Impairment of spermatogenesis in mice lacking a functional aromatase (cyp 19) gene

Unraveling the anti-androgenic mechanism of tris(2,3-dibromopropyl) isocyanurate (TBC) via the non-classical testosterone pathway and steroidogenesis: Potential human reproductive health implications

The decline in male reproductive health, characterized by diminishing sperm count and testosterone levels, has raised concerns about environmental influences, particularly endocrine-disrupting chemicals (EDCs). Tris(2,3-dibromopropyl)isocyanurate (TBC), a novel brominated flame retardant widely used in electronics, textiles, and furniture, has emerged as a significant environmental contaminant with potential reproductive health implications. In this study, we investigated the molecular mechanisms underlying TBC-induced reproductive toxicity, particularly focusing on its impact on steroidogenesis and androgen signaling pathways using the GC-1 spg cell line as an in vitro model. Exposure of GC-1 spg cells to TBC, alone or in combination with testosterone or the anti-androgen flutamide resulted in decreased metabolic activity and increased lactate dehydrogenase release, indicating cytotoxic effects. Furthermore, TBC exposure led to a reduction in progesterone synthesis, while testosterone production remained unaffected. Interestingly, estradiol synthesis was diminished after TBC exposure, suggesting a disruption in steroid hormone balance critical for spermatogenesis. Mechanistic investigations revealed alterations in key proteins involved in the non-classical testosterone pathway and steroidogenesis. TBC exposure downregulated epidermal growth factor receptor (EGFR), protein kinase B (AKT), and phosphorylated cyclic AMP response element-binding protein (p-CREB), indicating suppression of non-classical androgen signaling. Additionally, decreased levels of steroidogenic acute regulatory protein (StAR) and 3-beta-hydroxysteroid dehydrogenase (HSD3β1) suggest impaired steroidogenesis. Here we uncover the intricate molecular mechanisms underlying TBC-induced reproductive toxicity, highlighting its potential to disrupt steroid hormone synthesis and androgen signaling pathways. Understanding the adverse effects of TBC on male reproductive health is crucial for developing strategies to mitigate its environmental impact and safeguard human fertility.

Disruptions in reproductive health, sex hormonal profiles, and hypothalamic hormone receptors content in females of the C58/J mouse model of autism

Autism Spectrum Disorder (ASD) is characterized by differences in social communication and interaction, as well as areas of focused interests and/or repetitive behaviors. Recent studies have highlighted a higher prevalence of endocrine and reproductive disturbances among females on the autism spectrum, hinting at potential disruptions within the hypothalamus-pituitary-ovary (HPO) axis. This research aims to explore the reproductive health disparities in ASD using an animal model of autism, the C58/J inbred mouse strain, with a focus on reproductive performance and hormonal profiles compared to the C57BL/6J control strain. Our findings revealed that the estrous cycle in C58/J females is disrupted, as evidenced by a lower frequency of complete cycles and a lack of cyclical release of estradiol and progesterone compared to control mice. C58/J females also exhibited poor performance in several reproductive parameters, including reproductive lifespan and fertility index. Furthermore, estrogen receptor alpha content showed a marked decrease in the hypothalamus of C58/J mice. These alterations in the estrous cycle, hormonal imbalances, and reduced reproductive function imply dysregulation in the HPO axis. Additionally, our in-silico study identified a group of genes involved in infertility carrying single-nucleotide polymorphisms (SNPs) in the C58/J strain, which also have human orthologs associated with autism. These findings could offer valuable insights into the molecular underpinnings of neuroendocrine axis disruption and reproductive issues observed in ASD.

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.

Steroidogenesis and androgen/estrogen signaling pathways are altered in in vitro matured testicular tissues of prepubertal mice

Children undergoing cancer treatments are at risk for impaired fertility. Cryopreserved prepubertal testicular biopsies could theoretically be later matured in vitro to produce spermatozoa for assisted reproductive technology. A complete in vitro spermatogenesis has been obtained from mouse prepubertal testicular tissue, although with low efficiency. Steroid hormones are essential for the progression of spermatogenesis, the aim of this study was to investigate steroidogenesis and steroid signaling in organotypic cultures. Histological, RT-qPCR, western blot analyses, and steroid hormone measurements were performed on in vitro cultured mouse prepubertal testicular tissues and age-matched in vivo controls. Despite a conserved density of Leydig cells after 30 days of culture (D30), transcript levels of adult Leydig cells and steroidogenic markers were decreased. Increased amounts of progesterone and estradiol and reduced androstenedione levels were observed at D30, together with decreased transcript levels of steroid metabolizing genes and steroid target genes. hCG was insufficient to facilitate Leydig cell differentiation, restore steroidogenesis, and improve sperm yield. In conclusion, this study reports the failure of adult Leydig cell development and altered steroid production and signaling in tissue cultures. The organotypic culture system will need to be further improved before it can be translated into clinics for childhood cancer survivors.

Involvement of estrogen receptor alpha (ERα) and impairment of steroidogenesis after exposure to tris(2,3-dibromopropyl) isocyanurate (TBC) in mouse spermatogenic (GC-1 spg) cells in vitro

Good-quality reproductive cells are essential for reproduction. Endocrine disruptors are widely available in the environment and are known to have an adverse effect on spermatogenesis and steroidogenesis. One of them is tris(2,3-dibromopropyl) isocyanurate (TBC), i.e. one of the novel brominated flame retardants (NBFR). TBC is a widely distributed ingredient used in the production of flame retardants. Currently, it is known to affect the hormonal system, but the exact mechanism of its action is unknown. Therefore, the aim of the study was to determine whether TBC alone and in cotreatment with BHPI (estrogen receptor alpha antagonist) has an impact on the expression of nuclear receptors involved in the formation of steroid hormones, proteins, and enzymes responsible for steroidogenesis and the levels of steroid hormones (E2, P4, and T) in the GC-1 spg cell line as a mouse model of spermatogenic cells in vitro. Our results indicate that ERα is involved in the mechanism of TBC action, while no activation of PPARγ, AhR, and IGF-1R was observed. In addition, a decrease in the levels of most of the analyzed proteins and enzymes involved in steroid conversion was observed. Only Cyp19a1 was upregulated after TBC, BHPI, and TBC with BHPI cotreatment. In all the analyzed groups, a significant decrease in P4 and a subtle decrease in T and E2 were observed in the production and secretion of the hormones to the culture medium, compared to the control. The obtained results confirm the involvement of TBC in the dysregulation of steroid biosynthesis, which may affect male fertility.

Mutation of brain aromatase disrupts spawning behavior and reproductive health in female zebrafish

Aromatase (Cyp19a1) is the steroidogenic enzyme that converts androgens into bioactive estrogens, and hence is in a pivotal position to mediate reproduction and sexual behavior. In teleosts, there are two aromatase paralogs: cyp19a1a that is highly expressed in granulosa and Leydig cells in the gonads with critical function in sexual differentiation of the ovary, and cyp19a1b that is highly expressed in radial glial cells in the brain with unknown roles in reproduction. Cyp19a1 ^-/- mutant zebrafish lines were used to investigate the importance of the cyp19a1 paralogs for spawning behavior and offspring survival and early development. Mutation of cyp19a1b was found to increase the latency to the first oviposition in females. Mutation of cyp19a1b in females also increased the number of eggs spawned; however, significantly more progeny died during early development resulting in no net increase in female fecundity. This finding suggests a higher metabolic cost of reproduction in cyp19a1b ^-/- mutant females. In males, the combined mutation of both cyp19a1 paralogs resulted in significantly lower progeny survival rates, indicating a critical function of cyp19a1 during early larval development. These data establish the specific importance of cyp19a1b for female spawning behavior and the importance of the cyp19a1 paralogs for early larval survival.

