Blood-testis barrier: a review on regulators in maintaining cell junction integrity between Sertoli cells

The blood-testis barrier (BTB) is formed adjacent to the seminiferous basement membrane. It is a distinct ultrastructure, partitioning testicular seminiferous epithelium into apical (adluminal) and basal compartments. It plays a vital role in developing and maturing spermatocytes into spermatozoa via reorganizing its structure. This enables the transportation of preleptotene spermatocytes across the BTB, from basal to adluminal compartments in the seminiferous tubules. Several bioactive peptides and biomolecules secreted by testicular cells regulate the BTB function and support spermatogenesis. These peptides activate various downstream signaling proteins and can also be the target themself, which could improve the diffusion of drugs across the BTB. The gap junction (GJ) and its coexisting junctions at the BTB maintain the immunological barrier integrity and can be the "gateway" during spermatocyte transition. These junctions are the possible route for toxicant entry, causing male reproductive dysfunction. Herein, we summarize the detailed mechanism of all the regulators playing an essential role in the maintenance of the BTB, which will help researchers to understand and find targets for drug delivery inside the testis.

4-[1-Ethyl-1-methylhexy]-phenol induces apoptosis and interrupts Ca2+ homeostasis via ROS pathway in Sertoli TM4 cells

Biological effect of an individual nonylphenol (NP) isomer extremely relies upon the side chain structure. This research was designed to evaluate the impact of NP isomer, 4-[1-ethyl-1-methylhexy]-phenol (NP₆₅), on Sertoli cells in vitro. Sertoli TM4 cells were exposed to various concentration (0, 0.1, 1, 10, or 20 μM) of NP₆₅ for 24 h, and the outcomes indicated that treatment of NP₆₅ induced reactive oxygen species (ROS) generation, oxidative stress, and apoptosis for Sertoli TM4 cells. In addition, it was found that NP₆₅ exposure affected homeostasis of Ca²⁺ in Sertoli TM4 cells by increasing cytoplasm [Ca²⁺]i, inhibiting Ca²⁺-ATPase activity and decreasing cyclic adenosine monophosphate (cAMP) concentration. Pretreatment with ROS scavenger, N-acetylcysteine (NAC), attenuated NP₆₅-induced oxidative stress as well as apoptosis for TM4 cells. Furthermore, NAC blocked NP₆₅-induced disorders of Ca²⁺ homeostasis by attenuating the growth of intracellular [Ca²⁺]i and the inhibition of Ca²⁺-ATPase and cAMP activities. Thus, we have demonstrated that NP₆₅ induced apoptosis as well as acted as a potent inhibitor of Ca²⁺-ATPase activity and resulted in disorder of Ca²⁺ homeostasis in Sertoli TM4 cells; ROS participated in the process. Our results supported the view that oxidative stress acted an essential role within the development of apoptosis and Ca²⁺ overload in TM4 cells as a consequence of NP₆₅ stimulation.

Pyroglutamylated RFamide peptide (QRFP): Role in early testicular development in relation to Sertoli cell maturation in prepubertal mice

QRFP, an orexigenic neuropeptide, binds to its cognate receptor GPR103 and regulates various biological functions. We have recently shown that QRFP and its receptor are present in mice testes and that their expression is high during early postnatal period. The present study aimed to investigate the effect of sustained high level of QRFP on Sertoli cells proliferation and differentiation and to relate these events with germ cell differentiation and lumen formation in the seminiferous tubules in mice testes during prepubertal period. QRFP was injected intraperitoneally to male mice from postnatal day 5 to 16. Morphometric analysis and various markers related to Sertoli cell maturation (WT1, p27kip1, AMH, AR and CYP19A1) and germ cell proliferation and differentiation (PCNA, GDNF and c-Kit) were evaluated. QRFP administration caused an early lumen formation in the seminiferous tubules in testis of treated mice. Further, there was a significant increase in p27kip1 expression and a marked decrease in AMH expression in QRFP-treated mice compared to controls. However, no appreciable change was noted in AR expression in treated mice. QRFP treatment also caused an increase in c-Kit expression in treated mice compared to controls, suggesting an accelerated spermatogonial differentiation in testis of QRFP-treated mice. Taken together, the present results suggest that the prolonged high level of QRFP increases Sertoli cell maturation, which, in turn, plays a contributory role in increasing the pace of germ cell differentiation and formation of lumen in the seminiferous tubules.

Boosting effect of testosterone on GDNF expression in Sertoli cell line (TM4); comparison between TM3 cells-produced and exogenous testosterone

The Glial cell-derived neurotrophic factor (Gdnf) and testosterone induce the spermatogonial stem cells (SSCs) self-renewal and spermatogenesis, respectively. In present study the stimulating role of testosterone on Sertoli cells to produce Gdnf, and the possible effect of Gdnf on Gfrα1 and c-RET expressions were investigated. The TM4 cells (line Sertoli cells) were co-cultured with [0.1, 0.2 and 0.4 (ng/ml)] of exogenous and TM3 (line Leydig cells)-produced testosterones, and consequently the TM4-produced Gdnf concentration was evaluated. Next, the SSCs were co-cultured with the TM-4 derived media (endogenous Gdnf) and exogenous Gdnf [0.1, 0.2, and 0.4 ng/ml)]. The 0.1 and 0.2 ng/ml endogenous and 3 concentrations of exogenous testosterone up-regulated the Gdnf expression versus non-treated Sertoli cells. The TM4-produced and exogenous Gdnfs, in all concentrations, up-regulated the receptors expression. In conclusion, the testosterone, solely, stimulates the Gdnf synthesis and the Gdnf, individually, amplifies its receptor's expression at mRNA and protein levels.

Sumoylation and its regulation in testicular Sertoli cells

The molecular regulation of Sertoli cells and their crosstalk with germ cells has not been fully characterized. SUMO proteins are essential for normal development and are expressed in mouse and human Sertoli cells; However, the cell-specific role of sumoylation in those cells has only started to be elucidated. In other cell types, including granulosa cells, sumoylation is regulated by a SUMO ligase KAP1/Trim28. Deletion of KAP1 in Sertoli cells causes testicular degeneration; However, the role of KAP1 in those cells has not been identified. Here we show that both mouse and human Sertoli undergo apoptosis upon inhibition of sumoylation with a chemical inhibitor or via a siRNA technology. We have additionally detected changes in the Sertoli cell proteome upon the inhibition of sumoylation, and our data suggest that among others, the expression of ER/stress-related proteins is highly affected by this inhibition. Sumoylation may also regulate the NOTCH signaling which is important for the maintenance of the developing germ cells. Furthermore, we show that a siRNA-down-regulation of KAP1 in a Sertoli-derived cell line causes an almost complete inactivation of sumoylation. In conclusion, sumoylation regulates important survival and signaling pathways in Sertoli cells, and KAP1 can be a major regulator of sumoylation in these cells.

Direct reprogramming of human Sertoli cells into male germline stem cells with the self-renewal and differentiation potentials via overexpressing DAZL/DAZ2/BOULE genes

We propose a new concept that human somatic cells can be converted to become male germline stem cells by the defined factors. Here, we demonstrated that the overexpression of DAZL, DAZ2, and BOULE could directly reprogram human Sertoli cells into cells with the characteristics of human spermatogonial stem cells (SSCs), as shown by their similar transcriptomes and proteomics with human SSCs. Significantly, human SSCs derived from human Sertoli cells colonized and proliferated in vivo, and they could differentiate into spermatocytes and haploid spermatids in vitro. Human Sertoli cell-derived SSCs excluded Y chromosome microdeletions and assumed normal chromosomes. Collectively, human somatic cells could be converted directly to human SSCs with the self-renewal and differentiation potentials and high safety. This study is of unusual significance, because it provides an effective approach for reprogramming human somatic cells into male germ cells and offers invaluable male gametes for treating male infertility.

