Selective ablation of the androgen receptor in mouse sertoli cells affects sertoli cell maturation, barrier formation and cytoskeletal development

Potential role of mitochondria and endoplasmic reticulum in the response elicited by D-aspartate in TM4 Sertoli cells

D-Aspartic Acid (D-Asp) affects spermatogenesis by enhancing the biosynthesis of the sex steroid hormones acting either through the hypothalamus-pituitary-testis axis or directly on Leydig cells. Recently, in vitro studies have also demonstrated the direct effects of D-Asp on the proliferation and/or activity of germ cells. However, although D-Asp is present in Sertoli cells (SC), the specific role of the amino acid in these cells remains unknown. This study investigated the effects of D-Asp on the proliferation and activity of TM4 SC, focusing on the mitochondrial compartment and its association with the endoplasmic reticulum (ER). We found that D-Asp enhanced the proliferation and activity of TM4 cells as evidenced by the activation of ERK/Akt/PCNA pathway and the increase in the protein levels of the androgen receptor. Furthermore, D-Asp reduced both the oxidative stress and apoptotic process. An increase in mitochondrial functionality and dynamics, as well as a reduction in ER stress, were also found in D-Asp-treated TM4 cells. It is known that mitochondria are closely associated with ER to form the Mitochondrial-Associated Endoplasmic Reticulum Membranes (MAM), the site of calcium ions and lipid transfer from ER to the mitochondria, and vice versa. The data demonstrated that D-Asp induced stabilization of MAM in TM4 cells. In conclusion, this study is the first to demonstrate a direct effect of D-Asp on SC activity and to clarify the cellular/molecular mechanism underlying these effects, suggesting that D-Asp could stimulate spermatogenesis by improving the efficiency of SC.

Hormone Regulation in Testicular Development and Function

The testes serve as the primary source of androgens and the site of spermatogenesis, with their development and function governed by hormonal actions via endocrine and paracrine pathways. Male fertility hinges on the availability of testosterone, a cornerstone of spermatogenesis, while follicle-stimulating hormone (FSH) signaling is indispensable for the proliferation, differentiation, and proper functioning of Sertoli and germ cells. This review covers the research on how androgens, FSH, and other hormones support processes crucial for male fertility in the testis and reproductive tract. These hormones are regulated by the hypothalamic-pituitary-gonad (HPG) axis, which is either quiescent or activated at different stages of the life course, and the regulation of the axis is crucial for the development and normal function of the male reproductive system. Hormonal imbalances, whether due to genetic predispositions or environmental influences, leading to hypogonadism or hypergonadism, can precipitate reproductive disorders. Investigating the regulatory network and molecular mechanisms involved in testicular development and spermatogenesis is instrumental in developing new therapeutic methods, drugs, and male hormonal contraceptives.

Interaction between Chromodomain Y-like Protein and Androgen Receptor Signaling in Sertoli Cells Accounts for Spermatogenesis

Spermatogenesis is a highly regulated process dependent on androgen receptor (AR) signaling in Sertoli cells. However, the pathogenic mechanisms of spermatogenic failure, by which loss of AR impairs downstream target genes to affect Sertoli cell function, remain incompletely understood. By using microarray analysis, we identified several AR-regulated genes involved in the maturation of spermatogenesis, including chromodomain Y-like protein (CDYL) and transition proteins 1 (TNP-1), that were significantly decreased in ARKO mouse testes. AR and CDYL were found to co-localize and interact in Sertoli cells. The AR-CDYL complex bound to the promoter regions of TNP1 and modulated their transcriptional activity. CDYL acts as a co-regulator of AR transactivation, and its expression is decreased in the Sertoli cells of human testes from patients with azoospermia. The androgen receptor-chromodomain Y-like protein axis plays a crucial role in regulating a network of genes essential for spermatogenesis in Sertoli cells. Disruption of this AR-CDYL regulatory axis may contribute to spermatogenic failure. These findings provide insights into novel molecular mechanisms targeting the AR-CDYL signaling pathway, which may have implications for developing new therapeutic strategies for male infertility.

Steroid hormone signaling: multifaceted support of testicular function

Embryonic development and adult physiology are dependent on the action of steroid hormones. In particular, the reproductive system is reliant on hormonal signaling to promote gonadal function and to ensure fertility. Here we will describe hormone receptor functions and their impacts on testicular function, focusing on a specific group of essential hormones: androgens, estrogens, progesterone, cortisol, and aldosterone. In addition to focusing on hormone receptor function and localization within the testis, we will highlight the effects of altered receptor signaling, including the consequences of reduced and excess signaling activity. These hormones act through various cellular pathways and receptor types, emphasizing the need for a multifaceted research approach to understand their critical roles in testicular function. Hormones exhibit intricate interactions with each other, as evidenced, for example, by the antagonistic effects of progesterone on mineralocorticoid receptors and cortisol's impact on androgens. In light of research findings in the field demonstrating an intricate interplay between hormones, a systems biology approach is crucial for a nuanced understanding of this complex hormonal network. This review can serve as a resource for further investigation into hormonal support of male reproductive health.

Autophagy regulation and protein kinase activity of PIK3C3 controls sertoli cell polarity through its negative regulation on SCIN (scinderin)

Sertoli cells are highly polarized testicular cells that provide a nurturing environment for germ cell development and maturation during spermatogenesis. The class III phosphatidylinositol 3-kinase (PtdIns3K) plays core roles in macroautophagy in various cell types; however, its role in Sertoli cells remains unclear. Here, we generated a mouse line in which the gene encoding the catalytic subunit, Pik3c3, was specifically deleted in Sertoli cells (cKO) and found that after one round of normal spermatogenesis, the cKO mice quickly became infertile and showed disruption of Sertoli cell polarity and impaired spermiogenesis. Subsequent proteomics and phosphoproteomics analyses enriched the F-actin cytoskeleton network involved in the disorganized Sertoli-cell structure in cKO testis which we identified a significant increase of the F-actin negative regulator SCIN (scinderin) and the reduced phosphorylation of HDAC6, an α-tubulin deacetylase. Our results further demonstrated that the accumulation of SCIN in cKO Sertoli cells caused the disorder and disassembly of the F-actin cytoskeleton, which was related to the failure of SCIN degradation through the autophagy-lysosome pathway. Additionally, we found that the phosphorylation of HDAC6 at site S59 by PIK3C3 was essential for its degradation through the ubiquitin-proteasome pathway. As a result, the HDAC6 that accumulated in cKO Sertoli cells deacetylated SCIN at site K189 and led to a disorganized F-actin cytoskeleton. Taken together, our findings elucidate a new mechanism for PIK3C3 in maintaining the polarity of Sertoli cells, in which both its autophagy regulation or protein kinase activities are required for the stabilization of the actin cytoskeleton.Abbreviations: ACTB: actin, beta; AR: androgen receptor; ATG14: autophagy related 14; BafA1: bafilomycin A1; BECN1: beclin 1, autophagy related; BTB: blood-testis barrier; CASP3: caspase 3; CDC42: cell division cycle 42; CDH2: cadherin 2; CHX: cycloheximide; CTNNA1: catenin (cadherin associated protein), alpha 1; CYP11A1: cytochrome P450, family 11, subfamily A, polypeptide 1; EBSS: Earle's balanced salt solution; ES: ectoplasmic specialization; FITC: fluorescein isothiocyanate; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GCNA: germ cell nuclear acidic protein; GJA1: gap junction protein, alpha 1; H2AX: H2A.X variant histone; HDAC6: histone deacetylase 6; KIT: KIT proto-oncogene, receptor tyrosine kinase; LAMP1: lysosomal associated membrane protein 1; MAP3K5: mitogen-activated protein kinase kinase kinase 5; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; OCLN: occludin; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; PNA: arachis hypogaea lectin; RAC1: Rac family small GTPase 1; SCIN: scinderin; SQSTM1/p62: sequestosome 1; SSC: spermatogonia stem cell; STK11: serine/threonine kinase 11; TJP1: tight junction protein 1; TubA: tubastatin A; TUBB3: tubulin beta 3 class III; TUNEL: TdT-mediated dUTP nick-end labeling; UB: ubiquitin; UVRAG: UV radiation resistance associated gene; VIM: vimentin; WT1: WT1 transcription factor; ZBTB16: zinc finger and BTB domain containing 16.

