Cell biology of Leydig cells in the testis

FOXO4-DRI improves spermatogenesis in aged mice through reducing senescence-associated secretory phenotype secretion from Leydig cells

Male ageing is always accompanied by decreased fertility. The forkhead O (FOXO) transcription factor FOXO4 is reported to be highly expressed in senescent cells. Upon activation, it binds p53 in the nucleus, preventing senescent cell apoptosis and maintaining senescent cells in situ. Leydig cells play key roles in assisting spermatogenesis. Leydig cell senescence leads to deterioration of the microenvironment of the testes and impairs spermatogenesis. In this study, we observed that FOXO4-DRI, a specific FOXO4- p53 binding blocker, induced apoptosis in senescent Leydig cells, reduced the secretion of certain Senescence-Associated Secretory Phenotype and improved the proliferation of cocultured GC-1 SPG cells. In naturally aged mice, FOXO4-DRI-treated aged mice exhibited increased sperm quality and improved spermatogenesis.

REVERBA couples the circadian clock to Leydig cell steroidogenesis

The involvement of the molecular clock in regulating cell physiological processes on a specific time scale is a recognized concept, yet its specific impact on optimizing androgen production in Leydig cells has been unclear. This study aimed to confirm the role of the REVERBA (NR1D1) gene in controlling the transcription of key genes related to Leydig cell steroid production. We investigated daily variations by collecting Leydig cells from rats at various times within a 24-h period. Chromatin immunoprecipitation study showed a time-dependent pattern for genes linked to steroid production (Nur77, Star, Cyp11a1, and Cyp17a1), which closely matched the 24-h REVERBA levels in Leydig cells, peaking between zeitgeber time (ZT) 7-11. To understand the physiological significance of REVERBA's interaction with promoters of steroidogenesis-related genes, Leydig cells from rats at two different times (ZT7 and ZT16; chosen based on REVERBA expression levels), were treated with either an agonist (GSK4112) or an antagonist (SR8278). The results revealed that the REVERBA agonist stimulated gene transcription, while the antagonist inhibited it, but only when REVERBA was sufficiently present, indicating a reliance on REVERBA's circadian fluctuation. Moreover, this REVERBA-dependent stimulation had a clear impact on testosterone production in the culture medium, underscoring REVERBA's involvement in the circadian regulation of testosterone. This study indicates that REVERBA, in addition to being a core component of the cellular clock, plays a key role in regulating androgen production in Leydig cells by influencing the transcription of critical steroidogenesis-related genes.

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.

Therapeutic modulation of KIT ligand in melanocytic disorders with implications for mast cell diseases

KIT ligand and its associated receptor KIT serve as a master regulatory system for both melanocytes and mast cells controlling survival, migration, proliferation and activation. Blockade of this pathway results in cell depletion, while overactivation leads to mastocytosis or melanoma. Expression defects are associated with pigmentary and mast cell disorders. KIT ligand regulation is complex but efficient targeting of this system would be of significant benefit to those suffering from melanocytic or mast cell disorders. Herein, we review the known associations of this pathway with cutaneous diseases and the regulators of this system both in skin and in the more well-studied germ cell system. Exogenous agents modulating this pathway will also be presented. Ultimately, we will review potential therapeutic opportunities to help our patients with melanocytic and mast cell disease processes potentially including vitiligo, hair greying, melasma, urticaria, mastocytosis and melanoma.

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.

Fetal Leydig cells: What we know and what we don't

During male fetal development, testosterone plays an essential role in the differentiation and maturation of the male reproductive system. Deficient fetal testosterone production can result in variations of sex differentiation that may cause infertility and even increased tumor incidence later in life. Fetal Leydig cells in the fetal testis are the major androgen source in mammals. Although fetal and adult Leydig cells are similar in their functions, they are two distinct cell types, and therefore, the knowledge of adult Leydig cells cannot be directly applied to understanding fetal Leydig cells. This review summarizes our current knowledge of fetal Leydig cells regarding their cell biology, developmental biology, and androgen production regulation in rodents and human. Fetal Leydig cells are present in basement membrane-enclosed clusters in between testis cords. They originate from the mesonephros mesenchyme and the coelomic epithelium and start to differentiate upon receiving a Desert Hedgehog signal from Sertoli cells or being released from a NOTCH signal from endothelial cells. Mature fetal Leydig cells produce androgens. Human fetal Leydig cell steroidogenesis is LHCGR (Luteinizing Hormone Chronic Gonadotropin Receptor) dependent, while rodents are not, although other Gαs -protein coupled receptors might be involved in rodent steroidogenesis regulation. Fetal steroidogenesis ceases after sex differentiation is completed, and some fetal Leydig cells dedifferentiate to serve as stem cells for adult testicular cell types. Significant gaps are acknowledged: (1) Why are adult and fetal Leydig cells different? (2) What are bona fide progenitor and fetal Leydig cell markers? (3) Which signaling pathways and transcription factors regulate fetal Leydig cell steroidogenesis? It is critical to discover answers to these questions so that we can understand vulnerable targets in fetal Leydig cells and the mechanisms for androgen production that when disrupted, leads to variations in sex differentiation that range from subtle to complete sex reversal.

Pharmacotherapeutic potential of ginkgetin against polystyrene microplastics-instigated testicular toxicity in rats: A biochemical, spermatological, and histopathological assessment

Polystyrene microplastics (PSMPs) have emerged as a ubiquitous environmental toxicant that affects different organs including testes. Ginkgetin (GNG) is a biflavonoid that shows antioxidant properties. The current research was undertaken to evaluate the ameliorative potential of GNG against PSMPs-instigated testicular damages. Forty-eight albino rats (male) were randomly divided into 4 equal groups: control, PSMPs-treated group (0.01 mgkg-1), GNG + PSMPs-exposed group (25 mgkg-1 + 0.01 mgkg-1), and only GNG-supplemented group (25 mgkg-1). After 56 days of treatment, it was revealed that PSMPs significantly reduced the activity of glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GSR), while concurrently augmented the levels of lipid peroxidation marker, i.e., malondialdehyde (MDA) along with reactive oxygen species (ROS). Rats administered with PSMPs showed a significant reduction in the spermatogenic indices (sperm count, viability, and motility), HOS coiled tail sperm along with increased sperm structural deformities, i.e., tail, head, and mid-piece. Additionally, PSMPs exposure decreased the levels of testosterone, luteinizing (LH), and follicle-stimulating hormones (FSH). Besides, administration of PSMPs reduced the steroidogenic enzymes (13β-HSD, StAR, and 17β-HSD) and Bcl-2 expression, while augmented the caspase-3 and Bax expression. PSMPs also elevated the levels of inflammatory markers (IL-6, IL-1β, TNF-α, and NF-κB) and activity of COX-2 in the testes. Furthermore, PSMPs treatment induced various histopathological damages in the testes of rats. Therefore, findings of the current study suggested that GNG effectively mitigated the PSMPs-induced testicular toxicity owing to its chemoprotective potential possibly through its anti-inflammatory, antioxidant, anti-apoptotic, and androgenic properties.

Protective effect of TNFAIP3 on testosterone production in Leydig cells under an aging inflammatory microenvironment

BACKGROUND

The aging inflammatory microenvironment surrounding Leydig cells is linked to reduced testosterone levels in males. Tumor necrosis factor alpha-induced protein 3 (TNFAIP3) acts as a critical anti-inflammatory factor in various aging-related diseases. This study aims to investigate the protective effect of TNFAIP3 on testosterone production in Leydig cells under an aging inflammatory microenvironment.

METHODS

Bioinformatics analysis examined TNFAIP3 expression differences in aging rat testes and validated the findings in aging mouse testes. In vitro models of inflammation were established using two Leydig cell lines, with tumor necrosis factor alpha (TNF-α) as the inflammatory factor. Lentiviral transduction was utilized to manipulate TNFAIP3 expression in these cell lines. Transcriptomic sequencing identified differentially expressed genes in TNFAIP3-overexpressing cells.

