Adrenocorticotropic hormone directly stimulates testosterone production by the fetal and neonatal mouse testis

Fetal Leydig cells: What we know and what we don't

During male fetal development, testosterone plays an essential role in the differentiation and maturation of the male reproductive system. Deficient fetal testosterone production can result in variations of sex differentiation that may cause infertility and even increased tumor incidence later in life. Fetal Leydig cells in the fetal testis are the major androgen source in mammals. Although fetal and adult Leydig cells are similar in their functions, they are two distinct cell types, and therefore, the knowledge of adult Leydig cells cannot be directly applied to understanding fetal Leydig cells. This review summarizes our current knowledge of fetal Leydig cells regarding their cell biology, developmental biology, and androgen production regulation in rodents and human. Fetal Leydig cells are present in basement membrane-enclosed clusters in between testis cords. They originate from the mesonephros mesenchyme and the coelomic epithelium and start to differentiate upon receiving a Desert Hedgehog signal from Sertoli cells or being released from a NOTCH signal from endothelial cells. Mature fetal Leydig cells produce androgens. Human fetal Leydig cell steroidogenesis is LHCGR (Luteinizing Hormone Chronic Gonadotropin Receptor) dependent, while rodents are not, although other Gαs -protein coupled receptors might be involved in rodent steroidogenesis regulation. Fetal steroidogenesis ceases after sex differentiation is completed, and some fetal Leydig cells dedifferentiate to serve as stem cells for adult testicular cell types. Significant gaps are acknowledged: (1) Why are adult and fetal Leydig cells different? (2) What are bona fide progenitor and fetal Leydig cell markers? (3) Which signaling pathways and transcription factors regulate fetal Leydig cell steroidogenesis? It is critical to discover answers to these questions so that we can understand vulnerable targets in fetal Leydig cells and the mechanisms for androgen production that when disrupted, leads to variations in sex differentiation that range from subtle to complete sex reversal.

Enhanced bovine genome annotation through integration of transcriptomics and epi-transcriptomics datasets facilitates genomic biology

BACKGROUND

The accurate identification of the functional elements in the bovine genome is a fundamental requirement for high-quality analysis of data informing both genome biology and genomic selection. Functional annotation of the bovine genome was performed to identify a more complete catalog of transcript isoforms across bovine tissues.

RESULTS

A total of 160,820 unique transcripts (50% protein coding) representing 34,882 unique genes (60% protein coding) were identified across tissues. Among them, 118,563 transcripts (73% of the total) were structurally validated by independent datasets (PacBio isoform sequencing data, Oxford Nanopore Technologies sequencing data, de novo assembled transcripts from RNA sequencing data) and comparison with Ensembl and NCBI gene sets. In addition, all transcripts were supported by extensive data from different technologies such as whole transcriptome termini site sequencing, RNA Annotation and Mapping of Promoters for the Analysis of Gene Expression, chromatin immunoprecipitation sequencing, and assay for transposase-accessible chromatin using sequencing. A large proportion of identified transcripts (69%) were unannotated, of which 86% were produced by annotated genes and 14% by unannotated genes. A median of two 5' untranslated regions were expressed per gene. Around 50% of protein-coding genes in each tissue were bifunctional and transcribed both coding and noncoding isoforms. Furthermore, we identified 3,744 genes that functioned as noncoding genes in fetal tissues but as protein-coding genes in adult tissues. Our new bovine genome annotation extended more than 11,000 annotated gene borders compared to Ensembl or NCBI annotations. The resulting bovine transcriptome was integrated with publicly available quantitative trait loci data to study tissue-tissue interconnection involved in different traits and construct the first bovine trait similarity network.

CONCLUSIONS

These validated results show significant improvement over current bovine genome annotations.

Quantitative Characterization of Ectopic Adrenal Gene Expression in Fetal Testes in 21-Hydroxylase Deficient Mice

Testicular adrenal rest tumors (TART) are a frequent and fertility impairing long-term complication in males with classic congenital adrenal hyperplasia. Due to lack of clear experimental data on their origin, they are hypothesized to be derived from ectopic adrenocortical cells within testicular tissue mainly growing upon stimulation by chronically elevated levels of adrenocorticotropin (ACTH). Alternatively, a more totipotent embryological origin has been discussed as the potential source of these tumors. The aim of this study was to quantify alterations of ectopic expression of adrenocortical genes (CYP11B1, CYP11B2, CYP21, MC2R) and the Leydig cell specific marker (INSL3) in testicular tissue of fetal 21-hydroxylase deficient (21OHD) mice. Timed-pregnancy studies were performed using H-2aw18 (aw18)-mice. Testes and adrenals of E15.5 and E18.5 mouse fetuses were used for real-time PCR and immunohistochemistry. Gene expression levels were analyzed for genotype-dependent alterations and compared with immunohistochemistry. While enzymes of steroidogenesis showed a significant increased expression in adrenals of 21OHD mice at both E15.5 and E18.5 compared to wild-type (WT) mice, expression levels were unaltered in testes of 21OHD mice. When compared to WT adrenals a significant increase of INSL3 expression in adrenals of 21OHD mice at E15.5 and E18.5 was detected. Cells with adrenocortical properties in mice fetal testis differ from in situ adrenocortical cells in gene expression and growth at E15.5 and E18.5. These findings suggest that the different local regulation and different local niche in adrenals and testes influence growth of aberrant adrenal cells.

Evaluation of Ex Vivo Adrenocorticotropic Hormone Responsiveness of Human Fetal Testis

Testicular adrenal rest tumors (TARTs), commonly occurring in males with congenital adrenal hyperplasia, may arise from chronic stimulation of adrenocorticotropic hormone (ACTH)-sensitive cells in the testes. It is not yet established whether the human fetal testis (HFT) is responsive to ACTH. To investigate this, we cultured HFT tissue with and without ACTH for up to 5 days, and quantified adrenal steroid hormones and expression of adrenal steroidogenic enzymes. Fetal testis and adrenal tissue produced high levels of testosterone and cortisol, respectively, indicating viability. In contrast to fetal adrenal tissues, the expression of ACTH receptor MC2R was either absent or expressed at extremely low levels in ex vivo HFT tissue and no clear response to ACTH in gene expression or steroid hormone production was observed. Altogether, this study suggests that the HFT is unresponsive to ACTH, which would indicate that a TART does not arise from fetal testicular cells chronically exposed to ACTH in utero.

Interactive metabolic signatures of testicular testosterone with bilateral adrenalectomy in mice

The hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes have reciprocal relationships with steroidogenesis regulation. However, the relationship between testicular steroids and defective glucocorticoid production under chronic stress remains unclear. Metabolic changes of testicular steroids in bilateral adrenalectomized (bADX) 8-week-old C57BL/6 male mice were measured using gas chromatography-mass spectrometry. Twelve weeks after surgery, testis samples were obtained from the model mice, which were divided into tap-water (n = 12) and 1% saline (n = 24) supplementation groups, and their testicular steroid levels were compared with those of sham controls (n = 11). An increased survival rate with lower testicular levels of tetrahydro-11-deoxycorticosterone was observed in the 1% saline group compared to both the tap-water (p = 0.029) and sham (p = 0.062) groups. Testicular corticosterone levels were significantly decreased in both tap-water (4.22 ± 2.73ng/g, p = 0.015) and 1% saline (3.70 ± 1.69, p = 0.002) groups compared to those in sham controls (7.41 ± 7.39). Testicular testosterone levels tended to increase in both bADX groups compared to those in the sham controls. In addition, increased metabolic ratios of testosterone to androstenedione in tap-water (2.24 ± 0.44, p < 0.05) and 1% saline (2.18 ± 0.60, p < 0.05) mice compared to sham controls (1.87 ± 0.55) suggested increased production of testicular testosterone. No significant differences in serum steroid levels were observed. Defective adrenal corticosterone secretion and increased testicular production in bADX models revealed an interactive mechanism underlying chronic stress. The present experimental evidence suggests the crosstalk between the HPA and HPG axes in homeostatic steroidogenesis.

A rare homozygous variant of MC2R gene identified in a Chinese family with familial glucocorticoid deficiency type 1: A case report

Background

Melanocortin-2 receptor (MC2R), a member of the G protein-coupled receptor family, is selectively activated by adrenocorticotropic hormone (ACTH). variants in MC2R are associated with family glucocorticoid deficiency 1 (FGD1).

Case presentation

We first reported a Chinese family with two affected siblings with a homozygotic variant of c.712C>T/p.H238Y in MC2R, presenting with skin hyperpigmentation, hyperbilirubinemia, and tall stature. These individuals showed novel clinical features, including congenital heart defects, not been found in other FGD1 patients.

