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

Navigating the practical challenges and ethical dilemmas of surplus cryopreserved human embryos

Cryopreservation, the use of very low temperatures to preserve structurally intact living cells and tissues, has seen exponential growth in the field of in vitro fertilization (IVF). In the last decade, cryopreservation of embryos and freeze-all protocols have become an essential aspect and a prerequisite for a successful IVF outcome. Moreover, vitrification, which is a fast and safe cryopreservation method, has proved to be an effective choice for cryopreserving gametes and embryos. The increasing number of cryopreserved embryos worldwide in cryobanks and IVF clinics is an undisputable fact that raises important physiological, ethical, and moral considerations that merit careful examination and discussion. Many couples utilizing assisted reproduction will have a surplus of cryopreserved embryos, in other words they already have completed their family without exhausting all the embryos that were created and cryopreserved during the process. Additionally, the global IVF market has also experienced significant growth due to various factors, including advancements in technology, increased awareness about infertility treatments, and changing societal norms towards delayed parenthood. Thus, for the foreseeable future the number of cryopreserved embryos, and the phenomenon of surplus embryos will likely remain unresolved. In the present review, following a description of the cryopreservation method and the physiological changes during the cryopreservation of embryos, the bioethical issues raised by the surplus cryopreserved embryos will be discussed alongside possible solutions for resolving this phenomenon.

Immunotherapy in gestational trophoblastic neoplasia: advances and future directions

Gestational trophoblastic neoplasia (GTN) is a rare but aggressive malignancy that follows normal or aberrant pregnancies. Until the advent of immunotherapy in 2017, surgery and chemotherapy were the standard treatment modalities, with chemotherapy remaining the cornerstone. However, chemoresistance and high-risk disease present significant challenges in managing GTN. Recent advancements in immunotherapy, particularly immune checkpoint inhibitors (ICIs), have offered new hope for managing these difficult cases. This review provides the comprehensive overview of the mechanisms underlying ICIs in GTN, and explores the potential synergy of combining ICIs with targeted therapies, such as vascular endothelial growth factor and epidermal growth factor receptor inhibitors. We also provide an overview of the latest evidence on the use of ICIs in treating GTN, focusing on their effectiveness in both low- and high-risk cases, as well as in chemorefractory settings. In addition, we discuss ongoing clinical trials, immune-related adverse events associated with ICIs, biomarker-driven approaches, immunosuppressive tumor microenvironments, and the challenges posed with ICIs resistance. The review also explores future directions, including the integration of ICIs into standard regimens, the potential for personalized treatment based on tumor biology, and the importance of fertility preservation in young patients with GTN. In conclusion, while challenges remain, immunotherapy represents a promising frontier in GTN treatment, with the potential to improve outcomes and provide a more personalized approach to care.

One-step warming of vitrified human cleavage and blastocyst stage embryos does not adversely impact embryo survivability and subsequent developmental potential

STUDY QUESTION

Does one-step warming (OW), a simplified embryo warming protocol, adversely affect survival and developmental potential in vitrified cleavage or blastocyst stage embryos compared to standard multi-step warming (SW)?

SUMMARY ANSWER

OW showed no detrimental effects on survival and developmental potential compared to SW in cleavage and blastocyst stage embryos.

WHAT IS KNOWN ALREADY

While standard embryo warming protocols involve a multi-step procedure using a stepwise osmotic solution to avoid a rapid influx of water into the embryo, recent studies suggest that eliminating the stepwise warming process does not reduce embryo survival and embryo transfer outcomes. However, previous reports have focused primarily on pregnancy rates, and a more detailed analysis of the effects of rapid osmotic pressure changes on embryos is necessary to standardize the protocol.

STUDY DESIGN, SIZE, DURATION

This preliminary study includes donated 377 vitrified human embryos (177 cleavage and 200 blastocyst stage) from 210 patients approved for discard at the patient's consent. The embryos were randomly allocated and warmed using either SW or OW protocols. In the SW protocol, embryos were rinsed with a stepwise osmotic solution (thawing, dilution, and washing solutions), and the process was completed with a 13-min warming period. In the OW protocol, embryos were only rinsed in a single solution (thawing solution) for 1 min.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Post-warming embryos were cultured using a time-lapse incubator. Survival rate and developmental potential, including the occurrence of abnormal morphokinetics and the time required for blastocyst formation after warming of cleavage stage embryos, were compared between SW and OW. Embryos that developed into the blastocyst stage were morphologically evaluated. In the warming of blastocyst stage embryos, the survival rate was determined by the presence of blastocoel expansion, and the proportion of full re-expanded blastocysts was observed at 3- and 24-h post-warming. An in vitro adhesion assay was also performed on blastocysts after culture, and adhesion rate and outgrowth area were measured 24, 48, and 72 h after culture with fibronectin-precoated dishes.

