Increased testicular Sertoli cell population induced by an estrogen receptor antagonist

Gene Expression in Porcine Bulbourethral Glands

The porcine bulbourethral glands produce a gel-type secretion. Although the role of these contributions to reproductive success remains murky, the bulbourethral glands are major accessory sex glands in this species. Isometric growth in the early neonatal interval is followed by allometric growth in the late juvenile interval (6 to 11 weeks of age), while circulating endogenous steroids are low. The rate of allometric growth increases during the peripuberal interval (16 to 20 weeks of age) when systemic testosterone is relatively high. Gene expression for androgen receptor (AR) and for the steroid 5 alpha-reductase 2 (SRD5A2) enzyme that synthesizes the more potent androgen dihydrotestosterone from its precursor was evaluated by qPCR analyses of bulbourethral gland tissue. Tissues were collected from control boars (2 weeks to 40 weeks of age) and from littermates of these boars treated with letrozole to suppress endogenous estrogen synthesis. Gene expression for these two key proteins in androgen signaling was quite low during the initial allometric growth in the late juvenile and prepuberal intervals, suggesting that this initial growth was not primarily stimulated by androgens. These observations are consistent with a more direct estrogen-mediated inhibition of growth via GPER previously proposed, with the sensitivity extending into the late juvenile interval when estrogens as well as androgens are normally relatively low.

Development of Porcine Accessory Sex Glands

Accessory sex glands are recognized as targets of human disease and may have roles in reproductive success in livestock. The current experiments evaluated the influences of endogenous steroids on the development of porcine accessory sex glands, primarily in the neonatal period. When the aromatase inhibitor, letrozole, was used to inhibit the production of endogenous estrogens in the postnatal interval, growth of the seminal vesicles, prostate, and bulbourethral glands was stimulated. The weights of seminal vesicles, prostate, and bulbourethral glands approximately doubled at 6.5 weeks of age when the reduction in endogenous estrogens began at 1 week of age (p < 0.01). However, by 20 and 40 weeks of age, the weights of accessory sex glands were similar between the letrozole-treated boars and the vehicle-treated littermates indicating the growth stimulation was a transient effect when the treatment interval was short. The presence of both classical nuclear estrogen receptors and the G protein-coupled estrogen receptor in neonatal accessory sex glands indicated multiple signaling pathways might mediate the growth inhibition by endogenous estrogens. The absence of a detectable response when the classical estrogen receptors were blocked with fulvestrant (or when the androgen receptor was blocked with flutamide) suggests that endogenous estrogens act through the G protein-coupled estrogen receptor to inhibit the development of accessory sex glands during this neonatal to early juvenile interval.

Macrophages in juvenile pig testis: Link with increase in Sertoli cells induced by oestradiol suppression

Macrophage presence and location were evaluated in juvenile boar testes at the end of the first wave of Sertoli cell proliferation. Macrophage presence was compared in littermate boars treated with letrozole, a treatment which extended this first wave of proliferation beyond the sampling timepoint. Macrophages were identified as the CD68 positive cells following immunohistochemical labelling of paraffin sections and parenchymal macrophages enumerated. Macrophages present in a layer beneath the tunica albuginea received a score based on density and thickness of this layer. Density within the testicular parenchyma was highly variable in vehicle-treated boars (>100-fold) and did not differ from that observed in the letrozole-treated littermates. However, the macrophage layer beneath the tunica albuginea was denser and thicker in the letrozole-treated animals than in their vehicle-treated littermates. This suggests that macrophages might be involved in the letrozole-induced prolongation of Sertoli cell proliferation.

