Isolation of germ cells from leukemia and lymphoma cells in a human in vitro model: potential clinical application for restoring human fertility after anticancer therapy

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.

Deafening Silence of Male Infertility

Think about 6 loved ones of reproductive age in your life. Now imagine that 1 of these 6 individuals is suffering from infertility. Perhaps they feel alone and isolated, unable to discuss their heartbreak with their closest friends, family, and support network. Suffering in silence. In this editorial, we discuss the infertility journey through the lens of the patients, the providers, and the scientists who struggle with infertility each and every day. Our goal is to open a dialogue surrounding infertility, with an emphasis on dismantling the longstanding societal barriers to acknowledging male infertility as a disease. Through education, communication, compassion, and advocacy, together we can all begin to break the deafening silence of male infertility.

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.

Perspectives: Methods for Evaluating Primate Spermatogonial Stem Cells

Mammalian spermatogenesis is a complex, highly productive process generating millions of sperm per day. Spermatogonial stem cells (SSCs) are at the foundation of spermatogenesis and can either self-renew, producing more SSCs, or differentiate to initiate spermatogenesis and produce sperm. The biological potential of SSCs to produce and maintain spermatogenesis makes them a promising tool for the treatment of male infertility. However, translating knowledge from rodents to higher primates (monkeys and humans) is challenged by different vocabularies that are used to describe stem cells and spermatogenic lineage development in those species. Furthermore, while rodent SSCs are defined by their biological potential to produce and maintain spermatogenesis in a transplant assay, there is no equivalent routine and accessible bioassay to test monkey and human SSCs or replicate their functions in vitro. This chapter describes progress characterizing, isolating, culturing, and transplanting SSCs in higher primates.

[Reconstruction of spermatogonial niche for male fertility preservation]

Infertility is one of the late side effects of cancer treatment. Expansion of anti-cancer treatment allow patients to have more life time, however infertility is becoming a matter damaging QOL during the young cancer survivors. The passive strategy such as avoiding the gonad-toxic drug or decreasing the total volume of them and shielding the gonads against cancer therapy has been conducted. To preserve the fertility of young female, ovary tissue cryopreservation is becoming a standard over the world after the success of offspring from cryopreserved ovary tissue autograft was reported. Sperm preservation method is established for the male fertility preservation method, however this is only applicable for sexually matured male patients. For the sake of preserving fertility of sexually immature male patients, many trials using cryopreserved testis tissues or testicular cells have been undergone. Recently, in vitro gametogenesis from stem cell of the human and the mouse to primordial germ cell like cell has been achieved. Here the previous challenges and the latest reports for obtaining functional sperm from immature testis and the reconstruction of spermatogonial niche as a potential approach for preserving fertility procedure are described.

The initial maturation status of marmoset testicular tissues has an impact on germ cell maintenance and somatic cell response in tissue fragment culture

Successful in vitro spermatogenesis was reported using immature mouse testicular tissues in a fragment culture approach, raising hopes that this method could also be applied for fertility preservation in humans. Although maintaining immature human testicular tissue fragments in culture is feasible for an extended period, it remains unknown whether germ cell survival and the somatic cell response depend on the differentiation status of tissue. Employing the marmoset monkey (Callithrix jacchus), we aimed to assess whether the maturation status of prepubertal and peri-/pubertal testicular tissues influence the outcome of testis fragment culture. Testicular tissue fragments from 4- and 8-month-old (n = 3, each) marmosets were cultured and evaluated after 0, 7, 14, 28 and 42 days. Immunohistochemistry was performed for identification and quantification of germ cells (melanoma-associated antigen 4) and Sertoli cell maturation status (anti-Müllerian hormone: AMH). During testis fragment culture, spermatogonial numbers were significantly reduced (P < 0.05) in the 4- but not 8-month-old monkeys, at Day 0 versus Day 42 of culture. Moreover, while Sertoli cells from 4-month-old monkeys maintained an immature phenotype (i.e. AMH expression) during culture, AMH expression was regained in two of the 8-month-old monkeys. Interestingly, progression of differentiation to later meiotic stage was solely observed in one 8-month-old marmoset, which was at an intermediate state regarding germ cell content, with gonocytes as well as spermatocytes present, as well as Sertoli cell maturation status. Although species-specific differences might influence the outcome of testis fragment experiments in vitro, our study demonstrated that the developmental status of the testicular tissues needs to be considered as it seems to be decisive for germ cell maintenance, somatic cell response and possibly the differentiation potential.

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.

Review of injection techniques for spermatogonial stem cell transplantation

BACKGROUND

Although the prognosis of childhood cancer survivors has increased dramatically during recent years, chemotherapy and radiation treatments for cancer and other conditions may lead to permanent infertility in prepubertal boys. Recent developments have shown that spermatogonial stem cell (SSC) transplantation may be a hope for restoring fertility in adult survivors of childhood cancers. For this reason, several centres around the world are collecting and cryopreserving testicular tissue or cells anticipating that, in the near future, some patients will return for SSC transplantation. This review summarizes the current knowledge and utility of SSC transplantation techniques.

OBJECTIVE AND RATIONALE

The aim of this narrative review is to provide an overview of the currently used experimental injection techniques for SSC transplantation in animal and human testes. This is crucial in understanding and determining the role of the different techniques necessary for successful transplantation.

SEARCH METHODS

A comprehensive review of peer-reviewed publications on this topic was performed using the PubMed and Google Scholar databases. The search was limited to English language work and studies between 1994 (from the first study on SSC transplantation) and April 2019. Key search terms included mouse, rat, boar, ram, dog, sheep, goat, cattle, monkey, human, cadaver, testes, SSC transplantation, injection and technique.

