Androgens and the masculinization programming window: human-rodent differences

Role of the endocannabinoid system in gonadal development: Implications for endocrine disruption and reproductive toxicity

The endocannabinoid system (ECS) plays a pivotal role in reproductive physiology, including gonadal development, though its influence on testis and ovary development has only recently gained attention. The ECS comprises lipid-derived ligands such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG), along with cannabinoid receptors CB1 and CB2, which are expressed in various gonadal cells. Emerging research indicates that ECS signaling is critical for testosterone synthesis and gonadal cell proliferation and differentiation. This review explores the expression and function of ECS components in developing gonads, highlighting the differential roles of CB1 and CB2 receptors in species-specific contexts. Furthermore, the ECS has been suggested to be involved in the adverse effects of endocrine-disrupting chemicals (EDCs) on reproductive development. EDCs, such as phthalates, may interfere with ECS signaling, potentially leading to reproductive abnormalities that resemble the human Testicular Dysgenesis Syndrome (TDS). Understanding the molecular interactions between EDCs and the ECS could reveal novel mechanisms underlying reproductive toxicities. Future research should focus on the detailed localization and temporal expression of ECS components in fetal gonads, the mechanisms of cannabinoid-mediated testosterone inhibition, and the potential direct interaction of EDCs with the ECS. This knowledge could be crucial for developing strategies to mitigate reproductive health risks associated with EDC exposure.

Maternal coffee consumption and biomarkers of reproductive health in young, adult sons: a cohort study

It has been proposed that poor semen quality may have its origins from fetal programming due to environmental factors. We investigated whether maternal coffee consumption during early pregnancy was associated with biomarkers of reproductive health in adult sons in the Fetal Programming of Semen Quality (FEPOS) cohort. In 2017-2019, 1058 young men provided a semen and blood sample and self-measured their testis volume. Daily maternal coffee consumption was reported by the mothers around gestational week 17. We estimated relative percentage differences with 95 % confidence intervals (CI) for semen quality measures, testis volume, and reproductive hormone levels according to maternal coffee consumption during pregnancy. Maternal coffee consumption (yes/no (reference)) was associated with lower semen volume (-7.0 % (95 % CI:-12.9;-0.7)), lower proportion of morphologically normal spermatozoa (-8.3 % (95 % CI:-16.5;0.8)), higher proportion of non-progressive and immotile spermatozoa (4.3 % (95 % CI:-1.5;10.3)), and lower testis volume (-4.8 % (95 % CI:-9.0;-0.4)). No indication of a dose-response association or threshold effects was observed in the categorized and continuous analyses. No associations with reproductive hormone levels were observed in any of the analyses. Overall, the study does not provide obvious indications that maternal coffee consumption in early pregnancy deteriorates male offspring fecundity. While some minor changes were observed, most estimates were small with confidence intervals overlapping the null. Future studies, preferably with greater exposure contrast, are warranted before a conclusion can be drawn as to whether maternal coffee consumption during pregnancy constitutes a risk for reproductive health in adult sons.

Associations between maternal periconceptional exposure to PM2.5 and the risk of cryptorchidism: a case-control study of 4274

Currently, there is limited evidence regarding the association between prenatal exposure to environmental fine particulate matter (PM2.5) and the occurrence of cryptorchidism. The objective of this study was to evaluate the potential correlation between prenatal exposure to PM2.5 and the likelihood of cryptorchidism developing in offspring. We performed a 1:1 case-control study, defining the cases as children diagnosed with cryptorchidism at the Children's Hospital Affiliated to Chongqing Medical University from 2013 to 2017, while the control group comprised children born in the corresponding years who did not have any birth defects, chromosomal abnormalities, and had only trauma-related treatments. Between 2012 and 2017, monthly averages of PM2.5, other pollutants (O3, PM10) and temperature were gathered based on the geographical coordinates of patients' residences. The study assessed the correlation between the two using multivariate logistic regression model, and sensitivity analysis was conducted to assess the stability of the model. We included a total of 2137 cases and 2137 matched controls from 2013 to 2017. Our findings revealed that there was a positive association between exposure to PM2.5 during the first 2 months of pregnancy and the occurrence of cryptorchidism. According to this study, the development of cryptorchidism appears to be associated with maternal exposure to PM2.5 during early pregnancy.

Prenatal exposure to synthetic chemicals in relation to HPA axis activity: A systematic review of the epidemiological literature

BACKGROUND

Pregnant people are widely exposed to numerous synthetic chemicals with known endocrine-disrupting properties (e.g., phthalates, phenols, per- and poly-fluoroalkyl substances (PFAS)). To date, most epidemiological research on how endocrine-disrupting chemicals (EDCs) disrupt hormone pathways has focused on estrogens, androgens, and thyroid hormones. Far less research has examined the impact of EDCs on the hypothalamic-pituitary-adrenal (HPA) axis, despite its central role in the physiologic stress response and metabolic function.

OBJECTIVE

To systematically review the epidemiological literature on prenatal synthetic EDC exposures in relation to HPA axis hormones (e.g., corticotropin-releasing hormone, adrenocorticotropic hormone, cortisol, cortisone) in pregnant people and their offspring.

METHODS

A literature search of PubMed, Scopus, and Embase was conducted. Primary research studies were selected for inclusion by two independent reviewers and risk of bias was assessed using the Office of Health Assessment and Translation guidelines established by the National Toxicology Program with customization for the specific research topic. Data were extracted from each study and included in a qualitative synthesis.

RESULTS

22 published studies met the inclusion criteria. Phthalates were the most prevalent EDC studied, followed by PFAS, phenols, and parabens, with fewer studies considering other synthetic chemicals. Offspring glucocorticoids were the most commonly considered outcome, followed by maternal glucocorticoids and placental corticotropin-releasing hormone. There was considerable heterogeneity in methods across studies, particularly in HPA axis outcome measures and matrices, making cross-study comparisons challenging. Numerous studies suggested disruption of HPA axis hormones and sex differences in association, but results varied considerably across studies and EDC classes.

CONCLUSIONS

The limited literature to date suggests the HPA axis may be vulnerable to disruption by synthetic EDCs. Carefully designed studies that prioritize biospecimen collection specific to HPA axis hormones are needed along with greater standardization of biospecimen collection and analysis protocols to facilitate cross-study comparisons and interpretation.

Maternal use of nitrosatable drugs during pregnancy and adult male reproductive health: A population-based cohort study

BACKGROUND

Prenatal exposures to xenobiotics during the masculinization programming window are suggested to impact male fecundity later in life. Frequently used nitrosatable drugs, such as penicillins and beta2-agonists, contain amines or amides that may form teratogenic compounds in reaction with nitrite.

OBJECTIVES

We explored whether maternal nitrosatable drug use during gestation was associated with biomarkers of male fecundity in adulthood; moreover, the potential modifiable effect of nitrate and vitamin intake was investigated.

METHOD

We performed a cohort study in the Fetal Programming of Semen Quality cohort that includes semen characteristics, reproductive hormone concentrations, and measures of testis size on 1058 young adult sons in the Danish National Birth Cohort. Information on maternal use of nitrosatable drugs was obtained from questionnaires and interviews around gestational weeks 11 and 16. A multivariable negative binomial regression model was used to obtain relative differences in biomarkers of male fecundity for those whose mothers used nitrosatable drugs compared to those without such maternal use. In sub-analyses, the exposure was categorized according to nitrosatable drug type: secondary amine, tertiary amine, or amide. We investigated dose dependency by examining the number of weeks with intake and explored potential effect modification by low versus high maternal nitrate and vitamin intake from diet and nitrate concentration in drinking water. We added selection weights and imputed values of missing covariates to limit the risk of selection bias.

RESULTS

In total, 19.6% of the study population were born of mothers with an intake of nitrosatable drugs at least once during early pregnancy. Relative differences in biomarkers related to male fecundity between exposed and unexposed participants were negligible. Imputation of missing covariates did not fundamentally alter the results. Furthermore, no sensitive subpopulations were detected.

CONCLUSIONS

The results suggest that maternal use of nitrosatable drugs does not have a harmful influence on the male fecundity of the offspring.

The development of the external genitals in female human embryos and foetuses. Part 1: Perineal thick skin, clitoris and labia

Concomitant with the rupture of the cloacal membrane in the 6th week of development, the intermediate layer of the perineal-skin epithelium thickens. We investigated its distribution and the development of the corresponding subcutaneous compartments in serial sections of female human embryos and foetuses and prepared 3D reconstructions to establish topographic relations. The thick-skin area becomes restricted to the outlets of the genital and intestinal tracts. The clitoris and labia majora become identifiable at ~7 weeks. The mesenchymal mass inside the clitoris soon divides into the glans and the cavernous bodies. The clitoral hood forms between 10 and 14 weeks as a fold of tissue that extends from proximal to distal over the glans. Due to the caudal bending of the clitoral shaft, the labia majora gradually cover the clitoris after ~14 weeks. The labia minora form at ~8 weeks from the ridges of thick-skin epithelium that flank the genital exit. They are continuous ventrolaterally with the clitoral hood and ventromedially with the apex of the cavernous body. Dorsally, their dense subcutaneous mesenchymal core extends to the anal canal. Between 8 and 14 weeks, the urethra lengthens axially, while the vaginal vestibule extends ventrally. In this period, the urethral plate of female embryos is mitotically active but does not increase in volume, which suggests that it contributes to vestibular growth. In conclusion, we observed a temporal correlation between the development of the thick-skin epithelium and that of the external genitals, with a distribution that is reminiscent of the dihydrotestosterone-sensitive skin.

