Claudin and occludin expression and function in the seminiferous epithelium

Evaluation of ginger straw as a forage source for goats: Effects on performance, ruminal fermentation, meat quality and immunity

This study aimed to investigate the effects of ginger straw as a replacement of peanut straw on the growth, meat quality, rumen fermentation, and immunity of goats. In this study, 40 Huanghuai male goats, weighing 30 ± 0.5 kg at six months of age, were selected and randomly divided into four treatments: ginger straw 0% (G0), 5% (G5), 10% (G10) and 20% (G20) replacing peanut straw, with 10 goats in each treatment. Goat dry matter intake (DMI) improved as the proportion of peanut straws replaced with ginger straws increased (linear, P < 0.001, quadratic, P < 0.001). The highest average daily gain (ADG) and the lowest feed-to-gain ratio (F/G) were observed in G5 goats (P < 0.001). The digestibilities of neutral detergent fibre (NDF, P = 0.031) and acid detergent fibre (ADF, P = 0.014) were higher in the G5 group than in G10 and G20. With increasing ginger straw replacement, the plasma interleukin-10 (IL-10) levels increased (linear, P = 0.035, quadratic, P = 0.041). The microbial protein (MCP) increased as the proportion of ginger straw increased (linear, P = 0.034, quadratic, P = 0.041). The butyrate was increased (linear, P = 0.028, quadratic, P = 0.035) at all levels of ginger straw inclusion into the diet. A linear (P < 0.001) increase in the height of the jejunal mucosal villi was observed as the proportion of ginger straw in the diet increased. The tight junction protein 1 (TJP1) and claudin-1 mRNA expression in the jejunal mucosa were significantly higher in groups G5, G10, and G20 than in the G0 group (P < 0.001). In general, substituting peanut straw with ginger straw in goat diets promoted rumen fermentation and produced more volatile fatty acids and microbial proteins to meet the needs of goats for improved growth performance. Substituting ginger straw for peanut straw improved immunity and the intestinal barrier in goats and did not adversely affect meat quality. Replacing peanut straw with 5% ginger straw in the goat diet resulted in higher NDF digestibility and growth performance. Therefore, the replacement of peanut straw with 5% ginger straw in goat diets is recommended.

Exercise Training Alters the Hippocampal Expression of Blood-Brain Barrier Components and Behavior of Western Diet-Fed Female Rats

Overeating highly palatable foods typical of a Western diet (WD) has been linked to cognitive impairments in animal models and humans. Exercise training was proposed as an important behavioral intervention with beneficial effects, including improving peripheral insulin sensitivity, improving central functions such as learning and memory, and restoring a dysregulated blood-brain barrier (BBB). The purpose of the present study was to characterize the effect of exercise training in rats fed with the WD with special emphasis on BBB. Adult female Long Evans rats were subjected to 12 weeks of WD feeding (WD group), or simultaneous WD feeding and wheel-running training (WD/EX group), or were fed a WD for 6 weeks without training and then subjected to diet and training for an additional 6 weeks (WD_WD/EX group). A sedentary (untrained) group of lean rats was fed a standard rodent chow (CTR group). In all experimental groups, we measured behavioral and physiological parameters, and the hippocampal levels of proteins structurally and functionally related to BBB, including proinflammatory cytokines and products of elevated lipid peroxidation. Exercise training in combination with a WD decreased locomotor and exploratory activities and induced short-term memory impairments. The behavioral changes were accompanied by reduced levels of occludin, claudin-5, and ZO-1 proteins in the hippocampus, suggesting changes in the integrity and increased permeability of BBB. In the WD_WD/EX rats, we found increased hippocampal levels of malondialdehyde (MDA) and neurotrophins (Bdnf, Vegfa) suggesting that increased energy expenditure by obese rats stimulates endogenous protective processes. The training introduced after 6 weeks of WD feeding in rats showing an obese phenotype may suggest that the sequence and moment of presumably protective intervention (exercise training) could alleviate or, on the contrary, exacerbate the level of stress and its consequences.

Claudin-11 plays a pivotal role in the clathrin-mediated endocytosis of influenza A virus

Identification of host factors that play a key role in viral replication is of great importance for antiviral development. Metabotropic glutamate receptor subtype 2 (mGluR2) is the receptor to trigger clathrin-mediated endocytosis (CME), the major pathway by which influenza virus enters cells. However, other host factors almost certainly involved in the influenza virus CME are largely unknown. Here, we found that the four-transmembrane protein claudin-11 plays an integral part in influenza virus CME. Claudin-11 promotes the dissociation of KCa1.1 (potassium calcium-activated channel subfamily M alpha 1) from mGluR2 and, together with mGluR2, is internalized in virus-containing clathrin-coated pits (CCPs), where it regulates the depolymerization of polymerized F-actin, allowing the CCPs to mature. Importantly, over 60% of claudin-11-silenced mice survived infection with a lethal influenza virus. Our findings advance the understanding of influenza virus infection and provide a promising strategy for the development of host-based antiviral drugs.

Exposure to titanium dioxide nanoparticles disrupts the BTB by interfering with the assembly of stress granules in germ cells

Titanium dioxide nanoparticles (TiO2 NPs) are among the most prevalent nanomaterials utilized in industrial and medical fields. However, their impact on spermatogenesis and male fertility remains insufficiently characterized. This study addresses the reproductive toxicity of TiO2 NPs and elucidates the underlying molecular mechanisms involved. Our findings demonstrate that exposure to TiO2 NPs leads to a significant reduction in sperm count and motility. Specifically, TiO2 NPs disrupt the integrity of the blood-testis barrier (BTB) and compromise the cytoskeletal structure in both spermatogenic and Sertoli cells. Additionally, treatment with TiO2 NPs is associated with cell death and a decrease in the protein levels of BTB-related components, including N-cadherin, β-catenin, occludin, and ZO-1. Mechanistic investigations reveal that TiO2 NPs inhibit stress granule formation in germ cells subjected to heat stress and promote germ cell apoptosis via activation of the ATM/P53 signaling pathway. Collectively, our study highlights a potential connection between environmental health and reproductive health, revealing multiple detrimental effects of TiO2 NPs and uncovering previously unrecognized mechanisms by which nanomaterials may adversely impact the reproductive system.

Loss of cell junctional components and matrix alterations drive cell desquamation and fibrotic changes in Idiopathic Pulmonary Fibrosis

The distal bronchioles in Idiopathic Pulmonary Fibrosis (IPF) exhibit histopathological abnormalities such as bronchiolization, peribronchiolar fibrosis and honeycomb cysts that contribute to the overall architectural remodeling of lung tissue seen in the disease. Here we describe an additional histopathologic finding of epithelial desquamation in patients with IPF, wherein epithelial cells detach from the basement membrane of the distal bronchioles. To understand the mechanism driving this pathology, we performed spatial transcriptomics of the epithelial cells and spatial proteomics of the basement membrane of the distal bronchioles from IPF patients and patients with no prior history of lung disease. Our findings reveal a downregulation of cell junctional components, upregulation of epithelial-mesenchymal transition signatures and dysregulated basement membrane matrix in IPF distal bronchioles, facilitating epithelial desquamation. Further, functional assays identified regulation between Collagen IV in the matrix, and the junctional genes JUP and PLEC , that is crucial for maintaining distal bronchiolar homeostasis. In IPF, this balanced regulation between matrix and cell-junctions is disrupted, leading to loss of epithelial adhesion, peribronchiolar fibrosis and epithelial desquamation. Overall, our study suggests that in IPF the interplay between the loss of cell junctions and a dysregulated matrix results in desquamation of distal bronchiolar epithelium and lung remodeling, exacerbating the disease.

