Fertility preservation for prepubertal boys: lessons learned from the past and update on remaining challenges towards clinical translation

Evaluation and preservation of fertility in patients with hematologic malignancies

For patients with hematologic malignancies, novel therapeutic strategies offer the potential to achieve a complete clinical response and long-term survival. However, declining fertility has become a significant concern, impacting long-term quality of life. Conventional high-dose chemotherapy and radiotherapy are known to reduce fertility or cause sterility. Moreover, limited clinical data are available on the effects of newer therapies, such as targeted treatments and chimeric antigen receptor (CAR)-T cell therapy, on fertility. Additionally, there is no standard method for preserving fertility in these patients. Male patients can opt for sperm cryopreservation, whereas female patients may preserve fertility through embryo, oocyte, or ovarian tissue cryopreservation. However, preserving fertility in prepubescent patients remains particularly challenging. Therefore, hematologists must educate patients about the potential gonadal toxicity of cancer treatments and offer the most appropriate fertility preservation options.

In vivo and in vitro spermatogenesis in prepubertal mouse testes exposed to low gonadotoxic doses of cytarabine or Daunorubicin

The development of experimental models treated by chemotherapy is needed for elucidating the side effects of cancer treatments administered prior to puberty on male gonad function and the feasibility of restoring fertility from exposed testicular tissues. This study investigated for the first time the effects of cytarabine and daunorubicin administered before meiotic initiation on the first wave of mouse spermatogenesis under both in vivo or in vitro conditions. Prepubertal exposure to cytarabine did not exhibit immediate detrimental effects on testicular tissues, whereas daunorubicin administration resulted in a decreased spermatogonia-to-Sertoli cell ratio and diminished intratubular cell proliferation within three days post-treatment. While the completion of in vivo spermatogenesis was not hindered by chemotherapy exposure, a significant increase in the proportion of spermatozoa with fragmented DNA was observed in mice more than one month after treatment. In vitro spermatogenesis was also accomplished using prepubertal testicular tissues exposed to chemotherapy, indicating that neither cytarabine nor daunorubicin impeded the differentiation potential of spermatogonia into spermatozoa. However, in vitro conditions revealed an arrest in meiotic progression in a substantial proportion of seminiferous tubules and an elevated incidence of DNA double-strand breaks in intratubular cells compared to in vivo controls, irrespective of the treatment administered.

Testicular tissue cryopreservation and transplantation as a strategy for feline conservation: a review of research advances

As we humans continue our detrimental activities on the planet, the biodiversity loss is now seen as a big threat to entire ecosystem in which we all live. This issue becomes even more critical as we see a rapid increase in the number of animal species being listed as endangered, and a far greater rate of species extinction. We all know that felines play a crucial part in our ecosystems, it is therefore safe to argue that their conservation could play an important role in minimizing the biodiversity loss. Advanced reproductive biotechnologies including testicular tissue cryopreservation and transplantation are considered as effective tools for the conservation of animal species. As we have seen with the Giant Panda, these biotechnologies could offer new possibilities for the conservation of other endangered species including felines. Although previously a few wild feline spp. were conserved by this method, little is known about the factors influencing the efficiency of these methods. Therefore, if we are to maximize the conservation efforts, further optimization of these biotechnologies is required to achieve better conservation results. In this article, we present an overview of testicular tissue of felines and the factors influencing testicular tissue cryopreservation and testicular graft recovery in felines.

3D Bioprinted Coaxial Testis Model Using Human Induced Pluripotent Stem Cells:A Step Toward Bicompartmental Cytoarchitecture and Functionalization

Fertility preservation following pediatric cancer therapy programs has become a major avenue of infertility research. In vitro spermatogenesis (IVS) aims to generate sperm from banked prepubertal testicular tissues in a lab setting using specialized culture conditions. While successful using rodent tissues, progress with human tissues is limited by the scarcity of human prepubertal testicular tissues for research. This study posits that human induced pluripotent stem cells (hiPSCs) can model human prepubertal testicular tissue to facilitate the development of human IVS conditions. Testicular cells derived from hiPSCs are characterized for phenotype markers and profiled transcriptionally. HiPSC-derived testicular cells are bioprinted into core-shell constructs representative of testis cytoarchitecture and found to capture functional aspects of prepubertal testicular tissues within 7 days under xeno-free conditions. Moreover, hiPSC-derived Sertoli cells illustrate the capacity to mature under pubertal-like conditions. The utility of the model is tested by comparing 2 methods of supplementing retinoic acid (RA), the vitamin responsible for inducing spermatogenesis. The model reveals a significant gain in activity under microsphere-released RA compared to RA medium supplementation, indicating that the fragility of free RA in vitro may be a contributing factor to the molecular dysfunction observed in human IVS studies to date.

Analysis of toxicity and mechanisms of busulfan in non-obstructive azoospermia: A genomic and toxicological approach integrating molecular docking, single-cell sequencing, and experimentation in vivo

Environmental pollutants, including chemical contaminants, heavy metals, and pesticides, have been linked to adverse effects on male reproductive health, particularly sperm quality. Non-obstructive azoospermia (NOA) is a severe form of male infertility caused by intrinsic testicular dysfunction, leading to a complete absence of sperm in the ejaculate. Busulfan, an alkylating chemotherapeutic agent widely used to treat chronic myelogenous leukemia, is known to induce NOA through its toxic effects on spermatogonial stem cells (SSCs). This study aimed to identify key molecular targets and pathways disrupted by busulfan in the testicular environment. By integrating molecular docking, single-cell RNA sequencing, and in vivo experimentation, the study identified POLE and LRAT as critical proteins. These proteins were shown to interact strongly with busulfan, leading to genomic instability and increased germ cell apoptosis during spermatogenesis. Additionally, the immune landscape of NOA-affected testes revealed significant changes in immune cell infiltration, potentially worsening the condition. These findings offer new insights into the mechanisms of busulfan-induced NOA and suggest potential therapeutic targets for preserving male fertility in chemotherapy patients. This research advances the understanding of chemotherapy-induced reproductive toxicity and emphasizes the need for strategies to reduce its negative effects on fertility.

Experience and andrological follow-up after testicular tissue cryopreservation

RESEARCH QUESTION

What is the experience and mid- and long-term andrological health follow-up of (pre)pubertal males who have undergone testicular tissue freezing (TTF)?

