Prolonged exposure to dexamethasone alters the proteome and cellular phenotype of human testicular peritubular cells.

Human testicular peritubular cells (HTPCs) are smooth muscle cells, which in the testis form a small compartment surrounding the seminiferous tubules. Contractions of HTPCs are responsible for sperm transport, HTPCs contribute to spermatogenesis, have immunological roles and are a site of glucocorticoid receptor expression. Importantly, HTPCs maintain their characteristics in vitro, and thus can serve as an experimental window into the male gonad. Previously we reported consequences of 3-day treatment with Dexamethasone (Dex), a synthetic glucocorticoid and multi-purpose anti-inflammatory drug. However, as glucocorticoid therapies in man often last longer, we now studied consequences of a prolonged 7-day exposure to 1 µM Dex. Combining live cell imaging with quantative proteomics of samples taken from men, we confirmed our recent findings but more importantly, found numerous novel proteomic alterations induced by prolonged Dex treatment. The comparison of the 7-day treatment with the 3-day treatment dataset revealed that extracellular matrix- and focal adhesion-related proteins become more prominent after 7 days of treatment. In contrast, extended stimulation is, for example, associated with a decrease of proteins related to cholesterol and steroid metabolism. Our dataset, which describes phenotypic and proteomic alterations, is a valuable resource for further research projects investigating effects of Dex on human testicular cells.

Human spermatogonial stem cells and their niche in male (in)fertility: novel concepts from single-cell RNA-sequencing.

The amount of single-cell RNA-sequencing (scRNA-seq) data produced in the field of human male reproduction has steadily increased. Transcriptional profiles of thousands of testicular cells have been generated covering the human neonatal, prepubertal, pubertal and adult period as well as different types of male infertility; the latter include non-obstructive azoospermia, cryptozoospermia, Klinefelter syndrome and azoospermia factor deletions. In this review, we provide an overview of transcriptional changes in different testicular subpopulations during postnatal development and in cases of male infertility. Moreover, we review novel concepts regarding the existence of spermatogonial and somatic cell subtypes as well as their crosstalk and provide corresponding marker genes to facilitate their identification. We discuss the potential clinical implications of scRNA-seq findings, the need for spatial information and the necessity to corroborate findings by exploring other levels of regulation, including at the epigenetic or protein level.

Apelin is found in human sperm and testis and is raised in inflammatory pathological conditions.

Apelin/APJ receptor (R) is involved in many oxidative stress-induced pathological conditions. Since this system is not yet explored in male reproduction, we studied apelin/APJ-R in human semen and testis. Semen of 41 infertile patients with varicocele, genitourinary infections, unexplained infertility and 12 fertile men was analysed (WHO guidelines, 2021). Apelin was quantified by ELISA in seminal fluid and spermatozoa, interleukin (IL)-1ß in seminal fluid. Apelin/APJ-R were immunolocalized in spermatozoa and testis. Apelin was present in spermatozoa and its levels were negatively correlated with normal sperm morphology% (r = -0.857; p < 0.001), and positively with IL-1ß levels (r = 0.455; p < 0.001). Apelin and IL-1ß concentrations were increased in patients' samples with varicocele (apelin p < 0.01; IL-1ß p < 0.05) and infections (apelin p < 0.01; IL-1ß p < 0.001). By logistic regression analysis, apelin (OR 1.310; p = 0.011) and IL-1ß (OR 1.572; p = 0.005) were predictors of inflammatory diseases (varicocele, infections). Apelin and APJ-R immunofluorescence labels were weak in sperm tail of fertile men and intense along tail, cytoplasmic residues and post-acrosomal sheath of sperm from infertile men. In testis, apelin and APJ-R labels were evident in Leydig cells and weak inside the seminiferous tubule. Apelin/APJ-R system is present in human spermatozoa and testicular tissue and probably involved in human fertility.

A Determination of p97/VCP (Valosin Containing Protein) and SVIP (Small VCP Interacting Protein) Expression Patterns in Human Testis.

