Gonadal development in mammals at the cellular and molecular levels

Inactivation of JNK signalling results in polarity loss and cell senescence of Sertoli cell

As major somatic cells in the testis, Sertoli cell development is precisely regulated by numerous factors, and aberrant development of these cells is associated with male reproductive diseases. JNK signalling is evolutionarily conserved and involved in multiple critical biological processes. Here, we found that the double knockout of Jnk1 and Jnk2 resulted in aberrant localisation of Sertoli cells at early developmental stages, with most Sertoli cells being lost at later stages. Further studies revealed that the inactivation of JNK signalling caused polarity loss in Sertoli cells. In vitro-cultured Jnk1/2-DKO Sertoli cells exhibited a senescence-associated phenotype. Mechanistic studies demonstrate that JNK signalling is likely involved in establishing Sertoli cell polarity by regulating the expression of TGF-β2, mediated by c-Jun. The senescence of Sertoli cells in JNKs-deficient mice is caused by aberrant proteolysis of P27KIP1, mediated by c-Myc. This study demonstrates the role of JNK signalling in Sertoli cell development and functional maintenance, which may also represent an aetiology of male infertility in humans.

Reprograming skin fibroblasts into Sertoli cells: a patient-specific tool to understand effects of genetic variants on gonadal development

BACKGROUND

Disorders/differences of sex development (DSD) are congenital conditions in which the development of chromosomal, gonadal, or anatomical sex is atypical. With overlapping phenotypes and multiple genes involved, poor diagnostic yields are achieved for many of these conditions. The current DSD diagnostic regimen can be augmented by investigating transcriptome/proteome in vivo, but it is hampered by the unavailability of affected gonadal tissue at the relevant developmental stage. We try to mitigate this limitation by reprogramming readily available skin tissue-derived dermal fibroblasts into Sertoli cells (SC), which could then be deployed for different diagnostic strategies. SCs form the target cell type of choice because they act like an organizing center of embryonic gonadal development and many DSD arise when these developmental processes go awry.

METHODS

We employed a computational predictive algorithm for cell conversions called Mogrify to predict the transcription factors (TFs) required for direct reprogramming of human dermal fibroblasts into SCs. We established trans-differentiation culture conditions where stable transgenic expression of these TFs was achieved in 46, XY adult dermal fibroblasts using lentiviral vectors. The resulting Sertoli like cells (SLCs) were validated for SC phenotype using several approaches.

RESULTS

SLCs exhibited Sertoli-like morphological and cellular properties as revealed by morphometry and xCelligence cell behavior assays. They also showed Sertoli-specific expression of molecular markers such as SOX9, PTGDS, BMP4, or DMRT1 as revealed by IF imaging, RNAseq and qPCR. The SLC transcriptome shared about two thirds of its differentially expressed genes with a human adult SC transcriptome and expressed markers typical of embryonic SCs. Notably, SLCs lacked expression of most markers of other gonadal cell types such as Leydig, germ, peritubular myoid or granulosa cells.

CONCLUSIONS

The trans-differentiation method was applied to a variety of commercially available 46, XY fibroblasts derived from patients with DSD and to a 46, XX cell line. The DSD SLCs displayed altered levels of trans-differentiation in comparison to normal 46, XY-derived SLCs, thus showcasing the robustness of this new trans-differentiation model. Future applications could include using the SLCs to improve definitive diagnosis of DSD in patients with variants of unknown significance.

Sertoli Cell-Specific Activation of Transforming Growth Factor Beta Receptor 1 Leads to Testicular Granulosa Cell Tumor Formation

The transforming growth factor β (TGFβ) superfamily, consisting of protein ligands, receptors, and intracellular SMAD transducers, regulates fundamental biological processes and cancer development. Our previous study has shown that sustained activation of TGFβ receptor 1 (TGFBR1) driven by anti-Mullerian hormone receptor type 2 (Amhr2)-Cre in the mouse testis induces the formation of testicular granulosa cell tumors (TGCTs). As Amhr2-Cre is expressed in both Sertoli cells and Leydig cells, it remains unclear whether the activation of TGFBR1 in Sertoli cells alone is sufficient to induce TGCT formation. Therefore, the objective of this study was to determine whether Sertoli cell-activation of TGFBR1 drives oncogenesis in the testis. Our hypothesis was that overactivation of TGFBR1 in Sertoli cells would promote their transdifferentiation into granulosa-like cells and the formation of TGCTs. To test this hypothesis, we generated mice harboring constitutive activation of TGFBR1 in Sertoli cells using anti-Mullerian hormone (Amh)-Cre. Disorganized seminiferous tubules and tumor nodules were found in TGFBR1CA; Amh-Cre mice. A histological analysis showed that Sertoli cell-specific activation of TGFBR1 led to the development of neoplasms resembling granulosa cell tumors, which derailed spermatogenesis. Moreover, TGCTs expressed granulosa cell markers including FOXL2, FOXO1, and INHA. Using a dual fluorescence reporter line, the membrane-targeted tdTomato (mT)/membrane-targeted EGFP (mG) mouse, we provided evidence that Sertoli cells transdifferentiated toward a granulosa cell fate during tumorigenesis. Thus, our findings indicate that Sertoli cell-specific activation of TGFBR1 leads to the formation of TGCTs, supporting a key contribution of Sertoli cell reprogramming to the development of this testicular malignancy in our model.

Cellular architecture of the testis of Egyptian wild boar (Sus scrofa) in young and adult age

Testicular parenchyma is split into lobules, each lobule contains convoluted seminiferous tubules surrounded by myoid cells and the interstitial tissue contains groups of Leydig cells. The seminiferous tubules are lined by two groups of cells the first one is the spermatogenic cells and the second one is Sertoli cells.

Metalloproteases in gonad formation and ovulation

Changes in expression or activation of various metalloproteases including matrix metalloproteases (Mmp), a disintegrin and metalloprotease (Adam) and a disintegrin and metalloprotease with thrombospondin motif (Adamts), and their endogenous inhibitors (tissue inhibitors of metalloproteases, Timp), have been shown to be critical for ovulation in various species from studies in past decades. Some of these metalloproteases such as Adamts1, Adamts9, Mmp2, and Mmp9 have also been shown to be regulated by luteinizing hormone (LH) and/or progestin, which are essential triggers for ovulation in all vertebrate species. Most of these metalloproteases also express broadly in various tissues and cells including germ cells and somatic gonad cells. Thus, metalloproteases likely play roles in gonad formation processes comprising primordial germ cell (PGC) migration, development of germ and somatic cells, and sex determination. However, our knowledge on the functions and mechanisms of metalloproteases in these processes in vertebrates is still lacking. This review will summarize our current knowledge on the metalloproteases in ovulation and gonad formation with emphasis on PGC migration and germ cell development.