Maslinic acid supplementation prevents di(2-ethylhexyl) phthalate-induced apoptosis via PRDX6 in peritubular myoid cells of Chinese forest musk deer

Chinese forest musk deer (FMD), an endangered species, have exhibited low reproductive rates even in captivity due to stress conditions. Investigation revealed the presence of di(2-ethylhexyl) phthalate (DEHP), an environmental endocrine disruptor, in the serum and skin of captive FMDs. Feeding FMDs with maslinic acid (MA) has been observed to alleviate the stress response and improve reproductive rates, although the precise molecular mechanisms remain unclear. Therefore, this study aims to investigate the molecular mechanisms underlying the alleviation of DEHP-induced oxidative stress and cell apoptosis in primary peritubular myoid cells (PMCs) through MA intake. Primary PMCs were isolated and exposed to DEHP in vitro. The results demonstrated that DEHP significantly suppressed antioxidant levels and promoted cell apoptosis in primary PMCs. Moreover, interfering with the expression of PRDX6 was found to induce excessive reactive oxygen species (ROS) production and cell apoptosis in primary PMCs. Supplementation with MA significantly upregulated the expression of PRDX6, thereby attenuating DEHP-induced oxidative stress and cell apoptosis in primary PMCs. These findings provide a theoretical foundation for mitigating stress levels and enhancing reproductive capacity of in captive FMDs.

Correlation of Hand Digit Length Ratio, Anogenital Distance, and Severity of Hypospadias among Prepubertal Boys

Aims

Antenatal androgen exposure has been suggested as a contributing factor in hypospadias etiology. This study aimed to investigate the correlation between anogenital distance (AGD), index finger-to-ring finger ratio (2D:4D ratio), and hypospadias severity in prepubertal boys, with the goal of exploring these parameters as potential markers of genital anomalies in utero.

Materials and Methods

A cross-sectional observational study was conducted on boys under 8 years old presenting to our outpatient department (April 2020-December 2022). Those with hypospadias were included in the study group, whereas those without hypospadias formed the comparator group. Confounding factors (age, weight, and height) were accounted for using multivariate linear regression analysis. AGD, 2D:4D ratio, and hypospadias severity were measured during clinical visits, with still images taken for precise measurements. Statistical analysis was performed using the Mann-Whitney U and student's t-tests (software: STATA Version 14).

Results

Data were collected for 100 cases of hypospadias (26 proximal and 74 distal) and 50 controls. There was no significant difference in mean age between groups (P = 0.90). AGD was slightly lower in cases (3.44 ± 1.13 cm) compared to controls (3.70 ± 1.43) (P = 0.88). 2D:4D ratios were marginally higher in cases compared to controls (P = 0.12 for both hands).

Conclusions

Although our study did not find significant associations between AGD and 2D:4D ratios with hypospadias severity, it offers insights into the role of prenatal androgen in genital development. The lack of significance underscores the need for region-specific research, suggesting AGD and 2D:4D ratio may not universally apply as hypospadias markers.

An in vitro testicular organoid model for the study of testis morphogenesis, somatic cell maturation, endocrine function, and toxicological assessment of endocrine disruptors

Male reproductive capacity has fallen considerably in recent decades; in addition, the incidence of testicular cancer has increased in many developed countries. The cause of this phenomenon is unknown, but environmental toxicants are considered a major contributing factor. To study potential reproductive toxicants, robust in vitro testis models are needed. We have recently established a porcine testis organoid system with a high resemblance to the architectures of innate testis tissue. Here, we further investigated the testis morphogenesis, cell maturation, and endocrine function of the testis organoids. We also challenged this system with abiraterone, a steroidogenic inhibitor, to validate its suitability as an in vitro platform for endocrine toxicology tests. Our results showed that the testis cells in the organoids reorganize into testis cordal structures, and the cordal relative areas increase in the organoids over time of culture. Moreover, the diameters and cell numbers per cross-section of the cordal structures increased over time. Interestingly, Sertoli cells in the organoids gradually underwent maturational changes by showing increased expression of androgen receptors, decreased expression of the anti-müllerian hormone, and formation of the blood-testis barrier. Next, we confirmed that the organoids respond to hormonal stimulation and release multiple sex hormones, including testosterone, estradiol, and progesterone. Finally, we showed that the production of testosterone and estradiol in this system can be inhibited in response to the steroidogenic inhibitor. Taken together, our organoid system provides a promising in vitro platform for male reproductive toxicology studies on testis morphogenesis, somatic cell maturation, and endocrine production.

Endocrine disruption and male reproductive disorders: unanswered questions

Maternal exposure to endocrine-disrupting chemicals (EDCs) in human pregnancy is widely considered as an important cause of adverse changes in male reproductive health due to impaired foetal androgen production/action. However, the epidemiological evidence supporting this view is equivocal, except for certain phthalates, notably diethyl hexyl phthalate (DEHP). Maternal phthalate exposure levels associated with adverse reproductive changes in epidemiological studies are several thousand-fold lower than those needed to suppress foetal androgen production in rats, and direct studies using human foetal testis tissue show no effect of high phthalate exposure on androgen production. This conundrum is unexplained and raises fundamental questions. Human DEHP exposure is predominantly via food with highest exposure associated with consumption of a Western style (unhealthy) diet. This diet is also associated with increased exposure to the most common EDCs, whether persistent (chlorinated or fluorinated chemicals) or non-persistent (phthalates, bisphenols) compounds, which are found at highest levels in fatty and processed foods. Consequently, epidemiological studies associating EDC exposure and male reproductive health disorders are confounded by potential dietary effects, and vice versa. A Western diet/lifestyle in young adulthood is also associated with low sperm counts. Disentangling EDC and dietary effects in epidemiological studies is challenging. In pregnancy, a Western diet, EDC exposure, and maternal living in proximity to industrial sites are all associated with impaired foetal growth/development due to placental dysfunction, which predisposes to congenital male reproductive disorders (cryptorchidism, hypospadias). While the latter are considered to reflect impaired foetal androgen production, effects resulting from foetal growth impairment (FGI) are likely indirect. As FGI has numerous life-long health consequences, and is affected by maternal lifestyle, research into the origins of male reproductive disorders should take more account of this. Additionally, potential effects on foetal growth/foetal testis from the increasing use of medications in pregnancy deserves more research attention.

Longitudinal trends and correlation between autism spectrum disorder prevalence and sperm quality parameters (2000-2024): a comprehensive statistical analysis

Introduction

Over the past few decades, there has been growing concern about the concurrent trends of increasing Autism Spectrum Disorder (ASD) prevalence and declining sperm quality. These trends represent significant public health challenges that warrant thorough investigation of their underlying causes and implications.

Objectives

The primary objectives of this study are to analyze trends in ASD prevalence and sperm quality parameters from 2000 to 2024, assess the statistical significance and effect size of these trends, explore potential correlations between ASD prevalence and sperm quality parameters, and identify significant predictors among sperm quality parameters that influence ASD prevalence.

Methods

This study employed a longitudinal approach using multiple regression, time series analysis, ANOVA, Principal Component Analysis (PCA), hierarchical clustering, logistic regression, and cross-correlation analysis. Data on ASD prevalence were sourced from the CDC Autism and Developmental Disabilities Monitoring Network, while sperm quality data were collected from various published studies.

Results

The findings reveal significant negative associations between ASD prevalence and sperm quality parameters such as sperm concentration and motility, suggesting that better sperm quality is linked to lower ASD rates. Conversely, parameters like sperm DNA fragmentation (SDF), volume of ejaculate, pH level, and semen viscosity show positive associations with ASD prevalence, indicating higher values in these parameters correlate with higher ASD rates.

Conclusion

The study highlights the importance of maintaining reproductive health to potentially mitigate ASD risk and calls for further research to elucidate the underlying mechanisms driving these trends. These findings support the hypothesis that reproductive health factors play a crucial role in ASD etiology and suggest potential biological markers for assessing ASD risk.

Cryptorchidism and testicular cancer in the dog: unresolved questions and challenges in translating insights from human studies†

Cryptorchidism, the failure of one or both testes to descend into the scrotum, and testicular cancer show a strong correlation in both dogs and humans. Yet, long-standing medical debates persist about whether the location of undescended testes directly causes testicular cancer in humans or if both conditions stem from a common origin. Although testicular cancer is a prevalent disease in dogs, even less is known about its cause and correlation with testicular descent in this species. This review investigates the relation between these two disorders in dogs, drawing insights from human studies, and examines key biomarkers identified thus far. In addition, it explores potential causal links, including the impact of temperature on maturing testicular cells and a potential shared genetic origin. Notably, this literature review reveals significant differences between men and dogs in reproductive development, histological and molecular features of testicular tumors, and the prevalence of specific tumor types, such as Sertoli cell tumors in cryptorchid dogs and germ cell tumors in humans. These disparities caution against using dogs as models for human testicular cancer research and underscore the limitations when drawing comparisons between species. The paper concludes by suggesting specific research initiatives to enhance our understanding of the complex interplay between cryptorchidism and testicular cancer in dogs.

Maternal intake of paracetamol during pregnancy and biomarkers of male fecundity in young adult sons

Paracetamol is suggested to have endocrine disrupting properties possibly affecting fetal programming of reproductive health that might lead to impaired semen quality and changes in reproductive hormones. In this longitudinal study, we included 1058 young adult men born 1998-2000 into the Danish National Birth Cohort with follow-up at 18-21 years of age. The exposure, maternal intake of paracetamol, was modelled in three ways: dichotomized, trimester-specific, and as duration of exposure categorized into: short (1-2 weeks), medium (3-9 weeks) or long duration (>9 weeks) vs. no intake. Outcomes included semen characteristics, self-measured testis volume, and reproductive hormone levels. We used negative binominal regression to estimate the percentage difference and 95% confidence interval (CI) for each outcome. In total, 547 (48%) sons were prenatally exposed to paracetamol due to maternal intake at least once. Maternal intake of paracetamol during pregnancy was not associated with any of the biomarkers in the dichotomized or trimester-specific exposure models. For duration of exposure, sons of mothers with long duration of maternal intake of paracetamol showed tendencies towards lower semen concentration (-14% [95% CI: -31%; 8%]), a higher proportion of nonprogressive and immotile spermatozoa (8% [95% CI: -4%; 21%]) and higher DNA Fragmentation Index (16% [95% CI: -1%; 36%]) compared to son of mothers with no intake. Maternal intake of paracetamol during pregnancy was not clearly associated with biomarkers of male fecundity in adult sons. However, it cannot be ruled out that long duration of maternal intake of paracetamol might be associated with impaired semen characteristics.

