Structure and turnover of junctional complexes between principal cells of the rat epididymis

Single-cell and spatial transcriptomic investigation reveals the spatiotemporal specificity of the beta-defensin gene family during mouse sperm maturation

Low sperm motility is a significant contributor to male infertility. beta-defensins have been implicated in host defence and the acquisition of sperm motility; however, the regulatory mechanisms governing their gene expression patterns and functions remain poorly understood. In this study, we performed single-cell RNA and spatial transcriptome sequencing to investigate the cellular composition of testicular and epididymal tissues and examined their gene expression characteristics. In the epididymis, we found that epididymal epithelial cells display a region specificity of gene expression in different epididymal segments, including the beta-defensin family genes. In particular, Defb15, Defb18, Defb20, Defb25 and Defb48 are specific to the caput; Defb22, Defb23 and Defb26 to the corpus; Defb2 and Defb9 to the cauda of the epididymis. To confirm this, we performed mRNA fluorescence in situ hybridisation (FISH) targeting certain exon region of beta-defensin genes, and found some of their expression matched the sequencing results and displayed a close connection with epididimosome marker gene Cd63. In addition, we paid attention to the Sertoli cells and Leydig cells in the testis, along with fibroblasts and smooth muscle cells in the epididymis, by demonstrating their gene expression profile and spatial information. Our study provides a single-cell and spatial landscape for analysing the gene expression characteristics of testicular and epididymal environments and has important implications for the study of spermatogenesis and sperm maturation.

The significance of single-cell transcriptome analysis in epididymis research

As a crucial component of the male reproductive system, the epididymis plays multiple roles, including sperm storage and secretion of nutritive fluids for sperm development and maturation. The acquisition of fertilization capacity by sperm occurs during their transport through the epididymis. Compared with the testis, little has been realized about the importance of the epididymis. However, with the development of molecular biology and single-cell sequencing technology, the importance of the epididymis for male fertility should be reconsidered. Recent studies have revealed that different regions of the epididymis exhibit distinct functions and cell type compositions, which are likely determined by variations in gene expression patterns. In this research, we primarily focused on elucidating the cellular composition and region-specific gene expression patterns within different segments of the epididymis and provided detailed insights into epididymal function in male fertility.

Seasonal variations of the epididymis in donkeys (Equus asinus) with special reference to blood epididymal barrier

The epididymis, a key component of the male reproductive system, controls spermatozoa's maturation, fertility, and storage. The objective of this study is to evaluate the histological, ultrastructural, and immunohistochemical variations in the epididymis of donkeys that occur throughout the year. During the breeding season (spring) and nonbreeding seasons (summer, autumn, and winter), 20 epididymis were collected from adult, clinically healthy donkeys. Compared to non-breeding seasons, the epididymal duct displayed a more active lining epithelium and more sperm in the lumen during the breeding season. The epithelial height is the lowest and the lumen is the widest during the breeding season. Furthermore, the epididymal epithelium in the tail region exhibits undulations with polyps-like projections. The epididymal epithelium is composed mainly of the principal, basal, and dark cells. Tight junction between adjacent principal cells is more obvious in the breeding season as compared to the non-breeding seasons. However, intraepithelial lymphocytes, phagocytic, and other immune cells are more frequent in non-breeding seasons. β-catenin, which is a component of the adherent junctions between adjacent PCs, exhibits more immunoreactivity during the spring. On the other hand, iNOS, an indicator of oxidative stress, reacts positively during the summer. Additionally, during non-breeding seasons, autophagy was detected within the epididymal epithelium which may be linked to stress adaptation. In conclusion, our findings suggest that the histological and ultrastructural characteristics of the epididymal epithelium are more active during spring compared to other seasons of the year. RESEARCH HIGHLIGHTS: The study aimed to evaluate the histological, ultrastructural, and immunohistochemical variations in the blood epididymal barrier (BEB) and epididymal epithelium of donkeys that occur throughout the year. In comparison to non-breeding seasons, the epididymal duct displayed a more active lining epithelium and more sperm in the lumen during the breeding season. The epithelial height is the lowest and the lumen is the widest during the breeding season. The epididymal epithelium in the tail region exhibits undulations with polyps-like projections that increase the surface area. β-catenin, which is a component of the adherent junctions between adjacent PCs, exhibits more immunoreactivity during the spring. On the other hand, iNOS, an indicator of oxidative stress, reacts positively during the summer.

Reactive Oxygen Species and Their Consequences on the Structure and Function of Mammalian Spermatozoa

Significance: Among the 200 or so cell types that comprise mammals, spermatozoa have an ambiguous relationship with the reactive oxygen species (ROS) inherent in the consumption of oxygen that supports aerobic metabolism. Recent Advances: In this review, we shall see that spermatozoa need the action of ROS to reach their structural and functional maturity, but that due to intrinsic unique characteristics, they are, perhaps more than any other cell type, susceptible to oxidative damage. Recent studies have improved our knowledge of how oxidative damage affects sperm structures and functions. The focus of this review will be on how genetic and epigenetic oxidative alterations to spermatozoa can have dramatic unintended consequences in terms of both the support and the suppression of sperm function. Critical Issues: Oxidative stress can have dramatic consequences not only for the spermatozoon itself, but also, and above all, on its primary objective, which is to carry out fertilization and to ensure, in part, that the embryonic development program should lead to a healthy progeny. Future Directions: Sperm oxidative DNA damage largely affects the integrity of the paternal genetic material to such an extent that the oocyte may have difficulties in correcting it. Diagnostic and therapeutic actions should be considered more systematically, especially in men with difficulties to conceive. Research is underway to determine whether the epigenetic information carried by spermatozoa is also subject to changes mediated by pro-oxidative situations. Antioxid. Redox Signal. 37, 481-500.

The MAPK/ERK signaling pathway regulates the expression and localization of Cx43 in mouse proximal epididymis†

This study aimed to clarify the functional role of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK1/2)-signaling pathway in the expression and localization of connexin 43 (Cx43). Mice were treated with the mitogen-activated protein kinase kinase (MEK1/2) inhibitor, PD325901, which induced a progressive decrease in ERK1/2 phosphorylation (pERK) in the proximal epididymis of the mice, without affecting total ERK level. Cx43 staining with punctuated reactive sites was observed in the basolateral membranes in the initial segment (IS) of mouse epididymis. However, PD325901 induced a significant decrease in Cx43 labeling in the basolateral membranes. Interestingly, Cx43, which was undetectable in the apical region of epididymis under control conditions, showed a significant increase in the apical region after PD 325901 treatment. To confirm whether Cx43 was present in tight junctions (TJs) after PD 325901 treatment, PD325901-treated epididymis samples were double-labeled with Cx43 and zonula occludens (ZO)-1 (a TJ protein marker). Thereafter, confocal microscopy showed the colocalization of Cx43 and ZO-1 in the epididymis after PD325901 treatment. Collectively, our results indicated that PD325901 treatment induced a significant increase in Cx43 localization on TJs, where it was colocalized with ZO-1. Therefore, the study suggested that ERK phosphorylation is essential for the proper expression and localization of the gap junction (GJ) protein, and that the relationship between GJs and TJs could play an important role in establishing and maintaining microenvironmental homeostasis for sperm maturation in the IS of mouse epididymis.