DESIGN

This single-centre longitudinal retrospective cohort study reports on the mid- and long-term andrological health follow-up of (pre)pubertal males and young adults who underwent TTF for fertility preservation between January 2007 and December 2018. Medical characteristics and questionnaire data collected more than 18 months after TTF were analysed.

RESULTS

Thirty-six patients were revisited during a medical follow-up consultation. During follow-up after TTF, 72.7% of patients could not recollect their counselling consultation prior to TTF but 42.4% of them found information about the TTF process useful and sufficient. Parents' or legal guardians' feedback was more positive about the counselling consultation and the TTF process. After TTF and treatment, the majority of patients (76.9%) who provided a semen sample had non-obstructive azoospermia. Higher serum concentrations of FSH and LH and lower serum concentrations of inhibin B were associated with non-obstructive azoospermia compared with patients with oligozoospermia (P = 0.0182, P = 0.0245 and P = 0.0140 respectively). During cancer treatment, about half of pubertal patients reported sexual dysfunction, decreasing to approximately 20% after treatment. However, two patients had children using sperm donation and one patient had a child through natural pregnancy.

CONCLUSIONS

The involvement of parents or legal guardians is crucial in the decision-making process for fertility preservation in (pre)pubertal boys. Regular follow-up, including the use of questionnaires, is essential to provide guidance for fertility preservation programmes and information on fertility restoration options and to address the psychosocial aspects of fertility preservation.

The addition of 5-aminolevulinic acid to HBSS protects testis grafts during hypothermic transportation: a novel preservation strategy

The aim of this investigation was to determine the optimal storage medium for testicular hypothermic transportation and identify the ideal concentration for the application of the protective agent 5-aminolevulinic acid (5-ALA). Furthermore, this study aimed to explore the underlying mechanism of the protective effects of 5-ALA. First, we collected and stored mouse testicular fragments in different media, including Hank's balanced salt solution (HBSS; n = 5), Dulbecco's Modified Eagle Medium/Nutrient Mixture F-12 (DMEM/F12; n = 5), and alpha-minimum essential medium (αMEM; n = 5). Storage of testicular tissue in HBSS preserved the integrity of testicular morphology better than that in the DMEM/F12 group (P < 0.05) and the αMEM group (P < 0.01). Testicular fragments were subsequently placed in HBSS with various concentrations of 5-ALA (0 [control], 1 mmol l-1, 2 mmol l-1, and 5 mmol l-1) to determine the most effective concentration of 5-ALA. The 2 mmol l-1 5-ALA group (n = 3) presented the highest positive rate of spermatogonial stem cells compared with those in the control, 1 mmol l-1, and 5 mmol l-1 5-ALA groups. Finally, the tissue fragments were preserved in HBSS with control (n = 3) and 2 mmol l-1 5-ALA (n = 3) under low-temperature conditions. A comparative analysis was performed against fresh testes (n = 3) to elucidate the underlying mechanism of 5-ALA. Gene set enrichment analysis (GSEA) for WikiPathways revealed that the p38 mitogen-activated protein kinase (MAPK) signaling pathway was downregulated in the 2 mmol l-1 5-ALA group compared with that in the control group (normalized enrichment score [NES] = -1.57, false discovery rate [FDR] = 0.229, and P = 0.019). In conclusion, these data suggest that using 2 mmol l-1 5-ALA in HBSS effectively protected the viability of spermatogonial stem cells upon hypothermic transportation.

European Association of Urology/European Society for Paediatric Urology Guidelines on Paediatric Urology: Summary of the 2024 Updates

BACKGROUND AND OBJECTIVE

We present an overview of the 2024 updates for the European Association of Urology (EAU)/European Society for Paediatric Urology (ESPU) guidelines on paediatric urology to offer evidence-based standards for perioperative management, minimally invasive surgery (MIS), hydrocele, congenital lower urinary tract obstruction (CLUTO), trauma/emergencies, and fertility preservation.

METHODS

A broad literature search was performed for each condition. Recommendations were developed and rated as strong or weak on the basis of the quality of the evidence, the benefit/harm ratio, and potential patient preferences.

KEY FINDINGS AND LIMITATIONS

Recommendations for perioperative management include points related to fasting, premedication, antibiotic prophylaxis, pain control, and thromboprophylaxis in patients requiring general anaesthesia. MIS use is increasing in paediatric urology, with no major differences observed among different MIS approaches. For hydrocele, observation is the initial approach recommended. For persistent cases, treatment varies according to the type of hydrocele. CLUTO cases should be managed in tertiary centres with multidisciplinary expertise in prenatal and postnatal management. Neonatal valve ablation remains the mainstay of treatment, but associated bladder dysfunction requires continuous treatment. Among urological traumas and emergencies, renal trauma is still an important cause of morbidity and mortality. Conservative management has become the standard approach in haemodynamically stable children. Ischaemic priapism is a medical emergency and requires stepwise management. Initial management of nonischaemic priapism is conservative. Fertility preservation in prepubertal children and adolescents has become an increasingly relevant issue owing to the ever-increasing number of cancer survivors receiving gonadotoxic therapies. A major limitation is the scarcity of relevant literature.

CONCLUSIONS AND CLINICAL IMPLICATIONS

This summary of the 2024 EAU/ESPU guidelines provides updated guidance for evidence-based management of some paediatric urological conditions.

PATIENT SUMMARY

We provide a summary of the updated European Association of Urology/European Society for Paediatric Urology guidelines on paediatric urology. There are recommendations on steps to take before and immediately after surgery, management of hydrocele, congenital lower urinary tract obstruction, and urological trauma/emergencies, as well as preservation of fertility. Recommendations are based on a comprehensive review of recent studies.

Mapping the Development of Human Spermatogenesis Using Transcriptomics-Based Data: A Scoping Review

In vitro maturation (IVM) is a promising fertility restoration strategy for patients with nonobstructive azoospermia or for prepubertal boys to obtain fertilizing-competent spermatozoa. However, in vitro spermatogenesis is still not achieved with human immature testicular tissue. Knowledge of various human testicular transcriptional profiles from different developmental periods helps us to better understand the testis development. This scoping review aims to describe the testis development and maturation from the fetal period towards adulthood and to find information to optimize IVM. Research papers related to native and in vitro cultured human testicular cells and single-cell RNA-sequencing (scRNA-seq) were identified and critically reviewed. Special focus was given to gene ontology terms to facilitate the interpretation of the biological function of related genes. The different consecutive maturation states of both the germ and somatic cell lineages were described. ScRNA-seq regularly showed major modifications around 11 years of age to eventually reach the adult state. Different spermatogonial stem cell (SSC) substates were described and scRNA-seq analyses are in favor of a paradigm shift, as the Adark and Apale spermatogonia populations could not distinctly be identified among the different SSC states. Data on the somatic cell lineage are limited, especially for Sertoli cells due technical issues related to cell size. During cell culture, scRNA-seq data showed that undifferentiated SSCs were favored in the presence of an AKT-signaling pathway inhibitor. The involvement of the oxidative phosphorylation pathway depended on the maturational state of the cells. Commonly identified cell signaling pathways during the testis development and maturation highlight factors that can be essential during specific maturation stages in IVM.