Conclusions

We reported a Chinese family with affected siblings having a homozygotic variant of c.712C>T/p.H238Y in MC2R.Our report may expand the genetic and clinical spectrum of FGD1.

Emerging concepts on Leydig cell development in fetal and adult testis

Leydig cells (Lc) reside in the interstitial compartment of the testis and are the target of Luteinising hormone (LH) for Testosterone (T) production, thus critically regulates male fertility. Classical histological studies have identified two morphologically different populations of Lc during testicular development [fetal (FLc) and adult (ALc)]. Recent progress in ex vivo cell/organ culture, genome-wide analysis, genetically manipulated mouse models, lineage tracing, and single-cell RNA-seq experiments have revealed the diverse cellular origins with differential transcriptomic and distinct steroidogenic outputs of these populations. FLc originates from both coelomic epithelium and notch-active Nestin-positive perivascular cells located at the gonad-mesonephros borders, and get specified as Nr5a1 (previously known as Ad4BP/SF-1) expressing cells by embryonic age (E) 12.5 days in fetal mouse testes. These cells produce androstenedione (precursor of T, due to lack of HSD17β3 enzyme) and play critical a role in initial virilization and patterning of the male external genitalia. However, in neonatal testis, FLc undergoes massive regression/dedifferentiation and gradually gets replaced by T-producing ALc. Very recent studies suggest a small fraction (5-20%) of FLc still persists in adult testis. Both Nestin-positive perivascular cells and FLc are considered to be the progenitor populations for ALc. This minireview article summarizes the current understanding of Lc development in fetal and adult testes highlighting their common or diverse cellular (progenitor/stem) origins with respective functional significance in both rodents and primates. (227 words).

Lhb-/-Lhr-/- Double Mutant Mice Phenocopy Lhb-/- or Lhr-/- Single Mutants and Display Defects in Leydig Cells and Steroidogenesis

In the mouse, two distinct populations of Leydig cells arise during testis development. Fetal Leydig cells arise from a stem cell population and produce T required for masculinization. It is debated whether they persist in the adult testis. A second adult Leydig stem cell population gives rise to progenitor-immature-mature adult type Leydig cells that produce T in response to LH to maintain spermatogenesis. In testis of adult null male mice lacking either only LH (Lhb^-/-) or LHR (Lhr^-/-), mature Leydig cells are absent but fetal Leydig cells persist. Thus, it is not clear whether other ligands signal via LHRs in Lhb null mice or LH signals via other receptors in the absence of LHR in Lhr null mice. Moreover, it is not clear whether truncated LHR isoforms generated from the same Lhr gene promoter encode functionally relevant LH receptors. To determine the in vivo roles of LH-LHR signaling pathway in the Leydig cell lineage, we generated double null mutant mice lacking both LH Ligand and all forms of LHR. Phenotypic analysis indicated testis morpho-histological characteristics are identical among double null and single mutants which all showed poorly developed interstitium with a reduction in Leydig cell number and absence of late stage spermatids. Gene expression analyses confirmed that the majority of the T biosynthesis pathway enzyme-encoding mRNAs expressed in Leydig cells were all suppressed. Expression of thrombospondin-2, a fetal Leydig cell marker gene was upregulated in single and double null mutants indicating that fetal Leydig cells originate and develop independent of LH-LHR signaling pathway in vivo. Serum and intratesticular T levels were similarly suppressed in single and double mutants. Consequently, expression of AR-regulated genes in Sertoli and germ cells were similarly affected in single and double mutants without any evidence of any additive effect in the combined absence of both LH and LHR. Our studies unequivocally provide genetic evidence that in the mouse testis, fetal Leydig cells do not require LH-LHR signaling pathway and a one-to-one LH ligand-LHR signaling pathway exists in vivo to regulate adult Leydig cell lineage and spermatogenesis.

Transcriptional comparison of testicular adrenal rest tumors with fetal and adult tissues

BACKGROUND

Testicular adrenal rest tumors (TART) are a common complication of unknown cellular origin in patients with congenital adrenal hyperplasia (CAH). These benign tumors have both adrenal and testicular characteristics and are hypothesized to either derive from cells of adrenal origin from the fetal adrenogonadal primordium or by atypical differentiation of adult Leydig-progenitor cells.

OBJECTIVE

This study aims to unravel the identity and etiology of TART.

METHODS

Co-expression of adrenal-specific CYP11B1 and Leydig cell-specific HSD17B3 in TART was studied using immunohistochemistry. We studied the possibility of TART being derived from atypical differentiation of adult Leydig-progenitor cells by the quantification of adrenal-specific enzyme expression upon adrenocorticotrophic hormone (ACTH)-like stimulation of ex vivo cultured platelet-derived growth factor receptor alpha-positive cells. By comparing the transcriptome of TART (n = 16) with the transcriptome of fetal adrenal (n = 13), fetal testis (n = 5), adult adrenal (n = 11), and adult testis (n = 10) tissues, we explored the identity of TART.

RESULTS

We demonstrate co-expression of adrenal-specific CYP11B1 and testis-specific HSD17B3 in TART cells, indicating the existence of a distinct TART cell exhibiting both adrenal and testicular characteristics. Ex vivo cultured adult Leydig-progenitor cells did not express the ACTH-receptor MC2R but did express CYP11B1 upon stimulation. Unsupervised clustering of transcriptome data showed that TART was most similar to adult adrenal tissue, followed by adult testis tissue, and least similar to either fetal tissue.

CONCLUSION

Our data suggest that TART is induced - most likely via activation of a cAMP/protein kinase A-dependent receptor - from a progenitor cell into a unique mature adrenal-like cell type, sometimes exhibiting both adrenal and testicular features.

Role of the Melanocortin System in Gonadal Steroidogenesis of Zebrafish

In teleost, as in other vertebrates, stress affects reproduction. A key component of the stress response is the pituitary secretion of the adrenocorticotropic hormone (ACTH), which binds to the melanocortin 2 receptor (MC2R) in the adrenal glands and activates cortisol biosynthesis. In zebrafish, Mc2r was identified in male and female gonads, while ACTH has been shown to have a physiological role in modulating reproductive activity. In this study, the hypothesis that other melanocortins may also affect how the zebrafish gonadal function is explored, specifically steroid biosynthesis, given the presence of members of the melanocortin signaling system in zebrafish gonads. Using cell culture, expression analysis, and cellular localization of gene expression, our new observations demonstrated that melanocortin receptors, accessory proteins, antagonists, and agonists are expressed in both the ovary and testis of zebrafish (n = 4 each sex). Moreover, melanocortin peptides modulate both basal and gonadotropin-stimulated steroid release from zebrafish gonads (n = 15 for males and n = 50 for females). In situ hybridization in ovaries (n = 3) of zebrafish showed mc1r and mc4r in follicular cells and adjacent to cortical alveoli in the ooplasm of previtellogenic and vitellogenic oocytes. In zebrafish testes (n = 3), mc4r and mc1r were detected exclusively in germ cells, specifically in spermatogonia and spermatocytes. Our results suggest that melanocortins are, directly or indirectly, involved in the endocrine control of vitellogenesis in females, through modulation of estradiol synthesis via autocrine or paracrine actions in zebrafish ovaries. Adult zebrafish testes were sensitive to low doses of ACTH, eliciting testosterone production, which indicates a potential role of this peptide as a paracrine regulator of testicular function.

Non-Canonical Effects of ACTH: Insights Into Adrenal Insufficiency

Introduction

Adrenocorticotropic hormone (ACTH) is produced from proopiomelanocortin, which is predominantly synthetized in the corticotroph and melanotroph cells of the anterior and intermediate lobes of the pituitary gland and the arcuate nucleus of the hypothalamus. Although ACTH clearly has an effect on adrenal homeostasis and maintenance of steroid hormone production, it also has extra-adrenal effects that require further elucidation.

Methods

We comprehensively reviewed English language articles, regardless of whether they reported the presence or absence of adrenal and extra-adrenal ACTH effects.

Results

In the present review, we provide an overview on the current knowledge on adrenal and extra-adrenal effects of ACTH. In the section on adrenal ACTH effects, we focused on corticosteroid rhythmicity and effects on steroidogenesis, mineralocorticoids and adrenal growth. In the section on extra-adrenal effects, we have analyzed the effects of ACTH on the osteoarticular and reproductive systems, adipocytes, immune system, brain and skin. Finally, we focused on adrenal insufficiency.