Background and Objectives: The ubiquitin proteosome system (UPS) is a non-lysosomal pathway that functions in all eukaryotes. The transport of polyubiquitinated proteins to proteosomes takes place via the p97/Valosin-containing protein (VCP) chaperone protein. The p97/VCP binds to polyubiquitinated proteins, allowing these proteins to reach the proteasome and, thus, their destruction. In the case of p97/VCP deficiency, ubiquitinated proteins accumulate in the cell cytoplasm, and their subsequent failure to break down produces various pathological conditions. Small VCP interacting protein (SVIP) and p97/VCP proteins have not been studied in human testicular tissues from different postnatal periods. Therefore, in our study, we aimed to examine the expression of SVIP and p97/VCP in postnatal human testicular tissues. Our study aimed to contribute to further studies on the use of these proteins as testicular cell biomarkers in cases of unexplained male infertility. Materials and Methods: Immunohistochemical studies with the aim of determining the expression of p97/VCP and SVIP proteins in neonatal, prepubertal, pubertal, adult, and geriatric human testis tissues were performed. Results: In testicular sections obtained from a neonatal group, p97/VCP and SVIP were localized in different testicular and interstitial cells, and the lowest expression was observed in this group. While the expressions of these proteins were low in the neonatal period, they increased gradually in the prepubertal, pubertal and adult periods. The expression of p97/VCP and SVIP, which peaked in adulthood, showed a significant decrease in the geriatric period. Conclusions: As a result, the expression of p97/VCP and SVIP correlated with the increase in age, but it decreased significantly in older groups.

Human Testis Phosphoproteome Reveals Kinases as Potential Targets in Spermatogenesis and Testicular Cancer.

Spermatogenesis is a complex cell differentiation process that includes marked genetic, cellular, functional and structural changes. It requires tight regulation, because disturbances in any of the spermatogenic processes would lead to fertility deficiencies as well as disorders in offspring. To increase our knowledge of signal transduction during sperm development, we carried out a large-scale identification of the phosphorylation events that occur in the human male gonad. Metal oxide affinity chromatography using TiO2 combined with LC-MS/MS was conducted to profile the phosphoproteome of adult human testes with full spermatogenesis. A total of 8187 phosphopeptides derived from 2661 proteins were identified, resulting in the most complete report of human testicular phosphoproteins to date. Phosphorylation events were enriched in proteins functionally related to spermatogenesis, as well as to highly active processes in the male gonad, such as transcriptional and translational regulation, cytoskeleton organization, DNA packaging, cell cycle and apoptosis. Moreover, 174 phosphorylated kinases were identified. The most active human protein kinases in the testis were predicted both by the number of phosphopeptide spectra identified and the phosphorylation status of the kinase activation loop. The potential function of cyclin-dependent kinase 12 (CDK12) and p21-activated kinase 4 (PAK4) has been explored by in silico, protein-protein interaction analysis, immunodetection in testicular tissue, and a functional assay in a human embryonal carcinoma cell line. The colocalization of CDK12 with Golgi markers suggests a potential crucial role of this protein kinase during sperm formation. PAK4 has been found expressed in human spermatogonia, and a role in embryonal carcinoma cell response to apoptosis has been observed. Together, our protein discovery analysis confirms that phosphoregulation by protein kinases is highly active in sperm differentiation and opens a window to detailed characterization and validation of potential targets for the development of drugs modulating male fertility and tumor behavior.

Population-specific, recent positive directional selection suggests adaptation of human male reproductive genes to different environmental conditions.

BACKGROUND: Recent human transcriptomic analyses revealed a very large number of testis-enriched genes, many of which are involved in spermatogenesis. This comprehensive transcriptomic data lead us to the question whether positive selection was a decisive force influencing the evolution and variability of testis-enriched genes in humans. We used two methodological approaches to detect different levels of positive selection, namely episodic positive diversifying selection (i.e., past selection) in the human lineage within primate phylogeny, potentially driven by sperm competition, and recent positive directional selection in contemporary human populations, which would indicate adaptation to different environments. RESULTS: In the human lineage (after correction for multiple testing) we found that only the gene TULP2, for which no functional data are yet available, is subject to episodic positive diversifying selection. Using less stringent statistical criteria (uncorrected p-values), also the gene SPATA16, which has a pivotal role in male fertility and for which episodes of adaptive evolution have been suggested, also displays a putative signal of diversifying selection in the human branch. At the same time, we found evidence for recent positive directional selection acting on several human testis-enriched genes (MORC1, SLC9B1, ROPN1L, DMRT1, PLCZ1, RNF17, FAM71D and WBP2NL) that play important roles in human spermatogenesis and fertilization. Most of these genes are population-specifically under positive selection. CONCLUSION: Episodic diversifying selection, possibly driven by sperm competition, was not an important force driving the evolution of testis-enriched genes in the human lineage. Population-specific, recent positive directional selection suggests an adaptation of male reproductive genes to different environmental conditions. Positive selection acts on eQTLS and sQTLs, indicating selective effects on important gene regulatory functions. In particular, the transcriptional diversity regulated by sQTLs in testis-enriched genes may be important for spermatocytes to respond to environmental and physiological stress.