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.

Evaluating testicular tissue for future autotransplantation: focus on cancer cell contamination and presence of spermatogonia in tissue cryobanked for boys diagnosed with a hematological malignancy

STUDY QUESTION

What is the contamination rate by cancer cells and spermatogonia numbers in immature testicular tissue (ITT) harvested before the start of gonadotoxic therapy in boys with a hematological malignancy?

SUMMARY ANSWER

Among our cohort of boys diagnosed with acute lymphoblastic leukemia (ALL) and lymphomas, 39% (n = 11/28) had cancer cells identified in their tissues at the time of diagnosis and all patients appeared to have reduced spermatogonia numbers compared to healthy reference cohorts.

WHAT IS KNOWN ALREADY

Young boys affected by a hematological cancer are at risk of contamination of their testes by cancer cells but histological examination is unable to detect the presence of only a few cancer cells, which would preclude autotransplantation of cryobanked ITT for fertility restoration, and more sensitive detection techniques are thus required. Reduced numbers of spermatogonia in ITT in hematological cancer patients have been suggested based on results in a limited number of patients.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort study included 54 pre- and peri-pubertal boys who were diagnosed with a hematological malignancy and who underwent a testicular biopsy for fertility preservation at the time of diagnosis before any gonadotoxic therapy between 2005 and 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Among the 54 patients eligible in our database, formalin-fixed paraffin-embedded (FFPE) testicular tissue was available for 28 boys diagnosed either with ALL (n = 14) or lymphoma (n = 14) and was used to evaluate malignant cell contamination. Hematoxylin and eosin (H&E) staining was performed for each patient to search for cancer cells in the tissue. Markers specific to each patient's disease were identified at the time of diagnosis on the biopsy of the primary tumor or bone marrow aspiration and an immunohistochemistry (IHC) was performed on the FFPE ITT for each patient to evidence his disease markers. PCR analyses on the FFPE tissue were also conducted when a specific gene rearrangement was available.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean age at diagnosis and ITT biopsy of the 28 boys was 7.5 years (age range: 19 months-16 years old). Examination of ITT of the 28 boys on H&E stained sections did not detect malignant cells. Using IHC, we found contamination by cancerous cells using markers specific to the patient's disease in 10 of 28 boys, with a higher rate in patients diagnosed with ALL (57%, n = 8/14) compared with lymphoma (14%, n = 2/14) (P-value < 0.05). PCR showed contamination in three of 15 patients who had specific rearrangements identified on their bone marrow at the time of diagnosis; one of these patients had negative results from the IHC. Compared to age-related reference values of the number of spermatogonia per ST (seminiferous tubule) (Spg/ST) throughout prepuberty of healthy patients from a simulated control cohort, mean spermatogonial numbers appeared to be decreased in all age groups (0-4 years: 1.49 ± 0.54, 4-7 years: 1.08 ± 0.43, 7-11 years: 1.56 ± 0.65, 11-14 years: 3.37, 14-16 years: 5.44 ± 3.14). However, using a cohort independent method based on the Z-score, a decrease in spermatogonia numbers was not confirmed.

LIMITATIONS, REASONS FOR CAUTION

The results obtained from the biopsy fragments that were evaluated for contamination by cancer cells may not be representative of the entire cryostored ITT and tumor foci may still be present outside of the biopsy range.

WIDER IMPLICATIONS OF THE FINDINGS

ITT from boys diagnosed with a hematological malignancy could bear the risk for cancer cell reseeding in case of autotransplantation of the tissue. Such a high level of cancer cell contamination opens the debate of harvesting the tissue after one or two rounds of chemotherapy. However, as the safety of germ cells can be compromised by gonadotoxic treatments, this strategy warrants for the development of adapted fertility restoration protocols. Finally, the impact of the hematological cancer on spermatogonia numbers should be further explored.

STUDY FUNDING/COMPETING INTEREST(S)

The project was funded by a grant from the FNRS-Télévie (grant n°. 7.4533.20) and Fondation Contre le Cancer/Foundation Against Cancer (2020-121) for the research project on fertility restoration with testicular tissue from hemato-oncological boys. The authors declare that they have no conflict of interest.

TRIAL REGISTRATION NUMBER

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A 20-year overview of fertility preservation in boys: new insights gained through a comprehensive international survey

STUDY QUESTION

Twenty years after the inception of the first fertility preservation programme for pre-pubertal boys, what are the current international practices with regard to cryopreservation of immature testicular tissue?

SUMMARY ANSWER

Worldwide, testicular tissue has been cryopreserved from over 3000 boys under the age of 18 years for a variety of malignant and non-malignant indications; there is variability in practices related to eligibility, clinical assessment, storage, and funding.

WHAT IS KNOWN ALREADY

For male patients receiving gonadotoxic treatment prior to puberty, testicular tissue cryopreservation may provide a method of fertility preservation. While this technique remains experimental, an increasing number of centres worldwide are cryopreserving immature testicular tissue and are approaching clinical application of methods to use this stored tissue to restore fertility. As such, standards for quality assurance and clinical care in preserving immature testicular tissue should be established.

STUDY DESIGN SIZE DURATION

A detailed survey was sent to 17 centres within the recently established ORCHID-NET consortium, which offer testicular tissue cryopreservation to patients under the age of 18 years. The study encompassed 60 questions and remained open from 1 July to 1 November 2022.

