Ultrastructural studies demonstrate that epithelial polarity is established in cultured mouse pre-Sertoli cells by extracellular matrix components

Mice 3D testicular organoid system as a novel tool to study Zika virus pathogenesis

Zika virus (ZIKV) poses a serious threat to global public health due to its close relationship with neurological and male reproductive damage. However, deficiency of human testicular samples hinders the in-depth research on ZIKV-induced male reproductive system injury. Organoids are relatively simple in vitro models, which could mimic the pathological changes of corresponding organs. In this study, we constructed a 3D testicular organoid model using primary testicular cells from adult BALB/c mice. Similar to the testis, this organoid system has a blood-testis barrier (BTB)-like structure and could synthesize testosterone. ZIKV tropism of testicular cells and ZIKV-induced pathological changes in testicular organoid was also similar to that in mammalian testis. Therefore, our results provide a simple and reproducible in vitro testicular model for the investigations of ZIKV-induced testicular injury.

Effects of Different Biomaterials and Cellular Status on Testicular Cell Self-Organization

A multicellular organism's development is coupled with cellular self-organization, which is regulated by cell-cell interactions and cell-extracellular matrix (ECM) crosstalk. Testicular cells from different species such as mouse, rat, and porcine can self-organize into seminiferous tubules both in vitro and in vivo, but the understanding of the functional role of the ECM during this process is limited. Here, it is shown that mouse testicular cells encapsulated with the biomaterial Matrigel can self-organize into seminiferous tubules with blood-testis barrier (BTB) formation and Leydig cell differentiation. By varying the encapsulation method, a combination of sodium alginate and collagen is used to promote reorganization of seminiferous tubules, which resemble those in vivo. In addition, the self-organization ability of testicular cells declines with advanced cell age, and those germ cells play a pivotal role in this process. These findings will be helpful to understand the self-organization process of testicular cells and provide insights for the reconstruction of testes.

In-vitro spermatogenesis through testis modelling: Toward the generation of testicular organoids

Background

The testicular organoid concept has recently been introduced in tissue engineering to refer to testicular cell organizations modeling testicular architecture and function. The testicular organoid approach gives control over which and how cells reaggregate, which is not possible in organotypic cultures, thereby extending the applicability of in‐vitro spermatogenesis (IVS) systems. However, it remains unclear which culture method and medium allow reassociation of testicular cells into a functional testicular surrogate in‐vitro.

Objective

The aim of this paper is to review the different strategies that have been used in an attempt to create testicular organoids and generate spermatozoa. We want to provide an up‐to‐date list on culture methodologies and media compositions that have been used and determine their role in regulating tubulogenesis and differentiation of testicular cells.

Search method

A literature search was conducted in PubMed, Web of Science, and Scopus to select studies reporting the reorganization of testicular cell suspensions in‐vitro, using the keywords: three‐dimensional culture, in‐vitro spermatogenesis, testicular organoid, testicular scaffold, and tubulogenesis. Papers published before the August 1, 2019, were selected.

Outcome

Only a limited number of studies have concentrated on recreating the testicular architecture in‐vitro. While some advances have been made in the testicular organoid research in terms of cellular reorganization, none of the described culture systems is adequate for the reproduction of both the testicular architecture and IVS.

Conclusion

Further improvements in culture methodology and medium composition have to be made before being able to provide both testicular tubulogenesis and spermatogenesis in‐vitro.

Cell adhesion molecules expression pattern indicates that somatic cells arbitrate gonadal sex of differentiating bipotential fetal mouse gonad

