Immunolocalization of apelin receptor (APJ) in mouse seminiferous epithelium.

The apelin receptor (APJ) belongs to the member of the G protein-coupled receptor family, and expression of APJ has been reported in the different cell types of testis. The seminiferous tubules in the testis can be identified as different stages (I-XII). It has been also suggested that different factors could be expressed in stage and cell-specific manner in the seminiferous tubules. Recently, we also shown that expression of APJ is developmentally regulated in the testis from PND1 to PND42. Therefore, we analyzed the expression of APJ in the testis of adult mice by immunohistochemistry. Immunohistochemistry showed that the APJ was highly specific for the round and elongated spermatids with stage-dependent changes. The seminiferous tubules at stages I-VII showed APJ immunostaining in the spermatid steps 1-8, not steps of 13-16. The seminiferous tubules at stages IX-XII showed APJ immunostaining in the spermatid steps 9-12. These results suggested the possible role of APJ in the spermiogenesis process. The intratesticular administration of APJ antagonist, ML221 showed a few round spermatids in the seminiferous tubules and some of the tubules with complete absence of round spermatid. Overall, we present evidence that APJ expression in spermatid is dependent on the stages of the seminiferous epithelium cycle and APJ could be involved in the differentiation of round spermatid to elongated spermatid.

Rattus norvegicus Spermatogenesis Colony-Forming Assays.

Knowledge gaps persist on signaling pathways and metabolic states in germ cells sufficient to support spermatogenesis independent of a somatic environment. Consequently, methods to culture mammalian stem cells through spermatogenesis in defined systems have not been established. Lack of success at culturing mammalian stem cells through spermatogenesis in defined systems reflects an inability to experimentally recapitulate biochemical events that develop in germ cells within the testis-specific seminiferous epithelium. Complex germ and somatic cell associations that develop each seminiferous epithelial cycle support such a hypothesis, conceivably explaining why highly pure mammalian spermatogonia do not effectively develop into and through meiosis without somatic cells. Here, we outline an in vitro spermatogenesis colony-forming assay to study how differentiating spermatogonial syncytia develop from rat spermatogonial stem cell lines. Robust spermatogonial differentiation under defined culture conditions, once established, is anticipated to facilitate molecular biology studies on pre-meiotic steps in gametogenesis by providing soma-free bioassays to systematically identify spermatogenic factors that promote meiotic progression in vitro.

Cell adhesion function was altered during the seasonal regression of the seminiferous epithelium in the mink species Neovison vison.

Minks are seasonal breeders whose seminiferous epithelium undergoes regression through massive germ cell death, leaving only Sertoli cells and spermatogonial cells in the tubules. However, the molecular mechanisms that control this biological process remain largely unknown. This study describes a transcriptomic analysis of mink testes at various reproductive stages (active, regressing, and inactive). A comparison of seminiferous epithelium at different stages of reproduction shows that cell adhesion is altered during regression. In addition, genes and proteins involved in forming the blood-testis barrier (BTB) were examined in sexually active and inactive minks. The seminiferous epithelium in the testes of sexually inactive minks expressed occludin, but this expression was not discernibly observed in the testes of sexually active minks. There was no discernible expression of CX43 in the seminiferous epithelium in the testes of sexually inactive minks, but CX43 was expressed in the testes of sexually active minks. During the regression process, we observed a remarkable increase in the expression levels of Claudin-11, which is associated with Sertoli-germ cell junctions. In conclusion, these findings suggest a loss of Sertoli-germ cell adhesion, which may regulate postmeiotic cell shedding during testicular regression in mink.

Here, we report for the first time the molecular mechanisms of testicular regression in mink. Our results, together with studies on other animals' characteristic reproductive features, identify a cluster of events crucial to the seminiferous epithelium regression process in mammalian seasonal breeders and highlight perspectives unique to the mink.

Morphology of the male rat gonad after in Utero exposure to immunosuppressants.

