Response of the seminiferous epithelium of the rat testis to withdrawal of androgen: evidence for direct effect upon intercellular spaces associated with Sertoli cell junctional complexes

Ultrastructural study: in vitro and in vivo differentiation of mice spermatogonial stem cells

Mouse testicular tissue is composed of seminiferous tubules and interstitial tissue. Mammalian spermatogenesis is divided into three stages: spermatocytogenesis (mitotic divisions) in which spermatogonial stem cells (SSCs) turn into spermatocytes, followed by two consecutive meiotic divisions in which spermatocytes form spermatids. Spermatids differentiate into spermatozoa during spermiogenesis. Various factors affect the process of spermatogenesis and the organization of cells in the testis. Any disorder in different stages of spermatogenesis will have negative effects on male fertility. The aim of the current study was to compare the in vitro and in vivo spermatogenesis processes before and after transplantation to azoospermic mice using ultrastructural techniques. In this study, mice were irradiated with single doses of 14 Gy 60Co radiation. SSCs isolated from neonatal mice were cultured in vitro for 1 week and were injected into the seminiferous tubule recipient's mice. Testicular cells of neonatal mice were cultured in the four groups on extracellular matrix-based 3D printing scaffolds. The transplanted testes (8 weeks after transplantation) and cultured testicular cells in vitro (after 3 weeks) were then processed for transmission electron microscopy studies. Our study's findings revealed that the morphology and ultrastructure of testicular cells after transplantation and in vitro culture are similar to those of in vivo spermatogenesis, indicating that spermatogenic cell nature is unaltered in vitro.

Manipulation of fatty acid profiles in roosters' testes, alteration in sexual hormones, improvements in testicular histology characteristics and elevation sperm quality factor by L-carnitine

The present study was designed to investigate the effects of different levels of l-carnitine (LC) on sperm quality factor (SQF), alterations in testis fatty acid profiles, testicular histology and reproductive hormones in young roosters. Eighteen broiler breeders (Ross 308) weighed at 3 months of age. They were randomly classified while each group had six birds. There were three experimental groups based on the LC concentrations (i.e. LC-0, LC-250, LC-500 mg per kg of diet). After two weeks of adaptation, semen samples were collected and evaluated for seminal attributes every two weeks (from week 24 to week 34). At the end of the experiments, four roosters from each treatment group were sacrificed in order to analyze testicular histology, testis fatty acid profiles and reproductive hormones. Supplementing the diet with two of the LC levels for 22 weeks caused significant rise in sperm concentration, viability and SQF compared to that of the control group (P < 0.05). Quadratic analysis in terms of number of seminiferous tubules and spermatogenesis index were significant (P<0.05). Tubular differentiation index improved linearly by the increasing levels of LC supplementation (P<0.01). The analysis of fatty acid profiles showed that LC significantly (P < 0.05) reduced the percentages of C14:0, C21:0, total saturated fatty acids, total odd-chain fatty acids and n-6/n-3 ratio. Moreover, LC significantly increased the percentage of C20:5n-3 (Eicosapentaenoic acid; EPA) (P < 0.05). Analysis of the correlation coefficient revealed that the SQF is in consistency with EPA (r = 0.98; P < 0.04). In contrast, SQF negatively and significantly correlates with odd-chain fatty acids (r = - 0.99; P < 0.001). The desaturation index for C16 fatty acids (16:1cis/C16:0) negligibly increased linearly as LC was added to the diet (P < 0.05). Furthermore, LC caused the roosters to have significant (P < 0.05) high levels of total testosterone and FSH concentrations. The concentration of LH in different treatment groups, however, turned out to be similar in response to the different levels of LC. In conclusion, long-term supplementation of rooster diet with LC can have beneficial effects on SQF and testis histology. The benefits include alterations in testicular histology, reproductive hormones and testicular fatty acid profiles.

