Explore the vast range of titles available.

Spermatogenesis is fundamental to the establishment and maintenance of male reproduction, whereas its abnormality results in male infertility. Somatic cells, including Leydig cells, myoid cells, and Sertoli cells, constitute the microenvironment or the niche of testis, which is essential for regulating normal spermatogenesis. Leydig cells are an important component of the testicular stroma, while peritubular myoid cells are one of the major cell types of seminiferous tubules. Here we addressed the roles and mechanisms of Leydig cells and myoid cells in the regulation of spermatogenesis. Specifically, we summarized the biological features of Leydig cells and peritubular myoid cells, and we introduced the process of testosterone production and its major regulation. We also discussed other hormones, cytokines, growth factors, transcription factors and receptors associated with Leydig cells and myoid cells in mediating spermatogenesis. Furthermore, we highlighted the issues that are worthy of further studies in the regulation of spermatogenesis by Leydig cells and peritubular myoid cells. This review would provide novel insights into molecular mechanisms of the somatic cells in controlling spermatogenesis, and it could offer new targets for developing therapeutic approaches of male infertility.

The complex morphology of the Sertoli cells and their interactions with germ cells has been a focus of investigators since they were first described by Enrico Sertoli. In the past 50 years, information on Sertoli cells has transcended morphology alone to become increasingly more focused on molecular questions. The goal of investigators has been to understand the role of the Sertoli cells in spermatogenesis and to apply that information to problems relating tomale fertility. Sertoli cells are unique in that they are a nondividing cell population that is active for the reproductive lifetime of the animal and cyclically change morphology and gene expression. The numerous and distinctive junctional complexes and membrane specializations made by Sertoli cells provide a scaffold and environment for germ cell development. The increased focus of investigators on the molecular components and putative functions of testicular cells has resulted primarily from procedures that isolate specific cell types from the testicular milieu. Products of Sertoli cells that influence germ cell development and vice versa have been characterized from cultured cells and from the application of transgenic technologies. Germ cell transplantation has shown that the Sertoli cells respond to cues from germ cells with regard to developmental timing and has furthered a focus on spermatogenic stem cells and the stem cell niche. Very basic and universal features of spermatogenesis such as the cycle of the seminiferous epithelium and the spermatogenic wave are initiated by Sertoli cells and maintained by Sertoli-germ cell cooperation.

Abstract The reproductive endocrine systems are vastly different between males and females. This sexual dimorphism of the endocrine milieu originates from sex-specific differentiation of the somatic cells in the gonads during fetal life. Most gonadal somatic cells arise from the adrenogonadal primordium. After separation of the adrenal and gonadal primordia, the gonadal somatic cells initiate sex-specific differentiation during gonadal sex determination with the specification of the supporting cell lineages: Sertoli cells in the testis vs granulosa cells in the ovary. The supporting cell lineages then facilitate the differentiation of the steroidogenic cell lineages, Leydig cells in the testis and theca cells in the ovary. Proper differentiation of these cell types defines the somatic cell environment that is essential for germ cell development, hormone production, and establishment of the reproductive tracts. Impairment of lineage specification and function of gonadal somatic cells can lead to disorders of sexual development (DSDs) in humans. Human DSDs and processes for gonadal development have been successfully modeled using genetically modified mouse models. In this review, we focus on the fate decision processes from the initial stage of formation of the adrenogonadal primordium in the embryo to the maintenance of the somatic cell identities in the gonads when they become fully differentiated in adulthood.

The testis produces gametes through spermatogenesis and evolves rapidly at both the morphological and molecular level in mammals 1–6 , probably owing to the evolutionary pressure on males to be reproductively successful 7 . However, the molecular evolution of individual spermatogenic cell types across mammals remains largely uncharacterized. Here we report evolutionary analyses of single-nucleus transcriptome data for testes from 11 species that cover the three main mammalian lineages (eutherians, marsupials and monotremes) and birds (the evolutionary outgroup), and include seven primates. We find that the rapid evolution of the testis was driven by accelerated fixation rates of gene expression changes, amino acid substitutions and new genes in late spermatogenic stages, probably facilitated by reduced pleiotropic constraints, haploid selection and transcriptionally permissive chromatin. We identify temporal expression changes of individual genes across species and conserved expression programs controlling ancestral spermatogenic processes. Genes predominantly expressed in spermatogonia (germ cells fuelling spermatogenesis) and Sertoli (somatic support) cells accumulated on X chromosomes during evolution, presumably owing to male-beneficial selective forces. Further work identified transcriptomal differences between X- and Y-bearing spermatids and uncovered that meiotic sex-chromosome inactivation (MSCI) also occurs in monotremes and hence is common to mammalian sex-chromosome systems. Thus, the mechanism of meiotic silencing of unsynapsed chromatin, which underlies MSCI, is an ancestral mammalian feature. Our study illuminates the molecular evolution of spermatogenesis and associated selective forces, and provides a resource for investigating the biology of the testis across mammals.

