Developmental and hormonal regulation of the expression of oligodendrocyte-specific protein/claudin 11 in mouse testis

Identification of a valuable gene network for the diagnosis and treatment of non-obstructive azoospermia: in-silico analyses - experimental research

Introduction

Non-obstructive azoospermia (NOA) is an etiology of infertility in men. NOA may have various classifications; however, hypogonadotropic hypogonadism can be regarded as a class of NOA associated with genetic factors. Former studies have shown that noncoding RNA (ncRNA) plays an essential role in NOA incidence, but few studies have been performed on the NOA-related ncRNA interaction network. In the current study, genes, NOA-related microRNA (miRNA), and circular RNA (circRNA) were found by bioinformatics methods to offer a new perspective on NOA treatment.

Methods

The gonadotropin-releasing hormone receptor (GnRHR)-related protein-protein interaction (PPI) network was extracted by searching in 'string-database'. GO, KEGG, and Enrichr databases were used to identify pathways, molecular function, and biological processing. Four databases, including TargetScan, mirDIP, miRmap, and miRWalk, were used to extract miRNAs. At last, the circ2GO, circBase, and literature were used to identify circRNAs and their genes.

Results

The current study identified the four proteins associated with the GnRHR signaling; eight shared miRNAs that affect the expression of found proteins and 25 circRNAs and their origin genes that regulate the miRNAs' function.

Conclusion

The two miRNAs, hsa-miR-134-3p and hsa-miR-513C-3p, the three genes, VCAN, NFATC3, and PRDM5, and their associated circRNAs can perform as a valuable gene network in the diagnosis and treatment of NOA pathogenesis.

What do we know about blood-testis barrier? current understanding of its structure and physiology

Blood-testis barrier (BTB) creates a particular compartment in the seminiferous epithelium. Contacting Sertoli cell-Sertoli cell plasma membranes possess specialized junction proteins which present a complex dynamic of formation and dismantling. Thus, these specialized structures facilitate germ cell movement across the BTB. Junctions are constantly rearranged during spermatogenesis while the BTB preserves its barrier function. Imaging methods are essential to studying the dynamic of this sophisticated structure in order to understand its functional morphology. Isolated Sertoli cell cultures cannot represent the multiple interactions of the seminiferous epithelium and in situ studies became a fundamental approach to analyze BTB dynamics. In this review, we discuss the contributions of high-resolution microscopy studies to enlarge the body of morphofunctional data to understand the biology of the BTB as a dynamic structure. The first morphological evidence of the BTB was based on a fine structure of the junctions, which was resolved with Transmission Electron Microscopy. The use of conventional Fluorescent Light Microscopy to examine labelled molecules emerged as a fundamental technique for elucidating the precise protein localization at the BTB. Then laser-scanning confocal microscopy allowed the study of three-dimensional structures and complexes at the seminiferous epithelium. Several junction proteins, like the transmembrane, scaffold and signaling proteins, were identified in the testis using traditional animal models. BTB morphology was analyzed in different physiological conditions as the spermatocyte movement during meiosis, testis development, and seasonal spermatogenesis, but also structural elements, proteins, and BTB permeability were studied. Under pathological, pharmacological, or pollutant/toxic conditions, there are significant studies that provide high-resolution images which help to understand the dynamic of the BTB. Notwithstanding the advances, further research using new technologies is required to gain information on the BTB. Super-resolution light microscopy is needed to provide new research with high-quality images of targeted molecules at a nanometer-scale resolution. Finally, we highlight research areas that warrant future studies, pinpointing new microscopy approaches and helping to improve our ability to understand this barrier complexity.

Role of p38 MAPK Signalling in Testis Development and Male Fertility

The testis is an important male reproductive organ, which ensures reproductive function via the secretion of testosterone and the generation of spermatozoa. Testis development begins in the embryonic period, continues after birth, and generally reaches functional maturation at puberty. The stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), regulates multiple cell processes including proliferation, differentiation, apoptosis, and cellular stress responses. p38 MAPK signalling plays a crucial role in testis development by regulating spermatogenesis, the fate determination of pre-Sertoli, and primordial germ cells during embryogenesis, the proliferation of testicular cells in the postnatal period, and the functions of mature Sertoli and Leydig cells. In addition, p38 MAPK signalling is involved in decreased male fertility when exposed to various harmful stimuli. This review will describe in detail the biological functions of p38 MAPK signalling in testis development and male reproduction, together with its pathological role in male infertility.

Transcriptomic Analysis of Testicular Gene Expression in a Dog Model of Experimentally Induced Cryptorchidism

Cryptorchidism, a condition in which testes fail to descend from the abdomen into the scrotum, is a risk factor for infertility and germ cell cancer. Normally, tight junctions between adjacent Sertoli cells in the testes form a blood–testes barrier that regulates spermatogenesis; however, the effect of cryptorchidism on tight junctions is not well-understood. We established a model of heat-induced testicular damage in dogs using surgical cryptorchidism. We sequenced RNA to investigate whether certain transcripts are expressed at higher rates in heat-damaged versus normally descended testes. Claudins, cell adhesion molecules, were relatively highly expressed in cryptorchid testes: claudins 2, 3, 5, 11, and 18 were significantly increased in cryptorchid testes and reduced by orchiopexy. SOX9-positive Sertoli cells were present in the seminiferous tubules in both cryptorchid and control testes. Using real-time PCR and Western blot analysis to compare Sertoli cells cultured at 34 °C and 37 °C, we found that Sertoli cell claudins 2, 3, 5, 11, and 18 were significantly increased at 37 °C; however, accumulation was higher in the G0/G1 phase in Sertoli cells cultured at 34 °C. These results indicate that testicular hyperthermia caused by cryptorchidism affects claudin expression, regulated germ cell death, and the proliferation of Sertoli cells.

Inflammation of Gill Epithelia in Fish Causes Increased Permeation of Petrogenic Polar Organic Chemicals via Disruption of Tight Junctions

The epithelial cell layer that lines the gills of fish controls paracellular permeation of chemicals through tight junctions. The integrity of tight junctions can be affected by inflammation, which likely affects the bioavailability of chemicals. Here, the inflammation of the rainbow trout gill cell line RTgill-W1 was induced via exposure to bacterial lipopolysaccharides (LPS). Cells were then coexposed to extracts of oil sands process-affected water (OSPW), which contain complex mixtures of chemicals. After 24 h of exposure, cells exposed to LPS showed a reduction in transepithelial electrical resistance, an indicator of tight junction integrity. Quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis determined that abundances of transcripts of genes coding for tight junction proteins were significantly less in cells exposed to 20, 50, or 100 mg L^-1 LPS. Chemical analysis revealed increased permeation of constituents of OSPW across epithelia at all studied LPS concentrations. These in vitro findings were confirmed in vivo in rainbow trout exposed to LPS and OSPW for 48 h, which resulted in greater accumulation of chemicals relative to that for fish exposed to OSPW alone. Our results demonstrated that inflammation and disruption of tight junctions could lead to greater uptake of potentially harmful chemicals from the environment, which has implications for mixture risk assessment.

COVID-19 disrupts the blood-testis barrier through the induction of inflammatory cytokines and disruption of junctional proteins

OBJECTIVE

Junctional proteins are the most important component of the blood-testis barrier and maintaining the integrity of this barrier is essential for spermatogenesis and male fertility. The present study elucidated the effect of SARS-CoV-2 infection on the blood-testis barrier (BTB) in patients who died from severe acute respiratory syndrome coronavirus 2 (COVID-19) complications.

METHODS

In this study, lung and testis tissue was collected from autopsies of COVID-19 positive (n = 10) and negative men (n = 10) and was taken for stereology, immunocytochemistry, and RNA extraction.

RESULTS

Evaluation of the lung tissue showed that the SARS-CoV-2 infection caused extensive damage to the lung tissue and also increases inflammation in testicular tissue and destruction of the testicular blood barrier. Autopsied testicular specimens of COVID-19 showed that COVID-19 infection significantly changes the spatial arrangement of testicular cells and notably decreased the number of Sertoli cells. Moreover, the immunohistochemistry results showed a significant reduction in the protein expression of occluding, claudin-11, and connexin-43 in the COVID-19 group. In addition, we also observed a remarkable enhancement in protein expression of CD68 in the testes of the COVID-19 group in comparison with the control group. Furthermore, the result showed that the expression of TNF-α, IL1β, and IL6 was significantly increased in COVID-19 cases as well as the expression of occludin, claudin-11, and connexin-43 was decreased in COVID-19 cases.