Non-Breeding Eusocial Mole-Rats Produce Viable Sperm--Spermiogram and Functional Testicular Morphology of Fukomys anselli

Ansell’s mole-rats (Fukomys anselli) are subterranean rodents living in families composed of about 20 members with a single breeding pair and their non-breeding offspring. Most of them remain with their parents for their lifetime and help to maintain and defend the natal burrow system, forage, and care for younger siblings. Since incest avoidance is based on individual recognition (and not on social suppression) we expect that non-breeders produce viable sperm spontaneously. We compared the sperm of breeding and non-breeding males, obtained by electroejaculation and found no significant differences in sperm parameters between both groups. Here, we used electroejaculation to obtain semen for the first time in a subterranean mammal. Spermiogram analysis revealed no significant differences in sperm parameters between breeders and non-breeders. We found significantly larger testes (measured on autopsies and on living animals per ultrasonography) of breeders compared to non-breeders (with body mass having a significant effect). There were no marked histological differences between breeding and non-breeding males, and the relative area occupied by Leydig cells and seminiferous tubules on histological sections, respectively, was not significantly different between both groups. The seminiferous epithelium and to a lesser degree the interstitial testicular tissue are characterized by lesions (vacuolar degenerations), however, this feature does not hinder fertilization even in advanced stages of life. The continuous production of viable sperm also in sexually abstinent non-breeders might be best understood in light of the mating and social system of Fukomys anselli, and the potential to found a new family following an unpredictable and rare encounter with an unfamiliar female (“provoked or induced dispersal”). Apparently, the non-breeders do not reproduce because they do not copulate but not because they would be physiologically infertile. The significantly increased testes volume of breeding males (compared to non-breeders) is in agreement with previously found higher testosterone levels of breeders.

Male obesity and subfertility, is it really about increased adiposity?

The prevalence of overweight and obesity in reproductive-aged men is increasing worldwide, with >70% of men >18 years classified as overweight or obese in some western nations. Male obesity is associated with male subfertility, impairing sex hormones, reducing sperm counts, increasing oxidative sperm DNA damage and changing the epigenetic status of sperm. These changes to sperm function as a result of obesity, are further associated with impaired embryo development, reduced live birth rates and increased miscarriage rates in humans. Animal models have suggested that these adverse reproductive effects can be transmitted to the offspring; suggesting that men's health at conception may affect the health of their children. In addition to higher adiposity, male obesity is associated with comorbidities, including metabolic syndrome, hypercholesterolemia, hyperleptinemia and a pro-inflammatory state, all which have independently been linked with male subfertility. Taken together, these findings suggest that the effects of male obesity on fertility are likely multifactorial, with associated comorbidities also influencing sperm, pregnancy and subsequent child health.

Effect of beta-carotene on titanium oxide nanoparticles-induced testicular toxicity in mice

OBJECTIVE

This study evaluated the protective effect of beta-carotene (BC) on titanium oxide nanoparticle (TNP) induced spermatogenesis defects in mice.

MATERIALS AND METHODS

Thirty-two NMRI mice were randomly divided into four groups. BC group received 10 mg/kg of BC for 35 days. TNP group received 300 mg/kg TNP for 35 days. TNP+BC group initially received 10 mg/kg BC for 10 days and was followed by concomitant administration of 300 mg/kg TNP for 35 days. Control group received only normal saline for 35 days. Epididymal sperm parameters, testicular histopathology, spermatogenesis assessments and testosterone assay were performed for evaluation of the TNP and BC effects on testis.

RESULTS

Serum testosterone levels were markedly decreased in TNP-intoxicated mice. Epididymal sperm parameters including sperm number, motility and percentage of abnormality were significantly changed in TNP-intoxicated mice (p < 0.01). Histopathological criteria such as epithelial vacuolization, sloughing of germ cells and detachment were significantly increased in TNP-intoxicated mice (p < 0.001). BC+TNP treatment significantly prevented these changes (p < 0.05). BC also significantly elevates testosterone levels in BC+TNP group compared to TNP-treated mice (p < 0.01).

DISCUSSION AND CONCLUSION

The results of this study demonstrated that BC improved the spermatogenesis defects in TNP-treated mice. BC had a potent protective effect against the testicular toxicity and might be clinically useful.

