Cryostorage of testicular tissue and retransplantation of spermatogonial stem cells in the infertile male

Differentiation of human primary testicular cells in the presence of SCF using the organoid culture system

PURPOSE

Development of organoids using human primary testicular cells has remained a challenge due to the complexity of the mammalian testicular cytoarchitecture and culture methods. In this study, we generated testicular organoids derived from human primary testicular cells. Then, we evaluated the effect of stem cell factor (SCF) on cell differentiation and apoptosis in the testicular organoid model.

METHODS

The testicular cells were harvested from the three brain-dead donors. Human spermatogonial stem cells (SSCs) were characterized using immunocytochemistry (ICC), RT-PCR and flow cytometry. Testicular organoids were generated from primary testicular cells by hanging drop culture method and were cultured in three groups: control group, experimental group 1 (treated FSH and retinoic acid (RA)), and experimental group 2 (treated FSH, RA and SCF), for five weeks. We assessed the expression of SCP3 (Synaptonemal Complex Protein 3) as a meiotic gene, PRM2 (Protamine 2) as a post-meiotic marker and apoptotic genes of Bax (BCL2-Associated X Protein) and Bcl-2 (B-cell lymphoma 2), respectively by using RT-qPCR. In addition, we identified the expression of PRM2 by immunohistochemistry (IHC).

RESULTS

Relative expression of SCP3, PRM2 and Bcl-2 were highest in group 2 after five weeks of culture. In contrast, BAX expression level was lower in experimental group 2 in comparison with other groups. IHC analyses indicated the highest expression of PRM2 as a postmeiotic marker in group 2 in comparison to 2D culture and control groups but not find significant differences between experimental group 1 and experimental group 2 groups. Morphological evaluations revealed that organoids are compact spherical structures and in the peripheral region composed of uncharacterized elongated fibroblast-like cells.

CONCLUSION

Our findings revealed that the testicular organoid culture system promote the spermatogonial stem cell (SSC) differentiation, especially in presence of SCF. Developed organoids are capable of recapitulating many important properties of a stem cell niche.

Fertility preservation in pediatric healthcare: a review

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

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

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

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

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

Solid surface vitrification of goat testicular cell suspension enriched for spermatogonial stem cells

This study reports solid surface vitrification (SSV) of goat testicular cell suspensions (TCS) enriched for spermatogonial stem cells (SSCs). The TCS was isolated from pre-pubertal goat testis by enzymatic digestion, enriched for SSCs by filtration and differential plating, and were vitrified-warmed by SSV. The study showed that SSV could successfully vitrify goat TCS although the percentage of live cells in the vitrified-warmed group was lower (74.8 ± 4.1%) than in non-vitrified control (80.6 ± 6.27%). The vitrified-warmed TCS formed putative SSC colonies upon their in vitro culture, but the colony size of vitrified-warmed cells (24.3 ± 1.8 μm) was smaller than those of non-vitrified warmed cells (58.4 ± 2.5 μm). Mitochondrial activity (0.40 vs. 0.38 A U.), population doubling time (33.45 ± 1.25 h vs. 31.86 ± 1.90 h), and the cell proliferation rate (0.72 ± 0.10 vs. 0.75 ± 0.11 per day) of total cells (including putative SSCs and other somatic cells) did not differ (p > 0.05) between control and SSV vitrified-warmed groups. However, during in vitro culture for 96 h, vitrified-warmed cells showed significantly lower (0.75 vs. 1.33 A U.; p < 0.05) mitochondrial activity than non-vitrified controls. The DCFDA assay showed that ROS activity was significantly (p < 0.05) higher in vitrified-warmed cells (52.8 ± 4.1 A U) than non-vitrified control cells (32.8 ± 2.1 AU). In conclusion, our results suggest that SSC-enriched goat TCS could be successfully cryopreserved by SSV. However, ROS-induced damages to cell cytoplasmic components reduce their cellular proliferation and require further improvement in the protocol. To the best of our knowledge, this study is the first report on the SSV of SSC-enriched goat TCS.