Effect of anti-estrogen and anti-progesterone on spermatogenesis, testosterone production and expression of steroidogenic enzyme genes in adult male rats

The present study was planned to investigate the anti-spermatogenic and anti-steroidogenic effects of Clomiphene Citrate (CC) an anti-estrogen and Mifepristone (MT) an anti-progesterone in the testis of male rats. Following the oral administration of 1.0 mg and 5.0 mg/kg b.w/day of each for the duration of 30 and 60 days, quantitation of spermatogenesis, RIA for serum and intra-testicular testosterone levels, western blotting and RT-PCR for expression of StAR, 3β-HSD and P450arom enzymes in the testis was done. Clomiphene Citrate at 5.0 mg/kg b.w/day for 60 days significantly reduced testosterone (T) levels however the effect was not significant with the lower doses. Reproductive parameters in animals treated by Mifepristone remained mostly unaffected, however, a significant decline in testosterone levels and altered expression of selected genes was observed in 5.0 mg for the 30d treatment group. Clomiphene Citrate at higher doses affected the weights of the testis and secondary sex organs. Seminiferous tubules revealed hypo-spermatogenesis with a significant decrease in the number of maturing germ cells and a reduction in tubular diameter. Attenuation in serum testosterone was associated with the downregulation of expression in StAR, 3β-HSD, and P450arom mRNA and protein levels in the testis even after 30 d of CC administration. The results indicate that the anti-estrogen (Clomiphene Citrate) but not anti-progesterone (Mifepristone) induces hypo-spermatogenesis in rats which are associated with a downregulation of expression of two of the steroidogenic enzymes, 3β-HSD and P450arom mRNA and StAR protein.

The effects of letrozole-induced maternal hyperandrogenism on sexual behaviors, testicular histology, and serum biochemical traits in male offspring rats: An experimental study

Background

Intrauterine endocrine abnormalities have profound effects on the development of physiological disorders.

Objective

This study aimed to assess the effects of in utero exposure to letrozole (an aromatase inhibitor) and its late consequences on the reproductive and metabolic performance of an adult male offspring.

Materials and Methods

15 pregnant Sprague-Dawley rats (8 wk, 155 gr) were randomly assigned into 5 experimental groups (n = 3/each) and orally received either letrozole at doses of 0.25, 0.75, 1.00, and 1.25 mg/kg body weight (BW) or vehicle (control) on the gestation days of 16, 17, and 18. Pregnancy outcome, sexual behaviors on postnatal day 60, serum biochemical features, and the histopathology of testes were assessed in male offspring.

Results

Compared to control group, delayed labor (21.83 vs. 24.25, p < 0.0001) and reduced litter size (n = 12.25 vs. n = 2, p < 0.0001) were recorded in 1.25 mg/kg BW group. A reduction in high-density lipoprotein level and the elevation of testes weight, BW gain, anogenital distance, as well as the serum concentrations of testosterone, triglycerides, cholesterol, and glucose were observed in 1.25 mg/kg BW (p < 0.0001) and 1.00 mg/kg BW (p < 0.0001) groups in comparison to control. A larger number of anogenital female sniffing, pursuit, and mounting behaviors were also observed in 1.25 mg/kg BW group in comparison to control (p < 0.0001). Severe testicular defects including necrosis and disruption of the epithelium of seminiferous tubules, sloughing of epithelial cells, and spermatogenesis arrest were observed in letrozole-treated groups, in a dose-dependent manner.

Conclusion

Maternal exposure to letrozole can adversely affect the reproductive and metabolic performance of male offspring rats, suggesting an incomplete sex differentiation.

Genetic dissection of steroid-hormone modulated social behavior: Novel paralogous genes are a boon for discovery

Research across species has led to important discoveries on the functions of steroid hormones in the regulation of behavior. However, like in many fields, advancements in transgenic and mutagenic technology allowed mice to become the premier genetic model for conducting many experiments to understand how steroids control social behavior. Since there has been a general lack of parallel methodological developments in other species, many of the findings cannot be generalized. This is especially the case for teleost fish, in which a whole-genome duplication produced novel paralogs for key steroid hormone signaling genes. In this review, we summarize technical advancements over the history of the field of neuroendocrinology that have led to important insights in our understanding of the control of social behavior by steroids. We demonstrate that early mouse genetic models to understand these mechanisms suffered from several issues that were remedied by more precise transgenic technological advancements. We then highlight the importance of CRISPR/Cas9 gene editing tools that will in time bridge the gap between mice and non-traditional model species for understanding principles of steroid hormone action in the modulation of social behavior. We specifically highlight the role of teleost fish in bridging this gap because they are 1) highly genetically tractable and 2) provide a novel advantage in achieving precise genetic control. The field of neuroendocrinology is entering a new "gene editing revolution" that will lead to novel discoveries about the roles of steroid hormones in the regulation and evolutionary trajectories of social behavior.

Involvement of GLCCI1 in mouse spermatogenesis

Spermatid production is a complex regulatory process in which coordination between hormonal control and apoptosis plays a pivotal role in maintaining a balanced number of sperm cells. Apoptosis in spermatogenesis is controlled by pro-apoptotic and anti-apoptotic molecules. Hormones involved in the apoptotic process during spermatogenesis include gonadotrophins, sex hormones, and glucocorticoid (GC). GC acts broadly as an apoptosis inducer by binding to its receptor (glucocorticoid receptor: GR) during organ development processes, such as spermatogenesis. However, the downstream pathway induced in GC-GR signaling and the apoptotic process during spermatogenesis remains poorly understood. We reported previously that GC induces full-length glucocorticoid-induced transcript 1 (GLCCI1-long), which functions as an anti-apoptotic mediator in thymic T cell development. Here, we demonstrate that mature murine testis expresses a novel isoform of GLCCI1 protein (GLCCI1-short) in addition to GLCCI1-long. We demonstrate that GLCCI1-long is expressed in spermatocytes along with GR. In contrast, GLCCI1-short is primarily expressed in spermatids where GR is absent; instead, the estrogen receptor is expressed. GLCCI1-short also binds to LC8, which is a known mediator of the anti-apoptotic effect of GLCCI1-long. A luciferase reporter assay revealed that β-estradiol treatment synergistically increased Glcci1-short promotor-driven luciferase activity in Erα-overexpressing cells. Together with the evidence that the conversion of testosterone to estrogen is preceded by aromatase expression in spermatids, we hypothesize that estrogen induces GLCCI1-short, which, in turn, may function as a novel anti-apoptotic mediator in mature murine testis.