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

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

Expression of CSF1, AR, and SRD5A2 during Postnatal Development of the Boar Reproductive Tract

Simple Summary

Understanding the initial development of the male reproductive system, including the prostate, should provide insight into malfunctions in the adult male. Although changes in circulating androgens during development are characterized in multiple species, potential changes in the androgen receptor, in the enzyme that converts testosterone to the presumably more potent dihydrotestosterone, and in colony stimulating factor 1, a critical mediator of macrophage influence on organ development, were previously unknown and anticipated to be influenced by androgens and estrogens. Gene expression in the testis, prostate, and seminal vesicles of these three mediators of development, including responses to reduced testosterone or estrogens, were evaluated. Each of these three genes had a unique temporal pattern of expression during postnatal reproductive tract development. However, surprisingly minimal effects of altered steroid signaling were reported on the expression of these presumed pivotal genes.

Abstract

The male reproductive system develops from a minimally functioning gonad and nonfunctioning accessory sex glands in the neonate; sex steroids, presumed to be primary influencers of these changes, have been characterized in multiple species. This study focused on the expression of the androgen receptor as the principal mediator of androgen-induced signaling; the 5α reductase enzyme that converts testosterone to the more active dihydrotestosterone; and colony stimulating factor 1, a mediator of macrophage influence on organ development in the pig. The time points chosen to evaluate normal developmental changes during the juvenile and prepubertal intervals included the inflection time points of 6.5 weeks of age at the nadir of circulating estradiol and testosterone concentrations in juveniles, and 11 weeks of age, when these concentrations begin to increase. The role of sex steroid signaling in the regulation of gene expression was evaluated by the blockade of androgen and estrogen receptors and reduction in endogenous estrogens. Expression of colony stimulating factor 1 in the testes gradually decreased during development; developmental profiles in the prostate and seminal vesicles were clearly different. Interference with sex steroid signaling had no effect on the expression of these three genes in testicular tissue and minimal and transient effects in prostate and seminal vesicles.

Multifaceted epigenetic regulation of porcine testicular aromatase

Testicular aromatase catalyzes the synthesis of estradiol, which contributes to regulation of porcine Sertoli cell proliferation and postpubertal maintenance of Sertoli cell numbers. Although aromatase enzymatic activity decreases with age and is persistently reprogrammed by prepubertal treatment with the aromatase inhibitor letrozole, the molecular bases for regulation have not been identified. DNA methylation was examined as a potential regulatory mechanism using DNA from Leydig cells isolated from 16-, 40-, and 68-week-old boars and from 68- week-old littermates treated with the aromatase inhibitor, letrozole. Methylation levels of individual CpG dinucleotides located in the distal untranslated exon 1 of the relevant aromatase encoding gene, CYP19A3, were quite high in Leydig cell DNA, and increased further with maturity of boar (P < 0.05), while aromatase activity and transcript abundance decreased more than two-fold. However, reduced aromatase activity following letrozole treatment was not accompanied by altered DNA methylation. Testicular expression of miR378 was altered by prepubertal treatment with letrozole. The data provide evidence for two different epigenetic mechanisms that regulate aromatase expression and enzymatic activity in the boar testis.

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

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

Effects of letrozole administration on growth and reproductive performance in Markhoz goat bucklings