Integration and reanalysis of transcriptomics and methylomics data derived from blood and testis tissue of men with 47,XXY Klinefelter syndrome indicates the primary involvement of Sertoli cells in the testicular pathogenesis.

Klinefelter syndrome (KS; 47,XXY) is the most common sex chromosomal anomaly and causes a multitude of symptoms. Often the most noticeable symptom is infertility caused by azoospermia with testicular histology showing hyalinization of tubules, germ cells loss, and Leydig cell hyperplasia. The germ cell loss begins early in life leading to partial hyalinization of the testis at puberty, but the mechanistic drivers behind this remain poorly understood. In this systematic review, we summarize the current knowledge on developmental changes in the cellularity of KS gonads supplemented by a comparative analysis of the fetal and adult gonadal transcriptome, and blood transcriptome and methylome of men with KS. We identified a high fraction of upregulated genes that escape X-chromosome inactivation, thus supporting previous hypotheses that these are the main drivers of the testicular phenotype in KS. Enrichment analysis showed overrepresentation of genes from the X- and Y-chromosome and testicular transcription factors. Furthermore, by re-evaluation of recent single cell RNA-sequencing data originating from adult KS testis, we found novel evidence that the Sertoli cell is the most affected cell type. Our results are consistent with disturbed cross-talk between somatic and germ cells in the KS testis, and with X-escapee genes acting as mediators.

Effect of recombinant human vascular endothelial growth factor on testis tissue xenotransplants from prepubertal boys: a three-case study.

RESEARCH QUESTION: Does recombinant human vascular endothelial growth factor (VEGF-165) improve the efficiency of human immature testis tissue (ITT) xenotransplantation? DESIGN: ITT fragments from three prepubertal boys were cultured for 5 days with VEGF-165 or without (control) before xenotransplantation into the testes of immunodeficient mice. Xenotransplants were recovered at 4 and 9 months post-transplantation and vascularization, seminiferous tubule integrity, number of spermatogonia and germ cell differentiation were evaluated by histology and immunohistochemistry. RESULTS: Transplants from donor 1 and donor 2 treated with VEGF demonstrated higher vascular surface (P = 0.004) and vessel density (P = 0.011) overall and contained more intact seminiferous tubules (P = 0.039) with time, compared with controls. The number of spermatogonia was increased over time (P < 0.001) irrespective of treatment and donor, whereas, for the VEGF-treated transplants, the increase was even higher over time (P = 0.020). At 9 months, spermatocytes were present in the xenotransplants, irrespective of treatment. No transplants could be recovered from donor 3, who had already received treatment with cyclosporine for aplastic anaemia before biopsy. CONCLUSIONS: In-vitro pre-treatment of human prepubertal testis tissue with VEGF improved transplant vascularization in two out of three cases, resulting in improved seminiferous tubule integrity and spermatogonial survival during xenotransplantation. Although further studies are warranted, we suggest VEGF to be considered as a factor for improving the efficiency of immature testis tissue transplantation in the future.

Reassembly of adult human testicular cells: can testis cord-like structures be created in vitro?

