The effect of oestrogen and testosterone on the urethral seam of the developing male mouse genital tubercle

Simultaneous Occurrence of Hypospadias and Bilateral Cleft Lip and Jaw in a Crossbred Calf: Clinical, Computer Tomographic, and Genomic Characterization

Congenital abnormalities in animals, including abnormalities of the cleft lip and jaw and hypospadias have been reported in all domesticated species. They are a major concern for breeders due to the increased economic loss they entail. In this article, we described a congenital bilateral cheilognathoschisis (cleft lip and jaw) with campylognathia in association with penile hypospadias and preputial hypoplasia with failure of preputial fusion in a Bos taurus crossbred Piedmontese × Wagyu calf. Clinical examination, computed tomography, and whole genome sequencing were performed to describe and identify a possible cause of the abnormalities. Clinical examination revealed a bilateral cheilognathoschisis of approximately 4 cm in length and 3 cm in width in the widest part, with computer tomography analyses confirming the bilateral absence of the processus nasalis of the incisive bone and the lateral deviation of the processus palatinus towards the left side. Genomic data analyses identified 13 mutations with a high impact on the products of the following overlapped genes: ACVR1, ADGRA2, BHMT2, BMPR1B, CCDC8, CDH1, EGF, F13A1, GSTP1, IRF6, MMP14, MYBPHL, and PHC2 with ADGRA2, EGF, F13A1, GSTP1, and IRF6 having mutations in a homozygous state. The whole genome investigation indicates the involvement of multiple genes in the birth defects observed in this case.

On the Use and Interpretation of Areola/Nipple Retention as a Biomarker for Anti-androgenic Effects in Rat Toxicity Studies

Areola/nipple retention (NR) is an established biomarker for an anti-androgenic mode of action in rat toxicity studies. It is a mandatory measurement under several OECD test guidelines and is typically assessed in combination with anogenital distance (AGD). Both NR and AGD are considered retrospective biomarkers of insufficient androgen signaling during the masculinization programming window in male fetuses. However, there are still aspects concerning NR as a biomarker for endocrine disruption that remains to be clarified. For instance, can NR be regarded a permanent adverse effect? Is it a redundant measurement if AGD is assessed in the same study? Is NR equally sensitive and specific to anti-androgenic chemical substances as a shortening of male AGD? In this review we discuss these and other aspects concerning the use of NR as a biomarker in toxicity studies. We have collected available literature from rat toxicity studies that have reported on NR and synthesized the data in order to draw a clearer picture about the sensitivity and specificity of NR as an effect biomarker for an anti-androgenic mode of action, including comparisons to AGD measurements. We carefully conclude that NR and AGD in rats for the most part display similar sensitivity and specificity, but that there are clear exceptions which support the continued assessment of both endpoints in relevant reproductive toxicity studies. Available literature also support the view that NR in infant male rats signifies a high risk for permanent nipples in adulthood. Finally, the literature suggests that the mechanisms of action leading from a chemical stressor event to either NR or short AGD in male offspring are overlapping with respect to canonical androgen signaling, yet differ with respect to other mechanisms of action.

Endocrine disrupting chemicals in the pathogenesis of hypospadias; developmental and toxicological perspectives

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Penis development is regulated by a tight balance of androgens and estrogens.

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EDCs that impact androgen/estrogen balance during development cause hypospadias.

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Cross-disciplinary collaborations are needed to define a mechanistic link.

Hypospadias is a defect in penile urethral closure that occurs in approximately 1/150 live male births in developed nations, making it one of the most common congenital abnormalities worldwide. Alarmingly, the frequency of hypospadias has increased rapidly over recent decades and is continuing to rise. Recent research reviewed herein suggests that the rise in hypospadias rates can be directly linked to our increasing exposure to endocrine disrupting chemicals (EDCs), especially those that affect estrogen and androgen signalling. Understanding the mechanistic links between endocrine disruptors and hypospadias requires toxicologists and developmental biologists to define exposures and biological impacts on penis development. In this review we examine recent insights from toxicological, developmental and epidemiological studies on the hormonal control of normal penis development and describe the rationale and evidence for EDC exposures that impact these pathways to cause hypospadias. Continued collaboration across these fields is imperative to understand the full impact of endocrine disrupting chemicals on the increasing rates of hypospadias.

Foxa1 and Foxa2 orchestrate development of the urethral tube and division of the embryonic cloaca through an autoregulatory loop with Shh

Congenital anomalies of external genitalia affect approximately 1 in 125 live male births. Development of the genital tubercle, the precursor of the penis and clitoris, is regulated by the urethral plate epithelium, an endodermal signaling center. Signaling activity of the urethral plate is mediated by Sonic hedgehog (SHH), which coordinates outgrowth and patterning of the genital tubercle by controlling cell cycle kinetics and expression of downstream genes. The mechanisms that govern Shh transcription in urethral plate cells are largely unknown. Here we show that deletion of Foxa1 and Foxa2 results in persistent cloaca, an incomplete separation of urinary, genital, and anorectal tracts, and severe hypospadias, a failure of urethral tubulogenesis. Loss of Foxa2 and only one copy of Foxa1 results in urethral fistula, an additional opening of the penile urethra. Foxa1/a2 participate in an autoregulatory feedback loop with Shh, in which FOXA1 and FOXA2 positively regulate transcription of Shh in the urethra, and SHH feeds back to negatively regulate Foxa1 and Foxa2 expression. These findings reveal novel roles for Foxa genes in development of the urethral tube and in division of the embryonic cloaca.