Maternal supplementation of alpha-lipoic acid ameliorates prenatal cytarabine-induced mutilation in reproductive development and function in F1 male adult rats

AIMS

Cytarabine (CYT), a prevalent anticancer drug for blood cancers, detrimentally affects male reproductive development and function. Alpha-lipoic acid (ALA), a universal antioxidant, offers defense against chemical-induced reproductive dysfunction. Our study sought to explore ALA's protective role against prenatal CYT-induced reproductive impairment in F1 male adult rats.

MAIN METHODS

Pregnant rats were divided into 5 groups and administered normal saline, ALA 200 mg/kg, CYT 12.5 mg/kg, CYT 25 mg/kg, and CYT 25 mg/kg + ALA 200 mg/ kg from gestational day 8 to 21. On postnatal day 73, F1 male rats were sacrificed, and general, oxidative, steroidogenic, spermatogenic, histological, and morphometrical parameters were evaluated.

KEY FINDINGS

Prenatal CYT caused dose-dependent reductions in body weight, testis, and accessory gland weights; elevated oxidative stress; delayed puberty onset; sperm anomalies (decreased count, motility, viability, seminal fructose; increased morphological anomalies); impeded steroidogenesis (lower testosterone, follicle-stimulating hormone, luteinizing hormone, 3β-Hydroxysteroid dehydrogenase(HSD), 17β-HSD, and elevated cholesterol); and testicular histopathological and morphometric disturbances. Maternal supplementation of ALA was found to alleviate all the CYT-induced reproductive disruptions.

SIGNIFICANCE

The present work accentuates the beneficial actions of ALA against CYT-induced impairment in reproductive development and functions by combating disruptions in oxidative balance, steroidogenesis, spermatogenesis, and testicular histological aberrations. However, future experimental and clinical studies are warranted to explore the molecular mechanisms involved in the ALA's protection against prenatal CYT-induced testicular injury.

Cohort profile: The Copenhagen Analgesic Study-The COPANA cohort

BACKGROUND

Development of the gonads during fetal life is complex and vital for adult reproductive health. Cell and animal studies have shown an alarming effect of mild analgesics on germ cells in both males and females. More than 50% of pregnant women use mild analgesics during pregnancy, which potentially could compromise the reproductive health of the next generation.

OBJECTIVES

We present a research protocol designed to evaluate the effect of prenatal exposure to mild analgesics and endocrine-disrupting chemicals on gonadal function in the offspring.

POPULATION

Healthy, singleton pregnant women and their partners.

DESIGN

The COPANA cohort is a prospective, observational pregnancy and birth cohort.

METHODS

Participants were enrolled during the first trimester of pregnancy. Information on the use of mild analgesics was collected retrospectively 3 months prior to pregnancy and prospectively every 2 weeks throughout the study. We collected extensive data on lifestyle and reproductive health. Biospecimens were collected in the first trimester (maternal and paternal urine- and blood samples), in the third trimester in conjunction with a study-specific ultrasound scan (maternal urine sample), and approximately 3 months post-partum during the infant minipuberty period (maternal and infant urine- and blood samples). A comprehensive evaluation of reproductive function in the infants during the minipuberty phase was performed, including an ultrasound scan of the testis or ovaries and uterus.

PRELIMINARY RESULTS

In total, 685 pregnant women and their partners were included between March 2020 and January 2022. A total of 589 infants (287 males) and their parents completed the follow-up during the minipuberty phase (December 2020-November 2022).

CONCLUSIONS

The Copenhagen Analgesic Study holds the potential to provide novel and comprehensive insights into the impact of early and late prenatal exposure to mild analgesics and other endocrine-disrupting chemicals on future reproductive function in the offspring.

Enhanced identification of endocrine disruptors through integration of science-based regulatory practices and innovative methodologies: The MERLON Project

The prevalence of hormone-related health issues caused by exposure to endocrine disrupting chemicals (EDCs) is a significant, and increasing, societal challenge. Declining fertility rates together with rising incidence rates of reproductive disorders and other endocrine-related diseases underscores the urgency in taking more action. Addressing the growing threat of EDCs in our environment demands robust and reliable test methods to assess a broad variety of endpoints relevant for endocrine disruption. EDCs also require effective regulatory frameworks, especially as the current move towards greater reliance on non-animal methods in chemical testing puts to test the current paradigm for EDC identification, which requires that an adverse effect is observed in an intact organism. Although great advances have been made in the field of predictive toxicology, disruption to the endocrine system and subsequent adverse health effects may prove particularly difficult to predict without traditional animal models. The MERLON project seeks to expedite progress by integrating multispecies molecular research, new approach methodologies (NAMs), human clinical epidemiology, and systems biology to furnish mechanistic insights and explore ways forward for NAM-based identification of EDCs. The focus is on sexual development and function, from foetal sex differentiation of the reproductive system through mini-puberty and puberty to sexual maturity. The project aims are geared towards closing existing knowledge gaps in understanding the effects of EDCs on human health to ultimately support effective regulation of EDCs in the European Union and beyond.

Anogenital distance in a cohort of 169 infant boys with uni- or bilateral cryptorchidism including 18 boys with vanishing testes

STUDY QUESTION

Do different boys with different types of cryptorchidism exhibit different anogenital distances (AGDs)?

SUMMARY ANSWER

Length of AGD seemed to differ in different groups of patients with cryptorchidism.

WHAT IS KNOWN ALREADY

AGD, which is used as an indicator of prenatal androgen action, tends to be shorter in boys with cryptorchidism compared to unaffected boys. Shorter AGDs have also been reported in boys with hypospadias, in men with poor semen quality, and in men with testicular cancer.

STUDY DESIGN, SIZE, DURATION

A prospective descriptive cohort study was performed using data from consecutively selected boys with cryptorchidism (n = 169) operated in a single center over a period of 3 years (September 2019 to October 2022).

PARTICIPANTS/MATERIALS, SETTING, METHODS

AGD was measured in 169 infant boys, at 3 to 26 months of age, during anesthesia with a vernier caliper measuring the distance from the anus to the base of the scrotum (AGDAS) and from the anus to the anterior base of the penis (AGDAP) in two body positions according to the methods by 'The Infant Development and the Environment Study' (TIDES) and 'Cambridge Baby Growth Study', resulting in four mean values per patient (TIDES AGDAS/AP and Cambridge AGDAS/AP). Normal values for AGD by age were set by our hospital Department of Growth and Reproduction based on a large cohort of healthy infant boys (n = 1940). Testicular biopsies were performed at orchidopexy as a clinical routine. The germ cell number (G/T) and type Ad spermatogonia number (AdS/T) per cross-sectional tubule of at least 100 and 250 tubules, respectively were measured and related to normal samples. Blood samples were obtained by venipuncture for measuring serum LH, FSH, and inhibin B. They were analyzed in our hospital Department of Growth and Reproduction where the normal reference was also established. Correlations between the four mean AGD measurements for each boy were evaluated by Spearman rank correlation analyses. The AGD measurement of every boy was transferred to the multiple of the median (MoM) of the normal AGD for age and named MoM AGD.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 104 boysoperated for unilateral, and 47 boys operated for bilateral, undescended testes, whereas 18 boys had vanished testis including one boy with bilateral vanished testes. Only 6% of cases with vanished testes had a MoM AGD higher than the normal median compared to 32% with undescended testes (P < 0.05). MoM AGD increased with the age at surgery for boys with vanished testis (Spearman r = 0.44), but not for boys with undescended testes (Spearman r = 0.14). Boys with bilateral cryptorchidism had longer AGDs and more often had hypogonadotropic hypogonadism than boys with unilateral cryptorchidism (P < 0.005) and (P < 0.000001).

LIMITATIONS, REASONS FOR CAUTION

Although being the largest published material of AGD measurements of infant boys with cryptorchidism, one limitation of this study covers the quite small number of patients in the different groups, which may decrease the statistical power. Another limitation involves the sparse normal reference material on G/T and AdS/T. Finally, there are currently no longitudinal studies evaluating AGD from birth to adulthood and evaluating childhood AGD in relation to fertility outcome. Our study is hypothesis generating and therefore the interpretation of the results should be regarded as exploratory rather than reaching definite conclusions.

WIDER IMPLICATIONS OF THE FINDINGS

The study findings are in agreement with literature as the total included group of boys with cryptorchidism exhibited shorter than normal AGDs. However, new insights were demonstrated. Boys with vanished testis had shorter AGDs compared to unaffected boys and to boys with undescended testes. This finding challenges the current concept of AGD being determined in 'the masculinization programming window' in Week 8 to 14 of gestation. Furthermore, boys with bilateral cryptorchidism had longer AGDs and more often had hypogonadotropic hypogonadism than boys with unilateral cryptorchidism, suggesting that the lack of fetal androgen in hypogonadotropic hypogonadism is not that significant.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used and no competing interests are declared.

TRIAL REGISTRATION NUMBER

The trial was not registered in an ICMJE-recognized trial registry.