OUTCOMES

This review provides an extensive clinical overview of the current research in the field of human SSC transplantation. Rete testis injection with ultrasonography guidance currently seems the most promising injection technique thus far; however, the ability to draw clear conclusions is limited due to long ischemia time of cadaver testis, the relatively decreased volume of the testis, the diminishing size of seminiferous tubules, a lack of intratesticular pressure and leakage into the interstitium during the injection on human cadaver testis. Current evidence does not support improved outcomes from multiple infusions through the rete testes. Overall, further optimization is required to increase the efficiency and safety of the infusion method.

WIDER IMPLICATIONS

Identifying a favourable injection method for SSC transplantation will provide insight into the mechanisms of successful assisted human reproduction. Future research could focus on reducing leakage and establishing the optimal infusion cell concentrations and pressure.

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.

Separating mouse malignant cell line (EL4) from neonate spermatogonial stem cells utilizing microfluidic device in vitro

BACKGROUND

Some children who have survived cancer will be azoospermic in the future. Performing isolation and purification procedures for spermatogonial stem cells (SSC) is very critical. In this regard, performing the process of decontamination of cancerous cells is the initial step. The major objective of the present study is to separate the malignant EL4 cell line in mice and spermatogonial stem cells in vitro.

METHODS

The spermatogonial stem cells of sixty neonatal mice were isolated, and the procedure of co-culturing was carried out by EL4 which were classified into 2 major groups: (1) the control group (co-culture in a growth medium) and (2) the group of co-cultured cells which were separated using the microfluidic device. The percentage of cells was assessed using flow cytometry technique and common laboratory technique of immunocytochemistry and finally was confirmed through the laboratory technique of reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The actual percentage of EL4 and SSC after isolation was collected at two outlets: the outputs for the smaller outlet were 0.12% for SSC and 42.14% for EL4, while in the larger outlet, the outputs were 80.38% for SSC and 0.32% for EL4; in the control group, the percentages of cells were 21.44% for SSC and 23.28% for EL4 (based on t test (p ≤ 0.05)).

CONCLUSIONS

The present study demonstrates that the use of the microfluidic device is effective in separating cancer cells from spermatogonial stem cells.

Spermatogonial Stem Cell Culture in Oncofertility

Infertility caused by chemotherapy or radiation treatments negatively impacts patient-survivor quality of life. The only fertility preservation option available to prepubertal boys who are not making sperm is cryopreservation of testicular tissues that contain spermatogonial stem cells (SSCs) with potential to produce sperm and/or restore fertility. SSC transplantation to regenerate spermatogenesis in infertile adult survivors of childhood cancers is a mature technology. However, the number of SSCs obtained in a biopsy of a prepubertal testis may be small. Therefore, methods to expand SSC numbers in culture before transplantation are needed. Here we review progress with human SSC culture.

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.

Role of stem cells in fertility preservation: current insights

While improvements made in the field of cancer therapy allow high survival rates, gonadotoxicity of chemo- and radiotherapy can lead to infertility in male and female pre- and postpubertal patients. Clinical options to preserve fertility before starting gonadotoxic therapies by cryopreserving sperm or oocytes for future use with assisted reproductive technology (ART) are now applied worldwide. Cryopreservation of pre- and postpubertal ovarian tissue containing primordial follicles, though still considered experimental, has already led to the birth of healthy babies after autotransplantation and is performed in an increasing number of centers. For prepubertal boys who do not produce gametes ready for fertilization, cryopreservation of immature testicular tissue (ITT) containing spermatogonial stem cells may be proposed as an experimental strategy with the aim of restoring fertility. Based on achievements in nonhuman primates, autotransplantation of ITT or testicular cell suspensions appears promising to restore fertility of young cancer survivors. So far, whether in two- or three-dimensional culture systems, in vitro maturation of immature male and female gonadal cells or tissue has not demonstrated a capacity to produce safe gametes for ART. Recently, primordial germ cells have been generated from embryonic and induced pluripotent stem cells, but further investigations regarding efficiency and safety are needed. Transplantation of mesenchymal stem cells to improve the vascularization of gonadal tissue grafts, increase the colonization of transplanted cells, and restore the damaged somatic compartment could overcome the current limitations encountered with transplantation.

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.

In Vitro Cytotoxicity of Folate-Silica-Gold Nanorods on Mouse Acute Lymphoblastic Leukemia and Spermatogonial Cells

OBJECTIVE

The purpose of this study was to evaluate in vitro cytotoxicity of gold nanorods (GNRs) on the viability of spermatogonial cells (SSCs) and mouse acute lymphoblastic leukemia cells (EL4s).

MATERIALS AND METHODS

In this experimental study, SSCs were isolated from the neonate mice, following enzymatic digestion and differential plating. GNRs were synthesized, then modified by silica and finally conjugated with folic acid to form F-Si-GNRs. Different doses of F-Si-GNRs (25, 50, 75, 100, 125 and 140 μM) were used on SSCs and EL4s. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) proliferation assay was performed to examine the GNRs toxicity. Flow cytometry was used to confirm the identity of the EL4s and SSCs. Also, the identity and functionality of SSCs were determined by the expression of specific spermatogonial genes and transplantation into recipient testes. Apoptosis was determined by flow cytometry using an annexin V/propidium iodide (PI) kit.

RESULTS

Flow cytometry showed that SSCs and EL4s were positive for Plzf and H-2kb, respectively. The viability percentage of SSCs and EL4s that were treated with 25, 50, 75, 100, 125 and 140 μM of F-Si-GNRs was 65.33 ± 3.51%, 60 ± 3.6%, 51.33 ± 3.51%, 49 ± 3%, 30.66 ± 2.08% and 16.33 ± 2.51% for SSCs and 57.66 ± 0.57%, 54.66 ± 1.5%, 39.66 ± 1.52%, 12.33 ± 2.51%, 10 ± 1% and 5.66 ± 1.15% for EL4s respectively. The results of the MTT assay indicated that 100 μM is the optimal dose to reach the highest and lowest level of cell death in EL4s and in SSCs, respectively.