Unlike other organ anlagens, the primordial gonad is sexually bipotential in all animals. In mouse, the bipotential gonad differentiates into testis or ovary depending on the genetic sex (XY or XX) of the fetus. During gonad development cells segregate, depending on genetic sex, into distinct compartments: testis cords and interstitium form in XY gonad, and germ cell cysts and stroma in XX gonad. However, our knowledge of mechanisms governing gonadal sex differentiation remains very vague. Because it is known that adhesion molecules (CAMs) play a key role in organogenesis, we suspected that diversified expression of CAMs should also play a crucial role in gonad development. Using microarray analysis we identified 129 CAMs and factors regulating cell adhesion during sexual differentiation of mouse gonad. To identify genes expressed differentially in three cell lines in XY and XX gonads: i) supporting (Sertoli or follicular cells), ii) interstitial or stromal cells, and iii) germ cells, we used transgenic mice expressing EGFP reporter gene and FACS cell sorting. Although a large number of CAMs expressed ubiquitously, expression of certain genes was cell line- and genetic sex-specific. The sets of CAMs differentially expressed in supporting versus interstitial/stromal cells may be responsible for segregation of these two cell lines during gonadal development. There was also a significant difference in CAMs expression pattern between XY supporting (Sertoli) and XX supporting (follicular) cells but not between XY and XX germ cells. This indicates that differential CAMs expression pattern in the somatic cells but not in the germ line arbitrates structural organization of gonadal anlagen into testis or ovary.

Methods for the Study of Gonadal Development

Current knowledge on gonadal development and sex determination is the product of many decades of research involving a variety of scientific methods from different biological disciplines such as histology, genetics, biochemistry, and molecular biology. The earliest embryological investigations, followed by the invention of microscopy and staining methods, were based on histological examinations. The most robust development of histological staining techniques occurred in the second half of the nineteenth century and resulted in structural descriptions of gonadogenesis. These first studies on gonadal development were conducted on domesticated animals; however, currently the mouse is the most extensively studied species. The next key point in the study of gonadogenesis was the advancement of methods allowing for the in vitro culture of fetal gonads. For instance, this led to the description of the origin of cell lines forming the gonads. Protein detection using antibodies and immunolabeling methods and the use of reporter genes were also invaluable for developmental studies, enabling the visualization of the formation of gonadal structure. Recently, genetic and molecular biology techniques, especially gene expression analysis, have revolutionized studies on gonadogenesis and have provided insight into the molecular mechanisms that govern this process. The successive invention of new methods is reflected in the progress of research on gonadal development.

Direct reprogramming of fibroblasts into embryonic Sertoli-like cells by defined factors

Sertoli cells are considered the "supporting cells" of the testis that play an essential role in sex determination during embryogenesis and in spermatogenesis during adulthood. Their essential roles in male fertility along with their immunosuppressive and neurotrophic properties make them an attractive cell type for therapeutic applications. Here we demonstrate the generation of induced embryonic Sertoli-like cells (ieSCs) by ectopic expression of five transcription factors. We characterize the role of specific transcription factor combinations in the transition from fibroblasts to ieSCs and identify key steps in the process. Initially, transduced fibroblasts underwent a mesenchymal to epithelial transition and then acquired the ability to aggregate, formed tubular-like structures, and expressed embryonic Sertoli-specific markers. These Sertoli-like cells facilitated neuronal differentiation and self-renewal of neural progenitor cells (NPCs), supported the survival of germ cells in culture, and cooperated with endogenous embryonic Sertoli and primordial germ cells in the generation of testicular cords in the fetal gonad.

Histological and ultrastructural changes in the adult male albino rat testes following chronic crude garlic consumption

Several studies have presented Garlic (Allium sativum) as a restoring agent for testicular cells after exposure to different types of toxins, however, others have shown that it modified spermatogenesis and might have spermicidal effects. This work has been to assess the positive or negative effect of chronic crude garlic consumption on rat testes using light and transmission electron microscopy with reference to plasma testosterone and LH levels. Forty albino male rats were divided into group A (control) and group B (treated rats). Group B was further subdivided into B1, B2, and B3 subgroups which were administer crude garlic as 20% of their daily food for two, three and four months, respectively. The current study has been the first, to the best of our knowledge, to describe the apoptotic effect of chronic crude garlic consumption targeting Sertoli cells, germ cells and peritubular tissue including interstitial Leydig cells and myoid cells. This might be better explained by inflammatory than degenerative changes in the peritubular tissue and Leydig cells leading to a decrease in testosterone level. Consequently, Sertoli cells degenerate due to a decrease in testosterone and detachment from the basal lamina. Germ cells, which are completely dependent upon Sertoli cells and testosterone to complete there spermatogenesis will be affected. Testicular apoptosis with disruption in spermatogenesis following chronic crude garlic consumption could be correlated with two possible theories; being an anti-hypercholesterolemic agent, it might inhibit steroidogenesis resulting in a decrease in testosterone level and being one of the famous phytoestrogens it possibly has direct estrogen-like actions on adult male rat testes.