Conclusions

The role of ACTH in maintaining the function of the hypothalamic-pituitary-adrenal axis is well known. Conversely, if we broaden our vision and analyze its role as a potential treatment strategy in other conditions, it will be evident in the literature that researchers seem to have abandoned this aspect in studies conducted several years ago. We believe it is worth re-evaluating the role of ACTH considering its noncanonical effects on the adrenal gland itself and on extra-adrenal organs and tissues; however, this would not have been possible without the recent advances in the pertinent technologies.

Specific Transcriptomic Signatures and Dual Regulation of Steroidogenesis Between Fetal and Adult Mouse Leydig Cells

Leydig cells (LC) are the main testicular androgen-producing cells. In eutherian mammals, two types of LCs emerge successively during testicular development, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs). Both display significant differences in androgen production and regulation. Using bulk RNA sequencing, we compared the transcriptomes of both LC populations to characterize their specific transcriptional and functional features. Despite similar transcriptomic profiles, a quarter of the genes show significant variations in expression between FLCs and ALCs. Non-transcriptional events, such as alternative splicing was also observed, including a high rate of intron retention in FLCs compared to ALCs. The use of single-cell RNA sequencing data also allowed the identification of nine FLC-specific genes and 50 ALC-specific genes. Expression of the corticotropin-releasing hormone 1 (Crhr1) receptor and the ACTH receptor melanocortin type 2 receptor (Mc2r) specifically in FLCs suggests a dual regulation of steroidogenesis. The androstenedione synthesis by FLCs is stimulated by luteinizing hormone (LH), corticotrophin-releasing hormone (CRH), and adrenocorticotropic hormone (ACTH) whereas the testosterone synthesis by ALCs is dependent exclusively on LH. Overall, our study provides a useful database to explore LC development and functions.

The role of gonadotropins in testicular and adrenal androgen biosynthesis pathways-Insights from males with congenital hypogonadotropic hypogonadism on hCG/rFSH and on testosterone replacement

OBJECTIVE

To delineate the role of gonadotropins in male androgen biosynthesis pathways.

DESIGN

Case-control study.

PATIENTS AND MEASUREMENTS

Twenty five males with congenital hypogonadotropic hypogonadism (CHH) underwent hCG/rFSH and testosterone treatment sequentially. Serum steroid hormone profiles (testosterone precursors and metabolites) on both replacement regimens were analysed, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and compared to those of healthy controls, matched by age, BMI and serum testosterone.

RESULTS

On testosterone replacement, serum concentrations of the classic Δ4 pathway hormones progesterone and 17-hydroxy-progesterone (17-OHP), and the marker steroid of an alternative pathway of testosterone synthesis (androstenediol) were decreased, compared to controls. Androstanediol, a marker of the backdoor pathway of dihydrotestosterone (DHT) synthesis, was increased. 17-OH-pregnenolone, androstenedione and DHEAS (Δ5 pathway), three 11-oxygenated C19 androgens (11-keto-A4, 11-keto-T and 11-keto-DHT) and the testosterone (T) metabolites DHT and 17ß-oestradiol (E2) were similar to controls. On gonadotropin replacement, 17-OHP, 17-OH-pregnenolone, DHEAS and androstenedione, as well as DHT, androstenediol, and all 11-oxygenated C19 androgens were normal. Progesterone (Δ4 pathway) was slightly decreased, and androstanediol (backdoor DHT pathway) and E2 (T metabolite) were increased.

CONCLUSIONS

In males with CHH, serum steroid hormone profiles resemble those of healthy men, if hCG/rFSH is used for substitution. Gonadotropins contribute to steroid hormone production along the classic Δ4 pathway and co-activate an alternative pathway of testosterone biosynthesis via androstenediol. Backdoor DHT biosynthesis, Δ5 17-OH-pregnenolone, DHEA(S) and androstenedione synthesis and 11-oxygenated C19 androgen production are activated independently of gonadotropins. The androgen replacement modality used for treatment of hypogonadal males with absent or reduced endogenous LH/FSH secretion may impact on long-term health and quality of life.

Dynamics of androgens in healthy and hospitalized newborn foals

Background

Information on steroids derived from the adrenal glands, gonads, or fetoplacental unit is minimal in newborn foals.

Objective

To measure androgen concentrations in serum and determine their association with disease severity and outcome in hospitalized foals.

Animals

Hospitalized (n = 145) and healthy (n = 80) foals.

Methods

Prospective, multicenter, cross‐sectional study. Foals of ≤3 days of age from 3 hospitals and horse farms were classified as healthy and hospitalized (septic, sick nonseptic, neonatal maladjustment syndrome [NMS]) based on physical exam, medical history, and laboratory findings. Serum androgen and plasma ACTH concentrations were measured with immunoassays. Data were analyzed by nonparametric methods and univariate analysis.

Results

Serum dehydroepiandrosterone (DHEA), androstenedione, testosterone, and dihydrotestosterone (DHT) concentrations were higher upon admission in hospitalized foals (P <  .05), were associated with nonsurvival, decreased to 4.9‐10.8%, 5.7‐31%, and 30.8‐62.8% admission values in healthy, SNS, and septic foals, respectively (P < .05), but remained unchanged or increased in nonsurviving foals. ACTH:androgen ratios were higher in septic and NMS foals (P < .05). Foals with decreased androgen clearance were more likely to die (odds ratio > 3; P < .05).

Conclusions and Clinical Importance

Similar to glucocorticoids, mineralocorticoids, and progestagens, increased serum concentrations of androgens are associated with disease severity and adverse outcome in hospitalized newborn foals. In healthy foals, androgens decrease over time, however, remain elevated longer in septic and nonsurviving foals. Androgens could play a role in or reflect a response to disorders such as sepsis or NMS in newborn foals.

Melanocortin Receptor 4 (MC4R) Signaling System in Nile Tilapia

The melanocortin receptor 4 (MC4R) signaling system consists of MC4R, MC4R ligands [melanocyte-stimulating hormone (MSH), adrenocorticotropin (ACTH), agouti-related protein (AgRP)], and melanocortin-2 receptor accessory protein 2 (MRAP2), and it has been proposed to play important roles in feeding and growth in vertebrates. However, the expression and functionality of this system have not been fully characterized in teleosts. Here, we cloned tilapia MC4R, MRAP2b, AgRPs (AgRP, AgRP2), and POMCs (POMCa1, POMCb) genes and characterized the interaction of tilapia MC4R with MRAP2b, AgRP, α-MSH, and ACTH in vitro. The results indicate the following. (1) Tilapia MC4R, MRAP2b, AgRPs, and POMCs share high amino acid identity with their mammalian counterparts. (2) Tilapia MRAP2b could interact with MC4R expressed in CHO cells, as demonstrated by Co-IP assay, and thus decrease MC4R constitutive activity and enhance its sensitivity to ACTH_1-40. (3) As in mammals, AgRP can function as an inverse agonist and antagonist of MC4R, either in the presence or absence of MRAP2b. These data, together with the co-expression of MC4R, MRAP2b, AgRPs, and POMCs in tilapia hypothalamus, suggest that as in mammals, ACTH/α-MSH, AgRP, and MRAP2 can interact with MC4R to control energy balance and thus play conserved roles in the feeding and growth of teleosts.

A framework for high-resolution phenotyping of candidate male infertility mutants: from human to mouse

Male infertility is a heterogeneous condition of largely unknown etiology that affects at least 7% of men worldwide. Classical genetic approaches and emerging next-generation sequencing studies support genetic variants as a frequent cause of male infertility. Meanwhile, the barriers to transmission of this disease mean that most individual genetic cases will be rare, but because of the large percentage of the genome required for spermatogenesis, the number of distinct causal mutations is potentially large. Identifying bona fide causes of male infertility thus requires advanced filtering techniques to select for high-probability candidates, including the ability to test causality in animal models. The mouse remains the gold standard for defining the genotype-phenotype connection in male fertility. Here, we present a best practice guide consisting of (a) major points to consider when interpreting next-generation sequencing data performed on infertile men, and, (b) a systematic strategy to categorize infertility types and how they relate to human male infertility. Phenotyping infertility in mice can involve investigating the function of multiple cell types across the testis and epididymis, as well as sperm function. These findings will feed into the diagnosis and treatment of male infertility as well as male health broadly.