Temperature response of enriched pre-pubertal caprine male germline stem cells in vitro

The present study aims to evaluate culture temperature-dependent variation in survival, growth characteristics and expression of stress, pluripotency, apoptosis, and adhesion markers in enriched caprine male germline stem cells (cmGSCs). For this, testes from pre-pubertal bucks (4-5 months; n = 4) were used to isolated cells by a two-step enzymatic digestion method. After enrichment of cmGSCs by multiple methods (differential platting, Percoll density gradient centrifugation, and MACS), viability of CD90+ cells was assessed before co-cultured onto the Sertoli cell feeder layer at different temperatures (35.5, 37.0, 38.5, and 40.0 °C). The culture characteristics of cells were compared with MTT assay (viability); cluster-forming activity assay, SA-β1-gal assay (senescence), BrdU assay (proliferation), and transcript expression analyses by qRT-PCR. Moreover, the co-localization of pluripotency markers (UCHL-1, PLZF, and DBA) was examined by a double-immunofluorescence method. The cells grown at 37.0 °C showed faster proliferation with a significantly (p < 0.05) higher number of viable cells and greater number of cell clusters, besides higher expression of pluripotency markers. The transcript expression of HSPs (more noticeably HSP72 than HSP73), anti-oxidative enzymes (GPx and CuZnSOD), and adhesion molecule (β1-integrin) was significantly (p < 0.05) downregulated when grown at 35.0, 38.5, or 40.0 °C compared with 37.0 °C. The expression of pluripotency-specific transcripts was significantly (p < 0.05) lower in cmGSCs grown at the culture temperature lower (35.5 °C) or higher (38.5 °C and 40.0 °C) than 37.0 °C. Overall, the culture temperature significantly affects the proliferation, growth characteristics, and expression of heat stress, pluripotency, and adhesion-specific markers in pre-pubertal cmGSCs. These results provide an insight to develop strategies for the improved cultivation and downstream applications of cmGSCs.

Genetic Regulation of Avian Testis Development

As in other vertebrates, avian testes are the site of spermatogenesis and androgen production. The paired testes of birds differentiate during embryogenesis, first marked by the development of pre-Sertoli cells in the gonadal primordium and their condensation into seminiferous cords. Germ cells become enclosed in these cords and enter mitotic arrest, while steroidogenic Leydig cells subsequently differentiate around the cords. This review describes our current understanding of avian testis development at the cell biology and genetic levels. Most of this knowledge has come from studies on the chicken embryo, though other species are increasingly being examined. In chicken, testis development is governed by the Z-chromosome-linked DMRT1 gene, which directly or indirectly activates the male factors, HEMGN, SOX9 and AMH. Recent single cell RNA-seq has defined cell lineage specification during chicken testis development, while comparative studies point to deep conservation of avian testis formation. Lastly, we identify areas of future research on the genetics of avian testis development.

FSH mediated cAMP signalling upregulates the expression of Gα subunits in pubertal rat Sertoli cells

Follicle Stimulating Hormone (FSH) acts via FSH-Receptor (FSH-R) by employing cAMP as the dominant secondary messenger in testicular Sertoli cells (Sc) to support spermatogenesis. Binding of FSH to FSH-R, results the recruitment of the intracellular GTP binding proteins, either stimulatory Gαs or inhibitory Gαi that in turn regulate cAMP production in Sc. The cytosolic concentration of cAMP being generated by FSH-R thereafter critically determines the downstream fate of the FSH signalling. The pleiotropic action of FSH due to differential cAMP output during functional maturation of Sc has been well studied. However, the developmental and cellular regulation of the Gα proteins associated with FSH-R is poorly understood in Sc. In the present study, we report the differential transcriptional modulation of the Gα subunit genes by FSH mediated cAMP signalling in neonatal and pubertal rat Sc. Our data suggested that unlike in neonatal Sc, both the basal and FSH/forskolin induced expression of Gαs, Gαi-1, Gαi-2 and Gαi-3 transcripts was significantly (p < 0.05) up-regulated in pubertal Sc. Further investigations involving treatment of Sc with selective Gαi inhibitor pertussis toxin, confirmed the elevated expression of Gi subunits in pubertal Sc. Collectively our results indicated that the high level of Gαi subunits serves as a negative regulator to optimize cAMP production in pubertal Sc.

Rubicon prevents autophagic degradation of GATA4 to promote Sertoli cell function

Autophagy degrades unnecessary proteins or damaged organelles to maintain cellular function. Therefore, autophagy has a preventive role against various diseases including hepatic disorders, neurodegenerative diseases, and cancer. Although autophagy in germ cells or Sertoli cells is known to be required for spermatogenesis and male fertility, it remains poorly understood how autophagy participates in spermatogenesis. We found that systemic knockout mice of Rubicon, a negative regulator of autophagy, exhibited a substantial reduction in testicular weight, spermatogenesis, and male fertility, associated with upregulation of autophagy. Rubicon-null mice also had lower levels of mRNAs of Sertoli cell–related genes in testis. Importantly, Rubicon knockout in Sertoli cells, but not in germ cells, caused a defect in spermatogenesis and germline stem cell maintenance in mice, indicating a critical role of Rubicon in Sertoli cells. In mechanistic terms, genetic loss of Rubicon promoted autophagic degradation of GATA4, a transcription factor that is essential for Sertoli cell function. Furthermore, androgen antagonists caused a significant decrease in the levels of Rubicon and GATA4 in testis, accompanied by elevated autophagy. Collectively, we propose that Rubicon promotes Sertoli cell function by preventing autophagic degradation of GATA4, and that this mechanism could be regulated by androgens.

Androgens, known as “male” hormones, stimulate and activate their receptors in various tissues, including testicular cells and skeletal muscle cells, thereby maintaining spermatogenesis and muscle mass. Notably, androgens-dependent maintenance of male reproduction is of particular interest because the incidence of male infertility has increased in recent decades. Previous studies revealed that Androgen receptor knockout in Sertoli cells causes defective spermatogenesis, indicating a crucial role of androgens in Sertoli cells. Another study suggested that fatherhood-dependent downregulation of androgens could decrease male fertility, leading the male to concentrate on parenting existing offspring. However, it remains largely unknown how androgen regulates Sertoli cell function for male reproduction. In the present study, our results suggest that androgens regulate testicular levels of Rubicon, a negative regulator of autophagy, to control autophagic degradation of GATA4 that is required for Sertoli cell function. Because autophagy and androgens participate in various cellular processes, we anticipate that this study will provide a solid evidence for understanding such processes.

Fluorochloridone induces autophagy in TM4 Sertoli cells: involvement of ROS-mediated AKT-mTOR signaling pathway

BACKGROUND

Fluorochloridone (FLC), a selective pyrrolidone herbicide, has been recognized as a potential endocrine disruptor and reported to induce male reproductive toxicity, but the underlying mechanism is unclear. The aim of this study was to investigate the mechanism of FLC-induced reproductive toxicity on male mice with particular emphasis on the role of autophagy in mice' TM4 Sertoli cells.

METHODS

Adult C57BL/6 mice were divided into one control group (0.5% sodium carboxymethyl cellulose), and four FLC-treated groups (3,15,75,375 mg/kg). The animals (ten mice per group) received gavage for 28 days. After treatment, histological analysis, sperm parameters, the microstructure of autophagy and the expression of autophagy-associated proteins in testis were evaluated. Furthermore, to explore the autophagy mechanism, TM4 Sertoli cells were treated with FLC (0,40,80,160 μM) in vitro for 24 h. Cell activity and cytoskeletal changes were measured by MTT assay and F-actin immunofluorescence staining. The formation of autophagosome, accumulation of reactive oxygen species (ROS), expression of autophagy marker proteins (LC3, Beclin-1 and P62) and AKT-related pathway proteins (AKT, mTOR) were observed. The ROS scavenger N-acetylcysteine (NAC) and AKT agonist (SC79) were used to treat TM4 cells to observe the changes of AKT-mTOR pathway and autophagy.

RESULTS

In vivo, it showed that FLC exposure caused testicular injuries, abnormality in epididymal sperm. Moreover, FLC increased the formation of autophagosomes, the accumulation of LC3II/LC3I, Beclin-1 and P62 protein, which is related to the degradation of autophagy. In vitro, FLC triggered TM4 cell autophagy by increasing the formation of autophagosomes and upregulating of LC3II/LC3I, Beclin-1 and P62 levels. In addition, FLC induced ROS production and inhibited the activities of AKT and mTOR kinases. The Inhibition of AKT/mTOR signaling pathways and the activation of autophagy induced by FLC could be efficiently reversed by pretreatment of NAC. Additionally, decreased autophagy and increased cell viability were observed in TM4 cells treated with SC79 and FLC, compared with FLC alone, indicating that FLC-induced autophagy may be pro-death.

CONCLUSION

Taken together, our study provided the evidence that FLC promoted autophagy in TM4 Sertoli cells and that this process may involve ROS-mediated AKT/mTOR signaling pathways.