PARTICIPANTS/MATERIALS SETTING METHODS

Of the 17 invited centres, 16 completed the survey, with representation from Europe, Australia, and the USA. Collectively, these centres have cryopreserved testicular tissue from patients under the age of 18 years. Data are presented using descriptive analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Since the establishment of the first formal fertility preservation programme for pre-pubertal males in 2002, these 16 centres have cryopreserved tissue from 3118 patients under the age of 18 years, with both malignant (60.4%) and non-malignant (39.6%) diagnoses. All centres perform unilateral biopsies, while 6/16 sometimes perform bilateral biopsies. When cryopreserving tissue, 9/16 centres preserve fragments sized ≤5 mm3 with the remainder preserving fragments sized 6-20 mm3. Dimethylsulphoxide is commonly used as a cryoprotectant, with medium supplements varying across centres. There are variations in funding source, storage duration, and follow-up practice. Research, with consent, is conducted on stored tissue in 13/16 centres.

LIMITATIONS REASONS FOR CAUTION

While this is a multi-national study, it will not encompass every centre worldwide that is cryopreserving testicular tissue from males under 18 years of age. As such, it is likely that the actual number of patients is even higher than we report. Whilst the study is likely to reflect global practice overall, it will not provide a complete picture of practices in every centre.

WIDER IMPLICATIONS OF THE FINDINGS

Given the research advances, it is reasonable to suggest that cryopreserved immature testicular tissue will in the future be used clinically to restore fertility. The growing number of patients undergoing this procedure necessitates collaboration between centres to better harmonize clinical and research protocols evaluating tissue function and clinical outcomes in these patients.

STUDY FUNDING/COMPETING INTERESTS

K.D. is supported by a CRUK grant (C157/A25193). R.T.M. is supported by an UK Research and Innovation (UKRI) Future Leaders Fellowship (MR/S017151/1). The MRC Centre for Reproductive Health at the University of Edinburgh is supported by MRC (MR/N022556/1). C.L.M. is funded by Kika86 and ZonMW TAS 116003002. A.M.M.v.P. is supported by ZonMW TAS 116003002. E.G. was supported by the Research Program of the Research Foundation-Flanders (G.0109.18N), Kom op tegen Kanker, the Strategic Research Program (VUB_SRP89), and the Scientific Fund Willy Gepts. J.-B.S. is supported by the Swedish Childhood Cancer Foundation (TJ2020-0026). The work of NORDFERTIL is supported by the Swedish Childhood Cancer Foundation (PR2019-0123; PR2022-0115), the Swedish Research Council (2018-03094; 2021-02107), and the Birgitta and Carl-Axel Rydbeck's Research Grant for Paediatric Research (2020-00348; 2021-00073; 2022-00317; 2023-00353). C.E is supported by the Health Department of the Basque Government (Grants 2019111068 and 2022111067) and Inocente Inocente Foundation (FII22/001). M.P.R. is funded by a Medical Research Council Centre for Reproductive Health Grant No: MR/N022556/1. A.F. and N.R. received support from a French national research grant PHRC No. 2008/071/HP obtained by the French Institute of Cancer and the French Healthcare Organization. K.E.O. is funded by the University of Pittsburgh Medical Center and the US National Institutes of Health HD100197. V.B-L is supported by the French National Institute of Cancer (Grant Seq21-026). Y.J. is supported by the Royal Children's Hospital Foundation and a Medical Research Future Fund MRFAR000308. E.G., N.N., S.S., C.L.M., A.M.M.v.P., C.E., R.T.M., K.D., M.P.R. are members of COST Action CA20119 (ANDRONET) supported by COST (European Cooperation in Science and Technology). The Danish Child Cancer Foundation is also thanked for financial support (C.Y.A.). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

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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.

Cryopreservation of Ovarian and Testicular Tissue and the Influence on Epigenetic Pattern

Ovarian tissue cryopreservation (OTC) or testicular tissue cryopreservation (TTC) are effective and often the only options for fertility preservation in female or male patients due to oncological, medical, or social aspects. While TTC and resumption of spermatogenesis, either in vivo or in vitro, has still be considered an experimental approach in humans, OTC and autotransplantation has been applied increasingly to preserve fertility, with more than 200 live births worldwide. However, the cryopreservation of reproductive cells followed by the resumption of gametogenesis, either in vivo or in vitro, may interfere with sensitive and highly regulated cellular processes. In particular, the epigenetic profile, which includes not just reversible modifications of the DNA itself but also post-translational histone modifications, small non-coding RNAs, gene expression and availability, and storage of related proteins or transcripts, have to be considered in this context. Due to complex reprogramming and maintenance mechanisms of the epigenome in germ cells, growing embryos, and offspring, OTC and TTC are carried out at very critical moments early in the life cycle. Given this background, the safety of OTC and TTC, taking into account the epigenetic profile, has to be clarified. Cryopreservation of mature germ cells (including metaphase II oocytes and mature spermatozoa collected via ejaculation or more invasively after testicular biopsy) or embryos has been used successfully for many years in medically assisted reproduction (MAR). However, tissue freezing followed by in vitro or in vivo gametogenesis has become more attractive in the past, while few human studies have analysed the epigenetic effects, with most data deriving from animal studies. In this review, we highlight the potential influence of the cryopreservation of immature germ cells and subsequent in vivo or in vitro growth and differentiation on the epigenetic profile (including DNA methylation, post-translational histone modifications, and the abundance and availability of relevant transcripts and proteins) in humans and animals.

Fertility preservation in pediatric healthcare: a review

Survival rates for children and adolescents diagnosed with malignancy have been steadily increasing due to advances in oncology treatments. These treatments can have a toxic effect on the gonads. Currently, oocyte and sperm cryopreservation are recognized as well-established and successful strategies for fertility preservation for pubertal patients, while the use of gonadotropin-releasing hormone agonists for ovarian protection is controversial. For prepubertal girls, ovarian tissue cryopreservation is the sole option. However, the endocrinological and reproductive outcomes after ovarian tissue transplantation are highly heterogeneous. On the other hand, immature testicular tissue cryopreservation remains the only alternative for prepubertal boys, yet it is still experimental. Although there are several published guidelines for navigating fertility preservation for pediatric and adolescent patients as well as transgender populations, it is still restricted in clinical practice. This review aims to discuss the indications and clinical outcomes of fertility preservation. We also discuss the probably effective and efficient workflow to facilitate fertility preservation.