Interaction between CYP1A1/CYP17A1 polymorphisms and parental risk factors in the risk of hypospadias in a Chinese population

Hypospadias (HS) is a common congenital malformation of the genitourinary tract in males and its etiology is viewed as multifactorial, and studies about gene-environment interaction in the etiology of HS are rare. A total of 152 cases and 151 controls were selected in the present study. Information before and during pregnancy from questionnaires finished by mothers of subjects were extracted, and the relating data were analyzed to determine the risk factors of HS. Meanwhile, maternal genomic DNA was genotyped for the single nucleotide polymorphisms (SNPs) of CYP1A1 rs1048943 and CYP17A1 rs4919686. Results of multivariable logistic regression analyses showed that several factors were associated with hypospadias risk. Analysis of the distributions of SNPs in CYP1A1 and CYP17A1 genes showed that the mutant genotype CC (OR = 4.87) of CYP1A1 rs1048943, and mutant genotype CC (OR = 5.82), recessive genotype AC + CC (OR = 2.17) and allele C (OR = 1.77) of CYP17A1 rs4919686 significantly increased the risk of HS. In addition, the additive gene-environment interactions were also found in several models. Several maternal risk factors that are associated with HS risk can interact with CYP1A1/CYP17A1 polymorphisms, which lead to infants vulnerable to occurrence of HS in Chinese populations.

Placental pathology and hypospadias

BACKGROUND

Studies have shown that hypospadias is associated with placenta-mediated pregnancy complication (PMPC). The role of placental lesions is still unclear. We aimed to examine the association between hyposadias and placental pathology, and the effect of PMPC.

METHODS

Using data from the US Collaborative Perinatal Project in 1959-1966, we identified 15,780 male subjects (167 hypospadias) for analysis. Detailed placental examinations were conducted following a standard protocol. Subjects were divided into two groups according to whether they had PMPC, including small-for-gestational-age, pre-eclampsia/eclampsia or placental abruption. Logistic regression models were used to explore the association.

RESULTS

The prevalence of hypospadias was two times higher in subjects with PMPC than those without. Compared to pregnancies with PMPC but no hypospadias, those with both PMPC and hypospadias had significant higher prevalence of placental lesions, such as low placental weight, vascular lesions, villous lesions, and membranous insertion of cord (adjusted odds ratio (OR) ranging from 2.6 to 5.2) after adjusting for potential confounders. In subjects without PMPC, no significant difference of placental pathology was found between those with or without hypospadias.

CONCLUSION

About one third of hypospadias cases were complicated with PMPC and had a higher risk of placental lesions, suggesting heterogeneity of hypospadias etiology and mechanisms.

Diethylstilbestrol Regulates the Expression of LGR8 in Mouse Gubernaculum Testis Cells

BACKGROUND Hormonal effects on the gubernaculum can affect testicular descent. Diethylstilbestrol (DES) is a nonsteroidal synthetic estrogen that disrupts the outgrowth of gubernaculums, leading to testis maldescent. However, the underlying mechanisms remain elusive. MATERIAL AND METHODS The gubernaculum were removed from 3-day-old mice and cultured. The subcultured cells were randomly divided into a normal control group and experimental groups. The DES groups were administered 10 μg/ml, 1 μg/ml, 0.1 μg/ml, 0.01 μg/ml of diethylstilbestrol dissolved in dimethyl sulfoxide (DMSO) respectively. The cell morphology was observed under an inverted microscope, and leucine-rich repeat-containing G protein-coupled receptor 8 (LGR8) was localized by immunofluorescence. The expressions of LGR8 gene and protein in gubernaculum cells were quantified by RT-PCR and Flow Cytometer respectively. RESULTS DES treatment converted cells from a normal fibroblast-like morphology into a more refractile, spindle-shaped morphology or irregular elliptical shapes along with cytoplasmic shrinkage. LGR8 was expressed in the cytoplasmic membrane, DES dose-dependently downregulated LGR8 expression at low doses (≤1.0 μg/ml), but upregulated LGR8 at high doses (10 μg/ml) at both the mRNA and protein levels. CONCLUSIONS These results suggest that DES causes testicular maldescent by altering the LGR8 pathway in mouse gubernaculum testis cells.

Do endocrine disruptors cause hypospadias?

Introduction

Endocrine disruptors or environmental agents, disrupt the endocrine system, leading to various adverse effects in humans and animals. Although the phenomenon has been noted historically in the cases of diethylstilbestrol (DES) and dichlorodiphenyltrichloroethane (DDT), the term “endocrine disruptor” is relatively new. Endocrine disruptors can have a variety of hormonal activities such as estrogenicity or anti-androgenicity. The focus of this review concerns on the induction of hypospadias by exogenous estrogenic endocrine disruptors. This has been a particular clinical concern secondary to reported increased incidence of hypospadias. Herein, the recent literature is reviewed as to whether endocrine disruptors cause hypospadias.

Methods

A literature search was performed for studies involving both humans and animals. Studies within the past 5 years were reviewed and categorized into basic science, clinical science, epidemiologic, or review studies.

Results

Forty-three scientific articles were identified. Relevant sentinel articles were also reviewed. Additional pertinent studies were extracted from the reference of the articles that obtained from initial search results. Each article was reviewed and results presented. Overall, there were no studies which definitely stated that endocrine disruptors caused hypospadias. However, there were multiple studies which implicated endocrine disruptors as one component of a multifactorial model for hypospadias.

Conclusions

Endocrine disruption may be one of the many critical steps in aberrant development that manifests as hypospadias.

Diethylstilbestrol-induced mouse hypospadias: "window of susceptibility"

This review presents published and novel results that define the programming window for diethylstilbestrol (DES)-induced abnormal development of the mouse penis. These data indicate that DES has its greatest effect during the period of most intense penile morphogenesis, namely postnatal days 0-15 (P0-P15). Pregnant mice and their neonatal pups were injected subcutaneously with 200 ng/gbw DES every other day from embryonic day 12-18 (DES E12-E18), postnatal day 0-10 (DES P0-P10), embryonic day 12 to postnatal day 10 (DES E12-P10), postnatal day 5-15 (DES P5-P15), and postnatal day 10-20 (DES P10-P20). Aged-matched controls received sesame oil vehicle. After euthanasia at 10, 15, 20 and 60 days, penises were analyzed by gross morphology, histology and morphometry. Penises of all 5 groups of DES-treated mice were reduced in size, which was confirmed by morphometric analysis of internal penile structures. The most profound effects were seen in the DES E12-P10, DES P0-P10, and DES P5-P15 groups, thus defining a DES "programming window". For all parameters, DES treatment from P10 to P20 showed the most mild of effects. Adverse effects of DES on the MUMP cartilage and erectile bodies observed shortly after the last DES injection reverted to normality in the DES P5-P15, but not in the E12-P10 and P0-P10 groups, in which MUMP cartilage and erectile body malformations persisted into adulthood, again emphasizing a "window of susceptibility" in the early neonatal period.