Interplay between estrogen-related receptors and steroidogenesis-controlling molecules in adrenals. In vivo and in vitro study

Estrogen-related receptors (ERRs) α, β and γ appear to be novel molecules implicated in estrogen signaling. We blocked and activated ERRs in mouse (C57BL/6) adrenals and adrenocortical cells (H295R) using pharmacological agents XCT 790 (ERRα antagonist) and DY131 (ERRβ/γ agonist), respectively. Mice were injected with XCT 790 or DY131 (5 μg/kg bw) while cells were exposed to XCT 790 or DY131 (0.5 μg/L). Irrespectively of the agent used, changes in adrenocortical cell morphology along with changes in lutropin, cholesterol levels and estrogen production were found. Diverse and complex ERRs regulation of multilevel-acting steroidogenic proteins (perilipin; PLIN, cytochrome P450 side-chain cleavage; P450scc, translocator protein; TSPO, steroidogenic acute regulatory protein; StAR, hormone sensitive lipase; HSL and HMG-CoA reductase; HMGCR) was revealed. Blockage of ERRα decreased P450scc, StAR and TSPO expressions. Activation of ERRβ/γ increased P450scc, StAR and HMGCR while decreased HSL expressions. PLIN expression increased either after XCT 790 or DY131 treatment. Additionally, treatment with both XCT 790 or DY131 decreased activity of Ras/Raf, Erk and Akt indicating their involvement in control of morphology and steroidogenic function of cortex cells. ERRs are important in maintaining morpho-function of cortex cells through action in specific, opposite, or common manner on steroidogenic molecules.

Amniotic Fluid INSL3 Measured During the Critical Time Window in Human Pregnancy Relates to Cryptorchidism, Hypospadias, and Phthalate Load: A Large Case-Control Study

The period of the first to second trimester transition in human pregnancy represents a sensitive window for fetal organogenesis, particularly in regard to the development of the male reproductive system. This is a time of relative analytical inaccessibility. We have used a large national biobank of amniotic fluid samples collected at routine amniocentesis to determine the impacts of exogenous endocrine disruptor load on specific fetal biomarkers at this critical time. While adrenal and testicular steroids are highly correlated, they are also mostly positively influenced by increasing phthalate load, represented by the metabolites 7cx-MMeHP and 5cx-MEPP, by perfluorooctane sulfonate (PFOS) exposure, and by smoking, suggesting an adrenal stress response. In contrast, the testis specific biomarkers insulin-like peptide 3 (INSL3) and androstenedione are negatively impacted by the phthalate endocrine disruptors. Using a case-control design, we show that cryptorchidism and hypospadias are both significantly associated with increased amniotic concentration of INSL3 during gestational weeks 13-16, and some, though not all steroid biomarkers. Cases are also linked to a specifically increased variance in the Leydig cell biomarker INSL3 compared to controls, an effect exacerbated by maternal smoking. No influence of phthalate metabolites or PFOS was evident on the distribution of cases and controls. Considering that several animal and human studies have shown a negative impact of phthalate load on fetal and cord blood INSL3, respectively, the present results suggest that such endocrine disruptors may rather be altering the relative dynamics of testicular development and consequent hormone production, leading to a desynchronization of tissue organization during fetal development. Being born small for gestational age appears not to impact on the testicular biomarker INSL3 in second trimester amniotic fluid.

Comparative Aspects of Pre- and Postnatal Development of the Male Reproductive System

This review describes pre- and postnatal development of the male reproductive system in humans and laboratory animals, and highlights species differences in the timing and control of hormonal and morphologic events. Major differences are that the fetal testis is dependent on gonadotropins in humans, but is independent of such in rats; humans have an extended postnatal quiescent period, whereas rats exhibit no quiescence; and events such as secretion by the prostate and seminal vesicles, testicular descent, and the appearance of spermatogonia are all prenatal events in humans, but are postnatal events in rats. Major differences in the timing of the developmental sequence between rats and humans include: gonocyte transformation period (rat: postnatal day 0-9; human: includes gestational week 22 to 9 months of age); masculinization programming window (rat: gestational day 15.5-17.5; human: gestational week 9-14); and mini-puberty (rat: 0-6 hr after birth; human: 3-6 months of age). Endocrine disruptors can cause unique lesions in the prenatal and early postnatal testis; therefore, it is important to consider the differences in the timing of the developmental sequence when designing preclinical studies as identification of windows of sensitivity for endocrine disruption or toxicants will aid in interpretation of results and provide clues to a mode of action. Birth Defects Research 110:190-227, 2018. © 2017 Wiley Periodicals, Inc.

Leydig progenitor cells in fetal testis

Testicular Leydig cells play pivotal roles in masculinization of organisms by producing androgens. At least two distinct Leydig cell populations sequentially emerge in the mammalian testis. Leydig cells in the fetal testis (fetal Leydig cells) appear just after initial sex differentiation and induce masculinization of male fetuses. Although there has been a debate on the fate of fetal Leydig cells in the postnatal testis, it has been generally believed that fetal Leydig cells regress and are completely replaced by another Leydig cell population, adult Leydig cells. Recent studies revealed that gene expression patterns are different between fetal and adult Leydig cells and that the androgens produced in fetal Leydig cells are different from those in adult Leydig cells in mice. Although these results suggested that fetal and adult Leydig cells have distinct origins, several recent studies of mouse models support the hypothesis that fetal and adult Leydig cells arise from a common progenitor pool. In this review, we first provide an overview of previous knowledge, mainly from mouse studies, focusing on the cellular origins of fetal Leydig cells and the regulatory mechanisms underlying fetal Leydig cell differentiation. In addition, we will briefly discuss the functional differences of fetal Leydig cells between human and rodents. We will also discuss recent studies with mouse models that give clues for understanding how the progenitor cells in the fetal testis are subsequently destined to become fetal or adult Leydig cells.

Dynamic GnRH and hCG testing: establishment of new diagnostic reference levels

OBJECTIVE

Gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) stimulation tests may be used to evaluate the pituitary and testicular capacity. Our aim was to evaluate changes in follicular-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone after GnRH and hCG stimulation in healthy men and assess the impact of six single nucleotide polymorphisms on the responses.

DESIGN

GnRH and hCG stimulation tests were performed on 77 healthy men, 18-40 years (reference group) at a specialized andrology referral center at a university hospital. The potential influence of the tests was illustrated by results from 45 patients suspected of disordered hypothalamic-pituitary-gonadal axis.

METHODS

Baseline, stimulated, relative and absolute changes in serum FSH and LH were determined by ultrasensitive TRIFMA, and testosterone was determined by LC-MS/MS.

RESULTS

For the reference group, LH and FSH increased almost 400% and 40% during GnRH testing, stimulated levels varied from 4.4 to 58.8 U/L and 0.2 to 11.8 U/L and FSH decreased in nine men. Testosterone increased approximately 110% (range: 18.7-67.6 nmol/L) during hCG testing. None of the polymorphisms had any major impact on the test results. Results from GnRH and hCG tests in patients compared with the reference group showed that the stimulated level and absolute increase in LH showed superior identification of patients compared with the relative increase, and the absolute change in testosterone was superior in identifying men with Leydig cell insufficiency, compared with the relative increase.

CONCLUSIONS

We provide novel reference ranges for GnRH and hCG test in healthy men, which allows future diagnostic evaluation of hypothalamic-pituitary-gonadal disorders in men.

ACTH Receptor (MC2R) Specificity: What Do We Know About Underlying Molecular Mechanisms?

Coincidentally, the release of this Research Topic in Frontiers in Endocrinology takes place 25 years after the discovery of the adrenocorticotropic hormone receptor (ACTHR) by Mountjoy and colleagues. In subsequent years, following the discovery of other types of mammalian melanocortin receptors (MCRs), ACTHR also became known as melanocortin type 2 receptor (MC2R). At present, five types of MCRs have been reported, all of which share significant sequence similarity at the amino acid level, and all of which specifically bind melanocortins (MCs)-a group of biologically active peptides generated by proteolysis of the proopiomelanocortin precursor. All MCs share an identical -H-F-R-W- pharmacophore sequence. α-Melanocyte-stimulating hormone (α-MSH) and adrenocorticotropic hormone (ACTH) are the most extensively studied MCs and are derived from the same region. Essentially, α-MSH is formed from the first 13 amino acid residues of ACTH. ACTHR is unique among MCRs because it binds one sole ligand-ACTH, which makes it a very attractive research object for molecular pharmacologists. However, much research has failed, and functional studies of this receptor are lagging behind other MCRs. The reason for these difficulties has already been outlined by Mountjoy and colleagues in their publication on ACTHR coding sequence discovery where the Cloudman S91 melanoma cell line was used for receptor expression because it was a "more sensitive assay system." Subsequent work showed that ACTHR could be successfully expressed only in endogenous MCR-expressing cell lines, since in other cell lines it is retained within the endoplasmic reticulum. The resolution of this methodological problem came in 2005 with the discovery of melanocortin receptor accessory protein, which is required for the formation of functionally active ACTHR. The decade that followed this discovery was filled with exciting research that provided insight into the molecular mechanisms underlying the action of ACTHR. The purpose of this review is to summarize the advances in this fascinating research field.

