Origin, differentiation and regulation of fetal and adult Leydig cells

Phenotype-Genotype Discordance and a Case of a Disorder of Sexual Differentiation

Discordance between the genetic sex and phenotype seen on ultrasound can identify disorders of sexual development (DSD) that previously escaped detection until puberty. We describe a 46, XY disorder of sexual differentiation caused by a rare mutation in the SF1 gene (OMIM]184757, (NR5A1). The mutation (NR5A1)-c.205C > G (p. Arg69Gly) was discovered after a phenotype-genotype discrepancy was encountered during prenatal care. The baby with 46, XY DSD has female external genitalia but evidence of Y chromosome-related regression of Müllerian structures and the absence of palpable gonads. We discussed the literature on phenotype-genotype discrepancy and the importance of care coordination between the antenatal and postnatal teams to ensure a timely diagnosis of DSD.

Trace elements alone or in mixtures associated with unconventional natural gas exploitation affect rat fetal steroidogenesis and testicular development in vitro

Biomonitoring studies have shown that pregnant women living in regions of unconventional natural gas (UNG) exploitation have higher levels of trace elements. Whether developmental endocrine disruption can be expected at these exposure levels during pregnancy is unclear. In this study, we aimed to test the impact of five trace elements alone or in mixtures using in vitro cell- and tissue-based assays relevant to endocrine disruption and development. Manganese, aluminum, strontium, barium, and cobalt were tested at concentrations including those representatives of human fetal exposure. Using transactivation assays, none of the tested elements nor their mixture altered the human estrogen receptor 1 or androgen receptor genomic signalling. In the rat fetal testis assay, an organ culture system, cobalt (5 μg/l), barium (500 μg/l) and strontium (500 μg/l) significantly increased testosterone secretion. Cobalt and strontium were associated with hyperplasia and/or hypertrophy of fetal Leydig cells. Mixing the five elements at concentrations where none had an effect individually stimulated testosterone secretion by the rat fetal testis paralleled by the significant increase of 3β-hydroxysteroid dehydrogenase protein level in comparison to the vehicle control. The mechanisms involved may be specific to the fetal testis as no effect was observed in the steroidogenic H295R cells. Our data suggest that some trace elements in mixture at concentrations representative of human fetal exposure can impact testis development and function. This study highlights the potential risk posed by UNG operations, especially for the most vulnerable populations, pregnant individuals, and their fetus.

Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review

In mammals, gonadal somatic cell lineage differentiation determines the development of the bipotential gonad into either the ovary or testis. Sertoli cells, the only somatic cells in the spermatogenic tubules, support spermatogenesis during gonadal development. During embryonic Sertoli cell lineage differentiation, relevant genes, including WT1, GATA4, SRY, SOX9, AMH, PTGDS, SF1, and DMRT1, are expressed at specific times and in specific locations to ensure the correct differentiation of the embryo toward the male phenotype. The dysregulated development of Sertoli cells leads to gonadal malformations and male fertility disorders. Nevertheless, the molecular pathways underlying the embryonic origin of Sertoli cells remain elusive. By reviewing recent advances in research on embryonic Sertoli cell genesis and its key regulators, this review provides novel insights into sex determination in male mammals as well as the molecular mechanisms underlying the genealogical differentiation of Sertoli cells in the male reproductive ridge.

Toward understanding the role of the interstitial tissue architects: Possible functions of telocytes in the male gonad

Telocytes represent a relatively recently discovered population of interstitial cells with a unique morphological structure that distinguishes them from other neighboring cells. Through their long protrusions extending from the cell body, telocytes create microenvironments via tissue compartmentalization and create homo- and hetero-cellular junctions. These establish a three-dimensional network enabling the maintenance of interstitial compartment homeostasis through regulation of extracellular matrix organization and activity, structural support, paracrine and juxtracrine communication, immunomodulation, immune surveillance, cell survival, and apoptosis. The presence of telocytes has also been confirmed in testicular interstitial tissue of many species of animals. The objective of this review is to summarize recent findings on telocytes in the male gonad, on which conclusions have been deduced that indicate the involvement of telocytes in maintaining the cytoarchitecture of the testicular interstitial tissue, in the processes of spermatogenesis and steroidogenesis, and photoperiod-mediated changes in the testes in seasonally reproductive animals.

Effects of azithromycin exposure during pregnancy at different stages, doses and courses on testicular development in fetal mice

Azithromycin is a commonly used antibiotic during pregnancy, but some studies have suggested its potential developmental toxicity. Currently, the effects and mechanisms of prenatal azithromycin exposure (PAzE) on fetal testicular development are still unclear. The effects of prenatal exposure to the same drug on fetal testicular development could vary depending on different stages, doses, and courses. Hence, in this study, based on clinical medication characteristics, Kunming mice was administered intragastrically with azithromycin at different stages (mid-/late-pregnancy), doses (50, 100, 200 mg/kg·d), and courses (single-/multi-course). Fetal blood and testicular samples were collected on GD18 for relevant assessments. The results indicated that PAzE led to changes in fetal testicular morphology, reduced cell proliferation, increased apoptosis, and decreased expression of markers related to Leydig cells (Star), Sertoli cells (Wt1), and spermatogonia (Plzf). Further investigation revealed that the effects of PAzE on fetal testicular development were characterized by mid-pregnancy, high dose (clinical dose), and single course having more pronounced effects. Additionally, the TGFβ/Smad and Nrf2 signaling pathways may be involved in the changes in fetal testicular development induced by PAzE. In summary, this study confirmed that PAzE influences fetal testicular morphological development and multicellular function. It provided theoretical and experimental evidence for guiding the rational use of azithromycin during pregnancy and further exploring the mechanisms underlying its developmental toxicity on fetal testicles.

Effect of Fetal Pituitary-Testes Suppression on Brain Sexual Differentiation and Reproductive Function in Male Sheep

We previously demonstrated that treating fetal lambs on gestational day 62 with the long-acting gonadotrophin-releasing hormone (GnRH) antagonist degarelix (DG) suppresses pituitary-testicular function during midgestation. The objective of this study was to investigate whether impaired gonadotrophic drive during this fetal period has enduring effects on sexual differentiation and reproductive function in adult male sheep. We assessed the effects of prenatal administration of DG, with or without testosterone (T) replacement, on various sexually dimorphic behavioral traits in adult rams, including sexual partner preferences, as well as neuroendocrine responsiveness and testicular function. Our findings revealed that DG treatment had no effect on genital differentiation or somatic growth. There were some indications that DG treatment suppressed juvenile play behavior and adult sexual motivation; however, male-typical sexual differentiation of reproductive behavior, sexual partner preference, and gonadotropin feedback remained unaffected and appeared to be fully masculinized and defeminized. DG-treated rams showed an increased LH response to GnRH stimulation and a decreased T response to human chorionic gonadotropin stimulation, suggesting impaired Leydig cell function and reduced T feedback. Both effects were reversed by cotreatment with T propionate. DG treatment also suppressed the expression of CYP17 messenger RNA, a key enzyme for T biosynthesis. Despite the mild hypogonadism induced by DG treatment, ejaculate volume, sperm motility, and sperm morphology were not affected. In summary, these results suggest that blocking GnRH during midgestation does not have enduring effects on brain sexual differentiation but does negatively affect the testes' capacity to synthesize T.

DMRT1-mediated regulation of TOX3 modulates expansion of the gonadal steroidogenic cell lineage in the chicken embryo

During gonadal sex determination, the supporting cell lineage differentiates into Sertoli cells in males and pre-granulosa cells in females. Recently, single cell RNA-seq data have indicated that chicken steroidogenic cells are derived from differentiated supporting cells. This differentiation process is achieved by a sequential upregulation of steroidogenic genes and downregulation of supporting cell markers. The exact mechanism regulating this differentiation process remains unknown. We have identified TOX3 as a previously unreported transcription factor expressed in embryonic Sertoli cells of the chicken testis. TOX3 knockdown in males resulted in increased CYP17A1-positive Leydig cells. TOX3 overexpression in male and female gonads resulted in a significant decline in CYP17A1-positive steroidogenic cells. In ovo knockdown of the testis determinant DMRT1 in male gonads resulted in a downregulation of TOX3 expression. Conversely, DMRT1 overexpression caused an increase in TOX3 expression. Taken together, these data indicate that DMRT1-mediated regulation of TOX3 modulates expansion of the steroidogenic lineage, either directly, via cell lineage allocation, or indirectly, via signaling from the supporting to steroidogenic cell populations.

