Isolation, identification and differentiation of human spermatogonial cells on three-dimensional decellularized sheep testis

Recent Progress of Induced Spermatogenesis In Vitro

Sperm, a crucial gamete for reproduction in sexual reproduction, is generated through the proliferation, differentiation, and morphological transformations of spermatogonial stem cells within the specialized microenvironment of the testes. Replicating this environment artificially presents challenges. However, interdisciplinary advancements in physics, materials science, and cell engineering have facilitated the utilization of innovative materials, technologies, and structures for inducing in vitro sperm production. This article offers a comprehensive overview of research progress on inducing in vitro sperm production by categorizing techniques into two major systems based on matrix-based and non-matrix-based approaches, respectively. Detailed discussions are provided for both types of technology systems through comparisons of their similarities and differences, as well as research advancements. The aim is to provide researchers in this field with a comprehensive panoramic view while presenting our own perspectives and prospects.

Male fertility restoration: in vivo and in vitro stem cell-based strategies using cryopreserved testis tissue: a scoping review

IMPORTANCE

Advances in the treatment of childhood cancer have significantly improved survival rates, with more than 80% of survivors reaching adulthood. However, gonadotoxic cancer treatments endanger future fertility, and prepubertal males have no option to preserve fertility by sperm cryopreservation. In addition, boys with cryptorchidism are at risk of compromised fertility in adulthood.

OBJECTIVE

To investigate current evidence for male fertility restoration strategies, explore barriers to clinical implementation, and outline potential steps to overcome these barriers, a scoping review was conducted. This knowledge synthesis is particularly relevant for prepubertal male cancer survivors and boys with cryptorchidism.

EVIDENCE REVIEW

The review was conducted after the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews criteria and previously published guidelines and examined studies using human testis tissue of prepubertal boys or healthy male adults. A literature search in PubMed was conducted, and 72 relevant studies were identified, including in vivo and in vitro approaches.

FINDINGS

In vivo strategies, such as testis tissue engraftment and spermatogonial stem cell transplantation, hold promise for promoting cell survival and differentiation. Yet, complete spermatogenesis has not been achieved. In vitro approaches focus on the generation of male germ cells from direct germ cell maturation in various culture systems, alongside human induced pluripotent stem cells and embryonic stem cells. These approaches mark significant advancements in understanding and promoting spermatogenesis, but achieving fully functional spermatozoa in vitro remains a challenge. Barriers to clinical implementation include the risk of reintroducing malignant cells and introduction of epigenetic changes.

CONCLUSION

Male fertility restoration is an area in rapid development. On the basis of the reviewed studies, the most promising and advanced strategy for restoring male fertility using cryopreserved testis tissue is direct testis tissue transplantation.

RELEVANCE

This review identifies persistent barriers to the clinical implementation of male fertility restoration. However, direct transplantation of frozen-thawed testis tissue remains a promising strategy that is on the verge of clinical application.

Recent Progress of In Vitro 3D Culture of Male Germ Stem Cells

Male germline stem cells (mGSCs), also known as spermatogonial stem cells (SSCs), are the fundamental seed cells of male animal reproductive physiology. However, environmental influences, drugs, and harmful substances often pose challenges to SSCs, such as population reduction and quality decline. With advancements in bioengineering technology and biomaterial technology, an increasing number of novel cell culture methods and techniques have been employed for studying the proliferation and differentiation of SSCs in vitro. This paper provides a review on recent progress in 3D culture techniques for SSCs in vitro; we summarize the microenvironment of SSCs and spermatocyte development, with a focus on scaffold-based culture methods and 3D printing cell culture techniques for SSCs. Additionally, decellularized testicular matrix (DTM) and other biological substrates are utilized through various combinations and approaches to construct an in vitro culture microenvironment suitable for SSC growth. Finally, we present some perspectives on current research trends and potential opportunities within three areas: the 3D printing niche environment, alternative options to DTM utilization, and advancement of the in vitro SSC culture technology system.

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.

Biomaterials for Testicular Bioengineering: How far have we come and where do we have to go?

Traditional therapeutic interventions aim to restore male fertile potential or preserve sperm viability in severe cases, such as semen cryopreservation, testicular tissue, germ cell transplantation and testicular graft. However, these techniques demonstrate several methodological, clinical, and biological limitations, that impact in their results. In this scenario, reproductive medicine has sought biotechnological alternatives applied for infertility treatment, or to improve gamete preservation and thus increase reproductive rates in vitro and in vivo. One of the main approaches employed is the biomimetic testicular tissue reconstruction, which uses tissue-engineering principles and methodologies. This strategy pursues to mimic the testicular microenvironment, simulating physiological conditions. Such approach allows male gametes maintenance in culture or produce viable grafts that can be transplanted and restore reproductive functions. In this context, the application of several biomaterials have been proposed to be used in artificial biological systems. From synthetic polymers to decellularized matrixes, each biomaterial has advantages and disadvantages regarding its application in cell culture and tissue reconstruction. Therefore, the present review aims to list the progress that has been made and the continued challenges facing testicular regenerative medicine and the preservation of male reproductive capacity, based on the development of tissue bioengineering approaches for testicular tissue microenvironment reconstruction.