Classical cadherins in the testis: how are they regulated?

Cadherins (CDH) are crucial intercellular adhesion molecules, contributing to morphogenesis and creating tissue barriers by regulating cells' movement, clustering and differentiation. In the testis, classical cadherins such as CDH1, CDH2 and CDH3 are critical to gonadogenesis by promoting the migration and the subsequent clustering of primordial germ cells with somatic cells. While CDH2 is present in both Sertoli and germ cells in rodents, CDH1 is primarily detected in undifferentiated spermatogonia. As for CDH3, its expression is mainly found in germ and pre-Sertoli cells in developing gonads until the establishment of the blood-testis barrier (BTB). This barrier is made of Sertoli cells forming intercellular junctional complexes. The restructuring of the BTB allows the movement of early spermatocytes toward the apical compartment as they differentiate during a process called spermatogenesis. CDH2 is among many junctional proteins participating in this process and is regulated by several pathways. While cytokines promote the disassembly of the BTB by enhancing junctional protein endocytosis for degradation, testosterone facilitates the assembly of the BTB by increasing the recycling of endocytosed junctional proteins. Mitogen-activated protein kinases (MAPKs) are also mediators of the BTB kinetics in many chemically induced damages in the testis. In addition to regulating Sertoli cell functions, follicle stimulating hormone can also regulate the expression of CDH2. In this review, we discuss the current knowledge on regulatory mechanisms of cadherin localisation and expression in the testis.

Comparing the adult and pre-pubertal testis: Metabolic transitions and the change in the spermatogonial stem cell metabolic microenvironment

BACKGROUND

Survivors of childhood cancer often suffer from infertility. While sperm cryopreservation is not feasible before puberty, the patient's own spermatogonial stem cells could serve as a germ cell reservoir, enabling these patients to father their own children in adulthood through the isolation, in vitro expansion, and subsequent transplantation of spermatogonial stem cells. However, this approach requires large numbers of stem cells, and methods for successfully propagating spermatogonial stem cells in the laboratory are yet to be established for higher mammals and humans. The improvement of spermatogonial stem cell culture requires deeper understanding of their metabolic requirements and the mechanisms that regulate metabolic homeostasis.

AIM

This review gives a summary on our knowledge of spermatogonial stem cell metabolism during maintenance and differentiation and highlights the potential influence of Sertoli cell and stem cell niche maturation on spermatogonial stem cell metabolic requirements during development.

RESULTS AND CONCLUSIONS

Fetal human spermatogonial stem cell precursors, or gonocytes, migrate into the seminiferous cords and supposedly mature to adult stem cells within the first year of human development. However, the spermatogonial stem cell niche does not fully differentiate until puberty, when Sertoli cells dramatically rearrange the architecture and microenvironment within the seminiferous epithelium. Consequently, pre-pubertal and adult spermatogonial stem cells experience two distinct niche environments potentially affecting spermatogonial stem cell metabolism and maturation. Indeed, the metabolic requirements of mouse primordial germ cells and pig gonocytes are distinct from their adult counterparts, and novel single-cell RNA sequencing analysis of human and porcine spermatogonial stem cells during development confirms this metabolic transition. Knowledge of the metabolic requirements and their changes and regulation during spermatogonial stem cell maturation is necessary to implement laboratory-based techniques and enable clinical use of spermatogonial stem cells. Based on the advancement in our understanding of germline metabolism circuits and maturation events of niche cells within the testis, we propose a new definition of spermatogonial stem cell maturation and its amendment in the light of metabolic change.

In Vitro and In Vivo Models for Drug Transport Across the Blood-Testis Barrier

The blood-testis barrier (BTB) is a selectively permeable membrane barrier formed by adjacent Sertoli cells (SCs) in the seminiferous tubules of the testes that develops intercellular junctional complexes to protect developing germ cells from external pressures. However, due to this inherent defense mechanism, the seminiferous tubule lumen can act as a pharmacological sanctuary site for latent viruses (e.g., Ebola, Zika) and cancers (e.g., leukemia). Therefore, it is critical to identify and evaluate BTB carrier-mediated drug delivery pathways to successfully treat these viruses and cancers. Many drugs are unable to effectively cross cell membranes without assistance from carrier proteins like transporters because they are large, polar, and often carry a charge at physiologic pH. SCs express transporters that selectively permit endogenous compounds, such as carnitine or nucleosides, across the BTB to support normal physiologic activity, although reproductive toxicants can also use these pathways, thereby circumventing the BTB. Certain xenobiotics, including select cancer therapeutics, antivirals, contraceptives, and environmental toxicants, are known to accumulate within the male genital tract and cause testicular toxicity; however, the transport pathways by which these compounds circumvent the BTB are largely unknown. Consequently, there is a need to identify the clinically relevant BTB transport pathways in in vitro and in vivo BTB models that recapitulate human pharmacokinetics and pharmacodynamics for these xenobiotics. This review summarizes the various in vitro and in vivo models of the BTB reported in the literature and highlights the strengths and weaknesses of certain models for drug disposition studies. SIGNIFICANCE STATEMENT: Drug disposition to the testes is influenced by the physical, physiological, and immunological components of the blood-testis barrier (BTB). But many compounds are known to cross the BTB by transporters, resulting in pharmacological and/or toxicological effects in the testes. Therefore, models that assess drug transport across the human BTB must adequately account for these confounding factors. This review identifies and discusses the benefits and limitations of various in vitro and in vivo BTB models for preclinical drug disposition studies.

Longitudinal covariation of testosterone and sperm quality across reproductive stages in the zebra finch

Birds that breed opportunistically maintain partial activation of reproductive systems to rapidly exploit environmental conditions when they become suitable for breeding. Maintaining reproductive systems outside of a breeding context is costly. For males, these costs are thought to include continual exposure to testosterone. Males of seasonally breeding birds minimise these costs by downregulating testosterone production outside of a breeding context. Opportunistically breeding birds trade off the need to rapidly initiate reproduction with the costs of elevated testosterone production. One way opportunistically breeding males could minimise these costs is through fine scale changes in testosterone production across discrete reproductive stages which have a greater or lesser requirement for active sperm production. Although spermatogenesis broadly depends on testosterone production, whether changes in testosterone levels across the reproductive stages affect sperm quality and production is unknown. Here, we measured testosterone, sperm quality, and body condition in male zebra finches at discrete stages within reproductive bouts (egg laying, incubation, nestling provisioning, and fledging) and across two consecutive reproductive events in captive male zebra finches (Taeniopygia castanotis). We also examined associations between male testosterone, sperm quality/production, body condition, and nestling body condition. We found that testosterone levels varied across discrete reproductive stages with the lowest levels during incubation and the highest following chick fledging. Testosterone levels were positively associated with sperm velocity and the proportion of motile sperm but were not associated with male body condition. We found no associations between paternal body condition, testosterone levels, or sperm traits with nestling body condition (a proxy for the reproductive quality of a male and his partner). This study is the first to show that opportunistically breeding males vary testosterone synthesis and sperm traits at discrete stages within a reproductive event.