Proliferative and nonproliferative lesions of the rat and mouse male reproductive system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and differential diagnosis for classifying microscopic lesions observed in the male reproductive system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the Internet (http://goreni.org). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions of the male reproductive system in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Impact of obesity on male fertility, sperm function and molecular composition

Male obesity in reproductive-age men has nearly tripled in the past 30 y and coincides with an increase in male infertility worldwide. There is now emerging evidence that male obesity impacts negatively on male reproductive potential not only reducing sperm quality, but in particular altering the physical and molecular structure of germ cells in the testes and ultimately mature sperm. Recent data has shown that male obesity also impairs offspring metabolic and reproductive health suggesting that paternal health cues are transmitted to the next generation with the mediator mostly likely occurring via the sperm. Interestingly the molecular profile of germ cells in the testes and sperm from obese males is altered with changes to epigenetic modifiers. The increasing prevalence of male obesity calls for better public health awareness at the time of conception, with a better understanding of the molecular mechanism involved during spermatogenesis required along with the potential of interventions in reversing these deleterious effects. This review will focus on how male obesity affects fertility and sperm quality with a focus on proposed mechanisms and the potential reversibility of these adverse effects.

Intra-testicular injection of adenoviral constructs results in Sertoli cell-specific gene expression and disruption of the seminiferous epithelium

Spermatogenesis is a complex process that cannot be modelled in vitro. The somatic Sertoli cells (SCs) within the seminiferous tubules perform a key role in supporting maturation of germ cells (GCs). Progress has been made in determining what aspects of SC function are critical to maintenance of fertility by developing rodent models based on the Cre/LoxP system; however, this is time-consuming and is only applicable to mice. The aim of the present study was to establish methods for direct injection of adenoviral vectors containing shRNA constructs into the testis as a way of inducing target-selective knock-down in vivo. We describe here a series of experiments using adenovirus expressing a green fluorescent protein (GFP) transgene. Injection via the efferent ductules resulted in SC-specific expression of GFP; expression levels paralleled the amount of infective viral particles injected. At the highest doses of virus seminiferous tubule architecture were grossly disturbed and immune cell invasion noted. At lower concentrations, the expression of GFP was variable/negligible, the seminiferous tubule lumen was maintained but stage-dependent GC loss and development of numerous basal vacuoles was observed. These resembled intercellular dilations of SC junctional complexes previously described in rats and may be a consequence of disturbances in SC function due to interaction of the viral particles with the coxsackie/adenovirus receptor that is a component of the junctional complexes within the blood testis barrier. In conclusion, intra-testicular injection of adenoviral vectors disturbs SC function in vivo and future work will therefore focus on the use of lentiviral delivery systems.

Claudin-11 expression and localisation is regulated by androgens in rat Sertoli cells in vitro

Claudin-11 and occludin are protein components in tight junctions (TJs) between Sertoli cells which are important for the maintenance of the blood-testis barrier. Barrier formation occurs during puberty, with evidence suggesting hormonal regulation of both claudin-11 and occludin. This study aimed to investigate the regulation of claudin-11 and occludin mRNA expression by testosterone (T) and FSH and their immunolocalisation at rat Sertoli cell TJs in vitro, and to correlate any steroid regulation with the functional capacity of TJs. Sertoli cells formed functional TJs within 3 days as assessed by transepithelial electrical resistance (TER). Both T and dihydrotestosterone significantly (P < 0.01) increased TER twofold and claudin-11 mRNA two- to threefold within 3 days. FSH partially stimulated TER and claudin-11 mRNA, but estradiol had no effect. T also promoted claudin-11 localisation into extensive intercellular contacts. In contrast to claudin-11, Tand FSH did not change occludin mRNA expression, however, T promoted localisation of occludin at cell contacts in a similar manner to claudin-11. Addition of flutamide to T-stimulated cells caused a twofold decrease in both TER and claudin-11 mRNA expression, and resulted in the loss of both proteins from cell contacts. This effect was reversible following flutamide removal. It is concluded that androgens i) co-regulate claudin-11 mRNA expression and TER, implicating claudin-11 in TJ formation and ii) promote the localisation of claudin-11 and occludin at Sertoli cell contacts. Hence, the ability of androgens to maintain spermatogenesis in vivo is partly via their effects on TJ proteins and regulation of the blood-testis barrier.