MAIN RESULTS AND THE ROLE OF CHANCE

OW did not negatively impact survival rates in either cleavage (100% in both OW and SW groups) or blastocyst stage embryos (99% in both groups). Cleavage stage embryos warmed by OW had superior or comparable rates of morulation (96 vs 85%, P = 0.0387), blastulation (78 vs 73%, P = 0.4044), full-blastocyst formation (60 vs 53%, P = 0.3196), and expanded-blastocyst formation (56 vs 49%, P = 0.4056) compared to those warmed by SW. Time-lapse monitoring analysis revealed that the frequency of collapses was reduced in OW (30 vs 50%, P = 0.0410). Additionally, all other abnormal morphokinetics were equivalent between OW and SW (P > 0.05); moreover, the time required for blastocyst formation (P > 0.05) and the morphological quality after development into the blastocyst stage (P > 0.05) were not significantly different between OW and SW. In warming of blastocyst stage embryos, the time required for full re-expansion was longer with OW (3.20 ± 3.03 h vs 2.14 ± 2.17 h, P = 0.0008), but there was no significant difference in the proportion of full re-expanded blastocysts at 3- (67 vs 75%, P = 0.2417) and 24-h (98 vs 97%, P = 1.0000) post-warming. The in vitro adhesion assay showed no significant differences in adhesion rate and outgrowth area at all observation points (P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study was carried out as a preliminary trial using discarded embryos, which limited the number of embryos analyzed. Additionally, the impact on embryo transfer outcomes, such as clinical pregnancy and livebirth rates, remains unclear.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that OW is a safe and efficient alternative to SW protocols and may improve the efficiency of IVF laboratory workflow without impairing embryo potentials.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was obtained for this study. The authors have no conflicts of interest to declare related to this study.

TRIAL REGISTRATION NUMBER

N/A.

Best practices for cryopreserving sperm in Nonhuman Primates: a systematic review and meta-analysis

Nonhuman primates (NHPs) are in increasing demand as models for preclinical research. The availability of a highly efficient cryopreservation protocol for use with NHP sperm has potential to significantly alleviate this demand and contribute to rapid increases in overall number of NHPs available for biomedical research. Thus, this systematic review assesses the state-of-the-art in NHP sperm cryopreservation and uses meta-analyses to describe the impact of varied cryopreservation approaches on NHP sperm. We searched the literature deposited in PubMed, Scopus, and Web of Science databases through June 2024 to identify data relevant to the effect of sperm cryopreservation on quality of thawed sperm compared to fresh sperm across NHP species. All original NHP studies reporting sperm parameters both before cryopreservation and after thawing were included for analysis. In total, 32 articles were included for qualitative analysis and not surprisingly, all 32 studies demonstrated negative effects of cryopreservation on sperm parameters, Specifically, motility and viability were significantly decreased in thawed NHP sperm. While the method of sperm collection did not have a significant impact on recovery of motile sperm, significant variability was evident between species. Importantly, recovery of motile NHP sperm was greatest following rapid sperm freezing methods. This analysis provides critical insights into future research directions to enhance and optimize cryopreservation protocols in NHPs.

Sperm Human Biobanking: An Overview

The purpose of this article is to analyze in detail the advantages and disadvantages of sperm cryopreservation, focusing on the cellular and molecular changes that occur during these processes. The main issue is the cellular damage caused by ice crystal formation and osmotic imbalance, along with other secondary effects such as sperm motility and viability, as well as the acrosome reaction or oxidative stress. Another important aspect is the examination of how chromatin structure and DNA integrity affect sperm. Biochemical changes affecting enzyme activity and protein stability have also been analyzed. Finally, the article highlights emerging technologies aimed at reducing the damage caused by sperm cryopreservation, as well as the potential benefits of biobanks as an essential resource for addressing male infertility.

Evaluation of utilization of amplified blastocoel fluid DNA gel electrophoresis band intensity as an additional minimally invasive approach in embryo selection: A cross-sectional study

Background

Embryo selection for transfer is critical in assisted reproduction. The presence of DNA in the blastocoel cavity of human blastocysts is assumed to be a consequence of common preimplantation chromosomal abnormalities.

Objective

This study examined the relationship between the amount of blastocoel fluid (BF) DNA and the band intensity of amplified BF-DNA in gel electrophoresis, considering the influence of ploidy status.

