Sertoli cell development and function in an animal model of testicular dysgenesis syndrome

Triclosan inhibits testosterone biosynthesis in adult rats via inducing m6A methylation-mediated autophagy

Triclosan is a potent antibacterial compound widely used in everyday products. Whether triclosan affects Leydig cell function in adult male rats remains unknown. In this study, 0, 50, 100, or 200 mg/kg/day triclosan was gavaged to Sprague-Dawley male rats from 56 to 63 days postpartum. Triclosan significantly reduced serum testosterone levels at ≥ 50 mg/kg/day via downregulating the expression of Leydig cell gene Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, and Hsd17b3 and regulatory transcription factor Nr3c2 at 100-200 mg/kg. Further analysis showed that triclosan markedly increased autophagy as shown by increasing LC3II and BECN1 and decreasing SQSTM1. The mRNA m6A modification analysis revealed that triclosan significantly downregulated Fto expression at 200 mg/kg while upregulating Ythdf1 expression at 100 and 200 mg/kg, leading to methylation of Becn1 mRNA as shown by MeRIP assay. Triclosan significantly inhibited testosterone output in rat R2C Leydig cells at ≥ 5 μM via downregulating Fto and upregulating Ythdf1. SiRNA Ythdf1 knockdown can reverse triclosan-mediated mitophagy in R2C cells, thereby reversing the reduction of testosterone output. In summary, triclosan caused Becn1 m6A methylation by downregulating Fto and upregulating Ythdf1, which accelerated Becn1 translation, thus leading to the occurrence of autophagy and the decrease of testosterone biosynthesis.

Prenatal diethylhexylphthalate exposure disturbs adult Leydig cell function via epigenetic downregulation of METTL4 expression in male rats

Prenatal exposure to diethylhexyl phthalate (DEHP) has been linked with a decline in testosterone levels in adult male rats, but the underlying mechanism remains unclear. We investigated the potential epigenetic regulation, particularly focusing on N6-methyladenosine (m6A) modification, as a possible mechanism. Dams were gavaged with DEHP (0, 10, 100, and 750 mg/kg/day) from gestational day 14 to day 21. The male offspring were examined at the age of 56 days. Prenatal DEHP administration at 750 mg/kg/day caused a decline in testosterone concentrations, an elevation in follicle-stimulating hormone, a downregulated expression of CYP11A1 HSD3B2, without affecting Leydig cell numbers. Interestingly, Methyltransferase Like 4 (METTL4), an m6A methyltransferase, was downregulated, while there were no changes in METTL3 and METTL14. Moreover, CYP11A1 showed m6A reduction in response to prenatal DEHP exposure. Additionally, METTL4 expression increased postnatally, peaking in adulthood. Knockdown of METTL4 resulted in the downregulation of CYP11A1 and HSD3B2 and an increase in SCARB1 expression. Furthermore, the increase in autophagy protection in adult Leydig cells induced by prenatal DEHP exposure was not affected by 3-methyladenosine (3MA) treatment, indicating a potential protective role of autophagy in response to DEHP exposure. In conclusion, prenatal DEHP exposure reduces testosterone by downregulating CYP11A1 and HSD3B2 via m6A epigenetic regulation and induction of autophagy protection in adult Leydig cells as a response to DEHP exposure.

The construction of a testis transcriptional cell atlas from embryo to adult reveals various somatic cells and their molecular roles

BACKGROUND

The testis is a complex organ that undergoes extensive developmental changes from the embryonic stage to adulthood. The development of germ cells, which give rise to spermatozoa, is tightly regulated by the surrounding somatic cells.

METHODS

To better understand the dynamics of these changes, we constructed a transcriptional cell atlas of the testis, integrating single-cell RNA sequencing data from over 26,000 cells across five developmental stages: fetal germ cells, infants, childhood, peri-puberty, and adults. We employed various analytical techniques, including clustering, cell type assignments, identification of differentially expressed genes, pseudotime analysis, weighted gene co-expression network analysis, and evaluation of paracrine cell-cell communication, to comprehensively analyze this transcriptional cell atlas of the testis.

RESULTS

Our analysis revealed remarkable heterogeneity in both somatic and germ cell populations, with the highest diversity observed in Sertoli and Myoid somatic cells, as well as in spermatogonia, spermatocyte, and spermatid germ cells. We also identified key somatic cell genes, including RPL39, RPL10, RPL13A, FTH1, RPS2, and RPL18A, which were highly influential in the weighted gene co-expression network of the testis transcriptional cell atlas and have been previously implicated in male infertility. Additionally, our analysis of paracrine cell-cell communication supported specific ligand-receptor interactions involved in neuroactive, cAMP, and estrogen signaling pathways, which support the crucial role of somatic cells in regulating germ cell development.

CONCLUSIONS

Overall, our transcriptional atlas provides a comprehensive view of the cell-to-cell heterogeneity in the testis and identifies key somatic cell genes and pathways that play a central role in male fertility across developmental stages.

Environmentally relevant DEHP exposure during gestational and lactational period inhibits filamin a testicular expression

Toxicological studies have revealed that DEHP exposure during pregnancy may induce developmental disorders, especially in male offspring, leading to morphological and functional alterations in the reproductive system by mechanisms that should be investigated. Thus, the aim of this work was to analyze the testicular toxicity induced by an environmentally relevant DEHP dose during development and its impact on FLNA, a protein that participates in the blood-testis barrier assembly. We used male Wistar rats exposed to DEHP during pregnancy and lactation. The results showed that DEHP exposure during development and lactation increased body weight, decreased gonadal weight and shortened anogenital distance. This phthalate induced morphological changes in the testis, suggestive of hypospermatogenesis. DEHP exposure decreased the number of FLNA positive cells and the expression of FLNA and claudin-1 in prepubertal testes. Furthermore, DEHP inhibited FLNA and claudin-1 protein expression in adult male rats. These results indicated that exposure to DEHP during gestation and lactation perturbed testis development and suggested that FLNA is a target protein of DEHP, possibly contributing to the phthalate-induced damage on BTB.

TNFα stimulates the proliferation of immature Sertoli cells by attenuating UPS-degradation of cyclin D1 and leads to the delay of BTB maturation in pubertal rats

BACKGROUNDS

The Sertoli cell that plays a vital role during spermatogenesis is a known target of physiological and pathological factors affecting testicular development. Tumor necrosis factor alpha (TNFα) participates in the blood-testis barrier reconstruction, cell apoptosis, and inflammatory response by recognizing receptors on Sertoli cell. TNFα has also been shown to induce the proliferation of immature Sertoli cell in vitro, yet the mechanism still remains unclarified.

OBJECTIVES

This study was designed to investigate the effect of TNFα on blood-testis barrier development during puberty and the underlying mechanisms of TNFα-induced immature Sertoli cell proliferation.

MATERIALS AND METHODS

Immature male Sprague-Dawley rats of postnatal day 12 were intraperitoneally injected with TNFα. Biotin-labeled method was used to detect permeability of the developing blood-testis barrier after TNFα treatment, and the distribution of occludin and junctional adhesion molecule-A (JAM-A) were detected by immunofluorescence. Sertoli cells isolated from Sprague-Dawley rats of postnatal day 10 were cultured in vitro and treated with TNFα. Cell proliferation rate was reflected by Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assay. Immunoblot and quantitative polymerase chain reaction were used to detect the expression of proliferating cell nuclear antigen, Fbxo4, and cyclin D1. Immunoprecipitation was used to detect the ubiquitination of cyclin D1 and the interaction between Fbxo4 and cyclin D1. Ammonium pyrrolidinedithiocarbamate (PDTC) was applied to detect the effect of nuclear factor kappaB (NFκB) activity inhibition on TNFα-induced Sertoli cell proliferation. The adenoviral recombinant plasmid containing rat Fbxo4 gene was constructed to investigate the effect of Fbxo4 overexpression on Sertoli cell proliferation promoted by TNFα.

