Clinical potential and putative risks of fertility preservation in children utilizing gonadal tissue or germline stem cells

Enhancement of Vascularization and Ovarian Follicle Survival Using Stem Cells in Cryopreserved Ovarian Tissue Transplantation-A Systematic Review

The increase in cancer survival rates has put a focus on ensuring fertility preservation procedures for cancer patients. Ovarian tissue cryopreservation presents the only option for prepubertal girls and patients who require immediate start of treatment and, therefore, cannot undergo controlled ovarian stimulation. We aimed to provide an assessment of stem cells' impact on cryopreserved ovarian tissue grafts in regard to the expression of growth factors, angiogenesis promotion, tissue oxygenation, ovarian follicle survival and restoration of endocrine function. For this systematic review, we searched the Scopus and PubMed databases and included reports of trials using murine and/or human cryopreserved ovarian tissue for transplantation or in vitro culture in combination with mesenchymal stem cell administration to the grafting site. Of the 1201 articles identified, 10 met the criteria. The application of stem cells to the grafting site has been proven to support vascular promotion and thereby shorten the period of tissue hypoxia, which is reflected in the increased number of remaining viable follicles and faster recovery of ovarian endocrine function. Further research is needed before implementing the use of stem cells in OT cryopreservation and transplantation procedures in clinical practice. Complex ethical dilemmas make this process more difficult.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Cryoprotective Effect of Pentoxifylline on Spermatogonial Stem Cell During Transplantation into Azoospermic Torsion Mouse Model

Preserving the spermatogonial stem cells (SSCs) in long periods of time during the treatment of male infertility using stem cell banking systems and transplantation is an important issue. Therefore, this study was conducted to develop an optimal cryopreservation protocol for SSCs using 10 mM pentoxifylline (PTX) as an antioxidant in basal freezing medium. Testicular torsion-a mouse model for long-term infertility-was used to transplant fresh SSCs (n = 6), fresh SSCs treated with PTX (n = 6), cryopreserved SSCs with basal freezing medium (n = 6), and cryopreserved SSCs treated with PTX (n = 6). Eight weeks after germ cell transplantation, samples were assessed for proliferation, through evaluation of Ddx4 and Id4 markers, and differentiation via evaluation of C-Kit and Sycp3, Tnp1, Tnp2, and Prm1 markers. According to morphological and flow cytometry results, SSCs are able to form colonies and express Gfra1, Id4, α6-integrin, and β1-integrin markers. We found positive influence from PTX on proliferative and differentiative markers in SSCs transplanted to azoospermic mice. In the recipient testis, donor SSCs formed spermatogenic colonies and sperm. Respecting these data, adding pentoxifylline is a practical way to precisely cryopreserve germ cells enriched for SSCs in cryopreservation, and this procedure could become an efficient method to restore fertility in a clinical setup. However, more studies are needed to ensure its safety in the long term.

Ultrasensitive Detection and Depletion of Rare Leukemic B Cells in T Cell Populations via Immunomagnetic Cell Ranking

Rare CD19⁺ leukemic B cells present in purified T cell populations can cause disease relapse and even the failure of CD19-targeting CAR-T therapy as these rare cells have the ability to self-mask their surface CD19 and escape from the recognition of T cells. It is therefore critical to efficiently detect and robustly deplete rare leukemic B cells in samples of therapeutic T cells. Here, we present a novel microfluidic approach to address the challenges specific to quality control of therapeutic T cells - CAR-QC. CAR-QC utilizes immunomagnetic labeling with a highly selective microfluidic device to rank and isolate rare leukemic B cells in T cell populations. CAR-QC offers ultrasensitive detection of leukemic B cells at single-cell resolution and robust depletion efficiency up to 99.985%. We demonstrate that CAR-QC outperforms flow cytometry and magnetic-activated cell sorting for detecting or purifying spiked samples. In addition, we prove that the improved performance of CAR-QC helps to avoid the occurrence and possibly relapse of rare leukemic B cells in vitro.

Impact of Temperature and Time Interval Prior to Immature Testicular-Tissue Organotypic Culture on Cellular Niche

Cryopreservation of immature-testicular-tissue (ITT) prior to gonadotoxic treatment, while experimental, is the only recommended option for fertility preservation in prepubertal boys. The handling and manipulation of ITT before cryopreservation could influence the functionality of cells during fertility restoration, which this study explored by evaluating cellular niche and quality of mouse ITT subjected to various temperatures and time durations in vitro. ITT from 6-day-old mice were handled at ultraprofound-hypothermic, profound-hypothermic, and mild-warm-ischemic temperatures for varying time periods prior to 14-day organotypic culture. Viability, functionality, synaptonemal complex and chromatin remodeling markers were assessed. Results have shown that cell viability, testosterone level, and in vitro proliferation ability did not change when ITT were held at ultraprofound-hypothermic-temperature up to 24 h, whereas cell viability was significantly reduced (P < 0.01), when held at profound-hypothermic-temperature for 24 h before culture. Further, cell viability and testosterone levels in cultured cells from profound-hypothermic group were comparable to corresponding ultraprofound-hypothermic group but with moderate reduction in postmeiotic cells (P < 0.01). In conclusion, holding ITT at ultraprofound-hypothermic-temperature is most suitable for organotypic culture, whereas short-term exposure at profound-hypothermic-temperature may compromise postmeiotic germ cell yield post in vitro culture. This data, albeit in mouse model, will have immense value in human prepubertal fertility restoration research.