CONCLUSIONS

Overall, the present study demonstrated that SARS-CoV-2 could induce the up-regulation of the pro-inflammatory cytokine and down-regulation of junctional proteins of the BTB, which can disrupt BTB and ultimately impair spermatogenesis.

Murine Esophagus Expresses Glial-Derived Central Nervous System Antigens

Multiple sclerosis (MS) has been considered to specifically affect the central nervous system (CNS) for a long time. As autonomic dysfunction including dysphagia can occur as accompanying phenomena in patients, the enteric nervous system has been attracting increasing attention over the past years. The aim of this study was to identify glial and myelin markers as potential target structures for autoimmune processes in the esophagus. RT-PCR analysis revealed glial fibrillary acidic protein (GFAP), proteolipid protein (PLP), and myelin basic protein (MBP) expression, but an absence of myelin oligodendrocyte glycoprotein (MOG) in the murine esophagus. Selected immunohistochemistry for GFAP, PLP, and MBP including transgenic mice with cell-type specific expression of PLP and GFAP supported these results by detection of (1) GFAP, PLP, and MBP in Schwann cells in skeletal muscle and esophagus; (2) GFAP, PLP, but no MBP in perisynaptic Schwann cells of skeletal and esophageal motor endplates; (3) GFAP and PLP, but no MBP in glial cells surrounding esophageal myenteric neurons; and (4) PLP, but no GFAP and MBP in enteric glial cells forming a network in the esophagus. Our results pave the way for further investigations regarding the involvement of esophageal glial cells in the pathogenesis of dysphagia in MS.

Nutrient restriction synergizes with retinoic acid to induce mammalian meiotic initiation in vitro

The molecular machinery and chromosome structures carrying out meiosis are frequently conserved from yeast to mammals. However, signals initiating meiosis appear divergent: while nutrient restriction induces meiosis in the yeast system, retinoic acid (RA) and its target Stra8 have been shown to be necessary but not sufficient to induce meiotic initiation in mammalian germ cells. Here, we use primary culture of mouse undifferentiated spermatogonia without the support of gonadal somatic cells to show that nutrient restriction in combination with RA is sufficient to induce Stra8- and Spo11-dependent meiotic gene and chromosome programs that recapitulate the transcriptomic and cytologic features of in vivo meiosis. We demonstrate that neither nutrient restriction nor RA alone exerts these effects. Moreover, we identify a distinctive network of 11 nutrient restriction-upregulated transcription factor genes, which are associated with early meiosis in vivo and whose expression does not require RA. Our study proposes a conserved model, in which nutrient restriction induces meiotic initiation by upregulating key transcription factor genes for the meiotic gene program and provides an in vitro platform for meiotic induction that could facilitate research and haploid gamete production.

Establishment and functional characterization of a murine primary Sertoli cell line deficient of connexin43

The Sertoli cell (SC) specific connexin43 (Cx43) knockout (SCCx43KO) mouse line is ideal to gain insight into the mechanistic gap junction formation in SC and the seminiferous epithelium. A method for developing primary SC cultures from these mice was established, validated and successfully characterized via polymerase chain reaction, immunohistochemistry, immunofluorescence (IF), and Western blots (WB). It was evident that both knockout (KO) and wild-type (WT) primary cell cultures were similar in morphology. These highly pure SC cultures were subjected to cell proliferation assays indicating no notable proliferation in cultures of both genotypes. Measurements of cell monolayer integrity indicated significant increases in transepithelial electrical resistance and consequently in tight junction expression of the KO cultures. Using semi-quantitative WB and IF, tight junction protein claudin-11 was analyzed. These results support a role for Cx43 in regulating blood-testis barrier (BTB) function, composition, and dynamics in vitro. Thus, the SC deficient Cx43 cell cultures may provide a valuable in vitro tool for a better understanding of the mechanistic role of Cx43 in spermatogenesis and BTB assembly.

Expression of claudin-11 in canine prepubertal testes, and in canine adult testes showing normal spermatogenesis, impaired spermatogenesis, or testicular neoplasia

The blood-testis barrier (BTB) consists of different cell-to-cell connections, including tight junction proteins like claudin-11 (CLDN11). For dogs, only limited data is published dealing with these proteins in general. Therefore, their physiological relevance, their postnatal expression, and their distribution pattern in pathological conditions, e.g. in altered spermatogenesis and testicular neoplasia were assessed. Canine testes from routine castrations, and those sent in for diagnostic purposes were investigated. Based on morphological evaluation, the dogs and testes were divided into groups: (1) dogs with normal spermatogenesis, (2) four months old prepubertal dogs, (3) intratubular seminoma, (4) diffuse seminoma, (5) Sertoli cell tumours (SCT), (6) Leydig cell tumours (LCT), and (7) dogs with impaired spermatogenesis (e.g. mixed atrophy). In order to examine possible alterations of the BTB components, immunohistochemistry (IHC) and immunofluorescence using a commercial antibody against CLDN11 was performed. Sertoli cell (SC) nuclei (SOX9) and peritubular myoid cells (smooth-muscle-actin, SMA) were also assessed using IHC. Additionally, semi-quantitative Western-blot (WB) and RT-PCR analyses of CLDN11 were conducted. In tubules with normal spermatogenesis, IHC of CLDN11 revealed a basolateral staining at BTB localisation. In prepubertal cords, CLDN11 was diffusely expressed along the cytoplasmic extensions of SCs supposing that the BTB was neither built up nor functional, yet. A shift from weakly expressed CLDN11 between/in residual SCs in intratubular seminoma to only small CLDN11 immunopositive stained spots in the cytoplasm of remaining SOX9-positive SCs in diffuse seminoma was detectable. Reduction or even loss of CLDN11 expression in diffuse seminoma was confirmed using RT-PCR and WB analyses, thus indicating that in seminoma, CLDN11 was downregulated at transcriptional level and completely lost its sealing function. Basal SCs in SCT still showed a CLDN11/SOX9 co-localisation, suggesting that luminal neoplastic SCs undergo de-differentiation during tumour progression. In LCT, no CLDN11 was detectable. Dogs with mixed atrophy showed an upregulation of CLDN11 in tubules with spermatogenic arrest on mRNA and protein level, leading to the conclusion that within these tubules regulatory mechanisms lost their equilibrium. For the first time, the spatial expression of CLDN11 in prepubertal canine testis, impaired spermatogenesis, intratubular seminoma and its absence in diffuse seminoma and LCT was shown. Since altered CLDN11 levels could be part of adaptive mechanisms to modify BTB integrity, further functional investigations to characterize the canine BTB need to be conducted.

The Impact of Zinc Oxide Nanoparticles on Male (In)Fertility

Zinc oxide nanoparticles (ZnO NPs) are among nanoscale materials, attracting increasing attention owing to their exceptional set of characteristics, which makes these engineered nanoparticles a great option for improving the quality and effectiveness of diagnosis and treatment. The capacity of ZnO NPs to induce reactive oxygen species (ROS) production, DNA damage, and apoptosis represents a promise for their use in both cancer therapy and microbial treatment. However, their intrinsic toxicity together with their easy entrance and accumulation in organism have raised some concerns regarding the biomedical use of these NPs. Several studies have reported that ZnO NPs might induce cytotoxic effects on the male reproductive system, compromising male fertility. Despite some advances in this area, the knowledge of the effects of ZnO NPs on male fertility is still scarce. Overall, a brief outline of the major ZnO NPs biomedical applications and promises in terms of diagnostic and therapeutic use will also be explored. Further, this review intends to discuss the effect of ZnO NPs exposure on the male reproductive system and speculate their effects on male (in)fertility.

Importance of the Androgen Receptor Signaling in Gene Transactivation and Transrepression for Pubertal Maturation of the Testis

Androgens are key for pubertal development of the mammalian testis, a phenomenon that is tightly linked to Sertoli cell maturation. In this review, we discuss how androgen signaling affects Sertoli cell function and morphology by concomitantly inhibiting some processes and promoting others that contribute jointly to the completion of spermatogenesis. We focus on the molecular mechanisms that underlie anti-Müllerian hormone (AMH) inhibition by androgens at puberty, as well as on the role androgens have on Sertoli cell tight junction formation and maintenance and, consequently, on its effect on proper germ cell differentiation and meiotic onset during spermatogenesis.