KIF15 supports spermatogenesis via its effects on Sertoli cell microtubule, actin, vimentin, and septin cytoskeletons

Throughout spermatogenesis, cellular cargoes including haploid spermatids are required to be transported across the seminiferous epithelium, either toward the microtubule (MT) plus (+) end near the basement membrane at stage V, or to the MT minus (-) end near the tubule lumen at stages VI to VIII of the epithelial cycle. Furthermore, preleptotene spermatocytes, differentiated from type B spermatogonia, are transported across the Sertoli cell blood-testis barrier (BTB) to enter the adluminal compartment. Few studies, however, have been conducted to explore the function of MT-dependent motor proteins to support spermatid transport during spermiogenesis. Herein, we examined the role of MT-dependent and microtubule plus (+) end-directed motor protein kinesin 15 (KIF15) in the testis. KIF15 displayed a stage-specific expression across the seminiferous epithelium, associated with MTs, and appeared as aggregates on the MT tracks that aligned perpendicular to the basement membrane and laid across the entire epithelium. KIF15 also tightly associated with apical ectoplasmic specialization, displaying strict stage-specific distribution, apparently to support spermatid transport across the epithelium. We used a loss-of-function approach by RNAi to examine the role of KIF15 in Sertoli cell epithelium in vitro to examine its role in cytoskeletal-dependent Sertoli cell function. It was noted that KIF15 knockdown by RNAi that reduced KIF15 expression by ~70% in Sertoli cells with an established functional tight junction barrier impeded the barrier function. This effect was mediated through remarkable changes in the cytoskeletal organization of MTs, but also actin-, vimentin-, and septin-based cytoskeletons, illustrating that KIF15 exerts its regulatory effects well beyond microtubules.

Regulation of Cell Types Within Testicular Organoids

Organoids are 3-dimensional (3D) structures grown in vitro that emulate the cytoarchitecture and functions of true organs. Therefore, testicular organoids arise as an important model for research on male reproductive biology. These organoids can be generated from different sources of testicular cells, but most studies to date have used immature primary cells for this purpose. The complexity of the mammalian testicular cytoarchitecture and regulation poses a challenge for working with testicular organoids, because, ideally, these 3D models should mimic the organization observed in vivo. In this review, we explore the characteristics of the most important cell types present in the testicular organoid models reported to date and discuss how different factors influence the regulation of these cells inside the organoids and their outcomes. Factors such as the developmental or maturational stage of the Sertoli cells, for example, influence organoid generation and structure, which affect the use of these 3D models for research. Spermatogonial stem cells have been a focus recently, especially in regard to male fertility preservation. The regulation of the spermatogonial stem cell niche inside testicular organoids is discussed in the present review, as this research area may be positively affected by recent progress in organoid generation and tissue engineering. Therefore, the testicular organoid approach is a very promising model for male reproductive biology research, but more studies and improvements are necessary to achieve its full potential.

Changes in testicular gene expression following reduced estradiol synthesis: A complex pathway to increased porcine Sertoli cell proliferation

Porcine Sertoli cell number including number present at puberty is increased if testicular estradiol synthesis is reduced during the neonatal interval. Evaluating the changes in gene expression during the crucial interval of suppressed estradiol that leads to the increased Sertoli cell population will increase our understanding of Sertoli cell biology but this evaluation first required a more precise determination of the critical interval for treatment and timing of a detectable response. Previously, reduced testicular estrogens from 1 week of age were accompanied by increased Sertoli cell number at 6.5 weeks of age but the age at which Sertoli cell numbers were initially increased was unknown, one of the current objectives. Additional experiments were designed to further delineate the essential timing of treatment for the Sertoli cell response. Finally, changes in gene expression induced by the reduced estradiol synthesis were evaluated to elucidate molecular mechanisms. Experimental design typically consisted of one member of littermate pairs of boars treated with the aromatase inhibitor, letrozole, beginning at 1 week of age and the remaining member treated with canola oil vehicle. Weekly treatments continued through 5 weeks of age or tissue collection, whichever came first. Increases in Sertoli cell numbers were not detectable prior to 6.5 weeks of age and persistent treatment through 5 weeks of age was required to induce the increase in Sertoli cell numbers. This increase resulted from prolonging the first interval of Sertoli cell proliferation in the treated animals. Few genes exhibited dramatically altered transcription and similarities in pathway analysis or principal modified genes were quite limited in 2, 3, and 5-week-old boars. The critical timing and prolonged treatment required and the sequential changes in gene expression suggest a complex mechanism is involved in this model of increased proliferation of Sertoli cells.

Effect of EPA on Neonatal Pig Sertoli Cells "In Vitro": A Possible Treatment to Help Maintain Fertility in Pre-Pubertal Boys Undergoing Treatment With Gonado-Toxic Therapies

The incidence of cancer in pre-pubertal boys has significantly increased and, it has been recognized that the gonado-toxic effect of the cancer treatments may lead to infertility. Here, we have evaluated the effects on porcine neonatal Sertoli cells (SCs) of three commonly used chemotherapy drugs; cisplatin, 4-Hydroperoxycyclophosphamide and doxorubicin. All three drugs induced a statistical reduction of 5-hydroxymethylcytosine in comparison with the control group, performed by Immunofluorescence Analysis. The gene and protein expression levels of GDNF, were significantly down-regulated after treatment to all three chemotherapy drugs comparison with the control group. Specifically, differences in the mRNA levels of GDNF were: 0,8200 ± 0,0440, 0,6400 ± 0,0140, 0,4400 ± 0,0130 fold change at 0.33, 1.66, and 3.33μM cisplatin concentrations, respectively (**p < 0.01 at 0.33 and 1.66 μM vs SCs and ***p < 0.001 at 3.33μM vs SCs); 0,6000 ± 0,0340, 0,4200 ± 0,0130 fold change at 50 and 100 μM of 4-Hydroperoxycyclophosphamide concentrations, respectively (**p < 0.01 at both these concentrations vs SCs); 0,7000 ± 0,0340, 0,6200 ± 0,0240, 0,4000 ± 0,0230 fold change at 0.1, 0.2 and 1 µM doxorubicin concentrations, respectively (**p < 0.01 at 0.1 and 0.2 μM vs SCs and ***p < 0.001 at 1 μM vs SCs). Differences in the protein expression levels of GDNF were: 0,7400 ± 0,0340, 0,2000 ± 0,0240, 0,0400 ± 0,0230 A.U. at 0.33, 1.66, and 3.33μM cisplatin concentrations, respectively (**p < 0.01 at both these concentrations vs SCs); 0,7300 ± 0,0340, 0,4000 ± 0,0130 A.U. at 50 and 100 μM of 4- Hydroperoxycyclophosphamide concentrations, respectively (**p < 0.01 at both these concentrations vs SCs); 0,6200 ± 0,0340, 0,4000 ± 0,0240, 0,3800 ± 0,0230 A.U. at 0.l, 0.2 and 1 µM doxorubicin concentrations, respectively (**p < 0.01 at 0.1 and 0.2 μM vs SCs and ***p < 0.001 at 1 μM vs SCs). Furthermore, we have demonstrated the protective effect of eicosapentaenoic acid on SCs only at the highest concentration of cisplatin, resulting in an increase in both gene and protein expression levels of GDNF (1,3400 ± 0,0280 fold change; **p < 0.01 vs SCs); and of AMH and inhibin B that were significantly recovered with values comparable to the control group. Results from this study, offers the opportunity to develop future therapeutic strategies for male fertility management, especially in pre-pubertal boys.

The Molecular Mechanism of Sex Hormones on Sertoli Cell Development and Proliferation

Sustaining and maintaining the intricate process of spermatogenesis is liable upon hormones and growth factors acting through endocrine and paracrine pathways. The Sertoli cells (SCs) are the major somatic cells present in the seminiferous tubules and are considered to be the main regulators of spermatogenesis. As each Sertoli cell supports a specific number of germ cells, thus, the final number of Sertoli cells determines the sperm production capacity. Similarly, sex hormones are also major regulators of spermatogenesis and they can determine the proliferation of Sertoli cells. In the present review, we have critically and comprehensively discussed the role of sex hormones and some other factors that are involved in Sertoli cell proliferation, differentiation and maturation. Furthermore, we have also presented a model of Sertoli cell development based upon the recent advancement in the field of reproduction. Hence, our review article provides a general overview regarding the sex hormonal pathways governing Sertoli cell proliferation and development.