RESULTS

The in vivo experiment revealed a significant delay of blood-testis barrier maturation in pubertal rats caused by exogenous TNFα. TNFα (10 ng/ml) treatment in vitro was found to promote the proliferation of immature Sertoli cells, accompanied with increased NFκB activity and cyclin D1 protein level. The level of Fbxo4 and ubiquitination of cyclin D1 were decreased after TNFα treatment. Inhibitor of NFκB or overexpression of Fbxo4 could both reverse the TNFα-induced proliferation of immature Sertoli cells, meanwhile restore the ubiquitin-proteasome system-dependent degradation of cyclin D1. Overexpression of Fbxo4 could not affect the activation of NFκB caused by TNFα.

CONCLUSION

These results indicate that TNFα inhibits the ubiquitination and degradation of cyclin D1 through the NFκB pathway, thereby promoting the proliferation of immature Sertoli cell in vitro and inducing the delay of blood-testis barrier maturation in pubertal rats.

Testicular Sertoli Cell Hormones in Differences in Sex Development

The Sertoli cells of the testes play an essential role during gonadal development, in addition to supporting subsequent germ cell survival and spermatogenesis. Anti-Müllerian hormone (AMH) is a member of the TGF-β superfamily, which is secreted by immature Sertoli cells from the 8th week of fetal gestation. lnhibin B is a glycoprotein, which is produced by the Sertoli cells from early in fetal development. In people with a Difference or Disorder of Sex Development (DSD), these hormones may be useful to determine the presence of testicular tissue and potential for spermatogenesis. However, fetal Sertoli cell development and function is often dysregulated in DSD conditions and altered production of Sertoli cell hormones may be detected throughout the life course in these individuals. As such this review will consider the role of AMH and inhibin B in individuals with DSD.

Dimethylbisphenol A inhibits the differentiation of stem Leydig cells in adult male rats by androgen receptor (NR3C4) antagonism

Dimethylbisphenol A (DMBPA) is a novel alternative to bisphenol A. Whether short-term exposure to DMBPA affects Leydig cell regeneration remains unknown. The Leydig cell regeneration model was generated by intraperitoneal injection of 75 mg/kg ethane dimethane sulfonate (EDS) to adult male Sprague-Dawley rats. Leydig cell regeneration began on day 14 after EDS. Rats were gavaged with 0, 10, 50, or 200 mg/kg DMBPA from days 14-28 post-EDS, and Leydig cell regeneration was assessed on days 28 and 56 post-EDS. DMBPA significantly reduced serum testosterone levels on days 28 and 56 at 10 mg/kg and higher doses and sperm count in the caudal epididymis on day 56 at 200 mg/kg, without affecting estradiol, luteinizing hormone, and follicle-stimulating hormone. DMBPA had no effect on Leydig cell number but significantly down-regulated Scarb1 expression at ≥ 10 mg/kg on day 28, Cyp17a1 expression on day 28 at 200 mg/kg and on day 56 at ≥ 10 mg/kg. DMBPA markedly upregulated Srd5a1 expression at doses of 50 and 200 mg/kg on day 56 after EDS. DMBPA significantly down-regulated the expression of Sod1 and Nr3c4 at a dose of 200 mg/kg on day 28. Further semi-quantitative immunohistochemistry showed that DMBPA reduced NR3C4 levels in Leydig and Sertoli cells at 50 and 200 mg/kg. In vitro DMBPA treatment of immature Leydig cells for 24 h showed that it significantly reduced testosterone production at 10 and 50 μM, and further mechanistic studies showed that an NR3C4 agonist 7α-methyl-19-nortestosterone significantly reversed DMBPA-mediated suppression on testosterone output, but the estrogen receptor antagonist ICI 182,780 and G-coupled estrogen receptor 1 agonist G15 had no effect. In conclusion, DMBPA delays Leydig cell regeneration after short-term exposure during early Leydig cell regeneration via NR3C4 antagonism.

High-fat diet aggravates prenatal low-dose DEHP exposure induced spermatogenesis disorder: Characterization of testicular metabolic patterns in mouse offspring

Di-(2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer and has been identified as a male prenatal reproductive toxicant. A high fat diet (HFD) has also been suggested as another potential disruptor of male reproductive function. Despite this potential synergism between DEHP exposure and HFD, little is known about the concomitant effects of prenatal DEHP and a subsequent HFD exposure on male offspring reproductive injury. Here we established a mouse model of prenatal exposure to DEHP (0.2 mg/kg/day) to assess the testicular development and spermatogenesis in offspring subjected to obesogenic diet during the pubertal period. Gross phenotype, hormone profiles and the testicular metabolome were analyzed to determine the underlying mechanism. We found that prenatal exposure to low-dose DEHP resulted in decreased sperm density, decreased testosterone (T) levels, increased luteinizing hormone (LH) levels and testicular germ cell apoptosis. Furthermore, these injury phenotypes were aggravated by pubertal HFD treatment. Testicular riboflavin and biotin metabolites were enriched implying their roles in contributing HFD to exacerbate offspring spermatogenesis disorders due to prenatal low-dose DEHP exposure. Our findings suggest that pubertal HFD exacerbates reproductive dysfunction associated with prenatal exposure to low-dose DEHP in male adult offspring.

Effects of postnatal exposure to tetrabromobisphenol A on testis development in mice and early key events

Whether or not tetrabromobisphenol A (TBBPA) has reproductive developmental toxicity remains controversial. Here, we evaluated the effects of postnatal TBBPA exposure of dams (before weaning) and pups through drinking water (15, 150, 1500 ng/mL) on testis development in mice. On postnatal day (PND) 56, we found that TBBPA exerted little effects on testis weight, anogenital distance, sperm parameters, and the serum testosterone level, but resulted in dose-dependent reductions in the seminiferous tubule area coupled with decreased Sertoli cells and spermatogonia and the number of stage VII-VIII seminiferous tubules, and cytoskeleton damage in Sertoli cells, along with down-regulated expression of marker genes for Sertoli cells, spermatogonia and spermatocyte. Further study revealed that the reduced tubule area coupled decreased Sertoli cell and germ cell numbers and marker gene expression also occurred in TBBPA-treated testes on PND 7, along with reduced cell proliferation and disordered arrangement of Sertoli cell nuclei. On PND 15, most of these testicular alterations were still observed in TBBPA-treated males, and cytoskeleton damage in Sertoli cells became observable. All observations convincingly demonstrate that postnatal exposure to TBBPA disturbed testis development in early life and ultimately caused adverse outcomes in adult testes, and that cell proliferation inhibition, the reduction in the seminiferous tubule area coupled decreased Sertoli cell and germ cell numbers and marker gene expression, and cytoskeleton damage in Sertoli cells, are early events contributing to adverse outcomes in adult testes. Our study improves the understanding of reproductive developmental toxicity of TBBPA, highlighting its risk for human health.

Exposure to Dibutyl Phthalate and Reproductive-Related Outcomes in Animal Models: Evidence From Rodents Study

Background: Dibutyl phthalate (DBP) was an endocrine disruptor, which may lead to cancer and affects reproductive function when accumulated in the body. But the precise role of DBP in the reproductive system remained controversial.

Objective: We employed the meta-analysis to explore the relationship between DBP and reproductive-related outcomes.

Methods: We searched relevant literature in PubMed, EMBASE, and Web of Science databases. The standardized mean differences (SMDs) and their 95% CIs were measured by random-effects models. Funnel plots and Egger’s regression test were applied to assess publication bias.

Results: Finally, 19 literatures were included in this research. The outcomes revealed that DBP was negatively correlated with reproductive organs weight (testis weight: SMD: −0.59; 95% Cl: −1.23, −0.23; seminal vesicles weight: SMD: −0.74; 95% Cl: −1.21, −0.27; prostate weight: SMD: −0.46; 95% Cl: −0.76, −0.16) and sperm parameters (sperm morphology: SMD: 1.29; 95% Cl: 0.63, 1.94; sperm count: SMD: −1.81; 95% Cl: −2.39, −1.23; sperm motility: SMD: −1.92; 95% Cl: −2.62, −1.23).

Conclusion: Our research demonstrated that DBP may be negatively associated with reproductive-related indicators, especially at Gestation exposure period and middle dose (100–500 mg/kg/day).