Expression of claudin‑11 in a rat model of varicocele and its effects on the blood‑testis barrier

Varicocele (VC) is an abnormal tortuosity and venous distension of the pampiniform plexus in the spermatic cord. VC is the most common surgically correctable cause of male infertility. The purpose of the present study was to investigate the effects of VC on the tight junctions and the blood‑testis barrier (BTB) of Sertoli cells in the bilateral testes of rats. A model of VC was established by left renal vein narrowing in Sprague‑Dawley rats; control rats underwent dissection of the vein without narrowing. The bilateral testes were harvested at 4, 6 and 8 weeks after the operation. The relative expression of claudin‑11 and transforming growth factor (TGF)‑β in the testis was determined by reverse transcription‑polymerase chain reaction analysis and immunohistochemistry (IHC). The expression level of claudin‑11 was prominently downregulated in the VC model group compared with the control group, while the level of TGF‑β in the testes was higher in the VC group. IHC examination demonstrated that VC led to destruction of the integrity of the BTB, and the degree of destruction increased with time. Furthermore, it was also observed that unilateral VC affected contralateral testicular function. In conclusion, the present study partially explained the molecular mechanisms underlying the pathogenesis of VC and provided grounds for further research into the treatment of male infertility.

A Human Gonadal Cell Model From Induced Pluripotent Stem Cells

Sertoli cells are main players in the male gonads development and their study may shed light on 46,XY disorders of sex development (DSD). Mature primary Sertoli cells are incapable of proliferating in prolonged in vitro cultures and the available Sertoli cell models have several limitations since they derive from mouse or human cancer tissues. We differentiated human fibroblasts (HFs)-derived induced pluripotent stem cells into Sertoli-like cells (SLC) and, in order to characterize this new Sertoli cell model, we performed gene expression analyses by NextGeneration Sequencing techniques. This approach revealed that our putative SLC have reduced expression of pluripotency markers and expressed Sertoli cell markers such as SRY-Related HMG-Box 9 (SOX9), vimentin (VIM), and claudin-11 (CLDN-11). More in detail, the transcriptional profile analysis suggested that these cells are in an early stage of Sertoli cells maturation. Harnessing the power of induced pluripotent stem cells, we were able to generate SLC that show genetic and functional similarities to human Sertoli cells (HSerCs). SLC could become an excellent source of patient-specific Sertoli cells that could be of paramount benefit for both basic research and personalized medicine in sex development and reproductive medicine.

Involvement of Claudin-11 in Disruption of Blood-Brain, -Spinal Cord, and -Arachnoid Barriers in Multiple Sclerosis

It is important to understand the molecular mechanisms of barrier disruption in the central nervous system (CNS) of patients with multiple sclerosis (MS). The purpose of the present study was to clarify whether claudin-11 is involved in the disruption of two endothelial barriers (blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB)) and two epithelial barriers (blood-arachnoid barrier (BAB) and blood-CSF barrier (BCSFB)) in the CNS in MS. Immunohistochemical analysis revealed that, in both normal human and mouse, claudin-11 is co-localized with claudin-5 in the brain and spinal cord capillaries. The absolute protein expression level of claudin-11 was nearly equal to that of claudin-5 in rat brain capillaries, but was 2.81-fold greater in human brain capillaries. The protein expressions of claudin-11 were significantly downregulated in the brain and spinal cord capillaries of an MS patient and experimental autoimmune encephalomyelitis (EAE) mice. Specific downregulation of claudin-11 with siRNA significantly increased the transfer of membrane-impermeable FITC-dextran across human brain capillary endothelial cell (hCMEC/D3) monolayer. As for the epithelial barrier, claudin-11 protein expression was not decreased in choroid plexus epithelial cells forming the BCSFB in EAE mice, whereas it was decreased in brain and spinal cord meninges that form the BAB. Specific downregulation of claudin-11 with siRNA in a rat choroid plexus epithelial cell (TR-CSFB) monolayer significantly increased the permeability of FITC-dextran. In conclusion, our present findings indicate that claudin-11 expression at the BBB, BSCB, and BAB, but not the BCSFB, is downregulated in multiple sclerosis, impairing the functional integrity of these barriers.

Fine particle matter disrupts the blood-testis barrier by activating TGF-β3/p38 MAPK pathway and decreasing testosterone secretion in rat

Fine particle matter (PM) is correlated with male reproductive dysfunction in animals and humans, but the underlying mechanisms remain unknown. To investigate the toxic mechanism of PM, 32 male Sprague-Dawley (SD) rats were exposed to saline or PM_2.5 with the doses of 1.8, 5.4, and 16.2 mg/kg.b.w. via intratracheal instillation, respectively, one time every 3 days, in total times for 30 days. Sperm concentration, hormone level, the expressions of BTB-associated protein and the mitogen-activated protein kinase (MAPK) pathway, tumor necrosis factor α and transforming growth factor β3 levels were detected. The results showed a decrease in sperm number, testosterone and luteinizing hormone levels and altered ultrastructure of BTB in testis of rat after exposure to PM_2.5 . The protein levels of N-Cadherin, Occludin, Claudin-11, and Connexin-43 were significantly decreased in the testes. TGF-β3 content in testes showed increase, with the p-p38/p38 MAPK ratio also increasing after PM_2.5 exposure. These results demonstrate that PM_2.5 restrained the expressions of BTB-associated proteins through activating TGF-β3/p38 MAPK pathway and decreasing testosterone secretion, and therefore lead to the damage of BTB resulting in the decrease of sperm quality, which might be the potential reasons for its negative effects on spermatogenesis and male reproduction.

The effects of flutamide on cell-cell junctions in the testis, epididymis, and prostate

In this review, we summarize recent findings on the effect of the anti-androgen flutamide on cell-cell junctions in the male reproductive system. We outline developmental aspects of flutamide action on the testis, epididymis, and prostate, and describe changes in junction protein expression and organization of junctional complexes in the adult boar following prenatal and postnatal exposure. We also discuss findings on the mechanisms by which flutamide induces alterations in cell-cell junctions in reproductive tissues of adult males, with special emphasis on cytoplasmic effects. Based on the results from in vivo and in vitro studies in the rat, we propose that flutamide affects the expression of junction proteins and junction complex structure not only by inhibiting androgen receptor activity, but equally important by modulating protein kinase-dependent signaling in testicular cells. Additionally, results from studies on prostate cancer cell lines point to a role for the cellular molecular outfit in response to flutamide.

Loss of connexin43 in murine Sertoli cells and its effect on blood-testis barrier formation and dynamics

Connexin43 (Cx43) is the predominant testicular gap junction protein and in cases of impaired spermatogenesis, Cx43 expression has been shown to be altered in several mammals. Amongst other functions, Cx43 is supposed to regulate junction formation of the blood-testis barrier (BTB). The aim of the present study was to investigate the expression pattern of different tight junction (TJ) proteins of the murine BTB using SC-specific Cx43 knockout mice (SCCx43KO). Adult homozygous male SCCx43KO mice (SCCx43KO-/-) predominantly show an arrest of spermatogenesis and SC-only tubules that might have been caused by an altered BTB assembly, composition or regulation. TJ molecules claudin-3, -5 and -11 were examined in adult wild type (WT) and SCCx43KO-/- mice using immunohistochemistry (IHC) and quantitative real-time PCR (qRT-PCR). In this context, investigation of single tubules with residual spermatogenesis in SCCx43KO-/- mice was particularly interesting to identify a potential Cx43-independent influence of germ cells (GC) on BTB composition and dynamics. In tubules without residual spermatogenesis, a diffuse cytoplasmic distribution pattern for claudin-11 protein could be demonstrated in mutant mice. Nevertheless, claudin-11 seems to form functional TJ. Claudin-3 and -5 could not be detected immunohistochemically in the seminiferous epithelium of those tubules. Correspondingly, claudin-3 and -5 mRNA expression was decreased, providing evidence of generally impaired BTB dynamics in adult KO mice. Observations of tubules with residual spermatogenesis suggested a Cx43-independent regulation of TJ proteins by GC populations. To determine initial BTB formation in peripubertal SCCx43KO-/- mice, immunohistochemical staining and qRT-PCR of claudin-11 were carried out in adolescent SCCx43KO-/- and WT mice. Additionally, BTB integrity was functionally analysed using a hypertonic glucose fixative. These analyses revealed that SCCx43KO-/- mice formed an intact BTB during puberty in the same time period as WT mice, which however seemed to be accelerated.

Establishment, maintenance and functional integrity of the blood-testis barrier in organotypic cultures of fresh and frozen/thawed prepubertal mouse testes

STUDY QUESTION

Can the spatio-temporal formation of an intact blood-testis barrier (BTB), which is essential for the progression of spermatogenesis, be reproduced in cultures of fresh or frozen/thawed prepubertal mouse testes?