Momordica charantia Extract Protects against Diabetes-Related Spermatogenic Dysfunction in Male Rats: Molecular and Biochemical Study

More than 90% of diabetic patients suffer from sexual dysfunction, including diminished sperm count, sperm motility, and sperm viability, and low testosterone levels. The effects of Momordica charantia (MC) were studied by estimating the blood levels of insulin, glucose, glycosylated hemoglobin (HbA1c), testosterone (TST), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in diabetic rats treated with 250 and 500 mg/kg b.w. of the total extract. Testicular antioxidants, epididymal sperm characteristics, testicular histopathology, and lesion scoring were also investigated. Testicular mRNA expression of apoptosis-related markers such as antiapoptotic B-cell lymphoma-2 (Bcl-2) and proapoptotic Bcl-2-associated X protein (Bax) were evaluated by real-time PCR. Furthermore, caspase-3 protein expression was evaluated by immunohistochemistry. MC administration resulted in a significant reduction in blood glucose and HbA1c and marked elevation of serum levels of insulin, TST, and gonadotropins in diabetic rats. It induced a significant recovery of testicular antioxidant enzymes, improved histopathological changes of the testes, and decreased spermatogenic and Sertoli cell apoptosis. MC effectively inhibited testicular apoptosis, as evidenced by upregulation of Bcl-2 and downregulation of Bax and caspase-3. Moreover, reduction in apoptotic potential in MC-treated groups was confirmed by reduction in the Bax/Bcl-2 mRNA expression ratio.

Role of GPER-Mediated Signaling in Testicular Functions and Tumorigenesis

Estrogen signaling plays important roles in testicular functions and tumorigenesis. Fifteen years ago, it was discovered that a member of the G protein-coupled receptor family, GPR30, which binds also with high affinity to estradiol and is responsible, in part, for the rapid non-genomic actions of estrogens. GPR30, renamed as GPER, was detected in several tissues including germ cells (spermatogonia, spermatocytes, spermatids) and somatic cells (Sertoli and Leydig cells). In our previous review published in 2014, we summarized studies that evidenced a role of GPER signaling in mediating estrogen action during spermatogenesis and testis development. In addition, we evidenced that GPER seems to be involved in modulating estrogen-dependent testicular cancer cell growth; however, the effects on cell survival and proliferation depend on specific cell type. In this review, we update the knowledge obtained in the last years on GPER roles in regulating physiological functions of testicular cells and its involvement in neoplastic transformation of both germ and somatic cells. In particular, we will focus our attention on crosstalk among GPER signaling, classical estrogen receptors and other nuclear receptors involved in testis physiology regulation.

Characterization of rodent Sertoli cell primary cultures

Sertoli cells play a vital role in spermatogenesis by offering physical and nutritional support to the differentiating male germ cells. They form the blood-testis barrier and secrete growth factors essential for germ cell differentiation. Sertoli cell primary cultures are critical for understanding the regulation of spermatogenesis; however, obtaining pure cultures has been a challenge. Rodent Sertoli cell isolation protocols do not rule out contamination by the interstitial or connective tissue cells. Sertoli cell-specific markers could be helpful, but there is no consensus. Vimentin, the most commonly used marker, is not specific for Sertoli cells since its expression has been reported in peritubular myoid cells, mesenchymal stem cells, fibroblasts, macrophages, and endothelial cells, which contaminate Sertoli cell preparations. Markers based on transcription and growth factors also have limitations. Thus, the impediment to obtaining pure Sertoli cell cultures pertains to both the method of isolation and marker usage. The aim of this review is to discuss improvements to current methods of rodent Sertoli cell primary cultures, assess the properties of prepubertal versus mature Sertoli cell cultures, and propose steps to improve cellular characterization. Potential benefits of using contemporary approaches, including lineage tracing, specific cell ablation, and RNA-seq for obtaining Sertoli-specific transcript markers are discussed. Evaluating the specificity and applicability of these markers at the protein level to characterize Sertoli cells in culture would be critical. This review is expected to positively impact future work using primary cultures of rodent Sertoli cells.

Three-dimensional co-culture of human spermatogonial stem cells with Sertoli cells in soft agar culture system supplemented by growth factors and Laminin

Application of a three-dimensional (3D) culture system for in vitro proliferation and differentiation of human spermatogonial stem cells (SSCs) is a useful tool for the investigation of the spermatogenesis process and the management of male infertility particularly in prepubertal cancer patients. The main purpose of this study was to investigate the proliferation of human SSCs co-cultured with Sertoli cells in soft agar culture system (SACS) supplemented by Laminin and growth factors. Testicular cells were isolated from testes of brain-dead patients and cultured in two-dimensional (2D) culture system for 3 weeks. After 3 weeks, functional SSCs were evaluated by xenotransplantation and also identification of cells was assessed by immunocytochemistry, flow cytometry, and RT-PCR. Then, SSCs and Sertoli cells were transferred to the upper layer of SACS for 3 weeks. After 3 weeks, the number of colonies and the expression of specific SSCs and Sertoli cell markers, as well as apoptotic genes were evaluated. Our results showed that transplanted SSCs, migrated into the basement membrane of seminiferous tubules of recipient mice. The expression of PLZF, α6-Integrin, and Vimentin proteins in SSCs and Sertoli cells were observed in 2D and 3D culture systems. The expression rate of PLZF, α6-Integrin, Bcl2, and colony number in SACS supplemented by Laminin and growth factors group were significantly higher than non-supplemented groups (P ≤ 0.01), but the expression rate of c-kit and Bax in supplemented group were significantly lower than non-supplemented groups (P ≤ 0.05). This 3D co-culture system decreased apoptosis and increased propagation of human SSCs. Therefore, this designed system can be utilized to increase the proliferation of human SSCs in prepubertal male cancer and azoospermic men to obtain an adequate SSCs number to outotransplant success and in vitro spermatogenesis.

Dissecting Cell Lineage Specification and Sex Fate Determination in Gonadal Somatic Cells Using Single-Cell Transcriptomics

Sex determination is a unique process that allows the study of multipotent progenitors and their acquisition of sex-specific fates during differentiation of the gonad into a testis or an ovary. Using time series single-cell RNA sequencing (scRNA-seq) on ovarian Nr5a1-GFP⁺ somatic cells during sex determination, we identified a single population of early progenitors giving rise to both pre-granulosa cells and potential steroidogenic precursor cells. By comparing time series single-cell RNA sequencing of XX and XY somatic cells, we provide evidence that gonadal supporting cells are specified from these early progenitors by a non-sex-specific transcriptomic program before pre-granulosa and Sertoli cells acquire their sex-specific identity. In XX and XY steroidogenic precursors, similar transcriptomic profiles underlie the acquisition of cell fate but with XX cells exhibiting a relative delay. Our data provide an important resource, at single-cell resolution, for further interrogation of the molecular and cellular basis of mammalian sex determination.

[Influence of MGRN1 on the autophagy of Sertoli cells in mice]

OBJECTIVE

To study the effect of mahogunin ring finger-1 (MGRN1) on the autophagy of Sertoli cells in mice.

METHODS

Using RNA interference, we down-regulated the expression of MGRN1 in the mouse TM4 Sertoli cells cultured in vitro, determined the expressions of the autophagy-related proteins LC3-II/I, ATG-5 and ATG-7 by Western blot, and detected the autophagosomes in the TM4 cells by immunofluorescence and electron microscopy.

RESULTS

Western blot showed increased expressions of LC3-II/I, ATG-5 and ATG-7 in the mouse TM4 Sertoli cells after knockdown of MGRN1. Fluorescence microscopy revealed significantly more autophagosomes in the TM4 cells than in the control group (P < 0.05).

CONCLUSIONS

MGRN1 affects the autophagy of mouse Sertoli cells, and its specific molecular mechanism needs to be further studied.

Sertoli cell-only phenotype and scRNA-seq define PRAMEF12 as a factor essential for spermatogenesis in mice

Spermatogonial stem cells (SSCs) have the dual capacity to self-renew and differentiate into progenitor spermatogonia that develop into mature spermatozoa. Here, we document that preferentially expressed antigen of melanoma family member 12 (PRAMEF12) plays a key role in maintenance of the spermatogenic lineage. In male mice, genetic ablation of Pramef12 arrests spermatogenesis and results in sterility which can be rescued by transgenic expression of Pramef12. Pramef12 deficiency globally decreases expression of spermatogenic-related genes, and single-cell transcriptional analysis of post-natal male germline cells identifies four spermatogonial states. In the absence of Pramef12 expression, there are fewer spermatogonial stem cells which exhibit lower expression of SSC maintenance-related genes and are defective in their ability to differentiate. The disruption of the first wave of spermatogenesis in juvenile mice results in agametic seminiferous tubules. These observations mimic a Sertoli cell-only syndrome in humans and may have translational implications for reproductive medicine.