Prenatal DEHP exposure induces lifelong testicular toxicity by continuously interfering with steroidogenic gene expression

Background

Epidemiologic studies suggested the association between prenatal di-(2-ethylhexyl) phthalate (DEHP) exposure and disorders of sex development (DSD), adult male disorders, and reproductive aging. Inhibiting testosterone synthesis by interfering with steroidogenic gene expression induces testicular toxicity, however, whether prenatal DEHP exposure induces testicular toxicity through this mechanism remains uncertain.

Methods

C57BL/6JGpt male mice underwent different doses (0, 100, 500, 1,000 mg/kg) of prenatal DEHP exposure during gestational day 10 to delivery day, the testicular toxicity (genital development, testosterone, semen quality, and morphology of testis tissue) in the neonatal, post-puberal and middle-aged stages was observed, and the steroidogenic gene (Lhcgr, Star, Cyp11a1, Cyp17a1, Hsd17b3, and Hsd3b2) expression was analyzed by quantitative polymerase chain reaction (qPCR) and Western blot (WB). The interference of steroidogenic gene expression in TM3 cells after mono-(2-ethylhexyl) phthalate (MEHP) exposure was also explored for verification.

Results

Prenatal DEHP exposure induced immediate testicular injury in the neonatal stage [reduced anogenital distance (AGD) and intratesticular testosterone], DSD in the post-puberal stage (poor genital development), and reproductive aging in the middle-aged stage (obesity, reduced testosterone and semen quality, and atrophic seminiferous tubules), especially in the high dose. Prenatal DEHP exposure continuously interfered with steroidogenic gene expression (Hsd3b2, Hsd17b3) in RNA and protein levels. MEHP inhibited testosterone synthesis of TM3 cells by interfering with steroidogenic gene expression (Hsd3b2, Hsd17b3) in RNA and protein levels.

Conclusions

Prenatal DEHP exposure induces lifelong testicular toxicity by continuously interfering with steroidogenic gene expression, thus indicating the association between prenatal exposure and DSD, adult male disorders, and reproductive aging.

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.

Crucial Roles of the Mesenchymal Androgen Receptor in Wolffian Duct Development

Wolffian duct (WD) maintenance and differentiation is predominantly driven by the androgen action, which is mediated by the androgen receptor (AR). It is well established that the mesenchyme indicates the fate and differentiation of epithelial cells. However, in vivo developmental requirement of mesenchymal AR in WD development is still undefined. By designing a mesenchyme-specific Ar knockout (ARcKO), we discovered that the loss of mesenchymal Ar led to the bilateral or unilateral degeneration of caudal WDs and cystic formation at the cranial WDs. Ex vivo culture of ARcKO WDs invariably resulted in bilateral defects, suggesting that some factor(s) originating from surrounding tissues in vivo might promote WD survival and growth even in the absence of mesenchymal Ar. Mechanistically, we found cell proliferation was significantly reduced in both epithelial and mesenchymal compartments; but cell apoptosis was not affected. Transcriptomic analysis by RNA sequencing of E14.5 mesonephroi revealed 131 differentially expressed genes. Multiple downregulated genes (Top2a, Wnt9b, Lama2, and Lamc2) were associated with morphological and cellular changes in ARcKO male embryos (ie, reduced cell proliferation and decreased number of epithelial cells). Mesenchymal differentiation into smooth muscle cells that are critical for morphogenesis was also impaired in ARcKO male embryos. Taken together, our results demonstrate the crucial roles of the mesenchymal AR in WD maintenance and morphogenesis in mice.

Racial disparities affect the association between gestational urinary phthalate mixtures and infant genital measures

Background

Phthalates are ubiquitous anti-androgenic endocrine disrupting chemicals found in personal care products, medications, and many plastics. Studies have shown a racial disparity in phthalates exposure among U.S. women, which may also impact fetal development.

Methods

We conducted a prospective cohort study of gestational exposure to a phthalates mixture in a racially-diverse population to determine their association with genital development. Mid-gestation (18-22 weeks) urine was collected from 152 women who self-identified as non-Hispanic Black and 158 women who self-identified as non-Hispanic White in Charleston, South Carolina between 2011 and 2014. We measured eight phthalate monoester metabolites in urine using liquid chromatography tandem-mass spectrometry. Mid-gestational penile dimensions were measured using ultrasound and anogenital distances were measured postnatally. We used Bayesian kernel machine regression to estimate the associations among the mixture of phthalate metabolites and mid-gestation penile dimensions and postnatal anogenital distance measures among singleton male (n = 179) and female (n = 131) infants, adjusted for urinary specific gravity, maternal age, body mass index, education level, cigarette smoking, and gestational age at enrollment or birth weight z-score.

Results

We found a stronger association between greater phthalates and decreased anopenile distance among infants born to women who self-identified as Black. Mono (2-ethylhexyl) phthalate (MEHP) was the driving mixture component among Black women, and monobutyl phthalate (MBP) and monoethyl phthalate (MEP) were drivers among White women. We also identified a non-linear association between phthalates and lesser ultrasound penile volume among women who self-identified as Black with monoisobutyl phthalate (MiBP) and MBP being most important. We also found an association between greater phthalates and shorter anoclitoral distance among infants born to women who self-identified as Black, with MEP and monobenzyl phthalate (MBzP) contributing most to this association.

Conclusion

Our results suggest a disparity in the association between gestational exposure to a mixture of phthalates and fetal genital development among women who self-identified as Black compared to White.

Associations of Exposure to Air Pollution during the Male Programming Window and Mini-Puberty with Anogenital Distance and Penile Width at Birth and at 1 Year of Age in the Multicenter U.S. TIDES Cohort

BACKGROUND

Ambient air pollution may be a developmental endocrine disruptor. In animal models, gestational and perinatal exposure to diesel exhaust and concentrated particulate matter alters anogenital distance (AGD), a marker of prenatal androgen activity, in both sexes. Little is known in humans.

OBJECTIVES

We examined exposure to fine particulate matter (PM 2.5 ) and nitrogen dioxide (NO 2 ) in relation to human AGD at birth and at 1 year of age, focusing on exposures during critical windows of reproductive development: the male programming window (MPW; gestational weeks 8-14) and mini-puberty (postnatal months 1-3).

METHODS

The Infant Development and Environment Study (TIDES) recruited first trimester pregnant women (n = 687 ) at four U.S. sites (Minneapolis, Minnesota; Rochester, New York; San Francisco, California; and Seattle, Washington) from 2010 to 2012. We measured anus to clitoris (AGD-AC) and anus to fourchette (AGD-AF) in female infants at birth; in males, we measured anus to penis (AGD-AP), anus to scrotum (AGD-AS), and penile width at birth and at 1 year of age. Using advanced spatiotemporal models, we estimated maternal exposure to PM 2.5 and NO 2 in the MPW and mini-puberty. Covariate-adjusted, sex-stratified linear regression models examined associations between PM 2.5 and NO 2 and AGD.

RESULTS

In males, a 1 - μ g / m 3 increase in PM 2.5 exposure during the MPW was associated with shorter AGD at birth, but a longer AGD at 1 year of age (e.g., birth AGD-AP: β = - 0.35 mm ; 95% CI: - 0.62 , - 0.07 ; AGD-AS: β = 0.37 mm ; 95% CI: 0.02, 0.73). Mini-pubertal PM 2.5 exposure was also associated with shorter male AGD-AP (β = - 0.50 mm ; 95% CI: - 0.89 , - 0.11 ) at 1 year of age. Although not associated with male AGD measures, 1 -ppb increases in NO 2 exposure during the MPW (β = - 0.07 mm ; 95% CI: - 0.02 , - 0.12 ) and mini-puberty (β = - 0.04 mm ; 95% CI: - 0.08 , 0.01) were both associated with smaller penile width at 1 year of age. Results were similar in multipollutant models, where we also observed that in females AGD-AC was inversely associated with PM 2.5 exposure, but positively associated with NO 2 exposure.

DISCUSSION

PM 2.5 and NO 2 exposures during critical pre- and postnatal windows may disrupt reproductive development. More work is needed to confirm these novel results and clarify mechanisms. https://doi.org/10.1289/EHP12627.

The estimated effect of season and vitamin D in the first trimester on pubertal timing in girls and boys: a cohort study and an instrumental variable analysis

BACKGROUND

Season of birth has been associated with age at menarche. Maternal vitamin D levels in pregnancy may explain this effect. We investigated whether the season of first trimester or maternal 25-hydroxyvitamin D3 [25(OH)D3] levels were associated with pubertal timing in children.

METHODS

We conducted a follow-up study of 15 819 children born in 2000-03 from the Puberty Cohort, nested in the Danish National Birth Cohort (DNBC). Mean differences in attaining numerous pubertal markers, including a combined estimate for the average age at attaining all pubertal markers, were estimated for low (November-April) relative to high (May-October) sunshine exposure season in the first trimester using multivariable interval-censored regression models. Moreover, we conducted a two-sample instrumental variable analysis using season as an instrument for maternal first-trimester 25(OH)D3 plasma levels obtained from a non-overlapping subset (n = 827) in the DNBC.

RESULTS

For the combined estimate, girls and boys of mothers who had their first trimester during November-April had earlier pubertal timing than girls and boys of mothers whose first trimester occurred during May-October: -1.0 months (95% CI: -1.7 to -0.3) and -0.7 months (95% CI: -1.4 to -0.1), respectively. In the instrumental variable analysis, girls and boys also had earlier pubertal timing: respectively, -1.3 months (95% CI: -2.1 to -0.4) and -1.0 months (95% CI: -1.8 to -0.2) per SD (22 nmol/L) decrease in 25(OH)D3.

CONCLUSIONS

Both first pregnancy trimester during November-April and lower 25(OH)D3 were associated with earlier pubertal timing in girls and boys.