STUDY QUESTION: Can enzymatically dispersed testicular cells from adult men reassemble into seminiferous cord-like structures in vitro? SUMMARY ANSWER: Adult human testicular somatic cells reassembled into testicular cord-like structures via dynamic interactions of Sertoli and peritubular cells. WHAT IS KNOWN ALREADY: In vitro approaches using dispersed single cell suspensions of human testes to generate seminiferous tubule structures and to initiate their functionality have as yet shown only limited success. STUDY DESIGN, SIZE, DURATION: Testes from 15 adult gender dysphoria patients (mean ± standard deviation age 35 ± 9.3 years) showing spermatogonial arrest became available for this study after sex-reassignment surgery. In vitro primary testicular somatic cell cultures were generated to explore the self-organizing ability of testicular somatic cells to form testis cords over a 2-week period. Morphological phenotype, protein marker expression and temporal dynamics of cell reassembly were analyzed. PARTICIPANTS/MATERIALS, SETTING, METHODS: Cell suspensions obtained by two-step enzymatic digestion were plated onto glass coverslips in 24-well plates. To obtain adherent somatic cells, the supernatant was discarded on Day 2. The culture of the attached cell population was continued. Reassembly into cord-like structures was analyzed daily by microscopic observations. Endpoints were qualitative changes in morphology. Cell types were characterized by phase-contrast microscopy and immunohistochemistry. Dynamics of cord formation were recorded by time-lapse microscopy. MAIN RESULTS AND THE ROLE OF CHANCE: Primary adult human testicular cells underwent sequential morphological changes including compaction and reaggregation resulting in round or elongated cord-like structures. Time-lapse video recordings within the first 4 days of culture revealed highly dynamic processes of migration and coalescence of reaggregated cells. The cellular movements were mediated by peritubular cells. Immunohistochemical analysis showed that both SRY-related high mobility box 9-positive Sertoli and α-smooth muscle actin-positive peritubular myoid cells interacted and contributed to cord-like structure formation. LARGE SCALE DATA: Not applicable. LIMITATIONS, REASONS FOR CAUTION: Owing to scarcity of normal human testicular tissue, testes from gender dysphoria patients were used in the study. The regressed status might influence the experimental responses of primary cells. We observed basic morphological features resembling in vivo testicular cords, however, the proof of functionality (e.g. support of germ cells) will need further studies. WIDER IMPLICATIONS OF THE FINDINGS: The proposed in vitro culture system may open opportunities for examination of testicular cell interactions during testicular tubulogenesis. Further refinement of our approach may enable initiation of ex vivo spermatogenesis. STUDY FUNDING/COMPETING INTERESTS: The work was supported by EU-FP7-PEOPLE-2013-ITN 603568: 'Growsperm'. No conflict of interests is declared.

Ca2+ Signaling and IL-8 Secretion in Human Testicular Peritubular Cells Involve the Cation Channel TRPV2.

Peritubular cells are part of the wall of seminiferous tubules in the human testis and their contractile abilities are important for sperm transport. In addition, they have immunological roles. A proteomic analysis of isolated human testicular peritubular cells (HTPCs) revealed expression of the transient receptor potential channel subfamily V member 2 (TRPV2). This cation channel is linked to mechano-sensation and to immunological processes and inflammation in other organs. We verified expression of TRPV2 in peritubular cells in human sections by immunohistochemistry. It was also found in other testicular cells, including Sertoli cells and interstitial cells. In cultured HTPCs, application of cannabidiol (CBD), a known TRPV2 agonist, acutely induced a transient increase in intracellular Ca2+ levels. These Ca2+ transients could be blocked both by ruthenium red, an unspecific Ca2+ channel blocker, and tranilast (TRA), an antagonist of TRPV2, and were also abolished when extracellular Ca2+ was removed. Taken together this indicates functional TRPV2 channels in peritubular cells. When applied for 24 to 48 h, CBD induced expression of proinflammatory factors. In particular, mRNA and secreted protein levels of the proinflammatory chemokine interleukin-8 (IL-8/CXCL8) were elevated. Via its known roles as a major mediator of the inflammatory response and as an angiogenic factor, this chemokine may play a role in testicular physiology and pathology.

[Expression of IQCG in the human testis and its correlation with asthenospermia].

OBJECTIVE: To investigate the expression and location of IQ motif-containing G (IQCG) in the human testis, compare its expression in normal-motility sperm with that in the sperm of asthenospermia patients, and explore its possible mechanisms and its correlation with fertility. METHODS: The expression of the IQCG gene in the human testis was detected by RT-PCR and its location in the testis and sperm was determined by immunohistochemistry and immunofluorescence staining. Semen samples were collected from normal males, patients with asthenospermia, and fertile men that succeeded in artificial insemination with donor's sperm (AID), followed by analysis of the IQCG protein expression in different groups of samples by Western blot. RESULTS: Immunohistochemistry showed that IQCG was extensively expressed in the human testis, in the spermatocytes and spermatids, specifically in the sperm tail, weakly expressed or absent in the spermatogonial stem cells, and strongly expressed in the spermatogonial cells. The expression of IQCG was significantly lower in the asthenospermia patients than in the normal males (P= 0.041). Western blot manifested that IQCG was expressed in the semen of all the three groups of subjects, with statistically significant differences between the normal men and severe asthenospermia patients (P = 0.032) as well as between the fertile males and the severe asthenospermia group (P = 0.027) . CONCLUSIONS: IQCG may act on human sperm motility and its abnormal expression possibly reduces sperm motility and fertility. An insight into its action mechanisms may shed some new light on the etiology and treatment of asthenospermia.