Generation of Organized Porcine Testicular Organoids in Solubilized Hydrogels from Decellularized Extracellular Matrix

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

p53-Dependent pathway and the opening of mPTP mediate the apoptosis of co-cultured Sertoli-germ cells induced by microcystin-LR

Microcystin-LR (MC-LR), a potent endotoxin, can induce reproductive toxicity. In order to investigate the role and mechanisms of apoptosis (p53-dependent and mitochondrial pathways) of germ cells induced by MC-LR, the co-cultured primary Sertoli-germ cells from Sprague-Dawley rats were used for the experiments. Expression levels of proteins, genes, and mitochondrial membrane potential (MMP) were obtained after exposing co-cultured Sertoli-germ cells to MC-LR with or without the addition of the p53 inhibitor, pifithrin-α (PFT-α), and MMP inhibitor, cyclosporin A (CsA). Results indicated that MC-LR could activate p53-dependent pathway-associated proteins in Sertoli-germ cells, leading to a decrease in MMP (indicating the opening of mitochondrial permeability transition pore [mPTP] and the release of Cytochrome-c [Cyt-c]) from the mitochondria into the cytoplasm and eventually the induction of apoptosis. PFT-α inhibited the expression ofp53, ameliorated the MMP of the co-cultured Sertoli-germ cells, and prevented the release of Cyt-c from the mitochondria into the cytoplasm, which reduces the occurrence of apoptosis. Similarly, the decreased release of Cyt-c from the mitochondria into the cytoplasm and the declined level of apoptosis in Sertoli-germ cells induced by MC-LR were observed after the addition of CsA. These results indicated that the apoptosis of the co-cultured Sertoli-germ cells induced by MC-LR was mediated by the p53-dependent pathway, with the involvement of the opening of mPTP.

Treatment with, Resveratrol, a SIRT1 Activator, Prevents Zearalenone-Induced Lactic Acid Metabolism Disorder in Rat Sertoli Cells

Zearalenone (ZEA) interferes with the function of the male reproductive system, but its molecular mechanism has yet to be completely elucidated. Sertoli cells (SCs) are important in the male reproductive system. Silencing information regulator 1 (SIRT1) is a cell metabolism sensor and resveratrol (RSV) is an activator of SIRT1. In this study we investigated whether SIRT1 is involved in the regulation of ZEA-induced lactate metabolism disorder in SCs. The results showed that the cytotoxicity of ZEA toward SCs increased with increasing ZEA concentration. Moreover, ZEA induced a decrease in the production of lactic acid and pyruvate of SCs and inhibited the expression of glycolytic genes and lactic acid production-related proteins. ZEA also led to a decreased expression of SIRT1 in energy receptors and decreased ATP levels in SCs. However, the ZEA-induced cytotoxicity and decline in lactic acid production in SCs were alleviated by the use of RSV, which is an activator of SIRT1. In summary, ZEA decreased lactic acid production in SCs, while the treatment with an SIRT1 activator, RSV, restored the inhibition of lactic acid production in SCs and reduced cytotoxicity of ZEA toward SCs.

CAMSAP2 Is a Microtubule Minus-End Targeting Protein That Regulates BTB Dynamics Through Cytoskeletal Organization

During spermatogenesis, microtubule (MT) cytoskeleton in Sertoli cells confers blood-testis barrier (BTB) function, but the regulators and mechanisms that modulate MT dynamics remain unexplored. In this study, we examined the role of calmodulin-regulated spectrin-associated protein (CAMSAP)2 (a member of the CAMSAP/Patronin protein family), and a minus-end targeting protein (-TIP) that binds to the minus-end (i.e., slow-growing end) of polarized MTs involved in determining MT length, in Sertoli cell function. CAMSAP2 was found to localize at discrete sites across the Sertoli cell cytosol, different from end-binding protein 1 (a microtubule plus-end tracking protein that binds to the plus-end of MTs), and colocalized with MTs. CAMSAP2 displayed a stage-specific expression pattern, appearing as tracklike structures across the seminiferous epithelium in adult rat testes that lay perpendicular to the basement membrane. CAMSAP2 knockdown by RNA interference was found to promote Sertoli cell tight junction (TJ) barrier function, illustrating its role in inducing TJ remodeling under physiological conditions. To further examine the regulatory role of CAMSAP2 in BTB dynamics, we used a perfluorooctanesulfonate (PFOS)-induced Sertoli cell injury model for investigations. CAMSAP2 knockdown blocked PFOS-induced Sertoli cell injury by promoting proper distribution of BTB-associated proteins at the cell-cell interface. This effect was mediated by the ability of CAMSAP2 knockdown to block PFOS-induced disruptive organization of MTs, but also F-actin, across cell cytosol through changes in cellular distribution/localization of MT- and actin-regulatory proteins. In summary, CAMSAP2 is a regulator of MT and actin dynamics in Sertoli cells to support BTB dynamics and spermatogenesis.

Transcription Factor USF1 Is Required for Maintenance of Germline Stem Cells in Male Mice

A prerequisite for lifelong sperm production is that spermatogonial stem cells (SSCs) balance self-renewal and differentiation, yet factors required for this balance remain largely undefined. Using mouse genetics, we now demonstrate that the ubiquitously expressed transcription factor upstream stimulatory factor (USF)1 is critical for the maintenance of SSCs. We show that USF1 is not only detected in Sertoli cells as previously reported, but also in SSCs. Usf1-deficient mice display progressive spermatogenic decline as a result of age-dependent loss of SSCs. According to our data, the germ cell defect in Usf1-/- mice cannot be attributed to impairment of Sertoli cell development, maturation, or function, but instead is likely due to an inability of SSCs to maintain a quiescent state. SSCs of Usf1-/- mice undergo continuous proliferation, which provides an explanation for their age-dependent depletion. The proliferation-coupled exhaustion of SSCs in turn results in progressive degeneration of the seminiferous epithelium, gradual decrease in sperm production, and testicular atrophy. We conclude that the general transcription factor USF1 is indispensable for the proper maintenance of mammalian spermatogenesis.

Copper transporter 1 (CTR1) expression by mouse testicular germ cells, but not Sertoli cells, is essential for functional spermatogenesis

An imbalance in copper (Cu) tissue homeostasis has a degenerative effect on spermatogenesis and male fertility. The high-affinity Cu transporter 1 (CTR1; SLC31A1) is the major protein responsible for Cu acquisition in eukaryotes and is highly expressed in mouse testes. Studies on yeast and Drosophila have demonstrated the conserved essential function of Cu and CTR1 for meiosis and fertility, implying that CTR1 may play an essential function in mammalian spermatogenesis. In mice, spermatogenesis takes place within the seminiferous epithelium, where tight junctions between somatic Sertoli cells (SCs) create a specialized microenvironment for the development of meiotic germ cells (GCs) by tightly regulating the free transport of metabolites and ions to reach these cells. Here, it is demonstrated that within the seminiferous epithelium, CTR1 is expressed on the membrane of primary pachytene spermatocytes and SCs. To examine the physiological significance of CTR1 in spermatogenesis, mice with a GC-specific (Ctr1ΔGC) and SC-specific (Ctr1ΔSC) disruption of the Ctr1 gene were generated. The testis of Ctr1ΔGC mice exhibits a severe progressive loss of GCs starting at postnatal day (PND) 28 leading to testis hypoplasia by adulthood. No spermatogenic recovery was observed in Ctr1ΔGC testis beyond PND 41, despite the presence of FOXO-1 expressing undifferentiated spermatogonial cells. However, Ctr1ΔSC mice displayed functional spermatogenesis and were fertile, even though testicular Cu levels and Cu-dependent cellular activities were significantly reduced. These results reveal, for the first time, the importance of CTR1 expression by GCs for maintaining functional spermatogenesis.

Testis structure, spermatogonial niche and Sertoli cell efficiency in Neotropical fish

Neotropical icthyofauna represents one of the most diverse and extreme ecosystems in the world. Likewise, reproduction showed enormous diversity with different reproductive systems, modes and behavior. On the other hand, information on Neotropical fish species, in particular on male reproductive physiology is restricted to few species. This mini-review aimed to compile the existing information on spermatogenesis of Neotropical teleosts focusing on testis structure, spermatogonial niche and Sertoli cell efficiency. The first topic covers the histological analysis of the testicular structure, showing a conserved testicular pattern in relation to the phylogenetic position: basal species present anastomosing tubular testis (e.g. Astyanax altiparanae, Conorhynchos conirostris, Pimelodus maculatus, Lophiosilurus alexandri, Rhinelepis aspera, among others), while derived teleosts showed lobular testis (e.g. Cichlasoma dimerus, Cichla kelberi, Odontesthes bonariensis, Synbranchus marmoratus and others). Next to testicular structure, existing data showed that type A undifferentiated spermatogonia (A_und) is differentially distributed among the Neotropical species. A_und can be restricted at the blind-end of the germinal compartment (O. bonariensis), or spread along the germinal epithelium (A. altiparanae), or even distributed along the germinal epithelium but concentrated at the blind-end (C. kelberi and C. intermedia). Moreover, recent studies in A. altiparanae have demonstrated that within the germinal compartment, A_und have a preferential distribution in areas neighboring the interstitial compartment - the spermatogonial niche. The proximity with the interstitium suggests that interstitial cells, such as Leydig cells, are important for A_und maintenance in the testis. Finally, this mini-review highlighted Sertoli cell efficiency, showing that a single Sertoli cell can support a higher number of germ cells (80-140 spermatids) in Neotropical species evaluated at the moment (e.g. A. altiparanae, Hoplias malabaricus, Poecilia reticulata, Serrasalmus spilopleura, C. intermedia). Overall, this review provided basic and functional information on spermatogenesis of Neotropical species. More studies in this field are necessary since Neotropical region is considered one of the hotspot regions to discovery new species providing, therefore, new opportunities to investigate spermatogenesis in fish.

