Isolation and culture of epithelial cells from rat ductuli efferentes and initial segment epididymidis

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.

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

siRNA-mediated knockdown of sperm-associated antigen 11a (Spag11a) mRNA in epididymal primary epithelial cells affects proliferation: a transcriptome analyses

Differential expression of a variety of proteins in the four major regions of the epididymis contributes to maturation of spermatozoa and region-specific cellular functions as well. Proliferation of epithelial cells of the epididymis is highly controlled and thus is one of the major reasons for the nonoccurrence of cancers in this organ system. The molecular mechanisms and the contribution of region-specific genes in epithelial cell proliferation are not yet fully understood. In this study, for the first time, we analyzed the role of sperm-associated antigen 11a (Spag11a), a caput-specific beta-defensin-like antimicrobial gene in governing epididymal cell proliferation and global gene expression. siRNA-mediated knockdown of Spag11a mRNA in epididymal primary epithelial cells resulted in increased cell proliferation. Out of the 68,842 genes analyzed, 4182 genes were differentially expressed (2154 upregulated and 2028 downregulated). A variety of genes that participate in different cellular processes and pathways were differentially regulated. Genes that are important for epithelial cell proliferation were found to be differentially regulated and these changes were confirmed by real-time PCR. Overexpression of Spag11a in immortalized rat caput epididymal cells resulted in decreased proliferation capacity. Results of this study indicate that Spag11a plays a crucial role in governing epididymal epithelial cell proliferation.

Characterization of isolated rat caput epididymal primary epithelial cells: A molecular biology approach

Sperm maturation in the epididymis is a tightly regulated process which involves secretion and addition of a variety of proteins onto the sperm surface. The molecular mechanisms governing these processes has gained interest in the last decade. In vitro model systems to study the role of epididymal proteins in sperm maturation and other physiological process are very important. Isolation of epididymal cells, culture of epididymal explants and generation of immortalized cells were standardized to be used as in vitro models to study epididymal function. However, isolation and maintenance of primary cultures of epididymal epithelial cells seems to be the best option because of its closeness to the in vivo conditions. Though structural and morphological characterization of primary cultures of epididymal epithelial cells were carried out, the same were not conducted at the molecular level. In this study, we isolated adult rat epididymal primary epithelial cells (EPECs) and characterized them for their purity and cell specific expression of molecular markers. Isolated EPECs exhibited normal cell morphology and were sub cultured and maintained up to 3 weeks. EPECs expressed the epithelial marker, E-cadherin and their purity was estimated to be 73% using flow cytometry. EPECs abundantly expressed CRISP1, Urp1a, Pate-F, Crisp1, Ar and Spag11e, markers of epididymal cells and were negative for Urp1b and Pate, markers negative for epididymis. Results of our study provide a systematic characterization of EPECs at the molecular level and thus a refinement to the previously reported characterization methods.

Trehalose maintains vitality of mouse epididymal epithelial cells and mediates gene transfer

In the present study, trehalose was utilized to improve primary culture of mouse epididymal epithelial cells in vitro, and to enhance naked DNA delivery in epididymis in vivo. During the six-day culture, the proliferation activity of the cells in the medium with addition of trehalose was higher than that of those cells cultured in absence of trehalose (p<0.01). To determine the optimal concentration for cell proliferation, a series of trehalose concentrations (0, 60, 120, 180 mM) were tested, and the result indicated that the cell in the medium with 120 mM trehalose showed the highest proliferation potential. The epididymis epithelial cells were cultured in the medium containing 120 mM trehalose upon 16^th passage, and they continued expressing markers of epididymal epithelial cell, such as rE-RABP, AR and ER-beta. Our study also indicated that trehalose concentrations of 120–240 mM, especially 180 mM, could effectively enhance DNA delivery into the mouse epididymis epithelial cell in vitro. Moreover, trehalose could induce in vivo expression of exogenous DNA in epididymal epithelial cells and help to internalize plasmid into sperm,which did not influence motility of sperm when the mixture of trehalose (180 mM) and DNA was injected into epididymal lumen through efferent tubule. This study suggested that trehalose, as an effective and safer reagent, could be employed potentially to maintain vitality of mouse epididymal epthetial cells during long-term culture in vitro and to mediate in vitro and in vivo gene transfer.