The dosage of X-linked genes is accurately regulated with the development of fetal germ cells (FGCs) 1 , 2 . How aberrant dosage of X-linked genes impairs FGC development in humans remains poorly understood. FGCs of patients with Klinefelter syndrome (KS), who have an extra X chromosome, provide natural models for addressing this issue 3 . Here we demonstrate that most human FGCs in KS are arrested at an early stage, characterized by the upregulation of genes related to pluripotency, the WNT pathway and the TGF-β pathway, along with the downregulation of genes involved in FGC differentiation. The limited KS FGCs that are capable of reaching the late stage remain relatively naive. X chromosomes are not inactivated and the dosage of X-linked genes is excessive in KS FGCs. X-linked genes dominate the differentially expressed genes and are enriched in critical biological processes associated with the developmental delay of KS FGCs. Moreover, aberrant interactions between Sertoli cells and FGCs disrupt the migration of late FGCs to the basement membrane in KS. Notably, inhibition of the TGF-β pathway improves the differentiation of KS FGCs. Our findings elucidate how the extra X chromosome impairs the development of male FGCs and reveal the initial molecular events preceding germ cell loss in KS. In Klinefelter syndrome, gene dysregulation due to the extra X chromosome leads to delayed development of fetal germ cells (FGCs), and aberrant interactions between Sertoli cells and FGCs disrupt the migration of late FGCs to the basement membrane.

Cryopreservation of immature testicular tissue (ITT) prior to chemo/radiotherapy is now ethically accepted and is currently the only way to preserve fertility of prepubertal boys about to undergo cancer therapies. So far, three-dimensional culture of testicular cells isolated from prepubertal human testicular tissue was neither efficient nor reproducible to obtain mature spermatozoa, and ITT transplantation is not a safe option when there is a risk of cancer cell contamination of the testis. Hence, generation of testicular organoids (TOs) after cell selection is a novel strategy aimed at restoring fertility in these patients. Here, we created TOs using hydrogels developed from decellularized porcine ITT and compared cell numbers, organization and function to TOs generated in collagen only hydrogel. Organotypic culture of porcine ITT was used as a control. Rheological and mass spectrometry analyses of both hydrogels highlighted differences in terms of extracellular matrix stiffness and composition, respectively. Sertoli cells (SCs) and germ cells (GCs) assembled into seminiferous tubule-like structures delimited by a basement membrane while Leydig cells (LCs) and peritubular cells localized outside. TOs were maintained for 45 days in culture and secreted stem cell factor and testosterone demonstrating functionality of SCs and LCs, respectively. In both TOs GC numbers decreased and SC numbers increased. However, LC numbers decreased significantly in the collagen hydrogel TOs (p < 0.05) suggesting a better preservation of growth factors within TOs developed from decellularized ITT and thus a better potential to restore the reproductive capacity.

Spermatogenesis is a process of self-renewal of spermatogonial stem cells and their proliferation and differentiation to generate mature sperm. This process involves interactions between testicular somatic (mainly Sertoli cells) and spermatogonial cells at their different stages of development. The functionality of Sertoli cells is regulated by hormones and testicular autocrine/paracrine factors. In this study, we investigated the effects of follicle-stimulating hormone (FSH) and testosterone addition on Sertoli cell cultures that undergo hypotonic shock, with a primary focus on Sertoli cell activity. Cells were enzymatically isolated from testicular seminiferous tubules of 7-day-old mice. These cells were cultured in vitro for 3 days. Thereafter, some cultures were treated with hypotonic shock to remove germ cells. After overnight, fresh media without (control; CT) or with FSH, testosterone (Tes), or FSH+T were added to the hypotonic shock-treated or untreated (CT) cultures for 24 h. The morphology of the cultures and the presence of Sertoli cells and germ cells were examined. The expression of growth factors (CSF-1, LIF, SCF, GDNF) or other specific Sertoli cell factors [transferrin, inhibin b, androgen receptor (AR), androgen binding protein (ABP), FSH receptor (FSHR)] was examined by qPCR. Our immunofluorescence staining showed depletion/major reduction in VASA-positive germ cells in Sertoli cell cultures following hypotonic shock (HYP) treatment compared to untreated cultures (WO). Furthermore, the expression of the examined growth factors and other factors was significantly increased in HYP cultures compared to WO (in the CT). However, the addition of hormones significantly decreased the expression levels of the growth factors in HYP cultures compared to WO cultures under the same treatment. In addition, the expression of all other examined Sertoli cell factors significantly changed following HYP treatment compared to WO and following treatment with FSH and or T. However, the expression levels of some factors remained normal following the treatment of Sertoli cell cultures with one or both hormones (transferrin, Fsh-r, Abp, Ar). Thus, our results demonstrate the crucial role of germ cells in the functionality of Sertoli cells and the possible role of FSH and T in maintaining, at least partially, the normal activity of Sertoli cells following germ cell depletion in vitro by hypotonic shock treatment.