ITGA6+ Human Testicular Cell Populations Acquire a Mesenchymal Rather than Germ Cell Transcriptional Signature during Long-Term Culture

Autologous spermatogonial stem cell transplantation is an experimental technique aimed at restoring fertility in infertile men. Although effective in animal models, in vitro propagation of human spermatogonia prior to transplantation has proven to be difficult. A major limiting factor is endogenous somatic testicular cell overgrowth during long-term culture. This makes the culture both inefficient and necessitates highly specific cell sorting strategies in order to enrich cultured germ cell fractions prior to transplantation. Here, we employed RNA-Seq to determine cell type composition in sorted integrin alpha-6 (ITGA6+) primary human testicular cells (n = 4 donors) cultured for up to two months, using differential gene expression and cell deconvolution analyses. Our data and analyses reveal that long-term cultured ITGA6+ testicular cells are composed mainly of cells expressing markers of peritubular myoid cells, (progenitor) Leydig cells, fibroblasts and mesenchymal stromal cells and only a limited percentage of spermatogonial cells as compared to their uncultured counterparts. These findings provide valuable insights into the cell type composition of cultured human ITGA6+ testicular cells during in vitro propagation and may serve as a basis for optimizing future cell sorting strategies as well as optimizing the current human testicular cell culture system for clinical use.

Fertility Preservation for Pediatric and Adolescent Patients With Cancer: Medical and Ethical Considerations

Many cancers presenting in children and adolescents are curable with surgery, chemotherapy, and/or radiotherapy. Potential adverse consequences of treatment include sterility, infertility, or subfertility as a result of gonad removal, damage to germ cells as a result of adjuvant therapy, or damage to the pituitary and hypothalamus or uterus as a result of irradiation. In recent years, treatment of solid tumors and hematologic malignancies has been modified in an attempt to reduce damage to the gonadal axis. Simultaneously, advances in assisted reproductive technology have led to new possibilities for the prevention and treatment of infertility. This clinical report reviews the medical aspects and ethical considerations that arise when considering fertility preservation in pediatric and adolescent patients with cancer.

Purging of malignant cell contamination prior to spermatogonia stem cell autotransplantation to preserve fertility: progress & prospects

PURPOSE OF REVIEW

This systematic review evaluates the state of the art in terms of strategies used to detect and remove contaminated malignant cells from testicular biopsy prior to spermatogonia stem cells (SSCs) autotransplantation to restore fertility.

RECENT FINDINGS

Several trials have been done in past two decades to determine the reliable methods of detecting and purging cancer cells prior to SSCs autotransplantation.

SUMMARY

The success in treating childhood cancer has dramatically increased over the past few decades. This leads to increasing demand for a method of fertility preservation for patients with pediatric cancer, as many cancer therapies can be gonadotoxic. Storing the SSCs prior to chemo- or radiation therapies and transplanting them back has been tested as a method of restoring fertility in rodents and nonhuman primate models. This has promise for restoring fertility in childhood cancer survivors. One of the major concerns is the possibility of malignant cell presence in testicular tissue biopsies that could re-introduce cancer to the patient after SSCs autotransplantation. Non-solid cancers - especially hematologic malignancies - have the risk of being transplanted back into patients after SSCs cryopreservation even if they were only present in small number in the stored testicular tissue biopsy.

Experimental models of testicular development and function using human tissue and cells

The mammalian testis has two main roles, production of gametes for reproduction and synthesis of steroid- and peptide hormones for masculinization. These processes are tightly regulated and involve complex interactions between a number of germ and somatic cell-types that comprise a unique microenvironment known as the germ stem cell niche. In humans, failure of normal testicular development or function is associated with susceptibility to a variety of male reproductive disorders including disorders of sex development, infertility and testicular cancer. Whilst studies in rodent models have provided detailed insight into the signaling pathways and molecular mechanisms that regulate the testis, there are important species differences in testicular development, function and reproductive disorders that highlight the need for suitable experimental models utilising human testicular tissues or cells. In this review, we outline experimental approaches used to sustain cells and tissue from human testis at different developmental time-points and discuss relevant end-points. These include survival, proliferation and differentiation of cell lineages within the testis as well as autocrine, paracrine and endocrine function. We also highlight the utility of these experimental approaches for modelling the effects of environmental exposures on testicular development and function.

Cancer treatment in childhood and testicular function: the importance of the somatic environment

Testicular function and future fertility may be affected by cancer treatment during childhood. Whilst survival of the germ (stem) cells is critical for ensuring the potential for fertility in these patients, the somatic cell populations also play a crucial role in providing a suitable environment to support germ cell maintenance and subsequent development. Regulation of the spermatogonial germ-stem cell niche involves many signalling pathways with hormonal influence from the hypothalamo-pituitary-gonadal axis. In this review, we describe the somatic cell populations that comprise the testicular germ-stem cell niche in humans and how they may be affected by cancer treatment during childhood. We also discuss the experimental models that may be utilized to manipulate the somatic environment and report the results of studies that investigate the potential role of somatic cells in the protection of the germ cells in the testis from cancer treatment.