Morphometric study of the testis in sheep embryos using unbiased design-based stereology

Sheep have been used as translational models of human postnatal testicular development. However, the morphometric features of the normal developing testis in sheep embryos have not been previously investigated using stereology. The objective of the present work was to establish normal quantitative parameters for fetal testicular tissue components in sheep, using unbiased design-based stereological methods. Twenty-four sheep embryos were divided into four gestational age groups (9-11, 12-14, 15-17 and 18-20 weeks of gestation) on the basis of the embryos' crown-rump length. Isotropic, systematic uniform random sections of the left testes were obtained by employing the orientator method. Testicular total volume, the absolute and proportional volumes occupied by the seminiferous tubules and interstitial tissue, as well as the seminiferous tubule length, were estimated using the point-counting system and the unbiased counting frame principle. All the parameters, with the exception of the interstitial tissue's fractional volume, gradually increased along with gestational age, with the maximum increase especially seen in the late fetal stages. The proportional volume of the interstitial tissue, on the other hand, showed a decreasing trend along with increasing gestational age. The absolute volume of the testes, of the seminiferous tubules and of the interstitial tissue, and the length of the seminiferous tubules showed a significant (p< 0.05) positive linear correlation with gestational age. Several similarities were observed with human testicular embryogenesis. The stereological data emerging from the present study might prove useful as basic contribution to the fields of andrology and embryology and stimulate further research in these areas.

Role of peroxisome proliferator-activated receptor gamma (PPARγ) in the regulation of fatty acid metabolism related gene expressions in testis of men with impaired spermatogenesis

Although male infertility is a multifactorial syndrome in which genetic factors are responsible for up to 15 % of cases, there are few studies of genes involved in lipid metabolism and male infertility. Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcription factor in testis tissue. PPARγ binds to DNA and regulates the genes for fatty acid (FA) metabolism. Thus, it has a key role in male reproduction. The current study assessed the expressions of fatty acid desaturase 2 (FADS2), elongation of very-long-chain fatty acids-like 2 (ELOVL2), stearoyl-CoA desaturase-1 (SCD), and lipoprotein lipase (LPL) and incorporation of PPARγ in the promoter regions of these genes in testicular tissue biopsies from 30 infertile males who underwent testicular sperm extraction. The samples were classified into three groups: obstructive azoospermia (OA), which was the positive control (n = 10); round spermatid maturation arrest (SMA, n = 10); and Sertoli cell-only syndrome (SCOS, n = 10). There were significantly lower relative mRNA expression levels of the FADS2, ELOVL2, SCD, and LPL genes in the SCOS (P < 0.01) and SMA (P < 0.01) groups compared to the OA control group. We observed a significant decrease in chromatin incorporation of PPARγ on the promoter regions of the candidate FA metabolism genes (P < 0.05). For the first time, the present study results show that PPARγ is a strong mediator for regulation of FA metabolism in human testis tissue and we confirmed its critical role in normal spermatogenesis.

Morphology of the genital organs of male and female giant anteaters (Myrmecophaga tridactyla)

BACKGROUND

The giant anteater belongs to the supraorder Xenarthra which occupies a systematically isolated position among placental mammals. The species is categorized as Vulnerable by the International Union for Conservation of Nature, and understanding its reproductive characteristics is critical for future conservation efforts.

METHODS

Gross and microscopic anatomy of the genital organs of 23 male and 21 female adult and young roadkill giant anteaters in Brazil were studied.

RESULTS

Male giant anteaters presented a short conical penis, intraabdominal testes, and prostate, vesicular and bulbourethral glands. A tubular remnant of the partially fused Müllerian ducts extended from the seminal colliculus through the prostate gland, continued cranially in the genital fold, bifurcated, and attached with one elongation each to the left and right epididymal corpus. The structure presented a total length of up to 10 cm and contained a yellowish liquid in its lumen. Histologically, the caudal section of this structure resembled the female vagina, the middle portion corresponded to the uterus, and the extensions showed characteristics of uterine tubes. In adult female giant anteaters, ovoid ovaries with occasional seminiferous cord-like structures were observed. The animals possessed a simple uterus, which was directly continuous with the vaginal canal. The caudal portion of the vagina had two lumina, separated by a longitudinal septum and opening into two apertures into the vaginal vestibule, cranial to the urethral opening. In the urethral and the lateral vestibular wall, glandular structures with characteristics of male prostate and bulbourethral glands, respectively, were found. The vestibule opened through a vertical vulvar cleft to the exterior. A pair of well-differentiated Wolffian ducts with a central lumen originated ventrally at the vaginal opening into the vestibule and passed in a cranial direction through the ventral vaginal and uterine wall. Each duct extended highly coiled along the ipsilateral uterine tube until the lateral pole of the ovaries where it merged with the rete ovarii.

DISCUSSION

The reproductive morphology of giant anteaters reveals characteristics shared with other Xenarthrans: intraabdominal testes, a simple uterus, and a double caudal vagina. The persistence of well-differentiated genital ducts of the opposite sex in both males and females, however, singles them out among other species. These structures are the results of an aberration during fetal sexual differentiation and possess secretory functions. The possibility of a pathological degeneration of these organs should be considered in reproductive medicine of the species.

CONCLUSION

Knowledge of the unique reproductive characteristics of the giant anteater is essential for future reproductive management of the species. Additionally, further research on the peculiarities of the persisting genital duct structures might help to understand sexual differentiation in placental mammals in general.

Assessment of the Emerging Threat Posed by Perfluoroalkyl and Polyfluoroalkyl Substances to Male Reproduction in Humans

Per-fluoroalkyl and polyfluoroalkyl substances (PFAS) are a diverse group of synthetic fluorinated chemicals used widely in industry and consumer products. Due to their extensive use and chemical stability, PFAS are ubiquitous environmental contaminants and as such, form an emerging risk factor for male reproductive health. The long half-lives of PFAS is of particular concern as the propensity to accumulate in biological systems prolong the time taken for excretion, taking years in many cases. Accordingly, there is mounting evidence supporting a negative association between PFAS exposure and an array of human health conditions. However, inconsistencies among epidemiological and experimental findings have hindered the ability to definitively link negative reproductive outcomes to specific PFAS exposure. This situation highlights the requirement for further investigation and the identification of reliable biological models that can inform health risks, allowing sensitive assessment of the spectrum of effects of PFAS exposure on humans. Here, we review the literature on the biological effects of PFAS exposure, with a specific focus on male reproduction, owing to its utility as a sentinel marker of general health. Indeed, male infertility has increasingly been shown to serve as an early indicator of a range of co-morbidities such as coronary, inflammatory, and metabolic diseases. It follows that adverse associations have been established between PFAS exposure and the incidence of testicular dysfunction, including pathologies such as testicular cancer and a reduction in semen quality. We also give consideration to the mechanisms that render the male reproductive tract vulnerable to PFAS mediated damage, and discuss novel remediation strategies to mitigate the negative impact of PFAS contamination and/or to ameliorate the PFAS load of exposed individuals.

