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

Advanced 3Dimentional engineered microenvironment to improve of in vitro spermatogenesis: narrative review

Induction of in vitro spermatogenesis may be helpful in the treatment of infertility in azoospermic individuals and those undergoing chemotherapy. Different cultivation systems have been implemented to achieve this aim. This review study aimed to investigate the application of three-dimensional culture in the induction of in vitro spermatogenesis. Relevant studies published in English were identified using PubMed using a range of search terms related to the core focus on tissue engineering of male reproductive systems, in vitro spermatogenesis, germ cell preservation, 3D culture systems for in vitro spermatogenesis, a 3D culture of testis tissue with were last updated in end of 2023. Searches were not restricted to a particular time frame or species, although the emphasis within the review is on regenerative medicine in mammalian male fertility preservation and in vitro spermatogenesis. Spermatogenesis is one of the most complicated cellular differentiation processes in the body. Significant attempts have been made to control spermatogenesis to drive differentiation of male germ stem cells toward mature sperm. Current research efforts focus on providing appropriate microenvironmental conditions to support the process of in vitro spermatogenesis by applying the principles of cell transplantation, material science, and bioengineering. Regenerative medicine may open a new avenue to patients for restoration and maintenance of normal function in spermatogenesis. The techniques reviewed are still in development, and this paper can become the primary reference for a large body of scientists developing advanced tissue engineering for male germ cells or developing the next generation of reproductive medicine.

Bioengineering Approaches for Male Infertility: From Microenvironmental Regeneration to in vitro Fertilization

Male factor accounts for 30-50% of infertility cases and may occur due to congenital anomalies or acquired disorders. In such infertility cases where a limited number of mature sperm is produced, a solution is offered to patients with ART applications; however, these methods are inadequate in patients with germ cell aplasia due to damaged microenvironment. Since monolayer cell culture and static culture conditions do not provide the physical conditions of the 3D microenvironment, they have a limited effect on ensuring the execution of in vitro spermatogenesis properly. For this reason, current treatment approaches turn to biomaterial-implemented, microfluidic, and bioreactor systems where 3D physical conditions are provided. This book chapter focuses on static and dynamic culture conditions, as well as the use of biomaterials to increase the success of ex vivo spermatogenesis and microfluidic device-assisted sperm selection in ART.

Identification of novel cytoskeleton protein involved in spermatogenic cells and sertoli cells of non-obstructive azoospermia based on microarray and bioinformatics analysis

BACKGROUND

During mammalian spermatogenesis, the cytoskeleton system plays a significant role in morphological changes. Male infertility such as non-obstructive azoospermia (NOA) might be explained by studies of the cytoskeletal system during spermatogenesis.

METHODS

The cytoskeleton, scaffold, and actin-binding genes were analyzed by microarray and bioinformatics (771 spermatogenic cellsgenes and 774 Sertoli cell genes). To validate these findings, we cross-referenced our results with data from a single-cell genomics database.

RESULTS

In the microarray analyses of three human cases with different NOA spermatogenic cells, the expression of TBL3, MAGEA8, KRTAP3-2, KRT35, VCAN, MYO19, FBLN2, SH3RF1, ACTR3B, STRC, THBS4, and CTNND2 were upregulated, while expression of NTN1, ITGA1, GJB1, CAPZA1, SEPTIN8, and GOLGA6L6 were downregulated. There was an increase in KIRREL3, TTLL9, GJA1, ASB1, and RGPD5 expression in the Sertoli cells of three human cases with NOA, whereas expression of DES, EPB41L2, KCTD13, KLHL8, TRIOBP, ECM2, DVL3, ARMC10, KIF23, SNX4, KLHL12, PACSIN2, ANLN, WDR90, STMN1, CYTSA, and LTBP3 were downregulated. A combined analysis of Gene Ontology (GO) and STRING, were used to predict proteins' molecular interactions and then to recognize master pathways. Functional enrichment analysis showed that the biological process (BP) mitotic cytokinesis, cytoskeleton-dependent cytokinesis, and positive regulation of cell-substrate adhesion were significantly associated with differentially expressed genes (DEGs) in spermatogenic cells. Moleculare function (MF) of DEGs that were up/down regulated, it was found that tubulin bindings, gap junction channels, and tripeptide transmembrane transport were more significant in our analysis. An analysis of GO enrichment findings of Sertoli cells showed BP and MF to be common DEGs. Cell-cell junction assembly, cell-matrix adhesion, and regulation of SNARE complex assembly were significantly correlated with common DEGs for BP. In the study of MF, U3 snoRNA binding, and cadherin binding were significantly associated with common DEGs.

CONCLUSION

Our analysis, leveraging single-cell data, substantiated our findings, demonstrating significant alterations in gene expression patterns.

Generation of bovine decellularized testicular bio-scaffolds as a 3D platform for testis bioengineering

Accelerating the genetic selection to obtain animals more resilient to climate changes, and with a lower environmental impact, would greatly benefit by a substantial shortening of the generation interval. One way to achieve this goal is to generate male gametes directly from embryos. However, spermatogenesis is a complex biological process that, at present, can be partially reproduced in vitro only in the mouse. The development of reliable 3D in vitro models able to mimic the architecture and the physiological microenvironment of the testis, represents a possible strategy to facilitate ex vivo haploid male gamete generation in domestic species. Here we describe the creation of bovine testicular bio-scaffolds and their successful repopulation in vitro with bovine testicular cells. In particular, bovine testes are subjected to three different decellularization protocols. Cellular compartment removal and extracellular matrix preservation are evaluated. The generated bio-scaffolds are then repopulated with bovine testicular fibroblasts. The results obtained demonstrate that the decellularization protocol involving the use of 0.3% sodium dodecyl sulfate (SDS) for 12 h efficiently eliminates native cells, while preserving intact ECM composition and microstructure. Its subsequent repopulation with bovine fibroblasts demonstrates successful cell homing, colonization and growth, consistent with the scaffold ability to sustain cell adherence and proliferation. Overall, the generated 3D bio-scaffolds may constitute a suitable artificial niche for ex vivo culture of testicular cells and may represent a possible strategy to reproduce spermatogenesis in vitro.