Absence of Testicular Estrogen Leads to Defects in Spermatogenesis and Increased Semen Abnormalities in Male Rabbits

Estrogens are steroid hormones produced by the aromatization of androgens by the aromatase enzyme, encoded by the CYP19A1 gene. Although generally referred to as "female sex hormones", estrogen is also produced in the adult testes of many mammals, including humans. To better understand the function of estrogens in the male, we used the rabbit model which is an important biomedical model. First, the expression of CYP19A1 transcripts was localized mainly in meiotic germ cells. Thus, testicular estrogen appears to be produced inside the seminiferous tubules. Next, the cells expressing ESR1 and ESR2 were identified, showing that estrogens could exert their function on post-meiotic germ cells in the tubules and play a role during sperm maturation, since ESR1 and ESR2 were detected in the cauda epididymis. Then, CRISPR/Cas9 CYP19A1-/- genetically modified rabbits were analyzed. CYP19A1-/- males showed decreased fertility with lower sperm count associated with hypo-spermatogenesis and lower spermatid number. Germ/sperm cell DNA methylation was unchanged, while sperm parameters were affected as CYP19A1-/- males exhibited reduced sperm motility associated with increased flagellar defects. In conclusion, testicular estrogens could be involved in the spermatocyte-spermatid transition in the testis, and in the acquisition of sperm motility in the epididymis.

Molecular characterization and functional analysis of Esr1 and Esr2 in gonads of Chinese soft-shelled turtle (Pelodiscus sinensis)

Estrogens and their receptors play crucial roles in regulating the gonadal development of vertebrates. To clarify the roles of estrogen receptors in the gonadal development of turtles, estrogen receptors (Esr1 and Esr2) in Chinese soft-shelled turtle (Pelodiscus sinensis) were identified and characterized, and their function in gonads was investigated by intraperitoneal injection of agonist propylpyrazoletriol (PPT) and diarylpropionitrile (DPN), and antagonist ICI 182,780 (ICI). Ps-Esr1 encoded a 588 amino acid protein and Ps-Esr2 encoded a 556 amino acid protein. The two receptors contained classic domains, including the DNA-binding domain and ligand-binding domain, and amino acid sequences showed high homology with other turtles. Ps-Esr1 showed the highest expression in the testis, followed by the ovary and liver. However, Ps-Esr2 showed the highest expression in the ovary, followed by the brain and testis. Ps-Esr1 expression showed an up-regulation trend in gonadal differentiation. Histomorphometric analysis showed that the number of follicles increased in female juvenile turtles treated with DPN or PPT. In addition, Tsc2, GnRH, and Fshβ were up-regulated in ovaries of turtles treated with agonists, while Sycp3 and Picalm were up-regulated in testes of turtles treated with agonists. Treatment with the antagonist decreased the number of sperm in matured turtles. Stra8, Scyp3, Dmc1, Picalm, Evl, Boule, and Cdk1 were up-regulated in testis after antagonist treatment. The results indicated that Esr1 might play an important role in gonadal differentiation, and the two estrogen receptors might be involved in the spermatogenesis of the turtle. These results could provide a reference for further research on the function of the estrogen signal in male vertebrates.

Male reproductive cycle in a population of the endemic butterfly lizard, Leiolepis ocellata Peters, 1971 (Squamata: Agamidae) from northern Thailand

Background

Fundamental knowledge on the seasonal reproductive microanatomy and endocrinology of reptiles has been collected from several studies of various species. The present study was to determine annual changes in hormonal profiles, and detailed histomorphometric and histochemical characteristics of the entire male reproductive system of the tropical agamid lizard, Leiolepis ocellata.

Results

Male L. ocellata individuals (n = 75) collected from the territory of two provinces (Lampang and Tak) in northern Thailand exhibited annual variation in sex hormonal, histomorphometric, and histochemical characteristics of the male reproductive system. The reproductive cycle was subdivided into eight reproductive periods (early first active, first active, resting, second recrudescent, second active, regressive, quiescent, and first recrudescent), thus displaying a bimodal pattern with two actively reproductive periods. Circulating sex hormones (testosterone, estradiol, and progesterone) peaked in the first active (February) and the second active (June–July) periods. Likewise, gonadosomatic index (GSI) and histomorphometric variables of the testes and of the genital ducts (rete testis, ductuli efferentes, ductus epididymis, and ductus deferens) revealed their highest values in the first active period. Marked increase in protein and carbohydrate production was detectable in the ductuli efferentes during the active periods.

Conclusions

The male reproductive cycle of L. ocellata showed a biannual pattern of the hormonal profile, and detailed histomorphometric and histochemical characteristics of the entire reproductive system. Hence, the present study provides improved basic knowledge on the reptilian reproductive biology with comparative viewpoints to other reptiles.

Maternal exposure to genistein during pregnancy and oxidative DNA damage in testes of male mouse offspring

Background

Genistein is a dietary supplement with phyto-estrogenic properties. Therefore, high intake of genistein during pregnancy may have adverse effects on the genetic integrity of testes and germ cells of male offspring. In this study, we examined whether maternal exposure to genistein during pregnancy induced oxidative DNA damage in the male germline at adolescence.

Methods

Atm-ΔSRI mice have lower glucose-6-phosphate dehydrogenase (G6PDH) activity, which is important for maintaining levels of reduced glutathione and therefore these mice have an increased susceptibility to oxidative stress. Parental heterozygous Atm-ΔSRI mice received a genistein-rich or control diet, after which they were mated to obtain offspring. During pregnancy, mothers remained on the respective diets and after delivery all animals received control diets. Redox status and oxidative DNA damage were assessed in testes and sperm of 12 weeks old male offspring. Gene expression of Cyp1b1, Comt, and Nqo1 was assessed in testes, and DNA methylation as possible mechanism for transmission of effects to later life.

Results

Intake of genistein during pregnancy increased oxidative DNA damage in testes of offspring, especially in heterozygous Atm-ΔSRI mice. These increased DNA damage levels coincided with decreased expression of Comt and Nqo1. Heterozygous Atm-ΔSRI mice had higher levels of DNA strand breaks in sperm compared to wild type littermates, and DNA damage was further enhanced by a genistein-rich maternal diet. G6PDH activity was higher in mice with high maternal intake of genistein compared to control diets, suggesting compensation against oxidative stress. A positive correlation was observed between the levels of DNA methylation and oxidative DNA damage in testes.

Conclusion

These data indicate that prenatal exposure to genistein altered gene expression and increased DNA damage in testes and sperm of adolescent male offspring. These effects of genistein on DNA damage in later life coincided with alterations in DNA methylation.

Efficacy and safety of letrozole or anastrozole in the treatment of male infertility with low testosterone-estradiol ratio: a meta-analysis and systematic review

BACKGROUND

Aromatase inhibitors (AIs) have been used to treat male infertility for decades. However, due to the lack of large-scale randomized controlled studies and basic research, the efficacy and safety of AIs in the treatment of male infertility remain controversial. Therefore, it is necessary to conduct an evidence-based preliminary evaluation of the existing clinical trials of AIs in the treatment of male infertility.

METHOD

A comprehensive literature search were performed in PubMed, Embase, Cochrane, CNKI, VIP, CBM, and Wanfang databases through August 2021 for all studies. We conducted a systematic review with meta-analysis of the all available studies reporting sperm conventional parameters, gonadotropin and testosterone levels, and/or the pregnancy rate.

RESULTS

A total of 10 studies involving 666 patients were included. letrozole (LE) or anastrozole (AZ) administration increased significantly sperm concentration, total sperm count, and serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T) levels and testosterone to estradiol ratio (T/E2), but E2 levels were significantly reduced compared with baseline values. Compared with the control group, which included selective estrogen receptor modulators (SEMRs) or HCG, LE or AZ did not have any significant effect on sperm concentration, motility and morphology, except that AIs had less effect on sperm motility than the control group (WMD: -2.55; 95% CI:-4.11 to-1.00; P = 0.001).

