In vivo and in vitro sperm production: an overview of the challenges and advances in male fertility restoration.

Male infertility can be caused by genetic anomalies, endocrine disorders, inflammation, and exposure to toxic chemicals or gonadotoxic treatments. Therefore, several recent studies have concentrated on the preservation and restoration of fertility to enhance the quality of life for affected individuals. It is currently recommended to biobank the tissue extracted from testicular biopsies to provide a later source of spermatogonial stem cells (SSCs). Another successful approach has been the in vitro production of haploid male germ cells. The capacity of SSCs to transform into sperm, as in testicular tissue transplantation, SSC therapy, and in vitro or ex vivo spermatogenesis, makes them ideal candidates for in vivo fertility restoration. The transplantation of SSCs or testicular tissue to regenerate spermatogenesis and create embryos has been achieved in nonhuman mammal species. Although the outcomes of human trials have yet to be released, this method may soon be approved for clinical use in humans. Furthermore, regenerative medicine techniques that develop tissue or cells on organic or synthetic scaffolds enriched with bioactive molecules have also gained traction. All of these methods are now in different stages of experimentation and clinical trials. However, thanks to rigorous studies on the safety and effectiveness of SSC-based reproductive treatments, some of these techniques may be clinically available in upcoming decades.

Recovering Spermatogenesis By Protected Cryopreservation Using Metformin and Transplanting Spermatogonial Stem Cells Into Testis in an Azoospermia Mouse Model.

Cryopreservation and transplantation of spermatogonial stem cells (SSCs) may serve as a new method to restore male fertility in patients undergoing chemotherapy or radiotherapy. However, SSCs may be damaged during cryopreservation due to the production of reactive oxygen species (ROS). Therefore, different antioxidants have been used as protective agents. Studies have shown that metformin (MET) has antioxidant activity. The aim of this study was to assess the antioxidant and antiapoptotic effects of MET in frozen-thawed SSCs. In addition, the effect of MET on the proliferation and differentiation of SSCs was evaluated. To this end, SSCs were isolated from mouse pups aged 3-6 days old, cultured, identified by flow cytometry (ID4, INTEGRIN ß1+), and finally evaluated for survival and ROS rate. SSCs were transplanted after busulfan and cadmium treatment. Cryopreserved SSCs with and without MET were transplanted after 1 month of cryopreservation. Eight weeks after transplantation, the recipient testes were evaluated for the expression of apoptosis (BAX, BCL2), proliferation (PLZF), and differentiation (SCP3, TP1, TP2, PRM1) markers using immunohistochemistry, Western blot, and quantitative real-time polymerase chain reaction. The findings revealed that the survival rate of SSCs was higher in the 500 µm/mL MET group compared to the other groups (50 and 5000 µm/mL). MET significantly decreased the intracellular ROS production. Transplantation of SSCs increased the expression level of proliferation (PLZF) and differentiation (SCP3, TP1, TP2, PRM1) markers compared to azoospermia group, and their levels were significantly higher in the MET group compared to the cryopreservation group containing basic freezing medium (p < 0.05). MET increased the survival rate of SSCs, proliferation, and differentiation and decreased the ROS production and the apoptosis rate. Cryopreservation by MET seems to be effective in treating infertility.

Melatonin Promotes Differentiation of Human Spermatogonial Stem Cells Cultured on Three-Dimensional Decellularized Human Testis Matrix.

PURPOSE: The use of 3D (3-Dimensional) culture systems supported cell-to-cell and cell-to-extracellular matrix (ECM) interactions, proliferation, and differentiation of SSCs (Spermatogonial stem cells). The potential advantages of ECM-based scaffolds for in vitro spermatogenesis have been indicated in human and animal experiments. Furthermore, the strong antioxidant and anti-inflammatory activities of melatonin have improved in vitro manipulation of human SSCs in culture conditions. MATERIALS AND METHODS: SSCs were isolated from the testis of three dead-brain patients and then propagated for four weeks. The characterization of SSC colonies was done using real-time PCR (Polymerase chain reaction), ICC (Immunocytochemistry), and xenotransplantation to mice model. Decellularization of the human testis was performed using 0.3% sodium dodecyl sulfate (SDS) solution and 1% Triton X-100. Also, various characterizations of DTM (Decellularized testicular matrix ) were carried out using histological staining and DNA content analysis. The optimum dose of melatonin was selected by MTT (Methyl thiazol tetrazolium). SSCs were cultured in 4 groups: control, melatonin, ECM, and ECM-melatonin in a differentiation medium for four weeks. The expression of differentiation genes was evaluated by real-time polymerase chain reaction. In addition, the viability of cultured cells was assessed by MTT assay. RESULTS: The results of ICC and real-time PCR showed the expression of undifferentiated SSC markers (PLZF and GRFA1) in SSC colonies following the 2D culture of isolated SSCs. The presence of testicular ECM components after different staining methods; and the reduction of DNA content confirmed the proper decellularization process. Germ cell apoptosis significantly decreased in melatonin and ECM groups, and the higher viability of SSCs was seen in the ECM-melatonin group. The relative expression of GFRA1 and PRM2 decreased and increased in ECM and ECM-melatonin groups, respectively. CONCLUSION: Our study showed that the addition of melatonin to the human naturally-derived ECM scaffold could provide a suitable platform for inducing the differentiation and preserving the viability of SSCs.