AR regulates porcine immature Sertoli cell growth via binding to RNF4 and miR-124a

Sertoli cells are the only somatic cells in the seminiferous epithelium which directly contact with germ cells. Sertoli cells exhibit polarized alignment at the basal membrane of seminiferous tubules to maintain the microenvironment for growth and development of germ cells, and therefore play a crucial role in spermatogenesis. Androgens exert their action through androgen receptor (AR) and AR signalling in the testis is essential for maintenance of spermatogonial numbers, blood-testis barrier integrity, completion of meiosis, adhesion of spermatids and spermiation. In the present study, we demonstrated that AR gene could promote the proliferation of immature porcine Sertoli cells (ST cells) and the cell cycle procession, and accelerate the transition from G1 phase into S phase in ST cells. Meanwhile, miR-124a could affect the proliferation and cell cycle procession of ST cells by targeting 3'-UTR of AR gene. Furthermore, AR bound to the RNF4 via AR DNA-binding domain (DBD) and we verified that RNF4 was necessary for AR to regulate the growth of ST cells. Above all, this study suggests that AR regulates ST cell growth via binding to RNF4 and miR-124a, which may help us to further understand the function of AR in spermatogenesis.

3, 3', 5-Triiodo-L-thyronine affects polarity proteins of bovine Sertoli cells via WT1/non-canonical Wnt signaling pathway

To determine the role of 3, 3', 5-triiodo-L thyroxine (T3) in the differentiation of Sertoli cells (SCs) and the factors influencing maturity via the Wilms' tumor 1 (WT1)/non-canonical Wnt signaling pathway, high purity SCs were isolated from newborn calves' testes and cultured in vitro. The SCs were stimulated with T3, and co-treated with short interference (si) RNA to knockdown endogenous WT1 and non-canonical Wnt signalling inhibitor Wnt-c59. Our results suggested that the addition of different concentrations (0, 25, 50, and 100 nM) of T3 in the culture medium changed the expression of KRT-18 (SCs immature marker) and accelerated the differentiation of SCs. T3 (100 nM) treatment induced up-regulated expression of WT1 over time (p < 0.05), while the expression of polarity proteins (Par3, Par6b, and E-cadherin) and Wnt4 were affected to varying degrees (p < 0.05). SCs were treated simultaneously with T3 + Wnt-c59 and T3 + WT1 siRNA, and the results showed that T3 could affect the expression of polarity proteins via WT1/non-canonical Wnt signaling pathway. These data put together indicate that T3 plays a dependent role in the induction of bovine SCs differentiation via WT1/non-canonical Wnt signaling pathway in vitro. This study proposes for the first time that WT1 is a major target for T3.

Wilms' tumour 1 (WT1) negatively regulates the expression of connexin 43 via a non-canonical Wnt signalling pathway in cultured bovine Sertoli cells

The gap junction protein connexin (Cx) 43 between adjacent Sertoli cells (SCs) is the main testicular factor regulating the growth and development of SCs, and plays a vital role in controlling cell differentiation and maturation. However, the endogenous testicular factors that regulate Cx43 and the downstream signalling pathways that mediate Cx43-dependent SC differentiation are unclear. In this study, high-purity SCs were isolated from newborn calves' testes by differential adherence. The SCs were then cultured invitro and treated with short interference RNA to knockdown endogenous Wilms' tumour 1 (WT1). In WT1-knockdown SCs, Cx43 expression was upregulated. To elucidate the intracellular signalling mechanism of Cx43 in the differentiation and maturation of immature SCs, SCs were treated simultaneously with non-canonical Wnt signalling inhibitors CCG-1423 and GO-6983; in these SCs, Cx43 expression was upregulated. Together, these data indicate that WT1 negatively regulates the expression of Cx43 produced from SCs via a non-canonical Wnt signalling pathway in cultured bovine SCs.

Characteristics of seasonal spermatogenesis in the soft-shelled turtle

Spermatogenesis in reptiles is a seasonally dependent physiological process that is not temporally associated with male mating behavior. Characteristics of seasonal spermatogenesis in reptiles, however, remain largely unknown. In this review, there is a coverage of the characteristics of soft-shelled turtle, Pelodiscus sinensis, during seasonal spermatogenesis that provides insights into spermatogenesis of testudines. The seminiferous epithelium of P. sinensis are undergoing spermatogenesis during the summer and fall, but are quiescent throughout the rest of the year; germ cells progress through spermatogenic stages in a temporal rather than a spatial pattern. While apoptotic germ cells mainly appear in the non-spermatogenic phase, these are seldom present during active spermatogenesis. It is inferred that apoptosis may be one of the reasons for germ cell loss during the resting phase of spermatogenesis. During the period when spermatogenesis is occurring, Sertoli cells become very narrow and are in contact with several round/elongated spermatids. Many residual spermatozoa can be internalized and degraded within Sertoli cells by entosis during the non-spermatogenic phase, which precedes the next reproductive cycle in P. sinensis. In the late spermatogenic phase, round-shaped mitochondria of spermatids become elongated and swollen, subsequently forming a crescent-like shape and develop into "onion-like" shaped mitochondria. As spermiogenesis progresses, the endoplasmic reticulum of spermatids is transferred into a specialized structure called the "Chrysanthemum flower center", which may be a source of autophagosomal membranes. The information provided in this review will help improve understanding of characteristics of seasonal spermatogenesis, which will hopefully promote interest in the study of reptilian species.

Influence of Wilms' tumor suppressor gene WT1 on bovine Sertoli cells polarity and tight junctions via non-canonical WNT signaling pathway

Sertoli cells (SCs) are polarized epithelial cells and provide a microenvironment for the development of germ cells (GCs). The Wilms' tumor suppressor gene WT1 which support spermatogenesis is expressed explicitly in SCs. This study investigated the effect of WT1 on the polarity and blood-testis barrier (BTB) formation of bovine SCs in order to provide theoretical and practical bases for the spermatogenic process in mammals. In this study, newborn calf SCs were used as research material, and the RNAi technique was used to knockdown the endogenous WT1. The results show that WT1 knockdown did not affect the proliferation ability of SCs, but down-regulated the expression of polarity-associated proteins (Par3, Par6b, and E-cadherin), junction-associated protein (occludin) and inhibits transcription of downstream genes (WNT4, JNK, αPKC, and CDC42) in non-canonical WNT signaling pathway. WT1 also altered ZO-1 and occludin protein distribution. Overexpression of WNT1 did not affect the expression of Par6b, E-cadherin, and occludin, whereas the non-canonical WNT signaling pathway inhibitors wnt-c59, CCG-1423, and GO-6983 down-regulated the expression of Par6b, E-cadherin, and occludin respectively. This study indicates that WT1 mediates the regulation of several proteins involved in bovine SCs polarity maintenance and intercellular tight junctions (TJ) by non-canonical WNT signaling pathway.