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.

Molecular machinery providing copper bioavailability for spermatozoa along the epididymial tubule in mouse

Progressive functional maturation of spermatozoa is completed during the transit of these cells through the epididymis, a tubule structure connecting a testicle to a vas deferens. Epididymal epithelial cells by means of their secretory and absorptive functions determine a highly specialized luminal microenvironment containing multiple organic and inorganic components. The latter include copper ions, which due to their redox properties are indispensable for critical homeostatic processes occurring in spermatozoa floating in different part of epididymis but can be potentially toxic. Main purpose of our study was to determine epididymal region-dependent expression and localization of copper transporters ensuring a tight control of copper concentration in epididymal fluid. We also aimed at identifying proteins responsible for copper uptake by spermatozoa and verifying whether this process is coordinated with copper supply to superoxide dismutase 1 (SOD1), a copper-dependent antioxidant enzyme. Our study identifies two ATPases-ATP7A, ATP7B and Slc31a1, major copper importers/exporters depending on their differential expression on epididymal polarized epithelial cells of the caput, corpus, and cauda. Next, ceruloplasmin seems to be a chief protein transporting copper in the epididymal fluid and providing this biometal to spermatozoa. The entry of copper to germ cells is mediated by Slc31a1 and is correlated with both expressions of copper chaperone for superoxide dismutase (CCS), copper chaperone directly providing copper ions to SOD1 and with the expression and activity of the latter. Our results outline a network of cooperating copper binding proteins expressed in epididymal epithelium and in spermatozoa that orchestrate bioavailability of this microelement for gametes and protect them against copper toxicity.

Distribution pattern of ZO-1 and claudins in the epididymis of vampire bats

Epithelial cells connect with each other by tight junctions (TJs) in several tissues. In epididymides, TJs proteins form the blood-epididymis barrier (BEB), which is crucial for male fertility. However, little is known about BEB morphological and physiological aspects in wild animals. This study examines the region-specific distribution pattern of TJs proteins in D. rotundus' epididymis, assessing their regulation in rainy and dry season. The expression of zonula occludens-1 (ZO-1), and claudins (Cldn)-1, -3, and -4 were evaluated by confocal immunofluorescence and ELISA analysis. Herein, ZO-1 was strictly expressed in TJs, whereas Cldns were expressed in TJs and basolateral membranes of epithelial cells. Their co-localization and intensity of expression varied in the epididymal regions examined. The effect of season on protein expression was detected mainly in TJ proteins located in the proximal regions. As such, in the initial segment (IS), Cldn-3 and -4 were detected at low levels in basolateral membranes in the rainy season compared to the dry season. Furthermore, in the distal IS, Cldn-1 expression was lower in TJs of epithelial cells during the rainy season than the dry season. ZO-1 expression was higher in the cauda region than the corpus region by ELISA analysis. Additionally, in the corpus region, ZO-1 expression was higher in TJs during dry season compared to the rainy season. Our study sheds light on the understanding of BEB in D. rotundus, improving the knowledge of their reproductive biology.

Differential expression of cell-cell junction proteins in the testis, epididymis, and ductus deferens of domestic turkeys (Meleagris gallopavo) with white and yellow semen

Tight, adherens, and gap junctions are involved in the regulation of reproductive tissue function in male mammals. In birds, including domestic turkeys, intercellular interactions performed by junctional networks have not yet been studied. Furthermore, the cellular and molecular basis of yellow semen syndrome (YSS) in the turkey population remains poorly understood. Thus, the aim of the present study was 2-fold: first, to provide new information on the localization and expression of cell-cell junction proteins in the testis, epididymis, and ductus deferens of domestic turkeys and second, to compare expression of junctional protein genes between 2 turkey population, one that produces white normal semen (WNS) and the other that produces yellow abnormal semen. Expression of occludin, zonula occludens-1 (ZO-1), connexin 43 (Cx43), N- and E-cadherin, and β-catenin genes were investigated using 3 complementary techniques: quantitative real-time PCR, western blot, and immunohistochemistry. Compared to WNS testis, epididymis, and ductus deferens, YSS tissues exhibited downregulation of occludin and β-catenin mRNA (P < 0.05) and protein (P < 0.05 and P < 0.01, respectively) and upregulation of N- and E-cadherin mRNA (P < 0.001, P < 0.05, P < 0.01, respectively) and protein (P < 0.01, P < 0.05, and P < 0.05, respectively). In contrast, ZO-1 and Cx43 mRNA and protein were upregulated in YSS testis (P < 0.05 and P < 0.001, respectively) but not in epididymis and ductus deferens; both mRNAs and proteins were downregulated (P < 0.05) compared to the respective WNS epididymis and ductus deferens. Altered staining intensity of immunoreactive proteins in YSS vs. WNS reproductive tissue sections confirmed the gene expression results. The present study is the first to demonstrate altered levels of junctional protein gene expression in reproductive tissues of male YSS turkeys. These findings may suggest that subtle changes in junctional protein expression affect the microenvironment in which spermatozoa develop and mature and thus may have an impact on the appearance of yellow semen in domestic turkeys.

Seasonal expressions of androgen receptor, estrogen receptors, 5α-reductases and P450arom in the epididymis of the male muskrat (Ondatra zibethicus)

The steroid hormones not only exert various endocrine functions but also act as the autocrine or paracrine factors in different tissues of mammals. In the present study, the seasonal expressions of androgen receptor (AR), estrogen receptors alpha and beta (ERα and ERβ), aromatase cytochrome P450 (P450arom) and 5α-reductase 1, 2 were investigated in the epididymis of the muskrat. HE staining showed enlarged lumen and abundant sperm in the breeding season while reduced lumen with no sperm in the non-breeding season. The staining of AR was presented in nuclei of epithelial cells of the epididymis in both seasons. The immunostaining of ERα was localized in both nuclei and cytoplasm of epithelial cells of the epididymis during the breeding season, while the weak staining of ERα was only in the nuclei of epithelial cells during the non-breeding season. In contrast, ERβ signal was negative in the epididymis of the muskrat in both seasons. The positive signals for P450arom and 5α-reductase 1, 2 were found in the cytoplasm of epithelial and smooth muscle cells during both seasons. Moreover, the protein and mRNA expression levels of AR, ERα, P450arom and 5α-reductase 1, 2 were significantly higher in the epididymis during the breeding season than those of the non-breeding season, and the expression level of 5α-reductase 1 was higher when compared with 5α-reductase 2. In addition, the levels of testosterone (T) and dihydrotestosterone (DHT) in the epididymis and serum were remarkably higher during the breeding season. Taken together, these findings suggested androgen and estrogen might play an important endocrine or autocrine/paracrine role to regulate the epididymal functions of the muskrat.