The changed immunolocalization of START-domain-containing 6 (StarD6) during the development of testes in rat perinatal hypothyroidism

Thyroid hormones have an essential role in maintaining the normal developmental structure of testes during the neonatal stage. START-domain-containing 6 (StarD6) is exclusively expressed in germ cells during spermatogenesis; however, its biological role in rat perinatal hypothyroidism is not clear. After hypothyroidism was induced by daily administration of 0.05% 6-propyl-2-thiouracil (PTU), the pattern of StarD6 immunolocalization was examined from gestation day 15 to postnatal day 49. In normal rats, the labelling of StarD6 was confined to the germ cells from the third-week postpartum. In contrast, its immunoreactivity in hypothyroidal rats was not detected until the fourth-week postpartum. The immunolocalization pattern of StarD6 differed from that of normal adult rats during the seventh-week postpartum. StarD6 was clearly detected in the Leydig cells of the perinatal hypothyroid rats from the fifth-week postpartum. Therefore, StarD6 may play a pivotal role, not only in the spermatogenesis of normal rats, but also in the steroidogenesis of Leydig cells under perinatal hypothyroidism.

Developmental delay and unstable state of the testes in the rdw rat with congenital hypothyroidism

From the present study of the rdw rat, it is clear that the thyroid hormone is essential for the development and maintenance of the testes. In previous studies, the thyroid hormone has few serious effects on the testes except during the neonatal stage when the thyroid hormone receptor is mainly present. However, there is little knowledge concerning the prolonged effect of thyroid hormone deficiency throughout the rat's life span. In the present study, a morphological analysis was performed on the testes of rdw rats with congenital hypothyroidism. The rdw testes required a longer time to develop into the normal adult structure. Moreover, the developed, normal structure began to degenerate after full maturation. Specific characteristics of the rdw testes include: (i) a prolonged proliferation of Sertoli cells during postnatal development; (ii) a developmental delay in the appearance of spermatocytes and spermatid; (iii) direct contact with each other for both spermatocytes and spermatids, without Sertoli cell cytoplasm completely intervening between adjacent germ cells; (iv) subsequent apoptosis of germ cells after maturation; (v) reduction in the height of the seminiferous epithelium; and (vi) lower testosterone levels in the rdw rats, especially during old age. Thus, we conclude that the thyroid hormone plays an important role in developing and maintaining normal function of testes.

Gestational exposure to ethane dimethanesulfonate permanently alters reproductive competence in the CD-1 mouse

Although the adult mouse Leydig cell (LC) has been considered refractory to cytotoxic destruction by ethane dimethanesulfonate (EDS), the potential consequences of exposure during reproductive development in this species are unknown. Herein pregnant CD-1 mice were treated with 160 mg/kg on Gestation Days 11-17, and reproductive development in male offspring was evaluated. Prenatal administration of EDS compromised fetal testosterone (T) levels, compared with controls. EDS-exposed pups recovered their steroidogenic capacities after birth because T production by hCG-stimulated testis parenchyma from prepubertal male offspring was unchanged. However, prepubertal testes from prenatally exposed males contained seminiferous tubules (STs) devoid of germ cells, indicating a delay in spermatogenesis. In adults, some STs in exposed males still contained incomplete germ cell associations corroborating observed reductions in epididymal sperm reserves, fertility ratios, and litter size. Morphometry revealed an EDS-induced increase in interstitial area and a concomitant decrease in ST area, but stereology revealed an unexpected decrease in the number and size of the LCs per testis in exposed males. Paradoxically, there was an increase in both serum LH and T production by adult testis parenchyma, indicating that the LCs were hyperstimulated. These data demonstrate permanent lesions in LC development and spermatogenesis caused by prenatal exposure in mice. Thus, although adult mouse LCs are insensitive to EDS, EDS appears to have direct action on fetal LCs, resulting in abnormal testis development.