The structure-activity relationship (SAR) for phthalate-mediated developmental and reproductive toxicity in males

Testicular dysgenesis syndrome includes the hypospadias, cryptorchidism and abnormal fetal testis in male neonate. This is possibly caused by the environmental phthalates, which down-regulate the expression of androgen synthetic genes and Insl3 or directly inhibits steroidogenic enzymes. There are distinct structure-activity relationships (SARs) for phthalate-mediated developmental and reproductive toxicity. Here, we review the SAR for phthalate-mediated testicular dysgenesis syndrome. Of phthalates of straight side chains, C5-C6 ones are the most potent, C4 or C7 are moderate, C3 is weakest, and C1-2 or C8-13 are ineffective. The branching and unsaturation of side chains increases the toxicity. The cycling of side chains does not increase the toxicity.

Zoledronic acid induces cytogenetic toxicity in male germline cells of Swiss albino mice

This study mainly focuses on the cytogenetic toxicity induction by zoledronic acid (ZA), a nitrogen containing bisphosphonate (N-BPs) in the male germline cells of Swiss albino mice. A single intraperitoneal exposure with three different doses of ZA (2, 4, and 8 mg/kg body weight), toxicity was assessed by analyzing spermatogonial metaphase chromosome aberrations at 24 h, aberrant primary spermatocytes at week 4, and abnormal spermatozoa at week 8 posttreatment. Cyclophosphamide (40 mg/kg) and 0.9% NaCl were used as positive and vehicle controls respectively in the study. The results showed that there was a significant induction in the number of chromosomal aberrations especially at two doses of ZA (4 and 8 mg/kg) after 24 h in the spermatogonial cells (p < 0.001) compared to vehicle control. The transmission genetic damages were noticed as aberrant spermatocytes with atypical bivalents (X-Y/autosomal asynapsis) at 4 mg/kg of ZA (p < 0.01) and at 8 mg/kg of ZA (p < 0.001) at week 4 posttreatment. A statistically significant higher number of abnormal spermatozoa (sperm) were also noticed at week 8 posttreatment of both at 4 and 8 mg/kg of ZA (p < 0.001). Hence, from these genotoxicity studies, it can be concluded that ZA is genotoxic in male germline cells and has the potential of transmitting the genotoxic effects from spermatogonial cells to sperm in male Swiss mice.

Histological characteristics of the gonads of pig fetuses and their relationship with fetal anatomical measurements

The objective was to evaluate the histomorphometric characteristics of the testis and ovaries of pig fetuses at different gestational ages, as well as their correlation with some fetus measurements. Forty-four fetuses were separated for gender (male and female) and gestational age (50, 80 and 106days of gestation). After slaughter, fetuses had their body length, head and thoracic perimeters measured and their gonads submitted to histomorphometric analyses. The gonadal characteristics at different gestational ages were statistically compared, correlations with the fetal measurements were performed and equations to predict the gonadal characteristics from the fetal measurements were obtained. The testis weight logarithmically increased along pregnancy, whereas ovary weight increased in a linear manner. The cordonal length and number of Sertoli cells were positively correlated with the fetal measurements, being higher at 106days gestation, while the nuclear volume of these cells were negatively correlated. The total number of follicles was higher at day 80 and 106 of pregnancy. The number of oogonia decreased along the pregnancy, however, their nucleus size was increased. The number of follicles and volume of oogonia were positively correlated with the fetal measurements, while the number of oogonia was negatively correlated. Equations were obtained for the prediction of gonadal characteristics of fetuses. We concluded that in pigs testis cell proliferation, ovary development and histological organization was more pronounced during the final third of pregnancy. Fetal weight and size were strongly related to gonadal development, and can be used to estimate the histological characteristics of gonads.

Cytological study on Sertoli cells and their interactions with germ cells during annual reproductive cycle in turtle

Sertoli cells (SCs) play a central role in the development of germ cells within functional testes and exhibit varying morphology during spermatogenesis. This present study investigated the seasonal morphological changes in SCs in the reproductive cycle of Pelodiscus sinensis by light microscopy, transmission electron microscopy (TEM), and immunohistochemistry. During hibernation period with the quiescent of spermatogenesis, several autophagosomes were observed inside the SCs, the processes of which retracted. In early spermatogenesis, when the germ cells started to proliferate, the SCs contained numerous lipid droplets instead of autophagosomes. In late spermatogenesis, the SCs processes became very thin and contacted several round/elongated spermatids in pockets. At this time, abundant endoplasmic reticulum and numerous mitochondria were present in the SCs. The organization of the tight junctions and the adherens junctions between the SCs and germ cells also changed during the reproductive cycle. Moreover, SCs were involved in the formation of cytoplasmic bridges, phagophores, and exosome secretions during spermatogenesis. Tubulobulbar complexes (TBC) were also developed by SCs around the nucleus of the spermatid at the time of spermiation. Strong, positive expression of vimentin was noted on the SCs during late spermatogenesis compared with the hibernation stage and the early stage of spermatogenesis. These data provide clear cytological evidence about the seasonal changes in SCs, corresponding with their different roles in germ cells within the Chinese soft‐shelled turtle Pelodiscus sinensis.

Peroxisome proliferator-activated receptor gamma signaling in human sperm physiology

Peroxisome proliferator-activated receptor gamma (PPARγ) is a member of the PPARs, which are transcription factors of the steroid receptor superfamily. PPARγ acts as an important molecule for regulating energy homeostasis, modulates the hypothalamic-pituitary-gonadal (HPG) axis, and is reciprocally regulated by HPG. In the human, PPARγ protein is highly expressed in ejaculated spermatozoa, implying a possible role of PPARγ signaling in regulating sperm energy dissipation. PPARγ protein is also expressed in Sertoli cells and germ cells (spermatocytes). Its activation can be induced during capacitation and the acrosome reaction. This mini-review will focus on how PPARγ signaling may affect fertility and sperm quality and the potential reversibility of these adverse effects.

Long-term culture and significant expansion of human Sertoli cells whilst maintaining stable global phenotype and AKT and SMAD1/5 activation

BACKGROUND

Sertoli cells play key roles in regulating spermatogenesis and testis development by providing structural and nutritional supports. Recent studies demonstrate that Sertoli cells can be converted into functional neural stem cells. Adult Sertoli cells have previously been considered the terminally differentiated cells with a fixed and unmodifiable population after puberty. However, this concept has been challenged. Since the number of adult human Sertoli cells is limited, it is essential to culture these cells for a long period and expand them to obtain sufficient cells for their basic research and clinic applications. Nevertheless, the studies on human Sertoli cells are restricted, because it is difficult to get access to human testis tissues.

RESULTS

Here we isolated adult human Sertoli cells with a high purity and viability from obstructive azoospermia patients with normal spermatogenesis. Adult human Sertoli cells were cultured with DMEM/F12 and fetal bovine serum for 2 months, and they could be expanded with a 59,049-fold increase of cell numbers. Morphology, phenotypic characteristics, and the signaling pathways of adult human Sertoli cells from different passages were compared. Significantly, adult human Sertoli cells assumed similar morphological features, stable global gene expression profiles and numerous proteins, and activation of AKT and SMAD1/5 during long-period culture.