RESULTS

Bioinformatics analysis and validation experiments revealed increased inflammatory signaling and elevated TNFAIP3 expression in aging rat and mouse testes. TNFAIP3 knockdown worsened testosterone synthesis inhibition and apoptosis in cells, while TNFAIP3 overexpression reversed these effects. Transcriptome analysis identified alterations in the P38MAPK pathway following TNFAIP3 overexpression. TNFAIP3 knockdown enhanced TNF-induced P38MAPK signaling, whereas its overexpression attenuated this effect. TNFAIP3 was found to regulate testosterone synthesis by upregulating CEBPB expression.

CONCLUSIONS

TNFAIP3 exhibits inhibitory effects on apoptosis and promotes testosterone production in Leydig cells. The protective influence of TNFAIP3 on Leydig cells within an inflammatory microenvironment is likely mediated through by inhibiting the P38MAPK pathway and upregulating CEBPB expression.

A comprehensive review on endocrine toxicity of gaseous components and particulate matter in smog

Smog is a form of extreme air pollution which comprises of gases such as ozone, sulfur dioxide, nitrogen and carbon oxides, and solid particles including particulate matter (PM2.5 and PM10). Different types of smog include acidic, photochemical, and Polish. Smog and its constituents are hazardaous to human, animals, and plants. Smog leads to plethora of morbidities such as cancer, endocrine disruption, and respiratory and cardiovascular disorders. Smog components alter the activity of various hormones including thyroid, pituitary, gonads and adrenal hormones by altering regulatory genes, oxidation status and the hypothalamus-pituitary axis. Furthermore, these toxicants are responsible for the development of metabolic disorders, teratogenicity, insulin resistance, infertility, and carcinogenicity of endocrine glands. Avoiding fossil fuel, using renewable sources of energy, and limiting gaseous discharge from industries can be helpful to avoid endocrine disruption and other toxicities of smog. This review focuses on the toxic implications of smog and its constituents on endocrine system, their toxicodynamics and preventive measures to avoid hazardous health effects.

Impact of Chromium Picolinate on Leydig Cell Steroidogenesis and Antioxidant Balance Using an In Vitro Insulin Resistance Model

Leydig cells (LCs) play a pivotal role in male fertility, producing testosterone. Chromium (III) picolinate (CrPic3), a contentious supplement with antidiabetic and antioxidant properties, raises concerns regarding male fertility. Using a rodent LC line, we investigated the cytotoxicity of increasing CrPic3 doses. An insulin resistance (IR) model was established using palmitate (PA), and LCs were further exposed to CrPic3 to assess its antioxidant/antidiabetic activities. An exometabolome analysis was performed using 1H-NMR. Mitochondrial function and oxidative stress were evaluated via immunoblot. Steroidogenesis was assessed by quantifying androstenedione through ELISA. Our results uncover the toxic effects of CrPic3 on LCs even at low doses under IR conditions. Furthermore, even under these IR conditions, CrPic3 fails to enhance glucose consumption but restores the expression of mitochondrial complexes CII and CIII, alleviating oxidative stress in LCs. While baseline androgen production remained unaffected, CrPic3 promoted androstenedione production in LCs in the presence of PA, suggesting that it promotes cholesterol conversion into androgenic intermediates in this context. This study highlights the need for caution with CrPic3 even at lower doses. It provides valuable insights into the intricate factors influencing LCs metabolism and antioxidant defenses, shedding light on potential benefits and risks of CrPic3, particularly in IR conditions.

Pregabalin alters reproductive performance in male mice and causes congenital anomalies in offspring

CONTEXT

Pregabalin is an anticonvulsant drug with analgesic activity for the treatment of neuropathic pain.

AIMS

To valuate the toxicity of pregabalin in reproductive parameters, spermatogenesis, and teratogenicity in the offspring of mice.

METHODS

Twenty male mice were randomly distributed into two groups: PGB group and group C (n =10 per group). The animals in the PGB group received, via gavage, 200mg/kg of pregabalin diluted in distilled water daily, for a period of 45days. Group C received distilled water under the same experimental design.

KEY RESULTS

In the paternal parameters of the PGB group, there was a significant increase in the size of the testicles, morphological alterations in the spermatozoa, a decrease in the Johnsen score, an increase in the Leydig cells, and a decrease in the serum level of testosterone. In the intrauterine development parameters of females mated with males from the PGB group, a significant decrease in placental weight, weight and length of fetuses, and fetal viability rate was observed. There was a significant increase in the number of resorptions and post-implantation losses. The significant anomalies observed in the offspring were alteration in the size of the kidneys, absent metacarpals and phalanges, alteration in the sternum, and supernumerary thoracic vertebrae.

CONCLUSION

Results suggest that pregabalin had toxic effects on the reproductive function of male mice and teratogenic potential.

IMPLICATIONS

The findings of this study may provide new hypotheses, taking into account the risk-benefit ratio for male reproduction and offspring health.

Prolactin inhibitor changes testosterone production, testicular morphology, and related genes expression in cashmere goats

Prolactin has multifaceted roles in lactation, growth, metabolism, osmoregulation, behavior, and the reproduction of animals. This study aimed to investigate the involvement of prolactin in testicular function in cashmere goats. Twenty cashmere goats were randomly assigned to either the control group (CON) or the bromocriptine treatment group (BCR, bromocriptine, prolactin inhibitor). Blood and testis samples collected for analysis after 30 days of treatment. The results indicated that, compared with the CON group, BCR significantly decreased (p < 0.05) the serum concentrations of prolactin, and significantly increased (p < 0.05) the levels of testosterone and luteinizing hormone (LH) on day 30. The serum level of the follicle-stimulating hormone (FSH) was not affected (p > 0.05) by the treatment. The mean seminiferous tubule diameter and spermatogenic epithelium thickness were increased (p < 0.05) in the BCR group. Subsequently, we performed RNA sequencing and bioinformatics analysis to identify the key genes and pathways associated with the regulation of spermatogenesis or testosterone secretion function. A total of 142 differentially expressed genes (DEGs) were identified (91 were upregulated, 51 were downregulated). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that the DEGs were mainly involved in the extracellular matrix (ECM), hippo, and steroid hormone biosynthesis, which are related to testicular function. The expression of the genes SULT2B1, CYP3A24, and CYP3A74 in the steroid hormone biosynthesis pathway significantly increased (p < 0.05) in the BCR group, which was validated by qRT-PCR. These results provide a basis for understanding the mechanisms underlying the regulation of testicular function by prolactin in cashmere goats.

Small Molecule Cocktails Promote Fibroblast-to-Leydig-like Cell Conversion for Hypogonadism Therapy

Male hypogonadism arises from the inadequate production of testosterone (T) by the testes, primarily due to Leydig cell (LC) dysfunction. Small molecules possess several advantages, including high cell permeability, ease of synthesis, standardization, and low effective concentration. Recent investigations have illuminated the potential of small molecule combinations to facilitate direct lineage reprogramming, removing the need for transgenes by modulating cellular signaling pathways and epigenetic modifications. In this study, we have identified a specific cocktail of small molecules, comprising forskolin, DAPT, purmorphamine, 8-Br-cAMP, 20α-hydroxycholesterol, and SAG, capable of promoting the conversion of fibroblasts into Leydig-like cells (LLCs). These LLCs expressed key genes involved in testosterone synthesis, such as Star, Cyp11a1, and Hsd3b1, and exhibited the ability to secrete testosterone in vitro. Furthermore, they successfully restored serum testosterone levels in testosterone-castrated mice in vivo. The small molecule cocktails also induced alterations in the epigenetic marks, specifically H3K4me3, and enhanced chromosomal accessibility on core steroidogenesis genes. This study presents a reliable methodology for generating Leydig-like seed cells that holds promise as a novel therapeutic approach for hypogonadism.