One Sentence Summary

Two-way regulation of cell junctional proteins and matrix proteins drives cellular desquamation and fibrosis in the distal bronchioles of patients with Idiopathic Pulmonary Fibrosis.

Impacts of Acrylamide on testis and spermatozoa

Acrylamide (ACR) is an industrial chemical used to produce polyacrylamide, a synthetic polymer with a wide range of applications. Depending on the dosage, its presence in occupational and environmental sources poses potential health risks to humans and animals. ACR can be formed in starchy foods cooked at high temperatures. Its effects on human sperm are not well understood. Animal studies indicate that ACR induces toxicity in the male reproductive system through oxidative stress mechanisms. Exposure to ACR alters the normal structure of testicular tubules, leading to congestion, interstitial edema, degeneration of spermatogenic cells, formation of abnormal spermatid giant cells, and necrosis and apoptosis. It also disrupts the balance of important biomarkers such as malondialdehyde, nitric oxide, superoxide dismutase, catalase, and glutathione. ACR has a negative impact on mitochondrial function, antioxidant enzymes, ATP production, and sperm membrane integrity, resulting in decreased sperm quality. Furthermore, it interferes with the expression of steroidogenic genes associated with testosterone biosynthesis. This review explores the detrimental effects of ACR on sperm and testicular function and discusses the potential role of antioxidants in mitigating the adverse effects of ACR on male reproduction.

A first complete catalog of highly expressed genes in eight chicken tissues reveals uncharacterized gene families specific for the chicken testis

Based on next-generation sequencing, we established a repertoire of differentially overexpressed genes (DoEGs) in eight adult chicken tissues: the testis, brain, lung, liver, kidney, muscle, heart, and intestine. With 4,499 DoEGs, the testis had the highest number and proportion of DoEGs compared with the seven somatic tissues. The testis DoEG set included the highest proportion of long noncoding RNAs (lncRNAs; 1,851, representing 32% of the lncRNA genes in the whole genome) and the highest proportion of protein-coding genes (2,648, representing 14.7% of the protein-coding genes in the whole genome). The main significantly enriched Gene Ontology terms related to the protein-coding genes were "reproductive process," "tubulin binding," and "microtubule cytoskeleton." Using real-time quantitative reverse transcription-polymerase chain reaction, we confirmed the overexpression of genes that encode proteins already described in chicken sperm [such as calcium binding tyrosine phosphorylation regulated (CABYR), spermatogenesis associated 18 (SPATA18), and CDK5 regulatory subunit associated protein (CDK5RAP2)] but whose testis origin had not been previously confirmed. Moreover, we demonstrated the overexpression of vertebrate orthologs of testis genes not yet described in the adult chicken testis [such as NIMA related kinase 2 (NEK2), adenylate kinase 7 (AK7), and CCNE2]. Using clustering according to primary sequence homology, we found that 1,737 of the 2,648 (67%) testis protein-coding genes were unique genes. This proportion was significantly higher than the somatic tissues except muscle. We clustered the other 911 testis protein-coding genes into 495 families, from which 47 had all paralogs overexpressed in the testis. Among these 47 testis-specific families, eight contained uncharacterized duplicated paralogs without orthologs in other metazoans except birds: these families are thus specific for chickens/birds.NEW & NOTEWORTHY Comparative next-generation sequencing analysis of eight chicken tissues showed that the testis has highest proportion of long noncoding RNA and protein-coding genes of the whole genome. We identified new genes in the chicken testis, including orthologs of known mammalian testicular genes. We also identified 47 gene families in which all the members were overexpressed, if not exclusive, in the testis. Eight families, organized in duplication clusters, were unknown, without orthologs in metazoans except birds, and are thus specific for chickens/birds.

Maternal exposure to DON during lactation induces testicular toxicity in pubertal and adult offspring mice

Deoxynivalenol (DON), a type B trichothecene mycotoxin, commonly occurs in cereal grains, and poses significant health risks to humans and animals. Numerous studies reveal its obvious toxic effects on male reproductive performance as well as its ability to transfer from the lactating mother to the suckling offspring through colostrum and milk. The objective of this study was to evaluate the toxic effect of lactational DON exposure on testicular morphology, hormonal levels, inflammation, apoptosis and proliferation of germ cells, tight junction, and sperm quality in male offspring. Sixty-six male offspring mice from lactating dams exposed to DON were euthanized at PND 21 and PND 70 to investigate the reproductive toxicity. Our results indicated that maternal DON exposure had a significant impact on the weight and volume of the testes, caused testicular histopathology, and reduced testosterone levels by downregulating expressions of StAR, CYP11A1, and CYP17A1 in male offspring. We also found that maternal DON exposure led to testicular inflammation in male offspring, which was attributed to increased levels of inflammatory markers, including IL-1β, IL-6, TNF-α, and IFN-γ. Maternal DON exposure resulted in impaired tight junctions of Sertoli cells in male offspring, as evidenced by decreased expressions of ZO-1, Occludin, and Claudin-3. In addition, maternal DON exposure caused a reduction in the number of Sertoli cells and germ cells, ultimately leading to decreased sperm count and quality in adult male offspring. Collectively, these findings provide compelling evidence that maternal exposure to DON during lactation causes testicular toxicity in both pubertal and adult male offspring.

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.

Azilsartan improves urinary albumin excretion in hypertension mice

Hypertension is one of the most important risk factors for chronic kidney diseases, leading to hypertensive nephrosclerosis, including excessive albuminuria. Azilsartan, an angiotensin II type 1 receptor blocker, has been widely used for the treatment of hypertension. However, the effects of Azilsartan on urinary albumin excretion in hypertension haven't been reported before. In this study, we investigated whether Azilsartan possesses a beneficial property against albuminuria in mice treated with angiotensin II and a high-salt diet (ANG/HS). Compared to the control group, the ANG/HS group had higher blood pressure, oxidative stress, and inflammatory response, all of which were rescued by Azilsartan dose-dependently. Importantly, the ANG/HS-induced increase in urinary albumin excretion and decrease in the expression of occludin were reversed by Azilsartan. Additionally, it was shown that increased fluorescence intensity of FITC-dextran, declined trans-endothelial electrical resistance (TEER) values, and reduction of occludin and krüppel-like factor 2 (KLF2) were observed in ANG/HS-treated human renal glomerular endothelial cells (HrGECs), then prevented by Azilsartan. Moreover, the regulatory effect of Azilsartan on endothelial monolayer permeability in ANG/HS-treated HrGECs was abolished by the knockdown of KLF2, indicating KLF2 is required for the effect of Azilsartan. We concluded that Azilsartan alleviated diabetic nephropathy-induced increase in Uterine artery embolization (UAE) mediated by the KLF2/occludin axis.

