Transferrin overexpression alters testicular function in aged mice

Understanding the Underlying Molecular Mechanisms of Meiotic Arrest during In Vitro Spermatogenesis in Rat Prepubertal Testicular Tissue

In vitro spermatogenesis appears to be a promising approach to restore the fertility of childhood cancer survivors. The rat model has proven to be challenging, since germ cell maturation is arrested in organotypic cultures. Here, we report that, despite a meiotic entry, abnormal synaptonemal complexes were found in spermatocytes, and in vitro matured rat prepubertal testicular tissues displayed an immature phenotype. RNA-sequencing analyses highlighted up to 600 differentially expressed genes between in vitro and in vivo conditions, including genes involved in blood-testis barrier (BTB) formation and steroidogenesis. BTB integrity, the expression of two steroidogenic enzymes, and androgen receptors were indeed altered in vitro. Moreover, most of the top 10 predicted upstream regulators of deregulated genes were involved in inflammatory processes or immune cell recruitment. However, none of the three anti-inflammatory molecules tested in this study promoted meiotic progression. By analysing for the first time in vitro matured rat prepubertal testicular tissues at the molecular level, we uncovered the deregulation of several genes and revealed that defective BTB function, altered steroidogenic pathway, and probably inflammation, could be at the origin of meiotic arrest.

Ethanolic extract of Moringa oleifera leaves alleviate cyclophosphamide-induced testicular toxicity by improving endocrine function and modulating cell specific gene expression in mouse testis

ETHNOPHARMACOLOGICAL RELEVANCE

Moringa oleifera Lam. is known for its nutritional and ethno medicinal values due to the presence of wide array of phytochemicals with multiple biological activities. We have previously reported that ethanolic extract of Moringa oleifera leaves (MOE) ameliorated cyclophosphamide (CP)-induced testicular toxicity and improved functional integrity of spermatozoa as well as spermatogenic cells.

AIM OF THE STUDY

The present study was planned to investigate whether the mitigation of CP-induced testicular toxicity by MOE is mediated via modulation of endocrine profile, genes associated with function of different cell types and enhancement of DNA repair response in spermatogonial cells.

MATERIALS AND METHODS

Adult Swiss albino mice (8 week) were injected with CP (100 mg/kg, one dose in a week for 3 weeks) and MOE (100 mg/kg, 5 doses in a week for 4 weeks) either alone or in combination intraperitoneally. At 35 day post CP injection (first dose), the functional characteristics such as count, motility, head morphology and DNA integrity were assessed in epididymal spermatozoa. Key reproductive hormones like testosterone, follicle stimulating hormone (FSH) and Inhibin B concentration were analyzed in serum and testis. In addition, mRNA expression of genes pertaining to the function of Leydig, Sertoli and spermatogonial cells as well as antioxidant enzymes were evaluated in the testis. To understand the DNA damage and repair process in germ cells, prepubertal (2 week) mice were administered with single dose of CP (200 mg/kg) and/or MOE (100 mg/kg) and analyzed for expression of DNA damage (γ-H2AX, P53 and Caspase3) and repair genes (Rad51 and Ku80) in isolated spermatogonial cells at various time points after treatment.

RESULTS

CP administration resulted in decrease in count, motility and increase in morphological defects and DNA damage in spermatozoa. Testosterone level was marginally decreased while there was a significant increase in FSH (p < 0.001) and decrease in inhibin B (p < 0.05) observed in CP treated mice. Administration of MOE prior to CP, improved sperm functional characteristics, decreased FSH and increased inhibin B levels. Expression of Abp was down-regulated while Transferrin, Fshr and Gata4 (Sertoli cell specific genes) were up-regulated in testis treated with CP. Administration of CP down-regulated the expression of Oct4 and Ddx4 (Spermatogonia specific genes). MOE administration was shown to ameliorate CP-induced damage by modulating the expression of genes specific to Sertoli and spermatogenic cells. Furthermore, MOE treatment reduced CP-induced DNA damage as evident from lower percentage of γ-H2AX positive spermatogonial cells.

CONCLUSION

Administration of MOE mitigated CP-induced testicular damage by improving blood and, intra-testicular hormonal milieu as well as modulating the expression of genes pertaining to Sertoli and spermatogonial cells.

Semen Biochemical Components in Varicocele, Leukocytospermia, and Idiopathic Infertility

The evaluation of the seminal plasma plays a relevant role in the definition of male infertility and in assisted reproduction outcomes; for this reason, it would be recommended to find biochemical markers able to characterize sperm pathology. In this study, 53 infertile patients (grouped by the presence leukocytospermia, idiopathic infertility, or varicocele) and 10 fertile men were selected. Spermiogram was performed by light microscopy, and sperm ultrastructure was evaluated by transmission electron microscopy (TEM) mathematically elaborated. Testosterone (TESTO), estradiol (E2), ferritin (FERR), iron (Fe), transferrin (TRSF), triglycerides (TRG), cholesterol (CHOL), and isoprostanes (F₂-IsoPs) were detected in seminal plasma. Sperm characteristics and biochemical components were correlated by Spearman’s rank correlation coefficient in the whole population and in each group. The levels of TESTO and E2 were positively correlated with sperm quality in particular, and E2 was correlated with fertility index expressing the number of sperm free of ultrastructural defects evaluated by TEM. On the contrary, the indices of iron metabolism (FERR, Fe, and TRSF) were positively associated with low sperm quality and sperm necrosis, particularly in leukocytospermia and varicocele groups, pathologies in which an inflammatory status and oxidative stress condition are present. The study of the seminal plasma composition deserves attention because the levels of the various components seem to be associated with specific reproductive pathologies.

