Competence of Vitrified Oocytes in Mice

Advanced maternal age (AMA) is known to be related to the decrease in the quality and quantity of oocytes. Oocyte vitrification is now considered an established assisted reproductive technology for fertility preservation. However, it remains unclear whether the oocytes in older women are more sensitive to various insults during vitrification. Thus, we evaluated whether AMA affects cellular and molecular features and developmental outcomes of oocytes after vitrification in mice. The oocytes were grouped as young fresh (YF), young vitrified/warmed (YV), aged fresh (AF), and aged vitrified/warmed (AV). The survival rate of AV oocytes was significantly lower than that of YV oocytes. The rates of fertilization, cleavage, and blastocyst formation of AV oocytes were significantly lower than those of other groups. AV oocytes were represented as aberrations in mitochondria distribution, microvacuole size, and autophagosome formation, leading to delayed embryo development in mice. This delay was associated with a reduced number of total cells and trophectoderm in the blastocyst developed from AV oocytes. Collectively, AMA exaggerates the vulnerability of oocytes to cryo-damage that occurs during vitrification in mice, suggesting that the current vitrification protocols optimized for oocytes from young females should be modified for oocytes from aged women.

Morphokinetic evaluation of embryos generated from vitrified oocytes maintaining the meiotic spindle

Vitrification is a technique for preservation of human oocytes. There is still a lack of basic research about the possible effects of vitrification on subsequent embryos following oocyte vitrification. The purpose of this study was to evaluate the embryo morphokinetic parameters formed after fertilization of vitrified-warmed oocytes, where an intact meiotic spindle (MS) was observed pre- and post-cryopreservation. Matured oocytes after in vitro maturation were collected and MS evaluation was performed. The oocytes with MS were divided into two groups: fresh and post vitrification. After intra-cytoplasmic sperm injection, the oocytes were cultured in time lapse monitoring (TLM) and time of second polar body extrusion (SPBE), pronuclei appearance (tPNA), pronuclei fading (tPNF), formation of two to eight cells (t2 to t8), and irregular cleavage events [direct cleavage (DC), reverse cleavage (RC)] and vacuolation were assessed. The fertilization rate was not significantly different between the groups, although the rate of abnormal fertilization was higher in vitrification group compared with fresh group (23.5% VS 7.7%). Analysis of the TLM showed a significant delay in time points, including SPBE, tPNA, tPNF, t 2-cells cleavage in vitrification group (p = 0.02, p = 0.00, p = 0.002, P = 0.00, P = 0.01, respectively). In addition, t3 and t4 time points tended to be delayed in vitrification group (p = 0.05). Moreover, the higher level of DC, RC and vacuolation were noticed in the vitrification group (P˂0.05). In conclusion, despite MS maintenance after warming, TLM evaluation showed both a delay and abnormal cleavage patterns in generated embryos.

Cryopreservation of both male and female gametes leads to reduced embryo development and implantation potential

The objective of this study was to investigate the effect of oocyte and sperm cryopreservation on donated eggs submitted to intracytoplasmic sperm injection (ICSI) cycles. Medical charts of 122 oocyte recipients undergoing 152 oocyte recipient ICSI cycles, from 2017 to 2018, in a private university-affiliated in vitro fertilization (IVF) centre, were reviewed in this historical cohort study. Cycles were divided into four groups according to the gamete status: the FO/FS Group, recipients in which fresh oocytes were injected with fresh sperm (n = 19); the FO/CrS Group, recipients in which fresh oocytes were injected with cryopreserved sperm (n = 14); the CrO/FS Group, recipients in which cryopreserved oocytes were injected with fresh sperm (n = 85); and the CrO/CrS Group, recipients in which cryopreserved oocytes were injected with cryopreserved sperm (n = 34). Generalized mixed models fit by restricted maximum likelihood, followed by Bonferroni post hoc test for the comparison of means amongst groups were used to investigate the effect of cryopreservation on recipient ICSI outcomes. The results were expressed as mean differences with 95% confidence intervals and P-values. The main outcome measure was the implantation rate. Normal day 3 cleavage speed, blastocyst development and implantation rates were significantly lower in the CrO/CrS Group compared with the FO/FS Group. In conclusion, embryo developmental competence and implantation potential were reduced when vitrified oocytes were injected with frozen sperm in an egg-sharing donation programme.