Three-dimensional testicular organoid: a novel tool for the study of human spermatogenesis and gonadotoxicity in vitro.

Existing methods for evaluating the potential gonadotoxicity of environmental agents and pharmaceutical compounds rely heavily on animal studies. The current gold standard in vivo functional assays in animals are limited in their human predictive capacity. In addition, existing human two-dimensional in vitro models of testicular toxicity do not accurately reflect the in vivo situation. A more reliable testicular in vitro model system is needed to better assess the gonadotoxic potential of drugs prior to progression into clinical trials. The overall goal of this study was to develop a three-dimensional (3D) in vitro human testis organoid culture system for use as both a predictive first tier drug-screening tool and as a model of human testicular function. Multicellular human testicular organoids composed of Spermatogonial Stem Cells, Sertoli, Leydig and peritubular cells were created and evaluated over time for morphology, viability, androgen production and ability to support germ cell differentiation. Enzyme-linked immunosorbent assay measurements confirmed that the organoids produced testosterone continuously with and without hCG stimulation. Upregulation of postmeiotic genes including PRM1 and Acrosin, detected by quantitative-PCR, digital PCR and Immunofluorescence, indicated the transition of a small percentage of diploid to haploid germ cells. As a novel screening tool for reproductive toxicity, 3D organoids were exposed to four chemotherapeutic drugs, and they responded in a dose-dependent manner and maintained IC50 values significantly higher than 2D cultures. This 3D human testis organoid system has the potential to be used as a novel testicular toxicity-screening tool and in vitro model for human spermatogenesis.

Single-cell gene expression analysis reveals diversity among human spermatogonia.

STUDY QUESTION: Is the molecular profile of human spermatogonia homogeneous or heterogeneous when analysed at the single-cell level? SUMMARY ANSWER: Heterogeneous expression profiles may be a key characteristic of human spermatogonia, supporting the existence of a heterogeneous stem cell population. WHAT IS KNOWN ALREADY: Despite the fact that many studies have sought to identify specific markers for human spermatogonia, the molecular fingerprint of these cells remains hitherto unknown. STUDY DESIGN, SIZE, DURATION: Testicular tissues from patients with spermatogonial arrest (arrest, n = 1) and with qualitatively normal spermatogenesis (normal, n = 7) were selected from a pool of 179 consecutively obtained biopsies. Gene expression analyses of cell populations and single-cells (n = 105) were performed. Two OCT4-positive individual cells were selected for global transcriptional capture using shallow RNA-seq. Finally, expression of four candidate markers was assessed by immunohistochemistry. PARTICIPANTS/MATERIALS, SETTING, METHODS: Histological analysis and blood hormone measurements for LH, FSH and testosterone were performed prior to testicular sample selection. Following enzymatic digestion of testicular tissues, differential plating and subsequent micromanipulation of individual cells was employed to enrich and isolate human spermatogonia, respectively. Endpoint analyses were qPCR analysis of cell populations and individual cells, shallow RNA-seq and immunohistochemical analyses. MAIN RESULTS AND THE ROLE OF CHANCE: Unexpectedly, single-cell expression data from the arrest patient (20 cells) showed heterogeneous expression profiles. Also, from patients with normal spermatogenesis, heterogeneous expression patterns of undifferentiated (OCT4, UTF1 and MAGE A4) and differentiated marker genes (BOLL and PRM2) were obtained within each spermatogonia cluster (13 clusters with 85 cells). Shallow RNA-seq analysis of individual human spermatogonia was validated, and a spermatogonia-specific heterogeneous protein expression of selected candidate markers (DDX5, TSPY1, EEF1A1 and NGN3) was demonstrated. LIMITATIONS, REASONS FOR CAUTION: The heterogeneity of human spermatogonia at the RNA and protein levels is a snapshot. To further assess the functional meaning of this heterogeneity and the dynamics of stem cell populations, approaches need to be developed to facilitate the repeated analysis of individual cells. WIDER IMPLICATIONS OF THE FINDINGS: Our data suggest that heterogeneous expression profiles may be a key characteristic of human spermatogonia, supporting the model of a heterogeneous stem cell population. Future studies will assess the dynamics of spermatogonial populations in fertile and infertile patients. LARGE SCALE DATA: RNA-seq data is published in the GEO database: GSE91063. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Max Planck Society and the Deutsche Forschungsgemeinschaft DFG-Research Unit FOR 1041 Germ Cell Potential (grant numbers SCHO 340/7-1, SCHL394/11-2). The authors declare that there is no conflict of interest.