CONCLUSION

AIs may be effective in the treatment of male infertility. For male infertile patients planning assisted reproduction, discontinuation of AIs for 2-7 days prior to sperm retrieval may increase the success rate of fertilization. Further studies with larger sample sizes are needed to validate these findings. This article is protected by copyright. All rights reserved.

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.

Clinical application of aromatase inhibitors to treat male infertility

BACKGROUND

Infertility affects 15% of men and contributes to nearly half of all cases of infertility. Infertile men usually have impaired spermatogenesis, presenting as azoospermia or various degrees of asthenospermia and oligozoospermia. Spermatogenesis is a complex and coordinated process, which is under precise modulation by the hypothalamic-pituitary-gonadal (HPG) axis. An aberrant hormone profile, especially an imbalance between testosterone (T) and estradiol (E2), plays an essential role in male infertility. In the male, E2 is produced mainly from the conversion of T by the aromatase enzyme. Theoretically, reducing an abnormally elevated T:E2 ratio using aromatase inhibitors (AIs) could restore the balance between T and E2 and optimize the HPG axis to support spermatogenesis. For decades, AIs have been used to treat male infertility empirically. However, owing to the lack of large-scale randomized controlled studies and basic research, the treatment efficacy and safety of AIs in male infertility remain controversial. Therefore, there is a need to summarize the clinical trials and relevant basic research on the application of AIs in the treatment of male infertility.

OBJECTIVE AND RATIONALE

In this narrative review, we summarized the application of AIs in the treatment of male infertility, including the pharmacological mechanisms involved, clinical trials focused on patients with different types of infertility, factors affecting treatment efficacy and the side-effects.

SEARCH METHODS

A literature search was performed using MEDLINE/PubMed and EMBASE, focusing on publications in the past four decades concerning the use of AIs for treating male infertility. The search terms included AI, male infertility, letrozole, anastrozole, testolactone, azoospermia, oligozoospermia, aromatase polymorphisms, obesity and antiestrogens, in various combinations.

OUTCOMES

Clinical studies demonstrate that AIs, especially nonsteroidal letrozole and anastrozole, could significantly inhibit the production of E2 and its negative feedback on the HPG axis, resulting in increased T and FSH production as well as improved semen parameters in infertile men. Large-scale surveys suggest that obesity may result in symptoms of hypogonadism in both fertile and infertile males, such as decreased semen quality and attenuated sexual function, which can be improved by AIs treatment. Polymorphisms of the aromatase gene CYP19A1, including single nucleotide polymorphisms and tetranucleotide TTTA repeats polymorphism (TTTAn), also influence hormone profiles, semen quality and treatment efficacy of AIs in male hypogonadotropic hypogonadism and infertility. The side-effects of AIs in treating male infertility are various, but most are mild and well tolerated.

WIDER IMPLICATIONS

The application of AIs in treating male infertility has been off-label and empirical for decades. This narrative review has summarized the target patients, dose, treatment duration and side-effects of AIs. Polymorphisms of CYP19A1 that may affect AIs treatment efficacy were also summarized, but a full understanding of the mechanisms involved in AIs action requires further study.

Diverse role of endocannabinoid system in mammalian male reproduction

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

The genome of New Zealand trevally (Carangidae: Pseudocaranx georgianus) uncovers a XY sex determination locus

BACKGROUND

The genetic control of sex determination in teleost species is poorly understood. This is partly because of the diversity of mechanisms that determine sex in this large group of vertebrates, including constitutive genes linked to sex chromosomes, polygenic constitutive mechanisms, environmental factors, hermaphroditism, and unisexuality. Here we use a de novo genome assembly of New Zealand silver trevally (Pseudocaranx georgianus) together with sex-specific whole genome sequencing data to detect sexually divergent genomic regions, identify candidate genes and develop molecular makers.

RESULTS

The de novo assembly of an unsexed trevally (Trevally_v1) resulted in a final assembly of 579.4 Mb in length, with a N50 of 25.2 Mb. Of the assembled scaffolds, 24 were of chromosome scale, ranging from 11 to 31 Mb in length. A total of 28,416 genes were annotated after 12.8 % of the assembly was masked with repetitive elements. Whole genome re-sequencing of 13 wild sexed trevally (seven males and six females) identified two sexually divergent regions located on two scaffolds, including a 6 kb region at the proximal end of chromosome 21. Blast analyses revealed similarity between one region and the aromatase genes cyp19 (a1a/b) (E-value < 1.00E-25, identity > 78.8 %). Males contained higher numbers of heterozygous variants in both regions, while females showed regions of very low read-depth, indicative of male-specificity of this genomic region. Molecular markers were developed and subsequently tested on 96 histologically-sexed fish (42 males and 54 females). Three markers amplified in absolute correspondence with sex (positive in males, negative in females).

CONCLUSIONS

The higher number of heterozygous variants in males combined with the absence of these regions in females support a XY sex-determination model, indicating that the trevally_v1 genome assembly was developed from a male specimen. This sex system contrasts with the ZW sex-determination model documented in closely related carangid species. Our results indicate a sex-determining function of a cyp19a1a-like gene, suggesting the molecular pathway of sex determination is somewhat conserved in this family. The genomic resources developed here will facilitate future comparative work, and enable improved insights into the varied sex determination pathways in teleosts. The sex marker developed in this study will be a valuable resource for aquaculture selective breeding programmes, and for determining sex ratios in wild populations.

Co-treatment of testosterone and estrogen mitigates heat-induced testicular dysfunctions in a rat model

The two gonadal steroid hormones, testosterone and estrogen, regulate spermatogenesis by proliferation, differentiation, and apoptosis of testicular cells. It has been reported that heat stress or increased scrotal temperature impairs spermatogenesis in many mammals. Moreover, testicular heat stress has also been shown to suppress testosterone and estrogen biosynthesis. Furthermore, it is well known that testosterone and estrogen are important for testicular activity. Therefore, we hypothesised that exogenous testosterone and estrogen, alone or in combination, might alleviate the testicular activity in a heat-stressed rat model. To the best of our knowledge, this will be the first report of the exogenous treatment of both testosterone and estrogen in the heat-stressed rat. Our results showed that a combined testosterone and estrogen treatment significantly increased sperm concentration. The histopathological analysis also exhibited a normal histoarchitecture in the combined treatment group along with decreased oxidative stress. The improved spermatogenesis in the combined treatment group was also supported by the increase in PCNA, GCNA, tubule diameter, germinal epithelium height, and Johnsen score in the combined treatment group. Furthermore, the combined treatment also increased the expression of Bcl2, pStat3, and active caspase-3 and decreased expression of Bax. Thus, increased proliferation, apoptotic and anti-apoptotic markers, along with improved histology in the combined treatment group suggest that estrogen and testosterone synergistically act to stimulate spermatogenesis by increasing proliferation and differentiation of germ cells and may also remove the heat-induced damaged germ cells by apoptosis. Overall, the final mechanism of testosterone- and estrogen-mediated improvement of testicular activity could be attributed to amelioration of oxidative stress.