The protocol for immunosuppression of pregnant women is based on immunosuppressant panels. The aim of the study was to determine the influence of commonly applied combinations of immunosuppressants to pregnant rats on the morphology of the offspring' testes. Pregnant rats were treated with cyclosporin A (CsA), mycophenolate mofetil (MMF) and prednisone (Pred) (CMG); tacrolimus (Tc), MMF and Pred (TMG); CsA, everolimus (Ev) and Pred (CEG). Testes of mature offspring underwent morphological analysis. Mainly in the testes of CMG and TMG rats the morphological and functional changes were observed: immature germ cells (GCs) in the seminiferous tubule (ST) lumen, invaginations of the basement membrane, infolding to the seminiferous epithelium (SE), the ST wall thickening, increased acidophilia of Sertoli cells' (SCs) cytoplasm, large residual bodies near the lumen, dystrophic ST and tubules look like the Sertoli cell-only syndrome, Leydig cells with abnormal cell nucleus, hypertrophy of the interstitium, blurring of the boundary between ST wall and interstitium, a reduced number of GCs in the SE, vacuolation of the SE. In the CEG there were only a reduced number of GCs in some tubules and vacuolization of SCs. The safest combination of drugs was CEG, while the TMG and CMG were gonadotoxic.

Regulation of Sertoli cell function by planar cell polarity (PCP) protein Fjx1.

Four-jointed box kinase 1 (Fjx1) is a planar cell polarity (PCP) protein and a member of the Fat (FAT atypical cadherin 1)/Dchs (Dachsous cadherin-related protein)/Fjx1 PCP complex. Fjx1 is also a non-receptor Ser/Thr protein kinase capable of phosphorylating Fat1 at is extracellular cadherin domains when it is being transported across the Golgi system. As such, Fjx1 is a Golgi-based regulator of Fat1 function by determining its extracellular deposition. Herein, Fjx1 was found to localize across the Sertoli cell cytoplasm, partially co-localized with the microtubules (MTs) across the seminiferous epithelium. It was most notable at the apical ES (ectoplasmic specialization) and basal ES, displaying distinctive stage-specific expression. The apical ES and basal ES are the corresponding testis-specific cell adhesion ultrastructures at the Sertoli-elongated spermatid interface and the Sertoli cell-cell interface, respectively, consistent with the role of Fjx1 as a Golgi-associated Ser/Thr kinase that modulates the Fat (and/or Dchs) integral membrane proteins. Its knockdown (KD) by RNAi using specific Fjx1 siRNA duplexes versus non-targeting negative control siRNA duplexes was found to perturb the Sertoli cell tight junction function, as well as perturbing the function and organization of MT and actin. While Fjx1 KD did not affect the steady-state levels of almost two dozens of BTB-associated Sertoli cell proteins, including structural and regulatory proteins, its KD was found to down-regulate Fat1 (but not Fat2, 3, and 4) and to up-regulate Dchs1 (but not Dchs2) expression. Based on results of biochemical analysis, Fjx1 KD was found to be capable of abolishing phosphorylation of its putative substrate Fat1 at its Ser/Thr sites, but not at its Tyr site, illustrating an intimate functional relationship of Fjx1 and Fat1 in Sertoli cells.

Transcriptional regulation of spatiotemporal gene expression within the seminiferous epithelium: Mouse Acrv1 gene as a model.

Precise spatiotemporal expression of cohorts of differentiation markers unique to spermatogonia, spermatocytes, and round spermatids punctuates spermatogenesis and ensures its completion. For example, genes coding for the synaptonemal complex or the acrosome or flagellum are expressed sequentially in a developmental stage- and germ cell-specific manner. But the transcriptional mechanisms governing the spatiotemporal order of gene expression within the seminiferous epithelium are poorly understood. Using the round spermatid-specific Acrv1 gene, which codes for the acrosomal protein SP-10 as a model, we learned that (1) the proximal promoter itself contains all the necessary cis-regulatory sequences, (2) an insulator prevents somatic cell expression of the testis-specific gene, (3) RNA II polymerase is loaded on the Acrv1 promoter but paused in spermatocytes, thus ensuring precise transcriptional elongation in round spermatids, and that (4) a transcriptional repressor binding protein of 43 kilodaltons (TDP-43) plays a role in maintaining the paused state in spermatocytes. Although the Acrv1 enhancer element has been narrowed down to 50 bp and its binding to a 47 kDa testis-abundant nuclear protein shown, the identity of the putative transcription factor responsible for activation of round spermatid-specific transcription remains elusive. Human male infertility is idiopathic with limited treatment options. Understanding transcriptional regulation of spermatogenesis has the potential to lead to future therapies for male infertility.