Emerging concepts on Leydig cell development in fetal and adult testis

Leydig cells (Lc) reside in the interstitial compartment of the testis and are the target of Luteinising hormone (LH) for Testosterone (T) production, thus critically regulates male fertility. Classical histological studies have identified two morphologically different populations of Lc during testicular development [fetal (FLc) and adult (ALc)]. Recent progress in ex vivo cell/organ culture, genome-wide analysis, genetically manipulated mouse models, lineage tracing, and single-cell RNA-seq experiments have revealed the diverse cellular origins with differential transcriptomic and distinct steroidogenic outputs of these populations. FLc originates from both coelomic epithelium and notch-active Nestin-positive perivascular cells located at the gonad-mesonephros borders, and get specified as Nr5a1 (previously known as Ad4BP/SF-1) expressing cells by embryonic age (E) 12.5 days in fetal mouse testes. These cells produce androstenedione (precursor of T, due to lack of HSD17β3 enzyme) and play critical a role in initial virilization and patterning of the male external genitalia. However, in neonatal testis, FLc undergoes massive regression/dedifferentiation and gradually gets replaced by T-producing ALc. Very recent studies suggest a small fraction (5-20%) of FLc still persists in adult testis. Both Nestin-positive perivascular cells and FLc are considered to be the progenitor populations for ALc. This minireview article summarizes the current understanding of Lc development in fetal and adult testes highlighting their common or diverse cellular (progenitor/stem) origins with respective functional significance in both rodents and primates. (227 words).

10−7 M genistein partially alleviates 10−7 M MEHP unfavorable effects in a new modified fetal rat testis culture system

Background: Recent studies revealed that some common endocrine-disrupting chemicals (EDCs) including phthalates and phytoestrogens may exhibit low-dose effects properties. However, how low dose of these EDCs and their mixture would affect fetal rat testis development still needs further investigation. Moreover, testis organ culture system also needs further modification to provide an effective tool for ex vivo EDCs study.

Methods: We firstly modified the agarose organ culture system, in which fetal rat testes were cultured for 4 days (d1 to d4) on agarose gels held by Millicell inserts. Then we used the modified agarose culture system to study the combined effects of multiple EDCs exposure. 15.5 dpc fetal rat testes were isolated and treated with vehicle, MEHP (0.1 μmol/L), GEN (0.1 μmol/L) or MEHP (0.1 μmol/L) + GEN (0.1 μmol/L). Parameters concerning testicular cell development and function were evaluated, trying to gain insight into the early molecular events after multiple EDCs exposure.

Results: The development of somatic, germ cells and seminiferous tubule in 15.5 dpc fetal rat testis was better sustained in the modified agarose culture system. Based on the modified system, we found that MEHP at 0.1 μmol/L induced alterations in gonocyte markers, antioxidative enzyme activity as well as transient reduction of testosterone production, accompanied by mitochondria swelling in gonocytes and Sertoli cells. No obvious morphological and histological alterations were observed in all treated groups. However, coadministration of genistein at 0.1 μmol/L partially alleviated MEHP-induced fetal testis damage ex vivo through enhancement of antioxidative action. MEHP at low dose still showed weak endocrine disrupting properties but did not exhibit typical low-dose effects.

Conclusion: Our findings indicated that the modified agarose culture system could better mimic testicular microenvironment without obvious hypoxic cell damage. Furthermore, low dose of MEHP induced mild disruption to fetal testis development, cotreatment of genistein at low dose attenuated MEHP induced fetal testis injuries in part by balancing redox state, indicating that low dose of genistein may partially protect fetal testis from phthalates induced injury.

Behavior and Functional Roles of CD34+ Mesenchymal Cells in Mammalian Testes

Mammalian testes consist of seminiferous tubules within which Sertoli cells line up at the periphery and nurse germ cells, and of interstitia that harbor various cells such as peritubular myoid cells (PMCs), Leydig cells (LCs), vascular endothelial cells, immune cells such as macrophages, and mesenchymal (stromal) cells. Morphological studies have recently reported the presence of telocytes with telopodes in the interstitium of adult mouse, rat, and human testes. CD34⁺PDGFRα⁺ telocytes with long and moniliform telopodes form reticular networks with various cell types such as LCs, PMCs, and vessels, indicating their potential functions in cell–cell communications and tissue homeostasis. Functional studies have recently been performed on testicular interstitial cells and CD34⁺ cells, using 3D re-aggregate cultures of dissociated testicular cells, and cell cultures. Direct observation of CD34⁺ cells and adult LCs (ALCs) revealed that CD34⁺ cells extend thin cytoplasmic processes (telopodes), move toward the LC–CD34⁺ cell-re-aggregates, and finally enter into the re-aggregates, indicating the chemotactic behavior of CD34⁺ telocytes toward ALCs. In mammalian testes, important roles of mesenchymal interstitial cells as stem/progenitors in the differentiation and regeneration of LCs have been reported. Here, reports on testicular telocytes so far obtained are reviewed, and future perspectives on the studies of testicular telocytes are noted.

One Tool for Many Jobs: Divergent and Conserved Actions of Androgen Signaling in Male Internal Reproductive Tract and External Genitalia

In the 1940s, Alfred Jost demonstrated the necessity of testicular secretions, particularly androgens, for male internal and external genitalia differentiation. Since then, our knowledge of androgen impacts on differentiation of the male internal (Wolffian duct) and external genitalia (penis) has been drastically expanded upon. Between these two morphologically and functionally distinct organs, divergent signals facilitate the establishment of tissue-specific identities. Conversely, conserved actions of androgen signaling are present in both tissues and are largely responsible for the growth and expansion of the organs. In this review we synthesize the existing knowledge of the cell type-specific, organ specific, and conserved signaling mechanisms of androgens. Mechanistic studies on androgen signaling in the Wolffian duct and male external genitalia have largely been conducted in mouse model organisms. Therefore, the majority of the review is focused on mouse model studies.

Deciphering the origins and fates of steroidogenic lineages in the mouse testis

Leydig cells (LCs) are the major androgen-producing cells in the testis. They arise from steroidogenic progenitors (SPs), whose origins, maintenance, and differentiation dynamics remain largely unknown. Single-cell transcriptomics reveal that the mouse steroidogenic lineage is specified as early as embryonic day 12.5 (E12.5) and has a dual mesonephric and coelomic origin. SPs specifically express the Wnt5a gene and evolve rapidly. At E12.5 and E13.5, they give rise first to an intermediate population of pre-LCs, and finally to fetal LCs. At E16.5, SPs possess the characteristics of the dormant progenitors at the origin of adult LCs and are also transcriptionally closely related to peritubular myoid cells (PMCs). In agreement with our in silico analysis, in vivo lineage tracing indicates that Wnt5a-expressing cells are bona fide progenitors of PMCs as well as fetal and adult LCs, contributing to most of the LCs present in the fetal and adult testis.

A novel variant luteinizing hormone receptor in the first transmembrane helix of two homozygous Iranian patients: case report

Background

Leydig cell hypoplasia (LCH) is a rare autosomal recessive endocrine syndrome that affects the normal development of male external genitalia in 46, XY individuals and is one of the causes of disorder of sexual differentiation (DSD) in males. The responsible gene of LCH is LHCGR which is located on the chromosome 2 and its various mutations lead to different degrees of the disease ranging from micropenis to complete XY DSD.

Case presentation

In this study, we have investigated the clinical presentation and molecular findings of two siblings with complete male LCH and XY DSD. This is the first detailed report of individuals with LCH from Iran. It aimed to study the molecular and clinical characteristics of two sisters with type 1 LCH. Whole exome sequencing was used for these patients to find the underlying genetic cause of the disease. Our Iranian DSD patients had external genitalia (normal labia major and minor, the external opening of the urethra beneath the clitoris) and bilateral testicular tissues in the inguinal region, which were removed by surgical exploration.