Long-Term Fertility Function Sequelae in Young Male Cancer Survivors

With advances in cancer treatment, such as cytotoxic chemotherapy and radiotherapy, grave new sequelae of treatment have emerged for young cancer survivors. One sequela that cannot be overlooked is male infertility, with reportedly 15% to 30% of cancer survivors losing their fertility potential. Cytotoxic therapy influences spermatogenesis at least temporarily, and in some cases, permanently. The degree of spermatogenesis impairment depends on the combination of drugs used, their cumulative dose, and the level of radiation. The American Society of Clinical Oncology has created an index to classify the risks to fertility based on treatment. Medical professionals currently use this risk classification in fertility preservation (FP) programs. FP programs are currently being promoted to prevent spermatogenesis failure resulting from cancer treatment. For patients who are able to ejaculate and whose semen contains sperm, the semen (sperm) is cryopreserved. Moreover, for patients who lack the ability to ejaculate, those with azoospermia or severe oligozoospermia, and those who have not attained puberty (i.e., spermatogenesis has not begun), testicular biopsy is performed to collect the sperm or germ cells and cryopreserve them. This method of culturing germ cells to differentiate the sperm has been successful in some animal models, but not in humans. FP has recently gained popularity; however, some oncologists and medical professionals involved in cancer treatment still lack adequate knowledge of these procedures. This hinders the dissemination of information to patients and the execution of FP. Information sharing and collaboration between reproductive medicine specialists and oncologists is extremely important for the development of FP. In Japan, the network of clinics and hospitals that support FP is expanding across prefectures.

Biomaterials for Testicular Bioengineering: How far have we come and where do we have to go?

Traditional therapeutic interventions aim to restore male fertile potential or preserve sperm viability in severe cases, such as semen cryopreservation, testicular tissue, germ cell transplantation and testicular graft. However, these techniques demonstrate several methodological, clinical, and biological limitations, that impact in their results. In this scenario, reproductive medicine has sought biotechnological alternatives applied for infertility treatment, or to improve gamete preservation and thus increase reproductive rates in vitro and in vivo. One of the main approaches employed is the biomimetic testicular tissue reconstruction, which uses tissue-engineering principles and methodologies. This strategy pursues to mimic the testicular microenvironment, simulating physiological conditions. Such approach allows male gametes maintenance in culture or produce viable grafts that can be transplanted and restore reproductive functions. In this context, the application of several biomaterials have been proposed to be used in artificial biological systems. From synthetic polymers to decellularized matrixes, each biomaterial has advantages and disadvantages regarding its application in cell culture and tissue reconstruction. Therefore, the present review aims to list the progress that has been made and the continued challenges facing testicular regenerative medicine and the preservation of male reproductive capacity, based on the development of tissue bioengineering approaches for testicular tissue microenvironment reconstruction.

Pediatric oncofertility care in limited versus optimum resource settings: results from 39 surveyed centers in Repro-Can-OPEN Study Part I & II

PURPOSE

As a secondary report to elucidate the diverse spectrum of oncofertility practices for childhood cancer around the globe, we present and discuss the comparisons of oncofertility practices for childhood cancer in limited versus optimum resource settings based on data collected in the Repro-Can-OPEN Study Part I & II.

METHODS

We surveyed 39 oncofertility centers including 14 in limited resource settings from Africa, Asia, and Latin America (Repro-Can-OPEN Study Part I), and 25 in optimum resource settings from the USA, Europe, Australia, and Japan (Repro-Can-OPEN Study Part II). Survey questions covered the availability of fertility preservation and restoration options offered in case of childhood cancer as well as their degree of utilization.

RESULTS

In the Repro-Can-OPEN Study Part I & II, responses for childhood cancer and calculated oncofertility scores showed the following characteristics: (1) higher oncofertility scores in optimum resource settings than in limited resource settings for ovarian and testicular tissue cryopreservation; (2) frequent utilization of gonadal shielding, fractionation of anticancer therapy, oophoropexy, and GnRH analogs; (3) promising utilization of oocyte in vitro maturation (IVM); and (4) rare utilization of neoadjuvant cytoprotective pharmacotherapy, artificial ovary, in vitro spermatogenesis, and stem cells reproductive technology as they are still in preclinical or early clinical research settings.

CONCLUSIONS

Based on Repro-Can-OPEN Study Part I & II, we presented a plausible oncofertility best practice model to help optimize care for children with cancer in various resource settings. Special ethical concerns should be considered when offering advanced and innovative oncofertility options to children.

Desire for children and fertility preservation in transgender and gender-diverse people: A systematic review

The decision to pursue one's desire for children is a basic human right. For transgender and gender-diverse (TGD) people, gender-affirming care may alter the possibilities to fulfill one's desire for children due to the impact of this treatment on their reproductive organs. We systematically included 76 studies of varying quality describing the desire for children and parenthood; fertility counseling and utilization; and fertility preservation options and outcomes in TGD people. The majority of TGD people expressed a desire for children. Fertility preservation utilization rates were low as there are many barriers to pursue fertility preservation. The most utilized fertility preservation strategies include oocyte vitrification and sperm banking through masturbation. Oocyte vitrification showed successful outcomes, even after testosterone cessation. Sperm analyses when banking sperm showed a lower quality compared to cis male samples even prior to gender-affirming hormone treatment and an uncertain recovery of spermatogenesis after discontinuing treatment.

In vitro complete differentiation of human spermatogonial stem cells to morphologic spermatozoa using a hybrid hydrogel of agarose and laminin

Spermatogenesis refers to the differentiation of the spermatogonial stem cells (SSCs) located in the base seminiferous tubules into haploid spermatozoa. Prerequisites for in vitro spermatogenesis include an extracellular matrix (ECM), paracrine factors, and testicular somatic cells which play a supporting role for SSCs. Thus, the present study evaluated the potential of co-culturing Sertoli cells and SSCs embedded in a hybrid hydrogel of agarose and laminin, the main components of the ECM. Following the three-week conventional culture of human testicular cells, the cells were cultured in agarose hydrogel or agarose/laminin one (hybrid) for 74 days. Then, immunocytochemistry, real-time PCR, electron microscopy, and morphological staining methods were applied to analyze the presence of SSCs, as well as the other cells of the different stages of spermatogenesis. Based on the results, the colonies with positive spermatogenesis markers were observed in both culture systems. The existence of the cells of all three phases of spermatogenesis (spermatogonia, meiosis, and spermiogenesis) was confirmed in the two groups, while morphological spermatozoa were detected only in the hybrid hydrogel group. Finally, a biologically improved 3D matrix can support all the physiological activities of SSCs such as survival, proliferation, and differentiation.

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.

