Stage-dependent changes in spermatogenesis and Sertoli cells in relation to the onset of spermatogenic failure following withdrawal of testosterone

A North American study of anthropometric factors and semen quality

OBJECTIVE

To evaluate the association between anthropometric measures and semen parameters.

DESIGN

Cross-sectional study.

SUBJECTS

Male participants aged ≥21 years. We analyzed data from 659 males (1185 samples) participating in a semen testing substudy of the Pregnancy Online Study (PRESTO), a North American preconception cohort study. After enrollment, we invited males aged ≥21 years to perform at-home semen testing using the Trak system.

EXPOSURE(S)

Participants reported selected anthropometric variables (current weight, height, waist circumference, and weight at age 17 years) and covariate data via an online baseline questionnaire.

MAIN OUTCOME MEASURE(S)

We used generalized estimating equations models to estimate the percent difference in mean log-transformed semen parameter values and 95% confidence intervals (CI) for associations between selected anthropometric variables and semen volume (mL), sperm concentration (million/mL), and total sperm count (million), adjusting for sociodemographics, lifestyle factors, and medical history. We also evaluated World Health Organization-defined thresholds for low semen quality.

RESULT(S)

Percentage differences in mean log-transformed semen volume, sperm concentration, and total sperm count (95% CI) comparing current body mass index ≥35 vs. <25 kg/m2 were -6.3 (-15.8, 4.3), -6.4 (-24.6, 16.2), and -12.2 (-31.1, 11.8), respectively. Percentage differences (95% CIs) comparing waist circumferences of ≥42 vs. <31 inches were -4.2 (-15.0, 8.0), -6.4 (-27.6, 21.0), and -10.4 (-31.9, 17.9) for semen volume, sperm concentration, and total sperm count, respectively. Greater adult weight gain since age 17 years was associated with reduced semen volume (≥25 vs. <5 kg; percent difference, -9.7; 95% CI, -18.4, 0.1), but not sperm concentration or total sperm count. The highest categories of each anthropometric variable generally were associated with World Health Organization-defined low total sperm count (≤39 million).

CONCLUSION(S)

Selected anthropometric factors were associated modestly with poorer semen quality.

How much obesity and diabetes do impair male fertility?

BACKGROUND

Subfertility in obese and diabetic men during the reproductive age is evident, but the mechanisms by which obesity and diabetes mellitus cause male infertility are not entirely understood. The current study aimed to evaluate the effects and potential mechanisms of obesity and diabetes on male fertility.

METHODS

We enrolled control = 40, obese = 40, Lean-DM = 35, and Obese-DM = 35 individuals. The obesity-associated markers, diabetic markers, hormonal and lipid profile, inflammatory indices, and semen analysis were assessed in four experimental groups.

RESULTS

Our finding showed that diabetic markers were significantly increased in two diabetic groups, while obesity indices were markedly increased in two obese groups. Conventional sperm parameters were significantly lower in three groups compared with the control. Serum levels of total testosterone and sex hormone-binding globulin were significantly lower in men with obesity and DM compared with the control. There was a significant difference in the concentration of high-sensitivity C-reactive protein among four experimental groups. Moreover, serum leptin was significantly increased in obese DM, lean DM, and obese groups. Serum insulin levels had a positive correlation with metabolic-associated indices and high-sensitivity C-reactive protein levels, whereas it had a negative correlation with count, motility, and morphology.

CONCLUSIONS

Our findings showed the metabolic changes, hormonal dysfunction and inflammatory disturbance might be suspected mechanisms of subfertility in obese and diabetic subfertile men.

Unlocking the mystery associated with infertility and prostate cancer: an update

Male-specific reproductive disorders and cancers have increased intensely in recent years, making them a significant public health problem. Prostate cancer (PC) is the most often diagnosed cancer in men and is one of the leading causes of cancer-related mortality. Both genetic and epigenetic modifications contribute to the development and progression of PC, even though the exact underlying processes causing this disease have yet to be identified. Male infertility is also a complex and poorly understood phenomenon believed to afflict a significant portion of the male population. Chromosomal abnormalities, compromised DNA repair systems, and Y chromosome alterations are just a few of the proposed explanations. It is becoming widely accepted that infertility shares a link with PC. Much of the link between infertility and PC is probably attributable to common genetic defects. This article provides an overview of PC and spermatogenic abnormalities. This study also investigates the link between male infertility and PC and uncovers the underlying reasons, risk factors, and biological mechanisms contributing to this association.

Exercise improves testicular morphology and oxidative stress parameters in rats with testicular damage induced by a high-fat diet

Obesity and male infertility are problems that affect population. Exercise is a nonpharmacological way to reduce the negative health effects of obesity. The purpose of this study was to examine the effects of exercise on hormone levels, blood-testis barrier, and inflammatory and oxidative biomarkers in rats that became obese due to a high-fat diet (HFD). Male rats received a standard diet (STD group) or a HFD (HFD group) for 18 weeks. During the final 6 weeks of the experiment, swimming exercises (1 h/5 days/week) were given to half of these animals (STD + EXC and HFD + EXC groups). Finally, blood and testicular tissues were analysed by biochemical and histological methods. Body weight, leptin, malondialdehyde, interleukin-6, TNF-alpha and myeloperoxidase levels, apoptotic cells and DNA fragmentation were increased, and testis weight, insulin, FSH, LH, testosterone, glutathione and superoxide dysmutase levels, proliferative cells, ZO-1, occludin, and gap junction protein Cx43 immunoreactivity were decreased in the HFD group. All these hormonal, morphological, oxidative and inflammatory biomarkers were enhanced in the HFD + EXC group. It is thought that exercise protected testicular cytotoxicity by regulating hormonal and oxidant/antioxidant balances and testicular function, inhibiting inflammation and apoptosis, as well as preserving blood-testis barrier.