STAGETOOL, a Novel Automated Approach for Mouse Testis Histological Analysis.

Spermatogenesis is a complex differentiation process that takes place in the seminiferous tubules. A specific organization of spermatogenic cells within the seminiferous epithelium enables a synchronous progress of germ cells at certain steps of differentiation on the spermatogenic pathway. This can be observed in testis cross-sections where seminiferous tubules can be classified into distinct stages of constant cellular composition (12 stages in the mouse). For a detailed analysis of spermatogenesis, these stages have to be individually observed from testis cross-sections. However, the recognition of stages requires special training and expertise. Furthermore, the manual scoring is laborious considering the high number of tubule cross-sections that have to be analyzed. To facilitate the analysis of spermatogenesis, we have developed a convolutional deep neural network-based approach named "STAGETOOL." STAGETOOL analyses histological images of 4',6-diamidine-2'-phenylindole dihydrochloride (DAPI)-stained mouse testis cross-sections at ×400 magnification, and very accurately classifies tubule cross-sections into 5 stage classes and cells into 9 categories. STAGETOOL classification accuracy for stage classes of seminiferous tubules of a whole-testis cross-section is 99.1%. For cellular level analysis the F1 score for 9 seminiferous epithelial cell types ranges from 0.80 to 0.98. Furthermore, we show that STAGETOOL can be applied for the analysis of knockout mouse models with spermatogenic defects, as well as for automated profiling of protein expression patterns. STAGETOOL is the first fluorescent labeling-based automated method for mouse testis histological analysis that enables both stage and cell-type recognition. While STAGETOOL qualitatively parallels an experienced human histologist, it outperforms humans time-wise, therefore representing a major advancement in male reproductive biology research.

Acute effects of para-chloroamphetamine on testosterone and markers of apoptosis in seminiferous epithelium of prepubertal male rats.

Serotonin is a neurotransmitter that affects the secretion of gonadotropins and testosterone. In prepubertal male rats, serotonin has a stimulating role in testosterone secretion. Here, we used prepubertal male rats to study the effects of para-chloroamphetamine (pCA) on circulating testosterone and gonadotropins and markers of apoptosis in germ cells from day 1 to day 5 post-treatment. The intraperitoneal administration of pCA induced a significant reduction in concentrations of hypothalamic serotonin and circulating testosterone, but gonadotropins were not affected. In the seminiferous epithelium of pCA-treated rats, increased the number of germ cells positive to markers of apoptosis, concomitantly with alterations in morphometry and the presence of multinucleated germ cells. Levels of testosterone were reduced starting from 1 day after pCA was administered. The time window between the administration of the pCA and collection of samples was sufficient to detect changes in testosterone levels, in contrast with a previous work where no changes were found. There was a possible relationship between the reduction of testosterone and an increase in the number of germ cells positive to apoptosis markers. However, the mechanism that links pCA-testosterone-germ cell positive to markers of apoptosis is unknown. Our outcomes support the view that pCA exposure during the prepubertal stage has an acute impact on testosterone levels and affects the structure and physiology of seminiferous epithelium.

Cellular and molecular basis for the action of retinoic acid in spermatogenesis.

Spermatogenesis is a highly organized and regulated process that requires the constant production of millions of gametes over the reproductive lifetime of the mammalian male. This is possible because of an active stem cell pool and an ordered entry into the germ cell developmental sequence. The ordered entry is a result of the synthesis and action of retinoic acid allowing for the onset of spermatogonial differentiation and an irreversible commitment to spermatogenesis. The periodic appearance and actions of retinoic acid along the seminiferous tubules is a result of the interactions between germ cells and Sertoli cells that result in the generation and maintenance of the cycle of the seminiferous epithelium and is the subject of this review.

