Long-term spermatogonial survival in cryopreserved and xenografted immature human testicular tissue

Advancements in fertility preservation strategies for pediatric male cancer patients: a review of cryopreservation and transplantation of immature testicular tissue

Recently, there has been increasing emphasis on the gonadotoxic effects of cancer therapy in prepubertal boys. As advances in oncology treatments continue to enhance survival rates for prepubertal boys, the need for preserving their functional testicular tissue for future reproduction becomes increasingly vital. Therefore, we explore cutting-edge strategies in fertility preservation, focusing on the cryopreservation and transplantation of immature testicular tissue as a promising avenue. The evolution of cryopreservation techniques, from controlled slow freezing to more recent advancements in vitrification, with an assessment of their strengths and limitations was exhibited. Detailed analysis of cryoprotectants, exposure times, and protocols underscores their impact on immature testicular tissue viability. In transplantation strategy, studies have revealed that the scrotal site may be the preferred location for immature testicular tissue grafting in both autotransplantation and xenotransplantation scenarios. Moreover, the use of biomaterial scaffolds during graft transplantation has shown promise in enhancing graft survival and stimulating spermatogenesis in immature testicular tissue over time. This comprehensive review provides a holistic approach to optimize the preservation strategy of human immature testicular tissue in the future.

P407 hydrogel loaded with nitric oxide microbubbles promotes angiogenesis and functional improvement in testicular transplantation

Prepubertal male patients with cancer have decreased fertility after treatment, but there are currently no suitable means for fertility rescue. Testicular transplantation seems to be a promising treatment. The short-term insufficiency of blood supply after transplantation is the key problem that needs to be solved. In this research, nitric oxide (NO), a gas and small molecule transmitter with the effect of promoting angiogenesis, acted at the site of testicular transplantation. Herein, poloxamer-407 (P407) and lipid microbubble materials served as transport carriers for NO and helped NO to function at the transplant site. P407 hydrogel loaded with NO microbubbles (PNO) slowly released NO in vitro. The three-dimensional space of the hydrogel provided a stable environment for NO microbubbles, which is conducive to the continuous release of NO. In this study, 25% PNO (w/v) was selected, and the gelling temperature was 19.47 °C. The gelling efficiency was relatively high at body temperature. Rheological experiments showed that PNO, at this concentration, had stable mechanical properties. The results from in vivo experiments demonstrated that testicular grafts in the PNO group exhibited a notably accelerated blood flow recovery compared to the other groups. Additionally, the PNO group displayed a significant improvement in reproductive function recovery. In conclusion, PNO exhibited slow release of NO, and a small amount of NO promoted angiogenesis in testicular grafts and restored reproductive function.

In vitro spermatogenesis in artificial testis: current knowledge and clinical implications for male infertility

Men's reproductive health exclusively depends on the appropriate maturation of certain germ cells known as sperm. Certain illnesses, such as Klinefelter syndrome, cryptorchidism, and syndrome of androgen insensitivity or absence of testis maturation in men, resulting in the loss of germ cells and the removal of essential genes on the Y chromosome, can cause non-obstructive azoospermia. According to laboratory research, preserving, proliferating, differentiating, and transplanting spermatogonial stem cells or testicular tissue could be future methods for preserving the fertility of children with cancer and men with azoospermia. Therefore, new advances in stem cell research may lead to promising therapies for treating male infertility. The rate of progression and breakthrough in the area of in vitro spermatogenesis is lower than that of SSC transplantation, but newer methods are also being developed. In this regard, tissue and cell culture, supplements, and 3D scaffolds have opened new horizons in the differentiation of stem cells in vitro, which could improve the outcomes of male infertility. Various 3D methods have been developed to produce cellular aggregates and mimic the organization and function of the testis. The production of an artificial reproductive organ that supports SSCs differentiation will certainly be a main step in male infertility treatment.

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.

Impact of low- or moderate-risk gonadotoxic chemotherapy prior to testicular tissue freezing on spermatogonia quantity in human (pre)pubertal testicular tissue

STUDY QUESTION

What is the impact of low- or moderate-risk gonadotoxic chemotherapy received prior to testicular tissue freezing (TTF), and of the cancer itself, on spermatogonia quantity in testicular tissue from (pre)pubertal boys?

SUMMARY ANSWER

Vincristine, when associated with alkylating agents, has an additional adverse effect on spermatogonia quantity, while carboplatin has no individual contribution to spermatogonia quantity, in testicular tissue of (pre)pubertal boys, when compared to patients who have received non-alkylating chemotherapy.

WHAT IS KNOWN ALREADY

The improved survival rates after cancer treatment necessitate the inclusion of fertility preservation procedures as part of the comprehensive care for patients, taking into consideration their age. Sperm cryopreservation is an established procedure in post-pubertal males while the TTF proposed for (pre)pubertal boys remains experimental. Several studies exploring testicular tissue of (pre)pubertal boys after TTF have examined the tubular fertility index (TFI, percentage of seminiferous tubule cross-sections containing spermatogonia) and the number of spermatogonia per seminiferous tubule cross-section (S/T). All studies have demonstrated that TFI and S/T always decrease after the introduction of chemotherapeutic agents, especially those which carry high gonadotoxic risks such as alkylating agents.

STUDY DESIGN, SIZE, DURATION

Testicular tissue samples from 79 (pre)pubertal boys diagnosed with cancer (from 6 months to 16 years of age) were cryopreserved between May 2009 and June 2014. Their medical diagnoses and previous chemotherapy exposures were recorded. We examined histological sections of (pre)pubertal testicular tissue to elucidate whether the chemotherapy or the primary diagnosis affects mainly TFI and S/T.

PARTICIPANTS/MATERIALS, SETTING, METHODS

(Pre)pubertal boys with cancer diagnosis who had been offered TTF prior to conditioning treatment for hematopoietic stem cell transplantation were included in the study. All the patients had previously received chemotherapy with low- or moderate-risk for future fertility. We have selected patients for whom the information on the chemotherapy received was complete. The quantity of spermatogonia and quality of testicular tissue were assessed by both morphological and immunohistochemical analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

A significant reduction in the number of spermatogonia was observed in boys treated with alkylating agents. The mean S/T values in boys exposed to alkylating agents were significantly lower compared to boys exposed to non-alkylating agents (P = 0.018). In contrast, no difference was observed for patients treated with carboplatin as the sole administered alkylating agent compared to the group of patients exposed to non-alkylating agents. We observed an increase of S/T with age in the group of patients who did not receive any alkylating agent and a decrease of S/T with age when patients received alkylating agents included in the cyclophosphamide equivalent dose (CED) formula (r = 0.6166, P = 0.0434; r = -0.3759, P = 0.0036, respectively). The TFI and S/T decreased further in the group of patients who received vincristine in combination with alkylating agents (decrease of 22.4%, P = 0.0049 and P < 0.0001, respectively), but in this group the CED was also increased significantly (P < 0.0001). Multivariate analysis, after CED adjustment, showed the persistence of a decrease in TFI correlated with vincristine administration (P = 0.02).

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive study of testicular tissues obtained from (pre)pubertal boys who were at risk of infertility. The study population is quite heterogeneous, with a small number of patients in each sub-group. Our results are based on comparisons between patients receiving alkylating agents compared to patients receiving non-alkylating agents rather than chemotherapy-naive patients. The French national guidelines for fertility preservation in cancer patients recommend TTF before highly gonadotoxic treatment. Therefore, all the patients had received low- or moderate-risk gonadotoxic chemotherapy before TTF. Access to testicular tissue samples from chemotherapy-naive patients with comparable histological types of cancer was not possible. The functionality of spermatogonia and somatic cells could not be tested by transplantation or in vitro maturation due to limited sample sizes.

WIDER IMPLICATIONS OF THE FINDINGS

This study summarizes the spermatogonial quantity of (pre)pubertal boys prior to TTF. We confirmed a negative correlation between the cumulative exposure to alkylating agents and spermatogonial quantity. In addition, the synergistic use of vincristine in combination with alkylating agents showed a cumulative deleterious effect on the TFI. For patients for whom fertility preservation is indicated, TTF should be proposed for chemotherapy with a predicted CED above 4000 mg/m2. However, the data obtained from vincristine and carboplatin use should be confirmed in a subsequent study including more patients.