Testicular Tissue Cryopreservation and Ethical Considerations: A Scoping Review

Testicular tissue cryopreservation (TTCP) aims to preserve the future option of genetic reproduction for prepubescent cancer patients who are at risk of infertility as a result of their cancer therapies. This technology is experimental and currently only offered in the research context. As TTCP moves towards becoming more widely available, it is imperative that healthcare providers recognize the complex ethical issues surrounding this technology. This scoping review study identifies and assesses the range and depth of ethical concerns related to this testicular tissue cryopreservation technology. At present, no such scoping review of ethical concerns exists in the TTCP literature. The forty-three full-text articles included in this study yielded twenty-two different ethical considerations discussed in relation to TTCP. It was observed that these ethical considerations fit within a mainstream Principlism approach to bioethics. Accordingly, there are ethical gaps in the TTCP literature that can be identified with alternative moral lenses. In particular, it was found that ethical concerns related to context and relational aspects of identity were absent in nearly all ethical examinations of TTCP. Furthermore, only 9 per cent of articles reviewed in this study focused primarily on the ethics of TTCP, thus demonstrating a need for further in depth ethical analyses of this technology. The results of this study are important for supporting the ethical provision of TTCP and can contribute to policy and guideline development. The findings of this study demonstrate the need for greater depth and diversity in analyses of ethical considerations related to this technology.

Review: Gonadal functioning and preservation of reproductive fitness with juvenile systemic lupus erythematosus

Increased survival of children with juvenile systemic lupus erythematosus (jSLE) and improved prognosis have led to a change in the long-term health issues arising for jSLE patients. Preservation of gonadal functioning and fertility are of increasing importance for young adults with jSLE. Events during childhood, such as exposure to alkylating agents, may compromise the reproductive potential. Even in the absence of gonadotoxic therapies, fertility may be decreased through organs specific involvement with jSLE. Strategies to preserve the reproductive potential of girl and boys with jSLE are discussed. Lupus (2007) 16, 593—599.

Spermatogonial stem cell autotransplantation and germline genomic editing: a future cure for spermatogenic failure and prevention of transmission of genomic diseases

BACKGROUND

Subfertility affects approximately 15% of all couples, and a severe male factor is identified in 17% of these couples. While the etiology of a severe male factor remains largely unknown, prior gonadotoxic treatment and genomic aberrations have been associated with this type of subfertility. Couples with a severe male factor can resort to ICSI, with either ejaculated spermatozoa (in case of oligozoospermia) or surgically retrieved testicular spermatozoa (in case of azoospermia) to generate their own biological children. Currently there is no direct treatment for azoospermia or oligozoospermia. Spermatogonial stem cell (SSC) autotransplantation (SSCT) is a promising novel clinical application currently under development to restore fertility in sterile childhood cancer survivors. Meanwhile, recent advances in genomic editing, especially the clustered regulatory interspaced short palindromic repeats-associated protein 9 (CRISPR-Cas9) system, are likely to enable genomic rectification of human SSCs in the near future.

OBJECTIVE AND RATIONALE

The objective of this review is to provide insights into the prospects of the potential clinical application of SSCT with or without genomic editing to cure spermatogenic failure and to prevent transmission of genetic diseases.

SEARCH METHODS

We performed a narrative review using the literature available on PubMed not restricted to any publishing year on topics of subfertility, fertility treatments, (molecular regulation of) spermatogenesis and SSCT, inherited (genetic) disorders, prenatal screening methods, genomic editing and germline editing. For germline editing, we focussed on the novel CRISPR-Cas9 system. We included papers written in English only.

OUTCOMES

Current techniques allow propagation of human SSCs in vitro, which is indispensable to successful transplantation. This technique is currently being developed in a preclinical setting for childhood cancer survivors who have stored a testis biopsy prior to cancer treatment. Similarly, SSCT could be used to restore fertility in sterile adult cancer survivors. In vitro propagation of SSCs might also be employed to enhance spermatogenesis in oligozoospermic men and in azoospermic men who still have functional SSCs albeit in insufficient numbers. The combination of SSCT with genomic editing techniques could potentially rectify defects in spermatogenesis caused by genomic mutations or, more broadly, prevent transmission of genomic diseases to the offspring. In spite of the promising prospects, SSCT and germline genomic editing are not yet clinically applicable and both techniques require optimization at various levels.

WIDER IMPLICATIONS

SSCT with or without genomic editing could potentially be used to restore fertility in cancer survivors to treat couples with a severe male factor and to prevent the paternal transmission of diseases. This will potentially allow these couples to have their own biological children. Technical development is progressing rapidly, and ethical reflection and societal debate on the use of SSCT with or without genomic editing is pressing.

In vitro toxicity assay of cisplatin on mouse acute lymphoblastic leukaemia and spermatogonial stem cells

Testicular cancer is the most common cancer affecting men in reproductive age, and cisplatin is one of the major helpful chemotherapeutic agents for treatment of this cancer. In addition, exposure of testes cancer cells to cisplatin could potentially eliminate tumour cells from germ cells in patients. The aim of this study was to evaluate the effect of cisplatin on viability of mouse acute lymphoblastic leukaemia cell line (EL-4) and neonatal mouse spermatogonial cells in vitro. In this study, the isolated spermatogonial stem cells (SSC) and EL-4 were divided into six groups including control (received medium), sham (received DMSO in medium) and experimental groups which received different doses of cisplatin (0.5, 5, 10 and 15 μg ml(-1) ). Cells viability was evaluated with MTT assay. The identity of the cultured cells was confirmed by the expression of specific markers. Our finding showed that viability of both SSC and EL-4 cells was reduced with the dose of 15 μg/ml when compared to the control group (P ≤ 0.05). Also, the differences between the IC50 in doses 10 and 15 μg/ml at different time were significant (P ≤ 0.05). The number of TUNEL-positive cells was increased, and the BAX and caspase-3 expressions were upregulated in EL4 cells for group that received an effective dose of cisplatin). In conclusion, despite the dramatic effects of cisplatin on both cells, spermatogonial stem cells could form colony in culture.