Sertoli cells are essential nurse cells in the testis that regulate the process of spermatogenesis and establish the immune-privileged environment of the blood-testis-barrier (BTB). Here, we report the in vitro reprogramming of fibroblasts to human induced Sertoli-like cells (hiSCs). Initially, five transcriptional factors and a gene reporter carrying the AMH promoter were utilized to obtain the hiSCs. We further reduce the number of reprogramming factors to two, NR5A1 and GATA4, and show that these hiSCs have transcriptome profiles and cellular properties that are similar to those of primary human Sertoli cells. Moreover, hiSCs can sustain the viability of spermatogonia cells harvested from mouse seminiferous tubules. hiSCs suppress the proliferation of human T lymphocytes and protect xenotransplanted human cells in mice with normal immune systems. hiSCs also allow us to determine a gene associated with Sertoli cell only syndrome (SCO), CX43, is indeed important in regulating the maturation of Sertoli cells.

Sertoli cell death contributes to spermatogenesis impairment, which is associated with male infertility. Testicular ischemia-reperfusion (I/R) injury induces the cell death of germ cells and Sertoli cells, whereas inhibition of cell death ameliorates acute testicular I/R damage. The aim of the present study was to investigate the mechanism of I/R stress-induced cell death in TM4 cells. Oxygen-glucose deprivation and reoxygenation (OGD/R) was demonstrated to induce I/R injury and cell death in TM4 cells. Cell death was blocked by the reactive oxygen species (ROS) inhibitor N-acetylcysteine, as well as lipid peroxidation inhibitors Liproxstatin-1 and iron chelator deferoxamine; however, inhibitors of apoptosis, necrosis or autophagy had no effect. It was also demonstrated that iron and lipid ROS levels were elevated in I/R injury and that mitochondria decreased in size and increased in membrane density, which is indicative of ferroptosis. Furthermore, the generation of lipid ROS suggests iron accumulation and glutathione (GSH) depletion. The expression of ferroportin (Fpn) protein and mRNA was decreased in TM4 cells. Notably, overexpression of Fpn inhibited ferroptosis, lipid ROS generation and iron accumulation. In addition, GSH-dependent peroxidase 4 (GPX4) was inactivated via GSH depletion following I/R injury, whereas GPX4 activation blocked I/R-induced ferroptosis by reducing lipid ROS levels. The mitogen-activated protein kinase (MAPK) pathway was also investigated in the present study; it was observed that I/R-induced ferroptosis was blocked by inhibiting p38 MAPK activation. The results of the present study demonstrate that ferroptosis is a pervasive and dynamic type of cell death induced by OGD/R injury in Sertoli cells. This may provide a novel insight into the application of cytoprotection in testicular I/R damage-induced cell loss.

Sertoli cells (Sc) are the sole target of follicle-stimulating hormone (FSH) in the testis and attain functional maturation post-birth to significantly augment germ cell (Gc) division and differentiation at puberty. Despite having an operational microRNA (miRNA) machinery, limited information is available on miRNA-mediated regulation of Sc maturation and male fertility. We have shown before that miR-92a-3p levels decline in pubertal rat Sc. In response to FSH treatment, the expressions of FSH Receptor , Claudin11 and Klf4 were found to be elevated in pubertal rat Sc coinciding with our finding of FSH-induced decline in miR-92a-3p levels. To investigate the association of miR-92a-3p and spermatogenesis, we generated transgenic mice where such pubertal decline of miR-92a-3p was prevented by its overexpression in pubertal Sc under proximal Rhox5 promoter, which is known to be activated specifically at puberty, in Sc. Our in vivo observations provided substantial evidence that FSH-induced decline in miR-92a-3p expression during Sc maturation acts as an essential prerequisite for the pubertal onset of spermatogenesis. Elevated expression of miR-92a-3p in post-pubertal testes results into functionally compromised Sc, leading to impairment of the blood–testis barrier formation and apoptosis of pre-meiotic Gc, ultimately culminating into infertility. Collectively, our data suggest that regulation of miR-92a-3p expression is crucial for Sc-mediated induction of active spermatogenesis at puberty and regulation of male fertility. Graphical abstract