Prenatal DEHP Exposure Induces Premature Testicular Aging by Promoting Leydig Cell Senescence through the MAPK Signaling Pathways

Previous studies show that prenatal di-(2-ethylhexyl) phthalate (DEHP) exposure induces premature testicular aging. However, the evidence is weak, and the underlying mechanisms remain unclear. p38/extracellular signal-regulated kinase (ERK)/c-Jun NH(2)-terminal kinase (JNK) MAPK pathways participate in aging. Leydig cell (LC) senescence results in testicular aging. Whether prenatal DEHP exposure induces premature testicular aging by promoting LC senescence warrants further study. Here, male mice undergo prenatal exposure to 500 mg per kg per day DEHP, and TM3 LCs are treated with 200 µm mono (2-ethylhexyl) phthalate (MEHP). MAPK pathways, testicular toxicity, and senescent phenotypes (β-gal activity, p21, p16, and cell cycle) of male mice and LCs are explored. Prenatal DEHP exposure induces premature testicular aging in middle-aged mice (poor genital development, reduced testosterone synthesis, poor semen quality, increased β-gal activity, and upregulated expression of p21 and p16). MEHP induces LCs senescence (cell cycle arrest, increased β-gal activity, and upregulated expression of p21). p38 and JNK pathways are activated, and the ERK pathway is inactivated. In conclusion, prenatal DEHP exposure induces premature testicular aging by promoting LC senescence through MAPK signaling pathways.

Low placental weight may be involved in the etiology of congenital cryptorchidism in neonatal boys

INTRODUCTION

Several factors have been reported to be associated with the etiology of cryptorchidism; however, clear evidence regarding the risk factors for cryptorchidism is elusive. In the present study, we evaluated the clinical characteristics of cryptorchidism using the common neonatal intensive-care unit (NICU) database of the National Hospital Organization and explored one of possible factors associated with the development of cryptorchidism.

METHODS

A total of 7882 male neonates were included in this study. We separated them into two groups: those without cryptorchidism (n = 7852) and those with cryptorchidism (n = 30) at the time of discharge from the NICU. Cryptorchidism was defined as a condition in which the testis was located out of the scrotum on the route of descent at the time of NICU discharge. The associations between cryptorchidism and the maternal, placental, and neonatal information were analyzed. Analyses were performed statistically to compare nominal variables between the groups using Fisher's direct establishment calculation method and logistic regression analyses.

RESULTS

Univariate analyses showed the placental weight <10% tile (odds ratio 3.31, 95% confidence interval [CI] 1.18-8.64), birth height <-2 standard deviations (SD) (odds ratio 3.65, 95% CI 0.92-10.6), birth weight <-2SD (odds ratio 4.06, 95% CI 1.55-9.51), and small for gestational age (odds ratio 3.82, 95% CI 1.46-8.97) were significantly associated with the development of cryptorchidism. Multivariate analyses showed that placental weight <10th percentile (odds ratio 2.86, 95% CI 1.11-7.44) was significantly associated with the development of cryptorchidism.

DISCUSSION

Although, this study population was limited to infants admitted to the ICU, the data indicated a possible association between low placental weight and the development of cryptorchidism in neonatal boys.

Maternal vitamin D levels and male reproductive health: a population-based follow-up study

Maternal vitamin D levels during pregnancy may be important for reproductive health in male offspring by regulating cell proliferation and differentiation during development. We conducted a follow-up study of 827 young men from the Fetal Programming of Semen Quality (FEPOS) cohort, nested in the Danish National Birth Cohort to investigate if maternal vitamin D levels were associated with measures of reproductive health in adult sons. These included semen characteristics, testes volume, and reproductive hormone levels and were analysed according to maternal vitamin D (25(OH)D3) levels during pregnancy. In addition, an instrumental variable analysis using seasonality in sun exposure as an instrument for maternal vitamin D levels was conducted. We found that sons of mothers with vitamin D levels < 25 nmol/L had 11% (95% CI - 19 to - 2) lower testes volume and a 1.4 (95% CI 1.0 to 1.9) times higher risk of having low testes volume (< 15 mL), in addition to 20% (95% CI - 40 to 9) lower total sperm count and a 1.6 (95% CI 0.9 to 2.9) times higher risk of having a low total sperm count (< 39 million) compared with sons of mothers with vitamin D levels > 75 nmol/L. Continuous models, spline plots and an instrumental variable analysis supported these findings. Low maternal vitamin D levels were associated with lower testes volume and lower total sperm count with indications of dose-dependency. Maternal vitamin D level above 75 nmol/L during pregnancy may be beneficial for testes function in adult sons.

Testicular toxicity in mice exposed to terephthalic acid in utero and during lactation

Terephthalic acid (TPA) is a worldwide aromatic compound widely used to manufacture resins and the raw material for the polymerization reaction with ethylene glycol to produce polyethylene terephthalate, known as PET. The use of TPA extends to the synthesis of phthalates, plasticizers used in various industrialized products such as toys and cosmetics. The present study aimed to evaluate the testicular toxicity of terephthalic acid on male mice exposed in utero and during lactation to TPA in different developmental windows. The animals were treated intragastric with TPA at stock dispersal dosages corresponding to 0.0014 g/ml and 0.56 g/ml of TPA in 0.5% v/v carboxymethylcellulose as well as the control dose, composed solely of dispersion of carboxymethylcellulose (0.5% v/v). Four experimental windows were established: group I-treatment in utero, in the fetal period (gestational day-GD 10.5-18.5), with euthanasia at GD 18.5; group II-treatment in utero, in the fetal period (GD 10.5-18.5) and the lactational period (postnatal day (PND-15)), with euthanasia at 15 days; group III-treatment in utero in the fetal period (DG 10.5-18.5) with euthanasia at 70 days (age of sexual maturity, PND 70); group IV-treatment in utero, in the fetal period (GD 10.5-18.5) and the lactational period (PND-15), with euthanasia at 70 days (PND70). The results indicate that TPA changes the reproductive parameters (testicular weight, GI, penis size, and anogenital index) only at the dose of 0.56 g/ml in the fetal period. Data on the volumetric ratio of the testis elements show that the dispersion with the highest concentration of TPA significantly altered the blood vessel/capillary, lymphatic vessel, and connective tissue percentages. Only at the dose of 0.56 g/ml TPA was it effective in decreasing the Leydig and Sertoli cell numbers of the euthanized animals at GD 18.5. In group II, TPA increased the diameter and lumen of seminiferous tubules, which indicates that TPA accelerated the maturation process of Sertoli cells without changing the number and the nuclear volume of these cells. The Sertoli and Leydig cell numbers of the 70-day animals exposed to TPA in the gestational and lactational period were similar to the control. Therefore, the present study is the first in the literature to show that TPA presents a testicular toxicity during fetal (DG18.5) and postnatal life (PND15), without repercussion in adulthood (70 days).

Urinary concentration of phthalates and bisphenol A during minipuberty is associated with reproductive hormone concentrations in infant boys

BACKGROUND

The transient postnatal activation of the hypothalamic-pituitary-gonadal hormone axis is termed minipuberty and considered an important developmental period, which is highly sensitive to endocrine disruption. Here, we explore exposure-outcome associations during minipuberty between concentrations of potentially endocrine disrupting chemicals (EDCs) in urine of infant boys and their serum reproductive hormone concentrations.

METHODS

In total, 36 boys participating in the COPENHAGEN Minipuberty Study had data available for both urine biomarkers of target endocrine disrupting chemicals and reproductive hormones in serum from samples collected on the same day. Serum concentrations of reproductive hormones were measured by immunoassays or by LC-MS/MS. Urinary concentrations of metabolites of 39 non-persisting chemicals, including phthalates and phenolic compounds, were measured by LC-MS/MS. Nineteen chemicals had concentrations above the limit of detection in ≥50% of children and were included in data analysis. Associations of urinary phthalate metabolite and phenol concentrations (in tertiles) with hormone outcomes (age- and sex-specific SD-scores) were analysed by linear regression. Primarily, we focused on the EU regulated phthalates; butylbenzyl phthalate (BBzP), di-iso-butyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and di-(2-ethylhexyl) phthalate (DEHP) as well as bisphenol A (BPA). Urinary metabolites of DiBP, DnBP and DEHP were summed and expressed as ∑DiBPm, ∑DnBPm and ∑DEHPm.

RESULTS

Compared to boys in the lowest ∑DnBPm tertile, urinary concentration of ∑DnBPm was associated with concurrent higher luteinizing hormone (LH) and anti-Müllerian hormone (AMH) SD-scores as well as lower testosterone/LH ratio in boys in the middle ∑DnBPm tertile (estimates (CI 95%) 0.79 (0.04; 1.54), 0.91 (0.13; 1.68), and -0.88 (-1.58;-0.19), respectively). Further, higher insulin-like peptide 3 (INSL3) SD-scores and lower DHEAS SD-score in boys in the highest ∑DnBPm tertile (0.91 (0.12; 1.70) and -0.85 (-1.51;-0.18), respectively) were observed. In addition, boys in the middle and highest ∑DEHPm tertile had higher LH (1.07 (0.35; 1.79) and 0.71 (-0.01; 1.43), respectively) and in the highest ∑DEHPm tertile also higher AMH (0.85 (0.10; 1.61)) concentration SD-scores, respectively. Boys in the highest BPA tertile had significantly higher AMH and lower DHEAS concentration compared to boys in the lowest BPA tertile (1.28 (0.54; 2.02) and -0.73 (-1.45; -0.01)), respectively.

DISCUSSION

Our findings indicate that exposure to chemicals with known or suspected endocrine disrupting potential, especially the EU-regulated DnBP, DEHP and BPA, may modify male reproductive hormone concentrations in infant boys suggesting that minipuberty is a critical window sensitive to endocrine disruption.