SUMMARY ANSWER

Organotypic cultures allow the establishment and maintenance of major BTB components and the formation of a functional BTB in mouse testicular tissues.

WHAT IS KNOWN ALREADY

In vitro maturation of prepubertal testicular tissues is a promising approach to restore fertility in adult survivors of childhood cancer. Although gametes can be successfully obtained from prepubertal mouse testes in organotypic cultures, the spermatogenic yield remains low compared to in vivo controls.

STUDY DESIGN, SIZE, DURATION

Mouse testicular tissues were frozen using controlled slow freezing (CSF) or solid surface vitrification (SSV) procedures. A total of 158 testes (fresh n = 58, CSF n = 58 or SSV n = 42) from 6 to 7 days postpartum (dpp) mice were cultured at 34°C in basal medium (α-MEM, 10% KnockOut Serum Replacement, 5 μg/ml gentamicin) at a gas-liquid interphase (under 20% O2), with or without 10-6 M retinol, for 9, 16 and 30 days. In addition, 32 testes from 6-7, 15-16, 22-23 and 36-37 dpp mice were used as in vivo controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The mRNA levels of BTB genes (Claudin 3, Claudin 11, Zonula occludens 1 and Connexin-43), germ cell-specific genes (Sal-like protein 4, Kit oncogene, Stimulated by retinoic acid gene 8, Synaptonemal complex protein 3, Transition protein 1 and Protamine 2), markers of Sertoli cell immaturity/maturity (anti-Mullerian hormone, androgen receptor, cyclin-dependent kinase inhibitor 1b) and the androgen-regulated gene Reproductive homeobox 5 (Rhox5) were measured by quantitative RT-PCR (RT-qPCR). The localization of BTB proteins in seminiferous tubules was studied by immunohistochemistry and spermatogenic progression was evaluated histologically. The integrity of the BTB was assessed using a biotin tracer.

MAIN RESULTS AND THE ROLE OF CHANCE

Modest differences in Claudin 11 (Cldn11), Zonula occludens 1 (Zo-1), Connexin-43 (Cx43) transcript levels and in the localization of the corresponding proteins were found between in vitro cultures of fresh or frozen/thawed testes and in vivo controls (P < 0.05). However, a 32-77-fold decrease in Claudin 3 (Cldn3) mRNA levels and a lack of CLDN3 immunolabelling in 36-44% of seminiferous tubules were observed in 30-day organotypic cultures (P < 0.05). Although Sertoli cell maturation and the completion of a full spermatogenic cycle were achieved after 30 days of culture, meiotic and postmeiotic progression was altered in cultured testicular tissues (P < 0.05). Moreover, an increased BTB permeability and a decreased expression of Rhox5 were observed at the end of the culture period in comparison with in vivo controls (P < 0.05). Completion of spermatogenesis occurred in vitro in seminiferous tubules with an intact BTB, and in those expressing or lacking CLDN3.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

Further studies will be needed to determine whether the expression of other BTB components is altered and to decipher the reason for lower Cldn3 and Rhox5 mRNA levels in organotypic cultures.

WIDER IMPLICATIONS OF THE FINDINGS

This work contributes to a better understanding of the molecular mechanisms occurring in in vitro matured prepubertal testes. The organotypic culture system will have to be developed further and optimized for human tissue, before potential clinical applications can be envisaged.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by Rouen University Hospital, Ligue contre le Cancer (to L.D.), and co-supported by European Union and Région Normandie (to A.O.). Europe gets involved in Normandie with European Régional Development Fund (ERDF). The authors declare that they have no conflict of interest.

Functional changes in mRNA expression and alternative pre-mRNA splicing associated with the effects of nutrition on apoptosis and spermatogenesis in the adult testis

Background

The effects of nutrition on testis mass in the sexually mature male have long been known, however, the cellular and molecular processes of the testis response to nutrition was not fully understood.

Methods

We tested whether the defects in spermatogenesis and increases in germ cell apoptosis in the testis that are induced by under-nutrition are associated with changes in mRNA expression and pre-mRNA alternative splicing using groups of 8 male sheep fed for a 10% increase or 10% decrease in body mass over 65 days.

Results

We identified 2,243 mRNAs, including TP53 and Claudin 11, that were differentially expressed in testis from underfed and well-fed sheep (FDR < 0.1), and found that their expression changed in parallel with variations in germ cell numbers, testis size, and spermatogenesis. Furthermore, pairs of 269 mRNAs and 48 miRNAs were identified on the basis of target prediction. The regulatory effect of miRNAs on mRNA expression, in combination with functional analysis, suggests that these miRNAs are involved in abnormal reproductive morphology, apoptosis and male infertility. Nutrition did not affect the total number of alternative splicing events, but affected 206 alternative splicing events. A total of 159 genes, including CREM, SPATA6, and DDX4, were differentially spliced between dietary treatments, with functions related to RNA splicing and spermatogenesis. In addition, three gene modules were positively correlated with spermatogenesis-related phenotypic traits and negatively related to apoptosis-related phenotypic traits. Among these gene modules, seven (CFLAR, PTPRC, F2R, MAP3K1, EPHA7, APP, BCAP31) were also differentially expressed between nutritional treatments, indicating their potential as markers of spermatogenesis or apoptosis.

Conclusions

Our findings on significant changes in mRNAs and pre-mRNA alternative splicing under-nutrition suggest that they may partly explain the disruption of spermatogenesis and the increase germ cell apoptosis. However, more research is required to verify their causal effects in regulating spermatogenesis and germ cell apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3385-8) contains supplementary material, which is available to authorized users.

Effects of Morinda officinalis Polysaccharide on Experimental Varicocele Rats

Morinda officinalis is a traditional Chinese herbal medicine, which has been used to tonify the kidney and strengthen yang for a long time in China. In this study, the effects of M. officinalis Polysaccharide (MOP) on experimental varicocele adolescent rats were investigated. The result showed that varicocele destroyed the structure of the seminiferous epithelium and decreased the TJ protein expression (Occludin, Claudin-11, and ZO-1), testosterone (T) concentration in the left testicular tissue and serum, and serum levels of inhibin B (INHB), while increasing the levels of cytokines (TGF-β3 and TNF-α) in the left testicular tissue, as well as serum levels of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and antisperm antibody (AsAb). MOP repaired the damaged seminiferous epithelium and TJ and reduced the levels of cytokines (TGF-β3 and TNF-α) as well as serum levels of GnRH, FSH, LH, and AsAb, while upregulating TJ protein expression, T level in the left testicular tissue and serum, and serum INHB levels. In summary, we conclude that MOP promotes spermatogenesis and counteracts the varicocele-induced damage to the seminiferous epithelium and TJ, probably via decreasing cytokines (TGF-β3 and TNF-α) levels and regulating the abnormal sex hormones levels in experimental varicocele rats.

Regulation of the blood-testis barrier

The purpose of this review is to describe the endocrine and local testicular factors that contribute to the regulation of the blood-testis barrier (BTB), using information gained from in vivo and in vitro models of BTB formation during/after puberty, and from the maintenance of BTB function during adulthood. In vivo the BTB, in part comprised of tight junctions between adjacent somatic Sertoli cells, compartmentalizes meiotic spermatocytes and post-meiotic spermatids away from the vasculature, and therefore prevents autoantibody production by the immune system against these immunogenic germ cells. This adluminal compartment also features a unique biochemical milieu required for the completion of germ cell development. During the normal process of spermatogenesis, earlier germ cells continually cross into the adluminal compartment, but the regulatory mechanisms and changes in junctional proteins that allow this translocation step without causing a 'leak' remain poorly understood. Recent data describing the roles of FSH and androgen on the regulation of Sertoli cell tight junctions and tight junction proteins will be discussed, followed by an examination of the role of paracrine factors, including members of the TGFβ superfamily (TGFβ3, activin A) and retinoid signalling, as potential mediators of junction assembly and disassembly during the translocation process.

The Mammalian Blood-Testis Barrier: Its Biology and Regulation

Spermatogenesis is the cellular process by which spermatogonia develop into mature spermatids within seminiferous tubules, the functional unit of the mammalian testis, under the structural and nutritional support of Sertoli cells and the precise regulation of endocrine factors. As germ cells develop, they traverse the seminiferous epithelium, a process that involves restructuring of Sertoli-germ cell junctions, as well as Sertoli-Sertoli cell junctions at the blood-testis barrier. The blood-testis barrier, one of the tightest tissue barriers in the mammalian body, divides the seminiferous epithelium into 2 compartments, basal and adluminal. The blood-testis barrier is different from most other tissue barriers in that it is not only comprised of tight junctions. Instead, tight junctions coexist and cofunction with ectoplasmic specializations, desmosomes, and gap junctions to create a unique microenvironment for the completion of meiosis and the subsequent development of spermatids into spermatozoa via spermiogenesis. Studies from the past decade or so have identified the key structural, scaffolding, and signaling proteins of the blood-testis barrier. More recent studies have defined the regulatory mechanisms that underlie blood-testis barrier function. We review here the biology and regulation of the mammalian blood-testis barrier and highlight research areas that should be expanded in future studies.