Three-dimensional analysis and in vivo imaging for sperm release and transport in the murine seminiferous tubule.

Spermatozoa released from Sertoli cells must be transported to the epididymis. However, the mechanism of the luminal flow in seminiferous tubules has remained unclear to date. Therefore, in this study, we investigated luminal flow and movements in the seminiferous tubules by three-dimensional analysis and in vivo imaging. Serial 5-µm-thick mouse testicular sections at 50-µm-intervals were prepared and stained by Periodic Acid-Schiff-hematoxylin. After three-dimensional reconstruction of the seminiferous tubules, the localization of the released spermatozoa and the stages observed in the sections were recorded in each reconstructed tubule. Luminal movements in the seminiferous tubules were observed by in vivo imaging using a fluorescent-reporter mouse and two-photon excitation microscopy system. Spermatozoa without contact to the seminiferous epithelium were not accumulated toward the rete testis. Additionally, such spermatozoa were found on their way not only to the most proximal rete testis but also a more distant rete testis from any stage VIII seminiferous epithelia. In vivo imaging demonstrated that the direction of the flagella of spermatozoa attached to the seminiferous epithelium was repeatedly reversed. The epithelium at the inner curve of the seminiferous tubule was shaken more actively and had fewer spermatozoa attached compared with the epithelium at the outer curve. Our results hence suggest that the luminal flow in the seminiferous tubules is repeatedly reversed and that this physical force helps spermatozoa to be released from Sertoli cells. In brief: Spermatozoa are released from Sertoli cells and flow in the seminiferous tubule to the rete testis. Our results suggest that the luminal flow in the tubules is repeatedly reversed and that this physical force helps spermatozoa release from the Sertoli cells.

The PI3K/AKT signaling pathway: How does it regulate development of Sertoli cells and spermatogenic cells?

The PI3K/AKT signaling pathway is one of the most crucial regulatory mechanisms in animal cells, which can mainly regulate proliferation, survival and anti-apoptosis in cell lines. In the seminiferous epithelium, most studies were concentrated on the role of PI3K/AKT signaling in immature Sertoli cells (SCs) and spermatogonia stem cells (SSCs). PI3K/AKT signaling can facilitate the proliferation and anti-apoptosis of immature Sertoli cells and spermatogenic cells. Besides, in mature Sertoli cells, this pathway can disintegrate the structure of the blood-testis barrier (BTB) via regulatory protein synthesis and the cytoskeleton of Sertoli cells. All of these effects can directly and indirectly maintain and promote spermatogenesis in male testis.

Follicle-stimulating hormone regulates Notch signalling in the seminiferous epithelium of continuously and seasonally breeding rodents.

CONTEXT: Juxtacrine (contact-dependent) communication between the cells of seminiferous epithelium mediated by Notch signalling is of importance for the proper course of spermatogenesis in mammals. AIMS: The present study was designed to evaluate the role of follicle-stimulating hormone (FSH) in the regulation of Notch signalling in rodent seminiferous epithelium. METHODS: We explored the effects (1) of pharmacological inhibition of the hypothalamus-pituitary-gonadal (HPG) axis and FSH replacement in pubertal rats, and (2) of photoinhibition of HPG axis followed by FSH substitution in seasonally breeding rodents, bank voles, on Notch pathway activity. Experiments on isolated rat Sertoli cells exposed to FSH were also performed. Gene and protein expressions of Notch pathway components were analysed using RT-qPCR, western blot and immunohistochemistry/immunofluorescence. KEY RESULTS: Distribution patterns of Notch pathway proteins in bank vole and rat seminiferous epithelium were comparable; however, levels of activated Notch1 and Notch3, hairy/enhancer of split 1 (HES1) and hairy/enhancer of split-related with YRPW motif 1 (HEY1) in bank voles were dependent on the length of the photoperiod. In response to FSH similar changes in these proteins were found in both species, indicating that FSH is a negative regulator of Notch pathway activity in seminiferous epithelium. CONCLUSIONS: Our results support a common mechanism of FSH action on Notch pathway during onset and recrudescence of spermatogenesis in rodents. IMPLICATIONS: Interaction between FSH signalling and Notch pathway in Sertoli cells may be involved in spermatogenic activity changes of the testes occurring during puberty or photoperiod shift in continuously and seasonally breeding rodents, respectively.