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.

De novo testicular tissue generation from non-testicular cell lines, biologic and synthetic scaffolds: Current findings and future translational applications

In recent decades, reproductive science has revolutionized the options for biological parenthood for the 20-50% of infertility cases affected by male factors. However, current solutions exclude those who are infertile due to absent testicular tissue. This includes anorchic 46, XY individuals due to trauma or congenital factors and transgender men with a 46, XX genotype. There is a clinical need for methods to restore testicular function independent of pre-existing testicular tissue. This mini-review analyzes studies that have applied non-testicular cell lines to generate germline and non-germline testicular parenchymal components. While only 46, XY cell lines have been evaluated in this context to date, the potential for future application of cell lines from 46, XX individuals is also included. Additionally, the role of varied culture methods, media supplementation, and biologic and synthetic scaffolds to further support testicular parenchyma generation are critiqued. De novo testicular tissue generation in this manner will require a focus on both cellular and environmental aspects of tissue engineering. Put together, these studies highlight the future potential for expanded clinical, reproductive, and endocrine management options for individuals who are currently excluded from aspects of biologic reproduction most consistent with their gender identity and reproductive preferences.

Li-Doped Bioactive Ceramics: Promising Biomaterials for Tissue Engineering and Regenerative Medicine

Lithium (Li) is a metal with critical therapeutic properties ranging from the treatment of bipolar depression to antibacterial, anticancer, antiviral and pro-regenerative effects. This element can be incorporated into the structure of various biomaterials through the inclusion of Li chloride/carbonate into polymeric matrices or being doped in bioceramics. The biocompatibility and multifunctionality of Li-doped bioceramics present many opportunities for biomedical researchers and clinicians. Li-doped bioceramics (capable of immunomodulation) have been used extensively for bone and tooth regeneration, and they have great potential for cartilage/nerve regeneration, osteochondral repair, and wound healing. The synergistic effect of Li in combination with other anticancer drugs as well as the anticancer properties of Li underline the rationale that bioceramics doped with Li may be impactful in cancer treatments. The role of Li in autophagy may explain its impact in regenerative, antiviral, and anticancer research. The combination of Li-doped bioceramics with polymers can provide new biomaterials with suitable flexibility, especially as bio-ink used in 3D printing for clinical applications of tissue engineering. Such Li-doped biomaterials have significant clinical potential in the foreseeable future.

Effect of NMDA receptor agonist and antagonist on spermatogonial stem cells proliferation in 2- and 3- dimensional culture systems

BACKGROUND

The main purpose of this study was to investigate the effect of D-serine (DS) and Dizocilpine (MK-801) on the proliferation of spermatogonial stem cells (SSCs) in two-dimensional (2D) and three-dimensional (3D) culture systems.

METHODS AND RESULTS

The SSCs of male NMRI mice were isolated by enzymatic digestion and cultured for two weeks. Then, the identity of SSCs was validated by anti-Plzf and anti-GFR-α1 antibodies via immunocytochemistry (ICC). The proliferation capacity of SSCs was evaluated by their culture on a layer of the decellularized testicular matrix (DTM) prepared from mouse testis, as well as two-dimensional (2D) with different mediums. After two weeks of the initiation of proliferation culture on 3D and 2D medium, the pre-meiotic at the mRNA and protein levels were evaluated via qRT-PCR and flow cytometry methods, respectively. The results showed that the proliferation rate of SSCs in 3D culture with 50 mM glutamic acid and 20 mM D-serine was significantly different from other groups after 14 days treatment. mRNA expression levels of promyelocytic leukemia zinc finger (Plzf) in 3D cultures supplemented by 20 mM D-serine and 50 mM glutamic acid were considerably higher than the 3D control group (p < 0.001). The flow cytometry analysis revealed that the amount of Plzf in the 2D-culture groups of SSCs with 20 mM MK-801 was considerably lower compared to the 2D-culture control group (p < 0.001).

CONCLUSIONS

This study indicated that decellularized testicular matrix supplemented with D-serine and glutamic acid could be considered a promising vehicle to support cells and provide an appropriate niche for the proliferation of SSCs.