Post-Weaning Exposure to Sunset Yellow FCF Induces Changes in Testicular Tight and Gap Junctions in Rats: Protective Effects of Coenzyme Q10

Studies on adverse health consequences of azo dyes are limited and conflicting. Coenzyme Q10 (CoQ10) supplementation has been shown to have benefits associated with antioxidant and anti-inflammatory characteristics on several body systems. This work investigates the possible toxic effects of the widely used food additive sunset yellow and the probable protective effects of CoQ10 on testicular tight and gap junctions in rats by assessing molecular, immunohistochemical, and histopathological changes. Sixty Sprague-Dawley male weanling rats were randomly divided into six groups (n = 10). The rats received their treatments via daily oral gavages for 6 weeks. The treatments included as follows: low dose of sunset yellow (SY-LD) (2.5 mg/kg/day), high dose of sunset yellow (SY-HD) (70 mg/kg/day), CoQ10 (10 mg/kg/day), CoQ10 with low dose of sunset yellow (CoQ10 + LD), CoQ10 with high dose of sunset yellow (CoQ10 + HD), and distilled water as the control treatment. At the end of the experiment, the rats were anesthetized, and the testes were removed for molecular (real-time quantitative PCR), immunohistochemical, and histopathological (H & E staining) assessments. Claudin 11 and occludin gene expression significantly decreased in HD and CoQ10 + HD groups compared with the controls. Connexin 43 (Cx43) expression in the control and CoQ10 groups was significantly higher than in the HD group. The immunohistochemical and histopathological data were largely in line with these findings. The results showed that exposure to a high dose of sunset yellow led to disturbances in cell-to-cell interactions and testicular function. Simultaneous treatment with CoQ10 had some beneficial effects but did not completely improve these undesirable effects.

LncRNA5251 inhibits spermatogenesis via modification of cell-cell junctions

BACKGROUND

Male factors-caused decline in total fertility has raised significant concern worldwide. LncRNAs have been identified to play various roles in biological systems, including spermatogenesis. This study aimed to explore the role of lncRNA5251 in mouse spermatogenesis.

METHODS

The expression of lncRNA5251 was modulated in mouse testes in vivo or spermatogonial stem cells (C18-4 cells) in vitro by shRNA.

RESULTS

The sperm motility in two generations mice after modulation of lncRNA5251 (muF0 and muF1) was decreased significantly after overexpression of lncRNA5251. GO enrichment analysis found that knockdown lncRNA5251 increased the expression of genes related to cell junctions, and genes important for spermatogenesis in mouse testes. Meanwhile, overexpressing lncRNA5251 decreased the gene and/or protein expression of important genes for spermatogenesis and immune pathways in mouse testes. In vitro, knockdown lncRNA5251 increased the expression of genes for cell junction, and the protein levels of some cell junction proteins such as CX37, OCLN, JAM1, VCAM1 and CADM2 in C18-4 cells. LncRNA5251 is involved in spermatogenesis by modulation of cell junctions.

CONCLUSION

This will provide a theoretical basis for improving male reproductive ability via lncRNA.

The abundance and localization of claudin-1 and -5 in the adult tomcats (Felis catus) testis, tubules rectus, rete testis, efferent ductules, and epididymis

Tight junctions (TJ) are the anatomical component of blood-testis (BTB) and blood-epididymis (BEB) barriers and contain many proteins, including claudins. The presence of claudins in domestic cat testis and epididymis has not been previously described. This study aimed to determine whether claudin-1 and claudin-5 participate in the structure of BTB and BEB and whether their amounts differ between the testis and epididymal segments of adult cats, using Western blotting (WB) and immunohistochemistry. WB results demonstrated that claudin-1 was significantly lower in the testis than in all epididymal segments and higher in the corpus epididymis than in the cauda, while claudin-5 in the testis was significantly lower than in the caput and corpus. Claudin-1 was absent at the Sertoli-Sertoli junctions, while claudin-5 was detected at the level of the BTB during stages I and VIII. Both claudins were observed in the pachytene spermatocytes and the developing acrosome of the round and elongating spermatids. Claudin-5 was also detected in the cytoplasm of some spermatogonia, Sertoli cells, and late spermatid acrosome. In the epididymal segments, both claudins were localized to the area of the tight junctions and along the entire length of the lateral plasma membranes of adjacent principal cells and between principal and basal cells. These results may indicate that in the domestic cat, claudin-1 and -5 participate as both tight junction proteins and adhesion molecules in the BEB's structure, claudin 5 is a component of the BTB, and both proteins may be involved in postmeiotic germ cell development, especially acrosome development.

Embryonic 6:2 FTOH exposure causes reproductive toxicity by disrupting the formation of the blood-testis barrier in offspring mice

Previous studies have revealed nephrotoxicity, hepatotoxicity, subchronic developmental and reproductive toxicity in rats exposed to fluorotelomer alcohol (FTOH). However, the effects of embryonic 6:2 FTOH exposure on the reproductive system of offspring mice remain unclear. The purpose of this study is to explore the reproductive toxic effects of embryonic 6:2 FTOH exposure on offspring male mice and the related molecular mechanisms. Therefore, the pregnant mice were given corn oil or 6:2 FTOH by gavage from gestational days 12.5-21.5. The results demonstrated that embryonic 6:2 FTOH exposure resulted in disrupted testicular structure, low expression of tight junction protein between Sertoli cells (SCs), impaired blood-testis barrier (BTB) formation and maturation, reduced sperm viability and increased malformation, and induced testicular inflammation in the offspring of mice. Further in vitro studies showed that 6:2 FTOH treatment upregulated MMP-8 expression by activating AKT/NF-κB signaling pathway, which in turn enhanced occludin cleavage leading to the disruption of SCs barrier integrity. In summary, this study demonstrated that 6:2 FTOH exposure caused reproductive dysfunction in male offspring through disruption of BTB, which provided new insights into the effects of 6:2 FTOH exposure on the offspring.

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.

Two acquired mouse Y chromosome-linked genes, Prssly and Teyorf1, are dispensable for male fertility‡

Prssly (Protease, serine-like, Chr Y) and Teyorf1 (Testis expressed, chromosome Y open reading frame 1) are two acquired single-copy genes located on the distal tip of the non-pairing short arm of the mouse Y chromosome adjacent to telomeric sequence. Both genes lack X chromosome-linked homologues and are expressed in testicular germ cells. We first performed analysis of Prssly and Teyorf1 genomic sequences and demonstrated that previously reported Prssly sequence is erroneous and the true Prssly sequence is longer and encodes a larger protein than previously estimated. We also confirmed that both genes encode pseudogenes that are not expressed in testes. Next, using CRISPR/Cas9 genome targeting, we generated Prssly and Teyorf1 knockout (KO) mice and characterized their phenotype. To create Prssly KO mice, we targeted the conserved exon 5 encoding a trypsin domain typical for serine proteases. The targeting was successful and resulted in a frame shift mutation that introduced a premature stop codon, with the Prssly KO males retaining only residual transcript expression in testes. The Teyorf1 targeting removed the entire open reading frame of the gene, which resulted in no transcript expression in KO males. Both Prssly KO and Teyorf1 KO males were fertile and had normal testis size and normal sperm number, motility, and morphology. Our findings show that Prssly and Teyorf1 transcripts with potential to encode proteins are dispensable for male fertility.

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.