Blood-testis barrier and spermatogenesis: lessons from genetically-modified mice

The blood-testis barrier (BTB) is found between adjacent Sertoli cells in the testis where it creates a unique microenvironment for the development and maturation of meiotic and postmeiotic germ cells in seminiferous tubes. It is a compound proteinous structure, composed of several types of cell junctions including tight junctions (TJs), adhesion junctions and gap junctions (GJs). Some of the junctional proteins function as structural proteins of BTB and some have regulatory roles. The deletion or functional silencing of genes encoding these proteins may disrupt the BTB, which may cause immunological or other damages to meiotic and postmeiotic cells and ultimately lead to spermatogenic arrest and infertility. In this review, we will summarize the findings on the BTB structure and function from genetically-modified mouse models and discuss the future perspectives.

Peroxisome Proliferator-activated Receptor-D (PPARD) Coordinates Mouse Spermatogenesis by Modulating Extracellular Signal-regulated Kinase (ERK)-dependent Signaling

Ppard(-/-) mice exhibit smaller litter size compared with Ppard(+/+) mice. To determine whether peroxisome proliferator-activated receptor-D (PPARD) could possibly influence this phenotype, the role of PPARD in testicular biology was examined. Atrophic testes and testicular degeneration were observed in Ppard(-/-) mice compared with Ppard(+/+) mice, indicating that PPARD modulates spermatogenesis. Higher expression of p27 and decreased expression of proliferating cellular nuclear antigen in Sertoli cells were observed in Ppard(+/+) mice as compared with Ppard(-/-) mice, and these were associated with decreased Sertoli cell number in Ppard(+/+) mice. Cyclin D1 and cyclin D2 expression was lower in Ppard(+/+) as compared with Ppard(-/-) mice. Ligand activation of PPARD inhibited proliferation of a mouse Sertoli cell line, TM4, and an inverse agonist of PPARD (DG172) rescued this effect. Temporal inhibition of extracellular signal-regulated kinase (ERK) activation by PPARD in the testis was observed in Ppard(+/+) mice and was associated with decreased serum follicle-stimulating hormone and higher claudin-11 expression along the blood-testis barrier. PPARD-dependent ERK activation also altered expression of claudin-11, p27, cyclin D1, and cyclin D2 in TM4 cells, causing inhibition of cell proliferation, maturation, and formation of tight junctions in Sertoli cells, thus confirming a requirement for PPARD in accurate Sertoli cell function. Combined, these results reveal for the first time that PPARD regulates spermatogenesis by modulating the function of Sertoli cells during early testis development.

Roles of small RNAs in the effects of nutrition on apoptosis and spermatogenesis in the adult testis

We tested whether reductions in spermatozoal quality induced by under-nutrition are associated with increased germ cell apoptosis and disrupted spermatogenesis, and whether these effects are mediated by small RNAs. Groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days. Underfeeding increased the number of apoptotic germ cells (P < 0.05) and increased the expression of apoptosis-related genes (P < 0.05) in testicular tissue. We identified 44 miRNAs and 35 putative piRNAs that were differentially expressed in well-fed and underfed males (FDR < 0.05). Some were related to reproductive system development, apoptosis (miRNAs), and sperm production and quality (piRNAs). Novel-miR-144 (miR-98), was found to target three apoptotic genes (TP53, CASP3, FASL). The proportion of miRNAs as a total of small RNAs was greater in well-fed males than in underfed males (P < 0.05) and was correlated (r = 0.8, P < 0.05) with the proportion of piRNAs in well-fed and underfed males. In conclusion, the reductions in spermatozoal quality induced by under-nutrition are caused, at least partly, by disruptions to Sertoli cell function and increased germ cell apoptosis, mediated by changes in the expression of miRNAs and piRNAs.

Cardiotonic steroid ouabain stimulates expression of blood-testis barrier proteins claudin-1 and -11 and formation of tight junctions in Sertoli cells

The interaction of ouabain with the sodium pump induces signalling cascades resembling those triggered by hormone/receptor interactions. In the rat Sertoli cell line 93RS2, ouabain at low concentrations stimulates the c-Src/c-Raf/Erk1/2 signalling cascade via its interaction with the α4 isoform of the sodium pump expressed in these cells, leading to the activation of the transcription factor CREB. As a result of this signalling sequence, ouabain stimulates expression of claudin-1 and claudin-11, which are also controlled by a CRE promoter. Both of these proteins are known to be essential constituents of tight junctions (TJ) between Sertoli cells, and as a result of the ouabain-induced signalling TJ formation between neighbouring Sertoli cells is significantly enhanced by the steroid. Thus, ouabain-treated cell monolayers display higher transepithelial resistance and reduced free diffusion of FITC-coupled dextran in tracer diffusion assays. Taking into consideration that the formation of TJ is indispensable for the maintenance of the blood-testis barrier (BTB) and therefore for male fertility, the actions of ouabain described here and the fact that this and other related cardiotonic steroids (CTS) are produced endogenously suggest a direct influence of ouabain/sodium pump interactions on the maintenance of the BTB and thereby an effect on male fertility. Since claudin-1 and claudin-11 are also present in other blood-tissue barriers, one can speculate that ouabain and perhaps other CTS influence the dynamics of these barriers as well.

Claudin 11 inter-sertoli tight junctions in the testis of the korean soft-shelled turtle (Pelodiscus maackii)

Expression of claudin 11 (CLDN11), a tight junction (TJ) protein, was examined in the Korean soft-shelled turtle (Pelodiscus maackii) testis. Spermatogenesis began during the breeding season and peaked at the end of the breeding season. Spermiation started in summer and peaked in autumn. The deduced amino acid sequence of P. maackii CLDN11 was similar to those of avian and mammalian species. During the nonbreeding season when spermatogenesis and testosterone production were active, testicular Cldn11 levels were high. In the seminiferous epithelium, strong, wavy CLDN11 strands parallel to the basement membrane delaminate the spermatogonia, and early spermatocytes are in the open compartment. Otherwise, CLDN11 was found beneath the early spermatocytes and in the Sertoli cell cytoplasm. Punctate zonula occludens 1 (ZO-1) immunoreactivity was found within the CLDN11 strands parallel to the basement membrane or at the outermost periphery of the seminiferous epithelium close to the basal lamina. During the breeding season, when circulating testosterone levels and spermatogenic activity was low, testicular CLDN11 level was lower than those during the nonbreeding season. CLDN11 was found at apicolateral contact sites between adjacent Sertoli cells devoid of the postmeiotic germ cells. At this time, lanthanum tracer diffused to the adluminal compartment of seminiferous epithelium. In cultured testis tissues, testosterone propionate significantly increased the level of Cldn11 mRNA. In P. maackii testis, CLDN11 participates in the development of the blood-testis barrier (BTB), where the CLDN11 expression was coupled with spermatogenic activity and circulating androgen levels, indicating the conserved nature of TJs expressing CLDN11 at the BTB in amniotes.

Perfluorooctanoic acid disrupts the blood-testis barrier and activates the TNFα/p38 MAPK signaling pathway in vivo and in vitro

Perfluorooctanoic acid (PFOA) is correlated with male reproductive dysfunction in animals and humans, but the underlying mechanisms for this remain unknown. To explore the potential reproductive toxicity of PFOA, we studied blood-testis barrier (BTB) damage using in vivo and in vitro models. Male mice were gavage-administered PFOA (0-20 mg/kg/d) for 28 consecutive days, and breeding capacity and permeability of the Sertoli cell-based BTB were estimated. Primary Sertoli cells (SCs) were exposed to PFOA (0-500 μM) for 48 h, and transepithelial electrical resistance (TER) was assessed. Furthermore, BTB-associated protein expression, TNFα content, and phosphorylation and protein levels of the mitogen-activated protein kinase (MAPK) pathway were detected. An apparent decrease in mated and pregnant females per male mouse as well as litter weight was observed. Marked BTB damage was evidenced by increased red biotin fluorescence in the lumen tubular of the testes and the decrease in TER in SCs in vitro. The protein levels of claudin-11, connexin-43, N-cadherin, β-catenin, and occludin were significantly decreased in the testes and also in the SCs in vitro except for N-cadherin and β-catenin. TNFα content showed a dose-dependent increase in the testes and a dose- and time-dependent increase in the SCs, with the p-p38/p38 MAPK ratio also increasing in testes and SCs after PFOA exposure. Moreover, PFOA altered expressions of claudin-11, connexin-43, TNFα, and p-p38 MAPK were recovered 48 h after PFOA removal in the SCs. The SCs appeared to be target to PFOA, and the disruption of the BTB may be crucial to PFOA-induced reproductive dysfunction in mice.