Obesity and Male Reproduction: Do Sirtuins Play a Role?

Obesity is a major current public health problem of global significance. A progressive sperm quality decline, and a decline in male fertility, have been reported in recent decades. Several studies have reported a strict relationship between obesity and male reproductive dysfunction. Among the many mechanisms by which obesity impairs male gonadal function, sirtuins (SIRTs) have an emerging role. SIRTs are highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases that play a role in gene regulation, metabolism, aging, and cancer. SIRTs regulate the energy balance, the lipid balance, glucose metabolism, and adipogenesis, but current evidence also indicates a role for SIRTs in male reproduction. However, the majority of the studies have been conducted in animal models and very few have been conducted with humans. This review shows that SIRTs play an important role among the molecular mechanisms by which obesity interferes with male fertility. This highlights the need to deepen this relationship. It will be of particular interest to evaluate whether synthetic and/or natural compounds capable of modifying the activity of SIRTs may also be useful for the treatment of obesity and its effects on gonadal function. Although few studies have explored the role of SIRT activators in obesity-induced male infertility, some molecules, such as resveratrol, appear to be effective in modulating SIRT activity, as well as counteracting the negative effects of obesity on male fertility. The search for strategies to improve male reproductive function in overweight/obese patients is a challenge and understanding the role of SIRTs and their activators may open new interesting scenarios in the coming years.

Testicular morphometry as a tool to evaluate the efficiency of immunocastration in lambs

This study aimed to evaluate the efficiency of immunocastration in lambs using testicular morphometry. Thirty lambs were randomly divided into two treatments (subcutaneous administration of 1.0 mL and 0.5 mL of an anti-GnRH vaccine) and a control group (1.0 mL saline solution). The animals were vaccinated at four months of age, received a second dose 30 days later, and were slaughtered 90 days after the first vaccine dose. After slaughter, testicles were collected, and samples were removed for histological processing and evaluation of testicular morphometric parameters. Analysis of variance, Tukey’s test, and Kruskal–Wallis test were performed, with a 5% level of significance. There was a reduction in testicular weight, gonadosomatic index, seminiferous tubule diameter, germinal epithelium height, leydigosomatic index, and total tubule length. The total length per testicular gram increased in the immunocastrated group. Intrinsic spermatogenesis yield, Sertoli cell indices, and estimates of sperm and Sertoli cell production were reduced in the immunized groups (P < 0.05). The anti-GnRH vaccine in lambs at doses of 1.0 mL and 0.5 mL is sufficient to promote immunocastration, verified through severe changes in testicular morphometry from animals.

Molecular Mechanisms Underlying the Relationship between Obesity and Male Infertility

In recent decades, the worldwide prevalence of obesity has risen dramatically and is currently estimated to be around 20%. Obesity is linked to an increased risk of comorbidities and premature mortality. Several studies have shown that obesity negatively impacts male fertility through various mechanisms. This review aims to investigate the molecular mechanisms through which obesity impairs male reproduction, including obesity-associated hypogonadism and its effects on spermatogenesis, chronic inflammation, and oxidative stress. Obesity negatively impacts both conventional and biofunctional sperm parameters, and it also induces epigenetic changes that can be transferred to offspring. Moreover, obesity-related diseases are linked to a dysregulation of adipocyte function and micro-environmental inflammatory processes. The dysregulated adipokines significantly influence insulin signaling, and they may also have a detrimental effect on testicular function. Sirtuins can also play an important role in inflammatory and metabolic responses in obese patients. Understanding the molecular mechanisms that are involved in obesity-induced male infertility could increase our ability to identify novel targets for the prevention and treatment of obesity and its related consequences.

Weight Loss Through Bariatric Surgery in Men Presents Beneficial Effects on Sexual Function, Symptoms of Testosterone Deficiency, and Hormonal Profile

Introduction

Male obesity has a negative correlation with plasma testosterone (T) levels and sexual function (SF).

Aim

To evaluate the effect of weight loss through bariatric surgery (BS) on SF, low T symptoms, and hormonal profiles in obese men.

Methods

Thirty-three men who underwent BS participated in this cohort study. Before surgery, all participants underwent clinical examinations, including anthropometric, lipid, glycemic, and hormonal evaluations. SF was evaluated using the International Index of Erectile Function (IIEF) questionnaire; low T symptoms were evaluated using the Aging Males’ Symptoms (AMS) and Androgen Deficiency in the Aging Male (ADAM) questionnaires. The participants were reevaluated 6 months post-surgery.

Main outcome measures

Sex hormone profile, SF, and low T symptoms

Results

After BS, a significant increase in mean total T (201 ± 111–548 ± 190 ng/dL, P < .001), free T (5.8 ± 2.8–9.3 ± 3.4 ng/dL, P < .001), bioavailable T (110.3 ± 57.8–198.6 ± 74.3 ng/dL, P < .001), and sexual hormone-binding globulin (19.8 ± 13.7–54.6 ± 23.2 nmol/L, P < .001) levels. There was a significant decrease in estradiol (64.6 ± 27.4–29.2 ± 20.0 [pg/mL], P < .001). SF significantly improved. The total IIEF score increased 5.2 points (62.3 ± 7.4–67.5 ± 7.4, P = .004), erectile function subdomain increased 2.4 points (25.7 ± 4.1–28.1 ± 3.9, P = .011), desire subdomain increased 1.0 points (8.3 ± 1.5–9.3 ± 1.6, P = .006), and intercourse satisfaction subdomain increased 1.2 points (11.4 ± 1.9–12.6 ± 1.8, P = .012). Post-surgery, a 44% reduction (P = .001) was observed in the positive ADAM questionnaire, and improvements in all domains of the AMS questionnaire were found (P < .001).

