The low gonadotropin-independent constitutive production of testicular testosterone is sufficient to maintain spermatogenesis

The SPARC-related modular calcium binding 1 (Smoc1) regulated by androgen is required for mouse gubernaculum development and testicular descent

ABSTRACT

Testicular descent occurs in two consecutive stages: the transabdominal stage and the inguinoscrotal stage. Androgens play a crucial role in the second stage by influencing the development of the gubernaculum, a structure that pulls the testis into the scrotum. However, the mechanisms of androgen actions underlying many of the processes associated with gubernaculum development have not been fully elucidated. To identify the androgen-regulated genes, we conducted large-scale gene expression analyses on the gubernaculum harvested from luteinizing hormone/choriogonadotropin receptor knockout (Lhcgr KO) mice, an animal model of inguinoscrotal testis maldescent resulting from androgen deficiency. We found that the expression of secreted protein acidic and rich in cysteine (SPARC)-related modular calcium binding 1 (Smoc1) was the most severely suppressed at both the transcript and protein levels, while its expression was the most dramatically induced by testosterone administration in the gubernacula of Lhcgr KO mice. The upregulation of Smoc1 expression by testosterone was curtailed by the addition of an androgen receptor antagonist, flutamide. In addition, in vitro studies demonstrated that SMOC1 modestly but significantly promoted the proliferation of gubernacular cells. In the cultures of myogenic differentiation medium, both testosterone and SMOC1 enhanced the expression of myogenic regulatory factors such as paired box 7 (Pax7) and myogenic factor 5 (Myf5). After short-interfering RNA-mediated knocking down of Smoc1, the expression of Pax7 and Myf5 diminished, and testosterone alone did not recover, but additional SMOC1 did. These observations indicate that SMOC1 is pivotal in mediating androgen action to regulate gubernaculum development during inguinoscrotal testicular descent.

The effect of gonadotropin-inhibitory hormone on steroidogenesis and spermatogenesis by acting through the hypothalamic-pituitary-testis axis in mice

Gonadotropin inhibitory hormone (GnIH) is essential for regulating the reproduction of mammals and inhibiting testicular activities in mice. This study aimed to explore the mechanism of GnIH on spermatogenesis and steroidogenesis by acting through the hypothalamus-pituitary-testis axis of mice. Mice were subcutaneously injected with different doses of GnIH (1 μg/150 μL, 3 μg/150 μL, 6 μg/150 μL, 150 μL saline, twice daily) for 11 days. Subsequently, luteinizing hormone (LH), testosterone (T), and inhibin B (INH B) levels of peripheral blood were determined, and the expression of GnRH synthesis-related genes (GnRH-1, Kiss-1, NPY) and gonadotropin synthesis-related genes (FSH β, LH β, GnRH receptor) in the hypothalamus and pituitary gland were respectively detected. Additionally, the expression of steroidogenesis-related genes/proteins (P450scc, StAR and 3β-HSD) and spermatogenesis-related proteins/genes including LH receptor (LHR), androgen receptor (AR), heat shock factor-2 (HSF-2) and INH B were analyzed using western blot and q-PCR. Results showed that GnIH treatment significantly reduced the concentration of LH in the peripheral blood. Further analysis revealed that GnIH treatment markedly reduced the expression of GnRHImRNA and Kiss-1 mRNA in the hypothalamus, and mRNA levels of FSH β, LH β, and GnRHR genes in the pituitary. We also observed that GnIH treatment significantly decreased T levels and expression of the P450scc, StAR, and 3β-HSD proteins in the testis. Furthermore, GnIH treatment down-regulated LHR, AR proteins, and HSF-2 gene in the testis. Importantly, the INH B concentration of and INH βb mRNA levels significantly declined following GnIH treatment. Additionally, GnIH treatment may induce germ cell apoptosis in the testis of mice. In conclusion, GnIH may suppress spermatogenesis and steroidogenesis by acting through the hypothalamus-pituitary-testis axis in mice.

[Male contraception]

CONTEXT

Contraception is a major global health issue, which is still dominated by female contraception. Developments in male contraception could help redistribute the contraceptive burden.

METHODS

A literature search was carried out to review the existing options and the criteria for optimal contraception, to establish the principles of a male pre-contraception consultation, and to review the various research avenues with their advantages and disadvantages.

RESULTS

The new male contraception options are detailed, whether hormonal (androgen therapy, combination of progestins and testosterone) or non-hormonal, particularly thermal, with current results and avenues for improvement. Condom use and vasectomy remain the only 2 validated options. The recent development of minimally invasive vasectomy without the need for a scalpel and of occlusion techniques has simplified the procedure, minimised the risk of complications (pain, haematomas, post-vasectomy pain syndrome) and improved efficacy. The issues of regret and the possibility of repermeabilisation are also raised.

CONCLUSION

The question of male contraception will become increasingly important in consultations with urologists. The urologist will have to inform the patient, as required by law, before the vasectomy is performed, and provide the best possible advice on the technique, which will often be minimally invasive without the need for a scalpel. New reversible options should also broaden the range of options available on a routine basis, with a view to gradually moving towards contraceptive equity.

Successful Bilateral Sperm Retrieval in a Hypogonadal Patient with Non-Obstructive Azoospermia Showing Normal Serum 17-Hydroxyprogesterone Levels Suggestive of Normal Intratesticular Testosterone Production: A Case Report

The impact of hypogonadism on the probability of retrieving testicular sperm from patients with non-obstructive azoospermia (NOA) is still a matter of debate. Conflicting evidence in this field may be justified by the striking differences between serum and intratesticular testosterone (ITT) levels found in men with severe spermatogenic dysfunction, so that normal ITT levels may coexist with low serum testosterone levels. Here we report the case of a patient with NOA with a steadily reduced serum testosterone level irresponsive to hormonal stimulation with human chorionic gonadotropin. Supported by his normal serum 17-hydroxyprogesterone (17 OHP) levels, previously suggested to be marker of ITT levels, microdissection testicular sperm extraction was performed for both testes on two separate occasions, resulting in the retrieval of enough sperm for ICSI. Three ICSI cycles were then performed, one blastocyst was transferred, and five were cryopreserved. This case report suggests that normal serum 17 OHP levels, being suggestive of normal ITT levels, may support the decision to proceed with surgical sperm retrieval in hypogonadal patients with NOA, even for those irresponsive to hormonal treatment.

Revisiting the gonadotropic regulation of mammalian spermatogenesis: evolving lessons during the past decade

Spermatogenesis is a multi-step process of male germ cell (Gc) division and differentiation which occurs in the seminiferous tubules of the testes under the regulation of gonadotropins - Follicle Stimulating Hormone (FSH) and Luteinising hormone (LH). It is a highly coordinated event regulated by the surrounding somatic testicular cells such as the Sertoli cells (Sc), Leydig cells (Lc), and Peritubular myoid cells (PTc). FSH targets Sc and supports the expansion and differentiation of pre-meiotic Gc, whereas, LH operates via Lc to produce Testosterone (T), the testicular androgen. T acts on all somatic cells e.g.- Lc, PTc and Sc, and promotes the blood-testis barrier (BTB) formation, completion of Gc meiosis, and spermiation. Studies with hypophysectomised or chemically ablated animal models and hypogonadal (hpg) mice supplemented with gonadotropins to genetically manipulated mouse models have revealed the selective and synergistic role(s) of hormones in regulating male fertility. We here have briefly summarized the present concept of hormonal control of spermatogenesis in rodents and primates. We also have highlighted some of the key critical questions yet to be answered in the field of male reproductive health which might have potential implications for infertility and contraceptive research in the future.