CONCLUSION

Cell death increased with increasing concentrations of F-Si-GNRs. Following utilization of F-Si-GNRs, there was a significant difference in the extent of apoptosis between cancer cells and SSCs.

In vitro transplantation of spermatogonial stem cells isolated from human frozen-thawed testis tissue can induce spermatogenesis under 3-dimensional tissue culture conditions

Background

Sperm production is one of the most complex biological processes in the body. In vitro production of sperm is one of the most important goals of researches in the field of male infertility treatment, which is very important in male cancer patients treated with gonadotoxic methods and drugs. In this study, we examine the progression of spermatogenesis after transplantation of spermatogonial stem cells under conditions of testicular tissue culture.

Results

Testicular tissue samples from azoospermic patients were obtained and then these were freeze–thawed. Spermatogonial stem cells were isolated by two enzymatic digestion steps and the identification of these cells was confirmed by detecting the PLZF protein. These cells, after being labeled with DiI, were transplanted in azoospermia adult mice model. The host testes were placed on agarose gel as tissue culture system. After 8 weeks, histomorphometric, immunohistochemical and molecular studies were performed. The results of histomorphometric studies showed that the mean number of spermatogonial cells, spermatocytes and spermatids in the experimental group was significantly more than the control group (without transplantation) (P < 0.05) and most of the cells responded positively to the detection of DiI. Immunohistochemical studies in host testes fragments in the experimental group express the PLZF, SCP3 and ACRBP proteins in spermatogonial cells, spermatocyte and spermatozoa, respectively, which confirmed the human nature of these cells. Also, in molecular studies of PLZF, Tekt1 and TP1, the results indicated that the genes were positive in the test group, while not in the control group.

Conclusion

These results suggest that the slow freezing of SSCs can support the induction of spermatogenesis to produce haploid cells under the 3-dimensional testicular tissue culture.

Cryostorage of immature and mature human testis tissue to preserve spermatogonial stem cells (SSCs): a systematic review of current experiences toward clinical applications

While the survival rate of children with cancer is increasing, preserving fertility for prepubertal boys is still a challenge. Although intracytoplasmic sperm injection (ICSI) using frozen sperms has revolutionized infertility treatment, it is not applicable for the patients who undergo chemotherapy before puberty since spermatogenesis has not begun. Therefore, preserving spermatogonial stem cells (SSCs) as an experimental option can be provided to prepubertal patients at a risk of damage or loss of their SSCs due to cancer treatments and developmental or genetic disorders. Using frozen SSCs in testicular tissue, successful SSC autotransplantation in mouse and nonhuman primates has shown a promising future for SSC-based cell therapy. Cryopreservation of testicular tissue containing SSCs is the first step to translate SSC-based cell therapy into clinical male infertility treatment, and in the investigation into SSCs, it is very important to evaluate their quantity and functionality during this process. This systematic review summarizes the published data on cryopreservation techniques in human testis tissue for potential utilization in future clinical applications.

Development of Postmeiotic Cells In Vitro from Spermatogonial Cells of Prepubertal Cancer Patients

Aggressive chemotherapy in childhood often results in testicular damage and consequently jeopardizes future fertility. The presence of spermatogonial cells (SPGCs) in the testes of prepubertal cancer patient boys (PCPBs) can be used to develop future strategies for male fertility preservation. In the present study, we examined the presence of SPGCs in testes of chemotherapy-treated PCPBs and their ability to develop spermatogenesis in vitro using a three-dimensional culture system. Seven testicular biopsies were obtained from chemotherapy-treated PCPBs and one from a patient with β-thalassemia major. Isolated testicular cells were cultured in a methylcellulose culture system (MCS)-containing StemPro enriched with growth factors for 5-15 weeks. The presence of premeiotic, meiotic, and postmeiotic cells was examined by immunofluorescence staining and/or reverse transcription-polymerase chain reaction (RT-PCR) analysis. We observed SPGCs in the examined testicular biopsies. Isolated testicular cells cultured in MCS developed into colonies and contained premeiotic, meiotic, and postmeiotic cells. Furthermore, we identified sperm-like cells that had developed from testicular cells of a PCPB. Our results demonstrate, for the first time, the presence of biologically active SPGCs in testicular biopsies of chemotherapy-treated PCPBs and their capacity to develop in vitro to different stages of spermatogenesis, including the generation of sperm-like cells. This study may open the way for new therapeutic strategies for fertility preservation of PCPBs and for azoospermic patients.

Elimination of mouse tumor cells from neonate spermatogonial cells utilizing cisplatin-entrapped folic acid-conjugated poly(lactic-co-glycolic acid) nanoparticles in vitro

Background

Some male survivors of childhood cancer are suffering from azoospermia. In addition, spermatogonial stem cells (SSCs) are necessary for the improvement of spermatogenesis subsequent to exposure to cytotoxic agents such as cisplatin.

Objective

The aim of this study was to evaluate the anticancer activity of cisplatin-loaded folic acid-conjugated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) on mouse malignant cell line (EL4) and SSCs in vitro.

Methods

SSCs were co-cultured with mouse malignant cell line (EL4) cells and divided into four culture groups: 1) control (cells were co-cultured in the culture medium), 2) co-cultured cells were treated with cisplatin (10 μg/mL), 3) co-cultured cells were treated with cisplatin-loaded folic acid-conjugated PLGA NPs, and 4) co-cultures were treated with folic acid-conjugated PLGA for 48 hours. The NPs were prepared, characterized, and targeted with folate. In vitro release characteristics, loading efficiency, and scanning electron microscopy and transmission electron microscopy images were studied. Cancer cells were assayed after treatment using flow cytometry and TUNEL assay. The co-cultures of SSCs and EL4 cells were injected into seminiferous tubules of the testes after treating with cis-diaminedichloroplatinum/PLGA NPs.

Results

The mean diameter of PLGA NPs ranged between 150 and 250 nm. The number of TUNEL-positive cells increased, and the expression of Bax and caspase-3 were upregulated in EL4 cells in Group 4 compared with Group 2. There was no pathological tumor in testes after transplantation with treated co-cultured cells.