Emerging role for SRC family kinases in junction dynamics during spermatogenesis

SRC family kinases (SFKs) are known regulators of multiple cellular events, including cell movement, differentiation, proliferation, survival and apoptosis. SFKs are expressed virtually by all mammalian cells. They are non-receptor protein kinases that phosphorylate a variety of cellular proteins on tyrosine, leading to the activation of protein targets in response to environmental stimuli. Among SFKs, SRC, YES and FYN are the ubiquitously expressed and best studied members. In fact, SRC, the prototypical SFK, was the first tyrosine kinase identified in mammalian cells. Studies have shown that SFKs are regulators of cell junctions, and function in endocytosis and membrane trafficking to regulate junction restructuring events. Herein, we briefly summarize the recent findings in the field regarding the role of SFKs in the testis in regulating spermatogenesis, particularly in Sertoli-Sertoli and Sertoli-germ cell adhesion. While it is almost 50 years since the identification of the oncogene v-Src encoded by Rous sarcoma transforming virus, the understanding of SFK involvement during spermatogenesis in the testis remains far behind that in other epithelia and tissues. The goal of this review is to bridge this gap.

Testosterone augments FSH signaling by upregulating the expression and activity of FSH-Receptor in Pubertal Primate Sertoli cells

The synergistic actions of Testosterone (T) and FSH via testicular Sertoli cells (Sc) regulate male fertility. We have previously reported that the actions of these hormones (T and FSH) in infant monkey testes are restricted only to the expansion of Sc and spermatogonial cells. The robust differentiation of male Germ cells (Gc) occurs after pubertal maturation of testis. The present study was aimed to investigate the molecular basis of the synergy between T and FSH action in pubertal primate (Macaca mulatta) Sc. Using primary Sc culture, we here have demonstrated that T (but not FSH) downregulated AMH and Inhibin-β-B (INHBB) mRNAs in pubertal Sc. We also found that, prolonged stimulation of T in pubertal Sc significantly elevated the expression of genes involved in FSH signaling pathway like FSH-Receptor (FSHR), GNAS and RIC8B, and this was associated with a rise in cAMP production. T also augmented FSH induced expression of genes like SCF, GDNF, ABP and Transferrin (TF) in pubertal Sc. We therefore conclude that T acts in synergy with FSH signaling in pubertal Sc. Such a coordinated network of hormonal signaling in Sc may facilitate the timely onset of the first spermatogenic wave in pubertal primates and is responsible for quantitatively and qualitatively normal spermatogenesis.

Rabbit Sertoli Cells: Immunohistochemical Profile from Neonatal to Adult Age

Immunohistochemistry (IHC) on formalin-fixed paraffin-embedded tissue specimens is a widely used laboratory technique that allows the demonstration and the direct microscopical observation of antigens within tissue sections by means of specific antibodies. IHC is one the best tools to define the immunophenotype of a cell during maturation or neoplastic transformation.To investigate the immunophenotype of postnatal rabbit Sertoli cell, from neonatal to adult age, in this chapter, the immunohistochemical protocol described is one of the most common: the avidin-biotin complex (ABC) method.

Effects of Fluoride on Autophagy in Mouse Sertoli Cells

Fluoride had been reported to damage the structure and function of testicular tissues and reproductive cells; however, the mechanisms underlying its toxicity remained unclear. Autophagy plays a key role in reproductive function. In this study, we aimed to investigate the effect of fluoride on autophagy in Sertoli cells. Sertoli cells were exposed to 0, 0.125, 0.25, and 0.5 mM NaF for 24 h. The results showed that fluoride exposure up-regulated Beclin1 and p62 mRNA and protein expression levels with concomitant down-regulated mRNA and protein expression levels of LC3 and Atg5. In conclusion, exposure to fluoride impaired the autophagy process in Sertoli cells, which could be one of fluoride's mechanisms in male reproductive toxicity.

Scaffold-Based and Scaffold-Free Testicular Organoids from Primary Human Testicular Cells

Organoid systems take advantage of the self-organizing capabilities of cells to create diverse multi-cellular tissue surrogates that constitute a powerful novel class of biological models. Clearly, the formation of a testicular organoid (TO) in which human spermatogenesis can proceed from a single-cell suspension would exert a tremendous impact on research and development, clinical treatment of infertility, and screening of potential drugs and toxic agents. Recently, we showed that primary adult and pubertal human testicular cells auto-assembled in TOs either with or without the support of a natural testis scaffold. These mini-tissues harboured both the spermatogonial stem cells and their important niche cells, which retained certain specific functions during long-term culture. As such, human TOs might advance the development of a system allowing human in vitro spermatogenesis. Here we describe the methodology to make scaffold-based and scaffold-free TOs.

NRG1 signalling regulates the establishment of Sertoli cell stock in the mouse testis

Testis differentiation requires high levels of proliferation of progenitor cells that give rise to two cell lineages forming the testis, the Sertoli and the Leydig cells. Hence defective cell cycling leads to testicular dysgenesis that has profound effects on androgen production and fertility. The growth factor NRG1 has been implicated in adult Leydig cell proliferation, but a potential function in the fetal testis has not been analysed to date. Here we show that Nrg1 and its receptors ErbB2/3 are already expressed in early gonadal development. Using tissue-specific deletion, we further demonstrate that Nrg1 is required in a dose-dependent manner to induce proliferation of Sertoli progenitor cells and then differentiated Sertoli cells. As a result of reduced numbers of Sertoli cells, Nrg1 knockout mice display a delay in testis differentiation and defects in sex cord partitioning. Taken together Nrg1 signalling is essential for the establishment of the stock of Sertoli cells and thus required to prevent testicular hypoplasia.

[Estradiol benzoate induces abnormal proliferation of spermatogenic cells in the testis of infertile male mice]

OBJECTIVE

To explore the change in the proliferation of spermatogenic cells in the male mouse with infertility induced by exogenous estradiol benzoate (EB).

METHODS

Sixty male mice aged 4 weeks were randomly divided into a control, a low-dose EB, and a high-dose EB group to be injected intramuscularly with corn oil at 150 μl or EB at 5 or 10 mg/kg, respectively, every other day for 4 weeks. Then, we obtained the weight and indexes of the testis, performed HE staining of the paraffin sections of the testis tissue and epididymal cauda, counted the spermatozoa in the epididymal sperm suspension, and determined the expression of the proliferating cell nuclear antigen (PCNA), the mRNA expressions of CyclinA1, CyclinB1, VASA and p53, and the protein expressions of p53 and phosphorylated p53 in the testis by immunohistochemistry, qRT-PCR and Western blot, respectively.

RESULTS

In comparison with the controls, the mice treated with EB showed significantly decreased testicular indexes (P <0.05), no sperm in the sperm suspension or epididymal tubes, remarkably reduced numbers of spermatogonia, primary spermatocytes and Sertoli cells (P <0.05), down-regulated expression of PCNA (P <0.05) and mRNA expressions of CyclinA1, CyclinB1, PCNA and VASA in the seminiferous tubules (P <0.05), but a dose-dependent increase of the p53 level (P <0.05). Western blot revealed markedly higher levels of p53 protein expression and phosphorylation in the EB than in the control group (P <0.05) and even higher in the 10 mg/kg than in the 5 mg/kg EB group (P <0.05).

CONCLUSIONS

EB inhibited the proliferation of spermatogenic cells by down-regulating the expressions of cell cycle-related factors in a dose-dependent manner, which might contribute to abnormal proliferation of spermatogenic cells in the testis of infertile male mice.