A Comprehensive Review of the Impact of Chromium Picolinate on Testicular Steroidogenesis and Antioxidant Balance

Low testosterone (T) levels are a major cause of male infertility, as this hormone is crucial for several processes throughout the entire male reproductive tract. Leydig cells (LC) produce T through testicular steroidogenesis. Disrupted LC function can hinder steroid production and fertility. Among the factors that affect steroidogenesis, endocrine-disrupting chemicals (EDCs) raise concerns, as they disturb hormonal signaling. Chromium is classified as an EDC, and its main forms are hexavalent (Cr(VI)) and trivalent chromium (Cr(III)). While Cr(III) is controversially regarded as an essential metal, its compound Cr(III) picolinate (CrPic3) is used as a nutritional supplement due to its antidiabetic and antioxidant properties. This review aims to identify the possible effects of CrPic3 on testicular steroidogenesis and thus, on male fertility. The detriments caused by CrPic3 in LC include the inhibition of enzymes involved in steroidogenesis, and, as in other cells, the induction of mutagenesis and apoptosis. Remarkably, CrPic3 impacts male fertility through the alteration of reactive oxygen species (ROS), T levels, and sperm parameters (sperm motility and abnormal sperm count). However, gaps and inconsistencies exist in the literature concerning its effects on male fertility. Thus, further research is imperative to comprehend the underlying mechanisms of CrPic3 in the physiological processes relevant to male fertility, ensuring the supplement's safety for use by men.

Mouse Testicular Mkrn3 Expression Is Primarily Interstitial, Increases Peripubertally, and Is Responsive to LH/hCG

Studies in humans and mice support a role for Makorin RING finger protein 3 (MKRN3) as an inhibitor of gonadotropin-releasing hormone (GnRH) secretion prepubertally, and its loss of function is the most common genetic cause of central precocious puberty in humans. Studies have shown that the gonads can synthesize neuropeptides and express MKRN3/Mkrn3 mRNA. Therefore, we aimed to investigate the spatiotemporal expression pattern of Mkrn3 in gonads during sexual development, and its potential regulation in the functional testicular compartments by gonadotropins. Mkrn3 mRNA was detected in testes and ovaries of wild-type mice at all ages evaluated, with a sexually dimorphic expression pattern between male and female gonads. Mkrn3 expression was highest peripubertally in the testes, whereas it was lower peripubertally than prepubertally in the ovaries. Mkrn3 is expressed primarily in the interstitial compartment of the testes but was also detected at low levels in the seminiferous tubules. In vitro studies demonstrated that Mkrn3 mRNA levels increased in human chorionic gonadotropin (hCG)-treated Leydig cell primary cultures. Acute administration of a GnRH agonist in adult mice increased Mkrn3 expression in testes, whereas inhibition of the hypothalamic-pituitary-gonadal axis by chronic administration of GnRH agonist had the opposite effect. Finally, we found that hCG increased Mkrn3 mRNA levels in a dose-dependent manner. Taken together, our developmental expression analyses, in vitro and in vivo studies show that Mkrn3 is expressed in the testes, predominantly in the interstitial compartment, and that Mkrn3 expression increases after puberty and is responsive to luteinizing hormone/hCG stimulation.

Testicular toxicity in mice exposed to terephthalic acid in utero and during lactation

Terephthalic acid (TPA) is a worldwide aromatic compound widely used to manufacture resins and the raw material for the polymerization reaction with ethylene glycol to produce polyethylene terephthalate, known as PET. The use of TPA extends to the synthesis of phthalates, plasticizers used in various industrialized products such as toys and cosmetics. The present study aimed to evaluate the testicular toxicity of terephthalic acid on male mice exposed in utero and during lactation to TPA in different developmental windows. The animals were treated intragastric with TPA at stock dispersal dosages corresponding to 0.0014 g/ml and 0.56 g/ml of TPA in 0.5% v/v carboxymethylcellulose as well as the control dose, composed solely of dispersion of carboxymethylcellulose (0.5% v/v). Four experimental windows were established: group I-treatment in utero, in the fetal period (gestational day-GD 10.5-18.5), with euthanasia at GD 18.5; group II-treatment in utero, in the fetal period (GD 10.5-18.5) and the lactational period (postnatal day (PND-15)), with euthanasia at 15 days; group III-treatment in utero in the fetal period (DG 10.5-18.5) with euthanasia at 70 days (age of sexual maturity, PND 70); group IV-treatment in utero, in the fetal period (GD 10.5-18.5) and the lactational period (PND-15), with euthanasia at 70 days (PND70). The results indicate that TPA changes the reproductive parameters (testicular weight, GI, penis size, and anogenital index) only at the dose of 0.56 g/ml in the fetal period. Data on the volumetric ratio of the testis elements show that the dispersion with the highest concentration of TPA significantly altered the blood vessel/capillary, lymphatic vessel, and connective tissue percentages. Only at the dose of 0.56 g/ml TPA was it effective in decreasing the Leydig and Sertoli cell numbers of the euthanized animals at GD 18.5. In group II, TPA increased the diameter and lumen of seminiferous tubules, which indicates that TPA accelerated the maturation process of Sertoli cells without changing the number and the nuclear volume of these cells. The Sertoli and Leydig cell numbers of the 70-day animals exposed to TPA in the gestational and lactational period were similar to the control. Therefore, the present study is the first in the literature to show that TPA presents a testicular toxicity during fetal (DG18.5) and postnatal life (PND15), without repercussion in adulthood (70 days).

Epigenome editing based on CRISPR/dCas9p300 facilitates transdifferentiation of human fibroblasts into Leydig-like cells

Recently, Leydig cell (LCs) transplantation has a promising potential to treat male hypogonadism. However, the scarcity of seed cells is the actual barrier impeding the application of LCs transplantation. Utilizing the cutting-edge CRISPR/dCas9^VP64 technology, human foreskin fibroblasts (HFFs) were transdifferentiated into Leydig-like cells（iLCs） in previous study, but the efficiency of transdifferentiation is not very satisfactory. Therefore, this study was conducted to further optimize the CRISPR/dCas9 system for obtaining sufficient iLCs. First, the stable CYP11A1-Promoter-GFP-HFFs cell line was established by infecting HFFs with CYP11A1-Promoter-GFP lentiviral vectors, and then co-infected with dCas9^p300 and the combination of sgRNAs targeted to NR5A1, GATA4 and DMRT1. Next, this study adopted quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blot, and immunofluorescence to determine the efficiency of transdifferentiation, the generation of testosterone, the expression levels of steroidogenic biomarkers. Moreover, we utilized chromatin immuno-precipitation (ChIP) followed by quantitative polymerase chain reaction (ChIP-qPCR) to measure the levels of acetylation of targeted H3K27. The results revealed that advanced dCas9^p300 facilitated generation of iLCs. Moreover, the dCas9^p300-mediated iLCs significantly expressed the steroidogenic biomarkers and produced more testosterone with or without LH treatment than the dCas9^VP64-mediated. Additionally, preferred enrichment in H3K27ac at the promoters was detected only with dCas9^p300 treatment. The data provided here imply that the improved version of dCas9 can aid in the harvesting of iLCs, and will provide sufficient seed cells for cell transplantation treatment of androgen deficiency in the future.

Analysis of factors affecting testicular spermatogenesis capacity by using the tissue transcriptome data from GTEx

In human, endo- or exogeneous factors might alter the cellular composition, the endocrine and inflammatory micro-environments and the metabolic balance in testis. These factors will further impair the testicular spermatogenesis capacity and alter the transcriptome of testis. Conversely, it should be possible that the alteration of the transcriptomes in testes be used as an indicator to evaluate the testicular spermatogenesis capacity and to predict the causing factors. In this study, using the transcriptome data of human testes and whole blood which were collected by the genotype-tissue expression project (GTEx), we analyzed the transcriptome differences in human testes and explored those factors that affecting spermatogenesis. As a result, testes were clustered into five clusters according to their transcriptomic features, and each cluster of testes was evaluated as having different spermatogenesis capacity. High rank genes of each cluster and the differentially expressed genes in lower functional testes were analyzed. Transcripts in whole blood which may be associated with testis function were also analyzed by the correlation test. As a result, factors such as immune response, oxygen transport, thyrotropin, prostaglandin and tridecapeptide neurotensin were found associated with spermatogenesis. These results revealed multiple clues about the spermatogenesis regulation in testis and provided potential targets to improve the fertility of men in clinic.