Cellular junctions in the epididymis, a critical parameter for understanding male reproductive toxicology

Epididymal sperm maturation is a critical aspect of male reproduction in which sperm acquire motility and the ability to fertilize an ovum. Sperm maturation is dependent on the creation of a specific environment that changes along the epididymis and which enables the maturation process. The blood-epididymis barrier creates a unique luminal micro-environment, different from blood, by limiting paracellular transport and forcing receptor-mediated transport of macromolecules across the epididymal epithelium. Direct cellular communication between cells allows coordinated function of the epithelium. A limited number of studies have directly examined the effects of toxicants on junctional proteins and barrier function in the epididymis. Effects on the integrity of the blood-epididymis barrier have resulted in decreased fertility and, in some cases, the development of sperm granulomas. Studies have shown that in addition to tight junctions, proteins implicated in the maintenance of adherens junctions and gap junctions alter epididymal functions. This review will provide an overview of the types and roles of cellular junctions in the epididymis, and how these are targeted by different toxicants.

Odyssey of the spermatozoon

This Opinion piece is offered as a cursory overview of sperm development, function, and transport through the eyes of an equine veterinarian. My professional background is predominantly clinical in nature, but my fascination with sperm function and preservation has led to a fairly sizeable review of the scientific literature over the years in hopes of extracting laboratory findings that have application to my daily activities in the clinical arena. Spermatozoa are quite unique among cellular types with regard to both form and function, and represent the only endogenously derived cell type that exerts its action in a separate being. This paper takes the reader on a voyage with a mammalian spermatozoon, from its formative stages through its transport in the male and female reproductive tracts, and culminating with its interaction with an ovulated oocyte at the time of fertilization. Specific emphasis is placed on equine spermatozoa when notable research findings have been unveiled.

Steroid regulation of early postnatal development in the corpus epididymidis of pigs

Development of the epididymis including blood-epididymal barrier formation is not required until sperm reach the epididymis peripuberally. Regulation of this development in the early postnatal period is largely unknown. The current objectives were to evaluate potential roles of endogenous estrogen and androgen signaling during early development of the corpus epididymidis and to determine the timing of formation of the blood-epididymal barrier in the pig. Effects of endogenous steroids were evaluated using littermates treated with vehicle, an aromatase inhibitor (letrozole) to reduce endogenous estrogens, an estrogen receptor antagonist (fulvestrant) or an androgen receptor antagonist (flutamide). Phosphorylated histone 3 immunohistochemistry was used to identify proliferating epithelial cells. Lanthanum nitrate and electron microscopy were used to analyze formation of the blood barrier in the corpus epididymidis. Reducing endogenous estrogens increased the number of proliferating corpus epithelial cells at 6 and 6.5 weeks of age compared with vehicle-treated boars (P<0.01 and P<0.001 respectively). Blocking androgen receptors did not alter proliferation rate at 6.5 weeks of age. Although barrier formation was similar between 6 and 6.5 weeks of age in vehicle-treated animals, intercellular barriers increased in letrozole-treated littermates at 6.5 weeks of age. Fulvestrant treatment, which should mimic aromatase inhibition for regulation through ESR1 and ESR2 signaling but potentially stimulate endogenous estrogen signaling through the G protein-coupled estrogen receptor (GPER), had the opposite effect on aromatase inhibition. These responses in conjunction with the presence of GPER in the corpus epididymidis suggest early corpus epididymal development is regulated partially by GPER.

The blood-epididymis barrier and inflammation

The blood-epididymis barrier (BEB) is a critical structure for male fertility. It enables the development of a specific luminal environment that allows spermatozoa to acquire both the ability to swim and fertilize an ovum. The presence of tight junctions and specific cellular transporters can regulate the composition of the epididymal lumen to favor proper sperm maturation. The BEB is also at the interface between the immune system and sperm. Not only does the BEB protect maturing spermatozoa from the immune system, it is also influenced by cytokines released during inflammation, which can result in the loss of barrier function. Such a loss is associated with an immune response, decreased sperm functions, and appears to be a contributing factor to post-testicular male infertility. Alterations in the BEB may be responsible for the formation of inflammatory conditions such as sperm granulomas. The present review summarizes current knowledge on the morphological, physiological and pathological components associated with the BEB, the role of immune function on the regulation of the BEB, and how disturbance of these factors can result in inflammatory lesions of the epididymis.

The Role of the Immune Response in Chlamydia trachomatis Infection of the Male Genital Tract: A Double-Edged Sword

Chlamydia trachomatis (CT) is the most prevalent bacterial sexually transmitted infection in the world, with more than 100 million cases reported annually. While there have been extensive studies into the adverse effects that CT infection has on the female genital tract, and on the subsequent ability of these women to conceive, studies into the consequences on male fertility have been limited and controversial. This is in part due to the asymptomatic nature of the infection, where it is estimated that 50% of men with Chlamydia fail to show any symptoms. It is accepted, however, that acute and/or persistent CT infection is the causative agent for conditions such as urethritis, epididymitis, epididymo-orchitis, and potentially prostatitis. As with most infections, the immune system plays a fundamental role in the body’s attempts to eradicate the infection. The first and most important immune response to Chlamydia infection is a local one, whereby immune cells such as leukocytes are recruited to the site of infections, and subsequently secrete pro-inflammatory cytokines and chemokines such as interferon gamma. Immune cells also work to initiate and potentiate chronic inflammation through the production of reactive oxygen species (ROS), and the release of molecules with degradative properties including defensins, elastase, collagenase, cathespins, and lysozyme. This long-term inflammation can lead to cell proliferation (a possible precursor to cancer), tissue remodeling, and scarring, as well as being linked to the onset of autoimmune responses in genetically disposed individuals. This review will focus on the ability of the immune system to recognize and clear acute and persistent chlamydial infections in the male genital tract, and on the paradoxical damage that chronic inflammation resulting from the infection can cause on the reproductive health of the individual.