Androgens in male contraception

Rates of unplanned pregnancies are high globally, burdening women and families. Efforts to develop male contraceptive agents have been thwarted by unacceptable failure rates, side effects and a dearth of pharmaceutical industry involvement. Hormonal male contraception consists of exogenous androgens which exert negative feedback on the hypothalamic-pituitary-gonadal axis and suppress gonadotropin production. This in turn suppresses testicular testosterone production and sperm maturation. Addition of a progestin suppresses spermatogenesis more effectively in men. Contraceptive efficacy studies in couples have shown male hormonal methods are effective and reversible, but also may come with side effects related to sexual desire, acne and serum cholesterol and inconvenient methods of dosing and delivery. Recently, novel androgens as potential contraceptive agents are being evaluated in early clinical trials and look to overcome these drawbacks. Here we summarize landmark studies of prototype male hormonal contraceptives, showcasing recent advances and future prospects in this important area of public health.

The Roles of Luteinizing Hormone, Follicle-Stimulating Hormone and Testosterone in Spermatogenesis and Folliculogenesis Revisited

Spermatogenesis and folliculogenesis involve cell–cell interactions and gene expression orchestrated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). FSH regulates the proliferation and maturation of germ cells independently and in combination with LH. In humans, the requirement for high intratesticular testosterone (T) concentration in spermatogenesis remains both a dogma and an enigma, as it greatly exceeds the requirement for androgen receptor (AR) activation. Several data have challenged this dogma. Here we report our findings on a man with mutant LH beta subunit (LHβ) that markedly reduced T production to 1–2% of normal., but despite this minimal LH stimulation, T production by scarce mature Leydig cells was sufficient to initiate and maintain complete spermatogenesis. Also, in the LH receptor (LHR) knockout (LuRKO) mice, low-dose T supplementation was able to maintain spermatogenesis. In addition, in antiandrogen-treated LuRKO mice, devoid of T action, the transgenic expression of a constitutively activating follicle stimulating hormone receptor (FSHR) mutant was able to rescue spermatogenesis and fertility. Based on rodent models, it is believed that gonadotropin-dependent follicular growth begins at the antral stage, but models of FSHR inactivation in women contradict this claim. The complete loss of FSHR function results in the complete early blockage of folliculogenesis at the primary stage, with a high density of follicles of the prepubertal type. These results should prompt the reassessment of the role of gonadotropins in spermatogenesis, folliculogenesis and therapeutic applications in human hypogonadism and infertility.

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.

Emerging approaches to male contraception

Despite significant interests in contraception by men, effective methods of male contraception are limited to vasectomy and condoms. Recently, there have been several promising advances in male contraceptive research. This review will update readers on recent research in both hormonal and nonhormonal approaches to male contraception. Hormonal approaches to male contraception have been stymied by adverse effects, formulations requiring injections or implants, a 5% to10% nonresponse rate, as well as poor understanding of user acceptability. In the last several years, research has focused on novel, orally bioavailable androgens such as dimethandrolone undecanoate and 11β-methyl-19-nor-testosterone. Additionally, combinations of a topical testosterone gel combined with a gel containing segesterone acetate, a potent progestin, have shown promise in clinical trials recently. Simultaneously, significant preclinical progress has been made in several approaches to nonhormonal male contraceptives, including compounds that inhibit sperm motility such as eppin, compounds that inhibit retinoic acid binding or biosynthesis, and reversible approaches to obstruction of the vas deferens. It is imperative for these areas of research to continue making strides so that there is a gamut of contraceptive options for couples to choose from. Some of these approaches will hopefully reach clinical utility soon, greatly improving contraceptive choice for couples.

Hormonal Treatment of Men with Nonobstructive Azoospermia: What Does the Evidence Suggest?

Hormonal stimulation of spermatogenesis prior to surgery has been tested by some authors to maximize the sperm retrieval yield in patients with nonobstructive azoospermia. Although the rationale of such an approach is theoretically sound, studies have provided conflicting results, and there are unmet questions that need to be addressed. In the present narrative review, we reviewed the current knowledge about the hormonal control of spermatogenesis, the relationship between presurgical serum hormones levels and sperm retrieval rates, and the results of studies investigating the effect of hormonal treatments prior to microdissection testicular sperm extraction. We pooled the available data about sperm retrieval rate in patients with low vs. normal testosterone levels, and found that patients with normal testosterone levels had a significantly higher chance of successful sperm retrieval compared to those with subnormal T levels (OR 1.63, 95% CI 1.08–2.45, p = 0.02). These data suggest that hormonal treatment may be justified in patients with hypogonadism; on the other hand, the available evidence is insufficient to recommend hormonal therapy as standard clinical practice to improve the sperm retrieval rate in patients with nonobstructive azoospermia.

A Testis-Specific Long Noncoding RNA, Start, Is a Regulator of Steroidogenesis in Mouse Leydig Cells

The testis expresses many long noncoding RNAs (lncRNAs), but their functions and overview of lncRNA variety are not well understood. The mouse Prss/Tessp locus contains six serine protease genes and two lncRNAs that have been suggested to play important roles in spermatogenesis. Here, we found a novel testis-specific lncRNA, Start (Steroidogenesis activating lncRNA in testis), in this locus. Start is 1822 nucleotides in length and was found to be localized mostly in the cytosol of germ cells and Leydig cells, although nuclear localization was also observed. Start-knockout (KO) mice generated by the CRISPR/Cas9 system were fertile and showed no morphological abnormality in adults. However, in adult Start-KO testes, RNA-seq and qRT-PCR analyses revealed an increase in the expression of steroidogenic genes such as Star and Hsd3b1, while ELISA analysis revealed that the testosterone levels in serum and testis were significantly low. Interestingly, at 8 days postpartum, both steroidogenic gene expression and testosterone level were decreased in Start-KO mice. Since overexpression of Start in two Leydig-derived cell lines resulted in elevation of the expression of steroidogenic genes including Star and Hsd3b1, Start is likely to be involved in their upregulation. The increase in expression of steroidogenic genes in adult Start-KO testes might be caused by a secondary effect via the androgen receptor autocrine pathway or the hypothalamus-pituitary-gonadal axis. Additionally, we observed a reduced number of Leydig cells at 8 days postpartum. Collectively, our results strongly suggest that Start is a regulator of steroidogenesis in Leydig cells. The current study provides an insight into the overall picture of the function of testis lncRNAs.

Male Contraception

Unintended pregnancy is a global public health problem. Despite a variety of female contraceptive options, male contraceptive options are limited to the condom and vasectomy. Condoms have high failure rates and surgical vasectomy is not reliably reversible. There is a global need and desire for novel male contraceptive methods. Hormonal methods have progressed the furthest in clinical development and androgen plus progestin formulations hold promise as a marketable, reversible male contraceptive over the next decade. Investigators have tested androgen plus progestin approaches using oral, transdermal, subdermal, and injectable drug formulations and demonstrated the short-term safety and reversibility of hormonal male contraception. The most commonly reported side effects associated with hormonal male contraception include weight gain, acne, slight suppression of serum high-density cholesterol, mood changes, and changes in libido. Efficacy trials of hormonal male contraceptives have demonstrated contraceptive efficacy rates greater than that of condoms. Although there has been less progression in the development of nonhormonal male contraceptives, potentially reversible vaso-occlusive methods are currently in clinical trials in some countries. Various studies have confirmed both men and women's desire for novel male contraceptives. Barriers to development include an absence of investment from pharmaceutical companies, concerns regarding side effects and spermatogenic rebound with hormonal methods, and lack of clear reversibility and proven effectiveness of nonhormonal methods. The ultimate availability of male contraceptives could have an important impact on decreasing global unintended pregnancy rates (currently 40% of all pregnancies) and will be a step towards reproductive justice and greater equity in family planning.