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).

Differential Response of Transcription Factors to Activated Kinases in Steroidogenic and Non-Steroidogenic Cells

Hormone-induced Leydig cell steroidogenesis requires rapid changes in gene expression in response to various hormones, cytokines, and growth factors. These proteins act by binding to their receptors on the surface of Leydig cells leading to activation of multiple intracellular signaling cascades, downstream of which are several kinases, including protein kinase A (PKA), Ca2+/calmodulin-dependent protein kinase I (CAMKI), and extracellular signal-regulated protein kinase 1 and 2 (ERK1/2). These kinases participate in hormone-induced steroidogenesis by phosphorylating numerous proteins including transcription factors leading to increased steroidogenic gene expression. How these various kinases and transcription factors come together to appropriately induce steroidogenic gene expression in response to specific stimuli remains poorly understood. In the present work, we compared the effect of PKA, CAMKI and ERK1/2 on the transactivation potential of 15 transcription factors belonging to 5 distinct families on the activity of the Star gene promoter. We not only validated known cooperation between kinases and transcription factors, but we also identified novel cooperations that have not yet been before reported. Some transcription factors were found to respond to all three kinases, whereas others were only activated by one specific kinase. Differential responses were also observed within a family of transcription factors. The diverse response to kinases provides flexibility to ensure proper genomic response of steroidogenic cells to different stimuli.

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.

Tracking Immature Testicular Tissue after Vitrification In Vitro and In Vivo for Pre-Pubertal Fertility Preservation: A Translational Transgenic Mouse Model

Pediatric cancer survivors experiencing gonadotoxic chemoradiation therapy may encounter subfertility or permanent infertility. However, previous studies of cryopreservation of immature testicular tissue (ITT) have mainly been limited to in vitro studies. In this study, we aim to evaluate in vitro and in vivo bioluminescence imaging (BLI) for solid surface-vitrified (SSV) ITT grafts until adulthood. The donors and recipients were transgenic and wild-type mice, respectively, with fresh ITT grafts used as the control group. In our study, the frozen ITT grafts remained intact as shown in the BLI, scanning electron microscopy (SEM) and immunohistochemistry (IHC) analyses. Graft survival was analyzed by BLI on days 1, 2, 5, 7, and 31 after transplantation. The signals decreased by quantum yield between days 2 and 5 in both groups, but gradually increased afterwards until day 31, which were significantly stronger than day 1 after transplantation (p = 0.008). The differences between the two groups were constantly insignificant, suggesting that both fresh and SSV ITT can survive, accompanied by spermatogenesis, until adulthood. The ITT in both groups presented similar BLI intensity and intact cells and ultrastructures for spermatogenesis. This translational model demonstrates the great potential of SSV for ITT in pre-pubertal male fertility preservation.

Kiss1-dependent and independent release of luteinizing hormone and testosterone in perinatal male rats

Prenatal and postnatal biphasic increases in plasma testosterone levels derived from perinatal testes are considered critical for defeminizing/masculinizing the brain mechanism that regulates sexual behavior in male rats. Hypothalamic kisspeptin neurons are indispensable for stimulating GnRH and downstream gonadotropin, as well as the consequent testicular testosterone production/release in adult male rats. However, it is unclear whether kisspeptin is responsible for the increase in plasma testosterone levels in perinatal male rats. The present study aimed to investigate the role of Kiss1/kisspeptin in generating perinatal plasma LH and the consequent testosterone increase in male rats by comparing the plasma testosterone and LH profiles of wild-type (Kiss1^+/+) and Kiss1 knockout (Kiss1^-/-) male rats. A biphasic pattern of plasma testosterone levels, with peaks in the prenatal and postnatal periods, was found in both Kiss1^+/+ and Kiss1^-/- male rats. Postnatal plasma testosterone and LH levels were significantly lower in Kiss1^-/- male rats than in Kiss1^+/+ male rats, whereas the levels in the prenatal embryonic period were comparable between the genotypes. Exogenous kisspeptin challenge significantly increased plasma testosterone and LH levels and the number of c-Fos-immunoreactive GnRH neurons in neonatal Kiss1^-/- and Kiss1^+/+ male rats. Kiss1 and Gpr54 (kisspeptin receptor gene) were found in the testes of neonatal rats, but kisspeptin treatment failed to stimulate testosterone release in the cultured testes of both genotypes. These findings suggest that postnatal, but not prenatal, testosterone increase in male rats is mainly induced by central kisspeptin-dependent stimulation of GnRH and consequent LH release.

Functions of somatic cells for spermatogenesis in stallions

Spermatogenesis and testis development are highly structured physiological processes responsible for post-pubertal fertility in stallions. Spermatogenesis comprises spermatocytogenesis, meiosis, and spermiogenesis. Although germ cell degeneration is a continuous process, its effects are more pronounced during spermatocytogenesis and meiosis. The productivity and efficiency of spermatogenesis are directly linked to pubertal development, degenerated germ cell populations, aging, nutrition, and season of the year in stallions. The multiplex interplay of germ cells with somatic cells, endocrine and paracrine factors, growth factors, and signaling molecules contributes to the regulation of spermatogenesis. A cell-to-cell communication within the testes of these factors is a fundamental requirement of normal spermatogenesis. A noteworthy development has been made recently on discovering the effects of different somatic cells including Leydig, Sertoli, and peritubular myoid cells on manipulation the fate of spermatogonial stem cells. In this review, we discuss the self-renewal, differentiation, and apoptotic roles of somatic cells and the relationship between somatic and germ cells during normal spermatogenesis. We also summarize the roles of different growth factors, their paracrine/endocrine/autocrine pathways, and the different cytokines associated with spermatogenesis. Furthermore, we highlight important matters for further studies on the regulation of spermatogenesis. This review presents an insight into the mechanism of spermatogenesis, and helpful in developing better understanding of the functions of somatic cells, particularly in stallions and would offer new research goals for developing curative techniques to address infertility/subfertility in stallions.

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.

Fancd2os Reduces Testosterone Production by Inhibiting Steroidogenic Enzymes and Promoting Cellular Apoptosis in Murine Testicular Leydig Cells

BACKGRUOUND

It is well-established that serum testosterone in men decreases with age, yet the underlying mechanism of this change remains elusive.

METHODS

The expression patterns of Fancd2 opposite-strand (Fancd2os) in BALB/c male mice and testicular tissue derived cell lines (GC-1, GC-2, TM3, and TM4) were assessed using real-time polymerase chain reaction (RT-PCR), Western blot and immunofluorescence. The Fancd2os-overexpressing or knockdown TM3 cells were constructed by infecting them with lentivirus particles and were used to evaluated the function of Fancd2os. The testosterone production was measured using enzyme linked immunosorbent assay (ELISA) and the steroidogenic enzymes such as steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage (P450scc), and 3β-hydroxysteroid dehydrogenase (3β-HSD) were analysed using RT-PCR. The apoptosis of TM3 cells induced by ultraviolet light or testicular tissues was detected using flow cytometry, Western blot or dUTP-biotin nick end labeling (TUNEL) assays. Pearson correlation analysis was used to assess the correlation between the Fancd2os expression and TUNEL-positive staining in mouse testicular Leydig cells.

RESULTS

The Fancd2os protein was predominantly expressed in mouse testicular Leydig cells and its expression increased with age. Fancd2os overexpression inhibited testosterone levels in TM3 Leydig cells, whereas knockdown of Fancd2os elevated testosterone production. Fancd2os overexpression downregulated the levels of StAR, P450scc and 3β-HSD, while Fancd2os knockdown reversed this effect. Fancd2os overexpression promoted ultraviolet light-induced apoptosis of TM3 cells. In contrast, Fancd2os knockdown restrained apoptosis in TM3 cells. In vivo assays revealed that higher Fancd2os levels and mouse age were associated with increased apoptosis in Leydig cells and decreased serum testosterone levels. Pearson correlation analysis exhibited a strong positive correlation between the expression of Fancd2os and TUNEL-positive staining in mouse testicular Leydig cells.