Preserving children's fertility: two tales about children's right to an open future and the margins of parental obligations

The sources, extent and margins of parental obligations in taking decisions regarding their children's medical care are subjects of ongoing debates. Balancing children's immediate welfare with keeping their future open is a delicate task. In this paper, we briefly present two examples of situations in which parents may be confronted with the choice of whether to authorise or demand non-therapeutic interventions on their children for the purpose of fertility preservation. The first example is that of children facing cancer treatment, and the second of children with Klinefelter syndrome. We argue that, whereas decisions of whether to preserve fertility may be prima facie within the limits of parental discretion, the right to an open future does not straightforwardly put parents under an obligation to take actions that would detect or relieve future infertility in their children-and indeed in some cases taking such actions is problematic.

Preserving children's fertility: two tales about children's right to an open future and the margins of parental obligations

The sources, extent and margins of parental obligations in taking decisions regarding their children's medical care are subjects of ongoing debates. Balancing children's immediate welfare with keeping their future open is a delicate task. In this paper, we briefly present two examples of situations in which parents may be confronted with the choice of whether to authorise or demand non-therapeutic interventions on their children for the purpose of fertility preservation. The first example is that of children facing cancer treatment, and the second of children with Klinefelter syndrome. We argue that, whereas decisions of whether to preserve fertility may be prima facie within the limits of parental discretion, the right to an open future does not straightforwardly put parents under an obligation to take actions that would detect or relieve future infertility in their children-and indeed in some cases taking such actions is problematic.

Effects of vitamin A on in vitro maturation of pre-pubertal mouse spermatogonial stem cells

Testicular tissue cryopreservation is the only potential option for fertility preservation in pre-pubertal boys exposed to gonadotoxic treatment. Completion of spermatogenesis after in vitro maturation is one of the future uses of harvested testicular tissue. The purpose of the current study was to evaluate the effects of vitamin A on in vitro maturation of fresh and frozen-thawed mouse pre-pubertal spermatogonial stem cells in an organ culture system. Pre-pubertal CD1 mouse fresh testes were cultured for 7 (D7), 9 (D9) and 11 (D11) days using an organ culture system. Basal medium was supplemented with different concentrations of retinol (Re) or retinoic acid (RA) alone or in combination. Seminiferous tubule morphology (tubule diameter, intra-tubular cell type), intra-tubular cell death and proliferation (PCNA antibody) and testosterone level were assessed at D7, D9 and D11. Pre-pubertal mouse testicular tissue were frozen after a soaking temperature performed at -7°C, -8°C or -9°C and after thawing, were cultured for 9 days, using the culture medium preserving the best fresh tissue functionality. Retinoic acid at 10^-6M and retinol at 3.3.10^-7M, as well as retinol 10^-6M are favourable for seminiferous tubule growth, maintenance of intra-tubular cell proliferation and germ cell differentiation of fresh pre-pubertal mouse spermatogonia. Structural and functional integrity of frozen-thawed testicular tissue appeared to be well-preserved after soaking temperature at -8°C, after 9 days of organotypic culture using 10^-6M retinol. RA and Re can control in vitro germ cell proliferation and differentiation. Re at a concentration of 10^-6M maintains intra-tubular cell proliferation and the ability of spermatogonia to initiate spermatogenesis in fresh and frozen pre-pubertal mouse testicular tissue using a soaking temperature at -8°C. Our data suggested a possible human application for in vitro maturation of cryopreserved pre-pubertal testicular tissue.

[In vitro spermatogenesis… new horizon to restore fertility?]

The survival of the young boy after cancer has considerably progressed in recent years due to the efficiency of chemo/radiotherapy against the tumor cells. However, this treatment causes adverse effects on healthy tissues, including fertility. Freezing testicular tissue before highly gonadotoxic treatment is a prerequisite for preserving fertility in prepubertal boys that do not produce sperm yet. But which strategy proposes to restore fertility from frozen-thawed testicular tissue? One potential solution would be to consider an in vitro maturation of spermatogonial stem cells. In this article we trace the chronological development of in vitro spermatogenesis that resulted in mouse sperm production in vitro and give an overview of new challenges for the future.

Clinical review: Present and future prospects of male fertility preservation for children and adolescents

CONTEXT

Rapid progress in fertility preservation strategies has led to the investigation of ways in which fertile gametes could be generated from cryopreserved immature testicular tissue. Childhood cancer patients remain the major group that can benefit from these techniques. Other potential candidates include patients undergoing gonadectomy and patients with Klinefelter's syndrome and cryptorchid testes. This review aims to present an overview of the current state of knowledge in experimental germ cell transplantation, testicular tissue transplantation, and germ cell culture as fertility preservation methods for males.

METHODOLOGY

We included English articles published in PubMed as well as personal files with the focus on studies including human or nonhuman material.

MAIN FINDINGS

Germ cell and testicular tissue transplantation demonstrate clinical options to mature germ cells from immature primate testicular tissue. The most promising approach involves autologous grafting of immature testicular tissue, whereas germ cell maturation in vitro provides the best strategies to overcome problems of cancer contamination in cryopreserved testicular tissue. Three-dimensional and organ culture systems offer the possibility to differentiate immature male germ cells up to the stage of elongated spermatids. Further characterization of early germ cell development in humans is needed to modify these systems for clinical use.