Conclusion

Significant weight loss through BS improves erectile function, hormonal profile, and symptoms of T deficiency.

Machado FP, Rhoden EL, Pioner SR, et al. Weight Loss Through Bariatric Surgery in Men Presents Beneficial Effects on Sexual Function, Symptoms of Testosterone Deficiency, and Hormonal Profile. Sex Med 2021;9:100400.

Spermatogenesis in the Roborovski hamster (Phodopus roborovskii) and the Chinese hamster (Cricetulus griseus)

BACKGROUND

Spermatogenesis is an elaborately organized and tightly regulated differentiation process. The spermatogenesis duration is stable within a certain species but highly variable between species of the same family.

OBJECTIVES

In this study, the spermatogenesis duration of the Roborovski hamster was measured for the first time, and the spermatogenesis duration of the Chinese hamster was re-assessed.

MATERIALS AND METHODS

Stage classification and cycle length measurement were carried out by labeling the dividing cells with bromodeoxyuridine and an antibody-based chromogen as well as with the periodic acid-Schiff/hematoxylin stain. Analysis was conducted using reference calculation and linear regression. Morphological measurements completed our set of methods.

RESULTS

The mean duration of one seminiferous epithelium cycle was 8.58 ± 0.34 days (mean ± SEM; Phodopus roborovskii) and 16.59 ± 0.47 days (Cricetulus griseus) based on the reference calculation. Slightly higher results were obtained using linear regression analysis: 9.72 ± 0.41 days for P. roborovskii and 17.64 ± 0.61 days for C. griseus. Additionally, a newly developed exemplary flowchart was proposed for the Roborovski hamster to facilitate spermatogenesis stage classification also in other species. The Chinese hamster presented an unexpectedly high paired epididymides weight of 1.701 ± 0.046 g (mean ± SEM) although having a body weight of only 40.5 ± 0.7 g. However, no significant correlation between the relative epididymis weight and spermatogenesis duration in mammals (Spearman rank correlation: r = -0.119, p = 0.607, n = 21) or rodents could be found (r = 0.045, p = 0.903, n = 11).

CONCLUSION

Our data emphasize the stability of the spermatogenesis duration within species and its remarkable variability between species. Further research is needed to identify the principal mechanisms and selection drivers that are responsible for such stability within species and the variability between species.

Spinal muscular atrophy: Broad disease spectrum and sex-specific phenotypes

Spinal muscular atrophy (SMA) is one of the major genetic disorders associated with infant mortality. More than 90% of cases of SMA result from deletions of or mutations in the Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, does not compensate for the loss of SMN1 due to predominant skipping of exon 7. The spectrum of SMA is broad, ranging from prenatal death to infant mortality to survival into adulthood. All tissues, including brain, spinal cord, bone, skeletal muscle, heart, lung, liver, pancreas, gastrointestinal tract, kidney, spleen, ovary and testis, are directly and/or indirectly affected in SMA. Accumulating evidence on impaired mitochondrial biogenesis and defects in X chromosome-linked modifying factors, coupled with the sexual dimorphic nature of many tissues, point to sex-specific vulnerabilities in SMA. Here we review the role of sex in the pathogenesis of SMA.

Leydig cell genes change their expression and association with polysomes in a stage-specific manner in the adult mouse testis

Spermatogenesis in mammals occurs in a very highly organized manner within the seminiferous epithelium regulated by different cell types in the testis. Testosterone produced by Leydig cells regulates blood-testis barrier formation, meiosis, spermiogenesis, and spermiation. However, it is unknown whether Leydig cell function changes with the different stages of the seminiferous epithelium. This study utilized the WIN 18,446 and retinoic acid (RA) treatment regime combined with the RiboTag mouse methodology to synchronize male germ cell development and allow for the in vivo mapping of the Leydig cell translatome across the different stages of one cycle of the seminiferous epithelium. Using microarrays analysis, we identified 11 Leydig cell-enriched genes that were expressed in stage-specific manner such as the glucocorticoid synthesis and transport genes, Cyp21a1 and Serpina6. In addition, there were nine Leydig cell transcripts that change their association with polysomes in correlation with the different stages of the spermatogenic cycle including Egr1. Interestingly, the signal intensity of EGR1 and CYP21 varied among Leydig cells in the adult asynchronous testis. However, testosterone levels across the different stages of germ cell development did not cycle. These data show, for the first time, that Leydig cell gene expression changes in a stage-specific manner during the cycle of the seminiferous epithelium and indicate that a heterogeneous Leydig cell population exists in the adult mouse testis.