CONCLUSION

Our findings suggest that Fancd2os regulates testosterone synthesis via both steroidogenic enzymes and the apoptotic pathway.

Loss of Raptor induces Sertoli cells into an undifferentiated state in mice

In mammals, testis development is triggered by the expression of the sex-determining Y-chromosome gene SRY to commit the Sertoli cell (SC) fate at gonadal sex determination in the fetus. Several genes have been identified to be required to promote the testis pathway following SRY activation (i.e., SRY box 9 (SOX9)) in an embryo; however, it largely remains unknown about the genes and the mechanisms involved in stabilizing the testis pathway after birth and throughout adulthood. Herein, we report postnatal males with SC-specific deletion of Raptor demonstrated the absence of SC unique identity and adversely acquired granulosa cell-like characteristics, along with loss of tubular architecture and scattered distribution of SCs and germ cells. Subsequent genome-wide analysis by RNA sequencing revealed a profound decrease in the transcripts of testis genes (i.e., Sox9, Sox8, and anti-Mullerian hormone (Amh)) and, conversely, an increase in ovary genes (i.e., LIM/Homeobox gene 9 (Lhx9), Forkhead box L2 (Foxl2) and Follistatin (Fst)); these changes were further confirmed by immunofluorescence and quantitative reverse-transcription polymerase chain reaction. Importantly, co-immunofluorescence demonstrated that Raptor deficiency induced SCs dedifferentiation into a progenitor state; the Raptor-mutant gonads showed some ovarian somatic cell features, accompanied by enhanced female steroidogenesis and elevated estrogen levels, yet the zona pellucida 3 (ZP3)-positive terminally feminized oocytes were not observed. In vitro experiments with primary SCs suggested that Raptor is likely involved in the fibroblast growth factor 9 (FGF9)-induced formation of cell junctions among SCs. Our results established that Raptor is required to maintain SC identity, stabilize the male pathway, and promote testis development.

The function of nuclear hormone receptor 4A signaling in the human reproductive system: A review

AIM

This review aims to summarize the research focused upon the functions of nuclear hormone receptor 4A (NR4A) in the human reproductive system. The research questions addressed are to decipher what role the NR4A subfamily plays in the regulation of the human reproductive system and effects upon fertility issues through regulation of the expression of the NR4A subfamily.

METHODS

The electronic database PubMed was searched for studies published before November 2021. Keywords included "NR4A," "trophoblast," "decidualization," "folliculogenesis," "estrogen," "pregnancy," "Leydig cells," "fertility," and "reproductive." Relevant references from retrieved manuscripts and review articles were also searched manually.

RESULTS

NR4A subfamily are involved in trophoblast differentiation, endometrial decidualization, embryo adhesion, secretion of related hormones, and regulation of spontaneous term labor. Besides, many studies have provided strong evidence that they play critical roles in spermatogenesis. Furthermore, Multiple mechanisms can affect the expression of NR4As. Broadly, NR4A family receptors affect the human reproductive system in multiple ways.

CONCLUSIONS

Further research is needed to specifically dissect the functions and regulatory mechanisms of these receptors and their pharmaceutical antagonists and agonists. The connection between the NR4A subfamily and a variety of reproductive disorders needs to be proven experimentally such that further examination of human tissue is required to assess the role of these receptors in human reproductive diseases.

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.

Mechanism of Action of an Environmentally Relevant Organochlorine Mixture in Repressing Steroid Hormone Biosynthesis in Leydig Cells

Within Leydig cells, steroidogenesis is induced by the pituitary luteinizing hormone (LH). The binding of LH to its receptor increases cAMP production, which then activates the expression of genes involved in testosterone biosynthesis. One of these genes codes for the steroidogenic acute regulatory (STAR) protein. STAR is part of a complex that shuttles cholesterol, the precursor of all steroid hormones, through the mitochondrial membrane where steroidogenesis is initiated. Organochlorine chemicals (OCs) are environmental persistent organic pollutants that are found at high concentrations in Arctic areas. OCs are known to affect male reproductive health by decreasing semen quality in different species, including humans. We previously showed that an environmentally relevant mixture of OCs found in Northern Quebec disrupts steroidogenesis by decreasing STAR protein levels without affecting the transcription of the gene. We hypothesized that OCs might affect STAR protein stability. To test this, MA-10 Leydig cell lines were incubated for 6 h with vehicle or the OCs mixture in the presence or absence of 8Br-cAMP with or without MG132, an inhibitor of protein degradation. We found that MG132 prevented the OC-mediated decrease in STAR protein levels following 8Br-cAMP stimulation. However, progesterone production was still decreased by the OC mixture, even in the presence of MG132. This suggested that proteins involved in steroid hormone production in addition to STAR are also affected by the OC mixture. To identify these proteins, a whole cell approach was used and total proteins from MA-10 Leydig cells exposed to the OC mixture with or without stimulation with 8Br-cAMP were analyzed by 2D SDS-PAGE and LC-MS/MS. Bioinformatics analyses revealed that several proteins involved in numerous biological processes are affected by the OC mixture, including proteins involved in mitochondrial transport, lipid metabolism, and steroidogenesis.

Activation of Autophagy by Low-Dose Silica Nanoparticles Enhances Testosterone Secretion in Leydig Cells

Silica nanoparticles (SNPs) can cause abnormal spermatogenesis in male reproductive toxicity. However, the toxicity and toxicological mechanisms of SNPs in testosterone synthesis and secretion in Leydig cells are not well known. Therefore, this study aimed to determine the effect and molecular mechanism of low doses of SNPs in testosterone production in Leydig cells. For this, mouse primary Leydig cells (PLCs) were exposed to 100 nm Stöber nonporous spherical SNPs. We observed significant accumulation of SNPs in the cytoplasm of PLCs via transmission electron microscopy (TEM). CCK-8 and flow cytometry assays confirmed that low doses (50 and 100 μg/mL) of SNPs had no significant effect on cell viability and apoptosis, whereas high doses (more than 200 μg/mL) decreased cell viability and increased cell apoptosis in PLCs. Monodansylcadaverine (MDC) staining showed that SNPs caused the significant accumulation of autophagosomes in the cytoplasm of PLCs. SNPs activated autophagy by upregulating microtubule-associated protein light chain 3 (LC3-II) and BCL-2-interacting protein (BECLIN-1) levels, in addition to downregulating sequestosome 1 (SQSTM1/P62) level at low doses. In addition, low doses of SNPs enhanced testosterone secretion and increased steroidogenic acute regulatory protein (StAR) expression. SNPs combined with rapamycin (RAP), an autophagy activator, enhanced testosterone production and increased StAR expression, whereas SNPs combined with 3-methyladenine (3-MA) and chloroquine (CQ), autophagy inhibitors, had an opposite effect. Furthermore, BECLIN-1 depletion inhibited testosterone production and StAR expression. Altogether, our results demonstrate that low doses of SNPs enhanced testosterone secretion via the activation of autophagy in PLCs.

Dynamic Expression of the Homeobox Factor PBX1 during Mouse Testis Development

Members of the pre-B-cell leukemia transcription factor (PBX) family of homeoproteins are mainly known for their involvement in hematopoietic cell differentiation and in the development of leukemia. The four PBX proteins, PBX1, PBX2, PBX3 and PBX4, belong to the three amino acid loop extension (TALE) superfamily of homeoproteins which are important transcriptional cofactors in several developmental processes involving homeobox (HOX) factors. Mutations in the human PBX1 gene are responsible for cases of gonadal dysgenesis with absence of male sex differentiation while Pbx1 inactivation in the mouse causes a failure in Leydig cell differentiation and function. However, no data is available regarding the expression profile of this transcription factor in the testis. To fill this knowledge gap, we have characterized PBX1 expression during mouse testicular development. Real time PCRs and Western blots confirmed the presence Pbx1 mRNA and PBX1 protein in different Leydig and Sertoli cell lines. The cellular localization of the PBX1 protein was determined by immunohistochemistry and immunofluorescence on mouse testis sections at different embryonic and postnatal developmental stages. PBX1 was detected in interstitial cells and in peritubular myoid cells from embryonic life until puberty. Most interstitial cells expressing PBX1 do not express the Leydig cell marker CYP17A1, indicating that they are not differentiated and steroidogenically active Leydig cells. In adults, PBX1 was mainly detected in Sertoli cells. The presence of PBX1 in different somatic cell populations during testicular development further supports a direct role for this transcription factor in testis cell differentiation and in male reproductive function.