Conclusion

The PLGA NPs appeared to act as a promising carrier for cisplatin administration, which was consistent with a higher activation of apoptosis than free drug.

Tissue Engineering to Improve Immature Testicular Tissue and Cell Transplantation Outcomes: One Step Closer to Fertility Restoration for Prepubertal Boys Exposed to Gonadotoxic Treatments

Despite their important contribution to the cure of both oncological and benign diseases, gonadotoxic therapies present the risk of a severe impairment of fertility. Sperm cryopreservation is not an option to preserve prepubertal boys’ reproductive potential, as their seminiferous tubules only contain spermatogonial stem cells (as diploid precursors of spermatozoa). Cryobanking of human immature testicular tissue (ITT) prior to gonadotoxic therapies is an accepted practice. Evaluation of cryopreserved ITT using xenotransplantation in nude mice showed the survival of a limited proportion of spermatogonia and their ability to proliferate and initiate differentiation. However, complete spermatogenesis could not be achieved in the mouse model. Loss of germ cells after ITT grafting points to the need to optimize the transplantation technique. Tissue engineering, a new branch of science that aims at improving cellular environment using scaffolds and molecules administration, might be an approach for further progress. In this review, after summarizing the lessons learned from human prepubertal testicular germ cells or tissue xenotransplantation experiments, we will focus on the benefits that might be gathered using bioengineering techniques to enhance transplantation outcomes by optimizing early tissue graft revascularization, protecting cells from toxic insults linked to ischemic injury and exploring strategies to promote cellular differentiation.

PiwiRNA-651 as marker of treatment response and survival in classical Hodgkin lymphoma

PiwiRNAs, small non-coding RNAs processed by Piwi proteins, are involved in maintaining genome stability in germline cells. Recently, piwiRNA expression has been identified in some tumors. We have examined the potential reactivation of the Piwi/piwiRNA pathway in classical Hodgkin lymphoma (cHL). We found that Piwi proteins and three selected piwiRNAs, including piR-651, were expressed in cHL patients and cell lines, indicating that the Piwi/piwiRNA pathway is active in cHL. Interestingly, low levels of piR-651 were associated with lack of complete response to first-line treatment, as well as shorter disease-free and overall survival in a cohort of 94 cHL patients. At diagnosis, piR-651 was underexpressed in cHL serum samples compared to healthy controls, while after complete remission, piR-651 levels increased to levels similar to healthy controls. This is the first evidence that piwiRNAs are active in tumor and serum samples and impact prognosis in cHL.

Fertility restoration with spermatogonial stem cells

PURPOSE OF REVIEW

This review evaluates the state of the art in terms of challenges and strategies used to restore fertility with spermatogonial stem cells retrieved from prepubertal boys affected by cancer. Although these boys do not yet produce spermatozoa, the only option to preserve their fertility is cryopreservation of spermatogonial stem cells in the form of testicular cell suspensions or whole tissue pieces. Different techniques have been described to achieve completion of spermatogenesis from human, spermatogonial stem cells but none is yet ready for clinical application. A crucial point to address is gaining a full understanding of spermatogonial stem cell niche pathophysiology, where germ cells undergo proliferation and differentiation. Various fertility restoration approaches will be presented depending on the presence of an intact niche, dissociated niche, or reconstituted niche.

RECENT FINDINGS

Testicular organoids open the way to providing further insights into the niche. They can recreate the three-dimensional architecture of the testicular microenvironment in vitro, allowing a large number of applications, from physiology to drug toxicity investigations.

SUMMARY

In addition to the full elucidation of the niche microenvironment, achieving fertility restoration from cryopreserved human spermatogonial stem cells implies overcoming other important challenges. Testicular organoids might prove to be essential tools to progress in this field.

Cryopreservation of testicular tissue or testicular cell suspensions: a pivotal step in fertility preservation

BACKGROUND

Germ cell depletion caused by chemical or physical toxicity, disease or genetic predisposition can occur at any age. Although semen cryopreservation is the first reflex for preserving male fertility, this cannot help out prepubertal boys. Yet, these boys do have spermatogonial stem cells (SSCs) that able to produce sperm at the start of puberty, which allows them to safeguard their fertility through testicular tissue (TT) cryopreservation. SSC transplantation (SSCT), TT grafting and recent advances in in vitro spermatogenesis have opened new possibilities to restore fertility in humans. However, these techniques are still at a research stage and their efficiency depends on the amount of SSCs available for fertility restoration. Therefore, maintaining the number of SSCs is a critical step in human fertility preservation. Standardizing a successful cryopreservation method for TT and testicular cell suspensions (TCSs) is most important before any clinical application of fertility restoration could be successful.

OBJECTIVE AND RATIONALE

This review gives an overview of existing cryopreservation protocols used in different animal models and humans. Cell recovery, cell viability, tissue integrity and functional assays are taken into account. Additionally, biosafety and current perspectives in male fertility preservation are discussed.

SEARCH METHODS

An extensive PubMED and MEDline database search was conducted. Relevant studies linked to the topic were identified by the search terms: cryopreservation, male fertility preservation, (immature)testicular tissue, testicular cell suspension, spermatogonial stem cell, gonadotoxicity, radiotherapy and chemotherapy.

OUTCOMES

The feasibility of fertility restoration techniques using frozen-thawed TT and TCS has been proven in animal models. Efficient protocols for cryopreserving human TT exist and are currently applied in the clinic. For TCSs, the highest post-thaw viability reported after vitrification is 55.6 ± 23.8%. Yet, functional proof of fertility restoration in the human is lacking. In addition, few to no data are available on the safety aspects inherent to offspring generation with gametes derived from frozen-thawed TT or TCSs. Moreover, clarification is needed on whether it is better to cryopreserve TT or TCS.