Steroid receptors in the testis: implications in the physiology of prenatal and postnatal development and translation to clinical application

The testes are the main source of sex steroids in the male, especially androgens and to a lesser extent estrogens. In target cells, steroid hormones typically signal after binding to intracellular receptors, which act as transcription factors. Androgens and estrogens have ubiquitous functions in peripheral organs, but also have paracrine actions within the gonads where they are far more concentrated. The levels of steroid production by the testes vary throughout fetal and postnatal development: they are high in intrauterine life and in the first months after birth, then they decline and are almost undetectable in childhood and increase again during puberty to attain adult levels. The expression of the androgen and estrogen receptors also depict specific ontogenies in the various testicular cell types. The combination of intratesticular steroid concentration with the pattern of expression of the steroid hormone receptors defines androgen and estrogen action on Sertoli, germ and Leydig cells. Here, we review the ontogeny of expression of the androgen and estrogen receptors in the testis, its impact on testicular physiology during prenatal and postnatal development, as well as its implication on the pathophysiology of different disorders affecting gonadal function throughout life.

hnRNPH1 establishes Sertoli-germ cell crosstalk through cooperation with PTBP1 and AR, and is essential for male fertility in mice

Spermatogenesis depends on the crosstalk of Sertoli cells (SCs) and germ cells. However, the gene regulatory network establishing the communications between SCs and germ cells remains unclear. Here, we report that heterogeneous nuclear ribonucleoprotein H1 (hnRNPH1) in SCs is essential for the establishment of crosstalk between SCs and germ cells. Conditional knockout of hnRNPH1 in mouse SCs leads to compromised blood-testis barrier function, delayed meiotic progression, increased germ cell apoptosis, sloughing of germ cells and, eventually, infertility of mice. Mechanistically, we discovered that hnRNPH1 could interact with the splicing regulator PTBP1 in SCs to regulate the pre-mRNA alternative splicing of the target genes functionally related to cell adhesion. Interestingly, we also found hnRNPH1 could cooperate with the androgen receptor, one of the SC-specific transcription factors, to modulate the transcription level of a group of genes associated with the cell-cell junction and EGFR pathway by directly binding to the gene promoters. Collectively, our findings reveal a crucial role for hnRNPH1 in SCs during spermatogenesis and uncover a potential molecular regulatory network involving hnRNPH1 in establishing Sertoli-germ cell crosstalk.

Functions of Steroid Hormones in the Male Reproductive Tract as Revealed by Mouse Models

Steroid hormones are capable of diffusing through cell membranes to bind with intracellular receptors to regulate numerous physiological processes. Three classes of steroid hormones, namely androgens, estrogens and glucocorticoids, contribute to the development of the reproductive system and the maintenance of fertility. During the past 30 years, mouse models have been produced in which the expression of genes encoding steroid hormone receptors has been enhanced, partially compromised or eliminated. These mouse models have revealed many of the physiological processes regulated by androgens, estrogens and to a more limited extent glucocorticoids in the testis and male accessory organs. In this review, advances provided by mouse models that have facilitated a better understanding of the molecular regulation of testis and reproductive tract processes by steroid hormones are discussed.

Impact of endocrine disrupting chemicals and pharmaceuticals on Sertoli cell development and functions

Sertoli cells play essential roles in male reproduction, from supporting fetal testis development to nurturing male germ cells from fetal life to adulthood. Dysregulating Sertoli cell functions can have lifelong adverse effects by jeopardizing early processes such as testis organogenesis, and long-lasting processes such as spermatogenesis. Exposure to endocrine disrupting chemicals (EDCs) is recognized as contributing to the rising incidence of male reproductive disorders and decreasing sperm counts and quality in humans. Some drugs also act as endocrine disruptors by exerting off-target effects on endocrine tissues. However, the mechanisms of toxicity of these compounds on male reproduction at doses compatible with human exposure are still not fully resolved, especially in the case of mixtures, which remain understudied. This review presents first an overview of the mechanisms regulating Sertoli cell development, maintenance, and functions, and then surveys what is known on the impact of EDCs and drugs on immature Sertoli cells, including individual compounds and mixtures, and pinpointing at knowledge gaps. Performing more studies on the impact of mixtures of EDCs and drugs at all ages is crucial to fully understand the adverse outcomes these chemicals may induce on the reproductive system.

Cypermethrin inhibits proliferation of Sertoli cells through AR involving DAB2IP/PI3K/AKT signaling pathway in vitro

Cypermethrin (CP) exhibits anti-androgenic effects through antagonism on androgen receptor (AR) activation. This study was to identify whether AR-mediated disabled 2 interacting protein (DAB2IP)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway was involved in CP-induced mouse Sertoli cells (TM4) proliferation disorder. Real-Time Cell Analysis-iCELLigence system was to measure cell proliferation. Bioinformatic analyses were performed to identify AR-regulated genes. Quantitative Real-Time PCR and western blot were to detect the genes and proteins levels in AR-mediated DAB2IP/PI3K/AKT pathway. Results showed CP suppressed TM4 proliferation and the expression of AR. Activation of AR restored the inhibition efficacy of CP on TM4 proliferation. AR regulated DAB2IP expression and phosphorylation levels of PI3K and AKT in CP-exposed TM4 cells. In addition, knockdown of DAB2IP alleviated the inhibition efficacy of CP on cell proliferation and phosphorylation of PI3K and AKT. Taken together, AR was a modulator in CP-induced inhibition of Sertoli cells proliferation by negatively regulating DAB2IP/PI3K/AKT signaling pathway. The study may provide a new insight for the mechanisms of male reproductive toxicity induced by CP.

The Role of ZIP9 and Androgen Receptor in the Establishment of Tight Junctions between Adult Rat Sertoli Cells

The blood-testis barrier (BTB) is formed from tight junctions (TJs) between Sertoli cells. This dynamic structure, which establishes an immune-privileged environment protecting haploid germ cells formed in puberty from cells of the innate immune system, protects male fertility. Testosterone produced in Leydig cells is one of the main regulators of TJ protein expression and BTB dynamics. Nevertheless, although it has been assumed that testosterone effects on TJs and BTB are mediated through the classical androgen receptor (AR), newer results call the importance of this receptor into question. ZIP9, a recently identified androgen receptor of plasma membranes, mediates testosterone effects that promote the expression of TJ proteins and TJ formation in a rat Sertoli cell line that lacks the classical AR. Although these findings suggest that ZIP9 mediates these testosterone effects, participation of the classical AR in these events cannot be excluded. Here we used immortalized adult rat Sertoli cells that express both ZIP9 and AR and addressed the involvement of these receptors in the stimulation of TJ protein expression and TJ formation in response to testosterone and to the androgenic peptide IAPG that acts via ZIP9. We find that both testosterone and IAPG trigger the so-called non-classical signaling pathway of testosterone and stimulate the expression of TJ-associated proteins and TJ formation. Silencing classical AR expression had no effect on the responses, whereas silencing of ZIP9 expression completely blocked them. Our results demonstrate that ZIP9 is the sole androgen receptor involved in the regulation of TJ protein expression and TJ formation at the BTB.

The Fate of Leydig Cells in Men with Spermatogenic Failure

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

Differential expression and localization of tight junction proteins in the goat epididymis

The blood-epididymis barrier (BEB) forms a unique microenvironment that is crucial for the maturation, protection, transport, and storage of spermatozoa in the epididymis. To characterize the function of tight junctions (TJs), which are constitutive components of the BEB, we determined the expression and localization of TJ proteins such as zonula occludens (ZO)-1, 2, and 3, occludin, and claudin3 (Cldn3) during postnatal development in the goat epididymis. To assess the expression patterns of TJ proteins in immature (3 months of age) and mature (14 months of age) goat epididymides, two different experimental methods were used including immunofluorescence labeling and western blotting. We show that, ZO-1, 2, and 3, and occludin, were strictly expressed and localized to the TJs of the goat epididymis, whereas Cldn3 was present in basolateral membranes as well as TJs. All TJ proteins examined were more highly expressed in the immature epididymis compared to levels in mature tissue. In conclusion, our study indicates that at least five TJ proteins, namely ZO-1, ZO-2, ZO-3, occludin, and Cldn3, are present in TJs, and the expression strength and pattern of TJ proteins tend to be age dependent in the goat epididymis. Together, these data suggest that the distinct expression patterns of TJ proteins are essential for regulating components of the luminal contents in the epididymal epithelium and for forming adequate luminal conditions that are necessary for the maturation, protection, transport, and storage of spermatozoa in the goat epididymis.

What Does Androgen Receptor Signaling Pathway in Sertoli Cells During Normal Spermatogenesis Tell Us?