The Crosstalk between Melatonin and Sex Steroid Hormones

Melatonin, an indolamine mainly released from the pineal gland, is associated with many biological functions, namely, the modulation of circadian and seasonal rhythms, sleep inducer, regulator of energy metabolism, antioxidant, and anticarcinogenic. Although several pieces of evidence also recognize the influence of melatonin in the reproductive physiology, the crosstalk between melatonin and sex hormones is not clear. Here, we review the effects of sex differences in the circulating levels of melatonin and update the current knowledge on the link between sex hormones and melatonin. Furthermore, we explore the effects of melatonin on gonadal steroidogenesis and hormonal control in females. The literature review shows that despite the strong evidence that sex differences impact on the circadian profiles of melatonin, reports are still considerably ambiguous, and these differences may arise from several factors, like the use of contraceptive pills, hormonal status, and sleep deprivation. Furthermore, there has been an inconclusive debate about the characteristics of the reciprocal relationship between melatonin and reproductive hormones. In this regard, there is evidence for the role of melatonin in gonadal steroidogenesis brought about by research that shows that melatonin affects multiple transduction pathways that modulate Sertoli cell physiology and consequently spermatogenesis, and also estrogen and progesterone production. From the outcome of our research, it is possible to conclude that understanding the correlation between melatonin and reproductive hormones is crucial for the correction of several complications occurring during pregnancy, like preeclampsia, and for the control of climacteric symptoms.

Proteomic analysis reveals proteins and pathways associated with declined testosterone production in male obese mice after chronic high-altitude exposure

OBJECTIVE

Obesity is common in highland areas owing to lifestyle alterations. There are pieces of evidence to suggest that both obesity and hypoxia may promote oxidative stress, leading to hypogonadism in males. These findings indicate an increased risk of hypogonadism in obese males following hypoxia exposure. However, the mechanisms underlying the disease process remain unclear. The current study aims to explore the mechanism of testosterone production dysfunction in obese male mice exposed to a chronic high-altitude hypoxia environment.

METHODS

An obese male mouse model was generated by inducing obesity in mice via a high-fat diet for 14 weeks, and the obese mice were then exposed to a high-altitude hypoxia environment for 24 days. Sera and testicular tissues were collected to detect serum lipids, sex hormone level, and testicular oxidative stress indicators. Morphological examination was performed to assess pathological alterations in testicular tissues and suborganelles in leydig cells. Proteomic alterations in testicular tissues were investigated using quantitative proteomics in Obese/Control and Obese-Hypoxia/Obese groups.

RESULTS

The results showed that chronic high-altitude hypoxia exposure aggravated low testosterone production in obese male mice accompanied by increased testicular oxidative stress and histological damages. In total, 363 and 242 differentially expressed proteins (DEPs) were identified in the two comparison groups, Obese/Control and Obese-Hypoxia/Obese, respectively. Functional enrichment analysis demonstrated that several significant functional terms and pathways related to testosterone production were altered in the two comparison groups. These included cholesterol metabolism, steroid hormone biosynthesis, peroxisome proliferator-activated receptor (PPAR) signaling pathway, oxidative stress responses, as well as retinol metabolism. Finally, 10 representative DEPs were selected for parallel reaction monitoring verification. Among them, StAR, DHCR7, NSDHL, CYP51A1, FDPS, FDX1, CYP11A1, ALDH1A1, and GPX3 were confirmed to be downregulated in the two groups.

CONCLUSIONS

Chronic hypoxia exposure could exacerbate low testosterone production in obese male mice by influencing the expression of key proteins involved in steroid hormone biosynthesis, cholesterol biosynthesis, oxidative stress responses and retinol metabolism.

Dietary intake of probiotic fermented milk benefits the gut and reproductive health in mice fed with an obesogenic diet

Probiotics have been suggested as alternatives to pharmacological drugs in the treatment of a variety of medical problems, including obesity management, which is often linked to low sperm production. Also, probiotic fermented products are known to boost host immune response, immunosenescence, infection tolerance, and redox homeostasis, but their direct role in male fertility has been less investigated. This study assessed the effect of two probiotic strains, L. fermentum NCDC 400 and L. rhamnosus NCDC 610, and fructooligosaccharide (FOS) fermented milk supplementation. We identified the significantly reduced oxidative stress markers in the plasma and liver of HF diet-fed animals. We determined the role of key testicular enzymes of steroidogenic pathway genes StAR, P450scc, and 17βHSD in maintaining the testosterone concentration and restoring testicular structures. In conclusion, the present work illustrated the ability of both probiotics L. fermentum NCDC 400 and L. rhamnosus NCDC 610 as regulatory agents with beneficial effects on weight loss and endogenous testosterone with substantially improved sperm motility in male diet-induced obesity (DIO) models. Our findings indicate that fermented milk supplementation may be an alternative treatment for preventing obesity and other related metabolic syndromes.

Macroautophagy involved in testosterone synthesis in Leydig cells of male dairy goat (Capra hircus)

Testosterone is an important steroid hormone that is indispensable for male sexual development and the reproductive system. Leydig cells (LCs), where autophagy is extremely active, reside in the testicular interstitium and are the major sites of testosterone production. However, the ultrastructural characteristics and the functional role of autophagy in LCs of livestock remain unknown. In this study, the LCs of the dairy goats were investigated to identify the steroidogenic activity and autophagy levels at different ages of development by light microscopy, immunohistochemistry (IHC), immunofluorescence (IF), and transmission electron microscopy (TEM). Morphological results showed that the steroidogenic activity (3β-HSD staining) and ultrastructural characteristics of the LCs were changed with increasing age. TEM results demonstrated that the organelles involved in testosterone synthesis, e.g., smooth endoplasmic reticulum, mitochondria, and lipid droplets, were abundantly distributed within the cytoplasm of LCs in pubertal and adult testes. Moreover, autophagy activity was enhanced in the testes at pubertal and adult stages compared with that at the juvenile stage. Several different autophagic vacuoles, including pre-autophagosomes, autophagosomes, and autolysosomes, were observed within the cytoplasm of LCs from pubertal and adult testes. However, immunofluorescent staining and TEM results showed that no typical lipophagic or mitophagic vacuoles were observed in the cytoplasm of LCs. Furthermore, primary LCs from dairy goats were used to study the effect of autophagy on testosterone production. After treatment with 3-methyladenine (3-MA, an autophagy inhibitor), the primary LCs decreased testosterone production. In contrast, treatment with rapamycin (an autophagy activator), enhanced steroidogenesis in LCs. Collectively, these in vivo and in vitro results suggested that autophagy activity is related to steroidogenesis in LCs of dairy goats, which may ultimately influence the spermatogenesis and fertility of these animals.

