Male Reproductive Disorders and Fertility Trends: Influences of Environment and Genetic Susceptibility

Maternal exposure to DDT, DDE, and pyrethroid insecticides for malaria vector control and hypospadias in the VHEMBE birth cohort study, Limpopo, South Africa

Hypospadias is the ectopic opening of the urethra on the penis or scrotum. Exposure to estrogenic and/or anti-androgenic chemicals in utero may play an etiologic role. DDT and the pyrethroids cypermethrin and deltamethrin, are used to control malaria. DDT is estrogenic and its breakdown product DDE is anti-androgenic; cypermethrin and deltamethrin can also disrupt androgen pathways. We examined the relationship between maternal exposure to these insecticides during pregnancy and hypospadias among boys participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) in Limpopo Province, South Africa. We measured peripartum levels of p,p'-DDT and p,p'-DDE in maternal serum and urinary pyrethroid metabolites. We conducted urogenital examination on 359 one-year-old boys. A total of 291 (81.0 %) had phimosis, which prevented full urogenital examination, leaving a final sample of 68 boys for determination of the presence of hypospadias. Diagnosis was based on concordance of two independent physicians. We identified hypospadias in 23 of the 68 boys (34 %). Maternal urinary concentrations of cis-DCCA and trans-DCCA metabolites of cypermethrin and other pyrethroids, were associated with an increased risk for hypospadias, but the other metabolite 3-PBA was not (adjusted relative risk per 10-fold increase = 1.58, 95 % CI 1.07-2.34; 1.61, 95 % CI 1.09-2.36; and 1.48, 95 % CI 0.78-2.78, respectively). No associations were found between p,p'-DDT, p,p'-DDE, 3-PBA or cis-DBCA and hypospadias. We observed a high prevalence of hypospadias among boys without phymosis. Boys with higher prenatal exposure to pyrethroid insecticides were at higher risk of hypospadias. Our findings may have global implications given that pyrethroid insecticides are widely used for malaria control, in agriculture and for home use.

The inhibition of CFTR in the descended testis of SD rats with unilateral cryptorchidism induced by di-(2-ethylhexyl) phthalate (DEHP)

Di-(2-ethylhexyl) phthalate (DEHP) is a kind of environmental endocrine disruptors (EEDs), which has been confirmed to cause serious consequences, such as cryptorchidism. Patients with unilateral cryptorchidism still had oligospermia or infertility even if they received orchidopexy before puberty. Testicular dysgenesis syndrome (TDS) attributes this kind of problems to the abnormal testicular development during the embryonic period, and considers that the environmental exposure factors during pregnancy play a major role. Therefore, for unilateral cryptorchidism, even if one testicle has dropped to scrotum, it may be exposed to these substances and cause damage. Cystic fibrosis transmembrane conduction regulator (CFTR) is very important for the maturation of male reproductive system. Previously, cryptorchidism was thought to cause abnormal expression of heat sensitive protein CFTR in testis, but the expression of CFTR in healthy side (descended side) testis was not clear. In this study, we established SD rats with unilateral cryptorchidism by exposure to DEHP (500 mg/kg/day) during pregnancy, and detected the expression of CFTR and downstream signal NF-κB/COX-2/PGE2 in bilateral testis. Finally, we found that the expression of CFTR and downstream signal NF-κB/COX-2/PGE2 in the undescended testis was significantly abnormal, but the expression of them in the descended testis was also abnormal to some extent. Therefore, we speculate that in addition to high temperature will affect the expression of CFTR, there may be other factors that cause abnormal expression of CFTR induced by DEHP, and lead to abnormal male reproductive function eventually, but the specific mechanism needs to be further studied.

Urinary concentrations of polycyclic aromatic hydrocarbon and phthalate metabolite mixtures in relation to semen quality among men attending an infertility clinic

Previous studies have reported that exposure to phthalates and polycyclic aromatic hydrocarbons (PAHs) is individually associated with altered semen quality, but no human studies have evaluated their joint effects of exposure mixtures, a more real-world scenario. We aimed to explore urinary metabolite mixtures of phthalates and PAHs in associations with semen quality. Repeated spot-urine samples gathered from 695 men attending a fertility clinic were analyzed for urinary metabolites of eight phthalates and ten monohydroxylated-PAHs (OH-PAHs). Principal component analysis (PCA)-multivariable linear regression (MLR) model, quantile g-computation (qg-comp), and Bayesian kernel machine regression (BKMR) were applied to estimate the associations of urinary mixtures of phthalate and OH-PAH metabolites with semen quality. The overall effects of urinary mixtures of phthalate and PAH metabolites on semen quality were not statistically significant. However, hydroxynaphthalene (OHNa) factor identified from PCA was monotonically associated with decreased total sperm count and sperm concentration, whereas di(2-ethylhexyl) phthalate (DEHP) factor was non-monotonically related to increased progressive sperm motility and total sperm motility. Qg-comp and BKMR models confirmed these findings and identified 2-OHNa and 2-OHFlu as the primary negative contributors, whereas MEOHP and MEHP as the primary positive contributors. Our findings suggest that exposure to mixtures of naphthalene and DEHP is associated with altered semen quality. The finding is warranted to confirm in further well-designed epidemiological studies.

[Impact of lifestyle and environmental factors on male reproductive health]

The identification of potential environmental hazards is of clinical relevance for the diagnosis of male infertility. Knowledge about these factors will improve prevention of fertility disorders. Apart from drugs or factors related to lifestyle such as alcohol and tobacco smoke, various environmental and occupational agents, both chemical and physical, may impair male reproduction. Reproductive toxicity may evolve at the hypothalamic-pituitary, testicular, or posttesticular level; endpoints comprise deterioration of spermatogenesis and sperm function as well as endocrine disorders and sexual dysfunction. However, due to the complex regulation of the male reproductive system, information regarding single exogenous factors and their mechanisms of action in humans is limited. This is also due to the fact that extrapolation of results obtained from experimental animal or in vitro studies remains difficult. Nevertheless, the assessment of relevant exposures to reproductive toxicants should be carefully evaluated during diagnostic procedures of andrological patients.

Identification of a window of androgen sensitivity for somatic cell function in human fetal testis cultured ex vivo

BACKGROUND

Reduced androgen action during early fetal development has been suggested as the origin of reproductive disorders comprised within the testicular dysgenesis syndrome (TDS). This hypothesis has been supported by studies in rats demonstrating that normal male development and adult reproductive function depend on sufficient androgen exposure during a sensitive fetal period, called the masculinization programming window (MPW). The main aim of this study was therefore to examine the effects of manipulating androgen production during different timepoints during early human fetal testis development to identify the existence and timing of a possible window of androgen sensitivity resembling the MPW in rats.

METHODS

The effects of experimentally reduced androgen exposure during different periods of human fetal testis development and function were examined using an established and validated human ex vivo tissue culture model. The androgen production was reduced by treatment with ketoconazole and validated by treatment with flutamide which blocks the androgen receptor. Testicular hormone production ex vivo was measured by liquid chromatography-tandem mass spectrometry or ELISA assays, and selected protein markers were assessed by immunohistochemistry.

RESULTS

Ketoconazole reduced androgen production in testes from gestational weeks (GW) 7-21, which were subsequently divided into four age groups: GW 7-10, 10-12, 12-16 and 16-21. Additionally, reduced secretion of testicular hormones INSL3, AMH and Inhibin B was observed, but only in the age groups GW 7-10 and 10-12, while a decrease in the total density of germ cells and OCT4⁺ gonocytes was found in the GW 7-10 age group. Flutamide treatment in specimens aged GW 7-12 did not alter androgen production, but the secretion of INSL3, AMH and Inhibin B was reduced, and a reduced number of pre-spermatogonia was observed.

CONCLUSIONS

This study showed that reduced androgen action during early development affects the function and density of several cell types in the human fetal testis, with similar effects observed after ketoconazole and flutamide treatment. The effects were only observed within the GW 7-14 period-thereby indicating the presence of a window of androgen sensitivity in the human fetal testis.

Whole Exome Sequencing and In Silico Analysis of Human Sertoli in Patients with Non-Obstructive Azoospermia

Non-obstructive azoospermia (NOA) is a serious cause of male infertility. The Sertoli cell responds to androgens and takes on roles supporting spermatogenesis, which may cause infertility. This work aims to enhance the genetic diagnosis of NOA via the discovery of new and hub genes implicated in human NOA and to better assess the odds of successful sperm extraction according to the individual’s genotype. Whole exome sequencing (WES) was done on three NOA patients to find key genes involved in NOA. We evaluated genome-wide transcripts (about 50,000 transcripts) by microarray between the Sertoli of non-obstructive azoospermia and normal cells. The microarray analysis of three human cases with different non-obstructive azoospermia revealed that 32 genes were upregulated, and the expressions of 113 genes were downregulated versus the normal case. For this purpose, Enrich Shiny GO, STRING, and Cytoscape online evaluations were applied to predict the functional and molecular interactions of proteins and then recognize the master pathways. The functional enrichment analysis demonstrated that the biological process (BP) terms “inositol lipid-mediated signaling”, “positive regulation of transcription by RNA polymerase II”, and “positive regulation of DNA-templated transcription” significantly changed in upregulated differentially expressed genes (DEGs). The BP investigation of downregulated DEGs highlighted “mitotic cytokinesis”, “regulation of protein-containing complex assembly”, “cytoskeleton-dependent cytokinesis”, and the “peptide metabolic process”. Overrepresented molecular function (MF) terms in upregulated DEGs included “ubiquitin-specific protease binding”, “protease binding”, “phosphatidylinositol trisphosphate phosphatase activity”, and “clathrin light chain binding”. Interestingly, the MF analysis of the downregulated DEGs revealed overexpression in “ATPase inhibitor activity”, “glutathione transferase activity”, and “ATPase regulator activity”. Our findings suggest that these genes and their interacting hub proteins could help determine the pathophysiologies of germ cell abnormalities and infertility.