An oncological view on the blood-testis barrier

The function of the blood-testis barrier is to protect germ cells from harmful influences; thus, it also impedes the delivery of chemotherapeutic drugs to the testis. The barrier has three components: first, a physicochemical barrier consisting of continuous capillaries, Sertoli cells in the tubular wall, connected together with narrow tight junctions, and a myoid-cell layer around the seminiferous tubule. Second, an efflux-pump barrier that contains P-glycoprotein in the luminal capillary endothelium and on the myoid-cell layer; and multidrug-resistance associated protein 1 located basolaterally on Sertoli cells. Third, an immunological barrier, consisting of Fas ligand on Sertoli cells. Inhibition of P-glycoprotein function offers the opportunity to increase the delivery of cytotoxic drugs to the testis. In the future, visualisation of function in the blood-testis barrier may also be helpful to identify groups of patients in whom testis conservation is safe or to select drugs that are less harmful to fertility.

Sertoli cell ectoplasmic specializations in the seminiferous epithelium of the testosterone-suppressed adult rat

The Sertoli cell ectoplasmic specialization is a unique junctional structure involved in the interaction between elongating spermatids and Sertoli cells. We have previously shown that suppression of testicular testosterone in adult rats by low-dose testosterone and estradiol (TE) treatment causes the premature detachment of step 8 round spermatids from the Sertoli cell. Because these detaching round spermatids would normally associate with the Sertoli cell via the ectoplasmic specialization, we hypothesized that ectoplasmic specializations would be absent in the seminiferous epithelium of TE-treated rats, and the lack of this junction would cause round spermatids to detach. In this study, we investigated Sertoli cell ectoplasmic specializations in normal and TE-treated rat testis using electron microscopy and localization of known ectoplasmic specialization-associated proteins (espin, actin, and vinculin) by immunocytochemistry and confocal microscopy. In TE-treated rats where round spermatid detachment was occurring, ectoplasmic specializations of normal morphology were observed opposite the remaining step 8 spermatids in the epithelium and, importantly, in the adluminal Sertoli cell cytoplasm during and after round spermatid detachment. When higher doses of testosterone were administered to promote the reattachment of all step 8 round spermatids, newly elongating spermatids associated with ectoplasmic specialization proteins within 2 days. We concluded that the Sertoli cell ectoplasmic specialization structure is qualitatively normal in TE-treated rats, and thus the absence of this structure is unlikely to be the cause of round spermatid detachment. We suggest that defects in adhesion molecules between round spermatids and Sertoli cells are likely to be involved in the testosterone-dependent detachment of round spermatids from the seminiferous epithelium.

Morphometric studies on the testes of rats treated neonatally with oestrogen and subsequently with gonadotrophins and testosterone

The experiments involved male rats, which were given a single subcutaneous dose of 1 mg stilboestrol on the first day of life. Beginning on day 28, subgroups of the rats received either gonadotrophins or testosterone for 39 days. The weight of the testes, serum luteinizing hormone and testosterone levels were determined while sections of the testes were subjected to morphological analysis and morphometric measurements, based on computerized techniques. The results demonstrated that a single dose of oestrogen caused a reduction in the cross-sectional area of the seminiferous tubules and a reduction in the thickness of the seminiferous epithelium, accompanied by inhibition of spermatogenesis. The number of and area occupied by Leydig cells, as well as the size of their cell nuclei, were also diminished, and the levels of serum testosterone decreased by 73%. All the experimental animals manifested significantly increased serum luteinizing hormone levels. Stimulation with gonadotrophins markedly increased the number of Leydig cells, their size and the size of their cell nuclei. This was associated with significantly increased levels of serum testosterone. Under these conditions, the cross-sectional area of the seminiferous tubules and the thickness of seminiferous epithelium remained less than those in the untreated controls. Following stimulation with testosterone the pattern of the seminiferous tubules resembled that noted after stimulation with gonadotrophins; the number of Leydig cells was markedly reduced but the size of both the cells themselves and of their nuclei approached normal values.