Properties, metabolism and roles of sulfogalactosylglycerolipid in male reproduction

Sulfogalactosylglycerolipid (SGG, aka seminolipid) is selectively synthesized in high amounts in mammalian testicular germ cells (TGCs). SGG is an ordered lipid and directly involved in cell adhesion. SGG is indispensable for spermatogenesis, a process that greatly depends on interaction between Sertoli cells and TGCs. Spermatogenesis is disrupted in mice null for Cgt and Cst, encoding two enzymes essential for SGG biosynthesis. Sperm surface SGG also plays roles in fertilization. All of these results indicate the significance of SGG in male reproduction. SGG homeostasis is also important in male fertility. Approximately 50% of TGCs become apoptotic and phagocytosed by Sertoli cells. SGG in apoptotic remnants needs to be degraded by Sertoli lysosomal enzymes to the lipid backbone. Failure in this event leads to a lysosomal storage disorder and sub-functionality of Sertoli cells, including their support for TGC development, and consequently subfertility. Significantly, both biosynthesis and degradation pathways of the galactosylsulfate head group of SGG are the same as those of sulfogalactosylceramide (SGC), a structurally related sulfoglycolipid important for brain functions. If subfertility in males with gene mutations in SGG/SGC metabolism pathways manifests prior to neurological disorder, sperm SGG levels might be used as a reporting/predicting index of the neurological status.

Microcystin-leucine arginine (MC-LR) induced inflammatory response in bovine sertoli cell via TLR4/NF-kB signaling pathway

Sertoli cells were treated with 0, 20, 40, 60 and 80 μg/L of MC-LR to investigate its toxic effects, mechanism of action and immune response of the cells. Our results revealed that treatment containing 20 μg/L of MC-LR was non-toxic to the cells. Treatments containing 40, 60 and 80 μg/L of MC-LR reduced the cell viability, induced nuclear morphological changes and downregulated the blood-testis barrier constituent proteins within 48 h after treatment. The toll-like receptor 4 (TLR4) and nuclear factor-kappaB (NF-kB) were activated and significantly (P < 0.05) upregulated in cells treated with 40, 60 and 80 μg/L of MC-LR compared to the control. The pro-inflammatory cytokines were upregulated within 48 h after treatment. However commencing from 72 h, upregulation of anti-inflammatory cytokines and expression of blood-testis barrier constituent proteins was observed. This study indicates that MC-LR induced inflammatory response in bovine Sertoli cell via activation of TLR4/NF-kB signaling pathway.

Src family kinases (SFKs) and cell polarity in the testis

Non-receptor Src family kinases (SFKs), most notably c-Src and c-Yes, are recently shown to be expressed by Sertoli and/or germ cells in adult rat testes. Studies have shown that SFKs are involved in modulating the cell cytoskeletal function, and involved in endocytic vesicle-mediated protein endocytosis, transcytosis and/or recycling as well as intracellular protein degradation events. Furthermore, a knockdown to SFKs, in particular c-Yes, has shown to induce defects in spermatid polarity. These findings, coupled with emerging evidence in the field, thus prompt us to critically evaluate them to put forth a developing concept regarding the role of SFKs and cell polarity, which will become a basis to design experiments for future investigations.

Delineating the regulation of estrogen and androgen receptor expression by sex steroids during rat spermatogenesis

Estrogen receptors (ERα and β) and androgen receptor (AR) regulate various critical processes during spermatogenesis. Since spermatogenesis is very sensitive to hormonal stimuli and perturbations, it is important to understand the regulation of expression of these receptors by sex steroid hormones. Although many studies have reported deregulation of steroid receptors on endocrine disruption, there is no consensus on the regulation of their expression by steroid hormones during spermatogenesis, and a lack of clear understanding of the mechanism of regulation. Here, we evaluated the receptor expressions in a well-established exogenous estradiol administration model. We then investigated the mechanisms by which the individual receptors regulate their expression by binding to the respective hormone response elements upstream of these receptor genes. By further employing in vitro and in vivo models of ER and AR stimulation or antagonism, we delineated their regulation in a receptor subtype-specific manner. Our results indicate that ERα positively regulates expression of both the ERs; whereas, ERβ and AR negatively regulate expression of both ERβ and AR by direct binding to upstream regulatory regions. The perturbations in the levels of steroid receptors could be an important factor contributing to spermatogenic defects and male sub-fertility after estradiol and ER agonist treatment. Our study delineates the direct contribution of the individual steroid receptors in the regulation of their own expression.

Cell polarity and cytoskeletons-Lesson from the testis

Cell polarity in the adult mammalian testis refers to the polarized alignment of developing spermatids during spermiogenesis and the polarized organization of organelles (e.g., phagosomes, endocytic vesicles, Sertoli cell nuclei, Golgi apparatus) in Sertoli cells and germ cells to support spermatogenesis. Without these distinctive features of cell polarity in the seminiferous epithelium, it is not possible to support the daily production of millions of sperm in the limited space provided by the seminiferous tubules in either rodent or human males through the adulthood. In short, cell polarity provides a novel mean to align spermatids and the supporting organelles (e.g., phagosomes, Golgi apparatus, endocytic vesicles) in a highly organized fashion spatially in the seminiferous epithelium during the epithelial cycle of spermatogenesis. This is analogous to different assembling units in a manufacturing plant such that as developing spermatids move along the "assembly line" conferred by Sertoli cells, different structural/functional components can be added to (or removed from) the developing spermatids during spermiogenesis, so that functional spermatozoa are produced at the end of the assembly line. Herein, we briefly review findings regarding the regulation of cell polarity in the testis with specific emphasis on developing spermatids, supported by an intriguing network of regulatory proteins along a local functional axis. Emerging evidence has suggested that cell cytoskeletons provide the tracks which in turn confer the unique assembly lines in the seminiferous epithelium. We also provide some thought-provoking concepts based on which functional experiments can be designed in future studies.

Testosterone and Follicle Stimulating Hormone-Dependent Glyoxalase 1 Up-Regulation Sustains the Viability of Porcine Sertoli Cells through the Control of Hydroimidazolone- and Argpyrimidine-Mediated NF-κB Pathway

Because Sertoli cells (SCs) play a central role in germ cell survival, their death may result in marked germ cell loss and infertility. SCs are the only somatic cells within the seminiferous tubules and are essential for regulating spermatogenesis. Factors that enhance or diminish the viability of SCs may have profound effects on spermatogenesis. Yet the mechanisms underlying the maintenance of SC viability remain largely unknown. Glyoxalase 1 (Glo1) detoxifies methylglyoxal (MG), a highly reactive carbonyl species mainly formed during glycolysis, which is a potent precursor of cytotoxic advanced glycation end products (AGEs). Hydroimidazolone (MG-H1) and argpyrimidine (ArgPyr) are AGEs resulting from MG-mediated post-translational modification of arginine residues in various proteins. The role of Glo1 and MG-derived AGEs in regulating the fate of SCs has never been investigated. By using gene silencing and the specific MG scavenger, aminoguanidine, the authors demonstrate that Glo1, under testosterone and follicle-stimulating hormone control, sustains viability of porcine neonatal SCs through a mechanism involving the NF-κB pathway. Glo1 knockdown induces a mitochondrial apoptotic pathway driven by the intracellular accumulation of MG-H1 and ArgPyr that desensitizes NF-κB signaling by modifying the inhibitor of NF-κB kinase, IKKß. This is the first report describing a role for Glo1 and MG-derived AGEs in SC biology, providing valuable new insights into the potential involvement of this metabolic axis into spermatogenesis.

Glucose and glutamine handling in the Sertoli cells of transgenic rats overexpressing regucalcin: plasticity towards lactate production

Sertoli cells (SCs) possess the unparalleled ability to provide the germ line with growth factors and nutrients. Although SCs can oxidize amino acids, e.g., glutamine, they mostly metabolize glucose, producing high amounts of lactate, the germ cells preferential substrate. Regucalcin (RGN) is a calcium-binding protein that has been indicated as a regulator of cell metabolism. In this study, we investigated glucose and glutamine handling in the SCs of transgenic rats overexpressing RGN (Tg-RGN) comparatively with wild-type (Wt) littermates. Primary SCs isolated from adult Tg-RGN animals and maintained in culture for 24 hours, produced and exported more lactate, despite consuming less glucose. These observations were underpinned by increased expression of alanine transaminase, and augmented glutamine consumption, suggesting that alternative routes are contributing to the enhanced lactate production in the SCs of Tg-RGN rats. Moreover, lactate seems to be used by germ cells, with diminished apoptosis being detected in the seminiferous tubules of Tg-RGN animals cultured ex vivo. The obtained results showed a distinct metabolism in the SCs of Wt and Tg-RGN rats widening the roles assigned to RGN in spermatogenesis. These findings also highlighted the plasticity of SCs metabolism, a feature that would be exploited in the context of male infertility.