WIDER IMPLICATIONS

Fertility restoration techniques are very promising and expected to be implemented in the clinic in the near future. However, inter-center variability needs to be overcome and the gametes produced for reproduction purposes need to be subjected to safety studies. With the perspective of a future clinical application, there is a dire need to optimize and standardize cryopreservation and safety testing before using frozen-thawed TT of TCSs for fertility restoration.

Human spermatogonial stem cells display limited proliferation in vitro under mouse spermatogonial stem cell culture conditions

OBJECTIVE

To study the ability of human spermatogonial stem cells (hSSCs) to proliferate in vitro under mouse spermatogonial stem cell (mSSC) culture conditions.

DESIGN

Experimental basic science study.

SETTING

Reproductive biology laboratory.

PATIENT(S)

Cryopreserved testicular tissue with normal spermatogenesis obtained from three donors subjected to orchiectomy due to a prostate cancer treatment.

INTERVENTION(S)

Testicular cells used to create in vitro cell cultures corresponding to the following groups: [1] unsorted human testicular cells, [2] differentially plated human testicular cells, and [3] cells enriched with major histocompatibility complex class 1 (HLA^-)/epithelial cell surface antigen (EPCAM⁺) in coculture with inactivated testicular feeders from the same patient.

MAIN OUTCOME MEASURE(S)

Analyses and characterization including immunocytochemistry and quantitative reverse-transcription polymerase chain reaction for somatic and germ cell markers, testosterone and inhibin B quantification, and TUNEL assay.

RESULT(S)

Putative hSSCs appeared in singlets, doublets, or small groups of up to four cells in vitro only when testicular cells were cultured in StemPro-34 medium supplemented with glial cell line-derived neurotrophic factor (GDNF), leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF). Fluorescence-activated cell sorting with HLA^-/EPCAM⁺ resulted in an enrichment of 27% VASA⁺/UTF1⁺ hSSCs, compared to 13% in unsorted controls. Coculture of sorted cells with inactivated testicular feeders gave rise to an average density of 112 hSSCs/cm² after 2 weeks in vitro compared with unsorted cells (61 hSSCs/cm²) and differentially plated cells (49 hSSCS/cm²). However, putative hSSCs rarely stained positive for the proliferation marker Ki67, and their presence was reduced to the point of almost disappearing after 4 weeks in vitro.

CONCLUSION(S)

We found that hSSCs show limited proliferation in vitro under mSSC culture conditions. Coculture of HLA^-/EPCAM⁺ sorted cells with testicular feeders improved the germ cell/somatic cell ratio.

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.

Cryopreservation of testis tissues and in vitro spermatogenesis

Cancer treatments, either chemo‐ or radiotherapy, may cause severe damage to gonads which could lead to the infertility of patients. In post‐pubertal male patients, semen cryopreservation is recommended to preserve the potential to have their own biological children in the future; however, it is not applicable to prepubertals. The preservation of testis tissue which contains spermatogonial stem cells (SSCs) but not sperm would be an alternative measure. The tissues or SSCs have to be transplanted back into patients to obtain sperm; however, this procedure remains experimental, invasive, and is accompanied with the potential risk of re‐implantation of cancer cells. Recently, we developed an organ culture system which supports the spermatogenesis of mice up to sperm formation from SSCs. It was also shown that the tissues could be frozen for later sperm production, which resulted in the generation of offspring. Thus, it could be useful as a clinical application for preserving the reproductive potential of male pediatric cancer patients. The establishment of an optimized cryopreservation method and the development of a culture system for human testis tissue are expected in the future.

Testicular function and fertility preservation after treatment for haematological cancer

PURPOSE OF REVIEW

Treatment for high-risk or relapsed haematological malignancy with haematopoietic stem cell transplantation is known to cause infertility. Today, there are no established options for fertility preservation in pre-pubertal boys. This review aims to describe how therapy for haematological malignancy in childhood affects male fertility, and to summarize recent developments for fertility preservation in these patients.

RECENT FINDINGS

Eventual recovery of spermatogenesis is probable after chemotherapy-based conditioning for haematopoietic stem cell transplantation. However, conditioning with total body irradiation is associated with a very high risk of permanent infertility. For high-risk patients, auto-transplantation of cryopreserved testicular tissue or cells might represent an approach for fertility preservation; however, contamination of testis tissue with malignant cells may prevent their subsequent reintroduction into patients. Recent progress using in-vitro differentiation of germ cells combined with assisted reproductive techniques may, in the future, represent a suitable alternative to retransplantation.

SUMMARY

Particular care must be taken when assessing infertility risk in patients with haematological malignancy as reclassification to high risk may significantly increase the likelihood of treatment-related gonadotoxicity. Importantly, development of fertility preservation strategies in such high-risk patients must also take into account specific risks for haematological cancers including cancer cell contamination.

Granulocyte colony-stimulating factor prevents loss of spermatogenesis after sterilizing busulfan chemotherapy

OBJECTIVE

To determine whether granulocyte colony-stimulating factor (G-CSF) could prevent loss of spermatogenesis induced by busulfan chemotherapy via protection of undifferentiated spermatogonia, which might serve as an adjuvant approach to preserving male fertility among cancer patients.

DESIGN

Laboratory animal study.

SETTING

University.

ANIMAL(S)

Laboratory mice.

INTERVENTION(S)

Five-week-old mice were treated with a sterilizing busulfan dose and with 7 days of G-CSF or vehicle treatment and evaluated 10 weeks later (experiment 1) or 24 hours after treatment (experiment 2).

MAIN OUTCOME MEASURE(S)

Experiment 1: testis weights, epididymal sperm counts, testis histology. Experiment 2: PLZF immunofluorescent costaining with apoptotic markers. Molecular analysis of G-CSF receptor expression in undifferentiated spermatogonia.