Effects of spermatogenic cycle on Stem Leydig cell proliferation and differentiation

We reported previously that stem Leydig cells (SLC) on the surfaces of rat testicular seminiferous tubules are able to differentiate into Leydig cells. The proliferation and differentiation of SLCs seem likely to be regulated by niche cells, including nearby germ and Sertoli cells. Due to the cyclical nature of spermatogenesis, we hypothesized that the changes in the germ cell composition of the seminiferous tubules as spermatogenesis proceeds may affect tubule-associated SLC functions. To test this hypothesis, we compared the ability of SLCs associated with tubules at different stages of the cycle to differentiate into Leydig cells in vitro. SLCs associated with stages IX-XI were more active in proliferation and differentiation than SLCs associated with stages VII-VIII. However, when the SLCs were isolated from each of the two groups of tubules and cultured in vitro, no differences were seen in their ability to proliferate or differentiate. These results suggested that the stage-dependent local factors, not the SLCs themselves, explain the stage-dependent differences in SLC function. TGFB, produced in stage-specific fashion by Sertoli cells, is among the factors shown in previous studies to affect SLC function in vitro. When TGFB inhibitors were included in the cultures of stages IX-XI and VII-VIII tubules, stage-dependent differences in SLC development were reduced, suggesting that TGFB may be among the paracrine factors involved in the stage-dependent differences in SLC function. Taken together, the findings suggest that there is dynamic interaction between SLCs and germ/Sertoli cells within the seminiferous tubules that may affect SLC proliferation and differentiation.

Endocrine regulation of sperm release

Spermiation (sperm release) is the culmination of a spermatid’s journey in the seminiferous epithelium. After a long association with the Sertoli cell, spermatids have to finally ‘let go’ of the support from Sertoli cells in order to be transported to the epididymis. Spermiation is a multistep process characterised by removal of excess spermatid cytoplasm, recycling of junctional adhesion molecules by endocytosis, extensive cytoskeletal remodelling and final spermatid disengagement. Successful execution of all these events requires coordinated regulation by endocrine and paracrine factors. This review focuses on the endocrine regulation of spermiation. With the aim of delineating how hormones control the various aspects of spermiation, this review provides an analysis of recent advances in research on the hormonal control of molecules associated with the spermiation machinery. Because spermiation is one of the most sensitive phases of spermatogenesis to variations in hormone levels, understanding their molecular control is imperative to advance our knowledge of the nuances of spermatogenesis and male fertility.

Management of weight loss in obesity-associated male infertility: a spotlight on bariatric surgery

In recent years, there has been a paralleled increase between male obesity and infertility rates. Obesity is associated with impaired hypothalamic-pituitary-gonadal axis, aberrant semen parameters, and subfertility or infertility. Weight loss is strongly recommended for the management of obesity-associated infertility. Lifestyle modifications that include caloric restriction and increased physical activity have a short-lived impact. Bariatric surgery is a better and more durable weight loss alternative. Comprehensive information about the benefits of weight loss on obesity-associated male infertility following bariatric surgery is still emerging. In this review, we discuss the hormonal, physical and environmental mechanism contributing to obesity-associated infertility. We then assess weight loss approaches, which include lifestyle modification, medical and surgical approaches, that can improve fertility in obese men. This review focuses also on bariatric surgery for the management of obese men seeking fertility treatment. Anecdotal evidence suggesting that bariatric surgery can impair fertility is also discussed.

Male reproductive toxicity of CrVI: In-utero exposure to CrVI at the critical window of testis differentiation represses the expression of Sertoli cell tight junction proteins and hormone receptors in adult F1 progeny rats

The effect of gestational exposure to CrVI (occupational/environmental pollutant and target to Sertoli cells(SC)) was tested in a rat model during the testicular differentiation from the bipotential gonad may interrupt spermatogenesis by disrupting SC tight junctions(TJ) and it's proteins and hormone receptors. Pregnant Wistar rats were exposed to 50/100/200ppm CrVI through drinking water during embryonic days 9-14. On Postnatal day 120, testes were subjected to ion exchange chromatographic analysis and revealed increased level of CrIII in SCs and germ cells, serum and testicular interstitial fluid(TIF). Microscopic analyses showed seminiferous tubules atrophy and disruption of SC TJ, which also recorded decreased testosterone in TIF. mRNA and Protein expression analyses attested decreased level of Fshr, Ar, occludin and claudin-11 in SCs. Immunofluorescent detection revealed weak signal of TJ proteins. Taken together, we concluded that gestational exposure to CrVI interferes with the expression of SC TJ proteins due to attenuated expression of hormone receptors.

Gut Endotoxin Leading to a Decline IN Gonadal function (GELDING) - a novel theory for the development of late onset hypogonadism in obese men

Obesity is an increasing public health problem, with two-thirds of the adult population in many Western countries now being either overweight or obese. Male obesity is associated with late onset hypogonadism, a condition characterised by decreased serum testosterone, sperm quality plus diminished fertility and quality of life. In this paper we propose a novel theory underlying the development of obesity related hypogonadism- the GELDING theory (Gut Endotoxin Leading to a Decline IN Gonadal function). Several observational studies have previously reported an association between obesity related hypogonadism (low testosterone) and systemic inflammation. However, for the first time we postulate that the trans-mucosal passage of bacterial lipopolysaccharide (LPS) from the gut lumen into the circulation is a key inflammatory trigger underlying male hypogonadism. Obesity and a high fat/high calorie diet are both reported to result in changes to gut bacteria and intestinal wall permeability, leading to the passage of bacterial endotoxin (lipopolysaccharide- LPS) from within the gut lumen into the circulation (metabolic endotoxaemia), where it initiates systemic inflammation. Endotoxin is known to reduce testosterone production by the testis, both by direct inhibition of Leydig cell steroidogenic pathways and indirectly by reducing pituitary LH drive, thereby also leading to a decline in sperm production. In this paper we also highlight the novel evolutionary benefits of the GELDING theory. Testosterone is known to be a powerful immune-suppressive, decreasing a man's ability to fight infection. Therefore we postulate that the male reproductive axis has evolved the capacity to lower testosterone production during times of infection and resulting endotoxin exposure, decreasing the immunosuppressive influence of testosterone, in turn enhancing the ability to fight infection. While this response is adaptive in times of sepsis, it becomes maladaptive in the setting of "non-infectious" obesity related metabolic endotoxaemia.