Materials and Methods

This cross-sectional study categorizes blastocysts into 2 groups based on the array comparative genomic hybridization results by trophectoderm biopsy -the euploid and aneuploid group. After morphological scoring, a biopsy of BF was performed for whole genome amplification, followed by an assessment of band intensity and BF-DNA quantification. The relationship between BF-DNA levels, band intensity, and ploidy status were analyzed.

Results

The level of BF-DNA was higher in the aneuploid group compared to the euploid group, but the difference was not statistically significant (p = 0.2). We observed that the band intensity was affected by the ploidy status of the embryos, although this difference was not statistically significant (p = 0.059). Notably, electrophoresis band of all embryos with chromosomal loss was strong. No correlation was observed between embryo morphology and chromosomal ploidy (p = 0.8).

Conclusion

Our findings indicate that BF-DNA band intensity on agarose gel is not currently applicable for preimplantation embryo selection. It seems that embryos with chromosomal loss are more prone to DNA release to BF. The disrelation between embryo morphology and ploidy status represents the necessity of minimally invasive embryo screening methods based on ploidy status.

Utilisation of Cryopreserved Gametes in Cancer Patients who Underwent Fertility Preservation

Background

Cancer treatments such as chemotherapy and radiotherapy often compromise fertility by damaging gonadal function, creating a critical need for fertility preservation options. Despite advancements in fertility preservation techniques, there is a significant lack of research focused on their application in Asian cancer patients and their utilisation remains underexplored in this population.

Aim

This study aims to evaluate the utilisation rates and outcomes of cryopreserved gametes in cancer patients who underwent fertility preservation before their cancer treatment.

Settings and Design

This retrospective study was conducted at our hospital from January 2003 to May 2023. It investigated the utilisation of cryopreserved gametes in 557 male patients aged 15-50 years and 39 female patients aged 15-40 years who opted for fertility preservation before chemotherapy or radiotherapy.

Materials and Methods

Data were retrospectively collected, including patient demographics and fertility preservation outcomes. Various fertility preservation methods were employed based on patient suitability and availability. Participants were surveyed to identify reasons for non-utilisation of cryopreserved gametes. All data were collected and analysed following institutional ethical guidelines.

Statistical Analysis Used

Descriptive statistics were used to calculate utilisation rates and report clinical pregnancy and live birth rates. Reasons for non-usage were categorised into mortality, spontaneous pregnancies, financial constraints and social factors.

Results

Out of 596 participants, only 11 utilised their cryopreserved gametes, yielding a utilisation rate of 1.8%. Among those who used their gametes, clinical pregnancy rates were 66.66% for males and 50% for females, with live birth rates of 33.33% for males and 50% for females. Non-usage was primarily due to mortality, spontaneous pregnancies, financial constraints and social issues.

Conclusion

The utilisation rate of cryopreserved gametes was low at 1.8%. Challenges such as mortality, financial constraints and social factors highlight the need for improved counselling and a refined approach to fertility preservation, ensuring services better align with patients' future needs.

The Effects of Cancer Immunotherapy on Fertility: Focus on Hematological Malignancies

In recent years, cancer management has benefitted from new effective treatments, including immunotherapy. While these therapies improve cancer survival rates, they can alter immune responses and cause long-term side effects, of which gonadotoxic effects and the potential impact on male and female fertility are growing concerns. Immunotherapies, such as immune checkpoint inhibitors, immunomodulators, monoclonal antibodies, and CAR-T, can lead to elevated levels of proinflammatory cytokines and immune-related adverse events that may exacerbate fertility problems. Immunotherapy-related inflammation, characterized by cytokine imbalances and the activation of pathways such as AMPK/mTOR, has been implicated in the mechanisms of fertility impairment. In men, hypospermatogenesis and aspermatogenesis have been observed after treatment with immune checkpoint inhibitors, by direct effects on the gonads, particularly through the inhibition of cytotoxic T lymphocyte antigen-4. In women, both damage to ovarian reserves, recurrent pregnancy loss, and implantation failure have been documented, secondary to a complex interplay between immune cells, such as T cells and uterine NK cells. In this review, the impact of immunotherapy on fertility in patients with hematological cancers was analyzed. While this area is still underexplored, fertility preservation methods remain crucial. Future studies should investigate immunotherapy's effects on fertility and establish standardized preservation protocols.

Oncofertility and Fertility Preservation for Women with Gynecological Malignancies: Where Do We Stand Today?