Male Hormonal Contraception

The economic and public health burdens of unplanned pregnancies are evident globally. Since the introduction of the condom >300 years ago, assumptions about male willingness to participate in contraception, as well as concerns about failure rates and side effects, have stagnated the development of additional reversible male contraceptives. However, changing attitudes and recent research advances have generated renewed interest in developing reversible male contraceptives. To achieve effective and reversible suppression of spermatogenesis, male hormonal contraception relies on suppression of testicular testosterone and sperm production using an androgen-progestin combination. While these may be associated with side effects—changes in libido, weight, hematocrit, and cholesterol—recently, novel androgens and progestins have shown promise for a “male pill” with reduced side effects. Here we summarize landmark studies in male contraceptive development, showcase the most recent advances, and look into the future of this field, which has the potential to greatly impact global public health.

Amhr2-Cre-Mediated Global Tspo Knockout

Although the role of translocator protein (TSPO) in cholesterol transport in steroid-synthesizing cells has been studied extensively, recent studies of TSPO genetic depletion have questioned its role. Amhr2-Cre mice have been used to generate Leydig cell-specific Tspo conditional knockout (cKO) mice. Using the same Cre line, we were unable to generate Tspo cKO mice possibly because of genetic linkage between Tspo and Amhr2 and coexpression of Amhr2-Cre and Tspo in early embryonic development. We found that Amhr2-Cre is expressed during preimplantation stages, resulting in global heterozygous mice (gHE; Amhr2-Cre^+/–,Tspo^–/+). Two gHE mice were crossed, generating Amhr2-Cre–mediated Tspo global knockout (gKO; Tspo^–/–) mice. We found that 33.3% of blastocysts at E3.5 to E4.5 showed normal morphology, whereas 66.7% showed delayed development, which correlates with the expected Mendelian proportions of Tspo^+/+ (25%), Tspo^–/– (25%), and Tspo^+/– (50%) genotypes from crossing 2 Tspo^–/+ mice. Adult Tspo gKO mice exhibited disturbances in neutral lipid homeostasis and reduced intratesticular and circulating testosterone levels, but no change in circulating basal corticosterone levels. RNA-sequencing data from mouse adrenal glands and lungs revealed transcriptome changes in response to the loss of TSPO, including changes in several cholesterol-binding and transfer proteins. This study demonstrates that Amhr2-Cre can be used to produce Tspo gKO mice instead of cKO, and can serve as a new global “Cre deleter.” Moreover, our results show that Tspo deletion causes delayed preimplantation embryonic development, alters neutral lipid storage and steroidogenesis, and leads to transcriptome changes that may reflect compensatory mechanisms in response to the loss of function of TSPO.

Inhalation of welding fumes reduced sperm counts and high fat diet reduced testosterone levels; differential effects in Sprague Dawley and Brown Norway rats

Background

Previous studies have shown that inhalation of welding fumes may induce pulmonary and systemic inflammation and organ accumulation of metal, to which spermatogenesis and endocrine function may be sensitive. Also obesity may induce low-grade systemic inflammation. This study aimed to investigate the effects on sperm production of inhaled metal nanoparticles from stainless steel welding, and the potential exacerbation by intake of a high fat diet. Both the inbred Brown Norway and the outbred Sprague Dawley rat strains were included to study the influence of strain on the detection of toxicity. Rats were fed regular or high fat (HF) diet for 24 weeks and were exposed to 20 mg/m³ of gas metal arc-stainless steel (GMA-SS) welding fumes or filtered air for 3 h/day, 4 days/week for 5 weeks, during weeks 7–12. Outcomes were assessed upon termination of exposure (week 12) and after recovery (week 24).

Results

At week 12, the GMA-SS exposure induced pulmonary inflammation in both strains, without consistent changes in markers of systemic inflammation (CRP, MCP-1, IL-6 and TNFα). GMA-SS exposure lowered daily sperm production compared to air controls in Sprague Dawley rats, but only in GMA-SS Brown Norway rats also fed the HF diet. Overall, HF diet rats had lower serum testosterone levels compared to rats on regular diet. Metal content in the testes was assessed in a limited number of samples in Brown Norway rats, but no increase was obsedrved. At week 24, bronchoalveolar lavage cell counts had returned to background levels for GMA-SS exposed Sprague Dawley rats but remained elevated in Brown Norway rats. GMA-SS did not affect daily sperm production statistically significantly at this time point, but testicular weights were lowered in GMA-SS Sprague Dawley rats. Serum testosterone remained lowered in Sprague Dawley rats fed the HF diet.

Conclusion

Exposure to GMA-SS welding fumes lowered sperm production in two strains of rats, whereas high fat diet lowered serum testosterone. The effect on sperm counts was likely not mediated by inflammation or lowered testosterone levels. The studied reproductive outcomes seemed more prone to disruption in the Sprague Dawley compared to the Brown Norway strain.

Recent Developments in Male Contraception

Unplanned pregnancies are an ongoing global burden, posing health and economic risks for women, children, and families. Advances in male contraception have been historically stymied by concerning failure rates, problematic side effects, and perceived market limitations. However, increased interest in reliable and reversible options for male contraception have resulted in resurgent efforts to introduce novel contraceptives for men. Hormonal male contraception relies on exogenous androgens and progestogens that suppress gonadotropin production, thereby suppressing testicular testosterone and sperm production. In many men, effective suppression of spermatogenesis can be achieved by androgen-progestin combination therapy. Small-scale contraceptive efficacy studies in couples have demonstrated effectiveness and reversibility with male hormonal methods, but side effects related to mood, sexual desire and cholesterol remain concerning. A number of novel androgens have reached clinical testing as potential contraceptive agents; many of these have both androgenic and progestogenic action in a single, modified steroid, thereby holding promise as single-agent contraceptives. Currently, these novel steroids hold promise as both a "male pill" and long-acting injections. Among non-hormonal methods, studies of reversible vaso-occlusive methods (polymers that block transport of sperm through the vas deferens) are ongoing, but reliable reversibility and long-term safety in men have not been established. Proteins involved in sperm maturation and motility are attractive targets, but to date both specificity and biologic redundancy have been challenges for drug development. In this review, we aim to summarize landmark studies on male contraception, highlight the most recent advances and future development in this important field of public health and medicine.