Tracking Immature Testicular Tissue after Vitrification In Vitro and In Vivo for Pre-Pubertal Fertility Preservation: A Translational Transgenic Mouse Model

Pediatric cancer survivors experiencing gonadotoxic chemoradiation therapy may encounter subfertility or permanent infertility. However, previous studies of cryopreservation of immature testicular tissue (ITT) have mainly been limited to in vitro studies. In this study, we aim to evaluate in vitro and in vivo bioluminescence imaging (BLI) for solid surface-vitrified (SSV) ITT grafts until adulthood. The donors and recipients were transgenic and wild-type mice, respectively, with fresh ITT grafts used as the control group. In our study, the frozen ITT grafts remained intact as shown in the BLI, scanning electron microscopy (SEM) and immunohistochemistry (IHC) analyses. Graft survival was analyzed by BLI on days 1, 2, 5, 7, and 31 after transplantation. The signals decreased by quantum yield between days 2 and 5 in both groups, but gradually increased afterwards until day 31, which were significantly stronger than day 1 after transplantation (p = 0.008). The differences between the two groups were constantly insignificant, suggesting that both fresh and SSV ITT can survive, accompanied by spermatogenesis, until adulthood. The ITT in both groups presented similar BLI intensity and intact cells and ultrastructures for spermatogenesis. This translational model demonstrates the great potential of SSV for ITT in pre-pubertal male fertility preservation.

Melatonin in cryopreservation media improves transplantation efficiency of frozen-thawed spermatogonial stem cells into testes of azoospermic mice

Background

Cryostorage of spermatogonial stem cells (SSCs) is an appropriate procedure for long-term storage of SSCs for fertility preservation. However, it causes damage to cellular structures through overproduction of ROS and oxidative stress. In this study, we examined the protective effect of melatonin as a potent antioxidant in the basic freezing medium to establish an optimal cryopreservation method for SSCs.

Methods

SSCs were obtained from the testes of neonatal male mice aged 3–6 days. Then, 100 μM melatonin was added to the basic freezing medium containing DMSO for cryopreservation of SSCs. Viability, apoptosis-related markers (BAX and BCL2), and intracellular ROS generation level were measured in frozen–thawed SSCs before transplantation using the MTT assay, immunocytochemistry, and flow cytometry, respectively. In addition, Western blotting and immunofluorescence were used to evaluate the expression of proliferation (PLZF and GFRα1) and differentiation (Stra8 and SCP3) proteins in frozen–thawed SSCs after transplantation into recipient testes.

Results

The data showed that adding melatonin to the cryopreservation medium markedly increased the viability and reduced intracellular ROS generation and apoptosis (by decreasing BAX and increasing BCL2) in the frozen–thawed SSCs (p < 0.05). The expression levels of proliferation (PLZF and GFRα1) and differentiation (Stra8 and SCP3) proteins and resumption of spermatogenesis from frozen–thawed SSCs followed the same pattern after transplantation.

Conclusions

The results of this study revealed that adding melatonin as an antioxidant to the cryopreservation medium containing DMSO could be a promising strategy for cryopreservation of SSCs to maintain fertility in prepubertal male children who suffer from cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03029-1.

Organotypic Culture of Testicular Tissue from Infant Boys with Cryptorchidism

Organotypic culture of human fetal testis has achieved fertilization-competent spermatids followed by blastocysts development. This study focuses on whether the organotypic culture of testicular tissue from infant boys with cryptorchidism could support the development of spermatogonia and somatic cells. Frozen-thawed tissues were cultured in two different media, with or without retinoic acid (RA), for 60 days and evaluated by tissue morphology and immunostaining using germ and somatic cell markers. During the 60-day culture, spermatocytes stained by boule-like RNA-binding protein (BOLL) were induced in biopsies cultured with RA. Increased AR expression (p < 0.001) and decreased AMH expression (p < 0.001) in Sertoli cells indicated advancement of Sertoli cell maturity. An increased number of SOX9-positive Sertoli cells (p < 0.05) was observed, while the percentage of tubules with spermatogonia was reduced (p < 0.001). More tubules with alpha-smooth muscle actin (ACTA, peritubular myoid cells (PTMCs) marker) were observed in an RA-absent medium (p = 0.02). CYP17A1/STAR-positive Leydig cells demonstrated sustained steroidogenic function. Our culture conditions support the initiation of spermatocytes and enhanced maturation of Sertoli cells and PTMCs within infant testicular tissues. This study may be a basis for future studies focusing on maintaining and increasing the number of spermatogonia and identifying different factors and hormones, further advancing in vitro spermatogenesis.

Microfluidic and Static Organotypic Culture Systems to Support Ex Vivo Spermatogenesis From Prepubertal Porcine Testicular Tissue: A Comparative Study

Background:In vitro maturation of immature testicular tissue (ITT) cryopreserved for fertility preservation is a promising fertility restoration strategy. Organotypic tissue culture proved successful in mice, leading to live births. In larger mammals, including humans, efficiently reproducing spermatogenesis ex vivo remains challenging. With advances in biomaterials technology, culture systems are becoming more complex to better mimic in vivo conditions. Along with improving culture media components, optimizing physical culture conditions (e.g., tissue perfusion, oxygen diffusion) also needs to be considered. Recent studies in mice showed that by using silicone-based hybrid culture systems, the efficiency of spermatogenesis can be improved. Such systems have not been reported for ITT of large mammals.

Methods: Four different organotypic tissue culture systems were compared: static i.e., polytetrafluoroethylene membrane inserts (OT), agarose gel (AG) and agarose gel with polydimethylsiloxane chamber (AGPC), and dynamic i.e., microfluidic (MF). OT served as control. Porcine ITT fragments were cultured over a 30-day period using a single culture medium. Analyses were performed at days (d) 0, 5, 10, 20 and 30. Seminiferous tubule (ST) integrity, diameters, and tissue core integrity were evaluated on histology. Immunohistochemistry was used to identify germ cells (PGP9.5, VASA, SYCP3, CREM), somatic cells (SOX9, INSL3) and proliferating cells (Ki67), and to assess oxidative stress (MDA) and apoptosis (C-Caspase3). Testosterone was measured in supernatants using ELISA.

Results: ITT fragments survived and grew in all systems. ST diameters, and Sertoli cell (SOX9) numbers increased, meiotic (SYCP3) and post-meiotic (CREM) germ cells were generated, and testosterone was secreted. When compared to control (OT), significantly larger STs (d10 through d30), better tissue core integrity (d5 through d20), higher numbers of undifferentiated spermatogonia (d30), meiotic and post-meiotic germ cells (SYCP3: d20 and 30, CREM: d20) were observed in the AGPC system. Apoptosis, lipid peroxidation (MDA), ST integrity, proliferating germ cell (Ki67/VASA) numbers, Leydig cell (INSL3) numbers and testosterone levels were not significantly different between systems.