Proteomic study of the establishment of boar epididymal cell cultures

A proteomic approach was used in this study to follow the protein expression of epididymal cells during the different phases of a cell culture protocol which was able to obtain an epididymal cell monolayer. The secretory activity of intact proximal and middle caput epididymal fragments and caput, corpus and cauda epithelial cell monolayers was examined on different days of culture. Transcriptomic activity was also followed by RT-PCR for the mRNA of several previously identified major proteins. During the establishment of epididymal cell cultures, a progressive shift was found in the pattern of protein secretion. The normal epididymal protein profile, specific for each epididymal region, was progressively replaced by a less specific profile with the secretion of new proteins. A correlation between protein secretion and the presence of the mRNA of the marker proteins was observed only in the first phase of culture. Most of the new proteins which appeared were characteristic of the secretion of cell monolayers cultivated over several weeks. Despite the significant modifications of the epididymal cell secretome, the presence of new proteins secreted only by cell cultures originating from a specific epididymal region shows the presence of remaining endogenous differentiation.

Effect of culture conditions on the obtention of boar epididymal epithelial cell monolayers

The goal of this study was to investigate the effect of the collagenase digestion time, the initial density of fragments and the culture temperature on the obtention of a boar epididymal epithelial cell culture, which is a useful methodology for the study of epididymal functions. A confluent monolayer of caput, corpus and cauda epididymal epithelial cells was only obtained when an adequate enzymatic digestion of the connective tissue surrounding the epididymal tubule was performed. For the correct digestion of caput and corpus fragments two collagenase digestions of 2 and 1h, respectively, were enough. Cauda fragments, however, needed two collagenase digestions of 3h each. A confluent monolayer of caput, corpus and cauda epididymal epithelial cells was obtained regardless of the initial density tested (15, 30, 60 and 90fragments/well). However, cultures originated from 15 and 30fragments/well showed higher cell concentration during the first 2 weeks of culture than cultures originated from 60 and 90fragments/well. A confluent monolayer of caput, corpus and cauda epididymal epithelial cells was obtained at both 32 and 37 degrees Celsius, but at 32 degrees Celsius cells grew very slowly and confluence was not reached until a week later than it was with cells growing at 37 degrees Celsius. In conclusion, we have observed that the time of digestion with collagenase is an important factor for the successful establishment of boar epididymal cell monolayers, and that the initial density of fragments and the culture temperature should be taken into account.

Effects of peritoneal aluminum overload on polyamines and nitric oxide contents of testes and epididymis in the mice

Polyamines are involved in cellular growth, differentiation and regulation of oxidative stress. The present investigation was to determine the effect of aluminum (Al) toxicity on the nitric oxide products (NO(x)) and metabolism of polyamines in mouse testes and epididymis. Aluminum chloride, AlCl(3,) was administered intraperitoneally to CD-1 adult male mice at dosages of 0, 7 or 35mg Al/kg body weight/day for 14 days (C, LAL and HAL groups). Results obtained show that the weights of epididymis in HAL animals are significantly decreased due to Al administration. Al treatment significantly induced higher Al concentrations in serum, testis and epididymis tissue. In addition, the serum and testicular and epididymal NO(x) production in HAL and testicular NO(x) in LAH groups were increased remarkably compared to the control animals. On the contrary, the contents of putrescine and spermine in testis were significantly lower than the values of controls and LAL groups. The epididymal spermine levels of HAL animal also decreased significantly. It is suggested that the polyamine biosynthesis in the mouse testis and epididymis can be affected by Al, which is associated with the NO(x) production in the male reproductive toxicity.

Evaluation of boar sperm maturation after co-incubation with caput, corpus and cauda epididymal cultures

Boar sperm from the proximal caput epididymis were co-incubated with 1, 4, 7, 10 and 14-day old caput, corpus and cauda epididymal cultures for 24, 48 and 72 h. Boar kidney epithelial cells (LLC-PK1) and ECM alone were used as negative controls. Sperm motility, morphology and membrane integrity were studied to evaluate boar sperm maturation in vitro. Our results showed that epithelial cell monolayers (10, 14-day old) create a suitable microenvironment for the survival of proximal caput sperm and the maintenance of sperm motility over a 72 h period. Moreover, corpus epididymal tubule fragments in culture (1, 4-day old) are capable of promoting the migration of the cytoplasmic droplet along the sperm tail after 24h of co-incubation.