In vitro effects of cannabidiol and its main metabolites in mouse and human Sertoli cells

Cannabidiol (CBD) is a major cannabinoid present in extracts of the plant Cannabis sativa (marijuana). While the therapeutic effects of CBD on epilepsy have been demonstrated, less is understood regarding its potential adverse effects. Recent studies revealed that CBD induced toxicity in the male reproductive system of animal models. In this study, we used TM4, an immortalized mouse Sertoli cell line, and primary human Sertoli cells to evaluate the toxicities of CBD and its main metabolites, 7-carboxy-CBD and 7-hydroxy-CBD. CBD induced concentration- and time-dependent cytotoxicity in mouse and human Sertoli cells, which mainly resulted from the inhibition of the G1/S-phase cell cycle transition. CBD also inhibited DNA synthesis and downregulated key cell cycle proteins. Moreover, CBD reduced the mRNA and protein levels of a functional marker, Wilms' tumor 1. Similar to CBD, 7-carboxy-CBD and 7-hydroxy-CBD inhibited cellular proliferation and decreased DNA synthesis. 7-Carboxy-CBD was less cytotoxic than CBD, while 7-hydroxy-CBD showed comparable cytotoxicity to CBD in both mouse and human Sertoli cells. Compared to mouse Sertoli cells, CBD, 7-hydroxy-CBD, and 7-carboxy-CBD were more cytotoxic in human Sertoli cells. Our results indicate that CBD and its main metabolites can inhibit cell proliferation in mouse and human Sertoli cells.

Immunohistochemical insights into a hidden pathology: Canine cryptorchidism

Cryptorchidism is a common disorder in the canine population with some aspects still unclear. Although the bilateral condition is known to lead to fertility problems and predisposition to testicular cancer, the neoplastic risk for scrotal testis in unilateral cryptorchid dog is controversial. Therefore, the therapeutic approach to the canine unilateral cryptorchid is arbitrary so far. This study aimed to investigate precancerous testicular lesions, such as immaturity and atrophy, and compare them in scrotal and undescended testes using an in-depth diagnostic analysis based on immunophenotypic patterns. With this purpose, 26 adult male dogs of different ages and breeds, affected by unilateral or bilateral cryptorchidism were enrolled. After surgical removal, testes were examined immunohistochemically to assess their positivity for specific markers of the canine foetal/neonatal period, that is vimentin (VIM), cytokeratin (CK), desmin (DES), inhibin-α (INH), and anti-Müllerian hormone (AMH) in Sertoli cells, and placental alkaline phosphatase (PLAP) in germ cells. Except for the ubiquitous VIM, all the markers were more expressed in neoplastic gonads compared to healthy ones (P < 0.05). Similarly, testes detected with Sertoli cell-only tubules as well as with Sertoli cells hyperplasia showed higher expression than gonads without such alterations for CK, DES, AMH and PLAP, and for CK and DES, respectively (P < 0.05). The same trend was observed in undescended respect to scrotal testes even though their positivity was significant only for DES, INH and AMH (P < 0.05). Immunohistochemical positivity found in scrotal testes of unilateral cryptorchid dogs, even in absence of detectable anatomical abnormalities, was suggestive of precancerous lesions. Despite the limited sample size, this study could help to clarify the predisposition to neoplastic development in normally descended testes. These markers expression in adult life could allow identifying the early stages of the testicular carcinogenesis process besides suggesting a precautionary bilateral surgical approach in unilateral cryptorchid dogs.

A Comprehensive Assessment of Associations between Prenatal Phthalate Exposure and the Placental Transcriptomic Landscape

BACKGROUND

Phthalates are commonly used endocrine-disrupting chemicals that are ubiquitous in the general population. Prenatal phthalate exposure may alter placental physiology and fetal development, leading to adverse perinatal and childhood health outcomes.

OBJECTIVE

We examined associations between prenatal phthalate exposure in the second and third trimesters and the placental transcriptome at birth, including genes and long noncoding RNAs (lncRNAs), to gain insight into potential mechanisms of action during fetal development.

METHODS

The ECHO PATHWAYs consortium quantified 21 urinary phthalate metabolites from 760 women enrolled in the CANDLE study (Shelby County, TN) using high-performance liquid chromatography-tandem mass spectrometry. Placental transcriptomic data were obtained using paired-end RNA sequencing. Linear models were fitted to estimate separate associations between maternal urinary phthalate metabolite concentration during the second and third trimester and placental gene expression at birth, adjusted for confounding variables. Genes were considered differentially expressed at a Benjamini-Hochberg false discovery rate (FDR) p<0.05. Associations between phthalate metabolites and biological pathways were identified using self-contained gene set testing and considered significantly altered with an FDR-adjusted p<0.2.

RESULTS

We observed significant associations between second-trimester phthalate metabolites mono (carboxyisooctyl) phthalate (MCIOP), mono-2-ethyl-5-carboxypentyl phthalate, and mono-2-ethyl-5-oxohexyl phthalate and 18 genes in total, including four lncRNAs. Specifically, placental expression of NEAT1 was associated with multiple phthalate metabolites. Third-trimester MCIOP and mono-isobutyl phthalate concentrations were significantly associated with placental expression of 18 genes and two genes, respectively. Expression of genes within 27 biological pathways was associated with mono-methyl phthalate, MCIOP, and monoethyl phthalate concentrations.

DISCUSSION

To our knowledge, this is the first genome-wide assessment of the relationship between the placental transcriptome at birth and prenatal phthalate exposure in a large and diverse birth cohort. We identified numerous genes and lncRNAs associated with prenatal phthalate exposure. These associations mirror findings from other epidemiological and in vitro analyses and may provide insight into biological pathways affected in utero by phthalate exposure. https://doi.org/10.1289/EHP8973.

Sertoli cell-derived exosome-mediated transfer of miR-145-5p inhibits Leydig cell steroidogenesis by targeting steroidogenic factor 1

In the mammalian testis, two distinct populations of Sertoli cells (SCs), the immature SCs (ISCs) and adult SCs (ASCs), play significant roles in regulating the development and function of Leydig cells. However, the effect of different SC types on the function of Leydig cells is poorly understood. Here, our study showed that miR-145-5p expression was significantly different in SCs at different stages, with the highest expression observed in ISCs. Exosomes mediate the transfer of miR-145-5p from ISCs to Leydig cells. Overexpression of miR-145-5p in Leydig cells significantly downregulated steroidogenic gene expression and inhibited testosterone synthesis. Additionally, miR-145-5p functioned by directly targeted steroidogenic factor-1 (Sf-1) and downregulated the expression of SF-1, which further downregulated the expression of steroidogenic genes, induced accumulation of lipid droplets, and eventually suppressed testosterone production. These findings demonstrate that SC-derived miR-145-5p plays a significant role in regulating the functions of Leydig cells and may therefore serve as a diagnostic biomarker for male hypogonadism developmental abnormalities during puberty.

The Production of Testosterone and Gene Expression in Neonatal Testes of Rats Exposed to Diisoheptyl Phthalate During Pregnancy is Inhibited

Background: Diisoheptyl phthalate (DIHP) is a phthalate plasticizer, which is a branched phthalate. Here, we reported the effects of gestational exposure to DIHP on testis development in male rats.

Methods: Pregnant Sprague-Dawley rats were orally fed with vehicle (corn oil, control) or DIHP (10, 100, 500, and 1,000 mg/kg) from gestational day (GD) 12–21. At GD21, serum testosterone levels, the number and distribution of fetal Leydig cells, and testicular mRNA and protein levels, the incidence of multinucleated gonocytes, and focal testicular hypoplasia in the neonatal testis were measured.

Results: DIHP increased the fetal Leydig cell cluster size and decreased the fetal Leydig cell size with LOAEL of 10 mg/kg. DIHP did not affect the fetal Leydig cell number. DIHP significantly lowered serum testosterone levels, down-regulated the expression of steroidogenesis-related genes (Lhcgr, Star, Cyp11a1, Hsd3b1, Cyp17a1, and Hsd17b3) and testis descent-related gene (Insl3) as well as protein levels of cholesterol side-chain cleavage enzyme (CYP11A1) and insulin-like 3 (INSL3). DIHP dose-dependently increased the percentage of multinucleated gonocytes with the low observed adverse-effect level (LOAEL) of 100 mg/kg. DIHP induced focal testicular hypoplasia.