Exposure to automobile exhaust-derived PM2.5 induces spermatogenesis dysfunction by damaging UPRmt of prepubertal rats

Automobile exhaust-derived particulate matter 2.5 (PM2.5) can cause spermatogenic cell damage, potentially resulting in male infertility. This study uses male prepubertal Sprague Dawley (SD) rats to explore the molecular mechanisms by which automobile exhaust-derived PM2.5 causes spermatogenic cell damage and induces spermatogenesis dysfunction during sexual maturity by disrupting the mitochondrial unfolded protein response (UPR^mt) in spermatogenic cells. Male prepubertal SD rats were randomly divided into four groups: control (intratracheal instillation of normal saline), low-dose PM2.5 (5 mg/kg), high-dose PM2.5 (10 mg/kg), and PM2.5 10 mg/kg +Vit (100 mg/kg of vitamin C and 50 mg/kg of vitamin E). The rats were treated for four weeks, with five consecutive treatment days and two non-treatment days, followed by cohabitation. Testicular and epididymal tissues were harvested for analysis. The mitochondria in spermatogenic cells were observed under an electron microscope. UPR^mt-, oxidative stress-, and apoptosis-related markers in spermatogenic cells were examined. Spermatogenic cell numbers and conception rate declined significantly with increasing PM2.5 dose, with their mitochondria becoming vacuolated, swollen, and degenerated to varying degrees. The apoptosis of spermatogenic cells was abnormally enhanced in PM2.5 exposed groups compared to the control group. Spermatogenic cell numbers of conception rate gradually recovered, mitochondrial damage in spermatogenic cells was alleviated, and spermatogenic cell apoptosis was significantly reduced after vitamin intervention. In addition, protein levels of superoxide dismutase 1 (Sod1), nuclear factor erythroid 2-related factor 2 (Nrf2), and B-cell lymphoma 2 (Bcl-2) were significantly lower, while those of Bcl2-associated X apoptosis regulator (Bax), cleaved caspase 3 (Casp3), and cytochrome c (Cyt-c) and malondialdehyde (MDA) levels were significantly higher in the high-dose PM2.5 group than in the control group. The levels of UPR^mt-related proteins C/EBP homologous protein (Chop), heat shock protein 60 (Hsp60), and activating transcription factors 4 (Atf4) and 5 (Atf5) were higher in the low-dose PM2.5 group, lower in the high-dose PM2.5 group, and gradually recovered in PM2.5 10 mg/kg +Vit group. Our results show that exposure to automobile exhaust-derived PM2.5 induces oxidative stress responses, leads to post-sexual maturation UPR^mt dysfunction and mitochondrial impairment, and abnormally enhances spermatogenic cell apoptosis in prepubertal rats, resulting in male infertility.

Taxifolin increased semen quality of Duroc boars by improving gut microbes and blood metabolites

Taxifolin (TAX), as a natural flavonoid, has been widely focused on due to its strong anti-oxidation, anti-inflammation, anti-virus, and even anti-tumor activity. However, the effect of TAX on semen quality was unknown. The purpose of this study was to analyze the beneficial influences of adding feed additive TAX to boar semen in terms of its quality and potential mechanisms. We discovered that TAX increased sperm motility significantly in Duroc boars by the elevation of the protein levels such as ZAG, PKA, CatSper, and p-ERK for sperm quality. TAX increased the blood concentration of testosterone derivatives, antioxidants such as melatonin and betaine, unsaturated fatty acids such as DHA, and beneficial amino acids such as proline. Conversely, TAX decreased 10 different kinds of bile acids in the plasma. Moreover, TAX increased “beneficial” microbes such as Intestinimonas, Coprococcus, Butyrivibrio, and Clostridium_XlVa at the Genus level. However, TAX reduced the “harmful” intestinal bacteria such as Prevotella, Howardella, Mogibacterium, and Enterococcus. There was a very close correlation between fecal microbes, plasma metabolites, and semen parameters by the spearman correlation analysis. Therefore, the data suggest that TAX increases the semen quality of Duroc boars by benefiting the gut microbes and blood metabolites. It is supposed that TAX could be used as a kind of feed additive to increase the semen quality of boars to enhance production performance.

Systematic review of associations of polychlorinated biphenyl (PCB) exposure with declining semen quality in support of the derivation of reference doses for mixture risk assessments

BACKGROUND

Mixture risk assessments require reference doses for common health endpoints of all the chemicals to be considered together. In support of a mixture risk assessment for male reproductive health, we conducted a systematic review of the literature on associations between exposures to Polychlorinated Biphenyls (PCBs) and declines in semen quality. PCBs can act as Aryl-hydrocarbon Receptor (AhR)-agonists and Androgen Receptor (AR)-antagonists, both mechanisms which can affect sperm parameters. PCBs and other AR-antagonists can produce additive combination effects. Based on these observations our objective was to systematically gather data from animal and human studies to derive a reference dose for declines in semen quality for individual PCB.

METHODS

We systematically reviewed and evaluated the evidence in human epidemiological and experimental animal studies on associations between PCBs and deteriorations in semen quality. Human data and findings from animal studies with PCB mixtures were considered as supporting evidence. Information for individual congeners from animal studies was required for inclusion in mixture risk assessment. Using a robust confidence rating approach, we identified suitable studies to derive reference doses for individual PCB congeners.

RESULTS

Evaluation of human epidemiological studies revealed several reports of adverse effects on sperm parameters linked to PCB exposures, although some studies reported improved semen quality. Our review of experimental animal studies found that treatments with PCBs affected semen quality, in most cases adversely. We found robust evidence that PCB-118 and -169 were linked to declines in semen quality. Evidence for adverse effects of PCB-126, -132, -149, and -153 was moderate, whereas for PCB-77 it was slight and for PCB-180 indeterminate. Using widely accepted risk assessment procedures, we estimated reference dose values of 0.0029 µg/kg/day for PCB-118 and 0.00533 µg/kg/day for PCB-169. In addition, we derived values for PCB-126: 0.000073 µg/kg/day, PCB-132: 0.0228 µg/kg/day, PCB-149: 0.656 µg/kg/day, and PCB-153: 0.0058 µg/kg/day.

CONCLUSIONS

We found robust evidence for links between PCB exposure and deteriorations in semen quality, and derived reference doses for a set of congeners. We intend to use these values in combination with congener-specific exposure data in a mixture risk assessment for declines in semen quality, involving several other antiandrogenic chemicals.

Phthalate-induced testosterone/androgen receptor pathway disorder on spermatogenesis and antagonism of lycopene

Male infertility is an attracting growing concern owing to decline in sperm quality of men worldwide. Phthalates, in particular to di (2-ethylhexyl) phthalate (DEHP) or its main metabolite mono-2-ethylhexyl phthalate (MEHP), affect male reproductive development and function, which mainly accounts for reduction in male fertility. Lycopene (LYC) is a natural antioxidant agent that has been recognized as a possible therapeutic option for treating male infertility. Testosterone (T)/androgen receptor (AR) signaling pathway is involved in maintaining spermatogenesis and male fertility. How DEHP causes spermatogenesis disturbance and whether LYC could prevent DEHP-induced male reproductive toxicity have remained unclear. Using in vivo and vitro approaches, we demonstrated that DEHP caused T biosynthesis reduction in Leydig cell and secretory function disorder in Sertoli cell, and thereby resulted in spermatogenic impairment. Results also showed that MEHP caused mitochondrial damage and oxidative damage, which imposes a serious threat to the progress of spermatogenesis. However, LYC supplement reversed these changes. Mechanistically, DEHP contributed to male infertility via perturbing T/AR signaling pathway during spermatogenesis. Overall, our study reveals critical role for T/AR signal transduction in male fertility and provides promising insights into the protective role of LYC in phthalate-induced male reproductive disorders.

Developmental origins of adult diseases

The occurrence and mechanisms of developmental adult diseases have gradually attracted attention in recent years. Exposure of gametes and embryos to adverse environments, especially during plastic development, can alter the expression of certain tissue-specific genes, leading to increased susceptibility to certain diseases in adulthood, such as diabetes, cardiovascular disease, neuropsychiatric, and reproductive system diseases, etc. The occurrence of chronic disease in adulthood is partly due to genetic factors, and the remaining risk is partly due to environmental-dependent epigenetic information alteration, including DNA methylation, histone modifications, and noncoding RNAs. Changes in this epigenetic information potentially damage our health, which has also been supported by numerous epidemiological and animal studies in recent years. Environmental factors functionally affect embryo development through epimutation, transmitting diseases to offspring and even later generations. This review mainly elaborated on the concept of developmental origins of adult diseases, and revealed the epigenetic mechanisms underlying these events, discussed the theoretical basis for the prevention and treatment of related diseases.

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.

Estimation of Serum and Seminal Plasma Levels of Glactin-1 in Non-Obstructive Azoospermia Cases and Their Correlations with the Rate of Sperm Retrieval: A Comparative Prospective Study

BACKGROUND

Remarkably, the current study is one of the first to deploy galectin-1 (Gal-1) in determining the degree of impairment of spermatogenesis among cases with non-obstructive azoospermia (NOA) as well as utilizing it as a biomarker to predict the rate of sperm retrieval in these patients. The purpose of the study was to evaluate the seminal plasma and serum levels of Gal-1 in NOA patients as well as their correlations with Johnsen's tubular biopsy scoring (JTBS).