Conclusions

Genetic sequencing showed the homozygous variants of the LHCGR gene in the patients, a novel duplication variant in exon 11, c.1091dupT -or pLeu365Profs*5. This mutation is described as likely pathogenic. We think that this case report can widen the genotypic spectrum of the LHCGR variants. Moreover, this study emphasizes the significant rule of Whole Exome Sequencing in differentiating various causes of disorder of sexual differentiation.

The Fate of Leydig Cells in Men with Spermatogenic Failure

The steroidogenic cells in the testicle, Leydig cells, located in the interstitial compartment, play a vital role in male reproductive tract development, maintenance of proper spermatogenesis, and overall male reproductive function. Therefore, their dysfunction can lead to all sorts of testicular pathologies. Spermatogenesis failure, manifested as azoospermia, is often associated with defective Leydig cell activity. Spermatogenic failure is the most severe form of male infertility, caused by disorders of the testicular parenchyma or testicular hormone imbalance. This review covers current progress in knowledge on Leydig cells origin, structure, and function, and focuses on recent advances in understanding how Leydig cells contribute to the impairment of spermatogenesis.

Eicosanoid Biosynthesis in Male Reproductive Development: Effects of Perinatal Exposure to NSAIDs and Analgesic Drugs

Increasing rates of infertility associated with declining sperm counts and quality, as well as increasing rates of testicular cancer are contemporary issues in the United States and abroad. These conditions are part of the Testicular Dysgenesis Syndrome, which includes a variety of male reproductive disorders hypothesized to share a common origin based on disrupted testicular development during fetal and neonatal stages of life. Male reproductive development is a highly regulated and complex process that relies on an intricate coordination between germ, Leydig, and Sertoli cells as well as other supporting cell types, to ensure proper spermatogenesis, testicular immune privilege, and endocrine function. The eicosanoid system has been reported to be involved in the regulation of fetal and neonatal germ cell development as well as overall testicular homeostasis. Moreover, non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics with abilities to block eicosanoid synthesis by targeting either or both isoforms of cyclooxygenase enzymes, have been found to adversely affect male reproductive development. This review will explore the current body of knowledge on the involvement of the eicosanoid system in male reproductive development, as well as discuss adverse effects of NSAIDs and analgesic drugs administered perinatally, focusing on toxicities reported in the testis and on major testicular cell types. Rodent and epidemiological studies will be corroborated by findings in invertebrate models for a comprehensive report of the state of the field, and to add to our understanding of the potential long-term effects of NSAID and analgesic drug administration in infants.

Cell-Specific Expression Pattern of Toll-Like Receptors and Their Roles in Animal Reproduction

Toll-like receptors (TLRs), a part of the innate immune system, have critical roles in protection against infections and involve in basic pathology and physiology. Secreted molecules from the body or pathogens could be a ligand for induction of the TLR system. There are many immune and non-immune types of cells that express at a least single TLR on their surface or cytoplasm. Those cells may be a player in a defense system or in the physiological regulation mechanisms. Reproductive tract and organs contain different types of cells that have essential functions such as hormone production, providing an environment for embryo/fetus, germ cell production, etc. Although lower parts of reproductive organs are in a relationship with outsider contaminants (bacteria, viruses, etc.), upper parts should be sterile to provide a healthy pregnancy and germ cell production. In those areas, TLRs bear controller or regulator roles. In this chapter, we will provide current information about physiological functions of TLR in the cells of the reproductive organs and tract, and especially about their roles in follicle selection, maturation, follicular atresia, ovulation, corpus luteum (CL) formation and regression, establishment and maintenance of pregnancy, sperm production, maturation, capacitation as well as the relationship between TLR polymorphism and reproduction in domestic animals. We will also discuss pathogen-associated molecular patterns (PAMPs)-induced TLRs that involve in reproductive inflammation/pathology.

Diverse role of endocannabinoid system in mammalian male reproduction

Endocannabinoid system (ECS) is known for its modulatory role in numerous physiological processes in the body. Endocannabinoids (eCBs) are endogenous lipid molecules which function both centrally and peripherally. The ECS is best studied in the central nervous system (CNS), immune system as well as in the metabolic system. The role of ECS in male reproductive system is emerging and the presence of a complete enzymatic machinery to synthesize and metabolize eCBs has been demonstrated in male reproductive tract. Endocannabinoid concentrations and alterations in their levels have been reported to affect the functioning of spermatozoa. A dysfunctional ECS has also been linked to the development of prostate cancer, the leading cause of cancer related mortality among male population. This review is an attempt to provide an insight into the significant role of endocannabinoids in male reproduction and further summarize recent findings that demonstrate the manner in which the endocannabinoid system impacts male sexual behavior and fertility.

Distinctive functioning of STARD1 in the fetal Leydig cells compared to adult Leydig and adrenal cells. Impact of Hedgehog signaling via the primary cilium

STARD1 stimulates cholesterol transfer to mitochondrial CYP11A1 for conversion to pregnenolone. A cholesterol-binding START domain is guided by an N-terminal domain in a cell selective manner. Fetal and adult Leydig cells (FLC, ALC) show distinct Stard1 regulation. sm- FISH microscopy, which resolves individual molecules of Stard1 mRNA, shows uniformly high basal expression in each FLC. In ALC, in vivo, and cultured MA-10 cells, basal Stard1 expression is minimal. PKA activates loci asynchronously, with delayed splicing/export of 3.5 kb mRNA to mitochondria. After 60 min, ALC transition to an integrated mRNA delivery to mitochondria that is seen in FLC. Sertoli cells cooperate in Stard1 stimulation in FLC by delivering DHH to the primary cilium. There PTCH, SMO and cholesterol cooperate to release GLI3 to activate the Stard1 locus, probably by directing histone changes. ALC lack cilia. PKA then primes locus activation. FLC and ALC share similar SIK/CRTC/CREB regulation characterized for adrenal cells.

Cholesterol Contributes to Male Sex Differentiation Through Its Developmental Role in Androgen Synthesis and Hedgehog Signaling

Two specialized functions of cholesterol during fetal development include serving as a precursor to androgen synthesis and supporting hedgehog (HH) signaling activity. Androgens are produced by the testes to facilitate masculinization of the fetus. Recent evidence shows that intricate interactions between the HH and androgen signaling pathways are required for optimal male sex differentiation and defects of either can cause birth anomalies indicative of 46,XY male variations of sex development (VSD). Further, perturbations in cholesterol synthesis can cause developmental defects, including VSD, that phenocopy those caused by disrupted androgen or HH signaling, highlighting the functional role of cholesterol in promoting male sex differentiation. In this review, we focus on the role of cholesterol in systemic androgen and local HH signaling events during fetal masculinization and their collective contributions to pediatric VSD.

Specific Transcriptomic Signatures and Dual Regulation of Steroidogenesis Between Fetal and Adult Mouse Leydig Cells

Leydig cells (LC) are the main testicular androgen-producing cells. In eutherian mammals, two types of LCs emerge successively during testicular development, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs). Both display significant differences in androgen production and regulation. Using bulk RNA sequencing, we compared the transcriptomes of both LC populations to characterize their specific transcriptional and functional features. Despite similar transcriptomic profiles, a quarter of the genes show significant variations in expression between FLCs and ALCs. Non-transcriptional events, such as alternative splicing was also observed, including a high rate of intron retention in FLCs compared to ALCs. The use of single-cell RNA sequencing data also allowed the identification of nine FLC-specific genes and 50 ALC-specific genes. Expression of the corticotropin-releasing hormone 1 (Crhr1) receptor and the ACTH receptor melanocortin type 2 receptor (Mc2r) specifically in FLCs suggests a dual regulation of steroidogenesis. The androstenedione synthesis by FLCs is stimulated by luteinizing hormone (LH), corticotrophin-releasing hormone (CRH), and adrenocorticotropic hormone (ACTH) whereas the testosterone synthesis by ALCs is dependent exclusively on LH. Overall, our study provides a useful database to explore LC development and functions.