STUDY FUNDING/COMPETING INTEREST(S)

This study had financial support from a French national research grant PHRC No. 2008/071/HP obtained by the French Institute of Cancer and the French Healthcare Organization. The sponsors played no role in the study. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

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

The broad conceptualization of fertility preservation and restoration has become already a major concern in the modern western world since a large number of individuals often face it in the everyday life. Driven by different health conditions and/or social reasons, a variety of patients currently rely on routinely and non-routinely applied assisted reproductive technologies, and mostly on the possibility to cryopreserve gametes and/or gonadal tissues for expanding their reproductive lifespan. This review embraces the data present in human-focused literature regarding the up-to-date methodologies and tools contemporarily applied in IVF laboratories' clinical setting of the oocyte, sperm, and embryo cryopreservation and explores the latest news and issues related to the optimization of methods used in ovarian and testicular tissue cryopreservation.

Germplasm cryopreservation in bulls: Effects of gonadal tissue type, cryoprotectant agent, and freezing-thawing rates on sperm quality parameters

Germplasm preservation is crucial for reproductive programs involving farm and endangered species. This study describes the effects of slow-uncontrolled cryopreservation protocols on bovine sperm associated with testicular or epididymal tissues. Samples from the testis or epididymis (cauda) were cut into ∼0.5 or 1 cm³ fragments and cryopreserved using Me2SO (Dimethyl Sulfoxide) or glycerol-based cryoprotectants. Sperm were collected from testicular or epididymal tissue before and after freezing-thawing (38 °C or 40 °C) and kept at room temperature (RT) or 4 °C during handling. The parameters studied were viability, membrane integrity (HOS), motility, acrosome integrity, chromatin, and morphology. Pre-freezing parameters were lower in testicular sperm than epididymal: HOS+ and DNA integrity (P < 0.05). Normal-% pre-freezing testicular sperm morphology was lower than epididymal (43.3 ± 1.8% vs. 65.3 ± 14.8%). All testicular RT-kept sperm parameters decreased post-freezing, except for acrosome integrity, which remained constant (P > 0.05). There were no differences in Me2SO-frozen tissue sizes (P > 0.05). All epididymal RT-kept sperm parameters dropped post-freezing except for the constant DNA integrity (P > 0.05). 4^oC-kept sperm were fitter than those at RT (P < 0.05). 4^oC-kept testicular sperm viability, DNA, and membrane integrities declined after 38 °C or 40 °C thawing (P < 0.05). Acrosome integrity and motility remained unchanged after freezing (P > 0.05). 4^oC-kept epididymal sperm acrosome integrity, motility, and HOS+% severely dropped post-thawing (P < 0.05). Viability and DNA integrity were unchanged (38 °C vs. 40 °C; P > 0.05). Overall, post-freezing sperm morphology was unaffected (P > 0.05), but Dag defect was significantly lower in testicular samples (P < 0.05). Whole-epididymis parameters were maintained up to 24h at 4 °C (P > 0.05). In conclusion, testis-epididymis freezing protocols should use small tissue pieces, Me2SO-based cryoprotectants, and 4°C-kept samples to reduce sperm damage.

The Role of Promyelocytic Leukemia Zinc Finger (PLZF) and Glial-Derived Neurotrophic Factor Family Receptor Alpha 1 (GFRα1) in the Cryopreservation of Spermatogonia Stem Cells

The cryopreservation of spermatogonia stem cells (SSCs) has been widely used as an alternative treatment for infertility. However, cryopreservation itself induces cryoinjury due to oxidative and osmotic stress, leading to reduction in the survival rate and functionality of SSCs. Glial-derived neurotrophic factor family receptor alpha 1 (GFRα1) and promyelocytic leukemia zinc finger (PLZF) are expressed during the self-renewal and differentiation of SSCs, making them key tools for identifying the functionality of SSCs. To the best of our knowledge, the involvement of GFRα1 and PLZF in determining the functionality of SSCs after cryopreservation with therapeutic intervention is limited. Therefore, the purpose of this review is to determine the role of GFRα1 and PLZF as biomarkers for evaluating the functionality of SSCs in cryopreservation with therapeutic intervention. Therapeutic intervention, such as the use of antioxidants, and enhancement in cryopreservation protocols, such as cell encapsulation, cryoprotectant agents (CPA), and equilibrium of time and temperature increase the expression of GFRα1 and PLZF, resulting in maintaining the functionality of SSCs. In conclusion, GFRα1 and PLZF have the potential as biomarkers in cryopreservation with therapeutic intervention of SSCs to ensure the functionality of the stem cells.

What should be done in terms of fertility preservation for patients with cancer? The French 2021 guidelines

AIM

To provide practice guidelines about fertility preservation (FP) in oncology.

METHODS

We selected 400 articles after a PubMed review of the literature (1987-2019).

RECOMMENDATIONS

Any child, adolescent and adult of reproductive age should be informed about the risk of treatment gonadotoxicity. In women, systematically proposed FP counselling between 15 and 38 years of age in case of treatment including bifunctional alkylating agents, above 6 g/m2 cyclophosphamide equivalent dose (CED), and for radiation doses on the ovaries ≥3 Gy. For postmenarchal patients, oocyte cryopreservation after ovarian stimulation is the first-line FP technique. Ovarian tissue cryopreservation should be discussed as a first-line approach in case of treatment with a high gonadotoxic risk, when chemotherapy has already started and in urgent cases. Ovarian transposition is to be discussed prior to pelvic radiotherapy involving a high risk of premature ovarian failure. For prepubertal girls, ovarian tissue cryopreservation should be proposed in the case of treatment with a high gonadotoxic risk. In pubertal males, sperm cryopreservation must be systematically offered to any male who is to undergo cancer treatment, regardless of toxicity. Testicular tissue cryopreservation must be proposed in males unable to cryopreserve sperm who are to undergo a treatment with intermediate or severe risk of gonadotoxicity. In prepubertal boys, testicular tissue preservation is: - recommended for chemotherapy with a CED ≥7500 mg/m2 or radiotherapy ≥3 Gy on both testicles. - proposed for chemotherapy with a CED ≥5.000 mg/m2 or radiotherapy ≥2 Gy. If several possible strategies, the ultimate choice is made by the patient.

Male fertility preservation and restoration strategies for patients undergoing gonadotoxic therapies†

Medical treatments for cancers or other conditions can lead to permanent infertility. Infertility is an insidious disease that impacts not only the ability to have a biological child but also the emotional well-being of the infertile individuals, relationships, finances, and overall health. Therefore, all patients should be educated about the effects of their medical treatments on future fertility and about fertility preservation options. The standard fertility preservation option for adolescent and adult men is sperm cryopreservation. Sperms can be frozen and stored for a long period, thawed at a later date, and used to achieve pregnancy with existing assisted reproductive technologies. However, sperm cryopreservation is not applicable for prepubertal patients who do not yet produce sperm. The only fertility preservation option available to prepubertal boys is testicular tissue cryopreservation. Next-generation technologies are being developed to mature those testicular cells or tissues to produce fertilization-competent sperms. When sperm and testicular tissues are not available for fertility preservation, inducing pluripotent stem cells derived from somatic cells, such as blood or skin, may provide an alternative path to produce sperms through a process call in vitro gametogenesis. This review describes standard and experimental options to preserve male fertility as well as the experimental options to produce functional spermatids or sperms from immature cryopreserved testicular tissues or somatic cells.

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.

Fertility preservation in boys facing gonadotoxic cancer therapy

Patient survival following childhood cancer has increased with contemporary radiation and chemotherapy techniques. However, gonadotoxicity associated with treatments means that infertility is a common consequence in survivors. Novel fertility preservation options are emerging, but knowledge about these options amongst urologists and other medical professionals is lacking. Pre-pubertal boys generally do not produce haploid germ cells. Thus, strategies for fertility preservation require cryopreservation of tissue containing spermatogonial stem cells (SSCs). Few centres worldwide routinely offer this option and fertility restoration (including testicular tissue engraftment, autotransplantation of SSCs and in vitro maturation of SSCs to spermatozoa) post-thaw is experimental. In pubertal boys, the main option for fertility preservation is masturbation and cryopreservation of the ejaculate. Assisted ejaculation using penile vibratory stimulation or electroejaculation and surgical sperm retrieval can be used in a sequential manner after failed masturbation. Physicians should inform boys and parents about the gonadotoxic effects of cancer treatment and offer fertility preservation. Preclinical experience has identified challenges in pre-pubertal fertility preservation, but available options are expected to be successful when today's pre-pubertal boys with cancer become adults. By contrast, fertility preservation in pubertal boys is clinically proven and should be offered to all patients undergoing cancer treatment.

Limited spermatogenic differentiation of testicular tissue from prepubertal marmosets (Callithrix jacchus) in an in vitro organ culture system

PURPOSE

of the research: To achieve male fertility preservation and restoration, experimental strategies for in vitro germ cell differentiation are required. The effects of two different culture conditions on in vitro maintenance and differentiation of non-human primate germ cells was studied. Three testes from three 6-month-old marmosets were cultured using a gas-liquid interphase system for 12 days. Testicular maturation in pre-culture control and samples cultured in gonadotropin and serum supplemented and non-supplemented culture samples was evaluated using Periodic Acid-Schiff (PAS) and immunohistochemical stainings.