The cell-cell junctions of mammalian testes: I. The adhering junctions of the seminiferous epithelium represent special differentiation structures

The seminiferous tubules and the excurrent ducts of the mammalian testis are physiologically separated from the mesenchymal tissues and the blood and lymph system by a special structural barrier to paracellular translocations of molecules and particles: the "blood-testis barrier", formed by junctions connecting Sertoli cells with each other and with spermatogonial cells. In combined biochemical as well as light and electron microscopical studies we systematically determine the molecules located in the adhering junctions of adult mammalian (human, bovine, porcine, murine, i.e., rat and mouse) testis. We show that the seminiferous epithelium does not contain desmosomes, or "desmosome-like" junctions, nor any of the desmosome-specific marker molecules and that the adhering junctions of tubules and ductules are fundamentally different. While the ductules contain classical epithelial cell layers with E-cadherin-based adherens junctions (AJs) and typical desmosomes, the Sertoli cells of the tubules lack desmosomes and "desmosome-like" junctions but are connected by morphologically different forms of AJs. These junctions are based on N-cadherin anchored in cytoplasmic plaques, which in some subforms appear thick and dense but in other subforms contain only scarce and loosely arranged plaque structures formed by α- and β-catenin, proteins p120, p0071 and plakoglobin, together with a member of the striatin family and also, in rodents, the proteins ZO-1 and myozap. These N-cadherin-based AJs also include two novel types of junctions: the "areae adhaerentes", i.e., variously-sized, often very large cell-cell contacts and small sieve-plate-like AJs perforated by cytoplasm-to-cytoplasm channels of 5-7 nm internal diameter ("cribelliform junctions"). We emphasize the unique character of this epithelium that totally lacks major epithelial marker molecules and structures such as keratin filaments and desmosomal elements as well as EpCAM- and PERP-containing junctions. We also discuss the nature, development and possible functions of these junctions.

Postnatal exposure to flutamide affects CDH1 and CTNNB1 gene expression in adult pig epididymis and prostate and alters metabolism of testosterone

In both epididymis and prostate the dynamic cross-talk between the cells is hormonally regulated and, in part, through direct cell-to-cell interactions. Functionality of the male reproductive organs may be affected by exposure to specific chemicals, so-called 'reprotoxicants'. In this study we tested whether early postnatal and prepubertal exposure to anti-androgen flutamide altered the expression of adherens junction genes encoding E-cadherin (CDH1) and β-catenin (CTNNB1) in adult pig epididymis and prostate. In addition, the expression of mRNAs and proteins for 5α-reductase (ST5AR2) and aromatase (CYP19A1) were examined to show whether flutamide alters metabolism of testosterone. Thus, flutamide was injected into male piglets between Days 2 and 10 and between Days 90 and 98 postnatally (PD2 and PD90; 50 mg/kg bw), tissues that were obtained on postnatal Day 270. To assess the expression of the genes and proteins, real-time RT-PCR and Western blot were performed respectively. Moreover, adherens junction proteins were localized by immunohistochemistry. In response to flutamide, CDH1 and CTNNB1 expressions were down-regulated along the epididymis, mostly in PD2 group (p < 0.001, p < 0.01). In the prostate, CDH1 mRNA and protein expressions were significantly down-regulated (p < 0.01), whereas CTNNB1 mRNA was slightly up-regulated in both flutamide-treated groups. CTNNB1 protein level was markedly elevated in both PD2 (p < 0.001) and PD90 (p < 0.01) groups. In the epididymis, the expression of ST5AR2 and CYP19A1 was down- and up-regulated, respectively (p < 0.05), whereas in the prostate evident decrease in CYP19A1 expression (p < 0.001, p < 0.01, p < 0.05) was demonstrated. In both tissues, membranous immunolocalization of CTNNB1 suggests its involvement in cell-cell adhesion. Overall, flutamide administration resulted in suppression of androgen action in the epididymis and prostate leading to deregulation of CDH1 and CTNNB1 gene expressions which is probably caused by the alterations in the expression of ST5AR2 and CYP19A1 in both reproductive organs.

Epidermal growth factor regulates connexin 43 in the human epididymis: role of gap junctions in azoospermia

BACKGROUND

Gap junctions (GJs) allow for direct communication between adjacent cells. They are composed of connexons consisting of transmembrane proteins, connexins (Cxs). The objectives of this study were to determine if GJ proteins GJA1 (Cx43), GJB1 (Cx32) and GJB2 (Cx26) are present in the epididymis of men with a normal epididymis, to assess whether or not Cx expression and localization are altered in azoospermic patients, and to determine if epidermal growth factor (EGF) regulates GJA1 expression.

METHODS

Epididymides were obtained from men with localized testis cancer with active spermatogenesis and histologically normal epididymal tubule (group 1), men with non-obstructive azoospermia secondary to Sertoli-cell only syndrome (group 2) and from azoospermic men with normal spermatogenesis and epididymal obstruction (group 3). Epididymides were subdivided into three segments: caput, corpus and cauda. Quantitative real-time RT-PCR was performed to assess GJA1, GJB1, GJB2 and EGF receptor (EGFR) mRNA levels in epididymides from patients from each group (all n=3, except n=1 for caput blockage). A human caput epididymal cell line was then used to determine the role of EGFR signaling on the regulation of human epididymal GJA1.

RESULTS

Real-time RT-PCR analysis revealed that GJA1, GJB1, GJB2 and EGFR were expressed along the human epididymis. In the cauda epididymidis of group 2 and 3 men, we observed a significant decrease in GJA1 (P=0.0456 and P=0.0465, respectively) and GJB1 (P=0.0450 and P=0.0497, respectively) mRNA levels when compared with group 1 men. We also observed a decrease in EGFR mRNA levels (P=0.0358) in the cauda epididymidis of group 3 men when compared with group 1. Immunocytochemistry revealed that in the epididymis, GJA1 and EGFR were localized between basal and principal cells and between adjacent principal cells. In group 2 and 3 patients, however, we noted a dramatic increase in cytosolic immunostaining for both GJA1 and EGFR in both principal and basal cells. Using a human caput epididymal cell line derived from fertile men, we demonstrated that changes in GJA1 phosphorylation could be regulated by EGF (P=0.015) and the extracellular regulated kinase 1/2 signaling pathway (P=0.03). Furthermore, while the phosphoinositide-3-kinase (PI3K)/AKT signaling pathway did not alter GJA1 phosphorylation, treatment with PI3K/AKT inhibitor LY294002 significantly (P=0.024) inhibited the EGF-stimulated increase in GJA1 total protein levels at 24 h. Immunolocalization indicated that loss of PI3K/AKT signaling was associated with increased cytosolic localization of Cx43 in this cell line.