Oncofertility is a growing medical and research field that includes two main areas: oncology and reproductive medicine. Nowadays, the percentage of patients surviving cancer has exponentially increased, leading to the need for intervention for fertility preservation in both men and women. Specifically, gynecological malignancies in women pose an additional layer of complexity due to the reproductive organs being affected. In the present review, we report fertility preservation options with a cancer- and stage-specific focus. We explore the drawbacks and the necessity for planning fertility preservation applications during emergency statuses (i.e., the COVID-19 pandemic) and comment on the importance of repro-counseling for multifaceted patients during their oncological and reproductive journey.

Global status of research on fertility preservation in male patients with cancer: A bibliometric and visual analysis

Background

Recently, male fertility preservation before cancer treatment has become more prevalent. The research in this field has progressed over time, with some studies having a major impact and providing guidance for further research. However, the trends and hotspots of research on fertility preservation in male cancer patients may have changed; exploring them is essential for relevant research progress.

Design

We extracted relevant studies from the Web of Science Core Collection database, capturing information on the countries of study, affiliations, authors, keywords, as well as co-citations of references and journals. To identify publication trends, research strengths, key subjects, prominent topics, and emerging areas, we conducted a bibliometric analysis using CiteSpace.

Results

We included 3201 articles on fertility preservation in male cancer patients published over January 1999 to December 2023 were included. Although the relevant research growth rate was slow initially, the number of publications increased annually. Of all study countries, the United States, Germany, and Japan reported the earliest studies; the United States published the highest number of relevant studies. The US institutions remained at the forefront for all 25 years, and the US researcher Ashok Agarwal published the most articles. Literature co-citation analyses indicated a transformation in the study participants; they comprised a younger demographic (i.e., a large number of adolescent male patients underwent fertility preservation); moreover, fertility preservation techniques evolved from sperm cryopreservation to testicular tissue cryopreservation. Research on reproductive outcomes of sperm cryopreservation was the recent hotspot in male fertility preservation research, and the impact of immunotherapy and checkpoint inhibitors on male fertility requires further research.

Conclusions

Male fertility preservation will be a major future research focus, with closer connections and collaborations between countries and organizations. Our results present the historical data on the development of research on male fertility preservation in cancer patients, providing relevant insights for future research and development in this study area.

Influence of BMI, Cigarette Smoking and Cryopreservation on Tyrosine Phosphorylation during Sperm Capacitation

Capacitation involves tyrosine phosphorylation (TP) as a key marker. Lifestyle-related factors, such as obesity and smoking, are recognized for their adverse effects on semen quality and male fertility, yet the underlying mechanisms, including their potential impact on TP, remain unclear. Moreover, the effect of sperm cryopreservation on TP at the human sperm population level is unexplored. Flow cytometry analysis of global TP was performed on pre-capacitated, post-capacitated and 1- and 3-hours' incubated fresh and frozen-thawed samples from sperm donors (n = 40). Neither being overweight nor smoking (or both) significantly affected the percentage of sperm showing TP. However, elevated BMI and smoking intensity correlated with heightened basal TP levels (r = 0.226, p = 0.003) and heightened increase in TP after 3 h of incubation (r = 0.185, p = 0.017), respectively. Cryopreservation resulted in increased global TP levels after capacitation but not immediately after thawing. Nonetheless, most donors' thawed samples showed increased TP levels before and after capacitation as well as after incubation. Additionally, phosphorylation patterns in fresh and frozen-thawed samples were similar, indicating consistent sample response to capacitation stimuli despite differences in TP levels. Overall, this study sheds light on the potential impacts of lifestyle factors and cryopreservation on the dynamics of global TP levels during capacitation.

What is driving the global decline of human fertility? Need for a multidisciplinary approach to the underlying mechanisms

An intense period of human population expansion over the past 250 years is about to cease. Total fertility rates are falling dramatically all over the world such that highly industrialized nations, including China and the tiger economies of SE Asia, will see their populations decline significantly in the coming decades. The socioeconomic, geopolitical and environmental ramifications of this change are considerable and invite a multidisciplinary consideration of the underlying mechanisms. In the short-term, socioeconomic factors, particularly urbanization and delayed childbearing are powerful drivers of reduced fertility. In parallel, lifestyle factors such as obesity and the presence of numerous reproductive toxicants in the environment, including air-borne pollutants, nanoplastics and electromagnetic radiation, are seriously compromising reproductive health. In the longer term, it is hypothesized that the reduction in family size that accompanies the demographic transition will decrease selection pressure on high fertility genes leading to a progressive loss of human fecundity. Paradoxically, the uptake of assisted reproductive technologies at scale, may also contribute to such fecundity loss by encouraging the retention of poor fertility genotypes within the population. Since the decline in fertility rate that accompanies the demographic transition appears to be ubiquitous, the public health implications for our species are potentially devastating.