Morphological evidences indicate that the interference of cimetidine on the peritubular components is responsible for detachment and apoptosis of Sertoli cells

Cimetidine, referred as antiandrogenic agent, has caused alterations in the seminiferous tubules, including alterations in the peritubular tissue and death of myoid cells by apoptosis. Regarding the structural and functional importance of the peritubular tissue for the maintenance of Sertoli cells (SC), we purpose to investigate the SC-basement membrane interface, focusing the morphological features of SC and their interaction with the basement membrane in the affected tubules by cimetidine. Ten animals were distributed into two groups, control (CG) and cimetidine (CmG) which received saline solution and 50 mg of cimetidine per kg of body weight, respectively, for 52 days. The testes were fixed, dehydrated and embedded for analyses under light and transmission electron microscopy. Paraffin sections were submitted to the TUNEL method; sections of testes embedded in glycol methacrylate were submitted to PAS method and stained by H&E for morphological and quantitative analyses of Sertoli Cells. In the CmG, the SC nuclei were positive to the TUNEL method and showed typical morphological alterations of cell death by apoptosis (from early to advanced stages). A significant reduction in the number of Sertoli Cells was probably due to death of these cells by apoptosis. A close relationship between SC nuclear alterations (including a high frequency of dislocated nuclei from the basal portion) and damage in the peritubular tissue was observed. The ultrastructural analysis showed a parallelism between the gradual advancement of apoptotic process in SC and detachment of the anchoring sites (hemidesmosomes) of SC plasma membrane from the lamina densa. The presence of portions of lamina densa underlying the detached hemidesmosomes indicates a continuous deposition of lamina densa, resulting in the thickening of the basal lamina. The results indicate a possible disarrangement of the SC cytoskeleton, including the focal adhesion structure. These alterations are related to SC apoptosis and probably result from disturbs induced by cimetidine on the peritubular tissue.

Effects of glial cell line-derived neurotrophic factor on isolated developing mouse Sertoli cells in vitro

Cell proliferation is a key factor in sex determination where a size increase relative to the XX gonad is one of the first signs of testis differentiation. Moreover, proliferation of Sertoli cells during development is important in building up the stock of supporting cells necessary for subsequent successful fertility. Because proliferation is such an essential part of testis development, the hypothesis under long-term investigation is that it is under fail-safe control by multiple alternative growth factors. This study was undertaken to investigate the role of glial cell-derived neurotrophic factor (GDNF) on developing mouse Sertoli cells in vitro. Sertoli cells, isolated from mouse embryos at three stages of testis development, were maintained for 2-7 days in vitro (div) in the presence or absence of GDNF at 1, 10 and 100 ng mL(-1). Overall the presence of extracellular matrix gel had little effect on proliferative activity, but encouraged expression of the epithelial phenotype. A statistically significant difference in proliferation, assessed by immunocytochemical staining for proliferating cell nuclear antigen, was seen with GDNF at embryonic day (E)12.5 after 2 div (at both 10 and 100 ng mL(-1), P < 0.001) and 7 div (at both 10 and 100 ng mL(-1), P < 0.05); at E13.5 after 3 div (at both 10 and 100 ng mL(-1), P < 0.05) and at E14.5 after 7 div (100 ng mL(-1), P < 0.01), compared with controls cultured without growth factor. In conclusion, GDNF stimulates mitosis throughout this critical developmental window. The in vitro approach used here is a useful adjunct to the knockout mouse model and has been applied to show that GDNF exerts a proliferative effect on developing mouse Sertoli cells.