MECHANISMS IN ENDOCRINOLOGY: Hormonal regulation of spermatogenesis: mutant mice challenging old paradigms

The two pituitary gonadotrophins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and in particular LH-stimulated high intratesticular testosterone (ITT) concentration, are considered crucial for spermatogenesis. We have revisited these concepts in genetically modified mice, one being the LH receptor (R)-knockout mouse (LuRKO), the other a transgenic mouse expressing in Sertoli cells a highly constitutively active mutated Fshr (Fshr-CAM). It was found that full spermatogenesis was induced by exogenous testosterone treatment in LuRKO mice at doses that restored ITT concentration to a level corresponding to the normal circulating testosterone level in WT mice, ≈5 nmol/L, which is 1.4% of the normal high ITT concentration. When hypogonadal LuRKO and Fshr-CAM mice were crossed, the double-mutant mice with strong FSH signaling, but minimal testosterone production, showed near-normal spermatogenesis, even when their residual androgen action was blocked with the strong antiandrogen flutamide. In conclusion, our findings challenge two dogmas of the hormonal regulation of male fertility: (1) high ITT concentration is not necessary for spermatogenesis and (2) strong FSH stimulation can maintain spermatogenesis without testosterone. These findings have clinical relevance for the development of hormonal male contraception and for the treatment of idiopathic oligozoospermia.

Mouse models for the analysis of gonadotropin secretion and action

Gonadotropins are pituitary gonadotrope-derived glycoprotein hormones. They act by binding to G-protein coupled receptors on gonads. Gonadotropins play critical roles in reproduction by regulating both gametogenesis and steroidogenesis. Although biochemical and physiological studies provided a wealth of knowledge, gene manipulation techniques using novel mouse models gave new insights into gonadotropin synthesis, secretion and action. Both gain of function and loss of function mouse models for understanding gonadotropin action in a whole animal context have already been generated. Moreover, recent studies on gonadotropin actions in non-gonadal tissues challenged the central dogma of classical gonadotropin actions in gonads and revealed new signaling pathways in these non-gonadal tissues. In this Chapter, we have discussed our current understanding of gonadotropin synthesis, secretion and action using a variety of genetically engineered mouse models.

Can the evolution of male contraception lead to a revolution? Review of the current state of knowledge

Introduction

Great advances in medical research concerning methods of contraception have been achieved in recent years, however, more than 25% of couples worldwide still rely on condoms - a method with poor efficacy. Even though there is a spectrum of 11 different contraceptive methods for women, there are only 4 commonly used by men (condoms, periodic abstinence, withdrawal and vasectomy). In this review, advances and present, state-of-the-art, both hormonal and non-hormonal male contraceptive methods will be presented and evaluated. Potential novel targets that warrant greater research will be highlighted.

Material and methods

A comprehensive literature search without a time limit was performed using the Medline database on May 2017. The terms 'male contraception' in conjunction with 'reversible inhibition of sperm under guidance' (RISUG), 'hormonal', 'non-hormonal', 'vasectomy' or 'testosterone' were used. The articles were limited to those published in English, Polish or French.

Results

There are various contraceptives currently available to regulate male fertility. Vasectomy is still the most effective permanent form of male contraceptive with a failure rate lower than 1%. Reversible, non hormonal methods of male contraception, like reversible inhibition of sperm under guidance, are very promising and close to being introduced into the market. In regards to hormonal contraception research, the use of testosterone injections has been widely studied yet they often harbor undesirable side effects and require further development.

Conclusions

Despite continuous efforts worldwide, it seems that another several years of research is needed to provide safe, effective and affordable male contraceptives which will allow both men and women to participate fully in family planning.

Constitutively active follicle-stimulating hormone receptor enables androgen-independent spermatogenesis

Spermatogenesis is regulated by the 2 pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This process is considered impossible without the absolute requirement of LH-stimulated testicular testosterone (T) production. The role of FSH remains unclear because men and mice with inactivating FSH receptor (FSHR) mutations are fertile. We revisited the role of FSH in spermatogenesis using transgenic mice expressing a constitutively strongly active FSHR mutant in a LH receptor-null (LHR-null) background. The mutant FSHR reversed the azoospermia and partially restored fertility of Lhr-/- mice. The finding was initially ascribed to the residual Leydig cell T production. However, when T action was completely blocked with the potent antiandrogen flutamide, spermatogenesis persisted. Hence, completely T-independent spermatogenesis is possible through strong FSHR activation, and the dogma of T being a sine qua non for spermatogenesis may need modification. The mechanism for the finding appeared to be that FSHR activation maintained the expression of Sertoli cell genes considered androgen dependent. The translational message of our findings is the possibility of developing a new strategy of high-dose FSH treatment for spermatogenic failure. Our findings also provide an explanation of molecular pathogenesis for Pasqualini syndrome (fertile eunuchs; LH/T deficiency with persistent spermatogenesis) and explain how the hormonal regulation of spermatogenesis has shifted from FSH to T dominance during evolution.

Variable duration of reproductive suppression in male coyotes (Canis latrans) treated with a high dose of the gonadotrophin-releasing hormone agonist deslorelin

Effective and humane management strategies for coyotes (Canis latrans) remain elusive. We hypothesised that exposure to a high dose of a gonadotrophin-releasing hormone (GnRH) agonist would cause prolonged suppression of the reproductive axis. Two groups of male coyotes were administered 47 mg deslorelin in the form of either five 9.4-mg controlled-release Suprelorin (Peptech Animal Health, Macquarie Park NSW, Australia) implants (n = 3) or 10 4.7-mg implants (n = 5). In the first group, deslorelin suppressed plasma LH, testosterone and testes volume in two of three coyotes for three breeding seasons. In the second group, two of five deslorelin-treated coyotes had no sperm production after 1 year and plasma LH, FSH, testosterone and testes volume were suppressed. Although plasma gonadotropins and testosterone were suppressed in three treated coyotes in group two, testes volume and sperm production were evident. Because the duration of suppression differed among individual coyotes, we further hypothesised that a variation in deslorelin release underlay the variability. To test this, we analysed in vivo plasma profiles of deslorelin concentrations. These profiles suggested that deslorelin concentrations >100 pg mL–1 are required to maintain suppression in male coyotes. For field implementation, the development of an implant capable of releasing deslorelin for the life of the coyote is necessary.

Role of the teneurins, teneurin C-terminal associated peptides (TCAP) in reproduction: clinical perspectives

In humans, the teneurin gene family consists of four highly conserved paralogous genes that are the result of early vertebrate gene duplications arising from a gene introduced into multicellular organisms from a bacterial ancestor. In vertebrates and humans, the teneurins have become integrated into a number of critical physiological systems including several aspects of reproductive physiology. Structurally complex, these genes possess a sequence in their terminal exon that encodes for a bioactive peptide sequence termed the 'teneurin C-terminal associated peptide' (TCAP). The teneurin/TCAP protein forms an intercellular adhesive unit with its receptor, latrophilin, an Adhesion family G-protein coupled receptor. It is present in numerous cell types and has been implicated in gamete migration and gonadal morphology. Moreover, TCAP is highly effective at reducing the corticotropin-releasing factor (CRF) stress response. As a result, TCAP may also play a role in regulating the stress-associated inhibition of reproduction. In addition, the teneurins and TCAP have been implicated in tumorigenesis associated with reproductive tissues. Therefore, the teneurin/TCAP system may offer clinicians a novel biomarker system upon which to diagnose some reproductive pathologies.

Beyond the Condom: Frontiers in Male Contraception

Nearly half of all pregnancies worldwide are unplanned, despite numerous contraceptive options available. No new contraceptive method has been developed for men since the invention of condom. Nevertheless, more than 25% of contraception worldwide relies on male methods. Therefore, novel effective methods of male contraception are of interest. Herein we review the physiologic basis for both male hormonal and nonhormonal methods of contraception. We review the history of male hormonal contraception development, current hormonal agents in development, as well as the potential risks and benefits of male hormonal contraception options for men. Nonhormonal methods reviewed will include both pharmacological and mechanical approaches in development, with specific focus on methods which inhibit the testicular retinoic acid synthesis and action. Multiple hormonal and nonhormonal methods of male contraception are in the drug development pathway, with the hope that a reversible, reliable, safe method of male contraception will be available to couples in the not too distant future.