Endocrine Gland-Derived Vascular Endothelial Growth Factor/Prokineticin-1 in Cancer Development and Tumor Angiogenesis

A lot of data suggests endocrine gland-derived vascular endothelial growth factor (EG-VEGF) to be restricted to endocrine glands and to some endocrine-dependent organs. Many evidences show that EG-VEGF stimulates angiogenesis and cell proliferation, although it is not a member of the VEGF family. At the time, a lot of data regarding the role of this growth factor in normal development are available. However, controversial results have been published in the case of pathological conditions and particularly in malignant tumors. Thus, our present paper has been focused on the role of EG-VEGF in normal tissues and various malignant tumors and their angiogenic processes.

NR0B1 Frameshift Mutation in a Boy with Idiopathic Central Precocious Puberty

NR0B1 is the causative gene for X-linked adrenal hypoplasia congenita, characterized by adrenal insufficiency, hypogonadotropic hypogonadism, and infertility. We identified an NR0B1 frameshift mutation in a boy with precocious puberty who had no signs of adrenal insufficiency. Blood examination revealed elevated testosterone levels and gonadotropin hyperresponses to gonadotropin releasing hormone (GnRH) stimulation, together with normal adrenal hormone levels. GnRH analog treatment partially ameliorated his clinical features. Molecular analysis identified a p.Glu3fsAla*16 in NR0B1. These results expand the clinical manifestations of NR0B1 mutations to include central precocious puberty without adrenal insufficiency. NR0B1 mutations likely underlie androgen overproduction via GnRH-dependent and -independent mechanisms.

Mapping lineage progression of somatic progenitor cells in the mouse fetal testis

Testis morphogenesis is a highly orchestrated process involving lineage determination of male germ cells and somatic cell types. Although the origin and differentiation of germ cells are known, the developmental course specific for each somatic cell lineage has not been clearly defined. Here, we construct a comprehensive map of somatic cell lineage progression in the mouse testis. Both supporting and interstitial cell lineages arise from WT1⁺ somatic progenitor pools in the gonadal primordium. A subpopulation of WT1⁺ progenitor cells acquire SOX9 expression and become Sertoli cells that form testis cords, whereas the remaining WT1⁺ cells contribute to progenitor cells in the testis interstitium. Interstitial progenitor cells diversify through the acquisition of HES1, an indication of Notch activation, at the onset of sex determination. HES1⁺ interstitial progenitors, through the action of Sertoli cell-derived Hedgehog signals, become positive for GLI1. The GLI1⁺ interstitial cells eventually develop into two cell lineages: steroid-producing fetal Leydig cells and non-steroidogenic cells. The fetal Leydig cell population is restricted by Notch2 signaling from the neighboring somatic cells. The non-steroidogenic progenitor cells retain their undifferentiated state during fetal stage and become adult Leydig cells in post-pubertal testis. These results provide the first lineage progression map that illustrates the sequential establishment of somatic cell populations during testis morphogenesis.

Isolation and Characterization of Fetal Leydig Progenitor Cells of Male Mice

Fetal and adult Leydig cells develop in mammalian prenatal and postnatal testes, respectively. In mice, fetal Leydig cells (FLCs) emerge in the interstitial space of the testis at embryonic day 12.5 and thereafter increase in number, possibly through differentiation from progenitor cells. However, the progenitor cells have not yet been identified. Previously, we established transgenic mice in which FLCs are labeled strongly with enhanced green fluorescent protein (EGFP). Interestingly, fluorescence-activated cell sorting provided us with weakly EGFP-labeled cells as well as strongly EGFP-labeled FLCs. In vitro reconstruction of fetal testes demonstrated that weakly EGFP-labeled cells contain FLC progenitors. Transcriptome from the 2 cell populations revealed, as expected, marked differences in the expression of genes required for growth factor/receptor signaling and steroidogenesis. In addition, genes for energy metabolisms such as glycolytic pathways and the citrate cycle were activated in strongly EGFP-labeled cells, suggesting that metabolism is activated during FLC differentiation.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Molecular characterization of testicular adrenal rest tumors in congenital adrenal hyperplasia: lesions with both adrenocortical and Leydig cell features

CONTEXT

Testicular adrenal rest tumors (TART) are one of the major long term complications in patients with congenital adrenal hyperplasia. Although several adrenal-like properties have been assigned to these benign lesions, the etiology has not been confirmed yet.

OBJECTIVE

The aim of this study was to describe TART in more detail by analyzing several (steroidogenic) characteristics that may be classified as adrenal cortex or Leydig cell specific.

METHODS

Gene expression analysis by qPCR was performed for 14 genes in TART tissue (n = 12) and compared with the expression in healthy control fibroblasts (nonsteroidogenic control). In addition, a comparison was made with the expression levels in testis tissue (n = 9) and adrenal tissue (n = 13).

RESULTS

Nearly all genes were highly expressed in TART tissue, including all genes that encode the key steroidogenic enzymes. TART expression levels are in the majority almost identical to those found in adrenal tissue. The expression of adrenal cortex specific genes (CYP11B1, CYP11B2, and MC2R) in both TART and adrenal tissue is approximately 1000-10 000 times higher compared to that in testes samples. In addition, the Leydig cell markers INSL3 and HSD17B3 were not only found in testes, but also in TART, both at significantly higher levels than in the adrenal (p < 0.01).

CONCLUSION

Our study shows for the first time that TART have multiple steroidogenic properties, which include not only the expression of adrenal cortex but also of Leydig cell markers. Therefore, the origin of these tumors might be a more totipotent embryonic cell type.

Morphological and functional maturation of Leydig cells: from rodent models to primates

BACKGROUND

Leydig cells (LC) are the sites of testicular androgen production. Development of LC occurs in the testes of most mammalian species as two distinct growth phases, i.e. as fetal and pubertal/adult populations. In primates there are indications of a third neonatal growth phase. LC androgen production begins in embryonic life and is crucial for the intrauterine masculinization of the male fetal genital tract and brain, and continues until birth after which it rapidly declines. A short post-natal phase of LC activity in primates (including human) termed 'mini-puberty' precedes the period of juvenile quiescence. The adult population of LC evolves, depending on species, in mid- to late-prepuberty upon reawakening of the hypothalamic-pituitary-testicular axis, and these cells are responsible for testicular androgen production in adult life, which continues with a slight gradual decline until senescence. This review is an updated comparative analysis of the functional and morphological maturation of LC in model species with special reference to rodents and primates.

METHODS

Pubmed, Scopus, Web of Science and Google Scholar databases were searched between December 2012 and October 2014. Studies published in languages other than English or German were excluded, as were data in abstract form only. Studies available on primates were primarily examined and compared with available data from specific animal models with emphasis on rodents.

RESULTS

Expression of different marker genes in rodents provides evidence that at least two distinct progenitor lineages give rise to the fetal LC (FLC) population, one arising from the coelomic epithelium and the other from specialized vascular-associated cells along the gonad-mesonephros border. There is general agreement that the formation and functioning of the FLC population in rodents is gonadotrophin-responsive but not gonadotrophin-dependent. In contrast, although there is in primates some controversy on the role of gonadotrophins in the formation of the FLC population, there is consensus about the essential role of gonadotrophins in testosterone production. Like the FLC population, adult Leydig cells (ALC) in rodents arise from stem cells, which have their origin in the fetal testis. In contrast, in primates the ALC population is thought to originate from FLC, which undergo several cycles of regression and redifferentiation before giving rise to the mature ALC population, as well as from differentiation of stem cells/precursor cells. Despite this difference in origin, both in primates and rodents the formation of the mature and functionally active ALC population is critically dependent on the pituitary gonadotrophin, LH. From studies on rodents considerable knowledge has emerged on factors that are involved besides LH in the regulation of this developmental process. Whether the same factors also play a role in the development of the mature primate LC population awaits further investigation.

CONCLUSION

Distinct populations of LC develop along the life span of males, including fetal, neonatal (primates) and ALC. Despite differences in the LC lineages of rodents and primates, the end product is a mature population of LC with the main function to provide androgens necessary for the maintenance of spermatogenesis and extra-gonadal androgen actions.