Androgen receptor signaling pathway is necessary to complete spermatogenesis in testes. Difference between androgen binding location in Sertoli cell classifies androgen receptor signaling pathway into classical signaling pathway and non-classical signaling pathway. As the only somatic cell type in seminiferous tubule, Sertoli cells are under androgen receptor signaling pathway regulation via androgen receptor located in cytoplasm and plasma membrane. Androgen receptor signaling pathway is able to regulate biological processes in Sertoli cells as well as germ cells surrounded between Sertoli cells. Our review will summarize the major discoveries of androgen receptor signaling pathway in Sertoli cells and the paracrine action on germ cells. Androgen receptor signaling pathway regulates Sertoli cell proliferation and maturation, as well as maintain the integrity of blood-testis barrier formed between Sertoli cells. Also, Spermatogonia stem cells achieve a balance between self-renewal and differentiation under androgen receptor signaling regulation. Meiotic and post-meiotic processes including Sertoli cell - Spermatid attachment and Spermatid development are guaranteed by androgen receptor signaling until the final sperm release. This review also includes one disease related to androgen receptor signaling dysfunction named as androgen insensitivity syndrome. As a step further ahead, this review may be conducive to develop therapies which can cure impaired androgen receptor signaling in Sertoli cells.

Updates in Sertoli Cell-Mediated Signaling During Spermatogenesis and Advances in Restoring Sertoli Cell Function

Since their initial description by Enrico Sertoli in 1865, Sertoli cells have continued to enchant testis biologists. Testis size and germ cell carrying capacity are intimately tied to Sertoli cell number and function. One critical Sertoli cell function is signaling from Sertoli cells to germ cells as part of regulation of the spermatogenic cycle. Sertoli cell signals can be endocrine or paracrine in nature. Here we review recent advances in understanding the interplay of Sertoli cell endocrine and paracrine signals that regulate germ cell state. Although these findings have long-term implications for treating male infertility, recent breakthroughs in Sertoli cell transplantation have more immediate implications. We summarize the surge of advances in Sertoli cell ablation and transplantation, both of which are wedded to a growing understanding of the unique Sertoli cell niche in the transitional zone of the testis.

Localization and regulatory function of Yin Yang 1 (YY1) in chicken testis

In mammals, Yin Yang 1 (YY1), a pervasively expressed transcription factor related to many biological processes as an activator or inhibitor of the transcription of various genes, plays a critical role in the development of male gonads and spermatogenesis. Although the role of YY1 on the development of male gonads and spermatogenesis in mammals has been reported, its function on chicken testis are yet to be clarified. In this study, we used immunofluorescence analysis to investigate the location of YY1 in chicken testis. In embryo testis, YY1 was detected in spermatogonia and Sertoli cells, while in adult testis, YY1 was shown to be expressed in spermatogenic cells and Sertoli cells, but not in spermatozoa. Furthermore, we investigated the regulatory functions of YY1 in chicken testicular Sertoli cells by combining overexpression with RNA-sequencing. Overexpression of YY1 in Sertoli cells revealed a total of 2955 differentially expressed genes involved in various biological processes, such as male gonad development and seminiferous tubule development. Overexpression of YY1 also caused significant differences in the expression of the androgen receptor gene and the inhibin βA gene, two major genes involved in the regulation of spermatogonia in Sertoli cells. These observations indicate that YY1 may regulate the development and function of the gonads by affecting the secretion of cytokines and hormones in Sertoli cells to mediate the production and differentiation of spermatogonia.

Protein kinase A drives paracrine crisis and WNT4-dependent testis tumor in Carney complex

Large-cell calcifying Sertoli cell tumors (LCCSCTs) are among the most frequent lesions occurring in male Carney complex (CNC) patients. Although they constitute a key diagnostic criterion for this rare multiple neoplasia syndrome resulting from inactivating mutations of the tumor suppressor PRKAR1A, leading to unrepressed PKA activity, LCCSCT pathogenesis and origin remain elusive. Mouse models targeting Prkar1a inactivation in all somatic populations or separately in each cell type were generated to decipher the molecular and paracrine networks involved in the induction of CNC testis lesions. We demonstrate that the Prkar1a mutation was required in both stromal and Sertoli cells for the occurrence of LCCSCTs. Integrative analyses comparing transcriptomic, immunohistological data and phenotype of mutant mouse combinations led to the understanding of human LCCSCT pathogenesis and demonstrated PKA-induced paracrine molecular circuits in which the aberrant WNT4 signal production is a limiting step in shaping intratubular lesions and tumor expansion both in a mouse model and in human CNC testes.

Deficiency in Androgen Receptor Aggravates Traumatic Brain Injury-Induced Pathophysiology and Motor Deficits in Mice

Androgens have been shown to have a beneficial effect on brain injury and lower reactive astrocyte expression after TBI. Androgen receptors (ARs) are known to mediate the neuroprotective effects of androgens. However, whether ARs play a crucial role in TBI remains unknown. In this study, we investigated the role of ARs in TBI pathophysiology, using AR knockout (ARKO) mice. We used the controlled cortical impact model to produce primary and mechanical brain injuries and assessed motor function and brain-lesion volume. In addition, the AR knockout effects on necrosis and autophagy were evaluated after TBI. AR knockout significantly increased TBI-induced expression of the necrosis marker alpha-II-spectrin breakdown product 150 and astrogliosis marker glial fibrillary acidic protein. In addition, the TBI-induced astrogliosis increase in ARKO mice lasted for three weeks after a TBI. The autophagy marker Beclin-1 was also enhanced in ARKO mice compared with wild-type mice after TBI. Our results also indicated that ARKO mice showed a more unsatisfactory performance than wild-type mice in a motor function test following TBI. Further, they were observed to have more severe lesions than wild-type mice after injury. These findings strongly suggest that ARs play a role in TBI.

Insulin treatment to type 1 male diabetic rats protects fertility by avoiding testicular apoptosis and cell cycle arrest

BACKGROUND

Uncontrolled type 1 diabetes mellitus (T1D) impairs reproductive potential of males. Insulin treatment restores metabolic parameters but it is unclear how it protects male reproductive health. Herein, we hypothesized that insulin treatment to T1D rats protects testicular physiology by mediating mechanisms associated with apoptosis and cell cycle.

METHODS

Mature male Wistar rats (n = 24) were divided into 3 groups: control, T1D-induced (received 40 mg kg-1 streptozotocin) and insulin-treated T1D (Ins T1D; received 40 mg kg-1 streptozotocin and then treated 0.9 IU/100 gr of insulin for 56 days) (N = 8/group). Expression levels of intrinsic apoptosis pathways regulators (Bcl-2, Bax, Caspase-3 and p53) and core regulators of cell cycle machinery (Cyclin D1, Cdk-4 and p21) were determined in testicular tissue by immunohistochemistry (IHC) and RT-PCR techniques. The percentage of testicular apoptotic cells was evaluated by TUNEL staining.

RESULTS

Our data shows that insulin treatment to T1D rats restored (P < 0.05) T1D-induced increased of caspase-3 and p53 expression in testis. Moreover, the testis of T1D rats treated with insulin exhibited increased expression of Cyclin D1 and cdk-4, and a reduced expression of p21 when compared with the expression in testis of T1D rats. Finally, insulin treatment could fairly control T1D-induced apoptosis. Accordingly, treatment of T1D rats with insulin led to a remarkable reduction (p < 0.05) in the percentage of apoptotic cells in the testis.

CONCLUSIONS

Insulin treatment is able to restore the network expression of apoptosis and proliferation-related genes caused by T1D in the testis and via this mechanism, preserve the fertility of males.

Kpna6 deficiency causes infertility in male mice by disrupting spermatogenesis

Spermatogenesis is driven by an ordered series of events, which rely on trafficking of specific proteins between nucleus and cytoplasm. The karyopherin α family of proteins mediates movement of specific cargo proteins when bound to karyopherin β. Karyopherin α genes have distinct expression patterns in mouse testis, implying they may have unique roles during mammalian spermatogenesis. Here, we use a loss-of-function approach to determine specifically the role of Kpna6 in spermatogenesis and male fertility. We show that ablation of Kpna6 in male mice leads to infertility and has multiple cumulative effects on both germ cells and Sertoli cells. Kpna6-deficient mice exhibit impaired Sertoli cell function, including loss of Sertoli cells and a compromised nuclear localization of the androgen receptor. Furthermore, our data demonstrate devastating defects on spermiogenesis, including incomplete sperm maturation and a massive reduction in sperm number, accompanied by disturbed histone-protamine exchange, differential localization of the transcriptional regulator BRWD1 and altered expression of RFX2 target genes. Our work uncovers an essential role of Kpna6 in spermatogenesis and, hence, in male fertility.