This study evaluated the growth performance, testicular and semen characteristics, and hormonal profile of Markhoz (Iranian Angora) bucklings injected with letrozole (LTZ). Twenty-eight 4-4.5 month old bucks were randomly assigned into four groups and received either 0.25 mg/kg body weight (BW) LTZ subcutaneously (sc LTZ) or intramuscularly (im LTZ), and also sc (sc CONT) or im (im CONT) controls every week for 3 months. The study was performed at the beginning of the breeding season in Sanandaj Animal Husbandry Research Station (46.99 °E, 35.31 °N). The results showed that LTZ causes increased final body weight (25.78 ± 1.61 kg), higher average daily gain (104 ± 0.03 g/days), and decreased feed conversion ratio (7.81 ± 2.57) (P < 0.05). The pre-slaughter, hot, and cold carcass weights (27.56 ± 2.40, 11.45 ± 1.07 and 11.11 ± 1.05 kg, respectively) were (P < 0.05) heavier in LTZ groups while other carcass characteristics did not differ between groups. No differences occurred between the groups in biochemical parameters, except high-density lipoprotein levels (35.47 ± 2.43 mg/dL) which was higher in LTZ treatments (P < 0.05). LTZ-treated bucks had larger scrotal circumference (20.12 ± 5.75 cm), higher relative testicular weight (560.91 ± 78.59 mg/100 g BW) and volume (175.5 ± 29.71 cm³), greater diameter of seminiferous tubules (224.5 ± 5.21 μm), and number of Sertoli cells (8.39 ± 0.77) (P < 0.05). Semen volume (0.74 ± 0.16 mL), sperm concentration (2.64 ± 0.19 × 10^-9/mL), total sperm per ejaculate (1.95 ± 0.49 × 10^-9), and semen index (1248 ± 323) increased (P < 0.05) by LTZ treatments, while semen pH (6.77), motility (80.91%), progressive motility (76.75%), viability (83.35%), abnormality (13.70%), acrosome integrity (78.06%), and membrane integrity (80.05%) of sperm remained unaffected. Intratesticular and serum testosterone (T) levels (7.97 ± 0.89 ng/mg protein and 2.47 ± 0.59 ng/mL, respectively), serum luteinizing hormone (LH), growth hormone (GH) levels (1.71 ± 0.24 and 3.62 ± 0.33 ng/mL, respectively) of LTZ groups were elevated, whereas intratesticular and serum estradiol (E2) levels (84.14 ± 8.15 pg/mg protein and 32.33 ± 2.16 pg/mL, respectively) decreased (P < 0.05). No differences were recorded between the sc and im routes of LTZ administration in the measured parameters. To conclude, we have found that LTZ treatment improves growth and reproductive functions of goat bucklings associated with increased serum LH and GH, elevated T and reduced E2 levels in both serum and testis.

Serum estradiol levels in infertile men with non-obstructive azoospermia

PURPOSE

To report the different patterns of estradiol levels in infertile men with non-obstructive azoospermia and correlate these levels with their clinical and laboratory findings.

MATERIALS AND METHODS

A retrospective study was launched, and a retrieval of data for infertile men with non-obstructive azoospermia (n = 166) and fertile controls (n = 40) was performed. The retrieved data included demographics, clinical findings, scrotal duplex, semen analysis, and hormonal assay (testosterone, follicle-stimulating hormone, luteinizing hormone, prolactin, and estradiol).

RESULTS

Our findings showed a wide spectrum of estradiol concentrations. The patients were arranged into three groups (high, normal, and low estradiol groups). The normal estradiol group was the most prevalent (71.1%). Testosterone, gonadotrophins, testicular volumes, and the number of patients with jobs in polluted workplaces showed significant differences among the study groups (p = 0.001, <0.001, <0.001, and 0.004, respectively). Age, body mass index, varicocele prevalence, prolactin, and smoking habits did not show any significant differences among the groups. Obesity was lacking in the low estradiol group, but it had significantly higher prevalence in the normal (p = 0.013) or high group (p = 0.023) compared with the controls.

CONCLUSION

Serum estradiol, in infertile men with non-obstructive azoospermia, may be present at different levels. It is recommended that estradiol be measured in infertile men with non-obstructive azoospermia when there is an alteration in testosterone concentration, obesity, a polluted workplace occupation, or before trying hormonal therapy. Extended studies are highly recommended to provide a clear clue whether alterations in estradiol concentrations in men with non-obstructive azoospermia are the cause or a consequence of the condition.