Genetic polymorphisms in ESR1 and ESR2 genes, and risk of hypospadias in a multiethnic study population

PURPOSE

Estrogenic endocrine disruptors acting via estrogen receptors α (ESR1) and β (ESR2) have been implicated in the etiology of hypospadias, a common congenital malformation of the male external genitalia. We determined the association of single nucleotide polymorphisms in ESR1 and ESR2 genes with hypospadias in a racially/ethnically diverse study population of California births.

MATERIALS AND METHODS

We investigated the relationship between hypospadias and 108 ESR1 and 36 ESR2 single nucleotide polymorphisms in 647 cases and 877 population based nonmalformed controls among infants born in selected California counties from 1990 to 2003. Subgroup analyses were performed by race/ethnicity (nonHispanic white and Hispanic subjects) and by hypospadias severity (mild to moderate and severe).

RESULTS

Odds ratios for 33 of the 108 ESR1 single nucleotide polymorphisms had p values less than 0.05 (p = 0.05 to 0.007) for risk of hypospadias. However, none of the 36 ESR2 single nucleotide polymorphisms was significantly associated. In stratified analyses the association results were consistent by disease severity but different sets of single nucleotide polymorphisms were significantly associated with hypospadias in nonHispanic white and Hispanic subjects. Due to high linkage disequilibrium across the single nucleotide polymorphisms, haplotype analyses were conducted and identified 6 haplotype blocks in ESR1 gene that had haplotypes significantly associated with an increased risk of hypospadias (OR 1.3 to 1.8, p = 0.04 to 0.00001). Similar to single nucleotide polymorphism analysis, different ESR1 haplotypes were associated with risk of hypospadias in nonHispanic white and Hispanic subjects. No significant haplotype association was observed for ESR2.

CONCLUSIONS

The data provide evidence that ESR1 single nucleotide polymorphisms and haplotypes influence the risk of hypospadias in white and Hispanic subjects, and warrant further examination in other study populations.

Split median raphe: case series and brief literature review

We describe three cases of split median raphe of the penis (SMR) from our hospital newborn records from 2004 to 2013. One case was associated with median raphe cyst, one with skin hypochromia, and one with a scar-like aspect of the region of interest. SMR is thought to be the result of defective fusion of ectodermal tissue in the urethra and scrotum area or of defective growth of the perineal mesoderm around the urethra during gestation. Although SMR associated with other major penile congenital defects (epispadias, hypospadias, penile torsion, bifid scrotum, chordee) is common, isolated SMR is probably an underdiagnosed (although not rare) malformative condition. Recognizing SMR in a newborn may be of educational value to neonatologists because it leads to the search for and exclusion of the above-mentioned pathologic conditions.

Hypospadias and maternal intake of phytoestrogens

Experimental data indicate that gestational exposures to estrogenic compounds impact risk of hypospadias. We examined whether risk of hypospadias (i.e., a congenital malformation in which the opening of the penile urethra occurs on the ventral side of the penis) was associated with maternal intake of phytoestrogens, given their potential impact on estrogen metabolism. The analysis included data on mothers of 1,250 hypospadias cases and 3,118 controls who delivered their infants from 1997 to 2005 and participated in the National Birth Defects Prevention Study, a multistate, population-based, case-control study. After adjustment for several covariates, high intakes of daidzein, genistein, glycetin, secoisolariciresinol, total isoflavones, total lignans, and total phytoestrogens were associated with reduced risks; odds ratios comparing intakes ≥90th percentile with intakes between the 11th and 89th percentiles ranged from 0.6 to 0.8. For example, the odds ratio for total phytoestrogen intake was 0.7 (95% confidence interval: 0.5, 1.0). This study represents the first large-scale analysis of phytoestrogen intake and hypospadias. The observed associations merit investigation in additional populations before firm conclusions can be reached.

Diethylstilbestrol impairs the morphology and function of mouse gubernaculum testis in culture

Diethylstilbestrol (DES) is a nonsteroidal synthetic estrogen widely used in estrogen therapy. In animal models, exposure to DES disrupts the outgrowth of the gubernacula, leading to testis maldescent. However, it remains unclear whether the effects of DES on gubernaculum are direct or indirect, and the underlying mechanisms are largely obscure. In this study, mouse gubernaculum testis cells were isolated and treated by DES, and cell morphology and function were examined. The results showed that DES changed the morphology and inhibited the proliferation of gubernacular cells. Furthermore, DES increased intracellular [Ca(2+)] and induced F-actin rearrangement and stress fiber formation in gubernaculum testis cells in a dose-dependent manner. Taken together, these data suggest that DES impairs the morphology and inhibits the proliferation and contractility of gubernaculum testis cells. The experimental model we established and our observations based on this model help provide new insight into the role of DES in the etiology of cryptorchidism.

Molecular mechanisms of external genitalia development

External genitalia development occurs through a combination of hormone independent, hormone dependent, and endocrine pathways. Perturbation of these pathways can lead to abnormal external genitalia development. We review human and animal mechanisms of normal and abnormal external genitalia development, and we evaluate abnormal mechanisms that lead to hypospadias. We also discuss recent laboratory findings that further our understanding of animal models of hypospadias.

Expression of estrogen receptor alpha and beta is decreased in hypospadias

PURPOSE

Estrogenic endocrine disruptors acting via estrogen receptors α and β have been implicated in the etiology of hypospadias. However, the expression and distribution of estrogen receptors α and β in normal and hypospadiac human foreskins is unknown. We characterized the location and expression of estrogen receptors α and β in normal and hypospadiac foreskins.