Responsiveness of prepubertal crossbred bull calves to exogenous GnRH and its impact on reproductive hormones under tropical conditions

This study investigated the age related variations in luteinizing hormone (LH), androstenedione, testosterone, and total estrogens response to exogenous gonadotropin-releasing hormone (GnRH) in Holstein-Friesian (HF) × Tharparkar bull calves. Fifteen bull calves were selected and, based on their age, were divided into Group I (14-16 months, n = 5), Group II (9-12 months, n = 5), and Group III (6-8 months, n = 5). All bull calves were administered with 10 µg of GnRH intramuscularly. Blood samples were collected at an interval of 30 min commencing 1 h prior to GnRH treatment until 4 h post-GnRH treatment and thereafter, at an interval of 1 h for the next 3 h. Endocrine response in terms of pretreatment values, peak values, area under curve, and time taken to attain peak values for LH, androstenedione, testosterone, and total estrogens was evaluated in all the bull calves. Significant differences were observed in pretreatment values, peak concentrations, and area under curve for androstenedione and testosterone between the groups; with response being higher in Group I bull calves. The results indicated that the HF × Tharparkar bull calves of 14 months age and above respond to exogenous GnRH by secreting significant amounts of testosterone.

Male obesity and subfertility, is it really about increased adiposity?

The prevalence of overweight and obesity in reproductive-aged men is increasing worldwide, with >70% of men >18 years classified as overweight or obese in some western nations. Male obesity is associated with male subfertility, impairing sex hormones, reducing sperm counts, increasing oxidative sperm DNA damage and changing the epigenetic status of sperm. These changes to sperm function as a result of obesity, are further associated with impaired embryo development, reduced live birth rates and increased miscarriage rates in humans. Animal models have suggested that these adverse reproductive effects can be transmitted to the offspring; suggesting that men's health at conception may affect the health of their children. In addition to higher adiposity, male obesity is associated with comorbidities, including metabolic syndrome, hypercholesterolemia, hyperleptinemia and a pro-inflammatory state, all which have independently been linked with male subfertility. Taken together, these findings suggest that the effects of male obesity on fertility are likely multifactorial, with associated comorbidities also influencing sperm, pregnancy and subsequent child health.

Mouse Spermatogenesis Requires Classical and Nonclassical Testosterone Signaling

Testosterone acts though the androgen receptor in Sertoli cells to support germ cell development (spermatogenesis) and male fertility, but the molecular and cellular mechanisms by which testosterone acts are not well understood. Previously, we found that in addition to acting through androgen receptor to directly regulate gene expression (classical testosterone signaling pathway), testosterone acts through a nonclassical pathway via the androgen receptor to rapidly activate kinases that are known to regulate spermatogenesis. In this study, we provide the first evidence that nonclassical testosterone signaling occurs in vivo as the MAP kinase cascade is rapidly activated in Sertoli cells within the testis by increasing testosterone levels in the rat. We find that either classical or nonclassical signaling regulates testosterone-mediated Rhox5 gene expression in Sertoli cells within testis explants. The selective activation of classical or nonclassical signaling pathways in Sertoli cells within testis explants also resulted in the differential activation of the Zbtb16 and c-Kit genes in adjacent spermatogonia germ cells. Delivery of an inhibitor of either pathway to Sertoli cells of mouse testes disrupted the blood-testis barrier that is essential for spermatogenesis. Furthermore, an inhibitor of nonclassical testosterone signaling blocked meiosis in pubertal mice and caused the loss of meiotic and postmeiotic germ cells in adult mouse testes. An inhibitor of the classical pathway caused the premature release of immature germ cells. Collectively, these observations indicate that classical and nonclassical testosterone signaling regulate overlapping and distinct functions that are required for the maintenance of spermatogenesis and male fertility.

Cell-specific ablation in the testis: what have we learned?

Testicular development and function is the culmination of a complex process of autocrine, paracrine and endocrine interactions between multiple cell types. Dissecting this has classically involved the use of systemic treatments to perturb endocrine function, or more recently, transgenic models to knockout individual genes. However, targeting genes one at a time does not capture the more wide‐ranging role of each cell type in its entirety. An often overlooked, but extremely powerful approach to elucidate cellular function is the use of cell ablation strategies, specifically removing one cellular population and examining the resultant impacts on development and function. Cell ablation studies reveal a more holistic overview of cell–cell interactions. This not only identifies important roles for the ablated cell type, which warrant further downstream study, but also, and importantly, reveals functions within the tissue that occur completely independently of the ablated cell type. To date, cell ablation studies in the testis have specifically removed germ cells, Leydig cells, macrophages and recently Sertoli cells. These studies have provided great leaps in understanding not possible via other approaches; as such, cell ablation represents an essential component in the researchers’ tool‐kit, and should be viewed as a complement to the more mainstream approaches to advancing our understanding of testis biology. In this review, we summarise the cell ablation models used in the testis, and discuss what each of these have taught us about testis development and function.

Mechanisms linking obesity to male infertility

INTRODUCTION

Obesity in men is associated with infertility in numerous studies. The current trend for decline in semen parameters parallels the increasing prevalence of obesity worldwide. In addition to impaired semen quality, fertility among obese men may be affected by sexual dysfunction, endocrinopathy, aromatization activity, psychological and thermal effects, sleep apnea, leptin and minor toxins, and possibly the inflammatory and obstructive elements of epididymitis pathology. The variable degrees of certainty associated with these causes parallel the levels of supporting evidence. This search aims to shed lights on different conditions that obese men suffer from; as that makes the treatment of infertility more categorized.