CONCLUSIONS

Together, these data suggest that in azoospermic men decreased expression of EGFR may be responsible for decreasing GJA1 levels and increasing its cytosolic localization via the PI3K/AKT signaling pathway.

Role of microRNAs in controlling gene expression in different segments of the human epididymis

Background

The molecular mechanisms implicated in regionalized gene expression in the human epididymis have not yet been fully elucidated. Interestingly, more than 200 microRNAs (miRNAs) have been identified in the human epididymis and could be involved in the regulation of mRNA stability and post-transcriptional expression in this organ.

Methods

Using a miRNA microarray approach, we investigated the correlation between miRNA signatures and gene expression profiles found in three distinct regions (caput, corpus and cauda) of human epididymides from 3 donors. In silico prediction of transcript miRNA targets was performed using TargetScan and Miranda software's. FHCE1 immortalized epididymal cell lines were cotransfected with mimic microRNAs and plasmid constructs containing the 3′UTR of predicted target genes downstream of the luciferase gene.

Results

We identified 35 miRNAs differentially expressed in the distinct segments of the epididymis (fold change ≥2, P-value≤0.01). Among these miRNAs, miR-890, miR-892a, miR-892b, miR-891a, miR-891b belonging to the same epididymis-enriched cluster located on the X chromosome, are significantly more expressed in the corpus and cauda regions than in the caput. Interestingly, a strong negative correlation (r = −0,89, P-value≤0.001) was found between the pattern of expression of miR-892b and its potential mRNA target Esrrg (Estrogen Related Receptor Gamma) and with miR-145 and Cldn10 mRNA (r = −0,92, P-value≤0.001). We confirmed that miR-145 and miR-892b inhibit the expression of the luciferase reporter via Cldn10 and Esrrg 3′ UTRs, respectively.

Conclusion

Our study shows that the expression of miRNAs is segmented along the human epididymis and correlates with the pattern of target gene expression in different regions. Therefore, epididymal miRNAs may be in control of the maintenance of gene expression profile in the epididymis, which dictates segment-specific secretion of proteins and establishes physiological compartments that directly or indirectly affect sperm maturation and fertility.

Connexins and pannexins: Coordinating cellular communication in the testis and epididymis

Gap junctions and connexins are critical for coordinating cellular functions in complex epithelia. In recent years there has been increased interest in understanding the regulation and function of gap junctions in both the testis and epididymis. Studies in transgenic mice in which connexin 43 (Cx43) is mutated or is knocked down only in Sertoli cells have demonstrated the essential role of Cx43 in spermatogenesis and differentiation of Sertoli cells. In the epididymis developmental studies have shown a role for numerous connexins in the differentiation of epithelial cells and communication between the basal cells and both principal and clear cells. In both tissues several factors, such thyroid hormones and androgens, are important in regulating expression and function of connexins. Pannexins, which form cellular channels but are structurally similar to gap junction proteins, have been identified in both testis and epididymis and, in the epididymis, are regulated by androgens. The objective of this review is to summarize the advances that have been made on the role and regulation of connexins and pannexins in the testis and epididymis and their implication in spermatogenesis and sperm maturation.

Immunophysiology and pathology of inflammation in the testis and epididymis

The ability of spermatogenic cells to evade the host immune system and the ability of systemic inflammation to inhibit male reproductive function represent two of the most intriguing conundrums of male reproduction. Clearly, an understanding of the underlying immunology of the male reproductive tract is crucial to resolving these superficially incompatible observations. One important consideration must be the very different immunological environments of the testis, where sperm develop, and the epididymis, where sperm mature and are stored. Compared with the elaborate blood-testis barrier, the tight junctions of the epididymis are much less effective. Unlike the seminiferous epithelium, immune cells are commonly observed within the epithelium, and can even be found within the lumen, of the epididymis. Crucially, there is little evidence for extended allograft survival (immune privilege) in the epididymis, as it exists in the testis, and the epididymis is much more susceptible to loss of immune tolerance. Moreover, the incidence of epididymitis is considerably greater than that of orchitis in humans, and susceptibility to sperm antibody formation after damage to the epididymis or vas deferens increases with increasing distance of the damage from the testis. Although we still know relatively little about testicular immunity, we know less about the interactions between the epididymis and the immune system. Given that the epididymis appears to be more susceptible to inflammation and immune reactions than the testis, and thereby represents the weaker link in protecting developing sperm from the immune system, it is probably time this imbalance in knowledge was addressed.

The blood-testis and blood-epididymis barriers are more than just their tight junctions

The terms blood-testis barrier (BTB) or blood-epididymis barrier (BEB), are often described as Sertoli cell-Sertoli cell tight junctions (TJs) or TJs between the epithelial cells in the epididymis, respectively. However, in reality, the BTB and BEB are much more complex than just the TJ. The focus of this minireview is to remind readers that the complete BTB and BEB are comprised of three components: anatomical, physiological, and immunological. The TJs form the anatomical (physical) barrier that restricts passage of molecules and cells from entering or exiting the lumen. The physiological barrier is comprised of transporters that regulate movement of substances in or out of the lumen, thus creating a microenvironment, which is critical for the proper development and maturation of germ cells. The immunological barrier limits access by the immune system and sequesters the majority of the autoantigenic germ cells. Combined with the overall immune-privilege of the testis, this suppresses detrimental immune responses against the autoantigenic germ cells. These three components on their own do not create a complete functional barrier; instead, it is the interaction between all three components that create a barrier of maximal competence.

Expression and regulation of FAAP in the mouse epididymis

The focal adhesion-associated protein (FAAP), encoded by the murine D10Wsu52e gene, is named as involved in modulating cell adhesion dynamics. It is a highly conserved and ubiquitously expressed protein, and its human homologue HSPC117 has been identified in many protein complexes. However, the expression and regulation of the FAAP gene have not yet been well characterized. Herein, we demonstrate that FAAP mRNA and protein expression are highly regionalized in the mouse epididymis with predominant enrichment in the initial segment. During sexual maturation, FAAP mRNA is always expressed in the caput epididymides. Castration causes rapid and significant decrease of FAAP mRNA abundance within the initial segment, whereas testosterone replacement fails to reverse the regression. Unilateral orchidectomy and efferent duct ligation studies further validate that expression of the FAAP mRNA is highly dependent on the presence of luminal testicular factors rather than testosterone. Furthermore, FAAP expression in the initial segment is not affected by cryptorchism.