MATERIALS AND METHODS

We prospectively collected excess foreskin from 35 patients undergoing hypospadias repair and 15 patients undergoing elective circumcision. Hypospadias was classified as severe in 18 patients and mild in 17 based on the ectopic position of the meatus. mRNA expression levels in estrogen receptors α and β were quantified using reverse transcriptase polymerase chain reaction. Receptor location was characterized by immunohistochemical analysis. Additionally immunohistochemical analysis was performed in 4 archived human fetal penises.

RESULTS

Mean ± SD ages were similar for the circumcision (9.5±3 months) and hypospadias repair groups (9±3 months, p=0.75). mRNA expression levels in estrogen receptors α and β were significantly decreased in hypospadiac foreskin cases compared to controls (p<0.001), while no statistically significant differences were seen between foreskins with severe and mild hypospadias. Estrogen receptor β immunostaining was strong in normal foreskin but weak in hypospadiac foreskin. Estrogen receptor β immunoreactivity was most intense in the stratum basale and stratum spinosum. Estrogen receptor α immunostaining was weak in normal and mild hypospadias foreskin, and undetectable in severe hypospadias. Fetal penises expressed strong estrogen receptor β immunopositivity in the urethral plate epithelium, corpus spongiosum, corpora cavernosa and penile skin, while estrogen receptor α immunostaining was not detected.

CONCLUSIONS

These data demonstrate a difference in estrogen receptor α and β expression and location in the foreskin of patients with hypospadias compared to controls. These findings are consistent with aberrant estrogenic effects having a role in the etiology of hypospadias.

Ex-premature infant boys with hypospadias are similar in size to age-matched, ex-premature infant boys without hypospadias

OBJECTIVE

Studies have postulated that hypospadias, prematurity, and low birth weight are linked by defects in androgen signaling. To determine whether premature, hypospadiac boys are small and remain so, we compared their size at birth and at hypospadias repair to premature boys who underwent post-neonatal circumcision.

METHODS

We identified premature boys admitted to Texas Children's Hospital who underwent either hypospadias repair or circumcision after 4 months of age. Age, weight, and height at birth and surgery were recorded.

RESULTS

Fifty-four boys had hypospadias and 34 did not. For hypospadiac boys, the mean birth weight and age, height, and weight at surgery were lower than for boys without hypospadias. More importantly, length-for-age and weight-for-age percentiles were also lower for hypospadiac boys. When subset analysis was performed on boys younger than 2 years at surgery, however, there were no significant differences in height or weight between hypospadiac and non-hypospadiac boys.

CONCLUSION

Our series suggests that premature, hypospadiac boys are born smaller than age-matched, non-hypospadiac controls. However, there were no age-corrected size differences between hypospadiac and non-hypospadiac boys at surgery. This implies that hypospadiac boys exhibit post-neonatal 'rebound' growth. Global growth deficits, if any, do not persist in hypospadiac boys.

Polymorphism in CYP1A1, GSTMI,GSTT1 genes and organochlorine pesticides in the etiology of hypospadias

Exposure to endocrine-disrupting chemicals (EDCs) and maternal endogenous estrogen may cause hypospadias, common congenital anomaly. Several organochlorine pesticides (OCPs) have been reported to possess an endocrine-disrupting potential. Cytochrome P4501A1 (CYP1A1) and glutathione S-transferases (GSTM1 and GSTT1) of xenobiotic metabolizing enzyme family are involved in the metabolism of various environmental toxicants and steroidal hormones. Hence, the present study was designed to evaluate the role of CYP1A1, GSTM1, GSTT1 genes polymorphism, OCPs levels and risk of hypospadias. A total of 80 hypospadiac and 120 age-matched control boys were included. OCP levels in blood were determined using Gas Chromatograph equipped with electron capture detector (GC-ECD) and polymorphism in CYP1A1, GSTM1 and GSTT1 genes was evaluated by RFLP and multiplex PCR method. We observed significant high levels of β-hexachlorohexane (HCH), γ-HCH, and p, p′-dichlorodiphenyl-dichloroethylene ( p,p’-DDE) in the cases. CYP1A1 polymorphisms were not significantly different among cases and controls, whereas concomitant deletion of GSTM1 and GSTT1 genotypes was significantly higher in cases as compared to controls. However, after adjusting for low birth weight and maternal occupational exposure, the results did not remain significant but odds of risk was higher (OR = 1.72, p = 0.14) among cases. In conclusion, our study suggests irrespective of genetic predisposition, higher level of some OCPs may be associated with increased risk of hypospadias.

Immunohistochemical characterization of sonic hedgehog and its downstream signaling molecules during human penile development

Hypospadias is a common congenital anomalies, yet its molecular basis remains unknown. Recent studies have linked perturbations in the Hedgehog signaling pathway to hypospadias. However, the expression of Sonic hedgehog (Shh) has not been reported during genital development. Immunohistochemical staining for Shh and its receptors was applied to 10 human fetal penises ranging from 12 to 29 weeks gestation. The intensity of Shh staining was greatest in the urethral epithelium at 14 weeks gestation, correlating with the time of urethral tubularization. Results suggest a role for Shh in human male genital development.

Morphology of mouse external genitalia: implications for a role of estrogen in sexual dimorphism of the mouse genital tubercle

PURPOSE

We examined the role of androgens and estrogens in mammalian sexual differentiation by morphological characterization of adult wt and mutant mouse external genitalia. We tested the hypothesis that external genitalia development depends on androgen and estrogen action.

MATERIALS AND METHODS

We studied serial sections of the external genitalia of the CD-1 and C57BL6 wt strains of adult mice (Charles River Laboratories, Wilmington, Massachusetts). We recorded linear measurements of key structures in each specimen, including the urethra, erectile tissue, bone and cartilage. We used similar methodology to analyze mice mutant for estrogen receptor α (αERKO) and androgen receptor (X(Tfm)/Y) (Jackson Laboratory, Bar Harbor, Maine).