Sertoli-Sertoli and Sertoli-germ cell interactions and their significance in germ cell movement in the seminiferous epithelium during spermatogenesis

Spermatogenesis is the process by which a single spermatogonium develops into 256 spermatozoa, one of which will fertilize the ovum. Since the 1950s when the stages of the epithelial cycle were first described, reproductive biologists have been in pursuit of one question: How can a spermatogonium traverse the epithelium, while at the same time differentiating into elongate spermatids that remain attached to the Sertoli cell throughout their development? Although it was generally agreed upon that junction restructuring was involved, at that time the types of junctions present in the testis were not even discerned. Today, it is known that tight, anchoring, and gap junctions are found in the testis. The testis also has two unique anchoring junction types, the ectoplasmic specialization and tubulobulbar complex. However, attention has recently shifted on identifying the regulatory molecules that "open" and "close" junctions, because this information will be useful in elucidating the mechanism of germ cell movement. For instance, cytokines have been shown to induce Sertoli cell tight junction disassembly by shutting down the production of tight junction proteins. Other factors such as proteases, protease inhibitors, GTPases, kinases, and phosphatases also come into play. In this review, we focus on this cellular phenomenon, recapping recent developments in the field.

Dysplastic Development of Seminiferous Tubules and Interstitial Tissue in Rat Hypogonadic (hgn/hgn) Testes1

The hypogonadic rat is characterized by male sterility, reduced female fertility, and renal hypoplasia controlled by a single recessive allele (hgn) on chromosome 10. Plasma testosterone is low and levels of gonadotropins are high in adult male hgn/hgn rats, indicating that the cause of hypogonadism lies within the testis itself. We found that the postnatal growth of the seminiferous tubules was severely affected. Here we describe the details of postnatal testicular pathogenesis of the hgn/ hgn rats. In these rats, gonadal sex determination and initial differentiation of each type of testicular cell occur, but proliferation, differentiation, and maturation of these cells during postnatal testicular development is severely affected. Postnatal pathological changes include reduced proliferation and apoptotic cell death of Sertoli cells, abnormal mitosis and cell death of gonocytes, reduced deposition of extracellular matrix proteins into the basal lamina, lack of the formation of an outer basal lamina, formation of multiple layers of undifferentiated peritubular cells, and the delayed appearance and islet conformation of adult-type Leydig cells. Apoptotic cell death of Sertoli cells and disappearance of FSH receptor mRNA expression indicate that this mutant rat is a useful model for Sertoli cell dysfunction. The abnormalities listed above might be caused by defective interactions between Sertoli cells and other types of testicular cells. Because the results presented here strongly indicate that a normal allele for hgn encodes a factor playing a critical role in testicular development, the determination of the gene responsible for hgn and the analysis of early alterations of gene expression caused by mutations in this gene would provide important information on the mechanisms of testicular development.

Gonadal development in mammals at the cellular and molecular levels

In mammals, although sex is determined chromosomally, gonads in both sexes begin development as similar structures. Until recently it was widely held that female development constituted a "default" pathway of development, which would occur in the absence of a testis-determining gene. This master gene on the Y chromosome, SRY in the human and Sry in the mouse, is thought to act in a cell-autonomous fashion to determine that cells in the gonadal somatic population develop as pre-Sertoli cells. Triggering of somatic cell differentiation along the Sertoli cell pathway is therefore a key event; it was thought that further steps in gonadal differentiation would follow in a developmental cascade. In the absence of Sertoli cells, the lack of anti-Mullerian hormone would allow development of the female Mullerian duct and absence of Leydig cells would prevent maintenance of the Wolffian duct. Recent findings that female signals not only maintain the Mullerian duct and repress the Wolffian duct but also suppress the development of Leydig cells and maintain meiotic germ cells, together with the finding that an X-linked gene is required for ovarian development and must be silenced in the male, have shown that the female default pathway model is an oversimplification. Morphological steps in gonadal differentiation can be correlated with emerging evidence of molecular mechanisms; growth factors, cell adhesion, and signaling molecules interact together, often acting within short time windows via reciprocal control relationships.