Three-Generation Study of Male Rats Gestationally Exposed to High Butterfat and Bisphenol A: Impaired Spermatogenesis, Penetrance with Reduced Severity

Gestational high butterfat (HFB) and/or endocrine disruptor exposure was previously found to disrupt spermatogenesis in adulthood. This study addresses the data gap in our knowledge regarding transgenerational transmission of the disruptive interaction between a high-fat diet and endocrine disruptor bisphenol A (BPA). F0 generation Sprague-Dawley rats were fed diets containing butterfat (10 kcal%) and high in butterfat (39 kcal%, HFB) with or without BPA (25 µg/kg body weight/day) during mating and pregnancy. Gestationally exposed F1-generation offspring from different litters were mated to produce F2 offspring, and similarly, F2-generation animals produced F3-generation offspring. One group of F3 male offspring was administered either testosterone plus estradiol-17β (T + E2) or sham via capsule implants from postnatal days 70 to 210. Another group was naturally aged to 18 months. Combination diets of HFB + BPA in F0 dams, but not single exposure to either, disrupted spermatogenesis in F3-generation adult males in both the T + E2-implanted group and the naturally aged group. CYP19A1 localization to the acrosome and estrogen receptor beta (ERbeta) localization to the nucleus were associated with impaired spermatogenesis. Finally, expression of methyl-CpG-binding domain-3 (MBD3) was consistently decreased in the HFB and HFB + BPA exposed F1 and F3 testes, suggesting an epigenetic component to this inheritance. However, the severe atrophy within testes present in F1 males was absent in F3 males. In conclusion, the HFB + BPA group demonstrated transgenerational inheritance of the impaired spermatogenesis phenotype, but severity was reduced in the F3 generation.

Analyses of Molecular Characteristics and Enzymatic Activities of Ovine HSD17B3

17β-hydroxysteroid dehydrogenase type 3 (HSD17B3) converts androstenedione (A4) into testosterone (T), which regulates sex steroid production. Because various mutations of the HSD17B3 gene cause disorder of sex differentiation (DSD) in multiple mammalian species, it is very important to reveal the molecular characteristics of this gene in various species. Here, we revealed the open reading frame of the ovine HSD17B3 gene. Enzymatic activities of ovine HSD17B3 and HSD17B1 for converting A4 to T were detected using ovine androgen receptor-mediated transactivation in reporter assays. Although HSD17B3 also converted estrone to estradiol, this activity was much weaker than those of HSD17B1. Although ovine HSD17B3 has an amino acid sequence that is conserved compared with other mammalian species, it possesses two amino acid substitutions that are consistent with the reported variants of human HSD17B3. Substitutions of these amino acids in ovine HSD17B3 for those in human did not affect the enzymatic activities. However, enzymatic activities declined upon missense mutations of the HSD17B3 gene associated with 46,XY DSD, affecting amino acids that are conserved between these two species. The present study provides basic information and tools to investigate the molecular mechanisms behind DSD not only in ovine, but also in various mammalian species.

Epigenetic transgenerational inheritance, gametogenesis and germline development†

One of the most important developing cell types in any biological system is the gamete (sperm and egg). The transmission of phenotypes and optimally adapted physiology to subsequent generations is in large part controlled by gametogenesis. In contrast to genetics, the environment actively regulates epigenetics to impact the physiology and phenotype of cellular and biological systems. The integration of epigenetics and genetics is critical for all developmental biology systems at the cellular and organism level. The current review is focused on the role of epigenetics during gametogenesis for both the spermatogenesis system in the male and oogenesis system in the female. The developmental stages from the initial primordial germ cell through gametogenesis to the mature sperm and egg are presented. How environmental factors can influence the epigenetics of gametogenesis to impact the epigenetic transgenerational inheritance of phenotypic and physiological change in subsequent generations is reviewed.

Sex hormones regulate lipid metabolism in adult Sertoli cells: A genome-wide study of estrogen and androgen receptor binding sites

Optimal functioning of Sertoli cells is crucial for spermatogenesis which is under tight regulation of sex hormones, estrogen and androgen. Adult rat Sertoli cells expresses estrogen receptor beta (ERβ) and androgen receptor (AR), both of which regulate gene transcription by binding to the DNA. The present study is aimed to acquire a genome-wide map of estrogen- and androgen-regulated genes in adult Sertoli cells. ChIP-Seq was performed for ERβ and AR in Sertoli cells under physiological conditions. 30,859 peaks in ERβ and 9,594 peaks in AR were identified with a fold enrichment >2 fold. Pathway analysis for the genes revealed metabolic pathways to be significantly enriched. Since Sertoli cells have supportive functions and provide energy substrates to germ cells during spermatogenesis, significantly enriched metabolic pathways were explored further. Peaks of the genes involved in lipid metabolism, like fatty acid, glyceride, leucine, and sphingosine metabolism were validated. Motif analysis confirmed the presence of estrogen- and androgen-response elements (EREs and AREs). Moreover, transcript levels of enzymes involved in the lipid metabolic pathways were significantly altered in cultured Sertoli cells treated with estrogen and androgen receptor agonists, demonstrating functional significance of these binding sites. This study elucidates a mechanism by which sex hormones regulate lipid metabolism in Sertoli cells by transcriptionally controlling the expression of these genes, thereby shedding light on the roles of these hormones in male fertility.

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.

β-estradiol promotes the growth of primary human fetal spermatogonial stem cells via the induction of stem cell factor in Sertoli cells

BACKGROUND

Mammalian spermatogenesis is responsible for male fertility and is supported by the self-renewal and differentiation of spermatogonial stem cells (SSCs). Sertoli cells provide a supportive microenvironment for SSCs, in part by the production of stem cell factor (SCF), which is a potent regulator of spermatogonia proliferation and survival.

METHODS

We investigated the novel role of β-estradiol in modulating the proliferation and apoptosis of fetal SSCs via the regulation of SCF secretion in Sertoli cells isolated from human fetal testes. The proliferation of SSCs in the co-culture system was determined by colony formation and BrdU incorporation assays. TUNEL assay was used to measure SSC apoptosis in co-culture in response to treatment with control, β-estradiol, or the combination of β-estradiol and the estrogen receptor inhibitor ICI 182780.

RESULTS

In the system with purified human fetal Sertoli cells (MIS+/c-Kit-/AP-), β-estradiol upregulated the production of SCF in a dose- and time-dependent manner. In the co-culture system of primary human fetal SSCs (c-Kit+/SSEA-4+/Oct-4+/AP+) and Sertoli cells (MIS+), β-estradiol markedly increased the proliferation of SSCs. Moreover, SSC apoptosis was significantly inhibited by β-estradiol and was completely reversed by the combination of β-estradiol and ICI 182780.

CONCLUSION

Here we report, for the first time, that β-estradiol can induce the increase of SCF expression in human fetal Sertoli cells and regulates the growth and survival of human fetal SSCs. These novel findings provide new perspectives on the current understanding of the role of estrogen in human spermatogenesis.

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

Role of the kisspeptin/KISS1 receptor system in the testicular development of mice

BACKGROUND

Kisspeptin and its receptor KISS1R have been found to be essential regulators of reproductive function. Previous data have revealed the presence of Kiss1 and Kiss1r mRNAs in the hypothalamus and the testis of humans and rodents. However, the precise location and possible physiological role of the kisspeptin/KISS1R system in the testis remain ambiguous.