RESULT(S)

Ten weeks after treatment, busulfan-treated mice that also received treatment with G-CSF exhibited significantly better recovery of spermatogenesis and epididymal sperm counts than animals receiving busulfan alone. G-CSF led to increased numbers of PLZF+ spermatogonia 24 hours after treatment that was not accompanied by changes in apoptosis. To address the cellular target of G-CSF, mRNA for the G-CSF receptor, Csf3r, was found in adult mouse testes and cultured THY1+ (undifferentiated) spermatogonia, and cell-surface localized CSF3R was observed on 3% of cultured THY1+ spermatogonia.

CONCLUSION(S)

These results demonstrate that G-CSF protects spermatogenesis from gonadotoxic insult (busulfan) in rodents, and this may occur via direct action on CSF3R+ undifferentiated spermatogonia. G-CSF treatment might be an effective adjuvant therapy to preserve male fertility in cancer patients receiving sterilizing treatments.

Characterization of human spermatogonial stem cell markers in fetal, pediatric, and adult testicular tissues

Autologous spermatogonial stem cell (SSC) transplantation is a potential therapeutic modality for patients with azoospermia following cancer treatment. For this promise to be realized, definitive membrane markers of prepubertal and adult human SSCs must be characterized in order to permit SSC isolation and subsequent expansion. This study further characterizes the markers of male gonocytes, prespermatogonia, and SSCs in humans. Human fetal, prepubertal, and adult testicular tissues were analyzed by confocal microscopy, fluorescence-activated cell sorting, and qRT-PCR for the expression of unique germ cell membrane markers. During male fetal development, THY1 and KIT (C-Kit) are transient markers of gonocytes but not in prespermatogonia and post-natal SSCs. Although KIT expression is detected in gonocytes, THY1 expression is also detected in the somatic component of the fetal testes in addition to gonocytes. In the third trimester of gestation, THY1 expression shifts exclusively to the somatic cells of the testes where it continues to be detected only in the somatic cells postnatally. In contrast, SSEA4 expression was only detected in the gonocytes, prespermatogonia, SSCs, and Sertoli cells of the fetal and prepubertal testes. After puberty, SSEA4 expression can only be detected in primitive spermatogonia. Thus, although THY1 and KIT are transient markers of gonocytes, SSEA4 is the only common membrane marker of gonocytes, prespermatogonia, and SSCs from fetal through adult human development. This finding is essential for the isolation of prepubertal and adult SSCs, which may someday permit fertility preservation and reversal of azoospermia following cancer treatment.

Optimizing cryopreservation of human spermatogonial stem cells: comparing the effectiveness of testicular tissue and single cell suspension cryopreservation

OBJECTIVE

To determine whether optimal human spermatogonial stem cell (SSC) cryopreservation is best achieved with testicular tissue or single cell suspension cryopreservation. This study compares the effectiveness between these two approaches by using testicular SSEA-4+ cells, a known population containing SSCs.

DESIGN

In vitro human testicular tissues.

SETTING

Academic research unit.

PATIENT(S)

Adult testicular tissues (n=4) collected from subjects with normal spermatogenesis and normal fetal testicular tissues (n=3).

INTERVENTION(S)

Testicular tissue versus single cell suspension cryopreservation.

MAIN OUTCOME MEASURE(S)

Cell viability, total cell recovery per milligram of tissue, as well as viable and SSEA-4+ cell recovery.

RESULT(S)

Single cell suspension cryopreservation yielded higher recovery of SSEA-4+ cells enriched in adult SSCs, whereas fetal SSEA-4+ cell recovery was similar between testicular tissue and single cell suspension cryopreservation.

CONCLUSION(S)

Adult and fetal human SSEA-4+ populations exhibited differential sensitivity to cryopreservation based on whether they were cryopreserved in situ as testicular tissues or as single cells. Thus, optimal preservation of human SSCs depends on the patient's age, type of samples cryopreserved, and end points of therapeutic applications.

Testicular tissue cryopreservation and spermatogonial stem cell transplantation to restore fertility: from bench to bedside

Male infertility management has made significant progress during the past three decades, especially after the introduction of intracytoplasmic sperm injection in 1992. However, many boys and men still suffer from primary testicular failure due to acquired or genetic causes. New and novel treatments are needed to address these issues. Spermatogenesis originates from spermatogonial stem cells (SSCs) that reside in the testis. Many of these men lack SSCs or have lost SSCs over time as a result of specific medical conditions or toxic exposures. Loss of SSCs is critical in prepubertal boys who suffer from cancer and are going through gonadotoxic cancer treatments, as there is no option of sperm cryopresrvation due to sexual immaturity. The development of SSC transplantation in a mouse model to repopulate spermatozoa in depleted testes has opened new avenues of research in other animal models, including non-human primates. Recent advances in cryopreservation and in vitro propagation of human SSCs offer promise for human SSC autotransplantation in the near future. Ongoing research is focusing on safety and technical issues of human SSC autotransplantation. This is the time to counsel parents and boys at risk of infertility on the possibility of cryopreserving and banking a small amount of testis tissue for potential future use in SSC transplantation.

Eliminating acute lymphoblastic leukemia cells from human testicular cell cultures: a pilot study

OBJECTIVE

To study whether acute lymphoblastic leukemia (ALL) cells survive in a human testicular cell culture system.

DESIGN

Experimental laboratory study.

SETTING

Reproductive biology laboratory, academic medical center.

PATIENT(S)

Acute lymphoblastic leukemia cells from three patients and testicular cells from three other patients.

INTERVENTION(S)

Acute lymphoblastic leukemia cells were cultured alone or in combination with testicular cells, at various concentrations, in a system that has recently been developed to propagate human spermatogonial stem cells.

MAIN OUTCOME MEASURE(S)

Viability of ALL and testicular cells during culture was evaluated by flow cytometry using markers for live/dead cells. Furthermore, the presence of ALL cells among testicular cells was determined by highly sensitive (1:10,000 to 1:100,000 cells) patient-specific antigen-receptor minimal residual disease polymerase chain reaction. The presence of spermatogonia at the end of culture was determined by reverse transcription-polymerase chain reaction for ZBTB16, UCHL1, and GPR125.