Genetic ablation of androgen receptor signaling in fetal Leydig cell lineage affects Leydig cell functions in adult testis

It is commonly accepted that androgen-producing fetal Leydig cells (FLC) are substituted by adult Leydig cells (ALC) during perinatal testis development. The mechanisms influencing this process are unclear. We used mice with a retinoid acid receptor 2 promoter-Cre recombinase transgene (Rarb-cre) expressed in embryonic FLC precursors, but not in postnatal testis, and a dual fluorescent Cre recombinase reporter to label FLC and ALC in vivo. All FLC in newborn testis had the recombinant, whereas the majority of LC in adult testis had the nonrecombinant reporter. Primary LC cultures from adult testis had either recombinant (20%) or nonrecombinant (80%) cells, demonstrating that the FLC survive in adult testis and their ontogeny is distinct from ALC. Conditional inactivation of androgen receptor (AR) allele using the Rarb-cre transgene resulted in a 50% increase of AR-negative LC in adult testis. The mutant males became infertile with age, with all LC in older testis showing signs of incomplete differentiation, such as a large number of big lipid droplets, an increase of finger-like protrusions, and a misexpression of steroidogenic or FLC- and ALC-specific genes. We propose that the antiandrogenic exposure during early development may similarly result in an increase of FLC in adult testis, leading to abnormal LC differentiation.

Endocrinopathies in a boy with cryptic copy-number variations on 4q, 7q and Xp

We report a male patient with three copy-number variations (CNVs) and unique phenotype. He carried ~11.2 Mb terminal duplication on 4q, ~13.4 Mb terminal deletion on 7q and ~1.7 Mb interstitial duplication on Xp22.31, which were identified by array-based comparative genomic hybridization. He manifested mental retardation, mild brain anomalies and skeletal deformities ascribable to these CNVs, together with central precocious puberty and mild adrenocorticotropic hormone overproduction of unknown etiologies.

Sertoli cells control peritubular myoid cell fate and support adult Leydig cell development in the prepubertal testis

Sertoli cells (SCs) regulate testicular fate in the differentiating gonad and are the main regulators of spermatogenesis in the adult testis; however, their role during the intervening period of testis development, in particular during adult Leydig cell (ALC) differentiation and function, remains largely unknown. To examine SC function during fetal and prepubertal development we generated two transgenic mouse models that permit controlled, cell-specific ablation of SCs in pre- and postnatal life. Results show that SCs are required: (1) to maintain the differentiated phenotype of peritubular myoid cells (PTMCs) in prepubertal life; (2) to maintain the ALC progenitor population in the postnatal testis; and (3) for development of normal ALC numbers. Furthermore, our data show that fetal LCs function independently from SC, germ cell or PTMC support in the prepubertal testis. Together, these findings reveal that SCs remain essential regulators of testis development long after the period of sex determination. These findings have significant implications for our understanding of male reproductive disorders and wider androgen-related conditions affecting male health.

Identification of Leydig cell-specific mRNA transcripts in the adult rat testis

The adult population of Leydig cells acts to secrete testosterone which is essential for reproductive health and fertility in the adult male. However, other physiological functions of these cells are uncertain, and to address this issue a cell ablation model has been used to identify Leydig cell-specific mRNA transcripts. Ethane dimethane sulphonate (EDS) was synthesised by a novel process and was used to ablate Leydig cells in adult male rats previously treated with butane dimethane sulphonate (busulphan) to delete the germ cell population. Levels of mRNA transcripts were measured in the testis using microarrays 1, 3, 5, 8 and 12 days after EDS injection. During this period, there was a significant change in the levels of 2200 different transcripts with a marked decline in the levels of canonical Leydig cell transcripts, such as Cyp11a1, Cyp17a1 and Insl3. A total of 95 transcripts showed a similar decline in expression after EDS treatment, suggesting that they have a Leydig cell-specific origin. Analysis of selected transcripts confirmed that they were expressed specifically in Leydig cells and showed that most had a late onset of expression during adult Leydig cell development. Apart from transcripts encoding components of the steroidogenic apparatus, the most common predicted function of translated proteins was endogenous and xenotoxicant metabolism. In addition, a number of transcripts encode acute-phase proteins involved in reduction of oxidative stress. Results show that, in addition to androgen secretion, Leydig cells may have a critical role to play in protecting the testis from damage caused by toxicants or stress.

Insulin-Like Factor 3 and the HPG Axis in the Male

The hypothalamic-pituitary-gonadal (HPG) axis comprises pulsatile GnRH from the hypothalamus impacting on the anterior pituitary to induce expression and release of both LH and FSH into the circulation. These in turn stimulate receptors on testicular Leydig and Sertoli cells, respectively, to promote steroidogenesis and spermatogenesis. Both Leydig and Sertoli cells exhibit negative feedback to the pituitary and/or hypothalamus via their products testosterone and inhibin B, respectively, thereby allowing tight regulation of the HPG axis. In particular, LH exerts both acute control on Leydig cells by influencing steroidogenic enzyme activity, as well as chronic control by impacting on Leydig cell differentiation and gene expression. Insulin-like peptide 3 (INSL3) represents an additional and different endpoint of the HPG axis. This Leydig cell hormone interacts with specific receptors, called RXFP2, on Leydig cells themselves to modulate steroidogenesis, and on male germ cells, probably to synergize with androgen-dependent Sertoli cell products to support spermatogenesis. Unlike testosterone, INSL3 is not acutely regulated by the HPG axis, but is a constitutive product of Leydig cells, which reflects their number and/or differentiation status and their ability therefore to produce various factors including steroids, together this is referred to as Leydig cell functional capacity. Because INSL3 is not subject to the acute episodic fluctuations inherent in the HPG axis itself, it serves as an excellent marker for Leydig cell differentiation and functional capacity, as in puberty, or in monitoring the treatment of hypogonadal patients, and at the same time buffering the HPG output.

Molecular characterization and functional regulation of melanocortin 2 receptor (MC2R) in the sea bass. A putative role in the adaptation to stress

The activation of melanocortin 2 receptor (MC2R) by ACTH mediates the signaling cascade leading to steroid synthesis in the interrenal tissue (analogous to the adrenal cortex in mammals) of fish. However, little is known about the functional regulation of this receptor in fish. In this work described, we cloned sea bass MC2R from a liver cDNA. SbMC2R requires the melanocortin 2 receptor accessory protein (MRAP) for its functional expression. Dietary cortisol but not long-term stress protocols downregulated interrenal sbMC2R expression. Data suggest the existence of a negative feedback on interrenal sbMC2R expression imposed by local or systemic glucocorticoids. This feedback could be involved in long-term stress adaptation by regulating interrenal sensitivity to ACTH. ACTH-induced MC2R activation stimulates hepatic lipolysis, suggesting that ACTH may mediate stress-induced effects upstream of cortisol release.

Development of autoimmune hair loss disease alopecia areata is associated with cardiac dysfunction in C3H/HeJ mice

Alopecia areata (AA) is a chronic autoimmune hair loss disease that affects several million men, women and children worldwide. Previous studies have suggested a link between autoimmunity, stress hormones, and increased cardiovascular disease risk. In the current study, histology, immunohistology, quantitative PCR (qPCR) and ELISAs were used to assess heart health in the C3H/HeJ mouse model for AA and heart tissue response to adrenocorticotropic hormone (ACTH) exposure. Mice with AA exhibited both atrial and ventricular hypertrophy, and increased collagen deposition compared to normal-haired littermates. QPCR revealed significant increases in Il18 (4.6-fold), IL18 receptor-1 (Il18r1; 2.8-fold) and IL18 binding protein (Il18bp; 5.2-fold) in AA hearts. Time course studies revealed a trend towards decreased Il18 in acute AA compared to controls while Il18r1, Il18bp and Casp1 showed similar trends to those of chronic AA affected mice. Immunohistochemistry showed localization of IL18 in chronic AA mouse atria. ELISA indicated cardiac troponin-I (cTnI) was elevated in the serum and significantly increased in AA heart tissue. Cultures of heart atria revealed differential gene expression between AA and control mice in response to ACTH. ACTH treatment induced significant increase in cTnI release into the culture medium in a dose-dependent manner for both AA and control mice. In conclusion, murine AA is associated with structural, biochemical, and gene expression changes consistent with cardiac hypertrophy in response to ACTH exposure.