PRINCIPLE RESULTS

Gonadotropins and serum-supplemented tissues demonstrate up to meiotic differentiation (BOULE + Pachytene spermatocyte) and advanced localization of germ cells (MAGEA4+). Moreover, complex (with gonadotropin and marmoset monkey serum) conditions induced progression in somatic cell maturation with advanced seminiferous epithelial organization, maintenance of encapsulation of cultured fragments with peritubular-myoid cells, preservation of tubular structural integrity and architecture.

MAJOR CONCLUSIONS

We report stimulation-dependent in vitro meiotic transition in non-human primate testes. This model represents a novel ex vivo approach to obtain crucial developmental progression.

Fertility Preservation and Restoration Options for Pre-Pubertal Male Cancer Patients: Current Approaches

Fertility preservation for prepubertal male patients undergoing gonadotoxic therapies, potentially depleting spermatogonial cells, is an expanding necessity, yet most of the feasible options are still in the experimental phase. We present our experience and a summary of current and novel possibilities regarding the different strategies to protect or restore fertility in young male patients, before proceeding with chemotherapy or radiotherapy for malignances or other diseases. Adult oncological patients should always be counselled to cryopreserve the semen before starting treatment, however this approach is not suitable for prepubertal boys, who aren't capable to produce sperm yet. Fortunately, since the survival rate of pediatric cancer patients has skyrocketed in the last decade and it's over 84%, safeguarding their future fertility is becoming a major concern for reproductive medicine. Surgical and medical approaches to personalize treatment or protect the gonads could be a valid first step to take. Testicular tissue autologous grafting or xenografting, and spermatogonial stem cells (SSCs) transplantation, are the main experimental options available, but spermatogenesis in vitro is becoming an intriguing alternative. All of these methods feature both strong and weak prospects. There is also relevant controversy regarding the type of testicular material to preserve and the cryopreservation methods. Since transplanted cells are bound to survive based on SSCs number, many ways to enrich their population in cultures have been proposed, as well as different sites of injection inside the testis. Testicular tissue graft has been experimented on mice, rabbits, rhesus macaques and porcine, allowing the birth of live offspring after performing intracytoplasmic sperm injection (ICSI), however it has never been performed on human males yet. In vitro spermatogenesis remains a mirage, although many steps in the right direction have been performed. The manufacturing of 3D scaffolds and artificial spermatogenetic niche, providing support to stem cells in cultures, seems like the best way to further advance in this field.

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.

A review of methods for preserving male fertility

Male infertility is responsible for 50% of men's health problems and has always been a concern for personal and social issues. A survey of global statistics suggests an increase in infertility rate as one of the critical issues documented in studies. There are different ways of maintaining fertility in men, depending on their age. In this paper, we review the preservation methods used for fertility treatment in Iran and other countries. Available data were reviewed from Google Scholar, PubMed, Scopus, Web of Science, IranMedex, MEDLIB, IranDoc and Scientific Information Database and searched for articles published up to 2018, using the medical subject heading (MeSH) terms for cryopreservation, sperm, testicular, spermatogonia stem cell, male infertility and/or Iranian and in the world, to provide evidence from evaluation of fertility preservation the methods. Based the search strategy, 274 manuscripts were found. After reviewing the titles, abstracts and manuscripts in their entirety, 119 articles were obtained and selected according to the eligibility criteria. The 85 studies mentioned above were divided into three categories (sperm, testis, and spermatogonia stem cells (SSCs)), and methods of fertility preservation were investigated. Ways to maintain male fertility were different depending on age, and included sperm, testicular, and SSC freezing. The number of studies on testicular tissue and SSCs was low for human samples, and more studies are still needed. Sperm freezing at infertility centres is the top for male fertility preservation.

Assessment of the architecture and integrity of frozen-thawed testicular tissue from (pre)pubertal boys with cancer

BACKGROUND

Testicular tissue freezing is proposed for fertility preservation to (pre)pubertal boys with cancer before highly gonadotoxic treatment. Studies accurately comparing human (pre)pubertal testicular tissue quality before freezing and after thawing are exceptional. No study has reported this approach in a systematic manner and routine care.

OBJECTIVES

To assess the impact of a control slow freezing protocol on testicular tissue architecture and integrity of (pre)pubertal boys after thawing.

MATERIALS AND METHODS

(Pre)pubertal boys (n = 87) with cancer from 8 Reproductive Biology Laboratories of the French CECOS network benefited from testicular tissue freezing before hematopoietic stem cell transplantation. Seminiferous tubule cryodamage was determined histologically by scoring morphological alterations and by quantifying intratubular spermatogonia and the expression of DNA replication and repair marker in frozen-thawed testicular fragments.

RESULTS

A significant increase in nuclear and epithelial score alterations was observed after thawing (p < 0.0001). The global lesional score remained lower than 1.5 and comparable to fresh testicular tissue. The number of intratubular spermatogonia and the expression of DNA replication and repair marker in spermatogonia and Sertoli cells did not vary significantly after thawing. These data showed the good preservation of the seminiferous tubule integrity and architecture after thawing, as previously reported in our studies performed in prepubertal mice and rats.

DISCUSSION

The current study reports, for the first time, the development of a semi-quantitative analysis of cryodamage in human (pre)pubertal testicular tissue, using a rapid and useful tool that can be proposed in routine care to develop an internal and external quality control for testicular tissue freezing. This tool can also be used when changing one or several parameters of the freezing-thawing procedure.

CONCLUSION

Control slow freezing protocol without seeding maintains the seminiferous tubule architecture and integrity, the concentration of spermatogonia and the expression of DNA replication and repair marker in spermatogonia and Sertoli cells after thawing.

Targeting against the activity of the NLRP3 inflammasome is a potential therapy for rat testicular tissue cryopreservation and transplantation

The objective of the present experiment was to explore the role of NLRP3 inflammasome in the testicular tissue freezing, thawing and grafting; furthermore, the potential effect of a NLRP3 inhibitor on the function of testis transplant was explored. Tissues from male Wistar rats in pre-pubertal age were cryopreserved, thawed and auto-transplanted into the scrotum treated or not treated with the MCC950 (a NLRP3 inhibitor). After grafting, cryopreserved tissue was removed and analysed. Quantitative morphometric, immunohistochemical techniques and Western blotting were used to evaluate the survival of spermatogonia and the activation of the NLRP3 inflammasome after freezing/thawing/grafting. Moreover, serum IL-1β level was assessed with ELISA kits. The testicular transplants exhibited upregulated expression of the NLRP3 pathway meditors (NLRP3, IL-1β). In NLRP3 inhibition group, the rate of recovered grafts, the percentage of intact tubules and spermatogonial number were significantly higher than that in cryopreserved graft group. Moreover, serum concentration of IL-1β in NLRP3 inhibition group was significantly lower than that in cryopreserved graft group. Testicular tissue cryopreservation and transplantation exhibited upregulated expression of NLRP3 pathway and NLRP3 inflammasome blockade improves testicular graft function. These finding suggest that NLRP3 inflammasome is a therapeutic target for testicular tissue cryopreservation and transplantation.

Recent advances: fertility preservation and fertility restoration options for males and females

Fertility preservation is the process of saving gametes, embryos, gonadal tissues and/or gonadal cells for individuals who are at risk of infertility due to disease, medical treatments, age, genetics, or other circumstances. Adult patients have the options to preserve eggs, sperm, or embryos that can be used in the future to produce biologically related offspring with assisted reproductive technologies. These options are not available to all adults or to children who are not yet producing mature eggs or sperm. Gonadal cells/tissues have been frozen for several thousands of those patients worldwide with anticipation that new reproductive technologies will be available in the future. Therefore, the fertility preservation medical and research communities are obligated to responsibly develop next-generation reproductive technologies and translate them into clinical practice. We briefly describe standard options to preserve and restore fertility, but the emphasis of this review is on experimental options, including an assessment of readiness for translation to the human fertility clinic.

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.

Long-term follow-up of boys who have undergone a testicular biopsy for fertility preservation

STUDY QUESTION

What is the long-term reproductive health outcome of patients who have undergone testicular sampling for fertility preservation (FP) before and during the pubertal transition period?

SUMMARY ANSWER

In long-term follow-up after testicular sampling for FP, hormonal data showed that 33% of patients had primary seminiferous tubule insufficiency (high FSH) while semen analyses showed 52% of patients having a severe reduction in total sperm counts or complete absence of ejaculated sperm.