Junctional complexes of the blood-testis barrier in the Japanese quail (Coturnix Coturnix japonica)

This study investigated the developmental changes in the adherens junctions, gap junctions, as well as tight junctions forming the blood-testis barrier (BTB) in Japanese quail (Coturnix Coturnix japonica) testis. Testicular tissue from pre-pubertal, pubertal, adult, and aged Japanese quail were examined by immunohistochemistry and transmission electron microscopy (TEM). The tight junction proteins claudin-3, claudin-11, occludin and zonula occludens-1 (ZO-1), were generally localised in the cytoplasm of Sertoli cells, spermatogonia, and spermatocytes of pre-pubertal, pubertal, some adult birds. The adherens junction protein E-cadherin had a similar distribution pattern. During pre-pubertal development, the gap junction protein connexin-43 (Cx43) was only localised between Leydig cells in the testicular interstitium. However, TEM revealed the presence of gap junctions between cells of the seminiferous epithelium as early as the pre-pubertal stage. Furthermore, TEM confirmed the presence of tight and adherens junctions in the seminiferous epithelia of all age groups. The findings of this study document age-related differences in the immunolocalisation and intensity of the junctional proteins and the ultrastructure of the junctional complexes forming the BTB in quail testes. Additionally, the junctional complexes forming the BTB in the Japanese quail are well established prior to puberty. This study provides baseline information for the future evaluation of pathological changes in the BTB of avian species at different developmental stages.

Emerging organoid models to study the epididymis in male reproductive toxicology

The importance of the epididymis on sperm maturation and consequently male fertility has been well documented. The pseudostratified epithelium of the epididymis is comprised of multiple cell types, including principal cells, which are the most abundant, and basal cells. The role of basal cells has been unclear and has been a source of discussion in the literature. However, the recent demonstration that these cells are multipotent or adult stem cells has opened new areas of research in epididymal biology. One such avenue is to understand the regulation of these stem cells, and to exploit their properties to develop tools for toxicological studies to elucidate the effects of chemicals on cell differentiation and epididymal function in vitro. Studies in both rat and mouse have shown that purified single epididymal basal cells cultured under 3D conditions can proliferate and differentiate to form organoids, or mini organs. Furthermore, these epididymal basal stem cells can self-renew and differentiate into other epididymal cell types. It is known that during epididymal development, basal cells are derived from undifferentiated columnar cells, which have been reported to share common properties to stem cells. Like basal cells, these undifferentiated columnar cells can also form organoids under 3D culture conditions and can differentiate into basal, principal and clear cells. Organoids derived from either basal cells or columnar cells offer unique models for toxicology studies and represent an exciting and emerging approach to understand the epididymis.

The Role of ZIP9 and Androgen Receptor in the Establishment of Tight Junctions between Adult Rat Sertoli Cells

The blood-testis barrier (BTB) is formed from tight junctions (TJs) between Sertoli cells. This dynamic structure, which establishes an immune-privileged environment protecting haploid germ cells formed in puberty from cells of the innate immune system, protects male fertility. Testosterone produced in Leydig cells is one of the main regulators of TJ protein expression and BTB dynamics. Nevertheless, although it has been assumed that testosterone effects on TJs and BTB are mediated through the classical androgen receptor (AR), newer results call the importance of this receptor into question. ZIP9, a recently identified androgen receptor of plasma membranes, mediates testosterone effects that promote the expression of TJ proteins and TJ formation in a rat Sertoli cell line that lacks the classical AR. Although these findings suggest that ZIP9 mediates these testosterone effects, participation of the classical AR in these events cannot be excluded. Here we used immortalized adult rat Sertoli cells that express both ZIP9 and AR and addressed the involvement of these receptors in the stimulation of TJ protein expression and TJ formation in response to testosterone and to the androgenic peptide IAPG that acts via ZIP9. We find that both testosterone and IAPG trigger the so-called non-classical signaling pathway of testosterone and stimulate the expression of TJ-associated proteins and TJ formation. Silencing classical AR expression had no effect on the responses, whereas silencing of ZIP9 expression completely blocked them. Our results demonstrate that ZIP9 is the sole androgen receptor involved in the regulation of TJ protein expression and TJ formation at the BTB.

Differential expression and localization of tight junction proteins in the goat epididymis

The blood-epididymis barrier (BEB) forms a unique microenvironment that is crucial for the maturation, protection, transport, and storage of spermatozoa in the epididymis. To characterize the function of tight junctions (TJs), which are constitutive components of the BEB, we determined the expression and localization of TJ proteins such as zonula occludens (ZO)-1, 2, and 3, occludin, and claudin3 (Cldn3) during postnatal development in the goat epididymis. To assess the expression patterns of TJ proteins in immature (3 months of age) and mature (14 months of age) goat epididymides, two different experimental methods were used including immunofluorescence labeling and western blotting. We show that, ZO-1, 2, and 3, and occludin, were strictly expressed and localized to the TJs of the goat epididymis, whereas Cldn3 was present in basolateral membranes as well as TJs. All TJ proteins examined were more highly expressed in the immature epididymis compared to levels in mature tissue. In conclusion, our study indicates that at least five TJ proteins, namely ZO-1, ZO-2, ZO-3, occludin, and Cldn3, are present in TJs, and the expression strength and pattern of TJ proteins tend to be age dependent in the goat epididymis. Together, these data suggest that the distinct expression patterns of TJ proteins are essential for regulating components of the luminal contents in the epididymal epithelium and for forming adequate luminal conditions that are necessary for the maturation, protection, transport, and storage of spermatozoa in the goat epididymis.

Follicle-stimulating hormone-mediated decline in miR-92a-3p expression in pubertal mice Sertoli cells is crucial for germ cell differentiation and fertility

Sertoli cells (Sc) are the sole target of follicle-stimulating hormone (FSH) in the testis and attain functional maturation post-birth to significantly augment germ cell (Gc) division and differentiation at puberty. Despite having an operational microRNA (miRNA) machinery, limited information is available on miRNA-mediated regulation of Sc maturation and male fertility. We have shown before that miR-92a-3p levels decline in pubertal rat Sc. In response to FSH treatment, the expressions of FSH Receptor, Claudin11 and Klf4 were found to be elevated in pubertal rat Sc coinciding with our finding of FSH-induced decline in miR-92a-3p levels. To investigate the association of miR-92a-3p and spermatogenesis, we generated transgenic mice where such pubertal decline of miR-92a-3p was prevented by its overexpression in pubertal Sc under proximal Rhox5 promoter, which is known to be activated specifically at puberty, in Sc. Our in vivo observations provided substantial evidence that FSH-induced decline in miR-92a-3p expression during Sc maturation acts as an essential prerequisite for the pubertal onset of spermatogenesis. Elevated expression of miR-92a-3p in post-pubertal testes results into functionally compromised Sc, leading to impairment of the blood-testis barrier formation and apoptosis of pre-meiotic Gc, ultimately culminating into infertility. Collectively, our data suggest that regulation of miR-92a-3p expression is crucial for Sc-mediated induction of active spermatogenesis at puberty and regulation of male fertility.

Tetrapeptides Modelled to the Androgen Binding Site of ZIP9 Stimulate Expression of Tight Junction Proteins and Tight Junction Formation in Sertoli Cells

Androgens stimulate the expression of tight junction (TJ) proteins and the formation of the blood-testis barrier (BTB). Interactions of testosterone with the zinc transporter ZIP9 stimulate the expression of TJ-forming proteins and promote TJ formation in Sertoli cells. In order to investigate androgenic effects mediated by ZIP9 but not by the nuclear androgen receptor (AR), the effects of three tetrapeptides fitting the androgen binding site of ZIP9 were compared with those induced by testosterone in a Sertoli cell line expressing ZIP9 but not the AR. Three tetrapeptides and testosterone displaced testosterone-BSA-FITC from the surface of 93RS2 cells and stimulated the non-classical testosterone signaling pathway that includes the activation of Erk1/2 kinases and transcription factors CREB and ATF-1. The expression of the TJ-associated proteins ZO-1 and claudin-5 was triggered as was the re-distribution of claudin-1 from the cytosol to the membrane and nucleus. Furthermore, TJ formation was stimulated, indicated by increased transepithelial electrical resistance. Silencing ZIP9 expression by siRNA prevented all of these responses. These results are consistent with an alternative pathway for testosterone action at the BTB that does not involve the nuclear AR and highlight the significant role of ZIP9 as a cell-surface androgen receptor that stimulates TJ formation.