Organic anion transporter 6 (Slc22a20) specificity and Sertoli cell-specific expression provide new insight on potential endogenous roles

Organic anion transporter 6 (Oat6; Slc22a20), a member of the OAT family, was demonstrated previously to mediate the transport of organic anions (Am J Physiol Renal Physiol 291:F314-F321, 2006). In the present study, we sought to further delineate the function of murine Oat6 (mOat6) by analyzing the effect of select organic anions on mOat6-mediated transport by using a Chinese hamster ovary (CHO) cell line stably expressing mOat6 (CHO-mOat6). When examined, kinetic analysis demonstrated that the mechanism of inhibition of mOat6 and mOat3 was competitive. Homovanillic acid, 5-hydroxyindole acetic acid, 2,4-dihydroxyphenylacetate, hippurate, and dehydroepiandrosterone sulfate (DHEAS) each significantly reduced mOat6 activity with inhibitory constant (K(i)) values of 3.0 +/- 0.5, 48.9 +/- 10.3, 61.4 +/- 7.1, 59.9 +/- 4.9, and 38.8 +/- 3.1 microM, respectively. Comparison to K(i) values determined for mOat3 (67.8 +/- 7.2, 134.5 +/- 27.0, 346.7 +/- 97.9, 79.3 +/- 4.0, and 3.8 +/- 1.1 microM, respectively) revealed that there are significant differences in compound affinity between each transporter. Fluoroquinolone antimicrobials and reduced folates were without effect on mOat6-mediated uptake. Investigation of testicular cell type-specific expression of mOat6 by laser capture microdissection and quantitative polymerase chain reaction revealed significant mRNA expression in Sertoli cells, but not in Leydig cells or spermatids. Overall, these data should aid further refinements to the interpretation and modeling of the in vivo disposition of OAT substrates. Specifically, expression in Sertoli cells suggests Oat6 may be an important determinant of blood-testis barrier function, with Oat6-mediated transport of estrone sulfate and DHEAS possibly representing a critical step in the maintenance of testicular steroidogenesis.

Orchestration of occludins, claudins, catenins and cadherins as players involved in maintenance of the blood-epididymal barrier in animals and humans

Although spermatozoa are formed during spermatogenesis in the testis, testicular spermatozoa are immature and cannot swim or fertilize. These critical spermatozoal functions are acquired in the epididymis where a specific luminal environment is created by the blood-epididymal barrier; proteins secreted by epididymal principal cells bind to maturing spermatozoa and regulate the maturational process of the spermatozoa. In the epididymis, epithelial cell-cell interactions are mediated by adhering junctions, necessary for cell adhesion, and by tight junctions, which form the blood-epididymal barrier. The regulation of these cellular junctions is thought to represent a key determinant in the process of sperm maturation within the epididymis. Tight junctions between adjacent principal cells permit the formation of a specific microenvironment in the lumen of the epididymis that is essential for sperm maturation. Although we have made significant progress in understanding epididymal function and the blood-epididymal barrier, using animal models, there is limited information on the human epididymis. If we are to understand the normal and pathological conditions attributable to human epididymal function, we must clearly establish the physiological, cellular and molecular regulation of the human epididymis, develop tools to characterize these functions and develop clinical strategies that will use epididymal functions to improve treatment of infertility.

Gene Expression Profiling and Its Relevance to the Blood-Epididymal Barrier in the Human Epididymis1

The luminal environment along the epididymal duct is important for spermatozoal maturation. This environment is unique and created by the blood-epididymal barrier, which is formed by tight and adhering junctions. For the human epididymis, little information exists on the proteins that comprise these junctions. Our objectives were to assess the gene expression profiles in the different segments of the human epididymis and to identify the proteins that make up the blood-epididymal barrier. Using microarrays, we identified 2980 genes that were differentially expressed by at least 2-fold between the various segments. Of the many genes involved in diverse functions, were those that encoded adhesion proteins (cadherins and catenins) and tight junctional proteins (claudins [CLDN] and others). PCR analyses confirmed the microarray data. Immunolocalization of CLDNs 1, 3, 4, 8, and 10 revealed that the localization of CLDNs differed along the epididymis. In all three segments, CLDNs 1, 3, and 4 were localized to tight junctions, along the lateral margins of adjacent principal cells, and at the interface between basal and principal cells. CLDN8 was localized to tight junctions in all three segments, in addition to being localized in the caput along the lateral margins of principal cells, and in the corpus, at the interface between principal and basal cells. CLDN10, tight junction protein 1, and occludin were localized exclusively to tight junctions in all three epididymal segments. These data indicate that the epididymis displays a complex pattern of gene expression, which includes genes that are implicated in the formation of the blood-epididymal barrier, which suggests complex regulation of this barrier.

Activation of an SP binding site is crucial for the expression of claudin 1 in rat epididymal principal cells

Claudin 1 (CLDN1) is a tight junctional protein present in the epididymis. Limited information exists regarding the regulation of Cldn1 transcription. In the epididymis, the regulation of the 5' flanking region of genes coding for tight junctional proteins is unknown. The present objectives were to investigate the transcriptional regulation of the Cldn1 gene in the rat epididymis. A 1.8-kb sequence of the 5' flanking region of the rat Cldn1 gene was cloned. The transcriptional start site is an adenine located at the -198 position relative to the first codon, and 26 bp downstream of the putative TATA box. It is the only start site for the Cldn1 gene transcription in the rat epididymis. The Cldn1 promoter was inserted into a luciferase gene expression vector and transfected into a rat caput epididymal cell line (RCE-1). Sequential deletion analysis revealed that minimal promoter activity was achieved with the construct containing -61 to +164 bp of the promoter. This sequence contained a TATA box and two consensus SP1 binding sites. Electrophoretic mobility shift and supershift assays confirmed that SP1 and SP3 were present in RCE-1 cells and epididymal nuclear extracts, and that they bind to the 5' SP1 binding motif of the promoter. Site-directed mutagenesis of the 5' SP1 binding site resulted in a 4-fold decrease in transactivation of the minimal promoter sequence. These findings indicate that SP1 and SP3 bind to the Cldn1 promoter region, and that this interaction influences the expression of Cldn1 in the rat epididymis.