Application of Tissue-Specific Extracellular Matrix in Tissue Engineering: Focus on Male Fertility Preservation

In vitro spermatogenesis and xenotransplantation of the immature testicular tissues (ITT) are the experimental approaches that have been developed for creating seminiferous tubules-like functional structures in vitro and keeping the integrity of the ITTs in vivo, respectively. These strategies are rapidly developing in response to the growing prevalence of infertility in adolescent boys undergoing cancer treatment, by the logic that there is no sperm cryopreservation option for them. Recently, with the advances made in the field of tissue engineering and biomaterials, these methods have achieved promising results for fertility preservation. Due to the importance of extracellular matrix for the formation of vascular bed around the grafted ITTs and also the creation of spatial arrangements between Sertoli cells and germ cells, today it is clear that the scaffold plays a very important role in the success of these methods. Decellularized extracellular matrix (dECM) as a biocompatible, functionally graded, and biodegradable scaffold with having tissue-specific components and growth factors can support reorganization and physiologic processes of originated cells. This review discusses the common protocols for the tissue decellularization, sterilization, and hydrogel formation of the decellularized and lyophilized tissues as well as in vitro and in vivo studies on the use of the testis-derived dECM for testicular organoids.

Exosomes as Potential Biomarkers for Erectile Dysfunction, Varicocele, and Testicular Injury

INTRODUCTION

Optimal male reproductive health is dependent upon critical mediators of cell-cell communication: exosomes or extracellular vesicles. These vesicles are nano-sized particles released into a variety of bodily fluids, such as blood and semen. Exosomes are highly stable and can carry genetic and other molecules, including DNA, RNA, and proteins, which provide information about their origin cells.

OBJECTIVE

To identify exosomes as potential biomarkers or therapeutic mediators in male sexual and reproductive disorders like erectile dysfunction (ED), varicocele, and testicular injury.

METHODS

A PubMed search was performed to highlight all articles available relating to exosomes and extracellular vesicles in the pathogenesis of different male sexual and reproductive disorders, and their importance in clinical use as both diagnostic markers and potential therapeutic mediators.

RESULTS

Various male reproductive system disorders, such as ED, varicocele, and testicular injury, are linked to increased or decreased levels of exosomes. Exosomes have a higher number of molecules such as DNA, RNA, and proteins, which can give a more precise and comprehensive result when compared to other biomarkers. Exosomes can be considered as plausible diagnostic biomarkers for male sexual and reproductive diseases, with considerable advantages over other diagnostic procedures such as invasive tissue biopsy. Exosomes can carry cargo such certain drugs and therapeutic molecules making them a promising therapeutic approach. Several studies have begun to test treating various male sexual reproductive disorders with exosomes.

CONCLUSION

Exosomes deliver many components that can regulate gene expression and target signaling pathways. Understanding how extracellular vesicles can be utilized as biomarkers in diagnosing men, particularly those with idiopathic erectile dysfunction, will not only aid in diagnosis but also help with making therapeutic targets. Khodamoradi K, Golan R, Dullea A, et al. Exosomes as Potential Biomarkers for Erectile Dysfunction, Varicocele, and Testicular Injury. Sex Med Rev 2021;XX:XXX-XXX.

Decellularization of Male Reproductive Tissue

Decellularized testicular matrix (DTM) enables researchers to focus on the specific composition of the testicular extracellular matrix (ECM) and elucidate its role in spermatogenesis. Furthermore, it provides the natural architectural arrangement that could guide the reorganization of dissociated testicular cells in vitro. This is a key consideration as the presence of an authentic nutritive and endocrine support has been proven to be essential for in vitro spermatogenesis, at least in the mouse (Oliver and Stukenborg in Andrology 8:825-834, 2020; Richer et al. in Andrology 12741, 2019). Hence, scaffolds of DTM could be harnessed for the development of a human in vitro spermatogenesis culture system, which is a missing link in male fertility preservation and could be a possible treatment for nonobstructive azoospermia (Gassei and Orwig in Steril 105:256-266, 2016).

Exosomes as Biomarkers for Female Reproductive Diseases Diagnosis and Therapy

Cell-cell communication is an essential mechanism for the maintenance and development of various organs, including the female reproductive system. Today, it is well-known that the function of the female reproductive system and successful pregnancy are related to appropriate follicular growth, oogenesis, implantation, embryo development, and proper fertilization, dependent on the main regulators of cellular crosstalk, exosomes. During exosome synthesis, selective packaging of different factors into these vesicles happens within the originating cells. Therefore, exosomes contain both genetic and proteomic data that could be applied as biomarkers or therapeutic targets in pregnancy-associated disorders or placental functions. In this context, the present review aims to compile information about the potential exosomes with key molecular cargos that are dysregulated in female reproductive diseases which lead to infertility, including polycystic ovary syndrome (PCOS), premature ovarian failure (POF), Asherman syndrome, endometriosis, endometrial cancer, cervical cancer, ovarian cancer, and preeclampsia, as well as signaling pathways related to the regulation of the reproductive system and pregnancy outcome during these pathological conditions. This review might help us realize the etiology of reproductive dysfunction and improve the early diagnosis and treatment of the related complications.