New Insight into Molecular and Hormonal Connection in Andrology

Hormones and cytokines are known to regulate cellular functions in the testes. These biomolecules induce a broad spectrum of effects on various level of spermatogenesis, and among them is the modulation of cell junction restructuring between Sertoli cells and germ cells in the seminiferous epithelium. Cytokines and androgens are closely related, and both correct testicular development and the maintenance of spermatogenesis depend on their function. Cytokines also play a crucial role in the immune testicular system, activating and directing leucocytes across the endothelial barrier to the inflammatory site, as well as in increasing their adhesion to the vascular wall. The purpose of this review is to revise the most recent findings on molecular mechanisms that play a key role in male sexual function, focusing on three specific molecular patterns, namely, cytokines, miRNAs, and endothelial progenitor cells. Numerous reports on the interactions between the immune and endocrine systems can be found in the literature. However, there is not yet a multi-approach review of the literature underlying the role between molecular patterns and testicular and sexual function.

Cripto-1 as a Key Factor in Tumor Progression, Epithelial to Mesenchymal Transition and Cancer Stem Cells

Cripto-1 is an essential protein for human development that plays a key role in the early phase of gastrulation in the differentiation of an embryo as well as assists with wound healing processes. Importantly, Cripto-1 induces epithelial to mesenchymal transition to turn fixed epithelial cells into a more mobile mesenchymal phenotype through the downregulation of epithelial adhesion molecules such as E-cadherin, occludins, and claudins, and the upregulation of mesenchymal, mobile proteins, such as N-cadherin, Snail, and Slug. Consequently, Cripto-1’s role in inducing EMT to promote cell motility is beneficial in embryogenesis, but detrimental in the formation, progression and metastasis of malignant tumors. Indeed, Cripto-1 is found to be upregulated in most cancers, such as breast, lung, gastrointestinal, hepatic, renal, cervical, ovarian, prostate, and skin cancers. Through its role in EMT, Cripto-1 can remodel cancer cells to enable them to travel through the extracellular matrix as well as blood and lymphatic vessels to metastasize to different organs. Additionally, Cripto-1 promotes the survival of cancer stem cells, which can lead to relapse in cancer patients.

Pubertal down-regulation of Tetraspanin 8 in testicular Sertoli cells is crucial for male fertility

The alarming decline in sperm count has become a global concern in the recent decades. The division and differentiation of male germ cells (Gc) into sperm are governed by Sertoli cells (Sc) upon their functional maturation during puberty. However, the roles of genes regulating pubertal maturation of Sc have not been fully determined. We have observed that Tetraspanin 8 (Tspan8) is down-regulated in Sc during puberty in rats. However, there has been no in vivo evidence for a causal link between the down-regulation of Tspan8 expression and the onset of spermatogenesis as yet. To investigate this, we generated a novel transgenic (Tg) rat, in which the natural down-regulation of Tspan8 was prevented specifically in Sc from puberty up to adulthood. Adult Tg male rats showed around 98% reduction in sperm count despite having a similar level of serum testosterone (T) as the controls. Functional maturation of Sc was impaired as indicated by elevated levels of Amh and low levels of Kitlg and Claudin11 transcripts. The integrity of the blood testis barrier was compromised due to poor expression of Gja1 and Gc apoptosis was discernible. This effect was due to a significant rise in both Mmp7 and phospho P38 MAPK in Tg rat testis. Taken together, we demonstrated that the natural down-regulation of Tspan8 in Sc during puberty is a prerequisite for establishing male fertility. This study divulges one of the aetiologies of certain forms of idiopathic male infertility where somatic cell defect, but not hormonal deficiency, is responsible for impaired spermatogenesis.

Investigation of Prognostic Value of Claudin-5, PSMA, and Ki67 Expression in Canine Splenic Hemangiosarcoma

Splenic hemangiosarcoma (HSA) is a malignant tumor of endothelial cells that affects middle-aged and elderly dogs and is characterized by the formation of new blood vessels, commonly associated with necrotic and hemorrhagic areas. Despite its importance in veterinary medicine, few studies have identified markers with prognostic value for canine HSA. Thus, this study aimed to associate the clinicopathological findings (prostate-specific membrane antigen [PSMA], Claudin-5, and Ki67 gene and protein expression) with overall survival in HSA-affected patients. Fifty-three formalin-fixed and paraffin-embedded canine splenic HSA samples, previously diagnosed by histopathological examination, were used in this study. Claudin-5, PSMA, and Ki67 protein expression levels were evaluated by immunohistochemistry, and gene expression was evaluated by quantitative polymerase chain reaction. Claudin-5 protein overexpression was observed in patients with metastasis (p = 0.0078) and with stage III tumors compared to those with stage I and II tumors (p = 0.0451). In patients treated with surgery alone, low PSMA gene and protein expression (p = 0.05 and p = 0.0355, respectively) were associated with longer survival time. Longer survival time was observed in patients with a low Ki67 index (p = 0.0488). Our results indicate that Claudin-5 protein expression is associated with metastatic status, and PSMA gene and protein expression, and Ki67 index are associated with survival time.

Therapeutic effects of thymoquinone or capsaicin on acrylamide-induced reproductive toxicity in rats mediated by their effect on oxidative stress, inflammation, and tight junction integrity

In the field of environmental toxicology, endocrine-disrupting effects have become a major concern. The present research set out to investigate the possible reproductive toxicity of acrylamide. The research was also expanded to explore the protective effects of two nutraceuticals, thymoquinone (TQ) and capsaicin, against acrylamide-induced reproductive toxicity. Six groups of sixty male albino rats were created. Group 1 was used as a control. Rats were administered a daily dose of acrylamide and acted as the model in Group 2. TQ was provided to rats once a day in Group 3. Capsaicin was administered to rats once a day in Group 4. TQ was given once daily to rats exposed to acrylamide in Group 5. Rats were given capsaicin once a day for eight weeks after being exposed to acrylamide in Group 6. Acrylamide induced oxidative stress, testicular NF-κB/p65 expression, and down-regulated the expression of occludin, all of which can contribute to its testicular toxicity, while TQ or capsaicin removes all of these toxicity signs. TQ and capsaicin have shown efficacy in alleviating all of the acrylamide's toxic insults in the current reproductive toxicity model. Both nutraceuticals upregulated the expression of occludin in testicular tissue and restored tight junction integrity, in addition to their well-known antioxidant and anti-inflammatory effects, which were confirmed in this study.