Single-cell transcriptomic dissection of the toxic impact of di(2-ethylhexyl) phthalate on immature testicular development at the neonatal stage

Di(2-ethylhexyl) phthalate (DEHP) early exposure leads to immature testicular injury, and we aimed to utilize single-cell RNA (scRNA) sequencing to comprehensively assess the toxic effect of DEHP on testicular development. Therefore, we gavaged pregnant C57BL/6 mice with 750 mg/kg body weight DEHP from gestational day 13.5 to delivery and performed scRNA sequencing of neonatal testes at postnatal day 5.5. The results revealed the gene expression dynamics in testicular cells. DEHP disrupted the developmental trajectory of germ cells and the balance between the self-renewal and differentiation of spermatogonial stem cells. Additionally, DEHP caused an abnormal developmental trajectory, cytoskeletal damage and cell cycle arrest in Sertoli cells; disrupted the metabolism of testosterone in Leydig cells; and disturbed the developmental trajectory in peritubular myoid cells. Elevated oxidative stress and excessive apoptosis mediated by p53 were observed in almost all testicular cells. The intercellular interactions among four cell types were altered, and biological processes related to glial cell line-derived neurotrophic factor (GDNF), transforming growth factor-β (TGF-β), NOTCH, platelet-derived growth factor (PDGF) and WNT signaling pathways were enriched after DEHP treatment. These findings systematically describe the damaging effects of DEHP on the immature testes and provide substantial novel insights into the reproductive toxicity of DEHP.

Cocktails of NSAIDs and 17α Ethinylestradiol at Environmentally Relevant Doses in Drinking Water Alter Puberty Onset in Mice Intergenerationally

Non-steroidal anti-inflammatory drugs (NSAIDs) and 17α-ethinyl-estradiol (EE2) are among the most relevant endocrine-disrupting pharmaceuticals found in the environment, particularly in surface and drinking water due to their incomplete removal via wastewater treatment plants. Exposure of pregnant mice to NSAID therapeutic doses during the sex determination period has a negative impact on gonadal development and fertility in adults; however, the effects of their chronic exposure at lower doses are unknown. In this study, we investigated the impact of chronic exposure to a mixture containing ibuprofen, 2hydroxy-ibuprofen, diclofenac, and EE2 at two environmentally relevant doses (added to the drinking water from fetal life until puberty) on the reproductive tract in F1 exposed mice and their F2 offspring. In F1 animals, exposure delayed male puberty and accelerated female puberty. In post-pubertal F1 testes and ovaries, differentiation/maturation of the different gonad cell types was altered, and some of these modifications were observed also in the non-exposed F2 generation. Transcriptomic analysis of post-pubertal testes and ovaries of F1 (exposed) and F2 animals revealed significant changes in gene expression profiles and enriched pathways, particularly the inflammasome, metabolism and extracellular matrix pathways, compared with controls (non-exposed). This suggested that exposure to these drug cocktails has an intergenerational impact. The identified Adverse Outcome Pathway (AOP) networks for NSAIDs and EE2, at doses that are relevant to everyday human exposure, will improve the AOP network of the human reproductive system development concerning endocrine disruptor chemicals. It may serve to identify other putative endocrine disruptors for mammalian species based on the expression of biomarkers.

Maternal intake of folate and folic acid during pregnancy and markers of male fecundity: A population-based cohort study

BACKGROUND

Poor male fecundity is of concern, and a prenatal origin has been proposed. Folate, a methyl donor involved in DNA methylation, is essential for normal fetal development by regulating gene expression during different periods of fetal development. Thus, prenatal exposure to low maternal folate intake might have a programing function of the developing reproductive organs.

OBJECTIVES

To examine the association between maternal intake of folate from diet and folic acid from supplements during pregnancy and markers of fecundity in young men.

MATERIALS AND METHODS

We conducted a follow-up study using a Danish mother-son cohort of 787 young men born 1998-2000. Percentage differences in semen characteristics, testes volume, and reproductive hormone levels were analyzed according to total folate calculated as dietary folate equivalents from diet and supplements in midpregnancy, using multivariable negative binomial regression models. Total folate was analyzed in quintiles, continuous per standard deviation decrease (SD: 318 μg/day) and as restricted cubic splines.

RESULTS

Low maternal intake of total folate was associated with lower total sperm count (-5% (95% confidence intervals [CI]: -11%; 2%)), a lower proportion of non-progressive and immotile spermatozoa (-5% [95% CI: -8%; -3%]), and lower testes volume (-4% [95% CI: -6%; -2%]) per SD decrease in total folate intake. Spline plots supported these findings.

DISCUSSION

The finding of a lower proportion of non-progressive and immotile spermatozoa, and hence a higher proportion of motile spermatozoa, in men of mothers with a lower intake of total folate in midpregnancy was surprising and may be a chance finding.

CONCLUSION

Lower maternal intake of total folate in midpregnancy was associated with lower sperm count and lower testes volume, however, also with a lower proportion of non-progressive and immotile spermatozoa in adult men. Whether this actually affects the ability to obtain a pregnancy warrants further investigation.

Maternal fever during pregnancy and male offspring reproductive health: A longitudinal cohort study in young Danish males

BACKGROUND

Maternal fever during pregnancy has been associated with an increased risk of genital malformations, but the implication for long-term reproductive health in the offspring is unknown.

OBJECTIVES

To investigate associations between timing, duration, and temperature of fetal exposure to maternal fever and sons' semen quality, testicular volume, and levels of reproductive hormones in early adulthood. Further, to examine whether concurrent use of antipyretics and/or antibiotics modified the effect.

MATERIALS AND METHODS

We used the Fetal Programming of Semen Quality cohort consisting of men born to women enrolled in the Danish National Birth Cohort. Self-reported information on maternal fever was collected twice during pregnancy (median 16 and 31 pregnancy weeks) and categorized as any fever during pregnancy, fever during early pregnancy (weeks 1-15), and fever exclusively during late pregnancy (weeks 16-42). Semen quality and concentrations of reproductive hormones were measured at a clinical examination at the age of 18.9 years. We used negative binomial regression to examine the associations, adjusting for maternal age at birth, maternal smoking, family occupational status, and precision variables related to semen quality and hormonal levels, for example, abstinence time.

RESULTS

986 men were included in the study, of which 23% had mothers reporting at least one episode of fever. We found no strong indications of associations between maternal fever during pregnancy and male reproductive health in young men. Concurrent use of antipyretics and antibiotics did not modify the association.

DISCUSSION

Strengths include the large sample size, prospectively collected data, and the adjustment for maternal factors during pregnancy and important precision variables. A limitation is the crude self-reported information on maternal fever.

CONCLUSION

We found no evidence to support that timing, duration, or temperature of maternal fever during pregnancy has a long-term impact on semen characteristics, testicular volume, or level of reproductive hormones in male offspring.

Reproductive toxicity of maternal exposure to di(2-ethylhexyl)phthalate and butyl paraben (alone or in association) on both male and female Wistar offspring

Parabens and phthalates are commonly found as contaminants in human fluids and are able to provoke reproductive toxicity, being considered endocrine disruptors. To evaluate the effects of phthalate and paraben, alone or in combination, on reproductive development of the offspring, female pregnant Wistar rats were allocated in six experimental groups: Three control groups (gavage [CG], subcutaneous [CS], and gavage + subcutaneous) received corn oil as vehicle, and the remaining groups were exposed to di(2-ethylhexyl)phthalate (DEHP) (500 mg/kg, gavage), butyl paraben (BP) (100 mg/kg, subcutaneously), or MIX (DEHP + BP), from Gestational Day 12 until Postnatal Day (PND) 21. The following parameters were assessed on the offspring: anogenital distance and weight at PND 1, nipple counting at PND 13, puberty onset, estrous cycle, weights of reproductive and detoxifying organs, histological evaluation of reproductive organs, and sperm evaluations (counts, morphology, and motility). Female pups from MIX group presented reduced body weight at PND 1, lower AGD, and decreased endometrium thickness. Male animals showed decreased body weight at PND 1 and lower number of Sertoli cells on DEHP and MIX groups, MIX group revealed increase of abnormal seminiferous tubules, DEHP animals presented delayed preputial separation and higher percentage of immotile sperms, and BP males presented diminished number of Leydig cells. In conclusion, the male offspring was more susceptible to DEHP toxicity; even when mixed to paraben, the main negative effects observed seem to be due to antiandrogenic phthalate action. On the other hand, DEHP seems to be necessary to improve the effects of BP on reducing estrogen-dependent and increasing androgen-dependent events.

Applying the adverse outcome pathway concept for assessing non-monotonic dose responses: biphasic effect of bis(2-ethylhexyl) phthalate (DEHP) on testosterone levels

Male reproduction is one of the primary health endpoints identified in rodent studies for some phthalates, such as DEHP (Bis(2-ethylhexyl) phthalate), DBP (Dibutyl phthalate), and BBP (Benzyl butyl phthalate). The reduction in testosterone level was used as an intermediate key event for grouping some phthalates and to establish a reference point for risk assessment. Phthalates, and specifically DEHP, are one of the chemicals for which the greatest number of non-monotonic dose responses (NMDRs) are observed. These NMDRs cover different endpoints and situations, often including testosterone levels. The presence of NMDR has been the subject of some debate within the area of chemical risk assessment, which is traditionally anchored around driving health-based guidance values for apical endpoints that typically follow a clear monotonic dose-response. The consequence of NMDR for chemical risk assessment has recently received considerable attention amongst regulatory agencies, which confirmed its relevance particularly for receptor-mediated effects. The present review explores the relationship between DEHP exposure and testosterone levels, investigating the biological plausibility of the observed NMDRs. The Adverse Outcome Pathway (AOP) concept is applied to integrate NMDRs into Key Event Relationships (KERs) for exploring a mechanistic understanding of initial key events and possibly associated reproductive and non-reproductive adverse outcomes.