Conclusions: Using a modified culture system (AGPC), germ cell survival and the efficiency of porcine germ cell differentiation were moderately improved ex vivo. We assume that further optimization can be obtained with concomitant modifications in culture media components.

Recent Publication Trends in Radiotherapy and Male Infertility over Two Decades: A Scientometric Analysis

Radiotherapy, a popular cancer management procedure, negatively impacts reproductive health particularly by reducing the fertility potential. The purpose of this study was to analyze the research trend in radiotherapy associated with male infertility over the past 20 years (2000-May 2021). SCOPUS database was used to retrieve relevant scientometric data (publication per year, affiliation, journals, countries, type of document and area of research) for different subgenres of radiotherapy and male infertility. A total of 275 articles were published related to radiotherapy and male infertility, with the United States being the most dominant country in research output in this field. Radiotherapy and male infertility research have shown positive growth over the last two decades. In-depth analysis revealed that publications (n) related to radiotherapy and male infertility research mainly focused its impact on semen parameters (n = 155) and fertility preservation techniques (n = 169). Our scientometric results highlight a limited research focus on the field of radiotherapy and its impact on male reproductive hormones. Furthermore, a significant lack of research was noticed in the area of omics and male reproductive organs linked to radiotherapy. Substantial research is warranted to further decipher the effect of radiotherapy, at molecular level, leading to male infertility.

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.

Immature Testicular Tissue Engineered from Weaned Mice to Adults for Prepubertal Fertility Preservation—An In Vivo Translational Study

Male pediatric survivors of cancers and bone marrow transplantation often require adjuvant chemoradiation therapy that may be gonadotoxic. The optimal methods to preserve fertility in these prepubertal males are still under investigation. This manuscript presents an in vivo experiment which involved transplantation of immature testicular tissues (ITT) from transgenic donor, to wild-type recipient mice. Donors and recipients were age-mismatched (from 20-week-old donors to 3-week-old recipients, and vice versa) and the transplantation sites involved the abdomen, skin of the head, back muscle, and scrotum. The application of poly-l-lactic acid (PLLA) scaffold was also evaluated in age-matched donors and recipients (both 3-weeks-old). To quantitively evaluate the process of spermatogenesis after ITT transplantation and scaffold application, bioluminescence imaging (BLI) was employed. Our result showed that ITT from 3-week-old mice had the best potential for spermatogenesis, and the optimal transplantation site was in the scrotum. Spermatogenesis was observed in recipient mice up to 51 days after transplantation, and up to the 85th day if scaffold was used. The peak of spermatogenesis occurred between the 42nd and 55th days in the scaffold group. This animal model may serve as a framework for further studies in prepubertal male fertility preservation.

Application of Tissue-Specific Extracellular Matrix in Tissue Engineering: Focus on Male Fertility Preservation

In vitro spermatogenesis and xenotransplantation of the immature testicular tissues (ITT) are the experimental approaches that have been developed for creating seminiferous tubules-like functional structures in vitro and keeping the integrity of the ITTs in vivo, respectively. These strategies are rapidly developing in response to the growing prevalence of infertility in adolescent boys undergoing cancer treatment, by the logic that there is no sperm cryopreservation option for them. Recently, with the advances made in the field of tissue engineering and biomaterials, these methods have achieved promising results for fertility preservation. Due to the importance of extracellular matrix for the formation of vascular bed around the grafted ITTs and also the creation of spatial arrangements between Sertoli cells and germ cells, today it is clear that the scaffold plays a very important role in the success of these methods. Decellularized extracellular matrix (dECM) as a biocompatible, functionally graded, and biodegradable scaffold with having tissue-specific components and growth factors can support reorganization and physiologic processes of originated cells. This review discusses the common protocols for the tissue decellularization, sterilization, and hydrogel formation of the decellularized and lyophilized tissues as well as in vitro and in vivo studies on the use of the testis-derived dECM for testicular organoids.

Fertility preservation in the pediatric population-experience from a German Cryobank for ovarian tissue

Counseling children on the possibility of fertility preservation prior to a gonadotoxic treatment supports the decision-making process, taking into account that the patients are in a very vulnerable and mentally exhausting situation following the diagnosis. Referral to specialists can be optimized on-site by routing slips with contact addresses, phone numbers, and mail contacts; available time slots for consultation; possibly offers for cost coverage; and an easy-to-understand information leaflet about the different options available. Some of the options for fertility preservation in the prepubertal population especially are still experimental. The unique possibility of fertility preservation before the onset of the gonadotoxic therapy, which may cause premature ovarian insufficiency or azoospermia in the future, should be highlighted.

Testicular tissue cryopreservation for fertility preservation in prepubertal and adolescent boys: A 6 year experience from a Swiss multi-center network

Testicular tissue cryopreservation is the only option of fertility preservation in prepubertal boys. While it is considered experimental, since procedures to obtain mature spermatozoa from prepubertal testicular tissue are still under development, testicular tissue cryopreservation programs have emerged worldwide. Our aim was to study the feasibility and safety of a program of testicular tissue cryopreservation in prepubertal and adolescent boys facing gonadotoxic treatment in three University hospitals in Switzerland. Testicular tissue cryopreservation was accepted by 90% of families, with a total of 35 patients included. The average patient age was 8.5 years (range 7 months to 18.5 years). Malignancies were the most common diagnosis (31 patients, 88.6%) with 16 (45.7%) solid tumors and 15 (42.9%) hematological malignancies. Four (11.4%) patients had a benign condition. The main indication for testicular tissue cryopreservation was conditioning for hematologic stem cell transplantation (25 patients, 71.4%). Testicular tissue was cryopreserved according to the freezing protocol of Louvain Catholic University (Belgium), which includes either only immature testicular tissue freezing, or mature and immature testicular tissue freezing depending on the age of the patient and the presence or absence of haploid cells. The median number of spermatogonia per tubule cross-section was 2 (range 0-6) and spermatozoa were found in only one patient. Tumoral cells were found in one testicular biopsy of a leukemic patient. There were two minor adverse events and none of them required medical treatment or surgical revision. Five patients died during follow-up. Our data demonstrate the feasibility and safety of a program of testicular tissue cryopreservation coordinated by a multidisciplinary team of fertility preservation. Despite the experimental aspect of the procedure, the acceptation rate was high, which highlights the willingness of families and patients to participate in testicular tissue cryopreservation.