[Decline of secretory function of TM4 Sertoli cells stimulated by D-galactose in mice and its mechanism]

Objective To establish a model of decline in secretion of senescent TM4 cells in vitro induced by D-galactose (D-gal). Methods Different concentrations of D-Gal (25, 50, 100, 150, 200 and 250 mmol/L) were used to induce TM4 cell senescence. The viability of TM4 cells was detected by MTT assay. The cell cycle was analyzed by flow cytometry. The cell morphology was observed by light microscopy and the percentage of senescent cells was observed by senescence-associated β-galactosidase (SA-β-Gal) staining. The mRNA expression levels of P21, P16, glial-derived neurotrophic factor (GDNF) and stem cell factor (SCF) were detected by reverse transcription PCR. The protein expression levels of GDNF, SCF, nuclear factor erythroid 2 like 2 (NRF2), NAD(P)H dehydrogenase [quinone] 1 (NQO-1) and heme oxygenase-1 (HO-1) were detected by Western blot analysis. Results Compared with normal control group, D-Gal stimulation significantly decreased the cell viability in a concentration-dependent manner. The arrest of D-Gal-treated cells in G1 phase of cell cycle significantly increased, while it significantly decreased in S phase, and D-Gal induced cell cycle arrest at G0/G1 phase in TM4 cells. The percentages of SA-β-Gal positive cells increased significantly. The expression levels of P21 and P16 mRNAs were significantly up-regulated. The mRNA and protein levels of GDNF and SCF-1 were significantly down-regulated. Furthermore, the expression levels of oxidative stress-related protein NRF2, HO-1 and NQO-1 were significantly reduced. Conclusion The model of declined secretion function of senescent TM4 cells induced by D-Gal we established is stable and reliable. Its mechanism may be related to the down-regulation of NRF2 signaling pathway.

MiR-142-3p Inhibits TGF-β3-Induced Blood-Testis Barrier Impairment by Targeting Lethal Giant Larvae Homolog 2

BACKGROUND/AIMS

Transforming growth factor-β3 (TGF-β3) has been proved to perturb the blood-testis barrier (BTB) by accelerating junction protein endocytosis in Sertoli cells (SCs) to accommodate the traversing of preleptotene spermatocytes across the BTB around stage VIII in rat. Yet the molecular network underlying the impairment of TGF-β3 on BTB integrity is not fully elucidated. Our study herein was designed to investigate the participation of microRNA-142-3p (miR-142-3p), which has been reported to affect TGF-β3 signaling via different pathways, during BTB dynamics and the corresponding mechanisms.

METHODS

MiRNA mimic or agomiRNA was co-administered with or without TGF-β3 in the cultured SCs or in the rat testis. The SC permeability barrier function was reflected by measuring the transepithelial resistance (TER) and the permeability of the sodium fluorescein (Na-F). The BTB integrity was detected by the permeation of biotin. A luciferase reporter assay was used to testify the potential target of miR-142-3p, lethal giant larvae 2 (Lgl2). Laser capture microdissection (LCM) was applied to acquire cell components of different stages of seminiferious tubules, followed by detection of the expression levels of miR-142-3p, TGF-β3, and Lgl2 by qPCR. The SC barrier function was also detected as above in the presence of TGF-β3 after Lgl2 knockdown.

RESULTS

We revealed a reversion of TGF-β3-induced BTB impairment after miR-142-3p treatment both in vitro and in vivo. Meanwhile, the activation of Cdc42 and reduction in occludin aroused by TGF-β3 were also reversed by miR-142-3p. The predicted binding of miR-142-3p with 3'-untranslated region (3'-UTR) of Lgl2, was verified by the luciferase assay. Moreover, an increased Lgl2 level in TGF-β3-treated SCs was found and correlated stage-specific expressions of TGF-β3, miR-142-3p, and Lgl2 were revealed. Knockdown of Lgl2 in SCs was shown to partially antagonize the BTB disruption mediated by TGF-β3.

CONCLUSIONS

Collectively, our results suggest a resistance of miR-142-3p on the BTB impairment caused by TGF-β3 during the seminiferous epithelial cycle by targeting Lgl2.

Actin nucleator Spire 1 is a regulator of ectoplasmic specialization in the testis

Germ cell differentiation during the epithelial cycle of spermatogenesis is accompanied by extensive remodeling at the Sertoli cell-cell and Sertoli cell-spermatid interface to accommodate the transport of preleptotene spermatocytes and developing spermatids across the blood-testis barrier (BTB) and the adluminal compartment of the seminiferous epithelium, respectively. The unique cell junction in the testis is the actin-rich ectoplasmic specialization (ES) designated basal ES at the Sertoli cell-cell interface, and the apical ES at the Sertoli-spermatid interface. Since ES dynamics (i.e., disassembly, reassembly and stabilization) are supported by actin microfilaments, which rapidly converts between their bundled and unbundled/branched configuration to confer plasticity to the ES, it is logical to speculate that actin nucleation proteins play a crucial role to ES dynamics. Herein, we reported findings that Spire 1, an actin nucleator known to polymerize actins into long stretches of linear microfilaments in cells, is an important regulator of ES dynamics. Its knockdown by RNAi in Sertoli cells cultured in vitro was found to impede the Sertoli cell tight junction (TJ)-permeability barrier through changes in the organization of F-actin across Sertoli cell cytosol. Unexpectedly, Spire 1 knockdown also perturbed microtubule (MT) organization in Sertoli cells cultured in vitro. Biochemical studies using cultured Sertoli cells and specific F-actin vs. MT polymerization assays supported the notion that a transient loss of Spire 1 by RNAi disrupted Sertoli cell actin and MT polymerization and bundling activities. These findings in vitro were reproduced in studies in vivo by RNAi using Spire 1-specific siRNA duplexes to transfect testes with Polyplus in vivo-jetPEI as a transfection medium with high transfection efficiency. Spire 1 knockdown in the testis led to gross disruption of F-actin and MT organization across the seminiferous epithelium, thereby impeding the transport of spermatids and phagosomes across the epithelium and perturbing spermatogenesis. In summary, Spire 1 is an ES regulator to support germ cell development during spermatogenesis.

Hormone induced differential transcriptome analysis of Sertoli cells during postnatal maturation of rat testes

Sertoli cells (Sc) are unique somatic cells of testis that are the target of both FSH and testosterone (T) and regulate spermatogenesis. Although Sc of neonatal rat testes are exposed to high levels of FSH and T, robust differentiation of spermatogonial cells becomes conspicuous only after 11-days of postnatal age. We have demonstrated earlier that a developmental switch in terms of hormonal responsiveness occurs in rat Sc at around 12 days of postnatal age during the rapid transition of spermatogonia A to B. Therefore, such “functional maturation” of Sc, during pubertal development becomes prerequisite for the onset of spermatogenesis. However, a conspicuous difference in robust hormone (both T and FSH) induced gene expression during the different phases of Sc maturation restricts our understanding about molecular events necessary for the spermatogenic onset and maintenance. Here, using microarray technology, we for the first time have compared the differential transcriptional profile of Sc isolated and cultured from immature (5 days old), maturing (12 days old) and mature (60 days old) rat testes. Our data revealed that immature Sc express genes involved in cellular growth, metabolism, chemokines, cell division, MAPK and Wnt pathways, while mature Sc are more specialized expressing genes involved in glucose metabolism, phagocytosis, insulin signaling and cytoskeleton structuring. Taken together, this differential transcriptome data provide an important resource to reveal the molecular network of Sc maturation which is necessary to govern male germ cell differentiation, hence, will improve our current understanding of the etiology of some forms of idiopathic male infertility.

Identification of Proliferative and Apoptotic Sertoli Cells Using Fluorescence and Confocal Microscopy

Sertoli cells, the testicular somatic cells of the seminiferous epithelium, are vital for the survival of the epithelium. They undergo proliferation and apoptosis during fetal, neonatal, and prepubertal development. Apoptosis is increased in certain situations such as exposure to many substances, for example, toxics, or short photoperiod in the non-breeding season of some mammals. Therefore, it has always been considered that Sertoli cells that reach adulthood are quiescent cells, that is to say, nonproliferative, do not die, are terminally differentiated, and whose numbers remain constant. Recently, a degree of both proliferation and apoptosis has been observed in normal adult conditions, suggesting that consideration of this cell as quiescent may be subject to change. All this make it necessary to use histochemical techniques to demonstrate whether Sertoli cells are undergoing proliferation or apoptosis in histological sections and to allow the qualitative and quantitative study of these. In this chapter, we present two double-staining techniques that can be used for identifying Sertoli cells in proliferation or apoptosis by fluorescence microscopy. In both, the Sertoli cells are identified by an immunohistochemistry for vimentin followed by an immunohistochemistry for PCNA or a TUNEL histochemistry.