WHAT IS KNOWN ALREADY

During childhood and adolescence, both treatments for cancer and benign haematological diseases that require a bone marrow transplantation, can be detrimental to spermatogenesis by depleting the spermatogonial stem cell population. A testicular biopsy prior to chemotherapy or radiotherapy, even though still an experimental procedure, is now recommended for FP by European and USA oncofertility societies if performed within an institutional research setting. While short-term follow-up studies showed little to no post-operative complications and a normal testicular development after 1 year, data regarding the long-term follow-up of boys who have undergone this procedure are still lacking.

STUDY DESIGN, SIZE, DURATION

This is a longitudinal retrospective cohort study that reports on the long-term follow-up of pre- and peri-pubertal boys who have undergone a testicular biopsy for FP between May 2005 and May 2020. All the patients included in this study were referred to our programme by haematologists-oncologists who are part of a regional multi-centric collaborative care pathway.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Of the 151 boys referred to our FP programme, 139 parents/legal guardians accepted that their child undergo a testicular biopsy. Patient characteristics (i.e. age at biopsy, urogenital history, pubertal status at diagnosis), indications (disease type and dosage of gonadotoxic treatments), operative and post-operative data (biopsy volume, surgical complications), anatomopathological analyses (presence/absence of spermatogonia, Johnsen score) and reproductive data (semen analyses, FSH, LH, testosterone levels) were collected from the institutions' FP database and medical records or from the 'Brussels Health Network'. Cumulative alkylating agent treatment was quantified using the cyclophosphamide equivalent dose (CED). Patients who were 14 years or older at the time of the follow-up and in whom the testicular tissue was shown to contain spermatogonia were included in the reproductive outcome analysis. Comparison of the sperm count findings (absence/presence of spermatozoa) and FSH levels (high (≥10 IU/l)/normal) between patients who were either pre- (Tanner 1) or peri-pubertal (Tanner >1) at the time of the biopsy was done using the Mann-Whitney U or Fisher's tests. A multiple logistic regression was used to study the relationship between the hormone reproductive outcome (high versus normal FSH), as a proxy marker for fertility, and both the pubertal status (Tanner 1 versus Tanner >1) and Johnsen score at the time of the biopsy, while adjusting for CED.

MAIN RESULTS AND THE ROLE OF CHANCE

A testicular biopsy was performed in 139 patients either before (129/139) or after (10/139) the start of a gonadotoxic treatment. Post-operative complications occurred in 2.1% (3/139). At the time of the procedure, 88% (122/139) of patients were pre-pubertal and 12% (17/139) were peri-pubertal. The presence of spermatogonia was documented in 92% (128/139) of cases. Follow-up data were available for 114 patients after excluding 23 deceased and two patients lost to follow-up. A paediatric endocrinologist's follow-up including clinical examination and data on reproductive hormones was available for 57 patients (age ≥14) and 19 (33%) of these were found to have high FSH levels (20 ± 8.8 IU/l). There were 37 patients who had returned to the reproductive specialist's consultation for post-treatment fertility counselling and results on semen analysis were available in 27 of these cases; 14/27 (52%) had severely impaired semen parameters including 8 who were azoospermic. Among patients who received an alkylating agent-based treatment (n = 42), a peri-pubertal status (Tanner >1) at the time of diagnosis/biopsy was found to be associated with a higher risk of having primary testicular failure (defined by an FSH ≥ 10 IU/l) after treatment completion with an OR of 6.4 (95% CI 1.22-33.9; P = 0.03). Of all the patients, 2.6% had already fulfilled their wish to build a family or were actively seeking parenthood.

LIMITATIONS, REASONS FOR CAUTION

Although this is the largest cohort with follow-up data providing proxy markers of the reproductive potential of boys in whom a testicular biopsy for FP was performed before puberty or during the pubertal transition period, the amount of data provided is limited, and originating from a single programme. Further data collection to confirm the observations in other settings is therefore awaited.

WIDER IMPLICATIONS OF THE FINDINGS

Testicular sampling for FP should be offered to boys at risk of losing their fertility (and is recommended for those at high risk) as part of ethically approved research programmes. Long-term follow-up data on increasing numbers of boys who have undergone an FP procedure will help improve patient care in the future as patient-specific factors (e.g. urogenital history, age at gonadotoxic therapy) appear to influence their reproductive potential after gonadotoxic therapies.

STUDY FUNDING/COMPETING INTEREST(S)

FNRS-Télévie, the Salus Sanguinis Foundation and the Belgian Foundation against Cancer supported the studies required to launch the FP programme. The authors declare that they have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Pediatric and Adolescent Oncofertility in Male Patients-From Alpha to Omega

This article reviews the latest information about preserving reproductive potential that can offer enhanced prospects for future conception in the pediatric male population with cancer, whose fertility is threatened because of the gonadotoxic effects of chemotherapy and radiation. An estimated 400,000 children and adolescents aged 0–19 years will be diagnosed with cancer each year. Fertility is compromised in one-third of adult male survivors of childhood cancer. We present the latest approaches and techniques for fertility preservation, starting with fertility preservation counselling, a clinical practice guideline used around the world and finishing with recent advances in basic science and translational research. Improving strategies for the maturation of germ cells in vitro combined with new molecular techniques for gene editing could be the next scientific keystone to eradicate genetic diseases such as cancer related mutations in the offspring of cancer survivors.

Strategies for cryopreservation of testicular cells and tissues in cancer and genetic diseases

Cryopreservation of testicular cells and tissues is useful for the preservation and restoration of fertility in pre-pubertal males expecting gonadotoxic treatment for cancer and genetic diseases causing impaired spermatogenesis. A number of freezing and vitrification protocols have thus been tried and variable results have been reported in terms of cell viability spermatogenesis progression and the production of fertile spermatozoa. A few studies have also reported the production of live offspring from cryopreserved testicular stem cells and tissues in rodents but their replication in large animals and human have been lacking. Advancement in in vitro spermatogenesis system has improved the possibility of producing fertile spermatozoa from the cryopreserved testis and has reduced the dependency on transplantation. This review provides an update on various cryopreservation strategies for fertility preservation in males expecting gonadotoxic treatment. It also discusses various methods of assessing and ameliorating cryoinjuries. Newer developments on in vitro spermatogenesis and testicular tissue engineering for in vitro sperm production from cryopreserved SSCs and testicular tissue are also discussed.

Cryopreservation of grey wolf (Canis lupus) testicular tissue

Development of genomic preservation technologies for canids, especially for seasonally breeding species like the grey wolf (Canis lupus), is needed in advance of growing species conservation concerns. Here, we evaluated the efficacy of two cryopreservation protocols - needle immersion vitrification (NIV) and slow freezing (SF) on grey wolf (n = 7) testicular tissue morphology. NIV samples were equilibrated in a 7.5% v/v dimethyl sulfoxide (DMSO or Me2SO) + 7.5% ethylene glycol (EG) solution in minimum essential medium with 20% FBS for 10 min at 4 °C, then exposed to 15% DMSO + 15% EG + 0.5 M sucrose for 10 min at 4 °C before plunging into liquid nitrogen. For slow freezing, we assessed two cryoprotectant (CPA) strategies, DMSO, 15% v/v alone (SF-D) or 7.5% EG + 7.5% DMSO (SF-ED). Following thawing, there were no significant differences in seminiferous tubule area among treatment groups, although all cryopreserved tissues displayed reduced tubule size compared with fresh controls and increased apoptosis, the latter reaching significance for SF-D treated tissues. Slow freezing improved maintenance of testis architecture, with minimal detachment of seminiferous tubule basement membranes post-thaw. Spermatogonia densities were reduced in NIV tissues compared with fresh, with no differences in spermatocyte, spermatid, or Sertoli cell counts, or germ cell marker DDX4⁺ cell densities among groups. In sum, we conclude that slow freezing better maintained morphology of cryopreserved testicular tissues compared with needle vitrification with 15% each DMSO and EG and 0.5 M sucrose, and that DMSO + EG combination SF supports cell viability. This represents a first step in the development of male gonadal tissue preservation strategies for the grey wolf.

