Fertility Preservation for Prepubertal Patients at Risk of Infertility: Present Status and Future Perspectives

Exploring the Frontiers of Ovarian Tissue Cryopreservation: A Review

Objective: This paper serves as an up-to-date narrative review of the most effective methods and outcomes of ovarian tissue cryopreservation (OTC) with new data comparing this method to oocyte and embryo cryopreservation as well as its utility in restoration of endocrine function. Background: Data on OTC are becoming more available as more patients are achieving cancer remission and choosing to use their cryopreserved tissue to conceive or restore endocrine function. With OTC only recently becoming a non-experimental method of fertility preservation, it is important to evaluate, compare, and optimize current practices to improve live birth outcomes. Methods: A literature search of meta-analyses, systematic reviews, case series, retrospective studies, and randomized control trials was performed using the PubMed database with multiple search terms. Discussion: Current practices and outcomes of OTC remain heterogeneous, though they are becoming more streamlined with the emerging data on successful live births. Multiple aspects of OTC have been studied to optimize protocols, particularly methods of cryopreserving, in vitro maturation, and transplantation. In vitro follicle maturation is a novel application with emerging data on methods and outcomes. OTC is a versatile method not only for fertility preservation but also for hormone restoration as well. With wider usage of OTC, ethical dilemmas will need to be addressed. Conclusions: OTC can be used as fertility preservation for a variety of patients. Recent studies suggest it may be comparable to embryo cryopreservation, but with growing data on live births, comparative studies should continue to be performed. In vitro follicle maturation (IVFM) is a promising application of ovarian tissue harvesting. Data are lacking on cost-effectiveness, patient satisfaction, and morbidity associated with OTC.

Systematic Review of the Gonadotoxicity and Risk of Infertility of Soft Tissue Sarcoma Chemotherapies in Pre- and Postpubertal Females and Males

Increasing awareness of gonadotoxicity in cancer treatments and infertility risk is essential for counseling young cancer patients. While fertility preservation options are available in many countries, limited data on gonadotoxicity hinder recommendations, especially for soft tissue cancers. This review, part of the FertiTOX project (www.fertitox.com), organized by FertiPROTEKT (www.fertiprotekt.com), aims to address this knowledge gap to improve fertility preservation guidance. We performed a systematic literature search on gonadotoxicity in soft tissue sarcoma (STS) cancer treatments. Only patients without metastases or recurrent disease were considered. "Suspected infertility" was defined based on low ovarian reserve parameters, low inhibin B levels, high gonadotropin concentration, gonadal dysfunction, amenorrhea, oligomenorrhea, azoospermia, or oligozoospermia due to limited infertility data. The study quality was assessed using the Newcastle-Ottawa Scale. The search yielded 3309 abstracts, with 138 undergoing full-text analysis. Eight studies on STS were included. Suspected infertility was observed in 20 of 28 females (71.4%, range 0-100%) and 38 of 63 males (60.3%, range 34.8-100%) with STS. Six of the eight studies received high-quality scores on the NOS, while two received a fair score. Our data suggest a high risk of infertility from chemotherapy in pre- and postpubertal STS survivors. This underscores the importance of considering fertility preservation measures when counseling these patients.

The Australian New Zealand Consortium in Children, Adolescents, and Young Adults Oncofertility action plan

International and national oncofertility networks, including the US-led Oncofertility Consortium, FertiProtekt, and the Danish Network, have played pivotal roles in advancing the discipline of oncofertility over the last decade. Many other countries lack a shared approach to pediatric oncofertility health service delivery. This study aims to describe baseline oncofertility practices at Australian New Zealand Children's Haematology/Oncology Group centers in 2019-2021, describe binational priorities for care, and propose a 5-year action plan for best practice to be implemented by the newly formed Australian New Zealand Consortium in Children, Adolescents, and Young Adults (CAYA) Oncofertility (ANZCO).