METHODS

The current case control study included totally 48 patients with NOA whose ages ranged from 24 to 46 years old and 50 age matched healthy controls. Gal-1 levels were measured in both seminal plasma and serum of all subjects by the enzyme-linked immunosorbent assay (ELISA).

RESULTS

A significant negative correlation between seminal plasma levels of Gal-1 and JTBS was detected (r= -0.281, p=0.048) in the NOA cases. Interestingly, the receiver operating characteristic (ROC) curve had demonstrated that the cutoff value of seminal plasma levels of Gal-1 in determining azoospermia was >0.735 ng/ml and the area under the curve (AUC) was 0.858. The sensitivity, specificity, positive predictive, and negative predictive values for seminal plasma levels of Gal-1 were 76, 92, 90.5, and 79.3, respectively. In addition, sensitivity, specificity, positive predictive, and negative predictive values for serum levels of Gal-1 were 38, 66, 52.8, and 51.6, respectively.

CONCLUSION

Seminal plasma levels of Gal-1 are higher in NOA men versus healthy controls. Interestingly, negative correlation of seminal plasma levels of Gal-1 with JTBS was determined. Thus, it can be used as a good predictor for NOA cases.

Androgen Receptor Gene CAG Repeat Length Varies and Affects Semen Quality in an Ethnic-Specific Fashion in Young Men from Russia

Male infertility is a multi-factorial and multi-genetic disorder, and the prevalence of male infertility in the world is estimated at 5–35%. The search for the causes of male infertility allowed for identifying a number of genetic factors including a single X-linked gene of the androgen receptor (AR), and some of its alleles are assumed to negatively affect male fertility. Our aim was (1) to study the variability of the length of CAG repeats of the AR gene and possible associations in the AR CAG genetic variants with semen quality and reproductive hormone levels in a population-based cohort of men and (2) to estimate distributions of AR CAG repeat alleles and associations with semen parameters in different ethnic subgroups. The cohort of 1324 young male volunteers of different ethnicities (median age 23.0 years) was recruited from the general population of five cities of the Russian Federation, regardless of their fertility status. Semen quality (sperm concentration, motility and morphology), reproductive hormone levels (testosterone, estradiol, LH, FSH and inhibin B) and trinucleotide (CAG) n repeat polymorphism in exon 1 of the AR gene were evaluated. The semen samples were analyzed according to the WHO laboratory manual (WHO, 2010), serum hormones were measured by enzyme immunoassay, and the AR CAG repeat length was analyzed by direct sequencing of leukocyte DNA. The median AR CAG repeat length in men of our multi-ethnic population was 23 (range 6–39). In the entire study population, a significant difference (p ≤ 0.05) was found in the frequency distribution and the mean values for the CAG repeat length between the groups with normal (23.2 ± 3.3) and impaired semen quality (23.9 ± 3.2). Additionally, we demonstrated that the total sperm count, sperm concentration, progressive motility and normal morphology were lower in the category of long CAG repeats (CAG ≥ 25) compared with those in the category of short CAG repeats (CAG ≤ 19); however, hormonal parameters did not differ between the long and short CAG categories, with the exception of estradiol. Significant differences were observed in the AR CAG repeat length between the most common ethnic cohorts of Slavs (Caucasians), Buryats (Asians), and Yakuts (Asians). The Buryats and Yakuts had a higher number of CAG repeats than the Slavs (medians: Slavs—23; Buryats—24; Yakuts—25). The range of alleles differed among ethnicities, with the Slavs having the largest range (7–36 repeats, 24 alleles total), the Yakuts having the smallest range (18–32 repeats, 14 alleles total) and the Buryats having the middle range (11–39 repeats, 20 alleles total). The longer CAG repeats were associated with an impaired semen quality within the Slavic (CAG ≥ 25) and Buryat (CAG ≥ 28) groups, but this effect was not found in Yakuts. Hormonal parameters did not differ between the three CAG repeat categories in men of all ethnic groups. This is the largest Russian study of the distribution of AR CAG repeats and the search for association between length of AR CAG repeat tract and impaired spermatogenesis in men from the general population. Our results confirmed the association of longer CAG repeats with a risk of impaired semen quality, but this association can be modified by ethnic origin. Identification of the number of AR CAG repeats can be an effective tool to assess the risk of male subfertility and the control of androgen hormone therapy of reproductive diseases.

Preliminary prediction of semen quality based on modifiable lifestyle factors by using the XGBoost algorithm

Introduction

Semen quality has decreased gradually in recent years, and lifestyle changes are among the primary causes for this issue. Thus far, the specific lifestyle factors affecting semen quality remain to be elucidated.

Materials and methods

In this study, data on the following factors were collected from 5,109 men examined at our reproductive medicine center: 10 lifestyle factors that potentially affect semen quality (smoking status, alcohol consumption, staying up late, sleeplessness, consumption of pungent food, intensity of sports activity, sedentary lifestyle, working in hot conditions, sauna use in the last 3 months, and exposure to radioactivity); general factors including age, abstinence period, and season of semen examination; and comprehensive semen parameters [semen volume, sperm concentration, progressive and total sperm motility, sperm morphology, and DNA fragmentation index (DFI)]. Then, machine learning with the XGBoost algorithm was applied to establish a primary prediction model by using the collected data. Furthermore, the accuracy of the model was verified via multiple logistic regression following k-fold cross-validation analyses.

Results

The results indicated that for semen volume, sperm concentration, progressive and total sperm motility, and DFI, the area under the curve (AUC) values ranged from 0.648 to 0.697, while the AUC for sperm morphology was only 0.506. Among the 13 factors, smoking status was the major factor affecting semen volume, sperm concentration, and progressive and total sperm motility. Age was the most important factor affecting DFI. Logistic combined with cross-validation analysis revealed similar results. Furthermore, it showed that heavy smoking (>20 cigarettes/day) had an overall negative effect on semen volume and sperm concentration and progressive and total sperm motility (OR = 4.69, 6.97, 11.16, and 10.35, respectively), while age of >35 years was associated with increased DFI (OR = 5.47).

Conclusion

The preliminary lifestyle-based model developed for semen quality prediction by using the XGBoost algorithm showed potential for clinical application and further optimization with larger training datasets.

The Role of microRNAs in the Gonocyte Theory as Target of Malignancy: Looking for Potential Diagnostic Biomarkers

Some pediatric patients with cryptorchidism preserve cells with gonocyte characteristics beyond their differentiation period, which could support the theory of the gonocyte as a target for malignancy in the development of testicular neoplasia. One of the key molecules in gonocyte malignancy is represented by microRNAs (miRNAs). The goal of this review is to give an overview of miRNAs, a class of small non-coding RNAs that participate in the regulation of gene expression. We also aim to review the crucial role of several miRNAs that have been further described in the regulation of gonocyte differentiation to spermatogonia, which, when transformed, could give rise to germ cell neoplasia in situ, a precursor lesion to testicular germ cell tumors. Finally, the potential use of miRNAs as diagnostic and prognostic biomarkers in testicular neoplasia is addressed, due to their specificity and sensitivity compared to conventional markers, as well as their applications in therapeutics.

Whole-Genome Profile of Greek Patients with Teratozοοspermia: Identification of Candidate Variants and Genes

Male infertility is a global health problem that affects a large number of couples worldwide. It can be categorized into specific subtypes, including teratozoospermia. The present study aimed to identify new variants associated with teratozoospermia in the Greek population and to explore the role of genes on which these were identified. For this reason, whole-genome sequencing (WGS) was performed on normozoospermic and teratozoospermic individuals, and after selecting only variants found in teratozoospermic men, these were further prioritized using a wide range of tools, functional and predictive algorithms, etc. An average of 600,000 variants were identified, and of them, 61 were characterized as high impact and 153 as moderate impact. Many of these are mapped in genes previously associated with male infertility, yet others are related for the first time to teratozoospermia. Furthermore, pathway enrichment analysis and Gene ontology (GO) analyses revealed the important role of the extracellular matrix in teratozoospermia. Therefore, the present study confirms the contribution of genes studied in the past to male infertility and sheds light on new molecular mechanisms by providing a list of variants and candidate genes associated with teratozoospermia in the Greek population.

Development, Validation, and Application of a Human Reproductive Toxicity Prediction Model Based on Adverse Outcome Pathway

A growing number of environmental contaminants have been proved to have reproductive toxicity to males and females. However, the unclear toxicological mechanism of reproductive toxicants limits the development of virtual screening methods. By consolidating androgen (AR)-/estrogen receptors (ERs)-mediated adverse outcome pathways (AOPs) with more than 8000 chemical substances, we uncovered relationships between chemical features, a series of pathway-related effects, and reproductive apical outcomes─changes in sex organ weights. An AOP-based computational model named RepTox was developed and evaluated to predict and characterize chemicals' reproductive toxicity for males and females. Results showed that RepTox has three outstanding advantages. (I) Compared with the traditional models (37 and 81% accuracy, respectively), AOP significantly improved the predictive robustness of RepTox (96.3% accuracy). (II) Compared with the application domain (AD) of models based on small in vivo datasets, AOP expanded the ADs of RepTox by 1.65-fold for male and 3.77-fold for female, respectively. (III) RepTox implied that hydrophobicity, cyclopentanol substructure, and several topological indices (e.g., hydrogen-bond acceptors) were important, unbiased features associated with reproductive toxicants. Finally, RepTox was applied to the inventory of existing chemical substances of China and identified 2100 and 7281 potential toxicants to the male and female reproductive systems, respectively.