Autologous ectopic grafting of cryopreserved testicular tissue preserves the fertility of prepubescent monkeys that receive sterilizing cytotoxic therapy

Boys faced with future sterility as a result of the need of a sterilizing cancer therapy might avoid this fate by engraftment of cryopreserved immature testicular tissue after therapy is completed. Efforts to address this important survivorship issue have been encouraged by reports of the long-term survival and proliferation of human spermatogonia after xenotransplant of cryopreserved immature testicular tissue into immunocompromised murine hosts. However, spermatogenic arrest at the pachytene spermatocyte stage that occurs in this situation has been associated with a failure in sperm production. In this study, we used a prepubescent simian model to address the possibility that testicular tissue engraftment is insufficiently supported in the model to allow suitable maturation of germ cells. Briefly, we carried out autologous orthotopic grafting of cryopreserved testicular tissue from four prepubescent monkeys and one pubescent rhesus monkey after testicular irradiation and castration of the host animal. Five months after implantation of scrotal grafts, we determined that 3% to 7% of the autografts could be recovered with spermatogenesis proceeding through spermatozoa formation in 13% to 17% of the seminiferous tubules formed in the grafts. In contrast, Sertoli cell-only tubules were detected in parallel xenografts transplanted into immunocompromised mice. Our results show that cryopreservation of testicular tissue from prepubescent primates can maintain the fully functional capacity of spermatogonia to produce sperm, but that host conditions are critical for spermatogenic maturation. Furthermore, our results establish an initial perspective on the quantity of cryopreserved material needed to ensure success in preserving fertility through testicular tissue grafts.

Preservation of fertility in females treated for cancer

Advancements of diagnosis and treatment have substantially improved cancer survival rates in the last few decades. The increasing number of survivors focuses attention on long-term effects caused by cancer treatment and its impact on quality of life. Ovarian failure is one of the major sequelae of cytotoxic chemotherapy and/or radiotherapy in female children and reproductive-age women. Oncologists should address the patients about fertility preservation options before therapy. Embryo cryopreservation is the only well-established method for females in preserving fertility; however other strategies including ovarian suppression, ovarian transposition and cryopreservation of oocytes and ovarian tissue are still experimental. Patients need advice and to know which are the most practical options for them. This article reviews the available fertility preservation methods in women, and the related issues including normal physiology of the ovary, effect of anticancer therapy on fertility, role of the oncologist and ethics. We performed a MEDLINE search from 1971 to 2011 in a similar way as Jensen et al. 2011, using the following MeSH terms: antineoplastic agents; ovarian failure; premature; infertility, female; fertility preservation; child and cancer; reproductive technologies, assisted.

Fertile offspring derived from mouse spermatogonial stem cells cryopreserved for more than 14 years

BACKGROUND

Approximately 80% of childhood cancers can now be cured but a side effect of treatment results in about one-third of the surviving boys being infertile or severely subfertile when they reach reproductive age. Currently, more than 1 in 5000 men of reproductive age who are childhood cancer survivors suffer from this serious quality of life problem. It is possible to obtain a testicular biopsy before treatment to preserve the spermatogonial stem cells (SSCs) of the male by cryopreservation, but the results of long-term storage of SSCs on their subsequent functional ability to generate normal offspring has not been examined in any mammalian species. Moreover, it will be necessary to increase the number of these cryopreserved SSCs to remove any contaminating malignant cells and assure regeneration of spermatogenesis.

METHODS AND RESULTS

In this report, we demonstrate that long-term cryopreservation (>14 years) of testis cells from mouse, rat, rabbit and baboon safeguards SSC viability, and that these cells can colonize the seminiferous tubules of recipient testes. Moreover, mouse and rat SSCs can be cultured and re-establish complete spermatogenesis, and fertile mouse progeny without apparent genetic or epigenetic errors were generated by the sperm produced.

CONCLUSIONS

These findings provide a platform for fertility preservation in prepubertal boys undergoing gonadotoxic treatments.

Assessment of freezing procedures for rat immature testicular tissue

Fertility preservation has been included in the management of childhood cancer treatment. Cryopreservation of immature testicular tissue is the only available solution for pre-pubertal boys. Different freezing protocols have been developed in several species but without a clearly identified procedure. We tried to evaluate several protocols for cryopreservation of rat immature testicular tissue. Twelve different freezing protocols using different (i) cryoprotectant (dimethylsulphoxide [DMSO] or 1,2-propanediol [PROH]), (ii) cryoprotectant concentration (1.5M or 3M), (iii) equilibration time (30 or 60 min), (iv) equilibration temperature (4 °C or room temperature), (v) size of testicular fragment (7.5mg or 15 mg), (vi) package (straws or cryovials), were compared using cord morphological damage evaluation. A testicular tissue piece of 7.5mg cryopreserved in cryovial using 1.5M DMSO, an equilibration time of 30 min at 4 °C showed fewer morphological alterations than the other protocols tested. The selected freezing protocol was able to maintain rat immature testicular tissue architecture, functionality after testicular pieces organotypic culture, and could be proposed in a human application.

New advances on the expansion and storage of human spermatogonial stem cells

PURPOSE OF REVIEW

Fertility in adult life can be severely impaired by gonadotoxic therapies and with remarkable advancements in the treatment of childhood cancers there is a growing population of adult survivors of childhood malignancies. The aim of the study is to review the developments that have been made in spermatogonial stem cell research and potential future utility in fertility preservation.