Rapid Differentiation of Human Embryonic Stem Cells into Testosterone-Producing Leydig Cell-Like Cells In vitro

Background:

Leydig cells (LCs) are testicular somatic cells that are the major producers of testosterone in males. Testosterone is essential for male physiology and reproduction. Reduced testosterone levels lead to hypogonadism and are associated with diverse pathologies, such as neuronal dysfunction, cardiovascular disease, and metabolic syndrome. LC transplantation is a promising therapy for hypogonadism; however, the number of LCs in the testis is very rare and they do not proliferate in vitro. Therefore, there is a need for an alternative source of LCs.

Methods:

To develop a safer, simple, and rapid strategy to generate human LC-like cells (LLCs) from stem cells, we first performed preliminary tests under different conditions for the induction of LLCs from human CD34/CD73 double positive-testis-derived stem cells (HTSCs). Based on the embryological sequence of events, we suggested a 3-step strategy for the differentiation of human ESCs into LLCs. We generated the mesendoderm in the first stage and intermediate mesoderm (IM) in the second stage and optimized the conditions for differentiation of IM into LLCs by comparing the secreted testosterone levels of each group.

Results:

HTSCs and human embryonic stem cells can be directly differentiated into LLCs by defined molecular compounds within a short period. Human ESC-derived LLCs can secrete testosterone and express steroidogenic markers.

Conclusion:

We developed a rapid and efficient protocol for the production of LLCs from stem cells using defined molecular compounds. These findings provide a new therapeutic cell source for male hypogonadism.

Evaluation of testicular toxicity upon fetal exposure to bisphenol A using an organ culture method

Humans are exposed to a multitude of endocrine disruptor chemicals (EDCs) that can interfere with the action of endogenous hormones and the normal development of reproductive organs. Bisphenol A (BPA) is one of the most common EDCs found in the environment. Here, we evaluated BPA toxicity on fetal testes using an in vitro organ culture system. Mouse fetal testes sampled at 15.5 days post coitus were cultured in a medium containing BPA for 5 days. The number of germ cells was reduced by BPA treatment, whereas the number of Sertoli cells was slightly increased by BPA at the highest dose (100 μM). Consistently, BPA treatment reduced the protein and gene expression levels of germ cell markers, but it increased the expression levels of Sertoli cell markers. The expression levels of fetal Leydig cell markers such as Cyp11a1, Thbs2, Cyp17a1, and Pdgf-α were significantly increased, whereas those of adult Leydig cell markers such as Hsd17b3, Ptgds, Sult1e1, Vcam1, and Hsd11b1 were decreased in the testes exposed to BPA. Generally, Notch signaling restricts Leydig cell differentiation from progenitor cells during fetal testis development. The expression levels of Notch1, Notch2, Notch3, Hes1, Ptch1, Jag1, Jag2, c-Myc, Hey1, and Hey2, which are involved in Notch signaling, were markedly higher in BPA-treated fetal testes than in the controls, indicating that BPA interrupts fetal Leydig cell development. BPA also disrupted steroidogenesis in the fetal testis organ culture system. In conclusion, our study showed that BPA inhibits fetal germ cell growth, Leydig cell development, and steroidogenesis.

Insights into Gonadal Sex Differentiation Provided by Single-Cell Transcriptomics in the Chicken Embryo

Although the genetic triggers for gonadal sex differentiation vary across species, the cell biology of gonadal development was long thought to be largely conserved. Here, we present a comprehensive analysis of gonadal sex differentiation, using single-cell sequencing in the embryonic chicken gonad during sexual differentiation. The data show that chicken embryonic-supporting cells do not derive from the coelomic epithelium, in contrast to other vertebrates studied. Instead, they derive from a DMRT1⁺/PAX2⁺/WNT4⁺/OSR1⁺ mesenchymal cell population. We find a greater complexity of gonadal cell types than previously thought, including the identification of two distinct sub-populations of Sertoli cells in developing testes and derivation of embryonic steroidogenic cells from a differentiated supporting-cell lineage. Altogether, these results indicate that, just as the genetic trigger for sex differs across vertebrate groups, cell lineage specification in the gonad may also vary substantially.

Differential Disrupting Effects of Prolonged Low-Dose Exposure to Dichlorodiphenyltrichloroethane on Androgen and Estrogen Production in Males

Dichlorodiphenyltrichloroethane (DDT) is the most widespread, persistent pollutant and endocrine disruptor on the planet. Although DDT has been found to block androgen receptors, the effects of its low-dose exposure in different periods of ontogeny on the male reproductive system remain unclear. We evaluate sex steroid hormone production in the pubertal period and after maturation in male Wistar rats exposed to low doses of o,p'-DDT, either during prenatal and postnatal development or postnatal development alone. Prenatally and postnatally exposed rats exhibit lower testosterone production and increased estradiol and estriol serum levels after maturation, associated with the delayed growth of gonads. Postnatally exposed rats demonstrate accelerated growth of gonads and higher testosterone production in the pubertal period. In contrast to the previous group, they do not present raised estradiol production. All of the exposed animals exhibit a reduced conversion of progesterone to 17OH-progesterone after sexual maturation, which indicates putative attenuation of sex steroid production. Thus, the study reveals age-dependent outcomes of low-dose exposure to DDT. Prenatal onset of exposure results in the later onset of androgen production and the enhanced conversion of androgens to estrogens after puberty, while postnatal exposure induces the earlier onset of androgen secretion.

Leydig cell aging: Molecular mechanisms and treatments

Late-onset hypogonadism, resulting from deficiency in serum testosterone (T), affects the health and quality of life of millions of aging men. T is synthesized by Leydig cells (LCs) in response to luteinizing hormone (LH). LH binds LC plasma membrane receptors, inducing the formation of a supramolecular complex of cytosolic and mitochondrial proteins, the Steroidogenic InteracTomE (SITE). SITE proteins are involved in targeting cholesterol to CYP11A1 in the mitochondria, the first enzyme of the steroidogenic cascade. Cholesterol translocation is the rate-determining step in T formation. With aging, LC defects occur that include changes in SITE, an increasingly oxidative intracellular environment, and reduced androgen formation and serum T levels. T replacement therapy (TRT) will restore T levels, but reported side effects make it desirable to develop additional strategies for increasing T. One approach is to target LC protein-protein interactions and thus increase T production by the hypofunctional Leydig cells themselves.

Thyroid hormones, Sertoli cell proliferation and differentiation in progenies from carbamazepine-treated rat dams during pregnancy and lactation

Carbamazepine (CBZ) is used in the control of seizure and affective disorders, causing hypothyroidism. Thyroid hormones regulate the Sertoli cell proliferation and differentiation. Clinical aspects must be considered since epileptic fertile women need to continuously use CBZ during pregnancy and lactation. This study aimed to evaluate the effects of CBZ on testis development of rat offspring from dams treated during pregnancy/lactation. Rat dams received CBZ (20 mg kg^-1  day^-1 ) or vehicle by intra-peritoneal route during gestation and lactation. Progenies were euthanised at 4, 14, 41, 63 and 93-days post-partum (dpp) for the evaluation of T3, T4 and TSH plasma total levels. Testicular cross sections were submitted to anti-Ki67, anti-PCNA, anti-p27^kip1 and anti-transferrin immunolabelling for the evaluation of Sertoli cells. There was a significant reduction in p27^kip1 -positive Sertoli cell numerical densities and an increase in TSH level at 14 dpp. CBZ exposure affected the volume density of transferrin-positive immunolabelling at 63 dpp. These results suggest that CBZ may cause a dysregulation of the controller system of thyroid hormones homeostasis leading to an increase in the proliferation rate at the neonatal phase and a differentiation delay of the Sertoli cell, culminating in an altered function at late puberty. The occurrence of hypothyroidism cannot be completely discarded.