Nutrition affects Sertoli cell function but not Sertoli cell numbers in sexually mature male sheep

We tested whether the reversible effects of nutrition on spermatogenesis in sexually mature sheep were mediated by Sertoli cells. Rams were fed with diets designed to achieve a 10% increase (High), no change (Maintenance) or a 10% decrease (Low) in body mass after 65 days. At the end of treatment, testes were lighter in the Low than the High group (PP<0.05) in the expression of seven Sertoli cell-specific genes. Under-nutrition appeared to reverse cellular differentiation leading to disruption of tight-junction morphology. In conclusion, in sexually mature sheep, reversible reductions in testis mass and spermatogenesis caused by under-nutrition were associated with impairment of basic aspects of Sertoli cell function but not with changes in the number of Sertoli cells.

Effects of icariin on reproductive functions in male rats

The present study investigated the effects and potential mechanism(s) of action of icariin on the reproductive functions of male rats. Adult rats were treated orally with icariin at doses of 0 (control), 50, 100, or 200 mg/kg body weight for 35 consecutive days. The results show that icariin had virtually no effect on the body weight or organ coefficients of the testes or epididymides. However, 100 mg/kg icariin significantly increased epididymal sperm counts. In addition, 50 and 100 mg/kg icariin significantly increased testosterone levels. Real-time PCR suggests icariin may be involved in testosterone production via mRNA expression regulation of genes such as peripheral type benzodiazepine receptor (PBR) and steroidogenic acute regulatory protein (StAR). Furthermore, 100 mg/kg icariin treatment also affected follicle stimulating hormone receptor (FSHR) and claudin-11 mRNA expression in Sertoli cells. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels were measured in the testes; 50 and 100 mg/kg icariin treatment improved antioxidative capacity, while 200 mg/kg icariin treatment upregulated oxidative stress. These results collectively suggest that icariin within a certain dose range is beneficial to male reproductive functions; meanwhile, higher doses of icariin may damage reproductive functions by increasing oxidative stress in the testes.

Dermatopontin is a novel regulator of the CdCl2-induced decrease in claudin-11 expression

Cadmium (Cd) is a ubiquitous environmental heavy metal, which may be harmful to the reproductive functions through injury to the blood-testis barrier (BTB). However, the underlying mechanism of this adverse effect on the BTB remains uncharacterized. A preliminary study revealed that dermatopontin (DPT) expression was significantly increased in Cd chloride (CdCl2)-treated Sertoli cells in vitro, which suggested that an increase in DPT expression is crucial for CdCl2-induced BTB damage. To explore this further, in the present study we initially determined that DPT is expressed in testis Sertoli cells. The treatment of cells with CdCl2 resulted in a significant increase in DPT expression and a parallel decrease in claudin-11 expression, both in vivo and in vitro. To confirm the relationship between DPT and claudin-11, a DPT-silenced 15P-1 Sertoli cell model was established. We determined that DPT silencing could partly reduce the CdCl2-induced decrease in claudin-11 expression. Additionally, western blot analyses demonstrated that the p38 signaling pathway is involved in the effect of CdCl2 on DPT expression. In conclusion, the present study provides the first evidence that DPT may be a novel effector of CdCl2, highlighting the significant role of DPT in the regulation of claudin-11 expression.

Transcriptome profiling of the theca interna in transition from small to large antral ovarian follicles

The theca interna layer of the ovarian follicle forms during the antral stage of follicle development and lies adjacent to and directly outside the follicular basal lamina. It supplies androgens and communicates with the granulosa cells and the oocyte by extracellular signaling. To better understand developmental changes in the theca interna, we undertook transcriptome profiling of the theca interna from small (3-5 mm, n = 10) and large (9-12 mm, n = 5) healthy antral bovine follicles, representing a calculated >7-fold increase in the amount of thecal tissue. Principal Component Analysis and hierarchical classification of the signal intensity plots for the arrays showed no clustering of the theca interna samples into groups depending on follicle size or subcategories of small follicles. From the over 23,000 probe sets analysed, only 76 were differentially expressed between large and small healthy follicles. Some of the differentially expressed genes were associated with processes such as myoblast differentiation, protein ubiquitination, nitric oxide and transforming growth factor β signaling. The most significant pathway affected from our analyses was found to be Wnt signaling, which was suppressed in large follicles via down-regulation of WNT2B and up-regulation of the inhibitor FRZB. These changes in the transcriptional profile could have been due to changes in cellular function or alternatively since the theca interna is composed of a number of different cell types it could have been due to any systematic change in the volume density of any particular cell type. However, our study suggests that the transcriptional profile of the theca interna is relatively stable during antral follicle development unlike that of granulosa cells observed previously. Thus both the cellular composition and cellular behavior of the theca interna and its contribution to follicular development appear to be relatively constant throughout the follicle growth phase examined.

Vitamin A deprivation affects the progression of the spermatogenic wave and initial formation of the blood-testis barrier, resulting in irreversible testicular degeneration in mice

The blood testis-barrier (BTB) is essential for maintaining homeostasis in the seminiferous epithelium. Although many studies have reported that vitamin A (VA) is required for the maintenance of spermatogenesis, the relationships between the BTB, spermatogenesis and VA have not been elucidated. In this study, we analyzed BTB assembly and spermatogenesis in the testes of mice fed the VA-deficient (VAD) diet from the prepubertal period to adulthood. During the prepubertal period, no changes were observed in the initiation and progression of the first spermatogenic wave in mice fed the VAD diet. However, the numbers of preleptotene/leptotene spermatocytes derived from the second spermatogenic wave onwards were decreased, and initial BTB formation was also delayed, as evidenced by the decreased expression of mRNAs encoding BTB components and VA signaling molecules. From 60 days postpartum, mice fed the VAD diet exhibited apoptosis of germ cells, arrest of meiosis, disruption of the BTB, and dramatically decreased testis size. Furthermore, vacuolization and calcification were observed in the seminiferous epithelium of adult mice fed the VAD diet. Re-initiation of spermatogenesis by VA replenishment in adult mice fed the VAD diet rescued BTB assembly after when the second spermatogenic wave initiated from the arrested spermatogonia reached the preleptotene/leptotene spermatocytes. These results suggested that BTB integrity was regulated by VA metabolism with meiotic progression and that the impermeable BTB was required for persistent spermatogenesis rather than meiotic initiation. In conclusion, consumption of the VAD diet led to critical defects in spermatogenesis progression and altered the dynamics of BTB assembly.

Perinatal exposure to fluoxetine via placenta and lactation inhibits the testicular development in male rat offspring

Due to the widespread use of fluoxetine to treat depression, including pregnant and nursing women, the present study aimed to investigate the effects of in utero and lactational exposure to fluoxetine in rat offspring at post natal day 22. Wistar rat dams were orally treated with fluoxetine (5, 10, and 20 mg/kg) from day 13 gestation to day 21 lactation. Exposure to 10 and 20 mg/kg fluoxetine reduced the body and testis weights. The volume of the seminiferous tubules and epithelium were also reduced following 20 mg/kg fluoxetine exposure. The length of the seminiferous tubules and the population of Sertoli cells changed in offspring exposed to fluoxetine. The amount of seminiferous tubules lacking tubular lumen was higher in rats exposed to 20 mg/kg fluoxetine. Plasma testosterone showed no significant change. In conclusion, fluoxetine exposure via the placenta and lactation may inhibit and delay testicular development, adversely affecting several testicular parameters important for the establishment of sperm production in adulthood.