Tissue steroid levels in response to reduced testicular estrogen synthesis in the male pig, Sus scrofa

Production of steroid hormones is complex and dependent upon steroidogenic enzymes, cofactors, receptors, and transporters expressed within a tissue. Collectively, these factors create an environment for tissue-specific steroid hormone profiles and potentially tissue-specific responses to drug administration. Our objective was to assess steroid production, including sulfated steroid metabolites in the boar testis, prostate, and liver following inhibition of aromatase, the enzyme that converts androgen precursors to estrogens. Boars were treated with the aromatase inhibitor, letrozole from 11 to 16 weeks of age and littermate boars received the canola oil vehicle. Steroid profiles were evaluated in testes, prostate, and livers of 16, 20, and 40 week old boars using liquid chromatography/mass spectrometry. Testis, prostate, and liver had unique steroid profiles in vehicle-treated animals. Only C18 steroid hormones were altered by treatment with the aromatase inhibitor, letrozole; no significant differences were detected in any of the C19 or C21 steroids evaluated. Testis was the only tissue with significantly decreased free estrogens following treatment with the aromatase inhibitor; estrone and estradiol concentrations were lower (p < 0.05) in testes from 16, 20, and 40 week letrozole-treated boars. However, concentrations of the sulfated conjugates, estrone-sulfate and estradiol-sulfate, were significantly decreased (p<0.05) in 16 and 20 week boar testes, prostates, and livers from letrozole-treated boars. Hence, the distribution of estrogens between the free and conjugated forms was altered in a tissue-specific manner following inhibition of aromatase. The results suggest sulfated testicular estrogens are important estrogen precursors for the prostate, potentially enabling peripheral target tissues to synthesize free estrogens in the male pig.

Molecular Mechanisms and Signaling Pathways Involved in Sertoli Cell Proliferation

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

SULFATION PATHWAYS: Formation and hydrolysis of sulfonated estrogens in the porcine testis and epididymis

Boars exhibit high concentrations of sulfonated estrogens (SE) mainly originating from the testicular-epididymal compartment. Intriguingly, in porcine Leydig cells, sulfonation of estrogens is colocalized with aromatase and steroid sulfatase (STS), indicating that de novo synthesis of unconjugated estrogens (UE), their sulfonation and hydrolysis of SE occur within the same cell type. So far in boars no plausible concept concerning the role of SE has been put forward. To obtain new information on SE formation and hydrolysis, the porcine testicular-epididymal compartment was screened for the expression of the estrogen-specific sulfotransferase SULT1E1 and STS applying real-time RT-qPCR, Western blot and immunohistochemistry. The epididymal head was identified as the major site of SULT1E1 expression, whereas in the testis, it was virtually undetectable. However, SE tissue concentrations are clearly consistent with the testis as the predominant site of estrogen sulfonation. Results from measurements of estrogen sulfotransferase activity indicate that in the epididymis, SULT1E1 is the relevant enzyme, whereas in the testis, estrogens are sulfonated by a different sulfotransferase with a considerably lower affinity. STS expression and activity was high in the testis (Leydig cells, rete testis epithelium) but also present throughout the epididymis. In the epididymis, SULT1E1 and STS were colocalized in the ductal epithelium, and there was evidence for their apocrine secretion into the ductal lumen. The results suggest that in porcine Leydig cells, SE may be produced as a reservoir to support the levels of bioactive UE via the sulfatase pathway during periods of low activity of the pulsatile testicular steroidogenesis.

The role of estradiol in male reproductive function

Traditionally, testosterone and estrogen have been considered to be male and female sex hormones, respectively. However, estradiol, the predominant form of estrogen, also plays a critical role in male sexual function. Estradiol in men is essential for modulating libido, erectile function, and spermatogenesis. Estrogen receptors, as well as aromatase, the enzyme that converts testosterone to estrogen, are abundant in brain, penis, and testis, organs important for sexual function. In the brain, estradiol synthesis is increased in areas related to sexual arousal. In addition, in the penis, estrogen receptors are found throughout the corpus cavernosum with high concentration around neurovascular bundles. Low testosterone and elevated estrogen increase the incidence of erectile dysfunction independently of one another. In the testes, spermatogenesis is modulated at every level by estrogen, starting with the hypothalamus-pituitary-gonadal axis, followed by the Leydig, Sertoli, and germ cells, and finishing with the ductal epithelium, epididymis, and mature sperm. Regulation of testicular cells by estradiol shows both an inhibitory and a stimulatory influence, indicating an intricate symphony of dose-dependent and temporally sensitive modulation. Our goal in this review is to elucidate the overall contribution of estradiol to male sexual function by looking at the hormone's effects on erectile function, spermatogenesis, and libido.