Prenatal exposure to organophosphate esters is associated with decreased anogenital distance in offspring

BACKGROUND

Evidence from in vitro and rodent studies suggests that organophosphate esters (OPEs) may disrupt sex steroid hormone homeostasis, but no human studies, to date, have examined the effects of in utero exposure to OPEs on offspring reproductive development.

OBJECTIVE

Anogenital distance (AGD) is a sensitive biomarker of fetal hormonal milieu and has been used to assess reproductive toxicity. We evaluated the longitudinal effects of prenatal exposure to OPEs on the AGD of offspring from birth to 4 years.

METHODS

Based on Shanghai-Minhang Birth Cohort Study, pregnant women provided urine samples at a gestational age of 12-16 weeks, which were analyzed for eight OPE metabolites. AGD was measured in offspring at birth and 0.5, 1, and 4 years of age. We used generalized estimating equations (GEE) and Bayesian kernel machine regression (BKMR) models to estimate the associations of prenatal exposure to individual OPE metabolites and OPE mixtures with AGD stratified by sex.

RESULTS

A total of 733 mother-infant pairs were analyzed. Prenatal exposure to diphenyl phosphate and bis-(2-ethylhexyl) phosphate was associated with decreased AGD in boys in GEE models. Bis-(1-chloro-2-propyl) phosphate (BCIPP) showed a similar but marginally significant effect. Prenatal exposure to most OPE metabolites was associated with decreased AGD in girls, with the most profound association observed for bis (2-butoxyethyl) phosphate (BBOEP) and alkyl-OPEs. The OPE mixture was also inversely associated with AGD in both sexes. The single-exposure effects of BKMR models were largely consistent with those observed in the GEE models. In addition, alkyl-OPEs, particularly BBOEP, contributed the most to the decreased AGD in girls, while BCIPP contributed the most to the decreased AGD in boys.

CONCLUSIONS

This study provides the first human evidence that prenatal exposure to OPEs is associated with decreased AGD in offspring. The magnitude of these effects may vary depending on the structure of OPEs.

Maternal Exposure to Per- and Polyfluoroalkyl Substances (PFAS) and Male Reproductive Function in Young Adulthood: Combined Exposure to Seven PFAS

BACKGROUND

Concerns remain about the human reproductive toxicity of the widespread per- and polyfluoroalkyl substances (PFAS) during early stages of development.

OBJECTIVES

We examined associations between maternal plasma PFAS levels during early pregnancy and male offspring reproductive function in adulthood.

METHODS

The study included 864 young men (age range:18.9-21.2 y) from the Fetal Programming of Semen Quality (FEPOS) cohort established between 2017 and 2019. Plasma samples from their mothers, primarily from the first trimester, were retrieved from the Danish National Biobank and levels of 15 PFAS were measured. Seven PFAS had detectable levels above the limit of detection in >80% of the samples and were included in analyses. Semen quality, testicular volume, and levels of reproductive hormones and PFAS were assessed in the young men. We used weighted quantile sum (WQS) regression to estimate the associations between combined exposure to maternal PFAS and reproductive function, and negative binomial regression to estimate the associations of single substances, while adjusting for a range of a priori-defined fetal and postnatal risk factors.

RESULTS

By a 1-unit increase in the WQS index, combined maternal PFAS exposure was associated with lower sperm concentration (-8%; 95% CI: -16%, -1%), total sperm count (-10%; 95% CI: -17%, -2%), and a higher proportion of nonprogressive and immotile sperm (5%; 95% CI: 1%, 8%) in the young men. Different PFAS contributed to the associations with varying strengths; however, perfluoroheptanoic acid was identified as the main contributor in the analyses of all three outcomes despite the low concentration. We saw no clear association between exposure to maternal PFAS and testicular volume or reproductive hormones.

DISCUSSION

In a sample of young men from the general Danish population, we observed consistent inverse associations between exposure to maternal PFAS and semen quality. The study needs to be replicated in other populations, taking combined exposure, as well as emerging short-chain PFAS, into consideration. https://doi.org/10.1289/EHP10285.

Emerging organoid models to study the epididymis in male reproductive toxicology

The importance of the epididymis on sperm maturation and consequently male fertility has been well documented. The pseudostratified epithelium of the epididymis is comprised of multiple cell types, including principal cells, which are the most abundant, and basal cells. The role of basal cells has been unclear and has been a source of discussion in the literature. However, the recent demonstration that these cells are multipotent or adult stem cells has opened new areas of research in epididymal biology. One such avenue is to understand the regulation of these stem cells, and to exploit their properties to develop tools for toxicological studies to elucidate the effects of chemicals on cell differentiation and epididymal function in vitro. Studies in both rat and mouse have shown that purified single epididymal basal cells cultured under 3D conditions can proliferate and differentiate to form organoids, or mini organs. Furthermore, these epididymal basal stem cells can self-renew and differentiate into other epididymal cell types. It is known that during epididymal development, basal cells are derived from undifferentiated columnar cells, which have been reported to share common properties to stem cells. Like basal cells, these undifferentiated columnar cells can also form organoids under 3D culture conditions and can differentiate into basal, principal and clear cells. Organoids derived from either basal cells or columnar cells offer unique models for toxicology studies and represent an exciting and emerging approach to understand the epididymis.

Increasing incidence and spatial hotspots of hospitalized endometriosis in France from 2011 to 2017

Endometriosis is a female hormone-dependent disease, possibly related to endocrine disruptor exposure. We aimed to monitor this disease nationwide in France and analyze spatial trends at a fine scale to explore possible environmental contributing risk factors. We conducted a retrospective national descriptive study from 2011 to 2017 in females aged 10 years old and over, using comprehensive hospital discharge data. Cases were identified using ICD-10 N80 codes and were localized at their municipality of residence. We defined incident cases as the first hospital stay of patients, without a stay in at least the previous 5 years. We performed statistical analyses according to age and type of endometriosis, and we modeled the temporal, spatial and spatiotemporal trends. We identified 207,462 incident cases of all-type hospitalized endometriosis (83,112 for non-adenomyosis cases). The crude incidence rate for the study period was 9.85/10,000 person-years (3.95/10,000 for non-adenomyosis cases). From 2011 to 2017, the risk of all-type endometriosis increased by 8.5% (95% CI: 3.9; 13.4) (by 3.6% (95% CI: 0.6; 6.8) for non-adenomyosis cases). The risk was geographically heterogeneous, with 20 high-risk hotspots, showing similar results for non-adenomyosis cases. Shifting practice patterns, improved awareness and healthcare disparities interlinked with environmental risk factors could explain these trends.

Azole Fungicides and Their Endocrine Disrupting Properties: Perspectives on Sex Hormone-Dependent Reproductive Development

Azoles are antifungal agents used in both agriculture and medicine. They typically target the CYP51 enzyme in fungi and, by so doing, disrupt cell membrane integrity. However, azoles can also target various CYP enzymes in mammals, including humans, which can disrupt hormone synthesis and signaling. For instance, several azoles can inhibit enzymes of the steroidogenic pathway and disrupt steroid hormone biosynthesis. This is of particular concern during pregnancy, since sex hormones are integral to reproductive development. In other words, exposure to azole fungicides during fetal life can potentially lead to reproductive disease in the offspring. In addition, some azoles can act as androgen receptor antagonists, which can further add to the disrupting potential following exposure. When used as pharmaceuticals, systemic concentrations of the azole compounds can become significant as combatting fungal infections can be very challenging and require prolonged exposure to high doses. Although most medicinal azoles are tightly regulated and used as prescription drugs after consultations with medical professionals, some are sold as over-the-counter drugs. In this review, we discuss various azole fungicides known to disrupt steroid sex hormone biosynthesis or action with a focus on what potential consequences exposure during pregnancy can have on the life-long reproductive health of the offspring.

Fetal exposure to maternal cigarette smoking and male reproductive function in young adulthood

Maternal smoking during pregnancy constitutes a potential, major risk factor for adult male reproductive function. In the hitherto largest longitudinal cohort, we examined biomarkers of reproductive function according to maternal smoking during the first trimester and investigated whether associations were mitigated by smoking cessation prior to the fetal masculinization programming window. Associations between exposure to maternal smoking and semen characteristics, testicular volume and reproductive hormones were assessed among 984 young men from the Fetal Programming of Semen Quality (FEPOS) cohort. Maternal smoking was assessed through interview data and measured plasma cotinine levels during pregnancy. We applied negative binomial, logistic and linear regression models to estimate differences in outcomes according to levels of maternal smoking. Sons of light smokers (≤ 10 cigarettes/day) had a 19% (95% CI - 29%, - 6%) lower sperm concentration and a 24% (95% CI - 35%, - 11%) lower total sperm count than sons of non-smokers. These estimates were 38% (95% CI - 52%, - 22%) and 33% (95% CI - 51%, - 8%), respectively, for sons of heavy smokers (> 10 cigarettes/day). The latter group also had a 25% (95% CI 1%, 54%) higher follitropin level. Similarly, sons exposed to maternal cotinine levels of  > 10 ng/mL had lower sperm concentration and total sperm count. Smoking cessation prior to gestational week seven was not associated with a higher reproductive capacity. We observed substantial and consistent exposure-response associations, providing strong support for the hypothesis that maternal smoking impairs male reproductive function. This association persisted regardless of smoking cessation in early pregnancy.