Alkylating agents-induced gonadotoxicity in prepubertal males: Insights on the clinical and preclinical front

Rising cure rates in pediatric cancer patients warrants an increased attention toward the long-term consequences of the diagnosis and treatment in survivors. Chemotherapeutic agents can be gonadotoxic, rendering them at risk for infertility post-survival. While semen cryopreservation is an option that can be provided for most (post)pubertal boys before treatment, this is unfortunately not an option prepubertal in age, simply due to the lack of spermatogenesis. Over the last couple of years, studies have thus focused on better understanding the testis niche in response to various chemotherapeutic agents that are commonly administered and their direct and indirect impact on the germ cell populations. These are generally compounds that have a high risk of infertility and have been classified into risk categories in curated fertility guidelines. However, with it comes the lack of evidence and the challenge of using informative models and conditions most reflective of the physiological scenario, in short, the appropriate study designs for clinically relevant outcomes. Besides, the exact mechanism(s) of action for many of these "risk" compounds as well as other agents is unclear. Understanding their behavior and effect on the testis niche will pave the way for incorporating new strategies to ultimately combat infertility. Of the various drug classes, alkylating agents pose the highest risk of gonadotoxicity as per previously established studies as well as risk stratification guidelines. Therefore, this review will summarize the findings in the field of male fertility concerning gonadotoxicity of akylating agents as a result of chemotherapy exposure.

Current Status of Fertility Preservation in Pediatric Oncology Patients

Cancer poses significant emotional challenges for children and adolescents, despite improvements in survival rates due to new therapies. However, there is growing concern about the long-term effects, including fertility issues. This review examines recent advancements and future directions in fertility preservation within a pediatric population subjected to oncological therapies. Worldwide, there is variability in the availability of fertility preservation methods, influenced by factors like development status and governmental support. The decision to pursue preservation depends on the risk of gonadotoxicity, alongside factors such as diagnosis, treatment, clinical status, and prognosis. Currently, options for preserving fertility in prepubertal boys are limited compared to girls, who increasingly have access to ovarian tissue preservation. Adolescents and adults have more options available, but ethical considerations remain complex and diverse.

Research progress on mechanism of follicle injury after frozen ovarian tissue transplantation and protective strategies

The iatrogenic ovarian dysfunction caused by cancer treatment have been increasing, along with the age at onset of malignant tumors getting younger, the survival of cancer patients being longer, as well as the delayed childbearing age for females; therefore it becomes a major clinical challenge to preserve the fertility of these patients. Ovarian tissue cryopreservation is the only solution for female cancer patients in prepubertal ages and those who cannot delay gonadotoxic therapy. However, the successful rate of cryopreservation and transplantation of ovarian tissue is still low at present due to the risk of ischemia and hypoxia of grafted tissues. Abnormal activation of primordial follicle and ischemia-reperfusion injury after blood supply recovery also cause massive loss of follicles in grafted ovarian tissues. It has been tried in various studies to reduce the damage of follicles during freezing and transplantation by adding certain drugs, and extend the duration of endocrine and reproductive function in patients with ovarian transplantation. For example, melatonin, N-acetylcysteine, erythropoietin or other antioxidants are used to reduce oxidative stress; mesenchymal stem cells derived from different tissues, basic fibroblast growth factor, vascular endothelial growth factor, angiopoietin 2 and gonadotropin are used to promote revascularization; anti-Müllerian hormone and rapamycin are used to reduce abnormal activation of primordial follicles. This article reviews the research progress on the main mechanisms of follicle loss after ovarian tissue transplantation, including hypoxia, ischemia-reperfusion injury and associated cell death, and abnormal activation of follicles; and explores the methods of reducing graft follicle loss to provide reference for improving the efficiency of ovarian tissue cryopreservation and transplantation.

Ethical, legal, social, and policy issues of ovarian tissue cryopreservation in prepubertal girls: a critical interpretive review

PURPOSE

Despite the increasing number of childhood cancer survivors, significant advances in ovarian tissue cryopreservation (OTC) technique and medical societies' recommendations, fertility preservation (FP) and FP discussions are not always offered as a standard of care in the pediatric context. The aim of this literature review is to understand what ethical, legal, social, and policy issues may influence the provision of FP by OTC in prepubertal girls with cancer.

METHODS

A critical interpretive review of peer-reviewed papers published between 2000 and January 2023 was conducted, guided by the McDougall's version of the critical interpretive synthesis (Dixon-Woods), to capture recurring concepts, principles, and arguments regarding FP by OTC for prepubertal girls.

RESULTS

Of 931 potentially relevant papers, 162 were included in our analysis. Data were grouped into seven thematic categories: (1) risks of the procedure, (2) unique decision-making issues in pediatric oncofertility, (3) counseling, (4) cultural and cost issues, and (5) disposition of cryopreserved reproductive tissue.

CONCLUSION

This first literature review focusing on ethical, legal, social, and policy issues surrounding OTC in prepubertal girls highlights concerns in the oncofertility debate. Although OTC is no longer experimental as of December 2019, these issues could limit its availability and the child's future reproductive autonomy. This review concludes that specific actions must be provided to enable the offer of FP, such as supporting families' decision-making in this unique and complex context, and providing pediatric patients universal and full access to free or highly subsidized OTC.