RESULT(S)

The ALL cells cultured separately did not survive beyond 14 days of culture. When cultured together with testicular cells, even at extremely high initial concentrations (40% ALL cells), ALL cells were undetectable beyond 26 days of culture. Reverse transcription-polymerase chain reaction confirmed the presence of spermatogonia at the end of the culture period.

CONCLUSION(S)

Our pilot study shows that the described testicular cell culture system not only allows for efficient propagation of spermatogonial stem cells but also eliminates contaminating ALL cells.

Male infertility: non-surgical therapy

Infertility is defined as the inability of a couple to conceive after 12 months of unprotected intercourse and affects 15% of couples with male component of 50%. The failure of spermatogenesis can result from hypothalamic, pituitary or testicular disorders although in the majority of cases it remains idiopathic. The diagnostic process includes medical history, semen analysis, hormonal studies, genetic studies and radiological evaluation.

Targeted hormonal therapies are available for patients whose infertility is caused by altered levels of androgens, prolactin, or TSH. Main treatments aim to restore normal sexual function by administering testosterone and to increase spermatogenesis with pulsatile GnRH.

Fertility in men suffering from hypogonadotrophic hypogonadism can be restored through hormone therapy using GnRH or with the use of gonadotropins when there is hypothalamic failure. In the past, treatment options for the factors of idiopathic male infertility were mainly based on the use of anti-estrogens that cause an increased secretion of FSH and LH and therefore of testosterone.

Oxytocin promotes the progression of the sperm and increases the conversion of testosterone into dihydrotestosterone. The aromatase's inhibitors decrease the conversion of androgens to estrogens, increasing serum levels of androgens, resulting in an increased release of gonadotropins.

Two areas showed interesting future perspectives for the treatment of infertility: gene therapy and transplantation of spermatogonial stem cells.

Germline stem cells: toward the regeneration of spermatogenesis

Improved therapies for cancer and other conditions have resulted in a growing population of long-term survivors. Infertility is an unfortunate side effect of some cancer therapies that impacts the quality of life of survivors who are in their reproductive or prereproductive years. Some of these patients have the opportunity to preserve their fertility using standard technologies that include sperm, egg, or embryo banking, followed by IVF and/or ET. However, these options are not available to all patients, especially the prepubertal patients who are not yet producing mature gametes. For these patients, there are several stem cell technologies in the research pipeline that may give rise to new fertility options and allow infertile patients to have their own biological children. We will review the role of stem cells in normal spermatogenesis as well as experimental stem cell-based techniques that may have potential to generate or regenerate spermatogenesis and sperm. We will present these technologies in the context of the fertility preservation paradigm, but we anticipate that they will have broad implications for the assisted reproduction field.

Eliminating malignant contamination from therapeutic human spermatogonial stem cells

Spermatogonial stem cell (SSC) transplantation has been shown to restore fertility in several species and may have application for treating some cases of male infertility (e.g., secondary to gonadotoxic therapy for cancer). To ensure safety of this fertility preservation strategy, methods are needed to isolate and enrich SSCs from human testis cell suspensions and also remove malignant contamination. We used flow cytometry to characterize cell surface antigen expression on human testicular cells and leukemic cells (MOLT-4 and TF-1a). We demonstrated via FACS that EpCAM is expressed by human spermatogonia but not MOLT-4 cells. In contrast, HLA-ABC and CD49e marked >95% of MOLT-4 cells but were not expressed on human spermatogonia. A multiparameter sort of MOLT-4-contaminated human testicular cell suspensions was performed to isolate EpCAM+/HLA-ABC-/CD49e- (putative spermatogonia) and EpCAM-/HLA-ABC+/CD49e+ (putative MOLT-4) cell fractions. The EpCAM+/HLA-ABC-/CD49e- fraction was enriched for spermatogonial colonizing activity and did not form tumors following human-to-nude mouse xenotransplantation. The EpCAM-/HLA-ABC+/CD49e+ fraction produced tumors following xenotransplantation. This approach could be generalized with slight modification to also remove contaminating TF-1a leukemia cells. Thus, FACS provides a method to isolate and enrich human spermatogonia and remove malignant contamination by exploiting differences in cell surface antigen expression.

Spermatogonial stem cell preservation and transplantation: from research to clinic

STUDY QUESTION

What issues remain to be solved before fertility preservation and transplantation can be offered to prepubertal boys?

SUMMARY ANSWER

The main issues that need further investigation are malignant cell decontamination, improvement of in vivo fertility restoration and in vitro maturation.

WHAT IS KNOWN ALREADY

Prepubertal boys who need gonadotoxic treatment might render sterile for the rest of their life. As these boys do not yet produce sperm cells, they cannot benefit from sperm banking. Spermatogonial stem cell (SSC) banking followed by autologous transplantation has been proposed as a fertility preservation strategy. But before this technique can be applied in the clinic, some important issues have to be resolved.

STUDY DESIGN, SIZE DURATION

Original articles as well as review articles published in English were included in a search of the literature.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Relevant studies were selected by an extensive Medline search. Search terms were fertility preservation, cryopreservation, prepubertal, SSC, testis tissue, transplantation, grafting and in vitro spermatogenesis. The final number of studies selected for this review was 102.

MAIN RESULTS AND THE ROLE OF CHANCE

Cryopreservation protocols for testicular tissue have been developed and are already being used in the clinic. Since the efficiency and safety of SSC transplantation have been reported in mice, transplantation methods are now being adapted to the human testes. Very recently, a few publications reported on in vitro spermatogenesis in mice, but this technique is still far from being applied in a clinical setting.

LIMITATIONS, REASONS FOR CAUTION

Using tissue from cancer patients holds a potential risk for contamination of the collected testicular tissue. Therefore, it is of immense importance to separate malignant cells from the cell suspension before transplantation. Because biopsies obtained from young boys are small and contain only few SSCs, propagation of these cells in vitro will be necessary.