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.

Transplantation of rat frozen-thawed testicular tissues: Does fragment size matter?

Cryopreservation of testicular tissue from pre-pubertal boys before gonadotoxic treatment is an important step in fertility preservation. Yet, this approach remains experimental, and there is still few study measuring the effect of tissue size on the graft after cryopreservation and transplantation. The objective of this study is to detect the effect of varying tissue sizes on the efficacy of rat testicular tissue cryopreservation and transplantation. Varying sizes of rat testicular tissues were frozen-thawed and autografted. At the 30th day after grafting, the grafts were collected for histology assessment and immunohistochemistry assay for MAGE-A4 (germ cell marker) and CD34 (blood vessel marker). The transplant recovery, seminiferous tubule integrity, tubular diameter, spermatogonia number, and microsvessel density in testicular fragments sizing in 3 mm in length, 3 mm wide, and 3 mm in thickness were significantly lower than other groups. Whereas, the absorption rate of graft sizing in 1 mm in length, 1 mm in wide, and 1 mm in thickness was significantly higher than other groups. Testicular fragment sizing in 2-3 mm in length, 2-3 mm in wide, and 2 mm in thickness (8 mm³-18 mm³) is suitable for rat testicular tissue cryopreservation and transplantation.

Oxidative Stress Disrupted Prepubertal Rat Testicular Development after Xenotransplantation

In the past two decades, testicular tissue grafting and xenografting have been well established, with the production of fertilization-competent sperm in some studies. However, few studies have been carried out to observe the development of grafted prepubertal testicular tissue of rats and compare the biological differences between in situ testis and grafted testis. In this study, we established the prepubertal testicular tissue xenografting model using a 22-day-old rat and evaluated certain parameters, including testicular histology, testosterone production, and ultrastructure of the grafted testes. We also assessed gene expression of cell proliferation markers, testicular cell markers, and antioxidative defense system. Our results showed that 47 days after transplantation, intratesticular testosterone concentration was not significantly altered; however, cell proliferation, spermatogenesis, and Sertoli cell markers in the transplanted testes were significantly disrupted compared with the control group, accompanied by aggravated apoptosis and oxidative damage. Moreover, the transplanted testes showed smaller tubular diameter and disrupted spermatogenic epithelium with apparent vacuoles, distorted and degenerated germ cells with obscure nuclear margin, and no spermatids in the center of the tubules. Although testis xenografting has been extensively tested and attained great achievement in other species, the prepubertal rat testicular tissue xenografting to immunodeficient mice exhibited obvious spermatogenesis arrest and oxidative damage. The protocol still needs further optimization, and there are still some unknown factors in prepubertal rat testes transplantation.

Cellular Therapy via Spermatogonial Stem Cells for Treating Impaired Spermatogenesis, Non-Obstructive Azoospermia

Male infertility is a major health problem affecting about 8–12% of couples worldwide. Spermatogenesis starts in the early fetus and completes after puberty, passing through different stages. Male infertility can result from primary or congenital, acquired, or idiopathic causes. The absence of sperm in semen, or azoospermia, results from non-obstructive causes (pretesticular and testicular), and post-testicular obstructive causes. Several medications such as antihypertensive drugs, antidepressants, chemotherapy, and radiotherapy could lead to impaired spermatogenesis and lead to a non-obstructive azoospermia. Spermatogonial stem cells (SSCs) are the basis for spermatogenesis and fertility in men. SSCs are characterized by their capacity to maintain the self-renewal process and differentiation into spermatozoa throughout the male reproductive life and transmit genetic information to the next generation. SSCs originate from gonocytes in the postnatal testis, which originate from long-lived primordial germ cells during embryonic development. The treatment of infertility in males has a poor prognosis. However, SSCs are viewed as a promising alternative for the regeneration of the impaired or damaged spermatogenesis. SSC transplantation is a promising technique for male infertility treatment and restoration of spermatogenesis in the case of degenerative diseases such as cancer, radiotherapy, and chemotherapy. The process involves isolation of SSCs and cryopreservation from a testicular biopsy before starting cancer treatment, followed by intra-testicular stem cell transplantation. In general, treatment for male infertility, even with SSC transplantation, still has several obstacles. The efficiency of cryopreservation, exclusion of malignant cells contamination in cancer patients, and socio-cultural attitudes remain major challenges to the wider application of SSCs as alternatives. Furthermore, there are limitations in experience and knowledge regarding cryopreservation of SSCs. However, the level of infrastructure or availability of regulatory approval to process and preserve testicular tissue makes them tangible and accurate therapy options for male infertility caused by non-obstructive azoospermia, though in their infancy, at least to date.

Accelerated and Improved Vascular Maturity after Transplantation of Testicular Tissue in Hydrogels Supplemented with VEGF- and PDGF-Loaded Nanoparticles

Avascular transplantation of frozen-thawed testicular tissue fragments represents a potential future technique for fertility restoration in boys with cancer. A significant loss of spermatogonia was observed in xeno-transplants of human tissue most likely due to the hypoxic period before revascularization. To reduce the effect of hypoxia-reoxygenation injuries, several options have already been explored, like encapsulation in alginate hydrogel and supplementation with nanoparticles delivering a necrosis inhibitor (NECINH) or VEGF. While these approaches improved short-term (5 days) vascular surfaces in grafts, neovessels were not maintained up to 21 days; i.e., the time needed for achieving vessel stabilization. To better support tissue grafts, nanoparticles loaded with VEGF, PDGF and NECINH were developed. Testicular tissue fragments from 4-5-week-old mice were encapsulated in calcium-alginate hydrogels, either non-supplemented (control) or supplemented with drug-loaded nanoparticles (VEGF-nanoparticles; VEGF-nanoparticles + PDGF-nanoparticles; NECINH-nanoparticles; VEGF-nanoparticles + NECINH-nanoparticles; and VEGF-nanoparticles + PDGF-nanoparticles + NECINH-nanoparticles) before auto-transplantation. Grafts were recovered after 5 or 21 days for analyses of tissue integrity (hematoxylin-eosin staining), spermatogonial survival (immuno-histo-chemistry for promyelocytic leukemia zinc finger) and vascularization (immuno-histo-chemistry for α-smooth muscle actin and CD-31). Our results showed that a combination of VEGF and PDGF nanoparticles increased vascular maturity and induced a faster maturation of vascular structures in grafts.