Timing of spermatogonial stem cell transplantation affects the spermatogenic recovery outcome in mice

Spermatogonial stem cell transplantation (SSCT) is a strategy that has demonstrated to be feasible to restore spermatogenesis in animal models when it is performed shortly after the gonadotoxic onset to destroy their endogenous germ cells. However, in the case of boys subjected to fertility preservation, future transplantations will be performed with a delay of many years. In order to study how timing of SSCT affects donor-derived spermatogenic recovery in mice, we compared the percentage of spermatogenic tubule cross-sections within testes of 59 C57BL/6NCrl mice distributed in 6 groups: group 1, untreated mice controls (n = 9); group 2, mice that received a single dose of busulfan 40 mg/kg (n = 10); group 3, mice that received two additional doses of busulfan 10 mg/kg every 5 weeks (n = 10); group 4 (SSCT-A), mice subjected to a standard SSCT performed 5 weeks after a single injection of busulfan 40 mg/kg (n = 10); group 5 (SSCT-B), mice subjected to a delayed SSCT performed 15 weeks after a single injection of busulfan 40 mg/kg (n = 10); and group 6 (SSCT-C), mice subjected to a delayed SSCT with two additional doses of busulfan 10 mg/kg every 5 weeks (n = 10). Spermatogenic recovery in standard SSCT-A and SSCT-C groups ranged between 22.29 and 22.65%, compared with a lower recovery rate of 11.54% showed in the SSCT-B group. However, donor contribution resulted higher in standard SSCT-A, representing a 69.71% of cross-sections, compared with the rest of conditions ranging from 34.69 to 35.42%. Overall, we concluded that a delay in the SSCT from the gonadotoxic onset decreases the efficiency of donor-derived spermatogenic recovery in mice.

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

BACKGROUND

Childhood cancer incidence and survivorship are both on the rise. However, many lifesaving treatments threaten the prepubertal testis. Cryopreservation of immature testicular tissue (ITT), containing spermatogonial stem cells (SSCs), as a fertility preservation (FP) option for this population is increasingly proposed worldwide. Recent achievements notably the birth of non-human primate (NHP) progeny using sperm developed in frozen-thawed ITT autografts has given proof of principle of the reproductive potential of banked ITT. Outlining the current state of the art on FP for prepubertal boys is crucial as some of the boys who have cryopreserved ITT since the early 2000s are now in their reproductive age and are already seeking answers with regards to their fertility.

OBJECTIVE AND RATIONALE

In the light of past decade achievements and observations, this review aims to provide insight into relevant questions for clinicians involved in FP programmes. Have the indications for FP for prepubertal boys changed over time? What is key for patient counselling and ITT sampling based on the latest achievements in animals and research performed with human ITT? How far are we from clinical application of methods to restore reproductive capacity with cryostored ITT?

SEARCH METHODS

An extensive search for articles published in English or French since January 2010 to June 2020 using keywords relevant to the topic of FP for prepubertal boys was made in the MEDLINE database through PubMed. Original articles on fertility preservation with emphasis on those involving prepubertal testicular tissue, as well as comprehensive and systematic reviews were included. Papers with redundancy of information or with an absence of a relevant link for future clinical application were excluded. Papers on alternative sources of stem cells besides SSCs were excluded.

OUTCOMES

Preliminary follow-up data indicate that around 27% of boys who have undergone testicular sampling as an FP measure have proved azoospermic and must therefore solely rely on their cryostored ITT to ensure biologic parenthood. Auto-transplantation of ITT appears to be the first technique that could enter pilot clinical trials but should be restricted to tissue free of malignant cells. While in vitro spermatogenesis circumvents the risk linked to cancer cell contamination and has led to offspring in mice, complete spermatogenesis has not been achieved with human ITT. However, generation of haploid germ cells paves the way to further studies aimed at completing the final maturation of germ cells and increasing the efficiency of the processes.

WIDER IMPLICATIONS

Despite all the research done to date, FP for prepubertal boys remains a relatively young field and is often challenging to healthcare providers, patients and parents. As cryopreservation of ITT is now likely to expand further, it is important not only to acknowledge some of the research questions raised on the topic, e.g. the epigenetic and genetic integrity of gametes derived from strategies to restore fertility with banked ITT but also to provide healthcare professionals worldwide with updated knowledge to launch proper multicollaborative care pathways in the field and address clinical issues that will come-up when aiming for the child's best interest.

Histologic Analysis of Testes from Prepubertal Patients Treated with Chemotherapy Associates Impaired Germ Cell Counts with Cumulative Doses of Cyclophosphamide, Ifosfamide, Cytarabine, and Asparaginase

Cryopreservation of immature testicular tissue is an experimental strategy for the preservation of fertility in prepubertal boys that will be subjected to a gonadotoxic onset, as is the case of oncologic patients. Therefore, the objective of this study was to assess the impact of chemotherapeutic treatments on the testicular histologic phenotype in prepubertal patients. A total of 56 testicular tissue samples from pediatric patients between 0 and 16 years old (28 with at least one previous chemotherapeutic onset and 28 untreated controls) were histologically analyzed and age-matched compared. At least two 5-μm sections from testis per patient separated by a distance of 100 μm were immunostained for the germ cell marker VASA, the spermatogonial markers UTF1, PLZF, UCHL1, and SALL4, the marker for proliferative cells KI67, and the Sertoli cell marker SOX9. The percentage of tubule cross-sections positive for each marker and the number of positive cells per tubule cross-section were determined and association with the cumulative dose received of each chemotherapeutic drug was statistically assessed. Results indicated that alkylating agents, cyclophosphamide and ifosfamide, but also the antimetabolite cytarabine and asparaginase were associated with a decreased percentage of positive tubules and a lower number of positive cells per tubule for the analyzed markers. Our results provide new evidences of the potential of chemotherapeutic agents previously considered to have low gonadotoxic effects such as cytarabine and asparaginase to trigger a severe testicular phenotype, hampering the potential success of future fertility restoration in experimental programs of fertility preservation in prepubertal boys.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Effective cryopreservation protocol for preservation of male primate (Macaca fascicularis) prepubertal fertility

RESEARCH QUESTION

Can specimen types (cells versus tissues) and additive cryoprotectant agents contribute to efficient cryopreservation of primate spermatogonial stem cells (SSC)?

DESIGN

Testicular tissues or cells from four prepubertal monkeys were used in this study. The freezing efficacy of testicular tissue was compared with cell suspensions using conventional freezing media (1.4 mol/l dimethyl sulfoxide [DMSO]) and the efficacy of cryoprotectant additives (1.4 mol/l DMSO combined with trehalose 200 mmol/l, hypotaurine 14 mmol/l, necrostatin-1 50 µmol/l or melatonin 100 µmol/l) was evaluated in testicular tissue freezing.

RESULTS

The survival rate (46.0 ± 4.8% versus 33.7 ± 6.0%; P = 0.0286) and number of recovered cells (5.0 ± 1.5 × 10⁶ cells/g versus 0.7 ± 0.8 × 10⁶ cells/g; P = 0.0286) were significantly higher in frozen tissues than in frozen cell suspensions. After tissue freezing, a higher number of recovered PGP9.5⁺ cells were observed with 200 mmol/l trehalose treatment than in DMSO controls (2.4 ± 0.6 × 10⁶ cells/g versus 1.1 ± 0.3 × 10⁶ cells/g; P = 0.0164). Normal establishment of donor-derived colony was observed in SSC after tissue freezing with 200 mmol/l trehalose.

CONCLUSIONS

Testicular tissue freezing is more effective than single cell suspension freezing for higher recovery of undifferentiated spermatogonia. Moreover, it was verified that slow freezing using 200 mmol/l trehalose, 1.4 mol/l DMSO and 10% KnockOut™ Serum Replacement in Dulbecco's phosphate-buffered saline is an effective cryopreservation protocol for primate testicular tissue.

Fertility Preservation in Childhood Cancer: Endocrine Activity in Prepubertal Human Testis Xenografts Exposed to a Pubertal Hormone Environment

Simple Summary

Substantial strides have been made in treating childhood cancers; however, as a result of chemotherapy and radiotherapy, young males experience long-term side effects, including impaired fertility. Whilst prepubertal testicular tissue can be cryopreserved prior to gonadotoxic treatments, it remains to be determined how to generate mature gametes from the immature human testis tissue. Development of immature germ cells into sperm is a complex process, which is supported by mature Sertoli cells and testosterone produced from Leydig cells. We used an established testicular xenotransplantation model to investigate the effect of puberty hormones, known as gonadotrophins, on functional maturation of the spermatogonial stem cell (SSC) niche. Limited testosterone production and partial maturation of Sertoli cells occurred in prepubertal testis grafts, suggesting that longer periods of grafting and/or identification of additional factors are required to develop testicular transplantation as a model for fertility preservation in male survivors of childhood cancer.