Conclusion: Gestational exposure to DIHP causes testis dysgenesis in rats.

Do Males Affect Twinning Events? A Review of Current Findings/Twin Research Reviews: Monozygotic Twins Discordant for Parkinson's Disease; Fetal Loss in Twin Pregnancies Following Prenatal Diagnosis; Uterine Rupture and Repair in an Early Twin Pregnancy; Twin Study of Affectionate Communication/Human Interest: Conjoined Twins in a Triplet Set; Identical Twin Nurses Deliver Identical Twins; Identical Twins Discordant for COVID-19 Recovery Course; Identical Twins Pass Away from COVID-19; Archeological Finds of Oldest Identical Twins

Research into the origins of twinning has focused mostly on contributions from the female side of the family. A review of current findings suggests that possible male contributions to twinning events have been overlooked. This section is followed by brief reviews of twin research concerning monozygotic twins discordant for Parkinson's disease, fetal loss in twin pregnancies following prenatal diagnosis, uterine rupture and repair in an early twin pregnancy and a twin study of affectionate communication. The concluding portion of this article presents human interest stories involving twins that are both informative and poignant, namely conjoined twins in a triplet set, identical twin nurses who delivered identical twins, identical twins discordant for COVID-19 recovery course, identical twins who passed away from COVID-19 and archeological finds of the oldest identical twins.

Time response of rat testicular alterations induced by cryptorchidism and orchiopexy

Cryptorchidism is one of the main risk factors for infertility and testicular cancer. Orchiopexy surgery corrects cryptorchidism effects. Different models of cryptorchidism developed in the rat include surgery. We assessed testicular alterations in rats submitted to surgical cryptorchidism and examined their potential for reversibility at different time points in order to verify time dependency effect(s) on the recovery of the undescended testes. Cryptorchidism was induced in 3-week-old rats. Animals were euthanized 3, 6 or 11 weeks after surgery to evaluate the morphological progression of cryptorchidism-induced germinative epithelial alterations. Other groups underwent orchiopexy 3, 5 or 9 weeks after surgical cryptorchidism, before or after puberty. Animals were euthanized 3 or 8 weeks after orchiopexy. Controls underwent sham surgery at the same time points as the surgical groups. Cryptorchid testes showed decreased weight, germinative epithelial degeneration, apoptosis and vacuolation, corresponding to impairment of spermatogenesis and of Sertoli cells. Some tubules has a Sertoli cell-only pattern and atrophy. The intensity of damage was related to the duration of cryptorchidism. After orchiopexy, spermatogenesis completely recovered only when testicular relocation occurred before puberty and the interval for recovery was extended. These results indicate that age, sexual maturity and extension of germ cell damage were relevant for producing germ cell restoration and normal spermatogenesis. We provide original observations on the time dependency of testicular alterations induced by cryptorchidism and their restoration using morphologic, morphometric and immunohistochemical approaches. It may be useful to study germ cell impairment, progression and recovery in different experimental settings, including exposure to exogenous chemicals.

Intrauterine exposure to diethylhexyl phthalate disrupts gap junctions in the fetal rat testis

Fetal exposure to certain phthalate esters can disrupt testis development in rodents and lead to male reproductive disorders, but with a causal link less certain in humans. Di(2-ethylhexyl) phthalate (DEHP) is one of the most common phthalates found in the environment and in rodents it is known to induce serious testis toxicity, as well as male reproductive disorders including cryptorchidism, hypospadias, impaired spermatogenesis and reduced fertility. In this study, we show that perinatal DEHP exposure disrupts gap junction localization in fetal and postnatal rat testis and correlate these findings to morphological changes. The protein Connexin 43 (CX43), normally expressed strongly in testicular gap junctions, was markedly downregulated in Leydig cells of DEHP-exposed fetal testes. In the postnatal testes, CX43 expression was recovered in the DEHP-exposed animals, even though Leydig cell clusters and malformed cords with intratubular Leydig cells were still present.

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DEHP disrupts gap junction localization in fetal and postnatal rat testis.

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DEHP exposure reduces Cx43-positive gap junctions in Leydig cell clusters in fetal rat testis.

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Leydig cell gap junctions recover in postnatal testis after early life DEHP exposure.

A strategy to validate a selection of human effect biomarkers using adverse outcome pathways: Proof of concept for phthalates and reproductive effects

Human biomonitoring measures the concentrations of environmental chemicals or their metabolites in body fluids or tissues. Complementing exposure biomarkers with mechanistically based effect biomarkers may further elucidate causal pathways between chemical exposure and adverse health outcomes. We combined information on effect biomarkers previously implemented in human observational studies with mechanisms of action reported in experimental studies and with information from published Adverse Outcome Pathways (AOPs), focusing on adverse reproductive effects of phthalate exposure. Phthalates constitute a group of chemicals that are ubiquitous in consumer products and have been related to a wide range of adverse health effects. As a result of a comprehensive literature search, we present an overview of effect biomarkers for reproductive toxicity that are substantiated by mechanistic information. The activation of several receptors, such as PPARα, PPARγ, and GR, may initiate events leading to impaired male and female fertility as well as other adverse effects of phthalate exposure. Therefore, these receptors appear as promising targets for the development of novel effect biomarkers. The proposed strategy connects the fields of epidemiology and toxicology and may strengthen the weight of evidence in observational studies that link chemical exposures to health outcomes.

In utero exposure to hexavalent chromium disrupts rat fetal testis development

Hexavalent chromium (Cr⁶⁺) acts as an endocrine disruptor. Herein, we investigated effects of Cr⁶⁺ on the development of rat fetal Leydig and Sertoli cells, which support differentiation of the male reproductive tract in late gestation. Female pregnant Sprague Dawley rats were gavaged with potassium dichromate (0, 3, 6, and 12 mg/kg) from gestational days (GD) 12 to GD 21. Leydig and Sertoli cell function was evaluated by investigating serum testosterone levels, cell number and distribution, and the expression levels of Leydig and Sertoli cell genes and proteins. Cr⁶⁺ increased serum testosterone level at dose of 3 mg/kg (1.170 ± 0.121 ng/ml vs. 0.720 ± 0.082 ng/ml in the control), while lowered it at dose of 12 mg/kg (0.400 ± 0.098 ng/ml). In addition, it showed that Cr⁶⁺ dose-dependently reduced Leydig cell size and cytoplasmic size and decreased the percentage of medium fetal Leydig cell cluster at dose of 12 mg/kg. Further study demonstrated that the expression of Leydig cell (Lhcgr, Scarb1, and Hsd3b1) and Sertoli cell (Fshr, Pdgfa, and Lif) genes in the testis was upregulated at dose of 3 mg/kg while the expression of Lhcgr, Hsd17b3 and Igf1 was downregulated by Cr⁶⁺ at dose of 12 mg/kg. In conclusion, Cr⁶⁺ had biphasic effects on fetal Leydig cell development with low dose to stimulate testosterone production and high dose to inhibit it, possibly via biphasically regulating growth factor gene expression in fetal Sertoli cells.

A young testicular microenvironment protects Leydig cells against age-related dysfunction in a mouse model of premature aging

Testicular Leydig cells (LCs) are the primary source of circulating androgen in men. As men age, circulating androgen levels decline. However, whether reduced LC steroidogenesis results from specific effects of aging within LCs or reflects degenerative alterations to the wider supporting microenvironment is unclear; inability to separate intrinsic LC aging from that of the testicular microenvironment in vivo has made this question difficult to address. To resolve this, we generated novel mouse models of premature aging, driven by CDGSH iron sulfur domain 2 (Cisd2) deletion, to separate the effects of cell intrinsic aging from extrinsic effects of aging on LC function. At 6 mo of age, constitutive Cisd2-deficient mice display signs of premature aging, including testicular atrophy, reduced LC and Sertoli cell (SC) number, decreased circulating testosterone, increased luteinizing hormone/testosterone ratio, and decreased expression of steroidogenic mRNAs, appropriately modeling primary testicular dysfunction observed in aging men. However, mice with Cisd2 deletion (and thus premature aging) restricted to either LCs or SCs were protected against testicular degeneration, demonstrating that age-related LCs dysfunction cannot be explained by intrinsic aging within either the LC or SC lineages alone. We conclude that age-related LC dysfunction is largely driven by aging of the supporting testicular microenvironment.—Curley, M., Milne, L., Smith, S., Jørgensen, A., Frederiksen, H., Hadoke, P., Potter, P., Smith, L. B. A Young testicular microenvironment protects Leydig cells against age-related dysfunction in a mouse model of premature aging.