Adenylyl cyclase 3 deficiency results in dysfunction of blood-testis barrier during mouse spermiogenesis.

Human infertility has become a global medical and social health problem. Mice deficient in type 3 adenylyl cyclase (AC3), a key enzyme that synthesizes cyclic adenosine monophosphate (cAMP), develop male infertility, although the underlying molecular mechanisms remain unknown. We performed a label-free quantitative (LFQ) proteomics analyses to identify testicular differentially expressed proteins (DEPs) and their respective biological processes. Furthermore, histological examination demonstrated that AC3 deficiency in mice led to mild impairment of spermatogenesis, including the thinning of seminiferous epithelium and local lesions in the testis. We further identified that the integrity of the blood-testis barrier (BTB) was impaired in AC3 knockout (AC3-/-) mice accompanied with the reduction in the expression of tight junctions (TJs) and ectoplasmic specialization (ESs)-related proteins. In addition, the deletion of AC3 in mice also reduced the germ cell proliferation, increased apoptosis, and decreased lipid deposition in the seminiferous tubules. Collectively, our results revealed a role of AC3 in regulating the BTB integrity during spermatogenesis. Thus, our findings provide new perspectives for future research in male infertility.

Spermatogenesis in a vulnerable South American cervid, dwarf red brocket (Mazama rufina).

The brocket deer (Genus Mazama) is a highly diverse cervid group distributed from Mexico to Argentina, with a downward population trend. However, literature on the basic reproductive biology of the genus is scarce. This work aimed to study biometric, histological and stereological aspects of the testes of Dwarf Red Brocket (Mazama rufina). Testes from free-ranging adult brockets (n = 3) were retrieved from necropsies. Testes were histologically processed. From histological images, several stereological parameters were estimated, and seminiferous epithelium cycle morphology was described. Testes volumes were between 8.2 and 18.4 ml and weights from 8.3 to 19.4 g. Gonadosomatic index (% paired-testes weight to body weight) went from 0.17 to 0.64. The tubular cross-sectional diameter was 179.8 ± 2.8 µm. Estimated volume densities for parenchyma and interstitium were 78.8% and 21.2% respectively. There were (in millions/ml) 96.0 ± 13.1 germ cells and 37.7 ± 6.0 somatic cells. Specific cell densities were (all expressed in millions/ml) as follows: spermatogonia 13.1 ± 4.2; primary spermatocytes 43.1 ± 5.0; round spermatids 36.8 ± 8.0 (lower density near the caudal pole, p < 0.01); sustentacular (Sertoli) cells 16.8 ± 4.1 and interstitial endocrine (Leydig) cells 17.4 ± 3.4. Sertoli cell index (germ cells per Sertoli cell) was 6.72. Eight stages of the cycle were described, and frequencies estimated, resembling those of goats. M. rufina adult testis anatomy is similar to that of other cervids and domestic ruminants, with an apparently lower spermatogenic efficiency. This work is a first approximation to the physiology of the testis of M. rufina. Basic knowledge of the reproductive physiology of vulnerable species may allow biotechnological approaches for the restitution of animal populations.

Busulfan impairs blood-testis barrier and spermatogenesis by increasing noncollagenous 1 domain peptide via matrix metalloproteinase 9.