An Overview of Essential Microelements and Common Metallic Nanoparticles and Their Effects on Male Fertility

Numerous factors affect reproduction, including stress, diet, obesity, the use of stimulants, or exposure to toxins, along with heavy elements (lead, silver, cadmium, uranium, vanadium, mercury, arsenic). Metals, like other xenotoxins, can cause infertility through, e.g., impairment of endocrine function and gametogenesis or excess production of reactive oxygen species (ROS). The advancement of nanotechnology has created another hazard to human safety through exposure to metals in the form of nanomaterials (NMs). Nanoparticles (NPs) exhibit a specific ability to penetrate cell membranes and biological barriers in the human body. These ultra-fine particles (<100 nm) can enter the human body through the respiratory tract, food, skin, injection, or implantation. Once absorbed, NPs are transported to various organs through the blood or lymph. Absorbed NPs, thanks to ultrahigh reactivity compared to bulk materials in microscale size, disrupt the homeostasis of the body as a result of interaction with biological molecules such as DNA, lipids, and proteins; interfering with the functioning of cells, organs, and physiological systems; and leading to severe pathological dysfunctions. Over the past decades, much research has been performed on the reproductive effects of essential trace elements. The research hypothesis that disturbances in the metabolism of trace elements are one of the many causes of infertility has been unquestionably confirmed. This review examines the complex reproductive risks for men regarding the exposure to potentially harmless xenobiotics based on a series of 298 articles over the past 30 years. The research was conducted using PubMed, Web of Science, and Scopus databases searching for papers devoted to in vivo and in vitro studies related to the influence of essential elements (iron, selenium, manganese, cobalt, zinc, copper, and molybdenum) and widely used metallic NPs on male reproduction potential.

In vitro investigation of endocrine disrupting effects of pesticides on Ca2+-signaling in human sperm cells through actions on the sperm-specific and steroid-activated CatSper Ca2+-channel

BACKGROUND

Ca²⁺-signaling controls sperm cell functions necessary for successful fertilization. Multiple endocrine disrupting chemicals have been found to interfere with normal Ca²⁺-signaling in human sperm cells through an activation of the sperm-specific CatSper Ca²⁺-channel, which is vital for normal male fertility.

OBJECTIVES

We investigated 53 pesticides for their ability to interfere with CatSper mediated Ca²⁺-signaling and function in human sperm cells.

METHODS

Effects of the pesticides on Ca²⁺-signaling in human sperm cells were evaluated using a Ca²⁺-fluorometric assay. Effects via CatSper were assessed using the specific CatSper inhibitor RU1968. Effects on human sperm function and viability were assessed using an image cytometry-based acrosome reaction assay and the modified Kremer's sperm-mucus penetration assay.

RESULTS

28 of 53 pesticides were found to induce Ca²⁺-signals in human sperm cells at 10 µM. The majority of these 28 active pesticides induced Ca²⁺-signals through CatSper and interfered with subsequent Ca²⁺-signals induced by the two endogenous CatSper ligands progesterone and prostaglandin E₁. Multiple active pesticides were found to affect Ca²⁺-mediated sperm functions and viability at 10 µM. Low nM dose mixtures of the active pesticides alone or in combination with other environmental chemicals were found to significantly induce Ca²⁺-signals and inhibit Ca²⁺-signals induced subsequently by progesterone and prostaglandin E₁.

CONCLUSIONS

Our results show that pesticides, both alone and in low nM dose mixtures, interfere with normal Ca²⁺-signaling in human sperm cells in vitro in low nM concentrations. Biomonitoring of the active pesticides in relevant matrices such as blood and reproductive fluids is very limited and the effects of real time human pesticide exposure on human sperm cells and fertility thus remains largely unknown. To which extent human pesticide exposure affects the chances of a successful fertilization in humans in vivo needs further research.

Global patterns in testicular cancer incidence and mortality in 2020

With 74 500 new cases worldwide in 2020, testicular cancer ranks as the 20th leading cancer type, but is the most common cancer in young men of European ancestry. While testicular cancer incidence has been rising in many populations, mortality trends, at least those in high-income settings, have been in decline since the 1970s following the introduction of platinum-based chemotherapy. To examine current incidence and mortality patterns, we extracted the new cases of, and deaths from cancers of the testis from the GLOBOCAN 2020 database. In 2020, testicular cancer was the most common cancer in men aged 15 to 44 in 62 countries worldwide. Incidence rates were highest in West-, North- and South-Europe and Oceania (age-standardised rate, ASR ≥7/100 000), followed by North America (5.6/100 000 and lowest (<2/100 000) in Asia and Africa. The mortality rates were highest in Central and South America (0.84 and 0.54 per 100 000, respectively), followed by Eastern and Southern Europe, and Western and Southern Africa. The lowest mortality rates were in Northern Europe, Northern Africa and Eastern Asia (0.16, 0.14, 0.9 per 100 000, respectively). At the country level, incidence rates varied over 100-fold, from 10/100 000 in Norway, Slovenia, Denmark and Germany to ≤0.10/100 000 in Gambia, Guinea, Liberia, Lesotho. Mortality rates were highest in Fiji, Argentina and Mexico. Our results indicate a higher mortality burden in countries undergoing economic transitions and reinforce the need for more equitable access to testicular cancer diagnosis and treatment globally.

Profiling the 3D interaction between germ cell tumors and microenvironmental cells at the transcriptome and secretome level

The tumor microenvironment (TM), consisting of the extracellular matrix (ECM), fibroblasts, endothelial cells, and immune cells, might affect tumor invasiveness and the outcome of standard chemotherapy. This study investigated the cross talk between germ cell tumors (GCT) and surrounding TM cells (macrophages, T-lymphocytes, endothelial cells, and fibroblasts) at the transcriptome and secretome level. Using high-throughput approaches of three-dimensional (3D) co-cultured cellular aggregates, this study offers newly identified pathways to be studied with regard to sensitivity toward cisplatin-based chemotherapy or tumor invasiveness as a consequence of the cross talk between tumor cells and TM components. Mass-spectrometry-based secretome analyses revealed that TM cells secreted factors involved in ECM organization, cell adhesion, angiogenesis, and regulation of insulin-like growth factor (IGF) transport. To evaluate direct cell-cell contacts, green fluorescent protein (GFP)-expressing GCT cells and mCherry-expressing TM cells were co-cultured in 3D. Afterward, cell populations were separated by flow cytometry and analyzed by RNA sequencing. Correlating the secretome with transcriptome data indicated molecular processes such as cell adhesion and components of the ECM being enriched in most cell populations. Re-analyses of secretome data with regard to lysine- and proline-hydroxylated peptides revealed a gain in proteins, such as collagens and fibronectin. Cultivation of GCT cells on collagen I/IV- or fibronectin-coated plates significantly elevated adhesive and migratory capacity, while decreasing cisplatin sensitivity of GCT cells. Correspondingly, cisplatin sensitivity was significantly reduced in GCT cells under the influence of conditioned medium from fibroblasts and endothelial cells. This study sheds light on the cross talk between GCT cells and their circumjacent TM, which results in deposition of the ECM and eventually promotes a pro-tumorigenic environment through enhanced migratory and adhesive capacity, as well as decreased cisplatin sensitivity. Hence, our observations indicate that targeting the ECM and its cellular components might be a novel therapeutic option in combination with cisplatin-based chemotherapy for GCT patients.

Risk of cardiovascular disease in women and men with subfertility: the Trøndelag Health Study

OBJECTIVE

To investigate the association between subfertility and risk of cardiovascular disease (CVD) outcomes.

DESIGN

Prospective study.

SETTING

Population-based cohort.

PATIENT(S)

We studied 31,629 women and 17,630 men participating in the Trøndelag Health Study.

INTERVENTION(S)

Self-reported subfertility. As men were not directly asked about fertility, male partners of female participants were identified through linkage to the Medical Birth Registry of Norway and assigned the fertility information obtained from their partners.

MAIN OUTCOME MEASURE(S)

The primary outcomes were stroke and coronary heart disease in women and men with and without a history of subfertility. The secondary outcomes were myocardial infarction and angina (subgroups of coronary heart disease) and any CVD (stroke or coronary heart disease). Information on CVD was available by linkage to hospital records. We used Cox proportional hazards models adjusted for age at participation in the Trøndelag Health Study (linear + squared), birth year, smoking history, cohabitation, and education. Cardiometabolic factors were assessed in separate models.

RESULT(S)

A total of 17% of women and 15% of men reported subfertility. In women, subfertility was modestly associated with an increased risk of stroke (age-adjusted hazard ratio [aaHR], 1.19; 95% confidence interval [CI], 1.02-1.39; adjusted hazard ratio [aHR]; 1.18; 95% CI, 1.01-1.37) and coronary heart disease (aaHR, 1.19; 95% CI, 1.06-1.33; aHR, 1.16; 95% CI, 1.03-1.30) compared with fertile women. In men, we observed a weak positive association for stroke (aaHR, 1.11; 95% CI, 0.91-1.34; aHR, 1.10; 95% CI, 0.91-1.33) and a weak inverse association for coronary heart disease (aaHR, 0.92; 95% CI, 0.81-1.05; aHR, 0.93; 95% CI, 0.81-1.06).