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.

Spontaneously immortalized epithelial cells from mouse caput epididymidis

We report here on the characterization of tissue-culture cell lines derived from primary cultures of the mouse caput epididymidis epithelium. The cell lines were spontaneously immortalized without the use of transforming oncogenes. In defined conditions, our epididymal cells adopted various morphological features that resembles that of the in vivo epididymis epithelium such as a polarized organization and the presence of junctional structures at their apical/lateral membranes as revealed by electron microscopy analyses. Flow cytometry analysis revealed that we were dealing with homogenous cell populations that had reached a near-tetraploid state. RT-PCR assays were used in order to show that several genes that can be considered as markers of in vivo caput epididymidis epithelium activity were expressed in our cell lines confirming that these cells were indeed in a differentiated state close to their endogenous state.

In vitro culture of epithelial cells from the caput, corpus, and cauda epididymis of Sus domesticus

This work describes a protocol to culture epididymal epithelial cells from the caput, corpus, and cauda regions of Sus domesticus. Epididymal epithelial fragments were obtained by dissection and enzymatic digestion with collagenase. About 30 epididymal fragments from each epididymal region were cultured in 24-well culture plates with supplemented RPMI-1640 medium at 37 degrees C, 5% CO2 in air, and 100% humidity. A confluent monolayer of polygonal and tightly packed epithelioid cells from the three epididymal regions was obtained after 12-16 days in culture and maintained in vitro for more than 60 days. The proportion of epididymal epithelial cells in these cultures was assessed by immunofluorescent staining for cytokeratins. Throughout the 2 months of culture, about 80% of the cells were cytokeratin-positive. Electron microscopy observations indicated that cultured cells from caput, corpus, and cauda epididymal regions were tightly adhered to each other by junctional complexes and that stereocilia were present in their apical membranes. Moreover, the presence of an extensive rough endoplasmic reticulum, Golgi apparatus and numerous vesicles in the cytoplasm suggested that cultured cells maintained secretory and absorptive activities. These results show that the epididymal epithelial cells in culture from S. domesticus retain some fundamental features that characterize the epididymal epithelium in the intact organ. This system might be a valuable tool for studying the mechanism of sperm maturation in vitro, including epididymal cell secretions and the analysis of regional differences.

Immortalization by large T-antigen of the adult epididymal duct epithelium

The SV40 large T-antigen has been widely used to convert various cell types to a transformed phenotype, and also to induce progressive tumours in transgenic animals. The objectives of this review are to compare and discuss three different approaches to generate epididymal epithelial cell lines using the large T-antigen. In the first approach, retroviral transfection of primary cultures was used to immortalize canine epididymal cells in vitro; the other two approaches used transgenic mice expressing the large T-antigen. In one of these in vivo approaches, a construct consisting of the coding sequence of a temperature sensitive (ts) SV40 large T-antigen was inserted in a mouse genome. When the cells are exposed to the permissive temperature of 33 degrees C, functional expression of the large T-antigen occurs and cells start to proliferate. In the second in vivo approach a tissue-specific promoter, the 5kb GPX5 promoter, was used to direct expression of the large T-antigen to the epididymal duct epithelium.

Analysis of a human sperm CD52 glycoform in primates: identification of an animal model for immunocontraceptive vaccine development