Pathogenesis of Brucella epididymoorchitis-game of Brucella death

Brucellosis is a worldwide zoonotic disease caused by Brucella spp. Human infection often results from direct contact with tissues from infected animals or by consumption of undercooked meat and unpasteurised dairy products, causing serious economic losses and public health problems. The male genitourinary system is a common involved system in patients with brucellosis. Among them, unilateral orchitis and epididymitis are the most common. Although the clinical and imaging aspect of orchi-epididymitis caused by brucellosis have been widely described, the cellular and molecular mechanisms involved in the damage and the immune response in testis and epididymis have not been fully elucidated. In this review, we first summarised the clinical characteristics of Brucella epididymo-orchitis and the composition of testicular and epididymal immune system. Secondly, with regard to the mechanism of Brucella epididymoorchitis, we mainly discussed the process of Brucella invading testis and epididymis in temporal and spatial order, including i) Brucella evades innate immune recognition of testicular PRRs；ii) Brucella overcomes the immune storm triggered by the invasion of testis through bacterial lipoproteins and virulence factors, and changes the secretion mode of cytokines; iii) Brucella breaks through the blood-testis barrier with the help of macrophages, and inflammatory cytokines promote the oxidative stress of Sertoli cells, damaging the integrity of BTB; iv) Brucella inhibits apoptosis of testicular phagocytes. Finally, we revealed the structure and sequence of testis invaded by Brucella at the tissue level. This review will enable us to better understand the pathogenesis of orchi-epididymitis caused by brucellosis and shed light on the development of new treatment strategies for the treatment of brucellosis and the prevention of transition to chronic form. Facing the testicle with immunity privilege, Brucella is like Bruce Lee in the movie Game of Death, winning is survival while losing is death.HIGHLIGHTSWe summarized the clinical features and pathological changes of Brucellaepididymoorchitis.Our research reveals the pathogenesis of Brucella epididymoorchitis, which mainly includes the subversion of testicular immune privilege by Brucella and a series of destructive reactions derived from it.As a basic framework and valuable resource, this study can promote the exploration of the pathogenesis of Brucella and provide reference for determining new therapeutic targets for brucellosis in the future.

An in vitro bioassay to assess the potential global toxicity of waters on spermatogenesis: a pilot study

Many toxicants are present in water as a mixture. Male infertility is one of the environmental impacts in developed countries. Using our rat seminiferous tubule culture model, we evaluated the effects of waters of different origins, on several parameters of the seminiferous epithelium. Concentrated culture medium was diluted with the waters to be tested (final concentrations of the tested waters were between 8 and 80%). The integrity of the blood-testis barrier was assessed by the trans-epithelial electric resistance (TEER). The levels of mRNAs specific of Sertoli cells, of cellular junctions, of each population of germ cells, of androgen receptor, of estrogen receptor α, and of aromatase were also studied. We report, here, the results obtained with ten waters, some of them possessing a negative effect on spermatogenesis. The results showed that, according to the tested waters, their effects on the parameters studied might be quite different indicating many different mechanisms of toxicity, including some endocrine-disrupting effects. It has been reported that men with impaired semen parameters have an increased mortality rate suggesting semen quality may provide a fundamental biomarker of overall male health. Hence, we have developed a relevant in vitro bioassay allowing the evaluation of the potential toxicity of different types of waters on male fertility and to assess some aspects of their mechanism of action. In addition to the TEER measure, the number and/or the identity of the studied mRNAs can be largely increased and/or modified, thus enhancing the possibility of using this model as a "warning system."

Tight junctions and their regulation by non-coding RNAs

Tight junction (TJ) is a “zippering up” junction structure located at the uppermost portion of adjacent epithelial/endothelial cells in organs and tissues. TJs maintain the relative stability of intracellular substances and functions by closing or opening intercellular pathways, coordinating the entry and exit of molecules of different sizes and charges, and regulating the permeability of paracellular barrier. TJs also prevent microbial invasion, maintain epithelial/endothelial cell polarity, and regulate cell proliferation. TJs are widely present in the skin and mucosal epithelial barriers, intestinal epithelial barrier, glomerular filtration barrier, bladder epithelial barrier, blood-brain barrier, brain-blood tumor barrier, and blood-testis barrier. TJ dysfunction in different organs can lead to a variety of diseases. In addition to signal pathways, transcription factors, DNA methylation, histone modification, TJ proteins can also be regulated by a variety of non-coding RNAs, such as micro-RNAs, long-noncoding RNAs, and circular RNAs, directly or indirectly. This review summarizes the structure of TJs and introduces the functions and regulatory mechanisms of TJs in different organs and tissues. The roles and mechanisms of non-coding RNAs in the regulation of TJs are also highlighted in this review.

Regulation of Human Spermatogenesis

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].

The Effect of Lead Acetate and Quercetin on the Tight and Gap Junctions in the Mouse Testis

Environmental pollutant effects on fertility sometime are irretrievable. The aim of this study was to investigate the effect of lead acetate and quercetin on tight (claudin 11 and occludin) and gap junctional (connexin 43) proteins and the integrity of the blood-testis barrier status. Experimental groups, including the lead acetate (Pb), quercetin (QE), lead acetate with quercetin (Pb + QE), and control mice, were treated at least one spermatogenic cycle. Gene expression of claudin 11 and occludin decreased in Pb + QE, Pb, and QE compared with the control group. Connexin 43 (Cx43) expression in the control and Pb groups was lower than in Pb + QE and QE. The immunohistochemical data were generally in line with these findings. In conclusion, the results showed that Pb exposure led to disorders in cellular interactions that affect testicular function; however, simultaneous treatment with quercetin did not alleviate these effects. Graphical Abstract.

Oleanolic acid causes reversible contraception in male mice by increasing the permeability of the germinal epithelium

The effects of oleanolic acid (OA) on the fertility of male mice were investigated using both invivo and invitro experimental models. The experimental group (n=12) was treated with a daily dose of 30mgOAkg-1 bodyweight (i.p.), while the control group (n=6) received a daily dose of 10% ethanol solution (1mLkg-1 bodyweight). The effect of OA on the permeability status of TM4 Sertoli monolayers was investigated by measuring the transepithelial electrical resistance (TER), intracellular electrical resistance and semiquantitative RT-PCR. After 45 days, OA-treated males produced no pregnancies but in the control group, all 12 females were impregnated (69 offspring). Male mice, which demonstrated sterility when exposed to OA, recovered their fertility after 30 days (78 offspring). Testicular histological observations of OA-treated mice showed detachment of adjacent Sertoli-Sertoli cells. A control monolayer developed TER of 300-400 Ω.cm2, but OA (50, 100, 200µgL-1) treated monolayers developed TER of approximately 100Ω.cm2. Intracellular electrophysiological and RT-PCR data supported the premise that OA compromised tight junctional permeability. The study demonstrated reversible contraception in male mice by increasing the permeability of the germinal epithelium and further postulates that contraceptive reversibility is brought about by the reconstitution of the paracellular junctions between adjacent Sertoli cells.