Abstract

Survivors of childhood cancer are at risk for long-term treatment-induced health sequelae, including gonadotoxicity and iatrogenic infertility. At present, for prepubertal boys there are no viable clinical options to preserve future reproductive potential. We investigated the effect of a pubertal induction regimen with gonadotrophins on prepubertal human testis xenograft development. Human testis tissue was obtained from patients with cancer and non-malignant haematological disorders (n = 6; aged 1–14 years) who underwent testis tissue cryopreservation for fertility preservation. Fresh and frozen-thawed testis fragments were transplanted subcutaneously or intratesticularly into immunocompromised mice. Graft-bearing mice received injections of vehicle or exogenous gonadotrophins, human chorionic gonadotrophin (hCG, 20 IU), and follicle-stimulating hormone (FSH, 12.5 IU) three times a week for 12 weeks. The gross morphology of vehicle and gonadotrophin-exposed grafts was similar for both transplantation sites. Exposure of prepubertal human testis tissue xenografts to exogenous gonadotrophins resulted in limited endocrine function of grafts, as demonstrated by the occasional expression of the steroidogenic cholesterol side-chain cleavage enzyme (CYP11A1). Plasma testosterone concentrations (0.13 vs. 0.25 ng/mL; p = 0.594) and seminal vesicle weights (10.02 vs. 13.93 mg; p = 0.431) in gonadotrophin-exposed recipient mice were comparable to vehicle-exposed controls. Regardless of the transplantation site and treatment, initiation and maintenance of androgen receptor (AR) expression were observed in Sertoli cells, indicating commitment towards a more differentiated status. However, neither exogenous gonadotrophins (in castrated host mice) nor endogenous testosterone (in intact host mice) were sufficient to repress the expression of markers associated with immature Sertoli cells, such as anti-Müllerian hormone (AMH) and Ki67, or to induce the redistribution of junctional proteins (connexin 43, CX43; claudin 11, CLDN11) to areas adjacent to the basement membrane. Spermatogonia did not progress developmentally but remained the most advanced germ cell type in testis xenografts. Overall, these findings demonstrate that exogenous gonadotrophins promote partial activation and maturation of the somatic environment in prepubertal testis xenografts. However, alternative hormone regimens or additional factors for pubertal induction are required to complete the functional maturation of the spermatogonial stem cell (SSC) niche.

A prospective study on the long-term outcome of prepubertal and pubertal boys undergoing testicular biopsy for fertility preservation prior to hematologic stem cell transplantation

BACKGROUND

Few studies have reported the long-term outcomes of prepubertal and pubertal boys undergoing testicular biopsy for fertility preservation (FP).

PROCEDURE

This prospective longitudinal study examined 21 boys (aged 1.5-14.5 years) who underwent testicular biopsy for FP prior to allogeneic (n = 20) or autologous (n = 1) hematological stem cell transplantation (HSCT) between 2003 and 2010. During counseling, pubertal boys were encouraged to produce a sperm sample by masturbation , while prepubertal boys were presented with surgical testicular tissue retrieval as an option for experimental FP. Clinical outcomes included postoperative complications, pubertal development, and sex-hormone levels. Survivors approaching adulthood were encouraged to provide semen samples.

RESULTS

Twenty boys, including 14 in prepuberty and six in early puberty (Tanner stage 2-3), underwent open testicular biopsies. Two pubertal biopsies contained mature sperms, which were cryopreserved. Testicular tissue was vitrified in the remaining 18 cases. One pubertal boy (Tanner stage 4) underwent percutaneous testicular sperm aspiration and sperms obtained were cryopreserved. Postoperative complications (hematoma or infection) were rare. Overall, 14 boys survived >5 years (mean follow-up after HSCT, 7.2 years) and 11 showed advanced puberty. Semen samples were provided by five boys and obtained sperm were cryopreserved from two. Individuals at adulthood had normal testosterone levels but subnormal testicular size, high follicle stimulating hormone, and low inhibin B and anti-Müllerian hormone levels.

CONCLUSION

No long-term risks were detected during continuous clinical follow-up. Experimental testicular biopsies for FP were well accepted by the patients and families, despite the absence of methods to use prepubertal tissue for fertility treatment.

Leptin promotes proliferation of neonatal mouse stem/progenitor spermatogonia

PURPOSE

To keep and increase spermatogonial stem cell number (SSC) is the only available option for pediatric cancer survivors to maintain fertility. Leptin is secreted by the epididymal white adipose tissue and has receptors on stem/progenitor spermatogonia. The purpose of this study is to demonstrate dose- and time-dependent proliferative effect of leptin on stem/progenitor spermatogonia cultures from prepubertal mice testes.

METHODS

CD90.2 (+) stem/progenitor spermatogonia were isolated from the C57BL/6 mouse testis on postnatal day 6 and placed in culture. The proliferative effect of leptin supplementation was assessed by colony formation (diameter and number), WST proliferation assays, and xCELLigence real-time cell analysis (RTCA) on days 3, 5, and 7 of culture. Expressions of p-ERK1/2, p-STAT3, total STAT3, and p-SHP2 levels were determined by western blot analysis.

RESULTS

Leptin supplementation of 100 ng/ml increased the diameter (p = 0.001) and number (p = 0.01) of colonies in stem/progenitor spermatogonial cultures and caused higher proliferation by WST-1 (p = 0.009) compared with the control on day 7. The EC50 was calculated as 114 ng/ml for leptin by RTCA. Proliferative dose of leptin induced increased expression of p-ERK1/2 (p = 0.009) and p-STAT3 (p = 0.023) on stem/progenitor spermatogonia when compared with the untreated group.

CONCLUSION

The results indicated that leptin supplementation exhibited a dose- and time-dependent proliferative effect on stem/progenitor spermatogonia that was associated with increased expression of ERK1/2 and STAT3 pathways while maintaining their undifferentiated state. This output presents a new agent that may help to expand the stem/progenitor spermatogonia pool from the neonatal testis in order to autotransplant after cancer treatment.

Approaches and Technologies in Male Fertility Preservation

Male fertility preservation is required when treatment with an aggressive chemo-/-radiotherapy, which may lead to irreversible sterility. Due to new and efficient protocols of cancer treatments, surviving rates are more than 80%. Thus, these patients are looking forward to family life and fathering their own biological children after treatments. Whereas adult men can cryopreserve their sperm for future use in assistance reproductive technologies (ART), this is not an option in prepubertal boys who cannot produce sperm at this age. In this review, we summarize the different technologies for male fertility preservation with emphasize on prepubertal, which have already been examined and/or demonstrated in vivo and/or in vitro using animal models and, in some cases, using human tissues. We discuss the limitation of these technologies for use in human fertility preservation. This update review can assist physicians and patients who are scheduled for aggressive chemo-/radiotherapy, specifically prepubertal males and their parents who need to know about the risks of the treatment on their future fertility and the possible present option of fertility preservation.

Complete spermatogenesis in intratesticular testis tissue xenotransplants from immature non-human primate

STUDY QUESTION

Can full spermatogenesis be achieved after xenotransplantation of prepubertal primate testis tissue to the mouse, in testis or subcutaneously?

SUMMARY ANSWER

Intratesticular xenotransplantation supported the differentiation of immature germ cells from marmoset (Callithrix jacchus) into spermatids and spermatozoa at 4 and 9 months post-transplantation, while in subcutaneous transplants, spermatogenic arrest was observed at 4 months and none of the transplants survived at 9 months.

WHAT IS KNOWN ALREADY

Auto-transplantation of cryopreserved immature testis tissue (ITT) could be a potential fertility restoration strategy for patients with complete loss of germ cells due to chemo- and/or radiotherapy at a young age. Before ITT transplantation can be used for clinical application, it is a prerequisite to demonstrate the feasibility of the technique and identify the conditions required for establishing spermatogenesis in primate ITT transplants. Although xenotransplantation of ITT from several species has resulted in complete spermatogenesis, in human and marmoset, ITT has not been successful.

STUDY DESIGN, SIZE, DURATION

In this study, we used marmoset as a pre-clinical animal model. ITT was obtained from two 6-month-old co-twin marmosets. A total of 147 testis tissue pieces (~0.8-1.0 mm3 each) were transplanted into the testicular parenchyma (intratesticular; n = 40) or under the dorsal skin (ectopic; n = 107) of 4-week-old immunodeficient Swiss Nu/Nu mice (n = 20). Each mouse received one single marmoset testis tissue piece in each testis and 4-6 pieces subcutaneously. Xenotransplants were retrieved at 4 and 9 months post-transplantation and evaluations were performed with regards to transplant survival, spermatogonial quantity and germ cell differentiation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Transplant survival was histologically evaluated by haematoxylin-periodic acid Schiff (H/PAS) staining. Spermatogonia were identified by MAGE-A4 via immunohistochemistry. Germ cell differentiation was assessed by morphological identification of different germ cell types on H/PAS stained sections. Meiotically active germ cells were identified by BOLL expression. CREM immunohistochemistry was performed to confirm the presence of post-meiotic germ cells and ACROSIN was used to determine the presence of round, elongating and elongated spermatids.