RESULTS

Morphology in X(Tfm)/Y adult murine external genitalia was remarkably similar to that in wt females. Bone and clitoral length was similar in wt females and X(Tfm)/Y mice. Conversely the αERKO clitoris was 59% longer and bone length in αERKO females was many-fold longer than that in female wt mice or X(Tfm)/Y mutants. The αERKO clitoris contained cartilage, which is typical of the wt penis but never observed in the wt clitoris. Serum testosterone was not increased in female αERKO mice 10 days postnatally when sex differentiation occurs, suggesting that masculinization of the αERKO clitoris is not a function of androgen.

CONCLUSIONS

Masculinization of the αERKO clitoris suggests a role for estrogen in the development of female external genitalia. We propose that normal external genital development requires androgen and estrogen action.

Estrogen effects on fetal penile and urethral development in organotypic mouse genital tubercle culture

PURPOSE

We developed an organotypic genital tubercle culture system in vitro and used it to investigate the direct effects of the hyperestrogenic state on fetal mouse penile and urethral development.

MATERIALS AND METHODS

Genital tubercles were dissected from embryonic day 14.5 C57B/L6 male mouse fetuses and cultured using an air-liquid interface on a microporous membrane support soaked in synthetic medium. Cultures were separated into 4 groups. Groups 1 to 3 were supplied with 10 nM dihydrotestosterone, estradiol and 10 nM dihydrotestosterone plus estradiol, respectively. Group 4 was cultured in hormone-free medium. After 36 to 72-hour culture morphological, histological, proliferation, apoptosis, androgen signaling and activating transcription factor 3 analyses were done.

RESULTS

The physiological concentration of 10 nM dihydrotestosterone was essential for genital tubercle growth in vitro. Androgen induced growth and urethral development were significantly suppressed by high dose estrogen. Concurrently we observed increased apoptosis and decreased proliferation in the mesenchyma. Androgen signaling was disrupted and activating transcription factor 3, a factor related to hypospadias genesis, was up-regulated.

CONCLUSIONS

High dose estrogen suppressed male genital tubercle development in vitro. The organotypic genital tubercle culture system in vitro consisting of urethral epithelial and mesenchymal cells can recapitulate the hormonal sensitivity of fetal penile and urethral development. This method is potentially useful for studying the effects of various factors, particularly endocrine disruptors.

Genetic interactions of the androgen and Wnt/beta-catenin pathways for the masculinization of external genitalia

In most mammals, the sexually dimorphic development of embryos is typically achieved by the differentiation of the external genitalia. Hence, the sexual distinction of mammalian newborns is based on the external genital structure. Although it was shown in the 1940s and 1950s that androgen from the testes establishes the male sexual characteristics, the involvement of nongonadal and locally produced masculine effectors remains totally unknown. It is noteworthy that the disorders of fetal masculinization, including hypospadias, one of the most frequent birth defects, occur at a high frequency. Furthermore, their causative factors remain unclear. In this study, the involvement of the coordinated actions of androgen and the growth factor systems was genetically analyzed for the first time on mammalian reproductive organ formation. The results demonstrated that the Wnt/beta-catenin pathway is indispensable masculine factor for the external genital development. The bilateral mesenchymal region adjacent to the urethral plate epithelium displayed a sexually dimorphic activity of Wnt/beta-catenin signaling. Loss- and gain-of-function beta-catenin mutants displayed altered sexual development of the external genitalia. These results indicate the novel functions of the Wnt/beta-catenin pathway as a locally expressed masculine effector. This could be the first genetic study analyzing the roles of the genetic interactions between androgen and locally expressed growth factor signaling during the development of reproductive organs. These results also shed new insight on the reproductive genetics and the causative factors of genital disorders.

Bmp7 expression and null phenotype in the urogenital system suggest a role in re-organization of the urethral epithelium

Signaling by Bone morphogenetic proteins (Bmps) has multiple and diverse roles in patterning and morphogenesis of the kidney, eye, limbs and the neural tube. Here, we employed the Bmp7(lacZ) strain to perform a detailed analysis of Bmp7 expression and the null phenotype during development of the mouse urogenital system. The urethral compartment originates in mid-embryogenesis from the ventral part of the cloaca, a transient cavity at the caudal end of the hindgut. At mid-gestation, Bmp7 expression was detected within several specific domains in the cloacal epithelium and mesenchyme. In late embryogenesis, Bmp7 expression was present in the urethra, rectum, the urethral glands, corpus cavernosum, and in the male and female genital ducts. Importantly, loss of Bmp7 resulted in arrest in cloacal septation, and severe defects in morphogenesis of the genital urethra and mesenchyme. Together, our analysis of Bmp7 expression and the null phenotype, indicates that Bmp7 may play an important role in re-organization of the epithelium during cloacal septation and morphogenesis of the genital tubercle.

Di(2-ethylhexyl) phthalate (DEHP) increases transforming growth factor-beta1 expression in fetal mouse genital tubercles

Phthalates are known to elicit marked effects on the developing male reproductive tract as evidenced by hypospadias. Recently, transforming growth factor-beta1 (TGF-beta1) was postulated to play an essential role in the development of genital tubercles (GT), and TGF- beta1 was found to act as a phthalates-responsive gene. In this study, the effects of di(2-ethylhexyl) phthalate (DEHP) were examined on the expression of TGF-beta1 in fetal mice, as GT development is dependent upon this factor. Pregnant C57BL/6 mice were exposed to corn oil or DEHP (100, 200, or 500 mg/kg/d orally) from embryonic day 12 (ED12) to ED17. Data showed a significant inhibition of male fetal GT development following DEHP treatment. Hypospadic-like urethral orifice and abnormal urethra were evaluated macroscopically and by histology at ED19. By using reverse-transcription polymerase chain reaction (RT-PCR) and Western blot, the expression of TGF-beta1 was upregulated in DEHP-treated mice. These results suggest that hypospadias may be induced by DEHP exposure involving modification of TGF-beta1 levels.