Estrogens and development of the mouse and human external genitalia

The Jost hypothesis states that androgens are necessary for normal development of the male external genitalia. In this review, we explore the complementary hypothesis that estrogens can elicit abnormal development of male external genitalia. Herein, we review available data in both humans and mice on the deleterious effects of estrogen on external genitalia development, especially during the "window of susceptibility" to exogenous estrogens. The male and female developing external genitalia in both the human and mouse express ESR1 and ESR2, along with the androgen receptor (AR). Human clinical data suggests that exogenous estrogens can adversely affect normal penile and urethral development, resulting in hypospadias. Experimental mouse data also strongly supports the idea that exogenous estrogens cause penile and urethral defects. Despite key differences, estrogen-induced hypospadias in the mouse displays certain morphogenetic homologies to human hypospadias, including disruption of urethral fusion and preputial abnormalities. Timing of estrogenic exposure, or the "window of susceptibility," is an important consideration when examining malformations of the external genitalia in both humans and mice. In addition to a review of normal human and mouse external genital development, this article aims to review the present data on the role of estrogens in normal and abnormal development of the mouse and human internal and external genitalia. Based on the current literature for both species, we conclude that estrogen-dependent processes may play a role in abnormal genital development.

Primary human testicular PDGFRα+ cells are multipotent and can be differentiated into cells with Leydig cell characteristics in vitro

STUDY QUESTION

Is it possible to differentiate primary human testicular platelet-derived growth factor receptor alpha positive (PDGFRα⁺) cells into functional Leydig cells?

SUMMARY ANSWER

Although human testicular PDGFRα⁺ cells are multipotent and are capable of differentiating into steroidogenic cells with Leydig cell characteristics, they are not able to produce testosterone after differentiation.

WHAT IS KNOWN ALREADY

In rodents, stem Leydig cells (SLCs) that have been identified and isolated using the marker PDGFRα can give rise to adult testosterone-producing Leydig cells after appropriate differentiation in vitro. Although PDGFRα⁺ cells have also been identified in human testicular tissue, so far there is no evidence that these cells are true human SLCs that can differentiate into functional Leydig cells in vitro or in vivo.

STUDY DESIGN, SIZE, DURATION

We isolated testicular cells enriched for interstitial cells from frozen–thawed fragments of testicular tissue from four human donors. Depending on the obtained cell number, PDGFRα⁺-sorted cells of three to four donors were exposed to differentiation conditions in vitro to stimulate development into adipocytes, osteocytes, chondrocytes or into Leydig cells. We compared their cell characteristics with cells directly after sorting and cells in propagation conditions. To investigate their differentiation potential in vivo, PDGFRα⁺-sorted cells were transplanted in the testis of 12 luteinizing hormone receptor-knockout (LuRKO) mice of which 6 mice received immunosuppression treatment. An additional six mice did not receive cell transplantation and were used as a control.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human testicular interstitial cells were cultured to Passage 3 and FACS sorted for HLA-A,B,C⁺/CD34⁻/PDGFRα⁺. We examined their mesenchymal stromal cell (MSC) membrane protein expression by FACS analyses. Furthermore, we investigated lineage-specific staining and gene expression after MSC trilineage differentiation. For the differentiation into Leydig cells, PDGFRα⁺-sorted cells were cultured in either proliferation or differentiation medium for 28 days, after which they were stimulated either with or without hCG, forskolin or dbcAMP for 24 h to examine the increase in gene expression of steroidogenic enzymes using qPCR. In addition, testosterone, androstenedione and progesterone levels were measured in the culture medium. We also transplanted human PDGFRα⁺-sorted testicular interstitial cells into the testis of LuRKO mice. Serum was collected at several time points after transplantation, and testosterone was measured. Twenty weeks after transplantation testes were collected for histological examination.

MAIN RESULTS AND THE ROLE OF CHANCE

From primary cultured human testicular interstitial cells at Passage 3, we could obtain a population of HLA-A,B,C⁺/CD34⁻/PDGFRα⁺ cells by FACS. The sorted cells showed characteristics of MSC and were able to differentiate into adipocytes, chondrocytes and osteocytes. Upon directed differentiation into Leydig cells in vitro, we observed a significant increase in the expression of HSD3B2 and INSL3. After 24 h stimulation with forskolin or dbcAMP, a significantly increased expression of STAR and CYP11A1 was observed. The cells already expressed HSD17B3 and CYP17A1 before differentiation but the expression of these genes were not significantly increased after differentiation and stimulation. Testosterone levels could not be detected in the medium in any of the stimulation conditions, but after stimulation with forskolin or dbcAMP, androstenedione and progesterone were detected in culture medium. After transplantation of the human cells into the testes of LuRKO mice, no significant increase in serum testosterone levels was found compared to the controls. Also, no human cells were identified in the interstitium of mice testes 20 weeks after transplantation.

LARGE SCALE DATA

N/A

LIMITATIONS, REASONS FOR CAUTION

This study was performed using tissue from only four donors because of limitations in donor material. Because of the need of sufficient cell numbers, we first propagated cells to passage 3 before FACS of the desired cell population was performed. We cannot rule out this propagation of the cells resulted in loss of stem cell properties.

WIDER IMPLICATIONS OF THE FINDINGS

A lot of information on Leydig cell development is obtained from rodent studies, while the knowledge on human Leydig cell development is very limited. Our study shows that human testicular interstitial PDGFRα⁺ cells have different characteristics compared to rodent testicular PDGFRα⁺ cells in gene expression levels of steroidogenic enzymes and potential to differentiate in adult Leydig cells under comparable culture conditions. This emphasizes the need for confirming results from rodent studies in the human situation to be able to translate this knowledge to the human conditions, to eventually contribute to improvements of testosterone replacement therapies or establishing alternative cell therapies in the future, potentially based on SLCs.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by Amsterdam UMC, location AMC, Amsterdam, the Netherlands. All authors declare no competing interests.

Propofol induces apoptosis by activating caspases and the MAPK pathways, and inhibiting the Akt pathway in TM3 mouse Leydig stem/progenitor cells

Propofol is an anesthetic agent moderating GABA receptors in the nervous system. A number of studies have demonstrated that propofol exerts a negative effect on neural stem cell development in the neonatal mouse hippocampus. However, to the best of our knowledge, there is no study available to date illustrating whether neonatal exposure to propofol affects Leydig stem/progenitor cell development for normal male reproductive development and functions, and the regulatory mechanism remains elusive. In the present study, TM3 cells, a mouse Leydig stem/progenitor cell line, was treated with propofol. The data illustrated that propofol significantly reduced TM3 cell viability. TM3 subG1 phase cell numbers were significantly increased by propofol assayed by flow cytometric analysis. Annexin V/PI double staining assay of the TM3 Leydig cells also demonstrated that propofol increased TM3 cell apoptosis. In addition, cleaved caspase‑8, ‑9 and ‑3 and/or poly(ADP‑ribose) polymerase (PARP) were significantly activated by propofol in the TM3 cells. Furthermore, the expression levels of phospho‑JNK, phospho‑ERK1/2 and phospho‑p38 were activated by propofol in the TM3 cells, indicating that propofol induced apoptosis through the mitogen‑activated protein kinase (MAPK) pathway. Additionally, propofol diminished the phosphorylation of Akt to increase the apoptosis of TM3 cells. On the whole, the findings of the present study demonstrate that propofol induces TM3 cell apoptosis by activating caspases and MAPK pathways, as well as by inhibiting the Akt pathway in TM3 cells. These findings illustrate that propofol affects the viability of Leydig stem/progenitor cells possibly related to the development of the male reproductive system.

Neuromedin B regulates steroidogenesis, cell viability and apoptosis in rabbit Leydig cells

Mammalian bombesin-related peptide, neuromedin B (NMB) action is mediated by its receptor (NMBR), and NMB/NMBR system plays a major role in regulating hormone secretions, reproduction and cell growth. Here we report the functions of NMB in regulating steroidogenesis (testosterone synthesis), cell viability and apoptosis. The primary rabbit Leydig cells were employed as the paradigm for this research. We initially confirmed that NMBR is distributed in Leydig cells of rabbit testis, and a certain dose of NMB could increase the secretion of testosterone in primary cultured rabbit Leydig cells. Subsequently, the accumulated NMBR, StAR, CYP11A1, 3β-HSD and PKC protein could be induced by a certain dose of NMB in Leydig cells. Moreover, we found that NMB could decrease the cell viability, and decreased the expression of PCNA protein in Leydig cells; meanwhile, except for 100 nM, other doses of NMB could suppress the cell apoptosis, and regulate Caspase-3 protein expression in Leydig cells, respectively. These results identify that NMB may be a key factor in regulating testosterone synthesis through taking part in NMBR/PKC/steroidogenesis signaling pathway, as well as the cell viability and proliferation in rabbit Leydig cells.