Steroid regulation of early postnatal development in the corpus epididymidis of pigs

Development of the epididymis including blood-epididymal barrier formation is not required until sperm reach the epididymis peripuberally. Regulation of this development in the early postnatal period is largely unknown. The current objectives were to evaluate potential roles of endogenous estrogen and androgen signaling during early development of the corpus epididymidis and to determine the timing of formation of the blood-epididymal barrier in the pig. Effects of endogenous steroids were evaluated using littermates treated with vehicle, an aromatase inhibitor (letrozole) to reduce endogenous estrogens, an estrogen receptor antagonist (fulvestrant) or an androgen receptor antagonist (flutamide). Phosphorylated histone 3 immunohistochemistry was used to identify proliferating epithelial cells. Lanthanum nitrate and electron microscopy were used to analyze formation of the blood barrier in the corpus epididymidis. Reducing endogenous estrogens increased the number of proliferating corpus epithelial cells at 6 and 6.5 weeks of age compared with vehicle-treated boars (P<0.01 and P<0.001 respectively). Blocking androgen receptors did not alter proliferation rate at 6.5 weeks of age. Although barrier formation was similar between 6 and 6.5 weeks of age in vehicle-treated animals, intercellular barriers increased in letrozole-treated littermates at 6.5 weeks of age. Fulvestrant treatment, which should mimic aromatase inhibition for regulation through ESR1 and ESR2 signaling but potentially stimulate endogenous estrogen signaling through the G protein-coupled estrogen receptor (GPER), had the opposite effect on aromatase inhibition. These responses in conjunction with the presence of GPER in the corpus epididymidis suggest early corpus epididymal development is regulated partially by GPER.

Development of apical blebbing in the boar epididymis

Microvesicles are of increasing interest in biology as part of normal function of numerous systems; from the immune system (T cell activation) to implantation of the embryo (invasion of the trophoblasts) and sperm maturation (protein transfer in the epididymis). Yet, the mechanisms involved in the appearance of apical blebbing from healthy cells as part of their normal function remain understudied. Microvesicles are produced via one of two pathways: exocytosis or apical blebbing also termed ectocytosis. This work quantifies the histological appearance of apical blebbing in the porcine epididymis during development and examines the role of endogenous estrogens in regulating this blebbing. Apical blebbing appears at puberty and increases in a linear manner into sexual maturity suggesting that this blebbing is a mature phenotype. Endogenous estrogen levels were reduced with an aromatase inhibitor but such a reduction did not affect apical blebbing in treated animals compared with their vehicle-treated littermates. Epididymal production of apical blebs is a secretion mechanism of functionally mature principal cells regulated by factors other than estradiol.

mTOR is involved in 17β-estradiol-induced, cultured immature boar Sertoli cell proliferation via regulating the expression of SKP2, CCND1, and CCNE1

Mammalian target of rapamycin (mTOR) is known to be involved in mammalian cell proliferation, while S-phase kinase-associated protein 2 (SKP2) plays a vital role in the cell cycle. Within the testis, estrogen also plays an important role in Sertoli cell proliferation, although it is not clear how. The present study asked if mTOR is involved in 17β-estradiol-dependent Sertoli cell proliferation. We specifically assessed if extracellular signal-regulated kinase 1/2 (ERK1/2) and/or phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) exert convergent effects toward the activation of mTOR signaling, and if this signaling regulates the expression of SKP2 through retinoblastoma (RB) and early mitotic inhibitor 1 (EMI1) protein and on CCNE1 and CCND1 mRNA levels. Treatment with 17β-estradiol for 15-90 min activated mTOR, with mTOR phosphorylation peaking after 30 min. U0126 (5 μM), a specific inhibitor of (MEK1/2), and 10-DEBC (2 μM), a selective inhibitor of AKT, both significantly reduced 17β-estradiol-induced phosphorylation of mTOR. Rapamycin suppressed 17β-estradiol-induced Sertoli cell proliferation, appearing to act by reducing the abundance of SKP2, CCND1, and CCNE1 mRNA as well as RB and EMI1 protein. These data indicated that 17β-estradiol enhances Sertoli cell proliferation via mTOR activation, which involves both ERK1/2 and PI3K/AKT signaling. Activated mTOR subsequently increases SKP2 mRNA and protein expression by enhancing the expression of CCND1 and CCNE1, and inhibits SKP2 protein degradation by increasing EMI1 abundance.