Optimized Recovery of Immature Germ Cells after Prepubertal Testicular Tissue Digestion and Multi-Step Differential Plating: A Step towards Fertility Restoration with Cancer-Cell-Contaminated Tissue

Undifferentiated germ cells, including the spermatogonial stem cell subpopulation required for fertility restoration using human immature testicular tissue (ITT), are difficult to recover as they do not easily adhere to plastics. Due to the scarcity of human ITT for research, we used neonatal porcine ITT. Strategies for maximizing germ cell recovery, including a comparison of two enzymatic digestion protocols (P1 and P2) of ITT fragment sizes (4 mm3 and 8 mm3) and multi-step differential plating were explored. Cellular viability and yield, as well as numbers and proportions of DDX4+ germ cells, were assessed before incubating the cell suspensions overnight on uncoated plastics. Adherent cells were processed for immunocytochemistry (ICC) and floating cells were further incubated for three days on Poly-D-Lysine-coated plastics. Germ cell yield and cell types using ICC for SOX9, DDX4, ACTA2 and CYP19A1 were assessed at each step of the multi-step differential plating. Directly after digestion, cell suspensions contained >92% viable cells and 4.51% DDX4+ germ cells. Pooled results for fragment sizes revealed that the majority of DDX4+ cells adhere to uncoated plastics (P1; 82.36% vs. P2; 58.24%). Further incubation on Poly-D-Lysine-coated plastics increased germ cell recovery (4.80 ± 11.32 vs. 1.90 ± 2.07 DDX4+ germ cells/mm2, respectively for P1 and P2). The total proportion of DDX4+ germ cells after the complete multi-step differential plating was 3.12%. These results highlight a reduced proportion and number of germ cells lost when compared to data reported with other methods, suggesting that multi-step differential plating should be considered for optimization of immature germ cell recovery. While Poly-D-Lysine-coating increased the proportions of recovered germ cells by 16.18% (P1) and 28.98% (P2), future studies should now focus on less cell stress-inducing enzymatic digestion protocols to maximize the chances of fertility restoration with low amounts of cryo-banked human ITT.

Preservation of fertility in female and male prepubertal patients diagnosed with cancer

Over the past two decades, the importance of fertility preservation has grown not only in the realm of medical and clinical patient care, but also in the field of basic and applied research in human reproduction. With advancements in cancer treatments resulting in higher rates of patient survival, it is crucial to consider the quality of life post-cure. Therefore, fertility preservation must be taken into account prior to antitumor treatments, as it can significantly impact a patient's future fertility. For postpubertal patients, gamete cryopreservation is the most commonly employed preservation strategy. However, for prepubertal patients, the situation is more intricate. Presently, ovarian tissue cryopreservation is the standard practice for prepubertal girls, but further scientific evidence is required in several aspects. Testicular tissue cryopreservation, on the other hand, is still experimental for prepubertal boys. The primary aim of this review is to address the strategies available for possible fertility preservation in prepubertal girls and boys, such as ovarian cryopreservation/transplantation, in vitro follicle culture and meiotic maturation, artificial ovary, transplantation of cryopreserved spermatogonia, and cryopreservation/grafting of immature testicular tissue and testicular organoids.

Modelling in vitro gametogenesis using induced pluripotent stem cells: a review

In vitro gametogenesis (IVG) has been a topic of great interest in recent years not only because it allows for further exploration of mechanisms of germ cell development, but also because of its prospect for innovative medical applications especially for the treatment of infertility. Elucidation of the mechanisms underlying gamete development in vivo has inspired scientists to attempt to recapitulate the entire process of gametogenesis in vitro. While earlier studies have established IVG methods largely using pluripotent stem cells of embryonic origin, the scarcity of sources for these cells and the ethical issues involved in their use are serious limitations to the progress of IVG research especially in humans. However, with the emergence of induced pluripotent stem cells (iPSCs) due to the revolutionary discovery of dedifferentiation and reprogramming factors, IVG research has progressed remarkably in the last decade. This paper extensively reviews developments in IVG using iPSCs. First, the paper presents key concepts from groundwork studies on IVG including earlier researches demonstrating that IVG methods using embryonic stem cells (ESCs) also apply when using iPSCs. Techniques for the derivation of iPSCs are briefly discussed, highlighting the importance of generating transgene-free iPSCs with a high capacity for germline transmission to improve efficacy when used for IVG. The main part of the paper discusses recent advances in IVG research using iPSCs in various stages of gametogenesis. In addition, current clinical applications of IVG are presented, and potential future applications are discussed. Although IVG is still faced with many challenges in terms of technical issues, as well as efficacy and safety, novel IVG methodologies are emerging, and IVG using iPSCs may usher in the next era of reproductive medicine sooner than expected. This raises both ethical and social concerns and calls for the scientific community to cautiously develop IVG technology to ensure it is not only efficacious but also safe and adheres to social and ethical norms.