CONCLUSION(S)

We observed modestly increased risks of CVD outcomes in women and some weak associations in men, although with no strong statistical evidence on sex differences. We acknowledge that we were only able to include men linked to pregnancies ending at 12 completed gestational weeks or later, potentially resulting in selection bias and misclassification of history of subfertility in analyses of male partners. Despite the large sample size, our results indicate the need for larger studies to obtain precise results in both sexes and determine whether there are true sex differences.

Effect of Stress and Caffeine on Male Infertility

Caffeine is a natural psychoactive chemical found in beverages made from coffee. In addition, it is added by the manufacturers of a large number of sodas and energy drinks. It does this by stimulating both the brain and the central nervous system, enabling you to avoid being sleepy while still keeping you attentive. A state of emotional or physical tension is defined as stress. It can be induced through the experience of something or thinking of something that causes you to feel uncomfortable, irritated, or nervous. Your body's response to adversity or demand is what we call stress. Among couples, male infertility is common. A failure in spermatogenesis is accountable for nearly half of all occurrences of infertility in marriage. Ageing, psychological stress, diet, physical exercise, coffee, hot water, hot scrotum, and cell phone usage are some of the few modifiable lifestyle variables that have a role in the development of infertility. Many hypotheses have been proposed to establish the link between stress in the workplace, life events (war, earthquake, etc.), and inability to conceive have been linked to inferior or degraded semen quality. In this review, we will discuss the effect on male fertility of elements including quality of life (such as exercise, diet, and other alterations to one's daily routine) and psychological stress. In addition, the effects on male fertility of elevated scrotal temperature, improper dietary habits, and physical inactivity will be discussed. The loss in male fertility, mainly due to ageing, inappropriate lifestyles, and environmental factors, is a significant public health concern in this century. Couples can enhance their quality of life and increase their chances of naturally conceiving a child by altering their way of life and supplementing it with nutraceutical antioxidants and an organised educational, environmental, dietary, and physical exercise program.

Involvement of Porcine β-Defensin 129 in Sperm Capacitation and Rescue of Poor Sperm in Genital Tract Infection

In mammals, β-defensins have been reported to play pivotal roles in sperm protection and fertilization. However, the function and mechanism of porcine β-defensin 129 (pBD129) in the sperm remain unclear. Here, we demonstrate that pBD129 is a glycosylated protein and broadly exists in accessory sex glands and coats the sperm surface. We inhibited the pBD129 protein on the sperm surface with an anti-pBD129 antibody and found that sperm motility was not significantly affected; however, sperm acrosome integrity and tyrosine phosphorylation levels increased significantly with time (p < 0.05) during capacitation. These changes were accompanied by an increase in sperm Ca2+ influx, resulting in a significantly reduced in vitro fertilization cleavage rate (p < 0.05). Further investigation revealed that treatment with recombinant pBD129 markedly restored the sperm motility in semen contaminated with Escherichia coli. The results suggest that pBD129 is not only associated with poor sperm motility after genital tract infection but can also protect the spermatozoa from premature capacitation, which may be beneficial for semen preservation.

Spatiotemporal trends in human semen quality

Over the past four decades, studies of various designs have reported spatial and temporal trends in human semen quality. Several standardized-methodology studies in homogeneous populations that compare specific cities within a country or a continent provide clear evidence of geographical differences in sperm production, even over short distances within the same country. Human sperm production is widely believed to be declining over time, but evidence from the scientific literature is less clear. Studies based on repeated cross-sectional data from a single centre have shown mixed results. Among the numerous retrospective studies conducted in a single centre, only some included homogeneous groups of men and appropriate methods, and most of them suggest a temporal decrease in human sperm production in the geographical areas considered. Conclusions reporting temporal trends in sperm production that came from existing retrospective multicentre studies based on individual semen data and those using means, medians or estimates of sperm production are questionable, owing to intrinsic limitations in the studies performed. Regardless of study design, studies on the percentage of motile or morphologically normal spermatozoa are still limited by the inherent variability in assessment. Overall, available data do not enable us to conclude that human semen quality is deteriorating worldwide or in the Western world, but that a trend is observed in some specific areas. To understand these trends and contrasts in sperm and semen quality, prospective studies should be encouraged and combined with assessment of the male exposome.

Several studies over the past few decades have suggested that sperm quality varies by geographical region and might be subject to a temporal decline worldwide. However, the data supporting these conclusions have come from studies of various methodologies and heterogeneous populations, making them unreliable. In this in-depth Review, Chevrier and colleagues discuss the data surrounding discussion of spatiotemporal trends in semen parameters and consider how these trends and the factors promoting them interact.

The vast literature on human semen quality trends is extremely heterogeneous in terms of the populations studied and study designs, and so these studies have been unable to draw firm conclusions.

Understanding the data around spatiotemporal semen trends requires a focus on the methodological choices and application of criteria to filter findings from the studies with optimal design.

Numerous appropriately designed studies suggest unambiguous geographical contrasts in human sperm production; however, evidence of a decline in sperm production is reliable only in specific populations and cities in which studies with a complete set of quality criteria have been conducted.

By contrast, suggestions of a worldwide drop in human semen quality on the basis of retrospective multicentre studies cannot be substantiated, owing to intrinsic limitations in the studies performed.

Many and varied factors of variation, in particular the diverse modalities of assessment, do not enable us to conclude that clear temporal trends of sperm motility and normal morphology are present.

Progress in our understanding of the highlighted trends and their causal factors requires prospective studies that minimize all known biases combined with the assessment of men’s exposome.

Genetics of testicular cancer: a review

PURPOSE OF REVIEW

Testicular germ cell tumours (TGCTs) are the most common solid malignant cancer diagnosed in young males and the incidence is increasing. Understanding the genetic basis of this disease will help us to navigate the challenges of early detection, diagnosis, treatment, surveillance, and long-term outcomes for patients.

RECENT FINDINGS

TGCTs are highly heritable. Current understanding of germline risk includes the identification of one moderate-penetrance predisposition gene, checkpoint kinase 2 (CHEK2), and 78 low-to-moderate-risk single nucleotide polymorphisms identified in genome-wide-associated studies, which account for 44% of familial risk. Biomarker research in TGCTs has been challenging for multiple reasons: oncogenesis is complex, actionable mutations are uncommon, clonal evolution unpredictable and tumours can be histologically and molecularly heterogeneous. Three somatic mutations have thus far been identified by DNA exome sequencing, exclusively in seminomas: KIT, KRAS and NRAS. Several genetic markers appear to be associated with risk of TGCT and treatment resistance. TP53 mutations appear to be associated with platinum resistance. MicroRNA expression may be a useful biomarker of residual disease and relapse in future.

SUMMARY

The biology of testicular germ cells tumours is complex, and further research is needed to fully explain the high heritability of these cancers, as well as the molecular signatures which may drive their biological behaviour.

Estimating the effects of policies on infertility prevalence worldwide

Background

Infertility has troubled millions of people worldwide while always being an ignored issue. The high cost of treatment or lack of services placed a barrier to the alleviation of infertility status. Governments play a significant role to promote infertility-related policies for better access to infertility services and comprehensive supports for infertile people.

Methods

Data of infertility status indicators and infertility-related policies in ten representative countries were collected. An infertility-related policy system was established, then classification and quantification were processed according to specific criteria, and different policy implementation patterns were identified. The effectiveness of specific infertility-related policy and various patterns on infertility prevalence relief between 1990 and 2017 were evaluated via generalized linear models and analyses of covariance for the first time.

Results

Economic support policies would be less prioritized compared with social security policies, while economic support policy had a significant positive role in the decline of female infertility prevalence (β = -2·16, p = 0·042). In detail, insurance coverage and economic reward policies were crucial (β = -3·31, p = 0·031; β = -4·10, p = 0·025) with adjusted with covariates. The effect of economic support-oriented pattern was relatively better than other patterns for both male and female infertility prevalence relief. Nevertheless, the effectiveness of gradual-promotion pattern seemed preferable for male infertility prevalence relief while was similar with simultaneous-promotion pattern for females.

Conclusions

Our data-driven analysis revealed that insurance coverage and economic reward policies played the pivotal role in moderation of female infertility status. Economic support-oriented pattern and gradual-promotion pattern were preferable when promoting infertility-related policies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13802-9.

Increased androgen-related comorbidity in adolescents and adults born with hypospadias: a population-based study

Background

Hypospadias is a common congenital malformation often related to the effect of androgens in utero. While hypogonadism is associated with many potential health risks including metabolic and cardiovascular disease, the risk of clinical hypogonadism and comorbidities in men with hypospadias later in life has not been studied.

Objectives

Investigate the risk of hypogonadism and somatic comorbidities in adolescents and men born with hypospadias.

Materials and methods

We conducted a population‐based cohort study using Swedish registers. Associations between hypospadias and hypogonadism, delayed puberty, metabolic, and cardiovascular disease respectively were estimated using Cox proportional hazards regression. Body measurements from military conscription were analysed in a subpopulation as indicators of growth and cardiometabolic risk. We used sibling comparison analyses to control for familial confounding.

Results

Using register data, a total of 2,165,255 men including 9,714 men born with hypospadias were followed from the age of 10 to a maximum of 60 years. We found an association between hypospadias and hypogonadism (Hazard ratio (HR) 3.27, 95% confidence interval (CI) 2.33–4.59) which was more pronounced in proximal hypospadias. Men with hypospadias had shorter average height than their brothers and the general population. We further found an increased risk of delayed puberty (HR 1.49, 95% CI 1.08–2.07), diabetes mellitus type 2 (HR 1.57, 95% CI 1.18–2.09) and cardiovascular disease (HR 1.47, 95% CI 1.27–1.71).