Oocyte competence is independent of the ovulation trigger adopted: a large observational study in a setting that entails vitrified-warmed single euploid blastocyst transfer

PURPOSE

To assess whether the GnRH-agonist or urinary-hCG ovulation triggers affect oocyte competence in a setting entailing vitrified-warmed euploid blastocyst transfer.

METHODS

Observational study (April 2013-July 2018) including 2104 patients (1015 and 1089 in the GnRH-a and u-hCG group, respectively) collecting ≥1 cumulus-oocyte-complex (COC) and undergoing ICSI with ejaculated sperm, blastocyst culture, trophectoderm biopsy, comprehensive-chromosome-testing, and vitrified-warmed transfers at a private clinic. The primary outcome measure was the euploid-blastocyst-rate per inseminated oocytes. The secondary outcome measure was the maturation-rate per COCs. Also, the live-birth-rate (LBR) per transfer and the cumulative-live-birth-delivery-rate (CLBdR) among completed cycles were investigated. All data were adjusted for confounders.

RESULTS

The generalized-linear-model adjusted for maternal age highlighted no difference in the mean euploid-blastocyst-rate per inseminated oocytes in either group. The LBR per transfer was similar: 44% (n=403/915) and 46% (n=280/608) in GnRH-a and hCG, respectively. On the other hand, a difference was reported regarding the CLBdR per oocyte retrieval among completed cycles, with 42% (n=374/898) and 25% (n=258/1034) in the GnRh-a and u-hCG groups, respectively. Nevertheless, this variance was due to a lower maternal age and higher number of inseminated oocytes in the GnRH-a group, and not imputable to the ovulation trigger itself (multivariate-OR=1.3, 95%CI: 0.9-1.6, adjusted p-value=0.1).

CONCLUSION

GnRH-a trigger is a valid alternative to u-hCG in freeze-all cycles, not only for patients at high risk for OHSS. Such strategy might increase the safety and flexibility of controlled-ovarian-stimulation with no impact on oocyte competence and IVF efficacy.

How fixed versus variable gonadotropin dose during controlled ovarian stimulation could influence the management of infertility patients undergoing IVF treatment: a national Delphi consensus

AIM

Define how and when fixed starting gonadotropin doses can be used in current clinical ART practices in Italy.

METHODS

A Delphi conference consisting of three rounds was performed in order to define the ideal clinical conditions in which fixed-gonadotropin-dose during COS should be applied. During the conference, 19 statements about the current ART practice were provided to a panel of twenty-nine national experts. Median score was 5 (IQ:4-6) in all Delphi rounds.

RESULTS

Eleven statements (57.9%) were classified as shareable with high-degree of convergence, 2 (10.5%) as shareable with low convergence and 6 (31.6%) as un-shareable with high convergence. The panel reached high consensus regarding some statements: (i) fixed FSH-dose in normoresponders and poor-responder, (ii) importance of predicting ovarian response before COS, considering multiple markers to select the right stimulation protocol for each patient, (iii) importance of therapy simplification and standardization to improve efficiency during COS. Moreover, a low-convergence was reached about use of GnRH antagonist as first treatment line and drug storage at room temperature. However from these findings, the debate remains open regarding some other statements: (a) usefulness of Bologna-criteria to define poor-responders; (b) efficacy to change always stimulation protocol after a failure IVF; (c) utility of AMH-dosed with standardized automatic mode to define normo-responder patients; (d) usefulness to modify the dosage of 12.5 IU/die during COS to improve stimulation effectiveness.

CONCLUSION

Controlled ovarian stimulation remains a challenging clinical step in Assisted Reproductive Technique, especially in some specific patient groups for which no clinical consensus is available. This study is the first attempt to describe the shared clinical opinion regarding the fixed versus variable gonadotropin dose in the real IVF practice.