Hypospadias and anorectal malformations mediated by Eph/ephrin signaling

PURPOSE: Despite extensive research, the molecular basis of hypospadias and anorectal malformations is poorly understood, likely due to a multifactorial basis. The incidence of hypospadias is increasing, thus making research in this area warranted and timely. This review presents recent molecular work broadening our understanding of these disorders. MATERIALS AND METHODS: A brief review of our recent work and the literature on the role of Eph/ephrin signaling in hypospadias and anorectal malformations is presented. RESULTS: Genetically engineered mice mutant for ephrin-B2 or EphB2;EphB3 manifest a variety of genitourinary and anorectal malformations. Approximately 40% of adult male heterozygous mice demonstrate perineal hypospadias. Although homozygous mice die soon after birth, 100% of homozygous males demonstrate high imperforate anus with urethral anomalies and 100% of homozygous females demonstrate persistent cloaca. Male mice compound homozygous for EphB2(ki/ki);EphB3(Delta/Delta)/ also demonstrate hypospadias. CONCLUSIONS: These mouse models provide compelling evidence of the role of B-class Eph/ephrin signaling in genitourinary/anorectal development and add to our mechanistic and molecular understanding of normal and abnormal embryonic development. As research on the B-class Ephs and ephrins continues, they will likely be shown to be molecular contributors to the multifactorial basis of hypospadias and anorectal malformations in humans as well.

Risk factors for hypospadias in the estrogen receptor 2 gene

CONTEXT

Hypospadias is a common inborn error of the male genitalia of complex, and still elusive, etiology. The presence of active estrogen receptors (ESRs) in the developing male urethra, predominantly the ESR2, has suggested a role of estrogens in the otherwise androgen-dependent male genital differetiation. Moreover, imbalances between these two steroid hormones have been suggested to disturb the external genital development. This has been supported by the association between longer (CA)n variants in the ESR2 gene with lower androgen levels as well as with hypospadias.

OBJECTIVE

The aim of this study was to analyze the effect of ESR2 gene variants on the risk to hypospadias.

DESIGN, PARTICIPANTS, AND METHODS

Four haplotype-tagging single nucleotide polymorphisms (rs2987983, rs1887994, rs1256040, and rs1256062), the (CA)n polymorphism, and two additional promoter single nucleotide polymorphisms (rs10483774 and rs1271572), mapping to a transcription factor binding region, were typed and analyzed in a Swedish cohort of 354 boys with nonsyndromic hypospadias and 380 healthy controls.

RESULTS

Association was identified with longer variants of the (CA)n polymorphism in intron 6 and with a region of intense transcription factor binding, in the putative promoter region, mapping to rs2987983 and rs10483774. The two regions are in low-linkage disequilibrium, meaning that they are not necessarily inherited together as a haplotype; logistic regression analysis indicates that these two risk effects are not independent.

CONCLUSIONS

The present study evidences two nonindependent risk factors for hypospadias in the ESR2 gene. We discuss possible mechanisms that explain how these variants may affect male urethral development.

Progesterone Receptors in the Developing Genital Tubercle: Implications for the Endocrine Disruptor Hypothesis as the Etiology of Hypospadias

PURPOSE

In fetal mice genital tubercles the ontogenetic expression of progesterone receptors and the effect of in utero estrogen and testosterone exposure were investigated.

MATERIALS AND METHODS

To evaluate ontogenetic progesterone receptor expression genital tubercles from untreated fetuses at gestational days 12, 14, 16 and 18, and newborn pups were prepared for real-time reverse transcriptase-polymerase chain reaction or immunohistochemistry. To evaluate estrogen and testosterone effects pregnant dams were gavaged once daily with corn oil (vehicle), ethinyl estradiol or testosterone propionate from gestational days 12 through 17. At gestational day 19 the genital tubercles of delivered fetuses were harvested for morphological examination and then pooled for real-time reverse transcriptase-polymerase chain reaction.

RESULTS

Progesterone receptor protein was first detected at gestational day 12 in the urethral plate and mesenchyma. At later stages staining intensity increased with a greater progesterone receptor signal, especially in the urethra. Progesterone receptor mRNA expression showed different increasing patterns in each sex until birth. However, no difference was noted between male and female genital tubercles in terms of the distribution and quantity of progesterone receptor expression. In utero ethinyl estradiol led to 8.2, 9.7 and 5.2-fold increases in progesterone receptor mRNA in females and in males with and without hypospadias, respectively. Testosterone propionate significantly decreased progesterone receptor mRNA levels in females and males.

CONCLUSIONS

Progesterone receptors are expressed in developing genital tubercles, suggesting a direct role of progesterone in normal genital tubercle patterning. Their increasing expression until birth also implies increasing sensitivity of the genital tubercles to the effects of estrogenic and progestogenic endocrine disruptors during fetal life. Ethinyl estradiol and testosterone propionate lead to opposing effects on progesterone receptor expression, in addition to their opposing morphological effects on the genital tubercles. These findings expand our knowledge of genital tubercle morphogenesis and provide important information for understanding the effects of endocrine disruptors.

Studies of a co-chaperone of the androgen receptor, FKBP52, as candidate for hypospadias

BACKGROUND

Hypospadias is a common inborn error of the male urethral development, for which the aetiology is still elusive. Polymorphic variants in genes involved in the masculinisation of male genitalia, such as the androgen receptor, have been associated with some cases of hypospadias. Co-regulators of the androgen receptor start being acknowledged as possible candidates for hormone-resistance instances, which could account for hypospadias. One such molecule, the protein FKBP52, coded by the FKBP4 gene, has an important physiological role in up-regulating androgen receptor activity, an essential step in the development of the male external genitalia. The presence of hypospadias in mice lacking fkbp52 encouraged us to study the sequence and the expression of FKBP4 in boys with isolated hypospadias.