Summary: Two different mouse models delineate the morphological and functional impact of Kpna6 on spermatogenesis and Sertoli cell function and show that this protein is crucial for fertility in male mice.

Wuzi-Yanzong prescription alleviates spermatogenesis disorder induced by heat stress dependent on Akt, NF-κB signaling pathway

Akt and nuclear factor kappa B (NF-κB) signaling pathways are involved in germ cell apoptosis and inflammation after testicular heat stress (THS). We observed that after THS induced by the exposure of rat testes to 43 °C for 20 min, their weight decreased, the fraction of apoptotic testicular germ cells significantly increased, and the proliferation of germ cells was inhibited. In addition, THS lowered serum testosterone (T) level, whereas the levels of follicle stimulating hormone and luteinizing hormone were not significantly changed. The ultrastructure of the seminiferous tubules became abnormal after THS, the structure of the blood-testis barrier (BTB) became loose, and the Sertoli cells showed a trend of differentiation. The level of phosphorylated Akt was reduced, whereas the amount of phosphorylated NF-κB p65 was augmented by THS. Wuzi-Yanzong (WZYZ), a classic Chinese medicine prescription for the treatment of male reproductive dysfunctions, alleviated the changes induced by THS. In order to determine the mechanism of action of WZYZ, we investigated how this preparation modulated the levels of T, androgen receptor (AR), erythropoietin (EPO), EPO receptor, and Tyro-3, Axl, and Mer (TAM) family of tyrosine kinase receptors. We found that WZYZ activated the Akt pathway, inhibited the Toll-like receptor/MyD88/NF-κB pathway, and repaired the structure of BTB by regulating the levels of T, AR, TAM receptors, and EPO. In conclusion, these results suggest that WZYZ activates the Akt pathway and inhibits the NF-κB pathway by acting on the upstream regulators, thereby improving spermatogenesis deficit induced by THS.

Long-Term Maintenance of Viable Adult Rat Sertoli Cells Able to Establish Testis Barrier Components and Function in Response to Androgens

A protocol for the isolation and long-term propagation of adult rat Sertoli cells (SCs) using conditional reprogramming (CR) was developed and the formation of tight junctions as an in vitro model for the blood testis barrier (BTB) was studied. Three pure primary SC lines were isolated successfully and maintained for several months without significant changes in expression levels of SC-typical markers such as SRY-box transcription factor 9 (SOX9), transferrin, clusterin, androgen receptor (AR), and GATA binding protein 1 (GATA1). In addition to AR expression, the tight junction proteins, zonula occludens-1 (ZO-1) and the junctional adhesion molecule-3 (JAM-3), were upregulated and the SC barrier integrity was enhanced by testosterone. Peritubular/myoid cells did not increase the tightness of the SC. The cytokines, interleukin-6 (IL-6), bone morphogenetic protein-2 (BMP2), and transforming growth factor beta-3 (TGF-β3), negatively affected the tightness of the SC barrier. We have established a protocol for the isolation and long-term propagation of highly pure primary adult rat SCs, which are able to respond to androgen treatments, to form tight junctions and to maintain the mRNA expression of SC-specific genes. By applying this new method, adult SCs can now be analyzed in more detail and might serve as an in vitro model for the study of many SC functions.

Two distinct Sertoli cell states are regulated via germ cell crosstalk

Sertoli cells are a critical component of the testis environment for their role in maintaining seminiferous tubule structure, establishing the blood-testis barrier, and nourishing maturing germ cells in a specialized niche. This study sought to uncover how Sertoli cells are regulated in the testis environment via germ cell crosstalk in the mouse. We found two major clusters of Sertoli cells as defined by their transcriptomes in Stages VII-VIII of the seminiferous epithelium and a cluster for all other stages. Additionally, we examined transcriptomes of germ cell-deficient testes and found that these existed in a state independent of either of the germ cell-sufficient clusters. Together, we highlight two main transcriptional states of Sertoli cells in an unperturbed testis environment, and a germ cell-deficient environment does not allow normal Sertoli cell transcriptome cycling and results in a state unique from either of those seen in Sertoli cells from a germ cell-sufficient environment.

Nonclassical androgen and estrogen signaling is essential for normal spermatogenesis

Signaling by androgens through androgen receptor (AR) is essential to complete spermatogenesis in the testis. Similarly, loss of the main estrogen receptor, estrogen receptor 1 (ESR1; also known as ERα), results in male infertility, due in part to indirect deleterious effects on the seminiferous epithelium and spermatogenesis. Effects of steroid hormones are induced primarily through genomic changes induced by hormone-mediated activation of their intracellular receptors and subsequent effects on nuclear gene transcription. However, androgens and estrogens also signal through rapid nonclassical pathways involving actions initiated at the cell membrane. Here we review the data that nonclassical androgen and estrogen signaling pathways support processes essential for male fertility in the testis and reproductive tract. The recent development of transgenic mice lacking nonclassical AR or ESR1 signaling but retaining genomic nuclear signaling has provided a powerful tool to elucidate the function of nonclassical signaling in the overall response to androgens and estrogens. Results from these mice have emphasized that nonclassical signaling is essential for full responses to these hormones, and absence of either nonclassical or classical AR or ESR1 pathways produces abnormalities in spermatogenesis and the male reproductive tract. Although additional work is required to fully understand how classical and nonclassical receptor signaling synergize to produce full steroid hormone responses, here we summarize the known physiological functions of the classical and nonclassical androgen and estrogen signaling pathways in the testis and reproductive tract.

Lycium barbarum Polysaccharide Ameliorates Heat-Stress-Induced Impairment of Primary Sertoli Cells and the Blood-Testis Barrier in Rat via Androgen Receptor and Akt Phosphorylation

Male infertility induced by heat stress has been attracting more and more attention. Heat stress not only causes apoptosis of spermatocytes but also has adverse effects on Sertoli cells, further damaging spermatogenesis. Lycium barbarum polysaccharide (LBP) is the main bioactive component of Lycium barbarum, which has a protective effect on male reproduction, but its mechanism is still unclear. In this study, our results proved that LBP blocked the inhibitory effect on the proliferation activity of Sertoli cells after heat stress, reversed the dedifferentiation of Sertoli cells induced by heat stress, and ameliorated the structural integrity of the blood-testis barrier. In addition, it increased the expression of the androgen receptor and activated Akt signaling pathway to resist heat-stress-induced injury of Sertoli cells.

Novel Gene Regulation in Normal and Abnormal Spermatogenesis

Spermatogenesis is a complex and dynamic process which is precisely controlledby genetic and epigenetic factors. With the development of new technologies (e.g., single-cell RNA sequencing), increasingly more regulatory genes related to spermatogenesis have been identified. In this review, we address the roles and mechanisms of novel genes in regulating the normal and abnormal spermatogenesis. Specifically, we discussed the functions and signaling pathways of key new genes in mediating the proliferation, differentiation, and apoptosis of rodent and human spermatogonial stem cells (SSCs), as well as in controlling the meiosis of spermatocytes and other germ cells. Additionally, we summarized the gene regulation in the abnormal testicular microenvironment or the niche by Sertoli cells, peritubular myoid cells, and Leydig cells. Finally, we pointed out the future directions for investigating the molecular mechanisms underlying human spermatogenesis. This review could offer novel insights into genetic regulation in the normal and abnormal spermatogenesis, and it provides new molecular targets for gene therapy of male infertility.