Oocyte Biobanks: Old Assumptions and New Challenges

The preservation of fertility is a clinical issue that has been emerging considerably in recent decades, as the number of patients of childbearing age who risk becoming infertile for many reasons is increasing. The cryopreservation technique of oocytes has been developed for many years and nowadays constitutes a method of safe storage with impressive efficacy and high rates of successful thawing. The storage and use for research of oocytes taken for medical or non-medical can be carried out by both public and private structures, through egg sharing, voluntary egg donation and so-called “social freezing” for autologous use. This paper focuses on the oocyte bank as an emerging cryopreservation facility, in which a collaboration between public and private and the creation of a network of these biobanks can be useful in enhancing both their implementation and their functions. Good oocyte biobank practice would require that they be collected, stored, and used according to appropriate bioethical and bio-law criteria, collected and stored according to procedures that guarantee the best preservation of their structural components and a high level of safety, connected with appropriate procedures to protect the rights and privacy of the parties involved and associated with the results of the bio-molecular investigations that will be carried out gradually.

Fresh oocyte cycles yield improved embryo quality compared with frozen oocyte cycles in an egg-sharing donation programme

The objective of this study was to investigate any effect of cryopreservation of donated eggs on laboratorial and clinical outcomes of intracytoplasmic sperm injection (ICSI) cycles. This retrospective cohort study included 320 oocyte recipients undergoing 307 vitrified and 119 fresh oocyte recipient ICSI cycles, participating in an egg-sharing donation programme, from 2015 to 2018, in a private university-affiliated in vitro fertilization (IVF) centre. A review of donor and recipient ICSI cycles was charted. A general mixed models fit by restricted maximum likelihood, followed by Bonferroni post hoc test was used to compare the means between fresh and warm oocyte donation groups and investigate the effect of cryopreservation on recipient ICSI outcome. The main outcome measure was blastocyst development rates. Fertilization rate, high-quality embryo rates on days 2 and 3, normal cleavage speed rates on days 2 and 3, and blastocyst development rate were significantly higher for the fresh oocyte donation cycles compared with warmed oocyte donation cycles. In the egg-sharing donation programme, fertilization and embryo developmental competence were reduced when vitrified oocytes from infertile couples were used for ICSI compared with fresh oocytes.

Cryopreservation: An Overview of Principles and Cell-Specific Considerations

The origins of low-temperature tissue storage research date back to the late 1800s. Over half a century later, osmotic stress was revealed to be a main contributor to cell death during cryopreservation. Consequently, the addition of cryoprotective agents (CPAs) such as dimethyl sulfoxide (DMSO), glycerol (GLY), ethylene glycol (EG), or propylene glycol (PG), although toxic to cells at high concentrations, was identified as a necessary step to protect against rampant cell death during cryopreservation. In addition to osmotic stress, cooling and thawing rates were also shown to have significant influence on cell survival during low temperature storage. In general, successful low-temperature cell preservation consists of the addition of a CPA (commonly 10% DMSO), alone or in combination with additional permeating or non-permeating agents, cooling rates of approximately 1ºC/min, and storage in either liquid or vapor phase nitrogen. In addition to general considerations, cell-specific recommendations for hepatocytes, pancreatic islets, sperm, oocytes, and stem cells should be observed to maximize yields. For example, rapid cooling is associated with better cryopreservation outcomes for oocytes, pancreatic islets, and embryonic stem cells while slow cooling is recommended for cryopreservation of hepatocytes, hematopoietic stem cells, and mesenchymal stem cells. Yields can be further maximized by implementing additional pre-cryo steps such as: pre-incubation with glucose and anti-oxidants, alginate encapsulation, and selecting cells within an optimal age range and functional ability. Finally, viability and functional assays are critical steps in determining the quality of the cells post-thaw and improving the efficiency of the current cryopreservation methods.

Safety of Ovaleap® (Follitropin Alfa) in Infertile Women Undergoing Superovulation for Assisted Reproductive Technologies: A Multinational Comparative, Prospective Cohort Study

BACKGROUND

Ovaleap^® (follitropin alfa), a recombinant human follicle stimulating hormone, is a biosimilar medicinal product to Gonal-f^® and is used for ovarian stimulation. The main objective of this study was to assess the safety and effectiveness of Ovaleap^® compared to Gonal-f^® in one treatment cycle in routine clinical practice.