CONCLUSIONS

This study demonstrates that adult human Sertoli cells can be cultured for a long period and expanded with remarkable increase of cell numbers whilst maintaining their primary morphology, phenotype and signaling pathways. This study could provide adequate human Sertoli cells for reproductive and regenerative medicine.

Regeneration of Leydig cells in ectopically autografted adult mouse testes

Ectopic autografting of testis tissue is a promising approach for studying testicular development, male germline preservation and restoration of male fertility. In this study, we examined the fate of various testicular cells in adult mouse testes following ectopic autografting at 1, 2, 4 and 8 weeks post grafting. Histological examination showed no evidence of re-establishment of spermatogenesis in autografts, and progressive degeneration of seminiferous tubules was detected. Expression of germ cell-specific proteins such as POU5F1, DAZL, TNP1, TNP2, PRM1 and PRM2 revealed that, although proliferating and differentiating spermatogenic germ cells such as spermatogonia, spermatocytes and spermatids could survive in autografts until 4 weeks, only terminally differentiated germ cells such as sperm persisted in autografts until 8 weeks. The presence of Sertoli and peritubular myoid cells, as indicated by expression of WT1 and ACTA2 proteins, respectively, was evident in the autografts until 8 weeks. Interestingly, seminal vesicle weight and serum testosterone level were restored in autografted mice by 8 weeks post grafting. The expression of Leydig cell-specific proteins such as CYP11A1, HSD3B2 and LHCGR showed revival of Leydig cell (LC) populations in autografts over time since grafting. Elevated expression of PDGFRA, LIF, DHH and NEFH in autografts indicated de novo regeneration of LC populations. Autografted adult testis can be used as a model for investigating Leydig cell regeneration, steroidogenesis and regulation of the intrinsic factors involved in Leydig cell development. The success of this rodent model can have therapeutic applications for adult human males undergoing sterilizing cancer therapy.

Male germ cell development in humans

BACKGROUND

Germ cells are unique cells that possess the ability to transmit genetic information between generations. Detailed knowledge about the molecular and cellular mechanisms determining the fate of human male germ cells still remains sparse. This is partially due to ethical issues limiting the access to research material. Therefore, the mechanisms of proliferation, differentiation and apoptosis of human male germ cells still remain challenging study objectives.

METHODS

This review focuses on using English articles accessible in PubMed as well as personal files on the current knowledge of the molecular and cellular mechanisms connected with human testicular germ cell development, maturation failure and the possibility of fertility preservation in patients in whom there is a risk of gonadal failure. However, since rodents, particularly mice, offer the possibility of studying germ cell development by use of genetic modification techniques, some studies using animal models are also discussed.

CONCLUSION

This mini review focuses on the current knowledge about male germ cells. However, the reader is referred to two previous mini reviews focusing on testicular somatic cells, i.e. on Sertoli cells and Leydig cells.

Similar causes of various reproductive disorders in early life

During the past few decades, scientific evidence has been accumulated concerning the possible adverse effects of the exposure to environmental chemicals on the well-being of wildlife and human populations. One large and growing group of such compounds of anthropogenic or natural origin is referred to as endocrine-disrupting chemicals (EDCs), due to their deleterious action on the endocrine system. This concern was first focused on the control of reproductive function particularly in males, but has later been expanded to include all possible endocrine functions. The present review describes the underlying physiology behind the cascade of developmental events that occur during sexual differentiation of males and the specific role of androgen in the masculinization process and proper organogenesis of the external male genitalia. The impact of the genetic background, environmental exposures and lifestyle factors in the etiology of hypospadias, cryptorchidism and testicular cancer are reviewed and the possible role of EDCs in the development of these reproductive disorders is discussed critically. Finally, the possible direct and programming effects of exposures in utero to widely use therapeutic compounds, environmental estrogens and other chemicals on the incidence of reproductive abnormalities and poor semen quality in humans are also highlighted.

Insulin deprivation decreases caspase-dependent apoptotic signaling in cultured rat sertoli cells

Insulin is essential for the regulation of glucose homeostasis. Insulin dysfunction occurs in several pathologies, such as diabetes mellitus, which is associated with fertility problems. Somatic Sertoli cells (SCs) not only metabolize glucose to lactate, which is the central energy source used by developing germ cells, but also determine the germ cell population size. If a deregulation in SCs apoptosis occurs, it will affect germ cells, compromising spermatogenesis. As SCs apoptotic signaling is a hormonally regulated process, we hypothesized that the lack of insulin could lead to alterations in apoptotic signaling. Therefore, we examined the effect of insulin deprivation on several markers of apoptotic signaling in cultured rat SCs. We determined mRNA and protein expression of apoptotic markers as well as caspase-3 activity. SCs cultured in insulin deprivation demonstrated a significant decrease on mRNA levels of p53, Bax, caspase-9, and caspase-3 followed by a significant increase of Bax and decrease of caspase-9 protein levels relatively to the control. Caspase-3 activity was also decreased in SCs cultured in insulin deprivation conditions. Our results show that insulin deprivation decreases caspase-dependent apoptotic signaling in cultured rat SCs evidencing a possible mechanism by which lack of insulin can affect spermatogenesis and fertility.

Up-regulation of SOX9 in sertoli cells from testiculopathic patients accounts for increasing anti-mullerian hormone expression via impaired androgen receptor signaling

Background

Testosterone provokes Sertoli cell maturation and represses AMH production. In adult patients with Sertoli-cells-only syndrome (SCOS) and androgen insensitivity syndrome (AIS), high level of AMH expression is detected in Sertoli cells due to defect of androgen/AR signaling.

Objective

We postulated that up-regulation of SOX9 due to impairment of androgen/AR signaling in Sertoli cells might explain why high level of anti-Mullerian hormone (AMH) expression occur in these testiculopathic patients.

Methods

Biological research of testicular specimens from men with azoospermia or mouse. The serum hormone levels were studied in 23 men with obstructive azoospermia, 33 men with SCOS azoospermia and 21 volunteers with normal seminograms during a period of 4 years.

Immunohistochemical staining and reverse-transcription PCR were used to examine the relationships among AR, SOX9 and AMH expression in adult human and mouse testes. The ability of AR to repress the expression of SOX9 and AMH was evaluated in vitro in TM4 Sertoli cells and C3H10T1/2 cells.

Results

SCOS specimens showed up-regulation of SOX9 and AMH proteins but down-regulation of AR proteins in Sertoli cells. The mRNA levels of AR were significantly lower and the SOX9, AMH mRNA levels higher in all SCOS patients compared to controls (P< 0.05). The testosterone levels in the SCOS patients were within the normal range, but most were below the median of the controls. Furthermore, our invitro cell line experiments demonstrated that androgen/AR signaling suppressed the gene and protein levels of AMH via repression of SOX9.

Conclusions

Our data show that the functional androgen/AR signaling to repress SOX9 and AMH expression is essential for Sertoli cell maturation. Impairment of androgen/AR signaling promotes SOX9-mediated AMH production, accounts for impairments of Sertoli cells in SCOS azoospermic patients.