Low Doses of Glyphosate/Roundup Alter Blood-Testis Barrier Integrity in Juvenile Rats

It has been postulated that glyphosate (G) or its commercial formulation Roundup (R) might lead to male fertility impairment. In this study, we investigated the possible effects of G or R treatment of juvenile male rats on blood-testis barrier function and on adult male sperm production. Pups were randomly assigned to the following groups: control group (C), receiving water; G2 and G50 groups, receiving 2 and 50 mg/kg/day G respectively; and R2 and R50 groups receiving 2 and 50 mg/kg/day R respectively. Treatments were performed orally from postnatal day (PND) 14 to 30, period of life that is essential to complete a functional blood-testis barrier. Evaluation was done on PND 31. No differences in body and testis weight were observed between groups. Testis histological analysis showed disorganized seminiferous epithelium, with apparent low cellular adhesion in treated animals. Blood-testis barrier permeability to a biotin tracer was examined. A significant increase in permeable tubules was observed in treated groups. To evaluate possible mechanisms that could explain the effects on blood-testis barrier permeability, intratesticular testosterone levels, androgen receptor expression, thiobarbituric acid reactive substances (TBARS) and the expression of intercellular junction proteins (claudin11, occludin, ZO-1, connexin43, 46, and 50 which are components of the blood-testis barrier) were examined. No modifications in the above-mentioned parameters were detected. To evaluate whether juvenile exposure to G and R could have consequences during adulthood, a set of animals of the R50 group was allowed to grow up until PND 90. Histological analysis showed that control and R50 groups had normal cellular associations and complete spermatogenesis. Also, blood-testis barrier function was recovered and testicular weight, daily sperm production, and epididymal sperm motility and morphology did not seem to be modified by juvenile treatment. In conclusion, the results presented herein show that continuous exposure to low doses of G or R alters blood-testis barrier permeability in juvenile rats. However, considering that adult animals treated during the juvenile stage showed no differences in daily sperm production compared with control animals, it is feasible to think that blood-testis barrier impairment is a reversible phenomenon. More studies are needed to determine possible damage in the reproductive function of human juvenile populations exposed to low doses of G or R.

Scientific and Regulatory Policy Committee Best Practices: Documentation of Sexual Maturity by Microscopic Evaluation in Nonclinical Safety Studies

The sexual maturity status of animals in nonclinical safety studies can have a significant impact on the microscopic assessment of the reproductive system, the interpretation of potential test article-related findings, and ultimately the assessment of potential risk to humans. However, the assessment and documentation of sexual maturity for animals in nonclinical safety studies is not conducted in a consistent manner across the pharmaceutical and chemical industries. The Scientific and Regulatory Policy Committee of the Society of Toxicologic Pathology convened an international working group of pathologists and nonclinical safety scientists with expertise in the reproductive system, pathology nomenclature, and Standard for Exchange of Nonclinical Data requirements. This article describes the best practices for documentation of the light microscopic assessment of sexual maturity in males and females for both rodent and nonrodent nonclinical safety studies. In addition, a review of the microscopic features of the immature, peripubertal, and mature male and female reproductive system and general considerations for study types and reporting are provided to aid the study pathologist tasked with documentation of sexual maturity.

Androgen Actions in the Testis and the Regulation of Spermatogenesis

Testosterone is essential for spermatogenesis and male fertility. In this review, topics related to testosterone control of spermatogenesis are covered including testosterone production and levels in the testis, classical and nonclassical testosterone signaling pathways, cell- and temporal-specific expression of the androgen receptor in the testis and autocrine and paracrine signaling of testis cells in the testis. Also discussed are the contributions of testosterone to testis descent, the blood-testis barrier, control of gonocyte numbers and spermatogonia expansion, completion of meiosis and attachment and release of elongaed spermatids. Testosterone-regulated genes identified in various mouse models of idsrupted Androgen receptor expression are discussed. Finally, examples of synergism and antagonism between androgen and follicle-stimulating hormone signaling pathways are summarized.

Involvement of Testosterone Signaling in the Integrity of the Neurovascular Unit in the Male: Review of Evidence, Contradictions, and Hypothesis

Age-related central nervous system function decline and increased susceptibility of females compared to males with respect to prevalence of several neurodegenerative and neuropsychiatric diseases are both based on the principle that hormonal factors could be involved. These cerebral disorders are characterized by an alteration of blood-brain barrier (BBB) properties and chronic neuroinflammation, which lead to disease progression. Neuroinflammation, in turn, contributes to BBB dysfunction. The BBB and its environment, called the neurovascular unit (NVU), are crucial for cerebral homeostasis and neuronal function. Interestingly, sex steroids influence BBB properties and modulate neuroinflammatory responses. To date however, the majority of work reported has focused on the effects of estrogens on BBB function and neuroinflammation in female mammals. In contrast, the effects of testosterone signaling on the NVU in males are still poorly studied. The aim of this review was to summarize and discuss the literature, providing insights and contradictions to highlight hypothesis and the need for further investigations.

AR regulates porcine immature Sertoli cell growth via binding to RNF4 and miR-124a

Sertoli cells are the only somatic cells in the seminiferous epithelium which directly contact with germ cells. Sertoli cells exhibit polarized alignment at the basal membrane of seminiferous tubules to maintain the microenvironment for growth and development of germ cells, and therefore play a crucial role in spermatogenesis. Androgens exert their action through androgen receptor (AR) and AR signalling in the testis is essential for maintenance of spermatogonial numbers, blood-testis barrier integrity, completion of meiosis, adhesion of spermatids and spermiation. In the present study, we demonstrated that AR gene could promote the proliferation of immature porcine Sertoli cells (ST cells) and the cell cycle procession, and accelerate the transition from G1 phase into S phase in ST cells. Meanwhile, miR-124a could affect the proliferation and cell cycle procession of ST cells by targeting 3'-UTR of AR gene. Furthermore, AR bound to the RNF4 via AR DNA-binding domain (DBD) and we verified that RNF4 was necessary for AR to regulate the growth of ST cells. Above all, this study suggests that AR regulates ST cell growth via binding to RNF4 and miR-124a, which may help us to further understand the function of AR in spermatogenesis.

Crosstalk between Androgen-ZIP9 Signaling and Notch Pathway in Rodent Sertoli Cells

Our recent study demonstrated altered expression of Notch ligands, receptors, and effector genes in testes of pubertal rats following reduced androgen production or signaling. Herein we aimed to explore the role of nuclear androgen receptor (AR) and membrane androgen receptor (Zrt- and Irt-like protein 9; ZIP9) in the regulation of Notch pathway activation in rodent Sertoli cells. Experiments were performed using TM4 and 15P-1 Sertoli cell lines and rat primary Sertoli cells (PSC). We found that testosterone (10^-8 M-10^-6 M) increased the expression of Notch1 receptor, its active form Notch1 intracellular domain (N1ICD) (p < 0.05, p < 0.01, p < 0.001), and the effector genes Hey1 (p < 0.05, p < 0.01, p < 0.001) and Hes1 (p < 0.05, p < 0.001) in Sertoli cells. Knockdown of AR or ZIP9 as well as antiandrogen exposure experiments revealed that (i) action of androgens via both AR and ZIP9 controls Notch1/N1ICD expression and transcriptional activity of recombination signal binding protein (RBP-J), (ii) AR-dependent signaling regulates Hey1 expression, (iii) ZIP9-dependent pathway regulates Hes1 expression. Our findings indicate a crosstalk between androgen and Notch signaling in Sertoli cells and point to cooperation of classical and non-classical androgen signaling pathways in controlling Sertoli cell function.

Testis and blood-testis barrier in Covid-19 infestation: role of angiotensin-converting enzyme 2 in male infertility

Severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) that causes COVID-19 infections penetrates body cells by binding to angiotensin-converting enzyme-2 (ACE2) receptors. Evidence shows that SARS-CoV-2 can also affect the urogenital tract. Hence, it should be given serious attention when treating COVID-19-infected male patients of reproductive age group. Other viruses like HIV, mumps, papilloma and Epstein-Barr can induce viral orchitis, germ cell apoptosis, inflammation and germ cell destruction with attending infertility and tumors. The blood-testis barrier (BTB) and blood-epididymis barrier (BEB) are essential physical barricades in the male reproductive tract located between the blood vessel and seminiferous tubules in the testes. Despite the significant role of these barriers in male reproductive function, studies have shown that a wide range of viruses can still penetrate the barriers and induce testicular dysfunctions. Therefore, this mini-review highlights the role of ACE2 receptors in promoting SARS-CoV-2-induced blood-testis/epididymal barrier infiltration and testicular dysfunction.