In vitro testicular organogenesis from human fetal gonads produces fertilization-competent spermatids

Unlike most organs that mature during the fetal period, the male reproductive system reaches maturity only at puberty with the commencement of spermatogenesis. Robust modelling of human testicular organogenesis in vitro would facilitate research into mechanisms of and factors affecting human spermatogenic failure and male fertility preservation in prepubertal tumor patients. Here, we report successful recapitulation of human testicular organogenesis in vitro from fetal gonadal ridge. Our model displayed the formation of mature seminiferous epithelium and self-renewing spermatogonia. Remarkably, in vitro-derived haploid spermatids have undergone meiotic recombination, and showed increased genetic diversity as indicated by genetic analysis. Moreover, these spermatids were able to fertilize oocytes and support subsequent blastocyst formation. The in vitro testicular organogenesis system described here will play an important role in elucidating the regulation of human testis development and maintaining male fertility in prepubertal cancer patients.

Analysis of the developmental expression of small VCP-interacting protein and its interaction with steroidogenic acute regulatory protein in Leydig cells

Small VCP-interacting protein (SVIP) is a 9-kDa protein that is composed of 76 amino acids, and it plays a role in the endoplasmic reticulum-associated protein degradation (ERAD) pathway. Recent studies have shown that SVIP is an androgen-responsive protein and its expression is regulated by androgens. Because no data are available regarding the cellular localization and expression of SVIP in the mouse testis, where androgens are highly expressed, immunohistochemistry and western blotting were performed. In the fetal testis, we found that moderate but consistent staining of SVIP is present in the cytoplasm of Leydig cells. In prepubertal and adult life, SVIP remains present in Leydig cells as well as in the cytoplasm of some peritubular and Sertoli cells. From postnatal day 15 onward, SVIP is strongly expressed in the cytoplasm of Leydig cells. Furthermore, TM3, MA-10 Leydig and Sertoli cell lines were also used to evaluate the expression of SVIP. To identify the interacting partners, such as steroidogenic acute regulatory (STAR) protein, colocalization studies were performed by fluorescence microscopy, showing that STAR colocalized with SVIP in the adult mouse testis. The expression changes of STAR were studied by using SVIP siRNAs in Leydig cell line cultures. Depletion of SVIP resulted in decreased expression of STAR. Additionally, the number and size of lipid droplets were significantly increased in SVIP-depleted Leydig cells. Taken together, our data identify SVIP as a marker of Leydig cell lineage and as a regulator of STAR protein expression and lipid droplet status in Leydig cells.

Maternal Exposure to T-2 Toxin Induces Changes in Antioxidant System and Testosterone Synthesis in the Testes of Mice Offspring

Simple Summary

This study investigated the effects of maternal T-2 toxin exposure on the development of testis in the mice offspring. The detrimental effects were assessed by testicular weight, antioxidant capacity, and testosterone synthesis and secretion. Studies have shown that the toxin carried by the mother has bad effects on the testicular development of offspring at puberty, affecting the antioxidant system and testosterone synthesis in the testis, but the maternal exposure of T-2 toxin had no significant impact on the testes of offspring after sexual maturity, suggesting the recovery of reproductive function.

Abstract

T-2 toxin, the most toxic member of trichothecene mycotoxin, is widely distributed in cereals, and has been extensively studied, but few studies focus on the toxicity of maternal exposure to offspring. This study focused on the effects of maternal exposure to T-2 toxin (during gestation and lactation) on the testicular development of mice offspring. Dams were orally administered with T-2 toxin at 0, 0.005, or 0.05 mg/kg body weight from the late stage of gestation to the end of lactation. Testicular samples of the mice offspring were collected on the postnatal day 21, 28, and 56. The results showed significant decreases in body weight and testicular weight on the postnatal day 28. Moreover, significant inhibition of antioxidant system and testosterone synthesis was detected on the postnatal day 28. Furthermore, there were significant decreases in the gene expression levels of StAR and 3β-HSD, which are involved in testosterone synthesis. In general, present results demonstrated that maternal exposure to T-2 toxin during gestation and lactation led to bad effects on the capacity of antioxidant system and inhibited testosterone synthesis in testes during pre-puberty with no significant effects on post-puberty.

Characterization and differentiation of CD51+ Stem Leydig cells in adult mouse testes

It was reported previously that adult mouse stem Leydig cells (SLCs) express CD51 (integrin α-chain V). However, it is still unclear whether all CD51⁺ cells are SLCs. In the present study, we found that CD51⁺ cells can be classified into two sub-groups, a weakly-staining group (CD51⁺) and a strongly-staining group (CD51⁺⁺). The CD51⁺ cells expressed common SLC marker genes, including Nestin, Pdgfra and Coup-tf2, while CD51⁺⁺ cells did not express these genes. Instead, they expressed macrophage markers, such as F4/80, Cd115 and Tnfa. When these cells were induced to differentiate in vitro, the CD51⁺ cells, but not CD51⁺⁺ cells, formed Leydig cells. Overall, our results showed that although SLCs expressed CD51, not all CD51-expressing cells are SLCs. The cells that expressed high levels of CD51 are actually macrophages.

Leydig cells: formation, function, and regulation

Herein we summarize important discoveries made over many years about Leydig cell function and regulation. Fetal Leydig cells produce the high levels of androgen (testosterone or androstenedione, depending upon the species) required for differentiation of male genitalia and brain masculinization. Androgen production declines with loss of these cells, reaching a nadir at postpartum. Testosterone then gradually increases to high levels with adult Leydig cell development from stem cells. In the adult, luteinizing hormone (LH) binding to Leydig cell LH receptors stimulates cAMP production, increasing the rate of cholesterol translocation into the mitochondria. Cholesterol is metabolized to pregnenolone by the CYP11A1 enzyme at the inner mitochondrial membrane, and pregnenolone to testosterone by mitochondria and smooth endoplasmic reticulum enzymes. Cholesterol translocation to the inner mitochondrial membrane is mediated by a protein complex formed at mitochondrial contact sites that consists of the cholesterol binding translocator protein, voltage dependent anion channel, and other mitochondrial and cytosolic proteins. Steroidogenic acute regulatory protein acts at this complex to enhance cholesterol movement across the membranes and thus increase testosterone formation. The 14-3-3γ and ε adaptor proteins serve as negative regulators of steroidogenesis, controlling the maximal amount of steroid formed. Decline in testosterone production occurs in many aging and young men, resulting in metabolic and quality-of-life changes. Testosterone replacement therapy is widely used to elevate serum testosterone levels in hypogonadal men. With knowledge gained of the mechanisms involved in testosterone formation, it is also conceivable to use pharmacological means to increase serum testosterone by Leydig cell stimulation.

Deciphering Cell Lineage Specification during Male Sex Determination with Single-Cell RNA Sequencing

The gonad is a unique biological system for studying cell-fate decisions. However, major questions remain regarding the identity of somatic progenitor cells and the transcriptional events driving cell differentiation. Using time-series single-cell RNA sequencing on XY mouse gonads during sex determination, we identified a single population of somatic progenitor cells prior to sex determination. A subset of these progenitors differentiates into Sertoli cells, a process characterized by a highly dynamic genetic program consisting of sequential waves of gene expression. Another subset of multipotent cells maintains their progenitor state but undergoes significant transcriptional changes restricting their competence toward a steroidogenic fate required for the differentiation of fetal Leydig cells. Our findings confirm the presence of a unique multipotent progenitor population in the gonadal primordium that gives rise to both supporting and interstitial lineages. These also provide the most granular analysis of the transcriptional events occurring during testicular cell-fate commitment.