Collagen-based materials in male genitourinary diseases and tissue regeneration

Male genitourinary dysfunction causes serious physical or mental distress, such as infertility and psychological harm, which leads to impaired quality of life. Current conventional treatments involving drug therapy, surgical repair, and tissue grafting have a limited effect on recovering the function and fertility of the genitourinary organs. To address these limitations, various biomaterials have been explored, with collagen-based materials increasingly gaining attention for reconstructing the male genitourinary system due to their superior biocompatibility, biodegradability, low antigenicity, biomimetic 3D matrix characteristics, hemostatic efficacy, and tissue regeneration capabilities. This review covers the recent biomedical applications of collagen-based materials including treatment of erectile dysfunction, premature ejaculation, penile girth enlargement, prostate cancer, Peyronie's disease, chronic kidney disease, etc. Although there are relatively few clinical trials, the promising results of the existing studies on animal models reveal a bright future for collagen-based materials in the treatment of male genitourinary diseases.

Graphic Abstract

Application of Additive Manufacturing in Assisted Reproductive Techniques: What Is the Evidence? A Clinical and Technical Systematic Review of the Literature

Background and Objectives: This article investigates the transformative impact of 3D and bio 3D printing technologies in assisted reproductive technology (ART), offering a comprehensive review of their applications in improving reproductive outcomes. Materials and Methods: Following PRISMA guidelines, we conducted a thorough literature search focusing on the intersection of ART and additive manufacturing, resulting in the inclusion of 48 research papers. Results: The study highlights bio 3D printing's potential in revolutionizing female infertility treatments, especially in follicle complex culture and ovary printing. We explore the use of decellularized extracellular matrix (dECM) as bioink, demonstrating its efficacy in replicating the ovarian microenvironment for in vitro maturation of primordial oocytes. Furthermore, advancements in endometrial cavity interventions are discussed, including the application of sustained-release systems for growth factors and stem cell integration for endometrial regeneration, showing promise in addressing conditions like Asherman's syndrome and thin endometrium. We also examine the role of conventional 3D printing in reproductive medicine, including its use in educational simulators, personalized IVF instruments, and microfluidic platforms, enhancing training and precision in reproductive procedures. Conclusions: Our review underscores both 3D printing technologies' contribution to the dynamic landscape of reproductive medicine. They offer innovative solutions for individualized patient care, augmenting success rates in fertility treatments. This research not only presents current achievements but also anticipates future advancements in these domains, promising to expand the horizons for individuals and families seeking assistance in their reproductive journeys.

The Evolutionary Route of in vitro Human Spermatogenesis: What is the Next Destination?

Malfunction in spermatogenesis due to genetic diseases, trauma, congenital disorders or gonadotoxic treatments results in infertility in approximately 7% of males. The behavior of spermatogonial stem cells (SSCs) within three-dimensional, multifactorial, and dynamic microenvironment implicates a niche that serves as a repository for fertility, since can serve as a source of mature and functional male germ cells. Current protocols enable reprogramming of mature somatic cells into induced pluripotent stem cells (iPSCs) and their limited differentiation to SSCs within the range of 0-5%. However, the resulting human iPSC-derived haploid spermatogenic germ cell yield in terms of number and functionality is currently insufficient for transfer to infertility clinic as a therapeutic tool. In this article, we reviewed the evolution of experimental culture platforms and introduced a novel iPSCs-based approach for in vitro spermatogenesis based on a niche perspective bearing cellular, chemical, and physical factors that provide the complex arrangement of testicular seminiferous tubules embedded within a vascularized stroma. We believe that bioengineered organoids supported by smart bio-printed tubules and microfluidic organ-on-a-chip systems offer efficient, precise, personalized platforms for autologous pluripotent stem cell sources to undergo the spermatogenetic cycle, presenting a promising tool for infertile male patients with complete testicular aplasia.

Stem Cells and Infertility: A Review of Clinical Applications and Legal Frameworks

Infertility is a condition defined by the failure to establish a clinical pregnancy after 12 months of regular, unprotected sexual intercourse or due to an impairment of a person's capacity to reproduce either as an individual or with their partner. The authors have set out to succinctly investigate, explore, and assess infertility treatments, harnessing the potential of stem cells to effectively and safely treat infertility; in addition, this paper will present the legal and regulatory complexities at the heart of stem cell research, with an overview of the legislative state of affairs in six major European countries. For couples who cannot benefit from assisted reproductive technologies (ART) to treat their infertility, stem-cells-based approaches have been shown to be a highly promising approach. Nonetheless, lingering ethical and immunological uncertainties require more conclusive findings and data before such treatment avenues can become mainstream and be applied on a large scale. The isolation of human embryonic stem cells (ESCs) is ethically controversial, since their collection involves the destruction of human embryonic tissue. Overall, stem cell research has resulted in important new breakthroughs in the treatment of infertility. The effort to untangle the complex web of ethical and legal issues associated with such therapeutic approaches will have to rely on evidence-based, broadly shared standards, guidelines, and best practices to make sure that the procreative rights of patients can be effectively reconciled with the core values at the heart of medical ethics.