Prenatal exposure to excess chromium attenuates transcription factors regulating expression of androgen and follicle stimulating hormone receptors in Sertoli cells of prepuberal rats

We have reported that gestational exposure to hexavalent chromium (CrVI) represses androgen receptor (Ar) and follicle stimulating hormone receptor (Fshr) in Sertoli cells (SCs) of adult rats, while the mechanism underlying remains obscure. We tested the hypothesis "transient gestational exposure to CrVI during the critical embryonic windows of testicular differentiation and growth may have adverse impact on transcription factors controlling the expression of Ar and Fshr in SCs of the F₁ progeny". CrVI (K₂Cr₂O₇) was given through drinking water (50 ppm, 100 ppm and 200 ppm), to pregnant rats from gestational day 9-14 (testicular differentiation) and 15 to 21 (prenatal differentiation and proliferation of SC); male progenies were sacrificed on postnatal day 30 (Completion of postnatal SC maturation). A significant increase in free radicals and decrease in enzymatic and non-enzymatic antioxidants were observed in SCs of experimental rats. Real time PCR and western blot data showed decreased expression of Ar, Fshr, Inhibin B, Transferrin, Androgen binding protein, Claudin 11 and Occludin in SCs of experimental rats; concentrations of lactate, pyruvate and retinoic acid also decreased. Serum FSH, luteinizing hormone and estradiol increased, whereas testosterone and prolactin decreased in experimental rats. Western blot detection revealed decreased levels of transcription factors regulating Fshr viz., USF-1, USF-2, SF-1, c-fos, c-jun and GATA 1, and those of Ar viz., Sp-1, ARA54, SRC-1 and CBP in experimental rats, whereas the levels of cyclinD1 and p53, repressors of Ar increased. ChIP assay detected decreased USF-1 and USF-2 binding to Fshr promoter, and binding of Sp-1 to Ar promoter. We conclude that gestational exposure to CrVI affects SC structure and function in F₁ progeny by inducing oxidative stress and diminishing the expression of Ar and Fshr through attenuation of their specific transcriptional regulators and their interaction with the respective promoter.

Whole-body heat exposure causes developmental stage-specific apoptosis of male germ cells

Humans are occasionally exposed to extreme environmental heat for a prolonged period of time. Here, we investigated testicular responses to whole-body heat exposure by placing mice in a warm chamber. Among the examined tissues, the testis was found to be most susceptible to heat stress. Heat stress induces direct responses within germ cells, such as eukaryotic initiation factor 2α phosphorylation and stress granule (SG) formation. Prolonged heat stress (42°C for 6 hr) also disturbed tissue organization, such as through blood-testis barrier (BTB) leakage. Germ cell apoptosis was induced by heat stress for 6 hr in a cell type- and developmental stage-specific manner. We previously showed that spermatocytes in the early tubular stages (I-VI) form SGs for protection against heat stress. In the mid-tubular stages (VII-VIII), BTB leakage synergistically enhances the adverse effects of heat stress on pachytene spermatocyte apoptosis. In the late tubular stages (IX-XII), SGs are not formed and severe leakage of the BTB does not occur, resulting in mild apoptosis of late-pachytene spermatocytes near meiosis. Our results revealed that multiple stress responses are involved in germ cell damage resulting from prolonged heat stress (42°C for 6 hr).

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.

Effect of mirabegron on tight junction molecules in primary cultured rat Sertoli cells

Mirabegron is a selective beta3-adrenoceptor (β₃ -AR) agonist, which is commonly used for the treatment of overactive bladder. This medicine is associated with atrophy of reproductive organs in rats. However, no study has examined the detailed action and mechanism of its toxicity in reproductive cells. In this study, we examined the effect of mirabegron on primary cultured rat Sertoli cells. Firstly, RT-PCR and immunocytochemistry revealed that β₃ -AR was present in rat Sertoli cells. Then, primary cultured rat Sertoli cells were treated with mirabegron. Quantitative real-time PCR revealed that mirabegron treatment induced a significant increase in claudin-11 mRNA, which is crucial for spermatogenesis. Western blot analysis also showed that mirabegron treatment significantly activated p44/42 mitogen-activated protein kinase (MAPK). After additional treatment with U0126, a specific noncompetitive inhibitor of mitogen-activated protein kinase kinase (MAPKK), the upregulation of claudin-11 mRNA induced by mirabegron was reduced. At the same time, immunocytochemistry showed mirabegron treatment disturbed claudin-11 localisation to tight junction, which was recovered when treated with mirabegron in the presence of U0126. These results suggest that mirabegron treatment is associated with assembly of the blood-testis barrier through p44/42 MAPK pathway. These findings could explain one of the underlying mechanisms of reproductive toxicity induced by mirabegron.

Impaired Localization of Claudin-11 in Endometriotic Epithelial Cells Compared to Endometrial Cells

Claudins are the major components of tight junctions and are often deregulated in human cancer, permitting escape of cancer cells along with the acquisition of invasive properties. Similarly, endometrial cells also show invasive capabilities; however, the role of tight junctions in endometriosis has only rarely been examined. In this study, we analyzed the protein expression and localization of claudin-7 and claudin-11 in human eutopic and ectopic endometrium and endometrial cell lines. We identified claudin-7 primarily at the basolateral junctions of the glandular epithelial cells in eutopic endometrium as well as in the ectopic lesions in nearly all glands and cysts. Quantification of claudin-7 localization by HSCORE showed a slight increase in peritoneal and deep infiltrating endometriosis (DIE) compared to eutopic endometrium. In contrast, claudin-11 was localized mainly in the apicolateral junctions in nearly all glandular epithelial cells of the eutopic endometrium. Interestingly, we observed a deregulation of claudin-11 localization to a basal or basolateral localization in ovarian (P < .001), peritoneal (P < .01), and DIE (P < .05) and a moderately decreased abundance in ovarian endometriosis. In endometrial cell lines, claudin-7 was only present in epithelial Ishikawa cells, and silencing by small-interfering RNA increased cell invasiveness. In contrast, claudin-11 could be demonstrated in Ishikawa and endometriotic 12Z and 49Z cells. Silencing of claudin-11 decreased invasiveness of 12Z slightly but significantly in 49Z. We suggest that although claudin-7 and claudin-11 can be found in nearly all eutopic and ectopic epithelial cells, the impaired localization of claudin-11 in ectopic endometrium might contribute to the pathogenesis of endometriosis.

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.

Subchronic reproductive effects of 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFAES), an alternative to PFOS, on adult male mice

With a similar structure to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFAES) has been widely used as a mist suppressant in the chromium plating industry in China since the 1970s. After being disregarded for the past 30 years, 6:2 Cl-PFAES has now been detected in environmental matrices and human sera, suggesting potential health concerns. We carried out a subchronic exposure study to investigate the reproductive toxicity of 6:2 Cl-PFAES exposure (0, 0.04, 0.2, and 1.0 mg/kg/d body weight, 56 d) in adult male BALB/c mice. Results showed that relative epididymis and testis weights decreased in the 1.0 mg/kg/d group compared with the control. However, no changes were observed in the serum levels of testosterone, estradiol, follicle-stimulating hormone (FSH), or luteinizing hormone (LH), nor in the histopathological structure of the epididymis and testis and sperm count. In addition, 56 d of consecutive gavage of 1.0 mg/kg/d of 6:2 Cl-PFAES did not affect male mouse fertility. RNA sequencing showed that no genes were significantly altered in the testes after 6:2 Cl-PFAES exposure. Several testicular genes, which are sensitive to PFOS exposure, were also detected using Western blotting, and included steroidogenic proteins, STAR, CYP11A1, CYP17A1, and 3β-HSD and cell junction proteins, occludin, β-catenin, and connexin 43; however, none were changed after 6:2 Cl-PFAES exposure. Except for a decrease in the relative epididymis and testis weights in the 1.0 mg/kg/d group, 6:2 Cl-PFAES exposure for 56 d exerted no significant effect on the serum levels of reproductive hormones or the testicular mRNA profilesin adult male mice, implying a relative weak reproductive injury potential compared with that of PFOS.