Melatonin Protects Goat Spermatogonial Stem Cells against Oxidative Damage during Cryopreservation by Improving Antioxidant Capacity and Inhibiting Mitochondrial Apoptosis Pathway

Spermatogonial stem cells (SSCs) are the only adult stem cells that pass genes to the next generation and can be used in assisted reproductive technology and stem cell therapy. SSC cryopreservation is an important method for the preservation of immature male fertility. However, freezing increases the production of intracellular reactive oxygen species (ROS) and causes oxidative damage to SSCs. The aim of this study was to investigate the effect of melatonin on goat SSCs during cryopreservation and to explore its protective mechanism. We obtained SSCs from dairy goat testes by two-step enzymatic digestion and differential plating. The SSCs were cryopreserved with freezing media containing different melatonin concentrations. The results showed that 10⁻⁶ M of melatonin increased significantly the viability, total antioxidant capacity (T-AOC), and mitochondrial membrane potential of frozen-thawed SSCs, while it reduced significantly the ROS level and malondialdehyde (MDA) content (P < 0.05). Further analysis was performed by western blotting, flow cytometry, and transmission electron microscopy (TEM). Melatonin improved significantly the enzyme activity and protein expression of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) (P < 0.05), thereby activating the antioxidant defense system of SSCs. Furthermore, melatonin inhibited significantly the expression of proapoptotic protein (Bax) and increased the expression of antiapoptotic proteins (Bcl-2 and Bcl-XL) (P < 0.05). The mitochondrial apoptosis pathway analysis showed that the addition of melatonin reduced significantly the mitochondrial swelling and vacuolation, and inhibited the release of cytochrome C from mitochondria into the cytoplasm, thereby preventing the activation of caspase-3 (P < 0.05) and inhibiting SSC apoptosis. In addition, melatonin reduced significantly the autophagosome formation and regulated the expression of autophagy-related proteins (LC3-I, LC3-II, P62, Beclin1, and ATG7) (P < 0.05), thereby reversing the freeze-induced excessive autophagy. In summary, melatonin protected goat SSCs during cryopreservation via antioxidant, antiapoptotic, and autophagic regulation.

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

BACKGROUND

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

OBJECTIVE AND RATIONALE

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

SEARCH METHODS

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

OUTCOMES

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

WIDER IMPLICATIONS

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

Restorative functions of Autologous Stem Leydig Cell transplantation in a Testosterone-deficient non-human primate model

Rationale: Stem Leydig cells (SLCs) transplantation can restore testosterone production in rodent models and is thus a potential solution for treating testosterone deficiency (TD). However, it remains unknown whether these favorable effects will be reproduced in more clinically relevant large-animal models. Therefore, we assessed the feasibility, safety and efficacy of autologous SLCs transplantation in a testosterone-deficient non-human primate (NHP) model.

Methods: Cynomolgus monkey SLCs (CM-SLCs) were isolated from testis biopsies of elderly (> 19 years) cynomolgus monkeys by flow cytometry. Autologous CM-SLCs were injected into the testicular interstitium of 7 monkeys. Another 4 monkeys were injected the same way with cynomolgus monkey dermal fibroblasts (CM-DFs) as controls. The animals were then examined for sex hormones, semen, body composition, grip strength, and exercise activity.

Results: We first isolated CD271⁺ CM-SLCs which were confirmed to expand continuously and show potential to differentiate into testosterone-producing Leydig cells (LCs) in vitro. Compared with CM-DFs transplantation, engraftment of autologous CM-SLCs into elderly monkeys could significantly increase the serum testosterone level in a physiological pattern for 8 weeks, without any need for immunosuppression. Importantly, CM-SLCs transplantation recovered spermatogenesis and ameliorated TD-related symptoms, such as those related to body fat mass, lean mass, bone mineral density, strength and exercise capacity.