Intercellular adhesion molecule-1 is a regulator of blood-testis barrier function

The mechanism underlying the movement of preleptotene/leptotene spermatocytes across the blood-testis barrier (BTB) during spermatogenesis is not well understood largely owing to the fact that the BTB, unlike most other blood-tissue barriers, is composed of several co-existing and co-functioning junction types. In the present study, we show that intercellular adhesion molecule-1 [ICAM-1, a Sertoli and germ cell adhesion protein having five immunoglobulin (Ig)-like domains, in addition to transmembrane and cytoplasmic domains] is a regulator of BTB integrity. Initial experiments showed ICAM-1 to co-immunoprecipitate and co-localize with tight junction and basal ectoplasmic specialization proteins such as occludin and N-cadherin, which contribute to BTB function. More importantly, overexpression of ICAM-1 in Sertoli cells in vitro enhanced barrier function when monitored by transepithelial electrical resistance measurements, illustrating that ICAM-1-mediated adhesion can promote BTB integrity. On the other hand, overexpression of a truncated form of ICAM-1 that consisted only of the five Ig-like domains (sICAM-1; this form of ICAM-1 is known to be secreted) elicited an opposite effect when Sertoli cell barrier function was found to be perturbed in vitro; in this case, sICAM-1 overexpression resulted in the downregulation of several BTB constituent proteins, which was probably mediated by Pyk2/p-Pyk2-Y402 and c-Src/p-Src-Y530. These findings were expanded to the in vivo level when BTB function was found to be disrupted following sICAM-1 overexpression. These data illustrate the existence of a unique mechanism in the mammalian testis where ICAM-1 can either positively or negatively regulate BTB function.

Regulation of male fertility by CFTR and implications in male infertility

BACKGROUND

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated Cl(-) and HCO(3)(-) conducting channel, mutations of which are known to be associated with male infertility. However, the underlying mechanisms remain elusive.

METHODS

Literature databases were searched for papers on the topics related to CFTR and male fertility and infertility with relevant keywords. Unpublished data from authors' laboratory were also included for analysis.

RESULTS

Clinical evidence shows increased mutation frequency or reduced CFTR expression in men with congenital bilateral absence of vas deferens (CBAVD) or sperm abnormalities, such as azoospermia teratospermia and oligoasthenospermia. Studies on primary rodent Sertoli cells and germ cells, as well as testes from CFTR knockout mice or a cryptorchidism model, yield findings indicating the involvement of CFTR in spermatogensis through the HCO(3)(-)/sAC/cAMP/CREB(CREM) pathway and the NF-κB/COX-2/PGE(2) pathway. Evidence also reveals a critical role of CFTR in sperm capacitation by directly or indirectly mediating HCO(3)(-) entry that is essential for capacitation. CFTR is emerging as a versatile player with roles in mediating different signaling pathways pertinent to various reproductive processes, in addition to its long-recognized role in electrolyte and fluid transport that regulates the luminal microenvironment of the male reproductive tract.

CONCLUSIONS

CFTR is a key regulator of male fertility, a defect of which may result in different forms of male infertility other than CBAVD. It would be worthwhile to further investigate the potential of developing novel diagnostic and contraceptive methods targeting CFTR.

Enterocytes’ tight junctions: From molecules to diseases

Tight junctions (TJs) are structures between cells where cells appear in the closest possible contact. They are responsible for sealing compartments when epithelial sheets are generated. They regulate the permeability of ions, (macro) molecules and cells via the paracellular pathway. Their structure at the electron microscopic level has been well known since the 1970s; however, only recently has their macromolecular composition been revealed. This review first examines the major macromolecular components of the TJs (occludin, claudins, junctional adhesion molecule and tricellulin) and then the associated macromolecules at the intracellular plaque [zonula occludens (ZO)-1, ZO-2, ZO-3, AF-6, cingulin, 7H6]. Emphasis is given to their interactions in order to begin to understand the mode of assembly of TJs. The functional significance of TJs is detailed and several mechanisms and factors involved are discussed briefly. Emphasis is given to the role of intestinal TJs and the alterations observed or speculated in diverse disease states. Specifically, intestinal TJs may exert a pathogenetic role in intestinal (inflammatory bowel disease, celiac disease) and extraintestinal diseases (diabetes type 1, food allergies, autoimmune diseases). Additionally, intestinal TJs may be secondarily disrupted during the course of diverse diseases, subsequently allowing the bacterial translocation phenomenon and promoting the systemic inflammatory response, which is often associated with clinical deterioration. The major questions in the field are highlighted.

Gene expression profiling reveals new potential players of gonad differentiation in the chicken embryo

BACKGROUND

In birds as in mammals, a genetic switch determines whether the undifferentiated gonad develops into an ovary or a testis. However, understanding of the molecular pathway(s) involved in gonad differentiation is still incomplete.

METHODOLOGY/PRINCIPAL FINDINGS

With the aim of improving characterization of the molecular pathway(s) involved in gonad differentiation in the chicken embryo, we developed a large scale real time reverse transcription polymerase chain reaction approach on 110 selected genes for evaluation of their expression profiles during chicken gonad differentiation between days 5.5 and 19 of incubation. Hierarchical clustering analysis of the resulting datasets discriminated gene clusters expressed preferentially in the ovary or the testis, and/or at early or later periods of embryonic gonad development. Fitting a linear model and testing the comparisons of interest allowed the identification of new potential actors of gonad differentiation, such as Z-linked ADAMTS12, LOC427192 (corresponding to NIM1 protein) and CFC1, that are upregulated in the developing testis, and BMP3 and Z-linked ADAMTSL1, that are preferentially expressed in the developing ovary. Interestingly, the expression patterns of several members of the transforming growth factor β family were sexually dimorphic, with inhibin subunits upregulated in the testis, and bone morphogenetic protein subfamily members including BMP2, BMP3, BMP4 and BMP7, upregulated in the ovary. This study also highlighted several genes displaying asymmetric expression profiles such as GREM1 and BMP3 that are potentially involved in different aspects of gonad left-right asymmetry.

CONCLUSION/SIGNIFICANCE

This study supports the overall conservation of vertebrate sex differentiation pathways but also reveals some particular feature of gene expression patterns during gonad development in the chicken. In particular, our study revealed new candidate genes which may be potential actors of chicken gonad differentiation and provides evidence of the preferential expression of BMPs in the developing ovary and Inhibin/Activin subunits in the developing testis.

Estrogen-dependent gene expression in the mouse ovary

Estrogen (E) plays a pivotal role in regulating the female reproductive system, particularly the ovary. However, the number and type of ovarian genes influenced by estrogen remain to be fully elucidated. In this study, we have utilized wild-type (WT) and aromatase knockout (ArKO; estrogen free) mouse ovaries as an in vivo model to profile estrogen dependent genes. RNA from each individual ovary (n = 3) was analyzed by a microarray-based screen using Illumina Sentrix Mouse WG-6 BeadChip (45,281 transcripts). Comparative analysis (GeneSpring) showed differential expression profiles of 450 genes influenced by E, with 291 genes up-regulated and 159 down-regulated by 2-fold or greater in the ArKO ovary compared to WT. Genes previously reported to be E regulated in ArKO ovaries were confirmed, in addition to novel genes not previously reported to be expressed or regulated by E in the ovary. Of genes involved in 5 diverse functional processes (hormonal processes, reproduction, sex differentiation and determination, apoptosis and cellular processes) 78 had estrogen-responsive elements (ERE). These analyses define the transcriptome regulated by E in the mouse ovary. Further analysis and investigation will increase our knowledge pertaining to how E influences follicular development and other ovarian functions.

The influence of thermal environment and food availability on testosterone and gonadal recrudescence in male Chinese skinks [Plestiodon (Eumeces) chinensis]

Most animals show seasonal cycles of reproduction (including cycling of sex steroids). Environmental cues (e.g., temperature) likely play important roles in these seasonal variations but their exact contributions remain unclear. We conducted a two-factor experiment to elucidate the effects of thermal environments and food availability on growth in body mass, testosterone (T) levels and testes morphology in male Chinese skinks [Plestiodon (Eumeces) chinensis]. Skinks in the thermal environment mimicking spring (April) conditions grew slowly but had higher plasma T levels and larger testes with more viable sperms than those in the thermal environment mimicking summer (July) conditions. Skinks exposed to high food treatment grew faster and had higher plasma T levels and more viable sperms than those exposed to low food treatment. Male growth was negatively correlated with reproductive activity as indicated by T levels and testes size. Therefore, both temperature and food availability are important environmental factors that can affect the reproductive cycle of male lizards, and the mechanisms underlying the trade-off between growth and reproduction could involve the regulation of T levels.