Three populations of adult Leydig cells in mouse testes revealed by a novel mouse HSD3B1-specific rat monoclonal antibody

Leydig cells play a pivotal function in the synthesis of a male sex steroid, testosterone. The ability of the steroid production is dependent on the expression of the steroidogenic genes, such as HSD3B (3β-hydroxysteroid dehydrogenase/Δ5- Δ4 isomerase). It has been established that two different types of Leydig cells, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs), are developed in mammalian testes. FLCs and ALCs are characterized by different sets of marker gene expression. In the case of mouse Leydig cells, Hsd3b1 (Hsd3b type 1) is expressed both in FLCs and ALCs whereas Hsd3b6 (Hsd3b type 6) is expressed in ALCs but not in FLCs. However, because the antibodies established so far for HSD3B were unable to distinguish between the HSD3B1 and HSD3B6 isoforms, it remained unclear whether both of them are expressed in every ALC. Therefore, in the present study, we generated a rat monoclonal antibody specific for mouse HSD3B1. Intriguingly, this monoclonal antibody together with an antibody specific for HSD3B6 identified three populations of ALCs based on the expression levels of these HSD3Bs.

Role of epigenetic regulation in mammalian sex determination

Mammalian sex determination is triggered by activation of the mammalian sex-determining gene, Sry, in a spatially and temporally controlled manner. Because reduced or delayed Sry expression results in male-to-female sex reversal, male development is highly dependent on the accurate transcription of Sry. SRY dysregulation is a potential cause of human disorders of sex development (DSD). In addition to changes in DNA sequences, gene expression is regulated by epigenetic mechanisms. Epigenetic regulation ensures spatial and temporal accuracy of the expression of developmentally regulated genes. Epigenetic regulation such as histone tail modification, DNA methylation, chromatin remodeling, and non-coding RNA regulation engages several biological processes in multicellular organisms. In recent years, it has been revealed that various types of epigenetic regulation are involved in accurate gonadal differentiation in mammals. In particular, histone modification plays an integral part in sex determination, which is the first step of gonadal differentiation. Here, we focus on the findings on the epigenetic modifications that regulate Sry expression. Finally, we discuss the role of metabolism that potentially alters the epigenetic state in response to environmental cues.

Ontogenesis of human fetal testicular steroidogenesis at early gestational age

The onset of steroidogenesis in human fetal testes (HFT) during the first trimester is poorly investigated. One important unresolved question is the ontogeny of steroidogenic enzymes and formation of steroidogenic pathways in the HFT at early pregnancy. Our aim was to explore steroidogenesis, the expression of steroidogenic enzymes and their maturation in the HFT at gestational weeks (GW) 8-12. Steroids in the HFT were analyzed by gas chromatography/coupled to tandem mass spectrometry. The expression of steroidogenic enzymes in the HFT at GW8-12 was investigated by qPCR, automated Western blotting and immunohistochemistry. We demonstrated that the HFT at GW8-9 produced low level of testosterone via the Δ⁴ pathway and progesterone was the major steroid found in the testicular tissue. In contrast, more mature Leydig cells from the HFT at GW11-12 synthesized high levels of androgens via the Δ⁵ pathway. We also observed a significant upregulation of the expression of StAR, CYP11A1, CYP17A1 and its accessory proteins, P450 oxidoreductase (POR) and cytochrome b5 in the HFT at GW11-12 compared to GW8-9. Altogether, our data suggest that that human fetal Leydig cells differentiate rapidly at the end of the first trimester by acquiring capacity to express high levels of steroidogenic enzymes and switch from the Δ⁴ to the Δ⁵ pathways to synthesize high levels of androgens due to maturation of the CYP17-POR-b5 complex.

Effects of Osteocalcin on Synthesis of Testosterone and INSL3 during Adult Leydig Cell Differentiation

Proliferation and differentiation of adult Leydig cells are mainly completed in puberty. In many studies, apart from normal postnatal development process, it is widely indicated that, through administrating EDS, Leydig cell population is eliminated and regenerated. It is believed that osteocalcin released from osteoblasts, which is responsible for modulating bone metabolism, induces testosterone production in Leydig cells, independent of the HPG axis. In addition, INSL3 produced by Leydig cells, such as testosterone, plays a critical role in bone metabolism and is known to reflect the development process and functional capacities of Leydig cells. This study is aimed at investigating OC-mediated testosterone regulation and INSL3 synthesis during differentiation of adult Leydig cells that are independent of LH. For this purpose, male rats were divided into 2 groups: prepubertal normal rats and adult EDS-injected rats. Each group was divided into 4 subgroups in which GnRH antagonist or OC was applied. After adult Leydig cells completed their development, testicular tissue samples obtained from the sacrificed rats were examined by light-electron microscopic, immunohistochemical, and biochemical methods. Slight upregulation in 3βHSD, INSL3, and GPRC6A expressions along with the increase in serum testosterone levels was observed in groups treated with osteocalcin against GnRH antagonist. In addition, biochemical and microscopic findings in osteocalcin treated groups were similar to those in control groups. While there was no significant difference in the number of Leydig cells reported, the presence of a significant upregulation in INSL3 and GPRC6A expressions and the increase in serum testosterone and ucOC levels were observed. After evaluation of findings altogether, it is put forward that, for the first time in this study, although osteocalcin treatment made no significant difference in the number of Leydig cells, it increased the level of testosterone through improving the function of existing adult Leydig cells during normal postnatal development process and post-EDS regeneration. This positive correlation between osteocalcin-testosterone and osteocalcin-INSL3 is concluded to be independent of LH at in vivo conditions.

Assessing Autophagy in the Leydig Cells

Autophagy is an important intracellular degradation system which is implicated in many physiological and pathological processes. During autophagy, cytosolic constituents such as organelles and macromolecules are engulfed by autophagosome, and then they fuse with lysosomes for degradation and recycle of the engulfed components within the autolysosome to maintain cellular homeostasis. In male testis, the Leydig cells provide the major source of testosterone production. Autophagy is extremely active in Leydig cells and is involved in the steroid production. However, the precise role of autophagy in Leydig cells is still largely unknown. Thus, a comprehensive measurement of autophagic activity with different methods would shed light on our knowledge about the functional role of autophagy in regulating male reproductive physiology. In this chapter, we describe the morphological, cellular, and biochemical methods to monitor autophagy in Leydig cells.

Sulphur dioxide and arsenic affect male reproduction via interfering with spermatogenesis in mice

As two potential environmental hazards, sulphur dioxide (SO₂) and arsenic have adverse effects on male reproduction, but the mechanism of which and their combined toxicity are not clear. In this study, we investigate male reproductive toxicity with a focus on spermatogenesis by treating mice with 5 mg/m³ SO₂ and/or 5 mg/L arsenic. Our results showed that arsenic exposure caused significant decreases in water and food consumption and body weight in mice, whereas these changes were not observed in the SO₂-only group. Both SO₂ and arsenic reduced sperm counts, increased the percentage of sperm malformation, and induced abnormal testicular pathological changes. Elevated H₂O₂ and MDA contents, declined T-SOD activity, decreased spermatogenic cell counts, enhanced caspase-3 activity, and increased TUNEL-positive cells were also observed in mice exposed to SO₂ and/or arsenic. Moreover, SO₂ and arsenic co-exposure changed the mRNA levels of Bax and Bcl-2, decreased serum testosterone levels, and downregulated the expression of steroidogenic-related genes (LHR, StAR, and ABP) in mice. These findings provide a new theoretical basis for understanding how SO₂ and arsenic interfere with spermatogenesis leading to infertility. These results also suggest that SO₂ and arsenic co-exposure likely result in an additive effect on male reproductive toxicity in mice.

How does chemotherapy treatment damage the prepubertal testis?

Chemotherapy treatment is a mainstay of anticancer regimens, significantly contributing to the recent increase in childhood cancer survival rates. Conventional cancer therapy targets not only malignant but also healthy cells resulting in side effects including infertility. For prepubertal boys, there are currently no fertility preservation strategies in use, although several potential methods are under investigation. Most of the current knowledge in relation to prepubertal gonadotoxicity has been deduced from adult studies; however, the prepubertal testis is relatively quiescent in comparison to the adult. This review provides an overview of research to date in humans and animals describing chemotherapy-induced prepubertal gonadotoxicity, focusing on direct gonadal damage. Testicular damage is dependent upon the agent, dosage, administration schedule and age/pubertal status at time of treatment. The chemotherapy agents investigated so far target the germ cell population activating apoptotic pathways and may also impair Sertoli cell function. Due to use of combined chemotherapy agents for patients, the impact of individual drugs is hard to define, however, use of in vivo and in vitro animal models can overcome this problem. Furthering our understanding of how chemotherapy agents target the prepubertal testis will provide clarity to patients on the gonadotoxicity of different drugs and aid in the development of cytoprotective agents.