BACKGROUNDS: Sterility induced by anti-cancer treatments has caused significant concern, yet the mechanism and treatment exploration are little for male infertility after cancer therapy. Busulfan, the antineoplastic that was widely applied before bone marrow transplantation, was known to induce male reproductive disorder. OBJECTIVES: To investigate the effect of busulfan on blood-testis barrier function in adult rats and determine whether noncollagenous 1 domain peptide, the biologically active fragment proteolyzed from the collagen α3 chain (IV) by matrix metalloproteinase 9, was involved during this process. MATERIALS AND METHODS: Adult male rats were treated with one-dose or double-dose of busulfan (10 mg/kg) before euthanized at day 35. Blood-testis barrier integrity assay, HE staining, immunofluorescence, and Western blot were used to validate the effect of busulfan on blood-testis barrier permeability and spermatogenesis. JNJ0966 was applied to specifically inhibit the matrix metalloproteinase 9 activity. The polymerization activity of F-actin/G-actin and microtubule/tubulin in the testis were assessed by using commercial kits. RESULTS: A noteworthy blood-testis barrier injury and significant up-regulation of matrix metalloproteinase 9 activity and noncollagenous 1 level after a single-dose busulfan (10 mg/kg) treatment in adult rat testis were revealed. The application of JNJ0966 was found to decrease noncollagenous 1 level and rescue the busulfan-induced blood-testis barrier injury including the mis-localization of junction proteins across the seminiferous epithelium, by recovering the organization and polymerization of both F-actin and microtubule. The busulfan-induced spermatogenesis impairment was also improved by JNJ0966. CONCLUSION: These findings thus demonstrate that the elevation in matrix metalloproteinase 9 and noncollagenous 1 might participate in busulfan-induced blood-testis barrier disruption in adult male rats. As such, busulfan-induced male infertility could possibly be managed through interventions on noncollagenous 1 production.

Three-dimensional morphological analysis of spermatogenesis in aged mouse testes.

Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age. To investigate changes in spermatogenesis with aging, we reconstructed the seminiferous tubules of 12 mice aged 12 to 30 months from serial sections and examined age-related and region-specific alterations in the seminiferous epithelium and spermatogenic waves in three dimensions. The basic structure of the seminiferous tubules, including the numbers of tubules, terminating points, branching points, and total tubule length, did not change with age. Age-related alterations in spermatogenesis, primarily assessed by the formation of vacuoles in Sertoli cells, were detected in the seminiferous tubules at 12 months. The proportion of altered tubule segments with impaired spermatogenesis further increased by 24 months, but remained unchanged thereafter. Altered tubule segments were preferentially distributed in tubule areas close to the rete testis and those in the center of the testis. Spermatogenic waves became shorter in length with age. These results provide a basis for examining the decline of spermatogenesis not only with aging, but also in male infertility.

Loss of TDP-43 in male germ cells causes meiotic failure and impairs fertility in mice.

Meiotic arrest is a common cause of human male infertility, but the causes of this arrest are poorly understood. Transactive response DNA-binding protein of 43 kDa (TDP-43) is highly expressed in spermatocytes in the preleptotene and pachytene stages of meiosis. TDP-43 is linked to several human neurodegenerative disorders wherein its nuclear clearance accompanied by cytoplasmic aggregates underlies neurodegeneration. Exploring the functional requirement for TDP-43 for spermatogenesis for the first time, we show here that conditional KO (cKO) of the Tardbp gene (encoding TDP-43) in male germ cells of mice leads to reduced testis size, depletion of germ cells, vacuole formation within the seminiferous epithelium, and reduced sperm production. Fertility trials also indicated severe subfertility. Spermatocytes of cKO mice showed failure to complete prophase I of meiosis with arrest at the midpachytene stage. Staining of synaptonemal complex protein 3 and γH2AX, markers of the meiotic synaptonemal complex and DNA damage, respectively, and super illumination microscopy revealed nonhomologous pairing and synapsis defects. Quantitative RT-PCR showed reduction in the expression of genes critical for prophase I of meiosis, including Spo11 (initiator of meiotic double-stranded breaks), Rec8 (meiotic recombination protein), and Rad21L (RAD21-like, cohesin complex component), as well as those involved in the retinoic acid pathway critical for entry into meiosis. RNA-Seq showed 1036 upregulated and 1638 downregulated genes (false discovery rate <0.05) in the Tardbp cKO testis, impacting meiosis pathways. Our work reveals a crucial role for TDP-43 in male meiosis and suggests that some forms of meiotic arrest seen in infertile men may result from the loss of function of TDP-43.

Influence of hormonal imbalance on the integrity of seminiferous epithelium in the testes of adult rats chronically exposed to letrozole and rats exposed to soya isoflavones during the prenatal period, lactation, and up to sexual maturity.