Cell death during development of testis and cerebellum in the mutant mouse weaver

The murine mutation weaver confers early death during development on cells in testes, cerebellum, and midbrain. The results reported here support the hypothesis that the action of weaver is intrinsic to testes and independent of Sertoli cells: germ cells are the only testicular cell type seen to die in weaver homozygotes, while Sertoli cell-dependent development of the blood testis barrier is normal. This report includes characterization of patterns of germ cell death and cerebellar granule cell death in homozygous weavers with respect to that seen during normal development by in situ end-labeling of DNA and high-magnification light microscopy. Comparison of the spatial distribution of dying cells in the weaver's cerebellum with that of dividing cells revealed disarray in the external germinal zone. The results show that cells vulnerable to weaver die by apoptotic and nonapoptotic mechanisms and indicate that weaver-induced cell death is not the consequence of extended naturally occurring developmental cell death, although their timing overlaps. Thus, although the death of cells in each region is likely to be caused by the same mutation, a base pair substitution in the G protein-coupled inwardly rectifying potassium channel 2 gene, the cell death program activated differs depending on cell type.

Thymic regression and apoptosis in the rat after treatment with the Leydig cell cytotoxin ethylene dimethanesulphonate (EDS)

Ethylene dimethanesulphonate (EDS) is an alkylating agent which is widely assumed to specifically kill Leydig cells leaving other biological systems intact. However, after EDS treatment of the male rat the thymus reversibly involutes and the gonadal regional lymph nodes are activated. In the present experiments we have demonstrated that EDS has a direct action upon the thymus both in vivo and in vitro. EDS treatment of the intact and castrated male rat and the intact female rat caused regression of the thymus by up to 50% 3 days later. Total cellularity decreased while the proliferative index increased suggesting a compensatory mechanism. Thymocytes were exposed to EDS in vitro and the response compared to the glucocorticoid methylprednisolone (P), a well characterised thymic apoptotic stimulant. EDS and P increased apoptosis in the thymocyte as characterised by the appearance of cells containing nuclei with apoptotic morphology and with DNA fragmentation visualised by a characteristic ladder after agarose gel electrophoresis. The effects of both EDS and P were time and dose dependent but, in contrast to the effects in Leydig cells, P was the most effective apoptotic stimulus (for instance 100%-P compared to 30%-EDS or 7% control/DMSO after 24 h incubation). The immunological responses of the gonadal lymph nodes were not associated with testicular regression as it was seen in the castrated rat but may be related to a direct action upon the epididymis. In conclusion, tissue specificity of the Leydig cell cytotoxin needs to be extended to the thymus and epididymis. The mode of cell death in Leydig cells and thymocytes after both glucocorticoids and EDS is apoptosis which suggests that they possess some common mechanism(s) which is responsible for the toxicity of these diverse compounds.

Further observations on the early events that contribute to establishing the morphological pattern shown by the oestradiol suppressed testis

The analysis of the morphological response of the seminiferous epithelium to hormone suppression after hypophysectomy has been widely used in the study of spermatogenesis. Unlike hypophysectomy, which causes a sharp fall in gonadotropin levels, oestradiol treatment, although mimicking its effects, leads to a partial and progressive hormone suppression. We have chosen this model in order to clarify further the early morphological response of the seminiferous epithelium to hormone suppression. For this purpose, adult male rats, injected daily from 1-35 days with 50 micrograms oestradiol benzoate, were analyzed. Our observations showed that cell sloughing was the main cause of germ cell depletion in the oestradiol treated testis. After 17-18 days treatment, massive sloughing affected nearly all the germinal cells, but the correct synchronization of mitoses, meiosis and spermatid differentiation along the 14 stages of spermatogenesis was always well kept. Quantitative analysis showed that spermatogenic wave was well preserved in the oestradiol-treated animals and that sloughing was a stage-independent phenomenon.

Sertoli cell barrier dysfunction and spermatogenetic cycle breakdown in the human testis: a lanthanum tracer investigation

The introduction of nitrate of lanthanum in fixative solutions for testicular biopsies improves ultrastructural observations of the blood-testis barrier. In complete (normal) spermatogenesis, junctional specializations impede the diffusion of lanthanum into the adluminal compartment. They clearly exhibit a three-storied disposition in orthogonal sections. In maturation arrest, lanthanum passes easily through the junctional specializations surrounding the germ cells and up to the lumen. In irregular hypospermatogenesis, the Sertoli cell barrier is permeable, but diffusion of the tracer is less significant and variable. Unexpectedly, in germ cell aplasia, the barrier remains efficient