RECENT FINDINGS

Whereas intense interest and subsequent research surrounds the regenerative potential of spermatogonial stem cells, a recent article highlights the in-vitro propagation of human spermatogonial stem cells from testicular biopsies for future transplantation and restoration of fertility. Whereas in-vitro propagation of spermatogonial stem cells has been established in animal models this is the first study in humans.

SUMMARY

Spermatogonial stem cell transplantation began as a theoretical approach that currently is studied ardently by several research groups to make this a valid clinical option. Restoration of fertility following spermatogonial stem cell transplantation in animals suggests therapeutic potential for the technique in humans, and further research is proceeding to address the safety and efficacy of this technique.

Management of fertility preservation in prepubertal patients: 5 years' experience at the Catholic University of Louvain

BACKGROUND Since prepubertal boys cannot benefit from sperm banking, a potential alternative strategy for fertility preservation involves immature testicular tissue (ITT) banking aimed at preservation of spermatogonial stem cells. Survival of spermatogonia has been demonstrated after ITT freezing, which is considered ethically acceptable. We report the results of a pilot program set up for fertility preservation in prepubertal boys. METHODS All boys undergoing ITT cryobanking from May 2005 were identified from our clinical register. Data were collected from medical files. RESULTS Testicular tissue was retrieved from 52 prepubertal patients under 12 years of age and 10 peripubertal patients aged between 12 and 16 years, in whom no spermatozoa were identified in testicular biopsies. Malignant disease accounted for 80.6% of cases; the remaining patients suffered from benign disorders requiring gonadotoxic treatments. Mean ages, Tanner stages and occurrence rates of urogenital pathology were 6.43 ± 3.32 and 14 ± 1.23 years, I and I-IV, and 13.5 and 20% for pre- and peripubertal patients, respectively. Mean volumes of removed tissue were 20.1 ± 8.6 and 42.4 ± 15.6 mm(3) for pre- and peripubertal patients, respectively. No complications occurred during or after tissue retrieval and 93.5% of referred patients accepted ITT storage. The presence of spermatogonia, and thus the potential for later tissue use, was established in all of these patients. CONCLUSIONS The majority of cryopreserved samples showed reproductive potential. Storage was accepted by most parents. All parents and children considered this fertility preservation strategy a positive approach.

Testicular stem cells for fertility preservation: preclinical studies on male germ cell transplantation and testicular grafting

Spermatogonial stem cells open novel strategies for preservation of testicular tissue and fertility preservation in boys and men exposed to gonadotoxic therapies. This review provides an update on the physiology of spermatogonial stem cells in rodent and primate testes. Species-specific differences must be considered when new technologies on testicular stem cells are considered. Germ cell transplantation is presented as one novel and promising strategy. Whereas this technique has become an important research tool in rodents, a clinical application must still be regarded as experimental and many aspects of the procedure need to be optimized prior to a safe and efficient clinical application in men. Testicular grafting opens another exciting strategy for fertility preservation. Autologous and xenologous transfer of immature tissue revealed a high regenerative potential of immature testicular tissue. Grafting was applied in rodents and primates and resulted in the generation of sperm. Further research is needed before an application in humans can be considered safe and efficient. Despite the current limitations in regard to the generation of sperm from cryopreserved male germline cells and tissues, protocols for cryopreservation of testicular tissue are available and reveal a promising outcome. Since future improvements of germ cell transplantation and grafting approaches can be assumed, bioptic retrieval and cryopreservation of testicular tissue fragments should be performed in oncological patients at high risk of fertility loss since this is their only option to maintain their fertility potential.

Preservation and transplantation of porcine testis tissue

Grafting of immature mammalian testis tissue to mouse hosts can preserve the male germline. To make this approach applicable to a clinical or field situation, it is imperative that the testis tissue and/or spermatozoa harvested from grafted tissue are preserved successfully. The aim of the present study was to evaluate protocols for the preservation of testis tissue in a porcine model. Testis tissue was stored at 4 degrees C for short-term preservation or cryopreserved by slow-freezing, automated slow-freezing or vitrification for long-term storage. Preserved tissue was transplanted ectopically to mouse hosts and recovered xenografts were analysed histologically. In addition, spermatozoa were harvested from xenografts and cryopreserved. Total cell viability and germ cell viability remained high after tissue preservation. Complete spermatogenesis occurred in xenografts preserved by cooling up to 48 h, whereas spermatogenesis progressed to round spermatids in the xenografts that were frozen-thawed before grafting. Approximately 50% of spermatozoa harvested from xenografts remained viable after freezing and thawing. The in vivo developmental potential of cryopreserved tissue was reduced despite high post-thaw viability. Therefore, it is important to evaluate germ cell differentiation in vivo in addition to cell viability in vitro when optimising freezing protocols for testis tissue.