METHODS

Safety of Ovaleap^® Follitropin alfa in Infertile women undergoing superovulation for Assisted reproductive technologies (SOFIA) was a prospective cohort study conducted in six European countries. Eligible patients were infertile women undergoing superovulation for assisted reproductive technology, who were administered Ovaleap^® or Gonal-f^® for ovarian stimulation and were naïve to follicle stimulating hormone treatment. The recruitment ratio was 1:1. The primary endpoint was incidence proportion of ovarian hyperstimulation syndrome (OHSS) and the secondary endpoint was OHSS severity (Grades I, II, III). The effect of risk factors or potential confounders on the odds ratio for OHSS incidence as well as treatment effect on OHSS incidence was explored using univariate logistic regression. Pregnancy and live birth rates were also assessed.

RESULTS

A total of 408 women who were administered Ovaleap^® and 409 women who were administered Gonal-f^® were eligible for analysis. The incidence proportion of OHSS was 5.1% (95% CI: 3.4, 7.7) in the Ovaleap^® cohort and 3.2% (95% CI: 1.9, 5.4) in the Gonal-f^® cohort. This difference in OHSS incidence proportion between the two cohorts was not statistically significant neither before (p = 0.159) nor after univariate adjustment for each potential confounder (p > 0.05). The incidence proportion of OHSS severity grades was similar in the two treatment groups (3.4% versus 2.0% for Grade I, 1.2% versus 1.0% for Grade II, and 0.5% versus 0.2% for Grade III, in the Ovaleap^® and Gonal-f^® cohorts, respectively), without a significant statistical difference (p = 0.865, for each grade). Among patients who had embryo transfer, clinical pregnancy rates were 33% and 31% and live birth rates were 27% and 26%, in the two cohorts, respectively.

CONCLUSIONS

Findings from the SOFIA study indicate that the incidence proportions of OHSS and OHSS severity, as well as pregnancy and live birth rates, are similar between Ovaleap^® and Gonal-f^® treatments and corroborate the safety and effectiveness of Ovaleap^® as a biosimilar to Gonal-f^®.

On Ice: The impact of vitrification on the use of eggs in fertility treatment

The possibility to freeze sperm and embryos has long been available to men and women facing infertility as a result of an illness or medical treatment. However, the ability to successfully cryopreserve human eggs is comparatively recent. The introduction and increasing use of egg vitrification from the mid-2000s onwards, alongside the use of intracytoplasmic sperm injection, has seen improved ongoing clinical pregnancy rates compared with slow freezing methods. Despite concerns, the technology has been widely embraced by the scientific community and in recent years has been applied in a greater variety of contexts. In this short perspective paper, we consider two specific applications for the vitrification of human eggs in routine assisted reproduction practice: social egg freezing and the use of frozen eggs in egg donation. We suggest that vitrification is transforming the reproductive landscape in novel and complex ways and that we must be alert to the challenges, complexities and ethics of such developments, especially for those who may be excluded or marginalised by these techniques.

Development of a spermatogonia cryopreservation protocol for blue catfish, Ictalurus furcatus

Sustainability of channel catfish, Ictalurus punctatus ♀ × blue catfish, Ictalurus furcatus ♂ hybrid aquaculture relies on new innovative technologies to maximize fry output. Transplanting spermatogonial stem cells (SSCs) from blue catfish into channel catfish hosts has the potential to greatly increase gamete availability and improve hybrid catfish fry outputs. Cryopreservation would make these cells readily accessible for xenogenesis, but a freezing protocol for blue catfish testicular tissues has not yet been fully developed. Therefore, the objectives of this experiment were to identify the best permeating [dimethyl sulfoxide (DMSO), ethylene glycol (EG), glycerol, methanol] and non-permeating (lactose or trehalose with egg yolk or BSA) cryoprotectants, their optimal concentrations, and the best freezing rates (-0.5, -1.0, -5.0, -10 °C/min until -80 °C) that yield the highest number of viable type A spermatogonia cells. Results showed that all of these factors had significant impacts on post-thaw cell production and viability. DMSO was the most efficient permeating cryoprotectant at a concentration of 1.0 M. The optimal concentration of each cryoprotectant depended on the specific cryoprotectant due to interactions between the two factors. Of the non-permeating cryoprotectants, 0.2 M lactose with egg yolk consistently improved type A spermatogonia production and viability beyond that of the 1.0 M DMSO control. The overall best freezing rate was consistent at -1 °C/min, but similar results were obtained using -0.5 °C/min. Overall, we recommend cryopreserving blue catfish testicular tissues in 1.0 M DMSO with 0.2 M lactose and egg yolk at a rate of either -0.5 or -1 °C/min to achieve the best cryopreservation outcomes. Continued development of cryopreservation protocols for blue catfish and other species will make spermatogonia available for xenogenic applications and genetic improvement programs.