PATIENTS AND METHODS

The expression of FKBP52 in the genital skin of boys with hypospadias and in healthy controls was tested by immunohistochemistry. Mutation screening in the FKBF4 gene was performed in ninety-one boys with non syndromic hypospadias. Additionally, two polymorphisms were typed in a larger cohort.

RESULTS

Immunohistochemistry shows epithelial expression of FKBP52 in the epidermis of the penile skin. No apparent difference in the FKBP52 expression was detected in healthy controls, mild or severe hypospadias patients. No sequence variants in the FKBP4 gene have implicated in hypospadias in our study.

CONCLUSION

FKBP52 is likely to play a role in growth and development of the male genitalia, since it is expressed in the genital skin of prepubertal boys; however alterations in the sequence and in the expression of the FKBP4 gene are not a common cause of non-syndromic hypospadias.

Essential role for Co-chaperone Fkbp52 but not Fkbp51 in androgen receptor-mediated signaling and physiology

Fkbp52 and Fkbp51 are tetratricopeptide repeat proteins found in steroid receptor complexes, and Fkbp51 is an androgen receptor (AR) target gene. Although in vitro studies suggest that Fkbp52 and Fkbp51 regulate hormone binding and/or subcellular trafficking of receptors, the roles of Fkbp52 and Fkbp51 in vivo have not been extensively investigated. Here, we evaluate their physiological roles in Fkbp52-deficient and Fkbp51-deficient mice. Fkbp52-deficient males developed defects in select reproductive organs (e.g. penile hypospadias and prostate dysgenesis but normal testis), pointing to a role for Fkbp52 in AR-mediated signaling and function. Surprisingly, ablation of Fkbp52 did not affect AR hormone binding or nuclear translocation in vivo and in vitro. Molecular studies in mouse embryonic fibroblast cells uncovered that Fkbp52 is critical to AR transcriptional activity. Interestingly, Fkbp51 expression was down-regulated in Fkbp52-deficient males but only in affected tissues, providing further evidence of tissue-specific loss of AR activity and suggesting that Fkbp51 is an AR target gene essential to penile and prostate development. However, Fkbp51-deficient mice were normal, showing no defects in AR-mediated reproductive function. Our work demonstrates that Fkbp52 but not Fkbp51 is essential to AR-mediated signaling and provides evidence for an unprecedented Fkbp52 function, direct control of steroid receptor transcriptional activity.

Ontogeny of androgen receptor and disruption of its mRNA expression by exogenous estrogens during morphogenesis of the genital tubercle

PURPOSE

The ontogeny of androgen receptor expression in male and female mouse genital tubercles, and the effects of in utero ethinyl estradiol exposure on androgen receptor mRNA expression in the hypospadias model were studied.

MATERIALS AND METHODS

Androgen receptor mRNA expression was measured in mouse genital tubercles from fetuses and pups collected on gestational days 12, 14, 16 and 18, and from newborns using immunohistochemistry and real-time quantitative polymerase chain reaction. Pregnant dams were exposed to ethinyl estradiol or corn oil as controls from gestational days 12 to 17. Genital tubercles of gestational day 19 fetuses were then examined by further quantitative polymerase chain reaction analysis after identification of the seam area using a dissecting microscope to diagnose hypospadias in males.

RESULTS

Androgen receptor protein was detected in genital tubercles by gestational day 14. Androgen receptor mRNA expression increased gradually in each sex during normal development. However, female genital tubercles expressed a higher level of androgen receptor mRNA throughout development compared to male genital tubercles (p <0.0001). In utero ethinyl estradiol exposure led to a 5.4 and 4.5-fold increase in androgen receptor mRNA in the genital tubercles of female and male embryos (p = 0.004 and 0.001, respectively). Hypospadiac male genital tubercles showed increased androgen receptor mRNA expression compared to control males (p = 0.006). Levels in hypospadiac males did not differ from those in control females but they were less than those in ethinyl estradiol treated females (p >0.05 and 0.01, respectively).

CONCLUSIONS

Androgen receptor protein is expressed abundantly in male and female genital tubercles. Androgen receptor mRNA levels are higher in female than in male genital tubercles through development and they increase in response to in utero ethinyl estradiol exposure with ethinyl estradiol treated females having the highest levels of expression, followed by ethinyl estradiol treated hypospadiac males. We infer that higher estrogen in genital tubercles results in a physiological response of increased androgen receptor mRNA expression. We found no direct association between changes in androgen receptor mRNA expression and the presence or absence of hypospadias in males, suggesting that alterations in the expression of proteins other than or in addition to androgen receptor result in anomalous urethral development. This finding supports the idea that the etiology of hypospadias is multifactorial in origin.

Polymorphisms of estrogen receptor beta gene are associated with hypospadias

INTRODUCTION

Hypospadias is a common male congenital urethral malformation, defined as the displacement of the urethral meatus ventrally from the tip of the glans penis. The importance of androgen receptor in male external genitalia development has been well recognized. Recently, the presence of active estrogen receptors (ER) in the developing male external genitalia has also been demonstrated. There are two isoforms of the human estrogen receptor, ESR1 and ESR2, which occur, with distinct tissue and cell patterns of expression. We hypothesized that modifications in these nuclear receptors' genes could lead to hypospadias.

MATERIALS AND METHODS

We screened 60 boys with hypospadias for mutations in the coding regions of ESR1 and ESR2 genes, by denaturing high-performance liquid chromatography and automated sequence analysis. We also genotyped the CA repeat polymorphism in ESR2 and the TA repeat polymorphism in ESR1.

RESULTS

The CA repeat polymorphism in ESR2 is prolonged in hypospadias patients compared to controls (p < 0.05). Prolongation of this CA repeat polymorphism has previously been associated with lower levels of testosterone. Six patients presented the genetic variant 2681-4A > G (rs944050) in the heterozygous form in ESR2, which was a significantly higher frequency than in the control population (p < 0.05). One of these patients also presented a 266_267insC in exon 1 of ESR2, which is also a known single nucleotide polymorphism (SNP; rs3832949). In ESR1, no significant gene alteration was found to be associated with hypospadias.