Luteinizing hormone correlates with adrenal function in postmenopausal women

OBJECTIVE

In postmenopausal women, a relationship between luteinizing hormone (LH) and cortisol levels has been suggested. Furthermore, LH receptors in the adrenal gland have been shown to mediate adrenocorticotropic hormone-independent Cushing syndrome. In contrast, follicle-stimulating hormone (FSH) receptors have not been found in the adrenal gland. Our objective was to explore the relationship of LH with adrenal function in postmenopausal women, as assessed by 24-hour urinary free cortisol (UFC) and aldosterone excretion rate (AER).

METHODS

Participants were studied at a single time point in the fasting state in the Clinical Research Center of Brigham and Women's Hospital. We studied 36 postmenopausal women in sodium balance to control for variation in endogenous levels of plasma renin activity and angiotensin II. Serum cortisol, aldosterone, LH, and FSH levels were measured, as were 24-hour UFC and AER. Correlations were performed by calculation of Pearson's correlation coefficient.

RESULTS

Serum LH correlated significantly with log-transformed UFC (r = 0.43, P = 0.01) and inversely with log AER (r = -0.50, P = 0.002). We found no correlation of serum LH with serum cortisol or aldosterone, nor did we find correlation of FSH with these parameters.

CONCLUSIONS

In postmenopausal women, serum LH levels correlate significantly with UFC (positively) and AER (negatively). LH stimulation may induce subtle shifts in adrenal function toward cortisol secretion.

Melanocortin receptor accessory proteins in adrenal gland physiology and beyond

The melanocortin receptor (MCR) family consists of five G-protein-coupled receptors (MC1R-MC5R) with diverse physiological roles. MC1R controls pigmentation, MC2R is a critical component of the hypothalamic-pituitary-adrenal axis, MC3R and MC4R have a vital role in energy homeostasis and MC5R is involved in exocrine function. The melanocortin receptor accessory protein (MRAP) and its paralogue MRAP2 are small single-pass transmembrane proteins that have been shown to regulate MCR expression and function. In the adrenal gland, MRAP is an essential accessory factor for the functional expression of the MC2R/ACTH receptor. The importance of MRAP in adrenal gland physiology is demonstrated by the clinical condition familial glucocorticoid deficiency, where inactivating MRAP mutations account for ∼20% of cases. MRAP is highly expressed in both the zona fasciculata and the undifferentiated zone. Expression in the undifferentiated zone suggests that MRAP could also be important in adrenal cell differentiation and/or maintenance. In contrast, the role of adrenal MRAP2, which is highly expressed in the foetal gland, is unclear. The expression of MRAPs outside the adrenal gland is suggestive of a wider physiological purpose, beyond MC2R-mediated adrenal steroidogenesis. In vitro, MRAPs have been shown to reduce surface expression and signalling of all the other MCRs (MC1,3,4,5R). MRAP2 is predominantly expressed in the hypothalamus, a site that also expresses a high level of MC3R and MC4R. This raises the intriguing possibility of a CNS role for the MRAPs.

Sexually dimorphic testosterone secretion in prenatal and neonatal mice is independent of kisspeptin-Kiss1r and GnRH signaling

Kisspeptin, encoded by the Kiss1 gene, stimulates GnRH secretion and is therefore critical for sex steroid secretion at puberty and in adulthood. However, kisspeptin's role in regulating sex steroid secretion earlier in development is unexplored. In rodents, testosterone (T) levels are higher in prenatal and newborn males than females. We determined whether kisspeptin-Kiss1r and GnRH signaling plays a role in sexually dimorphic perinatal T secretion in mice. Our results demonstrate that 1) T levels in newborn males are elevated at 4 h but not 20 h after birth, but hypothalamic Kiss1 and neurokinin B (NKB) levels in males are not different between these time points (and both are lower than in females); 2) serum T levels in newborn Kiss1r knockout (KO) males are higher than in newborn females and similar to wild-type (WT) males; 3) perinatal hypothalamic progesterone receptor (Pgr) expression, which is dependent on circulating levels of gonadally produced T, is significantly higher in prenatal and newborn Kiss1r KO and WT males than similarly aged females; 4) multiple measures of testicular growth and function are not different between developing Kiss1r KO and WT mice until after postnatal d 5; and 5) GnRH neurons of newborn males do not exhibit high c-fos coexpression, and newborn hypogonadal (hpg) male mice (lacking GnRH) secrete elevated T, similar to newborn WT males. We conclude that, unlike in puberty and adulthood, elevated T secretion in prenatal and neonatal mice is independent of both kisspeptin and GnRH signaling, and the necessity of kisspeptin-Kiss1r signaling for testicular function is first apparent after d 5.

Eliminating SF-1 (NR5A1) sumoylation in vivo results in ectopic hedgehog signaling and disruption of endocrine development

Sumoylation is generally considered a repressive mark for many transcription factors. However, the in vivo importance of sumoylation for any given substrate remains unclear and is questionable because the extent of sumoylation appears exceedingly low for most substrates. Here, we permanently eliminated SF-1/NR5A1 sumoylation in mice (Sf-1(K119R, K194R, or 2KR)) and found that Sf-1(2KR/2KR) mice failed to phenocopy a simple gain of SF-1 function or show elevated levels of well-established SF-1 target genes. Instead, mutant mice exhibited marked endocrine abnormalities and changes in cell fate that reflected an inappropriate activation of hedgehog signaling and other potential SUMO-sensitive targets. Furthermore, unsumoylatable SF-1 mutants activated Shh and exhibited preferential recruitment to Shh genomic elements in cells. We conclude that the sumoylation cycle greatly expands the functional capacity of transcription factors such as SF-1 and is leveraged during development to achieve cell-type-specific gene expression in multicellular organisms.

Direct actions of ACTH on ovarian function of pseudopregnant rabbits

The present study sought to assess whether the receptors for adrenocorticotropic hormone (ACTH), MC2R, and for glucocorticoid (GR) are expressed in corpora lutea (CL) of pseudopregnant rabbits and whether ACTH and cortisol exert any direct action on luteal function. By immunohistochemistry, positive reaction for MC2R and GR was detectable within luteal cells of CL. The MC2R mRNA levels were five-fold less abundant in day 9 than in day 4 CL (P<0.01). At both stages, ACTH agonist (ACTH 1-24) increased progesterone and prostaglandin (PG) E(2) (PGE(2)) (P<0.01), but reduced PGF(2α) releases (P<0.01) in vitro. ACTH 1-24 injection increased plasma cortisol levels within 4h (P<0.01), but decreased (P<0.01) progesterone 24h later and for the following two days. ACTH administration to estrous rabbits caused a transitory increase in blood progesterone concentrations (P<0.01). Daily injections of ACTH did not modify progesterone profile following ovulation. In conclusion, ACTH directly up-regulates CL progesterone production in vitro via MC2R, but indirectly hampers luteal function via cortisol-GR associated mechanism.

Effects of melanocortins on fetal development

Melanocortins, adrenocorticotropic hormone (ACTH) and α-, β-, and γ-melanocyte-stimulating hormone (MSH) are produced in the placenta and secreted into embryos/fetuses. ACTH concentrations are higher in fetal plasma than in maternal plasma and peak at mid-gestation in rats, whereas ACTH production starts in the anterior lobe of the fetal pituitary at later stages. Melanocortin receptors (MC1-5R), receptors for ACTH and α-, β- and γ-MSH, are expressed in various adult organs. The specific function of these receptors has been well examined in the hypothalamic-pituitary-adrenocortical (HPA) axis and the HPA axis-like network in the skin, and anti-inflammatory effects for white blood cells have also been investigated. MC2R and/or MC5R are also expressed in the testis, lung, kidney, adrenal, liver, pancreas, brain and blood cells at different stages in mouse and rat embryos/fetuses. Melanocortins in embryos and fetuses promote maturation of the HPA axis and also contribute to the development of lung, testis, brain and blood cells. Recently, a unique ACTH function was revealed in fetuses: placental ACTH, which is secreted by the maternal leukemia inhibitory factor (LIF), and induces LIF secretion from fetal nucleated red blood cells. Finally, the maternal LIF-placental ACTH-fetal LIF signal relay regulates the LIF level and promotes neurogenesis in fetuses, which suggests that ACTH acts as a signal transducer or effector for fetal development in the maternal-fetal signal pathway.