MATERIAL AND METHODS

A PubMed search was conducted to identify clinical and pathological mechanisms linking obesity to male infertility.

RESULTS

Among the myriad of publications reviewed in this paper, impaired spermatogenesis and sexual dysfunction have been shown to drive other variables towards poor fertility potentials. The paper presented a new, detailed flow chart showing more factors and further interactions among conditions leading to infertility.

CONCLUSIONS

The prime hormonal defect in obese men is hypotestosteronaemia, which results in impaired spermatogenesis leading to poor fecundability. Studies have shown that most mechanisms accounting for reduced fertility potentials in overweight men are reversible.

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.

Obesogenic environment by excess of dietary fats in different phases of development reduces spermatic efficiency of wistar rats at adulthood: correlations with metabolic status

This study compares the impact of obesogenic environment (OE) in six different periods of development on sperm parameters and the testicular structure of adult rats and their correlations with sex steroid and metabolic scenario. Wistar rats were exposed to OE during gestation (O1), during gestation/lactation (O2), from weaning to adulthood (O3), from lactation to adulthood (O4), from gestation to sexual maturity (O5), and after sexual maturation (O6). OE was induced by a 20% fat diet, and control groups were fed a balanced diet (4% fat). Serum leptin levels and adiposity index indicate that all groups were obese, except for O1. Three progressive levels of impaired metabolic status were observed: O1 presented insulin resistance, O2 were insulin resistant and obese, and groups O3, O4, and O5 were insulin resistant, obese, and diabetic. These three levels of metabolic damage were proportional to the increase of leptin and decreased circulating testosterone. The impairment in the daily sperm production (DSP) paralleled these three levels of metabolic and hormonal damage being marginal in O1, increasing in O2, and being higher in groups O3, O4, O5, and O6. None of the OE periods affected the sperm transit time in the epididymis, and the lower sperm reserves were caused mainly by impaired DSP. In conclusion, OE during sexual maturation markedly reduces the DSP at adulthood in the rat. A severe reduction in the DSP also occurs in OE exposure during gestation/lactation but not in gestation, indicating that breast-feeding is a critical period for spermatogenic impairment under obesogenic conditions.

The death of sertoli cells and the capacity to phagocytize elongated spermatids during testicular regression due to short photoperiod in Syrian hamster (Mesocricetus auratus)

In the Syrian hamster (Mesocricetus auratus), an animal that displays testicular regression due to short photoperiod, germ cells are removed by apoptosis during this process and the apoptotic remains are phagocytized by Sertoli cells. The aim of this work was to investigate morphologically whether the testicular regression process due to short photoperiod leads to the apoptosis of Sertoli cells, and whether, during testicular regression, the elongated spermatids are eliminated through phagocytosis by Sertoli cells. To this end, we studied testis sections during testicular regression in Syrian hamster subjected to short photoperiod by means of several morphological techniques using conventional light microscopy (hematoxylin and eosin [H&E], semi-thin section vimentin, immunohistochemistry, SBA lectin, and TUNEL staining), fluorescence microscopy, and transmission electron microscopy (TEM). H&E and semi-thin sections identified Sertoli cells with a degenerated morphology. Greater portion of Sertoli cells that were positive for TUNEL staining were observed especially during the mild regression (MR) and strong regression (SR) phases. In addition, TEM identified the characteristic apoptotic changes in the nucleus and cytoplasm of Sertoli cells. Moreover, during testicular regression and using light microscopy, some elongated spermatids were seen in basal position next to the Sertoli cell nucleus. This Sertoli phagocytic activity was higher in MR and SR phases. TEM confirmed this to be the result of the phagocytic activity of Sertoli cells. In conclusion, during testicular regression in Syrian hamster due to short photoperiod, when germ cells are known to be lost through apoptosis, there is morphological evidences that Sertoli cells are also lost through apoptosis, while some elongated spermatids are phagocytized and eliminated by the Sertoli cells.

The regulation of spermatogenesis by androgens

Testosterone is essential for maintaining spermatogenesis and male fertility. However, the molecular mechanisms by which testosterone acts have not begun to be revealed until recently. With the advances obtained from the use of transgenic mice lacking or overexpressing the androgen receptor, the cell specific targets of testosterone action as well as the genes and signaling pathways that are regulated by testosterone are being identified. In this review, the critical steps of spermatogenesis that are regulated by testosterone are discussed as well as the intracellular signaling pathways by which testosterone acts. We also review the functional information that has been obtained from the knock out of the androgen receptor from specific cell types in the testis and the genes found to be regulated after altering testosterone levels or androgen receptor expression.

Proliferative and nonproliferative lesions of the rat and mouse male reproductive system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and differential diagnosis for classifying microscopic lesions observed in the male reproductive system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the Internet (http://goreni.org). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions of the male reproductive system in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Impact of obesity on male fertility, sperm function and molecular composition

Male obesity in reproductive-age men has nearly tripled in the past 30 y and coincides with an increase in male infertility worldwide. There is now emerging evidence that male obesity impacts negatively on male reproductive potential not only reducing sperm quality, but in particular altering the physical and molecular structure of germ cells in the testes and ultimately mature sperm. Recent data has shown that male obesity also impairs offspring metabolic and reproductive health suggesting that paternal health cues are transmitted to the next generation with the mediator mostly likely occurring via the sperm. Interestingly the molecular profile of germ cells in the testes and sperm from obese males is altered with changes to epigenetic modifiers. The increasing prevalence of male obesity calls for better public health awareness at the time of conception, with a better understanding of the molecular mechanism involved during spermatogenesis required along with the potential of interventions in reversing these deleterious effects. This review will focus on how male obesity affects fertility and sperm quality with a focus on proposed mechanisms and the potential reversibility of these adverse effects.