Pathological changes in Sertoli cells and dysregulation of divalent metal transporter 1 with iron responsive element in the testes of idiopathic azoospermia patients

Iron is essential for rapidly dividing spermatocytes during normal mammalian spermatogenesis. Decreased transferrin and transferrin receptor levels were observed in seminal plasma from idiopathic azoospermia (IA) patients, suggesting disturbed iron metabolism in IA testes. However, how Sertoli cells (SCs) contribute to the iron homoeostasis in IA is still unclear. In this study, we analysed 30 IA and 30 age-matched obstructive azoospermia (OA) patients undergoing testicular sperm aspiration (TESA). SCs hyperplasia was indicated by higher SC density and Ki-67 labelling index in the IA TESA specimens. The attenuated expression of superoxide dismutase (SOD) suggested an impaired antioxidative capacity in IA testes. We further detected increased levels of iron importer divalent metal transporter 1 with iron responsive element (DMT1 + IRE) in IA testes, whereas the increasing trend of iron exporter ferroportin 1 (FPN1) was not statistically significant. Next, we demonstrated that iron regulatory protein 1 (IRP1) and hypoxia-inducible factor-1α (HIF-1α), which can potentially bind to the IRE and hypoxia-responsive element in the DMT1 + IRE mRNA, were both up-regulated in IA testes. Unexpectedly, HIF-2α was down-regulated in IA testes. These results indicate that there is a dysregulation of DMT1 + IRE in IA testes, which might due to the up-regulation of IRP1 and HIF-1α.

Developmental exposure to Ethinylestradiol affects transgenerationally sexual behavior and neuroendocrine networks in male mice

Reproductive behavior and physiology in adulthood are controlled by hypothalamic sexually dimorphic neuronal networks which are organized under hormonal control during development. These organizing effects may be disturbed by endocrine disrupting chemicals (EDCs). To determine whether developmental exposure to Ethinylestradiol (EE2) may alter reproductive parameters in adult male mice and their progeny, Swiss mice (F1 generation) were exposed from prenatal to peripubertal periods to EE2 (0.1–1 μg/kg/d). Sexual behavior and reproductive physiology were evaluated on F1 males and their F2, F3 and F4 progeny. EE2-exposed F1 males and their F2 to F4 progeny exhibited EE2 dose-dependent increased sexual behavior, with reduced latencies of first mount and intromission, and higher frequencies of intromissions with a receptive female. The EE2 1 μg/kg/d exposed animals and their progeny had more calbindin immunoreactive cells in the medial preoptic area, known to be involved in the control of male sexual behavior in rodents. Despite neuroanatomical modifications in the Gonadotropin-Releasing Hormone neuron population of F1 males exposed to both doses of EE2, no major deleterious effects on reproductive physiology were detected. Therefore EE2 exposure during development may induce a hypermasculinization of the brain, illustrating how widespread exposure of animals and humans to EDCs can impact health and behaviors.

Depletion of the p43 mitochondrial T3 receptor increases Sertoli cell proliferation in mice

Among T3 receptors, TRα1 is ubiquitous and its deletion or a specific expression of a dominant-negative TRα1 isoform in Sertoli cell leads to an increase in testis weight and sperm production. The identification of a 43-kDa truncated form of the nuclear receptor TRα1 (p43) in the mitochondrial matrix led us to test the hypothesis that this mitochondrial transcription factor could regulate Sertoli cell proliferation. Here we report that p43 depletion in mice increases testis weight and sperm reserve. In addition, we found that p43 deletion increases Sertoli cell proliferation in postnatal testis at 3 days of development. Electron microscopy studies evidence an alteration of mitochondrial morphology observed specifically in Sertoli cells of p43−/− mice. Moreover, gene expression studies indicate that the lack of p43 in testis induced an alteration of the mitochondrial-nuclear cross-talk. In particular, the up-regulation of Cdk4 and c-myc pathway in p43−/− probably explain the extended proliferation recorded in Sertoli cells of these mice. Our finding suggests that T3 limits post-natal Sertoli cell proliferation mainly through its mitochondrial T3 receptor p43.