Comparison of global gene expression profiles of microdissected human foetal Leydig cells with their normal and hyperplastic adult equivalents.

STUDY QUESTION: Do human adult Leydig cells (ALCs) within hyperplastic micronodules display characteristics of foetal LCs (FLCs)? SUMMARY ANSWER: The gene expression profiles of FLCs and all ALC subgroups were clearly different, but there were no significant differences in expressed genes between the normally clustered and hyperplastic ALCs. WHAT IS KNOWN ALREADY: LCs are the primary androgen producing cells in males throughout development and appear in chronologically distinct populations; FLCs, neonatal LCs and ALCs. ALCs are responsible for progression through puberty and for maintenance of reproductive functions in adulthood. In patients with reproductive problems, such as infertility or testicular cancer, and especially in men with high gonadotrophin levels, LC function is often impaired, and LCs may cluster abnormally into hyperplastic micronodules (defined as clusters of >15 LCs in a cross-section). STUDY DESIGN, SIZE, DURATION: A genome-wide microarray study of LCs microdissected from human foetal and adult tissue samples (n = 12). Additional tissue specimens (n = 15) were used for validation of the mRNA expression data at the protein level. PARTICIPANTS/MATERIALS, SETTING, METHODS: Frozen human tissue samples were used for the microarray study, including morphologically normal foetal (gestational week 10-11) testis samples, and adult testis specimens with normal LC distribution, LC micronodules or LC micronodules adjacent to hCG-producing testicular germ cell tumours. Transcriptome profiling was performed on Agilent whole human genome microarray 4 × 44 K chips. Microarray data pre-processing and statistical analysis were performed using the limma R/Bioconductor package in the R software, and differentially expressed genes were further analysed for gene set enrichment using the DAVID Bioinformatics software. Selected genes were studied at the protein level by immunohistochemistry. MAIN RESULTS AND THE ROLE OF CHANCE: The transcriptomes of FLCs and ALCs differed significantly from each other, whereas the profiles of the normally clustered and hyperplastic ALCs were similar despite morphological heterogeneity. The study revealed several genes not known previously to be expressed in LCs during early development, including sulfotransferase family 2A member 1 (SULT2A1), WNT1-inducible signalling pathway protein 2 (WISP2), hydroxyprostaglandin dehydrogenase (HPGD) and insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1), whose expression changes were validated at the protein level. LARGE SCALE DATA: The transcriptomic data are deposited in ArrayExpress (accession code E-MTAB-5453). LIMITATIONS, REASONS FOR CAUTION: The small number of biological replicates and the necessity of RNA amplification due to the scarcity of human tissues, especially foetal specimens, are the main limitations of the study. Heterogeneous subpopulations of LCs within micronodules were not discriminated during microdissection and might have affected the expression profiling. The study was constrained by the lack of availability of truly normal controls. Testis samples used as 'controls' displayed complete spermatogenesis and were from patients with germ cell neoplasia but with undetectable hCG and normal hormone levels. WIDER IMPLICATIONS OF THE FINDINGS: The changes in LC morphology and function observed in patients with reproductive disorders possibly reflect subtle changes in the expression of many genes rather than regulatory changes of single genes or pathways. The study provides new insights into the development and maturation of human LCs by the identification of a number of potential functional markers for FLC and ALC. STUDY FUNDING AND COMPETING INTEREST(S): The study was supported by research grants from the Danish Cancer Society, the Capital Region's Research Fund for Health Research, Rigshospitalet's research funds, the Villum Kann Rasmussen Foundation, the Danish Innovation Fund, ReproUnion, Kirsten and Freddy Johansen's foundation and the Novo Nordisk Foundation. None of the funding agencies had any influence on the study. The authors declare no conflicts of interest.

Parallel assessment of the effects of bisphenol A and several of its analogs on the adult human testis.