METHODS

We first produced an anti-KISS1R immunoglobulin Y antibody for KISS1R identification. To detect the exact sites of KISS1R and kisspeptin expression in the testis, we conducted immunohistochemistry assays on sections of testes. We used real-time polymerase chain reactions to identify Kiss1r in mice and to determine the expression levels of testicular genes. Finally, to verify the upstream regulation on the Kisspeptin/KISS1 receptor system, we treated primary mouse Leydig cells and MA-10 cells with luteinizing hormone (LH) and Br-cAMP, respectively, and examined Kiss1 and Kiss1r mRNA expression.

RESULTS

Immunohistochemistry assays revealed that kisspeptin was expressed in Leydig cells and KISS1R was localized in the seminiferous tubules. With real-time polymerase chain reactions, we found Kiss1r mRNA was constitutively expressed in the mouse testis from birth until the postnatal fourth week. Furthermore, mRNA expression of Kiss1 was synchronized with that of Insl3 and Cyp19a. However, the expression of the LH receptor-encoding gene increased 1 week earlier than did Kiss1 expression. This indicated that the kisspeptin/KISS1R system in the testis may be controlled by LH and cAMP signaling pathways. Finally, we confirmed that Kiss1 mRNA expression was increased in both LH-treated primary Leydig cells and Br-cAMP-treated MA-10 cells (p < 0.05). On the other hand, cotreatment of both cell lines with Br-cAMP and a protein kinase A inhibitor RP-cAMP significantly suppressed 50% of Br-cAMP-induced Kiss1 expression (p < 0.05).

CONCLUSION

We discovered that Kiss1 expression in mouse Leydig cells was induced by LH through the cAMP/PKA pathway. Based on the presence of kisspeptin receptors on spermatids, we inferred that kisspeptin- and development-related factors have synergistic effects on spermatogenesis. Nevertheless, more studies are required to elaborate the role of the kisspeptin/KISS1R system in testicular development.

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.

Impact of Oral Supplementation of Different Levels of Tamoxifen on Productive and Reproductive Efficiencies and Carcass Traits of Avian48 and Arbor Acres Broilers

This research was aimed at estimating the effect of oral supplementation of Tamoxifen on productive efficiency, carcass characteristics, hormonal profile and gonadal structure of two broiler breeds. One hundred and eighty chicks of each breed of Avian48 and Arbor Acres were divided into three groups: control group; TAM10 group, supplied with 10 mg Tamoxifen/kg of body weight at 3, 5, 7 and 9 days of life; and TAM20 group, supplied at the same intervals with 20 mg Tamoxifen/kg of body weight. Both levels of Tamoxifen improved productive performance at early ages, but Arbor Acres produced better results with TAM20 levels than TAM10, while Avian48 breeds reacted adversely. On the contrary, Tamoxifen supplementation significantly decreased feed intake and feed conversion (after the first two weeks of life) compared to control with a higher level of decrease reported for TAM20 treatments than TAM10 and for Arbor Acres compared to Avian48 breed. Carcass traits were not affected significantly with Tamoxifen supplementation compared to control although Arbor Acres responded better to TAM20 and Avian48 for TAM10. With regard to the effect of Tamoxifen (TAM) on sex hormones, it could be concluded that TAM10 treatments showed a stimulating effect on the level of such hormones as compared with the TAM20 group with the most favourable results being clearly detectable in 42-day-old birds although both concentrations of Tamoxifen did not differ significantly from control. However, treatment of broiler chickens with Tamoxifen in different doses caused a gradual decrease in follicle production rate and eventually led to an increase of the atretic follicles in different stages of atresia. Finally, we can conclude that Tamoxifen supplementation can improve performance and carcass efficiency of broilers without changing the hormonal profile, however much research is required to estimate the best concentration required for each breed.

Effect of estrogen and stress on estrogen receptor 1 in the HPG axis of immature male Gallus gallus domesticus: Involvement of anti-oxidant system

Estrogen plays a key role in the regulation of reproductive behavior and control of the neuroendocrine system in both males and females. However, excessive quantity of exogenous estrogen produces a deleterious effect on the male reproductive system. To elucidate the mechanism by which estrogen modulates its receptor alpha (ESR1) in immature chicken during stress the study has been undertaken. The experiment investigated the physiological changes in the abundance of ESR1 in brain, pituitary and testes of immature male chickens after stress like water restriction. Twenty four immature male chickens were randomly assigned into four groups. The control group was provided with food and water ad libitum, second was water restricted 9 h each day for seven days (WR), third was treated with estradiol benzoate (EB) and fourth group was treated with EB followed by water restriction during last seven days of treatment (EB + WR). EB was administered at a dose of 0.5 mg/100 g/day for 12 days. EB administration as well as WR increases both the H₂O₂ and Malondialdehyde levels indicating oxidative stress in brain as well as in testis. Plasma corticosterone significantly increased in all groups while estradiol significantly decreased after water restriction. ESR1 protein was detected by immuno-fluorescence predominantly in the pre-optic area of the hypothalamus, pituitary and testes after EB administration. EB administration increases ESR1 proteins abundantly in the Sertoli cells, Leydig cells, spermatogonia and spermatids while WR decreases it. The decline in ESR1 proteins after EB administration during stress appears to be mediated by interaction of estrogen with hypothalamo-pituitary-adrenal (HPA) axis. Therefore, the findings substantiate the fact that WR and EB treatment increase the stress and alter the anti-oxidant enzymes via its receptor ESR1 in the brain, pituitary and testis of immature chicks. Moreover, these findings highlight the effect of estradiol in male chicks causing stress which is disrupting the normal physiological feedback mechanism in hormone release and the expression of receptor ESR1 along the hypothalamo-pituitary-gonadal (HPG) axis.

Copper oxychloride-induced testicular damage of adult albino rats and the possible role of curcumin in healing the damage

The current research study investigated the effect of 80 mg/kg b.wt./day curcumin (cur) against 50, 100, and 200 mg/kg copper oxychloride (COC) for 90 days induced testicular damage using histological, ultrastructural, and biochemical techniques. Histological and cellular abnormalities have been noted in seminiferous tubules of COC-treated group and treated group with Cur- and COC-treated group. The biochemical result showed that serum testosterone was significantly decreased in COC-treated rats and Cur COC-treated rats compared with the control groups. Testes copper content and malondialdehyde was increased, whereas the testes total antioxidant, manganese, ferrous, and zinc levels were decreased (p ≥ 0.05) compared to the control groups. In conclusion, the present work reported that the treatment of rats with 80 mg/kg body weight curcumin prior to treatment with COC did not mitigate the deleterious effects of COC and manifested no signs of protection.

Imidacloprid disrupts the endocrine system by interacting with androgen receptor in male mice

In the current study, six-week-old male ICR mice were administered imidacloprid (IMI) at concentrations of 3, 10 and 30 mg/L for a duration of 10 weeks to investigate the toxicity of IMI on the endocrine system. We observed that testicular morphology was severely impaired and damaged, and the levels of serum testosterone (T) and the expression of androgen receptor (AR) decreased significantly. Molecular docking analysis suggested that IMI docks into the active site of AR successfully and that three key hydrogen bonds were formed with the active site residues Glu11, Gln41 and Lys138. The binding free energy value of the AR-IMI complex suggested a stable binding between IMI and AR. All these results indicated that IMI could interact with AR. In addition, major genes in the testis involved in the synthesis of cholesterol and T were generally inhibited, and the serum cholesterol sources were also reduced. Moreover, the aromatase in male mice was lacking after subchronic IMI exposure. The data acquired from the present study indicated that IMI could lead to endocrine disruption by interacting with AR and influence the expression of genes involved in the production of T in male mice.