The Invasion and Reproductive Toxicity of QDs-Transferrin Bioconjugates on Preantral Follicle in vitro

The toxicity of QD has been extensively studied over the past decade. However, the potential toxicity of QDs impedes its use for clinical research. In this work, we established a preantral follicle in vitro culture system to investigate the effects of QD-Transferrin (QDs-Tf) bioconjugates on follicle development and oocyte maturation. The preantral follicles were cultured and exposed to CdTe/ZnTe QDs-Tf bioconjugates with various concentrations and the reproductive toxicity was assessed at different time points post-treatment. The invasion of QDs-Tf for oocytes was verified by laser scanning confocal microscope. Steroid production was evaluated by immunoassay. C-band Giemsa staining was performed to observe the chromosome abnormality of oocytes. The results showed that the QDs-Tf bioconjugates could permeate into granulosa cells and theca cells, but not into oocyte. There are no obvious changes of oocyte diameter, the mucification of cumulus-oocyte-complexes and the occurrence of aneulpoidy as compared with the control group. However, delay in the antrum formation and decrease in the ratio of oocytes with first polar body were observed in QDs-Tf-treated groups. The matured oocytes with first polar body decreased significantly by ~16% (from 79.6±10 % to 63±2.9 %) when the concentration of QDs-Tf bioconjugates exceeded 2.89 nmol·L^-1 (P < 0.05). Our results implied that the CdTe/ZnTe QDs-Tf bioconjugates were reproductive toxic for follicle development, and thus also revealed that this in vitro culture system of preantral follicle is a highly sensitive tool for study on the reproductive toxicity of nanoparticles.

Thyroid hormone limits postnatal Sertoli cell proliferation in vivo by activation of its alpha1 isoform receptor (TRalpha1) present in these cells and by regulation of Cdk4/JunD/c-myc mRNA levels in mice

Hypo- and hyperthyroidism alter testicular functions in the young. Among T3 receptors, TRalpha1 is ubiquitous, and its previously described knockout leads to an increase in testis weight and sperm production. We tested, for the first time, the hypothesis that TRalpha1-dependent regulation of Sertoli cell (SC) proliferation was directly regulated by TRalpha1 present in these cells. Thus, after crossing with the AMH-Cre line, we generated and analyzed a new line that expressed a dominant-negative TRalpha1 isoform (TRalpha(AMI)) in SCs only. So-called TRalpha(AMI)-SC (TRalpha(AMI/+) Cre(+)) mice exhibited similar phenotypic features to the knockout line: heavier testicular weight and higher sperm reserve, in comparison with their adequate controls (TRalpha(AMI/+) Cre(-)). SC density increased significantly as a result of a higher proliferative index at ages Postnatal Day (P) 0 and P3. When explants of control testes were cultured (at age P3), a significant decrease in the proliferation of SCs was observed in response to an excess of T3. This response was not observed in the TRalpha(AMI)-SC and knockout lines. Finally, when TRalpha(AMI) is present in SCs, the phenotype observed is similar to that of the knockout line. This study demonstrates that T3 limits postnatal SC proliferation by activation of TRalpha1 present in these cells. Moreover, quantitative RT-PCR provided evidence that regulation of the Cdk4/JunD/c-myc pathway was involved in this negative control.

Mammalian meiosis is more conserved by sex than by species: conserved co-expression networks of meiotic prophase

Despite the importance of meiosis to human reproduction, we know remarkably little about the genes and pathways that regulate meiotic progression through prophase in any mammalian species. Microarray expression profiles of mammalian gonads provide a valuable resource for probing gene networks. However, expression studies are confounded by mixed germ cell and somatic cell populations in the gonad and asynchronous germ cell populations. Further, widely used clustering methods for analyzing microarray profiles are unable to prioritize candidate genes for testing. To derive a comprehensive understanding of gene expression in mammalian meiotic prophase, we constructed conserved co-expression networks by linking expression profiles of male and female gonads across mouse and human. We demonstrate that conserved gene co-expression dramatically improved the accuracy of detecting known meiotic genes compared with using co-expression in individual studies. Interestingly, our results indicate that meiotic prophase is more conserved by sex than by species. The co-expression networks allowed us to identify genes involved in meiotic recombination, chromatin cohesion, and piRNA metabolism. Further, we were able to prioritize candidate genes based on quantitative co-expression links with known meiotic genes. Literature studies of these candidate genes suggest that some are human disease genes while others are associated with mammalian gonads. In conclusion, our co-expression networks provide a systematic understanding of cross-sex and cross-species conservations observed during meiotic prophase. This approach further allows us to prioritize candidate meiotic genes for in-depth mechanistic studies in the future.

Une nouvelle fonction pour la transferrine exprimée par le testicule

Chez l’homme, les oligospermies sévères sont associées à un faible taux de transferrine dans le liquide séminal. La transferrine apparaît comme un bon indicateur pour définir les dysfonctionnements testiculaires. Son niveau d’expression dans le testicule doit être parfaitement contrôlé. Elle y joue un rôl dans le transport du fer. Mais de récents résultats montrent l’existence d’une forme dimérique de la transferrine sertolienne comme puissant régulateur de la phagocytose des corps résiduels par les cellules de Sertoli.