Maternal supplementation of α-lipoic acid attenuates prenatal cytarabine exposure-induced oxidative stress, steroidogenesis suppression and testicular damage in F1 male rat fetus

Background

Cytarabine (Ara-C) is an anticancer drug, which is considered as the mainstay in the treatment of hematological malignancies, known to cause various teratogenic effects. Alpha-lipoic acid (ALA) is a natural antioxidant and its supplementation proved to improve pregnancy outcomes in several pathological conditions. We aimed at exploring the benefits of maternal supplementation of ALA against in-utero Ara-C exposure-induced testicular toxicity in rat fetuses.

Methods

Pregnant rats (dams) received normal saline (control group), ALA 200 mg/kg (ALA group), Ara-C 12.5 mg/kg (Ara-C 12.5 group), Ara-C 25 mg/kg (Ara-C 25 group), and Ara-C 25 mg/kg + ALA 200 mg/kg (protection group) from gestational day (GD)8 to GD21. Ara-C and ALA were administered via the intraperitoneal and oral routes, respectively. The day of parturition was considered as postnatal day (PND)1. On PND1, all the live male pups were collected. The maternal parameters evaluated include (a) food intake, (b) bodyweight, and (c) oxidative stress (OS) markers. The fetal parameters evaluated include (a) bodyweight, (b) anogenital distances (AGD), (c) testicular weight (d) testicular testosterone levels (e) testicular histopathology, and (f) morphometrical parameters.

Results

A significant and dose-dependent decrease in maternal food intake, weight gain, and an increase in oxidative stress (OS) were observed in the pregnant rats of the Ara-C groups as compared to pregnant rats of the control group. Further, a significant and dose-dependent (a) reduction in bodyweight, AGD, testicular weight, and testosterone levels, (b) increase in OS, and (c) structural and morphometrical anomalies in fetal testes were observed in fetuses of Ara-C groups as compared to fetuses of the control rats. These deleterious effects observed in the Ara-C groups were found to be diminished in the pregnant rats and fetuses of the Protection group as compared to the pregnant rats and fetuses of the Ara-C 25 group.

Conclusions

From the results of this study, we conclude that the maternal supplementation of ALA may ameliorate the Ara-C exposure-induced impairment in prenatal development and function of the testes in the rat fetuses. However, future experimental and clinical studies are warranted to explore the possible mechanisms involved in the protection offered by maternal supplementation of ALA against Ara-C induced testicular toxicity.

Graphical Abstract

The Fate of Leydig Cells in Men with Spermatogenic Failure

The steroidogenic cells in the testicle, Leydig cells, located in the interstitial compartment, play a vital role in male reproductive tract development, maintenance of proper spermatogenesis, and overall male reproductive function. Therefore, their dysfunction can lead to all sorts of testicular pathologies. Spermatogenesis failure, manifested as azoospermia, is often associated with defective Leydig cell activity. Spermatogenic failure is the most severe form of male infertility, caused by disorders of the testicular parenchyma or testicular hormone imbalance. This review covers current progress in knowledge on Leydig cells origin, structure, and function, and focuses on recent advances in understanding how Leydig cells contribute to the impairment of spermatogenesis.

Using Experimental Models to Decipher the Effects of Acetaminophen and NSAIDs on Reproductive Development and Health

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin (acetylsalicylic acid), diclofenac and ibuprofen (IBU), and analgesic drugs, such as acetaminophen (APAP, or paracetamol), are widely used to treat inflammation and pain. APAP and IBU are over-the-counter drugs and are among the most commonly taken drugs in the first trimester of pregnancy, even in combination. Furthermore, these drugs and their metabolites are released in the environment, and can be frequently detected in wastewater, surface water, and importantly in drinking water. Although their environmental concentrations are much lower than the therapeutics doses, this suggests an uncontrolled low-dose exposure of the general population, including pregnant women and young children, two particularly at risk populations. Epidemiological studies show that exposure to these molecules in the first and second trimester of gestation can favor genital malformations in new-born boys. To investigate the cellular, molecular and mechanistic effects of exposure to these molecules, ex vivo studies with human or rodent gonadal explants and in vivo experiments in rodents have been performed in the past years. This review recapitulates recent data obtained in rodent models after in utero or postnatal exposure to these drugs. The first part of this review discusses the mechanisms by which NSAIDs and analgesics may impair gonadal development and maturation, puberty development, sex hormone production, maturation and function of adult organs, and ultimately fertility in the exposed animals and their offspring. Like other endocrine disruptors, NSAIDs and APAP interfere with endocrine gland function and may have inter/transgenerational adverse effects. Particularly, they may target germ cells, resulting in reduced quality of male and female gametes, and decreased fertility of exposed individuals and their descendants. Then, this review discusses the effects of exposure to a single drug (APAP, aspirin, or IBU) or to combinations of drugs during early embryogenesis, and the consequences on postnatal gonadal development and adult reproductive health. Altogether, these data may increase medical and public awareness about these reproductive health concerns, particularly in women of childbearing age, pregnant women, and parents of young children.

Eicosanoid Biosynthesis in Male Reproductive Development: Effects of Perinatal Exposure to NSAIDs and Analgesic Drugs

Increasing rates of infertility associated with declining sperm counts and quality, as well as increasing rates of testicular cancer are contemporary issues in the United States and abroad. These conditions are part of the Testicular Dysgenesis Syndrome, which includes a variety of male reproductive disorders hypothesized to share a common origin based on disrupted testicular development during fetal and neonatal stages of life. Male reproductive development is a highly regulated and complex process that relies on an intricate coordination between germ, Leydig, and Sertoli cells as well as other supporting cell types, to ensure proper spermatogenesis, testicular immune privilege, and endocrine function. The eicosanoid system has been reported to be involved in the regulation of fetal and neonatal germ cell development as well as overall testicular homeostasis. Moreover, non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics with abilities to block eicosanoid synthesis by targeting either or both isoforms of cyclooxygenase enzymes, have been found to adversely affect male reproductive development. This review will explore the current body of knowledge on the involvement of the eicosanoid system in male reproductive development, as well as discuss adverse effects of NSAIDs and analgesic drugs administered perinatally, focusing on toxicities reported in the testis and on major testicular cell types. Rodent and epidemiological studies will be corroborated by findings in invertebrate models for a comprehensive report of the state of the field, and to add to our understanding of the potential long-term effects of NSAID and analgesic drug administration in infants.

Effects of endocrine disrupting chemicals on gonad development: Mechanistic insights from fish and mammals

Over the past century, evidence has emerged that endocrine disrupting chemicals (EDCs) have an impact on reproductive health. An increased frequency of reproductive disorders has been observed worldwide in both wildlife and humans that is correlated with accidental exposures to EDCs and their increased production. Epidemiological and experimental studies have highlighted the consequences of early exposures and the existence of key windows of sensitivity during development. Such early in life exposures can have an immediate impact on gonadal and reproductive tract development, as well as on long-term reproductive health in both males and females. Traditionally, EDCs were thought to exert their effects by modifying the endocrine pathways controlling reproduction. Advances in knowledge of the mechanisms regulating sex determination, differentiation and gonadal development in fish and rodents have led to a better understanding of the molecular mechanisms underlying the effects of early exposure to EDCs on reproduction. In this manuscript, we review the key developmental stages sensitive to EDCs and the state of knowledge on the mechanisms by which model EDCs affect these processes, based on the roadmap of gonad development specific to fish and mammals.

Endocrine disruptor chemicals. A review of their effects on male reproduction and antioxidants as a strategy to counter it

Endocrine disruptor chemicals are exogenous molecules that generate adverse effects on human health by destabilizing the homeostasis of endocrine system and affecting directly human reproductive system by inhibiting or activating oestrogenic or androgenic receptors. Endocrine disruptor chemicals generate transgenerational epigenetic problems, besides being associated with male infertility. Epidemiological data indicate that the increase in reproductive problems in males in the last 50 years is correlated with the increase of endocrine disrupting chemicals in the environment, being associated with a decrease in semen quality and direct effects on spermatozoa, such as alterations in motility, viability and acrosomal reaction, due to the generation of oxidative stress, and have also been postulated as a possible cause of testicular dysgenesis syndrome. Diverse antioxidants, such as C and E vitamins, N-acetylcysteine, selenium and natural vegetable extracts, are among the alternatives under study to counter the effects of endocrine disruptor chemicals. In some cases, the usage of them has given positive results and the opposite in others. In this review, we summarize the recent information about the effects of endocrine disruptor chemicals on male reproduction, on sperm cells, and the results of studies that have tested antioxidants as a strategy to diminish their harmful effects.

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.

Environmental Impacts on Male Reproductive Development: Lessons from Experimental Models

BACKGROUND

Male reproductive development in mammals can be divided into a gonadal formation phase followed by a hormone-driven differentiation phase. Failure of these processes may result in Differences in Sex Development (DSD), which may include abnormalities of the male reproductive tract, including cryptorchidism, hypospadias, infertility, and testicular germ cell cancer (TGCC). These disorders are also considered to be part of a testicular dysgenesis syndrome (TDS) in males. Whilst DSDs are considered to result primarily from genetic abnormalities, the development of TDS disorders is frequently associated with environmental factors.

SUMMARY

In this review, we will discuss the development of the male reproductive system in relation to DSD and TDS. We will also describe the experimental systems, including studies involving animals and human tissues or cells that can be used to investigate the role of environmental factors in inducing male reproductive disorders. We will discuss recent studies investigating the impact of environmental chemicals (e.g., phthalates and bisphenols), lifestyle factors (e.g., smoking) and pharmaceuticals (e.g., analgesics) on foetal testis development. Finally, we will describe the evidence, involving experimental and epidemiologic approaches, for a role of environmental factors in the development of specific male reproductive disorders, including cryptorchidism, hypospadias, and TGCC.

KEY MESSAGES

Environmental exposures can impact the development and function of the male reproductive system in humans. Epidemiology studies and experimental approaches using human tissues are important to translate findings from animal studies and account for species differences in response to environmental exposures.