STUDY QUESTION: Are bisphenol A (BPA) and BPA analogs (BPA-A) safe for male human reproductive function? SUMMARY ANSWER: The endocrine function of human testes explants [assessed by measuring testosterone and insulin-like factor 3 (INSL3)] was impacted by exposure of the human adult testis explants to BPA/BPA-A. WHAT IS KNOWN ALREADY: The few epidemiologic studies performed suggest that bisphenols have potential endocrine disruptive properties, but they did not identify clear and direct patterns of endocrine disruption. STUDY DESIGN, SIZE, DURATION: Adult human testis explants in culture were exposed to BPA and the analogs bisphenol F (BPF), bisphenol S (BPS), bisphenol E (BPE), bisphenol B (BPB) and bisphenol A diglycidyl ether (BADGE) at 10-9-10-5 M for 24 or 48 h. PARTICIPANTS/MATERIALS, SETTING, METHODS: Human adult testes were obtained from prostate cancer patients who had no hormone therapy, or from multiorgan donors. After ex vivo exposure to the investigated bisphenols, the measured outcomes were related to histopathology (gross morphology and germ cell viability determined by anti-caspase three immunohistochemistry), and the levels of testosterone, INSL3 and inhibin B were measured using immunoassays. The levels of mRNA encoding key enzymes of bisphenol biotransformation were investigated by quantitative PCR: UGT2B15 UDP (glucuronosyltransferase two family, polypeptide B15), GUSB (glucuronidase beta), SULT1A1 and 3 (sulfotransferase family 1 A member 1 and 3) and STS (steroid sulfatase). MAIN RESULTS AND THE ROLE OF CHANCE: A significant dose-dependent inhibition was found between testosterone levels measured in the culture medium and concentrations of BPA (P = 0.00778 at 24 h and P = 0.0291 at 48 h), BPE (P = 0.039) and BPF (P = 0.00663). The observed BPA and BPA-A-induced inhibition of testosterone production varied according to duration of exposure and BPA/BPA-A concentrations. BPA (10-9 M; P < 0.05), BPB (10-9 M; P < 0.05), BPS (10-9 and 10-8 M; P < 0.05) and BADGE (10-5 M; P < 0.05) increased Leydig cell INSL3 production. By contrast, BPE dose dependently inhibited INSL3 (P = 0.0372). Conversely, Sertoli cell function (inhibin B) and germ cell viability were not significantly affected by either bisphenols. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Environmental compounds cannot be deliberately administered to men, justifying the use of an ex vivo approach. A relatively low number of testes samples were available for analysis (n = 3, except for testosterone secretion with n = 5). The active concentrations of BPA and BPA-A used in the study were higher than those found in human biological fluids. WIDER IMPLICATIONS OF THE FINDINGS: Under our experimental conditions, direct exposure to BPA or BPA-A can result in endocrine disturbance in the adult human testis. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by Inserm (Institut National de la Santé et de la Recherche Médicale), EHESP-School of Public Health, University of Rennes1, by grants from the Agence Nationale de la Recherche (ANR; grant#ANR-13-CESA-0012-03 NEWPLAST) and Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail (ANSES; grant#EST-2010/2/046 (BPATESTIS)). All authors declare they have no current or potential competing financial interests.

Current insights into the sulfatase pathway in human testis and cultured Sertoli cells.

Within the human testis, large amounts of sulfated steroid hormones are produced. As shown in breast tissue and placenta, these might not only be excretion intermediates, but re-activated in target cells by steroid sulfatase (STS). This process is called sulfatase pathway and may play a pivotal role in para- and/or intracrine regulation by creating a local supply for steroid hormones. This requires a facilitated transport via uptake carriers and efflux transporters as these hydrophilic molecules cannot pass the cell membrane. Moreover, blood-testis barrier formation in the testis requires a transport through Sertoli cells (SCs) to reach germ cells (GCs). Sertoli cells are therefore expected to play a key role as gate-keepers for sulfatase pathway in human seminiferous epithelium. We analyzed the mRNA and protein expression of uptake carriers and efflux transporters like organic anion-transporting polypeptides (OATP2B1, OATP3A1) and multidrug resistance-related proteins (MRP1, MRP4) in testicular tissue and cultured Sertoli cells (FS1, HSEC). Additionally, expression pattern of STS as well as sulfonating enzymes (SULTs) were assessed. OATP2B1, OATP3A1 and STS were detected in SCs as well as GCs, whereas MRP1 is only expressed in SCs, and SULT1E1 only in Leydig cells, respectively. By transcellular transport of [H3]DHEAS in HSEC, we showed a functional transport of sulfated steroids in vitro. Our data indicate that steroid synthesis via sulfatase pathway in Sertoli cells in vivo and in vitro is possible and may contribute to paracrine and intracrine regulation employing the local supply of sulfated and free steroid hormones inside seminiferous tubules.