WIDER IMPLICATIONS OF THE FINDINGS

The ultimate use of the banked tissue will depend on the patient's disease. If the patient was suffering from a non-malignant disease, tissue grafting might be offered. In cancer patients, decontaminated cell suspensions will be injected in the testis. For patients with Klinefelter syndrome, the only option would be in vitro spermatogenesis. However, at present, restoring fertility in cancer and Klinefelter patients is not yet possible.

STUDY FUNDING/COMPETING INTEREST(S)

Research Foundation, Flanders (G.0385.08 to H.T.), the Institute for the Agency for Innovation, Belgium (IWT/SB/111245 to E.G.), the Flemish League against Cancer (to E.G.), Kom op tegen kanker (G.0547.11 to H.T.) and the Fund Willy Gepts (to HT). E.G. is a Postdoctoral Fellow of the FWO, Research Foundation, Flanders. There are no conflicts of interest.

Restoring fertility in sterile childhood cancer survivors by autotransplanting spermatogonial stem cells: are we there yet?

Current cancer treatment regimens do not only target tumor cells, but can also have devastating effects on the spermatogonial stem cell pool, resulting in a lack of functional gametes and hence sterility. In adult men, fertility can be preserved prior to cancer treatment by cryopreservation of ejaculated or surgically retrieved spermatozoa, but this is not an option for prepubertal boys since spermatogenesis does not commence until puberty. Cryopreservation of a testicular biopsy taken before initiation of cancer treatment, followed by in vitro propagation of spermatogonial stem cells and subsequent autotransplantation of these stem cells after cancer treatment, has been suggested as a way to preserve and restore fertility in childhood cancer survivors. This strategy, known as spermatogonial stem cell transplantation, has been successful in mice and other model systems, but has not yet been applied in humans. Although recent progress has brought clinical application of spermatogonial stem cell autotransplantation in closer range, there are still a number of important issues to address. In this paper, we describe the state of the art of spermatogonial stem cell transplantation and outline the hurdles that need to be overcome before clinical implementation.

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.

Separating spermatogonia from cancer cells in contaminated prepubertal primate testis cell suspensions

BACKGROUND

Chemotherapy and radiation treatments for cancer and other diseases can cause male infertility. There are currently no options to preserve the fertility of prepubertal boys who are not yet making sperm. Cryopreservation of spermatogonial stem cells (SSCs, obtained via testicular biopsy) followed by autologous transplantation back into the testes at a later date may restore fertility in these patients. However, this approach carries an inherent risk of reintroducing cancer.

METHODS

To address this aspect of SSC transplantation safety, prepubertal non-human primate testis cell suspensions were inoculated with MOLT4 T-lymphoblastic leukemia cells and subsequently sorted for cell surface markers CD90 (THY-1) and CD45.

RESULTS

Cancer cells segregated to the CD90-/CD45+ fraction and produced tumors in nude mice. Nearly all sorted DEAD box polypeptide 4-positive (VASA+) spermatogonia segregated to the CD90+/CD45- fraction. In a preliminary experiment, a purity check of the sorted putative stem cell fraction (CD90+/CD45-) revealed 0.1% contamination with cancer cells, which was sufficient to produce tumors in nude mice. We hypothesized that the contamination resulted from mis-sorting due to cell clumping and employed singlet discrimination (SD) in four subsequent experiments. Purity checks revealed no cancer cell contamination in the CD90+/CD45- fraction from three of the four SD replicates and these fractions produced no tumors when transplanted into nude mouse testes.

CONCLUSIONS

We conclude that spermatogonia can be separated from contaminating malignant cells by fluorescence-activated cell sorting prior to SSC transplantation and that post-sorting purity checks are required to confirm elimination of malignant cells.

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.

Contemporary concepts in the evaluation and management of male infertility

Infertility in men is a common condition. At the core of the medical evaluation of the male partner in a couple who are unable to conceive is the history and physical examination. Special attention should be directed to the patient's developmental history and any use of testosterone products. The physical examination focuses on the genitals, and includes assessments of the size and consistency of the testicles, epididymis, vas deferens, and presence of varicoceles. Although many sophisticated tests are available, semen analysis is still the most important diagnostic tool used to assess fertility, and includes parameters such as sperm count, motility and viability. Treatment of male factor infertility can involve targeted agents, in the case of specific conditions such as hypogonadotropic hypogonadism, or it can be empirical-using medical therapy or assisted conception techniques-for patients in whom no underlying cause has been identified. Although an all-encompassing treatment for male factor infertility has not yet been developed, the field offers many promising avenues of research.

Array comparative genomic hybridization analysis does not show genetic alterations in spermatozoa and offspring generated after spermatogonial stem cell transplantation in the mouse

BACKGROUND

The most promising procedure to restore fertility in male childhood cancer patients is spermatogonial stem cell transplantation (SSCT). Although the efficiency of SSCT has been proven in the mouse model, its safety needs to be investigated too before considering any implementation in the clinic. To examine the incidence of genetic abnormalities after SSCT, the karyotypes of donor-derived spermatozoa and offspring were analyzed.

METHODS

Donor cells were obtained from prepubertal mice and introduced in the seminiferous tubules of genetically sterile W/W(v) mice. Five to 10 months after SSCT, DNA was extracted from epididymal sperm to perform array comparative genomic hybridization (aCGH) analysis. In addition, spermatozoa, liver and kidney from the offspring were subjected to aCGH analysis.

RESULTS

Numerical chromosomal aberrations could not be detected in spermatozoa from transplanted males, nor in their offspring. The few genetic deviations (deletions, amplifications) observed were all polymorphisms.

CONCLUSIONS

No major genetic alterations could be detected after SSCT. These data are supportive for further development of SSCT as a strategy for fertility restoration.