The structural integrity of the germ cells in the seminiferous epithelium and the correct process of spermatogenesis are made possible by proteins that participate in the formation of different types of junctions. This study was performed on samples of the testes of 4 groups (2 experimental and 2 corresponding control) of male Wistar rats. In the first experimental group, the adult rats received letrozole - a nonsteroidal inhibitor of cytochrome P450 aromatase (P450arom). The second experimental group was exposed to soya isoflavones during the prenatal period, lactation, and up to sexual maturity. The aim of this study was to examine the immunoexpression of ß-catenin, N-cadherin, occludin, connexin43, annexin V, and advanced glycation end products (AGE) in the seminiferous epithelium of rat testes with chronic estrogen deficiency and of rats exposed to soya isoflavones. Series of sections of the testes were stained using PAS and silver impregnation. Moreover, immunohistochemistry tests were performed. A semi-quantitative determination of protein immunoexpression was performed using Image J. The number of annexin V positive Sertoli cells per tubule were counted manually. Comparisons between the experimental and corresponding control groups were performed using a non-parametric Mann-Whitney U test. The most common alterations were prematurely sloughed germ cells in the lumen of the seminiferous tubules and invaginations of the seminiferous tubules. We observed a lower number of annexin V positive Sertoli cells and a lower expression of N-cadherin and occludin in the seminiferous epithelium of both groups of rats with hormonal imbalances. Moreover, a higher expression of AGE, a lower expression of connexin 43 and a lower amount of reticular fibers in the basal lamina of seminiferous tubules was present in rats treated with letrozole and a higher expression of ß-catenin was found in rats exposed to soya isoflavones. The hormonal imbalance between androgens and estrogens resulted in a decreased number of annexin V positive Sertoli cells. This may be associated with a failed clearance of apoptotic germ cells that leads to disturbances in the blood-testis-barrier (BTB) by affecting the expression of junctional proteins in the seminiferous epithelium. Moreover, a decreased level of estrogens was also associated with an increased expression of AGEs and with a changed composition of basal lamina in the seminiferous tubules of rats. These changes could lead to germ cell sloughing and invaginations of the seminiferous tubules.

Wnt5a Regulates Junctional Function of Sertoli cells Through PCP-mediated Effects on mTORC1 and mTORC2.

The blood-testis barrier (BTB) and apical ectoplasmic specialization (ES), which are synchronized through the crosstalk of Sertoli cells and Sertoli germ cells, are required for spermatogenesis and sperm release. Here, we show that Wnt5a, a noncanonical Wnt signaling pathway ligand, is predominately expressed in both the BTB and apical ES and has a specific expression pattern during the seminiferous epithelium cycle. We employed siRNA to knockdown Wnt5a expression in testis and Sertoli cells, and then identified elongated spermatids that lost their polarity and were embedded in the seminiferous epithelium. Moreover, phagosomes were found near the tubule lumen. These defects were due to BTB and apical ES disruption. We also verified that the expression level and/or location of BTB-associated proteins, actin binding proteins (ABPs), and F-actin was changed after Wnt5a knockdown in vivo and in vitro. Additionally, we demonstrated that Wnt5a regulated actin dynamics through Ror2-mediated mTORC1 and mTORC2. This study clarified the molecular mechanism of Wnt5a in Sertoli cell junctions through the planar cell polarity (PCP) signaling pathway. Our findings could provide an experimental basis for the clinical diagnosis and treatment of male infertility caused by Sertoli cell junction impairment.

The Seminiferous Epithelial Cycle of Spermatogenesis: Role of Non-receptor Tyrosine Kinases.

Non-receptor tyrosine kinases (NRTKs) are implicated in various biological processes including cell proliferation, differentiation, survival, and apoptosis, as well as cell adhesion and movement. NRTKs are expressed in all mammals and in different cell types, with extraordinarily high expression in the testis. Their association with the plasma membrane and dynamic subcellular localization are crucial parameters in their activation and function. Many NRTKs are found in endosomal protein trafficking pathways, which suggests a novel mechanism to regulate the timely junction restructuring in the mammalian testis to facilitate spermiation and germ cell transport across the seminiferous epithelium.