Protective effect of Dioscorea zingiberensis ethanol extract on the disruption of blood-testes barrier in high-fat diet/streptozotocin-induced diabetic mice by upregulating ZO-1 and Nrf2

Testicular injury is the primary pathogenesis of diabetes-induced male infertility. Dioscorea zingiberensis (DZ), a traditional Chinese medicine (TCM) including saponins, flavonoids and cellulose, is used to treat diseases in the reproductive system. But the protective effects of DZ on diabetes-induced testicular injury remain poorly understood. In this study, the therapeutic effects of chronic oral DZ treatment on testis impairment in a diabetic mouse model were explored by assessing sperm morphology, blood-testes barrier (BTB) integrity and testicular histological examination. Our results showed that DZ significantly reversed BTB disruption, testicular tissue injury and abnormal sperm morphology in diabetic mice. Interestingly, diabetes-induced disruption of the BTB was associated with a decrease in the tight junction (TJ) protein zonula occludens-1 (ZO-1). Dioscorea zingiberensis effectively increased ZO-1 expression in testis tissue to restore the integrity of the BTB. Moreover, DZ treatment significantly reduced hyperglycaemia-induced increases in malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. Further mechanistic studies revealed that DZ substantially enhanced the expression of Nrf2, NOQ1 and HO-1, which indicated that DZ exerts potential antioxidant effects against testicular tissue damage via the activation of Nrf2. In conclusion, the protective effects of DZ rely on repairing the integrity of the BTB and on reducing oxidative stress damage by mediating ZO-1 and Nrf2. The study contributes to discovering the DZ possible mechanism of action.

Notch signaling regulates nuclear androgen receptor AR and membrane androgen receptor ZIP9 in mouse Sertoli cells

BACKGROUND

Notch signaling pathway is involved in contact-dependent communication between the cells of seminiferous epithelium, and its proper activity is important for undisturbed spermatogenesis.

OBJECTIVES

The aim was to assess the effect of Notch pathway inhibition on the expression of nuclear (AR) and membrane (ZIP9) androgen receptors and androgen-regulated genes, claudin-5 and claudin-11, in TM4 mouse Sertoli cell line.

MATERIALS AND METHODS

DAPT (γ-secretase inhibitor) treatment and recombination signal binding protein silencing were employed to reduce Notch signaling, whereas immobilized ligands were used to activate Notch pathway in TM4 cells. To reveal specific effect of each androgen receptor, AR or ZIP9 silencing was performed.

RESULTS

Notch pathway inhibition increased the expression of AR and ZIP9 mRNA and proteins (p < 0.01; p < 0.05) in TM4 cells, whereas incubation with Notch ligands, rDLL1 or rJAG1, reduced AR (p < 0.01; p < 0.001) and ZIP9 (p < 0.05; p < 0.01) expressions, respectively. Testosterone enhanced the expression of both receptors (p < 0.05; p < 0.01). Androgen-regulated claudin-5 and claudin-11 (p < 0.01; p < 0.001) and cAMP (p < 0.001) were elevated in Notch-inhibited cells, while activation of Notch signaling by DLL1 or JAG1 reduced claudin-11 or claudin-5 level (p < 0.01; p < 0.001), respectively.

DISCUSSION

Our findings indicate opposite effect of Notch and androgen signaling on the expression of androgen receptors in TM4 cells. We demonstrated that AR expression is regulated by DLL1-mediated Notch signaling, whereas JAG1 is involved in the regulation of ZIP9. The expression of both claudins and cAMP production is under inhibitory influence of Notch pathway. The effects of Notch signaling on claudin-5 and claudin-11 expression are mediated by ZIP9 and AR, respectively.

CONCLUSION

Notch signaling may be considered as an important pathway controlling Sertoli cell physiology, and its alterations may contribute to disturbed response of Sertoli cells to androgens.

Importance of the Androgen Receptor Signaling in Gene Transactivation and Transrepression for Pubertal Maturation of the Testis

Androgens are key for pubertal development of the mammalian testis, a phenomenon that is tightly linked to Sertoli cell maturation. In this review, we discuss how androgen signaling affects Sertoli cell function and morphology by concomitantly inhibiting some processes and promoting others that contribute jointly to the completion of spermatogenesis. We focus on the molecular mechanisms that underlie anti-Müllerian hormone (AMH) inhibition by androgens at puberty, as well as on the role androgens have on Sertoli cell tight junction formation and maintenance and, consequently, on its effect on proper germ cell differentiation and meiotic onset during spermatogenesis.

Gametogenesis: A journey from inception to conception

Gametogenesis, the process of forming mature germ cells, is an integral part of both an individual's and a species' health and well-being. This chapter focuses on critical male and female genetic and epigenetic processes underlying normal gamete formation through their differentiation to fertilization. Finally, we explore how knowledge gained from this field has contributed to progress in areas with great clinical promise, such as in vitro gametogenesis.

Hypogonadism and Cryptorchidism

Congenital cryptorchidism (undescended testis) is one of the most common congenital urogenital malformations in boys. Prevalence of cryptorchidism at birth among boys born with normal birth weight ranges from 1.8 to 8.4%. Cryptorchidism is associated with a risk of low semen quality and an increased risk of testicular germ cell tumors. Testicular hormones, androgens and insulin-like peptide 3 (INSL3), have an essential role in the process of testicular descent from intra-abdominal position into the scrotum in fetal life. This explains the increased prevalence of cryptorchidism among boys with diseases or syndromes associated with congenitally decreased secretion or action of androgens, such as patients with congenital hypogonadism and partial androgen insensitivity syndrome. There is evidence to support that cryptorchidism is associated with decreased testicular hormone production later in life. It has been shown that cryptorchidism impairs long-term Sertoli cell function, but may also affect Leydig cells. Germ cell loss taking place in the cryptorchid testis is proportional to the duration of the condition, and therefore early orchiopexy to bring the testis into the scrotum is the standard treatment. However, the evidence for benefits of early orchiopexy for testicular endocrine function is controversial. The hormonal treatments using human chorionic gonadotropin (hCG) or gonadotropin-releasing hormone (GnRH) to induce testicular descent have low success rates, and therefore they are not recommended by the current guidelines for management of cryptorchidism. However, more research is needed to assess the effects of hormonal treatments during infancy on future male reproductive health.

Testicular Degeneration and Infertility following Arbovirus Infection

Arboviruses can cause a variety of clinical signs, including febrile illness, arthritis, encephalitis, and hemorrhagic fever. The recent Zika epidemic highlighted the possibility that arboviruses may also negatively affect the male reproductive tract. In this study, we focused on bluetongue virus (BTV), the causative agent of bluetongue and one of the major arboviruses of ruminants. We show that rams that recovered from bluetongue displayed signs of testicular degeneration and azoospermia up to 100 days after the initial infection. Importantly, testicular degeneration was induced in rams experimentally infected with either a high (BTV-1_IT2006)- or a low (BTV-1_IT2013)-virulence strain of BTV. Rams infected with the low-virulence BTV strain displayed testicular lesions in the absence of other major clinical signs. Testicular lesions in BTV-infected rams were due to viral replication in the endothelial cells of the peritubular areas of the testes, resulting in stimulation of a type I interferon response, reduction of testosterone biosynthesis by Leydig cells and destruction of Sertoli cells and the blood-testis barrier in more severe cases. Hence, BTV induces testicular degeneration and disruption of spermatogenesis by replicating solely in the endothelial cells of the peritubular areas unlike other gonadotropic viruses. This study shows that a naturally occurring arboviral disease can cause testicular degeneration and affect male fertility at least temporarily.IMPORTANCE During the recent Zika epidemic, it has become apparent that arboviruses could potentially cause reproductive health problems in male patients. Little is known regarding the effects that arboviruses have on the male reproductive tract. Here, we studied bluetongue virus (BTV), an arbovirus of ruminants, and its effects on the testes of rams. We show that BTV was able to induce testicular degeneration in naturally and experimentally infected rams. Testicular degeneration was caused by BTV replication in the endothelial cells of the peritubular area surrounding the seminiferous tubules (the functional unit of the testes) and was associated with a localized type I interferon response, destruction of the cells supporting the developing germinal cells (Sertoli cells), and reduction of testosterone synthesis. As a result of BTV infection, rams became azoospermic. This study highlights that problems in the male reproductive tract caused by arboviruses could be more common than previously thought.