Effects of gestational exposure to di-n-butyl phthalate and mineral oil on testis development of the Mongolian gerbil

Phthalate esters are endocrine disrupters that can affect the development of the testis in a species-specific manner. However, their interference in the male gonads of the Mongolian gerbil is unknown. The aim of the present study was to evaluate whether gestational exposure to di-n-butyl phthalate (DBP) interferes with the development of the gerbil testis during the first six weeks of life. Males were evaluated at 1, 7, 14, 28, 35 and 42 days of age in an untreated (control) group or groups exposed from 8 to 23 days gestation to DBP (100 mg kg−1 day−1 in mineral oil) or vehicle by maternal gavage. DBP exposure impaired cell proliferation within the seminiferous cords at birth, but increased proliferation at the end of the first week, when higher testosterone concentrations were observed. The vehicle (mineral oil) reduced the total number of gonocytes and attenuated the decrease in testosterone concentrations at 7 days. The vehicle also altered gonocyte relocation at 14 days and increased oestrogen concentrations at 28 days by approximately 112%. In summary, both DBP and oil interfered in gonadal development and testosterone plasma concentrations in the first week of postnatal life. However, the changes observed at the beginning of puberty were not seen after exposure to DBP, indicating a more harmful effect of mineral oil in this period.

MiR-301b-3p/3584-5p enhances low-dose mono-n-butyl phthalate (MBP)-induced proliferation by targeting Rasd1 in Sertoli cells

To investigate the possible molecular mechanism of low concentration plasticizer mono-n-butyl phthalate (MBP) -induced juvenile Sertoli cells (SCs) proliferation, we evaluated global alterations of miRNA and mRNA expression in rat SCs treated with 0.1mM MBP. Microarray analysis revealed that miR-3584-5p and miR-301b-3p were up-regulated and their common target gene Dexamethasone-induced Ras-related protein 1 (Rasd1) was down-regulated. Further work suggested that SCs proliferation induced by low concentration MBP in vitro might be mediated by Rasd1 regulating ERK1/2 signaling pathway. The present study is first to investigate the effect of low-dose MBP on SCs proliferation and may enhance our understanding on the modes of action of low concentration MBP on male reproductive system. We hope the results will contribute to explain the causes of precocious puberty and testicular tumors induced by exogenous chemicals.

The effects of the obesogen tributyltin on the metabolism of Sertoli cells cultured ex vivo

Human exposure to environmental contaminants is widespread. Some of these contaminants have the ability to interfere with adipogenesis, being thus considered as obesogens. Recently, obesogens have been singled out as a cause of male infertility. Sertoli cells (SCs) are essential for male fertility and their metabolic performance, especially glucose metabolism, is under a tight endocrine control, being essential for the success of spermatogenesis. Herein, we studied the impact of the model obesogen tributyltin in the metabolic profile of SCs. For that, ex vivo-cultured rat SCs were exposed to increasing doses of tributyltin. SCs proliferation was evaluated by the sulforhodamine B assay and the maturation state of the cells was assessed by the expression of specific markers (inhibin B and the androgen receptor) by quantitative polymerase chain reaction. The metabolic profile of SCs was established by studying metabolites consumption/production by nuclear magnetic resonance spectroscopy and by analyzing the expression of key transporters and enzymes involved in glycolysis by Western blot. The proliferation of SCs was only affected in the cells exposed to the highest dose (1000 nM) of tributyltin. Notably, SCs exposed to 10 nM tributyltin decreased the consumption of glucose and pyruvate, as well as the production of lactate. The decreased lactate production hampers the development of germ cells. Intriguingly, the lowest levels of tributyltin were more prone to modulate the expression of key players of the glycolytic pathway. This is the first study showing that tributyltin reprograms glucose metabolism of SCs under ex vivo conditions, suggesting new targets and mechanisms through which obesogens modulate the metabolism of SCs and thus male (in)fertility.

Sertoli Cell Number Defines and Predicts Germ and Leydig Cell Population Sizes in the Adult Mouse Testis

Sertoli cells regulate differentiation and development of the testis and are essential for maintaining adult testis function. To model the effects of dysregulating Sertoli cell number during development or aging, we have used acute diphtheria toxin-mediated cell ablation to reduce Sertoli cell population size. Results show that the size of the Sertoli cell population that forms during development determines the number of germ cells and Leydig cells that will be present in the adult testis. Similarly, the number of germ cells and Leydig cells that can be maintained in the adult depends directly on the size of the adult Sertoli cell population. Finally, we have used linear modeling to generate predictive models of testis cell composition during development and in the adult based on the size of the Sertoli cell population. This study shows that at all ages the size of the Sertoli cell population is predictive of resulting testicular cell composition. A reduction in Sertoli cell number/proliferation at any age will therefore lead to a proportional decrease in germ cell and Leydig cell numbers, with likely consequential effects on fertility and health.

In Utero Exposure to Di( n-butyl)phthalate Induces Morphological and Biochemical Changes in Rats Postpuberty

Pregnant Sprague-Dawley rats were orally administered di( n-butyl)phthalate (DBP; 100 mg/kg/day) on gestation days (GD) 12 to 21. We investigated the male offspring and probed morphological alterations in Sertoli cells at 7, 9, 14, and 17 weeks of age. Parameters assessed in this study included offspring number, sex ratios, body weights, testis weights, seminiferous tubule (ST) profile numbers and diameters, number of vimentin-labeled Sertoli cells, and both testosterone and follicle-stimulating hormone (FSH) levels. Testicular weight/body weight ratios and the numbers and diameters of ST in maximum transverse testicular sections were statistically similar at weeks 7 and 9; however, at weeks 14 and 17, they were statistically different and displayed higher BrdU-positive Sertoli cells/Sertoli cell ratios in the DBP treatment group. Noteworthily, the serum FSH levels were higher and testicular testosterone levels were lower in the DBP treatment group. To our knowledge, the present study is the first to report that in utero DBP exposure significantly increased Sertoli cell numbers and their cellular proliferation from postpuberty to adulthood, with a significant decrease in testicular testosterone and an increase in FSH.

Dibutyl phthalate induced testicular dysgenesis originates after seminiferous cord formation in rats

Administration of dibutyl phthalate (DBP) to pregnant rats causes reproductive disorders in male offspring, resulting from suppression of intratesticular testosterone, and is used as a model for human testicular dysgenesis syndrome (TDS). DBP exposure in pregnancy induces focal dysgenetic areas in fetal testes that appear between e19.5–e21.5, manifesting as focal aggregation of Leydig cells and ectopic Sertoli cells (SC). Our aim was to identify the origins of the ectopic SC. Time-mated female rats were administered 750 mg/kg/day DBP in three different time windows: full window (FW; e13.5–e20.5), masculinisation programming window (MPW; e15.5–e18.5), late window (LW; e19.5–e20.5). We show that DBP-MPW treatment produces more extensive and severe dysgenetic areas, with more ectopic SC and germ cells (GC) than DBP-FW treatment; DBP-LW induces no dysgenesis. Our findings demonstrate that ectopic SC do not differentiate de novo, but result from rupture of normally formed seminiferous cords beyond e20.5. The more severe testis dysgenesis in DBP-MPW animals may result from the presence of basally migrating GC and a weakened basal lamina, whereas GC migration was minimal in DBP-FW animals. Our findings provide the first evidence for how testicular dysgenesis can result after normal testis differentiation/development and may be relevant to understanding TDS in human patients.