Male hormonal contraception: looking back and moving forward

Despite numerous contraceptive options available to women, approximately half of all pregnancies in the United States and worldwide are unplanned. Women and men support the development of reversible male contraception strategies, but none have been brought to market. Herein we review the physiologic basis for male hormonal contraception, the history of male hormonal contraception development, currents agents in development as well as the potential risks and benefits of male hormonal contraception for men.

Steroidogenic factor 1 differentially regulates fetal and adult leydig cell development in male mice

The nuclear receptor steroidogenic factor 1 (SF-1, AD4BP, NR5A1) is a key regulator of the endocrine axes and is essential for adrenal and gonad development. Partial rescue of Nr5a1(-/-) mice with an SF-1-expressing transgene caused a hypomorphic phenotype that revealed its roles in Leydig cell development. In contrast to controls, all male rescue mice (Nr5a1(-/-);tg(+/0)) showed varying signs of androgen deficiency, including spermatogenic arrest, cryptorchidism, and poor virilization. Expression of various Leydig cell markers measured by immunohistochemistry, Western blot analysis, and RT-PCR indicated fetal and adult Leydig cell development were differentially impaired. Whereas fetal Leydig cell development was delayed in Nr5a1(-/-);tg(+/0) embryos, it recovered to control levels by birth. In contrast, Sult1e1, Vcam1, and Hsd3b6 transcript levels in adult rescue testes indicated complete blockage in adult Leydig cell development. In addition, between Postnatal Days 8 and 12, peritubular cells expressing PTCH1, SF-1, and CYP11A1 were observed in control testes but not in rescue testes, indicating SF-1 is needed for either survival or differentiation of adult Leydig cell progenitors. Cultured prepubertal rat peritubular cells also expressed SF-1 and PTCH1, but Cyp11a1 was expressed only after treatment with cAMP and retinoic acid. Together, data show SF-1 is needed for proper development of fetal and adult Leydig cells but with distinct primary functions; in fetal Leydig cells, it regulates differentiation, whereas in adult Leydig cells it regulates progenitor cell formation and/or survival.

Androgen receptor roles in spermatogenesis and infertility

Androgens such as testosterone are steroid hormones essential for normal male reproductive development and function. Mutations of androgen receptors (AR) are often found in patients with disorders of male reproductive development, and milder mutations may be responsible for some cases of male infertility. Androgens exert their action through AR and its signalling in the testis is essential for spermatogenesis. AR is not expressed in the developing germ cell lineage so is thought to exert its effects through testicular Sertoli and peri-tubular myoid (PTM) cells. AR signalling in spermatogenesis has been investigated in rodent models where testosterone levels are chemically supressed or models with transgenic disruption of AR. These models have pinpointed the steps of spermatogenesis that require AR signalling, specifically maintenance of spermatogonial numbers, blood-testis barrier integrity, completion of meiosis, adhesion of spermatids and spermiation, together these studies detail the essential nature of androgens in the promotion of male fertility.

A novel inactivating mutation of the LH/chorionic gonadotrophin receptor with impaired membrane trafficking leading to Leydig cell hypoplasia type 1

OBJECTIVE

The LH/chorionic gonadotrophin receptor (LHCGR) is a G protein-coupled receptor (GPCR) that plays a central role in male sexual differentiation, regulation of ovarian follicular maturation, ovulation and maintenance of corpus luteum and pregnancy, as well as maintenance of testicular testosterone production. Mutations in the LHCGR gene are very rare. The aim of this work was to study the clinical and molecular characteristics of a rare familial LHCGR mutation.

METHODS

Five affected members of a family, including a phenotypically female, but genotypically male (46,XY), patient with Leydig cell hypoplasia type 1 and four genotypically female siblings with reproductive abnormalities, were studied genetically. Cell trafficking studies as well as signalling studies of mutated receptor were performed.

RESULTS

The five affected patients were all homozygous for a novel mutation in the LHCGR gene, a deletion of guanine in position 1850 (1850delG). This resulted in a frameshift affecting most of the C-terminal intracellular domain. In vitro studies demonstrated that the 1850delG receptor was completely incapable of transit to the cell membrane, becoming trapped within the endoplasmic reticulum. This could not be rescued by small-molecule agonist treatment or stimulated intracellularly by co-expression of a yoked human chorionic gonadotrophin.

CONCLUSIONS

This novel LHCGR mutation leads to complete inactivation of the LHCGR receptor due to trafficking and signalling abnormalities, which improves our understanding of the impact of the affected structural domain on receptor trafficking and function.

Genetic Models for the Study of Luteinizing Hormone Receptor Function

The luteinizing hormone/chorionic gonadotropin receptor (LHCGR) is essential for fertility in men and women. LHCGR binds luteinizing hormone (LH) as well as the highly homologous chorionic gonadotropin. Signaling from LHCGR is required for steroidogenesis and gametogenesis in males and females and for sexual differentiation in the male. The importance of LHCGR in reproductive physiology is underscored by the large number of naturally occurring inactivating and activating mutations in the receptor that result in reproductive disorders. Consequently, several genetically modified mouse models have been developed for the study of LHCGR function. They include targeted deletion of LH and LHCGR that mimic inactivating mutations in hormone and receptor, expression of a constitutively active mutant in LHCGR that mimics activating mutations associated with familial male-limited precocious puberty and transgenic models of LH and hCG overexpression. This review summarizes the salient findings from these models and their utility in understanding the physiological and pathological consequences of loss and gain of function in LHCGR signaling.

Sexual behavior attenuates the effects of chronic stress in body weight, testes, sexual accessory glands, and plasma testosterone in male rats

The aim of this study was to evaluate whether continuous sexual behavior could attenuate the effects of chronic stress on spermatogenesis, sexual glands, plasma testosterone and corticosterone in sexually experienced male rats. Rats were exposed to stress by immersion in cold water (ICW) daily for 20 or 50 consecutive days. Plasma testosterone and corticosterone, masculine sexual behavior, as well as the number of offspring, the epithelial area of seminiferous, prostatic and seminal glands were assessed. In stressed males, body and testicular weights decreased, male sexual behavior was disrupted, and adrenal weights increased. In males stressed for 50 days, prostate and seminal glands had lower weights compared with controls. Prostate and seminal epithelial areas also decreased in these males. Seminiferous tubules in testes from rats stressed for 20 or 50 days showed several degenerative signs, such as vacuoles in the basal epithelium, with picnotic indicia; moderate to severe exfoliation of degenerative germinal cells in the tubule lumen was also observed. In males stressed for 50 days a significant decrease in seminiferous epithelial area was observed from stages I-VIII, regardless of copulation. The litters from females that copulated with males stressed for 50 days decreased significantly. Chronic stress caused increase in plasma levels of corticosterone, which were higher in males stressed for 20 days than in males stressed for 50 days. Testosterone decreased in stressed males and it was lower in males stressed for 50 days. In stressed males allowed to copulate, body and testicular weights were similar to controls. Adrenal, seminal glands, and prostate weights, as well as epithelial areas of males stressed for 50 days allowed to copulate were also similar to controls. Corticosterone was lower than in males stressed for 50 days, but still higher than in controls. Testosterone in males stressed for 50 days and allowed to copulate was higher than in stressed males not allowed to copulate and control males without copulation, but still lower than in control copulating males. These results show that chronic stress causes germ cell loss in testes and a decrease in prostate and seminal epithelium, possibly as a result of testosterone decrease, affecting fertility. Continuous copulation can attenuate the effects of stress on testosterone levels and on the epithelial area in male sexual glands, but not on the seminiferous epithelium after 50 days of stress.