Ovarian Function and Spontaneous Pregnancy After Hematopoietic Stem Cell Transplantation for Leukemia Before Puberty: An L.E.A. Cohort Study

Ovarian function impairment and infertility are among the most frequent late effects after hematopoietic stem cell transplantation (HSCT). The aim of this study was to evaluate ovarian function, occurrence of premature ovarian insufficiency (POI), and spontaneous pregnancy in a large cohort of adult survivor women who had undergone HSCT for leukemia before puberty. We conducted a retrospective observational study in women from the national cohort L.E.A., the long-term French follow-up program after childhood leukemia. The median follow-up duration was 18 years (14.2-23.3) after HSCT. Among 178 women, 106 (60%) needed pubertal induction with hormone substitution treatment, whereas 72 (40%) had spontaneous menarche. After spontaneous menarche, 33 (46%) developed POI, mostly within 5 years of HSCT. Older age at time of HSCT and cryopreservation of ovarian tissue appeared as significant risk factors for POI. More than 65% of patients who underwent HSCT before the age of 4.8 years had spontaneous menarche, and almost 50% didn't have POI at last evaluation, whereas more than 85% with HSCT after the age of 10.9 years didn't have spontaneous menarche and needed induction of puberty with hormone replacement therapy. Twenty-two women (12%) had at least one spontaneous pregnancy, with 17 live-births, 14 miscarriages, 4 legal abortions, and 2 therapeutic abortions. These results add supplementary data to better counsel patients and their families on the chances of ovarian residual function and pregnancy after HSCT, as well as on the potential interest of fertility preservation.

Germ Cell Maintenance and Sustained Testosterone and Precursor Hormone Production in Human Prepubertal Testis Organ Culture with Tissues from Boys 7 Years+ under Conditions from Adult Testicular Tissue

Human prepubertal testicular tissues are rare, but organ culture conditions to develop a system for human in vitro-spermatogenesis are an essential option for fertility preservation in prepubertal boys subjected to gonadotoxic therapy. To avoid animal testing in line with the 3Rs principle, organ culture conditions initially tested on human adult testis tissue were applied to prepubertal samples (n = 3; patient ages 7, 9, and 12 years). Tissues were investigated by immunostaining and transmission electron microscopy (TEM), and the collected culture medium was profiled for steroid hormones by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Culture conditions proved suitable for prepubertal organ culture since SSCs and germ cell proliferation could be maintained until the end of the 3-week-culture. Leydig cells (LCs) were shown to be competent for steroid hormone production. Three additional testis tissues from boys of the same age were examined for the number of germ cells and undifferentiated spermatogonia (SPG). Using TEM micrographs, eight tissues from patients aged 1.5 to 13 years were examined, with respect to the sizes of mitochondria (MT) in undifferentiated SPG and compared with those from two adult testicular tissues. Mitochondrial sizes were shown to be comparable between adults and prepubertal boys from approximately 7 years of age, which suggests the transition of SSCs from normoxic to hypoxic metabolism at about or before this time period.

Achievement of complete in vitro spermatogenesis in testicular tissues from prepubertal mice exposed to mono- or polychemotherapy

The assessment of the impact of chemotherapies on in vitro spermatogenesis in experimental models is required before considering the application of this fertility restoration strategy to prepubertal boys who received these treatments before testicular tissue cryopreservation. The present work investigated the effects of exposure of prepubertal mice to mono- (vincristine or cyclophosphamide) and polychemotherapy (a combination of vincristine and cyclophosphamide) on the first wave of in vitro spermatogenesis. When testicular tissue exposed to monochemotherapy was preserved, polychemotherapy led to severe alterations of the seminiferous epithelium and increased apoptosis in prepubertal testes prior in vitro maturation, suggesting a potential additive gonadotoxic effect. These alterations were also found in the testicular tissues of polychemotherapy-treated mice after 30 days of organotypic culture and were associated with a reduction in the germ cell/Sertoli cell ratio. The different treatments neither altered the ability of spermatogonia to differentiate in vitro into spermatozoa nor the yield of in vitro spermatogenesis. However, more spermatozoa with morphological abnormalities and fragmented DNA were produced after administration of polychemotherapy. This work therefore shows for the first time the possibility to achieve a complete in vitro spermatogenesis after an in vivo exposure of mice to a mono- or polychemotherapy before meiotic entry.