Discussion

We found an increased risk of hypogonadism, metabolic and cardiovascular disease in men born with hypospadias, increasing with severity of phenotype, as well as impacted growth. These results indicate discruptions in androgen function past childhood, although some of the associations may be due to other underlying aetiologies.

Conclusion

Hypospadias is associated with an increased risk of androgen‐related comorbidity in adolescence and adulthood. We suggest that this can be considered clinically, while further research is needed, especially in older populations.

The changing landscape of immune cells in the fetal mouse testis

Fetal testis growth involves cell influx and extensive remodeling. Immediately after sex determination in mouse, macrophages enable normal cord formation and removal of inappropriately positioned cells. This study provides new information about macrophages and other immune cells after cord formation in fetal testes, including their density, distribution, and close cellular contacts. C57BL6J mouse testes from embryonic day (E) 13.5 to birth (post-natal day 0; PND0), were examined using immunofluorescence, immunohistochemistry, and RT-qPCR to identify macrophages (F4/80, CD206, MHCII), T cells (CD3), granulocytes/neutrophils (Ly6G), and germ cells (DDX4). F4/80⁺ cells were the most abundant, comprising 90% of CD45⁺ cells at E13.5 and declining to 65% at PND0. Changes in size, shape, and markers (CD206 and MHCII) documented during this interval align with the understanding that F4/80⁺ cells have different origins during embryonic life. CD3⁺ cells and F4/80⁻/MHCII⁺ were absent to rare until PND0. Ly6G⁺ cells were scarce at E13.5 but increased robustly by PND0 to represent half of the CD45⁺ cells. These immunofluorescence data were in accord with transcript analysis, which showed that immune marker mRNAs increased with testis age. F4/80⁺ and Ly6G⁺ cells were frequently inside cords adjacent to germ cells at E13.5 and E15.5. F4/80⁺ cells were often in clusters next to other immune cells. Macrophages inside cords at E13.5 and E15.5 (F4/80^Hi/CD206⁺) were different from macrophages at PND0 (F4/80^Dim/CD206⁻), indicating that they have distinct origins. This histological quantification coupled with transcript information identifies new cellular interactions for immune cells in fetal testis morphogenesis, and highlights new avenues for studies of their functional significance.

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.

Combined exposures to bisphenols, polychlorinated dioxins, paracetamol, and phthalates as drivers of deteriorating semen quality

BACKGROUND

Semen quality in men continues to decline in Western countries, but the contours of the issue remain obscure, in relation to contributing chemicals.

OBJECTIVES

To obtain more clarity about the chemicals that drive the deterioration of semen quality, we conducted a mixture risk assessment based on European exposures.

METHODS

We included chemicals capable of affecting semen quality after prenatal exposures, among them androgen receptor antagonists, substances that disrupt prostaglandin signalling, suppress testosterone synthesis, inhibit steroidogenic enzymes or activate the aryl hydrocarbon receptor. We employed the Hazard Index approach (HI), based on risk quotients of exposures in Europe and reference doses for reductions in semen quality. By summing up the risk quotients of the 29 chemicals included in the assessment we examined fold-exceedances of "acceptable" mixture exposures relative to an index value of 1. For bisphenols A, F, S, phthalates DEHP, DnBP, BBzP, DiNP, n-butyl paraben and paracetamol we relied on biomonitoring studies in which these 9 chemicals were measured together in the same subjects. This allowed us to construct personalised Hazard Indices.

RESULTS

Highly exposed subjects experienced combined exposures to the 9 chemicals that exceeded the index value of 1 by more than 100-fold; the median was a 17-fold exceedance. Accounting for median background exposures to the remaining 20 chemicals added a Hazard Index of 1.39. Bisphenol A made the largest contribution to the HI, followed by polychlorinated dioxins, bisphenols S and F and DEHP. Eliminating bisphenol A alone would still leave unacceptably high mixture risks. Paracetamol is also a driver of mixture risks among subjects using the drug.

CONCLUSIONS

Tolerable exposures to substances associated with deteriorations of semen quality are exceeded by a large margin. Bisphenols, polychlorinated dioxins, phthalates and analgesics drive these risks. Dedicated efforts towards lowering exposures to these substances are necessary to mitigate risks.

In vitro testicular toxicity of environmentally relevant endocrine-disrupting chemicals: 2D vs. 3D models of prepubertal Leydig TM3 cells

The testis is a priority organ for developing alternative models to assess male reproductive health hazards of chemicals. This study characterized a 3D in vitro model of murine prepubertal Leydig TM3 cells with improved expression of steroidogenesis markers suitable for image-based screening of testicular toxicity. This 3D scaffold-free spheroid model was applied to explore the impact of prototypical endocrine-disrupting chemicals (EDCs) and environmental reprotoxicants (benzo[a]pyrene, 2- and 9-methylanthracenes, fluoranthene, triclosan, triclocarban, methoxychlor) on male reproductive health. The results were compared to the male reprotoxicity potential of EDCs assessed in a traditional monolayer (2D) culture. The testicular toxicity was dependent not only on the type of culture (2D vs. 3D models) but also on the duration of exposure. Benzo[a]pyrene and triclocarban were the most active compounds, eliciting cytotoxic effects in prepubertal Leydig cells at low micromolar concentrations, which might be a mechanism contributing to their male reprotoxicity.

Male infertility and the impact of lifestyle in the Greek population: A case-control study

Background and Aims

Collection of epidemiological data has become a crucial step in every fertility evaluation, especially regarding idiopathic male infertility. Information on data such as tobacco smoking, alcohol intake, and body mass index can provide crucial information regarding the dynamics between fertility status and everyday practices. We aim to set the base for epidemiological studies on male infertility in the Greek population.

Methods

Four hundred and fourteen Greek volunteers were asked to fill in a questionnaire regarding their characteristics and lifestyle preferences, followed by a seminogram. Depending on their answers, they were divided into groups and data were analyzed for correlation with seminogram parameters using Spearman's rank correlation test.

Results

Our results indicate that a high body mass index (BMI) is negatively correlated with all three seminogram parameters (number, motility, and morphology) and exposure to radiation or chemicals is negatively correlated with sperm motility, with a p < 0.01.

Conclusions

These findings indicate negative correlations of BMI and exposure to radiation/chemicals with semen parameters in the Greek population. Such information can be used to plan a diagnostic approach or even therapeutic interventions.

Using alternative test methods to predict endocrine disruption and reproductive adverse outcomes: do we have enough knowledge?

Endocrine disrupting chemicals (EDCs) are a matter of great concern. They are ubiquitous in the environment, are considered harmful to humans and wildlife, yet remain challenging to identify based on current international test guidelines and regulatory frameworks. For a compound to be identified as an EDC within the EU regulatory system, a plausible link between an endocrine mode-of-action and an adverse effect outcome in an intact organism must be established. This requires in-depth knowledge about molecular pathways regulating normal development and function in animals and humans in order to elucidate causes for disease. Although our knowledge about the role of the endocrine system in animal development and function is substantial, it remains challenging to predict endocrine-related disease outcomes in intact animals based on non-animal test data. A main reason for this is that our knowledge about mechanism-of-action are still lacking for essential causal components, coupled with the sizeable challenge of mimicking the complex multi-organ endocrine system by methodological reductionism. Herein, we highlight this challenge by drawing examples from male reproductive toxicity, which is an area that has been at the forefront of EDC research since its inception. We discuss the importance of increased focus on characterizing mechanism-of-action for EDC-induced adverse health effects. This is so we can design more robust and reliable testing strategies using non-animal test methods for predictive toxicology; both to improve chemical risk assessment in general, but also to allow for considerable reduction and replacement of animal experiments in chemicals testing of the 21st Century.

LIN28 Family in Testis: Control of Cell Renewal, Maturation, Fertility and Aging

Male reproductive development starts early in the embryogenesis with somatic and germ cell differentiation in the testis. The LIN28 family of RNA-binding proteins promoting pluripotency has two members—LIN28A and LIN28B. Their function in the testis has been investigated but many questions about their exact role based on the expression patterns remain unclear. LIN28 expression is detected in the gonocytes and the migrating, mitotically active germ cells of the fetal testis. Postnatal expression of LIN28 A and B showed differential expression, with LIN28A expressed in the undifferentiated spermatogonia and LIN28B in the elongating spermatids and Leydig cells. LIN28 interferes with many signaling pathways, leading to cell proliferation, and it is involved in important testicular physiological processes, such as cell renewal, maturation, fertility, and aging. In addition, aberrant LIN28 expression is associated with testicular cancer and testicular disorders, such as hypogonadotropic hypogonadism and Klinefelter’s syndrome. This comprehensive review encompasses current knowledge of the function of LIN28 paralogs in testis and other tissues and cells because many studies suggest LIN28AB as a promising target for developing novel therapeutic agents.

Endocrine outcome and seminal parameters in young adult men born with hypospadias: A cross-sectional cohort study

BACKGROUND

Hypospadias affects around 1/200 newborn males. Intrauterine testicular dysfunction may underlie a subset of cases. The long-term endocrine and reproductive outcomes in these men remain largely unknown.

METHODS

Cross-sectional study in Ghent and Vienna University Hospitals to assess the endocrine and seminal parameters of young adult men (16-21 years) born with non-syndromic hypospadias (NSH) (n = 193) compared to healthy typical males (n = 50). Assessments included physical exam, semen analysis, hormone assays and exome-based gene panel analysis (474 genes).