Mouse models of altered gonadotrophin action: insight into male reproductive disorders

The advent of technologies to genetically manipulate the mouse genome has revolutionised research approaches, providing a unique platform to study the causality of reproductive disorders in vivo. With the relative ease of generating genetically modified (GM) mouse models, the last two decades have yielded multiple loss-of-function and gain-of-function mutation mouse models to explore the role of gonadotrophins and their receptors in reproductive pathologies. This work has provided key insights into the molecular mechanisms underlying reproductive disorders with altered gonadotrophin action, revealing the fundamental roles of these pituitary hormones and their receptors in the hypothalamic–pituitary–gonadal axis. This review will describe GM mouse models of gonadotrophins and their receptors with enhanced or diminished actions, specifically focusing on the male. We will discuss the mechanistic insights gained from these models into male reproductive disorders, and the relationship and understanding provided into male human reproductive disorders originating from altered gonadotrophin action.

Male contraception

Clear evidence shows that many men and women would welcome new male methods of contraception, but none have become available. The hormonal approach is based on suppression of gonadotropins and thus of testicular function and spermatogenesis, and has been investigated for several decades. This approach can achieve sufficient suppression of spermatogenesis for effective contraception in most men, but not all; the basis for these men responding insufficiently is unclear. Alternatively, the non-hormonal approach is based on identifying specific processes in sperm development, maturation and function. A range of targets has been identified in animal models, and targeted effectively. This approach, however, remains in the pre-clinical domain at present. There are, therefore, grounds for considering that safe, effective and reversible methods of contraception for men can be developed.

Endocrine control of spermatogenesis: Role of FSH and LH/ testosterone

Evaluation of testicular functions (production of sperm and androgens) is an important aspect of preclinical safety assessment and testicular toxicity is comparatively far more common than ovarian toxicity. This chapter focuses (1) on the histological sequelae of disturbed reproductive endocrinology in rat, dog and nonhuman primates and (2) provides a review of our current understanding of the roles of gonadotropins and androgens. The response of the rodent testis to endocrine disturbances is clearly different from that of dog and primates with different germ cell types and spermatogenic stages being affected initially and also that the end-stage spermatogenic involution is more pronounced in dog and primates compared to rodents. Luteinizing hormone (LH)/testosterone and follicle-stimulating hormone (FSH) are the pivotal endocrine factors controlling testicular functions. The relative importance of either hormone is somewhat different between rodents and primates. Generally, however, both LH/testosterone and FSH are necessary for quantitatively normal spermatogenesis, at least in non-seasonal species.

Reconstruction of mouse testicular cellular microenvironments in long-term seminiferous tubule culture

Research on spermatogonia is hampered by complex architecture of the seminiferous tubule, poor viability of testicular tissue ex vivo and lack of physiologically relevant long-term culture systems. Therefore there is a need for an in vitro model that would enable long term survival and propagation of spermatogonia. We aimed at the most simplified approach to enable all different cell types within the seminiferous tubules to contribute to the creation of a niche for spermatogonia. In the present study we describe the establishment of a co-culture of mouse testicular cells that is based on proliferative and migratory activity of seminiferous tubule cells and does not involve separation, purification or differential plating of individual cell populations. The co-culture is composed of the constituents of testicular stem cell niche: Sertoli cells [identified by expression of Wilm's tumour antigen 1 (WT1) and secretion of glial cell line-derived neurotrophic factor, GDNF], peritubular myoid cells (expressing alpha smooth muscle actin, αSMA) and spermatogonia [expressing MAGE-B4, PLZF (promyelocytic leukaemia zinc finger), LIN28, Gpr125 (G protein-coupled receptor 125), CD9, c-Kit and Nanog], and can be maintained for at least five weeks. GDNF was found in the medium at a sufficient concentration to support proliferating spermatogonial stem cells (SSCs) that were able to start spermatogenic differentiation after transplantation to an experimentally sterile recipient testis. Gdnf mRNA levels were elevated by follicle-stimulating hormone (FSH) which shows that the Sertoli cells in the co-culture respond to physiological stimuli. After approximately 2–4 weeks of culture a spontaneous formation of cord-like structures was monitored. These structures can be more than 10 mm in length and branch. They are formed by peritubular myoid cells, Sertoli cells, fibroblasts and spermatogonia as assessed by gene expression profiling. In conclusion, we have managed to establish in vitro conditions that allow spontaneous reconstruction of testicular cellular microenvironments.

Overlapping dose responses of spermatogenic and extragonadal testosterone actions jeopardize the principle of hormonal male contraception

Testosterone (T), alone or in combination with progestin, provides a promising approach to hormonal male contraception. Its principle relies on enhanced negative feedback of exogenous T to suppress gonadotropins, thereby blocking the testicular T production needed for spermatogenesis, while simultaneously maintaining the extragonadal androgen actions, such as potency and libido, to avoid hypogonadism. A serious drawback of the treatment is that a significant proportion of men do not reach azoospermia or severe oligozoospermia, commensurate with contraceptive efficacy. We tested here, using hypogonadal luteinizing hormone/choriongonadotropin receptor (LHCGR) knockout (LHR^−/−) mice, the basic principle of the T-based male contraceptive method, that a specific T dose could maintain extragonadal androgen actions without simultaneously activating spermatogenesis. LHR^−/− mice were treated with increasing T doses, and the responses of their spermatogenesis and extragonadal androgen actions (including gonadotropin suppression and sexual behavior) were assessed. Conspicuously, all dose responses to T were practically superimposable, and no dose of T could be defined that would maintain sexual function and suppress gonadotropins without simultaneously activating spermatogenesis. This finding, never addressed in clinical contraceptive trials, is not unexpected in light of the same androgen receptor mediating androgen actions in all organs. When extrapolated to humans, our findings may jeopardize the current approach to hormonal male contraception and call for more effective means of inhibiting intratesticular T production or action, to achieve consistent spermatogenic suppression.—Oduwole, O. O., Vydra, N., Wood, N. E. M., Samanta, L., Owen, L., Keevil, B., Donaldson, M., Naresh, K., Huhtaniemi, I. T. Overlapping dose responses of spermatogenic and extragonadal testosterone actions jeopardize the principle of hormonal male contraception.