Melamine causes testicular toxicity by destroying blood-testis barrier in piglets

Melamine (MA) exposure causes male reproductive toxicity, however, the mechanism remains unclear. In this study, we investigated the roles of the blood-testis barrier (BTB) in MA-induced reproductive toxicity in piglets. Male weaned piglets were exposed to MA concentrations of 0, 100, 300, and 1000 mg/kg in the diet for 10 weeks. They were euthanized on days 1, 7 and 14 after the final exposure. Body and organ weights, serum biochemistry and testosterone, gross and histopathological changes, and BTB ultrastructure and integrity were assessed. BTB junction protein expression levels and protein levels of the mitogen-activated protein kinase (MAPK) pathway in testes were measured. We found that MA dose-dependently decreased serum testosterone levels and caused gross and histopathological lesions in the testis and epididymis. Marked BTB damage was evidenced by abnormal changes in BTB ultrastructure and increased BTB permeability. Furthermore, MA decreased the protein levels of ZO-1, occludin, N-cadherin, and connexin-43, paralleled by increased the protein levels of p-Erk, p-JNK and p-p38 in testes, suggesting that MA disrupted BTB by downregulating the expressions of BTB junction proteins, with possible involvement of the MAPK signaling pathway. In conclusion, MA exposure gives rise to testicular toxicity in male piglets through destroying BTB integrity.

Role of the Na+/K+-ATPase ion pump in male reproduction and embryo development

Na⁺/K⁺-ATPase was one of the first ion pumps studied because of its importance in maintaining osmotic and ionic balances between intracellular and extracellular environments, through the exchange of three Na⁺ ions out and two K⁺ ions into a cell. This enzyme, which comprises two main subunits (α and β), with or without an auxiliary polypeptide (γ), can have specific biochemical properties depending on the expression of associated isoforms (α1β1 and/or α2β1) in the cell. In addition to the importance of Na⁺/K⁺-ATPase in ensuring the function of many tissues (e.g. brain, heart and kidney), in the reproductive tract this protein is essential for embryo development because of its roles in blastocoel formation and embryo hatching. In the context of male reproduction, the discovery of a very specific subunit (α4), apparently restricted to male germ cells, only expressed after puberty and able to influence sperm function (e.g. motility and capacitation), opened a remarkable field for further investigations regarding sperm biology. Therefore, the present review focuses on the importance of Na⁺/K⁺-ATPase on male reproduction and embryo development.

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 ubiquitous isoform of Na/K-ATPase (ATP1A1) regulates junctional proteins, connexin 43 and claudin 11 via Src-EGFR-ERK1/2-CREB pathway in rat Sertoli cells

Interaction of Na/K-ATPase with its ligand ouabain has been implicated in the regulation of various biological processes. The objective was to investigate roles of Na/K-ATPase isoforms in formation and function of junctional complexes in Sertoli cells. Primary cultures of Sertoli cells were obtained by enzymatic digestion of 20-day-old rat testes and grown on Matrigel-coated dishes for 7 days. Sertoli cells predominantly expressed the ubiquitous isoform of Na/K-ATPase (ATP1A1), confirmed by immunoblotting, PCR, immunofluorescence, and mass spectrometry. Treatment of Sertoli cells with 50 nM ouabain increased transepithelial electrical resistance (TER) and expression of claudin 11 (tight junctions) and connexin 43 (gap junctions), whereas 1 mM ouabain had opposite effects. Involvement of Src-EGFR-ERK1/2-CREB pathway in ouabain-mediated expression of claudin 11 and connexin 43 was evaluated. Incubation of Sertoli cells with 50 nM ouabain increased content of p-Src, p-EGFR, p-ERK1/2, and p-CREB; in contrast, 1 mM ouabain decreased phosphorylation of these signaling molecules. Preincubation of Sertoli cells with inhibitors of Src and MAPK pathways inhibited ouabain-induced effects on these signaling molecules, TER, and expression of claudin 11 and connexin 43. In conclusion, we inferred that ATP1A1 regulated Sertoli cell tight junctions and gap junctions through the Src-EGFR-ERK1/2-CREB pathway. Ouabain is an endogenous steroid; therefore, its interaction with ATP1A1 may be a critical signaling mechanism for the regulation of Sertoli cell function and male fertility.

Characterization of inter-Sertoli cell tight and gap junctions in the testis of turtle: Protect the developing germ cells from an immune response

It is conceivable that early developing germ cells must across the basal to the luminal region of seminiferous tubules (STs) during spermatogenesis is associated with extensive restructuring of junctional complex. However, very limited information is documented about these junctional complexes in reptiles. In the present study we have determined the localization of inter-Sertoli cell tight junctions (TJ's), protein CLDN11 and gap junction protein Cx43 during spermatogenesis in the testis. In early spermatogenesis, weak immunoreactivity of CLDN11and focal localization of Cx43 was observed around the Sertoli cell in the luminal region, but completely delaminated from the basal compartment of STs. In late spermatogenesis, strong focal to linear localization of CLDN11and Cx43 was detected at the points of contact between two Sertoli cells and around the early stages of primary spermatocytes in the basal compartment of STs. In late spermatogenesis, localization of CLDN11and Cx43 was drastically reduced and seen only around Sertoli cells and spermatogonia near the basal lamina. However, transmission electron microscopy revealed that inter-Sertoli cell tight junctions were present within the basal compartment of STs, leaving the spermatogonia and early primary spermatocytes in the basal region during mid spermatogenesis. Gap junctions were observed between Sertoli cells, and Sertoli cells with spermatogonia and primary spermatocytes throughout spermatogenesis. Moreover, adherens and hemidesmosomes junctions were observed during spermatogenesis. The above findings collectively suggest that the intensity and localization of TJ's and gap junctions vary according to the spermatogenetic stages that might be protected the developing germ cells from own immune response.

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.

Exogenous leptin affects sperm parameters and impairs blood testis barrier integrity in adult male mice

BACKGROUND

Serum leptin levels are augmented in obese infertile men and in men with azoospermia. They also correlate inversely with sperm concentration, motility and normal forms. The mechanisms underlying the adverse effects of excess leptin on male reproductive function remain unclear. The present study aimed to evaluate the effects of exogenous leptin on sperm parameters in mice and to explore the underlying mechanisms.

METHODS

We treated normal adult male mice with saline, 0.1, 0.5 or 3 mg/kg leptin daily for 2 weeks. After treatment, serum leptin levels, serum testosterone levels, sperm parameters and testicular cell apoptosis were evaluated. Blood testis barrier integrity and the expression of tight junction-associated proteins in testes were also assessed. We further verified the direct effects of leptin on tight junction-associated proteins in Sertoli cells and the possible leptin signaling pathways involved in this process.

RESULTS

After treatment, there were no significant differences in body weights, reproductive organ weights, serum leptin levels and serum testosterone levels between leptin-treated mice and control mice. Administration of 3 mg/kg leptin reduced sperm concentration, motility and progressive motility while increasing the percentage of abnormal sperm and testicular cell apoptosis. Mice treated with 3 mg/kg leptin also had impaired blood testis barrier integrity, which was related to decreased tight junction-associated proteins in testes. Leptin directly reduced tight junction-associated proteins in Sertoli cells, JAK2/STAT, PI3K and ERK pathways were suggested to be involved in this process.

CONCLUSIONS

Exogenous leptin negatively affects sperm parameters and impairs blood testis barrier integrity in mice. Leptin reduced tight junction-associated proteins in Sertoli cells, indicating that leptin has a direct role in impairing blood testis barrier integrity. Given the function of blood testis barrier in maintaining normal spermatogenesis, leptin-induced blood testis barrier impairment may be one of the mechanisms contributing to male subfertility and infertility.