Effects of neuromedin B on steroidogenesis, cell proliferation and apoptosis in porcine Leydig cells

Neuromedin B (NMB), a mammalian bombesin-related peptide, has numerous physiological functions, including regulating hormone secretions, cell growth, and reproduction, by binding to its receptor (NMBR). In this study, we investigated the effects of NMB on testosterone secretion, steroidogenesis, cell proliferation, and apoptosis in cultured primary porcine Leydig cells. NMBR was mainly expressed in the Leydig cells of porcine testes, and a specific dose of NMB significantly promoted the secretion of testosterone in the primary Leydig cells; moreover, NMB increased the expression of mRNA and/or proteins of NMBR and steroidogenic mediators (steroidogenic acute regulatory (STAR), CYP11A1, and HSD3B1) in the Leydig cells. In addition, specific doses of NMB promoted the proliferation of Leydig cells and increased the expression of proliferating cell nuclear antigen and Cyclin B1 proteins, while suppressing Leydig cell apoptosis and decreasing BAX and Caspase-3 protein expression. These results suggest that the NMB/NMBR system might play an important role in regulating boar reproductive function by modulating steroidogenesis and/or cell growth in porcine Leydig cells.

Recent progress in understanding the mechanisms of Leydig cell differentiation

Leydig cells in fetal and adult testes play pivotal roles in eliciting male characteristics by producing androgen. Although numerous studies of Leydig cells have been performed, the mechanisms for differentiation of the two cell types (fetal Leydig and adult Leydig cells), their developmental and functional relationship, and their differential characteristics remain largely unclear. Based on recent technical progress in genome-wide analysis and in vitro investigation, novel and fascinating observations concerning the issues above have been obtained. Focusing on fetal and adult Leydig cells, this review summarizes the recent progress that has advanced our understanding of the cells.

Midazolam activates caspase, MAPKs and endoplasmic reticulum stress pathways, and inhibits cell cycle and Akt pathway, to induce apoptosis in TM3 mouse Leydig progenitor cells

Background

Midazolam (MDZ) has powerful hypnosis, amnesia, anti-anxiety and anticonvulsant effects. Studies have shown that prenatally developmental toxicity of diazepam can be observed in many organs/tissues. However, it remains elusive in male reproductive system.

Materials and methods

TM3 mouse Leydig progenitor cell line was used to determine whether MDZ has any unfavorable effects.

Results

Midazolam significantly decreased cell viability in dose- and time-dependent manners in TM3 cells. In flow cytometry analysis, midazolam significantly increased subG1 phase cell numbers, and annexin V/PI double staining assay further confirmed that MDZ induced apoptosis in TM3 cells. Moreover, MDZ significantly induced the expression of caspase-8 and -3 proteins and the phosphorylation of JNK, ERK1/2 and p38. Besides, MDZ didn’t activate Akt pathway in TM3 cells. Furthermore, the expressions of p-EIF2α, ATF4, ATF3 and CHOP were induced by midazolam, suggesting that midazolam could induce apoptosis through endoplasmic reticulum (ER) stress in TM3 cells. Additionally, the expressions of cyclin A, cyclin B and CDK1 were inhibited by midazolam through the regulation of p53 in TM3 cells, indicating that midazolam could regulate cell cycle to induce apoptosis.

Conclusion

Midazolam could activate caspase, MAPKs and ER stress pathways and impede Akt pathway and cell cycle to induce apoptosis in TM3 mouse Leydig progenitor cells.

Aberrations in sperm DNA methylation patterns of males suffering from reduced fecundity

The purpose of this study was to evaluate the aberrations in sperm DNA methylation patterns of males suffering from reduced fecundity. A total of 108 males (65 males suffering from reduced fecundity as cases and 43 proven fertile males as a control) were included in the study. Thirty samples were subjected to 450K arrays as a screening phase, and then, three CpG sites located in the following genes: TYRO3, CGβ and FAM189A1 were selected to validate on 78 samples using deep bisulphite sequencing. A significant difference in the methylation level was found between cases and controls at all CpGs in TYRO3 gene-related amplicon (CpG1, p ≤ .003, CpG2, p ≤ .0001, CpG3, p ≤ .003 and CpG4, p ≤ .030) and CpG1 in CGβ gene-related amplicon (p ≤ .0001). Besides, a significant difference was found at two CpGs (CpG1, p ≤ .004 and CpG2, p ≤ .002) tested in the FAM189A1 gene-related amplicon. A significant correlation was found between the methylation level at CpG1 in the FAM189A1 gene and the different types of sperm motility. In conclusion, an alteration in the methylation levels of sperm DNA from males with reduced fecundity was showed. In addition, a relationship between variations in the methylation level of these CpGs and sperm motility has been observed.

Estrogen receptor-related receptor γ regulates testicular steroidogenesis through direct and indirect regulation of steroidogenic gene expression

Biosynthesis of testosterone, which mainly occurs in testicular Leydig cells, is controlled by steroidogenic proteins, such as StAR and P450c17. Although estrogen-related receptor gamma (ERRγ), an orphan nuclear receptor, is expressed in the testis, its role is not well understood. In this study, we investigated the expression of ERRγ in Leydig cells and its molecular action on testicular steroidogenesis. ERRγ is expressed in mouse Leydig cells from pre-pubertal stages. ERRγ overexpression in primary Leydig cells elevated the production of testosterone with a marked increase of P450c17 expression at both mRNA and protein levels, albeit decreased expression of StAR. Promoter-reporter analyses showed that ERRγ directly regulated the P450c17 promoter. Further deletion mutant analyses of the P450c17 promoter revealed that ERRγ activated expression of the P450c17 gene by binding to an ERRγ response element within the P450c17 promoter. Meanwhile, ERRγ suppressed cAMP-induced activation of the StAR promoter, which was likely due to ERRγ-mediated inhibition of the transcriptional activity of Nur77, which is induced by cAMP and regulates StAR gene expression in Leydig cells. Interestingly, ERRγ coexpression also decreased the protein level of Nur77, which occurred through proteasomal degradation, suggesting ERRγ-mediated regulation of steroidogenesis at another level. Taken together, these findings suggest that ERRγ regulates testicular steroidogenesis, both directly controlling and indirectly fine-tuning the expression of steroidogenic genes.

Efficacy and Safety of Continuous Subcutaneous Infusion of Recombinant Human Gonadotropins for Congenital Micropenis during Early Infancy

BACKGROUND

Early postnatal administration of gonadotropins to infants with congenital hypogonadotropic hypogonadism (CHH) can mimic minipuberty, thereby increasing penile growth. We assessed the effects of gonadotropin infusion on stretched penile length (SPL) and hormone levels in infants with congenital micropenis.

METHODS

Single-center study including 6 males with micropenis in case of isolated CHH (n = 4), panhypopituitarism (n = 1), and partial androgen insensitivity syndrome (PAIS; n = 1). Patients were evaluated at baseline, monthly and at the end of the study through a clinical examination (SPL, testicular position and size), serum hormone assays (testosterone, luteinizing hormone, follicle-stimulating hormone, inhibin B, anti-Müllerian hormone [AMH]), and ultrasound of penis/testes.

RESULTS

In CHH, significant increases occurred in serum testosterone (from undetectable level to 3.5 ± 4.06 ng/mL [12.15 ± 14.09 nmol/L]), SPL (from 13.8 ± 4.5 to 42.6 ± 5 mm; p < 0.0001), inhibin B (from 94.8 ± 74.9 to 469.4 ± 282.5 pg/mL, p = 0.04), and AMH (from 49.6 ± 30.6 to 142 ± 76.5 ng/mL, p = 0.03). Micropenis was corrected in all patients, except one. On treatment, in the patient with PAIS, SPL was increased from 13 to 38 mm.

CONCLUSIONS

Early gonadotropin infusion is a safe, well-tolerated and effective treatment. The effect in PAIS has not been reported previously. Long-term follow-up is needed to assess the impact, if any, on future fertility and reproduction.
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