Assessment of circulating hormones in regulatory toxicity studies II. Male reproductive hormones

When test article-related testicular toxicity or Leydig cell tumors are identified in nonclinical studies, the measurement of circulating hormones such as luteinizing hormone, follicle-stimulating hormone, inhibin, testosterone, or prolactin is often considered in order to aid mechanistic investigations or to identify potential biomarkers in man. Although some hormone levels are relatively constant, others are subject to wide variability owing to pulsatility of secretion, diurnal rhythms, and stress. To avoid being misled, it is important that this variation is factored into any study design that includes hormone measurements. Since all these possibilities start from the pathologist's reading of the tissue sections, we begin with a review of the morphologic changes that are tied to underlying alterations in hormones. We then provide the reader with basic information and representative hormone data, including coefficients of variation, for the major male reproductive hormones in the three main nonclinical species (rats, dogs, and cynomolgus monkeys). Power and probability tables for rats and dogs allow estimates of the number of animals or samples needed to provide a given likelihood of detecting a hormonal change of a given size. More importantly, we highlight the variability of this process and the real value in readers developing this information at their own site.

The development of an inducible androgen receptor knockout model in mouse to study the postmeiotic effects of androgens on germ cell development

A mouse model with a Sertoli cell (SC)-selective ablation of the androgen receptor (AR)-the SCARKO mouse-demonstrated that the effects of androgens on spermatogenesis depend on the presence of an active AR in SC. This model has been extremely valuable in the study of the effects of androgens on the initiation of spermatogenesis. However, due to the early (prenatal) inactivation of the AR SCARKO mice develop a complete block in meiosis, making it impossible to study the effects of androgens on postmeiotic steps of germ cell development. It would therefore be of interest to develop a model in which the AR can be ablated at any chosen time point. Here we used a mouse line ubiquitously expressing a tamoxifen (TM)-inducible Cre recombinase to develop an inducible AR knockout model (iARKO). It is shown that treatment with TM (3 mg/day) for five consecutive days efficiently inactivates the AR in testicular tissue and decreases the expression of known AR-target genes in SC (Rhox5, Spinlw1) without markedly affecting testicular cell composition one day after the final injection. TM treatment did, however, decrease serum gonadotropin levels and the expression of several Leydig cell genes (StAR, Cyp17a1, Insl3), resulting in decreased testosterone levels. Nevertheless, the intratesticular testosterone concentration still far exceeds the estimated concentrations required to saturate the AR. It may be concluded that the study of androgen-responsive postmeiotic genes in SC may be feasible using a TM-inducible AR knockout model provided that appropriate controls are included correcting for off-target effects of TM.

Clinical evaluation of non-surgical sterilization of male cats with single intra-testicular injection of calcium chloride

Background

Calcium chloride solution is an established injectable sterilant in dogs and other mammals. With cat populations a continuing problem, we sought to explore its first use in cats. Six cats per group were injected with 5%, 10% or 20% calcium chloride dihydrate in saline solution with lignocaine hydrochloride, a local anaesthetic.

Results

At the 60^th day post-injection, cat testes were collected and showed complete testicular necrosis and replacement by fibrous tissue; very low sperm counts; and reduction of serum testosterone by at least 70% in 20% dose. Androgenic enzyme activities and their expressions were also reduced in all the treated groups along with intra-testicular testosterone concentration was also low. Increased testicular lipid peroxidation, with reduced antioxidants and mitochondrial membrane potential, were evident following calcium chloride treatments. However, there were no apparent changes in serum concentrations of cortisol, fasting blood sugar level, blood urea nitrogen, packed cell volume, or total serum protein following calcium chloride injection, suggesting that this method of sterilization is not associated with any general stress response.

Conclusion

Calcium chloride solution demonstrates potential for androgenesis-eliminating nonsurgical sterilization of male cats in addition to its proven efficacy in dogs and other mammals.

Regulation of Sertoli-germ cell adhesion and sperm release by FSH and nonclassical testosterone signaling

Testosterone and FSH act in synergy to produce the factors required to maximize the production of spermatozoa and male fertility. However, the molecular mechanisms by which these hormones support spermatogenesis are not well established. Recently, we identified a nonclassical mechanism of testosterone signaling in cultured rat Sertoli cells. We found that testosterone binding to the androgen receptor recruits and activates Src tyrosine kinase. Src then causes the activation of the epidermal growth factor receptor, which results in the phosphorylation and activation of the ERK MAPK and the cAMP response element-binding protein transcription factor. In this report, we find that FSH inhibits testosterone-mediated activation of ERK and the MAPK pathway in Sertoli cells via the protein kinase A-mediated inhibition of Raf kinase. In addition, FSH, as well as inhibitors of Src and ERK kinase activity, reduced germ cell attachment to Sertoli cells in culture. Using pathway-specific androgen receptor mutants we found that the nonclassical pathway is required for testosterone-mediated increases in germ cell attachment to Sertoli cells. Studies of seminiferous tubule explants determined that Src kinase, but not ERK kinase, activity is required for the release of sperm from seminiferous tubule explants. These findings suggest the nonclassical testosterone-signaling pathway acts via Src and ERK kinases to facilitate the adhesion of immature germ cells to Sertoli cells and through Src to permit the release of mature spermatozoa. In contrast, FSH acts to limit testosterone-mediated ERK kinase activity and germ cell attachment.