Amodiaquine promotes testosterone production and de novo synthesis of cholesterol and triglycerides in Leydig cells

Testosterone is a hormone essential for male reproductive function. It is produced primarily by Leydig cells in the testicle through activation of steroidogenic acute regulatory protein and a series of steroidogenic enzymes, including a cytochrome P450 side-chain cleavage enzyme (cytochome P450 family 11 subfamily A member 1), 17α-hydroxylase (cytochrome P450 family 17 subfamily A member 1), and 3β-hydroxysteroid dehydrogenase. These steroidogenic enzymes are mainly regulated at the transcriptional level, and their expression is increased by the nuclear receptor 4A1. However, the effect on Leydig cell function of a small molecule-activating ligand, amodiaquine (AQ), is unknown. We found that AQ effectively and significantly increased testosterone production in TM3 and primary Leydig cells through enhanced expression of steroidogenic acute regulatory protein, cytochome P450 family 11 subfamily A member 1, cytochrome P450 family 17 subfamily A member 1, and 3β-hydroxysteroid dehydrogenase. Concurrently, AQ dose-dependently increased the expression of 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme in the cholesterol synthesis pathway, through induction of the transcriptional and DNA-binding activities of nuclear receptor 4A1, contributing to increased cholesterol synthesis in Leydig cells. Furthermore, AQ increased the expression of fatty acid synthase and diacylglycerol acyltransferase and potentiated de novo synthesis of fatty acids and triglycerides (TGs). Lipidomics profiling further confirmed a significant elevation of intracellular lipid and TG levels by AQ in Leydig cells. These results demonstrated that AQ effectively promotes testosterone production and de novo synthesis of cholesterol and TG in Leydig cells, indicating that AQ may be beneficial for treating patients with Leydig cell dysfunction and subsequent testosterone deficiency.

Successful transplantation of spermatogonial stem cells into the seminiferous tubules of busulfan-treated mice

Background

Spermatogonial stem cells (SSCs) in the testis are crucial for transferring genetic information to the next generation. Successful transplantation of SSCs to infertile men is an advanced therapeutic application in reproductive biology research.

Methods

In this experimental research, both in vitro and in vivo characterization of undifferentiated and differentiated SSCs were performed by morphology—immunocytochemistry (ICC), immunohistochemistry (IMH), Fluidigm Real-Time polymerase chain reaction (RT-PCR) and flow cytometry analysis. The isolated SSCs were finally microinjected into the rete testis of busulfan-treated mice.

The compact undifferentiated and more loosely connected round differentiated SSCs were isolated during testicular cell expansion from their specific feeder layer.

Results

ICC analysis indicated high and low expression levels of Zbtb16 in undifferentiated and differentiated germ cells. Also, IMH analysis showed different expression levels of Zbtb16 in the two different germ stem cell populations of the testicular tissue. While Fluidigm RT-PCR analysis indicated overexpression of the TAF4B germ cell gene, the expression of DAZL, VASA, and Zbtb16 were down-regulated during the differentiation of SSCs (P < 0.05). Also, flow cytometry analysis confirmed the significant downregulation of Itgb1 and Itga4 during differentiation. By transplantation of SSCs into busulfan-treated NOD/SCID mice, GFP-labeled sperm cells developed.

Conclusions

In the current study, we performed a transplantation technique that could be useful for the future microinjection of SSCs during infertility treatment and for studying in vivo differentiation of SSCs into sperm.

Spermatogonia (SSCs) in the testis transmit genetic information to the next generation. Successful SSC transplantation into infertile men is an advanced therapeutic application in reproductive biology research. In this experimental research, both in vitro and in vivo characterization of undifferentiated and differentiated SSCs were performed by morphology—immunocytochemistry (ICC), immunohistochemistry (IMH), Fluidigm Real-Time polymerase chain reaction (RT-PCR) and flow cytometry analysis. The isolated SSCs were finally microinjected into the rete testis of busulfan-treated mice. ICC analysis indicated high and low expression levels of Zbtb16 in undifferentiated and differentiated germ cells. IMH analysis showed different expression levels of Zbtb16 in both populations. Fluidigm RT-PCR analysis indicated overexpression of the TAF4B germ cell gene and the down-regulated expression of DAZL, VASA, and Zbtb16 during SSCs differentiation of (P < 0.05). Flow cytometry analysis confirmed the significant downregulation of Itgb1 and Itga4 during differentiation. By transplantation of SSCs into busulfan-treated NOD/SCID mice, GFP-labeled sperm cells developed. We performed a transplantation technique that could be useful for the future microinjection of SSCs during infertility treatment and for studying in vivo differentiation of SSCs into sperm. Data analysis confirmed that zbtb16 is expressed in the undifferentiated germ cells located on the basal membrane of seminiferous tubules and SSCs in vitro. Also, spermatogenesis was resumed, and fertility improved after transplantation of undifferentiated cells into busulfan-treated mice; thus, improvements in vitro SSCs transplantation, isolation and culture would be helpful in future clinical treatments to solve the reproductive problems of families influenced by infertility.

VCAM1-α4β1 integrin interaction mediates interstitial tissue reconstruction in 3-D re-aggregate culture of dissociated prepubertal mouse testicular cells

Roles of interstitial tissue in morphogenesis of testicular structures remain less well understood. To analyze the roles of CD34⁺ cells in the reconstruction of interstitial tissue containing Leydig cells (LCs), and testicular structures, we used 3D-reaggregate culture of dissociated testicular cells from prepubertal mouse. After a week of culture, adult Leydig cells (ALCs) were preferentially incorporated within CD34⁺ cell-aggregates, but fetal LCs (FLCs) were not. Immunofluorescence studies showed that integrins α4, α9 and β1, and VCAM1, one of the ligands for integrins α4β1 and α9β1, are expressed mainly in CD34⁺ cells and ALCs, but not in FLCs. Addition of function-blocking antibodies against each integrin and VCAM1 to the culture disturbed the reconstruction of testicular structures. Antibodies against α4 and β1 integrins and VCAM1 robustly inhibited cell-to-cell adhesion between testicular cells and between CD34⁺ cells. Cell-adhesion assays indicated that CD34⁺ cells adhere to VCAM1 through the interaction with α4β1 integrin. Live cell imaging showed that CD34⁺ cells adhered around ALC-aggregates. CD34⁺ cells on the dish moved toward the aggregates, extending filopodia, and entered into them, which was disturbed by VCAM1 antibody. These results indicate that VCAM1-α4β1 integrin interaction plays pivotal roles in formation of testicular interstitial tissues in vitro and also in vivo.

Inactivation of Wt1 causes pre-granulosa cell to steroidogenic cell transformation and defect of ovary development†

Wt1 gene encodes a nuclear transcription factor which is specifically expressed in ovarian granulosa cells and testicular Sertoli cells. Our previous studies demonstrated that Wt1 is required for the lineage specification of supporting cells and inactivation of Wt1 results in Sertoli cells to Leydig-like cells transformation. To test whether Wt1 is also involved in lineage maintenance of granulosa cells during ovary development, Wt1 was specifically deleted in pre-granulosa cells using Foxl2-cre. We found that the female Wt1-/flox; Foxl2-cre mice were infertile with atrophic ovaries and no growing follicles with multiple layers of granulosa cells were observed. A large number of 3β-HSD-positive steroidogenic cells were detected in ovaries of Wt1-/flox; Foxl2-cre mice during embryonic stage and these cells were derived from Foxl2-expressing pre-granulosa cells. The quantitative results showed the expression of granulosa cell marker genes (Foxl2, Follistatin) was downregulated and steroidogenic cell marker genes (3β-HSD, Cyp11a1, Star and Sf1) was dramatically increased in Wt1-/flox; Foxl2-cre ovaries. We also found that the meiosis of germ cells in Wt1-/flox; Foxl2-cre ovaries was delayed but not arrested. This study demonstrates that Wt1 is required for lineage maintenance of granulosa cells and inactivation of Wt1 results in pre-granulosa cells to steroidogenic cells transformation which in turn causes the defect of ovary development.

Advances in stem cell research for the treatment of primary hypogonadism

In Leydig cell dysfunction, cells respond weakly to stimulation by pituitary luteinizing hormone, and, therefore, produce less testosterone, leading to primary hypogonadism. The most widely used treatment for primary hypogonadism is testosterone replacement therapy (TRT). However, TRT causes infertility and has been associated with other adverse effects, such as causing erythrocytosis and gynaecomastia, worsening obstructive sleep apnoea and increasing cardiovascular morbidity and mortality risks. Stem-cell-based therapy that re-establishes testosterone-producing cell lineages in the body has, therefore, become a promising prospect for treating primary hypogonadism. Over the past two decades, substantial advances have been made in the identification of Leydig cell sources for use in transplantation surgery, including the artificial induction of Leydig-like cells from different types of stem cells, for example, stem Leydig cells, mesenchymal stem cells, and pluripotent stem cells (PSCs). PSC-derived Leydig-like cells have already provided a powerful in vitro model to study the molecular mechanisms underlying Leydig cell differentiation and could be used to treat men with primary hypogonadism in a more specific and personalized approach.