Changes in the immunolocalization of steroidogenic enzymes and the androgen receptor in raccoon (Procyon lotor) testes in association with the seasons and spermatogenesis

The raccoon is a seasonal breeder with a mating season in the winter. In a previous study, adult male raccoons exhibited active spermatogenesis with high plasma testosterone concentrations, in the winter mating season. Maintenance of spermatogenesis generally requires high testosterone, which is produced by steroidogenic enzymes. However, even in the summer non-mating season, some males produce spermatozoa actively despite low plasma testosterone concentrations. To identify the factors that regulate testosterone production and contribute to differences in spermatogenetic activity in the summer non-mating season, morphological, histological and endocrinological changes in the testes of wild male raccoons should be known. In this study, to assess changes in the biosynthesis, metabolism and reactivity of testosterone, the localization and immunohistochemical staining intensity of four steroidogenic enzymes (P450scc, P450c17, 3βHSD, P450arom) and the androgen receptor (AR) were investigated using immunohistochemical methods. P450scc and P450c17 were detected in testicular tissue throughout the year. Seasonal changes in testosterone concentration were correlated with 3βHSD expression, suggesting that 3βHSD may be important in regulating the seasonality of testosterone production in raccoon testes. Immunostaining of P450arom and AR was detected in testicular tissues that exhibited active spermatogenesis in the summer, while staining was scarce in aspermatogenic testes. This suggests that spermatogenesis in the raccoon testis might be maintained by some mechanism that regulates P450arom expression in synthesizing estradiol and AR expression in controlling reactivity to testosterone.

Germ-line activation of the luteinizing hormone receptor directly drives spermiogenesis in a nonmammalian vertebrate

In both mammals and teleosts, the differentiation of postmeiotic spermatids to spermatozoa (spermiogenesis) is thought to be indirectly controlled by the luteinizing hormone (LH) acting through the LH/choriogonadotropin receptor (LHCGR) to stimulate androgen secretion in the interstitial Leydig cells. However, a more direct, nonsteroidal role of LH mediating the spermiogenic pathway remains unclear. Using a flatfish with semicystic spermatogenesis, in which spermatids are released into the seminiferous lobule lumen (SLL), where they develop into spermatozoa without direct contact with the supporting Sertoli cells, we show that haploid spermatids express the homolog of the tetrapod LHCGR (Lhcgrba). Both native Lh and intramuscularly injected His-tagged recombinant Lh (rLh) are immunodetected bound to the Lhcgrba of free spermatids in the SLL, showing that circulating gonadotropin can reach the intratubular compartment. In vitro incubation of flatfish spermatids isolated from the SLL with rLh specifically promotes their differentiation into spermatozoa, whereas recombinant follicle-stimulating hormone and steroid hormones are ineffective. Using a repertoire of molecular markers and inhibitors, we find that the Lh-Lhcgrba induction of spermiogenesis is mediated through a cAMP/PKA signaling pathway that initiates the transcription of genes potentially involved in the function of spermatozoa. We further show that Lhcgrba expression in germ cells also occurs in distantly related fishes, suggesting this feature is likely conserved in teleosts regardless of the type of germ cell development. These data reveal a role of LH in vertebrate germ cells, whereby a Lhcgrba-activated signaling cascade in haploid spermatids directs gene expression and the progression of spermiogenesis.

Constitutive activity in gonadotropin receptors

Constitutively active mutants (CAMs) of gonadotropin receptors are, in general, rare conditions. Luteinizing hormone-choriogonadotropin receptor (LHCGR) CAMs provoke the dramatic phenotype of familial gonadotropin-independent isosexual male-limited precocious puberty, whereas in females, there is not yet any identified phenotype. Only one isolated follicle-stimulating hormone receptor (FSHR) CAM (Asp567Gly) has so far been detected in a single male patient, besides other FSHR weak CAMs linked to pregnancy-associated ovarian hyperstimulation syndrome or to impaired desensitization and internalization. Several animal models have been developed for studying enhanced gonadotropin action; in addition to unraveling valuable new information about the possible phenotypes of isolated FSHR and LHCGR CAMs in women, the information obtained from these mouse models has served multiple translational goals, including the development of new diagnostic and therapeutic targets as well as the prediction of phenotypes for mutations not yet identified in humans. Mutagenesis and computational studies have shed important information on the physiopathogenic mechanisms leading to constitutive activity of gonadotropin receptors; a common feature in these receptor CAMs is the release of stabilizing interhelical interactions between transmembrane domains (TMDs) 3 and 6 leading to an increase, with respect to the wild-type receptor, in the solvent accessibility at the cytosolic extension of TMDs 3, 5, and 6, which involves the highly conserved Glu/Asp-Arg-Tyr/Trp sequence. In this chapter, we summarize the structural features, functional consequences, and mechanisms that lead to constitutive activation of gonadotropin receptor CAMs and provide information on pharmacological approaches that might potentially modulate gonadotropin receptor CAM function.

Androgen synthesis in the gonadotropin-suppressed human testes can be markedly suppressed by ketoconazole

CONTEXT

The concentration of intratesticular testosterone (IT-T) required for human spermatogenesis is unknown because spermatogenesis can persist despite the markedly reduced IT-T concentrations observed with LH suppression. Methods to lower IT-T further are needed to determine the relationship between IT-T and spermatogenesis.

OBJECTIVE

The objective of the study was to determine the effect of inhibiting the synthesis and metabolism of testosterone (T) on IT-T in gonadotropin-suppressed human testes.

DESIGN/SETTING/PATIENTS

Forty normal men participated in a blinded, placebo-controlled, randomized trial at an academic center. INTERVENTION/OUTCOME MEASURES: All men were first administered the GnRH antagonist acyline to suppress LH. Forty-eight hours after acyline administration, subjects were randomly assigned to placebo, ketoconazole (to inhibit T synthesis) at 400 or 800 mg, dutasteride (to inhibit T metabolism) 2.5 mg, or anastrazole (to inhibit T metabolism) 1 mg, daily for 7 days (n = 8/group). Intratesticular steroid concentrations were measured 48 hours after acyline administration alone and again after 7 days of combination treatment.

RESULTS

After 7 days of combination treatment, the median IT-T (25th, 75th percentile) in the placebo group was 14 (8.0, 21.2) ng/mL. IT-T was reduced to 3.7 (2.5, 7.1) ng/mL in the ketoconazole 400 mg group and 1.7 (0.8, 4.0) ng/mL in the ketoconazole 800 mg group (P < .001 vs placebo for both comparisons). IT-T concentrations in the dutasteride and anastrazole groups were similar to placebo.

CONCLUSION

Combining inhibition of steroidogenesis with gonadotropin suppression lowers IT-T more than gonadotropin suppression alone. This combination might be useful to determine the minimum IT-T concentration necessary for human spermatogenesis, information essential for developing male hormonal contraceptives.

An approach to constitutional delay of growth and puberty

Constitutional delay of growth and puberty is a transient state of hypogonadotropic hypogonadism associated with prolongation of childhood phase of growth, delayed skeletal maturation, delayed and attenuated pubertal growth spurt, and relatively low insulin-like growth factor-1 secretion. In a considerable number of cases, the final adult height (Ht) does not reach the mid-parental or the predicted adult Ht for the individual, with some degree of disproportionately short trunk. In the pre-pubertal male, testosterone (T) replacement therapy can be used to induce pubertal development, accelerate growth and relieve the psychosocial complaints of the adolescents. However, some issues in the management are still unresolved. These include type, optimal timing, dose and duration of sex steroid treatment and the possible use of adjunctive or alternate therapy including: oxandrolone, aromatase inhibitors and human growth hormone.