Androgen receptor, aromatase, oestrogen receptor α/β and G protein-coupled receptor 30 expression in the testes and epididymides of adult sheep

The androgen receptor (AR) plays a key role in reproduction, and aromatase (P450arom), nuclear oestrogen receptors (ERs) α and β, and G protein-coupled receptor 30 (GPR30) are important for testicular and epididymal cell proliferation and development. In the study, we have investigated the expression and localization of AR, P450arom, ERα, ERβ and GPR30 in testes and epididymides of sexually mature sheep by quantitative reverse transcription-polymerase chain reaction, Western blotting and immunohistochemistry. The results demonstrate that the AR, P450arom and ERα levels in the caput and corpus epididymis were significantly lower than those in the testis and cauda epididymis (p < .05), the ERβ level in the testis was significantly higher than in the caput, corpus and cauda epididymis (p < .05), and the GPR30 level in the caput epididymis was significantly lower than in the testis and corpus and cauda epididymis (p < .05). These receptors were mainly detected in epididymal epithelial, basal, smooth muscle, Sertoli and Leydig cells, as well as in spermatozoa. Taken together, the results suggest that sheep epididymides and testes have the potential for estradiol synthesis and are the targets of both androgens and estradiol. These results provide a foundation for further studies on the mechanisms of androgens and estradiol signalling in the testes and epididymides of sheep.

Missing Information from the Estrogen Receptor Puzzle: Where Are They Localized in Bull Reproductive Tissues and Spermatozoa?

Estrogens are steroid hormones that affect a wide range of physiological functions. The effect of estrogens on male reproductive tissues and sperm cells through specific receptors is essential for sperm development, maturation, and function. Although estrogen receptors (ERs) have been studied in several mammalian species, including humans, they have not yet been described in bull spermatozoa and reproductive tissues. In this study, we analyzed the presence of all types of ERs (ESR1, ESR2, and GPER1) in bull testicular and epididymal tissues and epididymal and ejaculated spermatozoa, and we characterize them here for the first time. We observed different localizations of each type of ER in the sperm head by immunofluorescent microscopy. Additionally, using a selected polyclonal antibody, we found that each type of ER in bull sperm extracts had two isoforms with different molecular masses. The detailed detection of ERs is a prerequisite not only for understanding the effect of estrogen on all reproductive events but also for further studying the negative effect of environmental estrogens (endocrine disruptors) on processes that lead to fertilization.

Estrogens in Human Male Gonadotropin Secretion and Testicular Physiology From Infancy to Late Puberty

Several reports in humans as well as transgenic mouse models have shown that estrogens play an important role in male reproduction and fertility. Estrogen receptor alpha (ERα) and beta (ERβ) are expressed in different male tissues including the brain. The estradiol-binding protein GPER1 also mediates estrogen action in target tissues. In human testes a minimal ERα expression during prepuberty along with a marked pubertal up-regulation in germ cells has been reported. ERβ expression was detected mostly in spermatogonia, primary spermatocytes, and immature spermatids. In Sertoli cells ERβ expression increases with age. The aromatase enzyme (cP450arom), which converts androgens to estrogens, is widely expressed in human tissues (including gonads and hypothalamus), even during fetal life, suggesting that estrogens are also involved in human fetal physiology. Moreover, cP450arom is expressed in the early postnatal testicular Leydig cells and spermatogonia. Even though the aromatase complex is required for estrogen synthesis, its biological relevance is also related to the regulation of the balance between androgens and estrogens in different tissues. Knockout mouse models of aromatase (ArKO) and estrogen receptors (ERKOα, ERKOβ, and ERKOαβ) provide an important tool to study the effects of estrogens on the male reproductive physiology including the gonadal axis. High basal serum FSH levels were reported in adult aromatase-deficient men, suggesting that estrogens are involved in the negative regulatory gonadotropin feedback. However, normal serum gonadotropin levels were observed in an aromatase-deficient boy, suggesting a maturational pattern role of estrogen in the regulation of gonadotropin secretion. Nevertheless, the role of estrogens in primate testis development and function is controversial and poorly understood. This review addresses the role of estrogens in gonadotropin secretion and testicular physiology in male humans especially during childhood and puberty.

Ratio-dependent effects of quinestrol and levonorgestrel compounds (EP-1) on reproductive parameters of adult male Swiss mice

Fertility control is considered as the second-generation pest rodent management strategy. Most previous studies have focused on the dosage-dependent effects of quinestrol and levonorgestrel compounds (EP-1) at a ratio of 1:2, but the ratio-dependent effects of EP-1 have not been fully investigated, especially in male rodents. To test the ratio-dependent antifertility effects of EP-1 with different ratios (1:2, 1:1, and 2:1) on male Swiss outbred strain of laboratory mice, forty male mice were randomly assigned into four groups (n = 10). Mice in the three treatment groups were provided one of the three EP-1 mixture compounds for 3 successive days via gavage at a dosage of 50 mg/kg_{(body weight)}, and then all mice were sacrificed 15 days after the gavage treatment. Reproductive organ weights, sperm density and motility, levels of testosterone (T), estradiol (E2), luteinizing hormone (LH), and follicle stimulating hormone (FSH) in serum and/or testis, and androgen receptor (AR), estrogen receptor α (ERα), estrogen receptor β (ERβ), luteinizing hormone receptor (LHR), and aromatase in testis were determined. Each of the ratios of quinestrol and levonorgestrel significantly decreased the density and motility of sperm and induced atrophy of the epididymis and seminal vesicle. The combination of compounds also significantly reduced serum T and LH levels, increased testicular T levels and decreased testicular estradiol ERβ and aromatase levels. EP-1 delivered at a ratio of 1:1 induced the most significant effects on the reproductive parameters assessed and shows the potential for use in fertility control of male rodents.

Estrogen in the male: a historical perspective

Estrogens have traditionally been considered female hormones. Nevertheless, the presence of estrogen in males has been known for over 90 years. Initial studies suggested that estrogen was deleterious to male reproduction because exogenous treatments induced developmental abnormalities. However, demonstrations of estrogen synthesis in the testis and high concentrations of 17β-estradiol in rete testis fluid suggested that the female hormone might have a function in normal male reproduction. Identification of estrogen receptors and development of biological radioisotope methods to assess estradiol binding revealed that the male reproductive tract expresses estrogen receptor extensively from the neonatal period to adulthood. This indicated a role for estrogens in normal development, especially in efferent ductules, whose epithelium is the first in the male reproductive tract to express estrogen receptor during development and a site of exceedingly high expression. In the 1990s, a paradigm shift occurred in our understanding of estrogen function in the male, ushered in by knockout mouse models where estrogen production or expression of its receptors was not present. These knockout animals revealed that estrogen's main receptor (estrogen receptor 1 [ESR1]) is essential for male fertility and development of efferent ductules, epididymis, and prostate, and that loss of only the membrane fraction of ESR1 was sufficient to induce extensive male reproductive abnormalities and infertility. This review provides perspectives on the major discoveries and developments that led to our current knowledge of estrogen's importance in the male reproductive tract and shaped our evolving concept of estrogen's physiological role in the male.