LncRNA FENDRR promotes apoptosis of Leydig cells in late-onset hypogonadism by facilitating the degradation of Nrf2

This study aimed to investigate the role of lncRNA FENDRR in apoptosis of Leydig cells and the further mechanism. The apoptosis of Leydig cells (TM3 cell line) was induced by H₂O₂-treatment and detected by flow cytometry. The function of FENDRR was determined by in vitro and in vivo silencing experiments. The mechanism of FENDRR in regulating the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) was assessed by RNA immunoprecipitation, RNA pull-down, and ubiquitination assays. FENDRR expression was up-regulated in H₂O₂-treated TM3 cells. Knockdown of FENDRR augmented Nrf2 and HO-1 protein levels and testosterone production in H₂O₂-treated TM3 cells, whereas the apoptosis rate and caspase 3 activity were decreased. Mechanically, FENDRR bound to Nrf2 and promoted its ubiquitination and degradation. Nrf2 overexpression reversed the effects FENDRR overexpression on apoptosis, caspase 3 activity, and testosterone concentration in H₂O₂-treated TM3 cells. The in vivo experiments showed that FENDRR silence increased serum testosterone level and improved testosterone-related anti-depression behaviors of late-onset hypogonadism (LOH) mice. Our findings suggested that FENDRR could promote apoptosis of Leydig cells in LOH partly through facilitating Nrf2 degradation.

Flutamide treatment reveals a relationship between steroidogenic activity of Leydig cells and ultrastructure of their mitochondria

Our present knowledge on interrelation between morphology/ultrastructure of mitochondria of the Leydig cell and its steroidogenic function is far from satisfactory and needs additional studies. Here, we analyzed the effects of blockade of androgen receptor, triggered by exposure to flutamide, on the expression of steroidogenic proteins (1) and ultrastructure of Leydig cells' constituents (2). We demonstrated that increase in the expression level of steroidogenic (StAR, CYP11A1, 3β-HSD, and CYP19A1) proteins (and respective mRNAs) in rat testicular tissue as well as elevation of intratesticular sex steroid hormone (testosterone and estradiol) levels observed in treated animals correspond well to morphological alterations of the Leydig cell ultrastructure. Most importantly, up-regulation of steroidogenic proteins' expression apparently correlates with considerable multiplication of Leydig cell mitochondria and subsequent formation of local mitochondrial networks. Interestingly, we showed also that the above-mentioned processes were associated with elevated transcription of Drp1 and Mfn2 genes, encoding proteins implicated in mitochondrial dynamics. Collectively, our studies emphasize the importance of mitochondrial homeostasis to the steroidogenic function of Leydig cells.

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.

Recent Progress in Discovering the Role of Carotenoids and Their Metabolites in Prostatic Physiology and Pathology with a Focus on Prostate Cancer-A Review-Part I: Molecular Mechanisms of Carotenoid Action

Among the vast variety of plant-derived phytochemicals, the group of carotenoids has continuously been investigated in order to optimize their potential application in the area of dietary intervention and medicine. One organ which has been especially targeted in many of these studies and clinical trials is the human prostate. Without doubt, carotenoids (and their endogenous derivatives—retinoids and other apo-carotenoids) are involved in intra- and intercellular signaling, cell growth and differentiation of prostate tissue. Due to the accumulation of new data on the role of different carotenoids such as lycopene (LC) and β-carotene (BC) in prostatic physiology and pathology, the present review aims to cover the past ten years of research in this area. Data from experimental studies are presented in the first part of the review, while epidemiological studies are disclosed and discussed in the second part. The objective of this compilation is to emphasize the present state of knowledge regarding the most potent molecular targets of carotenoids and their main metabolites, as well as to propose promising carotenoid agents for the prevention and treatment of prostatic diseases.

Effects of SPATA6 on proliferation, apoptosis and steroidogenesis of Hu sheep Leydig cells in vitro

This study aimed to investigate the expression pattern of spermatogenesis associated protein 6 (SPATA6) in Hu sheep testis and to ascertain the effects of SPATA6 on sheep Leydig cells (LCs) function linked to spermatogenesis. In the present study, we detected a 1970 bp cDNA fragment of SPATA6 included a 1467 bp coding sequence which encoded 487 amino acids. Meanwhile, sheep SPATA6 shared 51.70%-97.41% amino acid sequences with its orthologs compared with other species. In addition, SPATA6 was highly expressed in testis and localized in cytoplasm and nucleus of LCs as well as spermatogenic cells at different stages. Compared to the negative control (NC), SPATA6 interference promoted apoptosis of LCs with the increase of BAX/BCL-2 mRNA and protein levels, while the results of SPATA6 overexpression were on the contrary. Meanwhile, cell cycle was blocked at G2/M phase and CDK1 and CCNB1 were down-regulated after SPATA6 interference. SPATA6 overexpression induced cell cycle transfer G0/G1 into S and G2/M phase with upregulation of CDK1, CDK4, CCND1 and CCND2. Moreover, the secretion of testosterone hormone and the expression of StAR in LCs with SPATA6 overexpression were significantly promoted. Overall, our data suggest that SPATA6 is an important functional molecule of spermatogenesis, via regulating the proliferation, apoptosis and testosterone biosynthesis of Hu sheep LCs. These findings will enhance the understanding of the roles of SPATA6 in sheep spermatogenesis.

DNA damage contributes to transcriptional and immunological dysregulation of testicular cells during Chlamydia infection

Chlamydia is the most commonly reported sexually transmitted bacterial infection, with 127 million notifications worldwide each year. Both males and females are susceptible to the pathological impacts on fertility that Chlamydia infections can induce. However, male chlamydial infections, particularly within the upper reproductive tract, including the testis, are not well characterized. In this study, using mouse testicular cell lines, we examined the impact of infection on testicular cell lineage transcriptomes and potential mechanisms for this impact. The somatic cell lineages exhibited significantly fragmented genomes during infection. Likely resulting from this, each of the Leydig, Sertoli and germ cell lineages experienced extensive transcriptional dysregulation, leading to significant changes in cellular biological pathways, including interferon and germ-Sertoli cell signalling. The cell lineages, as well as isolated spermatozoa from infected mice, also contained globally hypomethylated DNA. Cumulatively, the DNA damage and epigenetic-mediated transcriptional dysregulation observed within testicular cells during chlamydial infection could result in the production of spermatozoa with abnormal epigenomes, resulting in previously observed subfertility in infected animals and congenital defects in their offspring.

Transplantation of encapsulated human Leydig-like cells: A novel option for the treatment of testosterone deficiency

Previous studies have demonstrated that the transplantation of alginate-poly-ʟ-lysine-alginate (APA)-encapsulated rat Leydig cells (LCs) provides a promising approach for treating testosterone deficiency (TD). Nevertheless, LCs have a limited capacity to proliferate, limiting the efficacy of LC transplantation therapy. Here, we established an efficient differentiation system to obtain functional Leydig-like cells (LLCs) from human stem Leydig cells (hSLCs). Then we injected APA-encapsulated LLCs into the abdominal cavities of castrated mice without an immunosuppressor. The APA-encapsulated cells survived and partially restored testosterone production for 90 days in vivo. More importantly, the transplantation of encapsulated LLCs ameliorated the symptoms of TD, such as fat accumulation, muscle atrophy and adipocyte accumulation in bone marrow. Overall, these results suggest that the transplantation of encapsulated LLCs is a promising new method for testosterone supplementation with potential clinical applications in TD.