MAIN RESULTS AND THE ROLE OF CHANCE

Four months post-transplantation, 50% of the intratesticular transplants and 21% of the ectopic transplants were recovered (P = 0.019). The number of spermatogonia per tubule did not show any variation. In 33% of the recovered intratesticular transplants, complete spermatogenesis was established. Overall, 78% of the intratesticular transplants showed post-meiotic differentiation (round spermatids, elongating/elongated spermatids and spermatozoa). However, during the same period, spermatocytes (early meiotic germ cells) were the most advanced germ cell type present in the ectopic transplants. Nine months post-transplantation, 50% of the intratesticular transplants survived, whilst none of the ectopic transplants was recovered (P < 0.0001). Transplants contained more spermatogonia per tubule (P = 0.018) than at 4 months. Complete spermatogenesis was observed in all recovered transplants (100%), indicating a progressive spermatogenic development in intratesticular transplants between the two time-points. Nine months post-transplantation, transplants contained more seminiferous tubules with post-meiotic germ cells (37 vs. 5%; P < 0.001) and fewer tubules without germ cells (2 vs. 8%; P = 0.014) compared to 4 months post-transplantation.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Although xenotransplantation of marmoset ITT was successful, it does not fully reflect all aspects of a future clinical setting. Furthermore, due to ethical restrictions, we were not able to prove the functionality of the spermatozoa produced in the marmoset transplants.

WIDER IMPLICATIONS OF THE FINDINGS

In this pre-clinical study, we demonstrated that testicular parenchyma provides the required microenvironment for germ cell differentiation and long-term survival of immature marmoset testis tissue, likely due to the favourable temperature regulation, growth factors and hormonal support. These results encourage the design of new experiments on human ITT xenotransplantation and show that intratesticular transplantation is likely to be superior to ectopic transplantation for fertility restoration following gonadotoxic treatment in childhood.

STUDY FUNDING/COMPETING INTEREST(S)

This project was funded by the ITN Marie Curie Programme 'Growsperm' (EU-FP7-PEOPLE-2013-ITN 603568) and the scientific Fund Willy Gepts from the UZ Brussel (ADSI677). D.V.S. is a post-doctoral fellow of the Fonds Wetenschappelijk Onderzoek (FWO; 12M2815N). No conflict of interest is declared.

Fertility preservation in boys: recent developments and new insights †

BACKGROUND

Infertility is an important side effect of treatments used for cancer and other non-malignant conditions in males. This may be due to the loss of spermatogonial stem cells (SSCs) and/or altered functionality of testicular somatic cells (e.g. Sertoli cells, Leydig cells). Whereas sperm cryopreservation is the first-line procedure to preserve fertility in post-pubertal males, this option does not exist for prepubertal boys. For patients unable to produce sperm and at high risk of losing their fertility, testicular tissue freezing is now proposed as an alternative experimental option to safeguard their fertility.

OBJECTIVE AND RATIONALE

With this review, we aim to provide an update on clinical practices and experimental methods, as well as to describe patient management inclusion strategies used to preserve and restore the fertility of prepubertal boys at high risk of fertility loss.

SEARCH METHODS

Based on the expertise of the participating centres and a literature search of the progress in clinical practices, patient management strategies and experimental methods used to preserve and restore the fertility of prepubertal boys at high risk of fertility loss were identified. In addition, a survey was conducted amongst European and North American centres/networks that have published papers on their testicular tissue banking activity.

OUTCOMES

Since the first publication on murine SSC transplantation in 1994, remarkable progress has been made towards clinical application: cryopreservation protocols for testicular tissue have been developed in animal models and are now offered to patients in clinics as a still experimental procedure. Transplantation methods have been adapted for human testis, and the efficiency and safety of the technique are being evaluated in mouse and primate models. However, important practical, medical and ethical issues must be resolved before fertility restoration can be applied in the clinic.Since the previous survey conducted in 2012, the implementation of testicular tissue cryopreservation as a means to preserve the fertility of prepubertal boys has increased. Data have been collected from 24 co-ordinating centres worldwide, which are actively offering testis tissue cryobanking to safeguard the future fertility of boys. More than 1033 young patients (age range 3 months to 18 years) have already undergone testicular tissue retrieval and storage for fertility preservation.

LIMITATIONS REASONS FOR CAUTION

The review does not include the data of all reproductive centres worldwide. Other centres might be offering testicular tissue cryopreservation. Therefore, the numbers might be not representative for the entire field in reproductive medicine and biology worldwide. The key ethical issue regarding fertility preservation in prepubertal boys remains the experimental nature of the intervention.

WIDER IMPLICATIONS

The revised procedures can be implemented by the multi-disciplinary teams offering and/or developing treatment strategies to preserve the fertility of prepubertal boys who have a high risk of fertility loss.

STUDY FUNDING/COMPETING INTERESTS

The work was funded by ESHRE. None of the authors has a conflict of interest.

The study and manipulation of spermatogonial stem cells using animal models

Spermatogonial stem cells (SSCs) are a rare group of cells in the testis that undergo self-renewal and complex sequences of differentiation to initiate and sustain spermatogenesis, to ensure the continuity of sperm production throughout adulthood. The difficulty of unequivocal identification of SSCs and complexity of replicating their differentiation properties in vitro have prompted the introduction of novel in vivo models such as germ cell transplantation (GCT), testis tissue xenografting (TTX), and testis cell aggregate implantation (TCAI). Owing to these unique animal models, our ability to study and manipulate SSCs has dramatically increased, which complements the availability of other advanced assisted reproductive technologies and various genome editing tools. These animal models can advance our knowledge of SSCs, testis tissue morphogenesis and development, germ-somatic cell interactions, and mechanisms that control spermatogenesis. Equally important, these animal models can have a wide range of experimental and potential clinical applications in fertility preservation of prepubertal cancer patients, and genetic conservation of endangered species. Moreover, these models allow experimentations that are otherwise difficult or impossible to be performed directly in the target species. Examples include proof-of-principle manipulation of germ cells for correction of genetic disorders or investigation of potential toxicants or new drugs on human testis formation or function. The primary focus of this review is to highlight the importance, methodology, current and potential future applications, as well as limitations of using these novel animal models in the study and manipulation of male germline stem cells.

Fertility sparing strategies for pre- and peripubertal male cancer patients

Genetic parenthood following cancer therapy is considered to be a major factor of quality of life. Given the rising proportion of patients surviving cancer due to improved therapeutic protocols, it is an issue of growing importance. Hence, the efforts to preserve fertility have motivated researchers to develop options for the paediatric population facing fertility-threatening cancer therapies. In prepubertal boys who do not yet produce sperm, cryo-banking of testicular tissue containing spermatogonial stem cells (SSCs) is the only viable option for future fertility preservation. While proposed in a number of clinics worldwide, however, this strategy remains still experimental.

Transplanting the SSCs, or testicular tissue containing SSCs, back to the cured patient appears the most promising strategy. However, experiments performed with human testicular tissue in mice models reveal spermatogonial loss after transplantation, indicating the need for further optimisation of the transplantation procedure. The approach further poses the risk of reintroducing tumour cells back to the patient. In cases of haematological and blood-metastasising malignancies, in vitro generation of sperm combined with assisted reproductive technologies (ART), is the only possibility, avoiding reintroducing cancer cells. Although xenotransplantation would allow to recover sperm cells for ART being thus on the safe side with regard to cancer cells, the risk of infections with xeno-microbiological agents makes this option incompatible with clinical application. So far, offspring from in vitro matured sperm has only been achieved in mice. While human haploid germ cells, showing specific morphological features, expression of post-meiotic markers, as well as DNA and chromosome content, as well as fertilisation and development capacity, have been obtained by culturing spermatogonia or immature testicular tissue, the functionality of these cells still needs to be demonstrated. Despite the promising results obtained in recent years, further research is urgently warranted to establish a clinical tool offering these boys a fertility restoration option in the future. This mini-review will focus on current achievements and future challenges of fertility preservation in young boys and underscore the next steps required to translate experimental strategies into clinical practice.

Progress in translational reproductive science: testicular tissue transplantation and in vitro spermatogenesis

Since the birth of the first child conceived via in vitro fertilization 40 years ago, fertility treatments and assisted reproductive technology have allowed many couples to reach their reproductive goals. As of yet, no fertility options are available for men who cannot produce functional sperm, but many experimental therapies have demonstrated promising results in animal models. Both autologous (stem cell transplantation, de novo morphogenesis, and testicular tissue grafting) and outside-the-body (xenografting and in vitro spermatogenesis) approaches exist for restoring sperm production in infertile animals with varying degrees of success. Once safety profiles are established and an ideal patient population is chosen, some of these techniques may be ready for human experimentation in the near future, with likely clinical implementation within the next decade.