Experimentally induced testicular dysgenesis syndrome originates in the masculinization programming window

The testicular dysgenesis syndrome (TDS) hypothesis, which proposes that common reproductive disorders of newborn and adult human males may have a common fetal origin, is largely untested. We tested this hypothesis using a rat model involving gestational exposure to dibutyl phthalate (DBP), which suppresses testosterone production by the fetal testis. We evaluated if induction of TDS via testosterone suppression is restricted to the "masculinization programming window" (MPW), as indicated by reduction in anogenital distance (AGD). We show that DBP suppresses fetal testosterone equally during and after the MPW, but only DBP exposure in the MPW causes reduced AGD, focal testicular dysgenesis, and TDS disorders (cryptorchidism, hypospadias, reduced adult testis size, and compensated adult Leydig cell failure). Focal testicular dysgenesis, reduced size of adult male reproductive organs, and TDS disorders and their severity were all strongly associated with reduced AGD. We related our findings to human TDS cases by demonstrating similar focal dysgenetic changes in testes of men with preinvasive germ cell neoplasia (GCNIS) and in testes of DBP-MPW animals. If our results are translatable to humans, they suggest that identification of potential causes of human TDS disorders should focus on exposures during a human MPW equivalent, especially if negatively associated with offspring AGD.

In utero exposure of high-dose di-n-butyl phthalate resulted in opposite effects on testicular cell apoptosis in late embryonic and pubertal male rat offspring

Objective:

To investigate the effects of in utero exposure to high-dose di- n-butyl phthalate (DBP) on testicular cell apoptosis in late embryonic and pubertal male rat offspring.

Methods:

Twenty pregnant Sprague-Dawley (SD) rats were divided into two groups. During gestation day (GD) 12 to GD 19, control group was given 1 ml day−1 of olive oil and experimental group was given DBP 500 mg kg−1 day−1 by gavage. On GD 19.5 and postnatal day (PND) 45, the testes were removed. Morphological analysis of the testes was observed by transmission electron microscopy and hematoxylin and eosin (H&E) staining. Testicular cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). The expression of Bcl-2, Bax, and p53 was presented by immunohistochemistry (IHC) and western blot. Data of the two groups was compared using independent samples t-test and Mann–Whitney test by SPSS 20.0.

Results:

H&E staining showed that spermatogenetic cells were significantly decreased in DBP exposed pubertal rat testis. The apoptosis index of testes in DBP-treated group was significantly lower on GD 19.5 but higher on PND 45 than that of the controls ( p < 0.01). IHC and western blot revealed significantly increased expression of Bcl-2 in GD 19.5 rat testis and Bax and p53 in PND 45 rat testis after DBP exposure, compared with the control ( p < 0.05).

Conclusion:

In utero exposure of high-dose DBP resulted in opposite effects on testicular cell apoptosis in late embryonic and pubertal rat offspring. The overexpression of Bcl-2, Bax, and p53 might be related to the occurrence of abnormal apoptosis and finally produce male infertility.

Di(2-Ethylhexyl) Phthalate Exposure In Utero Damages Sertoli Cell Differentiation Via Disturbance of Sex Determination Pathway in Fetal and Postnatal Mice

Mice may share similar mechanism with human underlying reproductive toxicity induced by di(2-ethylhexyl) phthalate (DEHP), which is not supposed to be associated with decreased testicular testosterone. Pregnant mice were exposed to DEHP by gavage, with the dosage regime beginning at human relevant exposure level. After in utero DEHP exposure, loss of Sertoli cells and germ cells were observed in the male pups at postnatal days 21. And SRY-related HMG box 9 (SOX9), Fibroblast growth factor-9 (FGF9), and Double-sex and Mab-3 related transcripttion factor 1 (DMRT1) proteins were significantly downregulated by DEHP at 2 mg/kg/d and above, suggesting the depression of Sertoli cell differentiation. The repression of Sox9 genes expression was supported by whole-mount in situ hybridization and real-time real-time-quantitative PCR. The expressions of Cyp11α1 and Star were not significantly affected by in utero DEHP exposure, indicating the absence of effects on testosterone biosynthesis. Furthermore, the testosterone-independent pathway regulating Sertoli cells differentiation was disturbed in fetus by DEHP at 2 mg/kg/d and above during the critical time window of sex determination, involving Gadd45g → Gata4/Fog2 → Sry → Sox9 → Fgf9 The results suggest that in utero DEHP exposure damaged Sertoli cells in the postnatal life of mice offspring via disturbance of the differentiation regulating pathway, potentially inducing declines in spermatogenesis.

Analgesic exposure in pregnant rats affects fetal germ cell development with inter-generational reproductive consequences

Analgesics which affect prostaglandin (PG) pathways are used by most pregnant women. As germ cells (GC) undergo developmental and epigenetic changes in fetal life and are PG targets, we investigated if exposure of pregnant rats to analgesics (indomethacin or acetaminophen) affected GC development and reproductive function in resulting offspring (F1) or in the F2 generation. Exposure to either analgesic reduced F1 fetal GC number in both sexes and altered the tempo of fetal GC development sex-dependently, with delayed meiotic entry in oogonia but accelerated GC differentiation in males. These effects persisted in adult F1 females as reduced ovarian and litter size, whereas F1 males recovered normal GC numbers and fertility by adulthood. F2 offspring deriving from an analgesic-exposed F1 parent also exhibited sex-specific changes. F2 males exhibited normal reproductive development whereas F2 females had smaller ovaries and reduced follicle numbers during puberty/adulthood; as similar changes were found for F2 offspring of analgesic-exposed F1 fathers or mothers, we interpret this as potentially indicating an analgesic-induced change to GC in F1. Assuming our results are translatable to humans, they raise concerns that analgesic use in pregnancy could potentially affect fertility of resulting daughters and grand-daughters.

Effects of maternal and lactational exposure to 2-hydroxy-4-methoxybenzone on development and reproductive organs in male and female rat offspring

BACKGROUND

2-Hydroxy-4-methoxybenzophenone (HMB) is an ultraviolet (UV) absorbing compound used in many cosmetic products as a UV-protecting agent and in plastics for preventing UV-induced photodecomposition. HMB has been detected in over 95% of randomly collected human urine samples from adults and from premature infants, and it may have estrogenic potential.

METHODS

To determine the effects of maternal and lactational exposure to HMB on development and reproductive organs of offspring, time-mated female Harlan Sprague-Dawley rats were dosed with 0, 1000, 3000, 10,000, 25,000, or 50,000 ppm HMB (seven to eight per group) added to chow from gestation day 6 until weaning on postnatal day (PND) 23.

RESULTS AND CONCLUSION

Exposure to HMB was associated with reduced body and organ weights in female and male offspring. No significant differences were observed in the number of implantation sites/litter, mean resorptions/litter, % litters with resorptions, number and weights of live fetuses, or sex ratios between the control and HMB dose groups. Normalized anogenital distance in male pups at PND 23 was decreased in the highest dose group. Spermatocyte development was impaired in testes of male offspring in the highest dose group. In females, follicular development was delayed in the highest dose group. However, by evaluating levels of the compound in rat serum, the doses at which adverse events occurred are much higher than usual human exposure levels. Thus, exposure to less than 10,000 ppm HMB does not appear to be associated with adverse effects on the reproductive system in rats.

Phthalate esters affect maturation and function of primate testis tissue ectopically grafted in mice

Di-n-Butyl (DBP) and Di-(2-EthylHexyl) (DEHP) phthalates can leach from daily-use products resulting in environmental exposure. In male rodents, phthalate exposure results in reproductive effects. To evaluate effects on the immature primate testis, testis fragments from 6-month-old rhesus macaques were grafted subcutaneously to immune-deficient mice, which were exposed to 0, 10, or 500 mg/kg of DBP or DEHP for 14 weeks or 28 weeks (DBP only). DBP exposure reduced the expression of key steroidogenic genes, indicating that Leydig cell function was compromised. Exposure to 500 mg/kg impaired tubule formation and germ cell differentiation and reduced numbers of spermatogonia. Exposure to 10 mg/kg did not affect development, but reduced Sertoli cell number and resulted in increased expression of inhibin B. Exposure to DEHP for 14 week also affected steroidogenic genes expression. Therefore, long-term exposure to phthalate esters affected development and function of the primate testis in a time and dosage dependent manner.