The Wilms tumor gene, Wt1, is critical for mouse spermatogenesis via regulation of sertoli cell polarity and is associated with non-obstructive azoospermia in humans

Azoospermia is one of the major reproductive disorders which cause male infertility in humans; however, the etiology of this disease is largely unknown. In the present study, six missense mutations of WT1 gene were detected in 529 human patients with non-obstructive azoospermia (NOA), indicating a strong association between WT1 mutation and NOA. The Wilms tumor gene, Wt1, is specifically expressed in Sertoli cells (SCs) which support spermatogenesis. To examine the functions of this gene in spermatogenesis, Wt1 was deleted in adult testis using Wt1^flox and Cre-ER^TM mice strains. We found that inactivation of Wt1 resulted in massive germ cell death and only SCs were present in most of the seminiferous tubules which was very similar to NOA in humans. In investigating the potential mechanism for this, histological studies revealed that the blood–testis barrier (BTB) was disrupted in Wt1 deficient testes. In vitro studies demonstrated that Wt1 was essential for cell polarity maintenance in SCs. Further studies found that the expression of cell polarity associated genes (Par6b and E-cadherin) and Wnt signaling genes (Wnt4, Wnt11) were downregulated in Wt1 deficient SCs, and that the expression of Par6b and E-cadherin was regulated by Wnt4. Our findings suggest that Wt1 is important in spermatogenesis by regulating the polarity of SCs via Wnt signaling pathway and that WT1 mutation is one of the genetic causes of NOA in humans.

Infertility is one of the most common health problems, affecting about 15% of the couples in the world. In about half of these couples, infertility is related to male reproductive defect. Azoospermia is one of the major causes of male infertility in humans. Previous studies have found that the mutation or deletion of some genes is associated with azoospermia; however, the genetic cause of this remains largely unknown. In the present study, we detected Wt1 missense mutations in men with non-obstructive azoospermia (NOA). An essential function for WT1 in male spermatogenesis was confirmed by the use of a Wt1 conditional knockout mouse strain. Inactivation of Wt1 resulted in germ cell loss in mice, which was similar to NOA in human patients. Our data indicate that WT1 mutation is one genetic cause of male infertility and suggest that WT1 mutational analysis will be useful for diagnosis in a clinical setting.

Establishment of adult mouse Sertoli cell lines by using the starvation method

Sertoli cells were isolated from the testes of 6-week-old mice and stable Sertoli cell lines with higher proliferation rates were subcloned after starvation of primary cultured cells. After two rounds of this subcloning, 33 subcloned lines were selected on the basis of their proliferation rates. In addition, these subclones were screened according to their phagocytic activity and the characteristics of mature Sertoli cells, such as the expression of androgen receptors (ARs) and progesterone receptors, by using western blotting and immunocytochemical analysis, in addition to their morphology and proliferation rates. After the third round of subcloning, 12 subclones were selected for the final selection using RT-PCR for identification of genes specifically expressed by various testicular cells. Three clones were selected that expressed Sertoli-cell-specific genes, i.e. stem cell factor, clusterin, AR, α-inhibin, transferrin, Wilms' tumour-1, Müllerian inhibitory substance, sex-determining region Y-box 9, FSH receptor (Fshr) and occludin; however, these clones did not express globulin transcription factor 1, steroidogenic factor or androgen-binding protein. These clones also expressed growth and differentiation factors that act on germ cells, such as leukaemia inhibitory factor, transforming growth factor β1 and basic fibroblast growth factor 2, but did not express c-kit (specific for germ cells), LH receptor and 3β-hydroxyl-dehydrogenase (specific for Leydig cells). Immunocytochemical data confirmed the expression of clusterin in these clones. Furthermore, the Bromodeoxyuridine incorporation assay confirmed the proliferation activity of these clones throughFshrafter treatment with FSH. These clones are considered to be valuable tools for the study of Sertoli cell-specific gene expression and function.

Is the adult Sertoli cell terminally differentiated?

New data have challenged the convention that the adult Sertoli cell population is fixed and unmodifiable. The Sertoli cell has two distinct functions: 1) formation of the seminiferous cords and 2) provision of nutritional and structural support to developing germ cells. For these to occur successfully, Sertoli cells must undergo many maturational changes between fetal and adult life, the main switches occurring around puberty, including the loss of proliferative activity and the formation of the blood-testis barrier. Follicle-stimulating hormone plays a key role in promoting Sertoli cell proliferation, while thyroid hormone inhibits proliferative activity in early postnatal life. Together these regulate the Sertoli-germ cell complement and sperm output in adulthood. By puberty, the Sertoli cell population is considered to be stable and unmodifiable by hormones. But there is mounting evidence that the size of the adult Sertoli cell population and its maturational status is modifiable by hormones and that Sertoli cells can gain proliferative ability in the spermatogenically disrupted hamster and human model. This new information demonstrates that the adult Sertoli cell population, at least in the settings of testicular regression in the hamster and impaired fertility in humans in vivo and from mice and men in vitro, is not a terminally differentiated population. Data from the hamster now show that the adult Sertoli cell population size is regulated by hormones. This creates exciting prospects for basic and clinical research in testis biology. The potential to replenish an adult Sertoli-germ cell complement to normal in a setting of infertility may now be realized.

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.

Action mechanism of inhibin α-subunit on the development of Sertoli cells and first wave of spermatogenesis in mice

Inhibin is an important marker of Sertoli cell (SC) activity in animals with impaired spermatogenesis. However, the precise relationship between inhibin and SC activity is unknown. To investigate this relationship, we partially silenced both the transcription and translation of the gene for the α-subunit of inhibin, Inha, using recombinant pshRNA vectors developed with RNAi-Ready pSIREN-RetroQ-ZsGreen Vector (Clontech Laboratories, Mountain View, Calif). We found that Inha silencing suppresses the cell-cycle regulators Cyclin D1 and Cyclin E and up-regulates the cell-cycle inhibitor P21 (as detected by Western blot analysis), thereby increasing the number of SCs in the G1 phase of the cell cycle and decreasing the amount in the S-phase of the cell cycle (as detected by flow cytometry). Inha silencing also suppressed Pdgfa, Igf1, and Kitl mRNA levels and up-regulated Tgfbrs, Inhba, Inhbb, Cyp11a1, Dhh, and Tjp1 mRNA levels (as indicated by real-time polymerase chain reaction [PCR] analysis). These findings indicate that Inha has the potential to influence the availability of the ligand inhibin and its antagonist activin in the SC in an autocrine manner and inhibit the progression of SC from G1 to S. It may also participate in the development of the blood–testis barrier, Leydig cells, and spermatogenesis through its effect on Dhh, Tjp1, Kitl, and Pdgfa. Real-time PCR and Western blot analyses of Inha, Inhba, and Inhbb mRNA and Inha levels over time show that Inha plays an important role in the formation of round spermatid during the first wave of spermatogenesis in mice.