Characterization of a novel rat epididymal cell line to study epididymal function

The epididymis is an androgen-dependent organ that allows spermatozoa to become fully functional as they pass through this tissue. The specialized functions of the epididymis are mediated by interactions between epididymal epithelial cells and between epididymal cells and spermatozoa. Although the critical role of the epididymis in sperm maturation is well established, the mechanisms regulating cell-cell interactions remain poorly understood because of the lack of appropriate cell line models. We now report the characterization of a novel rat caput epididymal cell line (RCE) that was immortalized by transfecting primary cultures of rat epididymal cells with the simian virus 40 large T antigen. At the electron microscope level, the cell line was composed of epithelial principal cells with characteristics of in vivo cells; principal cells had well-developed Golgi apparatus, abundant endoplasmic reticulum cisternae, and few endosomes. RCE cells expressed the mRNAs coding for the androgen receptor, estrogen receptor alpha, and 4-ene-steroid-5-alpha-reductase types 1 and 2 as well as epididymal-specific markers Crisp-1 and epididymal retinoic acid binding protein. Epididymal retinoic acid binding protein expression was significantly induced with dihydrotestosterone, although this effect was not blocked by flutamide, suggesting that RCE cells are not androgen responsive. Neighboring cells formed tight and gap junctions characteristic of epididymal cells in vivo and expressed tight (occludin and claudin-1, -3, and -4) and gap junctional proteins (connexin-26, -30.3, -32, and -43). The RCE cell line displays many characteristics of epithelial principal cells, thus providing a model for studying epididymal cell functions.

Intranasal immunization with C. muridarum major outer membrane protein (MOMP) and cholera toxin elicits local production of neutralising IgA in the prostate

Successful control of sexually transmitted diseases (STDs) through vaccination will require the development of vaccine strategies that target protective immunity to both the female and male reproductive tracts (MRT). In the male, the immune privileged nature of the male reproductive tract provides a barrier to entry of serum immunoglobulins into the male reproductive ducts, thereby preventing the induction of protective immunity using conventional injectable vaccination techniques. In this study we investigated the potential of intranasal (IN) immunization to elicit anti-chlamydial immunity in BALB/c male mice. Intranasal immunization with Chlamydia muridarum major outer membrane protein (MOMP) admixed with cholera toxin (CT) resulted in high levels of MOMP-specific IgA in prostatic fluids (PF) and MOMP-specific IgA-secreting cells in the prostate. Prostatic fluid IgA inhibited in vitro infection of McCoy cells with C. muridarum. Using RT-PCR we also show that mRNA for the polymeric immunoglobulin receptor (PIgR), which transports IgA across mucosal epithelia, is expressed only in the prostate but not in other regions of the male reproductive ducts upstream of the prostate. These data suggest that using intranasal immunization to target IgA to the prostate may protect males against STDs while at the same time maintaining the state of immune privilege within the MRT.

Loss of nectin-2 at Sertoli-spermatid junctions leads to male infertility and correlates with severe spermatozoan head and midpiece malformation, impaired binding to the zona pellucida, and oocyte penetration

The members of the nectin/CD155 gene family represent a growing class of novel cell adhesion molecules of the immunoglobulin superfamily. In the present study, we describe the generation of a mouse line lacking a functional nectin-2 gene (nectin-2LacZ/LacZ) and analyze the resulting male-specific infertility phenotype. Although nectin-2LacZ/LacZ males produced normal amounts of motile spermatozoa, scanning electron microscopy revealed severe malformations of the spermatozoan head and midpiece. Besides a 4-fold reduction in migration of nectin-2LacZ/LacZ spermatozoa to the oviducts, in vitro binding to zona-intact mouse oocytes was reduced 6-fold. On the other hand, nectin-2LacZ/LacZ spermatozoa bound to zona-free hamster oocytes at near-wild type levels but, remarkably, failed to penetrate. In addition to the previously reported expression of nectin-2 and nectin-3 at Sertoli-spermatid junctions and of nectin-2 at inter-Sertoli cell junctions, we also found nectin-2 to localize at apical cell-cell junctions of the epididymal epithelium. Expression analysis of a LacZ knockin gene into the defunct nectin-2 gene in nectin-2LacZ/LacZ mice provided additional support for our earlier conjecture that in normal testis, nectin-2 is produced exclusively by Sertoli cells. Finally, we found Sertoli-spermatid junctions in nectin-2LacZ/LacZ mice to be virtually devoid of the actin-bundling protein espin, suggesting that ectoplasmic specializations fail to form in the absence of nectin-2. Our functional analyses indicate that the infertility phenotype of nectin-2-deficient male mice is caused by a combination of reduced migration to the oviduct, spermatozoa-zona binding, and sperm-oocyte fusion. We corroborate our previous description of a heterotypic adhesion complex between Sertoli cells and elongated spermatids that is maintained by nectin-2 and nectin-3, respectively.

Claudin-1 is not restricted to tight junctions in the rat epididymis

The blood-epididymal barrier creates a unique microenvironment critical for sperm maturation. There is little information on proteins comprising epididymal tight and adhering junctions or on factors regulating their expression. Claudins are a family of transmembrane proteins reported to be exclusively localized to tight junctions. In the present study the expression of claudin-l (Cl-1) was examined with respect to the different cell types of the epididymis and its various regions as well as its expression during postnatal development and regulation by testicular factors, using both immunocytochemistry and Northern blot analysis. RT-PCR of adult epididymal and testicular RNA (positive control) indicated that Cl-1 messenger RNA (mRNA) transcripts were present in all regions of the epididymis. In the adult, Cl-1 was localized immunocytochemically along the entire length of the lateral plasma membranes between adjacent principal cells, including apical areas containing tight junctions, as well as at the interface between principal and basal cells and along the basal plasma membrane of the epithelium in relation to the basement membrane. Northern blot analysis of adult epididymis with a rat Cl-1 complementary DNA indicated the presence of two hybridizing bands of 4.0 and 1.5 kb. Postnatally, in the caput-corpus and cauda epididymidis, mRNA levels for both transcripts were lowest on day 7. In the caput-corpus epididymidis, mRNA levels for the 1.5-kb transcript increased significantly between 7 and 14 days, whereas the levels of the 4.0-kb transcript were significantly higher by day 21. Postnatal studies revealed that in the initial segment and caput epididymidis, Cl-1 immunostaining was present along the entire length of the lateral plasma membranes of undifferentiated epididymal epithelial cells as early as day 7, including apical areas containing tight junctions. By day 21, staining was identical to that of adult animals, but as this is an age when androgen levels are not at their peak, the data would suggest that they are not a prominent factor regulating Cl-1 expression. Orchidectomy and orchidectomy plus testosterone replacement experiments revealed differences in Cl-1 immunostaining in the initial segment, suggesting that localization of Cl-1 in epididymal tight junctions is androgen dependant. Thus, Cl-1 expression in the initial segment appears to be only partially under the control of androgens. However, in all other epididymal regions, orchidectomy with or without testosterone replacement, revealed no changes to the normal staining pattern, suggesting that androgens do not regulate Cl-1 expression in these regions. Taken together, these studies demonstrate that Cl-1 expression in the epididymis is not localized exclusively to tight junctions, but appears along the entire interfaces of adjacent epithelial cells as well as along the basal plasma membrane, suggesting a role for Cl-1 as an adhesion molecule. The data also suggest that the regulation of Cl-1 in the epididymis is complex and multifactorial.