Ectopic porcine spermatogenesis in murine subcutis: tissue grafting versus cell-injection methods

Fragments of testis tissue from immature animals grow and develop spermatogenesis when grafted onto subcutaneous areas of immunodeficient mice. The same results are obtained when dissociated cells from immature testes of rodents are injected into the subcutis of nude mice. Those cells reconstitute seminiferous tubules and facilitate spermatogenesis. We compared these two methods, tissue grafting and cell-injection methods, in terms of the efficiency of spermatogenesis in the backs of three strains of immunodeficient mice, using neonatal porcine testicular tissues and cells as donor material. Nude, severe combined immunodeficient (SCID) and NOD/Shi-SCID, IL-2Rgammacnull (NOG) mice were used as recipients. At 10 months after surgery, the transplants were examined histologically. Both grafting and cell-injection methods resulted in porcine spermatogenesis on the backs of recipient mice; the percentage of spermatids present in the transplants was 67% and 22%, respectively. Using the grafting method, all three strains of mice supported the same extent of spermatogenesis. As for the cell-injection method, although SCID mice were the best host for supporting reconstitution and spermatogenesis, any difference from the other strains was not significant. As NOG mice did not show any better results, the severity of immunodeficiency seemed to be irrelevant for supporting xeno-ectopic spermatogenesis. Our results confirmed that tubular reconstitution is applicable to porcine testicular cells. This method as well as the grafting method would be useful for studying spermatogenesis in different kinds of animals.

Preservation of fertility in pediatric and adolescent patients with cancer

Many cancers that present in children and adolescents are curable with surgery, chemotherapy, and/or radiation therapy. Potential adverse consequences of treatment include sterility, infertility, or subfertility as a result of either gonad removal or damage to germ cells from adjuvant therapy. In recent years, treatment of solid tumors and hematologic malignancies has been modified in an attempt to reduce damage to the gonads. Simultaneously, advances in assisted reproductive techniques have led to new possibilities for the prevention and treatment of infertility. This technical report reviews the topic of fertility preservation in pediatric and adolescent patients with cancer, including ethical considerations.

Decontamination of leukemic cells and enrichment of germ cells from testicular samples from rats with Roser’s T-cell leukemia by flow cytometric sorting

Testicular germ cell transplantation is a novel strategy for preservation of fertility in prepubertal cancer patients, but the risk of reseeding tumor cells into cured patients presently limits clinical application of this approach. To date, no systematic evaluation of the limitations of surface marker-based decontamination of testicular samples with acute lymphoblastic leukemia has been performed. Here, surface markers for leukemic (CD4 and major histocompatibility complex class I) and germ cells (epithelia cell adhesion molecule) in testicular samples infiltrated with Roser’s T-cell leukemia were identified. These markers were then used to delete leukemic cells and/or select for germ cells by flow cytometry (FACS). The resulting cell populations were analyzed by FACS, immunocytochemistry, or evaluation of leukemia transmission in syngeneic piebald variegated rats. Simple positive selection of germ cells or deletion of leukemic cells using specific surface markers was unable to effectively decontaminate testicular samples. The poor specificity of spermatogonial surface markers and aggregation of germ and leukemic cells limited the positive selection of germ cells, while immunophenotypic variation among lymphoblastic leukemia cells prevented adequate deletion of leukemic cells. Enzymatic treatment to disperse the testicular cells and feature of the intratesticular environment contributed to this immunophenotypic variation. Only germ cell selection in combination with leukemic cell deletion prevented leukemia transmission in association with intratesticular injection of the sorted cells. However, with such combined sorting, only 0.23% of the original testicular cells were recovered. With presently available techniques, flow cytometric purification of germ cells from a leukemic donor is not sufficiently effective or safe for clinical use.

Characterization, cryopreservation, and ablation of spermatogonial stem cells in adult rhesus macaques

Spermatogonial stem cells (SSCs) are at the foundation of mammalian spermatogenesis. Whereas rare A(single) spermatogonia comprise the rodent SSC pool, primate spermatogenesis arises from more abundant A(dark) and A(pale) spermatogonia, and the identity of the stem cell is subject to debate. The fundamental differences between these models highlight the need to investigate the biology of primate SSCs, which have greater relevance to human physiology. The alkylating chemotherapeutic agent, busulfan, ablates spermatogenesis in rodents and causes infertility in humans. We treated adult rhesus macaques with busulfan to gain insights about its effects on SSCs and spermatogenesis. Busulfan treatment caused acute declines in testis volume and sperm counts, indicating a disruption of spermatogenesis. One year following high-dose busulfan treatment, sperm counts remained undetectable, and testes were depleted of germ cells. Similar to rodents, rhesus spermatogonia expressed markers of germ cells (VASA, DAZL) and stem/progenitor spermatogonia (PLZF and GFRalpha1), and cells expressing these markers were depleted following high-dose busulfan treatment. Furthermore, fresh or cryopreserved germ cells from normal rhesus testes produced colonies of spermatogonia, which persisted as chains on the basement membrane of mouse seminiferous tubules in the primate to nude mouse xenotransplant assay. In contrast, testis cells from animals that received high-dose busulfan produced no colonies. These studies provide basic information about rhesus SSC activity and the impact of busulfan on the stem cell pool. In addition, the germ cell-depleted testis model will enable autologous/homologous transplantation to study stem cell/niche interactions in nonhuman primate testes.

Methods of cryopreservation of testicular tissue with viable spermatogonia in pre-pubertal boys undergoing gonadotoxic cancer treatment

BACKGROUND

Banking of testicular tissue from pre-pubertal boys before gonadotoxic treatment is a crucial step in fertility preservation. We wanted to find optimal methods for cryopreservation of testicular tissue from pre-pubertal boys, modifying techniques developed for fetal and adult human testicular tissue cryopreservation.