Anomalies postnatales du développement de la spermatogenèse associées aux troubles de la migration testiculaire

La cryptorchidie, testicule non descendu dans sa position normale intrascrotale, est l’une des anomalies congénitales les plus fréquentes du système génital masculin. Le mécanisme de cette migration est un processus complexe encore mal connu. Plusieurs hypothèses étiologiques ont été avancées pour tenter d’expliquer la survenue de la cryptorchidie. L’existence d’une anomalie de la descente testiculaire, même traitée dans l’enfance, est un facteur de risque de cancer du testicule. Mais elle peut aussi se traduire à l’âge adulte par des anomalies des paramètres spermatiques et une atteinte de la fertilité. Dans la présente revue sont rassemblées les données concernant les anomalies du développement postnatal de la spermatogenèse observées en cas de troubles isolés de la migration du testicule et leurs conséquences à l’âge adulte sur les paramètres de la fertilité.

Ankrd7, a novel gene specifically expressed in Sertoli cells and its potential roles in Sertoli cell maturation

The somatic Sertoli cells play an essential role in testis determination and spermatogenesis by providing nutrition and structural support. In the current study, we report on the novel Ankrd7 gene that contains five ankyrin repeat domains. This gene was specifically expressed in Sertoli cells and was regulated in a maturation-dependent manner. Its expression was restricted to testicular tissue, and its mRNA could be detected in testes at as early as 14 dpp (days post partum) using RT-PCR analysis. In both testicular tissue sections and in vitro cultured Sertoli cells, the Ankrd7 protein was localized to the nucleus of the Sertoli cell. Immuno-histochemistry and immunocytochemistry investigations showed that the protein was detectable in testicular tissues at 20 dpp, at which time Sertoli cells were gradually differentiating into their mature cellular form. These results suggest that Ankrd7 is probably involved in the process of Sertoli cell maturation and in spermatogenesis.

The role of thyroid hormone in testicular development and function

Thyroid hormone is a critical regulator of growth, development, and metabolism in virtually all tissues, and altered thyroid status affects many organs and systems. Although for many years testis has been regarded as a thyroid hormone unresponsive organ, it is now evident that thyroid hormone plays an important role in testicular development and function. A considerable amount of data show that thyroid hormone influences steroidogenesis as well as spermatogenesis. The involvement of tri-iodothyronine (T(3)) in the control of Sertoli cell proliferation and functional maturation is widely accepted, as well as its role in postnatal Leydig cell differentiation and steroidogenesis. The presence of thyroid hormone receptors in testicular cells throughout development and in adulthood implies that T(3) may act directly on these cells to bring about its effects. Several recent studies have employed different methodologies and techniques in an attempt to understand the mechanisms underlying thyroid hormone effects on testicular cells. The current review aims at presenting an updated picture of the recent advances made regarding the role of thyroid hormones in male gonadal function.

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

Pregnancy exposure to di(n-butyl) phthalate (DBP) in rats induces a testicular dysgenesislike syndrome (TDS) in male offspring. Earlier studies suggested altered Sertoli cell development/maturation may result, especially in testes that become cryptorchid. This study quantitatively assessed Sertoli cell numerical and functional development in DBP-exposed rats and compared (unilaterally) cryptorchid and scrotal testes. Pregnant rats were gavaged with 500 mg/kg/day DBP or corn oil from embryonic (E) Days 13.5 to 21.5. Male offspring were sampled on E21.5 or Postnatal Day 6, 10, 15, 25, or 90. Sertoli cell number in DBP-exposed males was reduced by approximately 50% at E21.5 but recovered to normal by Days 25-90, accompanied by significant changes in plasma inhibin B and testosterone levels. Sertoli cell maturational development in DBP-exposed males, assessed using five protein markers (anti-müllerian hormone, cytokeratin, androgen receptor, CDKN1B, and Nestin), was largely normal, with some evidence of delayed maturation. However, in adulthood, Sertoli cells (SC) in areas lacking germ cells (Sertoli cell-only [SCO] tubules) often exhibited immature features, especially in cryptorchid testes. Sertoli cells in DBP-exposed animals supported fewer germ cells during puberty, but this normalized in scrotal testes by adulthood. Scrotal and especially cryptorchid testes from DBP-exposed animals exhibited abnormalities (SCO tubules, focal dysgenetic areas) at all postnatal ages. Cryptorchid testes from DBP-exposed animals exhibited more Sertoli cell abnormalities at Day 25 compared with scrotal testes, perhaps indicating more severe underlying Sertoli cell malfunction in these testes. Our findings support the concept of altered Sertoli cell development in TDS, especially in cryptorchid testes, but show that maturational defects in Sertoli cells in adulthood most commonly reflect secondary dedifferentiation in absence of germ cells.

Sexual dimorphism of gonadal development

Sexual dimorphism is a term describing morphological differences between the sexes, but is often extended to include all differences observed between females and males. Sex differentiation in vertebrates is by definition sexually dimorphic and starts at the level of the sex chromosomes. In this review the sexual dimorphism of gonadal differentiation is discussed, with a focus on human development. In the embryo, the indifferent gonadal anlagen harbours four different cell lineages with bipotential fates dependent on the sex of the individual. The different paths taken by these cell lineages in male and female development are reviewed, along with other sexually dimorphic features of gonadal development. These include sex-determining genes, timing of events, dependence on germ cells, spatial organization of stromal cells, steroidogenic cells types, and other aspects.

Characterization and distribution of hyaluronan and the proteoglycans decorin, biglycan and perlecan in the developing embryonic mouse gonad

The morphogenesis of tissues and organs requires dynamic changes in cells and in extracellular matrix components. It is known that various extracellular matrix molecules are of fundamental importance for gonad differentiation and growth. In the adult testis, the extracellular matrix represents an important component of the interstitium, participating in the transport of biologically active substances needed for the communication between different cellular components, as well as for the regulation of spermatogenesis and hormone production. The present study was designed in order to identify the proteoglycans biglycan, decorin and perlecan, as well as the glycosaminoglycan hyaluronan, during testis development in mouse embryos. Our data profile the chronology of testis differentiation, as well as the distribution of these extracellular matrix components during testis development in mice. We show that these extracellular matrix molecules are present early in the development of the gonads, suggesting that they play a role in gonad development. In addition, we found no decorin in the testicular cords. Furthermore, of the proteoglycans analysed, only biglycan was seen surrounding immature Sertoli cells and Leydig cell precursors in the testicular cords. This indicates that specific sets of extracellular matrix molecules are required in the various compartments of the developing gonad.