FINDINGS

All participants had experienced a spontaneous puberty, in spite of higher LH and INSL3 levels than typical males. Oligo- or azoospermia was observed in 32/172 (18·6%; 99%-CI: 12·2-27·4%) of NSH men; but in 5/16 (31·3%; 99%-CI: 11·1;62·4%) of complex NSH men and in 13/22 (59·1%; 99%-CI: 33·2-80·7%) of those born small for gestational age (SGA). No (likely) pathogenic coding variants were found in the investigated genes. Suboptimal statural growth affected 8/23 (34·8%; 99%-CI: 15·4-61·0%) of men born SGA with NSH.

INTERPRETATION

Spermatogenesis is significantly compromised in NSH men, especially in those born SGA or those with complex NSH. Long-term andrological follow-up is recommended, including end-pubertal semen analysis. No clear monogenic causes could be demonstrated in our cohort even in proximal or complex NSH. Being born SGA with NSH is frequently associated with poor catch-up growth, requiring growth hormone therapy in some.

FUNDING

Research grants from the European Society of Paediatric Endocrinology, the Belgian Society of Pediatrics, the Belgian Society of Pediatric Endocrinology and Diabetology and the Research Foundation Flanders (FWO).

Exposure to corticosteroids in the first trimester is associated with an increased risk of urogenital congenital anomalies

STUDY QUESTION

Does maternal exposure to first trimester corticosteroids in IVF/ICSI treatment result in an increased risk of congenital anomalies?

SUMMARY ANSWER

Children born with the aid of IVF/ICSI whose mothers were treated with adjuvant corticosteroids during the first trimester had an increased risk of cryptorchidism, hypospadias and talipes.

WHAT IS KNOWN ALREADY

Maternal exposure to corticosteroids may increase the risk of congenital anomalies such as cleft palate and neural tube defects. However, the existing studies have conflicting outcomes, are underpowered, and do not study a population undergoing IVF/ICSI, a group known to be at increased risk of abnormalities.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort analysis covering Monash IVF fertility clinics in Melbourne, Australia assessed the outcomes of 12 426 live births from both fresh and frozen embryo transfers between 2010 and 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

There were 618 live births included in our study group of mothers exposed to corticosteroids (oral prednisolone or dexamethasone) during their IVF/ICSI treatment, with the remainder of births not exposed to steroids (control, n = 11 808). The primary outcome measured was the presence of congenital anomalies and secondary outcomes were birth weight and gestation length. Multivariate binary logistic regression was used to assess the independent effects of corticosteroid exposure and the freezing of embryos, with adjustment for maternal age at oocyte retrieval, smoking status, number of cycles taken, BMI, etiology of the infertility and the use of ICSI. Results are presented as incidence rate ratios (IRRs) with 95% CIs.

MAIN RESULTS AND THE ROLE OF CHANCE

Amongst 12 426 live births, and 597 birth defects, multivariate logistic regression demonstrated there was an increased incidence in talipes equinovarus (1.33% vs 0.32%, adjusted IRR = 4.30, 95% CI = 1.93, 9.58; P < 0.001), hypospadias (0.66% vs 0.18%, adjusted IRR = 5.90, 95% CI = 2.09, 16.69; P = 0.001) and cryptorchidism (0.83% vs 0.19%, adjusted IRR = 5.53, 95% CI = 1.91, 15.42; P = 0.001) in the offspring of mothers exposed to corticosteroids compared to those who were unexposed. The incidence of neither neural tube defects nor cleft palate were significantly increased in babies exposed to corticosteroids. The sex ratio of infants exposed to corticosteroids during a fresh embryo transfer cycle significantly favored males but reverted to the normal sex ratio in infants conceived in frozen embryo transfer cycles.

LIMITATIONS, REASONS FOR CAUTION

This was a retrospective observational cohort study using administrative datasets with the potential for measurement error and unobserved confounding. Missing outcome data were obtained from patients using self-report leading to possible ascertainment bias. Given the rare incidence of some of the anomalies assessed, the study was underpowered to identify differences in abnormality rates for some specific anomalies.

WIDER IMPLICATIONS OF THE FINDINGS

The findings of this study, the largest of its kind, suggest that caution should be heeded when prescribing corticosteroids to women undergoing IVF/ICSI, given that this study has now identified three previously unassociated serious neonatal complications (talipes, hypospadias and cryptorchidism), plus a potential alteration in sex ratio. Physicians should be careful in using corticosteroids in the critical first trimester and should counsel patients regarding the potential risks of this treatment.

STUDY FUNDING/COMPETING INTEREST(S)

There was no funding sought or obtained for this study. K.T., V.T., B.V. and D.Z.-F. are employees or contractors to Monash IVF and hold a minority stock position in Monash IVF. R.J.W. reports no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Effect of a single-dose denosumab on semen quality in infertile men (the FITMI study): study protocol for a randomized controlled trial

Background

Infertility is a common problem globally and impaired semen quality is responsible for up to 40% of all cases. Almost all infertile couples are treated with either insemination or assisted reproductive techniques (ARTs) independent of the etiology of infertility because no medical treatment exists. Denosumab is an antibody that blocks RANKL signaling and inhibition of testicular RANKL signaling has been suggested to improve semen quality in a pilot study. This RCT aims to assess whether treatment with denosumab can improve spermatogenesis in infertile men selected by serum AMH as a positive predictive biomarker. This paper describes the design of the study.

Methods/design

FITMI is a sponsor-investigator-initiated, double-blinded, placebo-controlled 1:1, single-center, randomized clinical trial. Subjects will be randomized to receive either a single-dose denosumab 60 mg subcutaneous injection or placebo. The study will be carried out at the Department of Growth and Reproduction, Copenhagen University Hospital, Rigshospitalet, Copenhagen. The primary outcome of the study is defined as the difference in sperm concentration (millions pr. mL) one spermatogenesis (80 days) after inclusion.

Discussion

We describe a protocol for a planned RCT aimed at evaluating whether treatment with denosumab can improve the semen quality in infertile men selected by using serum AMH as a positive predictive biomarker. The results will provide evidence crucial for future treatment in a patient group where there is a huge unmet need.

Trial registration

Clinical Trials.gov NCT05212337. Registered on 14 January 2022.

EudraCT 2021–003,451-42. Registered on 23 June 2021.

Ethical committee H-21040145. Registered on 23 December 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06478-4.

Expression of membrane fusion proteins in spermatozoa and total fertilisation failure during in vitro fertilisation

Background

Couples increasingly experience infertility and seek help from assisted reproductive techniques to become pregnant. However, 5%–15% of the couples that are selected for in vitro fertilisation (IVF) experience a total fertilisation failure (TFF), where no zygotes develop despite oocytes and semen parameters appear to be normal. We hypothesise that TFF during IVF could be related to improper membrane fusion of gametes.

Objective

To investigate the membrane integrity and fusion proteins in spermatozoa from men in couples experiencing TFF.

Materials and methods

A total of 33 infertile couples, 17 of which experienced TFF during IVF and 16 matched control couples with normal IVF fertilisation rates, were selected and the men re‐called to deliver an additional semen sample. Proteins involved in gamete membrane fusion on spermatozoa (IZUMO1, SPESP1 and Syncytin‐1) as well as O‐glycosylation patterns (Tn and GALNT3), were investigated by immunofluorescence. The DNA fragmentation index, acrosomal integrity and viability of spermatozoa were determined by flow and image cytometry.

Results

No significant changes in the expression of GALNT3, Tn and Syncytin‐1 were observed between the TFF and control groups. The fraction of spermatozoa expressing SPESP1, the median IZUMO1 staining intensity, and the percentage of viable acrosome‐intact spermatozoa were significantly lower in the TFF group compared to controls. Furthermore, following progesterone‐induced acrosomal exocytosis, a significant difference in the fraction of spermatozoa expressing SPESP1 and the median IZUMO1 staining intensity were observed between the control and TFF group.

Discussion and conclusion

Our results indicate that acrosomal exocytosis, IZUMO1 and SPESP1 expression in spermatozoa could play a crucial role in achieving fertilisation during IVF. However, the size of our cohort was quite small, and our results need to be validated with quantitative methods in larger cohorts.

Toward a Mechanistic Understanding of Poly- and Perfluoroalkylated Substances and Cancer

Poly- and perfluoroalkylated substances (PFAS) are chemicals that persist and bioaccumulate in the environment and are found in nearly all human populations through several routes of exposure. Human occupational and community exposure to PFAS has been associated with several cancers, including cancers of the kidney, testis, prostate, and liver. While evidence suggests that PFAS are not directly mutagenic, many diverse mechanisms of carcinogenicity have been proposed. In this mini-review, we organize these mechanisms into three major proposed pathways of PFAS action-metabolism, endocrine disruption, and epigenetic perturbation-and discuss how these distinct but interdependent pathways may explain many of the proposed pro-carcinogenic effects of the PFAS class of environmental contaminants. Notably, each of the pathways is predicted to be highly sensitive to the dose and window of exposure which may, in part, explain the variable epidemiologic and experimental evidence linking PFAS and cancer. We highlight testicular and prostate cancer as models to validate this concept.