Man is not a big rat: concerns with traditional human risk assessment of phthalates based on their anti-androgenic effects observed in the rat foetus

Phthalates provide one of the most documented example evidencing how much we must be cautious when using the traditional paradigm based on extrapolation of experimental data from rodent studies for human health risk assessment of endocrine disruptors (EDs). Since foetal testis is known as one of the most sensitive targets of EDs, phthalate risk assessment is routinely based on the capacity of such compounds to decrease testosterone production by the testis or to impair masculinization in the rat during foetal life. In this paper, the well-established inhibiting effects of phthalates of the foetal Leydig cells function in the rat are briefly reviewed. Then, data obtained in humans and other species are carefully analysed. Already in January 2009, using the organotypic culture system named Fetal Testis Assay (FeTA) that we developed, we reported that phthalates might not affect testosterone production in human foetal testes. Several recent experimental studies using xenografts confirm the absence of detectable anti-androgenic effect of phthalates in the human foetal testes. Epidemiological studies led to contradictory results. Altogether, these findings suggest that phthalates effects on foetal Leydig cells are largely species-specific. Consequently, the phthalate threshold doses that disturb foetal steroidogenesis in rat testes and that are presently used to define the acceptable daily intake levels for human health protection must be questioned. This does not mean that phthalates are safe because these compounds have many deleterious effects upon germ cell development that may be common to the different studied species including human. More generally, the identification of common molecular, cellular or/and phenotypic targets in rat and human testes should precede the choice of the toxicological endpoint in rat to accurately assess the safety threshold of any ED in humans.

The Warburg effect revisited--lesson from the Sertoli cell

Otto Warburg observed that cancerous cells prefer fermentative instead of oxidative metabolism of glucose, although the former is in theory less efficient. Since Warburg's pioneering works, special attention has been given to this difference in cell metabolism. The Warburg effect has been implicated in cell transformation, immortalization, and proliferation during tumorigenesis. Cancer cells display enhanced glycolytic activity, which is correlated with high proliferation, and thus, glycolysis appears to be an excellent candidate to target cancer cells. Nevertheless, little attention has been given to noncancerous cells that exhibit a "Warburg-like" metabolism with slight, but perhaps crucial, alterations that may provide new directions to develop new and effective anticancer therapies. Within the testis, the somatic Sertoli cell (SC) presents several common metabolic features analogous to cancer cells, and a clear "Warburg-like" metabolism. Nevertheless, SCs actively proliferate only during a specific time period, ceasing to divide in most species after puberty, when they become terminally differentiated. The special metabolic features of SC, as well as progression from the immature but proliferative state, to the mature nonproliferative state, where a high glycolytic activity is maintained, make these cells unique and a good model to discuss new perspectives on the Warburg effect. Herein we provide new insight on how the somatic SC may be a source of new and exciting information concerning the Warburg effect and cell proliferation.

Fetal programming of adult Leydig cell function by androgenic effects on stem/progenitor cells

Fetal growth plays a role in programming of adult cardiometabolic disorders, which in men, are associated with lowered testosterone levels. Fetal growth and fetal androgen exposure can also predetermine testosterone levels in men, although how is unknown, because the adult Leydig cells (ALCs) that produce testosterone do not differentiate until puberty. To explain this conundrum, we hypothesized that stem cells for ALCs must be present in the fetal testis and might be susceptible to programming by fetal androgen exposure during masculinization. To address this hypothesis, we used ALC ablation/regeneration to identify that, in rats, ALCs derive from stem/progenitor cells that express chicken ovalbumin upstream promoter transcription factor II. These stem cells are abundant in the fetal testis of humans and rodents, and lineage tracing in mice shows that they develop into ALCs. The stem cells also express androgen receptors (ARs). Reduction in fetal androgen action through AR KO in mice or dibutyl phthalate (DBP) -induced reduction in intratesticular testosterone in rats reduced ALC stem cell number by ∼40% at birth to adulthood and induced compensated ALC failure (low/normal testosterone and elevated luteinizing hormone). In DBP-exposed males, this failure was probably explained by reduced testicular steroidogenic acute regulatory protein expression, which is associated with increased histone methylation (H3K27me3) in the proximal promoter. Accordingly, ALCs and ALC stem cells immunoexpressed increased H3K27me3, a change that was also evident in ALC stem cells in fetal testes. These studies highlight how a key component of male reproductive development can fundamentally reprogram adult hormone production (through an epigenetic change), which might affect lifetime disease risk.

Muscle glycogen synthase isoform is responsible for testicular glycogen synthesis: glycogen overproduction induces apoptosis in male germ cells

Glycogen is the main source of glucose for many biological events. However, this molecule may have other functions, including those that have deleterious effects on cells. The rate-limiting enzyme in glycogen synthesis is glycogen synthase (GS). It is encoded by two genes, GYS1, expressed in muscle (muscle glycogen synthase, MGS) and other tissues, and GYS2, primarily expressed in liver (liver glycogen synthase, LGS). Expression of GS and its activity have been widely studied in many tissues. To date, it is not clear which GS isoform is responsible for glycogen synthesis and the role of glycogen in testis. Using RT-PCR, Western blot and immunofluorescence, we have detected expression of MGS but not LGS in mice testis during development. We have also evaluated GS activity and glycogen storage at different days after birth and we show that both GS activity and levels of glycogen are higher during the first days of development. Using RT-PCR, we have also shown that malin and laforin are expressed in testis, key enzymes for regulation of GS activity. These proteins form an active complex that regulates MGS by poly-ubiquitination in both Sertoli cell and male germ cell lines. In addition, PTG overexpression in male germ cell line triggered apoptosis by caspase3 activation, proposing a proapoptotic role of glycogen in testis. These findings suggest that GS activity and glycogen synthesis in testis could be regulated and a disruption of this process may be responsible for the apoptosis and degeneration of seminiferous tubules and possible cause of infertility.

Prepubertal mouse testis growth and maturation and androgen production are acutely sensitive to di-n-butyl phthalate

Phthalates are plasticizers with widespread industrial, domestic, and medical applications. Epidemiological data indicating increased incidence of testicular dysgenesis in boys exposed to phthalates in utero are reinforced by studies demonstrating that phthalates impair fetal rodent testis development. Because humans are exposed to phthalates continuously from gestation through adulthood, it is imperative to understand what threat phthalates pose at other life stages. To determine the impact during prepuberty, we assessed the consequences of oral administration of 1 to 500 mg di-n-butyl phthalate (DBP)/kg/d in corn oil to wild-type (C57BL/6J) male mice from 4 to 14 days of age. Dose-dependent effects on testis growth correlated with reduced Sertoli cell proliferation. Histological and immunohistochemical analyses identified delayed spermatogenesis and impaired Sertoli cell maturation after exposure to 10 to 500 mg DBP/kg/d. Interference with the hypothalamic-pituitary-gonadal axis was indicated in mice fed 500 mg DBP/kg/d, which had elevated circulating inhibin but no change in serum FSH. Increased immunohistochemical staining for inhibin-α was apparent at doses of 10 to 500 mg DBP/kg/d. Serum testosterone and testicular androgen activity were lower in the 500 mg DBP/kg/d group; however, reduced anogenital distance in all DBP-treated mice suggested impaired androgen action at earlier time points. Long-term effects were evident, with smaller anogenital distance and indications of disrupted spermatogenesis in adult mice exposed prepubertally to doses from 1 mg DBP/kg/d. These data demonstrate the acute sensitivity of the prepubertal mouse testis to DBP at doses 50- to 500-fold lower than those used in rat and identify the upregulation of inhibin as a potential mechanism of DBP action.