Androgen initiates Sertoli cell tight junction formation in the hypogonadal (hpg) mouse

Sertoli cell tight junctions (TJs) form at puberty as a major component of the blood-testis barrier (BTB), which is essential for spermatogenesis. This study characterized the hormonal induction of functional Sertoli cell TJ formation in vivo using the gonadotropin-deficient hypogonadal (hpg) mouse that displays prepubertal spermatogenic arrest. Androgen actions were determined in hpg mice treated for 2 or 10 days with dihydrotestosterone (DHT). Follicle-stimulating hormone (FSH) actions were studied in hpg mice expressing transgenic human FSH (hpg+tgFSH) with or without DHT treatment. TJ formation was examined by mRNA expression and immunolocalization of TJ proteins claudin-3 and claudin-11, and barrier functionality was examined by biotin tracer permeability. Immunolocalization of claudin-3 and claudin-11 was extensive at wild-type (wt) Sertoli cell TJs, which functionally excluded permeability tracer. In contrast, seminiferous tubules of hpg testes lacked claudin-3, but claudin-11 protein was present in adluminal regions of Sertoli cells. Biotin tracer permeated throughout these tubules, demonstrating dysfunctional TJs. In hpg+tgFSH testes, claudin-3 was generally absent, but claudin-11 had redistributed basally toward the TJs, where function was variable. In hpg testes, DHT treatment stimulated the redistribution of claudin-11 protein toward the basal region of Sertoli cells by Day 2, increased Cldn3 and Cldn11 mRNA expression, then induced the formation of functional TJs containing both proteins by Day 10. In hpg+tgFSH testes, TJ protein redistribution was accelerated and functional TJs formed by Day 2 of DHT treatment. We conclude that androgen stimulates initial Sertoli cell TJ formation and function in mice, whereas FSH activity is insufficient alone, but augments androgen-induced TJ function.

Novel actions of progesterone: what we know today and what will be the scenario in the future?

Objectives

This article is aimed to review the novel actions of progesterone, which otherwise is considered as a female reproductive hormone. The article focuses on its important physiological actions in males too and gives an overview of its novel perspectives in disorders of central and peripheral nervous system.

Key findings

Progesterone may have a potential benefit in treatment of traumatic brain injury, various neurological disorders and male related diseases like benign prostatic hypertrophy (BPH), prostate cancer and osteoporosis. Norethisterone (NETA), a progesterone derivative, decreases bone mineral loss in male castrated mice suggesting its role in osteoporosis. In the future, progesterone may find use as a male contraceptive too, but still needs confirmatory trials for safety, tolerability and acceptability. Megestrol acetate, a progesterone derivative is preferred in prostatic cancer. Further, it may find utility in nicotine addiction, traumatic brain injury (recently entered Phase III trial) and Alzheimer's disease, diabetic neuropathy and crush injuries. Studies also suggest role of progesterone in stroke, for which further clinical trials are needed. The non genomic actions of progesterone may be in part responsible for these novel actions.

Summary

Although progesterone has shown promising role in various non-hormonal benefits, further clinical studies are needed to prove its usefulness in conditions like stroke, traumatic brain injury, neuropathy and crush injury. In male related illnesses like BPH and prostatic Ca, it may prove a boon in near future. New era of hormonal male contraception may be initiated by use of progesterone along with testosterone.

Animal models for aberrations of gonadotropin action

During the last two decades a large number of genetically modified mouse lines with altered gonadotropin action have been generated. These mouse lines fall into three categories: the lack-of-function mice, gain-of-function mice, and the mice generated by breeding the abovementioned lines with other disease model lines. The mouse strains lacking gonadotropin action have elucidated the necessity of the pituitary hormones in pubertal development and function of gonads, and revealed the processes from the original genetic defect to the pathological phenotype such as hypo- or hypergonadotropic hypogonadism. Conversely, the strains of the second group depict consequences of chronic gonadotropin action. The lines vary from those expressing constitutively active receptors and those secreting follicle-stimulating hormone (FSH) with slowly increasing amounts to those producing human choriogonadotropin (hCG), amount of which corresponds to 2000-fold luteinizing hormone (LH)/hCG biological activity. Accordingly, the phenotypes diverge from mild anomalies and enhanced fertility to disrupted gametogenesis, but eventually chronic, enhanced and non-pulsatile action of both FSH and LH leads to female and male infertility and/or hyper- and neoplasias in most of the gonadotropin gain-of-function mice. Elevated gonadotropin levels also alter the function of several extra-gonadal tissues either directly or indirectly via increased sex steroid production. These effects include promotion of tumorigenesis in tissues such as the pituitary, mammary and adrenal glands. Finally, the crossbreedings of the current mouse strains with other disease models are likely to uncover the contribution of gonadotropins in novel biological systems, as exemplified by the recent crossbreed of LHCG receptor deficient mice with Alzheimer disease mice.

Normal inhibin B levels suggest partial preservation of gonadal function in adult male patients with anorexia nervosa

INTRODUCTION

The impact of undernutrition on endocrine and exocrine gonadatrope function is poorly known in male anorexia nervosa (AN) patients.

AIM

The aim of this study was to compare the pituitary-gonadal function of male AN subjects with that of healthy controls, Kallmann syndrome (KS) patients, and female AN subjects.

METHODS

Observational monocentric cross-sectional study performed in 31 male and 25 female subjects with restrictive-type AN, 22 male and 20 female controls, and nine male KS patients.

MAIN OUTCOME MEASURES

Hormonal parameters are as follows: follicule stimulating hormone (FSH), luteinizing hormone (LH), sex hormone binding globulin, estradiol, testosterone, inhibin B, thyroid hormones, growth hormone (GH), insulin-like growth factor 1 (IGF-1), cortisol, adrenocorticotropic hormone (ACTH), dehydroepiandrosterone sulfate, and leptin.

RESULTS

Similar abnormalities of free T3, GH, IGF-I, cortisol, and leptin were found in men as in AN women with equivalent undernutrition status when compared with corresponding controls. Low levels of LH, FSH were found in both male and female AN patients. In male AN, total testosterone was found lower than in controls but higher than in KS, while a lack of estradiol was noticed in AN women. Sex hormones variations were directly related to weight gain only in AN men. No relationship was found between sex hormones and leptin variation for both sexes. In AN men, inhibin B levels were similar to that of controls and did not correlate with testosterone levels.

CONCLUSIONS

Significant differences of undernutrition impact on gonadal status were noticed between male and female AN subjects, including partial preservation of testosterone release and probable preservation of exocrine function, according to the normal inhibin B levels.

Physiologic role and regulation of intratesticular sex steroids

PURPOSE OF REVIEW

To summarize recent advances in our understanding of the role and regulation of intratesticular androgens, and their metabolites, in human spermatogenesis.

RECENT FINDINGS

Over the last few years, a number of studies have been published examining intratesticular sex steroid concentrations in normal men following gonadotropin manipulation and in the setting of impaired fertility. Advances in the field have been facilitated by the availability of more sensitive and specific assays for intratesticular sex steroid quantification. High levels of intratesticular androgens are required for normal spermatogenesis in men. However, the quantitative relationship between intratesticular testosterone concentrations and male fertility is not fully understood. In the setting of impaired spermatogenesis, intratesticular metabolites of testosterone may play a role in initiating or maintaining fertility.

SUMMARY

Advances in the precision of androgen measurements and recent studies examining intratesticular responses to hormonal manipulation have advanced our understanding of the testicular microenvironment. These advances have set the stage for future studies in this area which will be important for moving forward male hormonal contraceptive development and furthering our understanding of male reproductive pathology. Whether 'gonadotropin-independent' intratesticular androgen synthesis plays a role in human spermatogenesis will likely be a focus of investigation in the coming years.