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.

Advances of three-dimensional (3D) culture systems for in vitro spermatogenesis.

The loss of germ cells and spermatogenic failure in non-obstructive azoospermia are believed to be the main causes of male infertility. Laboratory studies have used in vitro testicular models and different 3-dimensional (3D) culture systems for preservation, proliferation and differentiation of spermatogonial stem cells (SSCs) in recent decades. The establishment of testis-like structures would facilitate the study of drug and toxicity screening, pathological mechanisms and in vitro differentiation of SSCs which resulted in possible treatment of male infertility. The different culture systems using cellular aggregation with self-assembling capability, the use of different natural and synthetic biomaterials and various methods for scaffold fabrication provided a suitable 3D niche for testicular cells development. Recently, 3D culture models have noticeably used in research for their architectural and functional similarities to native microenvironment. In this review article, we briefly investigated the recent 3D culture systems that provided a suitable platform for male fertility preservation through organ culture of testis fragments, proliferation and differentiation of SSCs.

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

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

Differentiation of human spermatogonial stem cells using a human decellularized testicular scaffold supplemented by platelet-rich plasma.

BACKGROUND: Effective culture systems for attachment, migration, proliferation, and differentiation of spermatogonial stem cells (SSCs) can be a promising therapeutic modality for preserving male fertility. Decellularized extracellular matrix (ECM) from native testis tissue creates a local microenvironment for testicular cell culture. Furthermore, platelet-rich plasma (PRP) contains various growth factors for the proliferation and differentiation of SSCs. METHODS: In this study, human testicular cells were isolated and cultured for 4 weeks, and SSCs were characterized using immunocytochemistry (ICC) and flow cytometry. Human testicular tissue was decellularized (0.3% SDS, 1% Triton), and the efficiency of the decellularization process was confirmed by histological staining and DNA content analysis. SSCs were cultured on the human decellularized testicular matrix (DTM) for 4 weeks. The viability and the expression of differentiation genes were evaluated by MTT and real-time polymerase chain reaction (PCR), respectively. RESULTS: Histological evaluation and DNA content analysis showed that the components of ECM were preserved during decellularization. Our results showed that after 4 weeks of culture, the expression levels of BAX, BCL-2, PLZF, and SCP3 were unchanged, while the expression of PRM2 significantly increased in the cells cultured on DTM supplemented with PRP (ECM-PRP). In addition, the expression of GFRA1 was significantly decreased in the ECM group compared to the control and PRP groups. Furthermore, the MTT test indicated that viability was significantly enhanced in cells plated on DTM supplemented with PRP. CONCLUSION: Our study demonstrated that DTM supplemented with PRP can provide an effective culture system for the differentiation and viability of SSCs.

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

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

Evaluation of PGK2 and ACR proteins in seminal plasma: suggestion of potential new biomarkers for prediction of sperm retrieval in non-obstructive azoospermia patients.

This study aimed to assess the role of testis-specific proteins, PGK2 and ACR, in the prediction of sperm retrieval results by microdissection testicular sperm extraction (micro-TESE) in men with non-obstructive azoospermia (NOA). This was a case-control study including 48 semen samples of NOA patients undergoing the micro-TESE procedure, 15 semen samples from normozoospermic men as the positive control, and 12 semen samples from obstructive azoospermia/post-vasectomy (OA/PV) as negative controls. We investigated the levels of PGK2 and ACR proteins by ELISA tests in seminal plasma samples. The ELISA results revealed a significantly higher concentration of PGK2 and ACR in the NOA patients with successful sperm retrieval (NOA+) in comparison to NOA patients with failed sperm retrieval (NOA-) group (p = 0.0001 in both cases). For the first time, the data from this study suggests that a seminal PGK2 concentration of 136.3 pg/ml and ACR concentration of 21.75 mIU/ml can be used as cut-off values for the prediction of micro-TESE outcomes in NOA patients. These findings may be useful to avoid unnecessary micro-TESE operations. Overall, the seminal levels of the PGK2 and ACR proteins may be useful in predicting sperm retrieval success by micro-TESE in NOA patients.

Germ cell differentiation of bone marrow mesenchymal stem cells.

Bone marrow mesenchymal stem cells (BM-MSCs) were first cultured under induction of retinoic acid (RA), Sertoli cells conditioned medium and RA + con (conditioned medium) as treatment groups. The presence of Sertoli cells was confirmed by immunocytochemistry of follicle-stimulating hormone receptor in Sertoli cells and flow cytometry by anti-Gata4 antibody. Cell viability and morphology of nucleus and cytoplasm of BM-MSCs were evaluated by MTT test and DAPI staining respectively. The expression of Oct4, Plzf, Scp3, Caspases 8, 9 and 3 genes was evaluated by RT-PCR. For increasing the accuracy of experiment, the expression of Vasa and SCP3 genes was investigated quantitatively by real-time PCR after 0, 5, 10, 15 days of culture. The results showed that the number of apoptotic cells increased in RA group. The expression of apoptosis genes (Caspases 3, 8 and 9) was also observed in this group all days of culture. Measurement of Vasa and Scp3 genes by RT-PCR confirmed the positive effects of retinoic acid on increasing of genes expression. So, in this study, a group with maximum expression of differentiation genes and minimum expression of apoptotic genes was RA + conditioned medium group. DNA fragmentation was not observed in all groups.