Distribution of sex chromosomes in dysgenetic gonads of mixed type

In a four-week-old child with female external and internal genitalia but with clitoris hypertrophy chromosome analysis from blood lymphocytes revealed a 46,XY karyotype. No deletion of Y chromosomal sequences was detected by PCR analysis of genomic DNA isolated from peripheral blood leucocytes. Because of the increased risk for gonadal tumours, gonadectomy was performed. Conventional cytogenetic analysis of the left dysgenetic gonad revealed a gonosomal mosaicism with a 45,X cell line in 27 of 50 metaphases. The dysgenetic left gonad demonstrated a significantly higher proportion (P = 0.005) of cells carrying a Y chromosome (46.3%) than the streak gonad from the right side (33.9%). Histomorphological examination of the left gonad revealed immature testicular tissue and rete-like structures as well as irregular ovarian type areas with cystic follicular structures. Interphase FISH analysis of the different tissues of this dysgenetic gonad demonstrated variable proportions of cells with an X and a Y chromosome. Whereas Sertoli cells and rete-like structures revealed a significantly higher proportion of XY cells in relation to the whole section of the dysgenetic gonad (P < 0.0001), almost all granulose-like cells carried no Y chromosome. The proportion of XY/X cells in theca-like cells and Leydig cells was similar to that of the whole dysgenetic gonad. In contrast to these findings, spermatogonia exclusively contained an XY constellation.

Genomic organization and structure of the 5'-flanking region of the TEX101 gene: alternative promoter usage and splicing generate transcript variants with distinct 5'-untranslated region

A novel germ cell-specific antigen, TEX101 (TES101-reactive protein), was previously identified using a monoclonal antibody directed against mouse testicular cells. TEX101 is specifically located on the plasma membrane of germ cells, and its expression in gonadal organs is sexually dimorphic. To understand the fundamental mechanism directing gene expression, the genomic organization of TEX101 was studied. The gene consists of five translated exons (exons 2-6) and three 5'-untranslated exons (exon 1a, 1b, and 1c), respectively. TEX101 forms three major transcripts classified by usage of the three 5'-untranslated exons. One form of TEX101 mRNA is transcribed from exon 1c and spliced to the common acceptor site in exon 2. In the second form of the transcript, exon 1a is spliced to exon 1b and exon 2 in a sequential manner. Splicing from exon 1a to exon 2, arises the third form of transcript. Reverse Transcription (RT)-polymerase chain reaction (PCR) analysis demonstrated differential expression pattern of the TEX101 transcripts between testis and ovary. Whereas the expression of transcript-1 is constitutive in male and female gonads, the transcript-2 and -3 are detected only after starting of the spermatogenesis. Luciferase reporter assays using GC-2spd(ts) cells, a cell line from immortalized mouse testicular cells, showed that the 5'-flanking sequence of exon 1c has higher promoter activity than exon 1a. Deletion analysis of the chimeric structures indicated that sequences essential to gene expression are present on the 5'-flanking region between -3186 and +14, where the cluster of five CAAT boxes is located. Taken together, these findings should facilitate an understanding of the regulation of TEX101 expression during gametogenesis.

Effects of growth factors on testicular morphogenesis

Since the discovery of the sex-determining gene Sry in 1990, research effort has focused on the events downstream of its expression. A range of different experimental approaches including gene expression, knocking-out and knocking-in genes of interest, and cell and tissue culture techniques have been applied, highlighting the importance of growth factors at all stages of testicular morphogenesis. Migration of primordial germ cells and the mesonephric precursors of peritubular myoid cells and endothelial cells to the gonad is under growth factor control. Proliferation of both germ cells and somatic cells within the gonadal primordium is also controlled by cytokines as is the interaction of Sertoli cells (with each other and with the extracellular matrix) to form testicular cords. Several growth factors/growth factor families (e.g., platelet-derived growth factor, fibroblast growth factor family, TGFbeta family, and neurotrophins) have emerged as key players, exerting an influence at different time points and steps in organogenesis. Although most evidence has emerged in the mouse, comparative studies are important in elucidating the variety, potential, and evolution of control mechanisms.

Gonadal effects of a mouse Denys-Drash syndrome mutation

Gonadal effects of the Denys-Drash syndrome (DDS) mutation Wt1(tmT396 )were examined in chimaeric and heterozygous mice. Since the only heterozygote was 41,XXY, Sertoli cell function was assessed by comparison with age-matched control XXY testes. Control XXY Sertoli cells showed immuno-expression of WT1 and androgen receptor (AR) indistinguishable from wild-type (40,XY), but expressed anti-Mullerian hormone (AMH). In contrast, DDS Sertoli cells showed only faint immuno-expression of WT1 and did not express AR or AMH. While XY<-->XY DDS chimaeras were male, XX<-->XY chimaeras were predominantly female. In the rare XX<-->XY DDS males the Sertoli cell lineage was largely derived from Wt1 mutant XY cells. We conclude that DDS mutant cells can form Sertoli cells, that the dominant mutation does not cause male sex reversal in mice but distorts the sex ratio of XX<-->XY chimaeras, and that there may be a link between WT1, AMH and AR expression by Sertoli cells in vivo.

Expression of Stat3 in germ cells of developing and adult mouse ovaries and testes

The Signal transducers and activators of transcription (Stat) family of proteins plays diverse roles during differentiation in many tissues. Stat3 is an essential mammalian gene, critical during embryonic development. In mammals, Stat3 is differentially distributed in the cytoplasm of mature oocytes and in preimplantation embryos suggesting that Stat3 may be involved in determination of polarity. Here, we report that Stat3 protein is expressed in the cytoplasm of oocytes from primordial, primary and secondary follicles in the adult ovary and in developing acrosomes of round spermatids in the adult testis. Stat3 is also expressed in gonocytes, prospermatogonia, oogonia and oocytes of embryonic and neonatal gonads.

Method for evaluating quality of cultured neonatal pig Sertoli cells

BACKGROUND

Sertoli cells (SC) in the testis secrete factors that nourish and immunoprotect developing spermatozoa, which have made them the focus of studies that aim to generate localized tolerance, particularly for transplantation and perhaps autoimmunity. Several methods have been described to isolate these cells, which include a two-step enzymatic digestion with limited assessment of the culture. Here we describe a one-step method, and a series of tests for determining purity, viability, and function of the cultured cells.

METHODS

We isolated SC from neonatal pigs using Liberase HI digestion. Viability and apoptosis of cultured cells were measured by flow cytometry with propidium iodide and annexin, respectively. Specific identification of the Sertoli type was made by immunodetection of Sox9, vimentin, and Mullerian inhibiting substance. Moreover, for functionality we were able to detect clusterin in the cultured cells by Western blot.

RESULTS

Our isolation method had a yield and purity similar to previous reports measured with two-step methods. Viability was 95.22 +/- 0.57% and apoptotic cells were 10.5 +/- 0.32% after 48 h in culture. At 7 days, practically all cells expressed Sox9, Mullerian inhibiting substance, clusterin, and vimentin.

CONCLUSIONS

We describe an alternative strategy for preparing and identifying cultured SC for further assays of metabolic activity or in transplantation models. Establishing a one-step Liberase-digestion method for isolation, evaluating viability and apoptosis by more sensitive methods, and detecting specific markers in culture can help to evaluate the quality of cultured cells. Specific cell markers for identifying SC may be critical when identifying SC outside the testis, in contrast with vimentin which is useful only for in situ cells.