A screen of repurposed drugs identifies AMHR2/MISR2 agonists as potential contraceptives

We identified the anti-Mullerian hormone (also known as Müllerian inhibiting substance or MIS) as an inhibitory hormone that induces long-term contraception in mammals. The type II receptor to this hormone, AMHR2 (also known as MISR2), represents a promising druggable target for the modulation of female reproduction with a mechanism of action distinct from steroidal contraceptives. We designed an in vitro platform to screen and validate small molecules that can activate MISR2 signaling and suppress ovarian folliculogenesis. Using a bone morphogenesis protein (BMP)–response element luciferase reporter cell–based assay, we screened 5,440 compounds from a repurposed drug library. Positive hits in this screen were tested for specificity and potency in luciferase dose–response assays, and biological activity was tested in ex vivo Mullerian duct regression bioassays. Selected candidates were further evaluated in ex vivo follicle/ovary culture assays and in vivo in mice and rats. Here, we report that SP600125, CYC-116, gandotinib, and ruxolitinib can specifically inhibit primordial follicle activation and repress folliculogenesis by stimulating the MISR2 pathway.

Testicular Tissue Banking for Fertility Preservation in Young Boys: Which Patients Should Be Included?

Due to the growing number of young patients at risk of germ cell loss, there is a need to preserve spermatogonial stem cells for patients who are not able to bank spermatozoa. Worldwide, more and more clinics are implementing testicular tissue (TT) banking programs, making it a novel, yet indispensable, discipline in the field of fertility preservation. Previously, TT cryopreservation was predominantly offered to young cancer patients before starting gonadotoxic chemo- or radiotherapy. Nowadays, most centers also bank TT from patients with non-malignant conditions who need gonadotoxic conditioning therapy prior to hematopoietic stem cell (HSCT) or bone marrow transplantation (BMT). Additionally, some centers include patients who suffer from genetic or developmental disorders associated with prepubertal germ cell loss or patients who already had a previous round of chemo- or radiotherapy. It is important to note that the surgical removal of TT is an invasive procedure. Moreover, TT cryopreservation is still considered experimental as restoration methods are not yet clinically available. For this reason, TT banking should preferably only be offered to patients who are at significant risk of becoming infertile. In our view, TT cryopreservation is recommended for young cancer patients in need of high-risk chemo- and/or radiotherapy, regardless of previous low-risk treatment. Likewise, TT banking is advised for patients with non-malignant disorders such as sickle cell disease, beta-thalassemia, and bone marrow failure, who need high-risk conditioning therapy before HSCT/BMT. TT retrieval during orchidopexy is also proposed for patients with bilateral cryptorchidism. Since patients with a medium- to low-risk treatment generally maintain their fertility, TT banking is not advised for this group. Also for Klinefelter patients, TT banking is not recommended as it does not give better outcomes than a testicular sperm extraction later in life.

Female Oncofertility: Current Understandings, Therapeutic Approaches, Controversies, and Future Perspectives

Recent advances in early detection and oncological therapies have ameliorated the survival rate of young cancer patients. Yet, ovarian impairment induced by chemotherapy and radiotherapy is still a challenging issue. This review, based on clinical and lab-based studies, summarizes the evidence of gonadotoxicity of chemoradiotherapy, the recent approaches, ongoing controversies, and future perspectives of fertility preservation (FP) in female patients who have experienced chemo- or radio-therapy. Existing data indicate that chemotherapeutic agents induce DNA alterations and massive follicle activation via the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Meanwhile, the radiation causes ionizing damage, leading to germ cell loss. In addition to the well-established methods, numerous therapeutic approaches have been suggested, including minimizing the follicle loss in cryopreserved ovarian grafts after transplantation, in vitro activation or in vitro growing of follicles, artificial ovarian development, or fertoprotective adjuvant to prevent ovarian damage from chemotherapy. Some reports have revealed positive outcomes from these therapies, whereas others have demonstrated conflictions. Future perspectives are improving the live birth rate of FP, especially in patients with adverse ovarian reserve, eliminating the risk of malignancy reintroducing, and increasing society’s awareness of FP importance.