Disruption of estrogen receptor signaling and similar pathways in the efferent ductules and initial segment of the epididymis

Seminiferous tubular atrophy may involve indirectly the disruption of estrogen receptor-α (ESR1) function in efferent ductules of the testis. ESR1 helps to maintain fluid resorption by the ductal epithelium and the inhibition or stimulation of this activity in rodent species will lead to fluid accumulation in the lumen. If not resolved, the abnormal buildup of fluid in the head of the epididymis and efferent ductules becomes a serious problem for the testis, as it leads to an increase in testis weight, tubular dilation and seminiferous epithelial degeneration, as well as testicular atrophy. The same sequence of pathogenesis occurs if the efferent ductule lumen becomes occluded. This review provides an introduction to the role of estrogen in the male reproductive tract but focuses on the various overlapping mechanisms that could induce efferent ductule dysfunction and fluid backpressure histopathology. Although efferent ductules are difficult to find, their inclusion in routine histological evaluations is recommended, as morphological images of these delicate tubules may be essential for understanding the mechanism of testicular injury, especially if dilations are observed in the rete testis and/or seminiferous tubules.

Signature Lesion:

The rete testis and efferent ductules can appear dilated, as if the lumens were greatly expanded with excess fluid or the accumulation of sperm. Because the efferent ductules resorb most of the fluid arriving from the rete testis lumen, one of two mechanisms is likely to be involved: a) reduced fluid uptake, which has been caused by the disruption in estrogen receptor signaling or associated pathways; or b) an increased rate of fluid resorption, which results in luminal occlusion. Both mechanisms can lead to a temporary increase in testicular weight, tubular dilation and atrophy of the seminiferous tubules.

Reduced endogenous estrogen and hemicastration interact synergistically to increase porcine sertoli cell proliferation

Both reduced endogenous estrogen and hemicastration stimulate proliferation of porcine Sertoli cells. The objective of these experiments was to compare the temporal patterns of response to each stimulus with the response to the combined stimuli as indications of shared or separate mechanisms. Within a replicate, one littermate was treated weekly with canola oil vehicle and remained intact; a second littermate was treated weekly with vehicle, and one testis was removed at Day 8; a third littermate was treated weekly with the aromatase inhibitor letrozole to reduce endogenous estrogens and remained intact; and the fourth littermate was treated weekly with letrozole, and one testis was removed at Day 8. Four replicates were evaluated at 2 wk of age, five replicates evaluated at 6.5 wk of age, and five replicates were evaluated at 11 wk of age, with treatment ceasing at 6 wk of age. Numbers of Sertoli cells were determined following GATA4 labeling using the optical dissector method. Levels of estradiol, estrogen conjugates, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and inhibin were determined by radioimmunoassay. Hemicastration appeared to have a rapid effect on Sertoli cell proliferation, but letrozole treatment had no apparent effect on Sertoli cell numbers at 2 wk of age. Both letrozole treatment and hemicastration had stimulated Sertoli cell proliferation by 6.5 wk of age, although the magnitude of the hemicastration response was much greater. Letrozole appeared to have minimal interaction with hemicastration at this age. Letrozole and hemicastration together increased Sertoli cell numbers at 11 wk of age compared with either treatment alone. Estradiol and estrogen conjugates were dramatically reduced by aromatase inhibition as anticipated; treatment-induced changes in inhibin, LH, or FSH were minimal. Differences in timing of response and positive interaction at 11 wk of age suggest that hemicastration and letrozole stimulate proliferation of Sertoli cells by two initially different pathways.