Endocrinology of the mammalian fetal testis

The testes are essential endocrine regulators of fetal masculinization and male development and are, themselves, subject to hormonal regulation during gestation. This review focuses, primarily, on this latter control of testicular function. Data available suggest that, in most mammalian species, the testis goes through a period of independent function before the fetal hypothalamic–pituitary–gonadal axis develops at around 50% of gestation. This pituitary-independent phase coincides with the most critical period of fetal masculinization. Thereafter, the fetal testes appear to become pituitary hormone-dependent, concurrent with declining Leydig cell function, but increasing Sertoli cell numbers. The two orders of mammals most commonly used for these types of studies (rodents and primates) appear to represent special cases within this general hypothesis. In terms of testicular function, rodents are born ‘early’ before the pituitary-dependent phase of fetal development, while the primate testis is dependent upon placental gonadotropin released during the pituitary-independent phase of development.

Expression of genes related to the hypothalamic-pituitary-adrenal axis in murine fetal lungs in late gestation

BACKGROUND

Lung maturation is modulated by several factors, including glucocorticoids. Expression of hypothalamic-pituitary-adrenal (HPA) axis-related components, with proposed or described local regulatory systems analogous to the HPA axis, was reported in peripheral tissues. Here, HPA axis-related genes were studied in the mouse developing lung during a period overlapping the surge of surfactant production.

METHODS

Expression of genes encoding for corticotropin-releasing hormone (CRH), CRH receptors (CRHR) 1 and 2beta, CRH-binding protein, proopiomelanocortin (POMC), melanocortin receptor 2 (MC2R), and glucocorticoid receptor was quantified by real-time PCR and localized by in situ hydridization in fetal lungs at gestational days (GD) 15.5, 16.5, and 17.5, and was also quantified in primary mesenchymal- and epithelial cell-enriched cultures. In addition, the capability of CRH and adrenocorticotropic hormone (ACTH) to stimulate pulmonary expression of enzymes involved in the adrenal pathway of glucocorticoid synthesis was addressed, as well as the glucocorticoid production by fetal lung explants.

RESULTS

We report that all the studied genes are expressed in fetal lungs according to different patterns. On GD 15.5, Mc2r showed peaks in expression in samples that have previously presented high mRNA levels for glucocorticoid synthesizing enzymes, including 11beta-hydroxylase (Cyp11b1). Crhr1 mRNA co-localized with Pomc mRNA in cells surrounding the proximal epithelium on GD 15.5 and 16.5. A transition in expression sites toward distal epithelial cells was observed between GD 15.5 and 17.5 for all the studied genes. CRH or ACTH stimulation of genes involved in the adrenal pathway of glucocorticoid synthesis was not observed in lung explants on GD 15.5, whereas CRH significantly increased expression of 21-hydroxylase (Cyp21a1) on GD 17.5. A deoxycorticosterone production by fetal lung explants was observed.

CONCLUSIONS

Temporal and spatial modulations of expression of HPA axis-related genes in late gestation are consistent with roles for these genes in lung development. Our data are likely to lead to valuable insights in relation to lung diseases originating from lung immaturity.

Steroidogenesis in the fetal testis and its susceptibility to disruption by exogenous compounds

Masculinization depends on adequate production of testosterone by the fetal testis within a specific "masculinization programming window." Disorders resulting from subtle deficiencies in this process are common in humans, and environmental exposures/lifestyle could contribute causally because common therapeutic and environmental compounds can affect steroidogenesis. This evidence derives mainly from rodent studies, but because there are major species differences in regulation of steroidogenesis in the fetal testis, this may not always be a guide to potential effects in the human. In addition to direct study of the effects of compounds on steroidogenesis, information also derives from study of masculinization disorders that result from mutations in genes in pathways regulating steroidogenesis. This review addresses this issue by critically reviewing the comparative timing of production and regulation of steroidogenesis in the fetal testis of humans and of rodents and its susceptibility to disruption; where there is limited information for the fetus, evidence from effects on steroidogenesis in the adult testis is considered. There are a number of fundamental regulatory differences between the human and rodent fetal testis, most notably in the importance of paracrine vs. endocrine drives during masculinization such that inactivating LH receptor mutations block masculinization in humans but not in rodents. Other large differences involve the steroidogenic response to estrogens and GnRH analogs and possibly phthalates, whereas for other compounds there may be differences in sensitivity to disruption (ketoconazole). This comparison identifies steroidogenic targets that are either vulnerable (mitochondrial cholesterol transport, CYP11A, CYP17) or not (cholesterol uptake) to chemical interference.

Down-regulation of murine testicular 17β-HSD3 and hepatic CYP1A2 enzymes by a bovine testes extract

Purpose

We investigated the effects of a bovine testes extract (BTE), which was developed as an alternative product for andropausal men, on expression of testicular enzymes responsible for sex hormone synthesis genes and a carcinogen activation related gene.

Methods

Expression of testicular CYP1A2, CYP11A1, CYP17, 3β-HSD, and 17β-HSD3 mRNAs as well as hepatic CYP1A2 mRNA were semi-quantitatively determined by RT-PCR. In addition, expression of hepatic CYP1A2 protein and methoxyresorufin O-demethylase activity were carried out.

Results

Bovine testes extract did not alter the testicular expression of CYP11A1, CYP17, and 3β-HSD mRNAs, while that of CYP11A1 was significantly down-regulated by testosterone. Interestingly, administration of BTE for 3 weeks significantly suppressed testicular 17β-HSD3 and hepatic CYP1A2 mRNA. Correspondingly, methoxyresorufin O-demethylase (MROD) activity and expression of hepatic CYP1A2 protein were significantly decreased.

Conclusions

These findings strongly suggested considering risks versus benefits and raised concerns regarding the use of BTE as an alternative medication or health supplement in andropausal men due to its potential for suppressing expression of both 17β-HSD3 and CYP1A2 mRNAs, testicular enzymes responsible for sex hormone gene synthesis.

Adrenocorticotropic hormone suppresses gonadotropin-stimulated estradiol release from zebrafish ovarian follicles

While stress is known to impact reproductive performance, the pathways involved are not entirely understood. Corticosteroid effects on the functioning of the hypothalamus-pituitary-gonadal axis are thought to be a key aspect of stress-mediated reproductive dysfunction. A vital component of the stress response is the pituitary secretion of adrenocorticotropic hormone (ACTH), which binds to the melanocortin 2 receptor (MC2R) in the adrenal glands and activates cortisol biosynthesis. We recently reported MC2R mRNA abundance in fish gonads leading to the hypothesis that ACTH may be directly involved in gonadal steroid modulation. Using zebrafish (Danio rerio) ovarian follicles, we tested the hypothesis that acute ACTH stimulation modulates cortisol and estradiol (E(2)) secretion. ACTH neither affected cortisol nor unstimulated E(2) release from ovarian follicles. However, ACTH suppressed human chorionic gonadotropin (hCG)-stimulated E(2) secretion in a dose-related manner, with a maximum decrease of 62% observed at 1 I.U. ACTH mL(-1). This effect of ACTH on E(2) release was not observed in the presence of either 8-bromo-cAMP or forskolin, suggesting that the mechanism(s) involved in steroid attenuation was upstream of adenylyl cyclase activation. Overall, our results suggest that a stress-induced rise in plasma ACTH levels may initiate a rapid down-regulation of acute stimulated E(2) biosynthesis in the zebrafish ovary, underscoring a novel physiological role for this pituitary peptide in modulating reproductive activity.

Structural and functional diversity of proopiomelanocortin in fish with special reference to barfin flounder

Proopiomelanocortin (POMC) is a precursor of adrenocorticotropic hormone (ACTH), melanocyte-stimulating hormone (MSH), and endorphin (END). We have characterized POMC systems in barfin flounder. The results revealed unique aspects of POMC systems. Notable features in terms of pituitary functions are the occurrence of three functional POMC genes, the mutation of an essential sequence in the beta-END in one of the genes, occurrence of alpha-MSH in addition to ACTH in the pars distalis of the pituitary, and expression of the three genes in a single cell. While MSHs stimulate pigment dispersion, expression of the POMC gene and plasma levels of MSH do not always respond to background color changes between black and white. The functions of MSHs in skin pigmentation are very unique, because acetylation at the N-terminal of alpha-MSH inhibits its pigment dispersing activity. This is in contrast to results from other teleosts and amphibians, in which acetylation increases the activity. In the skin, the POMC gene is expressed in the non-chromatophoric dermal cells, indicating that MSH produced in the skin de novo has a paracrine function. The detection of MSH peptides in skin extracts seems to show that the control of skin pigmentation by MSHs is twofold-endocrine control by the pituitary, and paracrine control by the skin itself. Thus, fish provide an interesting model to help understand the structural and functional diversity of POMC systems. In this review, we provide an overview of our recent studies on the characterization of molecules and biological significance of POMC systems in barfin flounder.