The effects of flutamide on cell-cell junctions in the testis, epididymis, and prostate

In this review, we summarize recent findings on the effect of the anti-androgen flutamide on cell-cell junctions in the male reproductive system. We outline developmental aspects of flutamide action on the testis, epididymis, and prostate, and describe changes in junction protein expression and organization of junctional complexes in the adult boar following prenatal and postnatal exposure. We also discuss findings on the mechanisms by which flutamide induces alterations in cell-cell junctions in reproductive tissues of adult males, with special emphasis on cytoplasmic effects. Based on the results from in vivo and in vitro studies in the rat, we propose that flutamide affects the expression of junction proteins and junction complex structure not only by inhibiting androgen receptor activity, but equally important by modulating protein kinase-dependent signaling in testicular cells. Additionally, results from studies on prostate cancer cell lines point to a role for the cellular molecular outfit in response to flutamide.

Loss of connexin43 in murine Sertoli cells and its effect on blood-testis barrier formation and dynamics

Connexin43 (Cx43) is the predominant testicular gap junction protein and in cases of impaired spermatogenesis, Cx43 expression has been shown to be altered in several mammals. Amongst other functions, Cx43 is supposed to regulate junction formation of the blood-testis barrier (BTB). The aim of the present study was to investigate the expression pattern of different tight junction (TJ) proteins of the murine BTB using SC-specific Cx43 knockout mice (SCCx43KO). Adult homozygous male SCCx43KO mice (SCCx43KO-/-) predominantly show an arrest of spermatogenesis and SC-only tubules that might have been caused by an altered BTB assembly, composition or regulation. TJ molecules claudin-3, -5 and -11 were examined in adult wild type (WT) and SCCx43KO-/- mice using immunohistochemistry (IHC) and quantitative real-time PCR (qRT-PCR). In this context, investigation of single tubules with residual spermatogenesis in SCCx43KO-/- mice was particularly interesting to identify a potential Cx43-independent influence of germ cells (GC) on BTB composition and dynamics. In tubules without residual spermatogenesis, a diffuse cytoplasmic distribution pattern for claudin-11 protein could be demonstrated in mutant mice. Nevertheless, claudin-11 seems to form functional TJ. Claudin-3 and -5 could not be detected immunohistochemically in the seminiferous epithelium of those tubules. Correspondingly, claudin-3 and -5 mRNA expression was decreased, providing evidence of generally impaired BTB dynamics in adult KO mice. Observations of tubules with residual spermatogenesis suggested a Cx43-independent regulation of TJ proteins by GC populations. To determine initial BTB formation in peripubertal SCCx43KO-/- mice, immunohistochemical staining and qRT-PCR of claudin-11 were carried out in adolescent SCCx43KO-/- and WT mice. Additionally, BTB integrity was functionally analysed using a hypertonic glucose fixative. These analyses revealed that SCCx43KO-/- mice formed an intact BTB during puberty in the same time period as WT mice, which however seemed to be accelerated.

How French media have portrayed ADHD to the lay public and to social workers

Two models of attention deficit hyperactivity disorder (ADHD) coexist: the biomedical and the psychosocial. We identified in nine French newspapers 159 articles giving facts and opinions about ADHD from 1995 to 2015. We classified them according to the model they mainly supported and on the basis of what argument. Two thirds (104/159) mainly supported the biomedical model. The others either defended the psychodynamic understanding of ADHD or voiced both models. Neurological dysfunctions and genetic risk factors were mentioned in support of the biomedical model in only 26 and eight articles, respectively. These biological arguments were less frequent in the most recent years. There were fewer articles mentioning medication other than asserting that medication must be combined with psychosocial interventions (14 versus 57 articles). Only 11/159 articles claimed that medication protects from school failure. These results were compared to those of our two previous studies. Thus, both French newspapers and the specialized press read by social workers mainly defended either the psychodynamic understanding of ADHD or a nuanced version of the biomedical model. In contrast, most French TV programmes described ADHD as an inherited neurological disease whose consequences on school failure can be counteracted by a very effective medication.

Establishment, maintenance and functional integrity of the blood-testis barrier in organotypic cultures of fresh and frozen/thawed prepubertal mouse testes

STUDY QUESTION

Can the spatio-temporal formation of an intact blood-testis barrier (BTB), which is essential for the progression of spermatogenesis, be reproduced in cultures of fresh or frozen/thawed prepubertal mouse testes?

SUMMARY ANSWER

Organotypic cultures allow the establishment and maintenance of major BTB components and the formation of a functional BTB in mouse testicular tissues.

WHAT IS KNOWN ALREADY

In vitro maturation of prepubertal testicular tissues is a promising approach to restore fertility in adult survivors of childhood cancer. Although gametes can be successfully obtained from prepubertal mouse testes in organotypic cultures, the spermatogenic yield remains low compared to in vivo controls.

STUDY DESIGN, SIZE, DURATION

Mouse testicular tissues were frozen using controlled slow freezing (CSF) or solid surface vitrification (SSV) procedures. A total of 158 testes (fresh n = 58, CSF n = 58 or SSV n = 42) from 6 to 7 days postpartum (dpp) mice were cultured at 34°C in basal medium (α-MEM, 10% KnockOut Serum Replacement, 5 μg/ml gentamicin) at a gas-liquid interphase (under 20% O2), with or without 10-6 M retinol, for 9, 16 and 30 days. In addition, 32 testes from 6-7, 15-16, 22-23 and 36-37 dpp mice were used as in vivo controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The mRNA levels of BTB genes (Claudin 3, Claudin 11, Zonula occludens 1 and Connexin-43), germ cell-specific genes (Sal-like protein 4, Kit oncogene, Stimulated by retinoic acid gene 8, Synaptonemal complex protein 3, Transition protein 1 and Protamine 2), markers of Sertoli cell immaturity/maturity (anti-Mullerian hormone, androgen receptor, cyclin-dependent kinase inhibitor 1b) and the androgen-regulated gene Reproductive homeobox 5 (Rhox5) were measured by quantitative RT-PCR (RT-qPCR). The localization of BTB proteins in seminiferous tubules was studied by immunohistochemistry and spermatogenic progression was evaluated histologically. The integrity of the BTB was assessed using a biotin tracer.

MAIN RESULTS AND THE ROLE OF CHANCE

Modest differences in Claudin 11 (Cldn11), Zonula occludens 1 (Zo-1), Connexin-43 (Cx43) transcript levels and in the localization of the corresponding proteins were found between in vitro cultures of fresh or frozen/thawed testes and in vivo controls (P < 0.05). However, a 32-77-fold decrease in Claudin 3 (Cldn3) mRNA levels and a lack of CLDN3 immunolabelling in 36-44% of seminiferous tubules were observed in 30-day organotypic cultures (P < 0.05). Although Sertoli cell maturation and the completion of a full spermatogenic cycle were achieved after 30 days of culture, meiotic and postmeiotic progression was altered in cultured testicular tissues (P < 0.05). Moreover, an increased BTB permeability and a decreased expression of Rhox5 were observed at the end of the culture period in comparison with in vivo controls (P < 0.05). Completion of spermatogenesis occurred in vitro in seminiferous tubules with an intact BTB, and in those expressing or lacking CLDN3.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

Further studies will be needed to determine whether the expression of other BTB components is altered and to decipher the reason for lower Cldn3 and Rhox5 mRNA levels in organotypic cultures.

WIDER IMPLICATIONS OF THE FINDINGS

This work contributes to a better understanding of the molecular mechanisms occurring in in vitro matured prepubertal testes. The organotypic culture system will have to be developed further and optimized for human tissue, before potential clinical applications can be envisaged.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by Rouen University Hospital, Ligue contre le Cancer (to L.D.), and co-supported by European Union and Région Normandie (to A.O.). Europe gets involved in Normandie with European Régional Development Fund (ERDF). The authors declare that they have no conflict of interest.

Cholesterol: A Gatekeeper of Male Fertility?

Cholesterol is essential for mammalian cell functions and integrity. It is an important structural component maintaining the permeability and fluidity of the cell membrane. The balance between synthesis and catabolism of cholesterol should be tightly regulated to ensure normal cellular processes. Male reproductive function has been demonstrated to be dependent on cholesterol homeostasis. Here we review data highlighting the impacts of cholesterol homeostasis on male fertility and the molecular mechanisms implicated through the signaling pathways of some nuclear receptors.