Sperm agglutination antigen-1 (SAGA-1) is a human male reproductive tract glycoform of CD52. Unique modification of CD52 N-linked oligosaccharide chains in the epididymis and vas deferens results in the appearance of a carbohydrate epitope that is localized over the entire surface of human spermatozoa. SAGA-1 was characterized by the sperm-inhibitory murine monoclonal antibody (mAb) S19, and it is the target antigen of a human mAb (H6-3C4) associated with antibody-mediated infertility. Collectively, sperm surface localization, antibody inhibition of sperm function, and potential reproductive-tissue specificity identify SAGA-1 as an attractive candidate contraceptive immunogen. To establish an animal model for the study of SAGA-1 in immunologic infertility and immunocontraceptive development, we investigated the appearance of the S19 carbohydrate epitope in nonhuman primates. The S19 mAb demonstrated little to no immunoreactivity by Western blot analysis with protein extracts of spermatozoa from the baboon, marmoset, bonnet, cynomolgus, and pigtailed macaques. Immunohistochemical analysis identified CD52 in the bonnet monkey epididymis; however, the N-linked carbohydrate moiety recognized by the S19 mAb, and unique to SAGA-1, was absent. In contrast, the S19 carbohydrate epitope was identified in chimpanzee sperm extracts by Western blot analysis and in chimpanzee epididymal tissue sections by immunohistochemical analysis, indicating that it is conserved in this close relative of the human. Chimpanzee testis, seminal vesicle, and prostate do not express the S19 epitope. Although anti-CD52 immunoreactivity was identified in the spleen, the carbohydrate moiety recognized by the S19 mAb was absent, corroborating data in the human that demonstrated tissue-specific glycosylation of sperm CD52. Immunofluorescent analysis indicated that the chimpanzee homologue of sperm CD52 was present over the entire spermatozoon. In addition, the S19 mAb agglutinated chimpanzee spermatozoa in a manner similar to the effect observed on human spermatozoa. These data indicate that the distinctive carbohydrate moiety of human sperm CD52 is present in the chimpanzee, and they identify the chimpanzee as the most appropriate primate model to study the potential of this unique CD52 glycoform as a contraceptive immunogen.

Estrogen and spermatogenesis

Although it has been known for many years that estrogen administration has deleterious effects on male fertility, data from transgenic mice deficient in estrogen receptors or aromatase point to an essential physiological role for estrogen in male fertility. This review summarizes the current knowledge on the localization of estrogen receptors and aromatase in the testis in an effort to understand the likely sites of estrogen action. The review also discusses the many studies that have used models employing the administration of estrogenic substances to show that male fertility is responsive to estrogen, thus providing a mechanism by which inappropriate exposure to estrogenic substances may cause adverse effects on spermatogenesis and male fertility. The reproductive phenotypes of mice deficient in estrogen receptors alpha and/or beta and aromatase are also compared to evaluate the physiological role of estrogen in male fertility. The review focuses on the effects of estrogen administration or deprivation, primarily in rodents, on the hypothalamo-pituitary-testis axis, testicular function (including Leydig cell, Sertoli cell, and germ cell development and function), and in the development and function of the efferent ductules and epididymis. The requirement for estrogen in normal male sexual behavior is also reviewed, along with the somewhat limited data on the fertility of men who lack either the capacity to produce or respond to estrogen. This review highlights the ability of exogenous estrogen exposure to perturb spermatogenesis and male fertility, as well as the emerging physiological role of estrogens in male fertility, suggesting that, in this local context, estrogenic substances should also be considered "male hormones."

Morphology and function of rooster efferent ductule epithelial cells in culture

Regulation of the excurrent ducts of the testis is not well understood, particularly in avian species. To investigate the role of steroid hormones in the male reproductive tract, we developed a primary cell culture of epithelia isolated from rooster ductuli efferentes (efferent ductules). Efferent ductules of the avian testis comprise 77% of the epididymal region and form a mass of tubules containing a heavily folded epithelium enmeshed in connective tissue. The epididymal region was separated by microdissection and small epithelial plaques isolated by serial digestion with collagenase, elastase and repeated pipetting. Isolated cell plaques were cultured in a bicameral chamber on Millicell-CM inserts coated with two layers of basement membrane matrix, consisting primarily of laminin and Types I and IV collagen. Active ciliary beat was observed before plating and this activity was maintained for 14 days in culture. Cell plaques attached within 24 h and outgrowths formed a confluent monolayer by 5-6 days. The epithelial nature of cultured cells was demonstrated by immunocytochemical staining for cytokeratin. Light and electron microscopy confirmed that morphology and polarity of the original epithelial cells were maintained in culture. Cultured efferent ductal epithelium was cuboidal in shape and maintained many of the cytoplasmic organelles typical of these cells in vivo. The uptake of cationic ferritin indicated the endocytotic activity of these cultured cells was maintained. Estrogen receptor mRNA expression was maintained in cultured cells. These data demonstrate avian efferent ductal epithelium can be isolated and grown in defined culture medium for the purpose of determining the role of hormones and other factors in regulating the function of the epididymal region in the bird.