Conclusion: For the first time, our short-term observations demonstrated that autologous SLCs can increase testosterone levels and ameliorate relevant TD symptoms in primate models. A larger cohort with long-term follow-up will be required to assess the translational potential of autologous SLCs for TD therapy.

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.

Potential use of stem cells for fertility preservation

BACKGROUND

Infertility and gonadal dysfunction can result from gonadotoxic therapies, environmental exposures, aging, or genetic conditions. In men, non-obstructive azoospermia (NOA) results from defects in the spermatogenic process that can be attributed to spermatogonial stem cells (SSC) or their niche, or both. While assisted reproductive technologies and sperm banking can enable fertility preservation (FP) in men of reproductive age who are at risk for infertility, FP for pre-pubertal patients remains experimental. Therapeutic options for NOA are limited. The rapid advance of stem cell research and of gene editing technologies could enable new FP options for these patients. Induced pluripotent stem cells (iPSC), SSC, and testicular niche cells, as well as mesenchymal stromal cells (aka medicinal signaling cells, MSCs), have been investigated for their potential use in male FP strategies.

OBJECTIVE

Here, we review the benefits and challenges for three types of stem cell-based approaches under investigation for male FP, focusing on the role that promising sources of MSC derived from human umbilical cord, specifically human umbilical cord perivascular cells (HUCPVC), could fulfill. These approaches are as follows: 1. isolation and ex vivo expansion of autologous SSC for in vivo transplantation or in vitro spermatogenesis; 2. in vitro differentiation toward germ cell and testicular somatic cell lineages using autologous SSC, or stem cells such iPSC or MSC; and 3. protection or regeneration of the spermatogenic niche after gonadotoxic insults in vivo.

CONCLUSION

Our studies suggest that HUCPVC are promising sources of cells that could be utilized in multiple aspects of male FP strategies.

Moderate hypoxia modulates ABCG2 to promote the proliferation of mouse spermatogonial stem cells by maintaining mild ROS levels

The aim of this study was to investigate the effects of different oxygen (O₂) concentrations on the growth of mouse spermatogonial stem cells (SSCs) and the possible mechanisms of cell proliferation in vitro. The SSCs from testicular cells were cultured in various O₂ concentrations (1%, 2.5%, 5%, and 20% O₂) for 7 days. Colonies of SSCs were identified morphologically and by immunofluorescence. The number of mouse SSC colonies and the area covered by them were measured. Cell cycle progression of the SSCs was analyzed to identify the state of cell proliferation. The effects of O₂ concentrations on the levels of intracellular reactive oxygen species (ROS) and expression of ATP binding cassette subfamily G member 2 (ABCG2) were also analyzed in the SSCs. Following culturing for 7 days, the SSCs were treated with Ko143 (a specific inhibitor of ABCG2) for 1 h, and the ROS level and expression of bcl-2, bax, and p53 were analyzed. The results showed that mouse SSCs formed compact colonies and had unclear borders in different O₂ concentrations for 7 days, and there were no major morphologic differences between the O₂ treatment groups. The expression of the SSC marker, GFR α1 was studied in each O₂ treatment group. The number and area of SSC colonies, and the number of GFR α1 positive cells were the highest in the 2.5% O₂ treatment group. Compared with other O₂ concentrations, the number of cells in G₀ cycle was significantly higher, while the level of intracellular ROS was lower at 1% O₂. Moreover, the intracellular ROS levels gradually increased with increasing O₂ concentration from 1% to 20%. The expression of ABCG2 in the SSCs cultured at 2.5% O₂ was higher than in the other O₂ groups. Inhibition of ABCG2 increased intracellular ROS generation, and the expression of the pro-apoptotic genes bax and p53, and decreased the expression of the anti-apoptotic gene bcl-2. In conclusion, moderate to low O₂ tension increases ABCG2 expression to maintain mild ROS levels, triggers the expression of the anti-apoptotic genes, suppresses the proapoptotic gene pathway, and further promotes the proliferation of mouse SSCs in vitro.