METHODS

Testicular tissue was collected from five pre-pubertal boys undergoing gonadotoxic treatment in a clinical programme. Two freezing protocols, originally developed for fetal and adult human testicular tissue, were applied for pre-pubertal testicular tissue cryopreservation. In both methods, 5% dimethyl sulphoxide (DMSO) was used as a cryoprotectant. The integrity of the tissue was investigated in non-frozen tissue cultured for 24 h and in cryopreserved-thawed tissue, using two different programmes. We also analysed frozen-thawed samples cultured for 24 h in comparison with untreated fresh fixed control tissue. Immunohistochemical analysis using anti-MAGE-A4, vimentin and CD34 monoclonal antibodies was performed in order to visualize and characterize the cryodamage of the different testicular cells and compartments. The structure of the tissue was evaluated using light microscopy. Qualitative control analysis was performed using transmission electron microscopy.

RESULTS

No clear structural changes were observed in the fresh, fresh cultured and cryopreserved testicular tissue after using the protocol developed for adult testicular tissue. The programme earlier successfully used for human fetal testicular tissue cryopreservation caused more tissue damage.

CONCLUSIONS

Pre-pubertal testicular tissue from boys facing gonadotoxic treatment survives cryopreservation, can be cryobanked and hopefully used for fertility preservation. Slow programmed freezing with DMSO as a cryoprotectant is efficient in maintaining the spermatogonia, Sertoli cells and stromal compartment during freezing, thawing and tissue culture.

Ovarian and testicular tissue xenografting: its potential for germline preservation of companion animals, non-domestic and endangered species

In the present paper we aim to review the development of both ovarian and testicular xenografting with specific emphasis on its usage for companion animals, non-domestic and endangered species. Ovarian and testicular tissue xenografting has been used successfully across a variety of species for the harvesting of mature gametes and subsequent fertilisation. It has become a novel and promising tool to explore various aspects of testicular development and function and was useful for determination of gonadotoxic treatments on xenografted gonads. In rodent animal models live births have been reported using gametes from xenografted gonadal tissue. Live births were also reported after grafting of human ovarian tissue. We envisage that it will not be long before the first live births across other species, including companion animals, non-domestic and endangered species, will be achieved.

Effect of cold storage and cryopreservation of immature non-human primate testicular tissue on spermatogonial stem cell potential in xenografts

BACKGROUND

Successful cryopreservation of gonadal tissue is an important factor in guaranteeing the fertility preservation via germ cell or testicular tissue transplantation. The aim of this study was to evaluate the effects of cooling and cryopreservation on spermatogonial stem cell survival and function of immature non-human primate testicular tissue xenografted to nude mice.

METHODS

Group 1 (control group) received subcutaneous grafts of fresh immature rhesus monkey testes. The treatment groups received grafts after 24 h cooling in ice-cold medium (Group 2), after 24 h of cryopreservation without cryoprotectant (Group 3), with ethylene glycol (Group 4: 1.4 M) or with dimethylsulphoxide (DMSO) (group 5: 1.4 M; group 6: 0.7 M), using cooling rates of 0.5 degrees C/min. The graft number, weight and histology were examined 3-5 months later.

RESULTS

After xenografting, grafts from fresh and cooled tissue showed good survival and spermatogenic induction to spermatocytes. Cryopreservation in 1.4 M DMSO also allowed grafts to initiate spermatogenesis. In contrast, 0.7 M DMSO and ethylene glycol showed inferior protection.

CONCLUSIONS

Our observations suggest that cryopreservation of immature primate testis is a feasible approach to maintain spermatogonial stem cells and may serve as a promising tool for fertility preservation of prepubertal boys. The possibility to delay the transplantation of cooled samples suggests an option for clinical centralization of testicular tissue cryopreservation.

Preserving the fertility of children with cancer

Moving beyond the uncertainties of risk, and limited, often difficult, preservation options, will require consensus and collaborative research.

The efficiency of magnetic-activated cell sorting and fluorescence-activated cell sorting in the decontamination of testicular cell suspensions in cancer patients

BACKGROUND

Before clinical application, the feasibility and safety of autologous testicular stem cell transplantation should be explored. Apart from limitations in their numbers, spermatogonial stem cells may also be contaminated by malignant cells. Therefore, both enrichment and decontamination before transplantation may be necessary. This study aimed at evaluating the decontaminating potential of magnetic-activated cell sorting (MACS) and/or fluorescence-activated cell sorting (FACS) for both murine and human testicular cell suspensions. In the mouse, the effectiveness of the transplantation technique after cell sorting was also assessed.

METHODS

Murine testicular cells were contaminated with 5% EL4 cells. Fresh and frozen-thawed suspensions were sorted using MACS (CD49f (+)) and FACS (CD49f(+), H-2Kb(-)) and evaluated by FACS, cell culture and transplantation into W/W(v) mice. Human testicular cells were contaminated with 5 or 0.05% CCRF-SB (SB) cells. Frozen-thawed suspensions were sorted using FACS (HLA class I(-)) and evaluated by FACS, cell culture and PCR for the B-cell receptor.

RESULTS

In the mouse, the sorted fractions contained 0.39% H-2K(b)-positive and 76.55% CD49f-positive cells. After transplantation, 1 in 20 recipient mice developed a malignancy. In the human experiments, an average of 0.58% SB cells was detected after sorting. In only 1 of 11 samples, there were no SB cells observed.

CONCLUSION

MACS and/or FACS are insufficient for completely depleting testicular tissue of malignant cells. Although more research on alternative decontamination techniques is necessary, developing a reliable method to screen a priori testicular tissue for malignant cells may be equally important.