Regulation of Translocator Protein 18 kDa (TSPO) Expression in Rat and Human Male Germ Cells.

Translocator protein 18 kDa (TSPO) is a high affinity cholesterol- and drug-binding protein highly expressed in steroidogenic cells, such as Leydig cells, where it plays a role in cholesterol mitochondrial transport. We have previously shown that TSPO is expressed in postnatal day 3 rat gonocytes, precursors of spermatogonial stem cells. Gonocytes undergo regulated phases of proliferation and migration, followed by retinoic acid (RA)-induced differentiation. Understanding these processes is important since their disruption may lead to the formation of carcinoma in situ, a precursor of testicular germ cell tumors (TGCTs). Previously, we showed that TSPO ligands do not regulate gonocyte proliferation. In the present study, we found that TSPO expression is downregulated in differentiating gonocytes. Similarly, in F9 embryonal carcinoma cells, a mouse TGCT cell line with embryonic stem cell properties, there is a significant decrease in TSPO expression during RA-induced differentiation. Silencing TSPO expression in gonocytes increased the stimulatory effect of RA on the expression of the differentiation marker Stra8, suggesting that TSPO exerts a repressive role on differentiation. Furthermore, in normal human testes, TSPO was located not only in Leydig cells, but also in discrete spermatogenic phases such as the forming acrosome of round spermatids. By contrast, seminomas, the most common type of TGCT, presented high levels of TSPO mRNA. TSPO protein was expressed in the cytoplasmic compartment of seminoma cells, identified by their nuclear expression of the transcription factors OCT4 and AP2G. Thus, TSPO appears to be tightly regulated during germ cell differentiation, and to be deregulated in seminomas, suggesting a role in germ cell development and pathology.

The total number of Leydig and Sertoli cells in the testes of men across various age groups - a stereological study.

The aim of this study was to estimate the total number of Sertoli and Leydig cells in testes from male subjects across the human lifespan, using an optimized stereological method for cell-counting. In comparison with many other organs, estimation of the total cell numbers in the testes is particularly sensitive to methodological problems. Therefore, using the optical fractionator technique and a sampling design specifically optimized for human testes, we estimated the total number of Sertoli and Leydig cells in the testes from 26 post mortem male subjects ranging in age from 16 to 80 years. The mean unilateral total number of Sertoli cells was 407 × 10(6) [range: 86 × 10(6) to 665 × 10(6) , coefficient of variation (CV) = 0.33], and the mean unilateral total number of Leydig cells was 99 × 10(6) (range: 47 × 10(6) to 245 × 10(6) , CV = 0.48). There was a significant decline in the number of Sertoli cells with age; no such decline was found for Leydig cells. Quantitative stereological analysis of post mortem tissue may help understand the influence of age or disease on the number of human testicular cells.

Human sperm liver receptor homolog-1 (LRH-1) acts as a downstream target of the estrogen signaling pathway.

In the last decade, the study of human sperm anatomy, at molecular level, has revealed the presence of several nuclear protein receptors. In this work, we examined the expression profile and the ultrastructural localization of liver receptor homolog-1 (LRH-1) in human spermatozoa. We evidenced the presence of the receptor by Western blotting and real time-RT-PCR. Furthermore, we used immunogold electron microscopy to investigate the sperm anatomical regions containing LRH-1. The receptor was mainly located in the sperm head, whereas its expression was reduced in the neck and across the tail. Interestingly, we observed the presence of LRH-1 in different stages of testicular germ cell development by immunohistochemistry. In somatic cells, it has been suggested that the LRH-1 pathway is tightly linked with estrogen signaling and the important role of estradiol has been widely studied in sperm cells. To assess the significance of LRH-1 in male gametes and to deepen understanding of the role of estrogens in these cells, we investigated important sperm features such as motility, survival and capacitation. Spermatozoa were treated with 10 nm estradiol and the inhibition of LRH-1 reversed the estradiol stimulatory action. From our data, we discovered that human spermatozoa can be considered a new site of expression for LRH-1, evidencing its role in sperm motility, survival and cholesterol efflux. Furthermore, we may presume that in spermatozoa the LRH-1 effects are closely integrated with the estrogen signaling, supporting LRH-1 as a downstream effector of the estradiol pathway on some sperm functions.

WITHDRAWN: Comparative proteome analysis of human testis from newborn, young adult, and aged men identified spermatogenesis-associated proteins.

Ahead of Print article withdrawn by publisher.