Androgens and spermatogenesis: lessons from transgenic mouse models

Transgenic mouse models have contributed considerably to our understanding of the cellular and molecular mechanisms by which androgens control spermatogenesis. Cell-selective ablation of the androgen receptor (AR) in Sertoli cells (SC) results in a complete block in meiosis and unambiguously identifies the SC as the main cellular mediator of the effects of androgens on spermatogenesis. This conclusion is corroborated by similar knockouts in other potential testicular target cells. Mutations resulting in diminished expression of the AR or in alleles with increased length of the CAG repeat mimick specific human forms of disturbed fertility that are not accompanied by defects in male sexual development. Transcriptional profiling studies in mice with cell-selective and general knockouts of the AR, searching for androgen-regulated genes relevant to the control of spermatogenesis, have identified many candidate target genes. However, with the exception of Rhox5, the identified subsets of genes show little overlap. Genes related to tubular restructuring, cell junction dynamics, the cytoskeleton, solute transportation and vitamin A metabolism are prominently present. Further research will be needed to decide which of these genes are physiologically relevant and to identify genes that can be used as diagnostic tools or targets to modulate the effects of androgens in spermatogenesis.

Non-classical actions of testosterone and spermatogenesis

Testosterone is essential to maintain spermatogenesis and male fertility. In the absence of testosterone stimulation, spermatogenesis does not proceed beyond the meiosis stage. After withdrawal of testosterone, germ cells that have progressed beyond meiosis detach from supporting Sertoli cells and die, whereas mature sperm cannot be released from Sertoli cells resulting in infertility. The classical mechanism of testosterone action in which testosterone activates gene transcription by causing the androgen receptor to translocate to and bind specific DNA regulatory elements does not appear to fully explain testosterone regulation of spermatogenesis. This review discusses two non-classical testosterone signalling pathways in Sertoli cells and their potential effects on spermatogenesis. Specifically, testosterone-mediated activation of phospholipase C and calcium influx into Sertoli cells is described. Also, testosterone activation of Src, EGF receptor and ERK kinases as well as the activation of the CREB transcription factor and CREB-mediated transcription is reviewed. Regulation of germ cell adhesion to Sertoli cells and release of mature sperm from Sertoli cells by kinases regulated by the non-classical testosterone pathway is discussed. The evidence accumulated suggests that classical and non-classical testosterone signalling contribute to the maintenance of spermatogenesis and male fertility.

Male infertility and the androgen receptor: molecular, clinical and therapeutic aspects

Idiopathic male infertility has previously been diagnosed imprecisely, and has been treated using regimes that are not based on a clear understanding of the underlying pathophysiology; however, this is gradually changing, and a more rational approach is being adopted. Testosterone and its metabolite, DHT, is allimportant for the maintenance of sperm production and this has led us to examine the AR for causes of male infertility. Some, but not all, androgen-binding studies have indicated that in a certain proportion of cases of male infertility, defective androgen binding occurs. The cloning of the AR gene allowed for a more rigorous examination of the molecular pathogenesis which turned out to be both subtle and heterogeneous. Genetic screening of a large group of men with defective spermatogenesis has indicated that up to 30% of infertile males could have variations in the androgenicity of their AR caused by polymorphisms in the length of the polyglutamine tract. Substitutions of the AR in the LBD and the DBD can also lead to reduced AR function and male infertility. In this regard, it is interesting to note that depressed spermatogenesis and prostate cancer represent opposite ends of the spectrum of AR action (Figure 6). Although empirical treatment of AR mutants in some cases has been shown to restore normal AR function and to improve spermatogenesis, a fully rational basis of treatment has to be based on an understanding of the crystallographic structure of the AR LBD. A full understanding could lead to the construction and the administration of ‘designer’ androgen analogues to treat male infertility caused by mutations of the AR gene.

Short-term antiandrogen flutamide treatment causes structural alterations in somatic cells associated with premature detachment of spermatids in the testis of pubertal and adult guinea pigs

In spite of widespread application of flutamide in the endocrine therapies of young and adult patients, the side effects of this antiandrogen on spermatogenesis and germ-cell morphology remain unclear. This study evaluates the short-term androgen blockage effect induced by the administration of flutamide to the testes of pubertal (30-day old) and adult (65- and 135-day old) guinea pigs, with an emphasis on ultrastructural alterations of main cell types. The testes removed after 10 days of treatment with either a non-steroidal antiandrogen, flutamide (10 mg/kg of body weight) or a pharmacological vehicle alone were processed for histological, quantitative and ultrastructural analysis. In pubertal animals, flutamide androgenic blockage induces spermatogonial differentiation and accelerates testes maturation, causing degeneration and detachment of primary spermatocytes and round spermatids, which are subsequently found in great quantities in the epididymis caput. In post-pubertal and adult guinea pigs, in addition to causing germ-cell degeneration, especially in primary spermatocytes, and leading to the premature detachment of spherical spermatids, the antiandrogen treatment increased the relative volume of Leydig cells. In addition, ultrastructural evaluation indicated that irrespective of age antiandrogen treatment causes an increase in frequency of organelles involved with steroid hormone synthesis in the Leydig cells and a dramatic accumulation of myelin figures in their cytoplasm and, to a larger degree, in Sertoli cells. In conclusion, the transient exposition of the guinea pigs to flutamide, at all postnatal ages causes some degenerative lesions including severe premature detachment of spermatids and accumulation of myelin bodies in Leydig and Sertoli cells, compromising, at least temporarily, the spermatogenesis.