Cryopreservation of Mammalian Oocytes: Slow Cooling and Vitrification as Successful Methods for Cryogenic Storage

Two basic methods for the laboratory-focused cryopreservation of mammalian oocytes are described, based on work with murine oocytes. One method uses a relatively low concentration of the cryoprotectant propanediol plus sucrose and requires controlled rate cooling equipment to achieve a slow cooling rate. This method has also produced live births from cryopreserved human oocytes. The second method, which is described here, employs a high concentration of the cryoprotectant dimethyl sulfoxide plus a low concentration of polyethylene glycol. This is a vitrification method, which involves ultra-rapid cooling by plunging standard straws into liquid nitrogen vapor, hence avoiding the need for specialized equipment, but requires technical ability to manipulate the oocytes quickly in the highly concentrated cryoprotectant solutions. Murine oocytes that have been vitrified using this technique have resulted in live births. Vitrification using other cryoprotectant mixtures is now a popular clinically accepted method for cryobanking of human oocytes.

Preservation of female genetic resources in feline species

The development of assisted reproduction techniques (ART) specifically for felids has been propagated for two main reasons: (i) most felids are threatened and faced with extinction in all or part of their native habitats (IUCN Red List of Threatened Species, www.catsg.org), and (ii) the domestic cat (Felis catus) can serve as a research model for the implementation of advanced assisted reproductive techniques (ART) to be applied in exotic cats. Domestic cat ovaries can be freshly obtained from veterinary clinics and are frequently used for research on preservation of genetic resources in feline species. The presented review will summarize recent advances and obstacles in biobanking of female genetic resources and discuss alternative approaches which are under investigation.

Fertility preservation for young adults, adolescents, and children with cancer

Options for fertility preservation (FP) through cryopreservation methods are currently available for young adults, adolescents, and children. Guidelines for FP have been provided by international clinical societies, and emergency procedures aimed at FP have been implemented into clinical practice worldwide. In this article, we review the current data on clinical standards of emergency FP in patients who are facing gonadotoxic effects of cancer treatment, and we also describe the methods that are still under development, usually denoted as experimental. In Sweden, programmes for FP have been established at large university hospitals, thus covering the whole country. The Swedish publicly financed health care covers both assisted reproduction for treatment of infertility and the cryopreservation of gametes or gonadal tissue when there is a medical indication, such as the risk to become infertile due to oncologic treatment; hence the access to FP is ensured for the whole population. At our centre at Karolinska University Hospital in Stockholm, methods for FP have been offered since 1988. In this article, we also review the oncologic indications for FP in our patient cohort of >3000 individuals during the period 1988-2018.

DNA fragmentation index (DFI) as a measure of sperm quality and fertility in mice

Although thousands of genetically modified mouse strains have been cryopreserved by sperm freezing, the likelihood of cryorecovery success cannot be accurately predicted using conventional sperm parameters. The objective of the present study was to assess the extent to which measurement of a sperm DNA fragmentation index (DFI) can predict sperm quality and fertility after cryopreservation. Using a modified TUNEL assay, we measured and correlated the DFI of frozen-thawed sperm from 83 unique mutant mouse strains with sperm count, motility and morphology. We observed a linear inverse correlation between sperm DFI and sperm morphology and motility. Further, sperm DFI was significantly higher from males with low sperm counts compared to males with normal sperm counts (P < 0.0001). Additionally, we found that viable embryos derived using sperm from males with high DFI (62.7 ± 7.2% for IVF and 73.3 ± 8.1% for ICSI) failed to litter after embryo transfer compared to embryos from males with low DFI (20.4 ± 7.9% for IVF and 28.1 ± 10.7 for ICSI). This study reveals that measurement of DFI provides a simple, informative and reliable measure of sperm quality and can accurately predict male mouse fertility.