CONCLUSIONS

Our results suggest that variations in the ESR2 might influence susceptibility to hypospadias.

Activating transcription factor 3 is up-regulated in patients with hypospadias

Hypospadias is a congenital anomaly of the genitalia characterized by abnormalities of the urethra and foreskin, with the urethral meatus located in an abnormal position anywhere from the distal ventral penile shaft to the perineum. Because the incidence of hypospadias is approximately 1/200-1/300 live male births, it is one of the most common congenital malformations, but its etiology is largely uncharacterized. Genomic analysis of hypospadic tissue indicated a potential role for activating transcription factor 3 (ATF3) in the development of this anomaly. ATF3 may be involved in homeostasis, wound healing, cell adhesion, or apoptosis, and normally it is expressed at a steady-state in quiescent cells. Additionally, it has been shown to be an estrogen-responsive gene, and the etiology of hypospadias may be related to in utero exposure to estrogenic or anti-androgenic compounds. We examined the expression of ATF3 in tissues from 28 children with hypospadias compared with 20 normal penile skin tissue samples from elective circumcision. Eighty-six percent of the hypospadias samples were immunohistochemically positive, compared with 13% of normal tissue samples. Seventy-five percent of hypospadias samples were positive from in situ hybridization, compared with 1% of circumcision samples. Our results indicate that ATF3 is up-regulated in the penile skin tissues of boys with hypospadias, suggesting a role for this transcription factor in the development of this abnormality. Because the etiology of hypospadias may include exposure to estrogenic compounds, the responsiveness of ATF3 to estrogen is also discussed.

The Effects of Subacute Inhalation of Di (2‐ethylhexyl) Phthalate (DEHP) on the Testes of Prepubertal Wistar Rats

In animal studies using oral dosing for short periods, di (2-ethylhexyl) phthalate (DEHP) is well known for its reproductive toxicity, especially for its testicular toxicity. However, extending the period of DEHP exposure in prepubertal rats resulted in significant increases in testosterone. This suggests that the reproductive effect of DEHP might be associated with the timing and the term of exposure. Moreover, the route of exposure may induce differences in its effect because tissue levels of metabolites of DEHP after inhalation are thought to be different from those after oral administration. We researched the effects of inhalation of DEHP on testes of prepubertal rats. Our results showed that inhalation of DEHP by 4-wk-old male Wistar rats at doses of 5 or 25 mg/m(3), 6 h per day, for 4 and 8 wk significantly increased the concentration of plasma testosterone and weight of seminal vesicles. However, the concentration of luteinizing hormone (LH), follicular stimulating hormone (FSH) and the expression of mRNAs of androgen biosynthesis enzyme, cytochrome P450 cholesterol side-chain-cleavage enzyme (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/17, 20 lyase (CYP17) and aromatase (CYP19) did not change. Rats with precocious testes did not increase in any of the DEHP groups. We also found that the estimated effective dose in this study was less than those reported in previous studies which used oral dosing. Our study showed that inhaled DEHP increased plasma testosterone concentrations in prepubertal rats and suggested that their effects were more sensitive to inhalation of DEHP than oral dosing.

Maternal genetic polymorphisms in CYP1A1, GSTM1 and GSTT1 and the risk of hypospadias

Hypospadias is one of the most common congenital anomalies. Increased exposure to environmental factors (endocrine-disrupting chemicals and smoking) or maternal endogenous estrogen may cause hypospadias because male sexual differentiation is dependent on normal androgen homeostasis. Moreover, interactions between genetic factors and cigarette smoking and other chemicals have been suggested. It has been demonstrated that the CYP1A1 metabolizes not only environmental chemicals but also estrogens, and glutathione-S-transferases (GSTs) are detoxification enzymes that protect cells from toxicants by conjugation with glutathione. In this study, to investigate the association of CYP1A1 (MspI), GSTM1 and GSTT1 polymorphisms with hypospadias, a case-control study of 31 case mothers who had boys with hypospadias and 64 control mothers was performed in Japan. These polymorphisms were investigated by PCR-based methods using DNA from peripheral lymphocytes. We found that the heterozygous CYP1A1 and heterozygous and homozygous CYP1A1 were less frequent in the case mothers than in the control mothers [adjusted odds ratio (OR)=0.17, 95% confidence interval (CI)=0.04-0.74, OR = 0.28, 95% CI = 0.08-0.97, respectively]. We found no effect of maternal smoking on the hypospadias risks among the gene polymorphisms. The results suggest that mothers with the CYP1A1 MspI variant allele may have a decreased risk for hypospadias.

Penile development is initiated in the tammar wallaby pouch young during the period when 5alpha-androstane-3alpha,17beta-diol is secreted by the testes

Virilization of the urogenital tract is under the control of testicular androgens in all mammals. In tammar young, prostate differentiation begins between d 20 and d 40 under the control of the testicular androgen 5alpha-androstane-3alpha,17beta-diol (5alpha-adiol), but uncertainties exist about the control of penile development. We performed longitudinal studies up to d 150 of pouch life to define normal penile development and the effects of androgen administration and castration. In control animals the male phallus was longer than the female phallus by d 48. Closure of the urethra in males begins around d 60 and continues to at least d 150. Administration of supraphysiological doses of testosterone to females caused penile development equivalent to that of the male and also induced partial closure of the urethral groove by d 150. Castration of male pouch young at d 25 prevented penile development, whereas the penis in males castrated at d 40, 80, or 120 had partial closure of the urethral groove. Administration of 5alpha-adiol to females from d 20-40 also caused partial closure of the urethral groove and some growth of the phallus at d 150, whereas 5alpha-adiol treatment from d 40-80 or 80-120 caused some penile growth but had little effect on urethral development. These findings, together with the fact that we found no sex differences in plasma levels of testosterone, dihydrotestosterone, 5alpha-adiol, dehydroepiandrosterone, or androstenedione from d 51-227, clearly indicate that the action of 5alpha-adiol between d 20 and 40 imprints later differentiation of the male penis.