Molecular dynamics of the blood-testis barrier components during murine spermatogenesis

The blood-testis barrier (BTB) separates the seminiferous epithelium into the adluminal and basal compartments. During murine spermatogenesis, preleptotene/leptotene spermatocytes migrate from the basal to the adluminal compartment through the BTB during stages VIII-IX. In the present study, we focused on the tight junction (TJ) molecules and analyzed their spatiotemporal expression during the murine seminiferous epithelial cycle. Structural analysis revealed that the principal components of the BTB, for example, claudin-3, claudin-11, occludin, and zonula occludens-1 (ZO-1), were localized at the basal and luminal sides of the preleptotene/leptotene spermatocytes during the migration stages (VIII-IX). Although we detected claudin-11, occludin, and ZO-1 throughout spermatogenesis, claudin-3 was only detected during stages VI-IX. Quantitative PCR using dissected seminiferous tubules from three stages (Early: II-VI, Middle: VII-VIII, Late: IX-I) clarified that the mRNA levels of TJ molecules were not correlated with the histoplanimetrical protein levels during spermatogenesis. Additionally, tubulobulbar complexes, considered to be involved in the internalization of TJ, were observed at the BTB site. Furthermore, a significant reduction in the mRNA levels of genes for the degradation of occludin (Itch) and endocytic recycling (Rab13) were observed during the Late and Middle stages, respectively. Therefore, we hypothesized that the lag between mRNA and protein expression of TJ molecules may be due to posttranslational modulation, for example, tubulobulbar complexes and endocytic recycling processes. In conclusion, these findings indicate that the integrity of the BTB is maintained throughout spermatogenesis, and the stage-specific localization of claudin-3 protein plays an important role in regulating BTB permeability.

Claudin-11 expression increased in spermatogenic defect in human testes

Expression of claudin-11, which builds up blood-testis barrier (BTB), was increased in decreased spermatogenesis, including in hypospermatogenesis, spermatocytic and maturation arrest, and Sertoli cell only (SCO) testes. Increased claudin-11 immunoreactivity was observed at the inter-Sertoli tight junctions in maturation arrest and in the cytoplasm of Sertoli cells in SCO. The late spermatogenic wave may negatively regulate claudin-11 gene activation and the subcellular localization of claudin-11 in Sertoli cells, thus altering the BTB in the human testis.

Tight junctions in the testis: new perspectives

In the testis, tight junctions (TJs) are found between adjacent Sertoli cells at the level of the blood-testis barrier (BTB) where they coexist with basal ectoplasmic specializations and desmosome-gap junctions. The BTB physically divides the seminiferous epithelium into two distinct compartments: a basal compartment where spermatogonia and early spermatocytes are found, and an adluminal compartment where more developed germ cells are sequestered from the systemic circulation. In order for germ cells (i.e. preleptotene spermatocytes) to enter the adluminal compartment, they must cross the BTB, a cellular event requiring the participation of several molecules and signalling pathways. Still, it is not completely understood how preleptotene spermatocytes traverse the BTB at stage VIII of the seminiferous epithelial cycle. In this review, we discuss largely how TJ proteins are exploited by viruses and cancer cells to cross endothelial and epithelial cells. We also discuss how this information may apply to future studies investigating the movement of preleptotene spermatocytes across the BTB.

Claudin and occludin expression and function in the seminiferous epithelium

Integral membrane proteins that contribute to function of the blood-testes barrier (BTB) in mice include claudins 3, 5 and 11 and occludin. Although claudin 11 is expressed throughout all stages of the seminiferous epithelial cycle, claudins 3 and 5 have specific expression at stage VIII. These differences in protein expression suggest that the interactions among, and functions of, these integral membrane proteins may shift over the course of the seminiferous epithelial cycle. Also, differences in expression among rodent species and men may make interpretation of studies across species challenging. This review will discuss the characteristics of claudins and occludin; the expression, regulation and function of these integral membrane proteins in the seminiferous epithelium; and how these properties relate to the unique features of BTB.

Gonadotropins regulate rat testicular tight junctions in vivo

Sertoli cell tight junctions (TJs) are an essential component of the blood-testis barrier required for spermatogenesis; however, the role of gonadotropins in their maintenance is unknown. This study aimed to investigate the effect of gonadotropin suppression and short-term replacement on TJ function and TJ protein (occludin and claudin-11) expression and localization, in an adult rat model in vivo. Rats (n = 10/group) received the GnRH antagonist, acyline, for 7 wk to suppress gonadotropins. Three groups then received for 7 d: 1) human recombinant FSH, 2) human chorionic gonadotropin (hCG) and rat FSH antibody (to study testicular androgen stimulation alone), and 3) hCG alone (to study testicular androgen and pituitary FSH production). TJ proteins were assessed by real-time PCR, Western blot analysis, and immunohistochemistry, whereas TJ function was assessed with a biotin permeation tracer. Acyline treatment significantly reduced testis weights, serum androgens, LH and FSH, and adluminal germ cells (pachytene spermatocyte, round and elongating spermatids). In contrast to controls, acyline induced seminiferous tubule permeability to biotin, loss of tubule lumens, and loss of occludin, but redistribution of claudin-11, immunostaining. Short-term hormone replacement stimulated significant recoveries in adluminal germ cell numbers. In hCG +/- FSH antibody-treated rats, occludin and claudin-11 protein relocalized at the TJ, but such relocalization was minimal with FSH alone. Tubule lumens also reappeared, but most tubules remained permeable to biotin tracer, despite the presence of occludin. It is concluded that gonadotropins maintain Sertoli cell TJs in the adult rat via a mechanism that includes the localization of occludin and claudin-11 at functional TJs.

Claudin 5 expression in mouse seminiferous epithelium is dependent upon the transcription factor ets variant 5 and contributes to blood-testis barrier function

The blood-testis barrier (BTB) is formed by tight junctions between Sertoli cells. Results of previous studies suggested that the barrier is deficient in ets variant 5 (ETV5) gene-deleted mice; therefore, microarray data were examined for changes in tight junction-associated genes. The tight junctional protein claudin 5 (CLDN5) was decreased in testes of 8-day-old Etv5(-/-) pups. The study reported herein examined the expression of CLDN5 in wild-type (WT) and Etv5(-/-) mice and evaluated its contribution to BTB function. CLDN5 protein expression was evaluated in 8-day-old WT and Etv5(-/-) and adult WT, Etv5(-/-), and W/W(v) testes by immunohistochemistry and in 8-day-old WT Sertoli cell-enriched and germ cell-enriched fractions by immunocytochemistry. Cldn5 mRNA expression was evaluated in 0- to 20-day-old and adult WT mice and in 8-day-old and adult Etv5(-/-) mice via quantitative PCR. Tracer studies were performed in adult WT, Etv5(-/-), and W/W(v) mice. The results indicate the following: 1) CLDN5 was expressed in Sertoli cells, spermatogonia, and preleptotene spermatocytes. 2) Seminiferous epithelial CLDN5 expression depended upon both the presence of germ cells and ETV5. 3) CLDN5 expression in testicular vascular endothelium and rete testis epithelium was ETV5 independent. 4) Cldn5 mRNA expression increased in the testes of juvenile mice at the time of BTB formation. 5) Testes of Etv5(-/-) and W/W(v) mice, which are both deficient in seminiferous epithelial CLDN5 expression, had biotin tracer leakage from the interstitial space into the seminiferous tubule lumen. In conclusion, CLDN5 is expressed in the seminiferous epithelium, appears to be regulated by multiple influences, and contributes to BTB function.

Claudin-11 is over-expressed and dislocated from the blood-testis barrier in Sertoli cells associated with testicular intraepithelial neoplasia in men

In mouse testis, claudin-11 is responsible for the formation of specific parallel TJ strands of the blood-testis barrier (BTB). Concerning the human BTB, there is no information about the transmembrane TJ proteins. We recently demonstrated the loss of functional integrity of the BTB in testicular intraepithelial neoplasia (TIN), associated with a dislocation of the peripheral TJ proteins ZO-1 and ZO-2. Here, we determined the expression and distribution of claudin-11 at the human BTB in seminiferous tubules with normal spermatogenesis (NSP) and TIN. Immunostaining of claudin-11 revealed intense signals at the basal BTB region in seminiferous epithelium with NSP. Within TIN tubules, claudin-11 immunostaining became diffuse and cytoplasmic. Double immunogold labeling demonstrated a co-localization of claudin-11 and ZO-1 at the inter-Sertoli cell junctions. Real-time RT-PCR of laser microdissected tubules showed an up-regulation of claudin-11 mRNA in TIN. Additionally, increased claudin-11 protein was observed by Western blot. We conclude that claudin-11 constitutes a TJ protein at the human BTB. In TIN tubules, claudin-11 is up-regulated and dislocated from the BTB. Therefore, the disruption of the BTB is related to a dysfunction of claudin-11 and not to a failure of its expression.