Human fetal testis xenografts are resistant to phthalate-induced endocrine disruption

BACKGROUND

In utero exposure to endocrine-disrupting chemicals may contribute to testicular dysgenesis syndrome (TDS), a proposed constellation of increasingly common male reproductive tract abnormalities (including hypospadias, cryptorchidism, hypospermatogenesis, and testicular cancer). Male rats exposed in utero to certain phthalate plasticizers exhibit multinucleated germ cell (MNG) induction and suppressed steroidogenic gene expression and testosterone production in the fetal testis, causing TDS-consistent effects of hypospadias and cryptorchidism. Mice exposed to phthalates in utero exhibit MNG induction only. This disparity in response demonstrates a species-specific sensitivity to phthalate-induced suppression of fetal Leydig cell steroidogenesis. Importantly, ex vivo phthalate exposure of the fetal testis does not recapitulate the species-specific endocrine disruption, demonstrating the need for a new bioassay to assess the human response to phthalates.

OBJECTIVES

In this study, we aimed to develop and validate a rat and mouse testis xenograft bioassay of phthalate exposure and examine the human fetal testis response.

METHODS

Fetal rat, mouse, and human testes were xenografted into immunodeficient rodent hosts, and hosts were gavaged with a range of phthalate doses over multiple days. Xenografts were harvested and assessed for histopathology and steroidogenic end points.

RESULTS

Consistent with the in utero response, phthalate exposure induced MNG formation in rat and mouse xenografts, but only rats exhibited suppressed steroidogenesis. Across a range of doses, human fetal testis xenografts exhibited MNG induction but were resistant to suppression of steroidogenic gene expression.

CONCLUSIONS

Phthalate exposure of grafted human fetal testis altered fetal germ cells but did not reduce expression of genes that regulate fetal testosterone biosynthesis.

Of mice and men (and rats): phthalate-induced fetal testis endocrine disruption is species-dependent

For over 15 years, reproductive toxicologists have explored the physiological outcomes and mechanism of fetal phthalate exposure to determine the risk posed to human male reproductive health. This review examines the fetal male reproductive system response to phthalate exposure across species including rat, mouse, and human, with emphasis on the testis. In the rat, in utero phthalate exposure causes male reproductive tract malformations, in large part, by targeting the testis and inhibiting fetal Leydig cell hormone production. Despite mouse phthalate pharmacokinetics being similar to the rat, inhibition of fetal Leydig cell hormone synthesis is not observed in the mouse. The species-specific differences in testicular response following in utero phthalate exposure and the discordant reaction of the rodent fetal testis when exposed to phthalates ex vivo versus in vivo have made determining risk to humans difficult, yet critically important. The recent use of fetal testis xenotransplants to study phthalate toxicity suggests that the human fetal testis responds like the mouse fetal testis; it appears refractory to phthalate-induced inhibition of testosterone production. Although this result is unfulfilling from the perspective of identifying environmental contributions to human reproductive maldevelopment, it has important implications for phthalate risk assessment.

Mono-(2-ethylhexyl) phthalate (MEHP) promotes invasion and migration of human testicular embryonal carcinoma cells

Testicular dysgenesis syndrome refers to a collection of diseases in men, including testicular cancer, that arise as a result of abnormal testicular development. Phthalates are a class of chemicals used widely in the production of plastic products and other consumer goods. Unfortunately, phthalate exposure has been linked to reproductive dysfunction and has been shown to adversely affect normal germ cell development. In this study, we show that mono-(2-ethylhexyl) phthalate (MEHP) induces matrix metalloproteinase 2 (MMP2) expression in testicular embryonal carcinoma NT2/D1 cells but has no significant effect on MMP9 expression. NT2/D1 cells also have higher levels of MYC expression following MEHP treatment. It is widely recognized that activation of MMP2 and MYC is tightly associated with tumor metastasis and tumor progression. Gelatin zymographic analysis indicates that MEHP strongly activates MMP2 in NT2/D1 cells. Addition of the MMP2-specific inhibitor SB-3CT inhibited MEHP-enhanced cell invasion and migration, demonstrating that MMP2 plays a functional role in promoting testicular embryonal carcinoma progression in response to MEHP exposure. Furthermore, we investigated genome-wide gene expression profiles of NT2/D1 cells following MEHP exposure at 0, 3, and 24 h. Microarray analysis and semiquantitative RT-PCR revealed that MEHP exposure primarily influenced genes in cell adhesion and transcription in NT2/D1 cells. Gap junction protein-alpha 1, vinculin, and inhibitor of DNA-binding protein-1 were significantly down-regulated by MEHP treatment, while claudin-6 and beta 1-catenin expression levels were up-regulated. This study provides insight into mechanisms that may account for modulating testicular cancer progression following phthalate exposure.

Foetal and post-natal exposure of sheep to sewage sludge chemicals disrupts sperm production in adulthood in a subset of animals

Exposure to ubiquitous, environmental chemicals (ECs) has been hypothesized as a cause for declining male reproductive health. Understanding the long-term effects of EC exposure on reproductive health in humans requires animal models and exposure to ‘real life’, environmentally relevant, mixtures during development, a life stage of particular sensitivity to ECs. The aim of this study was to evaluate the effects of in utero and post-natal exposure to environmentally relevant levels of ECs, via sewage sludge application to pasture, on the adult male sheep testis. Hormones, liver concentrations of candidate ECs and Sertoli and germ cell numbers in testes of adult rams that were exposed to ECs in sewage sludge in utero, and until weaning via maternal exposure, and post-weaning via grazing pastures fertilized with sewage sludge, were quantified. Evaluated as a single group, exposure to sludge ECs was without significant effect on most parameters. However, a more detailed study revealed that 5 of 12 sludge-exposed rams exhibited major spermatogenic abnormalities. These consisted of major reductions in germ cell numbers per testis or per Sertoli cell and more Sertoli cell-only tubules, when compared with controls, which did not show any such changes. The sludge-related spermatogenic changes in the five affected animals were significantly different from controls (p < 0.001); Sertoli cell number was unaffected. Hormone profiles and liver candidate EC concentrations were not measurably affected by exposure. We conclude that developmental exposure of male sheep to real-world mixtures of ECs can result in major reduction in germ cell numbers, indicative of impaired sperm production, in a proportion of exposed males. The individual-specific effects are presumed to reflect EC effects on a heterogeneous population in which some individuals may be more susceptible to adverse EC effects. Such effects of EC exposure in humans could have adverse consequences for sperm counts and fertility in some exposed males.

Developmental expression of p97/VCP (Valosin-containing protein) and Jab1/CSN5 in the rat testis and epididymis

BACKGROUND

The ubiquitin proteasome system (UPS) is a key player in regulating many cellular processes via proteasomal degradation of ubiquitinated proteins. Recently published data show that Jab1/CSN5 interacts with p97/VCP and controls the ubiquitination status of proteins bound to p97/VCP in mouse and human cells. However, coexpression of p97/VCP and Jab1/CSN5 in the developing rat testis and epididymis has not previously been studied.

METHODS

Testicular and epididymal tissues from 5-, 15-, 30-, and 60-day-old rats were examined by immunohistochemistry and Western blotting. Colocalisation of proteins was determined by immunofluorescence microscopy.

RESULTS

In the 5-day-old rat testis, p97/VCP and Jab1/CSN5 were specifically expressed in gonocytes. The expression of p97/VCP and Jab1/CSN5 significantly increased at day 15 and was found in spermatogonia, Sertoli cells and spermatocytes. In 30- and 60-day-old rat testes, p97/VCP indicated moderate to strong expression in Sertoli cells, spermatogonia, round and elongating spermatids. However, moderate to weak expression was observed in spermatocytes. Jab1/CSN5 showed strong expression in spermatogonia and spermatocytes, while relatively moderate expression was observed in round and elongating spermatids in 30- and 60-day-old rat testes. In contrast, in the epididymis, the expression of both proteins gradually increased from 5 to 60 days of age. After rats reached 2 weeks of age, the expression of both proteins was mostly restricted to the basal and principal cells of the caput epididymis.

CONCLUSIONS

Our study suggests that p97/VCP and Jab1/CSN5 could be an important part of the UPS in the developing rat testis and epididymis and that both proteins may be involved in the regulation of spermatogenesis and epididymal epithelial functions.