Effects of n-butylparaben on steroidogenesis and spermatogenesis through changed E₂ levels in male rat offspring

Parabens are widely used as antibacterial agents, which are concerned recently in the relationship between the use of parabens and reproductive toxicity. So that reassessment of the risk of parabens is needed. In this study, one of parabens, n-butylparaben (n-BP) was orally administered to pregnant Wistar rats (0, 64, 160, 400 and 1000 mg/kg/day) from gestation day (GD) 7 through postnatal day (PND) 21. Reduced anogenital distance (AGD) and delayed preputial separation (PPS) were observed in the male offspring. The weights of the testes were significantly reduced at PND 21-90. The weights of the epididymides were significantly reduced at all monitoring points, except PND 35. Seminal vesicle weights were significantly reduced on PND 21. Serum testosterone (T) was significantly decreased, especially on PND 49. The levels of 17β-estradiol (E2) showed an increase at each of the tested points except on PND 180. Serum luteinising hormone (LH) and follicle-stimulating hormone (FSH) levels in the n-BP treated groups were lower on PND 21, 35 and 49 but elevated on PND 90 compared to control levels. n-BP reduced epididymal cauda sperm counts and daily sperm production in a dose-dependent manner; this difference was statistically significant at exposure groups of 400 and 1000 mg/kg/day. The present study strongly suggests that exposure to n-BP in utero and during lactation has adverse effects on the reproductive system in male offspring, with a no observed adverse effect level (NOAEL) of 160 mg/kg/day. To our knowledge, this is the first study that reports increased E2 levels of male rats following n-BP exposure; we suggest that E2 levels may be considered as biomarkers for some endocrine disrupting chemicals (EDCs).

Skatole metabolism in the pigs with reduced testicular oestrogen synthesis

The objectives of the study were to investigate the involvement of oestrogens in the regulation of skatole levels in pigs. In total, 44 intact male pigs, siblings from 10 litters, were included in the study. Pigs were orally treated weekly with either 0.1 mg letrozole/kg body weight to reduce endogenous oestrogens or the canola oil vehicle. Fat and liver samples were collected at slaughter at 16, 20 and 40 weeks of age. Skatole and androstenone levels in fat and activities of hepatic cytochrome P4501A1, CYP1A2, CYP2A19 and CYP2E1 were analysed. Letrozole treatment did not significantly change either the levels of skatole or activities of skatole-metabolising enzymes, suggesting that oestrogens are not responsible for gender-related differences in skatole concentrations in porcine tissues.

The prepubertal testis: biomarkers and functions

PURPOSE OF REVIEW

Biomarkers of prepubertal testicular function have become widely available only in recent years. The aim of this review is to update the knowledge on key biomarkers used to assess hypogonadism in boys.

RECENT FINDINGS

Sertoli cells are the most representative cells of the prepubertal testis. Anti-Müllerian hormone and inhibin B are essential biomarkers of Sertoli cell function. Also, INSL3 arises as an additional marker of Leydig cell dysfunction.

SUMMARY

The widespread use of these biomarkers has enhanced our knowledge on the pathophysiology and diagnosis of prepubertal male hypogonadism. Beyond their well known germ-cell toxicity, oncologic treatments may also affect Sertoli cell function. Pathophysiology is not the same in all aneuploidies leading to infertility: while hypogonadism is not evident until mid-puberty in Klinefelter syndrome, it is established in early infancy in Down syndrome. In Noonan syndrome, the occurrence of primary hypogonadism depends on the existence of cryptorchidism, and Prader-Willi syndrome may present with either primary or combined forms of hypogonadism. Prepubertal testicular markers have also provided insights into the effects of environmental disruptors on gonadal function from early life, and helped dissipate concerns about testicular function in boys born preterm or small for gestational age or conceived by assisted reproductive technique procedures.