Impact of in Utero Rat Exposure to 17Alpha-Ethinylestradiol or Genistein on Testicular Development and Germ Cell Gene Expression

Although the decline in male fertility is believed to partially result from environmental exposures to xenoestrogens during critical developmental windows, the underlying mechanisms are still poorly understood. Experimental in utero exposures in rodents have demonstrated the negative impact of xenoestrogens on reproductive development, long-term adult reproductive function and offspring health. In addition, transcriptomic studies have demonstrated immediate effects on gene expression in fetal reproductive tissues, However, the immediate molecular effects on the developing germ cells have been poorly investigated. Here, we took advantage of a transgenic rat expressing the green fluorescent protein specifically in germ cells allowing purification of perinatal GFP-positive germ cells. Timed-pregnant rats were exposed to ethinylestradiol (EE2, 2 μg/kg/d), genistein (GE, 10 mg/kg/d) or vehicle by gavage, from gestational days (GD) 13–19; testes were sampled at GD20 or post-natal (PND) 5 for histological analysis and sorting of GFP-positive cells. While EE2-exposed females gained less weight during treatment compared to controls, neither treatment affected the number of pups per litter, sex ratio, anogenital distance, or body and gonadal weights of the offspring. Although GE significantly decreased circulating testosterone at GD20, no change was observed in either testicular histology or germ cell and sertoli cell densities. Gene expression was assessed in GFP-positive cells using Affymetrix Rat Gene 2.0 ST microarrays. Analysis of differentially expressed genes (DEGs) (p < 0.05; fold change 1.5) identified expression changes of 149 and 128 transcripts by EE2 and GE respectively at GD20, and 287 and 207 transcripts at PND5, revealing an increased effect after the end of treatment. Only about 1% of DEGs were common to both stages for each treatment. Functional analysis of coding DEG revealed an overrepresentation of olfactory transduction in all groups. In parallel, many non-coding RNAs were affected by both treatments, the most represented being small nucleolar and small nuclear RNAs. Our data suggest that despite no immediate toxic effects, fetal exposure to xenoestrogens can induce subtle immediate changes in germ cell gene expression. Moreover, the increased number of DEGs between GD20 and PND5 suggests an effect of early exposures with latent impact on later germ cell differentiation.

Effects of perfluorooctanoic acid in oxidative stress generation, DNA damage in cumulus cells, and its impact on in vitro maturation of porcine oocytes

Perfluorooctanoic acid is a synthetic compound mostly used in a wide range of consumer products with several adverse effects on somatic cells and gametes. It has been linked to hepatotoxic and carcinogenic effects, alterations in the immune system, endocrine, and reproductive alterations. In vivo studies show an increase in reactive oxygen species and DNA damage. However, the mechanisms by which this compound affects fertility, remain contradictory. Therefore, the aim of the present study was to evaluate the effect of perfluorooctanoic acid on oocyte viability and maturation, as well as the viability, generation of oxidative stress, and genotoxic damage in the cumulus cells exposed during in vitro maturation. This compound had a negative effect on oocyte viability (lethal concentration, LC₅₀  = 269 μM) and maturation (inhibition maturation concentration IM₅₀  = 75 μM), while in cumulus cells the LC₅₀ was 158 μM. The generation of reactive oxygen species evaluated in cumulus cells, protein carbonylation, and DNA damage, was significantly increased at 40 μM perfluorooctanoic acid. This study provides evidence that perfluorooctanoic acid causes reactive oxygen species generation, protein oxidation, and DNA damage in cumulus cells, compromising the maturation and viability of porcine oocyte, which may affect fertility.

Associations of Urinary Trichloroacetic Acid Concentrations with Spermatozoa Apoptosis and DNA Damage in a Chinese Population

Exposure to trichloroacetic acid (TCAA) has been associated with impaired semen quality; however, its association with spermatozoa apoptosis and DNA damage remains unclear. We, therefore, collected single semen and repeated urine samples from male partners of couples attending a reproductive center, which were measured for spermatozoa apoptosis and DNA damage parameters and TCAA concentrations, respectively. Multivariable linear regression models were used to explore the associations between urinary TCAA concentrations and spermatozoa apoptosis (n = 462) and DNA damage parameters (n = 512). After adjusting for potential confounders, positive dose-response relationships were found between urinary TCAA concentrations and percentage of tail DNA (tail%) and tail-distributed moment (TDM) (both p for trend <0.10). Compared with men in the lowest tertile of urinary TCAA concentrations, men in the highest tertile had a greater tail% and TDM of 6.2% (95% CI: 0.7, 12.2%) and 8.9% (95% CI: -1.9, 20.5%), respectively. Urinary TCAA concentrations were unrelated to spermatozoa apoptosis parameters in a dose-response manner. However, urinary TCAA concentrations were positively associated with the percentage of Annexin V⁺/PI^- spermatozoa (apoptotic cells), when urinary TCAA concentrations were modeled as continuous variables. Our results suggest that exposure to TCAA at concentrations in real-world scenarios may be associated with spermatozoa apoptosis and DNA damage.

Impacts of endocrine disrupting chemicals on reproduction in wildlife and humans

Endocrine disrupting chemicals (EDCs) are ubiquitous in aquatic and terrestrial environments. The main objective of this review was to summarize the current knowledge of the impacts of EDCs on reproductive success in wildlife and humans. The examples selected often include a retrospective assessment of the knowledge of reproductive impacts over time to discern how the effects of EDCs have changed over the last several decades. Collectively, the evidence summarized here within reinforce the concept that reproduction in wildlife and humans is negatively impacted by anthropogenic chemicals, with several altering endocrine system function. These observations of chemicals interfering with different aspects of the reproductive endocrine axis are particularly pronounced for aquatic species and are often corroborated by laboratory-based experiments (i.e. fish, amphibians, birds). Noteworthy, many of these same indicators are also observed in epidemiological studies in mammalian wildlife and humans. Given the vast array of reproductive strategies used by animals, it is perhaps not surprising that no single disrupted target is predictive of reproductive effects. Nevertheless, there are some general features of the endocrine control of reproduction, and in particular, the critical role that steroid hormones play in these processes that confer a high degree of susceptibility to environmental chemicals. New research is needed on the implications of chemical exposures during development and the potential for long-term reproductive effects. Future emphasis on field-based observations that can form the basis of more deliberate, extensive, and long-term population level studies to monitor contaminant effects, including adverse effects on the endocrine system, are key to addressing these knowledge gaps.

Evolution of the World Health Organization semen analysis manual: where are we?

The WHO (World Health Organization) manuals provide state-of-the-art guidance on how a semen analysis should be carried out. The much anticipated sixth edition of the WHO semen analysis manual has been released 10 years after its previous version and includes essential updates, such as new reference standards for semen volume and microscopic sperm characteristics of recent fathers. A well-conducted semen analysis remains an essential foundation of the infertility evaluation process and affects patient referral, diagnosis and treatment. However, a male infertility work-up primarily based on routine semen analysis does not provide men with an optimal fertility pathway; the primary reasons for routine semen analysis inadequacy in this context include its low predictive value for natural and assisted conception success, its inability to detect sperm DNA and epigenetic deficiencies that might negatively affect embryo development, implantation and offspring well-being, and the substantial overlap between semen parameters of fertile and subfertile individuals. Ideally, a full andrological assessment should be carried out by reproductive urologists in all men dealing with couple infertility and should include a detailed history analysis, physical examination, semen analysis, endocrine assessment and other tests as needed. Only through a complete male infertility work-up will relevant underlying medical and infertility conditions be revealed and potentially treated or alleviated. The ultimate goals of a comprehensive andrological assessment are to positively influence overall male health, pregnancy prospects and offspring well-being.

The Association of Certain Seminal Phthalate Metabolites on Spermatozoa Apoptosis: An Exploratory Mediation Analysis via Sperm Protamine

Earlier studies have suggested that exposure to phthalates (PAEs) may induce spermatozoa apoptosis. Sperm protamine as a molecular biomarker during spermatozoa apoptotic processes may mediate the association between PAE exposure and spermatozoa apoptosis. This study aimed to explore whether sperm protamine mediates the association of PAE exposure with spermatozoa apoptosis. We determined sperm protamine levels, 8 PAE metabolite concentrations in seminal plasma, and 3 spermatozoa apoptosis parameters among 111 men from an infertility clinic. The associations of PAEs as individual chemicals and mixtures with sperm protamine were determined. The mediating roles of protamine in the associations between PAEs and spermatozoa apoptosis parameters were examined by mediation analysis. After adjusting for confounders, we observed positive correlations between seminal plasma concentrations of mono(2-ethylhexyl) phthalate (MEHP) and sperm protamine-1 and protamine ratio. Estimates comparing highest vs. lowest quartiles of MEHP concentration were 4.65% (95% CI: 1.47%, 7.82%) for protamine-1 and 25.86% (95% CI: 3.05%, 53.73%) for protamine ratio. The quantile g-computation models showed that the adjusted protamine-1 per quartile increase in PAE mixture was 9.42% (95% CI: 1.00, 20.92) with MEHP being the major contributor. Although the joint association between PAE mixture and protamine ratio was negligible, MEHP was still identified as the main contributor. Furthermore, we found that protamine-2 and protamine ratio levels in the highest quartiles exhibited a decrease of 43.45% (95% CI: 60.54%, -19.75%) and an increase of 122.55% (95% CI: 60.00%, 209.57%) in Annexin V⁺/PI^- spermatozoa relative to the lowest quartiles, respectively. Mediation analysis revealed that protamine ratio significantly mediated 55.6% of the association between MEHP and Annexin V⁺/PI^- spermatozoa elevation (5.13%; 95% CI: 0.04%, 10.52%). Our findings provided evidence that human exposure to PAEs was associated with increased protamine levels which may mediate the process of spermatozoa apoptosis.