DNA fragmentation, antioxidant activity and histological structure of cryopreserved testicular tissue depending on sexual maturity and immunological status

The objective of this work was to determine a relationship between a frequency of DNA fragmentation, a level of antioxidant activity and a preservation of histological structure depending on initial status of fragments of seminiferous tubules of testes (FSTT) of rats at the stages of cryopreservation. FSTT of animals of different ages (immature, mature), as well as animals with changed immunological status (adjuvant arthritis) were cryopreserved. Slow uncontrolled freezing was used in a cryomedium of fibrin gel with 0.7 M glycerol. The results showed that viability, TAS, γGGT and G6PD activities had the highest values in the group of intact immature animals both in fresh FSTT and after exposure to cryomedium or cryopreservation, while the indexes of DNA fragmentation and ROS content had the lowest values. It was found that an increase in the DNA fragmentation rate occurred in parallel with a decrease in the values of antioxidant activity and membrane integrity. The spermatogenenic epithelium after cryopreservation differed between the groups in a relative number of cells with pathologically changed nuclei and the frequency of exfoliation of epithelial cells into the tubule cavity namely, there was a tendency to an increase in the damaging effects in the series, "Immature → Sexually mature → Autoimmune arthritis". The obtained data can be taken into account in the development of low-temperature preservation protocols using cryotechnologies, which will ensure the maintenance of the morphological and functional characteristics of FSTT depending on sexual maturity and immunological status.

Perceptions and experiences of fertility preservation in female patients with cancer in Greece

BACKGROUND

As advances in oncology have led to remarkable and steady improvements in the survival rates of patients with cancer and anticancer treatment can cause premature ovarian failure in women, fertility preservation (FP) has become a global public health concern and an integral part of the care for women diagnosed with cancer during reproductive age. However, for various reasons, FP remains underutilized for patients with cancer. There are substantial gaps in our knowledge about women's experiences and perceptions of the issue. This study aims to contribute to bridging that gap.

METHODS

This prospective qualitative study was conducted from March 2018 to February 2023. A combination of purposive and snowball sampling was used. Data were collected by semistructured interviews with nineteen reproductive-age women who had been recently diagnosed with cancer. Data were classified and analysed with a thematic analysis approach.

RESULTS

A variety of distinct themes and subthemes emerged from the analysis of the interview data. The cancer diagnosis emerged as a factor that considerably affects the women's attitudes towards biological parenthood: It can further increase their (strong) previous desire or decrease their previous (weak) desire. Women with a recent cancer diagnosis had not received adequate and multidisciplinary counselling, including clear and sufficient information. However, participants felt satisfied with the information they received because they either received the information they requested or remained in denial about the need to be informed (i.e., because they felt overwhelmed after the cancer diagnosis). Embryo cryopreservation emerged as a less desirable FP option for women with cancer. Participants showed respect for human embryos, not always for religious reasons. Surrogacy emerged as the last resort for most participants. Religious, social or financial factors did play a secondary (if any) role in women's decision-making about FP. Finally, male partners' opinions played a secondary role in most participants' decision-making about FP. If embryo cryopreservation was the selected option, partners would have a say because they were contributing their genetic material.

CONCLUSIONS

The findings that emerged from the data analysis were partly consistent with prior studies. However, we identified some interesting nuances that are of clinical importance. The results of this study may serve as a starting point for future research.

Feasibility and efficiency of delayed ovarian stimulation and metaphase II oocyte banking for fertility preservation and childbearing desire after fertility-impairing treatment

The aim of our study was to evaluate the feasibility and efficiency of delayed ovarian stimulation and metaphase II oocyte banking for fertility preservation after fertility-impairing treatment regardless of the initial disease. We conducted a cohort study based on population of women < 40 years of age with diminished ovarian reserve caused by fertility-impairing treatment (n = 129). Three groups of women were compared according to the type of initial disease: hematological malignancies, solid tumors, and benign diseases. The primary endpoint was the number of metaphase II oocytes collected per woman. We studied the cumulative live-birth rate per cycle with fertilized metaphase II oocyte, for women who wanted to conceive. We studied 245 delayed controlled ovarian stimulation cycles in 129 women: 201 for fertility preservation and 44 for in vitro fertilization and fresh embryo transfers. The number of metaphase II oocytes collected per woman after banking was similar in the three groups, with a mean of 10.7 ± 4.6, 12.3 ± 9.1, and 10.1 ± 7.6 metaphase II oocytes (p = 0.46), respectively. In the subgroup of women who wanted to conceive, the cumulative live birth rate per woman was 38%, with 8 live births for these 21 women. After fertility-impairing treatment, practitioners should discuss a fertility preservation procedure for banking metaphase II oocytes.