Exogenous Gonadotrophin Stimulation Induces Partial Maturation of Human Sertoli Cells in a Testicular Xenotransplantation Model for Fertility Preservation

The future fertility of prepubertal boys with cancer may be irreversibly compromised by chemotherapy and/or radiotherapy. Successful spermatogenesis has not been achieved following the xenotransplantation of prepubertal human testis tissue, which is likely due to the failure of somatic cell maturation and function. We used a validated xenograft model to identify the factors required for Leydig and Sertoli cell development and function in immature human testis. Importantly, we compared the maturation status of Sertoli cells in xenografts with that of human testis tissues (n = 9, 1 year-adult). Human fetal testis (n = 6; 14–21 gestational weeks) tissue, which models many aspects of prepubertal testicular development, was transplanted subcutaneously into castrated immunocompromised mice for ~12 months. The mice received exogenous human chorionic gonadotropin (hCG; 20IU, 3×/week). In xenografts exposed continuously to hCG, we demonstrate the maintenance of Leydig cell steroidogenesis, the acquisition of features of Sertoli cell maturation (androgen receptor, lumen development), and the formation of the blood–testis barrier (connexin 43), none of which were present prior to the transplantation or in xenografts in which hCG was withdrawn after 7 months. These studies provide evidence that hCG plays a role in Sertoli cell maturation, which is relevant for future investigations, helping them generate functional gametes from immature testis tissue for clinical application.

Effect of cryoprotectant-free vitrification versus conventional freezing on human testicular sperm motility: a prospective comparative study

This study aimed to demonstrate the effect of conventional freezing versus cryoprotectant-free vitrification on the recovery of testicular sperm motility. Testicular samples were obtained from 50 patients with azoospermia for testicular biopsy ± potential sperm storage. We retrieved 100 spermatozoa from each patient divided equally into two straws. They were frozen using conventional freezing as a control group and cryoprotectant-free vitrification in micro-capillary system using open-pulled straws. Seven days later, cryopreserved straws were thawed and assessed in duplicate. The mean sperm motility between the original spermatozoa sample and the post warming sample was reduced after conventional freezing compared to cryoprotectant-free vitrification (4.48 ± 2.09% versus 3.25 ± 1.92%, p < 0.001; 4.48 ± 2.09% vs 3.68 ± 1.93%, p < 0.001, respectively). There was a significant difference between the two methods regarding the mean sperm motility after warming (3.38 ± 1.86% versus 3.76 ± 1.88%, p = 0.015). The mean recovery percent of testicular sperm motility from the original sperm sample was lower (p = 0.02) after conventional freezing compared to cryoprotectant-free vitrification (78.4 ± 28.17% versus 85.37 ± 23.63%). Overall, the rate of post-thaw recovery of human testicular sperm motility improved using cryoprotectant-free vitrification compared to conventional freezing.

Significant Benefits of Nanoparticles Containing a Necrosis Inhibitor on Mice Testicular Tissue Autografts Outcomes

Fertility preservation for prepubertal boys relies exclusively on cryopreservation of immature testicular tissue (ITT) containing spermatogonia as the only cells with reproductive potential. Preclinical studies that used a nude mice model to evaluate the development of human transplanted ITT were characterized by important spermatogonial loss. We hypothesized that the encapsulation of testicular tissue in an alginate matrix supplemented with nanoparticles containing a necrosis inhibitor (NECINH-NPS) would improve tissue integrity and germ cells' survival in grafts. We performed orthotopic autotransplantation of 1 mm³ testicular tissue fragments recovered form mice (aged 4-5 weeks). Fragments were either non-encapsulated, encapsulated in an alginate matrix, or encapsulated in an alginate matrix containing NECINH-NPs. Grafts were recovered 5- and 21-days post-transplantation. We evaluated tissue integrity (hematoxylin-eosin staining), germ cells survival (immunohistochemistry for promyelocytic leukemia zinc-finger, VASA, and protein-boule-like), apoptosis (immunohistochemistry for active-caspase 3), and lipid peroxidation (immunohistochemistry for malondialdehyde). NECINH-NPs significantly improved testicular tissue integrity and germ cells' survival after 21 days. Oxidative stress was reduced after 5 days, regardless of nanoparticle incorporation. No effect on caspase-dependent apoptosis was observed. In conclusion, NECINH-NPs in an alginate matrix significantly improved tissue integrity and germ cells' survival in grafts with the perspective of higher reproductive outcomes.

Effect of cryopreservation on sperm DNA fragmentation and apoptosis rates in the testicular tissue of domestic cats

The objectives of the present study were to evaluate the damage caused by cryopreservation on sperm DNA and estimate the percentage of cell apoptosis in tissue after thawing. Testicles of cats were sectioned into of 0.3 cm³ and 0.5 cm³ fragments and evaluated for DNA damage using acridine orange and semi-quantitatively through histo-morphological and immunohistochemical methods (caspase-3). Other fragments were placed in cryotubes with diluent containing either 3% glycerol or 3% propanediol, and were cryopreserved. Evaluation using acridine orange indicated there was a difference with use of propanediol and glycerol on DNA damage in 0.5 cm³fragments, with the latter being more effective than the former for cryopreservation. Results from histomorphological evaluations indicated there was a greater cell integrity among germ cells that were not cryopreserved, based on criteria assessed (detachment of cells from basal membrane, retraction of seminiferous tubule epithelium, visibility of the spermatogonia nucleoli and nuclear spermatogonia condensation), for both sizes of fragments. The values for these variables decreased after cryopreservation, with there being no differences as a result of size of fragment stored or between cryoprotectants used (P > 0.05). The staining for caspase-3 differed for the cytoplasm, nuclei and germ cells. Assessment of these staining patterns indicated the fresh fragments had an amount of cell damage and there was a similar amount of damage detected in cryopreserved fragments. This finding indicated that there was considerable efficacy in preserving the tissue fragments with use of the freezing protocols that were evaluated in this study.

Vitamin E but Not GSH Decreases Reactive Oxygen Species Accumulation and Enhances Sperm Production during In Vitro Maturation of Frozen-Thawed Prepubertal Mouse Testicular Tissue

Freezing-thawing procedures and in vitro culture conditions are considered as a source of stress associated with increased reactive oxygen species (ROS) generation, leading to a damaged cell aerobic metabolism and consequently to oxidative stress. In the present study, we sought to investigate whether vitamin E (Vit E) or reduced glutathione (GSH) enhances sperm production by decreasing ROS accumulation during in vitro maturation of prepubertal mice testes. Testes of prepubertal mice were cryopreserved using a freezing medium supplemented or not supplemented with Vit E and were cultured after thawing. In presence of Rol alone in culture medium, frozen-thawed (F-T) testicular tissues exhibited a higher ROS accumulation than fresh tissue during in vitro culture. However, Vit E supplementation in freezing, thawing, and culture media significantly decreased cytoplasmic ROS accumulation in F-T testicular tissue during in vitro maturation when compared with F-T testicular tissue cultured in the presence of Rol alone, whereas GSH supplementation in culture medium significantly increased ROS accumulation associated with cytolysis and tissue disintegration. Vit E but not GSH promoted a better in vitro sperm production and was a suitable ROS scavenger and effective molecule to improve the yield of in vitro spermatogenesis from F-T prepubertal mice testes. The prevention of oxidative stress in the cytoplasmic compartment should be regarded as a potential strategy for improving testicular tissue viability and functionality during the freeze-thaw procedure and in vitro maturation.

Oncofertility: Pharmacological Protection and Immature Testicular Tissue (ITT)-Based Strategies for Prepubertal and Adolescent Male Cancer Patients

While the incidence of cancer in children and adolescents has significantly increased over the last decades, improvements made in the field of cancer therapy have led to an increased life expectancy for childhood cancer survivors. However, the gonadotoxic effect of the treatments may lead to infertility. Although semen cryopreservation represents the most efficient and safe fertility preservation method for males producing sperm, it is not feasible for prepubertal boys. The development of an effective strategy based on the pharmacological protection of the germ cells and testicular function during gonadotoxic exposure is a non-invasive preventive approach that prepubertal boys could benefit from. However, the progress in this field is slow. Currently, cryopreservation of immature testicular tissue (ITT) containing spermatogonial stem cells is offered to prepubertal boys as an experimental fertility preservation strategy by a number of medical centers. Several in vitro and in vivo fertility restoration approaches based on the use of ITT have been developed so far with autotransplantation of ITT appearing more promising. In this review, we discuss the pharmacological approaches for fertility protection in prepubertal and adolescent boys and the fertility restoration approaches developed on the utilization of ITT.