Cellular immunolocalization of occludin during embryonic and postnatal development of the mouse testis and epididymis

Cellular junctions in the testis and epididymis play crucial roles for the development and maturation of spermatozoa. In the testis, tight junctions between Sertoli cells form a functional blood testis barrier between 10 and 16 days of age, whereas the tight junctional blood epididymal barrier between adjacent epithelial cells is formed between days 18 and 21. In the present study, occludin, a constituent integral membrane protein of tight junctions, was localized by immunofluorescent confocal microscopy in embryonic (days 13.5-18.5), postnatal (days 5-23) and adult (day 70) mouse testes and epididymides to correlate its expression with the onset of tight junctions and eventual formation of these barriers. At embryonic days 13.5 and 16.5, low diffuse cytoplasmic levels of occludin were observed in cells of the testicular cords. By embryonic day 18.5, the level of occludin was still low but appeared as a filiform-like network streaming toward the center of the cord. At postnatal days 5 and 7 immunostaining became more intense and appeared to outline the periphery of Sertoli cells of seminiferous tubules. Postnatal day 14 marked the appearance of an intense, focal band-like localization of occludin at the base of the tubules, correlating with the appearance of a functional blood-testis barrier. By day 23 and in adults, expression of occludin was noted at the base of the tubule appearing as intense, wavy, discontinuous bands similar in appearance irrespective of the stage of the seminiferous epithelium cycle. In the developing epididymis, intense cytoplasmic immunostaining was present in epithelial cells of many epididymal tubules at embryonic day 13.5. By embryonic day 16.5, intense occludin immunostaining appeared along the lateral plasma membranes of epithelial cells, whereas at embryonic day 18.5, immunostaining was punctate and apically located, suggesting the presence of tight junctions by this age; similar immunostaining was noted at postnatal days 5 and 7. In the adult epididymis, distinct punctate apical staining was observed between adjacent principal cells of all epididymal regions except the proximal initial segment, where occludin was found only in association with narrow cells. These results indicate that in the epididymis, the appearance of occludin at apical sites between adjacent epithelial cells occurs during embryonic development suggesting that tight junctions form earlier than in the testis. While occludin was expressed in a similar pattern between Sertoli cells at all stages of the cycle in the adult testis, its expression in the adult epididymis was cell- and region-specific. Taken together these data suggest that different factors regulate occludin expression in the testis and epididymis.

Segment-specific changes with age in the expression of junctional proteins and the permeability of the blood-epididymis barrier in rats

In aging Brown Norway rats, there is a striking increase in the number of halo cells in the epididymis; this reflects an activation of the immune system. As the blood-epididymis barrier should protect from immunological attack, we hypothesized that there would be changes in the structure and function of this barrier with age. To test this hypothesis, we assessed the immunocytochemical localization of occludin, ZO-1, and E-cadherin, as well as the lanthanum nitrate permeability of the blood-epididymis barrier, in the epididymides of Brown Norway rats aged 3, 18, and 24 mo. In the initial segment, occludin, ZO-1, and E-cadherin immunostaining was observed at the apico-lateral junction between principal cells in the 3-mo-old animals; with increasing age, occludin and ZO-1 reactivity decreased, while E-cadherin staining increased along the lateral membrane between principal cells. In the caput, corpus, and cauda epididymidis, occludin, ZO-1, and E-cadherin immunostaining showed segment-specific and age-dependent differences in their staining patterns. The most dramatic changes were seen in the corpus epididymidis with age; the intense E-cadherin cytoplasmic staining that was observed at 3 mo was absent by 24 mo, and no occludin or ZO-1 reactivity was observed in older animals. The greatest penetration of lanthanum nitrate across the blood-epididymis barrier and in the lumen was seen in the aging corpus epididymidis, while there was no barrier permeability in the initial segment or cauda epididymidis of the aged animals. Taken together, these data indicate that there are segment-specific decreases in the structural and functional integrity of the blood-epididymis barrier with age, most notably in the corpus epididymidis.

Gene expression in the epididymis

The epididymis is a tubular organ exhibiting vectorial functions of sperm concentration, maturation, transport, and storage. The molecular basis for these functions is poorly understood. However, it has become increasingly clear that regional differences along the length of the duct play a role in epididymal physiology and that region-specific gene expression is involved in the formation of these differences. Although not an overtly segmented organ, the epididymis consists of a series of highly coiled "zones," separated by connective tissue septulae and distinct by cell morphology and their pattern of gene expression. Thus, it constitutes an interesting mammalian model to study how pattern formation is achieved by differential gene activity. A large number of epididymis-expressed genes have been cloned and analyzed at the molecular level, most of them have been characterized by a distinct temporal and spatial expression pattern within the organ. Only recently have theories been developed about how and when during ontogenesis this pattern formation takes place and what its significance might be. This review summarizes the current knowledge on regionalized gene expression in the epididymis and presents hypotheses concerning its ontogenetic origin and regulation in the adult.

Relationship of cytoskeletal filaments to annular gap junction expression in human adrenal cortical tumor cells in culture

In addition to the well-characterized surface gap junctions expressed at contact sites between cells, annular gap junction profiles have been localized within the cytoplasm of some cell populations. To study and characterize these annular profiles, gap junction protein type was demonstrated with Western blot and immunocytochemistry. The distribution of annular gap junctions and the relationships to cytoskeletal elements were demonstrated with immunocytochemical, transmission electron microscopic, or image analysis with confocal microscopy techniques. SW-13 adrenal cortical tumor cells expressed alpha1 gap junctions at areas of cell to cell contact. In addition, alpha1 gap junction annular profiles were seen within the cytoplasm. Actin and myosin II were found closely associated with these annular gap junctions, while no physical association between tubulin- or vimentin-containing fibers and gap junction protein could be established. Disruption of microfilaments with cytochalasin B treatment (10 microg/ml, 1 h) resulted in a decrease in the average number and an increase in the average size of annular gap junctions compared to control populations. The results are consistent with a role for cytoskeletal elements containing actin and myosin II in annular gap junction turnover.