The roles and mechanisms of Leydig cells and myoid cells in regulating spermatogenesis

Spermatogenesis is fundamental to the establishment and maintenance of male reproduction, whereas its abnormality results in male infertility. Somatic cells, including Leydig cells, myoid cells, and Sertoli cells, constitute the microenvironment or the niche of testis, which is essential for regulating normal spermatogenesis. Leydig cells are an important component of the testicular stroma, while peritubular myoid cells are one of the major cell types of seminiferous tubules. Here we addressed the roles and mechanisms of Leydig cells and myoid cells in the regulation of spermatogenesis. Specifically, we summarized the biological features of Leydig cells and peritubular myoid cells, and we introduced the process of testosterone production and its major regulation. We also discussed other hormones, cytokines, growth factors, transcription factors and receptors associated with Leydig cells and myoid cells in mediating spermatogenesis. Furthermore, we highlighted the issues that are worthy of further studies in the regulation of spermatogenesis by Leydig cells and peritubular myoid cells. This review would provide novel insights into molecular mechanisms of the somatic cells in controlling spermatogenesis, and it could offer new targets for developing therapeutic approaches of male infertility.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Genetic regulation of sex determination and maintenance in zebrafish (Danio rerio)

Over the last several decades zebrafish (Danio rerio) has become a major model organism for the study of vertebrate development and physiology. Given this, it may be surprising how little is known about the mechanism that zebrafish use to determine sex. While zebrafish are a gonochoristic species (having two sexes) that do not switch sex as adults, it was appreciated early on that sex ratios obtained from breeding lab domesticated lines were not typically a 1:1 ratio of male and female, suggesting that sex was not determined by a strict chromosomal mechanism. Here we will review the recent progress toward defining the genetic mechanism for sex determination in both wild and domesticated zebrafish.

History of Estrogen: Its Purification, Structure, Synthesis, Biologic Actions, and Clinical Implications

This mini-review summarizes key points from the Clark Sawin Memorial Lecture on the History of Estrogen delivered at Endo 2018 and focuses on the rationales and motivation leading to various discoveries and their clinical applications. During the classical period of antiquity, incisive clinical observations uncovered important findings; however, extensive anatomical dissections to solidify proof were generally lacking. Initiation of the experimental approach followed later, influenced by Claude Bernard's treatise "An Introduction to the Study of Experimental Medicine." With this approach, investigators began to explore the function of the ovaries and their "internal secretions" and, after intensive investigations for several years, purified various estrogens. Clinical therapies for hot flashes, osteoporosis, and dysmenorrhea were quickly developed and, later, methods of hormonal contraception. Sophisticated biochemical methods revealed the mechanisms of estrogen synthesis through the enzyme aromatase and, after discovery of the estrogen receptors, their specific biologic actions. Molecular techniques facilitated understanding of the specific transcriptional and translational events requiring estrogen. This body of knowledge led to methods to prevent and treat hormone-dependent neoplasms as well as a variety of other estrogen-related conditions. More recently, the role of estrogen in men was uncovered by prismatic examples of estrogen deficiency in male patients and by knockout of the estrogen receptor and aromatase in animals. As studies became more extensive, the effects of estrogen on nearly every organ were described. We conclude that the history of estrogen illustrates the role of intellectual reasoning, motivation, and serendipity in advancing knowledge about this important sex steroid.

Letrozole Monotherapy in Pre- and Early-Pubertal Boys Does Not Increase Adult Height

Background: Aromatase inhibitors (AIs) have been used in boys with idiopathic short stature (ISS) to promote growth despite the lack of actual data regarding treatment effect on adult height. In this study, we characterized adult heights and long-term follow-up in AI-treated boys with ISS. Methods: Adult heights and long-term follow-up data, including spine MRIs, of a randomized, double-blind, placebo-controlled trial of boys who were treated with letrozole (Lz) (2.5 mg/d) or placebo (Pl) for 2 years during prepuberty and early puberty. The mean bone ages at treatment cessation were 10.2 and 10.8 years, respectively. Results: Adult heights were similar between the boys treated with Lz (n = 10) and those who received Pl (n = 10) (164.8 ± 4.0 vs. 163.7 ± 3.7 cm, p = 0.49, respectively). In either group, the adult heights did not differ from predicted adult heights at start of the study [Pl: 163.7 (3.7) cm vs. 166.9 (3.3), p = 0.06; Lz: 164.8 (4.0) cm vs. 167.6 (7.9), p = 0.20, respectively]. Long-term follow-up data showed that the frequency of subjects with a vertebral deformity was similar between the groups (Lz, 29% and Pl, 22%, p = 0.20), and no single comorbidity was clearly enriched in either group. Conclusions: The Lz-treated boys had similar adult heights with the subjects who received Pl for 2 years, which indicates that the treatment is not beneficial when given to pre- or early-pubertal boys. Previously observed vertebral deformities ameliorated during follow-up, which supports the skeletal safety of Lz therapy in children and adolescents.

Molecular Mechanisms and Signaling Pathways Involved in Sertoli Cell Proliferation

Sertoli cells are somatic cells present in seminiferous tubules which have essential roles in regulating spermatogenesis. Considering that each Sertoli cell is able to support a limited number of germ cells, the final number of Sertoli cells reached during the proliferative period determines sperm production capacity. Only immature Sertoli cells, which have not established the blood-testis barrier, proliferate. A number of hormonal cues regulate Sertoli cell proliferation. Among them, FSH, the insulin family of growth factors, activin, and cytokines action must be highlighted. It has been demonstrated that cAMP/PKA, ERK1/2, PI3K/Akt, and mTORC1/p70SK6 pathways are the main signal transduction pathways involved in Sertoli cell proliferation. Additionally, c-Myc and hypoxia inducible factor are transcription factors which participate in the induction by FSH of various genes of relevance in cell cycle progression. Cessation of proliferation is a pre-requisite to Sertoli cell maturation accompanied by the establishment of the blood-testis barrier. With respect to this barrier, the participation of androgens, estrogens, thyroid hormones, retinoic acid and opioids has been reported. Additionally, two central enzymes that are involved in sensing cell energy status have been associated with the suppression of Sertoli cell proliferation, namely AMPK and Sirtuin 1 (SIRT1). Among the molecular mechanisms involved in the cessation of proliferation and in the maturation of Sertoli cells, it is worth mentioning the up-regulation of the cell cycle inhibitors p21Cip1, p27Kip, and p19INK4, and of the gap junction protein connexin 43. A decrease in Sertoli cell proliferation due to administration of certain therapeutic drugs and exposure to xenobiotic agents before puberty has been experimentally demonstrated. This review focuses on the hormones, locally produced factors, signal transduction pathways, and molecular mechanisms controlling Sertoli cell proliferation and maturation. The comprehension of how the final number of Sertoli cells in adulthood is established constitutes a pre-requisite to understand the underlying causes responsible for the progressive decrease in sperm production that has been observed during the last 50 years in humans.

Genetic regulation of sex determination and maintenance in zebrafish (Danio rerio)

Over the last several decades zebrafish (Danio rerio) has become a major model organism for the study of vertebrate development and physiology. Given this, it may be surprising how little is known about the mechanism that zebrafish use to determine sex. While zebrafish are a gonochoristic species (having two sexes) that do not switch sex as adults, it was appreciated early on that sex ratios obtained from breeding lab domesticated lines were not typically a 1:1 ratio of male and female, suggesting that sex was not determined by a strict chromosomal mechanism. Here we will review the recent progress toward defining the genetic mechanism for sex determination in both wild and domesticated zebrafish.